NM500耐磨钢的QLT热处理工艺

QLT heat treatment process of NM500 wear-resistant steel

对NM500耐磨钢进行940℃淬火+两相区淬火+回火(QLT)热处理,研究了两相区淬火温度(820~880℃)和回火温度(200~600℃)对试验钢显微组织和力学性能的影响。结果表明,在两相区淬火温度从820℃升至880℃的过程中,试验钢为马氏体和铁素体双相组织,且铁素体含量逐渐降低,马氏体含量增多,试验钢的强度和硬度提高,-40℃冲击吸收能量从67 J降低至33 J。在870℃两相区淬火,200~600℃范围内回火时,随回火温度的升高,板条马氏体和残留奥氏体逐渐分解,碳化物形态和分布发生变化;试验钢抗拉强度和硬度逐渐降低,低温冲击性能先降低后升高,试验钢达到良好强韧性匹配的回火温度区间为200~250℃。

NM500 wear-resistant steel was subjected to quenching at 940℃,intercritical quenching,and tempering(QLT)treatment,and the effects of the intercritical quenching temperature(820-880℃)and tempering temperature(200-600℃)on the microstructure and mechanical properties of the tested steel were investigated.The results show that the tested steel is martensitic and ferrite dual-phase after intercritical quenching from 820℃ to 880℃,and the ferrite content gradually decreases and martensite increases,and the strength and hardness of the tested steel increase,and the impact absorbed energy at -40℃ decreases from 67 J to 33 J.When intercritical quenched at 870℃ and tempered at the range of 200-600℃,with the increase of tempering temperature,the lath martensite and retained austenite gradually decompose,and the morphology and distribution of carbides change.The tensile strength and hardness gradually decrease,and the low temperature impact absorbed energy first decreases and then increases.The tempering temperature range for the tested steel to achieve a good match of strength and toughness is 200-250℃.