超高强度M54钢的预备热处理

Pre-heat treatment process of ultra high strength M54 steel

通过SEM、XRD、硬度及奥氏体含量测试等方法对超高强度M54钢预备热处理工艺进行了研究。结果表明：随着奥氏体化温度的提高,合金元素的未溶碳化物逐渐溶解,基体合金元素及碳元素含量提高,相应的硬度提高,当奥氏体化温度为840℃时,未溶相的残留最多,硬度最低,因此预备热处理最佳的奥氏体化温度为840℃;在630～690℃范围内退火,随着退火温度的升高,残留/逆转变奥氏体稳定性下降,退火后形成未回火的二次马氏体,硬度逐渐上升,因此退火最佳温度为630℃。630℃下退火,时间超过12 h后,硬度低于40 HRC,符合技术加工条件要求,因此,最佳预备热处理工艺为奥氏体化温度选择840℃,退火温度在630℃左右,退火时间应不低于12 h。

The pre-heat treatment process of ultra high strength M54 steel was studied by means of SEM,XRD,hardness and austenite content test. The results show that as the austenitizing temperature increases,the carbides of the alloying elements gradually dissolve,the matrix alloy elements and carbon elements increase,and the corresponding hardness increases. When the austenitizing temperature is 840 ℃,the amount of the undissolved carbides remains the most and the hardness is the lowest. Therefore,the optimum austenitizing temperature for the pre-preliminary heat treatment is 840 ℃. When annealed in the range of 630 ℃ to 690 ℃,with the increase of annealing temperature,the stability of the retained and the reverse transformation austenite is reduced,and the untempered secondary martensite formed during the annealing process makes the hardness gradually rise. Therefore,the optimum temperature for the annealing process is 630 ℃. When annealed at 630 ℃ for 12 h,the hardness of the steel can be below 40 HRC,which meet the requirements of technical processing conditions.Therefore,the optimum preliminary heat treatment process is 840 ℃ for the austenitizing temperature,630 ℃ for the annealing temperature,and no less than 12 h for the annealing time.