Metal treatment – Compositions – Heat treating
Patent
1990-03-07
1991-07-09
Yee, Deborah
Metal treatment
Compositions
Heat treating
164476, 164485, 164486, C21D 804
Patent
active
050302965
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
The present invention relates to a process for the production of a Cr-Ni type stainless steel sheet, by which the thickness of a cast strip is made almost the same as the product thickness by a synchronous continuous casting process in which the relative speed of the cast strip to the inner wall surface of a casting mold is the same. In particular, it relates to a process by which the microstructure is made finer from the cast strip stage to form a Cr-Ni type stainless steel sheet having excellent surface properties.
2. Background Art
In the conventional continuous casting process for the production of a stainless steel sheet, a slab having a thickness of more than 100 mm is formed by casting while vibrating a casting mold in the casting direction, the obtained slab is surface-finished, the slab is heated at a temperature higher than 1000.degree. C. in a heating furnace, and the slab is hot-rolled by a hot strip mill comprising rows of rough rolling machines and finish rolling machines, to form a hot strip having a thickness of several mm.
After the cold rolling of the obtained hot strip, to maintain the shape (flatness), quality and surface properties required for the final product, a hot-roll plate annealing for softening the hot strip, which has been subjected to a severe hot working, is carried out, and surface scale and the like removed first by a pickling process and then by grinding. In this conventional process for the production of a thick continuous cast slab, much energy is needed to heat the slab and carryout the processing, and thus this process is disadvantageous from the viewpoint of productivity. Furthermore, since a final product is prepared from an slab having a thickness of more than 100 mm through several processes, a texture is developed in a specific orientation in the obtained product, and therefore, when press-forming is carried out by a user, the anisotropy and many other application limitations must be taken into consideration.
To solve the above problems of the process for hot-rolling a thick continuous cast slab having a thickness of more than 100 mm, research has recently been made in to a process by which a cast strip (band steel) having the same or almost the same thickness as the hot strip is prepared during the continuous casting. For example, "Tetsu to Hagane", '85, A197 to '85, A256 discloses a process by which a hot strip is directly prepared by continuous casting. In this continuous casting process, a twin-drum method was used to obtain a cast strip having a thickness of 1 to 10 mm and a twin-belt method was used to obtain a cast strip having a thickness of 20 to 50 mm. This new casting process in which the relative speed of the cast strip to the inner wall surface of a casting mold is the same is called "a synchronous continuous casting process".
In this continuous casting process, however, a problem arises during the casting process, and the problems of quality and surface properties of the product remain.
In the process for preparing a cast strip (band steel) having the same or almost the same thickness equal as that of a hot strip, by continuous casting, since the processes of from the casting to the withdrawal of the product are simplified, the surface properties of the stainless steel product are easily influenced by the properties of the cast strip. Namely, to obtain a product having excellent surface properties, it is necessary to obtain an excellent cast strip.
DISCLOSURE OF THE INVENTION
Under this background, an object of the present invention is to provide a continuous casting process for the production of a stainless steel cast strip having a thickness of less than 10 mm, in which an excellent cast strip capable of providing a product having excellent surface properties and quality can be prepared.
More specifically, the object of the present invention is to provide a simple process capable of forming a Cr-Ni type stainless steel sheet which does not have an uneven gloss and surface defect called a "roping phenomenon" inhe
REFERENCES:
patent: 4420347 (1983-12-01), Ueda et al.
Abe Masayuki
Minamino Shigeru
Suehiro Toshiyuki
Sumitomo Hidehiko
Teraoka Shin-ichi
Nippon Steel Corporation
Yee Deborah
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