Structure and mechanical properties of the 03Kh14GNF steel after deformation and annealing

Abstract

It has been shown that the annealing of cold-worked 03Kh14GNF steel is accompanied by several strengthening and softening processes that take place in different temperature intervals. Therefore, the temperature dependence of its hardness has a complicated form; i.e., it contains several maxima and minima. The following processes should be noted: recovery and recrystallization of δ ferrite, precipitation of M 2(CN) carbonitrides and M 23C6 carbides from the α martensite, their dissolution in the γ phase, the formation of austenite with different stability, polygonization of the α martensite, etc. Tempering for 30 h can produce the level of mechanical properties required according to technical specifications for two processing regimes. These regimes are the annealing at 680°C and at 600°C, but in the second case the high plasticity is probably caused by the formation of a highly stable austenite that is retained down to room temperature. However, the degree of plasticity of this γ phase at room and lower temperatures is unknown. After annealing at 660°C, the steel does not achieve the level of ultimate strength of 480 N/mm2, which is required by the technical specifications. However, since the relative elongation of 35% exceeds the required magnitude, the required level of mechanical properties can apparently be produced by a decrease in the duration of annealing to 20–25 h.