热处理工艺对35NCD16合金钢组织和性能的影响

Effects of Heat Treatment on Microstructures and Mechanical Properties of 35NCD16 Alloy Steel

研究了热处理工艺对35NCD16合金钢组织和性能的影响,采用金相显微镜、扫描电镜、拉伸实验、硬度实验等设备及实验方法对875℃淬火,550℃、560℃、570℃和580℃不同温度回火后的材料进行组织观察和性能测试,分析其显微组织和力学性能变化规律,从而得出最佳热处理工艺参数.实验结果表明:875℃淬火+高温回火能有效改善35NCD16合金钢的显微组织,在实验温度范围内,35NCD16钢于550℃、560℃发生二次硬化现象,尤以550℃更为显著,此时硬度、抗拉强度、延伸率达到最大值,分别为42.07 HRC、1 309 MPa和15.42%,断口呈微孔聚集型特征,大韧窝中分布着小韧窝;温度超过560℃,则出现过时效现象,580℃时硬度降至35.13 HRC,抗拉强度降至1 048 MPa,延伸率降至12.83%.因此,35NCD16合金钢的最佳热处理工艺为875℃淬火+550℃回火.

In order to research the effects of heat treatment processing on the microstructure and mechanical properties of 35NCD16 alloy steel,the microstructures and properties of the materials after being quenched at 875℃ and tempered at 550 ℃,560 ℃,570 ℃ and 580 ℃,respectively,were observed and tested by metallomicroscope,SEM,tensile testing,hardness testing and fracture scanning.The variation of microstructures and mechanical properties were analysed,and the heat treatment processing was optimized.The results show that the microstructures of 35CND16 alloy steel improved effectively after quenching at 875 ℃ and high temperature tempering.In the range of experimental temperatures,secondary hardening of 35CND16 steel occurred at the temperature of 550 ℃ and 560 ℃,and it is more obvious at 550 ℃.The maximums of the hardness,the tensile strength and elongation are got,namely 42.07 HRC,1 309 MPa and 15.42%,respectively.The fractures are characterized as the type of micropore accumulation,and small dimples are distributed in big dimples.When the temperature is above 560 ℃,the overaging appeared.At 580 ℃,the hardness decreases to 35.13 HRC,the tensile strength is low to 1 048 MPa and elongation is 12.83%.As a result,quenching at 875 ℃ and tempering at 550 ℃ is the best heat treatment processing of 35CND16 alloy steel.