快速加热和短时保温对22MnB5钢组织与性能的影响

将快速加热、短时间保温及快速冷却的快速热处理方法应用于钢的热成形工艺中,利用连续退火试验机对材料热处理过程进行模拟试验,研究不同工艺参数下22MnB5钢相变点的变化规律以及组织与性能的演变规律,并揭示其机理。结果表明,加热速率增大提高了相变点温度,加热温度需要大于950 ℃才能保证完全奥氏体化。传统热成形工艺最终组织为全马氏体结构,而快速热处理工艺为马氏体、贝氏体和未溶碳化物共同组成的组织,且晶粒尺寸从11.50 μm细化至7.60 μm。在1000 ℃保温10 s时力学性能表现较好,此时抗拉强度相较于传统热成形工艺略有提高,且伸长率从6.39%提高至8.44%,产生这种具有优异性能的组织构成的原因与快速加热和短时间保温导致的成分不均匀有关。

Effects of rapid heating and short time holding on microstructure and properties of 22MnB5 steel

Rapid heat treatment method of rapid heating, short time holding and rapid cooling was applied to hot forming process of 22MnB5 steel. The simulation test of material thermal process was carried out by using continuous annealing tester to study the change rule of phase transformation point temperatures and the evolution rule of microstructure and properties of the 22MnB5 steel under different process parameters, and the corresponding mechanisms were revealed. The results show that the increase of heating rate increases the transformation point temperature, and the heating temperature needs to be higher than 950 ℃ to ensure complete austenitization. The final structure resulted by traditional hot forming process is full martensite structure, while that by the rapid heat treatment process is composed of martensite, bainite and undissolved carbide, and the grain size is refined from 11.50 μm to 7.60 μm. The mechanical properties are better when heating at 1000 ℃ for 10 s, the tensile strength is slightly improved compared with that by the traditional hot forming process, and the elongation is increased from 6.39% to 8.44%. The reason for the resulted microstructure with such excellent properties is related to the uneven composition caused by rapid heating and short time heat preservation.