球化退火工艺对渗碳用16MnCr5钢奥氏体晶粒度的影响  

Effect of spheroidization annealing process on austenite grain size of 16MnCr5 steel for carburizing

作　　者：郑晓伟 林再勇 张剑锋 金涛 Zheng Xiaowei;Lin Zaiyong;Zhang Jianfeng;Jin Tao(Wire Institute of Jiangyin Xingcheng Special Steel Co.,Ltd.,Jiangyin Jiangsu 214429,China)

机构地区：[1]江阴兴澄特种钢铁有限公司线材研究所,江苏江阴214429

出　　处：《金属热处理》2023年第5期283-286,共4页Heat Treatment of Metals

摘　　要：为研究16MnCr5钢热轧盘条改制过程中的球化退火对其奥氏体晶粒度的影响,对热轧盘条试样及分别在700、720、740、760、780℃保温5 h的等温球化退火试样进行940±5℃保温1 h水淬处理,测试试样的奥氏体晶粒度并对比分析。结果表明,通过轧制过程采用“双高”工艺(加热温度1200~1250℃,精轧温度950~980℃)及800~600℃之间快冷(采用风冷,冷却速度≥10℃·s^(-1)),保证铝、氮原子处于固溶态,晶粒度检测前的热处理过程中AlN均匀细小析出,使得16MnCr5钢奥氏体晶粒细小均匀。当在700、720℃进行球化退火时,AlN质点均匀细小析出,虽然发生Ostwald熟化长大,但仍小于临界半径,奥氏体晶粒仍细小均匀;随着退火温度的进一步升高,第二相粒子发生Ostwald熟化长大,局部区域的第二相粒子超过其临界半径,局部奥氏体晶粒异常长大而出现混晶。实际生产中,为获得均匀细小的奥氏体晶粒,同时获得良好的球化组织及力学性能,16MnCr5钢采用720℃进行球化退火。通过以上控制轧制过程及球化退火工艺,可实现16MnCr5钢的奥氏体晶粒度7.5~7级,满足奥氏体晶粒度≥5级,且没有混晶的要求。In order to study the effect of spheroidizing annealing on austenite grain size of 16MnCr5 steel hot rolled wire rods during the process of modification,hot-rolled wire rod specimen and specimens isothermally spheroidizing annealed at 700,720,740,760 and 780℃,respectively,for 5 h were subjected to water quenching at 940±5℃for 1 h.The austenite grain size of the specimens was measured and compared.The results show that the“double high”processes(heating temperature of 1200-1250℃,finishing rolling temperature of 950-980℃)and rapid cooling between 800-600℃(air cooling,cooling rate≥10℃/s)are used in the rolling process to ensure that aluminum and nitrogen atoms are in a solid solution state.During the heat treatment process before austenite grain detection,AlN is uniformly and finely precipitated,resulting in fine and uniform austenite grains in the 16MnCr5 steel.When spheroidizing annealed at 700 and 720℃,AlN particles are uniformly and finely precipitated.Although Ostwald aging and growth occur,the AlN particles are still smaller than the critical radius,and the austenite grains are still fine and uniform.With the further increase of spheroidizing annealing temperature,the second phase particles undergo Ostwald aging and growth.The second phase particles in local areas exceed the critical radius,and local austenite grains grow abnormally,resulting in mixed grains.In practical production,in order to obtain uniform and fine austenite grains,as well as good spheroidized microstructure and mechanical properties,16MnCr5 steel is spheroidizing annealed at 720℃.Through the above controlled rolling process and spheroidizing annealing process,the austenitic grain size of 16MnCr5 steel can reach 7.5 grade to 7 grade,meeting the requirements of austenitic grain size≥5 grade and without mixed grains.

关 键 词：16MnCr5钢 球化退火 晶粒度 混晶 

分 类 号：TG142.41[一般工业技术—材料科学与工程] TG156.2[金属学及工艺—金属材料]