摘要
使用热膨胀仪测定碳元素质量分数分别为0.36%、0.46%和0.74%的三种Cr-Mo-V系模具钢的连续冷却转变曲线,并结合光学显微镜(OM)、扫描电镜(SEM)及显微硬度仪分析碳元素对相变点、连续转变规律、组织以及硬度的影响。结果表明:随着碳含量的增加,三种钢的Ac_1点差别不大,Ac_(cm)点和M_s点则明显降低,0.46C和0.74C钢的Ac_(cm)点分别比0.36C钢降低了24℃和62℃,M_s点分别降低了39℃和109℃。在1 030℃下,三种钢均发生珠光体、贝氏体、马氏体相变。随着碳含量的提高,未溶碳化物含量增加,珠光体相区和贝氏体相区左移,完全马氏体的相变临界冷速增大,显微硬度也增大。
The continuous cooling transformation(CCT) diagrams of Cr-Mo-V die steels with different carbon contents(0.36%, 0.46% and 0.74%) were measured by dilatometry. The effects of carbon on the CCT diagrams, microstructure and hardness of Cr-Mo-V die steels were studied by optical microscopy(OM), scanning electron microscopy(SEM) and Vickers hardness test. The results show that the Cr-Mo-V die steels with different carbon contents have almost the same Ac_1 temperature, Ac_(cm) and M_s temperatures are decreased obviously. The Ac_(cm) temperatures of 0.46 C and 0.74 C steels are decreased by 24 ℃ and 62 ℃, and the M_s temperatures are decreased by 39 ℃ and 109 ℃ compared to 0.36 C steel, respectively. Three die steels appear pearlitic transformation, bainite transformation and martensitic transformation when austenited at 1 030 ℃. With the increasing of carbon content, the undissolved carbide content increases, the phase regions of pearlite and bainite in CCT curves shift to the left, the critical cooling rates of the complete martensite increase and the microhardness increases.
引文
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