超细化低碳贝氏体钢的回火组织稳定性及力学性能

The Tempering Microstructures and Mechanical Properties in an Ultra-fine Low Carbon Bainitic Steel

研究了弛豫 -析出控制相变 (RPC)技术生产的细晶低碳贝氏体钢回火后组织与性能的变化 ,并与控轧后空冷 (AC)以及传统的再加热淬火工艺 (RQ)得到的钢板的回火组织及性能进行了比较。采用RPC工艺得到的钢板经 5 0 0℃～ 70 0℃回火 1h后 ,随回火温度升高呈现软化 -硬化 -再软化的变化规律 ,采用AC工艺得到的钢板回火后硬度和强度的反复变化不明显 ,而经过RQ处理后的钢板随回火温度升高强度和硬度则单调下降。RPC和RQ钢板回火前的组织均为板条状贝氏体和少量粒贝的复合组织。回火后RPC钢板组织变化不明显 ,而RQ钢板随回火温度的升高板条很快消失 ,最终演变成多边形铁素体。实验结果表明 ,RPC钢板具有良好的热稳定性。

The microstructures and mechanical properties of an ultra fine low carbon bainitc steel processed by relaxation-precipitation controlling(RPC) phase transformation technology and tempered at 500℃～700℃ were investigated and were compared with that of the steel processed by reheating and quenching(RQ) and controlled rolling and air cooling(AC) technology.The hardness and strength the relaxed plate tempered at 500℃ to 700℃ for 1h demonstrate a softening-hardening-softening phenomenon. The hardness and strength of plate processed by AC are not obviously changed and that of the plate processed by RQ decrease rapidly as the temperature increases. The main microstructures of RPC steel and RQ steel both are bainite and little granular bainite before tempering. The microstructure of the steel processed by RPC does not change obviously after tempering. Otherwise, the boundary of bainitic laths in steel(processed by RQ) disappear quickly and finally a polygonal ferrite formes as tempering temperature increases. These results indicate that the microstructure of the steel manufactured by RPC technique possess high thermo-stability.