Solute-Segregation, Oxygen Content and the Transformation-Start Temperatures of Steel Welds

M. Strangwood and H.K.D.H. Bhadeshia


The high cooling rates associated with most arc-welding processes causes non-equilibrium solidification so that the final weld is compositionally heterogeneous. The effect of such segregation on the temperature at which the transformation from austenite to ferrite first occurs on cooling from the austenite phase field (Th), is investigated both experimentally and theoretically for reheated Fe-C-Mn-Si weld deposits and pure alloys. The role of oxygen concentration in influencing the transformation temperatures is also investigated. It is found that the effect of alloy segregation is to elevate Th, to an extend depending on the averate alloy concentratio. For homogeneous alloys, the agreement between experiment and theory for Th is reasonable, the former being a little higher than expected, but it is demonstrated that the discrepancy has only a small effect on calculations of weld microstructure. It is found that the oxygen content has no noticeable effect on the transformation start temperature of allotriomorphic ferrite in welds at the levels studied (about 200 ppm).

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. 495-504.

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