ME215 Final Exam
Four basic steps of Powder metallurgy are
- 1. Powder manufacture - 2. Mixing or blending - 3. Compacting - 4. Sintering
Dinking
used to blank shapes from low-strength materials such as rubber, fiber, or cloth
Lathe Collets
used to hold round stock of standard sizes
Roller burnishing
used to improve the size and finish of internal and external cylindrical and conical surfaces
vacuum degassing
a stream of molten metal passes through a vacuum chamber into a mold
Unilateral Tolerance
Deviation is in one direction from the nominal size
Forward extrusion
Diameter is decreased while length increase
Dispersion hardening
Dispersing second-phase particles through a base material
Operations:
Distinct action to produce a desired result or effect.
What can result from nonuniform temperatures and thermal stresses induced by welding?
Distortion or warping
Austempered ductile iron
Ductile cast iron which go to austempering heat treatment- provide double strength with same ductility compared to ductile cast iron, excellent strength-to-weight ratio
Graphite
Each carbon atom uses three of its electrons to form simple bonds to its three close neighbors. The fourth electron in the bonding level. The "spare" electrons in each carbon atom become delocalized over the whole of the sheet of atoms in one layer. They are no longer associated directly with any particular atom or pair of atoms. Are free to wander throughout the whole sheet.
Arc Furnaces
Electric arc is heat source; Fluxing material is used to create protective slag over the molten metal
Properties Determined by StressStrain Curve:
Engineering stress-strain diagram,Proportionality limits (Hooke's law), Elastic limit, Young's modulus (E), Measure of Stiffness, Resilience, Yield point, upper and lower, Maximal load,Breaking stress.
High-alloy cast iron
Enhance corrosion resistance and/or good elevated temperature service
Inspection
Ensures what is being manufactured will meet specifications
Testing
Evaluates product quality or performance
White cast iron
Excess carbon in form of iron-carbide - hard and brittle (provide high wear resistance)
Deformation processes
Exploit the ductility or plasticity of certain materials, mostly metals, and produce the desired shape by mechanically moving or rearranging the solid
Casting processes
Exploit the properties of a liquid as its flow into and flows into and assumes the shape of a prepared container, and the solidifies upon cooling
Shaving
Finishing operation in which a small amount of metal is sheared away from the edge of an already blanked part
Counterboring
Follows a drilling operation, or in with drilling with a custom tool. Purpose is to produce a flat bottom so that bolt head or nut is below the surface with enough clearance for a tool.
Elastic limit
For almost all materials almost the same as proportionality limit (for some slightly higher than proportionality limit)
High energy rate forming (HERF)
Form metals through the application of large amounts of energy in a very short time
Gas porosity
Gas that is not rejected from the liquid metal may be trapped upon solidification
Plastic Deformation in Polycrystalline Metals
Grain boundaries act as barriers to dislocation movements. Metals with more grains per unit area have greater strength, hardness, and impact resistance.
Notching
Removes segments from along the edge of an existing product
Precision
Repeatability of the process
Risers
Reservoirs of liquid metal that feed extra metal to the mold to compensate for solidification shrinkage
Ionic bond
Resulting from the electrostatic attraction of oppositely charged ions, it is non-directional (e.g. NaCl crystal). Materials joined by __________ have moderate to high strength, high hardness, brittleness, high melting point, and low electrical conductivity. The electrostatic attraction between the negative and positive ions forms a strong bonding force. produces electrically neutral structure by adopting the most stable configuration.
Covalent bond
Resulting from the sharing of electrons. Mostly by overlapping of half filled orbital's of two atoms. It is a directional bond. Produce materials with high strength, high melting points, brittle. Each atom achieves a stable electron configuration. Electrical conductivity depends on bond strength.
Rod Drawing
Rods reduce in section, elongate and become stronger (strain harden
Burnishing
Rubbing a smooth, hard object under pressure over the minute surface irregularities
Tools for measurement and inspection
Rulers, calipers, micrometers, and gages, precision devices(laser optics or vision systems that utilize electronics to interpret results)
eutectoid
S1 --> S2 + S3
Peritectoid
S1+S2->S3
Shell molding
Sand coated with a thermosetting plastic resin is dropped onto a heated metal pattern, which cures the resin, The shell segments are stripped from the pattern and assembled. When the poured metal solidifies the shell is broken away from the finished casting
Core
Sand or metal shape that is inserted into the mold to create internal features
Sand Casting
Sand, bonded with clay and water, is packed around a wood or metal pattern. The pattern is removed, and molten metal is poured into the cavity. When the metal has solidified, the mols is broken and the casting is removed.
Backward extrusion
Shapes hollow with a solid bottom
Simple shearing
Sheets of metal are sheared along a straight line
Countersinking
Similar to counterboring, but with a 60°, 82°, or 90° beveled bottom to accommodate flat-head screw or rivet.
Spray forming
Similar to spray deposition; powder material is inject into a plasma torch, particles melt and are propelled onto a shaped form or mandrel
Lap-welded pipe
Skelp has beveled edges and the rolls form the weld by forcing the lapped edges down
Cold forming
Slugs of material are squeezed into or extruded from shaped die cavities to produce finished parts of precise shape and size
Interatomic distances and size of atoms
Space occupied by electrons much smaller than electron shells space (vacant space). Bonding forces pull atoms together, but repelling forces between neighboring nuclei exist as well. Equilibrium distance=Sum of atomic radii to assign distinct size to atoms. Removing valence shell (bonding) reduces size of atom. Atoms oscillate around their equilibrium positions.
Butt-welded pipe
Steel skelp is heated to a specified hot-working temperature; The skelp rolls back on each other through rollers and produces a welded seam
Altered surface chemistry:
Steels contain insufficient carbon (<0.3%) to achieve the desired surface properties - Carburizing - Nitriding - Ionitriding - Ion carburing - Carbonitriding - Nitrocarburizing
Selective heating of the surface
Steels have a sufficient carbon (>0.3%) to achieve the desired surface hardness - Flame hardening - Induction hardening - Laser beam hardening - Electron beam hardening
Gap-frame presses - frames have the shape of letter "C"
Straight-sided presses - consist of a crown, two uprights, a base or bed, and one or more moving slides
Precipitation hardening or Age hardening
Strength is obtained from a nonequilibrium structure (coherent precipitate cluster)
Endurance limit (strength)
Stress below which material is safe from failing due cyclic load (S-N curve).
Atomic Structure and Electrical Properties
Structure of a materials influences its physical properties. Electrical conductivity is the net movement of a charge through a material. Electrical resistance of a metal depends on lattice imperfections and temperature. Best metallic conductors are pure metals with large grains at low temperatures
Dynamic Properties
Sudden loads or impacts (rapid varying in magnitude). Repeated cycles of loading and unloading. Frequent changes in mode of loading (tension to compression).
The continuous process:
liquid and gasses production systems (oil refineries)
Static loads
loads applied on the material do not vary or vary negligibly
Skelp is
long strips of steel used in welding
Tools
lowest mechanism in the production and are used to hold, shape or form the unfinished product.
Turret-type punch press
machine where as many as 60 separate punches and dies are contained with a turret that can quickly be rotated to provide specific tooling required for an operation
The job shop
machines situated by function and parts circulated in containers between them
Peening
mechanical working of surfaces by repeated blows of impelled shot or a round-nose tool
Extrusion
metal is compressed and forced to flow through a shaped die to form a product with a constant cross section
Engineering materials divided into
metallic and nonmetallic
Hot tears or cracks occur in
metals with large amounts of solidification shrinkage
Complex-phase (CP) steels:
microstructure of ferrite and bainite with small amount of martensite, retained austenite and pearlite
Dual-phase (DP) steels:
microstructure of ferrite and martensite
Die casting
molten metal is injected into closed metal dies under pressure ranging from 10 to 175 MPa. Pressure is maintained during solidification, after which the dies separate and the casting is ejected along with its attached sprues and runners. cores must be simple and retractable and take the form of moving metal segments
Centrifugal Casting
molten metal is introduced into a rotating sand, metal, or graphite mold and held against the mold wall by centrifugal force until its solidified
Twist Drills
most common drills have three parts - The body: consisting of spiral grooves called flutes, separated by lands - The point: a wide variety of geometry are used, but typically have a cone angel of 118°, and a rake angle of 24° - The shank: a straight or tapered section where the drill is clamped.
Forming
multiple bends are made with a single die; axes of deformation are linear and independent of the others o Drawing and stretching- axes of deformation are not linear or are not independent
Net-Shape and Near-Net-Shape Forging
net-shape or precision forging is process that forge as close the final shape as possible to minimize expense and waste
Superalloys and Other Metals Designed for High-Temperature Service
o Alloys based on nickel, iron, cobalt o Refractory metal: niobium, molybdenum, tantalum, rhenium, and tungsten o Intermetallic Compounds
Lead and Tin, and their alloys
o Lead and lead alloys - provide high density with strength and stiffness that are the lowest of engineering metals o Tin - use as a corrosion resistant coating on steel o Lead and tin are used together as bearing materials and solder.
Compacting
o Loose powder is ___________ and densified into a shape, known as green compact - Most _____________ is done with mechanical presses and rigid tools - Hydraulic and pneumatic presses are also used o If an extremely complex shape is desired, the powder may be encapsulated in a flexible mold, which is then immersed in a pressurized gas or liquid; Process is known as isostatic compaction (uniform pressure - pressure is applied in all direction)
Nickel-based alloy General properties and characteristics
o Outstanding strength and corrosion resistance at high temperatures o Good formability, creep resistance, strength and ductility at low temperatures o Wrought alloys are known as Monel, Hastelloy, Inconel, Incoloy, and others
Zinc-based alloys General Properties and Characteristics
o Over 50% of all metallic zinc is used for galvanizing o Steel or iron may be hot dipped or be coated using electrolytic plating - provide corrosion resistance o Also used as the base metal in many die casting alloys: can be cast close to dimensional tolerances
Graphite
o Properties of metals and nonmetals o Good thermal and electrical conductivity, Can withstand high temperatures , and Lubricity
Pearlite (cooling x→x')
o Steels having eutectoid composition of 0.77%C Austenite0.77%C, FCC → Ferrite0.02%C, BCC + Cementite6.67%C o Lamellar structure of 2 distinct phases: ferrite and cementite
Hypoeutectoid steel (cooling y→y')
o Steels having less than the eutectoid amount of carbon (<0.77%C) o A mixture of primary ferrite (proeutectoid ferrite) and regions of pearlite
Hypereutectoid steel (cooling z→z')
o Steels having more than the eutectoid amount of carbon (>0.77%C) o A mixture of primary cementite (proeutectoid cementite) and regions of pearlite
Tempering and age hardening
o aging is to sacrifice toughness and ductility for strength o temper is to sacrifice strength and hardness for ductility and toughness
Electroforming
The metal is deposited by plating
microstructure
observed on a microscopic scale.
Orbital Forging
A conical faced upper die is tilted or inclined so a portion of the cone is in contact with workpiece. The upper die then orbit about a central axis form uniform-radius disk shaped or conical products (such as gear blanks or bevel gears)
Advanced High-Strength Steels (AHSS) Types of AHSS
AHSS is primarily ferrite-phase, soft steels with varying amount of martensite, bainite or retained austenite - which offer high strength with enhanced ductility Improved formability Possibility of weight reduction
Swaging
Also known as rotary swaging and radial forging Uses external hammering to reduce the diameter or produce tapers or points on round bars of tubes
Steels for Electrical and Magnetic Applications
Amorphous metals - No crystal structure, grains, or grain boundaries - Magnetic domains can move freely - Properties are the same in all directions - Corrosion resistance is improved
The Three stages of Sintering
Burn-off (purge)- combusts any air and removes lubricants or binders that would interfere with good bonding High-temperature- desired solid-state diffusion and bonding occurs Cooling period- lowers the temperature of the products in a controlled atmosphere ****All three stages must be conducted in oxygen-free conditions****
AISI-SAE Classification System
First number indicates the major alloying elements Second number designates a subgrouping within the major alloy system Last two digits indicate the carbon percentage expressed as "points" i.e. AISI1080 - plain carbon steel with 0.80% carbon AISI 4340 - Mo-Cr-Ni alloy with 0.40% carbon
Copper and Copper Alloys Main properties
High electrical and thermal conductivity Useful strength with high ductility Corrosion resistance
o Slush Casting
Hot metal is poured into metal mold and is allowed to cool until the shell of desired thickness has formed. Mold is then inverted and remaining liquid is poured out used to produce hollow shapes; good surface detail; Variable wall thickness
Upset Forging
Increases the diameter of a material by compressing its length Both cold and hot upsetting Use spit dies that contain multiple position or cavity Upset-forging machine are often used to form heads on bolts and other fasteners, to shape valves, coupling and other small components
Fe3C, cementite (iron-carbide):
Intermetallic compound that forms at 6.67%C Hard and brittle
Magnesium and magnesium alloys and General Properties and Characteristics
Lightest of commercially important materials- Magnesium weight is 2/3 of Aluminum, 1⁄4 of steel Poor wear, creep, and fatigue properties Highest thermal expansion of all engineering metals Modulus of elasticity is less than that of aluminum, 1/5 or 1/6 of that of steel High energy absorptions and good damping
Thermoplastics
Linear polymer Heat-softening material : due to van der waal bonds are weaker at elevated temperature Reversible reaction at elevated temperature - material is able to recycle Most common thermoplastic polymers: polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyvinylchloride (PVC)
Special steels
Maraging steel - extremely high strength Steels for High-Temperature Service - for using at high temperature
α, ferrite (BCC):
Only 0.02 wt.% C in solid solution magnetic-nonmagnetic transition (Curie point) at 770°C below 770°C iron is ferromagnetic (magnetic) above 770°C iron is paramagnetic (nonmagnetic)
Tube Hydroforming
Process for manufacturing strong, lightweight, tubular components that replace an assembly of welded stampings Frequently used process for automotive industry
HSLA
Provide increased strength to weight ratio(Material with high strength-to-weight ratio is material that is strong and light weight) Modest increase in cost High yield strength, good weldability, and good corrosion resistance
Roll forging
Round or flat bar stock is reduced in thickness and increased in length Produces products such as axles, tapered levers, and leaf springs Little or no flash is produced
Aluminum and aluminum alloys General Properties and Characteristics
Second to steel in quantity and usage: used in transportation, packaging, containers, building construction, etc. Workability, light weight, corrosion resistance, thermal and electrical conductivity ( better than steel), optical reflectivity, easily finished Aluminum is about 1/3 the weight of steel for an equivalent volume Four to five times more expensive than steel per pound Biggest weakness of aluminum is its low modulus of elasticity (about 1/3 that of steel)
Automatic Hot Forging
Slabs, billets, and blooms can be slid into one end of a room a hot-forged products can emerge at the other end, with every process automated Attractive features: low cost input material, high production rates are high, Minimum labor, No flash or scrap, The as- forged structure is often suitable for machining, Good tolerances, Clean surfaces and low draft angles, Tool life is nearly double that of conventional forging. The limitation: high initial cost of the equipment , the restriction of large production quantities.
Free Machine steels
Steels machine readily and form small chips when cut -(smaller chip reduce friction and tool wear) Carbon steel with addition of S, Pb, Bi, Se, Te or P - to enhance machinability
Press Forging
The deformation is analyzed in term of forces or pressures (rather than energy) Slow squeezing action penetrates completely through the metal - produces a more uniform deformation and flow and longer time of contact between the die and workpiece Dies may be heated (isothermal forging) Presses are either mechanical or hydraulic (note: Hammer or impact forging - High speeds, short forming time, short contact times)
Impression-Die (Closed-die) Hammer Forging
The dies are shaped to control the flow of metal Upper piece attaches to the hammer and the lower piece to the anvil Metal flows and completely fills the die Excess metal may squeeze out of the die This metal is called flash Flashless forging (true closed-die forging) can be performed if the metal is deformed in a cavity that provides total confinement
Thermosets
a highly cross-linked or three-dimensional framework structure Produced by condensation polymerization Irreversible reaction at elevated temperature - material is unable to recycle Common thermosetting polymers: polyurethane (PUR), bakelite (PF), epoxies
Fiber-reinforced Composites
composite that continuous or discontinuous thin fibers of one material are embedded in a matrix common objective is high strength and lightweight Orientation of the fibers is important
Particulate Composites
consist of discrete particles of one material in a matrix of another material Dispersion strengthened materials have a small amount of hard, brittle, small-sized particles in a soft, metal matrix True particulate composites contain large amount of coarse particles : Grinding and cutting wheels Metal-matrix composites: ceramic or glass particles in metal matrices The properties of ___________ composite are usually isotropic
Titanium and titanium alloys and General properties and characteristics
is a strong, lightweight, corrosion resistant metal Less dense than steel (density is 56% that of steel), high strength-to-weight ratio Can be used in high temperature applications Disadvantages: high cost, fabrication difficulties, high energy costs for fabrication Abundant material, but is difficult to process from ore Aerospace applications, medical implants, bicycles, heat exchangers are common uses
Bake-Hardenable Steel
low carbon steel that is resistant to aging during normal storage, but begins to age during sheet metal forming A significant role in automotive applications
The flow shop
(ASSEMBLY LINE) mass production designated shop with specific manufacturing orientation
American Society of Testing and Materials
(ASTM) has standardized the testing methodologies for determining physical and mechanical properties. Important that the tests are standardized and reproducible. ASTM maintains and updates testing standards
Consumer goods
(Goods purchased directly by the consumer)
Producer goods
(Intermediate goods used to manufacture either producer or consumer goods),
Rockwell Test
(Penetration performed in two stages (minor and major load); Indenter ( small diameter ball or diamond tip)), Vickers Hardness Test-a diamond pyramid as indenter(Simple to conduct. No special preparation. Field testing. High accuracy in determining diamond diagonal. Cheap and reliable.)
Service Production systems
(Transportation, Banking, finance, savings and loans, insurance, health care, utilities, education, communication, entertainment, sporting events, etc)
Galvanizing
(bolts and knots): coating on the outside of the material to protect the material from corrosion.
Subatomic structure
(protons, neutrons, electrons)
Automatic Lathes
- Also called Swiss Screw machine - A specialized type of automatic turret lathe - Rod stock is automatically fed into the collet
Parts of the lathe
- Bed - Headstock - Tailstock - Quick-change gearbox - carriage assembly - ways
γ, austenite (FCC):
- Capable of dissolving more than 2% C in single phase solid solution - High formability due to the characteristic of FCC - Low strength, high ductility, and chemical uniform - heat treatment regime
Factors in selecting inspection equipment
- Gage capability - Linearity - Repeat accuracy - Stability - Magnification - Resolution
Deposition of an additional surface layer
- Ion plating - Ion implantation
Speed Lathes
- Limited to headstock, tailstock, and simple tool post. - Limited to 3-4 speeds - High spindle speeds, - For light work such a wood turning, metal polishing, or metal spinning
Geometric Tolerances
- Maximum allowable deviation of a form or position from the perfect geometry - Maximum material condition indicates that a part is made with the maximum allowable material -specified with respect to a datum or reference surface
Engine Lathes
- Most common type - Variable in design from low to high power designs - Broad range of lengths up to 60ft long - Features as described in Figure 22.8
Screw-type drives
- Offer great advantage coupled with an action that resembles a drop hammer - Popular in forging industries
Heat Treatments for Nonferrous Metals
- Produce a uniform, homogenous structure (rapid cooling can cause segregation solidification structure (coring) - Provide a stress relief - Induce recrystallization
Properties of composite materials depend on
- Properties of individual components - Relative amounts - Size, shape, and distribution - Orientation - Degree of bonding
Gage Blocks
- Provide industry with linear standards of high accuracy - Small, rectangular, square, or round in cross section - Made with steel or carbide - Two flat and parallel surfaces - Calibrated with light-beam interferometry - By combining blocks, any desired dimension can be obtained
Toolroom Lathes
- Specialized Engine lathe with greater accuracy. - Broader range of speeds and feeds - Greater versatility for tool and die manufacturing
Conventional milling or up milling
- The cutter rotates against the direction of feed of the workpiece. - The Chip is very thin at the beginning and increased along its length. - The cutter tends to push the work along and lift it upwards from the table.
Down milling the cutter rotation is the same as the direction of feed
- The maximum chip thickness is at the point of tooth contact with the work piece. Dulling the teeth more quickly - The work piece is pulled into the cutter, eliminating any effects from looseness of the work table feed screw.
Turret Lathes
- Turret on tool post rotates to position a variety of tools - Capstan wheel used to pull to away from work piece to position next tool - A number of tools set up on machine, each brought up in quick succession to complete the part in a single setup
Solid-state welding
- Use electrical resistance heating to form joints - Create joints without any melting of the workpiece or filler material
Crank driven press
- Used for most piercing and blanking operation and for simple drawing
Eccentric or cam drives
- Usedwheretheramstrokeisrathershort - Deep-drawingprocesses
What are the various methods Work pieces can be held by?
- Work piece mounted between centers - Work piece mounted within a single chuck - Work piece mounted within a collet - Work piece mounted on a faceplate
Metal infiltration
- a molten metal or alloy fills in pores under pressure or capillary action - to improve strength and toughness, seal pores before plating, improve machinability or corrosion resistance
Compression Bending
- the bending form remains stationary and the pressure tool moves along the surface of the workpiece
Apparent density
- the measure of a powder's ability to fill available space without external pressure - Low apparent density means that there is a large unfilled space - Final density is measured after compaction and sintering and is typically about twice the value of the apparent density
Aging step can divide precipitation-hardening materials into two types
-Natural aging material ages at room temperature - Artificial aging material requires elevated temperature to produce aging (considerable flexibility and control)
Stress-relief anneal
-Reduces residual stresses -Materials are heated and then slow cooled -Microstructures and mechanical properties remain unchanged
Direct extrusion
-Solid ram drives the entire billet to and through a stationary die - Must provide power to overcome friction
Graphite II
-The delocalized electrons are free to move anywhere within the sheet. Each electron is no longer fixed to a particular carbon atom. There is no direct contact between the delocalized electrons in one sheet and those in the neighboring sheets. The atoms within a sheet are held together by strong covalent bonds -stronger than in diamond. -Van der Walls forces hold the sheets together.
Process anneal
-cooling in air o specific procedure for low carbon steel (<0.25%C)
Casting
Describes both the process and the product when molten metal is poured and solidified in a mold
Production system
-is the total company and includes manufacturing systems. -unifies manufacturing system and other areas of the plant for information, design, analysis and control.
Spheroidizing anneal
-slow cooling o for high carbon materials (C > 0.60%) o Objective is to produce a structure in which all of the cementite is in the form of small spheroids or globules dispersed throughout a ferrite matrix
Six basic steps of casting
1). mold must be produced with mold cavity, having the desired shape and size of the part with allowance for shrinkage of solidifying material 2). Melting process: provides molten material at the proper temperature 3). Pouring technique: molten metal is poured into the mold at a proper rate to ensure that the molten metal is to completely fill the mold cavity and produce a fully dense casting and free of defects. 4).Solidification process 5). Mold removal: the casting is removed from the mold 6). Cleaning, finishing, and inspection operations: excess material along parting lines may have to be machined
Atom composition
: nucleus {protons (+), neutrons (neutral), high mass}. Electron (-) cloud, equal number as protons, arranged in shells and sub-shells. neutral charge balance. Atomic number; the number of protons in the nucleus of an atom of an element. Electron shell: a group of electrons with the same principal quantum number, n. Electron shells: shell-1(two electrons); shell-2 (eight electrons); shell-3 (max. 32 electrons). Stable configuration with 8 electrons in 3rd shell and up. Valence electrons: electrons in the outermost shells which are most often involved in bonding.
Process of precipitation hardening is a three-step sequence
: solution treatment → quench → aged
Spinning
A cold forming operation where sheet metal is rotated and shaped over a male form, or mandrel to produce rotationally symmetrical shapes such as spheres, hemispheres, cylinders, bells, and parabolas
Metallic bonding
A complete outer shell can not be formed by electron sharing or transfer. Positive ions are surrounded by wandering, universally shared valence electrons. Electrons are highly mobile. High electrical and thermal conductivity . Opaque. Bond strength, material strength, and melting point vary. Positive ions can now move within the structure without the breaking of discrete bonds. Basis of metal plasticity. Allows metals to be formed in a variety of ways.
Roll bending
A continuous form of three-point bending where plates, sheets, beams, pipes, and even rolled shapes and extrusions are bent to a desire curvature using forming rolls
Nibbling
A contour is progressively cut by producing a series of overlapping slits or notches
Indirect extrusion
A hollow ram pushes the die back through a stationary, confined billet - No relative motion, friction between billet and chamber is eliminated
Composite material
A material system made by mixture or combination of 2 of micro or macro-constituents different in chemical composition and insoluble in each other.
Impact Extrusion
A metal slug is positioned in a die cavity where it is struck by a single blow by a rapidly moving punch
Shear forming or flow turning
A modification of spinning and a reduction of the wall thickness occurs.
Evaporative pattern (full-mold and lost-foam) casting
A pattern containing a sprue, runners, and riser is made from single or multiple pieces of foamed plastics, such as polystyrene. It is dipped in a ceramic material, dried and positioned in a flask, where it is surrounded by loose sand. Molten metal is poured directly onto the pattern, which vaporizes and is vented through the sand.
Strain analysis
A pattern or grid is placed on the surface of a sheet; during deformation, the circles convert into ellipses, and the distorted pattern can be measured and evaluated
Forming limit diagram
A plot of the major strain and related minor strain on the surface of metal sheet, indicating the conditions for which fracture occurs
Roll forming
A process by which a metal strip is progressively bent as it passes through a series of forming rolls; Only bending takes place during this process, and all bends are parallel to one another
Sinter brazing
A process in which two or more separate pieces are joined by brazing while they are also being sintered
Cutoff
A punch and a die are used to separate a stamping or other product from a strip of stock
Nonconsumable electrode processes
A separate metal wire must be used to supply the filler metal
Stretch forming
A sheet of metal is gripped by two or more sets of jaws that stretch it and wrap it around single form block
Inspection of a product can be done in two main ways
Attributes and variables
Drawing and stretching
Axes of deformation are not linear or are not independent
General sequence of product design
Design → Material selection → process selection → production → evaluation → redesign/modification
Development of a Grain Structure
A small particle of solid forms from the liquid, as the metal solidifies. Lattice structure that forms is characteristic of a given material. Metal solidifies as atoms attach themselves to the small particle (nucleation and growth). Basic crystalline unit is called a unit cell and is repeated throughout the material. Grains are small continuous volumes of solid. Surfaces that divide grains are called grain boundaries. From the pool of molten metal many small particles having lattice parameters of given material form (nucleation). Crystal growth follows up until interference with neighbors forming grain boundaries upon solidification completion.
Uniaxial Tensile Test:
A standard specimen loaded in tension in testing machine. Test parameters: load (F), elongation (gage length) are monitored. By standardized test procedures data sets characteristic for specific materials are generated.
Additive manufacturing or direct digital manufacturing
A variety of processes developed to directly convert a computer-file "drawing" to a finished product without any intervening patterns, dies, or other tooling
Subpress dies or modular tooling
A wide variety of standardized, self-contained die sets;
Hardness
Ability of the material to resist to the plastic deformation.
Accuracy
Ability to hit what is aimed at
Manufacturing or Design defects:
Abrupt section changes, Excessively small fillets, Small holes. By fracture dynamics cracks can be dormant (do not change) or dynamic (crack growth rate).
Measurement
Act of measuring or being measured
Riser
Additional void in the mold that provides additional metal to compensate for shrinkage
Inter metallic compounds
Alloying element interact with atoms of base metal in definite proportion and definite geometric relationships.
Martensitic (Mart) steels:
Almost entirely martensite
End milling
Also called facing milling, the surface is generated is at a right angle to the cutter axis. Material is removed by the peripheral teeth and the face portion providing finishing action.
Draft
Angle or taper on a pattern that allows for easy removal of the casting from the mold
Pattern
Approximate duplicate of the part to be cast
misruns and cold shut
Are defects that occur when metal begins to freeze before it has completely filled the mold
Arch-frame presses
Are seldom used today, except with screw drives for coining
Fluxes
Are used to promote the formation of a better bond
Grain Shape and Anisotropy:
As a metal is deformed, the grains elongate in the direction of metal flow. Properties that vary with direction are called anisotropic(fiber alignment anisotropy, inherent anisotropy, grain alignment, High strength to weight ratio). Anisotropic behavior can create problems during manufacturing. Properties that are uniform in all directions are called isotropic.
Shrinkage of liquid
As it cools from the solidification temperature
Yield point
Beyond elastic limit no proportionality between stress and strain. Upper yield point (for low C steels); Lower yield point (for low C steels); Not well defined. Ultimate strength (maximum load).
Precision Boring
Bored holes often are bell mouthed due to tool deflection
Drag
Bottom half of the pattern, flask, mold or core
Failure
Breaking or fracture strength
Hardness Testing
Brinell Hardness Test (a penetrator (ball of D=10 mm) made of tungsten carbide or hardened steel ball of D=10 mm)
Consolidation processes
Build a desire shape by putting smaller pieces together. i.e. welding, brazing, soldering, adhesive bonding, and mechanical fasteners (chapters 30, 31, 32, 33)
Superplastic sheet forming
By producing sheet material with ultra-fine grain size, and performing the deformation at low strain rates and elevated temperature, elongations can exceed 100% and may be as high as 2000 to 3000%
Shaping processes:
Casting (molten metal's) or molding (plastic).
Bending impacts
Charpy test (impact at the center). Izod test (impact at the end). Tension impacts:
Surface Processes
Coating (electro plating, plasma, thermal spray), Cleaning (chemical agent, water jet, ice jet, etc), Surface treatment (carburizing).
Coining
Cold squeezing of metal while all of the surfaces are confined within a set of dies
Mold cavity
Combination of the mold material and cores
Compound dies
Combine processes sequentially during a single stroke of the ram
Destructive Testing
Components are subjected to conditions to induce failure
Fatigue
Components fail at less than ultimate tensile strength, and usually less than yield strength at cyclic loads. Fatigue depends on stress raisers (sharp corners, surface cracks, machining marks, etc.)
Alloy
Composed of metal and another solid substance (usually another metal).
Compression strength
Compression test which is similar to tensile test behavior but more difficult to conduct.
CNC
Computer Numeric Control
Steel processing
Continuous casting produces feedstock material (slab, bloom, billet, strand) that is used in forging or rolling,
Gates
Controlled entrances into mold cavity
Permanent dipole bond
Created by attraction of molecules which have permanent dipole moments. Each molecule have (+)&(-) charge centers separate by a distance
Indirect Fuel-Fired Furnace (or crucible furnace)
Crucibles or holding pots are heated externally which in turn heats the metal o Direct Fuel-Fired Furnace : Flame passes directly over molten metal
Engineering strain
Defined as elongation divided by initial gage length
Dislocation Theory of Slippage:
Deformation is the result of the progressive slippage of a localized disruption known as a dislocation. Localized imperfections. Edge dislocation. Edges of extra half-planes of atoms.
Warm working
Deformations produced at temperatures intermediate to cold and hot working
Solubility
Degree of solubility determines properties.
Grey cast iron:
Graphite flakes (act as a void in microstructure - no appreciable strength; positive features -reduce shrinkage, improve machinability, good resistance to adhesive wear and galling, good damping characteristics)
Resistance welding
Heat and pressure are combined to induced coalescence
Welding
Heat melt base metal, filler has compatible chemistry to base metal
Treatments operate continuously on a work piece
Heat treating, curving, galvanizing, plating, finishing, chemical cleaning and painting.
Phase transformations
Heated to form a single phase at an elevated temperature and subsequently transform to one or more low temperature phases upon cooling ( austenite →martensite)
Runners
Horizontal channels
If mold provides constraint during contraction time, tensile force can be generated within hot, weak casting, and cracking can occur. This is commonly called...
Hot tears
Grain growth
If a metal is held above its recrystallization temperature for a while, the grains will increase in size. Mechanical properties decrease as grain size increases. Temperatures should be controlled during processing so that the grain growth and therefore property changes are retarded.
Brittleness
If material fails with little or no ductility (concrete, chalk).
Fracture of Metals
If the material undergoes too much plastic deformation, a ____________ will occur. In a ductile fracture, plastic deformation occurs before the material breaks. In a brittle fracture, the break occurs before plastic deformation.
Proportional limit
Initial response is linear ( up to elasticity limit stress and strain are proportional)
Sustaining Technology
Innovations bring more value to the consumer. Improvements in materials, processes, and design.
Allowance
Intentional, desired difference between two mating parts
Tube drawing
Internal mandrels are used to control inside diameter of tubes (12 -250 mm in diameter)
Flanging
Involves a rolling operation on sheet metal in a similar manner as seams
Sizing
Involves squeezing all or select regions of products to achieve a thickness or enhance dimensional precision
Malleable cast iron
Irregularly shaped cluster of graphite -improved ductility compared to grey cast iron
Penetration
Is a defect when metal is too runny, it may flow into small voids in a sand mold. The final casting then contains small particles of embedded sand
True stress(S=F/Ao)
Is calculated in respect to actual area as it changes during the deformation process. These stresses do not differ significantly for small deformations.
True stress
Is defined by dividing the force by the cross sectional area. S=F/A
Filler metal
Is extra metal added between the two parts being welded.
Fatigue Failure
Is sensitive to sharp corners, surface cracks, gouges, etc. Fatigue life can be affected by changes in the environment (corrosion). Residual stresses can negatively impact fatigue life. Crack growth continues with each successive application of the load until failure
Milling
Is the basic process of progressive chip removal to produce a surface.
Stress
Is the force or the load being transmitted through the material's cross sectional area.
Straightening, Flattening, or Leveling
Is the opposite of bending, and the process is done before subsequent forming to ensure the use of flat or straight material
Recrystallization
Is the process of reducing the internal energy through new crystal formation. Metals that are plastically deformed below their ____________ temperature undergo cold working. The metals may then be _______________ so that further cold working may be done before fracture. Metals that are plastically deformed above their _____________ temperature are said to be hot worked. ____________ grains are constantly forming so that material will not be strain hardened.
Green strength
Is used to describe the strength of the pressed powder after compacting
Peritectic
L + S1 --> S2
Eutectic
L -> S1 + S2
monotectic
L1 --> L2 + S1
Syntectic
L1+L2->S1
Slitting
Lengthwise shearing process that is used to cut coils of sheet metal into several rolls of narrower width
Strain Hardening
Loading and unloading within the elastic region will result in cycling up and down the linear portion of the stress strain curve. When metals are plastically deformed, they become harder and stronger (strain hardening).
Hexagonal close-packed (HCP)
Low ductility and classified as brittle
Microalloyed steels
Low- and medium- carbon steels with small amounts (0.05-0.15%) of alloying elements (Nb, V, Ti, Mo, Zr, B, rare earth) - these additions form alloy carbides , nitrides or carbonitrides, whose primary is to provide grain refinement and/or precipitation strengthening These steels offer maximum strength with minimum carbon Preserves weldability, machinability, and formability
Spot facing
Machine minimum depth and diameter around hole to ensure full seating of a bolt head. Used on rough stock surfaces where corrosion or fatigue requirements require full
Tube bending
Material being bent is a tube or pipe
Molding material
Material that is packed around the pattern to provide the mold cavity Flask- rigid frame that holds the molding aggregate
Categories of operations
Materials handling and transport, processing, Packaging, inspecting and testing, storing.
Body-centered cubic (BCC)
Materials have high strength and moderate ductility
Limits Tolerance
Maximum and minimum dimensions
Flow rate
Measures the ease with which powder can be fed and distributed into a die
Shearing
Mechanical cutting of material without the formation of chips or the use of burning or melting
Assembly operations
Mechanical fastening, Soldering & brazing, Welding Press, shrink, or snap fittings, Adhesive bonding.
Joining Processes
Mechanical fastening, Soldering and brazing, Welding, Press, shrink, or snap fittings, Adhesive bonding, Assembly processes.
Elastic deformation
Mechanical properties are dependent on Type of lattice, Interatomic forces, Spacing between adjacent planes, Density of atoms on various planes. Poisson's ratio is the ratio of lateral contraction to axial tensile strain. Always less than 0.5; typically 0.3. Relatively low loads. Stretching or compressing of interatomic distance. Upon removal of load atoms resume original positions. Ratio of lateral contraction to axial tensile strain is Poisson's ratio.
Dross or slag
Metal oxides that occur from chemical reactions between molten metal and its surroundings
Grain size refinement
Metals with smaller grains tend to be stronger
Transformation induced plasticity (TRIP) steels
Microstructure of Ferrite , hard martensite or bainite and at least 5 vol% of retained austenite
permanent mold casting
Mold cavities are machined into mating metal die blocks, which are then preheated and clamped together. Molten metal is then poured into the mold and enters the cavity by gravity flow. After solidification, the mold is opened and the casting is removed
Tilt-Pour Permanent-Mold Casting
Mold is rotated to allow the molten metal to flow through the gating system and into the mold cavity with reduced free-fall and far less turbulence
atomic bonding
Molecule, crystal, amorphous aggregate
Strain Hardening or Work Hardening
Most metals become stronger when they are plastically deformed.
Transfer dies
Move individual parts from operation to operation within a single press
Mechanical press
Moving toward larger equipment.
Gating system
Network of channels that delivers the molten metal to the mold
Brazing and soldering
No melt of base metal, filler has different chemistry from base metal)
Types of stress
Normal (tension or compression), shear, hydrostatic pressure. By definition stress is force divided by cross-sectional area transmitting the load: S=F(force)/A(cross sectional area) N/m2, MPa, lb/ in2
NC is
Numeric Control
Growth
Occurs when heat of fusion is extracted from the liquid and the nucleated solid increases in size
Nucleation
Occurs when stable particles of solid form from within the molten liquid (undercooling) inoculation or grain refinement is the process of introducing solid particles into liquid before pouring into mold, to promote nucleation and uniform, fine-grained formation
Impregnation
Oil or other liquid is forced into the porous network to offer lubrication over an extended product lifetime
Material selection
Optimal combination of properties ( strength, ductility, hardness, etc.).Selected material meets processing requirements. Selected material meets operational requirement. Lower range price of selected material.
Deoxidation
Oxygen reacts with deoxidizers and produce solid metal oxide that are removed from the molten metal or become dispersed throughout the structure
Screw dislocation:
Parallel tearing of crystal plane. Barriers to dislocation motion: interstitials, substitutions, grain boundaries or free surface.
Brazing
Permanent joining of similar or dissimilar metals or ceramics (or composites) through the use of heat and a filler metal with melting temperature above 450o C but below the melting temperature of the materials to be joined.
Plastic deformation
Permanent shift of atom positions. Takes place along planes having the highest atom densities. Results in a permanent change in shape in the material that does not deteriorate its properties. occurs by the sliding of maximum-density planes in directions of closest packing.
Staking
Permanently joins parts together when a segment of one part protrudes through a hole in the other
Riveting
Permanently joins sheets or plates of material by forming an expanded head on the shank end of a fastener
Perforating
Piercing a large number of closely spaced holes
Hydraulic Press
Piston movement
Cold working
Plastic deformation below the recrystallization temperature
Hot working
Plastic deformation of metals at a temperature above the recrystallization temperature
Hubbing
Plastically forms recessed cavities in a workpiece
Bilateral Tolerance
Plus or minus deviation from the nominal size
Material defects:
Pores, Cracks, Inclusions.
Pouring cup
Portion of the gating system that controls the delivery of the metal
δ, δ-ferrite (BCC):
Present only at extremely elevated temperature (1394 - 1538°C)
Embossing
Press-working process in which raised lettering or other designs are impressed in sheet material
Low-Pressure Permanent-Mold Casting
Pressure difference induces upward flow
Ironing
Process that thins the walls of a drawn cylinder by passing it between a punch and a die where the gap is less than the incoming wall thickness
Forging
Processes that induce plastic deformation through localized compressive forces applied through dies
Low rate of heat input
Produce high total heat content, slow cooling rates, a large heat affected zone and resultant structures with low strength and hardness but high ductility.
High rate of heat input
Produce low total heat content, fast cooling rates, a small heat affected zone
Proof testing
Product is subjected to a load or pressure of some known and determined magnitude to simulate product life
Nondestructive testing
Products are examined in a way that it can still be used
Knuckle-joint drives
Provide a very high mechanical advantage along with fast action - Coining, sizing, Guerin forming
Austempering
Rapidly quench into liquid medium 15°C above Martensite start (Ms) temperature and held for sufficient time; austenite → bainite
Martempering
Rapidly quench into liquid medium 15°C above Martensite start (Ms) temperature and slow cool in air through martensite transformation; austenite → martensite
Microstructure Specification
Rate of nucleation & rate of solidification. Mech./Phys. properties depend on grain structure
Manufacturing process
Raw material/components are subjected to Manufacturing process (involving machinery, tooling, power, labor and cost) providing con. Transformed materials have higher value. raw materials are transformed into finished goods and/or components.
Negative ion
Received electrons and becomes negatively charged
Face-centered cubic (FCC)
Relatively weak materials and have excellent ductility.
Material removal processes
Remove selected segment from an initially oversized piece. i.e. machining
Molecular structure
Takes place when distinct number of atoms are held by primary bonds (molecules are free to move around) low melting and boiling point, eg. O2, H2O, and C2H4.
Temperature Effects
Temperatures effect the mechanical properties of materials. Ductile-brittle transition temperature is the temperature at which the response of the material goes from high energy absorption to low energy absorption. Creep is failure of a material due to long term exposure to elevated temperature.
Material Removal:
The best way to create flat surfaces, sharp corners, external and internal profiles and process brittle and surface properties altered materials. High accuracy and high quality surface finish process. In most cases economically superior to concurrent processes.
Allotropic transformation
The change from one to another lattice
Dependent variables are
The consequences of the independent variable selection (indirect control) Force or power requirements Material properties of the product Exit or final temperature Surface finish and precision Nature of the material flow
Coherency - a coherent precipitate
The crystallographic planes of the parent structure are continuous through the precipitate cluster, and the solute aggregate tends to distort the lattice to a substantial surrounding region
Deep drawing
The depth of product is greater than its diameter
Shallow drawing
The depth of product is less than its diameter
Machinability
The ease with which a metal can be machined to an acceptable surface finish. Require little power to cut, can be cut quickly, easily obtain a good finish, and do not wear the tooling much. Such materials are said to be free machining. ________ can be based on the measure of how long a tool lasts. Higher specific energies equal lower _____________. The surface finish is sometimes used to measure the machinability of a material. Soft, ductile materials tend to form a built up edge.
Compressibility
The effectiveness of applied pressure
Parting line
The interface which separates the cope and drag halves of the mold, flask, pattern, or core.
Engineering stress
The load divided by original cross-section area and elongation divided by original gage length to eliminate size effect. S= F/Ao
Blanking
The piece being punched out becomes the workpiece
Warm compaction
The powders are preheated prior to pressing, the metal is softened and responds better to applied pressure
Sintering
The pressed-powder compacts are heated in a controlled atmosphere to right below the melting point and temperature is high enough to permit solid-state diffusion and are held for sufficient time to permit bonding of the particles
Powder metallurgy (P/M) is
The process by which fine powdered materials are blended, pressed into a desired shape (compacted), and then heated (sintered) to bond surfaces
Continuous Casting
Used for the solidification of basic shapes for feedstock for deformation processes such as rolling and forging
Selective Laser Sintering
The process: - Spread heat fusable powder across the build chamber - A laser then scans over the surface, heating, and fusing those areas, joining particles, and the layer below • • - The elevator lowers, and the process repeats - Unfused powder acts as the support
Piercing
The punchout is the scrap and the remaining strip is the workpiece
Wire drawing
The same process as bar drawing except that it involves smaller-diameter material.
Partial Solid Solubility and Insolubility
The saturation point is the solubility limit of the two materials at a given temperature. If the temperature is decreased, the amount of solute that can be held in solution decreases. Two materials are insoluble if they can not be held in solution. In two phase region a tie-line should be constructed. The amount of each phase present: lever-law calculation using a tie-line.
Structure
The specific arrangement of electrons affect electrical, magnetic, thermal and optical properties. Electron configuration affects bonding of one atom to another. Atomic bonding produces a higher level of structure of a molecule, crystal, or amorphous aggregate. Imperfections affect mechanical properties. Size, shape, and arrangement of crystals produces a higher level of structure, microstructure.
Peripheral milling
The surface is generated by teeth located on the periphery of the cutter body. The surface is parallel with the axis of rotation of the cutter.
Draw Bending
The workpiece is clamped against a bending form and the entire assembly is rotated to draw the workpiece along a stationary pressure tool
Causes of dimensional changes during heat treatment
Thermal expansion during heating and thermal contraction during cooling - Uniform temperature changes - free of residual stresses; nonuniform temperature changes - residue stresses o Volume expansion and contraction (phase transformation): austenite transforms to martensite with a volume expansion of up to 4%
Piercing
Thick-walled seamless tubing can be made by rotary piercing
Roll extrusion
Thin walled cylinders are produced from thicker-wall cylinders
Cope
Top half of the pattern, flask, mold or core
I
Two metals completely soluble in each other.
II
Two metals soluble in liquid state and insoluble in solid state.
III
Two metals soluble in liquid state and partially soluble in solid state.
Progressive die sets
Two or more sets of punches and dies mounted in tandem
Tolerance
Undesirable but permissible deviation from a desired dimensions
Hot drawing operations
Used for forming relatively thick-walled parts of simple geometries, and material thickness may change significantly during the operation
Indexable drills
Used for high speed shallow holes in solid stock
Micro drills (pivot drills)
Used for holes 0.02 to 0.0001 inch diameter where grain boundaries and inclusion produce non- uniform material properties
Subland drills
Used for multi diameter holes
Manually operated press (foot-operated or kick press)
Used for very light work i.e. shearing small sheets and thin material
Toggle mechanisms
Used in drawing presses to actuate blank holder
Roughing
Used to remove large amounts of material using large depth of cuts and slow speeds. Requires less time to remove material, though dimensional accuracy and surface finish quality are lost.
Steel-rule die metal or other soft material
Used when the cut periphery is composed of simple lines and the material being cut is either soft
Finishing
Uses light passes with speeds as fine as necessary to produce the desired finish. One to two passes are usually required to produce a smooth finish.
Press Bending
Utilized a downward descending bend die, which pushes into the center of material that is supported on either side by wing die
Vacuum Permanent-Mold Casting
Vacuum is drawn on die assembly and atmospheric pressure in the chamber forces the metal upward
Sprue
Vertical portion of the gating system
Knoop Microhardness
Very small diamond penetrator exposed to loads between 25 and 3600g. Developed for very precise area hardness evaluation. Very thin samples can be tested.
Oxyfuel-Gas Welding
Welding process that uses flame produced by the combustion of a fuel gas and oxygen as the heat source
Primary processes reduce
a cast material into slabs, plates, and billets
Penetration is
a defect which occurs when the sand grains become embedded in the surface of the casting
An equilibrium phase diagram is
a diagram that shows the natural tendencies of a material or material system. Pressure, temperature, and composition are important. Transitions are encountered when a material changes phase. Sublimation occurs when a material goes from solid to a gas.
Manufacturing processes are strung together to create
a manufacturing system (M.S. formed by integration of manufacturing processes)
Composite material is
a nonuniform solid consisting of two or more different materials that are mechanically or metallurgically bonded together. Each of the constituent materials maintains its identity
Investment casting
a refractory slurry is formed around a wax or plastic pattern and allowed to harden. The pattern is then melted out and the mold is baked. Molten meal is poured into the mold and solidified. The mod is then broken away from the casting
Plasticity is the
ability of a material to flow as a solid without deterioration of properties
Damping capacity
ability of the material to absorb mechanical vibrations (impact energy) or damp them out quickly.
Steel is manufactured by
an oxidation process that decreases the amount of carbon, silicon, manganese, phosphorous, and sulfur in pig iron or steel scrap o Kelly-Bessemer process o Open-hearth process
Lathe Chucks
are adjustable mechanical vises that hold the work piece and transfer rotation motion from the drive motor to the work piece • come in two basic types - Three-jaw self-centering chucks - Four-jaw independent chucks
Furnace
are generally classified by heat source (electricity and combustible fuel) and style (batch or continuous)
Face plates
are used to mount irregular work pieces that can not be gripped with a chuck
Solidification shrinkage
as the liquid turns into solid
Solid metal contraction
as the solidified metal cools to room temperature
atom is a
basic unit of an element that can undergo chemical change
Water is an effective quenching medium
because of its high heat of vaporization and relatively high boiling point
Deforming processes
can be classified as primary or secondary processes
Hardness testing
can provide a close approximation of tensile strength (~500 times the Brinell hardness number for psi).
Amorphous structure
certain degree of local order, eg. glass, chalk. In an ______________ such as glass atoms have some degree of local order (with respect to neighbors), but as an aggregate the structure lacks orderly arrangement of atoms such as crystal structure.
Thermomechanical processing
combines the deformation and thermal processing into a single process which produces the desired shape and properties
Compacted graphite cast iron:
compacted graphite is intermediate to flake graphite of gray cast iron and nodular graphite of ductile iron
Nonmetallic
concrete, brick, wood, glass, rubber, plastics, composites, etc. (weaker, less ductile, less dense)
Bottoming dies
contact and compress the full area within the tooling
Normalizing
cooling in air o Cooling will be different in different locations o Properties will vary between the surface and interior o Hypoeutectoid steels, cooling results in excess ferrite and fine pearlite o Hypereutectoid steels, cooling results in excess cementite and fine pearlite
Annealing
cooling in furnace o Cost effective and time consuming o The furnace imposes cooling conditions at all locations o Result in identical structures and properties o Hypoeutectoid steels, cooling results in excess ferrite and coarse pearlite o Hypereutectoid steels, cooling results in excess cementite in dispersed spheroidal form and coarse pearlite
Complex internal cavities can be produced with
cores
Upset
decrease its length and increase its cross section
Young's modulus (modulus of elasticity) E
defined as ratio of stress and strain in this region
Physical properties are very important in material selection
density (weight), melting point, optical properties (color, transparency, opaqueness), thermal properties (specific heat, coefficient of thermal expansion, thermal conductivity), electrical conductivity and magnetic properties.
Physical properties are very important in material selection:
density (weight), melting point, optical properties (color, transparency, opaqueness, thermal properties (specific heat, coefficient of thermal expansion, thermal conductivity, electrical conductivity and magnetic properties)
Deformation processes have been designed to
exploit the plasticity of engineering materials
The linked cell shop:
fluently connected manufacturing cells by special information control
Deformation processes
forging, extrusion, rolling, bending etc.
Positive ion
gives away electrons and becomes positively charged
Laminar composite
has distinct layers of materials bonded together (thin coating, thick protective surfaces, cladding, bimetallic, laminates, sandwiches, etc) The properties of ___________ composites are always anisotropic
Water based polymer quenchants (synthetic quenchants)
have properties between oil and water and brine
Properties of Ceramics
high hardness, high compressive strength, and chemical inertness. Also low ductility and low tensile strength. The absence of free electrons is responsible for making ________ poor conductors of electricity and heat.
Secondary bonds
hold groups of polymer chains together to form the polymeric material
Covalent bonds
hold the atoms in the polymer molecules together. .
lathe center
hold the end of the work piece, providing support to preventing the work piece from deflecting during machining • can be mounted in the spindle hole, or in the tailstock quill • fall into two categories - Dead Center: solid steel tip that work piece spins against - Live Center: centers contact point is mounted on bearings and allowed to spin with work piece
Independent die set
holder and shoe are permanently aligned and guided by two or more guide pins
Filing
in that chips are removed by cutting teeth that are arranged in succession along the same plane on the surface of a tool called a file
Drawn out
increase its length and decrease its cross section
Strain hardening
increases strength by plastic deformation
Van der Waals force:
intermolecular force (weak force) of attraction between molecules caused by the electrons in the bonds between two atoms being attracted to the positive nucleus of another atom (e.g. layers of C-atoms in graphite held together).
Solid solution
interstitial, substitutional
Sheet-forming operations
involve the deformation of materials whose thickness and cross section remain relatively constant
Metallic (pure)
iron, copper, aluminum, magnesium, nickel, titanium, lead, tin, etc; or alloys: steel, bronze, brass, etc. {High strength, luster, good E/T conductivity, luster, high deformability without fracture, high density}.
Ceramics
is "an inorganic, nonmetallic solid that is prepared from powdered materials and is fabricated into products through the application of heat. The two most common chemical bonds for this material are covalent and ionic.
Seaming
is a bending operation that can be used to join the ends of sheet metal in some form of mechanical interlock; Common products include cans, pails, drums, and containers
Soldering
is a brazing-type operation where filler metal has a melting temperature below 450°C
Sheet Hydroforming
is a family of processes in which a rubber bladder backed by fluid pressure replaces either the solid punch or female die set
Phase
is a form of material having characteristic structure and properties. • More precisely: form of material with identifiable composition (chemistry), definable structure, and distinctive boundaries (interfaces) which separate it from other phases. phases can be continuous(air in the room) or discontinuous(salt grains in the shaker).
Cold heading
is a form of upset forging
Job and Station:
is a group of related operations generally done at one station(station is the area or location where production is done)
Heat treatment
is a process of controlled heating and cooling of materials for the purpose of altering their structures and properties, which changes in physical and mechanical properties can be introduced with no change in product shape.
Boring
is a variant of turning were the machining results in an internal cylindrical or conical surface.
polymers
is composed of many simple molecules that are repeating structural units called monomers.
A transfer press
is designed to accept a number of die sets, positioned side-by-side to create a multiple station (progressive die-type) operation.
Recrystallization anneal
is induced after a material has been cold worked to reduce strain hardening effects -Induces a change in size, shape, and distribution (phases are the same)
Plastic
is large molecules that are built up by the joining of smaller molecules
Manufacturing
is the ability to make goods and services to satisfy societal needs.
Bending
is the plastic deformation of metals about a linear axis with little or no change in the surface area
Sawing
is the process by which successive teeth, arranged in a narrow line, remove a small amount of material.
Turning
is the process of machining external cylindrical and conical surfaces
Materials processing
is the science and technology that converts a material into a product of a desired shape in the desired quantity
Broaching
is where a tool, with successively increasing tooth size, is moved through the workpeice, creating the desired shape with a single pass.
A solvus line on an equilibrium phase diagram shows a
limit to the materials solubility. If the two materials are completely soluble in one another, then the diagram is simple. The lowest temperature at which the material is 100% liquid is the liouidous line. The highest temperature at which the material is 100% solid is the solidus line. Between the two lines is a region where the liquid and solid solutions both exist.
Elastomer or elastic polymer -
linear polymer with large amount of elastic deformation when a force is applied The linear chain-type molecules are twisted or curled, like a coil spring - When forced is applied, the polymer stretches by uncoiling - When force is removed, the molecules recoil Cross-linking - process that links coil molecules to one another by strong covalent bonds - Small amount of cross-linking - soft and flexible elastomer ex. Rubber band - Large amount of cross-linking - harder, stiffer, brittle i.e. rubber used in bowling ball
Residue Stress
o are stresses that exist in a part independent of an applied stress o Undesirable residual stresses result in Cracking, Warping, Dimensional changes stress
Key effects on heat treatment
o carbon content : the larger carbon content, the higher strength, the higher hardness o alloy additions : related to the amounts and types of alloying elements; Primary reason to add an alloying element is to increase hardenability o various quenching condition
Precipitation hardening
o the most effective mechanism to strengthen nonferrous metals o a non-equilibrium heat treatment procedure o For precipitation hardening, Alloys must exhibit solubility that decreases with decreasing temperature
Processing heat treatments are used
o to increase strength o to prepare the material for fabrication o to improve machining characteristics o to reduce forming forces o to restore ductility for further processing
After solidification is completed, the casting will contract further as it cools to room temperature, called
patternmaker's contraction
Porosity is the
percentage of void volume, which can occur during P/M process
Lancing
piercing operation that forms either a line cut or hole
Copolymers
polymers composed of two or more different types of monomers
Particulate processes
pressing and sintering of metal powder and ceramics
Squeezed in closed impression dies
produce multidirectional flow
Four-slide or multislide machines are used to
produce small, intricately-shaped products from continuously-fed wire or coil strip
The project shop
product built on the spot of use (bridge, etc)
Fracture toughness is a
quantitative way of expressing a material's resistance to brittle fracture when a crack is present. If a material has a large value of fracture toughness it will probably undergo ductile fracture. Brittle fracture is very characteristic of materials with a low fracture toughness value. All materials contains flaws or defects.
Induction furnace
rapid melting and ease of controlling pollution
Ultra-High-Speed Machining Centers are used to
rapidly produce dies and include exceptionally high spindle speeds and material removal rates and they utilize ceramic ball bearings to improve spindle stiffness and spindle speeds.
Slabs are a
rectangular solid with a width greater than twice the thickness - used to produce plates, sheets, or strips
Reaming
remove small amounts of material to ensure exact hole size and improve hole surface finish
Friction is
resistance to sliding along an interface
Mechanical properties describe
response of material to applied forces or loads. Determined by standard laboratory tests. Testing methodology is crucial.
Metallic bond
resulting from sharing of delocalized outer shell electrons (electron charge cloud) by an aggregate of metal atoms. It is non-directional bond (e.g. elemental sodium).
Castings with large, flat surfaces are prone to
sand expansion defects
Non-coherency (Overage)
second-phase particles have their own crystal structure and distinct interphase boundaries
Specialized tips are used to produce
self centering holes where hole position is critical. - Helical tips - Four-facet tips - Racon - Bickford - Center core, or slot drills
Secondary processes reduce
shapes into finished or semifinished products
Piercing and Blanking
shearing operations where a part is removed from sheet material by forcing a shaped punch through the sheet and into a shaped die
Brine (5-7% NaCl or CaCl2)is
similar to water as a quenchant medium because of its high heat of vaporization and relatively high boiling point
Oil is utilized if
slower quenching rates are desired: the rate of heat extraction into boiling oil is slower than in boiling water - give slow cooling rate, thereby reduce quench cracks
Ductile or nodular cast iron:
smooth spheroidal graphite (or nodulizer) - provide ductility
Crystalline structure
solid metals & most minerals. Atoms arranged in geometric array called lattice (unit block repeated in space called unit cell).
Vacuum arc remelting (VAR), Vacuum induction melting (VIM)
solidify metal electrode, then metal electrode is remelted, molten droplets pass through a vacuum
Electroslag remelting (ESR)
solidify metal electrode, then remelting is conducted under a blanket of molten flux, Nonmetallic impurities float and are collected in the flux
Blooms have a
square or rectangular cross section
The strengthening of metals through plastic deformation is called
strain hardening or work hardening. Strength is increased substantially by strain hardening. As many products are being manufactured, strain hardening is also occurring.
Material properties are direct result of
structure & processing
Solid-solution strengthening
substitutional solutions or interstitial solutions
Stress and strain can occur as
tensile, compressive or shear.
Independent variables are
the aspects of the processes that the engineer or operator has direct control Starting material - initial properties and characteristics Starting geometry of the workpiece - size and shape Tool or die geometry Lubrication - to reduce friction Starting temperature Speed of operation Amount of deformation
Precoated steel sheet
the coating is applied when steel is still in the form of a long, continuous strip to reduce the cost and time consuming in finishing process
Over-aging
the decrease in hardness and strength of precipitation or age hardened materials.
Ductility
the degree of material deformation without the failure (rubber, metals). Evaluated by percent elongation ( % E.L.) prior to necking area and percent reduction in area (% R.A.).
Air bend dies produce
the desired geometry by simple three-point bending
Strain is
the distortion or deformation of a material from a force or a load
Consumable electrode processes,
the electrode melts to supply the needed filler metal to fill the voids in the joint.
Abrasion
the force necessary to plow the peaks of a harder material through a soft one
Adhesion
the force necessary to rip apart microscopic weldments that form between the two materials
Welding is
the permanent joining of two material bodies by coalescence produced by temperature, pressure and metallurgical conditions; result in the materials to melt or diffuse at the joint
Rolling operations reduce
the thickness or change the cross section of a material through compressive forces
Planing
the workpiece is reciprocated and the tool is fed at right angles to the cutting motion.
Ausforming
thermomechanical processes in which deformation and heat treatment are intimately combined. Material is heated to form austenite and then quenched to a temperature between pearlite and bainite; then slowly cool to produce bainite or rapidly quench to martensite
Bulk deformation processes are
those processes where the thickness or cross sections are reduced
Dormant defects are
those whose size remains unchanged through the lifetime of the part.
Dynamic defects change
through the life of the part.
Mandrels may be used
to produce hollow shapes or shapes with multiple longitudinal cavities
Materials removal
turning, drilling, milling, grinding and new techniques.
Hole cutters
used for holes in sheet stock
Spade drills
used for holes over 1 inch
Lathes
used for turning, boring, drilling and facing
Cupolas furnace
used to produce grey, nodular, and white cast iron is a refractory-lined, vertical steel shell into which alternating layers of carbon, iron, limestone, and alloy additions are charged and melted under forced air
Billets are
usually smaller than a bloom and has a square or circular cross section further rolled into finished product - structural shapes or semifinished product - bar, rod, tube, pipe
Fusion welding
where heat is applied to create molten material at the joint, which fuses the parts upon solidification
Solid State welding
where pressure and heat are used to cause the diffusion at the joint, causing the parts to fuse together
Shaping
where the workpiece is fed at right angles to the cutting motion between successive strokes of the tool.
Toughness
work per unit volume to fracture a material. Total area under the stress-strain curve. The toughness is the product of yield strength and uniform elongation.
How does one write a cnc or nc code?
• Programmers must first establish a reference or zero point. • Next the part is programmed, defining each step necessary to produce the part. • Each step defines the x, y, and z location, plus the spindle speed, feed speed, and tool changes from the previous step. • Following coding, the code is verified, typically by computer simulation • Finally the code is fed into the machine, either by tape or computer interface
Fused Deposition Modeling
• This is what most people think about when they think "3D printing" such as Makerbot • Thermoplastic material is extruded through a print head • A spool of thermoplastic is fed into the print head, then heated to a semi-liquid state, then deposited, and then cooled to solidify • The build cycle is very simple, the equipment is compact and low cost • Desktop models are suitable for office use in concept modeling and prototyping
