JP7648665B2 - Multi-stage rolling mill, maintenance and inspection method for multi-stage rolling mill, and method for using multi-stage rolling mill - Google Patents

Description

The present invention relates to a multi-stage rolling mill, a maintenance and inspection method for a multi-stage rolling mill, and a method for using a multi-stage rolling mill.

The patent document 1 relates to a set of stacked rolls with parallel longitudinal axes arranged in at least one single plane that is approximately perpendicular to the direction of strip motion, and describes how the longitudinal axis of one of the rolls is defined as the instantaneous axis of rotation, which is parallel to the line formed by the roll and passes through the center of mass of the roll.

Special Publication No. 2015-520031

Cluster-type rolling mills (hereafter sometimes referred to as "multi-stage rolling mills") are sometimes used as rolling mills for electrical steel sheets.

In such cluster-type rolling mills, coolant is sprayed onto the bite of the work roll to properly control the plate thickness, so the coolant nozzle must be placed close to the work roll.

The rolls here need to be replaced and inspected periodically, but in cluster-type rolling mills, the space between the upper and lower roll groups is narrow, making it difficult to easily access and inspect them for maintenance.

For example, Patent Document 1 describes how a table equipped with a spray device for lubricating and cooling the strip and rolls can be easily inserted and removed in and out of the rolling stand by sliding it in the longitudinal direction of the row of bearing rolls.

However, in the above conventional technology, the sliding direction of the table is the longitudinal direction of the rolls, so the stroke during sliding is long, and there is an issue that it takes time to move the table back to create a space between the upper and lower roll groups.

The present invention provides a multi-stage rolling mill that can form a space between upper and lower roll groups in a shorter time than conventional methods, a maintenance and inspection method for the multi-stage rolling mill, and a method for using the multi-stage rolling mill.

The present invention includes a number of means for solving the above-mentioned problems. One example of such a means includes a pair of work rolls for rolling a metal strip, multiple pairs of intermediate rolls supporting the pair of work rolls, multiple pairs of backing assemblies supporting the multiple pairs of intermediate rolls, an inner housing supporting the multiple pairs of backing assemblies, an outer housing supporting the inner housing from the inlet side and the outlet side in the rolling direction of the metal strip, and a coolant spray header configured to spray coolant onto the metal strip at the biting portion between the pair of work rolls, wherein the coolant spray header is configured to be movable in the rolling direction and/or the counter-rolling direction of the metal strip, and the coolant spray header has a connection portion at which an upper coolant spray header provided above the metal strip and a lower coolant spray header provided below the metal strip are connected on the outside in the width direction of the metal strip, and the connection portion is supported by a member outer than the inner housing in the rolling direction .

According to the present invention, it is possible to form a space between the upper and lower roll groups in a shorter time than in the past. Problems, configurations, and effects other than those described above will become clear from the explanation of the following examples.

FIG. 2 is a front view of a multi-stage rolling mill according to the embodiment. FIG. 2 is a front view showing a state in which the coolant spray header is retracted in the direction opposite to the rolling direction in the multi-stage rolling mill of the embodiment. FIG. 2 is a front view showing a state in which the space between the upper inner housing and the lower inner housing is opened and the upper work roll is removed in the multi-stage rolling mill of the embodiment. FIG. 2 is a front view showing a state in which the lower work roll and the lower first intermediate roll are removed and the upper first intermediate roll is supported by a support base in the multi-stage rolling mill of the embodiment. FIG. 2 is a front view showing a state in which an upper first intermediate roll has been removed in the multi-stage rolling mill of the embodiment. FIG. 2 is a front view showing a state in which a lower second intermediate roll has been removed in the multi-stage rolling mill of the embodiment. FIG. 2 is a front view showing a state in which an upper second intermediate roll and a lower backing assembly are removed in the multi-stage rolling mill of the embodiment. FIG. 4 is a front view showing another embodiment of a multi-stage rolling mill according to the present invention. FIG. 11 is a front view showing a state in which a lower inner housing is removed from the rolling mill in another embodiment of the multi-stage rolling mill according to the present invention.

The following describes an embodiment of the multi-stage rolling mill, the maintenance and inspection method for the multi-stage rolling mill, and the method of using the multi-stage rolling mill of the present invention, with reference to Figs. 1 to 9.

Figure 1 is a front view of a multi-stage rolling mill according to an embodiment. Figure 2 is a front view showing the state in which the coolant spray header has been retracted in the direction opposite to the rolling direction. Figure 3 is a front view showing the state in which the upper inner housing and the lower inner housing are spaced apart and the upper work roll has been removed. Figure 4 is a front view showing the state in which the lower work roll and the lower first intermediate roll have been removed and the upper first intermediate roll is supported by a support stand. Figure 5 is a front view showing the state in which the upper first intermediate roll has been removed. Figure 6 is a front view showing the state in which the lower second intermediate roll has been removed. Figure 7 is a front view showing the state in which the upper second intermediate roll and the lower backing assembly have been removed. Figure 8 is a front view showing another embodiment of a multi-stage rolling mill. Figure 9 is a front view showing the state in which the lower inner housing has been removed from the rolling mill.

In addition, in the drawings used in this specification, identical or corresponding components are given the same or similar reference numerals, and repeated explanations of these components may be omitted.

In the following, this embodiment will be described using an example of a 20-stage cluster-type multi-stage rolling mill that consists of an inner housing and an outer housing, and in which the divided upper and lower inner housings can be opened and closed vertically. However, the multi-stage rolling mill is not limited to this structure, and the structure of this embodiment can be applied to various multi-stage rolling mills.

First, the overall configuration of the multi-stage rolling mill of this embodiment will be explained using Figure 1.

The multi-stage rolling mill 1 of this embodiment shown in FIG. 1 is a cluster-type 20-stage rolling mill for rolling metal strip 5, and is particularly suitable for rolling hard materials such as stainless steel sheets, electromagnetic steel sheets, and copper alloys.

In FIG. 1, the multi-stage rolling mill 1 is equipped with a pair of upper and lower work rolls 10, two pairs of upper and lower first intermediate rolls 12, three pairs of upper and lower second intermediate rolls 14, and four pairs of upper and lower backing assemblies (A-axis, B-axis, C-axis, D-axis) and lower backing assemblies (E-axis, F-axis, G-axis, H-axis) (hereinafter collectively referred to as backing assemblies 20) consisting of split backing bearings, shafts, and saddles (all of which are omitted for convenience of illustration).

The pair of work rolls 10 are in direct contact with the metal strip 5 and roll the metal strip 5.

The upper and lower pair of work rolls 10 are each supported in contact with two upper and lower pairs of first intermediate rolls 12. In addition, these two upper and lower pairs of first intermediate rolls 12 are each supported in contact with three upper and lower pairs of second intermediate rolls 14.

The three pairs of upper and lower second intermediate rolls 14 are supported in contact with the backing assemblies 20 (A-axis, B-axis, C-axis, D-axis) located vertically above the metal strip 5, and the backing assemblies 20 (E-axis, F-axis, G-axis, H-axis) located vertically below the metal strip 5.

The multi-stage rolling mill 1 also includes an upper inner housing 30 that supports the upper backing assembly 20 (axis A, axis B, axis C, axis D) above the metal strip 5 in the vertical direction, and a lower inner housing 32 that supports the lower backing assembly 20 (axis E, axis F, axis G, axis H) below the metal strip 5 in the vertical direction.

The upper inner housing 30 and the lower inner housing 32 are supported by the outer housing 40 from the entry side and exit side in the rolling direction of the metal strip 5.

The push-up cylinder 60 is provided vertically below the lower inner housing 32 to support the lower inner housing 32, and is driven when creating a gap between the upper and lower rolls.

In addition, for roll cooling and rolling lubrication, the system is equipped with an entry coolant spray header 50a that sprays coolant from above and below on the entry side in the rolling direction of the metal strip 5 onto the engagement portion of the pair of upper and lower work rolls 10 with the metal strip 5, and an exit coolant spray header 50b that sprays coolant from above and below on the exit side in the rolling direction of the metal strip 5.

The inlet coolant spray header 50a is an upper inlet coolant spray header 52a located vertically above the metal strip 5 and a lower inlet coolant spray header 54a located vertically below the metal strip 5. The upper inlet coolant spray header 52a and the lower inlet coolant spray header 54a are connected together by an inlet connecting member 56a in the outer housing part on the drive side and/or operation side on the outer side of the width of the metal strip 5.

When viewed from the front side of the multi-stage rolling mill 1, this inlet coolant spray header 50a extends from the work roll 10 side to the outer housing 40 side, and is supported by outer members in the counter-rolling direction from the upper inner housing 30 and the lower inner housing 32.

In particular, in this embodiment, the inlet connection member 56a of the inlet coolant spray header 50a is supported by the outer housing 40 as a member that is outer in the counter -rolling direction than the upper inner housing 30 and the lower inner housing 32. Note that the inlet connection member 56a is not limited to being supported by the outer housing 40, and may be structured so as to pass through the outer housing 40 without contacting it, and to support the inlet coolant spray header with a mill guide on the outer side.

Similar to the inlet coolant spray header 50a, the outlet coolant spray header 50b is integrated with the outlet upper coolant spray header 52b located on the vertically upper side of the metal strip 5 and the outlet lower coolant spray header 54b located on the vertically lower side, connected by an outlet connecting member 56b in the outer housing part on the drive side and/or operation side on the outer side of the width direction of the metal strip 5.

When viewed from the front side of the multi-stage rolling mill 1, this outlet coolant spray header 50b extends from the work roll 10 side to the outer housing 40 side, and is supported by members on the outside in the rolling direction from the upper inner housing 30 and the lower inner housing 32.

In particular, in this embodiment, the outlet connection member 56b of the outlet coolant spray header 50b is supported by the outer housing 40 as a member on the outside in the rolling direction from the upper inner housing 30 and the lower inner housing 32. Note that the configuration is not limited to being supported by the outer housing 40, and the outlet coolant spray header can also be configured to pass through the outer housing 40 without contacting it, and to be supported by an outer mill guide.

In this embodiment, the entry coolant spray header 50a is further provided with a moving mechanism 45a that allows the tip of the entry coolant spray header 50a on the work roll 10 side to move in the anti-rolling direction of the metal strip 5, more specifically, as shown in FIG. 2, from the front side of the multi-stage rolling mill 1, to the outside of the rolling direction, further than the axis of the backing assembly 20 (axis D, axis E, center of the backing assembly 20) that is the furthest from the work roll 10 in the rolling direction. The exit coolant spray header 50b is further provided with a moving mechanism 45b that allows the tip of the exit coolant spray header 50b on the work roll 10 side to move in the rolling direction of the metal strip 5, more specifically, as shown in FIG. 2, from the front side of the multi-stage rolling mill 1, to the outside of the rolling direction, further than the axis of the backing assembly 20 (axis A, axis H, center of the backing assembly 20) that is the furthest from the work roll 10 in the rolling direction.

The configuration of the movement mechanisms 45a, 45b that allow the entry coolant spray header 50a to move beyond the axis of the backing assembly 20 that is the furthest from the work roll 10 in the rolling direction, so that its tip on the work roll 10 side is to the outside of the entry side in the rolling direction, and the exit coolant spray header 50b to move beyond the axis of the backing assembly 20 that is the furthest from the work roll 10 in the rolling direction, so that its tip on the work roll 10 side is to the outside of the exit side in the rolling direction, is not particularly limited, and various configurations can be adopted, such as hydraulic cylinders whose cylinders extend in the rolling direction or counter-rolling direction, ball screws, racks, pinions, etc. that convert rotational motion into linear motion, and are not particularly limited.

For example, during maintenance and inspection of the multi-stage rolling mill 1, the movement mechanisms 45a and 45b move the inlet coolant spray header 50a in the direction opposite to the rolling direction of the metal strip 5 and move the outlet coolant spray header 50b in the rolling direction of the metal strip 5. As a result, the tip of the inlet coolant spray header 50a opens outward relative to the D and E axes, and the tip of the outlet coolant spray header 50b opens outward relative to the A and H axes, as shown in FIG. 3, opening the gap between the upper inner housing 30 and the lower inner housing 32 to create space within the multi-stage rolling mill 1, allowing various roll reconfiguration tools to be proposed and reconfiguration to be performed in a short time.

As a result, it is easy to remove the upper work roll 10 by pulling it out in the width direction of the metal strip 5 as shown in FIG. 3, to remove the lower work roll 10 as shown in FIG. 4, and further, when removing the lower first intermediate roll 12 as shown in FIG. 4, it is easy to support and stabilize the upper first intermediate roll 12 with the support stand 70, to remove the upper first intermediate roll 12 as shown in FIG. 5, to remove the lower second intermediate roll 14 as shown in FIG. 6, to remove the upper second intermediate roll 14 and the lower backing assembly 20 as shown in FIG. 7, and further, to pull out and remove the upper backing assembly 20, making replacement work easier to carry out than in the past.

In addition, in the past, even when using an automatic reassembly device, the equipment was so large that it was common to remove each roll from the multi-stage rolling mill 1 one by one, which took time to replace. However, the configuration of this embodiment makes it possible to adopt various reassembly methods, such as stable reassembly of multiple rolls at the same time. In particular, it becomes possible to stably and efficiently replace the second intermediate roll 14 and backing assembly 20, which are currently performed using unstable Porter bar operation.

When only the work roll 10 is to be rearranged, the work roll 10 can be pulled out in the axial direction while the metal strip 5 remains threaded between the upper and lower work rolls 10. In contrast, when the first intermediate roll 12, the second intermediate roll 14, or the backing assembly 20 is to be rearranged, the metal strip 5 is pulled out from the beginning, and then the entry coolant spray header 50a and the exit coolant spray header 50b are retracted and the work roll 10 is removed.

In addition, the timing for moving the inlet coolant spray header 50a and the outlet coolant spray header 50b in the rolling direction or anti-rolling direction is not limited to maintenance inspections.

For example, when rolling the metal strip 5, when passing the leading end of the metal strip 5 between a pair of work rolls 10, the inlet coolant spray header 50a and the outlet coolant spray header 50b can be moved in the rolling direction and/or counter-rolling direction of the metal strip 5, so that they can be brought closer to the pair of work rolls 10 than during normal rolling.

In addition, during normal rolling of the metal strip 5, the inlet coolant spray header 50a and the outlet coolant spray header 50b can be moved away from the pair of work rolls 10 when threading the leading end.

Next, other configurations of multi-stage rolling mills will be explained using Figures 8 and 9.

In the multi-stage rolling mill 1A shown in Figures 8 and 9, the lower inner housing 32A is provided with wheels 80 for the lower monoblock housing at the bottom for moving the lower inner housing 32A in the width direction of the metal strip 5, and the lower inner housing 32A can be moved in the width direction of the metal strip 5 on the installation floor 85.

This makes it possible to simultaneously pull out the lower roll group (lower work roll 10, lower first intermediate roll 12, lower second intermediate roll 14, lower backing assembly 20 (E-axis, F-axis, G-axis, H-axis)) from the multi-stage rolling mill 1A, making it possible to attach and detach the rolls by operating a crane. This makes it easier to rearrange the rolls, especially the backing assembly 20, and makes it possible to reduce rearrangement time to less than half of the time required with conventional methods.

Next, we will explain the effects of this embodiment.

The multi-stage rolling mill 1, 1A of the present embodiment described above includes a pair of work rolls 10 for rolling the metal strip 5, multiple pairs of first intermediate rolls 12 and second intermediate rolls 14 supporting the pair of work rolls 10, multiple pairs of backing assemblies 20 supporting the multiple pairs of first intermediate rolls 12 and second intermediate rolls 14, an upper inner housing 30 and a lower inner housing 32 supporting the multiple pairs of backing assemblies 20, an outer housing 40 supporting the upper inner housing 30 and the lower inner housing 32 from the entry side and the exit side in the rolling direction of the metal strip 5, and an entry coolant spray header 50a and an exit coolant spray header 50b configured to spray coolant onto the metal strip 5 at the biting portion of the pair of work rolls 10, and the entry coolant spray header 50a and the exit coolant spray header 50b are configured to be movable in the rolling direction and/or the counter-rolling direction of the metal strip 5.

In a multi-stage rolling mill, if the tip of the coolant spray header is not aimed at the area between the work roll and the metal strip 5, the plate thickness will be disturbed, causing a disturbance to the control.

In addition, in a reversible rolling mill for rolling electromagnetic steel sheets, which is an example of a metal strip 5, the amount of coolant sprayed is controlled according to the pass and sheet speed, but if the nozzle tip does not approach close to the gap between the work roll and the metal strip 5, the tip of the coolant spray header will not reach the gap between the work roll and the metal strip 5.

For this reason, it is necessary to bring the nozzle close to the gap between the work roll and the metal strip 5, but this places space restrictions on the operation of rearranging the second intermediate roll and backing assembly of the multi-stage rolling mill, making smooth rearrangement difficult.

In contrast, in this embodiment, the inlet coolant spray header 50a and the outlet coolant spray header 50b can move in the rolling direction and the anti-rolling direction, so that a space between the roll groups can be formed by moving only a short distance, and the time required to form the space can be shortened compared to the conventional method. In addition, because the headers can move in the rolling direction and/or anti-rolling direction of the metal strip 5, vertical movement is essentially unnecessary, and the nozzle tip can be easily moved to the vicinity of the gap between the work roll 10 and the metal strip 5, so the load of adjustment for cooling can be significantly reduced compared to the conventional method.

In addition, the entry coolant spray header 50a and the exit coolant spray header 50b are shaped to extend from the work roll 10 side to the outer housing 40 side when viewed from the front side of the multi-stage rolling mill 1, and are supported by members on the outside in the rolling direction from the upper inner housing 30 and the lower inner housing 32. Therefore, even if the headers are long in the rolling direction, they can be easily moved in the rolling direction and anti-rolling direction, and can more easily respond to changes in rolling conditions, etc.

Furthermore, because the inlet coolant spray header 50a and the outlet coolant spray header 50b are supported by the outer housing 40, the position of the spray headers can be fixed relative to the pass line, eliminating the need for equipment or labor to adjust the angle of the nozzle at the tip of the headers, reducing the amount of work required during maintenance and inspection, and further improving work efficiency.

In particular, in the case of multi-stage rolling mills, the coolant spray headers were previously attached to the upper and lower inner housings, respectively, and so the nozzle spray angle had to be adjusted depending on the combination of the diameters of the work roll 10, first intermediate roll 12, and second intermediate roll 14, making it necessary to provide an angle adjustment device. However, as such a device is no longer necessary, various benefits are obtained, such as space savings and cost reduction.

The inlet coolant spray header 50a and the outlet coolant spray header 50b have an inlet upper coolant spray header 52a and an outlet upper coolant spray header 52b provided on the upper side of the metal strip 5, and an inlet lower coolant spray header 54a and an outlet lower coolant spray header 54b provided on the lower side of the metal strip 5, and the inlet connection member 56a and the outlet connection member 56b are connected on the outer side of the width direction of the metal strip 5. The inlet connection member 56a and the outlet connection member 56b are supported by members on the outer side of the rolling direction from the upper inner housing 30 and the lower inner housing 32, so that the upper header and the lower header of the metal strip 5 can be integrated, and the upper and lower headers can be moved at the same time, which has the effect of simplifying the configuration of the moving mechanisms 45a and 45b and improving the moving efficiency.

Furthermore, the inlet coolant spray header 50a and the outlet coolant spray header 50b are configured so that their tips on the work roll 10 side can be moved further outward in the rolling direction than the axis of the backing assembly 20, which is the farthest from the work roll 10 in the rolling direction when viewed from the front side of the multi-stage rolling mill 1. This allows sufficient space to be created for maintenance, etc., and the header movement distance can be made shorter than when the header is moved in the longitudinal direction of the roll, thereby shortening the time required to create the space.

In addition, the inlet coolant spray header 50a and the outlet coolant spray header 50b are arranged in a retracted position moved in the rolling direction, and when the pair of work rolls 10, the multiple pairs of first intermediate rolls 12, the second intermediate roll 14, and the lower backing assembly 20 of the multiple pairs of backing assemblies 20 provided on the lower side of the metal strip 5 are pulled out of the lower inner housing 32, a support cart is further provided that moves in the width direction of the metal strip 5 and holds the upper backing assembly 20 of the multiple pairs of backing assemblies 20 provided on the upper side of the metal strip 5 from below. Conventionally, each of the upper first intermediate roll 12 and the upper second intermediate roll 14 was lifted from above to prevent them from falling during roll replacement, but the support cart eliminates the need for a lifting device for the upper roll during roll replacement. In addition, it is now possible to pull the rolls out of the multi-stage rolling mill 1 with the second intermediate roll 14 bearing box still attached, which was removed to install the Porter bar device, eliminating the need to manually remove and install the bearing box in front of the multi-stage rolling mill 1, and in the case of an automatic exchange device, there is no need for the device itself.

Furthermore, the inner housing comprises an upper inner housing 30 provided above the metal strip 5 and a lower inner housing 32A provided below the metal strip 5, and the lower inner housing 32A is provided with wheels 80 for the lower monoblock housing at its lower part for moving the lower inner housing 32A in the width direction of the metal strip 5, so that the lower roll group can be simultaneously pulled out of the rolling mill, greatly improving the efficiency of the replacement work for the lower roll group.

In addition, according to the method of using the multi-stage rolling mill 1 of the present invention, when the leading end of the metal strip 5 is passed between a pair of work rolls 10, the inlet coolant spray header 50a and the outlet coolant spray header 50b are moved in the rolling direction and/or counter-rolling direction of the metal strip 5 to approach the pair of work rolls 10, and coolant can be effectively supplied at the time of biting when a large load is applied to the work rolls 10, thereby reducing the load.

Furthermore, during normal rolling of the metal strip 5, by moving the inlet coolant spray header 50a and the outlet coolant spray header 50b away from the pair of work rolls 10 compared to when the leading ends are threaded, it is possible to prevent the leading ends of the inlet coolant spray header 50a and the outlet coolant spray header 50b from coming too close to the work rolls 10 more than necessary.

＜Other＞
The present invention is not limited to the above-mentioned embodiment, and various modifications and applications are possible. The above-mentioned embodiment has been described in detail to explain the present invention in an easily understandable manner, and the present invention is not necessarily limited to having all of the configurations described.

1, 1A... Multi-stage rolling mill 5... Metal strip 10... Work roll 12... First intermediate roll 14... Second intermediate roll 20... Backing assembly 30... Upper inner housing 32, 32A... Lower inner housing 40... Outer housing (outer member in the rolling direction)
45a, 45b...moving mechanism 50a...inlet coolant spray header 50b...outlet coolant spray header 52a...inlet upper coolant spray header (upper coolant spray header)
52b...Outlet side upper coolant spray header (upper coolant spray header)
54a...Inlet side lower coolant spray header (lower coolant spray header)
54b...Outlet side lower coolant spray header (lower coolant spray header)
56a...inlet side connection member (connection portion)
56b...Outlet side connection member (connection portion)
60: Push-up cylinder 70: Support stand 80: Wheels for lower monoblock housing (insertion/removal part)
85...Installation floor

Claims (11)

A pair of work rolls for rolling a metal strip;
A plurality of pairs of intermediate rolls supporting the pair of work rolls;
a plurality of pairs of backing assemblies supporting the plurality of pairs of intermediate rolls;
an inner housing supporting the pairs of backing assemblies;
an outer housing supporting the inner housing from an inlet side and an outlet side in the rolling direction of the metal strip;
a coolant spray header configured to spray coolant onto the metal strip at the biting portion of the pair of work rolls;
The coolant spray header is configured to be movable in a rolling direction and/or a counter-rolling direction of the metal strip ;
the coolant spray header has a connection portion at which an upper coolant spray header provided on the upper side of the metal strip and a lower coolant spray header provided on the lower side of the metal strip are connected on the outer side in the width direction of the metal strip,
The connection portion is supported by a member that is on the outer side of the inner housing in the rolling direction.
Multi-stage rolling mill. In the multi-stage rolling mill according to claim 1,
The coolant spray header has a shape extending from the work roll side to the outer housing side when viewed from the front side of the multi-stage rolling mill, and is supported by a member that is outer than the inner housing in the rolling direction. In the multi-stage rolling mill according to claim 2,
The coolant spray header is supported by the outer housing. In the multi-stage rolling mill according to any one of claims 1 to 3 ,
The coolant spray header is configured such that, when viewed from the front side of the multi-stage rolling mill, the tip end of the coolant spray header on the work roll side can be moved to the outside in the rolling direction beyond an axis of the backing assembly that is furthest from the work roll in the rolling direction. In the multi-stage rolling mill according to any one of claims 1 to 3 ,
the coolant spray header is disposed at a retracted position moved in the rolling direction, and when the pair of work rolls, the multiple pairs of intermediate rolls, and a lower backing assembly of the multiple pairs of backing assemblies provided on the lower side of the metal strip are pulled out to outside the inner housing, the multi-stage rolling mill further comprises a carriage that moves in the width direction of the metal strip and holds from below an upper backing assembly of the multiple pairs of backing assemblies provided on the upper side of the metal strip. In the multi-stage rolling mill according to any one of claims 1 to 3 ,
the inner housing includes an upper inner housing provided above the metal strip and a lower inner housing provided below the metal strip,
the lower inner housing is provided at a lower portion with an insertion/removal section for moving the lower inner housing in the width direction of the metal strip. The method for maintaining and inspecting a multi-stage rolling mill according to claim 1 ,
withdrawing the pair of work rolls in a width direction of the metal strip;
a step of drawing out the pairs of intermediate rolls in a width direction of the metal strip;
and moving the coolant spray header in the rolling direction and/or the counter-rolling direction. The method for maintaining and inspecting a multi-stage rolling mill according to claim 7 ,
a step of disposing the coolant spray header at a retreated position moved in the rolling direction and/or the counter-rolling direction, and drawing out the pair of work rolls, the multiple pairs of intermediate rolls, and a lower backing assembly provided below the metal strip among the multiple pairs of backing assemblies, to the outside of the inner housing;
a step of moving a carriage that holds, from below, an upper backing assembly of the plurality of pairs of backing assemblies provided on the upper side of the metal strip in the width direction of the metal strip, thereby holding the upper backing assembly from below. The method for maintaining and inspecting a multi-stage rolling mill according to claim 7 ,
When the inner housing includes an upper inner housing provided above the metal strip and a lower inner housing provided below the metal strip,
The maintenance and inspection method for a multi-stage rolling mill further comprises the step of moving the lower inner housing in a width direction of the metal strip. A method for using the multi-stage rolling mill according to claim 1 , comprising the steps of:
a coolant spray header being moved in the rolling direction and/or the counter-rolling direction to approach the pair of work rolls when the leading end of the metal strip is threaded between the pair of work rolls. The method for using a multi-stage rolling mill according to claim 10 ,
a coolant spray header is moved away from the pair of work rolls when the leading end is threaded during normal rolling of the metal strip.

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