cast iron usually refers to grey iron

8/8/2019 Cast iron usually refers to grey iron

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Cast iron usually refers to grey iron, but also identifies a large group offerrousalloys,

which solidify with a eutectic. The colour of a fractured surface can be used to identify an

alloy. White cast iron is named after its white surface when fractured, due to itscarbideimpurities which allow cracks to pass straight through. Grey cast iron is named after its

grey fractured surface, which occurs because the graphitic flakes deflect a passing crack

and initiate countless new cracks as the material breaks.

Carbon (C) and silicon (Si) are the main alloying elements, with the amount ranging from2.1 to 4 wt% and 1 to 3 wt%, respectively. While this technically makes these base alloys

ternary Fe-C-Si alloys, the principle of cast iron solidification is understood from the

binary iron-carbon phase diagram. Since the compositions of most cast irons are aroundthe eutectic point of the iron-carbon system, the melting temperatures closely correlate,

usually ranging from 1,150 to 1,200 C (2,102 to 2,192 F), which is about 300 C

(572 F) lower than the melting point of pure iron.

Cast iron tends to bebrittle, except formalleable cast irons. With its relatively low

melting point, good fluidity, castability, excellent machinability, resistance todeformation and wear resistance, cast irons have become anengineering material with a

wide range of applications and are used in pipes, machines and automotive industry parts,such as cylinder heads (declining usage),cylinder blocksandgearboxcases (declining

usage). It is resistant to destruction and weakening by oxidisation (rust).

Contents

[hide]

1 Production

2 Typeso 2.1 Alloying elements

o 2.2 Grey cast iron

o 2.3 White cast iron

o 2.4 Malleable cast iron

o 2.5 Ductile cast iron

o 2.6 Table of comparative qualities of cast irons

3 Historical useso 3.1 Cast iron bridges

o 3.2 Buildings

o 3.3 Textile mills

4 See also

5 References

6 Further reading

7 External links

[edit] Production
http://en.wikipedia.org/wiki/Gray_ironhttp://en.wikipedia.org/wiki/Ferroushttp://en.wikipedia.org/wiki/Ferroushttp://en.wikipedia.org/wiki/Alloyhttp://en.wikipedia.org/wiki/Eutectichttp://en.wikipedia.org/wiki/Carbidehttp://en.wikipedia.org/wiki/Carbidehttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Siliconhttp://en.wikipedia.org/wiki/Binary_compoundhttp://en.wikipedia.org/wiki/Eutectic_pointhttp://en.wikipedia.org/wiki/Brittlehttp://en.wikipedia.org/wiki/Brittlehttp://en.wikipedia.org/wiki/Malleable_ironhttp://en.wikipedia.org/wiki/Malleable_ironhttp://en.wikipedia.org/wiki/Castabilityhttp://en.wikipedia.org/w/index.php?title=Engineering_material&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Engineering_material&action=edit&redlink=1http://en.wikipedia.org/wiki/Automotive_industryhttp://en.wikipedia.org/wiki/Cylinder_headhttp://en.wikipedia.org/wiki/Cylinder_blockhttp://en.wikipedia.org/wiki/Cylinder_blockhttp://en.wikipedia.org/wiki/Cylinder_blockhttp://en.wikipedia.org/wiki/Gearboxhttp://en.wikipedia.org/wiki/Gearboxhttp://en.wikipedia.org/wiki/Gearboxhttp://en.wikipedia.org/wiki/Cast_ironhttp://en.wikipedia.org/wiki/Cast_iron#Productionhttp://en.wikipedia.org/wiki/Cast_iron#Typeshttp://en.wikipedia.org/wiki/Cast_iron#Alloying_elementshttp://en.wikipedia.org/wiki/Cast_iron#Grey_cast_ironhttp://en.wikipedia.org/wiki/Cast_iron#White_cast_ironhttp://en.wikipedia.org/wiki/Cast_iron#Malleable_cast_ironhttp://en.wikipedia.org/wiki/Cast_iron#Ductile_cast_ironhttp://en.wikipedia.org/wiki/Cast_iron#Table_of_comparative_qualities_of_cast_ironshttp://en.wikipedia.org/wiki/Cast_iron#Historical_useshttp://en.wikipedia.org/wiki/Cast_iron#Cast_iron_bridgeshttp://en.wikipedia.org/wiki/Cast_iron#Buildingshttp://en.wikipedia.org/wiki/Cast_iron#Textile_millshttp://en.wikipedia.org/wiki/Cast_iron#See_alsohttp://en.wikipedia.org/wiki/Cast_iron#Referenceshttp://en.wikipedia.org/wiki/Cast_iron#Further_readinghttp://en.wikipedia.org/wiki/Cast_iron#External_linkshttp://en.wikipedia.org/w/index.php?title=Cast_iron&action=edit&section=1http://en.wikipedia.org/wiki/Gray_ironhttp://en.wikipedia.org/wiki/Ferroushttp://en.wikipedia.org/wiki/Alloyhttp://en.wikipedia.org/wiki/Eutectichttp://en.wikipedia.org/wiki/Carbidehttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Siliconhttp://en.wikipedia.org/wiki/Binary_compoundhttp://en.wikipedia.org/wiki/Eutectic_pointhttp://en.wikipedia.org/wiki/Brittlehttp://en.wikipedia.org/wiki/Malleable_ironhttp://en.wikipedia.org/wiki/Castabilityhttp://en.wikipedia.org/w/index.php?title=Engineering_material&action=edit&redlink=1http://en.wikipedia.org/wiki/Automotive_industryhttp://en.wikipedia.org/wiki/Cylinder_headhttp://en.wikipedia.org/wiki/Cylinder_blockhttp://en.wikipedia.org/wiki/Gearboxhttp://en.wikipedia.org/wiki/Cast_ironhttp://en.wikipedia.org/wiki/Cast_iron#Productionhttp://en.wikipedia.org/wiki/Cast_iron#Typeshttp://en.wikipedia.org/wiki/Cast_iron#Alloying_elementshttp://en.wikipedia.org/wiki/Cast_iron#Grey_cast_ironhttp://en.wikipedia.org/wiki/Cast_iron#White_cast_ironhttp://en.wikipedia.org/wiki/Cast_iron#Malleable_cast_ironhttp://en.wikipedia.org/wiki/Cast_iron#Ductile_cast_ironhttp://en.wikipedia.org/wiki/Cast_iron#Table_of_comparative_qualities_of_cast_ironshttp://en.wikipedia.org/wiki/Cast_iron#Historical_useshttp://en.wikipedia.org/wiki/Cast_iron#Cast_iron_bridgeshttp://en.wikipedia.org/wiki/Cast_iron#Buildingshttp://en.wikipedia.org/wiki/Cast_iron#Textile_millshttp://en.wikipedia.org/wiki/Cast_iron#See_alsohttp://en.wikipedia.org/wiki/Cast_iron#Referenceshttp://en.wikipedia.org/wiki/Cast_iron#Further_readinghttp://en.wikipedia.org/wiki/Cast_iron#External_linkshttp://en.wikipedia.org/w/index.php?title=Cast_iron&action=edit&section=1


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Cast iron is made by remeltingpig iron, often along with substantial quantities of scrap

iron and scrap steel and taking various steps to remove undesirable contaminants such as

phosphorus and sulphur. Depending on the application, carbon and silicon content arereduced to the desired levels, which may be anywhere from 2 to 3.5% and 1 to 3%

respectively. Other elements are then added to the melt before the final form is produced

by casting.[citation needed]

Iron is sometimes melted in a special type ofblast furnaceknown as a cupola, but moreoften melted in electric induction furnaces.[citation needed] After melting is complete, the

molten iron is poured into a holding furnace or ladle.

[edit] Types

Cast iron drain, waste and vent piping

[edit] Alloying elements

Cast iron's properties are changed by adding various alloying elements, oralloyants. Next

to carbon, silicon is the most important alloyant because it forces carbon out of solution.Instead the carbon forms graphitewhich results in a softer iron, reduces shrinkage, lowers

strength, and decreases density.Sulfur, when added, forms iron sulfide, which prevents

the formation of graphite and increaseshardness. The problem with sulfur is that it makesmolten cast iron sluggish, which causes short run defects. To counter the effects of sulfur,

manganeseis added because the two form intomanganese sulfide instead of iron sulfide.

The manganese sulfide is lighter than the melt so it tends to float out of the melt and into

the slag. The amount of manganese required to neutralize sulfur is 1.7sulfurcontent+0.3%. If more than this amount of manganese is added, thenmanganese carbide

forms, which increases hardness andchilling, except in grey iron, where up to 1% of

manganese increases strength and density.[1]

Nickel is one of the most common alloyants because it refines thepearlite and graphite

structure, improves toughness, and evens out hardness differences between section

thicknesses. Chromium is added in small amounts to the ladle to reduce free graphite,

produce chill, and because it is a powerfulcarbide stabilizer; nickel is often added inconjunction. A small amount oftin can be added as a substitute for 0.5% chromium.

Copperis added in the ladle or in the furnace, on the order of 0.5 to 2.5%, to decrease

chill, refine graphite, and increase fluidity.Molybdenumis added on the order of 0.3 to
http://en.wikipedia.org/wiki/Pig_ironhttp://en.wikipedia.org/wiki/Pig_ironhttp://en.wikipedia.org/wiki/Phosphorushttp://en.wikipedia.org/wiki/Sulphurhttp://en.wikipedia.org/wiki/Casting_(metalworking)http://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Blast_furnacehttp://en.wikipedia.org/wiki/Blast_furnacehttp://en.wikipedia.org/wiki/Blast_furnacehttp://en.wikipedia.org/wiki/Cupola_furnacehttp://en.wikipedia.org/wiki/Cupola_furnacehttp://en.wikipedia.org/wiki/Induction_furnacehttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/w/index.php?title=Cast_iron&action=edit&section=2http://en.wikipedia.org/w/index.php?title=Cast_iron&action=edit&section=3http://en.wikipedia.org/wiki/Alloyanthttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Siliconhttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Sulfurhttp://en.wikipedia.org/wiki/Sulfurhttp://en.wikipedia.org/wiki/Iron(II)_sulfidehttp://en.wikipedia.org/wiki/Iron(II)_sulfidehttp://en.wikipedia.org/wiki/Hardnesshttp://en.wikipedia.org/wiki/Hardnesshttp://en.wikipedia.org/wiki/Manganesehttp://en.wikipedia.org/wiki/Manganesehttp://en.wikipedia.org/wiki/Manganese_sulfidehttp://en.wikipedia.org/wiki/Manganese_sulfidehttp://en.wikipedia.org/wiki/Slaghttp://en.wikipedia.org/w/index.php?title=Manganese_carbide&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Manganese_carbide&action=edit&redlink=1http://en.wikipedia.org/wiki/Chill_(foundry)http://en.wikipedia.org/wiki/Chill_(foundry)http://en.wikipedia.org/wiki/Chill_(foundry)http://en.wikipedia.org/wiki/Cast_iron#cite_note-gillespie-0http://en.wikipedia.org/wiki/Nickelhttp://en.wikipedia.org/wiki/Pearlitehttp://en.wikipedia.org/wiki/Pearlitehttp://en.wikipedia.org/wiki/Chromiumhttp://en.wikipedia.org/wiki/Carbidehttp://en.wikipedia.org/wiki/Carbidehttp://en.wikipedia.org/wiki/Nickelhttp://en.wikipedia.org/wiki/Tinhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Molybdenumhttp://en.wikipedia.org/wiki/Molybdenumhttp://en.wikipedia.org/wiki/Molybdenumhttp://en.wikipedia.org/wiki/File:Cast_fe_and_cu_dwv_piping.jpghttp://en.wikipedia.org/wiki/File:Cast_fe_and_cu_dwv_piping.jpghttp://en.wikipedia.org/wiki/Pig_ironhttp://en.wikipedia.org/wiki/Phosphorushttp://en.wikipedia.org/wiki/Sulphurhttp://en.wikipedia.org/wiki/Casting_(metalworking)http://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/wiki/Blast_furnacehttp://en.wikipedia.org/wiki/Cupola_furnacehttp://en.wikipedia.org/wiki/Induction_furnacehttp://en.wikipedia.org/wiki/Wikipedia:Citation_neededhttp://en.wikipedia.org/w/index.php?title=Cast_iron&action=edit&section=2http://en.wikipedia.org/w/index.php?title=Cast_iron&action=edit&section=3http://en.wikipedia.org/wiki/Alloyanthttp://en.wikipedia.org/wiki/Carbonhttp://en.wikipedia.org/wiki/Siliconhttp://en.wikipedia.org/wiki/Graphitehttp://en.wikipedia.org/wiki/Sulfurhttp://en.wikipedia.org/wiki/Iron(II)_sulfidehttp://en.wikipedia.org/wiki/Hardnesshttp://en.wikipedia.org/wiki/Manganesehttp://en.wikipedia.org/wiki/Manganese_sulfidehttp://en.wikipedia.org/wiki/Slaghttp://en.wikipedia.org/w/index.php?title=Manganese_carbide&action=edit&redlink=1http://en.wikipedia.org/wiki/Chill_(foundry)http://en.wikipedia.org/wiki/Cast_iron#cite_note-gillespie-0http://en.wikipedia.org/wiki/Nickelhttp://en.wikipedia.org/wiki/Pearlitehttp://en.wikipedia.org/wiki/Chromiumhttp://en.wikipedia.org/wiki/Carbidehttp://en.wikipedia.org/wiki/Nickelhttp://en.wikipedia.org/wiki/Tinhttp://en.wikipedia.org/wiki/Copperhttp://en.wikipedia.org/wiki/Molybdenum


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1% to increase chill and refine the graphite and pearlite structure; it is often added in

conjunction with nickel, copper, and chromium to form high strength irons. Titaniumis

added as a degasser and deoxidizer, but it also increases fluidity. 0.15 to 0.5% vanadiumare added to cast iron to stabilize cementite, increase hardness, and increase resistance to

wearand heat. 0.1 to 0.3% zirconium helps to form graphite, deoxidize, and increase

fluidity.[1]

In malleable iron melts,bismuth is added, on the scale of 0.002 to 0.01%, to increase howmuch silicon can be added. In white iron,boronis added to aid in the production of

malleable iron; it also reduces the coarsening effect of bismuth.[1]

[edit] Grey cast iron

Main article: Grey iron

Grey cast iron is characterized by its graphitic microstructure, which causes fractures of

the material to have a grey appearance. It is the most commonly used cast iron and themost widely use cast material based on weight. Most cast irons have a chemical

composition of 2.5 to 4.0% carbon, 1 to 3% silicon, and the remainder is iron. Grey cast

iron has less tensile strengthand shock resistance than steel, however its compressivestrength is comparable to low and medium carbon steel.

[edit] White cast iron

With a lower silicon content and faster cooling, the carbon in white cast iron precipitatesout of the melt as the metastablephasecementite, Fe3C, rather than graphite. The

cementite which precipitates from the melt forms as relatively large particles, usually in a

eutectic mixture, where the other phase isaustenite(which on cooling might transform tomartensite). These eutectic carbides are much too large to provide precipitation hardening

(as in some steels, where cementite precipitates might inhibitplastic deformation by

impeding the movement ofdislocations through the ferrite matrix). Rather, they increasethe bulk hardness of the cast iron simply by virtue of their own very high hardness and

their substantial volume fraction, such that the bulk hardness can be approximated by a

rule of mixtures. In any case, they offerhardness at the expense oftoughness. Since

carbide makes up a large fraction of the material, white cast iron could reasonably beclassified as a cermet. White iron is too brittle for use in many structural components, but

with good hardness and abrasion resistance and relatively low cost, it finds use in such

applications as the wear surfaces (impellerandvolute) ofslurry pumps, shell liners and

lifter barsinball mills and autogenous grinding mills, balls and rings incoal pulverisers,and the teeth of abackhoe's digging bucket (although cast medium-carbon martensitic

steel is more common for this application).

It is difficult to cool thick castings fast enough to solidify the melt as white cast iron allthe way through. However, rapid cooling can be used to solidify a shell of white cast

iron, after which the remainder cools more slowly to form a core of grey cast iron. The
http://en.wikipedia.org/wiki/Titaniumhttp://en.wikipedia.org/wiki/Titaniumhttp://en.wikipedia.org/wiki/Vanadiumhttp://en.wikipedia.org/wiki/Wearhttp://en.wikipedia.org/wiki/Wearhttp://en.wikipedia.org/wiki/Zirconiumhttp://en.wikipedia.org/wiki/Cast_iron#cite_note-gillespie-0http://en.wikipedia.org/wiki/Bismuthhttp://en.wikipedia.org/wiki/Boronhttp://en.wikipedia.org/wiki/Boronhttp://en.wikipedia.org/wiki/Cast_iron#cite_note-gillespie-0http://en.wikipedia.org/wiki/Cast_iron#cite_note-gillespie-0http://en.wikipedia.org/w/index.php?title=Cast_iron&action=edit&section=4http://en.wikipedia.org/wiki/Grey_ironhttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Shock_resistancehttp://en.wikipedia.org/wiki/Compressive_strengthhttp://en.wikipedia.org/wiki/Compressive_strengthhttp://en.wikipedia.org/w/index.php?title=Cast_iron&action=edit&section=5http://en.wikipedia.org/wiki/Metastablehttp://en.wikipedia.org/wiki/Metastablehttp://en.wikipedia.org/wiki/Cementitehttp://en.wikipedia.org/wiki/Cementitehttp://en.wikipedia.org/wiki/Cementitehttp://en.wikipedia.org/wiki/Austenitehttp://en.wikipedia.org/wiki/Austenitehttp://en.wikipedia.org/wiki/Austenitehttp://en.wikipedia.org/wiki/Martensitehttp://en.wikipedia.org/wiki/Plastic_deformationhttp://en.wikipedia.org/wiki/Dislocationhttp://en.wikipedia.org/wiki/Hardnesshttp://en.wikipedia.org/wiki/Hardnesshttp://en.wikipedia.org/wiki/Toughnesshttp://en.wikipedia.org/wiki/Toughnesshttp://en.wikipedia.org/wiki/Cermethttp://en.wikipedia.org/wiki/Cermethttp://en.wikipedia.org/wiki/Impellerhttp://en.wikipedia.org/wiki/Impellerhttp://en.wikipedia.org/wiki/Volute_(disambiguation)http://en.wikipedia.org/wiki/Volute_(disambiguation)http://en.wikipedia.org/w/index.php?title=Slurry_pump&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Slurry_pump&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Lifter_bar&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Lifter_bar&action=edit&redlink=1http://en.wikipedia.org/wiki/Ball_millhttp://en.wikipedia.org/w/index.php?title=Autogenous_grinding_mill&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Autogenous_grinding_mill&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Coal_pulveriser&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Coal_pulveriser&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Coal_pulveriser&action=edit&redlink=1http://en.wikipedia.org/wiki/Backhoehttp://en.wikipedia.org/wiki/Backhoehttp://en.wikipedia.org/wiki/Titaniumhttp://en.wikipedia.org/wiki/Vanadiumhttp://en.wikipedia.org/wiki/Wearhttp://en.wikipedia.org/wiki/Zirconiumhttp://en.wikipedia.org/wiki/Cast_iron#cite_note-gillespie-0http://en.wikipedia.org/wiki/Bismuthhttp://en.wikipedia.org/wiki/Boronhttp://en.wikipedia.org/wiki/Cast_iron#cite_note-gillespie-0http://en.wikipedia.org/w/index.php?title=Cast_iron&action=edit&section=4http://en.wikipedia.org/wiki/Grey_ironhttp://en.wikipedia.org/wiki/Tensile_strengthhttp://en.wikipedia.org/wiki/Shock_resistancehttp://en.wikipedia.org/wiki/Compressive_strengthhttp://en.wikipedia.org/wiki/Compressive_strengthhttp://en.wikipedia.org/w/index.php?title=Cast_iron&action=edit&section=5http://en.wikipedia.org/wiki/Metastablehttp://en.wikipedia.org/wiki/Cementitehttp://en.wikipedia.org/wiki/Austenitehttp://en.wikipedia.org/wiki/Martensitehttp://en.wikipedia.org/wiki/Plastic_deformationhttp://en.wikipedia.org/wiki/Dislocationhttp://en.wikipedia.org/wiki/Hardnesshttp://en.wikipedia.org/wiki/Toughnesshttp://en.wikipedia.org/wiki/Cermethttp://en.wikipedia.org/wiki/Impellerhttp://en.wikipedia.org/wiki/Volute_(disambiguation)http://en.wikipedia.org/w/index.php?title=Slurry_pump&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Lifter_bar&action=edit&redlink=1http://en.wikipedia.org/wiki/Ball_millhttp://en.wikipedia.org/w/index.php?title=Autogenous_grinding_mill&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Coal_pulveriser&action=edit&redlink=1http://en.wikipedia.org/wiki/Backhoe


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resulting casting, called a chilled casting, has the benefits of a hard surface and a

somewhat tougher interior.

High-chromium white iron alloys allow massive castings (for example, a 10-tonneimpeller) to be sand cast, i.e., a high cooling rate is not required, as well as providing

impressive abrasion resistance.[citation needed]

[edit] Malleable cast iron

Main article: Malleable iron

Malleable iron starts as a white iron casting that is then heat treated at about 900 C

(1,650 F). Graphite separates out much more slowly in this case, so that surface tensionhas time to form it into spheroidal particles rather than flakes. Due to their loweraspect

ratio, spheroids are relatively short and far from one another, and have a lower cross

section vis-a-vis a propagating crack or phonon. They also have blunt boundaries, as

opposed to flakes, which alleviates the stress concentration problems faced by grey castiron. In general, the properties of malleable cast iron are more like mild steel. There is a

limit to how large a part can be cast in malleable iron, since it is made from white cast

iron.

[edit] Ductile cast iron

Main article: Ductile cast iron

A more recent development is nodularorductile cast iron. Tiny amounts ofmagnesiumorceriumadded to these alloys slow down the growth of graphite precipitates by bonding

to the edges of the graphite planes. Along with careful control of other elements andtiming, this allows the carbon to separate as spheroidal particles as the material solidifies.

The properties are similar to malleable iron, but parts can be cast with larger sections.

[edit] Table of comparative qualities of cast irons

Comparative qualities of cast irons[2]

Name

Nominal

composition

[% by

weight]

Form and

condition

Yield

strength

[ksi

(0.2%

offset)]

Tensile

strength

[ksi]

Elongation

[% (in

2 inches)]

Hardness

[Brinell

scale]

Uses

Grey cast

iron

(ASTM

A48)

C 3.4, Si 1.8,

Mn 0.5Cast 25 0.5 180

Engine

cylinderblocks,

flywheels,

gears,machine-

tool bases
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White

cast iron

C 3.4, Si 0.7,

Mn 0.6

Cast (as

cast) 25 0 450

Bearing

surfaces

Malleable

iron

(ASTMA47)

C 2.5, Si 1.0,

Mn 0.55

Cast

(annealed)33 52 12 130

Axlebearings,

track

wheels,automotive

crankshafts

Ductile or

nodular

iron

C 3.4, P 0.1,Mn 0.4,

Ni 1.0,

Mg 0.06

Cast 53 70 18 170Gears,camshafts,

crankshafts

Ductile or

nodular

iron

(ASTM

A339)

cast

(quench

tempered)

108 135 5 310

Ni-hard

type 2

C 2.7, Si 0.6,

Mn 0.5,

Ni 4.5,Cr 2.0

Sand-cast 55 550

High

strengthapplications

Ni-resist

type 2

C 3.0, Si 2.0,

Mn 1.0,Ni 20.0,

Cr 2.5

Cast 27 2 140

Resistance

to heat andcorrosion

[edit] Historical uses

A cast iron wagon wheel

Because cast iron is comparatively brittle, it is not suitable for purposes where a sharp

edge or flexibility is required. It is strong under compression, but not under tension. CastIron was first invented in China(see also: Du Shi) and poured into moulds to make

weapons and figurines. Historically, its earliest uses included cannon and shot.Henry

VIII initiated the casting ofcannoninEngland. Soon, English iron workers usingblast
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furnaces developed the technique of producing cast iron cannons, which, while heavier

than the prevailing bronze cannons, were much cheaper and enabled England to arm her

navy better. The ironmastersof the Wealdcontinued producing cast irons until the 1760sand armament was one of the main uses of irons after the Restoration.

Cast iron pots were made at many English blast furnaces at the time. In 1707, AbrahamDarby patented a method of making pots (and kettles) thinner and hence cheaper than his

rivals could. This meant that his Coalbrookdale furnaces became dominant as suppliers ofpots, an activity in which they were joined in the 1720s and 1730s by a small number of

othercoke-fired blast furnaces.

The development of the steam engineby Thomas Newcomen provided further market for

cast irons, since cast irons were considerably cheaper than thebrass of which the enginecylinders were originally made. John Wilkinson was a great exponent of cast iron, who,

amongst other things, cast the cylinders for many ofJames Watt's improved steam

engines until the establishment of the Soho Foundryin 1795.

[edit] Cast iron bridges

The use of cast iron for structural purposes began in the late 1770s, when Abraham DarbyIII built the Iron Bridge, although short beams had already been used, such as in the blast

furnaces at Coalbrookdale. Other inventions followed, including one patented by Thomas

Paine. Cast iron bridges became commonplace as the Industrial Revolution gatheredpace. Thomas Telford adopted the material for his bridge upstream at Buildwas, and then

for a canal trough aqueductat Longdon-on-Tern on theShrewsbury Canal.

It was followed by the Chirk Aqueductand the Pontcysyllte Aqueduct, both of which

remain in use following the recent restorations. Cast-iron beam bridges were used widelyby the early railways, such as the Water Street Bridge at the Manchesterterminus of the

Liverpool and Manchester Railway. Problems arose when a new bridge carrying the

Chester and Holyhead Railway across the River DeeinChestercollapsed in May 1847,less than a year after it was opened. The Dee bridge disasterwas caused by excessive

loading at the centre of the beam by a passing train, and many similar bridges had to be

demolished and rebuilt, often in wrought iron. The bridge had been erroneously designed,

being trussed with wrought iron straps, which were wrongly thought to reinforce thestructure. The centres of the beams were put into bending, with the lower edge in tension,

where cast iron, like masonry, is very weak.

The best way of using cast iron for bridge construction was by usingarches, so that allthe material is in compression. Cast iron, again like masonry, is very strong in

compression. Wrought iron, like most other kinds of iron and indeed like most metals in

general, is strong in tension, and also tough- resistant to fracturing. The relationship

between wrought iron and cast iron, for structural purposes, may be thought of asanalogous to the relationship between wood and stone.
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Nevertheless, cast iron continued to be used in inappropriate structural ways, until the

Tay Rail Bridgedisaster of 1879 cast serious doubt on the use of the material. Crucial

lugs for holding tie bars and struts in the Tay Bridge had been cast integral with thecolumns and they failed in the early stages of the accident. In addition, the bolt holes

were also cast and not drilled, so that all the tension from the tie bars was placed on a

corner, rather than being spread over the length of the hole. The replacement bridge wasbuilt in wrought iron and steel.

Further bridge collapses occurred, however, culminating in theNorwood Junction rail

accident of 1891. Thousands of cast iron rail underbridges were eventually replaced by

steel equivalents.

Original

Tay

Bridgefrom the

northFallen Tay Bridgefrom the north

The iron bridge

over theRiverSevern at

Coalbrookdale,

England

TheEglintonTournament Bridge,

North Ayrshire,

Scotland, built from

cast iron

The Pontcysyllte

Aqueduct,Llangollen,Wales,

viewed from the

ground

[edit] Buildings

Main article: Cast-iron architecture

Cast iron columnsenabledarchitects to build tall buildings without the enormously thickwalls required to construct masonry buildings of any height. Such flexibility allowed tall

buildings to have large windows. In urban centres like SoHo Cast Iron Historic District in

New York City, manufacturing buildings and early department stores were built with castiron columns to allow daylight to enter. Slender cast iron columns could also support the

weight that would otherwise require thick masonry columns or piers, opening up floor

spaces in factories, and sight lines in churches and auditoriums. The historicIronBuilding in Watervliet, New York, is a cast iron building.

[edit] Textile mills

Another important use was in textile mills. The air in the mills contained flammablefibres from the cotton,hemp, orwool being spun. As a result, textile mills had an

alarming propensity to burn down. The solution was to build them completely of non-

combustible materials, and it was found convenient to provide the building with an ironframe, largely of cast iron, replacing flammable wood. The first such building was at

Ditherington in Shrewsbury, Shropshire. Many other warehouses were built using cast
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iron columns and beams, although faulty designs, flawed beams or overloading

sometimes caused building collapses and structural failures.

During the Industrial Revolution, cast iron was also widely used for frame and otherfixed parts of machinery, including spinning and later weaving machines in textile mills.

Cast iron became widely used, and many towns had foundriesproducing industrial andagricultural machinery.
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Carbon steel

From Wikipedia, the free encyclopedia

Jump to: navigation,search

Ironalloyphasesvde

Ferrite (-iron, -iron)Austenite (-iron)

Pearlite (88% ferrite, 12% cementite)

Martensite

Bainite

Ledeburite (ferrite-cementite eutectic, 4.3% carbon)

Cementite(iron carbide, Fe3C)

Steel classes

Crucible stee lCarbon steel (2.1% carbon; low alloy)

Spring steel (low or no alloy)

Alloy steel (contains non-carbon elements)

Maraging steel(contains nickel)Stainless steel (contains 10.5% chromium)

Weathering steel

Tool steel(alloy steel for tools)

Other iron-based materials

Cast iron (>2.1% carbon)

Ductile ironGray iron

Malleable ironWhite iron

Wrought iron (contains slag)

Carbon steel, also called plain-carbon steel, issteel where the mainalloying constituent

is carbon. The American Iron and Steel Institute(AISI) defines carbon steel as: "Steel is

considered to be carbon steel when no minimum content is specified or required forchromium,cobalt, columbium,molybdenum, nickel, titanium, tungsten,vanadium or

zirconium, or any other element to be added to obtain a desired alloying effect; when the

specified minimum for copper does not exceed 0.40 percent; or when the maximumcontent specified for any of the following elements does not exceed the percentages

noted: manganese1.65, silicon0.60, copper0.60."[1]

The term "carbon steel" may also be used in reference to steel which is not stainless steel;

in this use carbon steel may include alloy steels.

As the carbon content rises, steel has the ability to become harderand strongerthrough

heat treating, but this also makes it less ductile. Regardless of the heat treatment, a higher
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carbon content reducesweldability. In carbon steels, the higher carbon content lowers the

melting point.[2]

Eighty-five percent of all steel used in the United Statesis carbon steel.[1]

Contents

[hide]

1 Types

o 1.1 Mild and low carbon steel

o 1.2 Higher carbon steels

2 Heat treatment

3 Case hardening

4 See also 5 References

6 Bibliography

[edit] Types

See also: SAE steel grades

Carbon steel is broken down in to four classes based on carbon content:

[edit] Mild and low carbon steel

Mild steel is the most common form of steel because its price is relatively low while itprovides material properties that are acceptable for many applications. Low carbon steel

contains approximately 0.050.15% carbon[1] and mild steel contains 0.160.29%[1]

carbon, therefore it is neither brittle norductile. Mild steel has a relatively low tensilestrength, but it is cheap and malleable; surface hardness can be increased through

carburizing.[3]

It is often used when large quantities of steel are needed, for example as structural steel.

The density of mild steel is approximately 7.85 g/cm3 (0.284 lb/in3)[4] and the Young'smodulus is 210,000 MPa (30,000,000 psi).[5]

Low carbon steels suffer fromyield-point runoutwhere the material has two yield points.

The first yield point (or upper yield point) is higher than the second and the yield drops

dramatically after the upper yield point. If a low carbon steel is only stressed to somepoint between the upper and lower yield point then the surface may developLder bands.[6]

[edit] Higher carbon steels
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Carbon steels which can successfully undergo heat-treatment have a carbon content in the

range of 0.301.70% by weight. Trace impurities of various otherelements can have a

significant effect on the quality of the resulting steel. Trace amounts ofsulfurinparticular make the steelred-short. Low alloy carbon steel, such asA36grade, contains

about 0.05% sulfur and melts around 1,4261,538 C (2,5992,800 F).[7]Manganese is

often added to improve the hardenability of low carbon steels. These additions turn thematerial into a low alloy steelby some definitions, but AISI's definition of carbon steel

allows up to 1.65% manganese by weight.

Medium carbon steel

Approximately 0.300.59% carbon content.[1] Balances ductility and strength and has

good wear resistance; used for large parts, forging and automotive components. [8]

High carbon steel

Approximately 0.60.99% carbon content.

[1]

Very strong, used for springs and high-strength wires.[9]

Ultra-high carbon steel

Approximately 1.02.0% carbon content.[1] Steels that can be tempered to great hardness.Used for special purposes like (non-industrial-purpose) knives, axles orpunches. Most

steels with more than 1.2% carbon content are made usingpowder metallurgy. Note that

steel with a carbon content above 2.0% is considered cast iron.

Steel can be heat treated which allows parts to be fabricated in an easily-formable soft

state. If enough carbon is present, the alloy can be hardened to increase strength, wear,and impact resistance. Steels are often wrought by cold working methods, which is the

shaping of metal through deformation at a low equilibrium or metastable temperature.

[edit] Heat treatment

Iron-carbonphase diagram, showing the temperature and carbon ranges for certain typesof heat treatments.
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Main article: Heat treatment

The purpose of heat treating carbon steel is to change the mechanical properties of steel,

usually ductility, hardness, yield strength, or impact resistance. Note that the electricaland thermal conductivity are slightly altered. As with most strengthening techniques for

steel, Young's modulus is unaffected. Steel has a higher solid solubility for carbon in theaustenite phase; therefore all heat treatments, except spheroidizing and process annealing,

start by heating to an austenitic phase. The rate at which the steel is cooled through theeutectoid reaction affects the rate at which carbon diffuses out of austenite. Generally

speaking, cooling swiftly will give a finerpearlite(until the martensite critical

temperature is reached) and cooling slowly will give a coarser pearlite. Cooling ahypoeutectoid (less than 0.77 wt% C) steel results in a pearlitic structure with -ferrite at

the grain boundaries. If it is hypereutectoid (more than 0.77 wt% C) steel then the

structure is full pearlite with small grains ofcementite scattered throughout. The relativeamounts of constituents are found using the lever rule. Here is a list of the types of heat

treatments possible:

Spheroidizing: Spheroidite forms when carbon steel is heated to approximately

700 C for over 30 hours. Spheroidite can form at lower temperatures but the timeneeded drastically increases, as this is a diffusion-controlled process. The result is

a structure of rods or spheres of cementite within primary structure (ferrite or

pearlite, depending on which side of the eutectoid you are on). The purpose is tosoften higher carbon steels and allow more formability. This is the softest and

most ductile form of steel. The image to the right shows where spheroidizing

usually occurs.[10]

Full annealing: Carbon steel is heated to approximately 40 C above Ac3 or Ac1for 1 hour; this assures all the ferritetransforms into austenite (although cementite

might still exist if the carbon content is greater than the eutectoid). The steel mustthen be cooled slowly, in the realm of 38 C (100 F) per hour. Usually it is justfurnace cooled, where the furnace is turned off with the steel still inside. This

results in a coarse pearlitic structure, which means the "bands" ofpearlite are

thick. Fully-annealed steel is soft and ductile, with no internal stresses, which isoften necessary for cost-effective forming. Only spheroidized steel is softer and

more ductile.[11]

Process annealing: A process used to relieve stress in a cold-worked carbon steel

with less than 0.3 wt% C. The steel is usually heated up to 550650 C for 1 hour,but sometimes temperatures as high as 700 C. The image rightward shows the

area where process annealing occurs.

Isothermal annealing: It is a process in which hypoeutectoid steel is heatedabove the upper critical temperature and this temperature is maintained for a time

and then the temperature is brought down below lower critical temperature and is

again maintained. Then finally it is cooled at room temperature. This method ridsany temperature gradient.

Normalizing: Carbon steel is heated to approximately 55 C above Ac3 or Acm for

1 hour; this assures the steel completely transforms to austenite. The steel is thenair-cooled, which is a cooling rate of approximately 38 C (68 F) per minute.
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This results in a fine pearlitic structure, and a more-uniform structure. Normalized

steel has a higher strength than annealed steel; it has a relatively high strength and

ductility.[12]

Quenching: Carbon steel with at least 0.4 wt% C is heated to normalizing

temperatures and then rapidly cooled (quenched) in water, brine, or oil to the

critical temperature. The critical temperature is dependent on the carbon content,but as a general rule is lower as the carbon content increases. This results in a

martensitic structure; a form of steel that possesses a super-saturated carbon

content in a deformed body-centered cubic (BCC) crystalline structure, properlytermed body-centered tetragonal (BCT), with much internal stress. Thus quenched

steel is extremely hard butbrittle, usually too brittle for practical purposes. These

internal stresses cause stress cracks on the surface. Quenched steel is

approximately three to four (with more carbon) fold harder than normalized steel.[13]

Martempering (Marquenching): Martempering is not actually a tempering

procedure, hence the term "marquenching". It is a form of isothermal heat

treatment applied after an initial quench of typically in a molten salt bath at atemperature right above the "martensite start temperature". At this temperature,

residual stresses within the material are relieved and some bainite may be formedfrom the retained austenite which did not have time to transform into anything

else. In industry, this is a process used to control the ductility and hardness of a

material. With longer marquenching, the ductility increases with a minimal loss in

strength; the steel is held in this solution until the inner and outer temperaturesequalize. Then the steel is cooled at a moderate speed to keep the temperature

gradient minimal. Not only does this process reduce internal stresses and stress

cracks, but it also increases the impact resistance.[14]

Quench and tempering: This is the most common heat treatment encountered,because the final properties can be precisely determined by the temperature and

time of the tempering. Tempering involves reheating quenched steel to a

temperature below the eutectoidtemperature then cooling. The elevatedtemperature allows very small amounts of spheroidite to form, which restores

ductility, but reduces hardness. Actual temperatures and times are carefully

chosen for each composition.[15]

Austempering: The austempering process is the same as martempering, exceptthe steel is held in the molten salt bath through the bainite transformation

temperatures, and then moderately cooled. The resulting bainite steel has a greater

ductility, higher impact resistance, and less distortion. The disadvantage ofaustempering is it can only be used on a few steels, and it requires a special salt

bath.[16]

[edit] Case hardening

Main article: Case hardening
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Case hardening processes harden only the exterior of the steel part, creating a hard, wear

resistant skin (the "case") but preserving a tough and ductile interior. Carbon steels are

not very hardenable; therefore wide pieces cannot be thru-hardened. Alloy steels have abetter hardenability, so they can through-harden and do not require case hardening. This

property of carbon steel can be beneficial, because it gives the surface good wear

characteristics but leaves the core tough.

[edit] See also

Cold working

Hot working

[edit] References

1. ^ abcdefgClassification of Carbon and Low-Alloy Steel, archived from the

original on 2010-03-11,http://www.webcitation.org/5o9SDyEAb, retrieved 2010-03-11.

2. ^ Knowles, Peter Reginald (1987),Design of structural steelwork(2nd ed.),Taylor & Francis, p. 1, ISBN9780903384599, http://books.google.com/books?

id=U6wX-3C8ygcC&pg=PA1.

3. ^ Engineering fundamentals page on low-carbon steel4. ^ Elert, Glenn,Density of Steel,

http://hypertextbook.com/facts/2004/KarenSutherland.shtml, retrieved 2009-04-

23.

5. ^ Modulus of Elasticity, Strength Properties of Metals - Iron and Steel,http://www.engineersedge.com/manufacturing_spec/properties_of_metals_strengt

h.htm, retrieved 2009-04-23.6. ^ Degarmo, p. 377.7. ^ Ameristeel article on carbon steel

8. ^ Engineering fundamentals page on medium-carbon steel

9. ^ Engineering fundamentals page on high-carbon steel10. ^ Smith, p. 388.

11. ^ Smith, p. 386.

12. ^ Smith, pp. 386387.13. ^ Smith, pp. 373377.

14. ^ Smith, pp. 389390.

15. ^ Smith, pp. 387-388.

16. ^ Smith, p. 391.

Stainless steel

From Wikipedia, the free encyclopedia

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Ironalloy phasesvde

Ferrite (-iron, -iron)
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ref-3http://hypertextbook.com/facts/2004/KarenSutherland.shtmlhttp://hypertextbook.com/facts/2004/KarenSutherland.shtmlhttp://en.wikipedia.org/wiki/Carbon_steel#cite_ref-4http://www.engineersedge.com/manufacturing_spec/properties_of_metals_strength.htmhttp://www.engineersedge.com/manufacturing_spec/properties_of_metals_strength.htmhttp://www.engineersedge.com/manufacturing_spec/properties_of_metals_strength.htmhttp://en.wikipedia.org/wiki/Carbon_steel#cite_ref-5http://en.wikipedia.org/wiki/Carbon_steel#cite_ref-6http://www.ameristeel.com/products/msds/docs/carbon_steel.pdfhttp://en.wikipedia.org/wiki/Carbon_steel#cite_ref-7http://efunda.com/materials/alloys/carbon_steels/medium_carbon.cfmhttp://en.wikipedia.org/wiki/Carbon_steel#cite_ref-8http://efunda.com/materials/alloys/carbon_steels/high_carbon.cfmhttp://en.wikipedia.org/wiki/Carbon_steel#cite_ref-9http://en.wikipedia.org/wiki/Carbon_steel#cite_ref-10http://en.wikipedia.org/wiki/Carbon_steel#cite_ref-11http://en.wikipedia.org/wiki/Carbon_steel#cite_ref-12http://en.wikipedia.org/wiki/Carbon_steel#cite_ref-13http://en.wikipedia.org/wiki/Carbon_steel#cite_ref-14http://en.wikipedia.org/wiki/Carbon_steel#cite_ref-15http://en.wikipedia.org/wiki/Stainless_steel#mw-headhttp://en.wikipedia.org/wiki/Stainless_steel#p-searchhttp://en.wikipedia.org/wiki/Ironhttp://en.wikipedia.org/wiki/Alloyhttp://en.wikipedia.org/wiki/Template:Steelshttp://en.wikipedia.org/wiki/Template_talk:Steelshttp://en.wikipedia.org/w/index.php?title=Template:Steels&action=edithttp://en.wikipedia.org/wiki/Ferrite_(iron)


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Stainless steel does not stain, corrode, or rust as easily as ordinary steel, but it is not stain-

proof.[3] It is also called corrosion-resistant steel orCRES when the alloy type and

grade are not detailed, particularly in the aviation industry. There are different grades andsurface finishes of stainless steel to suit the environment to which the material will be

subjected in its lifetime. Stainless steel is used where both the properties of steel and

resistance to corrosion are required.

Stainless steel differs from carbon steel by the amount of chromium present. Carbon steelrusts when exposed to air and moisture. This iron oxide film (the rust) is active and

accelerates corrosion by forming more iron oxide. Stainless steels contain sufficient

chromium to form a passive film of chromium oxide, which prevents further surfacecorrosion and blocks corrosion from spreading into the metal's internal structure.

Passivation only occurs if the mixture of chromium is high enough, or if the manufacturer

performs this last step.[citation needed]

Contents

[hide]

1 History

2 Properties

3 Applicationso 3.1 Architectural

o 3.2 Monuments and sculptures

4 Recycling and reuse

5 Types of stainless steel

o 5.1 Comparison of standardized steelso 5.2 Stainless steel grades

o 5.3 Stainless steel in 3D printing

6 Stainless steel finishes

7 See also

8 References

9 External links

[edit] History
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An announcement, as it appeared in the 1915New York Times, of the development of

stainless steel.[4]

A few corrosion-resistant iron artifacts survive from antiquity. A famous example is the

Iron Pillar of Delhi, erected by order ofKumara Gupta I around the yearAD 400. Unlikestainless steel, however, these artifacts owe their durability not to chromium, but to their

highphosphorus content, which, together with favorable local weather conditions,

promotes the formation of a solid protectivepassivation layerofiron oxides andphosphates, rather than the non-protective, cracked rust layer that develops on most

ironwork.

The corrosion-resistance of iron-chromium alloys was first recognized in 1821 by the

French metallurgist Pierre Berthier, who noted their resistance against attack by someacids and suggested their use incutlery. Metallurgists of the 19th century, however, were

unable to produce the combination of low carbon and high chromium found in most

modern stainless steels, and the high-chromium alloys they could produce were too brittle

to be practical.

In the late 1890s Hans GoldschmidtofGermany developed an aluminothermic (thermite)

process for producing carbon-free chromium. Between 1904 and 1911 several

researchers, particularly Leon Guilletof France, prepared alloys that would today beconsidered stainless steel.

Friedrich Krupp Germaniawerftbuilt the 366-ton sailing yacht Germania featuring a

chrome-nickel steel hull in Germany in 1908.[5] In 1911, Philip Monnartz reported on the

relationship between chromium content and corrosion resistance. On October 17, 1912Krupp engineers Benno Strauss and Eduard Maurer patentedaustenitic stainless steel.[6]

Similar developments were taking place contemporaneously in the United States, where

Christian Dantsizen and Frederick Becket were industrializing ferritic stainless steel. In

1912, Elwood Haynesapplied for U.S. patent on amartensitic stainless steel alloy, whichwas not granted until 1919.[7]

Also in 1912, Harry Brearleyof the Brown-Firth research laboratory inSheffield,

England, while seeking a corrosion-resistant alloy for gun barrels, discovered and
http://en.wikipedia.org/wiki/Stainless_steel#cite_note-NYT-3http://en.wikipedia.org/wiki/Iron_Pillar_of_Delhihttp://en.wikipedia.org/wiki/Kumara_Gupta_Ihttp://en.wikipedia.org/wiki/Kumara_Gupta_Ihttp://en.wikipedia.org/wiki/400http://en.wikipedia.org/wiki/Phosphorushttp://en.wikipedia.org/wiki/Passivation_layerhttp://en.wikipedia.org/wiki/Passivation_layerhttp://en.wikipedia.org/wiki/Iron_oxidehttp://en.wikipedia.org/wiki/Phosphatehttp://en.wikipedia.org/wiki/Phosphatehttp://en.wikipedia.org/wiki/Rusthttp://en.wikipedia.org/wiki/Francehttp://en.wikipedia.org/wiki/Pierre_Berthierhttp://en.wikipedia.org/wiki/Cutleryhttp://en.wikipedia.org/wiki/Cutleryhttp://en.wikipedia.org/wiki/Hans_Goldschmidthttp://en.wikipedia.org/wiki/Hans_Goldschmidthttp://en.wikipedia.org/wiki/Germanyhttp://en.wikipedia.org/wiki/Thermitehttp://en.wikipedia.org/w/index.php?title=Leon_Guillet&action=edit&redlink=1http://en.wikipedia.org/w/index.php?title=Leon_Guillet&action=edit&redlink=1http://en.wikipedia.org/wiki/Friedrich_Krupp_Germaniawerfthttp://en.wikipedia.org/wiki/Friedrich_Krupp_Germaniawerfthttp://en.wikipedia.org/wiki/Stainless_steel#cite_note-4http://en.wikipedia.org/w/index.php?title=Philip_Monnartz&action=edit&redlink=1http://en.wikipedia.org/wiki/Krupphttp://en.wikipedia.org/wiki/Austenitehttp://en.wikipedia.org/wiki/Austenitehttp://en.wikipedia.org/wiki/Stainless_steel#cite_note-5http://en.wikipedia.org/wiki/Ferrite_(iron)http://en.wikipedia.org/wiki/Elwood_Hayneshttp://en.wikipedia.org/wiki/Elwood_Hayneshttp://en.wikipedia.org/wiki/Martensitehttp://en.wikipedia.org/wiki/Martensitehttp://en.wikipedia.org/wiki/Stainless_steel#cite_note-6http://en.wikipedia.org/wiki/Harry_Brearleyhttp://en.wikipedia.org/wiki/Harry_Brearleyhttp://en.wikipedia.org/wiki/Firth_Brown_Steelshttp://en.wikipedia.org/wiki/Sheffield,_Englandhttp://en.wikipedia.org/wiki/Sheffield,_Englandhttp://en.wikipedia.org/wiki/Sheffield,_Englandhttp://en.wikipedia.org/wiki/File:Stainless_steel_nyt_1-31-1915.jpghttp://en.wikipedia.org/wiki/File:Stainless_steel_nyt_1-31-1915.jpghttp://en.wikipedia.org/wiki/Stainless_steel#cite_note-NYT-3http://en.wikipedia.org/wiki/Iron_Pillar_of_Delhihttp://en.wikipedia.org/wiki/Kumara_Gupta_Ihttp://en.wikipedia.org/wiki/400http://en.wikipedia.org/wiki/Phosphorushttp://en.wikipedia.org/wiki/Passivation_layerhttp://en.wikipedia.org/wiki/Iron_oxidehttp://en.wikipedia.org/wiki/Phosphatehttp://en.wikipedia.org/wiki/Rusthttp://en.wikipedia.org/wiki/Francehttp://en.wikipedia.org/wiki/Pierre_Berthierhttp://en.wikipedia.org/wiki/Cutleryhttp://en.wikipedia.org/wiki/Hans_Goldschmidthttp://en.wikipedia.org/wiki/Germanyhttp://en.wikipedia.org/wiki/Thermitehttp://en.wikipedia.org/w/index.php?title=Leon_Guillet&action=edit&redlink=1http://en.wikipedia.org/wiki/Friedrich_Krupp_Germaniawerfthttp://en.wikipedia.org/wiki/Stainless_steel#cite_note-4http://en.wikipedia.org/w/index.php?title=Philip_Monnartz&action=edit&redlink=1http://en.wikipedia.org/wiki/Krupphttp://en.wikipedia.org/wiki/Austenitehttp://en.wikipedia.org/wiki/Stainless_steel#cite_note-5http://en.wikipedia.org/wiki/Ferrite_(iron)http://en.wikipedia.org/wiki/Elwood_Hayneshttp://en.wikipedia.org/wiki/Martensitehttp://en.wikipedia.org/wiki/Stainless_steel#cite_note-6http://en.wikipedia.org/wiki/Harry_Brearleyhttp://en.wikipedia.org/wiki/Firth_Brown_Steelshttp://en.wikipedia.org/wiki/Sheffield,_Englandhttp://en.wikipedia.org/wiki/Sheffield,_England


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subsequently industrialized a martensitic stainless steel alloy. The discovery was

announced two years later in a January 1915 newspaper article in The New York Times.[4]

Brearley applied for a U.S. patent during 1915 only to find that Haynes had alreadyregistered a patent. Brearley and Haynes pooled their finding, and with a group of

investors formed the American Stainless Steel Corporation, with headquarters in

Pittsburgh, Pennsylvania. The metal was later marketed under the "Staybrite" brand byFirth Vickers in England and was used for the new entrance canopy for theSavoy Hotel

in London in 1929.[8]

[edit] Properties

High oxidation-resistance in airat ambient temperatureis normally achieved withadditions of a minimum of 13% (by weight) chromium, and up to 26% is used for harsh

environments.[9] The chromium forms apassivation layer ofchromium(III) oxide (Cr2O3)

when exposed to oxygen. The layer is too thin to be visible, and the metal remainslustrous. The layer is impervious to waterand air, protecting the metal beneath. Also, this

layer quickly reforms when the surface is scratched. This phenomenon is calledpassivation and is seen in other metals, such as aluminium and titanium. Corrosion-

resistance can be adversely affected if the component is used in a non-oxygenatedenvironment, a typical example being underwaterkeel bolts buried in timber.

When stainless steel parts such asnuts andboltsare forced together, the oxide layer can

be scraped off, causing the parts to weldtogether. When disassembled, the welded

material may be torn and pitted, an effect known asgalling. This destructive galling canbe best avoided by the use of dissimilar materials for the parts forced together, e.g.

bronze and stainless steel, or even different types of stainless steels (martensitic against

austenitic), when metal-to-metal wear is a concern. Nitronic alloys reduce the tendency to

gall through selective alloying with manganese and nitrogen. Threaded joints may also belubricated to prevent galling.

[edit] Applications

The pinnacle of New York's Chrysler Building is clad with type 302 stainless steel. [10]
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cast iron usually refers to grey iron

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