低碳微合金直接淬火钢的组织与力学性能

Microstructures and mechanical properties of low-carbon microalloyed direct-quenched steel

为了提高低碳直接淬火钢的强韧性能,对一种低碳Nb-V微合金钢进行了轧后直接淬火(DQ)和再加热淬火(RQ)热处理实验,分析了低碳直接淬火钢的的强韧化机理.采用光学显微镜、透射电子显微镜、硬度计、拉伸试验机以及冲击试验机研究了轧后热处理工艺对低碳Nb-V微合金钢组织和力学性能的影响.结果表明,DQ工艺钢马氏体板条间距细小,含有较多的位错亚结构,因此具有较高的强度和韧性.DQ工艺钢马氏体中的大量位错,促进了碳化物弥散析出,产生了显著的二次硬化效果.由于基体中固溶的Nb、V等元素推迟淬火马氏体在回火过程中的各种转变,以及回火时析出的细小弥散碳化物抑制马氏体铁素体回复、再结晶过程,DQ工艺钢表现出较高的回火稳定性.

Reheat-quenching（RQ） and direct-quenching（DQ） heat treatment experiments after rolling were carried out on a kind of low carbon Nb-V microalloyed steel in order to study the toughening and strengthening mechanisms for direct-quenching steel to improve its toughess and strength.Effect of heat treatment processes after rolling on microstructures and mechanical properties of the low-carbon Nb-V microalloyed steel was investigated by means of optical microscope,transparent electron microscope,hardmeter,tensile testing machine and impact testing machine.The experimental results show that DQ steel has shorter lath spacing and higher dislocation density than RQ steel,resulting in higher strength and toughness.A large amount of dislocation in martensite matrix of DQ steel promotes the precipitation of fine and dense carbides,leading to significant secondary hardening during tempering.DQ processed steel exhibits higher tempering resistance than RQ steel because a large number of dissolved Nb and V elements retard various changes of martensite during tempering,and fine and dense precipitates prohibit martensite ferrite from recovery and recrystallization.