쾌삭 303계 스테인레스강의 열간성형성에 미치는 균질화처리, Mn/S 비 및 델타-페라이트의 영향 = Effects of Homogenization Treatment, Mn/S ratio and -ferrite on the Hot Workability of Free-Machining 303-series Austenitic Stainless Steels

다국어 초록 (Multilingual Abstract)

To improve the hot-workability of free-machining austenitic stainless steel, we studied the effects of homogenization treatment, Mn/S ratio and the retained -ferrite on the hot-workability of 303 austenitic stainless steels. The reduction of area was measured as a function of homogenization temperature in the range of 1160-1250 ℃ and 1-50 s−1 using a Gleeble 3800. The hot-workability of the 303-series austenitic stainless steels reached a maximum value at a homogenization temperature of ~1240 ℃. The high temperature (e.g. ~1250 ℃) hot-workability increased with the Mn/S ratio and reached a constant value above ~7.0. At the same time, medium temperature (e.g. ~900 ℃) hot-workability increased linearly with the Mn/S ratio. The fraction of -ferrite decreased with increasing Mn/S ratio in STS 303-series VIM ingots.
The retained -ferrite was found to seriously deteriorate hot-workability at above a critical volume fraction.
The critical value was determined to be ~0.06. The Cr content in the (Mn, Cr) S compounds decreased with increasing Mn/S ratio. The hardness of (Mn, Cr) S increased with increasing Cr content. The hot ductility deteriorated with increasing Cr content within MnS. The evaluation of the harmful effects of Pbeq. on the hot workability of a STS 303 series billet was ineffective.

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