JPH07310200A - Production of high-brightness stainless steel - Google Patents

Abstract

PURPOSE:To produce a high-brightness stainless steel sheet by selectively producing a cold rolled stainless steel sheet rolled by tandem cold rolling mills, etc., featuring high production efficiency to desired high surface grades. CONSTITUTION:The stainless steel sheet having substantially its final thickness is rolled by the tandem cold rolling mills, etc., and is then passed through an electrolytic controlled according to the surface brightness of the cold rolled steel sheet and the surface brightness of the target surface grade, by which the surface brightness is improved and the surface brightness grades are selectively formed with single line. As a result, the high-brightness cold rolled stainless steel sheet is extremely efficiently produced with the single line.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a high-gloss stainless steel sheet for improving the surface of a stainless cold-rolled steel sheet to a desired surface gloss grade by passing the electrolytic cold-polishing step on the stainless cold-rolled steel sheet and controlling the electrolysis conditions. The present invention relates to a method of manufacturing (including steel strip, the same applies hereinafter).

[0002]

2. Description of the Related Art Stainless steel is not only excellent in corrosion resistance and workability, but also excellent in surface properties such as glossiness, so that it is widely used in building materials, household products, decorations, etc. Stainless steel sheets with various surface glosses are manufactured depending on the purpose of use. However, the surface gloss is substantially determined by the conditions such as surface roughness and diameter of work roll in cold rolling, lubricating oil, rolling speed, etc., so it is necessary to perform rolling according to the desired surface gloss. It was

N in the surface finish category of JIS G4305
o. High-brightness stainless cold-rolled steel sheets such as 2B finishing materials and BA finishing materials are described in, for example, "3rd Edition Steel Handbook, Vol. III (1)" (issued May 15, 1980, issued by Maruzen Co., Ltd.). 701-P. As shown in 707, cold rolling is performed using a high-gloss rolling oil such as neat oil in a mill having a small diameter work roll such as a Sendzimir mill or a small diameter cluster mill to obtain a stainless cold-rolled steel sheet having a target surface gloss.
In order to maintain the surface gloss, annealing / pickling process or bright annealing process was performed to obtain the desired mechanical properties. However, this method has a problem that the production efficiency is low because a low-speed lever mill having a small-diameter work roll such as a Sendzimir mill and a rolling speed of about 200 to 400 mpm is used.

Therefore, in recent years, for example, Japanese Patent Laid-Open No. 5-245550.
As shown in Japanese Patent Publication No. 3, Japanese Patent Laid-Open No. 3 (1994) -No. At this time, if high-gloss rolling oil is used in a high-speed mill, steel plate surface defects due to poor lubrication called heat scratches will occur.Therefore, rolling with both high cooling capacity and high lubrication for beef tallow, emulsions containing synthetic ester as the base oil, etc. It is necessary to use oil. However, when high-speed rolling is performed using the above-mentioned high cooling capacity / high lubrication rolling oil, the rolling oil is drawn into the roll bite, and as a result, numerous minute irregularities called oil pits are formed on the steel plate surface, resulting in a smooth surface. There was a problem that it was not possible to manufacture a high-gloss stainless steel plate.

Therefore, the low-gloss stainless steel sheet produced in this manner is limited to applications in which only corrosion resistance is important regardless of surface gloss, such as automobile exhaust system materials, or a high-gloss rolling oil is used with a Sendzimir mill or the like. It is necessary to smooth the oil pits described above by passing through a complicated process of rolling again using a steel sheet, which has low production efficiency.

[0006]

SUMMARY OF THE INVENTION Therefore, the purpose of the present invention is to temporarily achieve the object by a method such as rolling with high cooling capacity and high lubricating rolling oil in a high speed tandem mill having a large diameter work roll with high production efficiency. The problem is to produce a stainless steel sheet having a surface gloss lower than that of the above-mentioned surface gloss, and then to produce the desired high surface gloss grade without rolling with a high-gloss rolling oil in a Sendzimir mill or the like.

For example, Japanese Patent Laid-Open No. 63-134700 discloses a method of smoothing the surface of a metal strip by electrolytic polishing, and Japanese Patent Laid-Open No. 4-281000 discloses a method of electrolytically smoothing the surface of a magnetic steel sheet by electrolytic polishing. An apparatus for controlling the electrolytic conditions so as to measure the surface gloss after polishing and stabilize the surface gloss value at a predetermined value is disclosed, but both of them relate to mirror polishing the surface of a metal strip by electrolytic polishing, It was not possible to solve the problem of producing a wide range of surface gloss grades according to the present invention.

The present invention solves the above problems and improves the surface gloss by controlling the electrolytic polishing conditions on the surface of a stainless steel plate by applying an electrolytic polishing step after cold rolling to obtain a target surface gloss grade. The purpose is to provide a method of making different parts.

[0009]

That is, the gist of the present invention is to provide a cold rolling mill, preferably a work roll having a work roll diameter of 150 mmφ or more, or 30 cSt.
Cold rolling mill using rolling oil with a viscosity of (50 ° C) or more, or a work roll having a work roll diameter of 150 mmφ or more and a work roll surface roughness of 0.1 μmRa or more, or 30 cSt (50 ° C) or more By a cold rolling mill using a rolling oil having a viscosity, first, a stainless steel plate having a substantially final plate thickness or a stainless steel plate having a plate surface roughness of 0.1 μmRa or more and a substantially final plate thickness is rolled,
After that, if necessary, annealing is performed, and then, if necessary, light rolling, buffing, and pickling are performed by one or more kinds, and then an electrolytic polishing step is performed, and the electrolytic polishing conditions are set to those of the cold rolled steel sheet. The surface gloss is improved by controlling the electropolishing conditions such as line speed and electrolytic current according to the surface gloss and the target surface grade surface gloss, and by removing the oxide film generated by the above-mentioned annealing at the same time if necessary. This is a method for producing high-gloss stainless steel sheets, which is characterized by producing surface gloss grades separately in one line.

[0010]

The function of the present invention will be described in detail below. Converter,
Molten steel melted in a melting furnace such as an electric furnace is made into a slab through a continuous casting method, ingot casting, or slabbing method, and a normal stainless steel sheet that has been hot rolled and hot coil annealed / pickled is used as a cold rolled material. use.

Electrolytic polishing improves the luster of the surface of a stainless steel plate and makes it possible to produce a desired surface luster grade steel plate. The reason why electrolytic polishing is that the surface of an electropolished abrasive material is ground and smoothed by the ions in the electropolishing liquid. Therefore, the inventors have found that the desired surface gloss can be obtained by controlling the electropolishing conditions, particularly the line speed and the electrolysis current, that is, the electrolysis time per unit area and the electrolysis current density.

FIG. 1 shows a cold-rolled steel sheet obtained by rolling a SUS430 cold-rolled material having a thickness of 3 mm in a tandem cold rolling mill having a work roll diameter of 500 mmφ with a high cooling capacity and a highly lubricating rolling oil at a rolling speed of 800 mpm to a thickness of 1 mm. After annealing, the change in the glossiness of the steel sheet surface when electrolytic polishing was performed in a phosphoric acid-sulfuric acid-potassium dichromate solution while changing the line speed at an electrolytic current density of 100 A / dm ² was performed according to the method of JIS Z8741. It was measured. From the figure, glossiness (GS = 45 °)
The surface of stainless cold-rolled steel sheet with a value of about 200 increases in glossiness as the electrolytic current density increases, and
^{At 2} or more, a maximum gloss of 850, which exceeds the surface gloss equivalent to the BA finishing material, is obtained, and at more than 2 it saturates, and by controlling the line speed and electrolytic current, etc. It is clear that a surface gloss grade that

The cold rolling mill for rolling the stainless steel sheet according to the present invention is capable of performing high-speed and high-efficiency rolling with sufficient rolling oil drawn into the roll bite and without causing heat scratches on the steel sheet surface. A rolling mill with work rolls of different diameters, or high cooling capacity and high lubricity allows high-speed, high-efficiency rolling regardless of work roll diameters without causing heat scratches.
Using a rolling mill that uses rolling oil having a viscosity of 0 cSt (50 ° C.) or higher is highly effective.

Further, if the work roll surface roughness of the cold rolling mill is too low, or if the surface roughness of the stainless steel plate after cold rolling is too low, high speed rolling with high cooling capacity and high lubricating rolling oil is carried out. When it is carried out, the coefficient of friction between the steel plate and the work roll is excessively reduced, and rolling abnormalities such as chattering occur and stable rolling cannot be performed. Therefore, the work roll surface roughness is set to 0.1 μmRa or more, and the steel plate surface roughness is set to 0.1 μm.
When it is Ra or more, it is more advantageous in terms of productivity and economy.

Further, the stainless steel sheet rolled with a high-gloss rolling oil in a Sendzimir mill or the like is also subjected to the electrolytic polishing of the present invention to improve the gloss, for example, No. Two
The B finish can be a BA finish. Furthermore, the electrolytic polishing of the present invention is performed on a low-gloss stainless steel sheet rolled with a high cooling capacity and high lubricating rolling oil in a tandem mill having a large-diameter roll to improve the gloss. Needless to say, it is also possible to set a target specific surface gloss such as 2B finishing material or BA finishing material.

If the stainless steel plate is cold-rolled,
Since the steel sheet is hardened by rolling and has poor workability, continuous or batch annealing is usually performed. This is to improve the elongation, workability, etc. of the cold-rolled steel sheet and to improve the corrosion resistance, and after cooling at a temperature that causes recrystallization, cooling at a cooling rate that does not cause a Cr-deficient layer at grain boundaries. Is desirable. Even if this annealing is performed after cold rolling and before electropolishing, it has the same electropolishing effect as in the case where no annealing is performed. Furthermore, when a thin oxide film is generated on the surface of the steel sheet during the above-described annealing, the oxide film can be simultaneously removed by polishing during electrolytic polishing. Further, the stainless steel plate may be cold-rolled, then electrolytically polished, and then annealed for the above-mentioned purpose,
In this case, in order to maintain the surface gloss obtained by electropolishing,
Annealing and pickling are performed to dissolve and remove the oxide film on the steel sheet surface generated by annealing, or bright annealing is performed to suppress the formation of oxide film.

Further, if one or more pretreatments of light rolling, buffing, and pickling are performed before passing through the electrolytic polishing step, fine irregularities on the steel sheet surface after tandem cold rolling are reduced, and electrolytic polishing is performed. The desired surface gloss can be obtained in a shorter time than when used alone. Furthermore, by subjecting the above-mentioned stainless steel sheet subjected to electrolytic polishing and annealing to temper rolling, it is possible to manufacture a stainless steel sheet having more excellent flatness and no elongation at yield.

As described above, according to the method of the present invention, a stainless cold-rolled steel sheet manufactured with the same or different surface gloss until cold rolling is made to have a desired surface gloss in the electrolytic polishing step to obtain a surface gloss grade. Regardless of the rolling conditions, the surface gloss grade can be manufactured separately in the same manufacturing process, that is, in a single line.

[0019]

EXAMPLES Examples of the present invention will be shown below. Table 1 is thickness 3
mm SUS304 steel, SUS430 steel, SUS409
Steel and SUS444 steel cold rolled material with work roll diameter of 500 mm
A cold-rolled steel sheet rolled with a φ tandem cold rolling mill at a rolling speed of 800 mpm to a thickness of 1 mm using a high-cooling / highly-lubricating rolling oil is subjected to electrolytic polishing after cold rolling [Example of the invention- 1] After Cold Rolling, Annealing, and Electropolishing [Invention Example-2] After Cold Rolling, Electropolishing, and Annealing / Pickling [Invention Example-3] After cold rolling, electrolytic polishing, and then bright annealing [Invention Example-4] After cold rolling, then annealing and pickling were performed [Comparative Example-1]. Show.

In addition, after rolling with a high gloss rolling oil in a Sendzimir mill, followed by annealing and pickling [Comparative Example-
2] is shown. The electropolishing conditions used here are phosphoric acid-sulfuric acid-potassium dichromate as the electropolishing liquid, a liquid temperature of 60 ° C. and an electrolytic current density of 3,000 C / dm ² . Further, the glossiness was measured at GS = 45 ° using a reflectance measuring device based on JIS Z8741.

[0021]

[Table 1]

Table 2 shows SUS304 steel and SUS with a thickness of 3 mm.
430 steel cold-rolled material with work roll diameter 5 as in Table 1 above
A cold rolled steel sheet rolled to a thickness of 1 mm at a rolling speed of 800 mpm using a high cooling capacity and high lubricating rolling oil in a 00 mmφ tandem cold rolling mill was continuously annealed and then lightly rolled and buffed as a pretreatment before electrolytic polishing. The results of polishing and pickling are shown below. Here, electrolytic polishing and gloss measurement were also performed under the same conditions as in Table 1 above.

[0023]

[Table 2]

Table 3 shows SUS304 steel and SUS with a thickness of 3 mm.
430 steel cold-rolled material with work roll diameter 5 as in Table 1 above
A cold rolled steel sheet rolled to a thickness of 1 mm at a rolling speed of 800 mpm using a high cooling capacity / high lubricity rolling oil in a 00 mmφ tandem cold rolling mill was continuously annealed, and then electrolytic current density was changed during electrolytic polishing. The electrolytic polishing and the measurement of glossiness were conducted under the same conditions as in Table 1 above. As is clear from the table, the desired surface gloss can be obtained by the electrolytic current density, and the high gloss No. It is possible to manufacture stainless cold-rolled steel sheets with various surface luster such as 2B finish and BA finish.

[Table 3]

Table 4 shows SUS304 steel and SUS having a thickness of 3 mm.
430 steel cold-rolled material with work roll diameter 5 as in Table 1 above
A cold rolled steel sheet rolled to a thickness of 1 mm at a rolling speed of 800 mpm using a tandem cold rolling mill of 00 mmφ with a high cooling capacity and a high lubricating rolling oil was continuously annealed, and then the electrolytic current density was 2,000 C / dm ²
Other than that, electrolytic polishing and gloss measurement were performed under the same conditions as in Table 1 above. It should be noted that the heat scratches and chattering in Table 4 indicate "o" does not occur and "x" occurs.

[0026]

[Table 4]

[0027]

EFFECTS OF THE INVENTION According to the present invention, a high-gloss stainless steel sheet is manufactured with a surface gloss lower than the target surface gloss and the same surface gloss until cold rolling, and then electrolytic polishing is performed under the conditions according to the target gloss grade. It has become possible to separately manufacture high-gloss stainless cold-rolled steel sheets with the desired gloss. As a result, cold rolling can be performed with a highly efficient tandem cold rolling mill or the like without changing rolling conditions such as work roll surface roughness, and stainless cold rolled steel sheet can be manufactured very efficiently in a single line. It became so.

[Brief description of drawings]

FIG. 1 shows the relationship between electrolytic current density and surface gloss of a stainless cold-rolled steel sheet according to the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Takashi Okazaki Inventor Takashi Okazaki 1-1, Toibata-cho, Tobata-ku, Kitakyushu, Fukuoka New Nippon Steel Co., Ltd. Yawata Works (72) Ryohiro Shiroge Tobata, Kitakyushu, Fukuoka Prefecture No. 1-1, Hibata-cho, Shin-Nippon Steel Co., Ltd. In Yawata Works, Incorporated (72) Inventor, Kazuo Endo No. 1-1 Hibata-cho, Tobata-ku, Kitakyushu, Fukuoka Prefecture

Claims (14)

[Claims] 1. A cold rolling mill first rolls a stainless steel plate having a substantially final thickness, and then an electrolytic polishing step is performed, and the electrolytic polishing conditions are set to the surface gloss of the cold rolled steel plate and a target surface grade. A method for producing a high-gloss stainless steel plate, characterized by improving the surface gloss by controlling according to the surface gloss of the above, and separately producing surface gloss grades in a single line. 2. A cold rolling mill is first used to roll a stainless steel plate having a substantially final thickness, and then the stainless steel plate is annealed and then passed through an electrolytic polishing step to bring the electrolytic polishing conditions into the cold state. Manufacture of high-gloss stainless steel sheets characterized by improving surface gloss by controlling according to the surface gloss of hot-rolled / annealed steel sheet and the surface gloss of the target surface grade, and creating different surface gloss grades in a single line. Method. 3. A cold rolling mill first rolls a stainless steel plate having a substantially final thickness, and then an electrolytic polishing step is performed, and the electrolytic polishing conditions are set to the surface gloss of the cold rolled steel plate and a target surface grade. Manufacture of high-gloss stainless steel sheets, characterized by controlling the surface gloss of each of them and further improving the surface gloss by annealing, pickling or bright annealing, and creating different surface gloss grades in a single line. Method. 4. A cold rolling mill is first used to roll a stainless steel plate having a substantially final thickness, and then this stainless steel plate is annealed and then passed through an electrolytic polishing step to bring the electrolytic polishing conditions to the cold Controlling according to the surface gloss of the hot-rolled / annealed steel sheet and the surface gloss of the target surface grade, and at the same time improving the surface gloss by removing the oxide film generated by the above-mentioned annealing, and creating different surface gloss grades in a single line. And a method for producing a high-gloss stainless steel plate. 5. A stainless steel sheet having a final thickness is first prepared by a cold rolling machine having a work roll diameter of 150 mmφ or more or a cold rolling machine using a rolling oil having a viscosity of 30 cSt (50 ° C.) or more. Rolling, and then passing through the electrolytic polishing step, improve the surface gloss by controlling the electrolytic polishing conditions according to the surface gloss of the cold rolled steel sheet and the surface gloss of the target surface grade, and improve the surface gloss in a single line. A method for producing high-gloss stainless steel plates, which is characterized by producing different grades. 6. A stainless steel plate having a final final thickness is first rolled by a cold rolling machine having a work roll diameter of 150 mmφ or more or a cold rolling machine using a rolling oil having a viscosity of 30 cSt (50 ° C.) or more. Then, after this stainless steel sheet is annealed, it is passed through an electrolytic polishing step, and the electrolytic polishing conditions are controlled according to the surface gloss of the cold-rolled / annealed steel sheet and the surface gloss of the target surface grade. A method for producing a high-gloss stainless steel plate, which is characterized by improving gloss and separately producing surface gloss grades in a single line. 7. A stainless steel plate having a final thickness is first rolled by a cold rolling machine having a work roll diameter of 150 mmφ or more or a cold rolling machine using a rolling oil having a viscosity of 30 cSt (50 ° C.) or more. Then, the electrolytic polishing step is passed, the electrolytic polishing conditions are controlled according to the surface gloss of the cold rolled steel sheet and the surface gloss of the target surface grade, and the surface is further subjected to annealing / pickling or bright annealing. A method for producing a high-gloss stainless steel plate, which is characterized by improving gloss and separately producing surface gloss grades in a single line. 8. A stainless steel plate having a final thickness is first rolled by a cold rolling machine having a work roll diameter of 150 mmφ or more or a cold rolling machine using a rolling oil having a viscosity of 30 cSt (50 ° C.) or more. Then, after annealing the stainless steel sheet, the electrolytic polishing step is passed, and the electrolytic polishing conditions are controlled according to the surface gloss of the cold-rolled / annealed steel sheet and the surface gloss of the target surface grade and at the same time. A method for producing a high-gloss stainless steel sheet, characterized in that the surface gloss is improved by removing the oxide film generated by annealing, and surface gloss grades are produced separately in a single line. 9. A cold rolling mill having a work roll diameter of 150 mmφ or more and a work roll surface roughness of 0.1 μmRa or more, or a cold rolling mill using a rolling oil having a viscosity of 30 cSt (50 ° C.) or more, A stainless steel sheet having a surface roughness of 0.1 μmRa or more and having a non-glossy and substantially final thickness is rolled, and then passed through an electrolytic polishing step, and the electrolytic polishing conditions are set to the surface gloss of the cold rolled steel sheet and the target surface grade. A method for producing a high-gloss stainless steel sheet, characterized in that the surface gloss is improved by controlling the electrolytic polishing conditions according to the surface gloss, and the surface gloss grade is produced separately in a single line. 10. A cold rolling mill having a work roll diameter of 150 mmφ or more and a work roll surface roughness of 0.1 μmRa or more, or a cold rolling mill using a rolling oil having a viscosity of 30 cSt (50 ° C.) or more, Surface roughness 0.1 μm
A stainless steel plate having a non-glossy and substantially final thickness of Ra or more is rolled, and then this stainless steel plate is annealed and then passed through an electrolytic polishing step, and the electrolytic polishing conditions are set to those of the cold rolled / annealed steel plate. A method for producing a high-gloss stainless steel sheet, which is characterized by improving the surface gloss by controlling it according to the surface gloss and the surface gloss of a target surface grade, and separately producing the surface gloss grade in a single line. 11. A cold rolling machine having a work roll diameter of 150 mmφ or more and a work roll surface roughness of 0.1 μmRa or more, or a cold rolling machine using a rolling oil having a viscosity of 30 cSt (50 ° C.) or more, Surface roughness 0.1 μm
A stainless steel plate having a non-glossy and substantially final thickness of Ra or more is rolled and then passed through an electrolytic polishing step, and the electrolytic polishing conditions are set according to the surface gloss of the cold rolled steel sheet and the surface gloss of a target surface grade. A method for producing a high-gloss stainless steel sheet, which comprises controlling and further annealing / pickling or bright annealing to improve the surface gloss, and producing different surface gloss grades in a single line. 12. A cold rolling machine having a work roll diameter of 150 mmφ or more and a work roll surface roughness of 0.1 μmRa or more, or a cold rolling machine using a rolling oil having a viscosity of 30 cSt (50 ° C.) or more, Surface roughness 0.1 μm
A stainless steel plate having a non-glossy and substantially final thickness of Ra or more is rolled, and then this stainless steel plate is annealed and then passed through an electrolytic polishing step, and the electrolytic polishing conditions are set to those of the cold rolled / annealed steel plate. The surface gloss is controlled by controlling the surface gloss and the surface gloss of the target surface grade, and at the same time, the surface gloss is improved by removing the oxide film generated by the above-mentioned annealing, and the surface gloss grade is produced separately in a single line.
Method for manufacturing high-gloss stainless steel sheet. 13. The surface gloss grade is controlled by at least one of line speed and electrolytic current.
The method for producing a high-gloss stainless steel plate according to each of claims 1 to 12. 14. Light rolling, buffing,
The method for producing a high-gloss stainless steel sheet according to each of claims 1 to 13, characterized in that one or more kinds of pickling are performed.