Application To The Automotive Industry

: The Working Of Steel

The information given on the various parts of the Liberty engine

applies with equal force to the corresponding parts in the construction

of an automobile, truck or tractor. We recommend as first choice for

carbon-steel screw-machine parts material produced by the basic

open hearth process and having the following chemical composition;

Carbon, 0.150 to 0.250 per cent; manganese, 0.500 to 0.800 per

cent; phosphorus, 0.04
maximum per cent; sulphur, 0.075 to 0.150

per cent.

This material is very uniform and is nearly as free cutting as

bessemer screw stock. It is sufficiently uniform to be used for

unimportant carburized parts, as well as for non-heat-treated

screw-machine parts. A number of the large automobile manufacturers

are now specifying this material in preference to the regular bessemer


As second choice for carbon-steel screw-machine parts we recommend

ordinary bessemer screw stock, purchased in accordance with S. A.

E. specification No. 1114. The advantage of using No. 1114 steel

lies in the fact that the majority of warehouses carry standard

sizes of this material in stock at all times. The disadvantage

of using this material is due to its lack of uniformity.

The important criterion for transmission gears is resistance to

wear. To secure proper resistance to wear a Brinell hardness of

from 512 to 560 must be obtained. The material selected to obtain

this hardness should be one which can be made most nearly uniform,

will undergo forging operations the easiest, will be the hardest

to overheat or burn, will machine best and will respond to a good

commercial range of heat treatment.

It is a well-known fact that the element chromium, when in the form

of chromium carbide in alloy steel, offers the greatest resistance to

wear of any combination yet developed. It is also a well-known fact that

the element nickel in steel gives excellent shock-resisting properties

as well as resistance to wear but not nearly as great a resistance

to wear as chromium. It has been standard practice for a number of

years for many manufacturers to use a high nickel-chromium steel

for transmission gears. A typical nickel-chromium gear specification

is as follows: Carbon, 0.470 to 0.520 per cent; manganese, 0.500

to 0.800 per cent; phosphorus, 0.040 maximum per cent; sulphur,

0.045 maximum per cent; chromium, 0.700 to 0.950 per cent.

There is no question but that a gear made from material of such an

analysis will give excellent service. However, it is possible to

obtain the same quality of service and at the same time appreciably

reduce the cost of the finished part. The gear steel specified is

of the air-hardening type. It is extremely sensitive to secondary

pipe, as well as seams, and is extremely difficult to forge and

very easy to overheat. The heat-treatment range is very wide, but

the danger from quenching cracks is very great. In regard to the

machineability, this material is the hardest to machine of any

alloy steel known.