DE69623343T2 - ROLLING MILL, ROLLING METHOD AND ROLLING MACHINE - Google Patents

Description

The invention relates to a rolling mill according to the preamble of claim 1 or 2.

There are mainly two ways to roll metal flat stock, exclusively by a hot rolling process or by rolling a flat stock by a hot rolling process followed by a cold rolling process.

In the hot and cold rolling processes, the rolling techniques can be divided into two processes, reversing rolling and tandem rolling. In the hot rolling of carbon steel, a reversing roughing mill and a tandem type finishing mill with five to seven stands are used. As for hot rolling mills used for rolling stainless steel, a roughing mill and a reversing close rolling mill with furnace coilers on each side, called "Steckel mills", is the most commonly used design.

Rather than rough rolling mills and finishing mills, cold rolling mills are divided into two types: tandem rolling mills for the production of large series and reversing rolling mills for the production of smaller quantities.

In reversing rolling, five to nine passes are usual for hot rolling, while three to five passes are usual for cold rolling. In tandem rolling, five to seven stands are typical, while in cold rolling four to six stands are typical to achieve a product thickness in one pass.

For this reason, the difference in terms of production quantities between the reversing process and the tandem process is very large.

Furthermore, in JP-U-59-30308 it is disclosed that for rolling steel bars and wires into cylindrical shapes, a thrust mechanism for regulating the displacement of the center of the cylinders is provided, which improves the accuracy of the cylinder centering by using spherically shaped supports.

In JP-A-5-317918, a tilting or inclined part is provided on a sliding surface of a roll chock and a housing in order to significantly reduce the frictional resistance during raising and lowering of the roll chocks for the work rolls and the backup rolls in order to improve the thickness of the rolled material and the strip shape.

Currently, there is a large difference in production volume between the reversing and tandem processes, with no practical alternative in terms of intermediate production volume requirements.

Reverse rolling is carried out using individual rolling mills and one could assume that approximately twice Production volume should be possible if two rolling mills are used.

However, this is not the case for the following reason.

In the case of a hot rolling mill, the stand spacing is approximately 6 m. The leading end of the rolled material is then transported from one stand to the next, during which the sheet deforms and bends, so that the center of travel is shifted from the center and difficulties arise in the roll engagement at the next stand. If the roll engagement, i.e. gripping of the rolled material, is carried out offset from the center, strip bending and deformation occurs and the strip threading is not carried out properly, resulting in an incorrect cross-section and incorrect strip thickness.

In tandem rolling mills, each stand carries out rolling in one direction, so that the strip thickness does not change in one stand of the mill, and for this reason the deformation of the strip is not overly difficult to control. On the other hand, in reversing rolling processes, the direction of passage changes, so that the thickness of the rolled strip becomes thinner with each pass, i.e. the rolling conditions change. The leveling of the forming process must therefore be carried out with great skill and high accuracy, and if the most appropriate leveling control is not carried out, the strip will run out, i.e. it will deform.

Since the amount of strip deformation due to strip running off at the leading end is approximately proportional to the square of the length of the stand pitch, the amount of strip running off is very large when the stand pitch is 6 m. Therefore, the gripping of the strip by roll engagement on the following stand cannot be carried out in a smooth manner, and if roll engagement is made on a deformed strip, the strip deformation is aggravated because the strip is not fed into the center of the rolling mill.

Coilers are provided at the front and rear ends of a reversing cold rolling mill for winding and unwinding during rolling. During this time, the rear end of the strip usually remains wound on the coiler. Yield can be improved if the ends of the strip are rolled, but the passage and rewinding of the strip end onto the strip then becomes very time-consuming, so productivity decreases.

The distance between the centers of the scaffolds can be reduced from 6 m to 3.5 m. However, even at this distance, side guides are still required to guide the slab. However, this structure requires an airtight space between the two scaffolds, making operation and maintenance cumbersome.

In particular, when strip breakage and wrap-around occurs, the roller housing becomes an obstacle and the extraction of residues becomes extremely difficult.

EP-A-0 065 936 discloses, as the closest prior art, a rolling plant comprising a four-high rolling mill of the twin type in which two groups of rolls, each having two working rolls and two backup rolls, are arranged in a single rolling housing. For successful reversing rolling, it is absolutely essential to control each group of rolls individually.

In JP-A-05-177214 a rolling mill with a double duo stand is shown. The rolls of the stand are individually mounted in chocks, whereby chocks of the adjacent rolls are provided with a lateral tongue and groove arrangement to enable them to engage with each other.

From JP-A-07-308701 an arrangement is known which comprises a continuous casting device, a four-high roughing mill with a double stand, a shear, a furnace and a tandem rolling mill which has three six-high stands.

The object of the invention is to create an easy-to-maintain rolling mill with a high level of rolling efficiency with a minimized distance between the two sets of roll groups and in which the running off and bending of the strip is prevented.

A rolling mill according to the invention comprises a four-high rolling mill as defined in claim 1, which is equipped with roll groups consisting of upper and lower work rolls above and below a rolling stock and upper and lower back-up rolls which support the upper and lower work rolls, wherein two of the roll groups are housed in a single roll housing, and the drive takes place on one side in an axial direction of the roll groups, and the working operation takes place on the remaining side. The metal chocks of the work rolls support two work rolls as a single body on upper and lower sides and on separate drive and working sides.

Another rolling mill according to the invention comprises a six-high rolling mill as defined in claim 2, which is equipped with roll groups consisting of upper and lower work rolls above and below a rolling stock, upper and lower intermediate rolls supporting the upper and lower work rolls, and upper and lower backup rolls supporting the upper and lower intermediate rolls, wherein two of the roll groups are housed in a single roll housing, and the drive takes place on one side in an axial direction of the roll groups, and the working operation takes place on the remaining side. At least the metal chocks of the work rolls support two work rolls as a single body on upper and lower sides and on separate drive and working sides.

In a rolling process using the rolling mill according to the invention, intermediate rolls or backup rolls are driven for rolling.

A hot rolling mill according to the invention, as defined in claim 21, is equipped with a roughing mill and a finishing mill, wherein the hot rolling mill feeds heated material to the finishing mill or rolling a sheet cast at a thin sheet casting device as it is in a finishing mill. The finishing mill comprises a rolling mill as claimed in claim 1 or 2.

In addition, a hot rolling mill according to the invention can be equipped with two such finishing mills in tandem arrangement.

Short description of the drawings

Fig. 1 is a front view in cross section of a four-high rolling mill, which is a first embodiment of the present invention.

Fig. 2 is an exploded view of a four-high rolling mill in front cross section, which is the first embodiment of the present invention.

Fig. 3 is an exploded view of a six-high double rolling mill constituting the first embodiment of the present invention, in front cross-section.

Fig. 4 is a graph showing the results of measuring the friction coefficients depending on the hardness of the surfaces of the work rolls.

Fig. 5 is a representation of the results of the measurement of the friction coefficients depending on the slip ratio between the rollers.

Fig. 6 shows an example of a corresponding hot rolling mill of the state of the art.

Fig. 7 shows a representation of a hot rolling mill using the double rolling mill representing the first embodiment of the present invention during final cold rolling in the reversing process.

Fig. 8 is a diagram showing a hot rolling mill comprising a continuous thin sheet casting device and a tandem six-high rolling mill of the prior art.

Fig. 9 is a diagram showing a hot rolling mill including a continuous thin sheet casting device and the twin rolling mill of the present invention.

Fig. 10 is a diagram showing a hot rolling mill constituting the first embodiment of the present invention.

Fig. 11 is a diagram showing a hot rolling mill constituting the first embodiment of the present invention.

Fig. 12 is a diagram showing a hot rolling mill constituting the first embodiment of the present invention.

Fig. 13 is a diagram showing a hot rolling mill constituting the first embodiment of the present invention.

Fig. 14 is a diagram showing a hot rolling mill constituting the first embodiment of the present invention.

Fig. 15 is a plan view showing a mechanism for thrust support in the axial direction of the backup rolls of the double rolling mill according to the invention.

Fig. 16 is a diagram showing a reversing double rolling mill constituting the first embodiment of the present invention.

Fig. 17 is a diagram showing an arrangement of a reversing rolling mill of the prior art.

Best mode for carrying out the invention

The following is a description of the best mode for carrying out the present invention by means of preferred embodiments.

The present invention serves to provide two sets of roller groups within a single housing in such a way that a distance between the centers of the two sets of roller groups - compared to the example given above - is drastically reduced to 1.5 m or less.

This type of mill is abbreviated as "twin mill". In a twin mill, the distance between stands is one quarter of the 6 m of the ordinary tandem design and about 40% of the 3.5 m of the close tandem mill. Since the amount of strip deformation due to strip running is approximately proportional to the square of the distance between stands, there is a 94% reduction as shown in Table 1 compared to the strip deformation that occurs in the tandem mill arrangement. Table 1

As shown in Table 1, a conventional tandem mill has a stand-to-stand distance of 6 m and an assumed maximum strip travel of ±40 mm and therefore requires side guides.

A close tandem rolling mill has a distance of 3.5 m between the stands and a maximum strip travel of 13.6 mm and therefore also requires side guides.

In the double rolling mill according to the method of the invention, the distance between the stands, i.e. the distance between two sets of rolls, is 1.5 m and the maximum amount of strip travel is ±2.5 mm, so that no side guides are required. The invention is extremely effective in reducing the distance between the stands, the arrangement of strip guides and a strip tension measuring device is problematic.

This problem is solved by using metal chocks for work rolls shared by two groups of rolls, i.e. by using one-piece metal chocks.

As a result, tape threading guides can be formed as one piece and the tape protrudes, ensuring that there are no unevennesses so that the tape does not tilt or twist. Even if problems occur, the housing does not interfere.

This method can also be used to control the band curvature and shape.

During the tape threading process described above, the leading end of the threaded tape was described, but in reality, difficulties occur much more frequently at the trailing end of the threaded tape, which is called trailing end slippage.

The reason for this is the difference in reduction rate on both sides of the strip width caused by discrepancies in reduction level on the left and right sides, which causes bending of the strip. One thickness is thinner (over-reduced) and the other is thinner (under-reduced) than the desired thickness. This cause of bending in hot rolling is about three times greater at the trailing end than at the leading end. By shifting the trailing end into a bent state, the center of the strip is dramatically shifted from the center of the mill and the difference in the strip reduction rate in the width direction further worsens, so that the bending of the trailing end is further increased.

When this phenomenon occurs, the rear end of the strip material is rolled by the previous roller group so that the swinging movement of the rear end is limited, i.e. no bending of the rear end occurs.

The tail end bending starts from the strip material slipping on the preceding roller group, and when the distance between two roller groups is small, the space necessary for this phenomenon to occur is no longer available. In addition, when the distance between two roller groups is large, the strip bending occurs in proportion to approximately the cube of the tail end pull-out distance.

In reversing rolling mills, the ease with which the strip can be passed through a double rolling mill is far greater than that of a rolling mill with a single group of rolls. Therefore, in each double rolling mill, a uniform distribution of stresses occurs across the strip width, so that even if differences in the reduction rate occur on both sides of the strip width, the influences caused by strip bending, etc. are practically eliminated.

First embodiment

Fig. 1 shows an example in which the present invention is implemented as a rolling mill with a four-high rolling stand, and Fig. 2 shows an enlarged view of this rolling mill.

Two sets of four-high roll groups (rolling mill No. 1 and rolling mill No. 2 from the rolling material insertion side) are installed in a single housing 1.

Upper backup rolls 2, lower work rolls 3, lower backup rolls 2' and lower work rolls 3' form a set of roll groups, with two sets inside the housing 1, so that there are four backup rolls and four work rolls in total.

A set of roll groups then consists of a lower and upper working roll and a lower and upper support roll.

One-piece metallic chocks 4 and 4' are installed on the two upper work rolls 3 and the two lower work rolls 3'.

Strip threading guides 5 and 5' are attached to both one-piece metallic chocks 4 and 4' and can be moved up and down in view of changes in the diameter of the work rolls using a screw 29 attached to the one-piece metallic chocks 4 and 4' in such a way that the distance between the two work rolls is adjusted.

The belt threading guides 5 and 5' allow easy threading of the flat material between the two sets of rollers.

Reference numeral 6 denotes a tensiometer roller arranged approximately midway between the two sets of rollers, and reference numeral 7 denotes a weighing scale for measuring the tension.

The control of the tension can then be carried out in a simple manner by measuring the tension occurring in the center of the two sets of rollers using the tensiometer roller 6 and the weighing scale 7.

Lines 9 and 9' supply cooling water or roll cooling liquid, which both cools and lubricates.

The bearings 10 and 10' are installed in the metal chocks for use with the lower and upper support rolls and support the rolling load and transmit this force to the housing 1 via a reducing device 30 which applies the rolling load to the support rolls.

The rolling stock 22 flows in a direction from top left to right in the drawing and is rolled by the double rolling mill.

Reference numerals 11 and 11' denote pistons for use as roll balancing roll bender for dual operation.

The pistons 11 and 11' move the one-piece metallic chocks 4 and 4' up and down.

Reference numerals 12 and 12' denote fixed pistons for moving the cylinders 17 and 17' in the direction of travel using hydraulic pressure so that the one-piece metallic chocks are pressed from both sides by cylindrical or spherical supports 13 and 13'.

Reference numeral 15 denotes a wheel for exchanging the work rolls. When the lower support rolls 2' are lowered, the lower work rolls 3 are also lowered. The lower work rolls 3' are then brought in and out axially in the direction of the rolls via the rail 14 and the metal chocks 4' of the rolls, which are supported by stepped parts of the wheel 15.

At the same time, the metal chock 4 of the upper work roll is supported by a sliding stopper 18 formed integrally with the wheel 15 for simultaneous replacement of the upper and lower work rolls.

The reducing device 30 is designed independently for rolling mill No. 1 and rolling mill No. 2, so that both rolling mills can carry out reducing processes independently of one another.

The screw 21 sets a pass line height (pass line), this is the height at which the material to be rolled flows.

When separate reduction operations are carried out, the metallic chocks of the work rolls are tilted with respect to the horizontal.

It is therefore advisable to provide a cylindrical support 13 as a guide surface of the metallic chocks with a surface that is always able to act as a support, even if the metallic chocks are tilted.

Variations in the rolling diameter and the tilting of the metal chocks due to individual reduction processes of the individual sets of rolls can still be tracked.

In this embodiment, the work rolls can also perform cross rolling.

If the cooling liquid supplied from the supply line 9 is cooling water, a lubricant is supplied from the line 16 to the surface of the back-up rolls in order to reduce thrust forces when the work roll is in an inclined position with respect to the back-up roll.

The cylinders 17 and 17' are made to move in a direction opposite to the direction of strip passage using hydraulics. The upper and lower work rolls are crossed in opposite directions by the integral chocks 4 and 4' and the strip camber and shape can be controlled.

When this inclination method is used, the cylindrical supports 13 and 13' are used as spherical supports that respond to the corresponding displacement in the vertical and horizontal directions. By making the sliding surface of the metal chocks and the housing spherical, the inclination of the metal chocks in the vertical and horizontal directions can be followed, resulting in stability of the chocks and stability during rolling.

Although not shown in the drawings, two metal chocks etc. are provided for other rolls on a working side and a driving side and in the case of cross rolling, the cylinders 17 and 17' are designed to move in opposite directions on the driving and working sides.

In Fig. 1 and Fig. 2, the arrangement of the strip threading guides and the cooling water lines is preferably on the left side of rolling mill No. 1 (strip entry side) and on the right side of rolling mill No. 2 (strip exit side).

In addition, rather than a skew method for the work rolls alone, it is possible to use a skew method in which each of the rolling axes of the backup rolls and the work rolls are kept parallel to each other by intermittent supply from the lines 16 and 16' of a lubricant supply device and also by providing means for displacement in the horizontal direction on the chocks of the backup rolls.

Since the chocks of the work rolls are formed as one-piece roll chocks, the thrust in the axial direction is no different from that of the conventional method when retaining plates are provided on the entry and exit sides of the one-piece metal chocks, but for the backup rolls, retaining plates can only be provided on one side of the chocks of the backup rolls during normal operation, and there is a risk that offset load is applied to the thrust position.

If the chocks of the backup rolls are pressed from the housing side, the drift of the axes of the backup rolls can be prevented. However, if the thrust is large, a large pressing force is required, with the unfortunate result that the resistance force of the reducing operation has a negative influence on the control of the strip thickness.

In this case, this problem can be solved by providing holding plates 52 in the middle of all the metallic chocks 10 of the support rolls, as shown in Fig. 15.

The support plates 52 are carried by a bracket fixed to the housing 1 and interact with a roller bearing 50 fixed to the front end of a thrust arm fixed to the metallic chock 10 for use with the support rollers and transmitting thrust generated in the area of the support rollers 2 to the housing 1.

As shown above, the following results are achieved in this embodiment.

(1) In a basic structure for a double rolling mill of a four-high rolling mill, the distance between the two sets of roll groups can be made short by supporting the two work rolls using a one-piece metallic chock for work rolls which is made individually for lower and upper parts with the drive and working sides separated. In this embodiment, the distance can be made 1.5 m or less.

(2) By installing tape threading guides, threading the leading end of the tape can be made easier.

(3) Tensions between the stands can be measured, and the tension can be easily controlled by installing a tension meter.

(4) By providing cylindrical supports, the tilting caused by changes in the roll diameter can be of the chocks can be monitored. In addition, constant surface contact and stability of the chocks, ie rolling stability, can be maintained throughout.

(5) By crossing only the work rolls, an improvement in the performance of strip camber control and strip shape can be obtained.

(6) By crossing the work rolls and the backup rolls as one part, the generation of thrust forces between the work rolls and the backup rolls can be reduced, and the performance in controlling the strip curl and the strip shape can be increased.

(7) By providing spherical supports, the tilting of chocks due to changes in roll diameter can be tracked regardless of whether the work rolls are crossed or the work rolls and the backup rolls are crossed. In addition, constant surface contact can be maintained, and the stability of the chocks and rolling stability can be maintained throughout.

(8) By moving the work rolls in opposite directions in the axial direction, the performance in terms of controlling strip camber and strip shape can be improved, and a reduction in edge drop and a reduction in wear dispersion can be achieved.

(9) By providing thrust bearings in the axial direction with a single thrust bearing device on the roll axes, the loading of the thrust bearings of the support rolls by offset loads can be prevented.

(10) By pressing over the work roll chock and the sliding surface using hydraulic media, any gap that may occur is removed and thus the rolling stability can be maintained.

(11) By grinding the chock, a roll grinding operation can be simplified and the time required for grinding is shortened.

Second embodiment

Fig. 3 shows a double rolling mill of a six-high stand arrangement.

The difference from the four-high rolling stand arrangement of Fig. 1 and Fig. 2 is that two lower and two upper intermediate rolls 19 and 19' are provided. In this example, chocks 26 and 26' for the intermediate rolls are also used together as one piece.

Six-high rolling mills in which intermediate rolls are inserted in the axial direction are known from the prior art, but a method analogous to the method known from the prior art is also known in which a mechanism is installed which Rolls with an intermediate roll chock of one-piece structure are possible.

In this case, the shift position of the intermediate rolls of the two working rolls is the same, but the operation does not cause any difficulties, since this position is mainly determined by the strip width of the material to be rolled.

Minor differences are controlled by the work roll benders 11, 11', 27 and 27' and the intermediate roll benders 20, 20', 28 and 28'.

The drive rolls are usually the work rolls, however, if a small diameter of work rolls is preferred, the intermediate rolls are provided to provide the drive.

As described above, this embodiment produces the following results:

(1) In a basic structure of a double rolling mill for a six-high rolling mill, the distance between the two sets can be made short by supporting the two work rolls using one-piece metallic work roll chocks which are individually designed for lower and upper parts, with the driving sides and the working sides separated.

(2) A support for the belt structure can be easily provided by using metallic intermediate roll chocks for a double rolling process with a six-high rolling mill.

(3) In rolling mills operated by a drive method via the intermediate rolls or backup rolls, a large increase in roll grip can be achieved by using work roll benders.

(4) A further dramatic increase in roll grip can be achieved in double rolling mills by applying techniques in which intermediate rolls or backup rolls are driven by setting values of work roll benders to larger values than the present values.

(5) An increase in performance can be achieved by controlling the strip camber and shape by moving two lower and two upper intermediate rolls in opposite directions in the axial direction using common metallic chocks.

(6) An increase in performance can be achieved if the control of strip camber and strip shape is carried out together with edge drop reduction and wear dispersion, which can be achieved by moving two lower and two upper intermediate rolls in opposite directions in axial directions using common metallic chocks and also by moving the work rolls in opposite lower and upper directions in axial direction using common metallic chocks.

Third embodiment

In the following, an application of the invention to a hot reversing rolling mill is described.

The production capacity of a typical hot strip rolling mill with a tandem process finishing mill is three to six million tons per year.

In the plant shown in Fig. 6, a cast flat stock is rolled by the roughing mill 40 to a thickness of about 200 mm. The rolled material is then wound up by a coiler 41. The rolled material is then wound up and unwound by a coiler/uncoiler 42, then reversing rolling is carried out by the reversing mill 47.

However, a rolling mill with a production capacity of one to two million tons has yet to be realized.

Fig. 7 shows the double rolling mill according to the present invention, applied to a reversing finishing mill.

In the plant shown in Fig. 7, a cast flat material is rolled by the roughing mill 40 to a thickness of approximately 25 mm. The rolled material is then coiled by a coiler 41. The rolled material is then rolled and unrolled by a reel/uncoiler 42, and then reversing rolling is performed by a reversing double rolling mill 48 according to the present invention.

Compared to a single reversing mill, production can be doubled to 1.2 to 1.6 million tons with an increase in equipment costs of approximately 30%.

In the case of normal steel strip rolling, the reversing mills used therein, called "Steckel mills", were limited to the use of high pressure water in descaling to reduce the temperature of the strip material, which created problems in terms of surface quality. That is, these mills were primarily used for processing stainless material. However, this problem is solved in the present invention by reducing the number of passes by half, and the processing of carbon steel strips is thereby made possible.

In addition, since the flat pass is greatly improved, the flat pass or the speed of pulling out the tail end can be made faster than in the prior art, and the disadvantage of significantly reducing the temperature at the leading and trailing ends of a coil, which occurs in the prior art method, can be significantly improved.

On the other hand, in hot rolling of stainless material - in addition to preferential conditions where it is difficult for Scaling also occurs - there is the important advantage that the end sections of the strip of a strip thickness that can be easily cooled are heated by the furnace-coiler system of the Steckel rolling mill.

In addition, the biggest problem is that the tape bends when the end of the leading tape is pulled out, so that the pulling-out speed of the trailing end cannot be increased and the temperatures of the leading and trailing ends of the tape drop. Therefore, the tape becomes stiff and the quality of the tape curvature, etc. is reduced.

The twin rolling mill of the present invention enables a significant improvement in this problem and provides a process that can be used with conventional steels and stainless steels.

As already described, the guidance between the works is an important element, especially in reversing processes and, by using the process with one-piece chocks of the work rolls, the guidance must be continuous, without interruptions and without projections of the leading end.

As described above, by using a double-roll mill in the reversing rolling process, approximately twice the production quantity can be obtained with equipment costs that are 1.3 to 1.5 times higher than for reversing rolling with a single-roll mill.

Fourth embodiment

In the following, an application of the present invention to a thin flat product that is directly coupled to the hot strip rolling mill is described.

Traditionally, the thickness of the flat stock fed to the hot strip mill is approximately 200 mm, but in recent years, the flat stock has become considerably thinner, ranging from 50 to 70 mm, due to the development of continuous thin flat stock casting equipment.

The flat stock is rolled to a thickness of approximately 50 to 70 mm by a continuous thin flat stock casting device 45 and this rolled material is then wound up by the coiler 41. The rolled material is then unwound from the decoiler 43 and rolled by a tandem rolling mill with a six-high stand.

In this tandem rolling mill, a four-high rolling mill is arranged from the input side of the rolling material in a sequence of stand 60 (No. 1), stand 61 (No. 2), stand 62 (No. 3), stand 63 (No. 4), stand 64 (No. 5) and stand 65 (No. 6).

In this way, a process is carried out in which rough rolling is avoided and no rough rolling mill is required by making a sheet thickness small using a continuous furnace for thin sheet, followed by rolling using a 5 to 6-stand tandem mill or a process in which rolling is carried out continuously, is carried out with only continuous pouring upstream, and a flat stock is then cut off and passed through a tandem rolling mill.

Both processes require a guided extraction of the strip end on the tandem rolling mill.

Continuity in hot strip rolling mills is a long-held hope of the industry and, as this would eliminate or at least greatly reduce guided strip end pull-out, it would enable the rolling of thin material and thus increase yield.

For this reason, in the prior art method for large-scale hot strip rolling mills, a method was developed in which the trailing end of the strip and the leading end of a trailing strip were joined between a roughing mill and a finishing mill to achieve continuity.

The development of a new technology for this purpose requires considerable investment. If a continuous casting facility and a hot strip rolling mill are connected, continuity can be achieved without making changes or providing connecting facilities. However, the rolling speed at each stand is determined by a continuous casting speed. The continuous casting speed is currently limited to about 5 m per minute, which is slow for a rolling speed. In addition to the falling temperature of the strip, the prior art processes in question Scale is generated between stands where the distance between stands is 5 to 6 m. Then, when high pressure water is used for descaling, the temperature also drops and a prescribed finishing temperature cannot be maintained.

With current conventional results, the allowable cycle time to avoid the need for descaling is less than six seconds.

As a way of performing natural descaling between the roughing mills, the temperature is increased using induction heaters, etc. at the entry side of the finishing mill to produce descaling by entering the finishing mill.

As shown in Table 2, the time from exiting the No. 1 finishing mill to entering the No. 2 finishing mill is more than 7 seconds for a distance of 5 m, and the pass time is further increased when the reduction rate of the No. 1 mill is even lower or the continuous casting speed is lower than 5 m per minute. Therefore, descaling is required, and maintaining the finishing temperature (850ºC to 900ºC) becomes difficult. Table 2

The double rolling mill of the present invention can reduce this significantly, namely to 2.2 seconds.

This arrangement is shown in Fig. 9.

In the system of Fig. 9, a sheet is thin-rolled to a thickness of 50 to 70 mm by the continuous thin-sheet casting device 45, with the rolled material being wound up by the coiler 41. This rolled material is then uncoiled by the uncoiler 43 and then rolled for finishing by a double rolling mill with a four-high stand 49. This is the double rolling mill of the present invention.

In this example, a four-high double rolling mill according to the present invention is arranged as a finishing mill.

Preferably, however, the sheet is rolled by the continuous thin sheet casting device 45 for finishing as it is without being coiled.

If products with a thin strip thickness are required, finishing mill No. 3 is required, but since the rolling speed is high in these cases, a distance of 5 m between the mills is not a problem.

An increase in production and an improvement in rolling stability can be achieved by two double rolling mills in tandem arrangement .

Fifth embodiment

Next, the application of the present invention to a finishing mill of a conventional hot strip rolling mill will be described.

Generally, the number of stands in a hot finishing tandem mill is 4 to 7, with examples of configurations with 6 to 7 being the most commonly used.

The number of rolling mills increases with increasing production and high-speed rolling, but another important element is the strip thickness of the product.

To produce products with a thin strip thickness, a significant reduction in the thickness of a billet output from a roughing mill is required in the finishing mill.

If the reduction by a stand is significant, the strip throughput and strip shape deteriorate and the product quality drops.

This tendency increases with decreasing strip thickness and increasing rolling speed on stands of the subsequent stages.

Table 3 shows an example of a rolling scheme for rolling to a minimum strip thickness of 1.2 mm on a hot strip mill with six finishing mills.

A work roll diameter of 700 mm is used and a four-high rolling mill is used. Table 3

As can be seen from the example shown in Table 3, the reduction at the extreme end of the later scaffolds is smaller compared to the reduction at the front scaffolds.

The main reason for this, as well as for the deterioration of the tape shape and the deterioration of the plate surface quality, is that the failure rate of the tape guide/tail end pull-out increases significantly with increasing reduction rate.

In practice, a six-high rolling mill with high-quality control of the strip shape is used, but due to the reasons given above, it cannot be said that the reduction rate of the last stand increases significantly.

This is demonstrated by the fact that with increasing reduction rate at a rear stand the strip throughput deteriorates.

Therefore, if a double rolling mill is used as a final stand, the strip throughput is significantly improved and a significant reduction becomes possible.

To achieve this, a cross rolling mill arrangement with improved performance in terms of shape control or a six-high mill employing shape control using a small diameter work roll is preferred.

In this case, as shown in Fig. 10, with a combination comprising three ordinary rolling mills and one double rolling mill, rolling to 1.2 mm can be easily achieved.

With the system shown in Fig. 10, a flat stock cast by a continuous casting device 46 is rolled by the roughing mill 40 to a thickness of approximately 25 mm. The rolled material is then wound onto the coiler 41 and then unwound by the uncoiler 43 toward the side of the finishing mill.

The rolled material uncoiled from the decoiler 43 is then rolled for finishing by three conventional rolling mills (No. 1 stand 60, No. 2 stand 61 and No. 3 stand 62) and a double rolling mill with four-high stand of the present invention.

An example of the rolling scheme for this plant is shown in Table 4. Table 4

As shown in Fig. 11, when a double rolling mill 66 having small diameter work rolls is used as the double rolling mill, the reduction rate can be increased.

A small diameter means a radius of less than approximately 450 mm.

When twin mills are used on all stands, it is required that all mills be designed as six-high mills with small diameter work rolls in order to output 1.2 mm thick products from a 25 mm ingot using two twin mills.

In particular, for double rolling mills in the front stages, a drive via intermediate rolls is required, since driving the work rolls is strictly prohibited.

The corresponding rolling scheme is shown in Table 5. Table 5

For the following reasons, a work roll with a diameter of 700 to 800 mm is generally used in conventional hot strip rolling mills.

1) Since the rolling mills are mostly four-high mills, small diameter rolls cannot be used to maintain high quality strip curvature and strip shape.

2) With the exception of the special case of planetary rolling mills, in ordinary rolling mills with two-high, four-high and six-high stands, the basic rule is that the work rolls are driven during hot rolling.

For this reason, especially in the front stages, the roller diameter cannot be made small due to the strength of the torque transmission.

The diameter of the work rolls could not be changed significantly even in the later stages due to interchangeability, and even if a six-high rolling mill of the intermediate roll arrangement type is used, which is capable of using small diameters, the work roll drive must still be arranged within the allowable dimensions of the casing.

3) There is a restriction to small diameters in order to maintain the quality of the work rolls.

However, this problem was solved by a roller made of a new material called a high-speed steel roller.

In fact, problems related to the small diameter of the work roll - except for the drive - can be solved when a work roll, which is a high speed steel roll, is used in a six-high rolling mill with high-quality strip camber and strip shape control performance.

When a small diameter work roll is required in cold rolling, drive via backup rolls or via intermediate rolls is widely used.

If this method is applied to hot rolling, these problems should also be solved, but it can be assumed, for example, that slippage between the rolls occurs due to insufficient frictional force between the rolls when driven by intermediate rolls, and so far this has not actually been done.

As a result of clarifying this point, the present invention will confirm that sufficient reduction can be obtained by using small diameter work rolls for backup roll driving (the same applies to intermediate roll driving).

To obtain a certain reduction amount, the radius of the work rolls is set as Rw, a friction coefficient between a work roll and a material as ub, a friction coefficient between a drive roll and a work roll as Mr, a permissible maximum reduction amount after completion of the roll attack as Δhr, the reduction amount obtained during the roll attack as Δhb, the rolling load as P and K as the mill constant of the rolling mill, so that:

Δhr = 4ub²Rw

: for work roll drive

= 4u², Rw

: with intermediate roller drive... (1)

Δhb = ub²Rw - P/K

: for work roll drive

= ur²Rw - P/K

: with intermediate roller drive... (2)

From equations (1) and (2), it follows that Δhb is one quarter or less than Δhr, and the actual reduction amount is set to Δhb when measures such as rolling after tape gripping and thinning of a leading end of a covering material are not carried out.

Experimental results of the friction coefficients ub and Mr, which are essential factors determining the necessary diameters of the work roll, are shown in Figs. 4 and 5.

The friction coefficient ub of the working rolls and the leading end of the strip shows a strong correlation with the hardness of the surface of the rolls within the practical range, with ub decreasing with increasing roll hardness. Preferably, ub is measured at the Rolling mill of the previous stage shall be sized equal to or less than HS70 if a high amount of roll attack is required to maintain ub at 0.33.

On the other hand, the friction coefficient Mr between a work roll and a drive roll (e.g. an intermediate roll) is generated by slip between the rolls and at a slip ratio of about 1% in the case of water cooling, a maximum value of 0.3 is reached.

If the limit is considered and Mr is used at a slip ratio of 0.5%, Mr = 0.25%.

Assuming that P/K = 2400Tf/400Tf/mm = 6 mm and assuming a work roll diameter of 420 mm, i.e. Rw = 210 mm in case of work roll drive, Δhb = 0.332 210 - 6 = 16.8 mm and a reduction amount of 16.2 mm is obtained for the rolling mill No. 1 of Table 5.

On the other hand, when driven via the intermediate roll, Mr is used instead of ub, and Δhb is significantly reduced to Δhb = 0.252 · 210 - 6 = 13 - 6 = 7(mm).

Since in this case the rolling load is also reduced, an increase of 1 to 2 mm also occurs, which is significantly different from the increase of 16.8 mm that results from driving the work roll.

Next, a method is described that easily increases the errors of this intermediate roll driving method to the same performance as that of the work roll driving method.

When a strip is run under conditions of roll attack on the strip, using a maximum value of ub in the case of work roll drive, Mr < ub follows and hence slippage occurs between the work roll and the intermediate roll.

To avoid this, it is necessary to press the material with a force described by equation (3).

F = BSRw(ub - Mr)² ...(3)

Where B is the strip thickness and S is the yield stress.

The provision of a pressing device is not impossible, but since the material is dented by a pressing device arranged close to the rolling mill, this is not a targeted measure.

The method presented here sets the bending force of the existing work rolls to a value above a certain value without adding new equipment.

The friction coefficient Mr cannot be measured large.

However, the friction force is important and is the load between the rollers multiplied by Mr.

The load between the rolls is the sum of the rolling load and the work roll bending (or roll balancing) force.

If this bending force F is calculated from equation (3), the required bending force for each lower and upper work roll is:

Fw = F/(2ur)

= {BSRw(ub - Mr)²}/(2ur) ...(4).

Assuming that B = 1600 mm, Rw = 210 mm and S = 20 kg/mm² and, as above, ub = 33 and Mr = 0.25, it follows:

Fw = {1600 20 210 (0.33 - 0.25)²}/2 0.25 = 86 10³ kgf = 86 Tf

This is then the permissible bending force for a work roll diameter of 420 mm.

This result is a rolling result using a back-up roll drive process with a four-high mini-mill, where the roll attack power is strongly influenced by changes in the work roll balancing force, obtaining Δhb = 12 mm for a work roll of diameter 170 mm, thus proving the validity of the theory described above.

This result then proves that a sufficient reduction can be achieved with an intermediate roll drive, even if a small work roll is used.

For comparison with a conventional method for a tandem hot finishing mill, such as the series of finishing mills of Fig. 8, an example of a twin mill arranged as a rear stage is shown in Fig. 10 and an example in which two twin mills form the entire arrangement is shown in Fig. 11.

As shown in Fig. 12, three double rolling mills are provided according to the present invention, for which two double rolling mills 49 with four-high stands and one double rolling mill 66 with six-high stands are preferred.

Preferably, there is provided at least one four-high double rolling mill 67, which is provided in the front part and constitutes the input side of a series of finishing mills for the material to be rolled, as shown in Fig. 13 and in Fig. 14, and a six-high double rolling mill 66, which is provided in the rear part and constitutes the discharge side of the series of finishing mills.

In the hot rolling mills of Fig. 13 and 14, the diameter of the work rolls of the double rolling mill with four-high stand provided in the front part is preferably large and the diameter of the work rolls of the double rolling mill with six-high stand provided in the rear part is preferably small.

It can be seen that a large diameter is a diameter that exceeds 450 mm and a small diameter is a diameter that is less than or equal to 450 mm.

Measures to make the diameter of a work roll small are described above, but if the roll attack problem and the rolling force transmission problem can be solved, a small diameter of the work roll gives a tremendous advantage from the viewpoint of strong reducing force and economical use of energy, and a double rolling mill can be configured using a rolling mill of a method for which sufficient power control with respect to the strip camber and the strip shape can be guaranteed.

As described above, by designing a double rolling mill in tandem arrangement, production can be increased and rolling stability can be achieved.

Sixth embodiment

Next, an application of the present invention to a reversing type cold rolling mill will be described.

The most important feature of reversing cold rolling mills is that the production of rolled steel strip can be started with a low investment in equipment.

The expansion to a second and a third machine is possible by extending the superstructures, which are initially constructed from one machine.

On the other hand, a problem with reversing rolling mills is that the yield is low compared to tandem rolling mills.

The reason for this is that in the basic operation of reversing cold rolling, the strip of the first pass is sent to a reel without being rolled, and the leading end is gripped by a reel gripper so that it is wound on one or two reel rolls. The strip is then subjected to reduction by a rolling mill and rolling begins.

In reverse rolling, unrolled sections are left at the leading and trailing ends of the strip, so that the trailing end of the strip remains wound around the reel, with these remaining sections then becoming scrap.

This type of problem does not occur in tandem rolling mills because the whole strip is rolled, from the leading end to the trailing end. Therefore, the yield is high and the production quantity is very high compared to reversing rolling mills.

However, a tandem rolling mill requires a significant investment compared to reversing rolling mills and for this reason alone a tandem rolling mill is not often selected.

In comparison, the maintenance and operation of three or four identical reversing-type rolling mills is economically very inefficient.

In view of these circumstances, it would therefore be extremely advantageous to provide a rolling mill facility which would enable production volumes to be achieved midway between reversing and tandem rolling mills at a facility cost which is low in relation to production costs, while avoiding the reduction in yield associated with reversing rolling mills.

The double rolling mill is the perfect solution for this requirement.

Current single-stand reversing rolling mills typically require three to five rolling passes depending on the strip thickness of the product.

In a double rolling mill, two passes (four rollings) are standard, although cases of three passes (six rollings) and one pass (twice rolling) are also carried out for thick products.

The configuration for this procedure is shown in Fig. 7.

Fig. 7 shows a four-high double rolling mill according to the present invention which performs a reversing finish rolling process, wherein the rolled material is moved forward and backward by the coiler/decoiler 42 and is reverse rolled by a reversing four-high double rolling mill 48 for finishing.

For cold rolling, a double mill with a six-high stand, commonly referred to as an "HC mill", or a UC mill with increased capacity for cold rolling is preferred.

These double rolling mills can be considered as a tandem rolling mill with duo stand with high-quality strip guiding/end pull-out, as already described.

The case where rolling is possible with two rolls, i.e. in one pass, means that the same operation as for two tandem rolls is possible and the yield is not reduced since unrolled areas, which occur in known reversing processes, no longer occur.

However, a problem arises when the number of passes is 2, i.e. when rolling occurs four times.

This is because the rolling mill that performs the first pass also performs the rolling of the last pass.

The leading and trailing ends of a wound coil are cut by an ordinary moving shear and this area is then cooled to harden, so that when the returning sharp shape is rolled, the probability of damage to the work rolls is high.

If a rolling pass is performed only once, the leading end is rounded and there is no concern about damage of the roll in subsequent rolling, but if the final rolling is carried out using the work roll that performed the first rolling, damage to this roll will be transmitted to the strip and the product quality will be reduced.

This problem does not occur if sharp areas of the leading end of the coil are removed by a gripping device or a grinding device while waiting for rolling.

This is now described for the operation of a reversing roll with two passes (rolling four times) for the case discussed above.

The first pass is essentially the same as in tandem rolling and is stopped when the leading end of the strip being fed and the following end of the coil to be rolled come to the entry side of mill No. 1 so as to prevent the end of the coil from damaging the roll. The reversing rolling is then started and the final pull-out is carried out in the same manner as for ordinary tandem arrangements.

The length of the unrolled sections in this process and in the known single-stand reversing mill are now compared.

The yield of producing a final strip thickness of 0.6 mm by performing four passes in which a 2.5 mm coil of starting material is wound around is reduced by an amount of 30%, is compared as an example.

This arrangement is shown in Fig. 16 and 17.

In a first pass of the known method of Fig. 17, the length of the unrolled section with a strip thickness of the starting material coil of 2.5 mm, a strip thickness of the product of 0.6 mm, a distance between the rolling mill and the roll of 4 m and a wound length of the front end of 3 m in the first pass is (4 m + 3 m) · (2.5 mm/0.6 mm) = 29 mm.

If the reduction rate of thickness due to the reduction in the first pass is 0.7, the length of the unrolled billets in the second pass is (4 m + 3 m) · (2.5 mm · 0.7/0.6 mm) = 20.4 m.

If the length of the unrolled section in the third and fourth passes is set to zero, the total length La of the unrolled section using the known method is La = 29 + 20.4 = 49.4 m.

In the double rolling mill of the present invention as shown in Fig. 16, if the distance between the roll groups is set to 1.5 m and the length of the unrolled portion in the first pass is set to zero, in the second pass it is 1.5 m · (2.5 mm · 0.7/0.6 mm) = 4.4 m, that is, the total length of the unrolled portion section according to the present invention is Lb = 4.4 m.

When comparing the lengths of the product’s thickness deformation for incompletely rolled sections, an improvement of 45 m (La - Lb = 49.4 - 4.4 m) can be observed.

In the case of a width of 1 m and a unit weight of 15Tf, the total winding length Lc for a product thickness of 0.6 mm is Lc = 15000/(7.85 · 0.6) = 3190 m. The increase in yield in a double rolling mill is then (La - Lb)/Lc = (49.4 - 4.4)/3190 = 0.014.

It is therefore possible to increase the yield by 1.4% with a double-roll mill according to the present invention.

Production is approximately doubled because a product can be manufactured using half as many runs.

In order to reduce the downtime, in standard two-pass rolling, the material roll unwinding side and the roll winding side are taken as the same side so that the roll withdrawal process and the strip passage and winding of the next roll do not interfere with each other, whereby an arrangement for the strip passage in which the unwound roll can be immediately wound up is preferred.

Since the equipment costs are 15% compared to known reversing processes and the production is 200%, the production is improved by 30% in relation to the equipment costs.

By using a double rolling mill in reversing rolling processes, production can be approximately doubled, with equipment costs that are 1.3 to 1.5 times the equipment costs of single rolling mill reversing.

According to the invention, a rolling mill, a rolling method and a rolling plant are provided which can be easily maintained and enable excellent rolling efficiency, while shortening the distance between two sets of roll groups and preventing strip deformation due to strip running and strip bending of the rolled material.

Claims (22)

1. Rolling mill with a four-high rolling stand equipped with roll groups consisting of upper and lower working rolls (3, 3') above and below a rolling stock (22) and upper and lower support rolls (2, 2') supporting the upper and lower working rolls, respectively, two of these roll groups being accommodated in a single roll housing (1) and a drive being provided on one side in an axial direction of the roll groups and a working operation being provided on the remaining side, characterized in that the metal chocks (4, 4') of the working rolls (3, 3') support two working rolls (3, 3; 3', 3') as a single body on lower and upper sides and on separate drive and working operation sides. 2. Rolling mill with a six-high rolling stand equipped with roll groups consisting of upper and lower work rolls (3, 3') above and below a rolling stock (22), upper and lower intermediate rolls (19, 19') supporting the upper and lower work rolls respectively, and upper and lower backup rolls (2, 2') supporting the upper and lower intermediate rolls respectively, two of these roll groups being accommodated in a single roll housing (1) and a drive on one side in an axial direction of the roll groups and a Working operation takes place on the remaining side, characterized in that at least the metallic chocks (4, 4') of the working rolls (3, 3') support two working rolls (3, 3; 3', 3') as a single body on lower and upper sides and on separate drive and working operation sides. 3. Rolling mill according to claim 1 or claim 2, in which strip threading guides for threading the strips of the rolling stock between the two groups of rolls are attached to the metallic chocks (4, 4') of the working rolls (3, 3'). 4. Rolling mill according to one of claims 1 to 3, in which a tension meter (6) for detecting the tension of the rolled stock (22) is present on at least one of the metallic chocks (4') for the upper and lower work rolls (3, 3'). 5. Rolling mill according to one of claims 1 to 4, in which cylindrical supports (13, 13') are provided on sliding elements of the metallic clamping pieces (4, 4') of the work rolls (3, 3') and of the housing (1) such that sliding surfaces of the metallic clamping pieces of the work rolls and of the housing maintain surface contact with respect to an inclination of the metallic clamping pieces. 6. Rolling mill according to claim 1, wherein, in rolling the rolling stock (22), the two upper work rolls (3, 3) and the two lower work rolls (3', 3') of the two sets of roll groups are inclined in opposite directions in a horizontal plane having an intersection point of a path center line at the center a width direction of the rolling stock and a center line for the axial direction of both roll groups as the center. 7. A rolling mill according to claim 1, wherein, in rolling the rolling stock (22), the two upper work rolls (3, 3), the two upper backup rolls (2, 2), the two lower work rolls (3', 3') and the two lower backup rolls (2,', 2') of the two sets of roll groups are inclined in opposite directions up and down in a horizontal plane which takes an intersection point of a path center line at the center of a width direction of the rolling stock and a center line for the axial direction of both roll groups as a center. 8. A rolling mill according to claim 6 or claim 7, wherein spherical supports (13, 13') are provided on sliding elements of the metallic chocks (4, 4') of the work rolls and the roll housing (1) in such a manner that sliding surfaces of the metallic chocks of the work rolls and the roll housing maintain surface contact with respect to an inclination in the horizontal and vertical directions of the metallic chocks. 9. Rolling mill according to claim 1, wherein the two upper work rolls (3, 3) and the two lower work rolls (3', 3') and the two lower backup rolls (2,', 2') of the two sets of roll groups are displaced in opposite directions in axial directions. 10. Rolling mill according to claim 2, in which metallic chocks (26, 26') for the intermediate rolls (19, 19') support two intermediate rolls (19, 19; 19', 19') as individual pieces separately on the upper and lower sides and on the drive and operating sides. 11. Rolling mill according to claim 10, in which the two upper intermediate rolls (19, 19) and the two lower intermediate rolls (19', 19') are displaced axially in opposite directions via the metallic chocks (26, 26') of the intermediate rolls. 12. Rolling mill according to claim 11, in which the two upper work rolls (3, 3) and the two lower work rolls (3', 3') are displaced axially in opposite directions via the metallic chocks (4, 4') of the work rolls substantially simultaneously with the axial movement of the two upper intermediate rolls (19, 19) and the two lower intermediate rolls (19', 19'). 13. Rolling mill according to one of the preceding claims, in which a thrust in the axial direction of the support rolls is taken up by a thrust bearing device (10, 10') on the center line of the roll axis. 14. Rolling mill according to one of the preceding claims, in which a rolling mill drive which drives the intermediate rolls or the backup rolls comprises means for setting roll benders (11, 11') of the working rolls to a greater than a predetermined Setpoint at the time of gripping the strip of rolling stock. 15. Rolling mill according to one of the preceding claims, in which a means (12, 12'; 17, 17') for pressing using hydraulics is provided such that a distance between the sliding surface of the metallic chock and the sliding surface of the housing at least at the sliding element of the metallic chock (4, 4') for the work roll (3, 3') becomes small. 16. Use of a rolling mill according to claim 1 or 2 for carrying out the rolling. 17. A rolling method according to claim 16, wherein the work roll benders are set to a value equal to or greater than a predetermined set value at the time at which the rolling stock is gripped. 18. Rolling method according to claim 16 or 17, in which one rolling mill or several rolling mills are arranged in a rolling direction and the rolling is carried out in one direction. 19. Rolling method according to claim 16 or 17, in which reversing rolling is carried out. 20. Rolling method according to one of claims 16 to 19, in which the working rolls or the intermediate rolls are alternately ground, one roll at a time, by a grinding machine ground while remaining attached to the metal chocks and performing the rolling. 21. A hot rolling mill equipped with a roughing mill and a finishing mill, wherein the hot rolling mill rolls hot material in the finishing mill or rolls a flat material cast by a thin flat material casting device as it is in a finishing mill, wherein the finishing mill comprises a rolling mill according to claim 1 or 2. 22. Hot rolling mill according to claim 21, in which two of the finishing mills (66) are arranged one behind the other.