Metal treatment – Stock – Ferrous
Patent
1997-11-03
1998-12-29
Yee, Deborah
Metal treatment
Stock
Ferrous
148542, C22C 3840, C21D 802
Patent
active
058535012
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention provides a low anisotropic Cr--Ni-based stainless steel hot-rolled sheet and a process for its production.
BACKGROUND ART
A technique has been developed in recent years for obtaining cast strips with a thickness of 10 mm or less by direct casting from molten steel, and actual apparatuses therefor have been tested. With the new technique, it is possible to simplify or even eliminate the hot rolling process.
Conventionally, slabs with thicknesses of over 100 mm have required hot rolling with a hot rolling mill involving a large consumption of energy, and thus the advantages of simplifying or eliminating the hot rolling step include not only lowering of production costs, but also benefits from the standpoint of the environment. Hereunder, the process including the step of casting a thin strip with a thickness of 10 mm or less from molten steel will be referred to as the "new process", and the process including hot rolling a slab into a hot-rolled strip will be referred to as the "existing hot rolling process".
Conventionally, when Cr--Ni-based stainless steel hot-rolled annealed sheets, typically 18% Cr-8% Ni steel, are produced by the existing hot rolling process, a hot rolling reduction of about 98% or greater results in development of a strong hot rolling texture, and after annealing of the
By casting of thin cast strips without the hot rolling step in the new which is a characteristic of hot-rolled annealed sheets, and thus produce a steel strip with low anisotropy. However, the resulting thin cast strip solidified structures.
Attempts have also been made to hot roll cast strips using the new process. For example, in Japanese Patent Application No. 61-141433, a Cr--Ni-based stainless steel cast strip is subjected to hot rolling at 800.degree. C. or higher to a reduction of 50% or less followed by cold rolling to produce a thin sheet product, by which it is possible to produce a thin sheet with excellent surface quality; however, the anisotropy of such hot-rolled steel sheets had not been studied.
SUMMARY OF THE INVENTION
The present invention allows efficient production of Cr--Ni-based stainless steel hot-rolled strips with low anisotropy, which have been difficult to produce by conventional processes.
The present invention has the following construction which is designed to achieve the object described above.
The gist thereof is the provision of a low-anisotropic Cr--Ni-based hot-rolled stainless steel strip which has a texture with (100), (110), (111), (311) and (211) rolling plane normal direction (ND), which have an orientation intensity from 0.5 to 1.5 in an inverse pole figure as measured for a 1/4 section of the sheet thickness, as well as a process for producing a low anisotropic Cr--Ni-based hot-rolled stainless steel sheet by continuously casting Cr--Ni-based stainless molten steel into a cast strip with a thickness of 1.5 mm to 6 mm using a continuous casting machine wherein the mould walls move in synchronization with the cast strip, hot rolling it in a temperature range of 950.degree.-1,150.degree. C. within 60 seconds after the cast strip has left the mould at a reduction of 25 to 35% to make a hot-rolled strip, and then performing heat treatment wherein the hot-rolled strip is held for 5 to 60 seconds in a temperature range of 950.degree.-1,200.degree. C.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a graph showing the influence on the anisotropy of a hot-rolled annealed sheet of the hot rolling temperature and the hot rolling reduction of a cast strip.
FIG. 2 is a graph showing the details of the influence on the respective crystal orientations of a hot-rolled annealed sheet of the hot rolling reduction rate during hot rolling of a cast strip.
FIG. 3 is a graph showing the influence on anisotropy of a hot-rolled annealed sheet of the annealing conditions during annealing, after hot rolling of a cast strip.
THE MOST PREFERRED EMBODIMENTS
In the existing hot rolling process, the high hot rolling reduction rate results in development of a {110
REFERENCES:
patent: 4420347 (1983-12-01), Ueda et al.
patent: 4812176 (1989-03-01), Tanaka et al.
patent: 4824491 (1989-04-01), Tanaka et al.
Ishimaru Eiichiro
Teraoka Shin-ichi
Nippon Steel Corporation
Yee Deborah
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