Structure and mechanical properties of low-carbon structural steels hardened in mill flux

Abstract

1. A structure providing for a yield point of no less than σy = 350 N/mm2 in combionation with sufficiently high cold resistance is formed when a rolled product of low-carbon steel St3 is hardened in mill flux. 2. The use of rapid surface cooling (600–800°/sec) is most effective for the acquisition of appreciably higher strength (σy = 400–600 N/mm2); as a result, temper martensite with a different hardness throughout the section (the hardness of the surface layers is 100 HV higher than that of the core) is formed in the surface layers. 3. Subgrain and grain-boundary hardening, dispersion hardening, and the dispersion of the pearlitic component (quasi-eutectoid) make the basic contribution to the strength increase in low-carbon steels. The theoretically maximum obtainable yield point for low-carbon steels σy = 800–900 N/mm2.