ibles at an intense white heat, cast carefully
into iron molds, and the resulting ingot forged into bars under
a crude trip hammer. This melting practice is still in use for
crucible steel, and will be described further on page 4.

THE WORKING OF STEEL

ANNEALING, HEAT TREATING AND HARDENING

OF

CARBON AND ALLOY STEEL

CHAPTER I

STEEL MAKING

There are four processes now used for the manufacture of steel.
These are: The Bessemer, Open Hearth, Crucible and Electric Furnace
Methods.

BESSEMER PROCESS

The bessemer process consists of charging molten pig iron into
a huge, brick-lined pot called the bessemer converter, and then
in blowing a current of air through holes in the bottom of the
vessel into the liquid metal.

The air blast burns the white hot metal, and the temperature increases.
The action is exactly similar to what happens in a fire box under
forced draft. And in both cases some parts of the material burn
easier and more quickly than others. Thus it is that some of the
impurities in the pig iron--including the carbon--burn first, and
if the blast is shut off when they are gone but little of the iron
is destroyed. Unfortunately sulphur, one of the most dangerous
impurities, is not expelled in the process.

A bessemer converter is shown in Fig. 1, while Fig. 2 shows the
details of its construction. This shows how the air blast is forced
in from one side, through the trunnion, and up through the metal.
Where the steel is finished the converter is tilted, or swung on
its trunnions, the blast turned off, and the steel poured out of
the top.

OPEN HEARTH PROCESS

The open hearth furnace consists of a big brick room with a low
arched roof. It is charged with pig iron and scrap through doors
in the side walls.

[Illustration: FIG. 1.--A typical Bessemer converter.]

Through openings at one end of the furnace come hot air and gas,
which burn in the furnace, producing sufficient heat to melt the
charge and refine it of its impurities. Lime and other nonmetallic
substances are put in the furnace. These melt, forming a "slag"
which floats on the metal and aids materially in the refining
operations.

In the bessemer process air is forced _through_ the metal. In the
open-hearth furnace the metal is protected from the flaming gases
by a slag covering. Therefore it is reasonable to suppose that
the final product will not contain so much gas.

[Illustration: FIG. 2.--Action of Bessemer con