STUDY OF THE HARDNESS IN THE HEAT AFFECTED ZONE IN WELDING OF A 4130 AISI STEEL HARDENED BY HEAT TREATMENT

Abstract

In present study the effect of welding current (heat input) and preheating temperature on minimum hardness behavior in 4130 AISI (30XMA) steel in initial state of thermal treatment at maximum hardness heat affected zone is evaluated. Different deposits on sheet metal are made, using a welding process with consumable electrode and gaseous protection, GMAW, in correspondence with a factorial experiment design. As result, was obtained a regression equation and a nomogram that allow to predict the minimum hardness in the heat affected zone. It was concluded that the minimum hardness in the studied zone decreases as the welding current and the preheating temperature increases, which can affect its service behavior when subjected to high speed impacts.