JPS609829A - Production of austenitic stainless steel plate for road mirror - Google Patents

Abstract

PURPOSE:To produce a titled steel plate which is free from generation of a wrinkled pattern on the polished surface of a specular surface by melting a specifically composed austenitic stainless steel and subjecting the steel to deoxidizing, continuous casting, hot rolling and cold rolling under specific conditions. CONSTITUTION:An austenitic stainless steel contg., by wt%, <=0.15% C, <=2.0% Si, <=4.0% Mn, 15-20% Cr, 5-14% Ni, 0.03-0.10% N and the balance consisting of Fe and unavoidable impurities is melted. Si and Mn are used without using Al and Ti for deoxidation in the stage of melting. A slab is then manufactured by a continuous casting mold with application of electromagnetic stirring. The slab is hot-rolled at least twice and is further cold-rolled at least twice at about >=30% draft in rolling, by which a thin steel plate for a road mirror is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an austenitic stainless steel plate for road mirrors, and particularly to a method for manufacturing a thin austenitic stainless steel plate that does not produce wrinkle-like patterns on the mirror-polished surface of road mirrors.

Conventionally, austenitic stainless steel such as SU 304 is generally used for road mirrors, but road mirrors have excellent burnt surface gloss due to their functionality.
Moreover, even the smallest defects and imperfections cannot be allowed to remain. However, when a road mirror is manufactured using a commercially available 5US304 thin plate, fine wrinkle-like patterns occur on the surface of the mirror in parallel to the rolling direction, causing distortion in the image. This requires a large number of polishing steps, and improvements are desired.

In order to meet these demands, the present inventors conducted long-term research and found that they added a limited amount of nitrogen to austenitic stainless steel, and added At and T1 for deoxidation during melting. It has been found that such wrinkle-like patterns do not occur in road mirrors if the cast structure is improved by electromagnetic stirring, hot rolling, and cold rolling without using it.

Originally, the wrinkle-like pattern that occurs on road mirrors does not occur during the pressing and polishing process, but already occurs during the normal cold rolling process.
Since it is difficult to observe with the normal naked eye on a B or 2D finished surface, it is simply overlooked and can be clearly detected by light polishing in a direction perpendicular to the rolling direction.

Furthermore, even in the hot-rolled sheet, a streak pattern, which is thought to be related to the wrinkle pattern, is observed near the center of the sheet thickness. On the other hand, the slight wrinkled pattern on road mirrors is similar to the above-mentioned wrinkled pattern and streaky pattern on cold-rolled sheets and hot-rolled sheets.

As a result of various studies on the causes of the wrinkled pattern observed in road mirrors, the present inventors found that columnar crystals with a single orientation were observed in continuous casting slabs, which are economically advantageous compared to blooming materials. It was found that if the cast structure of the dent is not sufficiently destroyed and remains even after cold rolling, wrinkle-like patterns are likely to occur.The countermeasures for this are electromagnetic stirring, hot rolling at least twice, and at least twice. It was found that cold rolling is quite effective. However, it has been found that the wrinkled pattern can be greatly improved by adding a small amount (0.03% or more) of N to such upper tenitic stainless steel.

In the present invention, At
, avoiding the use of Ti and deoxidizing with Si and Mn is a necessary condition;
When using non-metallic inclusions, the non-metallic inclusions change to B-type or C-type, and composite inclusions of At and Ti tend to fall off during polishing, causing a defect called "meda kako", which significantly deteriorates the mirror-like surface after polishing. Therefore, in the present invention, Si, Mn is
It is deoxidized by

Next, the reason why the range of components of the austenitic stainless steel is limited in the present invention will be described.

C: The wrinkle pattern can be reduced as the amount of C increases, but if it exceeds 0.15%, the corrosion resistance will deteriorate significantly, so the upper limit is set at 0.15%.

Si, Mn + Sj, and Mn are necessary elements for deoxidation, and in the present invention, At and Ti do not deoxidize (
Since deoxidation is performed with only Si and Mn, it is necessary to make up for the lack of deoxidation, so it is a burden to make it high, but if the amount of Sl is too large, the phase resistance will harden, making pressing difficult and causing trouble in manufacturing the road mirror. Therefore, the upper limit is set to 2.0%. Furthermore, if Mn exceeds 4%, the surface gloss of the cold-rolled sheet will deteriorate significantly and the number of polishing steps will increase, so the upper limit should be set at 4.0%.
shall be.

lJi: If Ni is less than 5%, an austenite-phase composite fiber cannot be obtained, and if the amount of other C is increased to form an austenite-phase, the workability will be significantly deteriorated, so the lower limit is set at 5%. do.

On the other hand, increasing Ni is advantageous in terms of austenite stability, but increases cost.
is an important element for corrosion resistance, but if it is less than 15%, it will easily rust when used outdoors such as road mirrors, while if it is 20%, hot workability will deteriorate significantly, so the upper limit should be set. Of course, if the Ni content is in balance with the austenite balance, the occurrence of wrinkled patterns will be slight. Tamashi 0.1
If it exceeds 0%, the yield strength increases significantly and the shape after press working deteriorates, so the upper limit is set to 0.10%.

In the present invention, an austenitic stainless steel slab having the above-mentioned components is manufactured by continuous casting by deoxidizing by Mn and Si without strong deoxidizing by Aj and Ti. The resulting slab has columnar crystals and has directionality, but when electromagnetic stirring is applied during continuous casting, the resulting slab becomes fine equiaxed crystals and has improved directionality. On the other hand, when the continuous casting slab is subjected to hot rolling or cold rolling at least twice during rolling, the strong directionality of lining up in a specific direction is improved, and it becomes possible to have any direction. It becomes a crystal and has less directionality. This is more effective as the number of rolling increases, but it also increases costs, so usually 2
The desired objective can be achieved by rolling twice, and the reduction ratio is preferably 30% or more.

Examples of the present invention will be shown below.

a) Table 1 below shows the chemical composition of the test steel.

c3 c5 d c3 ci c3 c3 cl cl
c+(b) Manufacturing conditions are shown below.

(1) Method of applying electromagnetic stirring ((■) Method of hot rolling twice) Method of cold rolling twice ff) The methods of (1), (It), @) are appropriately combined.

(V) Conventional method 30 was manufactured in an electric furnace (vOD) → continuous casting [:j50X1
(m , intermediate polishing (
The following shows the occurrence of wrinkle-like patterns on the specimens that have been subjected to final polishing (puff polishing containing chromium oxide) using a grindstone of +600 to 1200.

Table 2 1 (1) 1 Not occurred 1 Passed 2 (1) ■ 1 5 (1) 1 1 ' (1) IT tt o It 5 (1) y rt 3 Fail 6 (2 )1 1 Pass 7 (31If tt 1tt 8 (41m tt 1 It 9 (5) N tt O' tt lo f6) 1 Occurrence 1 Fail 11 (6)
V tt 2 u 12 (7) V tt 2 It 13 (8) V u 2 p 14 (9) ■ Does not occur 4 〃 15QO)' V Occurs 2 u (Note) In the table, wrinkle pattern occurrence status ■

[Brief explanation of the drawing]

The attached drawing is a chart showing the relationship between the N content and the occurrence of wrinkled patterns in austenitic stainless steel. Patent applicant: Nippon Stainless Co., Ltd. (and 1 other person) Continued from page 1 of the 1st page 0 Inventors: Takao Kotaki, Naoetsu Research Institute, 2-12-1 Minato-cho, Joetsu City, Japan 0 Inventors: Yoshikazu Kataoka, Ibaraki Japan Stainless Steel Co., Ltd. Kashima Works, 2 Hikari, Inuza Hikari, Kashima-cho, Kashima-gun, Ibaraki Prefecture 0 inventors Katsuzo Abe, 2 Hikari Inuza, Kashima-cho, Kashima-gun, Kashima-gun, Ibaraki Prefecture 0 inventors Saito Sanbe 8-2 Honshio-cho, Shinjuku-ku, Tokyo Japan Stainless Steel Co., Ltd. Inventor: Akira Tsunematsu - Sumitomo Metal Industries, Ltd. Wakayama Steel Works, 1850 Minato, Wakayama City Applicant: Sumitomo Metal Industries, Ltd. Higashi-ku, Osaka Kitahama 5-15

Claims (1)

[Scope of Claims] 1. When manufacturing austenitic stainless steel, manufacturing a slab by continuous casting, and hot-rolling and cold-rolling the slab to manufacture a thin steel plate for a road mirror, austenitic stainless steel Components in weight%: C≦0.15%, Si≦2.0%, Mn≦4.0%
. 0r15~20%, Ni 5~14%, NO,03~
0.10%. Austenite for road mirrors, characterized in that the balance consists of Fe and unavoidable impurities, and deoxidization during melting does not use At or Ti, and electromagnetic stirring is applied during continuous casting. A method for manufacturing stainless steel sheets. 2. When melting austenitic stainless steel, producing a system slab by continuous casting, and hot rolling and cold rolling the slab to produce a thin steel plate for road mirrors, the composition of the austenitic stainless steel is adjusted to % by weight. And, C≦015%, Si≦2.0%, Mn≦4.0%. Cr15-20%, Ni 5-14%, NO, 03-
0.10%. The remainder consists of Fe and unavoidable impurities, and deoxidization during melting does not use AL or Ti, and hot rolling is performed at least twice. A method for manufacturing an austenitic stainless steel plate for road mirrors. 3. When melting austenitic stainless steel, producing a system slab by continuous casting, and hot-rolling and cold-rolling the slab to produce a thin steel plate for road mirrors, the composition of the austenitic stainless steel was determined by weight. %, C≦0.15%, 131≦2.0%, Mn≦4.0
%. Cr15-20%, Ni 5-14%, NO, 03-
0.10%. A road mirror characterized in that the remainder consists of re and unavoidable impurities, and that At and Ti are not used for deoxidation during melting, and that cold rolling is performed at least twice. −A method for producing an austenitic stainless steel plate for 4. When austenitic stainless steel is melted, a slab is manufactured by continuous casting, and the slab is hot-rolled and cold-rolled to manufacture a thin steel plate for road mirrors, the composition of the austenitic stainless steel is determined by weight%. , C≦015%, Si≦2.0%, MnS2.0%. Cr15-20%, Ni 5-14%, NO, 03-
0.10%. The remainder consists of Fe and unavoidable impurities, and deoxidation during melting is performed without using At or Ti, and by electromagnetic stirring, at least two hot rolling steps, and at least two cold rolling steps. A method for manufacturing an austenitic stainless steel plate for a road mirror, characterized in that each process is applied in combination of at least two processes.