Effects of Fiber Laser Welding Speeds on Microstructures and Properties of E36 Steel Butt Joints

Abstract

A 6 kW fiber laser YSL-6000 was chosen to weld the E36 steel with a thickness of 6 mm. The effects of laser welding speeds on the welded joint appearance were examined, and the microstructures and properties on the typical butt joints were investigated. Results showed that narrow and fully penetrated welded joints without obvious defects could be obtained at different welding speeds. With the welding speed increasing, the welding seam width decreased, and the welding seam (WS) and heat affected zone (HAZ) hardness increased. The microstructures of weld metal and HAZ were consisted of martensite, but the contents of it were significantly different. Welding speeds had no remarkable effect on the tensile strength and yield strength, except elongation. But the increase of welding speeds resulted in improvement of micro-hardness, which reached the maximum value of 426.38 HV at 45 mm/s. Weld metals of different welded joints were active in corrosion solution, and corrosion potential became more negative with the welding speeds increased from 35 mm/s to 50 mm/s, except at 45 mm/s.