Carbon-steel Forgings





Low-stressed, carbon-steel forgings include such parts as carbureter

control levers, etc. The important criterion for parts of this type

is ease of fabrication and freedom from over-heated and burned

forgings. The material used for such parts was S. A. E. No. 1,030

steel, which is of the following chemical composition: Carbon, 0.250

to 0.350 per cent; manganese, 0.500 to 0.800 per cent; phosphorus,

0.045 maximum per cent; sulphur, 0.050 maximum per cent.



To obtain good machineability, all forgings produced from this

steel were heated to a temperature of from 1,575 to 1,625 deg.F. to

refine the grain of the steel thoroughly and quenched in water

and then tempered to obtain proper machineability by heating to a

temperature of from 1,000 to 1,100 deg.F. and cooled slowly or quenched.



Forgings subjected to this heat treatment are free from hard spots

and will show a Brinell hardness of 177 to 217, which is proper for

all ordinary machining operations. Great care should be taken not

to use steel for parts of this type containing less than 0.25 per

cent carbon, because the lower the carbon the greater the liability

of hard spots, and the more difficult it becomes to eliminate them.

The only satisfactory method so far in commercial use for the

elimination of hard spots is to give forgings a very severe quench

from a high temperature followed by a proper tempering heat to

secure good machine ability as outlined above.



The important carbon-steel forgings consisted of the cylinders,

the propeller-hubs, the propeller-hub flange, etc. The material

used for parts of this type was S. A. E. No. 1,045 steel, which

is of the following chemical composition: Carbon, 0.400 to 0.500

per cent; manganese, 0.500 to 0.800 per cent; phosphorus, 0.045

maximum per cent; sulphur, 0.050 maximum per cent.



All forgings made from this material must show, after heat treatment,

the following minimum physical properties: Elastic limit, 70,000;

lb. per square inch, elongation in 2 in., 18 per cent, reduction

of area, 45; per cent, Brinell hardness, 217 to 255.



To obtain these physical properties, the forgings were quenched in

water from a temperature of 1,500 to 1,550 deg.F., followed by tempering

to meet proper Brinell requirements by heating to a temperature

of 1,150 to 1,200 deg.F. and cooled slowly or quenched. No trouble

of any kind was ever experienced with parts of this type.



The principal carbon-steel pressed parts used on the Liberty engine

were the water jackets and the exhaust manifolds. The material

used for parts of this type was S. A. E. No. 1,010 steel, which

is of the following chemical composition: Carbon, 0.05 to 0.15 per

cent; manganese, 0.30 to 0.60 per cent; phosphorus, 0.045 maximum

per cent; sulphur, 0.045 maximum per cent.



No trouble was experienced in the production of any parts from

this material with the exception of the water jacket. Due to the

particular design of the Liberty cylinder assembly, many failures

occurred in the early days, due to the top of the jacket cracking

with a brittle fracture. It was found that these failures were

caused primarily from the use of jackets which showed small scratches

or die marks at this joint and secondarily by improper annealing of

the jackets themselves between the different forming operations.

By a careful inspection for die marks and by giving the jackets

1,400 deg.F. annealing before the last forming operation, it was possible

to completely eliminate the trouble encountered.





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