MSE 2100: Chapter 11
Carbon concentrations in medium-carbon steel
0.25 - 0.60 wt%
Carbon concentration range of high-carbon steels
0.60 - 1.4 wt%
Graphite formation promoted by silicon concentrations above:
1 wt%
Three steps of heat treatment for medium-carbon alloys
1) Austenitizing 2) Quenching 3) Tempering
Three reasons for widespread use of ferrous alloys
1) Availability as a natural resource 2) Economical processing methods 3) Extremely versatile
Applications of HSLA steel (4)
1) Bridges 2) Towers 3) Support columns 4) Pressure vessels
Applications of low-carbon steel
1) Car body components 2) Structural beams
Components commonly added to med-carbon alloys in order to improve strength-ductility combinations
1) Chromium 2) Nickel 3) Molybdenum
Applications of high-carbon steels
1) Cutting tools 2) Tools 3) Dies 4) High-strength wire
Four advantages of low-carbon steel
1) Ductility 2) Toughness 3) Easy to work with 4) Cheapest to produce
The two types of alloys:
1) Ferrous 2) Nonferrous
Applications of high-strength stainless steels
1) Gas turbines 2) High-temp steam boilers 3) Heat-treating furnaces 4) Aircraft 5) Missiles 6) Nuclear power generating units
Three characteristics of high-carbon steel in comparison to low- and med-
1) Hardest 2) Strongest 3) Least ductile
Three stages of annealing
1) Heating 2) Hold at temperature 3) Cooling
Three limitations to ferrous alloys
1) High density 2) Low electrical conductivity 3) Vulnerable to corrosion
Advantages of HSLA
1) Higher strengths than plain low-carbon steel 2) More resistant to corrosion
Benefits of CGIs
1) Higher thermal conductivity 2) Better resistance to thermal shock 3) Lower oxidation at elevated temperatures
Three characteristics of aluminum alloys
1) Low density 2) High electrical and thermal conductivities 3) Corrosion resistance
Three classifications of SS
1) Martensitic 2) Ferritic 3) Austenitic
Corrosion resistance can be enhanced in SS with the addition of __ and __.
1) Nickel 2) Molybdenum
Internal residual stress develops in metals as a result of:
1) Plastic deformation 2) Nonuniform cooling 3) Phase transformation that is induced upon cooling
Applications of med-carbon steel
1) Railway wheels & tracks 2) Gears 3) Crankshafts 4) Structural components
Purposes of annealing
1) Relieve stresses 2) Increase softness, ductility, and toughness 3) Produce a specific microstructure
The two types of precipitation hardening
1) Solution heat treatment 2) Precipitation heat treatment
Applications of superalloys
1) Turbines 2) Nuclear reactors 3) Petrochemical equipment
Two downsides of low-carbon steel
1) Weak 2) Soft
Silicon content range in gray cast iron
1.0 - 3.0 wt%
Compacted graphite iron (CGI) range of silicon content
1.7 - 3.0 wt%
Combined concentrations of alloying elements (besides copper) in HSLA steel
10 wt%
Ductility range of ferritic ductile iron
10% - 20% EL
Minimum chromium concentration in stainless steel
11 wt%
Minimum carbon concentration of cast iron
2.14 wt%
Carbon content range in gray cast iron
2.5 - 4.0 wt%
Ductility of low-carbon steel
25% EL
Typical yield strength for low-carbon steel
275 MPa
Most cast iron has a carbon concentration range of:
3.0 - 4.5 wt%
Range of carbon content in CGI
3.1 - 4.0 wt%
Ferritic ductile irons have tensile strengths ranging from __ to __.
380 MPa, 480 MPa
Range of tensile strengths for low-carbon steel
415 - 550 MPa
Heat treated HSLA can have tensile strengths exceeding
480 MPa
Low-carbon steels concentration
<0.25 wt% carbon
Wrought alloys
Compliant to mechanical deformation
Steels
Fe-C alloys that may contain other alloying elements
Which type of alloy is most widely produced?
Ferrous
HSLA
High-strength, low alloy
Ferrous alloys
Iron is the primary component
Cast alloys
So brittle that forming or shaping is impractical
Properties maximized in spheroidized steels
Softness, ductility
Hardenability
ability of an alloy to be hardened by the formation of martensite as a result of a given heat treatment
Alloy steels
additional alloying elements (besides carbon and manganese) are added in specific amounts
Solution heat treatment
all solute atoms are dissolved to form a single phase solid solution
First two digits in steel classification number
alloy content
Normalizing
an annealing heat treatment intended to refine the grains
Most common copper alloy type
brasses
Last two digits in steel classification number
carbon concentration
The mechanical properties of steels are greatly affected by:
carbon concentration
Refractory metals
characterized by extremely high melting temperatures
Predominant alloying element in stainless steel
chromium
Process annealing negates the effects of __
cold working
Strengthening method for low-carbon steels
cold working
Mechanical strength of aluminum is enhanced through
cold working and alloying
Tendency to form graphite is dependent on __ and ___
composition, rate of cooling
Primary alloying element in bronze
copper
Stainless steel is highly resistant to:
corrosion
Disadvantage of cold working and alloying of alumninum
decreased corrosion resistance
Jominy end-quench test
determine hardenability
Heat-treated med-carbon steels sacrifice __ and __ for __
ductility, toughness, strength
Microstructure components for low-carbon steel
ferrite and pearlite
Cast iron is classified as a ____ alloy.
ferrous
CGI has a microstructure that is intermediate between:
gray iron and ductile iron
High-carbon steels are almost always used in a __ and __ condition.
hardened, tempered
Precipitation hardening
hardening by formation of precipitates
HSLA steel strengthening method
heat treatment
Annealing
heat treatment where a material is exposed to a high temperature and then slowly cooled
Temper designation
indicates mechanical and/or heat treatment to which the aluminum alloy has been subjected
Severity of quench
indicates rate of cooling
HSLA steel has a low/medium/high-carbon content
low
Full annealing is used in ___ steels that will be machined or experience plastic deformation
low- and medium-carbon
Three classification levels of steel based on carbon content:
low-, medium-, and high-
Carbon classification of steels is most commonly produced:
low-carbon
Cast iron has a higher/lower melting temperature than steel
lower
Material with lowest density of all structural metals
magnesium
White iron is used to produce:
malleable iron
Hardenability, simple def
qualitative measure of the rate at which hardness drops off with distance into the specimen as a result of diminished martensite content
Ductile (nodular) iron
result of adding magnesium and/or cerium to gray iron before casting
Which type of precipitation hardening involves a higher temperature?
solution
Jominy end-quency test procedure
specimen heated, then sprayed with water
Applications for which med-carbon is used require combination of high ___, ____, and ____.
strength, wear resistance, toughness
Metal that is immune to chemical attack under 150 deg C
tantalum
Microstructures of tempered medium-carbon alloys
tempered martensite
Medium-carbon alloys are most often used in the ___ condition
tempering
Specific strength
tensile strength - specific gravity ratio
SS is classified based on:
the primary phase constituent of the microstructure
Precipitation heat treatment involves both temperature and ___ as important factors
time
Austenitizing
transformation of an alloy to austenite
Metal with highest melting temp
tungsten
Alloying elements are added to high-carbon steels to result in:
very hard, wear-resistant carbide compounds
The primary disadvantage of ferrous alloys
vulnerable to corrosion
Microstructure of CGI resembles
worms
Primary alloying element in brasses
zinc
