Study on Pulsed Gas Tungsten Arc Lap Welding Techniques for 304L Austenitic Stainless Steel

• Published in: Crystals (Basel) Vol. 14; no. 8; p. 715
• Main Authors: Jiang, Yi, Wu, Jiafeng, Zhou, Chao, Han, Qingqing, Hua, Chunjian
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.08.2024
• Subjects: Austenite; austenitic stainless steel; Austenitic stainless steels; Austenitizing; Base metal; Corrosion resistance; Crystal defects; Dimpling; Ductile fracture; Electrodes; Engineering; Ferrite; Gas tungsten arc welding; Grain size; heat input; Iron compounds; Lap joints; Lap welding; Liquefied natural gas; Mechanical properties; mechanical property; Metal industry; Methods; Microhardness; Microstructure; Morphology; P-GTAW; Phase transitions; Stainless steel; Stress concentration; Tensile strength; Tensile tests; Weld defects; weld formation; Welded joints; Welding; Welding parameters; X-ray diffraction; China; Germany
• ISSN: 2073-4352; 2073-4352
• DOI: 10.3390/cryst14080715

The lap welding process for 304L stainless steel welded using the pulsed gas tungsten arc welding (P-GTAW) procedure was studied, and the effects of the pulse welding parameters (the peak current, background current, duty cycle, pulse frequency, and welding speed) on the macroscopic morphology, microstructure, and mechanical properties of the resultant lap joints were investigated. Tensile tests, hardness measurements, and SEM/EDS/XRD analyses were conducted to reveal the characterization of the joint. The relationships between the welding parameters; certain joint characteristic dimensions (the weld width, D; the weld width on the lower plate, La; the weld depth on the lower plate, P; and the minimum fusion radius, R); and the maximum tensile bearing capacity were studied. The weld zone was primarily composed of vermicular ferrite, skeletal ferrite, and austenite, and no obvious welding defects, precipitation, or phase transformations were evident in the weld. Microhardness tests demonstrated that the weld microhardness was highest in the base metal zone and lowest in the weld zone. As the heat input increased, the average microhardness decreased. The hardness difference reached 17.6 Hv10 due to the uneven grain size and the transformation of the structure to ferrite in the weld. The fracture location in welded joints varied as the heat input changed. In some parameter combinations, the weld tensile strength was significantly higher than that of the base material, with fractures occurring in the weld. Scanning electron microscopy results exhibited an obvious dimple morphology, which is a typical form of ductile fracture. XRD revealed no significant phase changes in the weld zone, with a higher intensity of the austenite diffraction peaks compared to the ferrite diffraction peaks.