Abstract
The effects of welding current, electrode force, and welding time in a resistance spot weld were studied to investigate the effectiveness of welded joints between a thin EN10130: DC04 material and a thicker 817M40 part, through analysis of the microstructural and mechanical properties. All welded specimens were subjected to tensile testing at room temperature (25°C) and sub-zero temperature (-46°C) to test the strength of the welded joints. No full button failure was observed at either room temperature or sub-zero temperature after optimization of the weldng parameters. The fusion zone was observed to consist mainly of martensitic phase, due to rapid quenching, while the HAZ was composed of clusters of martensite in a ferrite and bainite matrix. The base 817M40 metal remained fully ferritic after welding. The hardness was found to increase with increasing welding current. An increase in nugget size, indicating good fusion of the weld, was observed with an increase in the welding current.
Highlights
817M40 steel, known as EN24T, is a Ni-Cr-Mo high hardenability, high tensile strength, and high wear resistance steel
In the current study we investigated the effects of welding current, welding time, and electrode force on the tensile shear strength of resistance spot welded joints at different temperatures
Tensile properties The influence of welding current, electrode force, and welding time on the nugget diameter, energy absorbed before fracture, as well as the maximum load experienced before fracture are presented in Figure 8 for samples pulled at room temperature and at sub-zero temperature (–46°C)
Summary
817M40 steel, known as EN24T, is a Ni-Cr-Mo high hardenability, high tensile strength, and high wear resistance steel. EN24T can be heat treated to obtain a wide range of improved mechanical properties (Ramazani et al, 2015; Khan et al, 2008; Choi et al, 2011). The most widely used method for joining two different materials such as EN24T and EN1030:DC04 is resistance spot welding (RSW), due to the fact that different configurations can be obtained with this method (Al-Mukhtar and Doos, 2013; Ghazanfari and Naderi, 2013; Wan, Wang, and Zhang, 2014; Pouranvari, 2011). The welding current has been found to be an influential parameter in determining the strength of the weld joint, since an increase in welding current leads to an increased heat flow, which influences the microstructural changes (Ghazanfari and Naderi, 2013; Raut and AchwaL, 2014). The different weld regions whose microstructure impacts the mechanical properties of the welded
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