JPH10249403A - Manufacture of metallic sheet excellent in gloss - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the gloss on the surface of a material to be rolled, and to make it endurable for long time by fitting a sintered hard alloy sleeve having a specific Young's modulus with the composite rolls of the work rolls of a pass when performing cold rolling to the metallic sheet by a reversing mill, and specifying the outside diameter of the sleeve. SOLUTION: When performing the cold rolling to the metallic sheet 1 by the reversing mill, the composite rolls to be used is the one manufactured by fitting the sintered hard alloy sleeve whose Young's modulus is 35000khf/mm<2> or over with a steel-cored material. The thickness of the sleeve is 3% or over of the outside diameter of the roll, and the sleeve surface is ground in the axial direction. And, the composite rolls are used for the work rolls of at least either pass. When either pass is not a final pass, in the final pass in which conventional rolls are used, since there is a possibility that an oil pit is reintroduced, it is preferable that the final pass is included in either pass. For the sintered hard alloy to be used for the sleeve of the composite rolls, WC (tungsten carbide) is suitable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a metal sheet having excellent gloss, and more particularly to a method for producing a metal sheet by cold reverse rolling.

[0002]

2. Description of the Related Art Conventionally, in cold rolling of a metal plate using a pair of upper and lower work rolls, for example, in order to improve the surface gloss of a metal plate such as a stainless steel plate, it is necessary to use a super roll such as a tungsten carbide (hereinafter, WC) alloy roll. It is known that a hard alloy roll may be used.

Further, when a cemented carbide roll is used as a work roll of a cold tandem rolling mill or a reverse rolling mill, a cemented carbide sleeve is added to a core made of a conventional steel material in order to reduce costs. A method of fitting is known. A roll formed by manufacturing a WC alloy sleeve and fitting it to a steel shaft is disclosed in JP-B-58-31243, JP-A-57-11708 and the like. Have been described.

[0004] In addition, for example, Japanese Patent Application Laid-Open No. 5-96309 discloses that rolling using a steel-based work roll having an axially polished grain (hereinafter referred to as an axial polishing roll) is also effective in improving gloss. Is disclosed.

[0005]

When cold-rolling a cemented carbide roll as a work roll as described above, for example, when rolling using the roll in the final pass of cold reverse rolling, the material to be rolled is On the surface of the surface, a minute defect called a scratch due to the transfer of the work roll ground is generated. If such scratches are present on the sheet surface, the scratches remain even after the cold rolling subsequent steps of annealing, pickling, and temper rolling, and the sheet surface gloss of the final product is reduced by a steel roll. There is a problem that it is only slightly improved as compared with the case where is used.

Further, the roll formed by fitting the WC alloy-based sleeve to a steel-based core material is a small-sized roll applied to wire rods and strip rolling, and is used as a cold rolled work roll. In order to improve the gloss, it is necessary to increase both the roll diameter and the roll barrel, and the cost is high,
In addition, since a high surface pressure acts on almost half or more of the roll barrel, it is necessary to limit the physical properties of the roll material or the thickness of the sleeve to a specific range.

[0007] Further, when rolling is performed using an axial polishing roll in cold reverse rolling, the surface of the steel sheet is smoothed by the relative slip between the rolling roll and the surface of the material to be rolled in the rolling direction, and the gloss is improved. Therefore, the surface roughness of the roll surface caused by the heat treatment progressed very quickly, and there was a problem that the gloss improving effect was not maintained when the rolling was continued. The present invention has been made in view of the above-mentioned problems relating to plate surface gloss, and when producing a metal plate by cold reverse rolling, is to produce a metal plate having excellent gloss that can significantly improve and maintain the surface gloss of a material to be rolled. The aim is to propose a method.

[0008]

Means for Solving the Problems The present invention relates to a composite in which a metal plate is cold-rolled by a reverse rolling mill and a cemented carbide sleeve having a Young's modulus of 35,000 kgf / mm ² or more is fitted to a steel core. A roll whose sleeve thickness is equal to 3
% Or more, and a composite roll obtained by polishing the sleeve surface in the axial direction is used as a work roll in at least one of the passes.

In the present invention, it is preferable that at least one of the paths includes a final path.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The glossiness of a metal plate surface depends on the surface roughness. Usually, on the surface of a metal plate such as a steel plate after rolling, a micro defect having a depth of about several tens of μm called an oil pit generated by rolling oil biting into a roll bite, and a transfer of a work roll grinding mark. There is a micro defect called a scratch having a depth of about several μm.

[0011] When rolling using a cemented carbide roll as a work roll, the roll flatness due to the rolling load is smaller than when rolling using a steel-based work roll, the oil film inside the roll bite becomes thinner, and the oil Pits are reduced. Therefore, the inventors first paid attention to the Young's modulus of the roll. That is, it has been found that when the Young's modulus of the roll increases, the flatness of the roll during rolling decreases, and as a result, the bite angle can be increased, the oil film becomes thinner, and the number of oil pits decreases.

FIG. 2 shows the Young's modulus of the roll and the gloss of the steel sheet surface after rolling (JIS Z 8741 Glossiness measurement method (GS20 °)).
Is a graph showing the relationship between the roll Young's modulus is 2100
It can be seen that the gloss increases little by little as the value increases from 0 kgf / mm ^2, and the gloss increases remarkably when the value is about 35000 kgf / mm ² or more. From this, in the present invention,
One of the requirements is that a roll having a Young's modulus of 35000 kgf / mm ² or more is used as a work roll in at least one of the passes in cold reverse rolling.

If any one of these passes is not the final pass, the oil pit may be re-introduced in the final pass using a conventional roll, so that any one of the passes includes the final pass. Is preferred. As a result of further study, increasing the Young's modulus of the roll increases the gloss of the steel sheet surface after rolling due to the reduction of oil pits, but at the same time, the grinding film of the roll is transferred to the steel sheet surface because the oil film becomes thinner It was found that the scratches increased and the gloss improvement margin was reduced.

On the other hand, in rolling by a steel roll polished in the axial direction, the roll and the surface of the steel sheet relatively slide in the rolling direction in the roll bite, and the roll grinding smoothes the surface of the steel sheet. Defects are reduced, but the abrasion of the roll grinding progresses much faster than in rolling using a roll polished in the normal circumferential direction, and if rolling is continued, the gloss level at the beginning of rolling is not maintained. The frequency of replacement had to be increased, and it was not in a state that could withstand normal process production.

The present inventors have studied to solve these problems, and as a result, have found that the wear of the cemented carbide roll hardly progresses during the rolling operation. Then, the cemented carbide roll polished in the axial direction is used. An abrasion-promoting experiment was performed by using the same, and it was found that the cemented carbide roll polished in the axial direction hardly wears the grinding pit unlike the conventional steel roll polished in the axial direction.

Further, by the test rolling of the stainless steel sheet using the cemented carbide roll, the generation of oil pits and scratches can be effectively suppressed, and the steel sheet has a synergistic effect of improving the roll material and improving the polishing direction of the roll. The gloss of the roll is greatly improved, and the frequency of roll changes
They found that the replacement frequency was the same as the replacement frequency of cemented carbide rolls with grinding edges in the circumferential direction, and was significantly lower than that of conventional steel rolls.

Therefore, in the present invention, it is added to the requirement that the roll satisfying the Young's modulus range is a cemented carbide roll polished in the axial direction. However, when a cemented carbide roll is used as a work roll for cold rolling, for example, considering the use of a WC (tungsten carbide) -based cemented carbide, the entire work roll may be integrated with a WC alloy. There is a problem that the manufacturing cost becomes extremely high.

Therefore, in the present invention, as the cemented carbide roll, a sleeve-type composite roll having a structure in which a surface layer portion of the roll in contact with the metal plate is made of a cemented carbide sleeve and fitted with a steel material roll core material is used. Added to the requirements.
However, when such a composite roll is used, the flatness of the roll during rolling may be different from that of the WC alloy integrated roll. The gloss of the steel sheet surface after rolling is greatly related to the flat roll radius. In the case of a composite roll, the flat radius does not differ greatly from that of the WC alloy integrated roll, and both performance and cost are achieved in order to reduce manufacturing costs. WC
It is extremely important to set the thickness of the outer layer optimally.

From this point of view, the inventors diligently studied the optimum sleeve thickness of a composite roll formed by fitting a WC alloy sleeve to a steel core material by analysis using a finite element method (FEM) and rolling experiments. The result is shown in FIG. 3, the increase rate and the ratio t / r of the WC layer thickness t and the roll radius r of the composite roll, for flattening roll radius R WC alloy integral roll (flat roll radius _{R 0) (R-R 0} ) /
This is a graph showing the relationship with R ₀ . t / r (%
Rolls with 0% are steel integrated rolls (Young's modulus 21000k)
gf / mm ² ), and the 100% roll is a WC alloy integrated roll (Young's modulus: 35,000 to 62000 kgf / mm ² ), and the middle is a composite roll.

As shown in FIG.₀) / R
₀Is about 70% for a steel integrated roll (t / r = 0%)
On the other hand, a composite roller with a WC outer layer thickness of 3% or more of the roll radius
(T / r ≧ 3%), within 10%, WC alloy
It is possible to obtain a sufficient gloss improvement effect comparable to one roll
New knowledge has been obtained that it is possible. Further
In addition, the thickness of the WC outer layer is set to 10% or more of the roll radius (t / r ≧ 10
%), (RR) ₀) / R₀Within 2%
And understand that it is possible to achieve higher effects.
Was.

Based on the above new findings, in the present invention, the preferable range of the thickness of the cemented carbide sleeve, which is the outer layer of the composite roll, is set to 3% or more of the roll radius. Since the upper limit of t / r should be appropriately set according to the margin of the roll cost, it is not determined from the present invention. As the cemented carbide used for the sleeve of the composite roll, WC (tungsten carbide) is suitable, and it is more preferable to add Co, Ni, Cr, Ti or the like to the alloy to improve the fracture toughness.

[0022]

The following is a comparison between the conventional method and the invention method. In a 12-stage cold reverse rolling mill shown in FIG.
A SUS430 (ferritic) stainless steel plate was used as a material to be rolled (metal plate) 1 and rolled in five passes to a finish thickness of 0.8 mm. In FIG. 1, each rolling mill includes a pair of work rolls 2, intermediate rolls 3A and 3B, and a backup roll 4 respectively.
A to 4C.

The work rolls in the first to fourth passes are steel rolls polished in the conventional circumferential direction, and the work rolls in the fifth pass are (a) 3% of the roll diameter according to the embodiment of the present invention. A WC-Co12% alloy (Young's modulus: 58000 kgf / mm ² ) sleeve that has a sleeve thickness and is polished in the axial direction. A composite roll in which a sleeve is fitted to the steel shaft center. This is a comparative example. (B) Axial polished
WC-Co 12% alloy integrated roll, and (c) circumferentially polished WC-Co 12% alloy integrated roll, (d) axially polished steel-based integrated roll (5% chromium cast steel), e)
The above rolling was continuously performed for 10 coils under the following five conditions, namely, a steel-based integrated roll polished in the circumferential direction,
The change in the glossiness of the product surface after annealing, pickling, temper rolling, and buffing was investigated. The gloss was measured based on the JIS Z 8741 gloss measurement method (GS20 °).

FIG. 4 shows an embodiment (a), a comparative example (b), and a conventional example.
It is a transition diagram of the glossiness according to the number of rolling coils of (c)-(e). From comparison between the condition (d) of the conventional steel rolls and the condition (e) of the circumferential polishing rolls, the glossiness immediately after the start of the rolling was higher under the condition (d). Although it is further improved, it can be seen that the wear of the grinding line progresses remarkably quickly and the glossiness immediately falls to the level of the condition (e). In addition, under the condition (c) using the WC-Co12% alloy integrated roll of the circumferential polishing, the glossiness level is persistent, but the level is the condition using the steel-based integrated roll of the axial polishing (d ) Is not much different from the start of rolling (initial stage). On the other hand, under the condition (b) using the WC-Co12% alloy integrated roll of the axial polishing, which is the comparative example, the initial level of the glossiness is further improved and the durability is good. And WC-12 of the embodiment
Under the condition (a) using the% Co alloy composite roll, a result equivalent to the condition (b) of the comparative example in which the best result is obtained can be obtained at a low roll cost.

Thus, it was confirmed that the surface gloss of the steel sheet was remarkably improved and the effect was maintained by rolling using the cemented carbide composite roll polished in the axial direction. In addition, the same rolling mill was used for each of the first to fourth passes using the roll under the condition (a), and the other passes were also performed using the roll under the condition (e). The gloss level did not decrease with the number, and the gloss level improved as the pass order using the roll of the condition (a) came later (about 430 when used in the first pass, and 480 when used in the fourth pass). degree).

In the same rolling mill, the roll under the condition (a) is continuously used in the first to fifth passes to perform rolling, and the roll after rolling, annealing, pickling, temper rolling, and buffing is used. Inspection of the glossiness of the product surface revealed that the roll was changed at a level similar to that of FIG. 4 (a) when only the fifth pass was used. It has been confirmed that unnecessary high-efficiency rolling is possible.

It goes without saying that the present invention is not limited to the range of the number of steps, the type of metal plate, the plate thickness and the like of the reverse rolling mill used in the embodiment.

[0028]

According to the present invention, it is possible to efficiently and stably produce a metal plate having much better surface gloss than conventional ones by cold reverse rolling.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an example of a cold reverse rolling mill train suitable for carrying out the present invention.

FIG. 2 is a graph showing the relationship between the Young's modulus of a roll and the glossiness of a material to be rolled.

[3] increase rate for the ratio t / r of the WC layer thickness t and the roll radius r of the composite roll, flat roll radius R WC alloy integral roll (flat roll radius _{R 0) (R-R 0} ) /
4 is a graph showing a relationship with R ₀ .

FIG. 4 is a transition diagram of glossiness according to the number of rolling coils in Example (a), Comparative Example (b), and Conventional Examples (c) to (e).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rolled material (metal plate) 2 Work roll 3A, 3B Intermediate roll 4A-4C Backup roll

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuhito Kenmochi 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Prefecture Inside the Technical Research Institute of Kawasaki Steel (72) Inventor Masato Iri 1 Kawasaki-cho, Chuo-ku, Chiba-shi, Chiba Address: Kawasaki Steel Corporation Chiba Works (72) Inventor Hajime Nagai 1 Kawasaki-cho, Chuo-ku, Chiba-shi

Claims (2)

[Claims] A composite roll comprising a steel plate and a cemented carbide sleeve having a Young's modulus of 35,000 kgf / mm ² or more when a metal plate is cold-rolled by a reverse rolling mill. Using a composite roll having a diameter of 3% or more of the outer diameter of the roll and the sleeve surface polished in the axial direction as a work roll in at least one of the passes. . 2. The method of claim 1, wherein said at least one path includes a last path.