Chapter 7

Sigma phase

Brittle compound that forms at elevated temperatures and coats grain boundaries, thereby producing a brittle crack path through the metal.

Alloy steel

Steels containing more than 1.65% manganese, 0.60% silicon, or 0.60% copper are usually designated as alloy steels. Also, a steel is considered to be an alloy steel if a definite or minimum amount of other alloying element is specified.

Continuous casting

produces the feedstock material for subsequent forging or rolling operations.

Hot work tool steel

provide strength and hardness during prolonged exposure to elevated temperature

Deoxidation

rejection of oxygen during process

High speed tool steel

the poorest toughness and machinability

Ferrous metals

containing iron

Advanced high strength steel (AHSS)

-primarily ferrite-phase, soft steels with varying amounts of martensite, bainite, and retained austenite, which offer high strength with enhanced ductility

Steel

A form of iron that is both durable and flexible. It was first mass-produced in the 1860s and quickly became the most widely used metal in construction, machinery, and railroad equipment.

Sensitization

A localized depletion of chromium can occur when elevated temperatures allow chromium carbides to form along grain boundaries

Hardenability

A measure of the depth to which full hardness can be obtained under a normal hardening cycle and is related primarily to the amounts and type of alloying elements.

White cast iron

A type of iron that has all of its excess carbon in the form of iron carbide and receives its name from the white surface that appears when the material is fractured. Features promoting its formation are those that favor cementite over graphite: a low carbon equivalent (1.8 to 3.6% carbon, 0.5 to 1.9% silicon, and 0.25 to 0.8% manganese) and rapid cooling.

Precipitation hardenable stainless steel

Alloys that are basically martensitic or austentitic types modified by the addition of alloying elements such as AL that permit the precipitation of hard intermetallic compounds at the low temperatures used to temper the martensite.

Stainless steel

An alloy containing a minimum of 12% chromium, sometimes with nickel, manganese, or molybdenum as additional alloying element.

High strength low alloy (HSLA) steel

Any of a group of low carbon steels containing less than 2% alloys in a chemical composition specifically developed for increased strength, ductility and resistance to corrosion.

High carbon steel

Contains a lot of carbon so is extremely strong, it is used for powerful cutting tools however will fracture, not bend.

Pig iron

Crude iron that is drawn from a blast furnace and cast into pigs

Nodular cast iron

Ductile cast iron is quite similar to gray cast iron in composition, stronger when the graphite is present in rounded spheres or nodules. this is the result of the addition of small amounts of manganese or rare earth elements like cerium.

Nodulizer

During graphite formation, if magnesium is added just prior to solidification, the graphite will form as smooth-surface spheres.

High alloy steel

Expensive alloy of iron mixed with relatively large proportions of other metals e.g. stainless steel which contains nickel and chromium.

Tool steel

High Carbon, high strength, ferrous alloys that have been modified by alloy additions to provide a desired balance of strength, toughness, and wear resistance.

Cast steel

If a ferrous casting alloy contains less than about 2.0% carbon, it is considered to be a cast steel

Soft magnetic materials

Magnetic material that is easy to magnetise and demagnetise

Medium carbon steel

Medium carbon steel contains between 0,3% and 0,8% carbon.

Microalloyed steel

Occupies a position between carbon steels and the alloy grades in terms of both cost and performance, and are being used increasingly as substitutes for heat-treated steels in the manufacture of small- to medium-sized discrete parts. In essence, these steels offer maximum strength with minimum carbon, while simultaneously preserving weldability, machinability, and formability.

Ladle metallurgy

Refers to a variety of processes designed to provide final purification and to fine tune both the chemistry and temperature of the melt.

AISI

SAE identification system- Both plain-carbon and low-alloy steels are identified by a four-digit number, where the first number indicates the major alloying elements and the second number designates a subgrouping within the major alloy system.

Cold work tool steel

The alloy additions and higher hardenability of the oil- or air-hardening grades (O and A designations, respectively) enable hardening by less severe quenches.

Ladles

The molten metal is poured from the steelmaking furnaces into containment vessels, known as

Vacuum induction melting (VIM)

The process when melting is done using induction heating. (In a vacuum)

Free machining steel

These steels machine readily and form small chips when cut. The smaller chips reduce the length of contact between the chip and cutting tool, thereby reducing the associated friction and heat,

Plain carbon steel

When Mn, P, S, and Si are present in steel in a normal quantity.

True stainless steels

When damaged, this tough, adherent, corrosion-resistant oxide (which is only 1-2 nanometers thick) actually heals itself, provided oxygen is present, even in very small amounts. Materials that form this superior protective oxide are known as the true stainless steels

Mottled zone

Where regions of white and gray cast iron occur in the same component, there is generally a transition region comprised of both white an

Ferritic stainless steel

With sufficient chromium and a low level of carbon, a corrosion-resistant iron alloy can be produced that is ferrite at all temperatures below solidification

Cast iron

a ferrous casting alloy containing more than 2% carbon

Gray cast iron

a type of cast iron the promotes the formation of graphite

Air hardenable tool steel

air-hardening grades enable hardening by less severe quenches.

Low alloy steel

an alloy of iron and carbon, with other elements added for increased strength.

Martensitic stainless steel

an alloy of stainless steel where carbon is added and the chromium content is reduced to a level where the material can be austenite at high temperature and ferrite at low.

Maraging steel

an alloy of steel that contains between 15% and 25% nickel plus significant amounts of cobalt, molybdenum, and titanium....in a low-carbon steel

Martensitic (Mart) steels

are almost entirely martensite and can have tensile strengths up to 1700 MPa (245 ksi)

Austenitic stainless steel

are easily identified by their nonmagnetic characteristic (the ferritic and martensitic stainlesses are attracted to a magnet). They are highly resistant to corrosion in almost all media (except hydrochloric acid and other halide acids and salts) and may be polished to a mirror finish,

Electroslag remelting (ESR)

can be used to produce extremely clean, gas-free metal. A solid electrode is again melted and recast using an electric current, but the entire remelting is conducted under a blanket of molten flux.

Compacted graphite cast iron (CGI)

characterized by a graphite structure that is intermediate to the flake graphite of gray iron and the nodular graphite of ductile iron, and it tends to possess some of the desirable properties and characteristics of each.

Duplex stainless steel

contain between 18 and 25% chromium, 4 to 7% nickel, and up to 4% molybdenum;

High chromium tool steel

contains between 10-18% chromium and are air hardening and offer outstanding deep hardening wear resistance

Degasification

decontamination of the molten weld metal

Austempered ductile iron (ADI)

ductile iron that has undergone a special austempering heat treatment to modify and enhance its properties,4 has emerged as a significant engineering material.

Inoculation

ferrosilicon is injected into the melt to promote the formation of graphite

Dual phase steels

form when we quench material from a temperature that is above the A1 but below the A3, where the structure consists of ferrite and high-carbon austenite.

Bake hardenable steel

has assumed a significant role in automotive sheet applications. These low-carbon steels are processed in such a way that they are resistant to aging during normal storage but begin to age during sheet metal forming. A subsequent expo- sure to heat during the paint-baking operation completes the aging process and adds an additional 35 to 70 MPa (5 to 10 ksi), raising the final yield strength to approximately 275 MPa (40 ksi).

Complex phase (CP) steels

have a microstructure of ferrite and a higher volume fraction of hard phases (marten- site and bainite), strengthened further by a fine precipitate of niobium, titanium, or vanadium carbides or nitrides.

Amorphous metals

he material has no crystal structure, grains, or grain boundaries, (1) the magnetic domains can move freely in response to magnetic fields, (2) the properties are the same in all directions, and (3) corrosion resistance is improved. The high magnetic strength and low hysteresis losses offer the possibility of smaller, lighter-weight magnets.

Constructional alloys

here the desired properties are typically developed by a separate thermal treatment and the specific alloy elements tend to be selected for their effect on hardenability

Water hardenable tool steel

high-carbon plain-carbon steels. They are the least expensive variety and are used for a wide range of parts that are usually quite small and not subject to severe usage or elevated temperature

Vacuum degassing

in which an ingot mold is placed in an evacuated chamber, and a stream of molten metal passes through a vacuum during pouring

Alloys

materials composed of two or more different elements, and they tend to exhibit their own characteristic properties.

Shock resisting tool steel

offer the high toughness needed for impact applications. Low carbon content (approximately 0.5% carbon) is usually specified to assure the necessary toughness, with carbide-forming alloys providing the necessary abrasion resistance, hardenability, and hot-work characteristics.

Transformation induced plasticity (TRIP) steels

steels containing a matrix of ferrite combined with hard martensite or bainite and at least 5 vol% or retained austenite.

High alloy cast iron

the austenitic gray cast irons, which contain about 14% nickel, 5% copper, and 2.5% chromium, offer good corrosion resistance to many acids and alkalis at temperatures up to about 800°C (1500°F).

Vacuum arc remelting (VAR)

when an electric arc is used to remove gas from steel. similar to consumable-electrode remelting

Consumable electrode remelting

where an already-solidified metal electrode replaces the ladle of molten metal. As the electrode is progressively remelted, molten droplets pass through a vacuum, and the extremely high surface area again provides an effective means of gas removal.

Malleable cast iron

white cast iron that is exposed to an extended heat treatment and has significantly improved ductility compared to gray cast iron