EP0240825A2 - Lubricant system for plate and shape-rolling mills - Google Patents

Abstract

Lubricant system for sheet metal and profile rolling mills, containing a solid lubricant, an adhesive component and / or a thickener, as well as water as a carrier medium. This lubricant system is sprayed as a suspension onto the working cylinders in the roll stand, the water evaporating at least partially and a firmly adhering, waterproof, lubricating and separating layer being formed on the working cylinders.

Description

The invention relates to a lubricant system for sheet metal and profile rolling mills.

It is known from CH-PS 596 294 and 609 728 to use lubricants containing graphite, alkylene polymers or copolymers, film stabilizers and suspension aids for the lubrication of mandrels in rolling mills for the production of seamless tubes. The lubricants are sprayed onto the hot thorns in the form of an aqueous suspension, the water evaporating and leaving a lubricating film in which the graphite particles in the alkylene polymer are present in a uniform distribution. If the mandrel in the mill stand is inserted into the billet, the alkylene polymer melt forms a hydrodynamic lubricating film. During the rolling process, the alkylene polymer burns and the resulting gases are able to act as separators. The remaining graphite can absorb current and local load peaks and generally acts as a dry lubricant.
The attempt to transfer the lubricant mentioned specifically to the sheet metal and profile rolling processes failed. In view of the much longer time available for applying the lubricant suspension, the evaporation of the carrier medium and the formation of a uniformly thick, waterproof, lubricating layer, the known lubricants could no longer suffice.

The object of the invention was to provide a lubricant system which is easy to use and leaves behind a lubricant in the form of a film which ensures perfect lubrication between sheets and profiles and the rolls of a rolling mill.

According to the invention, this is done with a lubricant system for sheet metal and profile rolling mills, which is a lubricating component
a) from the series of solid lubricants and at least one of components b) and c), the components
b) an adhesive component from the series of organic water-insoluble adhesives which disintegrate at temperatures up to 300 ° C. and have a softening point of 20 to 180 ° C., and
c) a thickener for aqueous suspensions from the series of alginates, celluloses, starches, gums, clays, alone or in a mixture with one another, and
a component
d) in the form of a liquid, as a carrier medium.

The lubricant system is used in sheet metal and profile rolling mills, with the slabs usually being fed to mechanical descaling from a pusher furnace in a highly heated state. Immediately thereafter, the slabs run, for example, into a continuous finishing series with usually 6 to 7 roll stands. The rolled sheet or profile is then cooled and wound up.

A roll stand essentially consists of two opposing working cylinders, the sheet or profile being guided through the roll gap. The slabs have a temperature of approx. 1200 ° C when they enter the first mill stand and the sheet or profile formed from it still has a temperature of around 1000 ° C in the third stand. Therefore, the rolling cylinders have to be cooled with considerable amounts of water.

According to the invention, a lubricant system is expediently used which contains 25 to 95% by weight of component a) and 5 to 75% by weight of components b) and c) and with d) a suspension containing a), b) and c) from 5 to 30% by weight in d).

The substances belonging to component a) include solid lubricants, expediently from the series graphite, MoS₂, CaF₂ and BN. Mixtures of these can optionally also be used. Synthetic graphite with a grain size of less than 100 micrometers is preferably used.

Component b) includes substances from the range of organic, water-insoluble, optionally water-swellable adhesives which disintegrate at temperatures up to 300 ° C. and have a softening point of 20 to 180 ° C.
From this series, useful hydrocarbon resins from the series include coumarone indene resins with a softening point of 105 to 145 ° C., aliphatic and / or aromatic petroleum resin mixtures with 4 to 10 carbon atoms in the base molecules, terpene resins, rosin derivatives, polyisobutylene, Polyamide resins with an average molecular weight of 6000 to 9000, and mixtures thereof.
Adhesive components made from hydrocarbon resins are, for example, thermoplastic resins made from aromatic petroleum cuts.

The polyamide resins with a molecular weight of 6000-9000 and with adhesive properties include the reactive polyamide resins.
Furthermore, rosin and the derivatives of polymerized rosin or modified esters of rosin can be added to component b).
Mixtures of the compounds mentioned can optionally also be used.
In the context of the present invention, bitumen, such as Grahamite and Gilsonite, must also be mentioned in the series of the adhesive components b). However, all the advantages cannot be achieved with this, in particular the transmission effect is absent.
Component b) can also advantageously be a mixture of at least one of the compounds mentioned with paraffins or waxes. However, the paraffins or waxes should not amount to more than 50% by weight of the total amount of resin.

Component c) comprises the series of thickeners used for the preparation of aqueous suspensions. The alginates, celluloses, such as alkyl and hydroxyalkyl celluloses, carboxymethyl celluloses, hydroxyethyl celluloses and hydroxypropyl celluloses, gums, such as guar gum, agar gum, gum arabic, ghatti gum, karaya gum, tragacanth gum, carob carob- Gum, tamarind gum and xanthan gum, pectins, polyacrylamides, polyacrylic acids and their homologues, polyethylene glycol, polyethylene oxide, polyvinyl alcohol, polyvinyl acetate, polyvinylpyrrolidone, starch and its modifications, paste, such as starch and cellulose paste, Carrageenan, polysaccharides, water glass, clays, especially the highly plastic clays, montmorrillonite, bentonite, kaolin, modified montmorrillonite, hectorite, attapulgite and the derivatives of the above-mentioned groups of substances and mixtures of the above-mentioned substances with one another, the clays as inorganic substances not more than 20% by weight of the component c) should be used.

Further expedient compositions of lubricant systems contain 30 to 90% by weight, preferably 40 to 90% by weight, of component a).
Components b) and c) should be 5 to 75% by weight of all three components a), b) and c) and can be from 0 to 75% by weight of component b) and 0 to 75% by weight of component c) consist.

Preferred compositions contain 25 to 95% by weight of component a) and 5 to 75% by weight of component b).
Such lubricant systems are characterized by the fact that the dry lubricant adheres quickly and safely to the roller surface.

Further preferred compositions contain 25 to 95% by weight of component a) and 5 to 75% by weight of component c). The high proportion of thickeners ensures that there is a stable, aqueous suspension and that good evaporation and adhesion of the dry lubricant on the rollers can be observed even after the carrier medium has evaporated. Excellent results can be achieved with a system containing 40 to 95% by weight of component a) and 5 to 60% by weight of component c).

Component d) is the carrier medium for the components mentioned. Water can preferably be used as the carrier medium. Water volatilizes easily at the processing and application temperatures of the lubricant system without leaving or developing harmful fumes or decomposition products.
A carrier medium is necessary in order to bring the various components into a processable, ie spreadable and preferably sprayable, form. A homogeneous suspension is produced using the carrier medium. The composition according to the invention also ensures homogeneity during the transport of the suspension to the processing site and after spraying. Already during the spraying and at the latest when the lubricant system hits the roller cylinders, the carrier medium evaporates at least partially, while the remaining components, still in homogeneous distribution, form a firmly adhering, now waterproof film. As soon as the rolling cylinders come into contact with the sheet or profile, the organic components start to burn off and thus create a gas separation pad. The graphite particles are adhered to while the organic components are still present and are able to develop their lubricating effect evenly distributed. In addition, the graphite also remains fully retained in its lubricating properties after all organic components have been removed.

It can be advantageous to add up to 5% by weight of water glass to the lubricant system. The water glass on the one hand has a lubricating effect at high temperatures and on the other hand is a film former for the lubricants.

To prevent bacterial attack, especially in the presence of starch or paste, the lubricant is advantageously admixed with amounts of 0.1 to 3% by weight of a bactericide or biocide.

Suspension aids and surfactants are also not essential for the stability of the suspension and are sometimes also undesirable. The stability of the suspension is primarily aimed at by means of the viscosity using the thickeners.

It can be assumed that the hydrodynamic lubricating film as described in the prior art, for example in CH-PS 596 294, cannot form in the present application, since the lubricant remains on the roll surface until the sheet is processed or Profile is too short. It has now been found that the specific requirements with regard to lubrication and separation in sheet metal and profile rolling are met with the lubricant according to the invention.

Furthermore, it was found that the lubricant system according to the present invention produces a transfer effect. The scaffolds following the scaffold lubricated with a lubricant according to the present invention also have considerable energy savings and wear reduction. This is done without lubricating the subsequent stands.

The lubricants according to the invention can be produced in such a way that the individual components are premixed without the carrier medium. These components are usually in dry, powdered form, whereby the grain size of the powder can be predetermined and selected and mixed together according to the requirements. The dry powder mixture can then be easily packaged and transported. In the area of the rolling mill, the dry lubricant powder can be mixed in a suitable mixer with the carrier medium, usually water, to form the required lubricant system in the form of a stable, homogeneous suspension. This suspension remains stable over long periods of time and is then advantageously applied via spray nozzles at 20 to 150 bar and in quantities of 0.5 to 5 l / min. applied to the roller cylinders per spray nozzle.

example 1

By premixing dry
35% by weight graphite (grain size less than 100 micrometers)
40% by weight of hydrocarbon resin, with a softening point of 100 ° C
10% by weight starch paste
5% by weight carboxymethyl cellulose
10% by weight bentonite
a solid lubricant was produced, which was suspended with water in an intensive mixer to form a solid lubricant system with a solids content of 10% by weight.
The suspension was at 60 bar through 8 nozzles each with 1.2 l / min. sprayed onto the two working cylinders of the first stand of a finishing line within a sheet metal rolling mill over the entire width of the roll.
The rolled sheets had a significantly improved quality, which was noticeable by an improved roughness, that is to say an excellent surface quality. Another key feature was a reduction in the energy consumption of the roll stand by an average of 15% and a reduction in roller wear by 35%. In addition, it was found that there was a transmission effect, so that the second stand still shows a 10% reduction in energy consumption and 8% reduced roller wear, and the 3rd stand still shows an 8% reduced energy consumption.

Example 2

The procedure was as in Example 1; again a solid lubricant system with a solids content of 10% by weight was produced in an aqueous suspension, the solid lubricant
88% by weight graphite (grain size less than 100 micrometers)
1% by weight water glass and
11% by weight alkyl cellulose
contained. This suspension was applied using 8 nozzles in an amount of 0.7 l / min. and nozzle sprayed onto the working cylinders of the 1st stand. The result is shown in the table.

Example 3

The following solid lubricant systems, each in the form of aqueous suspensions, with a solids content of 5% by weight were produced:

When used for sheet metal rolling in the first stand of the rolling mill, results were obtained with regard to energy absorption and roller wear, which were comparable to the results from Examples 1 and 2.

Claims (7)

1. Lubricant system for sheet metal and profile rolling mills, characterized in that it contains 25 to 95 wt .-% of a lubricating component a) from the range of solid lubricants and 5 to 75 wt .-% of one of components b) and c), wherein the components
b) an adhesive component from the series of organic water-insoluble adhesives which disintegrate at temperatures up to 300 ° C. and have a softening point of 20 to 180 ° C., and
c) a thickener for aqueous suspensions from the series of alginates, celluloses, starches, gums, clays, alone or in a mixture with one another, and
a component
d) in the form of a liquid, as the carrier medium, component d) forming a suspension with a), b) and c) of 5 to 30% by weight in d). 2. Lubricant system according to claim 1, characterized in that it contains 30 to 90 wt .-%, preferably 40 to 90 wt .-%, of component a). 3. Lubricant system according to claims 1 and 2, characterized in that it contains 25 to 95 wt .-% of component a) and 5 to 75 wt .-% of component b). 4. Lubricant system according to claims 1 and 2, characterized in that it contains 25 to 95 wt .-% of component a) and 5 to 75 wt .-% of component c). 5. Lubricant system according to claims 1 and 2, characterized in that it is 40 to 95 wt .-% of component a) and 6 to 60 wt .-% of the compo nente c) contains. 6. Lubricant system according to claims 1 to 5, characterized in that component a) comprises graphite, MoS₂, CaF₂ and BN, component b) hydrocarbon resins from the series coumarone-indene resins, aliphatic and / or aromatic petroleum resin mixtures with 4 to 10 C. -Atoms in the base molecules, terpene resins, rosin derivatives, polyisobutylene, polyamide resins with an average molecular weight of 6000 to 9000 and mixtures thereof and mixtures of the substances mentioned with waxes and paraffins, the waxes and paraffins not more than 50% by weight. % of the total amount of resin comprises, which comprises component c) alginates, cellulose ethers, gums, pectins, polyacrylamides, polyacrylic acids, polyethylene glycol, polyethylene oxides, polyvinyl alcohols, polyvinyl acetate, polyvinylpyrrolidone, starch, paste, polysaccharides, water glass, clays and mixtures thereof, wherein clays include make up inorganic substances not more than 15 wt .-% of said component c) t, and component d) comprises water as the carrier medium. 7) Process for lubricating rollers in the production of sheets and profiles in sheet metal or profile rolling mills by means of a lubricant system according to claims 1 to 6, characterized in that a suspension with 5 to 30 wt .-% content of components a) and at least one of the components b) and c) is applied in a carrier medium d) to the two working cylinders of at least one roll stand, the carrier medium escaping at least partially in gaseous form during application and a firmly adhering, water-resistant lubricating and separating layer forms on the working cylinders.