Q345/40Cr钢双金属环件的热处理工艺及组织性能

对热辗扩Q345钢/40Cr钢双金属环件进行860～950℃淬火和520～610℃回火处理，并对热处理后的组织和性能进行了观察、分析和测试。双金属环件在890℃淬火后，进行不同温度回火，测试其力学性能。结果表明，淬火后晶粒细化，随着淬火温度的升高，晶粒变大。40Cr钢硬度先下降后升高，Q345钢硬度稍微下降，结合层靠近40Cr钢一侧硬度先下降后升高，靠近Q345钢一侧硬度下降。在860℃淬火时，40Cr钢一侧合金元素未完全溶解，在890℃淬火效果最佳。随着回火温度的升高，双金属环件的抗拉强度和硬度下降；40Cr钢的伸长率提高，Q345钢和结合层的伸长率先升高后降低；双金属环件的冲击性能提高。结合层断口在Q345钢一侧。双金属环件在890℃淬火、550℃回火后综合性能最好，可以满足实际使用要求。

Heat treatment process and microstructure and properties of Q345/40Cr bimetal ring

Rolled Q345/40Cr bimetal rings were quenched at 860-950 ℃ and tempered at 520-610 ℃, the microstructure and properties after heat treatment was observed, analyzed and tested. The results show that the grains are refined after quenching, and coarsened with the increase of quenching temperature. The hardness of the 40Cr steel and hardness of its adjacent bonding layer decreases first and then increases, while the hardness of the Q345 steel decreases slightly, and the hardness of its adjacent bonding layer decreases. The alloying elements in the 40Cr steel side dissolves incompletely when quenched at 860 ℃, and the optimal quenching temperature is 890 ℃. The results of mechanical properties tests show that after 890 ℃ quenching and with the increase of tempering temperature, the tensile strength and hardness of the bimetal ring decrease, the elongation of the Q345 steel and its adjacent bonding layer increases first and then decreases, and the impact property of the bimetal ring is improved. The fracture position of bonding layer is on the side of Q345 steel. The comprehensive performance of the bimetal ring is the best after quenching at 890 ℃ and tempering at 550 ℃, which meets the practical application requirements.