Heat Treatment of Soft and Medium Steel: Theory and Practice of the Preliminary Heat Treatments Designed to Give Maximum Toughness to Steel Used for Machine Parts (Classic Reprint)

Excerpt from Heat Treatment of Soft and Medium Steel: Theory and Practice of the Preliminary Heat Treatments Designed to Give Maximum Toughness to Steel Used for Machine Parts

It has been often observed that man progresses from the simple and wasteful to the complex and economical. Progress in metallurgical art is no exception. From direct iron and steel (made from ore in simple forges, and in one operation) we have come as far as the mild steel of commerce, made from ore through an intermediate impure blast-furnace product, pig iron.

Further progress may he expected along the same lines. A growing demand for the maximum of strength in the minimum of weight is inevitable, an end attainable by a further complication in process: either super-refining, perhaps in electric furnaces, or heat treatment carried far beyond the practices now commonly used on small parts of good quality.

Metallurgists and metallographists have only recently been impressed with the fact that various impurities and addition agents may affect the properties of finished steel fax in excess of that expected by their apparent amount. Precise data along these lines are almost entirely lacking; therefore Dr. Giolitti's present book, containing the first systematic discussion of their effect on commercial heat treatment, should prove a powerful stimulus toward their study; proving as he does the tremendous advantages to be gained by their elimination or suppression. Especially respectful attention will be given by those who have been baffled by so-called "flakes" and "woody fractures" - a disease of metals well understood and under control in the Italian works managed by the author - and by the many consumers and producers who will ultimately be dealing in alloy steel casting? of high strength and toughness, such as have been under tonnage production abroad for several years.

Previously published texts and theoretical treatises have illustrated the relationships between iron and carbon in the form of a diagram for complete equilibrium, giving all too scant attention to the difficulties of reaching this ideal. If for nothing else, Dr. Giolitti's volume should be of great usefulness for its insistence that commercial heat treatment of steel depends primarily upon the diffusion of carbon and other soluble substances contained, gaseous or solid. In turn the approach to equilibrium is profoundly affected by the speed of cooling, the spacing of centers of crystallization, the content of insoluble non-metallic inclusions and their physical and chemical constitution, the temperature of transformation and the thermal hysteresis.

He who would master his metal, must master these things.

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