JP2003053493A - Austenitic stainless steel sheet excellent in uniformity of surface glossiness and its production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an austenitic stainless steel sheet which is produced by a twin roll casting method and is excellent in the uniformity of surface glossiness and to provide its production method. SOLUTION: The austenitic stainless steel sheet produced by the twin roll casting method and excellent in the uniformity of the surface glossiness is characterized in that in the case of measuring Ni composition distribution by extracting a range of 1 mm2 at >=10 positions per 1 m2 surface except the surface oxidized layer, a half value width in the Ni composition distribution is <=0.6 mass% at >=80% positions thereof.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an austenitic stainless steel sheet produced by a twin roll casting method and a method for producing the same.

[0002]

2B with austenitic stainless steel sheet
A steel sheet called a material is produced by continuous annealing, rough rolling, coil flaw removal, cold rolling, final continuous annealing, and temper rolling using a hot rolled steel strip or a steel strip formed by twin roll casting as a raw material.

The hot rolled steel strip is a hot rolled slab cast by a continuous casting method and has a fibrous structure. Further, the twin-roll cast steel strip is obtained by solidifying molten steel into a plate shape by the twin-roll casting method, and has a structure in which the solidified structure remains. Each of the steel strips has a thickness of 2 to 4 mm, and is further annealed or rolled to finish a steel sheet as a product.

The continuous annealing is a process for making the distribution of the constituent elements in the steel strip uniform, and after the continuous annealing, mechanical scale removal or pickling is performed in order to remove the scale formed on the surface layer of the steel strip. . Rough rolling is a process for removing the bending of the steel strip caused by continuous annealing and correcting the shape of the steel strip.

Coil flaw removal is a process of removing the surface layer of a steel strip in order to suppress flaws generated in the surface layer when the steel strip is further rolled and annealed. In coil flaw removal, an endless grinding belt is pressed against the surface of a steel strip to rotate and the surface layer of the steel strip is scraped while injecting oil. There are multiple grinding belts for coil flaw removal, the roughness of the first grinding belt is high, and the roughness of the belt for finish grinding is reduced to enhance the gloss of the steel plate of the product.

Cold rolling is a process in which a steel strip is cold rolled so that a steel sheet having a nearly final thickness is obtained. Further, the final continuous annealing is a process of removing the strain that has entered the steel sheet by cold working by annealing, and removes the scale formed on the surface layer of the steel sheet by annealing by salt treatment or pickling. In temper rolling, finishing is performed so that the surface of the finally annealed steel plate becomes flat.

The method for producing these steel strips and cold-rolled steel sheets is described in, for example, the Stainless Steel Handbook (3rd edition, published by The Nikkan Kogyo Shimbun, edited by The Stainless Association, 1995, p. 839).

A method for manufacturing a steel strip by the twin roll casting method is disclosed in Japanese Patent Laid-Open No. 7-268556. In general, in a steel strip produced by the twin roll casting method, molten steel solidifies at a high speed in contact with the twin rolls, so segregation of constituent elements in the surface layer of the steel strip is small, and the solidification rate becomes slower as it goes inside the steel strip. Therefore, the degree of segregation of the constituent elements increases. The relationship between these solidifications and the segregation of the constituent elements is described in, for example, Journal of Japan Institute of Metals, Volume 40 (2001), p. 150.

[0009]

The uniformity of the surface gloss of the austenitic stainless steel sheet produced by the twin roll casting method is influenced by the conditions of the above production process. In particular, in the steel sheet produced by the twin roll casting method, there is a problem that the segregation of the component elements caused by solidification is large and this affects the uniformity of surface gloss. Therefore, an object of the present invention is to solve this problem and to provide an austenitic steel sheet having excellent surface gloss uniformity and a method for producing the same.

[0010]

The present invention is intended to solve the above-mentioned problems, and the gist thereof is as follows. (1) An austenitic stainless steel sheet manufactured by a twin roll casting method, in which 10 or more 1 mm ² regions are extracted per 1 m ² of the surface, excluding the surface oxide layer, and N
When the i composition distribution is measured, the half-value width of the Ni composition distribution is 0.6% by mass or less at 80% or more of the positions, and austenitic stainless steel excellent in surface gloss uniformity. steel sheet. (2) In the production of an austenitic stainless steel sheet by the twin roll casting method, when 10 or more 1 mm ² regions are extracted per 1 m ² of the surface and the Ni composition distribution is measured, at 80% or more of the areas, the Ni composition is measured. The method for producing an austenitic stainless steel sheet having excellent surface gloss uniformity, which comprises grinding the surface layer so that the half-value width of the composition distribution is 0.6% by mass or less.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, in order to improve the uniformity of surface gloss in an austenitic stainless steel sheet produced by a twin roll casting method, it is utilized that segregation of constituent elements is extremely small in the surface layer of a steel strip. did. In particular,
The element with the largest change in segregation of the constituent elements is N
It was found that i was i and it was clarified that the uniformity of surface gloss can be controlled by controlling the composition distribution of Ni in the surface layer. Specifically, the composition distribution of Ni on the surface layer of the steel plate is controlled by adjusting the grinding amount for coil flaw removal according to the steel strip.

The composition distribution of Ni in the austenitic stainless steel sheet produced by the twin roll casting method is analyzed by the electron probe microanalysis method or the fluorescent X-ray analysis method. The electron probe microanalysis method is a method of performing qualitative / quantitative analysis by irradiating a sample with a focused electron beam in a vacuum and detecting a characteristic X-ray emitted from the sample. On the other hand, the fluorescent X-ray analysis method is a method of performing qualitative / quantitative analysis by irradiating a sample with characteristic X-rays and detecting the characteristic X-rays emitted from the sample. The fluorescent X-ray analysis method can also analyze minute regions. The analysis region and depth by the electron probe microanalysis method and the fluorescent X-ray analysis method are about 1 μm and about 10 μm, respectively, depending on the analysis conditions.

Since the surface gloss uniformity of austenitic stainless steel sheet appears in the range of 0.1 mm to 10 mm, the surface gloss uniformity can be analyzed by associating it with the composition distribution in an area of about 1 mm square. Is suitable. Therefore, the electron probe microanalysis method and the fluorescent X-ray analysis method have sufficient spatial resolution to investigate the composition distribution in the region of about 1 mm ² , so that the surface composition and gloss uniformity of the austenitic stainless steel sheet are Suitable to find out.

FIG. 1 shows that the area cut out from an austenitic stainless steel sheet produced by twin roll casting is 1
An example is shown in which the composition distribution of Ni in the surface layer of the sample of mm ² is obtained by the electron probe microanalysis method.
To trim the shape of the steel plate, cut off the coil end,
A sample for measurement was randomly cut out from the sample. The compositional distribution of Ni is an example in which the horizontal axis represents the Ni composition and the vertical axis represents the proportion of regions having the respective Ni compositions. In FIG.
“A” is a result of the Ni composition distribution in a portion having a good surface gloss, and “b” is a result of the Ni composition distribution in a portion having a poor surface gloss. The half-value width in the composition distribution of Ni in each result is 0.55% by mass,
It was 0.62% by mass. In the region where the half-value width of the composition distribution of Ni is 0.6% by mass or less, the size distribution of crystal grains is relatively uniform, which causes the surface gloss to be uniform.

Needless to say, the more the area where Ni is distributed with a half-value width of 0.6% or less on the surface of the steel sheet, the better. It has been found that if 80%, preferably 90% or more of the areas satisfy this condition, the surface gloss can be visually judged to be uniform, which is in good agreement with the visual judgment of pass / fail. Therefore, the simplest method is to extract 10 areas of 1 mm ² per 1 m ² of the surface and measure the Ni composition distribution.
It is confirmed that the half width of the composition distribution of i is 0.6% by mass or less. It is preferable from the viewpoint of operation management that the area of 1 mm ² should be as many as 10 or more, and that the area of 1 m ² for which the distribution should be measured should be sampled as much as possible in the rolling direction or the width direction.

As described above, according to the present invention, the uniform Ni composition distribution formed on the surface layer of the austenitic stainless steel sheet produced by the twin roll casting method is utilized, and the Ni composition distribution is maintained on the steel sheet to obtain the surface gloss. Provided are a steel sheet with improved uniformity and a manufacturing method.

[0017]

EXAMPLES Examples of an austenitic stainless steel sheet produced by the twin roll casting method of the present invention and a production method thereof will be described. C: 0.03 and Si: in mass%
0.5, Mn: 0.6, P: 0.03, S: 0.00
2. Ni: 8.1, Cr: 18.4, the balance was made by melting an austenitic stainless steel consisting of inevitable impurities and Fe, and a steel strip having a plate thickness of 2.5 mm was manufactured by a twin roll casting method. After removing the scale of this steel strip and performing pickling, coil flaw removal is performed in several stages so that steel sheets with different Ni composition distributions in the surface layer can be obtained, and thereafter,
A steel plate was manufactured by a known method. The end portion of the coil, which is clearly inferior in the form of the steel sheet, and the width of 20 to 50 mm was cut off.

Table 1 shows 1 m ² produced by these methods.
In the steel sheet, the 1 mm ² region at 10 locations was randomly extracted, and the half-value width of the composition distribution of Ni on the surface of each location was calculated. 3 shows the results of examining the relationship between the surface glossiness and the surface gloss uniformity of the steel sheet. ⊚ indicates that the surface glossiness uniformity is extremely good, ∘ indicates good, and x indicates poor.

[0019] [ Table 1 ] Number surface gloss of a portion FWHM of Ni composition distribution becomes less Table wt% by 0.6 visual uniformity 10 ◎ 10 ◎ 9 ◎ 9 ◎ 8 ○ 7 × 5 × 3 ×

When the half-width of the Ni composition distribution is 0.6 mass% or less at 8 points or more, the surface gloss uniformity becomes good, and at 9 points or more, it is very good, and the product yield is also high. It will be good.

[0021]

According to the present invention, the uniformity of the surface gloss is N
Since it can be judged by a quantitative index called i concentration distribution, and it can also give a guide as to how much the surface layer should be polished depending on the steel type and operating conditions, so the surface gloss of the austenitic stainless steel sheet manufactured by the twin roll casting method is uniform. The austenitic stainless steel sheet with improved properties and excellent surface gloss uniformity can be stably manufactured. That is, it can be said that the yield of the austenitic steel sheet produced by the twin roll casting method can be increased and the production value is extremely high.

[Brief description of drawings]

FIG. 1 is a diagram showing a Ni composition distribution in an area of 1 mm2 on the surface of an austenitic stainless steel sheet manufactured by a twin roll casting method, in which the abscissa represents the Ni composition and the ordinate represents the ratio of the regions having the respective Ni compositions. is there.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazumi Seki             20-1 Shintomi, Futtsu City Nippon Steel Co., Ltd.             Inside the surgical development headquarters F-term (reference) 4E004 DA13 NB07 NC02

Claims (2)

[Claims] 1. An austenitic stainless steel sheet produced by a twin roll casting method, in which 10 or more 1 mm ² regions are extracted per 1 m ² of the surface, excluding the surface oxide layer, and the Ni composition distribution was measured. Occasionally, the full width at half maximum of the Ni composition distribution is 0.6% by mass or less at 80% or more thereof, and an austenitic stainless steel sheet having excellent surface gloss uniformity. 2. In the production of an austenitic stainless steel sheet by the twin roll casting method, 10 per 1 m ² of surface is produced.
When the area of 1 mm ² above the location is extracted and the Ni composition distribution is measured, the surface layer is ground so that the half-value width of the Ni composition distribution is 0.6 mass% or less at the location of 80% or more. A method for producing an austenitic stainless steel sheet having excellent surface gloss uniformity, comprising: