Metal founding – Combined – Including continuous casting apparatus
Patent
1996-12-03
1999-05-18
Ryan, Patrick
Metal founding
Combined
Including continuous casting apparatus
164423, 164428, 164415, 266103, B22D11/12;11/66
Patent
active
059042044
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus wherein a stainless steel is cast into a thin strip-like slab, having a thickness of not more than 10 mm, which is then hot-rolled to a steel sheet product. In particular, the present invention relates to an apparatus for the production of a stainless steel strip having an excellent surface quality.
BACKGROUND ART
A technique where a molten steel is cast directly into a thin strip-like slab having a thickness of not more than 10 mm has recently been developed and tested using actual equipment. This new technique can simplify or eliminate the step of hot rolling.
A slab having a thickness exceeding 100 mm has hitherto been hot-rolled by means of a hot-rolling mill, consuming much energy. Therefore, the simplification or elimination of the step of hot rolling has been desired from the viewpoint of lower production costs as well as of the environment. The process involving the step of casting a molten steel into a thin strip-like slab having a thickness of not more than 10 mm will be hereinafter referred to as the "new process," while a process involving the step of hot-rolling a slab to a thin strip-like slab will be hereinafter referred to as the "current process."
The production of a cold-rolled sheet of a Cr-Ni-base stainless steel, represented by a 18%Cr-8%Ni steel, or a Cr-base stainless steel by the new process has posed a problem of surface roughening (called "orange peel" or "roping") created on the surface of products.
For example, an article in ZAIRYO TO PUROSESU (Current Advances in Materials and Processes) Vol. 3 (1990), p. 770, published by The Iron and Steel Institute of Japan describes a phenomenon of deterioration in surface quality of sheet products of SUS304 produced by the new process. According to this article, orange peel-like surface roughening (roping) is described to be created on the surface of a cold-rolled steel sheet due to the presence of coarse grains in the material before finish cold rolling. In order to prevent this phenomenon, the refinement of grains of the material before the finish cold rolling by the following two means is described to be useful. the hot-rolled sheet. For example, it is hot-rolled at 1200.degree. C. with a reduction ratio of 16% and subjected to solution treatment at 1150.degree. C. for one min. intermediate annealing being performed therebetween. For example, it is rolled at room temperature with a reduction ratio of 10% and subjected to intermediate annealing and then to finish rolling.
Further, an article in ZAIRYO TO PUROSESU (Current Advances in Materials and Processes) Vol. 4 (1991), p. 996, discloses that, although the surface roughening (roping) of a cold-rolled sheet can be alleviated by subjecting the cold-rolled sheet to temper rolling with a high reduction ratio, this technique deteriorates the quality, particularly the elongation, of the material, necessitating the regulation of the steel composition so as to be brought to a .gamma.-phase unstable composition system, i.e., high Md30. For example, it describes that roping and workability (elongation) can be made comparable with those in the case of the current process by bringing Md30 to 30.degree. C. and conducting temper rolling with a reduction ratio of 1%.
Furthermore, an article in ZAIRYO TO PUROSESU (Current Advances in Materials and Processes) Vol. 4 (1991), p. 997 describes that the surface roughening (roping) of a cold-rolled sheet can be alleviated by designing the constituents so as to increase the .delta.-ferrite content, thereby providing a .gamma.-phase unstable composition.
Furthermore, Japanese Unexamined Patent Publication (Kokai) No. 2-133528 describes that hot rolling, at a temperature of 900.degree. C. or above, with a reduction ratio of not more than 60% results in the recrystallization of the texture of the thin strip-like slab, alleviating roping. This technique is described to alleviate the roping independently of the practice of annealing after hot rolling. Further, regarding the heat history of the str
REFERENCES:
patent: 4494929 (1985-01-01), Fujioka et al.
patent: 5584337 (1996-12-01), Nakashima et al.
patent: 5634257 (1997-06-01), Kajiwara et al.
Zairyo to Purosesu (Current Advances in Materials and Processes), vol. 3, 1990, p. 770.
Zairyo to Purosesu (Current Advances in Materials and Processes), 1991, vol. 4, p. 996.
Zairyo to Purosesu (Current Advances in Materials and Processes), 1991, vol. 4, p. 997.
Arai Takashi
Ishimaru Eiichirou
Nohara Yoshikatsu
Oka Hideki
Shoda Shunji
Lin I.-H.
Nippon Steel Corporation
Ryan Patrick
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