316L不锈钢薄板焊缝成形及力学性能研究

Forming and Mechanical Properties of Welds in 316L Stainless Steel Sheet

目的减少1 mm厚度316L不锈钢薄板在焊接生产过程中出现的缺陷等问题,并提高不锈钢薄板焊缝成形质量和焊接接头力学性能。方法采用脉冲激光焊接技术实现对厚度1 mm的316L不锈钢薄板的精确焊接,并利用金相显微镜、维氏硬度计、万能拉伸试验机和扫描电镜对焊缝的表面形貌、微观结构、力学性能、断口形貌进行表征分析。结果当激光功率为403 W、输出电流为150 A、焊接速度为150 mm/min、离焦量为−5.525 mm时,焊缝正反面的形貌规则无缺陷。焊缝区内的微观结构主要由δ-铁素体和奥氏体2种晶粒构成,相较于母材及热影响区,焊缝区晶粒尺寸更细小均匀,平均硬度为156HV,表现出更高的硬度特性。焊接接头的抗拉强度和屈服强度均值分别达到643.28 MPa和305.95 MPa,相对于母材的强度分别提高了7%和49%;平均断后伸长率为37.2%,达到原始母材伸长率的55%;断裂呈现韧性断裂的塑性变形和延展性特征。结论优化调整焊接工艺参数后,1 mm厚度316L不锈钢薄板的焊缝成形质量提高,无缺陷且微观组织分布均匀,焊接接头强度显著提高。

The work aims to reduce problems such as defects in the welding production process of 316L stainless steel sheet with a thickness of 1 mm,and to improve the weld forming quality of stainless steel sheet and the mechanical properties of its welded joints.Pulsed laser welding technology was used to accurately weld 316L stainless steel sheet with a thickness of 1 mm,and the surface morphology,microstructure,mechanical properties and fracture morphology of the welded joints were charac-terized by metallurgical microscope,Vickers hardness tester,universal tensile testing machine and scanning electron microscope for analysis.When the laser power was 403 W,the output current was 150 A,the welding speed was 150 mm/min,and the de-focus amount was−5.525 mm,the morphology of the front and back surfaces of the weld was regular without defects.The mi-crostructure in the weld zone was mainly composed of two grain,δ-ferrite and austenite.The grain in the weld zone was finer and more uniform than that in the base metal and the heat-affected zone,and the average hardness was 156HV,showing higher hardness characteristics.The average tensile strength and yield strength of the welded joints reached 643.28 MPa,305.95 MPa,respectively,increased by 7%and 49%compared with the base material strength.The average elongation after fracture was 37.2%,reaching 55%elongation rate of the original base material.The form of fracture was toughness fracture with characteris-tics of plastic deformation and ductility.After the welding process parameters are optimized and adjusted,the weld forming quality of 316L stainless steel sheet with a thickness of 1 mm is high.There is no defect,the microstructure distribution is uni-form,and the strength of welded joints is significantly improved.