Heat Treatment of an Experimental Steel Designed to Produce 8 in. Thick Cast Armor of Acceptable Shock Properties

摘要

A highly alloyed Manganese: Nickel: Chromium: Molybdenum steel heat treated to a hardness of 270 Brinell in an 8 in thick section was found to be temper embrittled to the extent of approximately 5 ft.lbs. at the surface and from 15 to 20 ft.lbs. at the center of the section in spite of the fact that the sample was water quenched after tempering, demonstrating that the cooling rates of heavy sections are insufficiently rapid to avoid the temper brittleness transformation. Quench cracking would probably interfere with the commercial use of steel of the subject composition. Satisfactory properties can be obtained in heavy sections in the hardness range of 200-250 Brinell by the use of compositions producing predominately bainitic structures upon quenching, allowing the use of lower alloy contents, thus minimizing both temper brittleness and quench cracking.