MXPA06007346A - Method for lubricating milling material - Google Patents

Abstract

Disclosed is a method for rolling milling material, especially for hot wide-strip rolling in a finishing train or a continuous casting and rolling plant, in which a lubricant is applied directly to the surface of the working rollers or indirectly to the surface of the support rollers, the lubricant then being transferred to the surface of the working rollers, before the milling material is fed into the roller gap of a roll stand. A highly adhesive lubricant film forms on the surface of the working roller, said lubricant film resulting in a reduction of friction in the roller gap as an intermediate layer between the roller and the milling material. According to the inventive method, the lubricant is applied along the entire length of the milling material such that the lubricating effect comes into play along the entire length of the milling material.

Description

PROCEDURE FOR GREASING MATERIAL PE LAMINATION FIELD OF THE INVENTION The invention relates to a method of rolling rolling material, especially for the hot rolling of broad bands in a finishing train or in a rolling mill, in which a grease medium is directly applied. on the surface of the working cylinders or indirectly on the surface of the supporting cylinders with transfer to the surface of the working cylinders, before introducing the rolling material into the roll gap of a roll stand, thereby a very adherent grease film is formed on the surface of the work rolls, which leads to a reduction of the friction in the roll gap as an intermediate layer between the roll and the rolling stock.

BACKGROUND OF THE INVENTION It is known to use a greasing of the roll gap in rolling mills with high loads during hot rolling. In this case, however, the greasing is connected but delayed in the front part of the band, after the first pass in the corresponding box and again disconnects something before the exit of the end of the band. This type of operation it acts, disadvantageously in the rolling process, depending on the effect of the greasing. DE 21 05 975 discloses an apparatus for automatically feeding oil to a hot rolling box through which a work piece is passed. The apparatus comprises an oil spraying device for the rolling stand, means for feeding oil to the spraying device, means for starting the operation of the oil supply means shortly after the leading end of the workpiece. it is directed through the roll stand and means for terminating the operation of the oil feed means shortly before the rear end of the workpiece reaches the roll stand. US 6 266 985 Bl discloses a process according to which, in hot rolling, the corners and ends of the rolling material to be laminated are applied with a grease medium. DE 20 11 923 discloses a method and a device for the application of a fatliquoring medium on a work piece in a hot strip mill, in which in a four-roll rolling stand provided with two cylinders of work and two support cylinders, fatliquoring medium and atomization air are released in several spray nozzles. The spray nozzles are arranged transversely through the width of at least one of these support cylinders. As soon as the workpiece is inserted into the work cylinders, the grease medium is applied to the support cylinders and from there it is subsequently supplied to the work cylinders. The flow of grease medium and atomizing air towards the nozzles stas soon as the workpiece leaves the working cylinders. The starting point for the transport of the grease medium is the first pass in the box in question. In this process or in this device it is disadvantageous that a film of closed fatliquoring medium must first be formed on the surface of the support cylinders, which is transferred in the gap between the support cylinders / work rolls to the surface of the cylinders of job. From here the grease medium reaches the interstice of cylinders. Until the grease medium reaches the rolling material, too much time passes (several seconds), depending on the circumferential speed of the cylinders and the diameter of the cylinders. In a process of this type or in a device of this type, no new fatliquor is fed to the front part of the strip at the inlet, which leads in a short time to too high rolling forces. Basically, rolling in the frictionless roller gap is not possible, because only with sufficient friction is the lamination material gripped and stretched across the Cylinder gap Always ensure that the so-called grip and pitch conditions are met. With regard to a minimum necessary friction, the condition. Grip, which describes the proportions of the rolling material at the start, is essentially more critical than the step condition. As for the passage condition, the cylinder gap is completely filled with the rolling material. When one of the two conditions or both conditions are not met, a slip appears, ie a slip between the rolls and the rolling stock.

In addition to the coefficient of friction, which describes the friction itself, the contact angle and the rolling speed have an important role. With an increasing rolling speed, the gripping force decreases. As for the contact angle, which depends on the thickness of the rolling material that is introduced, the relative decrease in thickness during the rolling and the diameter of the rolls mean that it must always be lower than the friction angle to enable rolling without slippage. With a distribution of the usual reduction, the contact angle decreases in finishing trains from the first to the last box. Consequently, the greatest grip problems, a slip at the beginning of the rolling material, appear in the first finishing box.

Since the gripping condition at the start of the rolling material is more difficult to achieve than the passing condition in the rolling material, the greasing of the roll gap is initiated in such a way that the greasing is activated just after the first pass. in each box, and something is deactivated before the output of the rolling stock. In this way, enough revolutions of the working cylinders are maintained to completely burn off the fatliquoring material that is on the surface of the cylinders. This avoids endangering the grip at the start of the next rolling material. By means of the greasing strategy described, two different load levels are given within the rolling material, so it is assumed that the pre-band or fine slab is introduced into the finishing train with homogeneous characteristics throughout the length and without acceleration. A high load level at the beginning and at the end of the rolling material (without greasing effect) and a low level of rolling force in the rest of the areas of the rolling material (active greasing). By reducing the rolling force during active greasing, which can amount to up to 50% and more, the bending deformation of the work rolls is modified. This also modifies the state of flatness (considerably in the back boxes) and the profile (considerably in the front boxes) of the rolling stock. If there is a flexing of the working cylinders in each box as an adjustment element, in case of large reductions in rolling force, the adjustment limits are often reached. The consequence is a more unstable march of the rolling material, especially in the case of laminations of thin strips. It is usual to limit the reduction of the rolling force to a value of approximately 20%.

SUMMARY OF THE INVENTION The invention is therefore based on the objective of providing a process for the application of a greasing medium on a surface of work or support cylinders that allows an improvement of the rolling process, leading to a reduction in wear of the cylinders and that decreases the energy consumption of the finishing train. This object is achieved according to the invention by the characterizing features of claim 1. Advantageous configurations of the invention are indicated in the dependent claims.

DETAILED DESCRIPTION OF THE INVENTION If a greasing system is activated that transports the fatliquoring medium from a reserve tank through ducts and nozzles to the work or support cylinders, already 5 to 15 seconds before the introduction of the rolling material in the rolling stand, all the dead times in the greasing system are compensated so that, in any case , already before the first pass a film of closed grease has been formed on the working cylinder. The decisive advantage of the method according to the invention is that a constant level of rolling force is obtained for each case over the entire length of the rolling material, since a lubrication is maintained over the entire length of the rolling material. Due to the constancy of the rolling force, further reductions in the rolling force can be achieved, for example from 40 to 50%, so that the load of the rolling mill with respect to wear and energy consumption clearly decreases. In addition, by reducing the higher rolling force, the wear of the working cylinders is also reduced and thus the dwell time (useful life) of the cylinders is extended. The advantages of the process according to the invention are therefore: - level of constant rolling force; - no modification of the state of flatness, related to the rolling force; - no modification of the profile of the band, related to the rolling force; - since the forces at the beginning and at the end of the rolling material are also clearly reduced, vibrations of the box and damage to the cylinders can be more effectively avoided; - this results in a greater tolerance for redistribution of the reduction and with this optimized runway drawings are obtained during the rolling of critical products; since the state of flatness at the end of the rolling material is not modified by the rolling force, a defective rolling at the start of the rolling material can be avoided. It is a requirement for the use of the greasing according to the invention that the gripping conditions at the start of the rolling material are ensured. The application of the fatliquoring medium according to the invention in a finishing train or in a rolling mill is advantageously possible from the second box and for all subsequent boxes without restrictions. In the first finishing box, due to the large thickness of the rolling material (greater contact angle), no greasing medium is generally applied. In order to apply the fatliquoring medium according to the invention already in the second finishing box, the present relations of the respective installation. Among which are, for example: - the state of the rolling surface after grinding, - the diameter of the working cylinders, - the material of the working cylinders, - the thickness of the band introduced, the relative reduction adjusted, - the state of the surface of the laminated material introduced (slag, temperature, roughness, material, etc.), the grease medium used, the amount of grease medium, the speed of rolling. If the contact angle is located in the critical zone, at the beginning of the rolling material the greasing effect is limited upwards by a smaller amount of fatliquoring medium or by a modified fatliquoring means, that is to say that it has other characteristics. With the use of the method according to the invention for the application of the grease medium on a surface of cylinders it is recommended to prepare the model of the runway plane of the finishing train for this operation. In this regard, at least one bending of the adaptation matrix should be provided so as not to impair the adapted operation without greasing the roll gap. In physical models it is very advantageous to establish different groups of friction coefficients, for the greased and non-greased state, for the start-up as well as during the introduction of new products and to avoid higher adaptation values. Each modification of the friction is linked to a modification of the advance, that is, with a modification or alteration of the mass flow. An alteration of this type must be regulated by the regulation system, which can lead to considerable difficulties in the case of laminations of critical thin bands. Another advantage of the method according to the invention is that, in the case of a constant greasing, a constant advance is achieved which in turn results in a constant mass flow. With ferritic cylinders, the greasing of the roll gap is adjusted to favorably influence the shear texture on the surface. The application according to the invention of the fatliquoring means causes a homogeneous surface texture over the entire length of the rolling material. In the greasing system, to prevent delay times when activating greasing, the construction of a closed circuit with feedback to the fatliquoring medium tank and an installation of a 3/2 switchable valve is foreseen. tracks in front of the mixer for the fatliquoring medium (for example a static tube mixer).

Claims (6)

1. Process for lamination of rolling stock, especially for the hot rolling of wide strips in a finishing train or in a rolling mill installation, in which a fatliking medium is applied directly on the surface of the working rolls or indirectly on the surface of the support cylinders with transfer to the surface of the working cylinders, before the rolling material enters the roll gap of a rolling stand, whereby a very adherent grease film is formed on the surface of the working cylinders which leads to a reduction of the friction in the rolling channel as an intermediate layer between the rolls and the rolling material, characterized in that the fatliking medium is applied over the entire length of the rolling stock and the The fatliquoring effect is therefore active over the entire length of the rolling material.

Method according to claim 1, characterized in that a greasing system is connected, which transports the fatliquoring medium from a reserve tank through ducts and nozzles to the working or support cylinders, from 5 to 15 seconds before the introduction of the rolling material in the rolling stand.

3. Process according to claim 1, characterized in that the fatliquoring means is applied in the second and in each of the following boxes.

4. Method according to claim 1, characterized in that the fatliquoring medium is applied in the third and in each of the following boxes. Method according to claim 1, characterized in that the fatliquoring medium is applied in the second and in any of the following boxes. Method according to claim 1, characterized in that the fatliquoring medium is applied in the third and in any of the following boxes. SUMMARY In a process for the lamination of rolling stock, especially for the hot rolling of broad bands in a finishing train or a rolling mill, in which a grease medium is applied directly on the surface of the rolls of work or indirectly on the surface of the support cylinders with transfer to the surface of the working cylinders before the rolling material is introduced into the roll gap of a rolling stand, thereby forming a film of grease very adherent on the surface of the working cylinders, which leads to a reduction of the friction in the interstice of cylinders as intermediate layer between the cylinders and the rolling material, the fatliquoring medium is applied over the entire length of the rolling material being active therefore the effect of greasing over the entire length of the rolling material.