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采用Gleeble-1500D型热力模拟试验机对DP980钢在不同温度(750,850,950 ℃)下保温2 min,然后以不同的冷速(10,20,50 ℃·s-1)进行冷却,之后进行变形量为0.2%和2%的预应变,再进行170 ℃×20 min的烘烤硬化处理,研究了热处理温度和冷速对DP980钢烘烤硬化性能的影响.结果表明:DP980钢具有较高的烘烤硬化性能,烘烤硬化处理后,铁素体中析出很多尺寸为10~20 nm的析出相;当热处理温度为750 ℃和850 ℃时,烘烤硬化值随冷速的增加先减小后增大;当热处理温度为950 ℃时,烘烤硬化值随冷速增加而先增大后减小;在相同的冷速下,烘烤硬化值受热处理温度的影响很大,且冷速越大,影响也越大;当热处理温度为850 ℃、冷速为50 ℃·s-1时,烘烤硬化值最高,此时的组织为细小的马氏体板条和铁素体.

With the help of Gleeble-1500D thermomechanical simulator, the effects of heat treatment temperature and cooling rate on bake-hardening properties of DP980 steel were studied.The steel was treated at different temperature (750 ℃, 850 ℃ and 950 ℃) for 2 min, and followed by cooling with cooling rates of 10, 20, 50 ℃·s-1;after that, pre-strains were carried out at deformation amounts of 0.2% and 2%, at last the bake-hardening aging process was completed at 170 ℃ for 20 min.The results show that, DP980 steel has higher bake-hardening property because there are a lot of precipitates with size of 10-20 nm in ferrite after bake-hardening treatment;when heat treatment temperature was 750 ℃ and 850 ℃, the bake-hardening value firstly decreased and then increased as the cooling rate increased.But When the heat treatment temperature was 950 ℃, the bake-hardening value exhibited the contrary trend.At the same cooling rate, the bake-hardening value is greatly affected by the heat treatment temperature, and the influence on the bake-hardening value would be greater when the cooling rate more faster.When the heat treatment temperature was 850 ℃ and the cooling rate was 50 ℃·s-1, the highest bake-hardening could be obtained, and the microstructure of the steel was fine martensite laths and ferrite.