摘要
针对新设计的4140钢在热膨胀仪测定其相变点的基础上,利用Gleeble-3800热力模拟试验机对其进行不同的球化退火(亚温球化退火、逐步冷却球化退火和等温球化退火)热模拟。结果表明,进行亚温球化退火试验时,即使长时间保温,原马氏体区域已经球化,而原贝氏体区域才刚开始球化;进行逐步冷却球化退火试验时,球化率提高至75%,且随着加热温度的升高,片状渗碳体含量增加;等温球化退火工艺试验采用760℃加热+720℃等温时,4140钢球化率可提升至82%,硬度也满足用户≤185 HBW的要求,但微区有碳化物聚集现象,因此根据Thermo-Calc计算4140钢等温转变曲线,在等温球化退火前增加一个700℃的预热段。结合改进后的预热+等温球化退火工艺试验,在现场连续式热处理炉生产线上实现满足设计要求的4140圆钢,球化率≥90%,布氏硬度≤175 HBW,且组织均匀。
Based on the phase transition points of a new designed 4140 steel determined using a dilatometer, the Gleeble-3800 thermal simulator was used to conduct different spheroidizing annealing simulations, including subcritical spheroidizing annealing, step cooling spheroidizing annealing, and isothermal spheroidizing annealing. The results show that during subcritical spheroidizing annealing, even after a long holding time, the original martensitic region is spheroidized, while the original bainitic region just begins to spheroidize. In the step cooling spheroidizing annealing test, the spheroidization rate is increased to 75%, and as the heating temperature increases, the amount of lamellar cementite also increases. For the isothermal spheroidizing annealing process, heating at 760 ℃ followed by isothermal holding at 720 ℃ results in a spheroidization rate of 82%, with hardness meeting the user's requirement of ≤185 HBW. However, localized carbide aggregation is observed. Therefore, based on Thermo-Calc calculations of the isothermal transformation curve for the 4140 steel, a preheating stage at 700 ℃ is added before the isothermal spheroidizing annealing. With the optimized preheating+isothermal spheroidizing annealing process, the continuous heat treatment furnace in the production line successfully produces 4140 round steel that meets the design specifications, achieving spheroidization rate of ≥90%, Brinell hardness of ≤175 HBW, with uniformly distributed microstructure.
作者
陶涛
陈颖
熊兵
赵海洋
张世平
Tao Tao;Chen Ying;Xiong Bing;Zhao Haiyang;Zhang Shiping(Nanjing Iron and Steel Co.,Ltd.,Nanjing Jiangsu 210044,China)
出处
《金属热处理》
CAS
CSCD
北大核心
2024年第12期85-90,共6页
Heat Treatment of Metals
关键词
4140钢
球化退火
球化率
布氏硬度
4140 steel
spheroidizing annealing
spheroidization rate
Brinell hardness
