不锈钢母材及其焊缝金属材料单拉本构关系研究

为研究国产双相型S22053和奥氏体S30408不锈钢母材及其焊缝金属材料的单拉本构关系和破坏模式，对4组共12个材性试样进行了单向拉伸试验，并对其破坏截面进行了电镜扫描。基于试验曲线，利用修正的Ramberg-Osgood （R-O）模型对材料本构关系参数进行了拟合，进而对不锈钢母材和焊缝金属的单拉本构关系进行了对比分析。结果表明：不锈钢母材和焊缝金属材料均发生韧性破坏，其本构关系都表现出明显的非线性；焊缝金属材料的屈服强度和极限强度均高于不锈钢母材，而延性低于母材；修正的R-O模型与母材和焊缝金属材料试验曲线吻合良好；在焊缝连接承载力精确分析中，应考虑焊缝金属材料与母材本构关系的差异，分别使用相应的本构关系模型。

RESEARCH ON THE TENSILE STRESS-STRAIN RELATION OF STAINLESS STEEL BASE MATERIAL AND ITS WELD METAL MATERIAL

To study the tensile stress-strain relation and the failure mechanism of two stainless steel types (duplex grade S22053 and austenitic grade S30408 stainless steel made in China) and the corresponding weld metals, tensile tests were conducted on four groups of test specimens including three duplicate specimens in each. The fracture micro-mechanism was analyzed by using the scanning electron microscopy (SEM) on the fracture surfaces of the specimens. Based on the experimental stress-strain curves, the parameters of the material constitutive models were obtained by curve-fitting using the modified Ramberg-Osgood equations. Comparisons of the tensile stress-strain relation were made between the base metal and weld metal. The results indicated that both base metal and weld metal fractured in a ductile manner, and their stress-strain relations exhibited significant nonlinearity. Compared with the base metal, the weld metal had a higher yield strength and ultimate tensile strength, but lower ductility. The stress-strain relations of the base metal and the weld metal obtained in the tests can be well fitted by the modified Ramberg-Osgood equations. The differences of stress-strain relation between base metal and weld metal should be taken into consideration, and the corresponding constitutive model should be used separately in the accurate load capacity analysis of welded stainless steel connections.