Mechanics and Mechanical Engineering Vol. 21, No. 4 (2017) 971–984 c ⃝ Lodz University of Technology Effect of the Shielding Gas Flow Rate on Mechanical Properties and Microstructure of Structural Steel (IS2062) Welds S. A. Rizvi Mechanical Engineering Department Indian Institute of Technology (BHU) Varanasi, India Faculty member in UP Jamia Millia Islamia New Delhi, India sarizvi1@jmi.ac.in saritbhu@gmail.com S. P. Tewari Mechanical Engineering Department Indian Institute of Technology (BHU) Varanasi, India Received (22 September 2017) Revised (9 October 2017) Accepted (13 October 2017) Structural steel is frequently used for industrial purpose as it is more economical as compared to other steels .In the present research article an attempt has been made to find, how the mechanical properties and microstructure properties of the IS2062 structural steel are affected by the different welding parameters such as shielding gas flow rate, voltage, wire feed speed and welding current. In this research work 75%Ar+25%CO 2 , is used as shielding gas because it is a best shielding gas mixture for getting a good quality mechanical properties and micro structural properties of welded joint. For study of fracture mode of tensile fracture, SEM test carried out which help to understand the factor influence the microstructure and it is found that the Fractures of tensile samples are brittle in nature which shows the low ductility and brittle fracture. Micro hardness values change throughout weld metal varying by shielding gas flow rate. Keywords : acicular ferrite, SEM, inclusion, shielding gas, fracture mode, mechanical properties. 1. Introduction Gas Metal Arc Welding (GMAW) is a joining process, in which arc is established between a continuous, copper coated consumable wire and the metal being welded. Fig 1 shows working principle of GMAW process while Fig 2 shows actual set up of process. In a GMAW a welding torch, electric power source, shielding gas & a wire