Advanced high strength steels are being increasingly used in the automotive industry to reduce weight and improve fuel economy. However, due to increased physical properties and chemistry of high strength steels, it is difficult to directly substitute these materials into production processes currently designed for mild steels. New process parameters and process-related issues must be developed and understood for high strength steels. Among all issues, endurance of the electrode cap is the most important. In this paper, electrode wear characteristics of hot-dipped galvanized dual-phase (DP600) steels and the effect on weld quality are firstly analysed. An electrode displacement curve which can monitor electrode wear was measured by a developing experimental system using a servo gun. A neuro-fuzzy inference system based on the electrode displacement curve is developed for minimizing the effect of a worn electrode on weld quality by adaptively adjusting input variables based on the measured electrode displacement curve when electrode wear occurs. A modified current curve is implemented to reduce the effects of electrode wear on weld quality using a developed neuro-fuzzy system.
Weld bonding, which is a combination of resistance spot welding and adhesive bonding, is finding application in vehicle structures that involve advanced high-strength steels. The strength of weld-bonded specimens is attributed to the strength of the weld nugget and adhesive strength. The existence of an insulating epoxy adhesive layer causes a rise in contact resistance and current density during the welding stage, and thus enhances the heat input. The aim of the present study is to explore the mechanical properties and microstructure of the weld nugget in weld-bonded dual-phase steel by means of comparison with a spot-welded nugget. Tensile-shear tests, weld lobe determination, microstructural characterization, and microhardness tests of weld-bonded and spot-welded specimens were conducted. The results of tensile-shear tests show that the weld nuggets of weld-bonded specimens have a higher tensileshear force and energy absorption, and exhibit button-pullout fracture more easily at lower welding current. The weld lobe of weld-bonded dual-phase steel is too narrow. The results of microstructural characterization and microhardness tests indicate that, compared with resistance spot welding specimens, weld-bonded specimens have a larger nugget size at lower current; finer martensite and lower hardness in the heat-affected zone; and slightly more ferrite and lower hardness in the fusion zone. The comparative results are useful for optimizing the processing parameters and improving the weld quality of weld bonding.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.