奥氏体化对含Nb NM500低合金高强度耐磨钢晶粒和硬度的影响

Influence of Austenitizing on Grain Size and Hardness of High Strength Low Alloy Wear-resistant Steel NM500 Containing Nb

研究了奥氏体化工艺参数对在国产NM500低合金高强度耐磨钢化学成分的基础上添加微合金元素Nb的试验钢的奥氏体晶粒长大趋势和组织硬度的影响,从而优化淬火工艺参数,使试验钢获得细小的晶粒和组织,在保证试验钢硬度的前提下,提高其冲击韧性。结果表明,含Nb量为0.043%的试验钢的奥氏体粗化温度为950℃,在950℃以下水淬获得的奥氏体晶粒尺寸细小,能使试验钢获得更好的冲击韧性。在850℃保温后水淬,随淬火保温时间的增加,试验钢组织硬度先增加后降低。为使试验钢到达NM500的硬度指标要求,淬火保温时间不能过长,控制在40 min以下为宜。

The influences of austenitizing process parameters on the austenitic grain growth trend and hardness of the microstructure of Nb microalloyed steel based on the chemical composition of domestic NM500 were investigated, so as to optimize the quenching process parameters, and make the test steel get fine grain size and microstructure, to improve the impact toughness on the premise of guarantee the hardness of test steel. The results show that： the austenitic coarsening temperature of test steel containing 0.043% of Nb is 950 ℃, the austenitic grain size is tiny with water quenching at 950 ℃,which can make the test steel get better impact toughness. The hardness of test steel increases before reducing with the increase of the quenching time of heat preservation at 850 ℃. The quenching heat preservation time should not be too long, it is advisable to control under 40 min, in order to make the hardness of test steel reaches the index requirements of NM500.