Improvement of Single-Sided Resistance Spot Welding of Austenitic Stainless Steel Using Radial Magnetic Field

2020 ◽  
Vol 143 (3) ◽  
Author(s):  
Lin Qi ◽  
Fangzhou Li ◽  
Qingxin Zhang ◽  
Ye Xu ◽  
Xiaohui Han ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Resistance Spot Welding ◽  
Spot Welding ◽  
Permanent Magnets ◽  
High Strength Steels ◽  
Austenitic Stainless Steels ◽  
Weld Quality ◽  
Radial Magnetic Field ◽  
Resistance Spot ◽  
Welding Processes

Abstract Magnetically assisted resistance spot welding (MA-RSW), which uses a pair of mutually repulsive ring-shaped axially magnetized magnets, has been demonstrated to have significant effect on weld quality of high strength steels and light metals. However, in manufacturing of metro car bodies, single-sided resistance spot welding processes is frequently adopted to achieve better surface quality, which poses a big challenge to the traditional double-sided MA-RSW apparatus. In this study, single-sided MA-RSW apparatus with four arc-shaped radially magnetized permanent magnets was developed to adapt the demand of the single-sided RSW process, and 1.5 + 2.5 mm austenitic stainless steels (ASSs) are used to evaluate its effectiveness in terms of weld quality and surface indentation. Meanwhile, a 3D finite element model taking three types of MA-RSW apparatus into account was created to reveal the improvement mechanism of the single-sided MA-RSW apparatus. The results showed that the novel single-sided MA-RSW apparatus can produce stronger radial magnetic field in effective welding region and thus provide a great potential and promotion effect to the weld quality in terms of macro-morphology, surface indentation, microstructure, microhardness, and mechanical properties.

Expulsion Intensity Monitoring and Modeling in Resistance Spot Welding Based on Electrode Displacement Signals

2020 ◽  
Author(s):  
Yu-Jun Xia ◽  
Yan Shen ◽  
Lang Zhou ◽  
Yong-Bing Li
Keyword(s):  
Resistance Spot Welding ◽  
Spot Welding ◽  
Low Carbon Steel ◽  
Sheet Thickness ◽  
High Strength Steels ◽  
High Strength ◽  
Material Strength ◽  
Low Carbon ◽  
Resistance Spot ◽  
Electrode Displacement

Abstract Weld expulsion is one of the most common welding defects during resistance spot welding (RSW) process especially for high strength steels (HSS). In order to control and eventually eliminate weld expulsion in production, accurate assessment of the expulsion severity should be the first step and is urgently required. Among the existing methods, real-time monitoring of RSW-related process signals has become a promising approach to actualize the online evaluation of weld expulsion. However, the inherent correlation between the process signals and the expulsion intensity is still unclear. In this work, a commonly used process signal, namely the electrode displacement and its instantaneous behavior when expulsion occurs are systematically studied. Based upon experiments with various electrodes and workpieces, a nonlinear relation between the weight of expelled metal and the sudden displacement drop accompanied by the occurrence of weld expulsion is observed, which is mainly influenced by electrode tip geometry but not by material strength or sheet thickness. The intrinsic relationship between this specific signal feature and the magnitude of expulsion is further explored through geometrical analysis, and a modified analytical model for online expulsion evaluation is finally proposed. It is shown that the improved model could be applied to domed electrodes with different tip geometries and varying workpieces ranging from low carbon steel to HSS. The error of expulsion estimation could be limited within ±20.4 mg (±2σ) at a 95% confidence level. This study may contribute to the online control of weld expulsion to the minimum level.

A Comparative Study of AC and MFDC Resistance Spot Welding

2004 ◽  
Author(s):  
Wei Li ◽  
Daniel Cerjanec
Keyword(s):  
Comparative Study ◽  
Resistance Spot Welding ◽  
Spot Welding ◽  
Welding Process ◽  
Welding Current ◽  
Median Frequency ◽  
Resistance Spot ◽  
Secondary Voltage ◽  
Nugget Growth ◽  
Welding Processes

This paper presents a comparative study of the AC and MFDC resistance spot welding process. Two identical welders were used; one with a single phase AC and the other with a median frequency DC weld control. Both welders were instrumented such that the primary and secondary voltage and current could be collected. A nugget growth experiment was conducted to compare the weld size and energy consumption in the AC and MFDC welding processes. It is found that the MFDC process generally produces larger welds with the same welding current. However, this difference is more prominent when the welding current is low. Overall the AC welding process consumes more energy to make a same size weld. The larger the welding current is used, the less efficient the AC process becomes.

scholarly journals Liquid Metal Embrittlement of Galvanized TRIP Steels in Resistance Spot Welding

Metals ◽  
2020 ◽  
Vol 10 (6) ◽  
pp. 787 ◽  
Author(s):  
Wook-Sang Jeon ◽  
Ashutosh Sharma ◽  
Jae Pil Jung
Keyword(s):  
Liquid Metal ◽  
Resistance Spot Welding ◽  
Spot Welding ◽  
High Strength Steels ◽  
High Strength ◽  
Liquid Metal Embrittlement ◽  
Surface Cracks ◽  
Resistance Spot ◽  
Research Activities ◽  
Microscopic Features

Liquid metal embrittlement (LME) in Zn-coated steels is a serious issue in automotive design. The risk of rising LME surface cracks in resistance spot welding (RSW) of Zn-coated high strength steels has triggered significant research activities across the globe. This paper presents a state-of-the-art review of the various phenomena and issues related to LME during RSW. Various aspects of LME surface cracks have been described in this review, focusing on the macro- and microscopic features of LME, spot weld cracks, the sensitivity of the LME cracks towards surface locations, welding conditions, and susceptibility to high strength and galvanized steels. We also focus on the effects of various processing factors, such as temperature, stress, microstructure, and the nature of the galvanized layer, related to studies with actual spot welds LME cracks. Finally, we summarize the possible mechanisms of embrittlement and the remedies for minimizing LME cracks, with suitable guidelines to suppress surface cracks during RSW.

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