Steel and its Heat Treatment

Abstract

THE heat treatment of steels is an art of recent growth. Twenty years ago it could scarcely be said to exist. Such as it was, it usually consisted in “heating to a red heat” for annealing, or perhaps the instructions called for “harden at a bright red and temper to a straw colour.” It was an art guarded with much secrecy and confined chiefly to makers of tools. Pyrometers, structural changes, and a knowledge of the thermal equilibrium diagram of the steel in question were not even thought of. To-day it may he said without exaggeration that modern engineering practice at its best would be impossible were it not based largely upon an art which requires for its performance scientific knowledge, skill, and judgment of a very high order. With the exception of steels very low in carbon, there is scarcely one—certainly no alloy steel—which does not require a precisely defined heat treatment, depending upon thern purpose to which it is to be put, if the best value is to be got out of it. Of this the steels used in the automobile industry furnish a conspicuous illustration. The frame, the front and rear axles, the steering parts, springs, crank-shafts, and gears, all have a more or less severe duty to perform and require steels possessing particular qualities of strength, toughness, resilience, endurance, shock resistance, and good wearing properties, which are obtained by suitable heat treatment.

Steel and its Heat Treatment.

By Denison K. Bullens. Second impression, with additions. Pp. vii + 441. (New York: J. Wiley and Sons, Inc.; London: Chapman and Hall, Ltd., 1916.) Price 17s. 6d. net.