The iron is placed in a large retort called a converter, being poured,
while at a melting heat, directly from the blast furnace into the
converter. While the iron in the converter is molten, blasts of air are
forced through the liquid, making it still hotter and burning out the
impurities together with the carbon and manganese. These two elements are
then restored to the iron by adding spiegeleisen (an alloy of iron, carbon
and manganese). A converter holds from 5 to 25 tons of metal and requires
about 20 minutes to finish a charge. This makes the cheapest steel.
[Illustration: Figure 3.--An Open Hearth Furnace]
_Open hearth steel_ is made by placing the molten iron in a receptacle
while currents of air pass over it, this air having itself been highly
heated by just passing over white hot brick (Figure. 3). Open hearth steel
is considered more uniform and reliable than Bessemer, and is used for
springs, bar steel, tool steel, steel plates, etc.
_Aluminum_ is one of the commonest industrial metals. It is used for
gear cases, engine crank cases, covers, fittings, and wherever lightness
and moderate strength are desirable.
Aluminum is about one-third the weight of iron and about the same weight as
glass and porcelain; it is a good electrical conductor (about one-half as
good as copper); is fairly strong itself and gives great strength to other
metals when alloyed with them. One of the greatest advantages of aluminum
is that it will not rust or corrode under ordinary conditions.
Pages:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25