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通过在不同温度高温回火,研究了回火温度对含Nb高碳钢力学性能的影响;对比分析在演变过程中Nb对其组织与性能的影响。结果表明:高碳淬火组织为板条马氏体和孪晶马氏体,随回火温度的升高,逐渐转变为大尺寸的渗碳体+等轴铁素体。强度和硬度都随回火温度升高而逐渐降低,而伸长率和断面收缩率则随回火温度的升高而逐渐增大;含Nb高碳钢的塑性和强度都要优于不含Nb的高碳钢。原因是添加Nb可以通过细化晶粒(原奥氏体晶粒和马氏体亚结构尺寸、再结晶铁素体晶粒大小)、抑制位错回复提高位错密度的形式提高强度,同时也因细化晶粒,促进碳化物析出而提高塑性。
The effect of tempering temperature on the mechanical properties of Nb-containing high carbon steel was studied by tempering at different temperatures. The effect of Nb on the microstructure and properties of Nb-containing high carbon steel during the evolution was comparatively analyzed. The results show that the high-carbon quenched microstructure is lath martensitic and twinned martensite. With the increase of tempering temperature, the high-carbon quenched microstructure gradually transforms into large-size cementite and equiaxed ferrite. Both the strength and the hardness decrease gradually with the increase of tempering temperature, while the elongation and the reduction of area gradually increase with the increase of tempering temperature. The ductility and strength of Nb-containing high carbon steel are better than those without Nb high-carbon steel. The reason is that the addition of Nb improves the strength by refining the grain size (the size of the original austenite grains and the martensite substructure, the recrystallized ferrite grain size), suppressing dislocation recovery and increasing the dislocation density, and Improve the ductility by refining grains and promoting carbide precipitation.