JP3591194B2 - Operating method of double cold rolling mill for manufacturing ultra-thin steel sheet - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention solves the inferior shape of the steel strip due to the change of the roll crown of the work roll in the # 2 stand, which is inevitable in cold rolling of ultra-thin steel sheets, particularly in cold secondary rolling using a double cold rolling mill. We try to avoid it effectively.
[0002]
[Prior art]
Conventionally, an ultra-thin steel sheet is rolled by a double cold rolling mill (hereinafter, referred to as “DR mill”) having a configuration as shown in FIG. 1 after annealing a steel strip subjected to ordinary cold rolling. I have.
By the way, in this DR mill, rolling oil is supplied at the # 1 stand entry side, the steel strip is rolled to almost the target sheet thickness with the rolling oil adhered to the surface thereof, and the steel strip is continuously rolled to the # 2 stand. , Rolling is usually performed for the purpose of adjusting the surface roughness of the steel strip and adjusting the plate shape.
[0003]
In the rolling by the DR mill having the above-described configuration, when rolling is performed by the # 1 stand, the temperature of the steel strip increases due to the heat generated during processing and the frictional heat between the work roll and the steel strip. Therefore, when the steel strip passes through the # 2 stand, the temperature of the work roll of the # 2 stand rises. As a result, there is a problem that the roll crown changes due to thermal expansion, and the plate shape of the steel strip is easily disturbed.
[0004]
Regarding this point, a method of controlling the shape of a plate by controlling a roll crown using a work roll bending device has been conventionally known, and a steel strip between stands has been disclosed as disclosed in Japanese Patent Application Laid-Open No. 7-16639. Prior arts such as a method of installing a water cooling device to cool a steel strip and keep the roll crown of a # 2 stand work roll constant have been known.
[0005]
[Problems to be solved by the invention]
However, the shape control by the roll bending device can control the ear growth and the belly expansion, but cannot control the composite expansion and the quarter expansion control as shown in FIGS. 2 (a) to 2 (d). Further, in the method of cooling the steel strip by disposing the steel strip cooling device between the stands, it may not be possible to cool the steel strip to room temperature depending on operating conditions such as when the rolling speed is high or when the rolling reduction is high. . For these reasons, in the case of the prior art, a change in the roll crown of the work roll in the # 2 stand is inevitable, and a problem remains in that the poor shape of the plate cannot be eliminated.
[0006]
SUMMARY OF THE INVENTION An object of the present invention is to propose an operation method capable of solving the above-mentioned problems of the related art which have occurred in cold rolling using a DR mill.
[0007]
[Means for Solving the Problems]
The present invention is based on the finding that the shape of a steel strip can be controlled with almost no heat generated by machining in a DR mill # 2 stand (1-2% rolling reduction) if appropriate operating conditions are set. (The shape in the # 1 stand can be completely recreated in the # 2 stand).
That is, according to the present invention, when performing cold rolling of a steel strip using a DR mill, first, the rolled material has a thickness of 1 to 2 times larger than the target final thickness in the first rolling by the # 1 stand. %, Cooled to room temperature + 10 ° C. or lower, and then rolled at a rolling reduction of 1-2% in a # 2 stand for shape control and sheet surface roughness control. This is a method of operating a double cold rolling mill for manufacturing thin steel sheets.
The normal temperature defined in the present invention is a temperature range of 0 to 50 ° C, more preferably a temperature range of 10 to 30 ° C.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
In cold rolling using a DR mill, the first rolling is performed by rolling the sheet thickness to be 1 to 2% thicker than the target sheet thickness, cooling to room temperature + 10 ° C or less, and then rolling at a rolling reduction of 1 to 2%. When performed in the 2nd stand, the heat transmitted from the steel strip to the # 2 stand work roll and the processing heat by rolling in the # 2 stand are reduced, and the work roll temperature does not rise in the # 2 stand. There is almost no change in the roll crown, and the shape of the steel strip is stabilized. In the present invention, in the second rolling following the first rolling, the rolling reduction is set to 1 to 2%, because heat generation can be avoided by keeping the rolling reduction in the second rolling within this range. It is.
[0009]
【Example】
Using a DR mill having the structure shown in FIG. 1 above, a steel strip (steel type: low carbon material or extremely low carbon material) having a thickness of 0.150 mm in the # 1 stand is 0.102 mm. Rolling to 0.100 mm was performed in the # 2 stand, and the fluctuation of the roll crown and the exit plate shape in the # 2 stand were examined as the influence of the cooling temperature after rolling by the # 1 stand. The results are shown in FIGS. 3 (a), (b) and FIG.
[0010]
As is clear from FIGS. 3 (a) and 3 (b), when the conditions deviated from the conditions specified in the present invention were accompanied by changes in the roll crown, it was difficult to maintain the quality of the steel strip. In rolling (rolling in the # 2 stand), the temperature of the steel strip was cooled to room temperature, and when rolling was performed at a low reduction rate of 1 to 2%, the temperature distribution in the axial direction of the work roll in the # 2 stand (roll The temperature distribution in the width direction was almost uniform as shown in FIG. 4, and it was confirmed that a steel strip having a good shape could be stably obtained.
[0011]
【The invention's effect】
As described above, according to the present invention, the fluctuation of the roll crown of the work roll in the # 2 stand, which is inevitable in cold rolling using a DR mill, can be made extremely small, so that good quality can be obtained. Steel strip can be manufactured stably.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a DR mill.
FIGS. 2A to 2D are diagrams showing quarter elongation.
FIG. 3 (a) is a graph showing the relationship between the inlet steel strip temperature and the outlet shape of the steel strip, and FIG. 3 (b) is a graph showing the relationship between the inlet steel strip temperature and the roll crown of the work roll. It is.
FIG. 4 is a diagram showing the temperature in the roll axis direction of a # 2 stand work roll.

Claims (2)

In performing cold rolling of a steel sheet using a double cold rolling mill consisting of # 1 stand and # 2 stand,
First, the rolled material is rolled in a state where the plate thickness is 1 to 2% thicker than the target final plate thickness in the first rolling by the # 1 stand, cooled to room temperature + 10 ° C or lower, and then the rolling reduction is set to 1 to 10. 2. A method for operating a double cold rolling mill for producing ultra-thin steel sheets, wherein the rolling is performed by a # 2 stand at 2%. The method according to claim 1, wherein the normal temperature is in a temperature range of 0 to 50C, more preferably 10 to 30C.

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