It can be concluded from the concepts of [I] that the purpose of alloying carburizing steels is to raise their hardenability (by diminishing the critical rate of quenching) and to ensure inheritance of the fine-grained structure. "'Excess" a.lloying that exceeds the necessary level tbr the given problem influences negatively the working capacity of the hardened parts, because it elevates the threshold cold brittleness of the steels [I]. Nickel alloying is an exception because its presence in any amotmt increases the reliability of parts operating trader high loads.The GAZ plant produces carburizing gears tbr its cars from steels alloyed with chromium, manganese, nickel, and molybdenum. The introduction of the alloying additives into these steels provides quite high parameters of the adaptability to manufacture under various kinds of mechanical and heat treatment and a specific level of hardenability. The latter is necessary lbr providing the requisite hardness of the core of the teeth. In GAZ practice the lower bottom of the standardized hardness at the base of the teeth is 3 0 -3 2 HRC. When the quenching is pertbnned in carburizing installation where the quenching medium is a mineral oil, the use of these steels does not provide the requisite hardness in comparatively massive (from the standpoint of the conditions of quenching cooling) parts. In this connection, we analyzed the effect of the composition of steels of the class in question on their hardenability. For this purpose we used the results of chemical analyses and standard tests tbr hardenability performed by the method o f end quenching [2] for a multitude of specimens and a variety of conditions of metallurgical production (Table 1).
M E T H O D S OF S T U D YThe hardenability o f the steels was characterized by the quantity Lhm, i.e., the distance (in ram) from the surface of J Gorky Automobile Plant Joint-Stock Company (GAZ), Nizhny Novgorod, Russia.