Reaustenisation in Steel Weld Deposits

J. R. Yang and H.K.D.H. Bhadeshia


The process of reaustenitisation in weld deposits, beginning with a microstructure of acicular ferrite and austenite, has been studied in order to enable the prediction of the reheated microstructure of welds. The transformation mechanism by which the original acicular ferrite formed is found to strongly influence the reaustenitisation process. The reverse transformation from ferrite does not occur immediately when the temperature is raised, even though the alloy may be in the ferrite plus austenite phase field. Reaustenitisation only begins when the carbon concentration of the residual austenite exceeds its equilibrium carbon concentration. This is a direct consequence of the fact that the acicular ferrite transformation ceases before the lever rule is satisfied. A theory has been developed, which explains the experimental data, including the fact that the degree of reaustenitisation varies with temperature above the Ae3 curve.

Proceedings of an International Conference on Welding Metallurgy of Structural Steels,
The Metallurgical Society of the AIME, Warrendale, Pennsylvania.
Edited by J. Y. Koo, 1987, pp. 594-563.

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