摘要:
通过测量点焊接头的熔核直径、熔透率,检测接头抗剪力、硬度,分析接头显微组织构成及形态,评价DP780冷轧板电阻点焊性能,并给出试验条件下的可焊工艺范围,以及最优工艺参数。结果表明:DP780冷轧板点焊性能良好,当电极压力为3 k N时,焊接电流可取810 k A,焊接时间可取200400 ms,但焊接电流10 k A,焊接时间400 ms不可取;电极压力为4 k N时,焊接电流可取89 k A,焊接时间可取200400 ms,但焊接电流9 k A,焊接时间400 ms不可取;最优工艺参数为焊接电流9 k A,焊接时间300 ms,电极压力4 k N;熔核区显微组织为粗大板条状马氏体+铁素体,马氏体呈现柱状晶形态,热影响区显微组织为块状马氏体+铁素体;母材硬度(HV)为240,熔核区硬度(HV)为420。
Abstract:
In this paper,the spot welding performance of DP780 cold rolled sheet was evaluated by measuring the nugget diameter and penetration rate,detecting the shear force,texting the hardness of the welded joints,amd analyzing the microstructure and morphology,in order to propose the weldable process scope and the optimized technological parameters under test conditions. The result showed that,the spot welding performance of DP780 cold rolled sheet was good. When the electrode pressure was 3 k N,the welding current could be selected from 8 to 10 k A,and the welding time could be selected from 200 ms to 400 ms,while the welding current was 10 k A,then welding time 400 ms could not be selected. When the electrode pressure was 4 k N,the welding current could be selected from 8 to 9 k A,the welding time could be selected from 200 ms to 400 ms,while the welding current was 9 k A,then welding time 400 ms could not be selected.The optimized technological parameters under test conditions are as follows: welding current 9 k A,welding time 300 ms,electrode pressure 4 k N.Microstructural observation showed that; nugget zone was composed of coarse lath martensite and ferrite,the martensite presented columnar morphology,the microstructure of HAZ was blocky martensite and ferrite; the hardness in base metal and nugget zone were 240 HV and 420 HV,respectively.
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