Analysis of the solidification modes in the areas surrounding the GTAW welding pool on a TRIP steel

Abstract

The present research work carried out studies on a TRIP steel, starting from an AISI 1018 load with additions of ferromanganese and ferrosilicon that was subsequently subjected to an intercritical annealing heat treatment, to obtain said AHSS, to then be welded and determine the solidification mode or modes present in said steel. The heat treatment route was based on two stages 1) Intercritical annealing and 2) Isothermal bainite treatment, to obtain the characteristic microstructure of these steels which are ferrite, bainite, martensite and retained austenite, in different percentages. 

The welding process used was the autogenous GTAW process, considering as main variables the feed speed and voltage, as well as the cooling medium to be able to analyze the area of interest (ZF). To determine the solidification modes, it was necessary to determine the temperature gradient (G) and the solidification rate (R), to correlate them and determine these morphologies.