MICROSTRUCTURE ANALYSIS OF XAR STEEL PLATE WELDED BY MAG WELDING METHOD USING DIFFERENT WELDING CURRENTS

Abstract

The aim of this study is to investigate the effect of welding current on microstructure in combining
XAR (eXtra Wear Resistance) steels with MAG welding method. The most important parameter
during the welding process is the heat input. The desired microstructure can be obtained by
controlling the heat input. Because microstructure is the most important factor affecting all
mechanical properties. In this study, the effect of welding current intensity on microstructure in
combining XAR 500 steel of 4 mm thickness used in heavy duty machine with MAG welding
method was investigated. In the preparation of welded samples, MAG welding robot with speed,
voltage and current control is used. Three different welding current densities were selected as
welding current intensity 140A, 160A and 180A. Welding speed was kept constant at 350mm / min.
In order to test the effect of the welding speed, the welding current was kept constant at 160A and at
speeds of 300mm / min, 400mm / min and 450mm / min. Arc length is selected as 1mm. The gas
flow rate was kept constant at 10mm / min. SG-2 welding wire with 1mm thickness was used as
additional metal. Mixed gas with 86% CO2, 12% CO2 and 2% O2 was used as welding gas. The
effect of welding current on microstructure was investigated in all welded samples. Microstructures
obtained from welded joints were analyzed. As a result, it is observed that the microstructure is
homogenous and the residual metal nitrides precipitate. It has been observed that the grain size
decreases with the increase of heat input depending on the welding current.