AISI letter prefixes refer to the process used in steel making
which affect the properties of the steel products. (B) Acid
Bessemer Carbon Steel, (C) Basic Open Hearth Steel, (D) Acid Open
Hearth Steel, (E) Electric Furnace Alloy Steel.Steel Making
Open-hearth process,also calledSiemens-martin Process,
steelmaking technique that for most of the 20th century accounted
for the major part of all steel made in the world.William Siemens,
a German living in England in the 1860s, seeking a means of
increasing the temperature in a metallurgical furnace, resurrected
an old proposal for using the waste heat given off by the furnace;
directing the fumes from the furnace through a brick checkerwork,
he heated the brick to a high temperature, then used the same
pathway for the introduction of air into the furnace; the preheated
air materially increased the flame temperature.
Blister SteelIn order to convert wrought iron into steelthat is,
increase the carbon contenta carburization process was used. Iron
billets were heated with charcoal in sealed clay pots that were
placed in large bottle-shaped kilns holding about 10 to 14 tons of
metal and about 2 tons of charcoal. When the kiln was heated,
carbon from the charcoal diffused into the iron.
Crucible steel Technique for producing fine or toolsteel. The
earliest known use of the technique occurred in India and central
Asia in the early 1st millennium.The steel was produced by heating
wroughtironwith materials rich incarbon, such as charcoal in closed
vessels. It was known as wootz and later asDamascus steel. The
crucible process appeared in northern Europelikely as a result of
trade contact with the Middle Eastwhere it was used to make the
high-qualityUlfbehrtswords used by theVikings. The process was
devised again in Britain about 1740 byBenjamin Huntsman,who
established a steelworks at Sheffield, Eng., where the steel was
made by melting blister steel in clay crucibles at a temperature of
1,500 to 1,600 C (2,700 to 2,900 F), using coke as a fuel.
Originally, the charge in the crucible weighed about 6 kilograms,
but by 1870 it had increased to 30 kilograms.Electric furnace
Heating chamber with electricity as the heat source for
achieving very high temperatures to melt and alloy metals and
refractories. The electricity has no electrochemical effect on the
metal but simply heats it.Modern electric furnaces generally are
eitherarc furnacesor induction furnaces. A third type,
theresistance furnace, is still used in the production of silicon
carbide and electrolytic aluminum; in this type, thefurnacecharge
(i.e.,thematerialto be heated) serves as the resistance element. In
one type of resistance furnace, the heat-producing current is
introduced by electrodes buried in the metal
Bessemer Furnace It consisted of a large vessel charged with
molten iron, through which cold air was blown. There was a
spectacular reaction resulting from the combination of impurities
in the iron manufacturing inBessemer convertersa kind of
low-phosphorus steel known asThomas steel. In theThomas-Gilchrist
processthe lining used in the converter is basic rather than
acidic, and it captures the acidic phosphorus oxides formed upon
blowing air through molten iron made from the high-phosphorus iron
ore prevalent in Europe.
Basic oxygen process
(>BOP),a steelmaking method in which pure oxygen is blown
into a bath of molten blast-furnace iron and scrap. The oxygen
initiates a series of intensively exothermic (heat-releasing)
reactions, including the oxidation of such impurities as carbon,
silicon, phosphorus, and manganese.The advantages of using pure
oxygen instead of air in refining pigironintosteelwere recognized
as early as 1855 by Henry Bessemer, but the process could not be
brought to commercial fruition until the 20th century, when large
tonnages of cheap, high-purity oxygen became available.
