JP2951424B2 - In-line skin pass dull eye transfer method in continuous annealing equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Industrial applications] In recent years, focusing on steel sheets for automatic use,
A steel plate that has good deep drawability using ultra-low carbon steel and has excellent clarity on painted surfaces (hereinafter simply referred to as a high clarity steel plate)
The demand for is increasing. Here, the above sharpness is
It is evaluated from the glossiness determined by the amount of diffuse reflection on the painted surface of the coated steel sheet and the image clarity determined by the magnitude of the image distortion.

[0002] In order to obtain the above-mentioned high-definition steel sheet, it is necessary to carry out laser dulling with a laser dulling work roll having uniform dimensions and uniform irregularities on a predetermined basis in skin pasul finish rolling. It is important to transfer the uniform dull pattern to the steel sheet accurately. This laser dull basis weight is also advantageously used for mat dull finish. On the other hand, in order to simplify the manufacturing process, an inline skin pass mill is arranged at the outlet side of recent continuous annealing equipment, and annealing and skin pass rolling are performed continuously.

[0003] Under such circumstances, the present invention provides a method for accurately transferring a laser dull line to a steel sheet in dull finish rolling by an in-line skin pass using a laser dulling work roll in a continuous annealing facility. It is intended to propose.

[0004]

2. Description of the Related Art Conventionally, in skin pass rolling, a work roll having a dull surface formed by shot blasting or electric discharge machining has been used in order to impart a dull shape to a steel plate surface except for a tinplate original plate. For example, for the purpose of improving the sharpness of a painted surface, a laser dulling work roll with a uniform and uniform dull pattern by laser processing has been used. In order to transfer the dull line to the steel sheet properly, a high degree of control has been required in skin pass rolling. However, in the past rolling with an in-line skin pass mill, especially when manufacturing a laser dulled steel sheet having good deep drawability using ultra-low carbon steel, when the laser dull weight is insufficient at the end of the steel sheet Therefore, the yield was reduced.

[0005] As a method for preventing unevenness in the roughness of the steel plate surface, the applicant company disclosed in Japanese Patent Application Laid-Open No. Sho 60-12204 a method in which the intermediate rolls of the front stand and the rear stand were reversed with a 6Hi mill. A dull finish temper rolling method that shifts in the direction has been proposed, but the disclosed example is directed to reducing the dull roughness of the steel sheet due to the abrasion of the dull of the work roll. It is not suitable when it is important to transfer the uniform dull portion of the roll accurately to the steel sheet surface.

[0006]

SUMMARY OF THE INVENTION The present invention is intended to advantageously solve the above-mentioned improper transfer of dull lines, and in order to obtain good deep drawability with a steel plate for automobiles or the like, the material is extremely small. It must be a low-carbon steel. In order to maintain the good deep drawability unique to ultra-low carbon steel, the elongation percentage in skin pass rolling must be 1% or less. In order to prevent the abrasion of the dull, wet rolling using a temper rolling solution must be performed, and in order to simplify the process, rolling must be performed using an inline skin pass mill (work roll diameter of about 450 mm). Even
An object of the present invention is to propose a method of accurately transferring a uniform dull pattern of a laser dull work roll onto a steel sheet surface.

[0007] Rolling in an off-line skin pass mill reduces the occurrence of dull transfer defects. Therefore, in order to reduce yield loss due to dull transfer defects, annealing and skin pass rolling have been used. Despite the equipment configuration that can be performed continuously, the process had to be divided and skin pass rolling had to be processed online.

[0008]

SUMMARY OF THE INVENTION The present invention relates to low elongation rolling of an ultra-low carbon steel strip in an in-line skin pass mill, and there is a portion where the steel sheet surface and the work roll surface do not sufficiently contact during rolling. Through various experimental studies, the present inventors have found the necessary conditions for reducing the occurrence of transfer defects in the dull pattern.

That is, the gist of the present invention is that a very low carbon steel strip having a C content of 0.005 wt% or less is subjected to cold rolling and then to continuous annealing. Using a work roll with a roll diameter of less than 490 mm, applying a descent bending force to the work roll, and performing wet skin pass rolling at an elongation of 1% or less, in an in-line skin pass roll in continuous annealing equipment. Transfer method.

Further, when performing the above dull finish rolling,
This is an inline skin pass dull pattern transfer method in a continuous annealing facility, which comprises performing wet skin pass rolling at an elongation of 1% or less using a work roll having a roll diameter of 490 mm or more for laser dulling.

[0011]

According to the present invention, in order to obtain good deep drawability, an ultra-low carbon steel strip is used as a material, and in a dull finish rolling in an in-line skin pass mill using a laser dulling work roll, the uniformity of a laser dulling work roll is obtained. The aim is to accurately and uniformly transfer the dull pattern to the steel plate surface.

In general, when the material is extremely low carbon steel, the elongation percentage in skin pass rolling is 1% or less, and wet rolling is performed, it is difficult to transfer the dull of the work roll to the steel sheet surface. Acts disadvantageously. Therefore, dull pattern transfer failure is likely to occur at the end of the steel sheet under these conditions, but these are essential from the viewpoint of obtaining good deep drawability and practicality. The above is described in more detail below.

[0013] In order to obtain good deep drawability, it is necessary to use ultra-low carbon steel as a material. However, this ultra-low carbon steel has a significantly higher rolling load in a skin pass mill than low carbon steel. To decline. This reduction in the rolling load is disadvantageous when the dull of the work roll is transferred to a steel sheet.

On the other hand, in order to increase the rolling load, the rolling reduction in skin pass rolling, that is, the elongation, may be increased. However, increasing this elongation impairs the deep drawability of the steel sheet. become.

FIG. 1 is a graph showing the relationship between the elongation in skin pass rolling of an ultra low carbon steel strip and the tensile properties of the steel sheet.
As is clear from FIG. 1, when the elongation in skin pass rolling exceeds 1%, the yield stress and the tensile strength increase, the elongation decreases, and the good deep drawability unique to ultra-low carbon steel is obtained. Disappears. Therefore, the elongation percentage in skin pass rolling must be 1% or less, and there is a limit to increasing the rolling load by increasing the rolling reduction in skin pass rolling.

Further, in skin pass rolling using a laser dulling work roll, it is necessary to perform wet rolling using a temper rolling solution. That is, when transferring dulls to a steel sheet by skin pass rolling using a dulling work roll, generally, non-lubricated dry rolling without using a temper rolling liquid is more advantageous in transferring dulls, Non-lubricated dry rolling without using a temper rolling liquid is applied to a part of the work roll which is dulled by shot blasting or electric discharge machining (for example, disclosed in JP-A-61-56703). Example) Using a laser dulling work roll, in the case of the present invention for the purpose of accurately transferring the uniform dull to the steel sheet surface, in the dry rolling, the dull of the work roll is worn out. The desired roundness cannot be obtained at an early stage, and its service life is less than 1/5 of that of wet rolling, and its practicality is lost. Therefore, wet rolling using a temper rolling liquid is required.

Next, when transferring the dull of the laser dulling work roll to the steel sheet surface, even if there are various disadvantages as described above, the dull stitch can be accurately transferred to the end of the steel sheet. The skin-pasdal-eye transfer method, that is, a bending condition and a roll diameter added to a work roll, which are the most significant features of the present invention, will be described below with experimental results.

Bending Conditions Applied to Work Roll Generally, in skin pass rolling, rolling is performed by applying an increasing bending force to a work roll due to the stability of the rolling. The first aspect of the present invention is based on the finding that the bending conditions of a work roll of laser dulling in in-line skin pass rolling greatly affect the transfer of the work roll to the steel sheet surface of the dull cross section.

FIG. 2 shows that, after continuous annealing, using a very low carbon steel strip of 0.003 wt%, a wet skin pass rolling with an elongation of 0.7% was performed by a laser dull work roll.
The relationship between the bending force applied to the work roll and the diameter of the work roll, and the good / bad (three-level evaluation) of dull transfer to the steel sheet surface at a position 10 mm from the steel sheet end is shown. As is clear from FIG. 2, when the increase bending force is applied to the work roll, the work roll diameter is 490 mm.
The transfer failure occurs when the value is less than the above, but when the decrease venting force is applied, the transfer failure does not occur.

Therefore, by applying a bending bending force to a laser dulling work roll having a roll diameter of less than 490 mm, good transfer of dulls can be obtained even at a position of a steel plate end of 10 mm.

Work Roll Diameter The second aspect of the present invention is, as described above, the occurrence of dull transfer failure portions in normal wet rolling using an offline skin pass mill (applying an increase bending force to a work roll). Therefore, as a result of conducting various comparative studies on differences from the rolling conditions by the in-line skin pass mill, it was found that the cause was found to be the work roll diameter.

Here, a 4Hi mill is generally used as an off-line skin pass mill, and its work roll diameter is in the range of 520 mm to 600 mm. 6 with high shape control ability to control the flatness of
Hi mill is used, so the work roll diameter is
It ranges from 425mm to 475mm.

FIG. 3 shows that ordinary ultra-low carbon steel strip (C: 0.003 wt%) after continuous annealing is subjected to a normal wet skin pass rolling (work rolls are applied with an increase bending force) by a laser dulling work roll. The relationship between the work roll diameter using elongation as a parameter and the linear load during rolling (total rolling load / sheet width), and the transfer of dull lines to the steel sheet surface at a position 10 mm from the end of the steel sheet. (Three-step evaluation). As is clear from FIG. 3, if the diameter of the work roll is 490 mm or more, no transfer failure occurs in the dull shape.

As described above, when a very low carbon steel strip is subjected to low elongation and wet skin pass rolling by an in-line skin pass mill using a laser dulling work roll, a decrease venting force is applied to the work roll. Alternatively, by making the work roll diameter 490 mm or more, the dull stitch of the laser dulling work roll can be accurately transferred to the steel plate surface to the steel plate end.

As described above, by applying the present invention, for example, when manufacturing a high-definition steel sheet having a good deep drawability of an ultra-low carbon steel, it is conventionally necessary to cut off defective transfer portions. Had been slit in the range of 50 mm to 100 mm in the width direction of the board, but slits of 10 mm or less were sufficient, and the yield loss was 1/10 that of the conventional range of 8% to 16%. Decreased to below.

[0026]

EXAMPLE Example 1 Melted in a converter and subjected to ordinary hot rolling and cold processing C: 0.00
A 3 wt% ultra-low carbon steel strip is subjected to continuous annealing, followed by laser dull finish rolling using an inline skin pass mill,
High-definition steel sheets with a thickness of 0.75 mm and a width of 1430 mm were manufactured.

In the laser dull finish rolling, the roll diameter
Using a 455 mm laser dulling work roll, wet rolling using a temper rolling solution at an elongation of 0.7%, and the bending force applied to the work roll (added to the chocks) is 2T of the decrease bending force ( Applicable example) The test was performed under the two conditions of adding an increase bending force of 21T (comparative example).

With respect to each of the steel sheets manufactured under the above conditions, the microcratering transfer rate R of the dent was measured from the end of the steel sheet in the width direction of the steel sheet. FIG. 4 shows the measurement results.

Here, the micro crater ring transfer rate R is, as shown in the illustration of the ring transfer rate in FIG. 5, the central angle θ _R of the ring-shaped convex portion on the roll surface and this is the steel sheet surface. The center angle θ _P of the ring-shaped concave portion when the image was transferred to the substrate was measured with a microscope and calculated by the following equation.

As is clear from FIG. 4, in the comparative example, the transfer rate R of the micro crater is greatly reduced at the end of the steel sheet, but the decrease is small in the adapted example.

Example 2 C which was melted in a converter and subjected to ordinary hot rolling and cold rolling:
A 0.003 wt% ultra low carbon steel strip is dull finish rolled by an in-line skin pass mill following continuous annealing to a sheet thickness of 0.75%.
mm, 1430 mm wide high-definition steel sheet was manufactured.

The dull finish rolling is performed with a roll diameter of 520 m.
m: Applicable example and 475mm: Comparative example, using two types of laser dulling work rolls, wet rolling using a temper rolling fluid at an elongation of 0.7%, and a work roll of 15T
(Added to the chock).

With respect to each of the steel sheets manufactured under the above conditions, the microcratering transfer rate R at the bulge in the sheet width direction from the steel sheet end was measured in the same manner as in Example 1.
These results are shown in FIG.

As is clear from FIG. 6, the transfer rate R of the micro crater in the comparative example is greatly reduced at the end of the steel sheet, but the decrease is small in the adapted example.

[0035]

According to the present invention, following continuous annealing, in dull finish rolling by an in-line skin pass mill using a laser dulling work roll, the bending conditions added to the work roll or the work roll diameter are optimized. According to the present invention, the dull of the work roll is accurately transferred to the steel plate surface, and according to the present invention,
Yield loss due to improper transfer of dull lines can be greatly reduced, and the present invention can be advantageously applied to laser dulling of high-definition steel plates having good deep drawability.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between the elongation in skin pass rolling and the tensile properties of a steel sheet.

FIG. 2 is a graph showing the relationship between the bending force applied to a work roll and the diameter of the work roll in skin pass rolling using a laser dulling work roll, and the good or bad transfer of dull marks at a position 10 mm from the end of the steel sheet. is there.

FIG. 3 shows the relationship between the work roll diameter using elongation as a parameter and the linear load during rolling in skin pass rolling using a laser dulling work roll, and the transfer of dull lines to the steel sheet surface at a position 10 mm from the end of the steel sheet. 6 is a graph showing the relationship between the good and bad.

FIG. 4 shows the distance (in the sheet width direction) from the steel sheet end when the increase bending force is applied to the work roll and the decrease bending force is added to the work roll by skin pass rolling using a laser dulling work roll. It is a graph which shows the relationship with the micro crater ring transfer rate R.

FIG. 5 is an explanatory diagram of a micro crater ring transfer rate R.

FIG. 6 is a graph showing a relationship between a distance from a steel plate end (in a plate width direction) and a micro crater ring transfer rate when two types of work roll diameters are used in skin pass rolling using a laser dull work roll. .

Continuation of the front page (56) References JP-A-54-100961 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) B21B 1/22

Claims (2)

(57) [Claims] 1. A roll having a laser dulling surface when cold rolling a C: 0.005 wt% or less ultra low carbon steel strip and then performing continuous annealing, and performing dull finish rolling subsequent to the continuous annealing. An inline skin pass dull pattern transfer method in a continuous annealing facility, wherein a work roll having a diameter of less than 490 mm is used, and a wet skin pass rolling at an elongation of 1% or less is performed by applying a decrease bending force to the work roll. 2. A roll having a laser dulling surface when cold rolling a C: 0.005 wt% or less ultra low carbon steel strip and then performing continuous annealing, and performing dull finish rolling subsequent to the continuous annealing. Using a work roll with a diameter of 490mm or more,
An inline skin pass dull pattern transfer method in continuous annealing equipment, wherein wet skin pass rolling is performed at an elongation of 1% or less.