Title

INFLUENCE OF AlN AND TiN PRECIPITATION ON STEEL HOT DUCTILITY DURING CONTINUOUS CASTING

Authorship

CARDOSO, S. L.; ABUSHOSHA, R.; MINTZ, B.

CARDOSO, S. L.

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ABUSHOSHA, R.

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MINTZ, B.

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DOI

10.5151/2594-5327-49v5-295-308

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Abstract

A series of steels with varying Al and N levels have been examined, in order to assess which of the two elements Al or N is more detrimental to hot ductility. The steels were heated to 1330°C and cooled at 60°C/min to the test temperature and tensile tested in the temperature range 1000–700°C at a strain rate of 3 × 10⁻⁵ s⁻¹. Ductility was found to be related to the soluble Al and N contents, with no indication of one element being more detrimental than the other. A high Al and/or N level was required to give precipitation of AlN and cause a deterioration in the hot ductility. However, when temperature cycling was introduced prior to testing to make conditions more akin to the commercial continuous casting operation, precipitation was encouraged and ductility was impaired at lower Al and N levels. Titanium additions were also examined and found to give improved ductility. The major part of this improvement came from refinement in the grain size but part also came from removal of N as TiN, this precipitate being coarser and so less detrimental to hot ductility than AlN.

Keywords

continuous casting, hot ductility, AlN, TiN, steel