METALLURGISTS must supply engineers with data on the physical properties of steels so that the skill of both can be used, particularly for machinery in which light weight is essential. The engineer who has not a metallurgical department at his command cannot be sure of duplicating results claimed by steel makers, and the physical-property data that have been given in the S.A.E. HANDBOOK are based on minimum results, for safety.
More complete information as to what actually can be expected is desirable, and a subcommittee has had a large number of tests made on identical samples from several heats of two alloy steels. The results for these two steels have been coordinated in probability curves that were developed with the aid of frequency charts.
Some steels are not uniform in their physical properties in large sections. The author presents suggestions for steels that are suitable for large sections, with the strengths that can be expected from them. Gear steels are treated in a brief analysis, and European practice is cited for gear steels and automobile construction in general, including a table of recommendations made by a British standardizing body.