METHOD AND DEVICE FOR LUBRICATING ROLLERS AND A ROLLED STRIP OF A ROLLING STAND

A method for lubricating rolls, especially work rolls of a rolling stand, and rolling stock passed between the rolls during the rolling operation, in which a lubricant-gas mixture, a lubricant-water-gas mixture, a lubricant-water mixture and/or a grease-medium mixture is applied to the rolls or the rolling stock on the run-in side of the rolling stand, wherein the mixture is prepared with at least one mixing device in the area upstream of the rolling stand.

DETAILED DESCRIPTION OF THE INVENTION

A rolling installation1(FIG. 1) comprises two work rolls2,3, which are supported between two backup rolls4,5and roll rolling stock6(FIG. 3). In this operation, a lubricant, especially a first and a second oil, or additional oils and water are first supplied via separate supply lines7,8, and9. First, the two oils are mixed together. Alternatively, only one oil or the other is used. The desired amounts of water and the two oils are adjusted by metering pumps10,11and pumped to a mixer12. A dispersion or emulsion of the two liquids brought together in this way is formed downstream of the mixer12. To avoid separation of the mixture, the distance between the mixer12and control valves13downstream of the mixer is preferably very small, or the mixer and control valves are constructed as a single unit. The control valves13are distributed over the entire width of the upper work roll2. If relatively long pipelines cannot be avoided, turbulence plates (mixers) are installed a certain distance apart in the lines. The pipeline cross section is preferably selected as small as possible in order to realize a flow rate as high as possible and thus a short conveyance time. To be able to adjust a lubricant load over the width of the work roll2and also to be able to adjust it as a function of the width of the rolling stock6that is being processed, the control valves13deliver lubricant to downstream atomizing nozzles14, which are designed as 2-component mixing nozzles, according to the width of the rolling stock6. In the atomizing nozzles14, air is added to the mixture of lubricant and water. The air is supplied through a line15with a pressure controller for adjusting the air pressure. The amounts of lubricant or oil and the amounts of water are adjusted by a computer model and/or an automatic control device, which takes into account the various lubricating properties as a function of the strip material to be rolled, the strip speed, the draft, the temperatures and other parameters. The activation of the control valves13and the amounts pumped by the metering pumps10,11are coordinated with each other. The automatic control device determines the lubricant concentrations or the types of lubricants and also carries out automatic crown and flatness control of the rolled strip6. Unflatness of the rolled strip6is then compensated by adjusting the amounts of lubricant supplied or by varying other parameters. If necessary, the level of rolling force can be controlled by varying the amount of oil, the type of oil, the concentration of oil in the water and/or the oil mixing proportions.

In a simplified embodiment of the rolling installation1(FIG. 2), there are no control valves13. In this case, the flow through the atomizing nozzles14is manually adjusted or results from the adjustment of the metering pump. In another embodiment (FIG. 3), the lubricant-water-air mixture is applied directly to the underside of the rolling stock6. Control valves13are also provided in this case.

In another embodiment (FIG. 4), water, the lubricant, for example, oil, and air are first supplied through separate lines7,9,15and then applied to the upper work roll2by atomizing nozzles14or17in the form of 3-component nozzles, wherein the mixing and atomizing of the fluids constitute a unit in the atomizing nozzles17. However, in this case as well, control devices can be provided, which individually control the supply of the given fluid to the individual atomizing nozzles17or to a group of atomizing nozzles. Preferably, all of the individual automatic control devices are integrated in an automatic control system, which determines the volume and the mixing proportions of the fluids that are delivered by the atomizing nozzles17to the work roll2or the rolling stock6. Naturally, in all of the embodiments (FIGS. 1 to 4), analogous designs are provided or can be provided for supplying a lubricant-water-air mixture to the lower work roll3and/or to the upper side of the rolling stock6.

An atomizing nozzle17(FIG. 5) is realized as an internal mixer pressure mixing nozzle with an inner chamber18, into which water and two lubricants are fed at one end through a supply line19and, if necessary, are mixed by means of, e.g., turbulence plates36or a pipe constriction37. The operation of mixing the liquids takes place just before the atomization. The mixer and nozzle constitute a unit here. Two lines20,21first carry the lubricants into the supply line19immediately before the lubricants are delivered into the inner chamber18. A gas, especially air, enters the inner chamber18through another feed line22and is mixed in the inner chamber18with the mixture of water and the two lubricants. The mixture then leaves the nozzle orifice23in a conical spray and strikes the surface of a roll or the surface of the rolling stock6. Since the lubricant (for example, oil) or a plurality of lubricants is the most important component, it is also possible, in accordance with the invention, to control only the individual amount of oil per atomizing nozzle17and to control the other components in sections, i.e., over relatively large sections of the width of a roll and/or the width of the rolling stock6. The lubricant or lubricants can also be applied solely with the use of compressed air, i.e., without the use of water. In this case, a 2-component nozzle is used.

Especially in the case of cold rolling, it is important that the lubricant film acts completely over the entire width of the rolling stock6. If the oil film breaks down, undesirable scratches are produced on the surface. To guarantee redundancy of the lubricant effect, two or more rows24,25(FIG. 6) of atomizing nozzles17are preferably provided opposite a roll, for example, work roll2, or opposite the rolling stock6. The atomizing nozzles17in the two or more rows24,25are preferably offset from one another. Alternatively, a one-row nozzle spray bar can be used, whose nozzles have a large angle of spray, so that double coverage is realized. This means that if one nozzle fails, the adjacent nozzles cover this area.

Similarly to the embodiments illustrated inFIGS. 1 and 3, other embodiments of the invention have automatic control devices26(FIG. 7), with which the supply of the lubricant to each atomizing nozzle14is individually controlled over the entire width of the strip. The overall effect of the lubrication can be further influenced by varying the amounts of water and air. In the case of hot rolling, lubricant is applied to at least one of the work rolls2,3, while in the case of cold rolling, lubricant is preferably applied to the rolling stock6.

According to another variant (FIG. 8), lubricant and air are brought together in a mixing block27. The air carries the lubricant to the atomizing nozzles14. Each of the nozzles14is individually fed. The water is supplied to the nozzles14separately.

In the mixing block27(FIG. 9), first the lubricant and air from the lines7and15are brought together. The mixture is then fed by a line28to a 2-component nozzle29, in which it is combined with water supplied by the line8. The 2-component nozzle29is designed as an external mixer. This means that the lubricant-air mixture and the water do not come together until they reach the nozzle orifice30. The mixing is made possible by two hollow cones formed by the fluids spraying into each other. The advantage of this 2-component nozzle29is that saponification is prevented, since the lubricant and water do not come into contact with each other until they arrive at the nozzle orifice30. The water supply can be shut off to realize pure lubricant-air lubrication.

In a 2-component nozzle31(FIG. 10), which is designed as an internal mixer with an inner chamber32, oil and water are first introduced together into the inner chamber32through a feed line33, and air is introduced separately. Turbulence plates34or a venturi tube is installed in the oil-water supply line33to guarantee thorough mixing of the media.

A 3-component nozzle (FIG. 11) likewise has an inner chamber32, into which the media oil, water and air are separately fed through lines7,8, and15. The liquid media are thus not mixed until they reach the inner chamber32, and they are then atomized and sprayed.

When one wishes to use an oil-air mixture without having to add water as an additional component, then in the case of hot rolling, provision is made for fire protection, when necessary, by producing a water curtain that shields the oil-air mixture towards the outside by means of water spray bars38,39(FIG. 12). In addition, shielding walls40,41are placed around the oil-air mist produced by the atomizing nozzles14. The oil-air mist can be exhausted to the outside. The shielding walls40,41as well as the nozzle spray bars14are designed to swivel in order to improve the shielding and to allow the nozzles to be placed just in front of the roll. Similar exhausting is also provided for the lubricant application to the rolling stock (in the case of cold rolling).

In another embodiment of the invention, to control the surface structure (flatness, uniform state of stress) of the rolled strip6, a flatness measuring roller42(FIG. 13) or other type of contactless (optical) flatness measuring system is provided to determine unevenness of the rolled strip6. This measuring system transmits signals via a signal line43to an evaluation unit (not shown here). The evaluation unit generates signals for controlling or regulating the atomizing nozzles14or control valves13to deliver properly adjusted amounts of lubricant to the work roll2over the width of the strip. Parabolic or higher order strip flatness can be influenced by the amount or concentration of lubricant delivered per zone. Naturally, corresponding automatic control can also be applied with respect to the lower work roll3. The atomizing nozzles14can also spray the lubricant directly onto the rolling stock6to influence the strip flatness and the strip stress distribution over the width of the strip.