热处理工艺对铝硅镀层热成形钢组织性能的影响

为深入理解不同热处理工艺参数对铝硅镀层热成形钢组织性能的影响规律,主要研究了加热温度和保温时间对铝硅镀层热成形钢的硬度、微观组织、镀层厚度和镀层成分的影响。结果表明,当加热温度不大于 900 ℃ 时,铝硅镀层热成形钢的硬度随着保温时间的增加而增加;当加热温度大于 900 ℃ 时,铝硅镀层热成形钢的硬度随着保温时间的增加而下降。当加热温度为850~930 ℃,保温时间为 4、8 min 时铝硅镀层热成形钢的微观组织在模具淬火冷却过程中均转化成为马氏体。在相同加热温度下,铝硅镀层热成形钢合金层的厚度随着保温时间的增加而增大,当加热温度升高至 930 ℃ 时,镀层因氧化而挥发严重,导致镀层变薄,所以铝硅镀层热成形钢的加热温度应控制在 930 ℃ 以下。保温温度升高、保温时间增加导致元素扩散显著,聚集的硅元素含量和面积由于其不断向四周扩散而降低。同时铁元素大量扩散到镀层中,镀层中铁元素含量增加显著。高温下,镀层发生明显的氧化反应,氧化反应促进了微孔洞的形核和长大。

Influence of heat treatment process on microstructure and property of Al-Si coated hot forming steel

In order to study the effect of heat treatment process parameters on the microstructure and property of Al-Si coated hot forming steel, the effect of heating temperature and soaking time on hardness, microstructure, layer thickness and layer content of Al-Si-coated hot forming steel was mainly researched. The results show that when heating temperature is not higher than 900 ℃, the hardness of Al-Si-coated hot forming steel increases with the increase of soaking time. When the heating temperature is higher than 900 ℃, the hardness of Al-Si-coated hot forming steel decreases with the increase of soaking time. When heating temperature is 850-930 ℃, and soaking time are 4 min and 8 min, the microstructure transfers to martensite phase during die quenching process. At a constant heating temperature, the layer thickness of Al-Si-coated hot forming steel increases with the increase of soaking time. When the heating temperature increases to 930 ℃, the coating volatilizes seriously due to oxidation, which makes the layer to be thinner. So, heating temperature of Al-Si-coated hot forming steel should be controlled below 930 ℃. The increase of heating temperature and soaking time enhances the element diffusion, so the concentration of Si element continually diffuses around and decreases the content and area of concentrated Si element. At the same time, Fe element diffuses into coating layer significantly and the content of Fe element increases. The coating oxidizes remarkably at elevated temperature. The oxidation accelerates the nucleation and growth of microvoid.