Login| Sign Up| Help| Contact|

Patent Searching and Data


Title:
METHOD OF IMPROVEMENT FOR A ROLLED PRODUCT MANUFACTURING PROCESS
Document Type and Number:
WIPO Patent Application WO/2005/105333
Kind Code:
A1
Abstract:
A method for controlling the rolling process of a rolled product, such as a steel, aluminium or plastic product. Controlling the rolling process refers to the minimization of the periodic machine-direction gauge variation of a rolled product and/or the minimization of roll force fluctuation and/or the control of surface roughness and/or the reduction of vibration and/or the extension of a service life for a rolling apparatus and/or the control of thermal expansion. Rolls, such as backing rolls, are provided with a run-out by machining a desired shape in the roll shell and/or roll neck and/or bearing components, such as a bearing bush. Said desired shape is non-circular and/or it is established by varying the bush thickness and/or a desired path is provided for the centre of rotation of a workpiece.

Inventors:
KUOSMANEN PETRI OLAVI (FI)
JUHANKO JARI PEKKA (FI)
VAEAENAENEN PEKKA TAPIO (FI)
Application Number:
PCT/FI2005/050136
Publication Date:
November 10, 2005
Filing Date:
April 27, 2005
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
ROLLRES INTERNAT OY (FI)
KUOSMANEN PETRI OLAVI (FI)
JUHANKO JARI PEKKA (FI)
VAEAENAENEN PEKKA TAPIO (FI)
International Classes:
B21B31/02; B21B31/07; B21B37/00; F16C13/02; B21B13/02; B21B; (IPC1-7): B21B37/00
Foreign References:
DD230163A31985-11-27
US4516212A1985-05-07
Attorney, Agent or Firm:
LEITZINGER OY (Helsinki, FI)
Download PDF:
Claims:
Claims
1. A method for controlling the rolling process of a rolled product, such as a steel, aluminium or plastic product, characterized in that rolls, such as backing rolls, are provided with a desired type of runout by machining a desired shape in the roll shell and/or roll neck and/or bearing components, such as a bearing bush, in such a manner that said desired shape is noncircular, the bush thickness varies and/or a desired path is provided for the centre of rotation of a workpiece.
2. A method as set forth in claim 1 , characterized in that controlling the rolling process refers to the minimization of the periodic machinedirection gauge variation of a rolled product and/or the minimization of roll force fluctuation and/or the control of surface roughness and/or the reduction of vibration and/or the extension of a service life for a rolling apparatus and/or the control of thermal expansion.
3. A test geometry method for implementing the method of claims 1 2, characterized in that a target geometry for rolls is determined experimentally by measuring the roll force fluctuation caused by a known runout and/or the gauge variation of a product to be rolled, such as a steel web, followed by machining the rolls for a known modification geometry and/or a change of runout profile; and by measuring then the force fluctuation and/or gauge variation caused by said rolls, followed by working out the size of modification for example by means of vector calculation for determining thereby the desired real geometry.
4. A method as set forth in claims 1 2, characterized in that the geometry to be machined on the rolls is determined in a calculated manner, such as by means of the element model of a roller unit or a single roll, said element model of a roll including at least a key and/or a keyway.
5. A method as set forth in claims 1 2, characterized in that the geometry to be machined on the rolls is determined by means of a calibration run effected prior to a rolling process and without a material to be rolled, such that the variation caused by each roll is determined from measuring signals, for example by means of synchronized averaging which is synchronised to the roll.
6. A method as set forth in claims 1 2, characterized in that the geometry to be machined on the rolls is determined from the periodic machinedirection variation of a rolled product, such as from gauge variation.
7. A method as set forth in claims 1 2, characterized in that the geometry to be machined on the rolls is determined from the roll force fluctuation of a roller unit and/or from the variation of a roll clearance.
8. A method as set forth in any of claims 1 3, characterized in that the geometry to be machined on the rolls is determined experimentally by a test geometry method.
9. A method as set forth in any of claims 1 2, characterized in that the non circular geometry to be machined on the shell of a roll is produced by means of a desired crosssectional shape which is 3D machined on a bearing assembly (9) used at the time of machining, such that the final machining is conducted without 3D machining.
10. A method as set forth in any of claims 1 9, characterized in that the geometry determined and machined by a method according to any of claims 1 9 is made more precise by supplementing the machined geometry with a geometry consistent with a residual error measured by a method according to any of claims 59.
11. A method as set forth in any of claims 1 10, characterized in that the machined geometry is measured by a multipoint measurement, such as a four point measurement.
12. A method as set forth in any of claims 1 11 , characterized in that the geometry to be machined is produced by a 3D grinding machine.
Description:
Method of improvement for a rolled product manufacturing process

The invention relates to a method for reducing the periodic machine-direction gauge variation of a rolled product, such as a steel, aluminium or plastic web, and for improving the runnability as well as cutting maintenance costs of a rolling process by reducing the roll force fluctuation of a roller unit resulting from elasticity variation in the bearing assemblies of rolls or the flexural rigidity fluctuation or uneven thermal expansion of a roll, or from some other systematic structural error in a single roll or roller unit, by machining the external roll surface or the bearing assembly used in rolling or the bearing assembly used in machining for a geometry capable of reducing the fluctuation of a roll force in rolling process.

The rolling assembly or roller unit consists of a set of rollers and its support structures. A rolling mill comprises a number of units complemented by various control devices and drive units. There are usually two, three or even more rolls in a roller unit. Major rolling operations are performed by means of four-roll mill for attaining required roll forces. The working rolls, through which the metal passes, are relatively small in diameter and have backing rolls of a larger diameter above and below transmitting a force to the working rolls.

It is prior knowledge that the gauge of a steel web is calculable by applying the equation

wherein a web gauge is represented by h , a roll clearance by SA , a roll force by F1 , and a roller unit's elastic constant by M . The roll force is a result of several factors, such as a gap clearance or roll clearance and deformations of the roller unit. Procedures necessary for gauge control include for example measurements regarding a total roll force and a gap setting, as well as a reference value for gauge measurement. It is prior known that the roll clearance is adjusted by means of electromotor driven screws and hydraulic cylinders. The equipment is manually operated or automated and capable of performing a fine adjustment of the clearance during a rolling operation.

Aspects that should be regarded in the adjustment of a roll clearance include variation of an incoming gauge, width and steel type variation, as well as temperature variation and strength variation resulting therefrom. The implementation of adjustment requires at least a setting value for the roll clearance and positional data regarding the roll clearance. The roll clearance and the roll force are affected at least by process-related disturbances, such as heating of rolls and roller units, as well as a run-out of the rolls. Another aspect to be considered is the film thickness variation of a bearings lubricating oil. An objective for automated gauge control (AGC) is to maintain a loaded roll clearance constant for obtaining a gauge as constant as possible over the entire length of a web. The control is based for example on a web gauge measured after of the roller unit or a force measurement of the roller unit. The AQC system takes into consideration the deformation of roller units subjected to a load. It is also possible to make a compensation for roll force fluctuation resulting from temperature variations of roller units and temperature variations of a steel web.

It is prior knowledge that in steel industry the term roll eccentricity can be used not only in reference to the eccentricity of rolls as defined in standard ISO 1101 but also more generally to all types of roll-inflicted periodic variation, such as gauge fluctuation of the end product in rolling direction, fluctuation of the roll force, variation of surface roughness, or vibration. I n this specification, the term roll eccentricity is used according to the standard.

It is prior known that signals measured from an end product or roller units display low-frequency flutter resulting from the mutual diametral ratios between rolls. The operation of AGC systems is hampered by this flutter.

The prior art shows various methods of correction for the effects of roll eccentricity. There are numerous methods and an objective therein is to use a real-time rolling line control for reducing a gauge variation of the web resulting from a run-out of the rolls. The methods can be divided in three groups.

1. A fundamental principle in passive run-out correction methods is to render the clearance adjustment insensitive to disturbances resulting from a run-out of the rolls, such that the clearance control need not be performed as a function of the rotational angle of a roll. These run-out correction methods have not been designed in view of reducing the gauge variation of a rolled steel web.

2. Active run-out correction methods require the detection of a run-out component in the rolls and the generation of a correction signal derived therefrom for a roll clearance controller. The run-out component can be worked out, among other things, from roll force, clearance gap, exit gauge of a steel web, and from tension variation of a web. The methods are further categorized on the basis of signal processing methods: analysing methods and synthesizing methods.

I n analysing methods, the run-out component is determined from measured quantities mathematically, for example by means of Fourier analysis.

I n synthesizing methods, the control quantity is worked out by reproducing the roll run-out component either by mechanical or electrical means.

3. Preventive run-out correction methods have been designed to produce such rolling conditions that the gauge variation of a steel web will be reduced without any procedures during the course of rolling.

It is prior knowledge that backing and working rolls display run-out. This causes variation of a roll clearance, which is synchronised to the rotation of the roll, and/or fluctuation of a roll force. This cannot be directly accounted for in an AGC system because, without filtering, it might lead to even higher fluctuations by compensating the roll force in an opposite direction. This is due to the fact that normally, when the roll force increases the roll clearance must be downsized, but when run-out increases the roll clearance must be opened up. It is prior known that the roundness error, run-out and diameter variation of a cylindrical workpiece, such as a paper machine roll, can be reduced by moving a working tool, such as a grinding wheel or a lathe tool, as a function of the workpiece's rotational angle and longitudinal axis, such that the distance of a tool from the centre of rotation of a workpiece is maintained substantially constant or as desired in the direction of the longitudinal axis. I n paper and steel industry, this machining method is generally referred to as 3D machining. The respective grinding method is referred to as 3D grinding and the turning method as 3D turning.

It is prior knowledge that cylindrical workpieces, such as paper machine rolls, can be machined for non-circularity and/or eccentricity in order to upgrade their operation in process conditions with respect to traditionally machined rolls. Said machining method is referred to as predictive 3D machining.

It is prior known that the periodic contact pressure fluctuation of paper machine rolls can be reduced by means of a non-circular cross-section geometry, said geometry being created by 3D machining.

It is prior known that the true roundness profile of backing rolls can be measured by means of a multi-point measurement, such as a four-point measurement.

The bearing assemblies for rolls include a slide bearing assembly and a roller bearing assembly. The most common bearing assembly comprises a traditional oil- lubricated slide bearing, wherein a tapered roll neck is fitted with a bush having a cylindrical outer surface (slide surface). Rotation of the bush on the neck is blocked either by means of a key or a keyless anti-rotation means.

It is prior known that roll run-out is affected by at least the following errors in a bearing system: non-circularity of a neck and/or non-circularity of a bearing bush and/or gauge variation and/or discontinuities on bush periphery caused especially by keys.

It is prior known that in a key-equipped slide bearing construction 5, the key or keyway causes periodic fluctuation which is synchronised to the roll. The gauge control process of a web is hampered by this. The keyway required by a key must always be made with a clearance. As the roll is rotating, the load-carrying force working in the bearing transmits across the bearing bush, whereby the bush deforms when in line with the keyway.

It is prior known that a keyless bearing construction 6 reduces the run-out of rolls with respect to a key-equipped arrangement.

Since a majority of the world's steel works built in the 60's and 70's continue to use a key-equipped construction, solving the problem would have a major economical significance.

The object of the invention is accomplished on the basis of characterizing features set forth in the appended claims.

A few exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings, in which

Rg. 1 shows graphically an periodic force fluctuation 21 as measured from a roller unit. This force fluctuation is reproduced in the end product. The figure depicts the effect of a roll key appearing once per cycle 20.

Rg. 2 shows schematically a roller unit design, including working rolls 24 and backing rolls 23 along with bearings 26 therefor. The figure depicts a product 25 to be rolled, and a reduction or a gauge downsizing which takes place therein. Other components: hydraulic cylinders 11 , position sensors 12 in conjunction with the hydraulic cylinders, a pressure measurement 13, force sensors 14, roll clearance measuring sensors 15, a gauge measurement 16 for a rolled product, as well as synchronization marks 31.

Rg. 3 shows schematically a backing roll 23. A key 1 is included in a tapered section 8 of the neck. Machining a shell 7 of the rolls is usually supported by the cones 8 or separate journals 9. Sometimes the rolls are also ground with the bearing system partially disassembled or in their bearings.

Rg. 4 shows schematically a key-equipped 6 and keyless 5 bearing assembly for a roll. The key 1 is used for blocking the rotation of an inner bearing bush 2. I n the keyless bearing system, the attachment of an inner bush 3 to the neck is prevented without a key by means of an auxiliary bush 4.

Fig. 5 shows schematically a 3D machining process by means of a grinding wheel 29 movable relative to the roll's 7 rotational angle, and a target geometry 27 for the roll. During the course of grinding the roll has journals of its both ends resting in a grinding machine as supported by chocks 17. I n view of grinding geometry, the essential support is provided by a rear bracket 18, which is generally disposed, as viewed from the grinding wheel, straight behind the roll or slightly below the horizontal line.

Rg. 6 shows schematically a geometric correction depicted in embodiment 2 for a bearing surface during machining, which enables machining the shell for the desired target geometry 27, such as, for example, by machining the bearing surface at key angle for a recess 28 as desired.

Rg. 7 shows schematically an arrangement depicted in embodiment 3, in which the roll has its shell ground traditionally to circularity. The compensatory run-out needed during the course of rolling is achieved by providing the roll neck 8 with a desired path for the centre of rotation, for example by machining the neck cone to become higher 29 in line with the key to compensate for deflections of the key construction.

Rg. 8 shows schematically an arrangement, wherein the roll has its shell ground to circularity. The compensatory run-out needed during the course of rolling is achieved by providing the bearing bush 2 with a desired path for the centre of rotation by machining the bush for a desired wall thickness variation 30, for example by machining the bush for more thickness in line with the key 1 to compensate for deflections of the key construction.

In this specification, the term test geometry method refers to:

Measuring the variation of roll force caused by the run-out of a prior known roll geometry and/or the gauge fluctuation of a product to be rolled, such as a steel web. Machining rolls for a desired geometry and/or a run-out profile, followed by measuring the force fluctuation and/or gauge fluctuation caused by said rolls. Calculating the size of a known variation and determining a desired real geometry. The method is analogous for example to a balancing test mass method with the exception that the calculation must be performed by including one or more vector components of geometry and/or run-out which are synchronised to the rotation of a roll.

Exam ple of em bodim ent 1 .

A method of the invention is apt for example for the following preferred application:

A force fluctuation in roller units as depicted in fig. 1 has been detected in a hot rolling process of steel web (fig. 2).

Measuring signals are used for determining a fluctuation caused by each roll, for example by means of synchronized averaging synchronised to the roll and/or a Fourier analysis.

The force fluctuation is observed to display flutter as well as periodic variation which is synchronised to the backing rolls 23. The flutter is explained by a relative difference between roll diameters.

The assembly of backing rolls comprises a key construction 6 according to figs. 2-3. It is detected from measuring signals that the sharpest peak of force fluctuation coincides with the key 1. FEM calculation (finite-element method) indicates that the most significant error is a flexure caused by the keyway, which appears in the force fluctuation signal (fig. 1 ) as a comparatively sharp spike once per cycle 20. I n addition, the keyway 1 causes variation in flexural stiffness, which appears as a minor, almost sinusoidal interference twice per cycle.

A target shape obtained for example by FEM calculation can be used in a method of the invention as a basis in the process of working out a desired final shape.

I n a method of the invention according to embodiment 1 , the backing rolls are designed with a desired run-out by machining the shell of a roll for a desired shape. The objective is to obtain such a cross-section geometry and such a path for the centre of rotation which jointly compensate for load variations resulting from the structure and/or thermal expansion of a backing roll and to achieve thereby a more constant quality for the end product and an improved runnability for the rolling mill.

I n practice, for example, the shell of both backing rolls is machined for a bulge of a few tens of micrometers on the opposite side from the keyway 1 (fig. 5).

The installation of compensation machined backing rolls in a roller unit is followed by performing a calibration run of the roller unit for determining a dead zone for the measuring signal of an AQC system, i.e. a signal fluctuation range within which the AGC does not respond to signal fluctuation.

I n a calibration run, the roller unit is driven, for example without a rolled product, at a running speed which is generally slower than the production rate. The employed load rate can be equal to a real load rate used in production.

By virtue of compensation machined rolls the fluctuation of a signal will be substantially reduced, thus making the AQC more readily responsive to real variations which call for adjustment.

The process of hot rolling a web involves machine-direction gauge variation measurement of end product and force fluctuation measurement of a roller unit 10 with force sensors. I n addition, the displacement of loading cylinders 11 is measured by position sensors 12 and the hydraulic pressure by pressure sensors.

The conclusion based on measuring signals is that the fluctuations of signals measured by all sensors of a roller unit have been reduced and so has the gauge variation of a rolled product. The runnability of an entire rolling process has improved.

The precision of a machined geometry is upgraded in the next machining cycle by supplementing the machined geometry with a geometry consistent with a residual error measured from the rolling process and/or the product. With the method of embodiment 1 , the roll treated with predictive 3D machining can also be machined for deformations resulting from thermal expansion of the roll.

I n rolls, machined with residual error correction, the signal fluctuations measured by the sensors of a roller unit are further reduced and the quality of an end product further improved. The inventive method also enables extending the service life of rolls.

I n the process of cold rolling a hot-rolled web, the improved longitudinal gauge profile improves the runnability and efficiency of a cold rolling line, as well as reduces the gauge variation and surface roughness variation of an end product. Running speed can also be raised.

Exam ple of em bodim ent 2. Machining the shell of a roll for a compensation shape by means of a non-circular bearing surface used at the time of machining.

A method of the invention is apt for example for the following application:

A target geometry (27) intended for the roll can be determined for example with the same methods as those used in embodiment 1.

The non-circular geometry to be machined in the shell of a roll is obtained by means of a desired cross-sectional shape machined in a bearing assembly, such as a slide neck (9), used at the time of machining. The shape given to the neck by machining and the support arrangements for a bearing assembly used in the roll at the time of machining establish a certain systematic wobbling path. What is reproduced in machining as the shape of a roll shell is principally a component co-directional with the tool used for cutting the wobbling path for the roll.

A target geometry intended for the bearing neck can be for example as that shown in fig. 6.

The final machining for a geometry intended for the shell can be performed without 3D machining.

An advantage of embodiment 2 is that the use of predictive 3D machining can be limited to the machining of bearing surfaces used at the time of machining. I n certain cases, the work can be done in a concentrated manner with a single grinding machine or subcontractor, as well as there is a possibility of using a possibly lighter, perhaps even mobile 3D machining apparatus. Neither is compensation grinding necessary in connection with every routine shell machining operation.

Exam ple of em bodim ent 3. Machining the bearing assembly of a roll for a compensation shape.

A method of the invention is apt for example for the following application:

The shape machined in the bearing assembly establishes a certain systematic wobbling path. The component of this path, which is parallel to the roll gap, appears as a compensatory run-out.

I n embodiment 3, the roll shell is ground to a circular shape. The compensatory run-out needed during the course of rolling is obtained by establishing a desired path for the centre of rotation in the bearing assembly of a roll. A target run-out for the roll can be determined for example with the same methods as those used in embodiment 1. The shape machined in the bearing assembly is established in a roll neck 8 or in a component of the bearing assembly, such as a bearing bush 3. I n the case of a bearing bush (fig. 8), it is important to control its thickness profile, since in the process of assembling the bearing system, the bush conforms to the shape of the neck.

An advantage of embodiment 3 is that the use of predictive 3D machining can be limited to the machining of bearing components used at the time of rolling. I n certain cases, the work can be done in a concentrated manner with a single grinding machine or subcontractor, as well as there is a possibility of using a possibly lighter, perhaps even mobile 3D machining apparatus. The bearing bush, for example, can be easily transported elsewhere for 3D machining. Neither is compensation grinding necessary in connection with every routine shell machining operation.

The embodiments are not limited solely to the foregoing examples. I n addition, there may be integrated embodiments, such that the rolling process, and especially the roll clearance, is controlled as desirable with respect to end product quality and runnability.

The embodiments are not limited solely to key-equipped rolls but, instead, the inventive method can be applied preferably also to keyless rolls and rolls with roller bearings.

Exam ple of em bodim ent 4. Utilization of a test geometry method.

The inventive method can be applied as in embodiment 1 , but the target geometry is determined by using a test geometry method as described above.