Continuous Cooling Phase Transformation Behavior of 40Cr13 Plastic Mold Steel

doi:10.20057/j.1003-8620.2024-00007

Abstract

Abstract: The continuous cooling phase transformation behavior has important guiding significance for formulating the heat treatment process of steel. In this paper， the thermal expansion method was used to measure the continuous cooling phase transformation curves of 40Cr13 mold steel at different cooling rates （0.5 ℃/s-20 ℃/s）. The microstructure and Vickers hardness of the material after phase transformation at different cooling rates were analyzed using scanning electron microscopy and microhardness tester， The phase transition behavior of 40Cr13 mold steel was observed in situ under high-temperature confocal laser microscopy （HTCLSM）. The results showed that the critical transition point A_c1 was 836 ℃ and A_c3 was 903 ℃； Martensite transformation occured in the cooling rate range of 0.5 ℃/s-20 ℃/s. As the cooling rate increased， the distribution of carbides in the steel became more uniform. When the cooling rate increased from 0.5 °C/s to 3 °C/s， the average hardness value of the sample increased from 417 HV to 550 HV. As the cooling rate continued to increase， the average hardness value of the sample finally stabilized at 560-580 HV. When the cooling rate was 3 °C/s， it was observed under HTCLSM that the starting temperature of martensite transformation was 214.5 °C. As the temperature decreased， the number of martensite increased， and the martensite laths grow in different directions and the thickness of the laths in the same direction decreased.

Key words: Plastic Mold Steel, 40Cr13, CCT Curve, HTCLSM, Martensitic Transformation

摘要： 连续冷却相变行为对制定钢的热处理工艺具有重要指导意义，采用热膨胀法开展了40Cr13模具钢不同冷却速率（0.5 ~ 20 ℃/s）连续冷却相变曲线的测定，利用扫描电镜和显微硬度仪分别对不同冷速下相变后的材料组织形貌和维氏硬度进行检测分析，在高温共聚焦激光显微镜（HTCLSM）下对其相变行为进行原位观察，结果表明，40Cr13模具钢的临界转变点A_c1为836 ℃，A_c3为903 ℃；在 0.5 ~ 20 ℃/s 的冷却速率范围内均出现马氏体相变，随着冷速增加，钢中碳化物的分布更加均匀。当冷速由0.5 ℃/s增大到3 ℃/s时，样品平均硬度值由417 HV提高到550 HV，随着冷速继续增加，样品平均硬度值最终稳定在560～580 HV。对冷却速率（v）和维氏硬度（Hv）进行拟合，拟合公式为H_v=564.49-185.78/exp(v-1.88)。当冷却速率为3 ℃/s时，HTCLSM下观察到马氏体开始转变温度为214.5 ℃，随着温度降低马氏体数量增加，马氏体板条沿不同方向生长，且同方向的板条厚度减小。

关键词: 塑料模具钢, 40Cr13, 连续冷却转变曲线, 高温激光共聚焦, 马氏体相变

CLC Number:

TG142

Su Mengmeng, Chen Wei, Tang Jiali, Zhong Liangmei, Xu Xiangyu, Fu Jianxun. Continuous Cooling Phase Transformation Behavior of 40Cr13 Plastic Mold Steel[J]. Special Steel, 2024, 45(5): 113-118.

苏蒙蒙, 陈炜, 唐佳丽, 钟亮美, 徐翔宇, 付建勋. 40Cr13塑料模具钢连续冷却相变行为[J]. 特殊钢, 2024, 45(5): 113-118.

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