scholarly journals Effect of Microstructure and Texture on Mechanical Properties of Resistance Spot Welded High Strength Steel 22MnB5 and 5A06 Aluminium Alloy

Metals ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 685
Author(s):  
Xiaoqing Jiang ◽  
Shujun Chen ◽  
Jinlong Gong ◽  
Zhenyang Lu

The present study aims to investigate the effect of microstructure and texture on mechanical properties of resistance spot welding of high strength steel 22MnB5 and 5A06 aluminium alloy as a function of welding parameters. The pseudo-nugget zones (NZs) at the steel side have undergone full recrystallisation with a fine-grained ferrite structure containing a small amount of retained austenite and a high hardness of approximately 500 HV, which is a 35% increase in hardness compared to the base material (BM) with fine lath martensitic structure. The NZs at the Al side contain both a recrystallisation texture and shear texture. Higher tensile shear strength with increasing weld time could be linked to the random texture at the Al side. The highest tensile shear strength was achieved at an intermetallic layer thickness of 4 mm.

Author(s):  
Abozar Barimani-Varandi ◽  
Abdolhossein Jalali Aghchai

The present work studied the enhancement of the tensile shear strength for joining AA6061-T6 aluminium to galvanized DP590 steel via electrically-assisted mechanical clinching (EAMC) using an integrated 2D FE model. To defeat the difficulties of joining low-ductility aluminium alloy to high-strength steel, the electroplastic effect obtained from the electrically-assisted process was applied to enhance the clinch-ability. For this purpose, the results of experiments performed by the chamfering punches with and without electrically-assisted pre-heating were compared. Joint cross-section, failure load, failure mode, fracture displacement, material flow, and failure mechanism were assessed in order to study the failure behaviour. The results showed that the joints clinched at the EAMC condition failed with the dominant dimpled mechanism observed on the fracture surface of AA6061 side, achieved from the athermal effect of the electroplasticity. Besides, these joints were strengthened 32% with a much more fracture displacement around 20% compared with non-electrically-assisted pre-heating.


Author(s):  
Ming Lou ◽  
YongBing Li ◽  
YaTing Li ◽  
GuanLong Chen

The hybrid use of dissimilar lightweight materials, such as aluminum alloy and advanced high strength steel (AHSS), has become a critical approach to reduce the weight of ground transportation vehicles. Self-piercing riveting (SPR) as a preferred cold-forming fastening method is facing problems like weak interlocking and insufficient penetration, due to the reduced formability of AHSS. In this paper, a new process named electroplastic self-piercing riveting (EP-SPR) was proposed to reduce the deformation resistance of AHSS DP780, by applying a direct current (dc) to it during the riveting process. The influence of dc on force and displacement characteristics throughout the riveting process, joint physical attributes and quasi-static performances for two sheet combinations, e.g., AA6061-T6 to DP780 (combination 1) and DP780 to AA6061-T6 (combination 2), were studied and compared with the traditional SPR joints. The results showed that compared with the traditional SPR joints, the EP-SPR ones increased by 12.5% and 23.3% in tensile-shear strength and cross-tension strengths for combination 1, respectively. For combination 2, even though the EP-SPR joints decreased by 5.8% in tensile-shear strength, it could reduce the penetration risk of bottom AA6061-T6, and present a better energy absorption capability for the increased undercut amount. In addition, the corresponding cross-tension strength of EP-SPR joints still increases by 6.1%.


This study was intended to optimize the resistance Spot Welding Parameters (RSW) of sheet metals joints. The variation parameters selected were electrode force, welding current and welding time of 1.2 mm thickness low carbon steel. The settings of process parameters were conducted according to the L9 Taguchi orthogonal array in randomized way. The optimum process parameter was then obtained by using signal to noise ratio and analyzed further on the significant level by using Analysis of Variance (ANOVA). The developed response has been found well fitted and can be effectively used for tensile shear strength prediction. The optimum parameters achieved were electrode force (2.3 kN), welding time (10 cycles) and welding current (8 kA). Based on the ANOVA, it was found that the electrode force is a vital parameter in controlling the tensile shear strength as compared to welding time and welding current.


Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 831 ◽  
Author(s):  
Choi ◽  
Hwang ◽  
Kim ◽  
Kang ◽  
Kang

The quality of the resistance spot weld is predicted qualitatively using information from the weld’s external apparent image. The predicting tool used for weld qualities was a convolution neural network (CNN) algorithm with excellent performance in pattern recognition. A heat trace image of the weld surface was used as information on the external apparent image of welds. The materials used in the experiment were advanced high strength steel (AHSS) with 980 MPa strength, and uncoated cold-rolled (CR) steel sheets and galvannealed (GA) steel sheets were used. The quantitatively predicted weld quality information contained tensile shear strength, nugget diameter, fracture mode of welds, and expulsion occurrence. The predicted performance of the verification step of the model determined through the learning process was as follows; the predicted error rate for tensile shear strength and nugget diameter were 2.2% and 2.6%, respectively. And the predicted accuracy on fracture mode and expulsion occurrence was 100%.


2013 ◽  
Vol 423-426 ◽  
pp. 876-880 ◽  
Author(s):  
Pasquale Russo Spena ◽  
Manuela De Maddis ◽  
Franco Lombardi ◽  
Fabio D’Aiuto

In this study, advanced high manganese austenitic steel sheets were welded by resistance spot welding at different welding parameters. The effects of welding current, clamping force, number of the current impulse, and duration of each current impulse were examined. Based on Taguchis method, an L-27(313) orthogonal array was employed for carrying out resistance spot welding tests. The welded sheets were subjected to tensile-shear tests in order to determine the strength of the welded joints. Basically, the results showed that tensile-shear strength increase with clamping force at the medium and high effective welding time (>400 ms). However, the occurrence of micro cracks within the welded joints may justify the scattering of tensile-shear strength values.


2014 ◽  
Vol 675-677 ◽  
pp. 23-26
Author(s):  
Nan Nan Wang ◽  
Ran Feng Qiu ◽  
Wei Jian Peng ◽  
Hong Xin Shi

Mild steel Q235 and stainless steel SUS304 were welded using resistance spot welding with an interlayer of Ni. The mechanical properties of the joint were examined, the effects of welding parameters on the nugget size and tensile shear strength were investigated. Both the tensile shear strength and nugget diameter increased with the increasing of welding current and welding time, whereas they decreased with the increasing of electrode pressure. The results indicate that the tensile shear strength of joint welded by resistance spot welding with a Ni interplayer is higher in comparison with that obtained by conventional resistance spot weling.


Metals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 1077 ◽  
Author(s):  
Seungmin Shin ◽  
Sehun Rhee

In this study, lap joint experiments were conducted using galvanized high-strength steel, SGAFH 590 FB 2.3 mmt, which was applied to automotive chassis components in the gas metal arc welding (GMAW) process. Zinc residues were confirmed using a semi-quantitative energy dispersive X-ray spectroscopy (EDS) analysis of the porosity in the weld. In addition, a tensile shear test was performed to evaluate the weldability. Furthermore, the effect of porosity defects, such as blowholes and pits generated in the weld, on the tensile shear strength was experimentally verified by comparing the porosity at the weld section of the tensile test specimen with that measured through radiographic testing.


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