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Open AccessArticle

Effect of Weld Current on the Microstructure and Mechanical Properties of a Resistance Spot-Welded TWIP Steel Sheet

Engineering Faculty, Mechanical Engineering Department, Uludag University, 16059 Gorukle-Bursa, Turkey
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Metals 2017, 7(12), 519; https://doi.org/10.3390/met7120519
Received: 30 September 2017 / Revised: 1 November 2017 / Accepted: 14 November 2017 / Published: 23 November 2017
(This article belongs to the Special Issue Alloy Steels)
In this study the effect of the weld current on the microstructure and mechanical properties of a resistance spot-welded twinning-induced plasticity (TWIP) steel sheet was investigated using optical microscopy, scanning electron microscopy–electron back-scattered diffraction (SEM–EBSD), microhardness measurements, a tensile shear test and fractography. Higher weld currents promoted the formation of a macro expulsion cavity in the fusion zone. Additionally, higher weld currents led to a higher indentation depth, a wider heat-affected zone (HAZ), coarser grain structure and thicker annealing twins in the HAZ, and a relatively equiaxed dendritic structure in the centre of the fusion zone. The hardness values in the weld zone were lower than that of the base metal. The lowest hardness values were observed in the HAZ. No strong relationship was observed between the hardness values in the weld zone and the weld current. A higher joint strength, tensile deformation and failure energy absorption capacity were obtained with a weld current of 12 kA, a welding time of 300 ms and an electrode force of 3 kN. A complex fracture surface with both brittle and limited ductile manner was observed in the joints, while the base metal exhibited a ductile fracture. Joints with a higher tensile shear load (TSL) commonly exhibited more brittle fracture characteristics. View Full-Text
Keywords: TWIP steel; resistance spot welding; weld current; microstructure; mechanical properties; fractography TWIP steel; resistance spot welding; weld current; microstructure; mechanical properties; fractography
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Tutar, M.; Aydin, H.; Bayram, A. Effect of Weld Current on the Microstructure and Mechanical Properties of a Resistance Spot-Welded TWIP Steel Sheet. Metals 2017, 7, 519.

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