冷却工艺对40CrMoNbVTi钢组织和性能的影响

研究了冷却工艺对40CrMoNbVTi钢组织和性能的影响。结果表明,780 ℃淬火油冷、550 ℃回火后试样具有较高的抗拉强度和冲击吸收能量,分别为1250 MPa和78.63 J;20%聚乙二醇商用淬火液冷却后的抗拉强度为1140 MPa,冲击吸收能量为80.7 J;油冷及20%聚乙二醇淬火液冷却后组织为索氏体组织和少量的铁素体。860 ℃淬火雾冷/空冷+550 ℃回火后试样的抗拉强度分别为1010 MPa和945 MPa,冲击吸收能量分别为35.7 J及38.4 J,组织为回火索氏体或粒状贝氏体。780 ℃淬火油冷/商用淬火液冷却是较为合适的淬火冷却工艺。780 ℃淬火油冷/20%聚乙二醇淬火液冷却+550 ℃回火后冲击断裂机制为韧性断裂,860 ℃淬火雾冷/空冷550 ℃回火后冲击断裂机制为脆性断裂,增加淬火冷却速度可以改善冲击断口形貌。

Effect of cooling process on microstructure and properties of 40CrMoNbVTi steel

Effect of cooling process on microstructure and properties of 40CrMoNbVTi steel was studied. The results show that the specimens quenched at 780 ℃, oil cooled and tempered at 550 ℃ have higher tensile strength and impact absorbed energy, which are 1250 MPa and 78.63 J, respectively. After cooling by 20% polyethylene glycol quenching solution, the tensile strength is 1140 MPa, and the impact absorbed energy is 80.7 J. The microstructure is sorbite and a small amount of ferrite after oil cooling and 20% polyethylene glycol quenching solution cooling. The tensile strength of the specimens quenched at 860 ℃, fog cooled/air cooled, and tempered at 550 ℃ is 1010 MPa and 945 MPa respectively, the impact absorbed energy is 35.7 J and 38.4 J, respectively, and the microstructure is tempered sorbite or granular bainite. Quenching at 780 ℃, oil cooling/commercial quenching solution cooling are more suitable quenching cooling processes. The impact fracture mechanism of quenching at 780 ℃, oil cooling/20% polyethylene glycol quenching cooling, tempering at 550 ℃ is ductile fracture, while the impact fracture mechanism of quenching at 860 ℃, fog cooling/air cooling, tempering at 550 ℃ is brittle fracture. Increasing the quenching cooling rate can improve impact fracture morphology.