WO2020121657A1

WO2020121657A1 - Work roll for rolling, rolling machine equipped with same, and rolling method

Info

Publication number: WO2020121657A1
Application number: PCT/JP2019/041848
Authority: WO
Inventors: 植野　雅康; 拓郎矢▲崎▼; 木島　秀夫; 三宅　勝
Original assignee: Ｊｆｅスチール株式会社
Priority date: 2018-12-12
Filing date: 2019-10-25
Publication date: 2020-06-18
Also published as: MX2021007044A; EP3895818A4; CN113195123B; CN113195123A; JP6680426B1; JPWO2020121657A1; EP3895818B1; EP3895818A1

Abstract

[Problem] To provide a work roll for rolling that is capable, when temper rolling a high strength steel strip, of effectively performing rolling while stabilizing the product quality even when the rolling distance advances, and a temper rolling method using the same. [Solution] The work roll for rolling 2 has: a drum part 2x comprising a superhard alloy with a Young's modulus of 450 GPa or greater; and an uneven layer 2y formed over the drum part 2x, having an arithmetic mean roughness Ra ranging from 2.0 to 10.0 μm, and comprising granular chrome.

Description

Work roll for rolling, rolling machine provided with the same, and rolling method

The present invention relates to a work roll for rolling for rolling a high-strength steel strip, a rolling mill provided with the work roll, and a rolling method.

Conventionally, a temper rolling mill is known that applies a light reduction of, for example, a reduction rate of 1% or less to a steel strip. The steel strip is uniformly stretched by a temper rolling mill and its shape is corrected to obtain a predetermined flatness. Further, temper rolling improves mechanical properties such as elongation at yield, tensile strength and elongation, and properties of steel strip such as surface roughness. In recent years, with the increase in the added value of steel strips, the demand for hard steel strips represented by high-strength steel has increased. In particular, in the case of a high-strength steel sheet having a tensile strength of 980 MPa or more, a very high rolling load is required to secure the elongation required for shape correction.

Therefore, various temper rolling methods for high-strength steel sheets have been conventionally proposed (see, for example, Patent Documents 1 to 3). Patent Document 1 discloses a method of performing temper rolling with the surface average roughness Ra of a work roll used in temper rolling being in the range of 3.0 to 10.0 μm. Patent Document 2 discloses a method of using, as a roll material, a cemented carbide composed of tungsten carbide (WC) and cobalt (Co) having a Young's modulus of 500 GPa or more in the surface layer portion. Patent Document 3 discloses a method of temper rolling with a roll having a roll surface Young's modulus of 450 GPa or more and a surface roughness Ra of 1 μm or more and 10 μm or less.

JP, 2008-173684, A JP, 2017-119303, A JP, 2011-189404, A

The surface of the work roll for rolling described in Patent Documents 1 to 3 described above has a predetermined arithmetic average roughness due to the dull processing. Generally, when performing dull machining, it is conceivable to use a shot blasting method, an electric discharge dull machining method, or the like, as described in Patent Document 1. However, in these methods, as the rolling distance increases, problems such as a decrease in surface roughness due to wear or progress of cracks may occur. Then, if a defect occurs in the work roll for rolling, repair or replacement work is required, and there is a problem that stable operation of rolling work is difficult.

It is an object of the present invention to provide a work roll for rolling, a rolling mill provided with the work roll, and a rolling method capable of performing stable operation of rolling when temper rolling a high-strength steel strip. And

The present invention has the following configurations in order to solve these problems.
[1] A body made of a cemented carbide having a Young's modulus of 450 GPa or more,
A concavo-convex layer formed on the outer peripheral surface of the body portion, which has an arithmetic mean roughness in the range of 2.0 to 10.0 μm and is made of granular chrome;
A work roll for rolling characterized in that
[2] The work roll for rolling according to [1], wherein the uneven layer is formed by depositing granular chromium by chromium plating.
[3] A temper rolling mill comprising one or more stands equipped with the work roll according to [1] or [2].
[4] A temper rolling method comprising performing temper rolling with an elongation percentage of 0.2% or more by using one or more temper rolling machines equipped with the work roll for rolling according to [3].

As described above, according to the work roll for rolling, the rolling mill provided with the work roll, and the rolling method, the work roll for rolling having the arithmetic average roughness in the range of 2.0 to 10.0 μm is formed on the outer peripheral surface of the body. However, by having a concavo-convex layer made of granular chrome, it is possible to suppress the occurrence of work roll defects such as a decrease in surface roughness due to wear or the development of cracks even if the rolling distance advances, and a stable operation of rolling work is performed. It can be performed.

It is a schematic diagram which shows the preferable embodiment of the rolling mill 10 which used the work roll 2 for rolling of this invention. It is a surface enlarged photograph which shows an example of the uneven|corrugated layer 2y of the work roll 2 for rolling in the temper rolling mill of FIG. It is a graph which shows an example of the change of surface roughness with respect to plating time. It is a graph which shows an example of the change of the rolling load with respect to the elongation rate in the prior art examples 1 and 2, the comparative example 1, and the example 1 in Table 1. It is a surface enlarged photograph when the surface of a cemented carbide is dull-processed by conventional electric discharge dull processing. It is a graph which shows the change of roll surface roughness with respect to the rolling length of a work roll at the time of performing a rolling experiment using the work roll for rolling of Table 3.

An embodiment of the present invention will be described below. FIG. 1 is a schematic diagram showing a preferred embodiment of a rolling mill 10 using the work roll for rolling of the present invention. The rolling mill 10 of FIG. 1 performs temper rolling of a wide steel strip having a tensile strength of 980 MPa or more, for example. The temper rolling mill 10 has a pair of rolling work rolls 2 and a backup roll 3 that supports each rolling work roll 2. The pay-off reel 5 is arranged in the front stage of the temper rolling mill 10, and the tension reel 6 is arranged in the rear stage of the temper rolling mill 10. Then, while the steel strip 1 is being tensioned by the payoff reel 5 and the tension reel 6, the steel strip 1 is rolled down by the work roll 2 for rolling, and the steel strip 1 has a predetermined elongation (for example, 0.2 to 1.0). %) is added. However, as a means for applying tension to the steel strip 1, a bridle roll may be arranged before or after the temper rolling mill 10.

The work roll 2 for rolling has a structure in which a body 2x made of cemented carbide is fixed to a shaft material, for example. The body portion 2x is made of a cemented carbide having a Young's modulus of 450 GPa or more, for example, tungsten carbide (WC) is 86% by mass% and the balance is a cemented carbide. When the Young's modulus is 450 GPa or more, even during temper rolling of a high-strength steel plate, the rolling work roll 2 is deformed into a flat shape and the rolling work roll 2 and the steel strip 1 come into contact with each other in the roll bite. It is possible to prevent the arc length from increasing and prevent an excessive rolling load from being applied to the work roll 2 for rolling.

An uneven layer 2y made of granular Cr is formed on a portion of the body 2x corresponding to the roll barrel surface. The concavo-convex layer 2y is formed with concavities and convexities including a surface morphology formed by depositing granular chromium by chrome plating, and has an arithmetic average roughness (hereinafter referred to as "surface roughness") Ra of 2. It is formed in the range of 0 to 10.0 μm. The uneven layer 2y may be formed on at least the roll barrel surface of the body 2x, and may be formed on the entire outer peripheral surface of the body 2x.

Here, in temper rolling with a rolling reduction of 1.0% or less, if rolling is performed using the rolling work roll 2 having a high surface roughness Ra, the rolling load is reduced. This is because a phenomenon (stretching effect) in which a portion of the work roll 2 that has been removed by pushing in the convex portion of the work roll 2 appears as elongation due to the rough unevenness of the work roll 2 for rolling being transferred to the surface of the steel strip becomes remarkable. Conceivable.

If the surface roughness Ra is less than 2.0 μm, when the irregularities of the work roll 2 for rolling pierce the steel sheet to cause plastic deformation, adjacent irregularities interfere with each other, and a sufficient stretching effect cannot be obtained. In particular, in order to exert the stretching effect, the surface roughness Ra of the work roll 2 for rolling is preferably 3.0 μm or more. Under the temper rolling conditions that give a low elongation rate of about 0.2%, by setting the surface roughness Ra of the work roll to more than 4.0 μm, the interval between the adjacent convex portions becomes sufficiently large. Almost no interference of plastic deformation. Therefore, in order to effectively exert the elongation effect and reduce the load, it is desirable that the surface roughness Ra of the uneven layer 2y is more than 4.0 μm.

On the other hand, when the surface roughness Ra of the uneven layer 2y is larger than 10.0 μm, it is industrially very difficult to stably perform the work for increasing the surface roughness on the work roll 2 for rolling. It is also undesirable from the viewpoint of roll life. Therefore, the surface roughness Ra of the work roll is preferably 10.0 μm or less.

The concavo-convex layer 2y is formed of granular Cr having chromium deposited by chromium plating. First, in order to improve the adhesion between the surface of the body 2x and the chrome plating as a pretreatment for the chrome plating, after the surface of the body 2x is polished to have a surface roughness Ra=0.2 μm, for example. Further, the surface roughness Ra is 0.8 μm by sandblasting or the like. After that, the surface of the body 2x is cleaned and chromium plated.

In the chromium plating treatment, for example, the plating bath temperature is lowered to 50° C. or lower, and the chromium plating is performed under the condition of high current density of 60 A/dm ² or higher. Thereby, the grain size of Cr crystal grains deposited on the surface of the body portion 2x can be increased. That is, in the hard chrome plating used industrially, the form and hardness of deposited Cr vary depending on the electroplating conditions (plating bath temperature, current density, plating time). Generally, widely used bright plating is processed under conditions of a plating bath temperature of 50 to 60° C. and a current density of 40 to 60 A/dm ² in order to smooth the surface. On the other hand, since the uneven layer 2y described above must have unevenness satisfying a predetermined surface roughness Ra, the plating bath temperature is lowered to 50° C. or lower and the high current density condition of 60 A/dm ² or higher is set. In this way, the deposited chromium is made to be granular.

FIG. 2 is an enlarged surface photograph showing an example of the uneven layer of the work roll for rolling in the temper rolling mill of FIG. 1. Chromium plating conditions for the concavo-convex layer 2y in FIG. 2 are as follows: a plating solution containing chromic acid (CrO ₃ ) and sulfuric acid (H ₂ SO ₄ ) is used, a plating bath temperature is 37° C., a current density is 120 A/dm ² , and plating is performed. The time was set to 150 min. Then, by depositing Cr, a granular uneven layer 2y was formed on the surface of the body 2x. When the surface roughness Ra at this time was measured by a contact type roughness meter, the surface roughness Ra was 3.9 μm. Further, no cracks or the like were generated on the uneven layer 2y.

The surface roughness Ra of the uneven layer 2y is controlled by the plating time. FIG. 3 shows changes in the surface roughness Ra after plating when only the plating time is changed under the plating conditions of FIG. The surface roughness Ra increases as the plating time increases, and can be controlled to a desired surface roughness Ra by changing the plating conditions. Here, it is preferable that the average grain size of Cr deposited by chrome plating on the roll surface is 50 μm or more. This is for effectively exerting the extension effect due to the depression and depression on the surface of the steel sheet. By increasing the average grain size of Cr, the interval between the adjacent irregularities can be increased, and the interference between the adjacent irregularities when piercing the surface of the steel sheet and causing plastic deformation can be reduced.

<Experiment on rolling load>
A rolling experiment was conducted to confirm the effect of reducing the rolling load by the work roll 2 for rolling having the uneven layer 2y. In the experiment, a high-tensile steel plate having a plate thickness of 0.215 mm, a plate width of 20 mm, a length of 200 mm, and a yield stress of 1500 MPa was used as a test material. Further, as the temper rolling mill 10, a four-stage rolling mill having a work roll diameter of φ70 mm was used, and the rolling of a strip without tension was performed under dry conditions without lubrication. This is a model experiment in which the roll diameter and the plate thickness of the test material were set to 1/7 for the actual rolling of high-strength steel plates for automobiles.

The four types of work rolls shown in Table 1 were used as work rolls, the roll reduction position was changed, and the relationship between the elongation measured from the change in strip length before and after rolling and the rolling load during rolling was investigated.

In Table 1, Comparative Example 1 (No. 1) uses 2% Cr steel having a Young's modulus of 206 GPa as the material of the body 2x, and the surface is finished by grinding with a grindstone to have a surface roughness Ra=0.2 μm. is there. In Conventional Example 1 (No. 2), 2% Cr steel is used as the material of the body 2x, and the surface is finished by electric discharge dull machining to have a surface roughness Ra=3.0 μm. Conventional Example 2 (No. 3) uses tungsten carbide (WC) as a material of the body portion 2x in an amount of 86% by mass% and the balance is made of a cemented carbide and has a Young's modulus of 503 GPa. .. The surface is polished by a grindstone and has a surface roughness Ra=0.2 μm. In Example 1 (No. 4), the same cemented carbide as in Conventional Example 2 (No. 3) was used as the material of the body 2x, and the surface of the body 2x was dulled by chrome plating to obtain a surface roughness. The uneven layer 2y having Ra=2.5 μm is formed.

FIG. 4 is a graph showing the relationship between elongation rate and width load in Conventional Examples 1 and 2, Comparative Example 1 and Example 1. As shown in FIG. 4, comparing the width loads of Comparative Example 1 (No. 1) in which the roll material is 2% Cr steel and Conventional Example 1 (No. 2), the width load for the same elongation is surface roughness. It is understood that the larger conventional example 1 (No. 2) has a smaller size, and the stretching effect by pushing the convex portion of the surface of the work roll for rolling into the steel plate surface is obtained.

On the other hand, in Conventional Example 2 (No. 3) in which the material of the body 2x is cemented carbide, the width load for the same elongation is smaller than that in Conventional Example 1 (No. 2), and the Young's modulus of the roll is It can be seen that the effect of suppressing the flat deformation due to the increase is obtained. In Example 1 (No. 4), the load was smaller than that of Conventional Example 2 (No. 3) due to both the effect of stretching due to the indentation of the convex portion on the surface of the work roll for rolling and the effect of suppressing the flat deformation of the roll. Therefore, it can be seen that the effect of reducing the rolling load is high.

The elongation in temper rolling is usually in the range of 0.2 to 1.0%, and in this range, the flatness of the steel strip becomes better as the elongation increases. The elongation percentage refers to the rate of change in the length of the steel strip in the longitudinal direction before and after rolling. When the elongation is 0.2% or more, even the high-strength cold-rolled steel strip can be sufficiently shaped, and the flatness of the front surface and the back surface of the steel strip can be substantially improved. Further, in order to make the rolling load applied to the work rolls and the temper rolling mill 10 equal to or lower than the withstand load of the temper rolling mill, the elongation rate applied to the steel strip is preferably 0.5% or less.

<Continuous operation experiment>
In order to evaluate the soundness of the roll surface during continuous operation, a rolling test was performed in which two rolling work rolls of Comparative Example 2 and Example 2 shown below were rotated while being pressed with a constant surface pressure. Comparative Example 2 uses a cemented carbide (Young's modulus 503 GPa) containing 86% by weight of tungsten carbide (WC) and the balance of cobalt as the material of the body 2x, and the surface is directly subjected to electric discharge dull machining. The surface roughness Ra was finished to 3.0 μm.

FIG. 5 shows an enlarged photograph of the surface of the concavo-convex layer when dull machining is performed by direct electric discharge machining on the body 2x of cemented carbide as in Comparative Example 2. As shown in FIG. 5, a crack CK is formed on the surface by an impact during electric discharge machining. It is known that a crack CK occurs when a material such as a cemented carbide, which is mainly composed of brittle ceramics, is subjected to electric discharge machining.

On the other hand, Example 2 uses a cemented carbide (Young's modulus 503 GPa) containing tungsten carbide (WC) at 86% by mass and balance cobalt as the material of the body 2x, and the surface is plated with chromium. The uneven layer 2y is provided to finish the surface roughness Ra=3.0 μm.

As a continuous operation experiment, a 4-roll mill with a work roll diameter of 70 mm and a barrel width of 40 mm was used, and the work roll was pressed at a load of 1.8 tons and rotated at a speed of 50 mpm. The maximum pressure acting on the work rolls during the experiment was generated in the elastic contact region between the pressed work rolls, and was 1011 MPa under the present conditions. This is approximately the same as the surface pressure level acting on the work rolls in the temper rolling mill used in an actual continuous annealing line or the like. In the experiment, the rolling test time was changed, and the surface of the work roll at each time was observed with a magnifying microscope to confirm the presence or absence of cracks on the surface of the work roll and the presence or absence of cracks or peeling. Table 2 shows a summary of the experimental results.

In Table 2, it was confirmed that cracks were formed on the roll surface in the initial stage in Comparative Example 2 in which a predetermined surface roughness Ra was provided by electric discharge dull machining (see FIG. 5). When rolling is performed with a work roll for rolling having this crack, the crack develops as the rolling time increases due to the stress acting on the work roll for rolling during rolling. As a result, the roll surface was cracked and peeled off after rolling for 300 minutes. On the other hand, in the work roll for rolling which was dull-processed by chrome plating, no cracks or breaks were confirmed (=“healthy” in Table 2), and it was found that the roll can be used stably.

<Continuous operation experiment 2>
Further, in order to evaluate the maintainability of the roll roughness during continuous operation, a rolling experiment was performed using four rolling work rolls of Comparative Example 3, Comparative Example 4 and Example 3 and Example 4 shown in Table 3 below. Carried out.

In Comparative Example 3, 2% Cr steel having an elastic modulus of 206 GPa was used as the material of the body 2x, and the surface was subjected to electric discharge dull machining to have a surface roughness Ra=4.5 μm. Comparative Example 4 uses a cemented carbide (elastic modulus 450 GPa) containing 80% by mass of tungsten carbide (WC) and the balance of cobalt as the material of the body 2x, and discharges without chrome plating. The surface roughness Ra was finished to 4.5 μm by dull processing.

On the other hand, in Example 3, as the material for the body portion 2x, a cemented carbide (containing elastic modulus 450 GPa) containing 80% by mass of tungsten carbide (WC) and the balance of cobalt was used, and the surface was roughened by chrome plating. Layer 2y was applied and the surface roughness was finished to 4.5 μm. The average grain size of the Cr deposited at this time was 60 μm.

Example 4 is a roll in which granular chromium was deposited on the surface of the roll by the same method as in Example 3 described above, and then the plating conditions were changed and hard chrome plating with a plating thickness of 1 μm was applied again. The reason why the hard chrome plating is performed again by changing the plating conditions is as follows. When granular Cr is deposited on the surface to form irregularities under the plating conditions of low plating bath temperature (50° C. or less) and large current density (60 A/dm ² ), the Vickers hardness of chromium plating is about 700 to 900. Become. On the other hand, when ordinary hard chrome plating is performed under conditions of a plating bath temperature of 50 to 60° C. and a current density of about 40 to 60 A/dm ² , the hard chrome plating has a Vickers hardness of about 900 to 1100. At this time, when granular chromium was deposited on the roll surface by the same method as in Example 3 and then hard chrome plating was performed again by changing the plating conditions, very hard plating was performed on the outermost surface of the work roll for rolling. This is because a film is formed and wear resistance can be further improved.

As described above, the thickness of the hard chrome plating again is set to 1 μm, because when the plating is performed with a thickness greater than that, the unevenness of the grain formed in the initial stage becomes small and the elongation in temper rolling This is because the effect is reduced. That is, by depositing granular chrome in the initial plating and then again performing hard chrome plating of the thin film, the hardness of the plating film surface can be increased without changing the roughness pattern formed by the granular chrome. .. For this reason, it is desirable that the thickness of the hard chrome plating again be applied within the range of 0.5 to 10 μm.

Then, four types of work rolls for rolling having a roll diameter of φ70 mm and a barrel width of 40 mm shown in Table 3 were used as rolling work rolls of the four-high rolling mill, and a continuous coil rolling experiment with tension was carried out. As the material to be rolled, a high-tensile steel plate having a plate thickness of 0.215 mm, a plate width of 20 mm, and a yield stress of 1500 MPa was used. Coil rolling was carried out under a dry condition without lubrication under a condition that the rolling load per unit width was 0.2 ton/mm under the condition that the inlet/outlet side tension was 100 MPa. At this time, the change in roll surface roughness with respect to the rolling length of each roll was measured.

FIG. 6 is a graph showing changes in roll surface roughness with respect to the rolling length of the work rolls when a rolling experiment was performed using the work rolls for rolling in Table 3. As shown in FIG. 6, in Comparative Example 3 in which the 2% Cr steel roll was subjected to the electric discharge dull processing, it was found that the roughness was significantly reduced as the rolling length was increased. In the roll of Comparative Example 4 in which the cemented carbide is made to have a high roughness by direct electric discharge dull machining, since the hardness of the cemented carbide is extremely high, the maintainability of the roll roughness with respect to the rolling length is the best. However, after the rolling of 1.67 km, cracks were generated on the roll surface, and further rolling became difficult. This is because, as described above, cracks are formed when direct electric discharge machining is performed on the cemented carbide, and the cracks propagate due to the stress applied during rolling, which makes it difficult to use in actual rolling.

On the other hand, in Examples 3 and 4 of the present invention, although the roughness decreases due to the initial wear, it can be seen that the roughness retention against the rolling length thereafter is significantly superior to Comparative Example 3. In particular, it can be seen that Example 4 in which a thin film of hard chrome plating is applied to the surface exhibits excellent roughness retention.

According to the above-described embodiment, the rolling is performed by forming the concavo-convex layer 2y formed on the outer peripheral surface of the body 2x and having a surface roughness Ra in the range of 2.0 to 10.0 μm and made of granular chrome. Even if the distance advances, it is possible to reduce deterioration of the work roll such as a decrease in surface roughness Ra due to wear or the occurrence of cracks, and to perform stable temper rolling. In particular, the rolling load can be reduced only by changing the material and the surface processing method of the work roll 2 for rolling used in the temper rolling mill 10, and it is not necessary to change the equipment itself such as the roll diameter. , Its industrial value is great.

In particular, among high-strength steels, steel sheets produced by continuous annealing accompanied by quenching and tempering treatments have the shape (flatness) of the steel strip due to the thermal stress during the quenching treatment and the transformation stress generated along with the transformation of the metal structure. Is easy to get worse. Such a defective shape of the steel strip cannot be eliminated even by flattening the shape of the steel strip by cold rolling before annealing. Therefore, it is necessary to correct the shape of the annealed steel strip by temper rolling.

Also, high-strength steel sheets with a tensile strength of 980 MPa or more are used as materials for automobile parts, and are formed into parts by pressing. In order to improve oil retention during press working, it is necessary to have dull finish (uneven finish) on the surface of the steel sheet. The dull finish of the surface of the steel strip 1 is usually controlled by dulling the surface of the work roll 2 for rolling of the temper rolling mill 10 and transferring the unevenness to the steel plate.

The elongation during temper rolling is controlled by the tension applied to the steel strip and the work roll reduction position. In order to obtain a higher elongation rate, a higher tension and a higher rolling load than in the past are required. Particularly, in temper rolling of a high-strength steel strip having a tensile strength exceeding 980 MPa, the deformation resistance of the steel strip itself is extremely high, and a larger rolling load is required.

Normal temper rolling mills are often not designed on the premise of such temper rolling of high-strength steel strip.In temper rolling of high-strength steel strip, the rolling load is the load-bearing capacity of the rolling mill. Will exceed. Here, it is conceivable to reduce the rolling load by changing the structure of the temper rolling mill from a four-stage type to a six-stage type and reducing the work roll diameter. However, there is a problem that a large amount of equipment remodeling is required and the cost is high.

In this way, the higher the tensile strength steel that requires shape correction, the higher the rolling load and the more difficult it is to deal with existing temper rolling. Therefore, it is the actual situation that the shape is corrected by using a leveler or the like in the subsequent steps, which causes a problem of an increase in manufacturing cost and a longer delivery time due to the addition of steps.

Therefore, by processing the surface of the work roll 2 for rolling with a surface roughness Ra of 2.0 to 10.0 μm or less, it is possible to obtain a desired rolling effect while reducing the rolling load. The body 2x is made of a cemented carbide having a Young's modulus of 450 GPa or more. This makes it possible to obtain a desired linear load without increasing the roll diameter even when rolling a high-strength steel sheet having a tensile strength of 980 MPa or more.

On the other hand, when the above-described surface roughness Ra of 2.0 to 10.0 μm or less is formed by electric discharge dull machining, the surface roughness Ra of the work roll for rolling decreases due to wear as the rolling distance advances, and the rolling load The effect of maintaining low may not be obtained.

Therefore, the concavo-convex layer 2y is formed of granular chrome formed by chrome plating. As a result, it is possible to form the uneven layer 2y having no cracks, and it is possible to obtain Vickers hardness in which the surface is not easily worn even when repeatedly rolled. Further, when the uneven layer 2y is formed of granular chrome, since the projections of the granular chrome have a spherical shape, local stress concentration during rolling is reduced, and wear resistance is higher than that in the case of ordinary chrome plating coating. improves. As a result, it is possible to reduce the frequency of work roll repairs and replacements, and to perform stable rolling process operations.

Further, by performing temper rolling with an elongation of 0.2% or more using one or more rolling mills 10, even a high-strength cold-rolled steel strip can be sufficiently shape-corrected. The flatness of the front and back surfaces of the strip can be made generally good.

The embodiment of the present invention is not limited to the above embodiment, and various modifications can be added. Although the present technology illustrates the case where it is applied to an independent temper rolling mill shown in FIG. 4, it is installed inline in a continuous process line such as a continuous annealing line (CAL) or a continuous hot dip galvanizing line (CGL). It can also be applied to rolling mills.

1 Steel Strip 2 Work Roll for Rolling 2x Body 2y Concavo-convex Layer 3 Backup Roll 5 Payoff Reel 6 Tension Reel 10 Temper Rolling Mill CK Crack Ra Arithmetic Average Roughness (Surface Roughness)

Claims

A body made of a cemented carbide with a Young's modulus of 450 GPa or more,
A concavo-convex layer formed on the outer peripheral surface of the body portion, which has an arithmetic mean roughness in the range of 2.0 to 10.0 μm and is made of granular chrome;
A work roll for rolling characterized in that
The work roll for rolling according to claim 1, wherein the uneven layer is formed by depositing granular chromium by chrome plating.
A rolling mill equipped with the work roll for rolling according to claim 1 or 2.
A rolling method characterized by performing temper rolling with an elongation of 0.2% or more by using one or more rolling mills according to claim 3.