Electrode clamping force regulation of servo gun mounted on resistance spot welding robot

Resistance spot welding of aluminum (Al5754) to magnesium (AZ31B) alloys results in the formation of a variety of solidification microstructures and intermetallic compounds that may affect the in-service performance of the weld. This study evaluates the relationship between the welding parameters and the properties of the weld nugget that is formed, and clarifies the morphological and microstructural evolutions within the weld regions during the low-current “small-scale” resistance spot welding of Al5754 to AZ31B. The investigations included a combination of microstructural characterization and thermodynamic analysis of the weld region. The results show that the welding time and clamping force parameters have significant effects on the properties of the nugget formed. The optimal welding parameters were found to be 300 ms welding time and 800 N clamping force. Weld nuggets formed with lower welding time and clamping force were undersized and contained extensive porosity. Meanwhile, a clamping force above 800 N caused gross deformation of the test samples and the expulsion of the molten metal during the welding process. The most significant microstructural changes occurred at the weld/base metal interfaces due to the formation of Al17Mg12 and MgAl2O4 intermetallic compounds as well as significant compositional variation across the weld pool. The thermal gradient across the weld pool facilitated the formation of several microstructural transitions between equiaxed and columnar dendrites.

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Resistance Spot Welding of Advanced High Strength TWIP Steels

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.423-426.876 ◽

2013 ◽

Vol 423-426 ◽

pp. 876-880 ◽

Cited By ~ 3

Author(s):

Pasquale Russo Spena ◽

Manuela De Maddis ◽

Franco Lombardi ◽

Fabio D’Aiuto

Keyword(s):

Shear Strength ◽

Welded Joints ◽

Resistance Spot Welding ◽

Spot Welding ◽

Welding Parameters ◽

Clamping Force ◽

Tensile Shear Strength ◽

Tensile Shear ◽

Resistance Spot ◽

Current Impulse

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.

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