冷作模具钢7Cr7Mo2V2SiNi棒材低倍组织异常分析及退火工艺改进

Analysis on Abnormal Macrostructure of 7Cr7Mo2V2SiNi Cold Work Die Steel Bar and Improvement on Its Annealing Process

采用880℃×20h退火的7Cr7Mo2V2SiNi棒材的低倍组织出现明暗相间的似粗晶的组织,金相观察组织为黑白交替的正常粒状珠光体(暗处)和异常铁素体(亮处)。经分析得出,由于退火温度高和保温时间短,导致出现了没有析出粒状碳化物的铁素体组织。通过降低退火温度至780℃和延长保温时间至45h,消除了低倍异常组织,获得了均匀分布的粒状珠光体组织。

The alternating bright and dark structure similar to coarse grains was found on the macrostructure of 7Cr7Mo2V2SiNi bar after annealed at 880℃×20h,and metallographic observation showed that the structure was alternatively distributed normal globular pearlite(dark)and abnormal ferrite(bright).Analysis showed that the ferrite without globular carbide precipitation was caused by higher annealing temperature and shorter holding time.By decreasing the annealing temperature to 780℃and prolonging the holding time to 45h,the abnormal macrostructure can be eliminated,and the uniform globular pearlite can be obtained.