Study on Metallurgical Characteristic of Weld Metal for Gray Cast Irons - Weld Microstructure and Crack Sensitivity -

Abstract

Joining of grey cast iron by fusion welding has much difficulties for its extremely low ductility and low toughness because of the flake form of the graphite. And the brittle microstructure, i.e. ledeburite may be formed during fusion welding by its rapid cooling rates. By these kinds of welding problem, preheat and post heat treatment temperature must be increased to avoid weld crack or welding problems.In order to avoid these fusion welding problem, friction welding of cast iron was carried out for improving joint soundness, establishing friction welding variables.There is no factor for evaluating friction weldability in continuous drive type friction welding. In this point of view,this study proposed the parameters for calculating friction weld heat input. The results obtained are as follows ; 1. There was a close relationship between tensile strength and flash appearance of friction welded joint. 2. Tensile strength was decreased and flash was severely oxidized as increasing frictional heating time. 3. As increased forging pressure P 2 , flash had a large crack and tensile strength was decreased. 4. As powdered graphite by rotational frictional force induced flat surface and hindered plastic flow of metal ,tensile strength of welded joint was decreased. 5. Heat input for continuous drive type friction welding could be calculated by the factors of P 1 , P 2 and upset distance(δ).

Effect of Ti/N Ratio on TiN Particles, Microstructures, and Toughness of Heat‐Affected Zone After High Heat Input Welding of the Ca‐Treated Steel Plates

“…As a result, the grains will begin to grow. The thermal stability of TiN particles can be improved by increasing the N content in steel, [ 2,16 ] but excessive N content will reduce the toughness of HAZ. The addition of the proper amount of Ti can promote the precipitation of fine TiN particles, which can inhibit the growth of austenite grains during the HHIW process.…”