Research on Spot Welding Process of Hot Galvanizing DP780

In this paper,the spot weldability of hot galvanizing DP780 had been investigated and the spot welding parameters had been optimized.The spot welding performance of hot galvanizing DP780 had been evaluated by measuring the nugget diameter,penetration rate and indentation depth,observing the microstructure,texting the hardness,detecting the shear force and tensile force of welded joints. The result showed that,the spot welding performance of hot galvanizing DP780 was good because of the high alloy content,while the welding process window was narrow.When the electrode pressure was 3.5 kN,and the welding current was 9.5 kA,the welding time could be selected from 300 to 400 ms.When the welding current was 10.5~11. 5 kA,the welding time could be select from 200 to 400 ms. The microstructure of hot galvanizing DP780 weld joint was composed of martensite and ferrite,resulting in a low plasticity ratio of only 10% ~30% and somewhat high hardness.The failure form of welded spot was melt nugget stripping.