Effect of austenitizing conditions on structural transformations in phase cold-worked austenite and the properties of high-strength structural steel with carbide-intermetallide hardening

Abstract

In many alloy steels, the reverse a --, "y transformation occurs upon heating under conditions when complete structural inheritance is realized, and it is accompanied by formation of phase cold-workedThe effect of simultaneous increase in strength and plasticity in many structural steels subjected to high-temperature thermomechanical treatment is well known and has been well studied [1]. It has been shown that such a combination of properties in the steels after high-temperature thermomechanical treatment is due to a number of structural factors: the higher degree of fragmentation and uniformity of the elements of the micro-and substructure of the martensite [1-4] inherited from the austenite, and also the peculiar (toothed or sinuous) shape of the boundaries of the former austenite grains [1][2][3][4][5].* Formation of such specific structure in quenched steel becomes possible only when during high-temperature thermomechanical treatment we can present development of recrystallization the hot-deformed austenite. However, satisfaction of this condition is a major technological complication of high-temperature thermomechanical treatment, since it is difficult to combine with the need to ensure high deformability of the austenite. Thus realization of the indicated positive effect of hightemperature thermomechanical treatment forces us to regulate strictly the temperature and mechanical force parameters of the treatment, to control carefully the length of the post-deformation interval for stimulation of polygonization processes in the austenite, to increase its resistance to recrystallization [1].We can suggest that effects analogous to those produced by high-temperature thermomechanical treatment can be obtained in a number of steels by another route, without application of plastic deformation as a result of mechanical force, if we take into account the similarity between the structures of hot-deformed and phase cold-worked austenite [5]. We know tha~ in many alloy steels, the reverse a --, ",1, transformation occurs preferentially by shear upon heating, which when the difference between the specific volumes of these phases is significant leads to formation of phase cold-worked austenite [6]. This allows *In most papers determining the effect of high-temperature thermomechanical treatment on the properties of steels, the investigations have been carried out on small samples. In this case, high plasticity is obtained due to the scale factor. Furthermore, the effect of high-temperature thermomechanical treatment in a number of cases (as in this work) is connected with disintegration of the grain (Ed. note).