Prediction of Weld Metal Microstructure in Laser Beam Welded Clad Steel

Abstract

In dissimilar welded joints, data for the phase composition of the fusion zone may be taken from the phase equilibrium diagram composed in the course of experimental observation of phases. Results are given in the article for test laser welding of low-carbon steel plates, clad with austenitic stainless steel, and specimens are studied demonstrating perfection of the welded section austenitic microstructure. This confirms the data about the reliability of martensite-austenite boundaries studied by D. T. Kotecki on the example of chromiumnickel deposits prepared by submerged arc welding on carbon steel plates. Welds are studied by optical and scanning electron microscopy, and microhardness is determined by the Vickers method. The content of the main substitution alloying elements is calculated by means of energy-dispersion spectroscopy. The nitrogen content is determined using a hot gas extraction method and carbon is determined proceeding from the chemical composition of the deposited and base materials. It is established that the chromium and nickel content in points of the welded section with an entirely austenitic microstructure is specified by coordinates Creq and Nieq in accordance with the austenite-martensite boundary proposed by Kotecki. Therefore, the results obtained confirm the possibility of predicting welded section microstructure from the position of this boundary, even in the case of joints welded with a laser beam with moderate solidification and cooling rates.