波纹管内高压成形焊接区变形特征研究

准确建立焊接管材母材、热影响区和焊缝的材料力学模型,是焊接波纹管内高压胀形工艺分析的前提条件。基于焊接区单向拉伸试验和硬度测试等条件建立焊接区混合材料准则,确定了热影响区和焊缝的材料力学模型。通过波纹管液压胀形工艺仿真与试验,研究胀形液体压力和凹模初始高度等工艺参数对波纹管变形特征的影响,并结合变形前后的组织分析发现,焊接区的枝状晶组织使成形后波纹管焊接区与母材壁厚存在差异,并且变形后马氏体相的存在促进裂纹的形核,引起后期使用中的应力腐蚀破裂。

Research on the Deformation Feature of Welded Zone in Hydroformed Bellows

It is the prerequisite for analyzing bellows internal high pressure bulging to create the material and mechanical model precisely for welded tube including parent metal, heat affected zone and welded bead. In this study, the material model was created by a mixture material criterion based on the uniaxial tensile test and microhardness test of welded zone. The influence of internal pressure and die parameters on the deformation feature of tube was studied by the hydroforming test and numerical simulation. Microstructure analysis shows that the dendritic crystal in welded zone makes thickness difference between parent metal and welded zone after bulging, and martensite appeared after deformation can promote the formation of crack and induce the stress corrosion cracking of bellows in later use.