THE control of grain size has facilitated the development of new steels and modifications in heat-treating processes, Mr. Davis announces. His paper deals with modern progress in the steel mill, the employment of the Carbometer and Turbidimeter, lime-silica ratio and the newer deoxidizers employed to aid steel quality. The internally heated immersion bath has been a distinct advancement in salt-bath hardening and enables longer pots to be practical, he explains. Dry cyaniding with ammonia gas may eventually obsolete cyanides and activated baths, in the opinion of the author. Gas carburizing gradually is supplanting box carburizing, he reports, and many large heat-treating units carburize, quench wash and temper mechanically. Also, a late gas carburizing furnace eliminates the employment of a muffle.
The principle of tube combustion or radiant heating, he relates, is being used extensively in atmosphere-controlled furnaces for sheet and strip annealing, furnaces for short-cycle malleable annealing, and other heat-treating applications. He prognosticates the future possibilities of induction hardening, and outlines the present status of its development.