热输入对DP980激光焊组织和力学性能的影响

Effect of heat input on microstructure and mechanical properties of DP980 laser welded steel

为了研究DP980钢的焊接性能,采用3种不同的激光焊接工艺进行焊接试验。结果表明,熔融区为板条马氏体,热影响区为马氏体、铁素体和回火马氏体,随着热输入增加,上下表面的熔宽逐渐增大,强塑积逐渐减小,热影响区的软化程度逐渐恶化。从熔融区到母材,显微硬度的变化趋势是先降低后升高。焊接接头静态拉伸失效位置均在亚临界热影响区,拉伸断口为韧性断口,随着热输入增加,杯状韧窝逐渐转变为较大的抛物线状韧窝,通过分析不同热输入条件下焊接接头的静态拉伸应变场云图,可知在塑性变形阶段,熔融区两侧呈双峰形貌,随着热输入的增加,软化区的面积逐渐增大,颈缩易出现在熔融区两侧的软化区部位。

The microstructure and mechanical properties of laser welded joints of DP980 steel with three different heat inputs were studied. The results show that the fusion zone is lath martensite, the heat affected zone is martensite, ferrite and tempered martensite. With the increase of heat input, the upper and lower width of weld zone increases gradually, the product of strength and elongation decreases gradually, and the softening degree of the HAZ worsens gradually. From the fusion zone to the base metal, the microhardness decreases firstly and then increases. The static tensile failure positions of welded joints are all in sub-critical heat-affected zone, and the tensile fracture are toughness fracture. With the increase of heat input, cup-shaped dimples are gradually transformed into larger parabolic dimples. By analyzing the static tensile strain distribution profile of welded joints with three heat inputs, in the plastic deformation stage, the two sides of the melt zone show a bimodal shape. With the increase of heat input, the area of the softening zone increases gradually. Necking is easy to appear in the soft zone on both sides of the fusion zone.