Fig. 8 — An effect of welding parameters on weld nugget diameter. Fig. 9 — An effect of welding parameters on the weld nugget current. However, after the critical welding parameters, the strength starts to decrease because of the excessive heat input and expulsion. Cold deformation before welding increases the strength of the resistance spot welded TRIP800 steels. 2) The button diameter and button size ratio of welds for producing PF mode that results in acceptable strength and good surface quality should be at least 4√t and 0.14–0.30, respectively, in cold-deformed TRIP800 weldments. 3) The strength increases with an increase in electrode indentation depth and button diameter before severe expulsion occurs. 4) Cold deformation of TRIP800 steels increases the hardness and the strength of the weldment. 5) Three distinct failure modes were observed and the strength of the weldment increase in the order of IF, PIF, and PF modes. 6) Deformed TRIP800 steel hardness is found approximately 100 HV0.5 higher than those of the as-received sample. The button hardness increases with increasing heat input due to martensite transformation. 7) The weld lobe was produced to determine the acceptable strength and desired surface quality associated with welding parameters. Cold deformation of TRIP800 steel shrinks the weld lobe area and sets back the weld lobe curves for lower welding currents at the same welding times. WELDING RESEARCH Acknowledgment The authors thank the Karabük University project office for its kind support. 1. Krizan, D., and De Cooman, B. C. 2008. Analysis of the strain-induced martensitic transformation of retained austenite in cold rolled micro-alloyed TRIP steel. Steel Res Int. 79(7): 513-s to 522-s. 2. Wiewiorowska, S. 2010. Determination of content of retained austenite in steels with trip effect deformed at different strain rates. Steel Res. Int. 81: 262-s to 265-s. 3. Khan, M. I., Kuntz, M. L., Biro, E., MARCH 2016 / WELDING JOURNAL 83-s height. Fig. 10 — An effect of welding parameters on the electrode indentation depth. Fig. 11 — An effect of welding parameters on the weld nugget size ratio. References
Welding Journal | March 2016
To see the actual publication please follow the link above