Effects of HFRW Variables on Weldded Joint Quality of the Ferritic Stainless Steel to Cr-Mo Low Alloy Steel in Heat Recovery Steam Generator

Abstract

Heat recovery steam generator (HRSG) is obviously a very desirable and environmental friendly energy source, increasing thermal efficiency while reducing energy costs is possible through the use of industrial boilers. In this study, the effect of high frequency resistance welding (HFRW) variable factors on joints between AISI 409 stainless steel finned to 2 ¼ Cr-1Mo alloy steel tube as helical finned tube was investigated. So HFRW was implemented on actual samples by changing multiple factors including travel speed, electric potential, current of welding and fin pitch. Meanwhile metallography of weld joint, tensile strength and hardness tests were carried out several sections of the samples according to international standard fin tube. The diffusion zone indicating metallurgical joining more than 90% was measured at the weld interface, with applying optimum welding parameters, fin-tipand tube-tipposition and hydraulic pressure jack setting on squeeze rollers. Furthermore as the lower pitch and fin thickness are selected, the higher quality of fin tube welding joint is achieved. On the other hand as the pitch and fin thickness are reduced, the output transfer surface treatment in final process diminished. However, this paper presents emphasis on finned tube manufacturing processes and the best weld parameters conditions have been reached a sound joint.