新热处理工艺对低碳Nb-Ti微合金钢组织性能的影响

采用不同的新淬火工艺路径，研究再加热温度和弛豫过程对低碳Nb-Ti微合金钢组织性能的影响.结果表明，试样经再加热后直接淬火时，随着再加热温度的升高，析出物数量迅速下降，尺寸增加且分布更加不均匀，且马氏体板条束增大，板条宽度减小；当再加热温度为850℃时，试样经弛豫至700℃后再淬火时，其析出物数目与直接淬火相比减少，平均尺寸增加且分布更加不均匀.当再加热温度为900℃经弛豫至700℃后再淬火时，Nb-Ti碳氮化物大量在原有析出物表面进一步析出；钢材最佳再加热温度为900℃，且空冷20s时抗拉强度达到最大值，抗拉强度可提高24MPa.

Effects of New Heat Treatment Process on Microstructure and Mechanical Properties of Low Carbon Nb Ti Micro alloyed Steels

The test steels were quenched to room temperature using a new heat treatment process， and the effects of the reheating temperature and relaxation quenching process on microstructure and mechanical properties of low carbon Nb Ti micro alloyed steels were investigated. The results showed that the number of precipitates decreased， while the mean size increased with the size distribution getting even nonuniform. The martensitic lath bundle size growed and the size of each martensitic lath decreased with the increase of the reheating temperature. Compared with the sample quenched directly， the number of precipitates in the sample reduced， which was reheated to 850℃ and then relaxed by slowly cooling to 700℃ before quenching. Its mean diameter increased and the size distribution was more uneven. When the sample was reheated to 900℃ and also relaxed by slowly cooling to 700℃ before quenching， (Nb， Ti)x(CN)y continued to precipitate on the surface of intrinsic granular precipitates. The best reheating temperature was 900℃. Moreover， the tensile strength of the sample which was air cooled about 20s increasesd 24MPa and reached its maximum value.