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本文通过临界区退火后水淬,及在450℃等温不同时间后水淬以获得不同低温转变产物及体积分数的F+M,F+B+M和F+B组织,探讨热处理工艺对显微组织的影响,研究了低温转变产物性质及体积分数对拉伸,延伸凸缘性及塑性应变比r值的影响。结果表明,低温转变产物贝氏体代替马氏体大大改善了延伸凸缘性能,并提高了r值。F+10％BⅡ+1～2％M的复相组织具有最好的综合性能。研究发现,适当的低温转变产物体积分数及尺寸,降低低温转变产物与铁素体的硬度比,良好的总延伸率是改进低碳含铌车轮用钢冲压成型性的主要因素。
In this paper, F + M, F + B + M and F + B were obtained by water quenching in the critical zone after annealing and water quenching at different isothermal temperatures of 450 ℃ for different low temperature transformation products and volume fractions, The influences of the properties of low temperature transformation products and the volume fraction on the tensile, stretch flangeability and plastic strain ratio r were studied. The results show that the low temperature transformation product bainite instead of martensite greatly improved the performance of extended flange, and increased r value. F + 10% BⅡ + 1 ~ 2% M complex phase with the best overall performance. It is found that proper volume fraction and size of low temperature transformation products, low hardness ratio of low temperature transformation products and ferrite and good total elongation are the main factors to improve the stamping formability of low carbon niobium-containing wheel steel.