奥氏体化温度对40CrNiMo钢组织和性能的影响

Effect of austenizing temperature on microstructure and mechanical properties of 40CrNiMo steel

详细研究了奥氏体化温度对中碳调质钢40CrNiMo的淬透性、以0.7℃/s淬火后组织及调质处理后组织和性能的影响。研究结果显示,随着奥氏体化温度从800提高至1 000℃,材料的淬透性逐渐增加,尤其是当奥氏体化温度提高至950℃以后,淬透性增加幅度显著变大。当奥氏体化温度为800℃时,组织中存在相对多的铁素体,使得淬火后材料的硬度较低,但回火后具有最佳的韧性;奥氏体化温度为900℃时,高温回火后试样具有最高的强度,但塑性较低。随着奥氏体化温度的升高,材料的断裂机制发生明显变化,拉伸断裂均为典型韧性断裂,断口均为韧窝组成,而冲击断裂逐渐由韧窝断裂方式转变为解理或准解理断裂方式,当奥氏体化温度超过900℃后,断口形貌以典型河流花样为主。

Effect of austenizing temperature on hardenability,microstructure of 40CrNiMo steel after quenching at a cooling rate of 0.7℃/s and microstructure and mechanical properties of 40CrNiMo steel after tempering was stud-ied.Results showed that with increasing temperature from 800to 1000℃,the hardenability was increased gradual-ly,especially when the temperature exceeded 950℃.When the austenitizing temperature was 800℃,there was some ferrite in the microstructure,resulting in lower hardness but higher toughness.When the austenitizing temper-ature was 900℃,the specimen possessed the highest strength but the ductility was lower.The fracture mechanism was also changed with increasing temperature,especially for impact specimens.All tensile specimens exhibited duc-tile fracture with dimples in the fracture surface.However,impact specimens changed from dimple fracture to cleav-age or quasi-cleavage fracture,with more typical river pattern in the fracture surface when the austenitizing tempera-ture exceeded 900℃.