Analysis of welding in comparable steel grades : Influence of steel grade on the welding process

Abstract: This master thesis is written to examine the influence of different low carbon steel sheet materials on the GMAW welding process. During welding the properties of the base material influence the productivity of the welding process. The purpose of this thesis is to examine how the choice of material and welding speed affect the welding process and the productivity. A literature survey was performed to describe the welding technique and the differences in manufacturing for the sheet materials as well as the effect of alloying and welding on the sheet material. Defects in the weld and methods used to determine them are explained. Test pieces of the different sheet materials were welded with the GMAW process and examined. The result shows that there is a variation in the welding process regarding weld penetration. Measurements also show that welding speed and gap have little influence on the hardness of the weld and heat-affected zone and that the S355MC is more likely to suffer from a narrower toe transition radius than S355NL and S355MC Si. This and the higher area in the Y2 region for the S355MC could indicate a stronger inward flow in the weld pool during welding possibly a result of surface active agents such as oxygen and sulphur.