Abstract
In order to clarify the effect of tip velocity on the weld solidification process of hot-work tool steel (SKD61) during the welding, the information about microstructure evolution was obtained by the combination of liquid tin quenching and Time Resolved X-ray Diffraction (TRXRD) technique using intense synchrotron radiation. From the experimental results, it was found that the solidification mode was changed from FA mode (L→L+δ→L+δ+γ→L+γ→γ) to A mode (L→L+γ→γ) at high tip velocity. Moreover, the effect of tip velocity on the microstructure selection during solidification between the primary δ — ferrite and the primary γ — austenite was theoretically proven by the KGT model. Therefore, it was understood that the solidification cracking susceptibility of hot-work tool steel (SKD61) weld metal was increased due to the δ to γ transition of the primary phase.
