• V. Chandrasekaran
• V. Subravel

To increase the efficiency of the automotive vehicles, materials with high strength, good formability and crash resistance are required. The advanced high strength steels (AHSS) are widely used in automotive sectors due to their excellent formability and crash resistance characteristics. Dual phase (DP) steel is a family of AHSS which consists of ferrite matrix with martensite islands. Resistance Spot Welding (RSW) is one of the most prevalent and preferred welding processes for joining automotive body parts. RSW of DP steel has become a very important issue due to an increased number of application in auto-body structures. In this investigation, similar joints of DP600 steel in lap joint configuration were fabricated using RSW process. The process parameters were optimized using DOE (design of experiments) and the welds joints were fabricated using the obtained DOE matrix. The tensile shear fracture load (TSFL) of joints was evaluated using universal testing machine. An empirical relationship was developed to be predict load (Tensile shear fracture) carrying capability of RSW joints of DP600 steel Response Surface Methodology (RSM) was used to optimize the RSW parameter to attain maximum load carrying capability. From this investigation, it is understood that increase in welding current increases the nugget zone size as well as the higher degree of softening in HAZ. The tensile shear strength was found to be increased with increase in welding current up to a certain limit and then it decreases. The microhardness profile shows a peak hardness in nugget zone and the hardness is lower in the HAZ. The softening of HAZ is mainly attributed to inter-critical heating during welding.

Dual phase steel, Resistance spot welding, Tensile shear fracture, Microstructures

"Assesment of Welding Current on Mechanical Properties and Microstructural Characterstics of Resistence Spot Welding", International Journal of Emerging Technologies and Innovative Research (www.jetir.org), ISSN:2349-5162, Vol.3, Issue 4, page no.365-372, April-2016, Available :http://www.jetir.org/papers/JETIR1701747.pdf

"Assesment of Welding Current on Mechanical Properties and Microstructural Characterstics of Resistence Spot Welding", International Journal of Emerging Technologies and Innovative Research (www.jetir.org | UGC and issn Approved), ISSN:2349-5162, Vol.3, Issue 4, page no. pp365-372, April-2016, Available at : http://www.jetir.org/papers/JETIR1701747.pdf