Pressure part pipe headers in thermal power plants are being mostly manufactured using high strength alloy steel materials. Conventional method of welding the pipe header joints has been carried out by using Gas Tungsten Arc Welding (GTAW) root pass followed subsequent passes by Shielded Metal Arc Welding (SMAW) processes. In order to develop an alternate welding process with improved the weld quality, a full Gas Metal Arc Welding (GMAW) technology (Modified short arc process as Surface Tension Transfer (STT) root pass followed subsequent passes by pulsed current GMAW process) for header weld joints have been established. This paper deals with the analysis of micro hardness and microstructure properties of the alloy steel weld joints welded by modified GMAW process and comparison with respect to conventional Shield Metal Arc weld joint properties of alloy steel grade 22 material.