热处理工艺对5Cr5Mo2V钢组织与性能的影响

利用洛氏硬度计及场发射扫描电镜等研究了奥氏体化温度和回火温度对热锻模具用钢5Cr5Mo2V组织和性能的影响。结果表明:试验钢经过不同温度的淬火和回火处理后,组织均为回火马氏体+残留奥氏体+碳化物。当5Cr5Mo2V钢在920~1030 ℃淬火时,随淬火温度升高硬度值增加并于1030 ℃达到最大值62.53 HRC,之后硬度值趋于稳定,且在1030 ℃淬火时晶粒较为细小,超过1030 ℃淬火晶粒开始粗化;试验钢在480~550 ℃回火时,硬度值随回火温度升高逐渐增加,并于550 ℃出现二次硬化峰值,但在此温度下试验钢的冲击性能为最低,此后随回火温度升高冲击性能逐渐增加,当回火温度为600 ℃时,试验钢在维持较高硬度(49 HRC)的同时,冲击吸收能量可达21 J,故5Cr5Mo2V钢的最佳热处理工艺为:1030 ℃淬火30 min后油冷,随后在600 ℃回火(2 h)2次空冷。

Effect of heat treatment process on microstructure and properties of 5 Cr5 Mo2 V steel

Effects of austenitizing temperature and tempering temperature on microstructure and properties of the 5 Cr5 Mo2 V steel for hot forging die were studied by Rockwell hardness tester and field emission scanning electron microscopy. The results show that after different quenching and tempering treatments,the microstructure of all the tested steel specimens is composed of tempered martensite,retained austenite and carbides. When quenched at 920-1030 ℃,the hardness of the 5 Cr5 Mo2 V steel increases with the increase of quenching temperature and reaches the maximum value of 62. 53 HRC at 1030 ℃,and then the hardness tends to be stabilized when quenched above1030 ℃ . The grains are finer when quenched at 1030 ℃,but the grains start to coarsen when the quenching temperature exceeds 1030 ℃ .As tempered at 480-550 ℃,the hardness gradually increases with the increase of tempering temperature and a secondary hardening peak appears at 550 ℃ . The impact absorbed energy of the tested steel is the lowest at 550 ℃,but when the tempering temperature is higher than550 ℃,the impact properties of the tested steel gradually increase. When the tempering temperature is 600 ℃,the steel maintains a relatively high hardness( 49 HRC) and the impact absorbed energy can reach 21 J. It is concluded that the optimum heat treatment process for the 5 Cr5 Mo2 V steel is quenching at 1030 ℃ for 30 min with oil cooling and then tempering twice at 600 ℃ for 2 h with air cooling.