Influence of Heat Treatment on Rolling and Final Properties of Welded Steels 1.4404 and 1.4571

Abstract

This study investigates the influence of heat treatment on the properties of welded steels 1.4404 and 1.4571 of high thickness concerning the forming properties by rolling and the final properties. The weld seam is a region in the work piece where the material can have a higher resistance to deformation. The strength of the weld seam is often higher than in the parent metal. Therefore a suitable pre-heat treatment (1050°C for 30 min) was applied to the weld seam and heat affected zone within the cold rolling process to achieve a more homogeneous distribution of strength and ductility over the entire work piece. A second heat treatment (1050°C for 60 min) after the rolling was done to obtain the solution annealed structure of the steels. To compare the effect of the heat treatments and of the deformation during rolling (work hardening) tensile tests were performed after each process step. Here both materials behave slightly differently. Metallographic investigations show how the microstructure is influenced and give a clear picture of the fracture occurring. Force – time behaviour during rolling was monitored and provides information about the improvements by the preliminary heat treatment. Cold rolling of welded plates is characterized by a force peak just when the weld seam is within the gap of the rolls. The application of heat treatment has been found to lower that force peak and ensures less distortion in shape during the cold rolling passes.

Research on the Causes and Treatment of Weld Zone Fracture in Cold Rolled High Strength Steel Rolling Process

“…In previous literature related to weld seam breakage, typical examples include Zhang, Fan et al [11] improving the welding quality of multiphase steel by changing laser welding power and welding speed; Tober, Gerhard et al [12] found that appropriate heat treatment can make the strength and ductility of the welded joint more uniform, thereby improving the welding quality; Kumar, Nitin et al [13] studied the effect of welding machine process parameters on the microstructure and mechanical properties of dual phase DP780 steel and CR340 steel dissimilar welding; Pawar, Sachin et al [14] found that the presence of insulation impurities in water reduces the welding quality at the weld seam of cold rolled galvanized sheet; Fan, Jiafei et al [15] studied the effect of different laser intensities on the mechanical properties of strip welds in cold continuous rolling mills. The above literature indicates that the process parameters of the welding machine have a significant impact on the quality of cold continuous rolling welds, but there is no specific solution.…”