JP2002120003A - Method for adjusting surface roughness of steel strip and steel strip - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an adjusting method of the surface roughness of a steel strip by which all the required qualities such as shape straightening, the mechanical property and surface roughness of the steel strip are secured without lowering productivity and quality. SOLUTION: First, temper rolling for adjusting the material with a temper rolling mill 2 is performed and a specified mechanical property is attained by imparting a specified expansion rate. In the case that shape straightening is performed, a shape controlling actuator such as a work-roll bender which is provided on the temper rolling mill 2 is used. At this time, because a specified surface roughness is imparted with a surface roughness imparting device 3 at the next stage, the shape controlling actuator such as the work-roll bender or the like can be used in the temper rolling mill 2 without worrying about the transfer irregularity or the like, so the steel strip excellent in shape accuracy is manufactured.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for imparting surface roughness to a steel strip and adjusting the surface roughness. More specifically, the present invention relates to a technique for stabilizing steel strip without reducing productivity and quality. The present invention relates to a method for imparting the required surface roughness to a steel strip surface, and a steel strip whose surface roughness is adjusted by these methods.

[0002]

2. Description of the Related Art In recent years, users' needs for the surface of a steel strip have been diverse, and the required surface condition of the steel strip has been different depending on the use. The surface of a steel strip called “bright finish” has few irregularities and is generally used for applications requiring a high glossiness, such as a reflector or a building material for exterior use. On the other hand, steel strips called dull finish have been known to improve the retention of lubricating oil for processing during press forming by providing irregularities on the surface, and are effective in preventing seizure and scratches during forming. I have. For steel strips for automobiles and the like, steel strips having a center line average roughness Ra specified in JIS B 0601 within a certain range are required in order to ensure formability.

[0003] In the same dull finish, JIS B 06
By reducing the size of the filtering center line waviness Wca, which is a long-wavelength component of the surface roughness specified in 10, it is possible to produce a steel strip excellent in press formability and post-painting sharpness. No. 5-15901,
Such a steel strip is used as an outer panel for automobiles and the like.

The surface roughness of such a dull-finished steel strip is imparted by using a dull roll whose surface roughness has been adjusted during temper rolling as a work roll and transferring the roll surface roughness to the steel strip surface. Is common. However, the transfer of roll surface roughness in temper rolling is mainly governed by the elongation rate during rolling, and as the elongation rate increases, the rate at which the roll surface roughness is transferred to the steel strip (transfer rate) increases. Go. Therefore, in order to obtain a steel strip having a target surface roughness by temper rolling with a roll having a certain surface roughness, there is an optimum elongation rate.

On the other hand, in the temper rolling, the mechanical properties of the steel strip are adjusted simultaneously with the provision of the surface roughness, and the mechanical properties of the steel strip vary depending on the elongation given during rolling. At this time, the elongation rate given to the steel strip has an optimum value depending on the material. Therefore, in order to obtain various target surface roughnesses, it is necessary to prepare rolls with different surface roughnesses and perform temper rolling under the constraints of the elongation ratio range for obtaining the target mechanical properties. was there. In temper rolling in a continuous line such as a continuous annealing line or hot-dip galvanizing line, if the rolls are changed to rolls with various surface roughnesses according to the material and target surface roughness, the number of roll changeovers will increase. This causes a problem that productivity is greatly reduced.

As a method for solving such a problem, by adjusting the film thickness of the lubricating liquid formed in the roll bite at the time of temper rolling, a steel strip having a roll surface roughness independent of the elongation rate can be obtained. Japanese Patent Laid-Open Publication No. 8-215
No. 708.

[0007] This method is characterized in that a lubricating liquid and a gas are mixed by a nozzle installed on the inlet side of the rolling mill, and the lubricating liquid is converted into extremely small droplets and sprayed onto the mist onto the steel strip. At this time, the liquid film thickness in the roll bite is controlled by changing the liquid pressure and the gas pressure and adjusting the flow rate and the droplet diameter.

When a liquid film having a constant thickness is formed in a roll bite as in a normal wet rolling method, the volume of the lubricating liquid is almost incompressible and does not decrease even when a high pressure is applied. If the thickness is large, the surface roughness of the roll is not transferred as it is, and the surface roughness of the steel strip is reduced. On the other hand, in the case of the dry rolling method, since there is no lubricating liquid between the roll surface and the steel strip, the transfer rate of the roll surface roughness at the same elongation rate becomes larger than that of the wet rolling method. Therefore, if the liquid film thickness formed in the roll bite is controlled, the transfer rate of the roll surface roughness can be controlled independently of the elongation rate.

[0009]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open No. Hei 8-21
The method disclosed in Japanese Patent No. 5708 has the following problems. That is, the roll surface roughness of the dull roll surface usually decreases due to abrasion and adhesion of the plating film with an increase in pressure elongation. When the roll surface roughness decreases, the surface roughness of the steel strip obtained under the same rolling conditions decreases, and even in a region where the target surface roughness is large, even if the liquid film thickness is reduced, a predetermined value is obtained. Steel strips with surface roughness cannot be obtained. Therefore, after rolling a certain amount, it is necessary to change to a roll having a predetermined surface roughness.

Further, since the transfer rate of the roll surface roughness which can be controlled by the liquid film thickness in the cutting tool is not so large,
It is difficult to manufacture steel strips having significantly different target surface roughnesses on the same roll. In particular, in the case where a steel strip requiring a bright finish and a steel strip requiring a dull finish are continuously manufactured, it is necessary to change the rolls without fail.

Furthermore, in temper rolling, a shape control actuator such as a work roll bender for changing a roll crown is used to correct the shape of a steel strip.
When a shape control actuator is used, the pressure distribution in the width direction is not uniform, and as a result, the transfer of the roll surface roughness in the width direction is not uniform. Such non-uniform transfer is observed as a surface unevenness of the steel strip, and in some cases, a problem in product quality. As described above, it is difficult to impart various desired surface roughnesses in the longitudinal direction and the width direction at the same time while adjusting the material and correcting the shape in the passivation rolling, which is a conventional technique.

The present invention has been made in view of such circumstances, and solves the problems of the prior art described above, without reducing the productivity and quality, without reducing the shape, mechanical properties of the steel strip, and surface roughness. It is an object of the present invention to provide a method for adjusting the surface roughness of a steel strip, which can ensure all required quality such as steel strip, and a steel strip whose surface roughness is adjusted by these methods.

[0013]

A first means for solving the above-mentioned problem is a method for adjusting the surface roughness of a steel strip, which is arranged on an upstream side or a downstream side of a temper rolling mill. A method for adjusting the surface roughness of a steel strip (claim 1), characterized by using a device for controlling the surface roughness of the steel strip.

In the present means, the temper rolling mill is used mainly or exclusively for correcting the shape of the steel strip and for imparting an elongation rate for imparting desired mechanical properties to the steel strip. The adjustment of the roughness is performed by a device for controlling the surface roughness of the steel strip provided separately from the temper rolling mill. Therefore, compared to the conventional case where all of these are controlled by a temper rolling mill, there is no restriction due to mutual interference, and a desired shape, mechanical characteristics, and surface roughness can be easily obtained. Can be.
Further, since it is not necessary to change the rolls of the temper rolling mill according to the surface roughness to be given to the steel strip, the number of times of changing the rolls can be reduced, and the equipment operation rate can be increased.

[0015] A second means for solving the above-mentioned problems is as follows.
The first means, wherein a work roll having a smooth finish is used as a work roll of the temper rolling mill (claim 2).

In the present means, when a device for controlling the surface roughness of the steel strip is provided downstream of the temper rolling mill, the apparatus may be used when the surface roughness of the steel strip entering the temper rolling mill changes. Also, since the work roll having a smooth finish is used in the temper rolling mill, the surface of the steel strip is once smoothed. After that, since the steel strip surface roughness is adjusted by a device that controls the surface roughness of the steel strip, which is provided downstream of the temper rolling mill,
The device for controlling the surface roughness of the steel strip is only required to impart a predetermined roughness to the steel strip having a smooth surface,
Control can be performed accurately.

Even when a device for controlling the surface roughness of the steel strip is provided upstream of the temper rolling mill, the applied surface roughness does not change much due to the temper rolling. By giving an extra surface roughness by estimating the degree of the surface roughness, the target surface roughness can be obtained. However, the former is more preferred.

A third means for solving the above-mentioned problem is as follows.
The first means or the second means, wherein the device for controlling the surface roughness is a device for projecting solid particles onto the surface of the steel strip (Claim 3).

Apparatuses for projecting solid particles onto the surface of a steel strip, such as shot blasting and shot peening, are widely used, and include the kinetic energy and particle diameter of shots, the amount of projection per unit area, By changing the hardness or the like of the projectile, the surface roughness of the steel strip can be easily controlled to a predetermined value.

A fourth means for solving the above-mentioned problem is:
The first means or the second means, wherein the device for controlling the surface roughness is a device for projecting solid particles together with a liquid onto the surface of the steel strip (Claim 4).

This means uses so-called liquid honing to control the surface roughness. Liquid honing (or wet blasting) is based on the same principle of surface blasting as shot blasting. By mixing solid particles in a high-pressure fluid, particles accelerated by the high-pressure fluid collide with the surface of the workpiece, causing plastic deformation. Causes deformation.

A fifth means for solving the above problem is as follows.
In any one of the first to fourth means, the steel strip is a galvanized steel strip (Claim 5).

The galvanized steel strip is subjected to the fourth to fourth steps.
The surface roughness can be controlled without restricting the shape and mechanical properties by using the means of (1), so that the required surface roughness can be given accurately. And the sharpness after painting can be easily improved. Further, since the galvanized steel strip has a soft film hardness, the surface roughness can be easily imparted without using a rolling roll. Further, when the surface roughness is applied to the galvanized steel sheet by the temper rolling mill, the roll roughness is greatly reduced due to the adhesion of zinc. In the present means, such a phenomenon is prevented from occurring. You can also.

A sixth means for solving the above-mentioned problem is as follows.
The fifth means is characterized in that the galvanized steel strip is a galvanized steel strip whose plating film is mainly composed of an η phase (claim 6).

In the case of a galvanized steel sheet whose plating film is mainly composed of an η phase, since the film itself is soft, an indentation is easily formed when solid particles are projected, and the surface roughness can be easily imparted. . In addition, products generally require higher roughness than alloyed hot-dip galvanized steel sheets. Therefore, in the prior art, the average roughness of the rolling roll had to be increased, which caused a problem that the peak count could not be increased beyond a certain value. That is, the effect of the present invention appears more significantly as compared with the method of imparting roughness by temper rolling to a galvanized steel sheet in which a plating film mainly includes an η phase.

A seventh means for solving the above-mentioned problem is as follows.
A steel strip whose surface roughness is adjusted by any one of the first to sixth means (claim 7).

As described above, the steel strip according to the present invention is one in which the application of the elongation rate for imparting the shape correction and the predetermined mechanical properties and the application of the surface roughness are performed separately. Therefore, each of these properties is within the target value and can be used for a predetermined purpose.

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram for explaining the basic concept of one embodiment of the present invention. In FIG. 1, 1
Denotes a steel strip, 2 denotes a temper rolling mill, and 3 denotes a surface roughness imparting device.

The feature of this embodiment is shown in FIG.
As shown in (a) and (b), a surface roughness imparting device 3 for controlling the surface roughness is disposed in front of or behind the temper rolling mill 2 to provide a function of imparting surface roughness, and a temper rolling. This is the point that the functions of the machine for shape correction and material adjustment are separated.

In (a), first, temper rolling is performed in a temper rolling mill 2 to adjust the material, and a predetermined mechanical property is obtained by giving a predetermined elongation. When performing shape correction, a shape control actuator such as a work roll bender provided in the temper rolling mill 2 is used. At this time, since a predetermined surface roughness is provided by the surface roughness providing device 3 in the next step, the shape control actuator such as a work roll bender must be used in the temper rolling mill 2 without concern for uneven transfer. Therefore, a steel strip having excellent shape accuracy can be manufactured.

At this time, it is preferable to use a roll having a smooth finish such as a so-called bright finish as a work roll of the temper rolling mill 2. Steel strip 1 entering temper rolling mill 2
Has a variety of surface roughnesses and surface roughness with large variations, if the temper rolling is performed using a work roll with a smooth finish, the outlet side of the temper rolling mill 2, that is, the surface roughness imparting device 3 The surface roughness of the steel strip at the entry side can be made uniform and small without any variation.

The surface roughness Rar of the work roll used
Must be 1.6 times or less the target roughness Ras of the steel strip. The reason is described below. 0.5 ~
An elongation of about 2.0% is provided. At this time, the steel strip surface roughness Rat after rolling is represented by the following equation (1). Here, α is the transfer rate, which increases with the elongation rate.
The value is about 0.6. Rat = α · Rar (1) Since the maximum value of the transfer rate α in the normal temper rolling is about 0.6, the target surface roughness Rat of the steel strip after rolling should be provided by the surface roughness providing device 3. In order not to exceed the surface roughness Ras, it is necessary to satisfy the formula (2). From now on, as shown in the formula (3), the surface roughness Ra of the roll must be less than 1.6 times the target surface roughness Ras of the steel strip. Something is needed. Ras> 0.6 × Rar ... (2) Rar <1.66 × Ras ... (3) By temper rolling using such rolls, material adjustment and shape correction are performed, and at the same time there is little variation below the target surface roughness Ras. Steel strip adjusted to uniform surface roughness
The surface roughness can be controlled to the target surface roughness by the surface roughness imparting device 3, and the surface roughness is very excellent. In addition, rolling can be performed with one kind of work roll having a smooth finish in a temper rolling mill, and the initial roll roughness does not decrease when a conventional dull roll is used, so that the frequency of roll change is greatly reduced. .

As shown in FIG. 1B, when the surface roughness applying device 3 is arranged in front of the temper rolling mill 2, a predetermined surface roughness is first applied by the surface roughness applying device 3. You. Thereafter, in order to perform material adjustment and shape correction by the temper rolling mill 2, temper rolling is performed using a roll having a smooth finish. At this time, the difference from (a) is that the projections of the irregularities imparted to the steel strip 1 by the surface roughness imparting device 3 are smoothed by temper rolling to reduce the surface roughness Ra of the steel strip. However, the target steel strip surface roughness Ra (s) can be obtained if the roughness is given by the surface roughness imparting device 3 in consideration of the change in Ra in advance.

In the temper rolling mill 2, a predetermined elongation is given to obtain a target mechanical property. In addition, when a work roll bender is used to perform shape correction, if a roll with a smooth surface is used, the change in the transfer rate due to the difference in pressure distribution in the width direction is about 0.1 to 0.2, and the surface roughness of the steel strip As a result, only a change of 0.1 μm or less occurs, and there is no problem in product quality. That is, a steel strip having excellent shape accuracy can be obtained by sufficiently using the shape control actuator. Further, as in the case of (a), since a work roll having a smooth finish is used as the work roll, the initial roll roughness does not decrease, so that the frequency of roll change is reduced.

As a method of independently controlling the surface roughness, there is, for example, shot blasting or shot peening. This is a processing method in which the solid particles 4 (hereinafter, referred to as shots) are projected onto the surface of the workpiece 5 at a high speed as shown in FIG. 2, and the kinetic energy of the shot causes the surface of the workpiece to undergo plastic deformation. Raised indentations are formed.

The shape (depth, pitch) of the indentation formed at this time is determined by the kinetic energy of the shot, the particle diameter, the projection amount per unit area, and the hardness of the workpiece.
Therefore, the surface roughness can be controlled by previously determining the optimum projection conditions for the target surface roughness of the steel strip. At this time, in the extreme surface layer where plastic deformation occurs, the surface hardness increases due to work hardening. The increase in surface hardness has a favorable effect on improving the wear resistance of the steel strip, the galling resistance during press forming, and the seizure resistance.

Liquid honing (or wet blasting) has the same principle of surface processing as shot blasting. By mixing solid particles in a high-pressure fluid,
Particles accelerated by the high-pressure fluid collide with the surface of the workpiece and cause plastic deformation. As means for independently imparting surface roughness, there are laser processing, electron beam processing and the like in addition to the above-described methods using shot blasting and liquid honing.

Therefore, the step of imparting a predetermined steel strip surface roughness with the apparatus for controlling the surface roughness as described above, and the temper rolling using a work roll having a smooth finish are performed. By separating the steps of correcting the shape and adjusting the mechanical properties of the steel strip, a high-quality steel strip can be manufactured without lowering the productivity.

FIG. 3 is a schematic view of a hot-dip galvanized steel strip production line using one embodiment of the present invention. In the following drawings, the same reference numerals are given to the components shown in the preceding drawings, and the description thereof may be omitted. In FIG. 3, 6 is a payoff reel, 7 is an annealing furnace, 8 is a galvanizing bath, 9 is a wiping nozzle, 10 is a work roll, 16 is a cleaning device, 17 is a tension reel, and 18 is a surface roughness meter.

The steel strip produced through the cold rolling is unwound from the pay-off reel 6, passed through an annealing furnace 7, and then dipped in a hot-dip galvanizing bath 8 to be plated. The amount of plating on the steel strip coming out of the plating bath is adjusted by the wiping nozzle 9. Further, a temper rolling mill 2 that performs material adjustment and shape correction is disposed downstream of the plating apparatus. The temper rolling mill 2 is a four-high rolling mill.
A 0.3 μm bright roll is used. The steel strip 1 which is given a predetermined elongation rate by the temper rolling mill 2 and whose shape is corrected by the operation of the work roll bender and adjusted to have a uniform surface roughness is provided with a surface roughness provided downstream thereof. The target surface roughness is controlled by the device 3.

The steel strip given a predetermined surface roughness by the surface roughness applying device 3 is passed through a cleaning device 16 for cleaning the surface of the steel strip, if necessary, and then wound up by a tension reel 17. Product. At this time, a device 18 for measuring the surface roughness of the steel strip is disposed between the surface roughness applying device 3 and the tension reel 17, and if there is a deviation from the measured result to the target surface roughness, shot projection is performed. By feeding back the conditions, a steel strip having a target surface roughness can be stably manufactured.

If the present invention is applied to a method for producing a galvanized steel strip having a soft coating film hardness and a large reduction in roll roughness due to the adhesion of zinc, as described in claim 5 and claim 6, the effect is obtained. A large, galvanized steel strip may be a hot-dip galvanized steel strip as shown here,
Thereafter, the steel strip may be subjected to a chemical conversion treatment such as chromate.

The present invention can be applied not only to a production line for a galvanized steel strip, but also to a continuous annealing line in which no plating treatment is performed, or a batch-type temper rolling line as shown in FIG. In the batch type temper rolling line, the steel strip 1 unwound by the payoff reel 6 has a surface roughness Ra =
By the temper rolling mill 2 using a work roll of 0.3 μm,
A predetermined elongation is given, and the shape is corrected by the operation of the work roll bender, and at the same time, the surface is adjusted to have a uniform surface roughness.

Thereafter, the target surface roughness is controlled by the surface roughness imparting device 3. The steel strip provided with a predetermined surface roughness by the surface roughness imparting device 3 passes through a cleaning device 16 for cleaning the surface of the steel strip, if necessary, and is then wound up by a tension reel 17 to form a product. Become. At this time, a device 18 for measuring the surface roughness of the steel strip is arranged between the surface roughness imparting device 3 and the tension reel 17, and if there is a deviation from the measured result to the target surface roughness, the shot projection condition is set. It is also possible to stably produce a steel strip having a target surface roughness by feeding back to the steel strip.

In this embodiment, the surface roughness imparting device 3 is of a shot peening type, and has a structure as shown in FIG. In FIG. 5, 11 is a chamber, 12a to 12d are shot projecting devices, 13a and 13
b is a shot supply device, 14a and 14b are dust collectors, 15
Reference numerals a and 15b denote cleaner blowers.

The shot projecting device 12 is placed in the chamber 11.
However, they are arranged so as to obtain a uniform projection density distribution over the entire width of the steel strip 1. The device for projecting the shot may be either a pneumatic accelerator for accelerating the shot with compressed air or a mechanical accelerator for applying a centrifugal force to the shot using a centrifugal rotor or the like to project the shot. A fixed amount of solid particles is supplied to the shot projecting device 12 from the shot supplying device 13 and projected onto the surface of the steel strip 1. The shot projected on the steel strip 1 inside the chamber 11 scatters around and falls to the lower part of the chamber 11.

The dropped shot is collected, sent to the shot supply devices 13a and 13b again, circulated and projected on the steel strip. Normally, the shot supply device 13 is provided with a separator, and foreign matter mixed in the shot and crushed and fine shot are separated and sent to the dust collectors 14a and 14b. On the other hand, fine particles that do not fall to the lower part inside the chamber and stay on the front and back surfaces of the steel strip are removed by the cleaner blower 15.
a, 16b.

[0048]

FIG. 3 shows the results when the present invention is applied to the hot-dip galvanized steel strip production line shown in FIG. 3 and when the prior art is used for comparison. Surface roughness imparting device 3
Is a shot blasting device, and the shot projecting device is a pneumatic accelerator.

<Example 1> FIG. 6 is a view showing the results of an investigation on the change in surface roughness of a hot-dip galvanized steel sheet with respect to elongation. Conventional example 1 has a roll diameter of 650 mm and a roll barrel length of 200
The results are obtained when a hot-dip galvanized steel sheet having a thickness of 0.8 mm and a width of 1200 mm was produced at a line speed of 90 mpm using a temper rolling roll having a thickness of 0 mm and a center line average roughness Ra of 3.0 μm. At this time, the elongation rate is 0.8% and the target surface roughness of the steel strip is Ra = 1.1 to 1.3 μm. However, as the elongation increases, the roll roughness decreases due to roll wear and the adhesion of zinc. At the same time, the Ra of the steel strip decreases. The steel strip Ra at the time of rolling 30 km is 1.0 μm, and the target surface roughness cannot be secured, so the rolls are changed.

On the other hand, in Example 1 using the present invention, a hot-dip galvanized steel sheet having a thickness of 0.8 mm and a width of 1200 mm was rolled with a roll diameter of 650 mm, a roll barrel length of 2000 mm, and a center line average roughness Ra = 0.3 μm. After temper rolling was performed using a roll, alumina particles having a particle size of φ55 μm were used as shots, accelerated by compressed air at a pressure of 0.4 MPa, and projected onto the steel strip surface at a projection rate of 6 kg / min. At this time, even if the elongation was increased, the surface roughness of the steel strip did not change, and even after rolling 200 km, the surface roughness of the steel strip was 1.2 μm, so there was no need to change the rolls. The productivity was greatly improved as compared with Conventional Example 1.

Example 2 Table 1 shows one example of a production cycle in a hot-dip galvanized steel sheet production line.
The mechanical properties and surface roughness of the steel strip vary depending on the user specifications.

[0052]

[Table 1] (Table 1)

FIG. 7 shows a roll diameter of 650 mm and a roll barrel length of 2
000 mm, center line average roughness Ra 2.0 μm, using a work roll of 3.0 μm, 4.0 μm, shows the relationship of the surface roughness of the steel strip to the elongation rate when performing temper rolling of the steel strip . The circles in the figure are plots of the target elongation and the target surface roughness in the manufacturing cycle shown in Table 1. It is not possible to satisfy user specifications for all materials with the same roll, and there is no other way but to change the roll surface roughness, and it is necessary to change rolls. On the other hand, FIG. 8 is a view showing a change in the surface roughness of the steel strip with respect to the shot projection conditions when alumina particles having a particle size of φ128 μm are projected on the steel strip surface by shot peening.

Example 2 shows the result of projecting shots after performing temper rolling at an elongation ratio of 0.8 to 1.5% using a bright roll having a surface roughness Ra of 0.2 μm. On the other hand, Example 3 is a result of a case in which alumina particles having a particle diameter of φ128 μm are projected onto an unpressurized steel strip, and then temper rolling is performed with a roll having a surface roughness Ra of 0.2 μm. In either case, it is possible to change the surface roughness of the steel strip by increasing the pressure of the compressed air in the accelerator, and it is possible to obtain the target surface roughness for all the insertion cycle materials shown in Table 1. it can. At this time, all the materials obtained a predetermined tensile strength regardless of whether or not shot peening was performed before or after temper rolling.

<Embodiment 3> FIG. 9 shows the variation of the center line average roughness Ra between the edge portion and the center portion of the galvanized steel strip on the vertical axis, and the steepness of the product on the horizontal axis. Conventional example 2 has a roll diameter of 650 mm, a roll barrel length of 2000 mm, and a center line average roughness R.
Using a temper rolling roll of a = 3.0 μm, a sheet thickness of 1.2 mm and a sheet width of 1
The results are obtained when a 600 mm hot-dip galvanized steel sheet is manufactured at a line speed of 90 mpm. At this time, the entry shape of the steel strip is steep
The medium elongation is 2.0%, and the shape is corrected by using a work roll bender in a temper rolling mill. The shape of the steel strip after rolling had a steepness of 0.2% and was sufficiently flat, but transfer unevenness was observed at the edge and the center of the steel strip, which was a problem in product quality.

In Conventional Example 3, a hot-dip galvanized steel sheet having a thickness of 1.2 mm and a width of 1600 mm was formed at a line speed using a temper rolling roll having a roll diameter of 650 mm, a roll barrel length of 2000 mm, and a center line average roughness Ra of 3.0 μm. This is the result when manufactured at 90 mpm.
At this time, the entry side shape of the steel strip had a steepness of 2.0% medium elongation. At this time, no work roll bender was used.
Although no transfer unevenness occurs in the width direction, the steepness after rolling is 1.6%, and the shape is not completely corrected.

On the other hand, in Example 4 using the present invention, the roll diameter was 650 mm, the roll barrel length was 2000 mm, and the center line average roughness Ra = 0.
After temper rolling using a 3m temper rolling roll, a steel shot with a particle size of 50μm is projected at a pressure of 0.5MPa and a distance of 100mm to produce a hot-dip galvanized steel sheet with a thickness of 1.2mm and a width of 1600mm. This is the result when manufacturing at a speed of 90 mpm. At this time, the entry shape of the steel strip is a medium elongation with a steepness of 2.0%,
The shape was corrected by a temper rolling mill. The shape of the product is 0.4% in steepness, and a flat shape is obtained.
Further, when the surface state was visually observed, a favorable surface state was obtained over the entire width of the steel strip.

In Example 5, after a steel shot having a particle diameter of 50 μm was projected at a pressure of 0.5 MPa and a distance of 100 mm, the roll diameter was 650 mm, the roll barrel length was 2000 mm, and the center line average roughness R was
The results are obtained when a hot-dip galvanized steel sheet having a thickness of 1.2 mm and a width of 1600 mm was manufactured at a line speed of 90 mpm with a roll of a = 0.3 μm. At this time, the entry side shape of the steel strip is a medium elongation with a steepness of 2.0%, and the shape of the product is a steepness of 0.2%, and a flat shape is obtained. When the surface condition was observed, a favorable surface condition was obtained over the entire width of the steel strip.

[0059]

As described above, in the present invention, the temper rolling mill is mainly or exclusively used to correct the shape of the steel strip and to provide the steel strip with an elongation rate for giving desired mechanical properties. The surface roughness of the steel strip is adjusted by a device that controls the surface roughness of the steel strip, which is provided separately from the temper rolling mill. As compared with a case where control is performed by a machine, restrictions due to mutual interference are eliminated, and a desired shape, mechanical characteristics, and surface roughness can be easily obtained. Further, since it is not necessary to change the rolls of the temper rolling mill according to the surface roughness to be given to the steel strip, the number of times of changing the rolls can be reduced, and the equipment operation rate can be increased.

[Brief description of the drawings]

FIG. 1 is a diagram for explaining a basic concept of an embodiment of the present invention.

FIG. 2 is a view showing an outline of a shot blasting or shot peening equipment.

FIG. 3 is a schematic view of a production line for a hot-dip galvanized steel strip using an example of an embodiment of the present invention.

FIG. 4 is a schematic diagram of a batch temper rolling line using an example of an embodiment of the present invention.

FIG. 5 is a schematic diagram showing an example of a shot peening type surface roughness providing device.

FIG. 6 is a diagram showing the results of examining the change in surface roughness of a hot-dip galvanized steel sheet with respect to elongation (Examples and Comparative Examples).

FIG. 7 is a diagram illustrating a relationship (comparative example) between the elongation percentage and the surface roughness of the steel strip when temper rolling of the steel strip is performed.

FIG. 8 is a diagram showing a change in surface roughness of a steel strip with respect to shot projection conditions (Example) when alumina particles are projected on the steel strip surface by shot peening.

FIG. 9 is a diagram showing the relationship between the amount of change in the center line average roughness Ra between the edge portion of the galvanized steel strip and the center portion and the steepness of the product (Example and Comparative Example).

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Steel strip, 2 ... Temper rolling mill, 3 ... Surface roughness provision apparatus, 4
... solid particles, 5 ... workpiece, 6 ... pay-off reel, 7 ...
Annealing furnace, 8: zinc plating bath, 9: wiping nozzle, 1
0: Work roll, 11: Chamber, 12a to 12d
... Shot projection device, 13a, 13b ... Shot supply device, 14a, 14b ... Dust collector, 15a, 15b ... Cleaner blower, 16 ... Cleaning device, 17 ... Tension reel, 18 ... Surface roughness meter

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhiro Soya 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Nihon Kokan Co., Ltd. (72) Shogo Tomita 1-2-1, Marunouchi, Chiyoda-ku, Tokyo Sun F-term (reference) in Honko Pipe Co., Ltd. 4E002 AD06 BB09 BC05 BD10 CB03 CB08 CB09 4K044 AA02 AB02 BA12 BB01 CA07 CA11

Claims (7)

[Claims] 1. A method for adjusting the surface roughness of a steel strip, characterized by using a device for controlling the surface roughness of the steel strip, which is arranged on the upstream side or the downstream side of the temper rolling mill. How to adjust the surface roughness of steel strip. 2. The method for adjusting the surface roughness of a steel strip according to claim 1, wherein a work roll having a smooth finish is used as a work roll of the temper rolling mill. Adjustment method. 3. The method for adjusting the surface roughness of a steel strip according to claim 1 or 2, wherein the device for controlling the surface roughness is a device for projecting solid particles onto the surface of the steel strip. A characteristic method of adjusting the surface roughness of a steel strip. 4. The method for adjusting the surface roughness of a steel strip according to claim 1 or 2, wherein the device for controlling the surface roughness is a device for projecting solid particles together with a liquid onto the surface of the steel strip. A method for adjusting the surface roughness of a steel strip. 5. The method for adjusting the surface roughness of a steel strip according to claim 1, wherein the steel strip is a galvanized steel strip. Method. 6. The method for adjusting the surface roughness of a steel strip according to claim 5, wherein the galvanized steel strip is a galvanized steel strip whose plating film mainly comprises an η phase. To adjust the surface roughness of the strip. 7. One of claims 1 to 7
A steel strip whose surface roughness has been adjusted by the method for adjusting the surface roughness of a steel strip described in the section.