Resistance spot weldability of lightweight steel with a high Al content

• Published in: Metals and materials international Vol. 23; no. 2; pp. 341 - 349
• Main Authors: Hwang, Insung, Kim, Dongcheol, Kang, Munjin, Kwak, Jae-Hyun, Kim, Young-Min
• Format: Journal Article
• Language: English
• Published: Seoul The Korean Institute of Metals and Materials 01.03.2017; Springer Nature B.V; 대한금속·재료학회
• Subjects: Acceptability; Alternating current; Characterization and Evaluation of Materials; Chemistry and Materials Science; Direct current; Ductile fracture; Ductility; Electrodes; Engineering Thermodynamics; Ferrite; Fracture surfaces; Heat affected zone; Heat and Mass Transfer; Lightweight; Machines; Magnetic Materials; Magnetism; Manufacturing; Martensite; Materials Science; Mechanical properties; Metallic Materials; Microstructure; Processes; Research methodology; Scanning electron microscopy; Shear strength; Shear tests; Solid Mechanics; Steel; Weight reduction; Weld metal; Weldability; Welding; Welding current; Welding machines; 재료공학; welding; microstructure; scanning electron microscopy (SEM); lightweight steel; high aluminum content
• ISSN: 1598-9623; 2005-4149
• DOI: 10.1007/s12540-017-6349-x

Using alternating current (AC)- and direct current (DC)-type welders, the resistance spot weldability of lightweight steel was evaluated under various electrode forces, welding currents, and times. The acceptable welding conditions were specified; however, these had very narrow ranges and there was little difference between the conditions determined for the AC- and DC-type welding. In both types of welding with electrode forces of of 300 kg f and 400 kg f , the acceptable weld currents were 5.0 kA and 5.5 kA, respectively. Also, the nugget size increased with the welding current. Under the acceptable welding conditions, there were no significant changes in the maximum tensile shear strength and nugget size, as 6.4-6.6 kN and 4.1-4.3 mm, respectively. The microstructure of weld metals was consisted of martensite, austenite and ferrite. And the small fraction of martensite was founded in the heat affected zone (HAZ), therefore the weld metal had the greatest hardness, and HAZ softening did not occur in this study. Considering the fracture surface, cleavage and ductile fracture were investigated because of the existence of martensite and ferrite in the welds.