GRAIN-BOUNDARY MELTING DURING RAPID BEATING OF ALLOY-STEELS AND THE OUTLOOK FOR ITS APPLICATION

Phase transformations during solidification and melting of alloy steels were analysed. These steels undergo following transformations in the range of sub-solidus temperatures: L=delta-F, peritectic reaction delta-F+L= A, eutectic reaction L=A+ interstitial phases. Using rapid heating of corrosion resistant steels by passing the electric current it was established that under particular heating rates the melting of grain boundary eutectic precedes A-delta-F transformation and facilitates the formation of the liquid phase in austenite dendritic branches. Realization of this effect in laser welding allows one to improve by a factor of three structure homogenity and the whole complex of mechanical properties.