采用X射线衍射仪、扫描电子显微镜、电子万能试验机、洛氏硬度计和冲击试验机等，研究了冷处理温度和保温时间对M35高速钢显微组织和性能的影响。结果表明:冷处理使M35钢中一次碳化物数量减少、二次碳化物弥散析出;随着冷处理温度的降低，碳化物分布较均匀、尺寸增大;随着冷处理时间的延长，二次碳化物数量增多、聚集程度增大;冷处理温度和保温时间对钢回火后硬度的影响较小，但对冲击韧性和抗弯强度的影响较大;冷处理温度越低，钢的冲击韧性和抗弯强度越高，-190℃冷处理2 h的钢冲击韧度和抗弯强度分别为62.3 J/cm²和4 950 MPa;随着冷处理时间的延长，钢的冲击韧性先升高后降低、抗弯强度逐渐升高，-90℃冷处理6 h的钢冲击韧度最高，为57.3 J/cm²,-90℃冷处理10 h的钢抗弯强度最高，为4 810 MPa。

Effects of cryogenic treatment temperatures and times at the temperature on microstructure and properties of M35 high speed steel were investigated by X-ray diffractometer,scanning electron microscope,universal tensile tester,Rockwell hardness tester and impact tester.The results showed that(a) the cryogenic treatment caused primary carbides to reduce in amount and secondary carbides to precipitate dispersively in the M35 steel;(b) with the decrease in cryogenic treatment temperature,the carbides exhibited a more uniform distribution and an increase in size;(c) with the extension of cryogenic treatment time,the secondary carbides increased in both amount and aggregation degree;(d) the temperature and time of cryogenic treatment had less effect on the hardness and more significant effect on both impact toughness and bending strength for the steel after tempering;(e) the lower the cryogenic treatment temperature,the higher the impact toughness and bending strength were,the impact toughness and bending strength of the steel cryogenically treated at -190 ℃ for 2 h were 62. 3 J/cm² and 4 950 MPa,respectively;(f) with the extension of cryogenic treatment time,the impact toughness of the steel increased at first and then decreased,and its the bending strength increased gradually,the steel cryogenically treated at 90 ℃ for 6 h exhibited impact toughness as the highest as 57. 3 J/cm²,and the steel cryogenically treated at -90 ℃ for 10 h exhibited bending strength as the largest as 4 810 MPa.