DE102021111658A1 - High temperature metal forming lubricant - Google Patents

Abstract

Lubricant and its use for the hot forming of metals and method for producing pipes in an extrusion or extrusion process using the lubricant, the lubricant containing a composition of 10% by weight to 55% by weight aluminum oxide, 30% by weight % to 90% by weight of potassium phosphate, 0% by weight to 25% by weight of sodium phosphate and 0% by weight to 20% by weight of additives, with the proportions of sodium, potassium, aluminum and phosphorus in the lubricant composition, expressed as weight percent of their respective oxides, 0 wt% to 20 wt% Na ₂ O, 8 wt% to 60 wt% K ₂ O, 10 wt% to 55 wt% Al ₂ O ₃ and 8% by weight to 45% by weight P ₂ O ₅ .

Description

subject of the invention

The invention relates to a high-temperature lubricant for the hot forming of metals, such as rolling, pressing, forging, drawing or shaping. The high-temperature lubricant according to the invention can advantageously be used in particular in the production of seamless pipes by means of extrusion.

Background of the Invention

Glasses containing silicon (silicate glass) have mainly been used to date as lubricants for metal forming at very high temperatures and pressures, such as those that occur during the extrusion of steel, because they have good lubricating and thermal insulation properties.

During the extrusion of tubes, the silicate glass in powder form is applied to the inner and outer surfaces of a pre-punched hollow block of steel. This application of lubricant is also referred to as the so-called "breading". In addition, a ring or disc is formed from the silicate glass powder (so-called "press ring" or "press disc", sometimes also referred to as "cookie", "disc", or "pad") and placed in front of the die (extrusion tool) curious; excited. The glass powder melts when it comes into contact with the approx. 900 -1250 °C hot steel surface and forms a viscous hydrodynamic lubricant film, which protects the tools (inner mandrel and die) and at the same time is intended to enable the pipes to be extruded in the first place.

The high-temperature viscosity of silicate glasses is one of the most important factors in their lubricating properties. A very high viscosity is selected for the press ring, which is clamped in front of the die. The "breading" for the inner and outer surfaces of the hollow block can have the same or a slightly lower but still high viscosity.

Despite the advantageous lubricating properties of the lubricants based on silicate glass for this application, disadvantages also have to be accepted, such as residues of the silicate glass sticking to the surfaces of the manufactured workpiece, which after cooling have been removed by pickling processes with hydrofluoric acid (HF). or mixtures of hydrofluoric acid, sulfuric acid and nitric acid must be removed.

Hydrofluoric acid is a strong contact poison which leads to severe chemical burns. In addition, fluoride ions in the human body block the calcium and magnesium metabolism and inhibit important enzymes. The necessary use of hydrofluoric acid and the elimination of the silicates dissolved in it therefore represent the highest demands on occupational safety and a significant environmental impact. In addition, the pickling process is very complex. It requires the treatment of the workpiece in various acid baths one after the other, which also take up considerable spatial capacities in the case of pipes, depending on their length, and can take several hours. The silicates dissolved in the acid baths are precipitated with lime in an acid treatment plant, filtered off and then have to be disposed of.

Other lubricants are known for the hot forming of metals which do not require such pickling processes with hydrofluoric acid, but which have other disadvantages. Some of the lubricants have relatively low melting points and their viscosity is too low at the temperatures used for steel forming by means of extrusion, which is why they are not readily suitable for this application.

In the case of high-temperature applications, lubricants containing graphite are used, among other things, because graphite is particularly heat-resistant and therefore a suitable lubricant additive and, itself and in combination with mineral oils and inorganic salts, has particularly good lubricating properties. A disadvantage of lubricants containing graphite, however, is that the high carbon content can lead to carburization of the metal surface of the workpiece. This can result in defective end products with poor further processing or material properties. The result is a high level of rejects.

object of the invention

The object of the present invention was therefore to provide a high-temperature lubricant for the hot forming of metals, in particular for the extrusion of pipes, which behaves comparably well in terms of lubricating properties, melting behavior and high-temperature viscosity as the known silicate-glass lubricants, but overcomes their disadvantages , in particular the use of hydrofluoric acid to remove lubricant residues from the deformed workpiece.

Description of the invention

This object is achieved by a lubricant for the hot forming of metals, which contains a composition of 10% to 55% by weight Alumina, Al ₂ O ₃ 30% to 90% by weight Potassium phosphates, selected from orthophosphate, diphosphate, condensed phosphates and mixtures thereof, 0 wt% to 25 wt% Sodium phosphates, selected from orthophosphate, diphosphate, condensed phosphates and mixtures thereof, 0 wt% to 20 wt% Additives selected from alkali and alkaline earth metal salts of saturated and unsaturated fatty acids having 6 to 26 carbon atoms, pyrogenic silicon dioxide, phosphates of the alkaline earth metals calcium and/or magnesium,
or which is made from a solidified melt of this composition,
wherein the proportions of sodium, potassium, aluminum and phosphorus in the lubricant composition, expressed as percentages by weight of their respective oxides, 0 wt% to 20 wt% Well ₂ O 8 wt% to 60 wt% _K2O 10 wt% to 55 wt% _{Al2O3 _} 8 wt% to 45 wt% _{P2O5 _}
be.

The high-temperature lubricant according to the invention can be used as a mixture of its starting compounds (aluminum oxide, potassium phosphate, sodium phosphate, additives). In an alternative embodiment, the high-temperature lubricant is made from a solidified melt of its insert compounds. Depending on the presence of the solidified melt, it is comminuted, for example by grinding or other customary methods, in order to obtain a powdery, fine-grained, coarse-grained or granular material.

The lubricant is either fine or coarse-grained and used in a scattering or free-flowing form, e.g. for use as a breading, or in a compacted form of the particulate components with or without the addition of a binder, e.g. as a press ring or press disc.

An essential advantage of the lubricant according to the invention is that it behaves comparably well with the known silicate-glass lubricants in terms of lubricating properties, melting behavior and high-temperature viscosity. At the same time, adhesions of the lubricant on the workpiece produced can be washed off with water because at least parts of the adhesions are water-soluble, so that the adhesions can be removed with water. It is therefore not necessary to pickle the workpiece with hydrofluoric acid to remove adhesions of the lubricant from the workpiece. The use of hydrofluoric acid and the associated disadvantages of silicate glass lubricants are therefore no longer necessary.

It has been found that the advantageous lubricating properties, the melting behavior and the high-temperature viscosity of the lubricant according to the invention are essentially determined by the proportions of aluminum oxide and potassium and sodium phosphates. The additives which can also be used according to the invention have no significant or only a slight effect on the lubricating properties melting behavior and high-temperature viscosity, but they can have a beneficial effect on the handling, application and storage life of the lubricant, for example by improving flowability, reducing the risk of clumping through water absorption, etc.

In addition, the high-temperature viscosity of the lubricant according to the invention can advantageously be varied and adjusted by changing the ratio of potassium and sodium phosphates to aluminum oxide. What is surprising here is that the aluminum oxide, which is actually known as an abrasive, is essential for the positive properties of the lubricant according to the invention.

The lubricant according to the invention shows particular advantages in the extrusion of seamless pipes, in particular pipes made of stainless steel. The lubricant according to the invention also proved surprisingly advantageous in the extrusion of tubes made of nickel and titanium alloys, which, as materials that are difficult to form, place special demands on the extrusion dies and the lubricants. It was surprisingly found that, in contrast to known silicate-glass lubricants, the lubricant according to the invention exhibits increased adhesion to these materials and is therefore particularly suitable for the extrusion of tubes made of nickel and titanium alloys. Examples of nickel and titanium alloys that can advantageously be extruded with the lubricant according to the invention are the types R-Ni99.2 (DIN 17740 2.4066), NiMn2 (DIN 17741 2.4110), Ti1 - Ti3, Ti1Pd, Ti2Pd (DIN 17861), Ti3Pd (DIN 17860).

In a preferred embodiment, the lubricant according to the invention consists of a composition of 10% by weight to 55% by weight aluminum oxide, 30% by weight to 90% by weight potassium phosphate, 0% by weight to 25% by weight sodium phosphate and 0% to 20% by weight of additives or is made from a solidified melt of this composition.

In a further embodiment, the composition of the lubricant contains 0% by weight to 10% by weight of additives, preferably 0% by weight to 5% by weight of additives or no additives. The lubricant according to the invention particularly preferably contains no graphite.

In a preferred embodiment of the lubricant according to the invention, a portion or all of the potassium phosphates and sodium phosphates are selected from the group consisting of tetrasodium pyrophosphate, Na ₄ P ₂ O ₇ , tetrapotassium pyrophosphate, K4P207, sodium tripolyphosphate, Na ₅ P ₃ O ₁₀ , Potassium tripolyphosphate, K ₅ P ₃ O ₁₀ , sodium metaphosphate, (NaPO ₃ ) ₃ , potassium metaphosphate, (KPO ₃ ) ₃ , sodium polyphosphate, (NaPO ₃ ) _n and potassium polyphosphate, (KPO ₃ ) _n . Potassium phosphates can have the advantage of better solubility, lower reactivity with the metal surface and a higher melting temperature than analogous sodium phosphates.

The aluminum oxide, Al ₂ O ₃ , of the lubricant according to the invention is selected from α-Al ₂ O ₃ , γ-Al ₂ O ₃ and a mixture of both modifications, with γ-Al ₂ O ₃ being preferred, for example as a raw material with advantage usable alumina. The aluminum oxide increases the viscosity of the lubricant in the molten state, so that a sufficiently viscous lubricating film is formed and an improved lubricating effect can be achieved compared to known lubricants.

In one embodiment, the composition of the lubricant according to the invention consists of 10% to 30% by weight tetrapotassium pyrophosphate, K ₄ P ₂ O ₇ , 20% to 80% by weight Potassium tripolyphosphate, K ₅ P ₃ O ₁₀ , 0 wt% to 25 wt% Sodium tripolyphosphate, Na ₅ P ₃ O ₁₀ and 10% to 55% by weight Alumina, Al ₂ O ₃ , preferably 10% to 30% by weight tetrapotassium pyrophosphate, K ₄ P ₂ O ₇ , 30% to 70% by weight Potassium tripolyphosphate, K ₅ P ₃ O ₁₀ , ..5% by weight to 20% by weight Sodium tripolyphosphate, Na ₅ P ₃ O ₁₀ and 10% to 55% by weight Alumina, Al ₂ O ₃ , particularly preferred 15% to 25% by weight tetrapotassium pyrophosphate, K ₄ P ₂ O ₇ , 40% to 60% by weight Potassium tripolyphosphate, K ₅ P ₃ O ₁₀ , ..5% by weight to 15% by weight Sodium tripolyphosphate, Na ₅ P ₃ O ₁₀ and 15% to 55% by weight Alumina, Al ₂ O ₃ ,
where optionally 0% by weight to 20% by weight of the additives according to the invention can also be present.

In a further embodiment, the composition of the lubricant according to the invention consists of 0 wt% to 30 wt% tetrapotassium pyrophosphate, K ₄ P ₂ O ₇ , 30% to 80% by weight Potassium tripolyphosphate, K ₅ P ₃ O ₁₀ , 0 wt% to 25 wt% Sodium tripolyphosphate, Na ₅ P ₃ O ₁₀ and 10% to 55% by weight Alumina, Al ₂ O ₃ ,
where optionally 0% by weight to 20% by weight of the additives according to the invention can also be present.

In a further embodiment, the composition of the lubricant according to the invention consists of 30% to 80% by weight tetrapotassium pyrophosphate, K ₄ P ₂ O ₇ , 0 wt% to 30 wt% Potassium tripolyphosphate, K ₅ P ₃ O ₁₀ , 0 wt% to 25 wt% Sodium tripolyphosphate, Na ₅ P ₃ O ₁₀ and 10% to 55% by weight Alumina, Al ₂ O ₃ ,
where optionally 0% by weight to 20% by weight of the additives according to the invention can also be present.

The lubricant of the present invention is a solid consisting of a mixture of the particulate components of the composition or of ground, crushed or otherwise comminuted particulate components of a solidified melt prepared from the composition.

The lubricant according to the invention can be used particularly advantageously as a “press ring” or “press disk” in extrusion. In a preferred embodiment, therefore, the particulate components of the lubricant are present in a form compacted by pressing and/or using a binder to form a disc or ring.

The additives which can be used with advantage according to the invention include alkali metal and alkaline earth metal salts of saturated and unsaturated fatty acids having 6 to 26 carbon atoms. Preferred fatty acid residues are selected from the group of fatty acids consisting of caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenic acid, icosenic acid, erucic acid, nervonic acid, Linoleic acid, linolenic acid, arachidonic acid, timnodonic acid and clupanodonic acid. Salts of palmitic acid, margaric acid, stearic acid and/or arachidic acid are particularly preferred. In particular, calcium or magnesium salts of palmitic acid, margaric acid, stearic acid and/or arachidic acid are preferred.

It has been shown that the use of a fatty acid salt reduces the clumping of the components of the lubricant composition and thus the pourability can be improved. In addition, better storage stability is achieved. It is assumed that the fatty acid salt attaches itself to the grains of other components of the composition and in this way a clumping Punging of the grains is prevented or reduced, moisture is kept away from the grains and thereby the shelf life as well as the trickling and flow behavior of the lubricant is improved.

In one embodiment of the invention, the fatty acid salt is present in the composition in an amount of from 0.1 to 15% by weight, preferably from 1 to 10% by weight, particularly preferably from 3 to 7% by weight.

The additives that can be used advantageously according to the invention also include phosphates of the alkaline earth metals calcium and/or magnesium, with hydroxyapatite [Ca ₅ (PO ₄ ) ₃ OH] and/or tricalcium phosphate [Ca ₃ (PO ₄ ) ₂ ] being particularly preferred since they are inter alia improve the pourability of the composition. Monocalcium phosphate is less suitable as it causes clumping when the air is humid.

In one embodiment of the invention, the calcium and/or magnesium phosphates are contained in the composition in an amount of 0.5 to 10% by weight, preferably 1 to 5% by weight.

The additives that can be used advantageously according to the invention also include pyrogenic silicon dioxide (CAS No.: 112945-52-5 and 60842-32-2), which is also referred to as pyrogenic silica and consists entirely of amorphous silicon dioxide particles (SiO ₂ ), which are aggregated into larger units. Pyrogenic silicon dioxide is also suitable for improving the pourability of the composition.

The present invention also encompasses the use of the lubricant described herein in the manufacture of pipes, preferably seamless pipes, in the extrusion or extrusion process. Particularly preferred is the use of the lubricant in a form of the particulate components of the lubricant compacted by pressing and/or using a binder to form a disk or a ring.

The present invention also includes a method for producing pipes, preferably seamless pipes, in an extrusion or extrusion process, wherein at least one lubricant according to the invention is used for lubrication. In one embodiment of the method, the lubricant according to the invention is used in a form of the particulate components of the lubricant compacted into a disc or ring, the disc or ring preferably being clamped in front of the mold of the extrusion tool (die).

A further lubricant is expediently applied to the inner and/or outer surfaces of the hollow block of the workpiece material which has been pre-punched for the manufacture of the tube. This can be a lubricant with the same composition as the lubricant used for the compacted disc or ring. However, it is advantageous if the additional lubricant is a lubricant according to the invention with a higher proportion of potassium phosphate and/or sodium phosphate than the lubricant compacted to form a disk or a ring.

In a further embodiment of the method according to the invention, a composition is used as a further lubricant for application to the inner and/or outer surfaces of the hollow block pre-punched for pipe production, which consists exclusively of potassium phosphates, sodium phosphates or mixtures thereof and a proportion of 0 wt % to 10% by weight of additives, the potassium and sodium phosphates being selected from orthophosphate, diphosphate, condensed phosphates and mixtures thereof and the additives being selected from alkali and alkaline earth metal salts of saturated and unsaturated fatty acids having 6 to 26 carbon atoms, pyrogenic silicon dioxide, phosphates of the alkaline earth metals calcium and/or magnesium.

The potassium phosphates and/or sodium phosphates of the further lubricant are preferably selected from the group consisting of tetrasodium pyrophosphate, Na ₄ P ₂ O ₇ , tetrapotassium pyrophosphate, K ₄ P ₂ O ₇ , sodium tripolyphosphate, Na ₅ P ₃ O ₁₀ , potassium tripolyphosphate , K ₅ P ₃ O ₁₀ , sodium metaphosphate, (NaPO ₃ ) ₃ , potassium metaphosphate, (KPO ₃ ) ₃ , sodium polyphosphate, (NaPO ₃ ) _n and potassium polyphosphate, (KPO ₃ ) _n and/or the fatty acid residues of the alkali and alkaline earth metal salts the additives of the other lubricant are selected from the group of fatty acids consisting of caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenic acid, icosenic acid, erucic acid , nervonic acid, linoleic acid, linolenic acid, arachidonic acid, timnodonic acid and clupanodonic acid. The further lubricant particularly preferably consists of potassium tripolyphosphate without further additives (0% by weight) or with up to 10% by weight of additives.

The invention is explained in more detail below using examples and the description of the materials and methods used. However, the examples are not to be construed as limiting the scope of the invention.

examples

Extrusion process (experimental)

Comparative tests with lubricants according to the invention were carried out on an experimental extrusion press (horizontal design) for the production of seamless pipes, which can reach a maximum total force of 8 MN (Mega-Newton). Unless otherwise stated, a pre-drilled cylindrical stainless steel blank (hollow cylinder) of steel quality 1.4301 according to DIN 17600 with a mass of approx. 15 kg was used to manufacture the pipes. Tubes with an outside diameter×wall thickness of Ø36 mm×4 mm, Ø42 mm×7 mm or Ø47 mm×10 mm were produced from the hollow cylinder. The stretch ratio of the material achieved in the tests when extruding the tubes was about 12.5-13.7: 1 (at Ø36 mm × 4 mm), 6.8: 1 (at Ø42 mm × 7 mm) and 4.6 : 1 (at Ø47 mm × 10 mm). The maximum punch speed was approx. 50 mm/s.

Before forming and applying the lubricant, the hollow cylinder was heated in an electric furnace to a temperature of approx. 1200 °C for 2 hours. First, the hot outer lateral surface of the hollow cylinder was then coated with the lubricant by rolling it on a roller table at an angle of 5.5° to the horizontal, on which the lubricant was applied in powder form. Subsequently, the lubricant in powder form was applied to the inner surface of the hollow cylinder with a spoon. In addition to this "breading" on the outside and inside of the hollow cylinder, a dimensionally stable compression ring previously made from lubricant powder using a manual spindle press was placed in front of the die of the extrusion press. The hollow cylinder was inserted into the receiver of the extruder and formed into a tube with the ram of the extruder, guided by a mandrel inserted in the center.

A person skilled in the art can easily determine the amounts of lubricant to be used by simple tests. In the present example, approx. 240-280 g/m ² were used for the "breading" on the surfaces of the hollow cylinder and approx. 50-200 g/m 2 for the pressing ring.

During the forming, the total force to be applied (F _G ), the die force (F _M ), the frictional force (F _R ) and the punch speed (V _St ) were recorded over the punch path. 1 shows an example of the course of a force-displacement diagram for a lubricant composition according to the invention in the extrusion test described above. The frictional force (F _R ) provides information about the lubricating effect of the lubricant formulations used. The lower the frictional force, the better the lubricating effect.

Manufacturing lubricants

To produce lubricant compositions according to the invention and also comparative compositions, the powdered or crystalline components were weighed out and mixed. For some extrusion tests, the lubricant composition was premelted and then ground. For this purpose, the lubricant composition was melted in an aluminum oxide crucible in an electric furnace at 1150° C. for one hour, the melt was poured onto stainless steel rails and, after cooling and solidifying, crushed in a jaw crusher.

The following products were used for the sodium and potassium phosphates and the aluminum oxide: tetrapotassium pyrophosphate (K ₄ P ₂ O ₇ ; CAS number 7320-34-5) potassium tripolyphosphate ( _K5P3O10 ; _CAS number _13845-36-8 ) potassium polyphosphate ((KPO ₃ ) _n ; CAS number 7790-53-6) sodium tripolyphosphate (Na ₅ P ₃ O ₁₀ ; CAS number 7758-29-4) aluminum oxide (γ-Al ₂ O ₃ , CAS number 1344-28-1)

Determination of the water solubility of the lubricant

To determine the water solubility or washability of the lubricant from a metal surface, a stainless steel wire was immersed in the melt of the lubricant at 1250° C., then pulled out and the melt was allowed to solidify. The wire with the adhering solidified melt was immersed in a beaker filled with about 450 ml of water at a temperature of 60° C., the water being kept in motion by means of a magnetic stirrer. It was observed whether and in what time the solidified melt adhering to the wire was loosened or at least detached from the wire. recipes E.g. invention components Composition [% by weight] Oxides [wt%] 1 _{K4P2O7 _ _} 70.0% by weight K-Phos. 0.0% by weight Well ₂ O _{Al2O3 _} 30.0% by weight _{Al2O3 _} 39.9% by weight _K2O 30.0% by weight _{Al2O3 _} 30.1% by weight _{P2O5 _} 2 _{K4P2O7 _ _} 60.0% by weight K-Phos. 0.0% by weight Well ₂ O _{Al2O3 _} 40.0% by weight _{Al2O3 _} 34.2% by weight _K2O 40.0% by weight _{Al2O3 _} 25.8% by weight _{P2O5 _} 3 _{K4P2O7 _ _} 52.5% by weight K-Phos. 0.0% by weight Well ₂ O _{Al2O3 _} 47.5% by weight _{Al2O3 _} 29.9% by weight _K2O 47.5% by weight _{Al2O3 _} 22.6% by weight _{P2O5 _} 4 _{K4P2O7 _ _} 50.0% by weight K-Phos. 0.0% by weight Well ₂ O _{Al2O3 _} 50.0% by weight _{Al2O3 _} 28.5% by weight _K2O 50.0% by weight _{Al2O3 _} 21.5% by weight _{P2O5 _} 5 _{K5P3O10 _ _} 67.4% by weight K-Phos. 4.3% by weight Well ₂ O _{Na5P3O10 _ _} 10.2% by weight Na-Phos. 36.3% by weight _{K2O K4P2O7 _ _} 19.4% by weight _{Al2O3 _} 19.4% by weight _{Al2O3 _ Al2O3 _} 3.0% by weight additive 37.0% by weight _{P2O5 _} mg stearate 6 _{K4P2O7 _ _} 55.0% by weight K-Phos. 0.0% by weight Well ₂ O _{Al2O3 _} 45.0% by weight _{Al2O3 _} 31.4% by weight _K2O 45.0% by weight _{Al2O3 _} 23.6% by weight _{P2O5 _} 7 _{K4P2O7 _ _} 58.8% by weight K-Phos. 0.0% by weight Well ₂ O _{Al2O3 _} 41.2% by weight _{Al2O3 _} 33.5% by weight _K2O weight wt. 41.3 wt% _{Al2O3 _} 25.2% by weight _{P2O5 _} 8th _{K5P3O10 _ _} 80.0% by weight K-Phos. 0.0% by weight Well ₂ O _{Al2O3 _} 20.0% by weight _{Al2O3 _} 45.6% by weight _K2O weight 20.0% by weight _{Al2O3 _} 34.4% by weight _{P2O5 _} 9 _{K5P3O10 _ _} 85.0% by weight K-Phos. 0.0% by weight Well ₂ O _{Al2O3 _} 15.0% by weight _{Al2O3 _} 48.5% by weight _K2O 15.0% by weight _{Al2O3 _} 36.5% by weight _{P2O5 _}
K-Phos = potassium phosphates; Na-Phos.: Sodium phosphate formulations Example comparison components Composition [% by weight] Oxides [wt%| P1 _{K5P3O10 _ _} 97.0% by weight K-Phos. 0.0% by weight Well ₂ O mg stearate 3.0% by weight additive 50.9% by weight _K2O 0.0% by weight _{Al2O3 _} 46.1% by weight _{P2O5 _} p2 _{Na3P3O9 _ _} 100% by weight Na-Phos 30.4% by weight Well ₂ O 0.0% by weight _K2O 0.0% by weight _{Al2O3 _} 69.6% by weight _{P2O5 _} P3 _{K5P3O10 _ _} 100.0% by weight K-Phos. 0.0% by weight Well ₂ O 52.5% by weight _K2O 0.0% by weight _{Al2O3 _} 47.5% by weight _{P2O3 _} V1 (KPO ₃ ) _n 78.7% by weight K-Phos. 0.0% by weight Well ₂ O _{Fe2O3 _} 21.3% by weight _{Fe2O3 _} 31.4% by weight _K2O 0.0% by weight _{Al2O3 _} 47.3% by weight _{P2O5 _} v2 (KPO ₃ ) _n 85.3% by weight K-Phos. 0.0% by weight Well ₂ O _{Al2O3 _} 14.7% by weight _{Al2O3 _} 34.1% by weight _K2O 14.7% by weight _{Al2O3 _} 51.3% by weight _{P2O5 _} V3 (KPO ₃ ) _n 82.2% by weight K-Phos. 0.0% by weight Well ₂ O _{Al2O3 _} 17.8% by weight _{Al2O3 _} 32.8% by weight _K2O 17.8% by weight _{Al2O3 _} 49.4% by weight _{P2O5 _} V4 _{Na3P3O9 _ _} 70.0% by weight Na-Phos. 21.3% by weight Well ₂ O (NaPO ₃ ) _n 30.0% by weight _{Al2O3 _} 0.0% by weight _{K2O Al2O3 _} 30.0% by weight _{Al2O3 _} 48.7% by weight _{P2O5 _} V5 _{Na3P3O9 _ _} 18.0% by weight K-Phos. 12.8% by weight Well ₂ O (NaPO ₃ ) _n 42.0% by weight Na-Phos. 21.0% by weight _{K2O K4P2O7 _ _} 40.0% by weight _{Al2O3 _} 18.0% by weight _{Al2O3 _ Al2O3 _} 48.2% by weight _{P2O5 _}
K-Phos = potassium phosphates; Na-Phos.: Sodium phosphate water solubility sample Water solubility test stainless steel wire 1 completely dissolved/washed off after approx. 4-5 min 3 completely dissolved/washed off after approx. 4-5 min V1 no solubility; Attempt stopped after 2 hours v2 no solubility; Attempt stopped after 2 hours V3 no solubility; Attempt stopped after 2 hours

Results of the extrusion tests

The extrusion tests were carried out as described above. The same or different lubricant compositions were used for the "breading" and the "press ring". With different lubricant compositions, a lubricant with a slightly lower viscosity was selected for the "breading" than for the "press ring". Attempt pipe dimensions Breading recipe "Press ring" recipe Excessive press force [MN] Max. friction force [MN] Stationary friction force [MN] A ∅36mm×4mm 2 ¹⁾ 3 ¹⁾ 1.8 1.0 0.5-0.3 B ∅36mm×4mm P1 ²⁾ 5 ³⁾ 1.9 1.3 0.2-0.5 C ∅47mm×10mm 7 ¹⁾ 7 ¹⁾ 0.1 0.8 0.8-0.2 D ∅42mm×6mm 9 ³⁾ 8 ³⁾ 0.9 0.5 0.15 E ∅42mm×6mm 9 ³⁾ 9 ³⁾ 0.7 0.7 0.2 f ∅36mm×4mm P3 ²⁾ P2 ³⁾ "Plug" 2.2 --- G ∅36mm×4mm P3 ²⁾ V4 ³⁾ "Plug" 2.8 --- H ∅36mm×4mm silicate glass ⁴⁾ silicate glass ⁴⁾ 1.0 "Plug" 2.1 1.1 I ∅36mm×4mm P3 ²⁾ V5 ¹⁾ "Plug" 3.0 ---
¹⁾ = pre-melted + ground
²⁾ = granules
³⁾ = powder
⁴⁾ = ground

Claims (15)

Lubricant for hot metal forming, containing a composition of 10% to 55% by weight Alumina, Al ₂ O ₃ , 30% to 90% by weight Potassium phosphates, selected from orthophosphate, diphosphate, condensed phosphates and mixtures thereof, 0 wt% to 25 wt% Sodium phosphates, selected from orthophosphate, diphosphate, condensed phosphates and mixtures thereof, 0 wt% to 20 wt% Additives selected from alkali and alkaline earth metal salts of saturated and unsaturated fatty acids having 6 to 26 carbon atoms, pyrogenic silicon dioxide, phosphates of the alkaline earth metals calcium and/or magnesium, or which is made from a solidified melt of this composition, wherein the proportions of sodium, potassium, aluminum and phosphorus in the lubricant composition, expressed as percentages by weight of their respective oxides, 0 wt% to 20 wt% Well ₂ O 8 wt% to 60 wt% _K2O 10 wt% to 55 wt% _{Al2O3 _} 8 wt% to 45 wt% _{P2O5 _} be. lubricant after claim 1 , characterized in that it consists of a composition of 10% to 55% by weight aluminum oxide, 30% to 90% by weight potassium phosphate 0% to 25% by weight sodium phosphate and 0% by weight to 20% by weight of additives or from a solidified melt of this composition. Lubricant according to any one of the preceding claims, characterized in that a proportion or all of the potassium phosphates and sodium phosphates are selected from the group consisting of tetrasodium pyrophosphate, Na ₄ P ₂ O ₇ , tetrapotassium pyrophosphate, K ₄ P ₂ O ₇ , sodium tripolyphosphate , Na ₅ P ₃ O ₁₀ , potassium tripolyphosphate, K ₅ P ₃ O ₁₀ , sodium metaphosphate, (NaPO ₃ ) ₃ , potassium metaphosphate, (KPO ₃ ) ₃ , sodium polyphosphate, (NaPO ₃ ) _n and potassium polyphosphate, (KPO ₃ ) _n . Lubricant according to one of the preceding claims, characterized in that the aluminum oxide, Al ₂ O ₃ , is selected from α-Al ₂ O ₃ , γ-Al ₂ O ₃ and a mixture of both modifications, the aluminum oxide preferably being γ-Al ₂ O is ₃ . Lubricant according to any one of the preceding claims, characterized in that the composition 10% to 30% by weight tetrapotassium pyrophosphate, K4P207, 20% to 80% by weight Potassium tripolyphosphate, K ₅ P ₃ O ₁₀ , 0 wt% to 25 wt% Sodium tripolyphosphate, Na ₅ P ₃ O ₁₀ and 10% to 55% by weight Alumina, Al ₂ O ₃ . Lubricant according to one of the preceding claims, characterized in that the composition contains 0% by weight to 10% by weight or 0% by weight to 5% by weight or no additives. A lubricant according to any one of the preceding claims, characterized in that it consists of a mixture of the particulate components of the composition or of ground, crushed or otherwise comminuted particulate components of a solidified melt prepared from the composition. Lubricant after one of Claims 6 and 7 , characterized in that the particulate components are compacted into a body in the form of a disc or ring by pressing and/or using a binder. Lubricant according to any one of the preceding claims, characterized in that the fatty acid residues of the alkali and alkaline earth metal salts are selected from among the additives from the group of fatty acids consisting of caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, behenic acid , lignoceric acid, cerotic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenic acid, icosenoic acid, erucic acid, nervonic acid, linoleic acid, linolenic acid, arachidonic acid, timnodonic acid and clupanodonic acid. Use of the lubricant according to one of the preceding claims in the manufacture of pipes, preferably seamless pipes, in the extrusion or extrusion process. Use of the lubricant after claim 10 in a form of the particulate components of the lubricant compacted into a disc or ring by pressing and/or using a binder. A method for producing pipes, preferably seamless pipes, in an extrusion or extrusion process, wherein for lubrication at least one lubricant according to one of Claims 1 until 9 is used. procedure after claim 12 , wherein the lubricant is used in a form of the particulate components of the lubricant that is compacted into a disk or a ring, the disk or the ring preferably being clamped in front of the extrusion tool (die). procedure after Claim 13 , wherein a further lubricant is applied to the inner and/or outer surfaces of a hollow block of the workpiece material which has been pre-punched for the manufacture of the pipe, the further lubricant being a) a lubricant according to one of Claims 1 until 9 with a higher proportion of potassium phosphates and/or sodium phosphates than the lubricant compacted into a disk or a ring, or b) exclusively of potassium phosphates, sodium phosphates or mixtures thereof and a proportion of 0% by weight to 10% by weight of additives, the potassium and sodium phosphates being selected from orthophosphate, diphosphate, condensed phosphates and mixtures thereof and the additives being selected from alkali and alkaline earth metal salts of saturated and unsaturated fatty acids having 6 to 26 carbon atoms, fumed silica, phosphates the alkaline earth metals calcium and/or magnesium are selected. procedure after Claim 14 , wherein the potassium phosphate and/or sodium phosphate of the further lubricant are selected from the group consisting of tetrasodium pyrophosphate, Na ₄ P ₂ O ₇ , tetrapotassium pyrophosphate, K ₄ P ₂ O ₇ , sodium tripolyphosphate, Na ₅ P ₃ O ₁₀ , Potassium tripolyphosphate, K ₅ P ₃ O ₁₀ , sodium metaphosphate, (NaPO ₃ ) ₃ , potassium metaphosphate, (KPO ₃ ) ₃ , sodium polyphosphate, (NaPO ₃ ) _n and potassium polyphosphate, (KPO ₃ ) _n and/or the fatty acid residues of the alkali and alkaline earth metal salts are selected from the additives of the further lubricant from the group of fatty acids, consisting of caproic acid, caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, margaric acid, stearic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, palmitoleic acid, oleic acid, elaidic acid, vaccenic acid, icosenic acid, erucic acid, nervonic acid, linoleic acid, linolenic acid, arachidonic acid, timnodonic acid and clupanodonic acid.

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