冷却速率对新型高硬度预硬化塑料模具钢组织和性能的影响

Effect of cooling rate on microstructure and properties of new high hardness pre-hardening plastic mould steel

采用Formast-FII热膨胀仪测定了新型高硬度预硬化塑料模具钢3Cr2MnNiMoV在不同冷速下的连续冷却转变曲线(CCT)并采用光学显微镜、扫描电镜以及显微硬度仪等观察分析了试验钢的组织和硬度。结果表明:冷却速率为0.03~0.15℃/s,3Cr2MnNiMoV钢中相变主要产物为贝氏体;冷却速率为0.3~16℃/s时,相变主要产物为马氏体;冷却速率在0.03~0.3℃/s变化范围内时,随冷速的增加,试验钢的显微硬度增加,贝氏体铁素体由等轴状变为板条状生长,最终合并成块状铁素体;等轴铁素体长大合并形成的块状铁素体中马奥岛尺寸大、数量少、排列不规则;板条铁素体长大合并形成的块状铁素体中马奥岛尺寸小,数量多、以平行方式排列;当冷速在0.3~16℃/s时,冷却速率对试验钢的马氏体转变以及硬度没有影响。

The continuous cooling transition(CCT)curves of a new type of high hardness pre-hardening plastic mould steel 3 Cr2 MnNiMoV at different cooling rates was measured by Formast-FII thermal expansion instrument and the microstructure and hardness of the steel were analyzed by means of optical microscope,scanning electron microscopy and microhardness test.The results show that the main transformation product of the steel is bainite when the cooling rate is 0.03-0.15℃/s,and turns to martensite when the cooling rate is 0.3-16℃/s.When the cooling rate is in the range of 0.03-0.3℃/s,with the increase of the cooling rate,the microhardness of the steel increases,and the bainitic ferrite grows from equiaxed to lath,and finally merges into a massive ferrite.In the massive ferrite formed by equiaxed ferrite growth,the size of the M-A island is large,the quantity is small,and the arrangement is irregular.In the massive ferrite formed by lath ferrite growth,the M-A island is small in size,large in quantity,and arranged in parallel.When the cooling rate is 0.3-16℃/s,the cooling rate has no effect on the martensite transformation and hardness of the steel.