DD212657A1 - METHOD FOR PROVIDING SAME FRICTION RELATIONSHIPS THROUGH THE ROLLING WIDTH - Google Patents

Abstract

The invention relates to the production of cold-rolled sheets and films. As a special field of application, the production of aluminum foil is considered. The aim of the invention is to increase the cost of Folienwalzgeruesten with improved quality and Weiterverarbeitbarkeit the film can be achieved. At the same time, the power consumption of the rolling stand can be reduced by reducing the rolling pressure, the strip tear frequency is reduced, the output on film is increased and the mechanical components are relieved. The invention has the object of demonstrating a method by means of which the Reibungsverhaeltnisse in the nip during the entire rolling process over the entire bale width can be better adapted. According to the invention, this is achieved by determining a temperature and pressure profile, determined for a specific roll stand and one or more determined roll passes, over the roll bale width as the basis for producing an associated surface roughness characteristic over d. Bale width on the work rolls by grinding serves.

Description

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Title of the invention

Method for ensuring equal friction conditions across the nip width

Field of application of the invention

The field of application of the invention extends to rolling mills for cold rolling of sheets and strips. As a special field of application, the production of aluminum foil is considered.

Characteristic of the known technical solutions

As a decisive quality criterion in the production of aluminum foil, the flatness of the film is considered. It is dependent on a variety of influencing factors, such as properties and uniformity of the rolling stock, tape entry and exit, rolling speed, lubricant, stitch loss, rolling force, pressure distribution in the nip, roll crowning, rolling temperature and many others.

A special influence on a precise rolling process exert the friction conditions and the pressure distribution over the nip width. The coefficient of friction between the rolling material and the rolls can be regulated by the composition of the lubricant, the surface condition of the material and the rolls, and by the hydrodynamic action of the rolling speed. In rolling aluminum alloy thin sheets, the material is usually controlled by changing the rolling speed, and at a higher rolling speed, the thickness of the oil film becomes larger due to the hydrodynamic effect, thereby lowering the coefficient of friction and resulting in a larger thickness decrease.

From Dutch patent application 71.09275 a continuous regulation of the coefficient of friction by means of an adjustment of the composition of the coolant and lubricant during the spraying of this rolling agent on the rollers is known.

In DE-OS 2908641 a method for monitoring the flatness / flatness of cold-rolled sheets and foils is described in which, in deviation of a same percentage reduction in thickness over the entire width of the rolled material, the roll pressure is changed by supplying different temperature rolling agent.

In the method described in DE-OS 2554246 for controlling the flatness during rolling of strip material, the strip temperature is determined over the bandwidth and utilized the measured values for controlling the roll cooling device and / or for controlling the roll bending device for adjusting the roll crowning. To avoid bumps on finished rolled products, two Japanese patents are still known.

For example, in Japanese Patent Publication No. 10855/74, a roll bending method is described in which an uneven strip is to be straightened during the rolling over the entire width. This is achieved by applying an asymmetric rolling force in the widthwise and transverse directions to the belt during rolling.

Further, in Japanese Patent Publication No. 117138/70, there has been proposed a method of controlling thermally induced crowning. In this method, a lubricating oil is sprayed through lubricating oil nozzles over the work rolls and back-up rolls, whereby the power or flow rate of the lubricating oil for cooling the rolls in the transverse direction of the rolled strip is changed by controlling the spray amount of the lubricating oil, whereby the distribution or the profile of said thermal crowning of the rolls is regulated.

These already known methods and devices are not suitable for ensuring equal friction conditions in the roll gap of rolling stands mitteis which in particular Aiuminiumfolie should be rolled.

A disadvantage has been found in these methods that the friction conditions in the roll gap can be ausgegeregeit only up to a certain rolling speed. With eiiier increase in the rolling speed, as is desirable in particular in aluminum foil production, a compensation is no longer possible safely.

Object of the invention

The object of the invention is to increase the rolling speed while improving the quality of the film and reducing the drive power while reducing the burden of the film rolling stand can be achieved.

Explanation of the essence of the invention

The technical deficiency described in the characteristic of the known technical solutions can be attributed to the fact that the surface roughness is ground substantially constantly over the entire roll bale. "In order to eliminate this cause, the object of the invention is to provide a method by means of which the friction conditions in the roll gap can be better regulated throughout the entire rolling process over the entire bale width and a particular roll pass temperature and pressure profile across the roll barrel width is used as the basis for producing an analogous surface roughness characteristic across the bale width on the grinding machine .. The economized surface roughness parameters such as roughness R ₁₇₁ , average roughness R _z and arithmetic are favorable Mean roughness R _a over the bale width approximately constant to grind and the curve of the reflectance / gloss is to match the determined temperature and pressure profile.

embodiment

If the new ground work rolls are inserted in the mill stand, then it can be assumed that they have the same temperature over the entire roll bale width. During the rolling process, this condition changes such that the temperature due to the rolling work in the center of the bale reaches a minimum value which increases unevenly again to the bale ends. Due to the pressure distribution in the nip at the same time, which initially drops to a minimum value from a certain value in the center of the bale towards the bale edges, and then rises again to a maximum value up to the strip edge, the friction conditions are additionally influenced. Due to the temperature and pressure distribution in the nip creates an expiring band, which has different unplane zones distributed over the roll width.

According to the invention, the temperature and pressure profile of the warmed work rolls over the entire bale width is determined in a known manner and as a basis for the surface roughness profile to be ground following

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used in the rolling mill to be used work roll. The desired surface roughness profile is determined on the roll grinding machine by varying the machining parameters such as wheel speed, longitudinal feed, infeed, roll speed, number of firing strokes, and the like. Ä. Achieved. ,

It is not only about the standardized surface roughness parameters, such as surface roughness R _m , average roughness R ₂ and arithmetic average roughness R _a , as they are usually to be determined in production with Werkstattmeßgeräten particular stylus devices to vary, but it also applies such standardized characteristics (by design TGL-RGW 1155), such as the mean square profile slope and the mean arithmetic profile slope. However, the last two parameters are difficult to determine under production conditions on the machine. Their qualitative and quantitative expression, however, they find in the readings of optical surface sensors as a value for the reflection behavior or the gloss of the ground surface.

Claims (4)

-3- 246 412 8 invention claims Anspruch [en] A process for ensuring equal friction ratios across the roll width in the production of cold rolled sheets and films, wherein the stock is passed between a rotating set of rolls having a defined surface roughness, characterized in that the determined for a particular rolling mill and one or more determined rolling passes temperature and Pressure profile over the roll barrel width serves as a basis for the production of an associated surface roughness characteristic over the bale width on the work rolls by grinding. 2. Method according to item 1,
characterized by the standardized surface roughness parameters, such as roughness R _m , average roughness R ₂ and arithmetic mean roughness R _a, are ground approximately uniformly over the bale width and the reflectivity has a curve associated with that of the determined temperature and pressure profile. 3. Method according to item 1 and 2, characterized by, ~. in that zones of unevenness on the work rolls to be ground are assigned to zones of different roughness / microroughness due to the strip leaving the roll gap. 4. Method according to item 1 to 3, characterized in that in the sections in which the strip edges move during the rolling process, the micro-roughness profile is additionally adapted.