Enhanced mechanical properties of martensitic stainless steels resistance spot welds enabled by in situ rapid tempering

Abstract

Resistance spot weldability of martensitic stainless steels is impaired by the formation of brittle martensite in the fusion zone (FZ). In this paper, in situ rapid tempering via applying a second pulse current after a first melting/solidification pulse during resistance spot welding of AISI 420 martensitic stainless steel sheets was used as a pathway to enhance the toughness of the FZ. By using proper second pulse conditions, the FZ with reduced hardness can be generated which is featured by a decomposed martensitic structure with nano-sized carbide precipitations. The improved toughness as a consequence of this modified microstructure resulted in remarkable enhancement of the peak load and energy absorption of the spot welds compared to the singlepulse welds.

Comparative Study of Classification Algorithms for Quality Assessment of Resistance Spot Welding Joints From Pre- and Post-Welding Inputs

“…Manufacturers in the automotive industry face an increasingly competitive environment [1]. Remarkably, resistance spot welding (RSW) is a critical manufacturing technology in such sector [2], [3], since its high speed and adaptability for automation render it suitable for mass production [4]. The number of RSW joints per vehicle is very high (around 5000 according to Xia et al [5]), and there can be significant variability in the quality of each of them due to the fact that RSW is a complex process [6], [7]; more precisely, the heat generated by an electrical current has to be substantial enough to promote local melting and the formation of a weld nugget at the faying interface [8], [9], while at the same time the amount of heat is influenced by the electrical conductivity…”

Effect of Welding Time Variation in Resistance Spot Welding on Mechanical Properties of Dissimilar Joints on Mild Steel and AISI 304 Stainless Steel

“…The automotive industry continues to grow in the face of competitive competition [1]. Resistance spot welding (RSW) is an important manufacturing technology [2][3], its advantages include low cost, high production efficiency, high welding time and adaptability to automation so that it can be used for mass production [4][5]. The characteristics of the resistance spot with dissimilar materials are very decisive to get a good weld joint, welding time, welding current, electrode force, preheat current, and electrode shape are one of the welding parameters, so that welding joints in automotive vehicles become safer as a solution to answer the needs passenger safety [6][7].…”

Comparative Study of Classification Algorithms for Quality Assessment of Resistance Spot Welding Joints From Pre- and Post-Welding Inputs

“…Manufacturers in the automotive industry face an increasingly competitive environment [1]. Remarkably, resistance spot welding (RSW) is a critical manufacturing technology in such sector [2,3], since its high speed and adaptability for automation render it suitable for mass production [4].The number of RSW joints per vehicle is very high (around 5000 according to Xia et al [5]), and there can be significant variability in the quality of each of them due to the fact that RSW is a complex process [6,7]; more precisely, the heat generated by an electrical current has to be substantial enough to promote local melting and the formation of a weld nugget at the faying interface [8,9], while at the same time the amount of heat is influenced by the electrical conductivity of the materials to be joined and by their surface condition, as well as by the thermal conductivity of the electrodes that are water-cooled and act as heat sinks [9].…”