2%铝质量分数超高碳钢的球化退火工艺

Spheroidizing process of ultrahigh carbon steel with 2% aluminum addition

为获得完全球化的超高碳钢组织,基于离异共析转变机制对2%铝质量分数超高碳钢进行球化退火工艺研究。研究发现,由于成分的不均匀性,超高碳钢锻态组织由片层间距不一致的珠光体和网状碳化物组成,单纯使用离异共析工艺无法使其完全球化;2%铝质量分数超高碳钢锻态组织网状碳化物厚度在1μm以下,Acm温度以下正火即可获得片层均匀细小的珠光体并消除网状碳化物;提高正火温度能显著减少正火组织中长条和短棒状碳化物的数量,利于获得较好的球化组织。2%铝质量分数超高碳钢经900~925℃正火后在830℃奥氏体化并在760℃等温4 h后获得了由超细铁素体+细小球状渗碳体组成的完全球化组织。

In order to obtain a fully spheroidizing microstructure,the spheroidizing annealing process for ultra-high carbon steel with 2% aluminum addition（UHCS-2 Al）was studied based on the mechanism of divorced eutectoid transformation. It is found that the forging microstructure of the ultra-high carbon steel with aluminum addition is composed of the pearlite with different interlamellar spacing and the continuous carbide networks due to the inhomogeneity of the composition. It is difficult to make it completely spheroidization only by using divorced eutectoid transformation process. The thickness of carbide networks is below 1 μm,normalizing below Acmtemperature can obtain uniform and fine pearlites and eliminate carbide networks. It can also reduce the number of strip shape carbides in normalizing microstructure by increasing the normalizing temperature,which is beneficial to get better spheroidizing microstructure. The complete spheroidizing microstructure for UHCS-2Al consisted of ultrafine ferrite and fine spherical cementite was obtained after normalizing at 900-925 ℃,austenitizing at 830 ℃ and then isothermal treatment for 4 h at 760 ℃.