PL142820B1 - High-temperature resisting grease for use in hot plastic working of metals - Google Patents

Description

The subject of the invention is a high-temperature grease for chipless hot forming of metals, containing a solid lubricant and an organic product that decomposes without hot residue. Swiss Patent No. 596294 discloses a high-temperature grease consisting of graphite, polymer or alkylene copolymer. and dispersant. The polymer used in such lubricants burns out without residue during the plastic working of the metal, and it can be assumed that the polymer alloy at first and then its gaseous decomposition products have a lubricating effect. DE-OS No. 2430249 describes the lubricant high temperature for hot forming of metals, based on phosphate-borate glass, a lubricating additive and a residue-free organic product that produces a propelling action. These known lubricants exhibit excellent lubricating performance. For use at high temperature, especially when used on tools or workpieces that exhibit a temperature above 350 ° C and in particular 600 ° C and above, a sharp drop in lubricating performance has been observed, however. The addition of phosphate-borate melting products. alkali metal gives a product which, as a further drawback, shows insufficient wetting properties on hot surfaces. In order to eliminate this disadvantage, it was necessary to stabilize the lubricating dispersion with silicic acids. For their part, however, silicic acids have a bad influence on the behavior of the lubricant and the service life of the tools. It is an object of the invention to provide a high-temperature lubricant which would not have the disadvantages mentioned above and would lead to dense and completely effective lubricating films at a temperature above 600 ° C. This object is achieved by means of a high-temperature grease containing a solid lubricant and an organic product with no hot decomposing residues, according to the invention in that the grease also contains an unlimited additive in the form of a mixture with a hardly dissolving or insoluble polyphosphate, a boron compound and alkali metal silicate, and an organic stabilizing agent, and optionally water. The inorganic additive is preferably a mixture of 0.2-25% by weight boron compound, 0.2-98.8% by weight polyphosphate and 1-99.6% by weight of alkali metal silicate. In a preferred embodiment, the lubricant comprises polyphosphate in insoluble or sparingly soluble form. The polyphosphates used are preferably Madreir salts or Kurrol salts. These are compounds of the type represented by the formula (NaPO 3) n in which n is a number from 6 to 50,000, preferably from 6 to 10,000. The boron compound can be used in a soluble form, and preferably in a sparingly soluble or insoluble form. For example, borax, orthoboric acid, B203, KB508-4H20 or basic zinc tetraborate can be used as the bfot compound. The alkali metal silicate used is preferably water glass. sodium or potassium water glass with a content of 21-47% SiOz. The use of the insoluble or sparingly soluble compound indicated as preferred is particularly advantageous due to the wetting of hot surfaces, especially due to the uniform thickness of the high-temperature lubricant layer on the surfaces of the tools and / or workpieces at a temperature above 35 ° C, and especially at a temperature of 600 ° C and above. The quantitative ratios of individual components in a high-temperature grease may correspond, for example, to the following composition: 1 - 90% by weight of a solid lubricant, 1-50 wt.% Organic product without hot decomposition residues, 1-80 wt.% Inorganic of this additive and 0.2-80% by weight of an organic stabilizing agent. Preferably, the high temperature lubricant for use at temperatures up to 350 ° C contains at most 50% by weight, and for use at 600 ° C and above contains a linearly decreasing amount up to 5% or less by weight of an organic product with no hot decomposition residue. A typical lubricant for use at 350 ° C may therefore contain 40-90% by weight of solid lubricant, 10-50% by weight organic product, 0.2-5% by weight of an inorganic additive and 0.2-5% by weight of an organic stabilizing agent. For lubricants which are to be used at a temperature of 600 ° and above, a suitable composition is, for example, as follows: 10-90% by weight of solid lubricant, 1.15% by weight of organic product, 10-80% by weight of inorganic additive and 0.2-4% by weight of an organic stabilizing agent. Graphite, MoS2 (molybdenum disulfide) may be used as a solid lubricant, CaF ^ or BN. Among the solid lubricants, graphite leads to S. especially good results. Of the graphite series, preferred are high-purity, e.g., greater than 96%, and an average grain size of at most 300 µm. The best results can be obtained with graphite having a purity degree of 99.5% and an average grain size of 100 µm. Residual, hot-melt organic products are, for example, alkylene homopolymers or copolymers. These include homo- and copolymers of arylalkenes, alpha-unsaturated acids and esters, p, y-unsaturated acids and esters, alkenes (monoolehines, diolefins, etc.), vinyl esters, vinyl alcohols, unsaturated dibasic acids and esters ( dicarboxylic acids and their esters), alkyl and acyclic acid esters and esters The homopolymer or copolymer may be polyethylene, polymethyl methacrylate, polystyrene, polybutadiene, polyvinyl acetate, vinyl polypropionate, copolymer of methyl methacrylate and styrene, copolymer of methylene and methacrylate methyl styrene, polyallyl phthalate, polypropylene, styrene butadiene copolymer, poly methyl acrylate, vinyl acetate dibutyl maleate copolymer, vinyl acetate ethylene copolymer, and polyisobutylene. These polymers can be used singly or in mixtures with one another. The high temperature lubricant may also contain a number of further additives. These include microbiologically active ingredients and wetting agents. Particularly advantageous in lubricants according to the invention is the complete absence of silicic acid, which is usually in the form of highly-dispersive silica, and in the case of compositions containing polyphosphates, it should be used as a stabilizer. Silicic acid is undesirable as it has a negative influence on the behavior of the lubricant and the life of the tools. In the case of the known formulations, the problem of stabilizing high-temperature grease was impossible to solve by replacing silicic acid by, for example, celluloses or polysaccharides. Such mixtures had a tendency to coagulate in the aqueous suspension and then became unusable. These difficulties were eliminated. Due to the mixture according to the invention, consisting of an inorganic additive and an organic stabilizing agent. According to the invention, the high temperature lubricant should be used in the form of a 5 to 50% by weight water dispersion. This dispersion expediently has a viscosity of 500-15,000 cp at 10-30 ° C. Organic stabilizing agents already contained in the high-temperature grease may prove sufficient to achieve this viscosity of the dispersion. However, it is also possible to control the viscosity by means of thickeners or a mixture of thickeners. Of the numerous suitable thickeners, for example, water-soluble polysaccharides, alkylcelluloses, polyvinyl alcohols, polyacrylates, polyvinylpyrrolidone and, if appropriate, not minerals, such as clays. As mentioned, high temperature grease is usually used in the form of a water dispersion. These water dispersions can be applied to the tool and / or the workpiece, which can reach a temperature of 100 ° C to above 900 ° C C. Upon contact with a hot surface, the water evaporates and a uniform thickness is formed. If the use of a dispersion is inappropriate, the high temperature grease can also be used in a powdered form *. The tool and / or the workpiece, for example, are powdered, coated with grease or dragged. Lubricants according to the invention! they are especially suitable for use at temperatures around 600 ° C and above. The high thermal stability of these lubricants, and in particular the stability of the lubricant film, is achieved essentially due to the high content of inorganic additive. The high-temperature lubricant according to the invention is therefore suitable, for example, for the lubrication of tools, e.g. mandrels, core materials or dies, and for the lubrication of workpieces, e.g. Tubular sleeves or tubes, when hot-formed in so-called multiple tube mills, that is, in multiple rolling stands (6-8 stands), in continuous mills, in pilgrim mills, in the so-called in assel mills, which are such rolling stands, where three cylinders with each axis shifted by 120 ° are rolled on a tubular sleeve which, together with the mandrel, rotates around its own axis, in devices with lava flow, in rod presses or in presses for The following examples illustrate the invention in more detail. Example I. A high temperature grease was prepared with 70% by weight of water and 30% by weight of active lubricating ingredients, consisting of: 54% by weight 96% pure crystalline graphite, 11 % by weight of insoluble sodium metaphosphate (Madrell's salt), 5% by weight of borax, 10% by weight of sodium silicate (water glass with a molar ratio of SiO 2: Na 2 O = 3.3), 18% by weight of polyethylene in the form of a powder [with a purity index 70 g / 10 minutes flow according to ASTM D No. 1238-73 T], 2% by weight of alkylcellulose. This high temperature lubricant showed a viscosity of 1900 Cps, measured at 20 C according to Epprechf using Rheomat 15 devices by Contraves. This preparation showed the most favorable properties when used at a relatively low temperature of 20-250 ° C in continuous and pilgrim mills. The preparation was sprayed on a tool (eg a mandrel) with a spray device. The friction coefficient was 0.037. Example II. The high temperature grease was formulated as a dispersion in 70 wt% water. The lubricant-active ingredients corresponded to the formulation of Example 1, but 5% by weight of basic zinc tetraborate was used instead of borax. The high temperature grease had a viscosity of 2600 Cps at 20 ° C. The grease used in continuous or pilgrim mills led to an improvement in the water resistance of the applied layer and a better adhesion when used at 20-250 ° C. The friction coefficient was 0.030. Example III. For use at a temperature of 400 ° -900 ° C., a high-temperature grease was prepared in the form of a dispersion in 70% by weight; water with lubricant-active ingredients was 63%. Graphite-, 16 wt.% ittet * -sodium phosphate (MadrelPa salt), 10 wt.% borax, 10 wt.% sodium silicate and 2 wt.% alkylcellulose, which "had a viscosity of 1600 Cps at 20 ° C. At a tool temperature of 400-900 ° C, this grease was sprayed onto the tools, creating an even layer of grease During the machining of the workpiece, it was possible to observe an even course of the current draw for the rolling stand, which allows the conclusion of favorable friction conditions. The friction coefficient was 0.043. EXAMPLE IV The preparation of the formulation according to Example III was repeated, but instead of borax, the same amount of basic zinc tetraborate was introduced, and a dispersion with a viscosity of 2100 Cps at 20 ° C was obtained, as a result of which the adhesion of the lubricant to the tool was improved again. The friction coefficient was 0.030. 25 Claims 30 1. High-temperature grease for chipless hot forming metals, containing a solid lubricant and an organic product that decomposes without leaving hot, characterized in that the lubricant also contains an inorganic additive [3S in the form of a mixture of sparingly soluble or insoluble polyphosphate, a compound of boron and alkali silicate, and an organic stabilizing agent and possibly water. 2. Grease according to claim The composition of claim 1, wherein the inorganic added acid is in the form of a mixture of 0.02-25% by weight of boron compound, 0.2-98.8% by weight of polyphosphate and 1-99.6% by weight of alkali metal silicate. 3. A lubricant according to claim 1, characterized in that the polyphosphate is Madrell's or Kurrol's salts. 4. A lubricant according to claim 1 or 2, characterized in that it contains a sparingly soluble boron compound. A carbon lubricant according to claim 1, characterized in that the boron compound is mono or mixed as borax, orthoboric acid, B203, KB508-4H20 or basic zinc tetraborate. Sodium water glass or potassium water glass with a content of 21-47% SiOr 7. A lubricant according to claim 1, characterized in that the organic stabilizing agent is composed of single or mixed polyvinyl acetate, polyvinyl alcohol, polysaccharides, polyvinyl butyrates, polyvinyl butyrals, polyacrylates, polystyrenes or celluloses 8. Grease wed lug claim. A lubricant according to claim 7, characterized in that the cellulose is preferably alkyl cellulose. 142 820 T 8. A lubricant according to claim 1, characterized in that The process of claim 1, characterized in that it contains from 1 to 90% by weight of solid lubricant, preferably from 50 to 95% by weight of water. graphite, 1-50 wt.% organic product with no hot decomposition residue, 1L. Lubricant according to claim 1, replacing 10 wt.% inorganic additive and 0.2-5 wt.% organic product - 80 wt.% organic stabilizing agent. no hot decomposing residue Zakl. Graph. Radom - 131/88 85t20 copies A4 Price PLN 220 PL

Claims (10)

1. Claims 30 1. High-temperature grease for chipless hot forming of metals, containing solid lubricant and an organic product which decomposes without residue when hot, characterized in that the grease also contains an inorganic additive [3S in the form of a mixture of sparingly soluble or insoluble polyphosphate, a compound of boron and alkali metal silicate, and an organic stabilizing agent, and optionally water. 2. Grease according to claim The composition of claim 1, wherein the inorganic added acid is in the form of a mixture of 0.02-25% by weight of boron compound, 0.2-98.8% by weight of polyphosphate and 1-99.6% by weight of alkali metal silicate. . 3. Grease according to claims A method according to claim 1, characterized in that the polyphosphates are either Madrell's or Kurrol's salts. 4. Grease according to claims A compound according to claim 1 or 2, characterized in that it contains a sparingly soluble boron compound. 5. Grease according to claims The process of claim 1, wherein the boron compound is mono or mixed as borax, orthoboric acid, B203, KB508-4H20 or basic zinc tetraborate. 6. Carbide grease The method of claim 1 or 2, characterized in that the alkali metal silicate is sodium water glass or potassium water glass with the content of 21 ^ 47% SiOr 7. Grease according to claims The process of claim 1, wherein the organic stabilizing agent is polyvinyl acetate, polyvinyl alcohol, polyvinyl alcohol, polysaccharides, polyvinyl butyrals, polyvinyl butyrals, polyacrylates, polystyrenes or celluloses in admixture with each other. 8. Grease according to claims The cellulose according to claim 7, characterized in that the cellulose is preferably alkyl celluloses. 142 820 T 8 9. Grease according to claims According to claim 1, characterized in that 10. Grease according to claims A process as claimed in claim 1, characterized in that it contains from 1 to 90% by weight of solid lubricant, preferably from 50 to 95% by weight of water. graphite, 1-50 wt.% organic product with no hot decomposition residue, 1L. Lubricant according to claim 1, replacing 10 wt.% inorganic additive and 0.2-5 wt.% organic product - 80 wt.% organic stabilizing agent. no hot decomposing residue. Zakl. Graph. Radom - 131/88 85t20 copies A4 Price PLN 220 PL