SIMULATING MICROSTRUCTURE DEVELOPMENT IN HIGH-CARBON STEEL CROSS-WIREWELDING

Cross-wire welding is a resistance welding process for joining steel b ars into steel grids. The ''wire meshes'' discussed in this paper are made from high-carbon steel, which gives the product good wear resista nce, but increases the difficulty of welding. Cracks sometimes develop during or after welding in high-carbon steel cross-wires unless an ap propriate postweld heating schedule is applied. The purpose of our com puter simulation is to predict the microstructure development, especia lly in the heat-affected zone, to control the properties of the final product. An empirical grain-growth equation was derived from Jominy le st samples to predict the initial temperature contour in the heal-affe cted zone at the end of welding current input. A two-dimensional postw eld heating algorithm has been developed to simulate the thermal histo ry of the heat-affected zone during the cooling stages. A reaction kin etics algorithm based on the hardenability work of Kirkaldy and co-wor kers has been modified to fit the resistance-welded high-carbon steel bars. The rate and extent of the decomposition of austenite into its d aughter products in the welds were calculated. Experimental observatio n of microstructures in welded bars with different postweld current sc hedules was carried out. The algorithm was found to be in general agre ement with the experimental results.