M. Sadeghi - Department of Materials Engineering, Karaj Branch, Islamic Azad University, Karaj, Iran
H. Sabet - Department of Materials Engineering, Karaj Branch, Islamic Azad University, Karaj, Iran
H. Razavi - Department of Materials Engineering, Iran University of Science & Technology, Tehran, Iran

Environment friendly industrial fin tube boilerused a heat recovery system generator (HRSG) is the core facility of a combined cycle power plant (CCPP) that recycles thermal energy from a gas turbine and creates high temperature and high pressure gas. Serrated finned tubes and solid finned tubes are two types of helically finned tubes made by high-frequency resistance welded (HFRW). Solid and serrated fins are widely consumed solutions for improving heat transfer in fired heaters. The important fact that designers or engineers often overlook while selecting the fins is that serrated fins can provide larger surface area and significantly higher fin efficiency compared with solid fins. Carbon steel and alloy steel tube according to ASTM A192 and ASTM A213. As well as carbon steel and alloy steel coil strips according to ASTM A1008 and ASTM A240-TP409. International standard for tests of high frequency resistance welded fins according ASME and ASTM used for metallography fusion weld, tensile strength and hardness. This paper presents the microstructures welding of helically fin tube boiler, with particular emphasis on HFRW.