模拟过火后汽车结构钢DP780的组织演变及力学性能变化  

Microstructure evolution and mechanical properties changes of automotive structural steel DP780 after simulated post-fire

作　　者：王为民 亓海全 笪仲钟[1,2] 李文通 万宇 郭春成 刘安奇 韩向楠 WANG Wei-min;QI Hai-quan;DA Zhong-zhong;LI Wen-tong;WAN Yu;GUO Chun-cheng;LIU An-qi;HAN Xiang-nan(School of Materials Science and Engineering,Guilin University of Technology,Guilin 541004,China;Key Laboratory of Nonferrous Metals and Materials Processing New Technology,Ministry of Education,Guilin University of Technology,Guilin 541004,China)

机构地区：[1]桂林理工大学材料科学与工程学院,广西桂林541004 [2]桂林理工大学有色金属及材料加工新技术教育部重点试验室,广西桂林541004

出　　处：《材料热处理学报》2024年第1期138-147,共10页Transactions of Materials and Heat Treatment

基　　金：广西科技重大专项(桂科AA22067079)。

摘　　要：采用热处理模拟手段,设定加热温度、保温时间和冷却方式,研究汽车结构钢DP780钢经火灾受热后的组织演变和力学性能变化。结果表明:在200~700℃加热条件下,DP780钢的显微组织均为铁素体和马氏体,但温度升高后,铁素体晶粒长大,马氏体发生再结晶;无论空冷还是水冷,随加热温度的升高,DP780钢的屈服强度和抗拉强度先略有提高后快速下降,伸长率略低于原始母材。在800~1000℃加热条件下,空冷和水冷对DP780钢的组织和性能产生明显影响。800℃加热时,空冷和水冷组织均由原始铁素体、再生铁素体和马氏体构成,但后者马氏体体积分数显著增加,强度远高于前者;900~1000℃加热时,奥氏体晶粒长大,形成粗大的贝氏体和马氏体组织,强度高但塑性低。DP780钢的高温(200~700℃)力学性能与室温力学性能相比,当拉伸温度低于400℃时,强度提高,伸长率降低,高于400℃时强度急剧下降,伸长率升高。结果证实,只要DP780钢在200~1000℃受热,其综合力学性能均会发生下降,这将对采用DP780钢制结构件的事故车辆的继续服役产生一定的安全隐患。By using heat treatment simulation methods,setting heating temperature,holding time and cooling method,the microstructure evolution and mechanical properties changes of automotive structural steel DP780 after being heated in a fire were studied.The results show that the microstructure of the DP780 steel is ferrite and martensite after being heated at 200-700℃,but the ferrite grain grows and martensite recrystallizes after the temperature increases;whether air-cooled or water-cooled,with the increase of heating temperature,the yield strength and tensile strength of the DP780 steel first slightly increase and then rapidly decrease,and the elongation is slightly lower than the original base material.Under heating conditions of 800-1000℃,air cooling and water cooling have a significant influence on the microstructure and properties of the DP780 steel.When heated at 800℃,the air cooling and water cooling microstructure of the steel is composed of original ferrite,regenerated ferrite and martensite,but the volume fraction of martensite in the latter is significantly increased,and the strength is much higher than the former.When heated at 900-1000℃,the austenite grain grows to form coarse bainite and martensite structure with high strength but low plasticity.The mechanical properties of the DP780 steel at high temperatures(200-700℃)were compared to those at room temperature.When the tensile temperature is below 400℃,the strength increases and the elongation decreases,and when the tensile temperature is above 400℃,the strength sharply decreases and the elongation increases.The results confirm that as long as the DP780 steel is heated at 200-1000℃,its comprehensive mechanical properties will decrease,which will pose a certain safety hazard for the continued service of accident vehicles using DP780 steel structural components.

关 键 词：DP780双相钢 力学性能 显微组织 车辆火灾 

分 类 号：TG142.4[一般工业技术—材料科学与工程]