Experimental Research on Structure and Performance of Joints in Cold-Rolled Rectangular Hollow Sections

Abstract

The microstructure and mechanical behavior of welded joints under different technologies were compared for investigating the influence of technological parameters on microstructure and property of weld seam on thick-walled cold-rolled-forming high frequency induction welded (HFIW) tubes. The results show that microstructure of joints consists of a decarburized layer, an overheated area, a recrystallized zone and a partially-recrystallized zone. The opening angle and the welding surface energy (WSE) are important factors affecting microstructure and weld quality. The width of the heat-affected zone is proportional to the WSE. With increase of the WSE, the mean bend angle increases first and decrease later, showing a "mountain-peak" variation. The optimum WSE decreases with decrease of the opening angle because the smaller the opening angle is, the higher the heating efficiency is. The influence of processing parameter on the bending capability of joints is remarkable, while which on the impact toughness can be ignored.