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<p>In the present study, resistance spot welding (RSW) with varying weld currents of 7 to 15&#xa0;kA, in steps of 1&#xa0;kA, on DP590 steel sheet of 1.2&#xa0;mm thickness has been carried out to find an optimum current for defect-free welds. Based on the results, it was observed that 9&#xa0;kA is a critical current and failure at 9&#xa0;kA was observed in the base metal in a pull-out failure mode. Below this critical current (9&#xa0;kA), the failure mostly occurred in the nugget in an interfacial failure mode. The temperature measured at the nugget zone was close to 1598&#xa0;°C(1871&#xa0;K ± 5&#xa0;K) at this critical current. EBSD analysis showed that increasing welding current from 7&#xa0;kA to 11&#xa0;kA expanded the heat-affected zone, with 11&#xa0;kA causing significant microstructural changes and defects. Moreover, the EBSD analysis highlighted that RSW current influenced nugget size, austenite grain structure, grain reference orientation deviation (GROD), and the resultant martensite microstructures. The importance of the EBSD was to establish the role of RSW current on the development of martensite and parent austenite microstructure by appropriate reconstruction technique which is not found in the literature. These parameters control mechanical properties and variant selection in rapidly solidified martensite. The variations in grain boundary density and martensitic structure highlighted the influence of welding parameters on mechanical properties. The shear strength values obtained for 9.0&#xa0;kA and 10&#xa0;kA showed very minor difference and were 12.2&#xa0;kN and 13.1&#xa0;kN, respectively. The micro-hardness profile showed around 140% increase in hardness values in the FZ as compared to the base metal. This work uniquely explored the correlation between RSW current, nugget diameter, and microstructural evolution in rapidly solidified martensite.</p>

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Resistance Spot Welding (RSW) of Dual-Phase (DP590) Steel

  • 期刊论文

  • 发表日期：

    2025年10月22日

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  • Vimal Singh,
  • Manish M. Pande,
  • K. Bhanumurthy,
  • Vikram Chavan,
  • Indradev Samajdar

摘要

In the present study, resistance spot welding (RSW) with varying weld currents of 7 to 15 kA, in steps of 1 kA, on DP590 steel sheet of 1.2 mm thickness has been carried out to find an optimum current for defect-free welds. Based on the results, it was observed that 9 kA is a critical current and failure at 9 kA was observed in the base metal in a pull-out failure mode. Below this critical current (9 kA), the failure mostly occurred in the nugget in an interfacial failure mode. The temperature measured at the nugget zone was close to 1598 °C(1871 K ± 5 K) at this critical current. EBSD analysis showed that increasing welding current from 7 kA to 11 kA expanded the heat-affected zone, with 11 kA causing significant microstructural changes and defects. Moreover, the EBSD analysis highlighted that RSW current influenced nugget size, austenite grain structure, grain reference orientation deviation (GROD), and the resultant martensite microstructures. The importance of the EBSD was to establish the role of RSW current on the development of martensite and parent austenite microstructure by appropriate reconstruction technique which is not found in the literature. These parameters control mechanical properties and variant selection in rapidly solidified martensite. The variations in grain boundary density and martensitic structure highlighted the influence of welding parameters on mechanical properties. The shear strength values obtained for 9.0 kA and 10 kA showed very minor difference and were 12.2 kN and 13.1 kN, respectively. The micro-hardness profile showed around 140% increase in hardness values in the FZ as compared to the base metal. This work uniquely explored the correlation between RSW current, nugget diameter, and microstructural evolution in rapidly solidified martensite.