JP2011152577A - Rolling roll and method of rolling steel strip - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling roll wherein the growth of thermal crown is suppressed and the variation of the thermal crown profile is remarkably mitigated. <P>SOLUTION: This invention relates to the rolling roll which is composed of an outer layer 1, an intermediate layer 2 and a shaft material 3, wherein the thermal conductivities of the material composed of the outer layer 1 and the material composed of the intermediate layer 2 are larger than the thermal conductivity of the material composed of the shaft material 3. In the outer layer 1 and the intermediate layer 2 which are larger in a rise of temperature, the heat input from the material to be rolled is positively and effectively diffused in the axial direction of the roll, so that the absolute values of the quantities of thermal expansion of the outer layer 1 and the intermediate layer 2 and the steep variation of the thermal crown profile in the axial direction of the roll are suppressed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a rolling roll for rolling a steel strip and the like, and more specifically to a rolling method of a steel strip using the same. More specifically, thermal crown growth associated with the progress of rolling is small, and schedule-free rolling or The present invention relates to a rolling roll suitable for high-efficiency rolling and a steel strip rolling method using the same.

  In rolling steel strips, particularly hot rolling steel strips, the temperature of the material to be rolled is as high as about 800 to 1050 ° C. Therefore, as the rolling progresses, the thermal crown is in the range where the rolling roll comes into contact with the material to be rolled. A so-called trapezoidal thermal expansion occurs. In addition, since the contact surface with the material to be rolled becomes high temperature, the surface pressure acting between the material to be rolled and the rolling roll, and further between the reinforcing roll such as the rolling roll and the backup roll becomes very high. The wear of the rolling roll also progresses sequentially.

  In the rolling of hot-rolled steel strip, so-called schedule-free rolling, in which rolling is performed while arbitrarily changing the material and dimensions (particularly the sheet width) of the material to be rolled, is aimed at from the viewpoint of productivity. Generally, in the rolling of hot-rolled steel strip, in order to ensure the desired finishing dimensions that differ from coil to coil, especially the plate crown and plate shape, which are the plate thickness profile, the roll roll surface profile such as thermal crown and roll wear Based on this, setting of plate crown / plate shape control actuators such as a work roll bender, a roll cloth, and a roll shift is performed (see, for example, Patent Document 1). However, for schedule-free rolling, it is indispensable to appropriately control the trapezoidal roll surface profile due to the development of the thermal crown. Hereinafter, the reason will be described with reference to FIGS.

  As shown in FIG. 8, when the narrow coil is continuously rolled, a trapezoidal thermal crown develops at the plate width position of the material to be rolled (steel strip). In this state, when the next coil (i + 1 coil) wider than the previous coil (i coil) is rolled, the plate thickness is steep at the position outside the trapezoidal thermal crown within the plate width. As shown in FIG. 9, a plate thickness profile called reverse crown profile is obtained. Normally, the thickness profile of the hot-rolled steel strip is a profile that gradually decreases from the center of the plate width to the end of the plate width, while the reverse crown profile has a thickness that decreases gradually from the center of the plate width to the end of the plate width. It is a plate thickness profile in which the plate thickness increases again in the vicinity of the width end. When a reverse crown profile occurs, for example, the tolerance value of the crown from the customer cannot be satisfied, or scratches occur near the plate edge in the cold rolling process after hot rolling, or extreme ear waves It becomes a big problem such as the occurrence of a shape and the like and hinders the plate passing.

In order to solve the above-described problem, a roll surface profile control method has been proposed as a means for preventing the occurrence of a reverse crown profile (see, for example, Patent Document 2 and Patent Document 3).
In the method of controlling the thermal crown profile shown in Patent Document 2, an induction heating device is provided in the vicinity of both ends of the rolling roll, and the plate width of the next coil is compared with the plate width of the next coil. In order to prevent deterioration of the plate crown and plate shape, the position of the surface of the rolling roll corresponding to the plate end of the next coil is heated so that necessary thermal expansion can be obtained.

Moreover, the control method of the thermal crown profile shown in Patent Document 3 is such that the cooling water amount distribution increases from the central portion in the coil plate width direction toward the plate end portion, and the portion that is not in contact with the material to be rolled. It is intended to eliminate the steep gradient of the thermal crown profile that develops in a trapezoidal shape by blocking the roll cooling water or extremely reducing the flow rate.
As another conventional technique, in a high-speed rolling composite roll, a material with high thermal conductivity is used for the intermediate layer, and the amount of heat input to the rolling roll by contact with a high-temperature rolling material is positive in the roll axis direction. There has been proposed a composite roll that is dispersed in the thermal dispersion to reduce the thermal crown (see, for example, Patent Document 4).

JP-A-7-75812 Japanese Patent Laid-Open No. 2004-98068 Japanese Patent Laid-Open No. 11-129010 JP-A-10-230307 Japanese Patent Laid-Open No. 10-5823 International Publication No. 2006/088065 JP 2005-330583 A

pref. shimane. jp / hoodou / files / B842571E-CFAE-4808-8207-8D643DE13E55. pdf

However, each of the conventional techniques described above has the following problems.
First, in the setting method of the plate crown and plate shape actuators disclosed in Patent Document 1, the crown profile control amount by the actuator is almost parabolic in the plate width direction with the plate width center as a minimum point, that is, the roll surface is convex. There is a problem that there is an effect of forming the shape, and only the crown profile control by this actuator has a problem that a change in the roll surface profile due to a sharp thermal crown around the sheet width end of the material to be rolled and roll wear cannot be compensated.

  In the method shown in Patent Document 2, although the effect of changing the roll surface profile is recognized, there is a concern that the plate shape may be abruptly disturbed when introduced to only one stand of a continuous rolling mill composed of a plurality of stands. At that time, it is considered necessary to apply to a plurality of consecutive stands. In addition, if water adheres to the induction heating device due to splashing of roll cooling water, etc., the device will be destroyed due to an electrical short-circuit accident, so perfect waterproofing measures are essential, and it can be a very expensive facility. Inevitable. In addition, there is a risk of roll surface hardness reduction due to high density heat generation on the surface due to induction heating, roll cracking due to thermal stress, and occurrence of a spalling accident.

In the method shown in Patent Document 3, the effect of changing the roll surface profile is recognized, but the effect is very slight, and it is considered difficult to cope with an arbitrary rolling schedule in the schedule-free rolling. .
Regarding the composite roll for rolling shown in Patent Document 4, according to the study by the present inventors, the effect of changing the roll surface profile including the outer layer is negligible only by using a high thermal conductivity material only for the intermediate layer. Yes, the expansion of schedule-free rolling is very limited. Further, according to the embodiment, a material having a significantly larger thermal expansion than that of the shaft material is used only for the intermediate layer, and when the temperature rises due to the progress of rolling, the interface between the intermediate layer and the shaft material There is also concern about the danger of delamination and the occurrence of major troubles such as breakage of the roll.

Accordingly, an object of the present invention is to solve the above-described problems of the prior art, and to provide a rolling roll in which the growth of the thermal crown is suppressed and the change in the thermal crown profile can be greatly reduced.
Another object of the present invention is to provide a method of rolling a steel strip that uses such a rolling roll and can more effectively mitigate thermal crown profile changes.

In order to solve the above-mentioned problems, the present inventors have conducted intensive studies and found a rolling roll capable of remarkably suppressing the growth of thermal crown accompanying the progress of rolling and a rolling method of a steel strip using the rolling roll. .
The present invention has been made on the basis of such findings and has the following gist.
[1] A rolling roll composed of an outer layer, an intermediate layer and a shaft, wherein the thermal conductivity of the material constituting the outer layer and the material constituting the intermediate layer is higher than the thermal conductivity of the material constituting the shaft A rolling roll that is large.
[2] The rolling roll according to [1], wherein the thermal expansion coefficient of the material constituting the outer layer, the intermediate layer, and the shaft member is such that outer layer <intermediate layer <shaft member.
[3] The rolling roll according to the above [1] or [2], wherein the outer layer is made of a cemented carbide.

[4] A rolling roll according to any one of the above [1] to [3], wherein the intermediate layer is made of a copper-based alloy.
[5] A method for rolling a steel strip using the rolling roll according to any one of [1] to [4], wherein the rolling roll is cooled in the following (a) and / or (b), and the rolling In roll cooling, the roll cooling range in the rolling roll axial direction is equivalent to the strip width of the steel strip (however, in the case of (b) below, it is equivalent to the strip width of the preceding strip), and roll cooling is performed in the outer range. A method of rolling a steel strip characterized by not performing the above.
(A) At least a part during rolling from the tip of the steel strip to the tail end (b) At least a part between the passes of the preceding steel strip and the trailing steel strip

In the rolling roll of the present invention, the growth of the thermal crown at the time of rolling is suppressed, and the change in the thermal crown profile is greatly relaxed. Thereby, the dramatic expansion of the schedule-free rolling and the significant improvement in rolling efficiency can be realized.
Moreover, according to the rolling method of the steel strip of this invention, a thermal crown profile change can be relieve | moderated more effectively.

The longitudinal cross-sectional view which shows one Embodiment of the rolling roll of this invention The figure which shows the example of the thermal crown profile of the surface of a rolling roll in the hot finishing rolling using the rolling roll and rolling method of this invention Drawing showing the result of FIG. 2 as the thermal crown amount corresponding to the plate width of the material to be rolled The effect of the rolling method according to the present invention is shown. In the hot finish rolling performed using the rolling roll of the present invention, the thermal crown profile on the surface of the rolling roll is applied when the rolling method of the present invention is not applied and when not applied. Drawing showing an example FIG. 4 shows the result of FIG. 4 as a thermal crown amount corresponding to the sheet width of the material to be rolled. Drawing showing an example of the thermal crown profile on the surface of a rolling roll in hot finish rolling using a conventional rolling roll Drawing showing the result of FIG. 6 as the thermal crown amount corresponding to the plate width of the material to be rolled Explanatory drawing showing the generation mechanism of reverse crown profile Explanatory drawing showing examples of normal crown profile and reverse crown profile Explanatory drawing which shows an example of the cooling condition of the rolling roll in the rolling method of this invention Explanatory drawing which shows an example of the cooling condition of the rolling roll in the rolling of a conventional system

FIG. 1 is a longitudinal sectional view showing an embodiment of a rolling roll of the present invention.
This rolling roll is composed of an outer layer 1, an intermediate layer 2, and a shaft member 3, and has a structure in which the intermediate layer 2 is interposed between the outer layer 1 and the shaft member 3, and the outer peripheral surface of the outer layer 1 has a roll barrel surface. The shaft material 3 constitutes a roll shaft.
Conventionally, high-speed rolls, high-chromium rolls, adamite rolls, Ni grain rolls and the like have been widely used for rolling steel strips, and in particular, high-speed rolls are used in the hot-rolling process of steel strips with a large thermal crown. It is common. A high-speed roll is manufactured by a continuous build-up casting method, a centrifugal casting method, or the like in which a high-speed steel is continuously built up on a forged steel shaft, and is generally a two-layer structure including a shaft and an outer layer constituting a roll barrel It is. On the other hand, a typical structure of the cemented carbide roll is, for example, as shown in Patent Document 5, in which a composite material ring and a shaft material are fitted and coupled. The composite ring is made of metal powder in which cobalt carbide is mixed with tungsten carbide and sintered at the same time on the outer periphery of a molten inner layer ring such as cast steel, forged steel, graphite cast steel, carbon steel, alloy carbon steel, etc., and at the same time diffusion bonded. Alternatively, the outer layer ring made of cemented carbide is formed by CIP or the like separately from the inner layer ring, and the outer layer ring and the inner layer ring are diffusion bonded by HIP. In this case, it is preferable to form the bonding layer using an appropriate binder according to the composition of the inner layer ring and the outer layer ring. Then, the composite ring is fitted and fixed to a metal shaft material such as cast steel, forged steel, or cast iron by a shrink fitting process to complete a rolling roll. Although the method for manufacturing the rolling roll of the present invention is not particularly limited, for example, it can be obtained by a method similar to the conventional method for manufacturing a cemented carbide roll as described above. The rolling roll is configured by being fitted and fixed to 3. In this rolling roll, the outer layer material of the composite ring constitutes the outer layer 1, and the inner layer material constitutes the intermediate layer 2.

In the rolling roll of the present invention, the thermal conductivity of the material constituting the outer layer 1 and the material constituting the intermediate layer 2 is made larger than the thermal conductivity of the material constituting the shaft member 3.
In a conventional two-layer rolling roll such as a high-speed roll, the thermal conductivity of the outer layer is lower than that of the shaft material, and the coefficient of thermal expansion is almost the same as that of the shaft material. Therefore, the temperature in the heat input range from the material to be rolled tends to rise, and a trapezoidal thermal crown is formed. On the other hand, the rolling roll of this invention has the outer layer 1 and the intermediate | middle layer 2 with a large temperature rise because the thermal conductivity of the material which each comprises the outer layer 1 and the intermediate | middle layer 2 is larger than the thermal conductivity of the shaft material 3. The heat input from the material to be rolled is actively and efficiently diffused in the roll axis direction, and the absolute value of the thermal expansion amount of the outer layer 1 and the intermediate layer 2 and the sharp change of the thermal crown profile in the roll axis direction It is possible to suppress. Furthermore, the temperature distribution in the roll axis direction is also relaxed for the shaft 3 having a lower thermal conductivity than the outer layer 1 and the intermediate layer 2, and as a result, the effect of relaxing the thermal expansion distribution in the roll axis direction is obtained. As a result, thermal crown growth that grows as rolling progresses is suppressed, and abrupt changes in the thermal crown profile generated at the boundary between the contact and non-contact portions of the steel strip can be prevented. It becomes.

Moreover, in the rolling roll of this invention, it is preferable that the magnitude | size of the coefficient of thermal expansion of the material which each comprises the outer layer 1, the intermediate | middle layer 2, and the shaft material 3 is outer layer 1 <intermediate layer 2 <shaft material 3.
As described above, when a material having a higher thermal expansion coefficient than the shaft material is used only for the intermediate layer as in Patent Document 4, delamination is caused at the interface between the intermediate layer and the shaft material due to the difference in the thermal expansion amount between the intermediate layer and the shaft material. Will occur. This is because the radial displacement amount between the intermediate layer (1.7 × 10 ⁻⁵ / K) having a large thermal expansion amount and the shaft member (1.3 × 10 ⁻⁵ / K) having a small thermal expansion amount is 30. This is because a large tensile stress is generated in the radial direction at the interface. In addition, since the temperature distribution is higher on the outer peripheral side and lower on the central side by inputting heat from the outer peripheral side in the rolling roll, there is a problem that the difference in thermal expansion between the intermediate layer and the shaft material is more likely to be further increased. . On the other hand, in the present invention, the thermal expansion coefficients of the materials of the outer layer 1, the intermediate layer 2, and the shaft member 3 are set so as to be opposite to the temperature distribution in the roll radial direction (outer layer 1> intermediate layer 2> shaft member 3). By increasing in order, the difference in the amount of thermal expansion between the layers can be reduced, and the risk of troubles such as delamination can be reduced.

  The outer layer 1 of the rolling roll is preferably composed of cemented carbide. Cemented carbide has outstanding wear resistance compared to high speed steel, has a thermal conductivity of 80 W / (m · K) or higher and a low thermal expansion coefficient (1/2 to 1/3 of steel). have. In order to realize complete schedule-free rolling, it is necessary to maintain a good thickness profile and shape in the sheet width direction, suppress thermal crown growth of the rolling roll, and suppress local roll wear. Is essential. It can be said that the cemented carbide having the above characteristics is one of the most suitable materials for the roll outer layer material exhibiting such performance. That is, the thermal crown can be greatly reduced because heat is diffused in the roll axis direction and the amount of expansion is small. Moreover, since it is excellent in abrasion resistance, the local abrasion produced | generated in the steel strip edge vicinity which is one of the obstruction factors of a schedule free rolling is reduced significantly. Conventionally, cemented carbide has been used for rolling rolls, and, for example, cemented carbide alloys such as WC—Co and Ti—Cr—Mo are suitable.

The intermediate layer 2 of the rolling roll is preferably composed of a copper-based alloy. Pure copper is a good thermal conductive material with a thermal conductivity of 400 W / (m · K), about 10 times that of steel, but its thermal expansion is 1.7 × 10 ⁻⁵ / K, which is 30-40% of steel. However, it is difficult to apply the present invention to a rolling roll for the reasons described above. On the other hand, among copper-based alloys based on copper, for example, there are materials having both good thermal conductivity and low thermal expansion, such as copper Cr alloy and copper carbon alloy. An alloy is suitable as a material for the intermediate layer 2.

As a copper-type alloy used for the intermediate | middle layer 2, a copper-type alloy as shown by patent document 6, 7 can be used, for example. The copper-based alloy disclosed in Patent Document 6 is a composite material of carbon fiber and copper (copper whose metal structure is recrystallized) substantially aligned in one direction, and is a carbon fiber plated with copper. Are stacked, pressure-sintered (discharge plasma sintering) at a predetermined temperature and pressure, and recrystallized from a copper metal structure. In the data disclosed by the inventors of Patent Document 6 in another non-patent document 1, although the characteristics vary depending on the blending ratio of the carbon fibers, the thermal conductivity is 460 to 630 W / (m · K). It has a very good good thermal conductivity and is shown to have a coefficient of thermal expansion of 0.6 to 1.4 × 10 ⁻⁵ / K. From this, when applying the copper-based alloy to the intermediate layer 2 of the rolling roll of the present invention, the characteristics of high thermal conductivity and low thermal expansion are satisfied with respect to the shaft member 3 by adjusting the blending ratio of the carbon fibers. What should I do?

Further, the copper-based alloy having a high thermal conductivity and a low coefficient of thermal expansion shown in Patent Document 7 is a Cu—Cr alloy composed of Cr and the balance of Cu and inevitable impurities, and is composed of Cr alone or Cr and Cu. The powder is sintered and the sintered body is infiltrated into copper and then subjected to an aging heat treatment, or manufactured by a melting, casting, rolling method or the like. Although the characteristics of the Cu-Cr alloy shown in Patent Document 7 change depending on the Cr content and the aging temperature, the thermal conductivity is 134 to 350 W / (m · K), and the thermal expansion coefficient is 0.9 to 1. It is shown to be 67 × 10 ⁻⁵ / K. Therefore, when applying the copper-based alloy to the intermediate layer 2 of the rolling roll of the present invention, by adjusting the Cr content and the aging temperature, the shaft material 3 has high thermal conductivity and low thermal expansion characteristics. It should be satisfied.

There are no particular restrictions on the material constituting the shaft material 3 of the rolling roll, and a metal material such as cast steel, forged steel, or cast iron generally used for the shaft material of the rolling roll may be used. For example, referring to the data shown in Patent Document 1, the physical property value of the shaft member 3 is 42 W / (m · K) and the coefficient of thermal expansion is 1.3 × 10 ⁻⁵ / K. For example, it may have a physical property value of that level, but there is no particular limitation as long as the conditions of the present invention are satisfied.
The thicknesses of the outer layer 1 and the intermediate layer 2 of the rolling roll are not particularly limited, and may be determined in consideration of the rolling pitch in the applied rolling line, the rolling material temperature, the crown control actuator capability, and the like.

Next, the steel strip rolling method of the present invention will be described.
In this rolling method, when rolling a steel strip using the rolling roll of the present invention, the rolling roll is cooled in the following (a) and / or (b). The roll cooling range in the direction is equivalent to the plate width of the steel strip (however, in the case of (b) below, it is equivalent to the plate width of the preceding steel strip), and roll cooling is not performed in the outer range.
(A) At least a part during rolling from the tip of the steel strip to the tail end (b) Between the passes of the preceding steel strip and the trailing steel strip (after passing the tail end of the preceding steel strip, until the leading end of the trailing steel strip) The control of the roll cooling range according to the method of the present invention is usually performed in (a) above, and according to the length of time between the passes of the preceding steel strip and the subsequent steel strip, the thermal crown is controlled. In consideration of the state of occurrence of the above, it may be performed in the above (b) as necessary, but may be performed only in the above (b) depending on the rolling roll to be used, the rolling form, the state of occurrence of the thermal crown, or the like.
In addition, the control of the roll cooling range in the above (a) and (b) may be performed during the whole period of each of (a) and (b), or may be performed during a part of the period, and the occurrence of thermal crown It may be selected as appropriate in consideration of the above.

  Normally, cooling of the rolling roll is performed by injecting cooling water to the entire length of the roll barrel, and the entire length of the roll barrel is within the roll cooling range. For this reason, as shown in FIG. 11, when using a cooling means in which a plurality of cooling headers 5 are arranged in the roll axis direction, the cooling water 6 is injected from all the cooling headers 5 regardless of the plate width of the steel strip 4. Then, the rolling roll is cooled. On the other hand, in the rolling method of the present invention for controlling the roll cooling range, as shown in FIG. 10, the cooling header 5 is only at the position corresponding to the plate width of the steel strip 4 (inside the steel strip plate width). Then, the cooling water 6 is sprayed to cool the rolling roll. In order to control the roll cooling range, for example, an electromagnetic valve may be provided in each cooling header 5 and the ON / OFF control of cooling water injection from each cooling header 5 may be performed by opening and closing the electromagnetic valve.

  The purpose of the present invention is to reduce the absolute value of the thermal crown of the rolling roll and to alleviate a sharp change in the thermal crown profile in the roll axis direction, and for that purpose, contact with the material to be rolled. It is effective to positively diffuse the heat input by the heat in the roll axis direction and raise the temperature in the non-contact range with the material to be rolled. Therefore, when rolling the steel strip, the rolling roll of the present invention having the above-described effects is used, and the cooling range in the rolling roll axis direction is equivalent to the plate width of the steel strip, and in the range outside it By not performing cooling of the rolling roll, that is, by not performing roll cooling in a non-contact range with the steel strip, the heat input to the contact portion of the steel strip on the rolling roll surface can be efficiently transferred in the rolling roll axial direction. The thermal crown profile produced at the boundary between the steel strip contact portion and the non-contact portion is more effectively prevented from being diffused and a more remarkable relaxation effect of the thermal crown profile is obtained.

The rolling roll and rolling method of the present invention are particularly suitable for hot finish rolling where thermal crowns are likely to grow, but for other rolling processes, for example, rolling steel strips such as cold rolling and temper rolling. Can also be applied.
In addition, with thermal crown control using crown control actuators such as roll benders and roll cloths, the gap between the upper and lower rolls along the roll axis direction can only be changed to a parabolic shape, leading to the growth of conventional trapezoidal thermal crowns. However, the rolling roll and the rolling method of the present invention can obtain the effects of thermal crown control using these crown control actuators.

The effects of the rolling roll and the rolling method of the present invention are as follows. For example, the outer layer 1 is a cemented carbide alloy, the intermediate layer 2 is a copper-based alloy shown in Patent Document 6, and the shaft roll 3 is composed of a forged steel material. It verified and evaluated based on the analysis result by a thermoelastic FEM. For comparison, the effect of the conventional high-speed roll was similarly evaluated.
FIG. 2 shows an example of a thermal crown profile on the surface of the rolling roll in hot finish rolling using the rolling roll and rolling method of the present invention, and FIG. 3 shows the result of FIG. 2 as a thermal equivalent to the sheet width of the material to be rolled. It is shown as a crown amount. The analysis condition is a result corresponding to the F7 stand in continuous rolling with the same width of 1200 mm. The roll dimensions are: roll diameter φ650 mm, barrel length 2057 mm, outer layer 1 thickness 55 mm, and intermediate layer 2 thickness 75 mm. The analysis results are as follows: rolling time 60 sec + coil time 30 sec as non-steady analysis, each state after 10, 20, 30 coil rolling, and thermal equilibrium as steady analysis (continuous rolling, that is, infinitely long) The result in the state where the coil was rolled is shown. FIG. 6 shows an example of a thermal crown profile on the surface of a rolling roll in hot finish rolling using a conventional high-speed roll, and FIG. 7 shows the result of FIG. 6 as a thermal crown corresponding to the sheet width of the material to be rolled. It is shown as a quantity.
Table 1 shows the thermal conductivity and thermal expansion coefficient of the rolling roll used in the above analysis.

  According to the analysis results for the present invention, the profile of the roll surface grows almost in parallel with the progress of rolling, and according to FIG. 3, the thermal crown profile at 10 to 30 coils hardly changes. In addition, it can be seen that the profile is substantially parabolic. Furthermore, although the absolute value of the thermal crown increases in continuous rolling, the thermal crown amount corresponding to the sheet width is reduced as compared with that after 30 coil rolling. This is because heat input due to contact with the material to be rolled diffuses in the roll axis direction, and the temperature distribution in the roll axis direction is relaxed. On the other hand, in the conventional high-speed roll shown in FIG. 6, the thermal crown profile is already trapezoidal when 10 coils are rolled, and the absolute value increases with the progress of rolling. This is because the temperature rise in the heat input range due to contact with the material to be rolled is large, and the amount of thermal crown corresponding to the plate width in continuous rolling has grown enormously as shown in FIG. Comparing FIG. 3 and FIG. 7, it can be seen that the thermal crown amount corresponding to the plate width according to the present invention is reduced to about ¼ that of the prior art, and the profile is also greatly different from the parabolic shape.

4 and 5 show the effect of the rolling method according to the present invention, and FIG. 4 shows hot finish rolling using the rolling roll of the present invention, to which the rolling method of the present invention is applied. FIG. 5 shows an example of the thermal crown profile on the surface of the rolling roll for the case (cooling range of the rolling roll: equivalent to the plate width) and the case where the rolling method of the present invention is not applied (cooling range of the rolling roll: total roll barrel length). 4 shows the result of FIG. 4 as a thermal crown amount corresponding to the sheet width of the material to be rolled. According to this, the rolling method according to the present invention, that is, the cooling range in the axial direction of the rolling roll is equivalent to the strip width of the steel strip, and the rolling roll is not cooled in the outer range, thereby the steel strip plate. It can be seen that the thermal expansion outside the width increases, and as a result, the amount of thermal crown corresponding to the plate width is greatly reduced.
The above analysis assumes rolling of the same width, but according to the present invention, a parabolic thermal crown profile is used instead of a trapezoidal thermal crown profile as in the prior art. It is easy to freely change the sheet width within the cycle without causing the problem of the reverse crown profile as shown, and a very large effect can be obtained for schedule-free rolling.

DESCRIPTION OF SYMBOLS 1 Outer layer 2 Middle layer 3 Shaft material 4 Steel strip 5 Cooling header 6 Cooling water

Claims (5)

  It is a rolling roll composed of an outer layer, an intermediate layer and a shaft, and the thermal conductivity of the material constituting the outer layer and the material constituting the intermediate layer is greater than the thermal conductivity of the material constituting the shaft. A featured rolling roll.   The rolling roll according to claim 1, wherein the material constituting the outer layer, the intermediate layer, and the shaft material has a coefficient of thermal expansion that is outer layer <intermediate layer <shaft material.   The rolling roll according to claim 1 or 2, wherein the outer layer is made of a cemented carbide.   The rolling roll according to any one of claims 1 to 3, wherein the intermediate layer is made of a copper-based alloy. It is the rolling method of the steel strip using the rolling roll in any one of Claims 1-4, Comprising: While cooling a rolling roll in following (a) and / or (b), in cooling of this rolling roll, The roll cooling range in the rolling roll axis direction is equivalent to the strip width of the steel strip (however, in the case of (b) below, it is equivalent to the strip width of the preceding steel strip), and roll cooling is not performed outside the range. A method of rolling a steel strip characterized by
(A) At least a part during rolling from the tip of the steel strip to the tail end (b) At least a part between the passes of the preceding steel strip and the trailing steel strip

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