加热时间对镀锌高强钢板液态金属脆性的影响  

Effect of heating time on liquid metal embrittlement of galvanized steel sheet

作　　者：范金卓 任英[2] 任强 张立峰 FAN Jin-zhuo;REN Ying;REN Qiang;ZHANG Li-feng(School of Mechanical Engineering,Yanshan University,Qinhuangdao 066004,Hebei,China;School of Metallurgy and Ecological Engineering,University of Science and Technology Beijing,Beijing 100083,China;School of Mechanical and Materials Engineering,North University of Technology,Beijing 100114,China)

机构地区：[1]燕山大学机械工程学院,河北秦皇岛066004 [2]北京科技大学冶金与生态工程学院,北京100083 [3]北方工业大学机械与材料工程学院,北京100114

出　　处：《钢铁》2023年第5期124-130,共7页Iron and Steel

基　　金：河北省省级科技计划资助项目(20311004D)。

摘　　要：电阻焊接技术是汽车车身结构和零件拼接的主要连接技术。但是镀锌高强钢板材在电阻焊接过程中会发生液态金属脆现象,造成焊点开裂。为了改善DH980镀锌高强钢板的液态金属脆性断裂难题,研究了加热时间对DH980镀锌高强钢板拉伸脆性断裂的影响机理。采用高温拉伸试验模拟镀锌高强钢板电阻焊接的过程,在800℃下分别对镀锌高强钢和不镀锌高强钢进行拉伸试验。试验结果表明,镀锌高强钢试样的抗拉强度小于不镀锌试样的抗拉强度。在800℃下对镀锌高强钢试样分别保温10、20、30、40 s后拉伸,发现保温10、30、40 s的试样的抗拉强度比不保温试样的抗拉强度大。使用扫描电子显微镜观察拉断后样品的微观相貌和镀层变化情况,发现拉断后的试样的镀锌层主要由α(Zn)+L相和α(Zn)相组成。α(Zn)+L相为α(Zn)与液态锌的混合相,使得镀锌高强钢在拉伸试验过程中存在液态金属。同时,镀锌高强钢试样收到拉伸应力的作用,满足了液态金属脆现象发生的条件,即存在液态金属且钢基体受到拉伸应力的作用。因此在800℃下对DH980镀锌高强钢进行拉伸试验会发生液态金属脆现象。随着保温时间的延长,靠近钢基体位置的α(Zn)+L相逐渐转变为α(Zn)相。α(Zn)相在800℃下为固态,可以避免钢基体与液态锌接触。因此,增大保温时间可以对DH980镀锌钢板的液态金属脆起到一定的抑制作用。Resistance welding technology is the main connection technology of automobile body structure and parts splicing.However,liquid metal embrittlement will occur in the resistance welding process of galvanized high-strength steel sheet,which will cause weld joint cracking.In order to improve the problem of liquid metal brittle fracture of DH980 high strength galvanized steel sheet,the influence mechanism of heating time on tensile brittle fracture of DH980 high strength galvanized steel sheet was studied.High temperature tensile test is used to simulate the process of resistance welding of galvanized high strength steel plate.The experimental results show that the tensile strength of the galvanized high-strength steel sample is less than that of the non galvanized sample.At 800℃,the galvanized high-strength steel samples were insulated for 10,20,30 and 40 s respectively,and then stretched.It was found that the tensile strength of the samples insulated for 10 s,30 s and 40 s was greater than that of the samples without insulation.The scanning electron microscope was used to observe the micro appearance and coating change of the sample after tensile fracture.It was found that the zinc coating of the sample after tensile fracture was mainly composed ofα(Zn)+L phase sumα(Zn)phase composition.α(Zn)+L phase isα.The mixed phase of(Zn)and liquid zinc makes the galvanized high-strength steel have liquid metal during the tensile test.At the same time,the galvanized high-strength steel sample is subject to tensile stress,which meets the conditions for the occurrence of liquid metal brittleness,that is,there is liquid metal and the steel matrix is subject to tensile stress.Therefore,liquid metal embrittlement will occur when DH980 galvanized high strength steel is tensile tested at 800℃.With the increase of the heating time,theα(Zn)+L phase near the steel matrix gradually transformed intoα(Zn)phase.Theα(Zn)phase was solid at 800℃,which avoided the contacting of the steel matrix and the liquid Zn.Therefore,the increa

关 键 词：DH980钢 高强钢 镀锌钢 液态金属脆 高温拉伸 

分 类 号：TG142.1[一般工业技术—材料科学与工程]