EP0909309A1

EP0909309A1 - Lubricant and use thereof

Info

Publication number: EP0909309A1
Application number: EP97927005A
Authority: EP
Inventors: Norbert Aurin
Original assignee: Chemische Fabrik Budenhiem KG
Current assignee: Chemische Fabrik Budenhiem KG
Priority date: 1996-07-02
Filing date: 1997-06-11
Publication date: 1999-04-21
Anticipated expiration: 2017-06-11
Also published as: ES2165063T3; DE19780631D2; EP0909309B1; DE59704881D1; WO1998000483A1; ATE206745T1; AU3165297A; US6177386B1

Abstract

The invention relates to a lubricant which can be used as a mandrel lubricant with a content of 75 to 90 wt. % of graphite and contains 1 to 10 wt. % of a phosphate. Said lubricant can also contain 1 to 4 wt % alkali silicate, 1 to 10 wt. % bentonite, 0.5 to 1 wt. % silico-phosphate and common solid lubricants. Said lubricant is preferably used as an aqueous suspension with a solid content of 20 to 40 wt. %.

Description

Lubricant and its use

Lubricants used in the hot forming of metals have long been known. Such lubricants consist for example of mixtures of graphite and mineral oil. Such mixtures decompose at the usual application temperatures of 1100 to 1300 ° C and result in a strong environmental impact.

Lubricants that are used in the manufacture of seamless tubes for the lubrication of the so-called mandrel bars must meet special requirements and therefore consist of graphite and mixtures of substances that provide these special properties. For example, DE-B-2 350 716 describes a high-temperature lubricant made from 10 to 90% graphite, 2 to 60% alkylene polymer or copolymer, 0.2 to 8% suspension aid and 2 to 40% film stabilizer. EP-A-0 554 822 describes a lubricant which, in addition to graphite, contains one or more clay minerals from the smectite class, polysaccharide and a nonionic surfactant.

Overall, the previously known lubricants contain, in addition to graphite, organic and thus decomposable substances and / or additives which heavily contaminate the wastewater that arises later, for example through sludge formation, and thus represent a great environmental burden.

The object on which the invention is based was therefore to obtain a lubricant which, in particular, can be used as a mandrel lubricant, which, in addition to graphite, contains essentially no organic substances which can be carbonized as far as possible and has as little environmental damage as possible with regard to the wastewater pollution.

According to the invention, this object is achieved with a lubricant with a content of 75 to 90% by weight of graphite, which is characterized in that it contains 1 to 10% by weight of phosphates.

The advantage of the lubricants according to the invention over those according to the prior art, in particular over dome lubricants, can be seen in the fact that they need not contain any organic substances and preferably do not contain any organic substances at all, so that the graphite is the only decomposable component. They therefore preferably contain only inorganic substances. Graphite, which has the main lubricating effect of such lubricants, consists of pure carbon, which burns at high application temperatures in an oxygen-containing environment, producing carbon dioxide, which creates a gas cushion on which the first

REPLACEMENT BLART (RULE 26) Line based on the separation of tube and mandrel bar.

The other ingredients of the lubricant have the task of producing a uniform lubricating film, causing the lubricating film to dry quickly and avoiding damage to the mandrel rod or the inner surface of the pipe. According to the invention, these objects are primarily achieved by the phosphates, which form a low-viscosity, reactive melt at the high application temperatures, which is able to dissolve scale and similar impurities and thus to avoid their harmful effect.

The lubricants according to the invention preferably contain 85 to 90% by weight of graphite and advantageously 3 to 5% by weight of phosphates.

It is particularly expedient to use a phosphate mixture of tetrasodium diphosphate, primary zinc orthophosphate, primary manganese orthophosphate, disodium dihydrogen diphosphate and potassium polyphosphate as phosphates in the lubricant according to the invention. This phosphate mixture advantageously contains 25 to 50, preferably 33 to 43% by weight of tetrasodium diphosphate, 1 to 20, preferably 3 to 11% by weight of primary zinc orthophosphate, 0.5 to 20, preferably 1 to 10% by weight of primary manganese orthophosphate, 2 to 25 , preferably 5 to 15% by weight disodium dihydrogen diphosphate and 8 to 35, preferably 15 to 25% by weight potassium polyphosphate. A phosphate mixture fine-tuned for this purpose contains about 38% by weight of tetrasodium diphosphate, about 7% by weight of primary zinc orthophosphate, about 5% by weight of primary manganese orthophosphate, about 10% by weight of disodium dihydrogen diphosphate and about 20% by weight of potassium polyphosphate.

Advantageously, the phosphate mixture added to the lubricant as phosphates additionally contains 5 to 25, preferably 10 to 20% by weight of boric acid and / or 0.5 to 15, preferably 1 to 10% by weight of hydroxyapatite. The finely tuned phosphate mixture listed above appropriately contains about 15% by weight of boric acid and about 5% by weight of hydroxyapatite.

In addition to the 1 to 10% by weight of phosphates, in particular the preferred phosphate mixture given above, and the 95 to 90% by weight of graphite, the lubricant according to the invention advantageously also contains 1 to 4, preferably 2 to 2.5% by weight of alkali silicate, in particular sodium disilicate , and / or 1 to 10, preferably 4 to 6% by weight of bentonite, preferably commercial bentonite 34 with 6 m ² / g BET surface area, and / or 0.5 to 1, preferably 0.7 to 0.9% by weight. % Silicophosphate, which enhance the effect of the phosphate mixture described above. The latter percentages relate to the total weight of the solids content of the lubricant according to the invention, while the percentages of the phosphate Mixtures including those of boric acid and hydroxyapatite refer to the total solids weight of the phosphate mixture alone.

Any graphite customary for lubricants, natural or synthetic graphite, expediently one with high crystallinity and an ash content below 5% can be used as graphite. As sodium silicate, one with a ratio of SiO ₂ : Na ^ -O of 2 is expediently used. The silicophosphate used advantageously contains about 22% SiO ₂ and about 54% P ₂ 0 ₅ .

The mandrel lubricants according to the invention are preferably used as aqueous suspensions with a solids content of 20 to 40% by weight, preferably 25 to 35% by weight. The lubricant is applied in the usual way by spraying the suspension onto the mandrel bar after it has left the cooling bath and is transported back to the rolling process.

The lubricants according to the invention can advantageously also contain customary solid lubricants, such as calcium fluoride, cryolite, antimony trioxide, molybdenum sulfide, zinc pyrophosphate, boron nitride or iron III pyrophosphate.

The unexpected effectiveness of the lubricant additives or lubricants according to the invention has been tested in a large number of investigations and trials. By applying a lubricant according to the invention to the mandrel head, there is no longer any danger of getting stuck and up to 50 blocks can be rolled over a mandrel. In contrast, punching high-alloy steel by cross rolling over a mandrel used to cause significant failures because it was often impossible to remove the mandrel that was seized in the tube. Even if this was successful, the mandrel wear was so high that on average only 3.8 blocks could be rolled over one mandrel.

Even with the so-called pilger rolling of austenitic pipes from the pre-drilled blocks, there are considerable advantages with the lubricant according to the invention. The technical process consists in that a long, initially cold mandrel of uniform thickness is fed into a previously perforated, glowing bob. This is then carried through the pilgrim rolling mill with the slug in the pilgrim step, ie alternately forwards and backwards. There, with the help of eccentrically shaped rollers, a kind of rolling and forging process is carried out, which forms a seamless tube step by step, which is rolled over the entire length of the pilgrim mandrel. This creates pipes of considerable length. Out of these, the meanwhile thorn that has become glowing can be pulled out again. In the prior art, this was often unsuccessful, so that the finished tube had to be welded off the mandrel and destroyed in the process. If separation was successful, the required separation pressure was very high, on average 200 atm. When lubricating the mandrels with the lubricants according to the invention, which are applied as a viscous solution, the required separation pressure drops on average to 20, at most to 60 atm. The thorns no longer get stuck.

Very good successes have also been achieved in the manufacture of seamless tubes on the push bench. Here, the heated billet is pushed by means of a bumper through a system of continuously narrowing rings or non-driven rolling calibers, whereby the billet is reduced and stretched. The material flowing backwards should slide over the bumper as little as possible without excessive friction. It was found that the lubrication of the bumper with the lubricants according to the invention leads to very good results and that, in particular, the welds and grooves which occur with oil-graphite lubrication are eliminated.

Even in hot extrusion, for example flywheels, the application of very thin layers of the lubricants according to the invention has proven itself very well. While with oil-graphite lubrication the die made of alloy material was often quickly destroyed by cracking, so that it had to be replaced frequently, the service life of the die is doubled by the lubricant according to the invention. Only an energetic cleaning is necessary, but not a complete renewal of the mold.

The application technology advantages of the lubricants according to the invention are as follows:

- no environmental impact from decomposition products of organic ingredients,

- No sludge formation when cooling and rinsing the used Dorπstange, as z. B. is the case when using clay-containing lubricants,

- No damage to the mandrel rods or the inner surface of the tube by sanding and scoring scale particles and the like.

example 1

A lubricant according to the invention was prepared in the form of a 30% aqueous slurry, the solids content of which had the following composition: 85 parts by weight of natural graphite with 95% purity in the form of carbon

3 parts by weight of bentonite

2.5 parts by weight of sodium silicate with a ratio of Si0 ₂ : Na <> 0 of 2.0

0.8 parts by weight of a silicophosphate

8.7 parts by weight of a phosphate mixture

40 parts by weight of tetrasodium diphosphate

5 parts by weight of primary zinc orthophosphate

5 parts by weight of manganese orthophosphate

10 parts by weight of disodium dihydrogen phosphate

20 parts by weight of potassium polyphosphate

5 parts by weight of boric acid

5 parts by weight of hydroxyapatite

The mandrel bars in circulation were sprayed with the above-mentioned lubricant on an MPM line for the production of seamless steel tubes. After the water content had evaporated, the layer weight of the dry lubricant film was 60 g / m ^{2 of} the surface of the mandrel bar.

No smoldering gases were generated on contact with the hot steel during the rolling process. A suction device was not necessary.

In contrast, when using a lubricant according to the prior art, 150 mg of carbonization gas per cubic meter of exhaust air had to be disposed of.

Example 2

A lubricant according to the invention was produced in the form of a 15% by weight aqueous slurry, the solids content of which consisted of the following components:

73 parts by weight of a synthetic graphite with a purity of more than 98% carbon

3.5 parts by weight of bentonite

3.0 parts by weight of sodium silicate with a SiO ₂ : agO ratio of 2.2

0.5 part by weight of a silicophosphate with 22% by weight SiO ₂ and 54% by weight P ₂ O ₅

20 parts by weight of a phosphate mixture

35 parts by weight of tetrasodium pyrophosphate 10 parts by weight of primary zinc phosphate

5 parts by weight of manganese orthophosphate

5 parts by weight of disodium dihydrogen phosphate

15 parts by weight of potassium polyphosphate

20 parts by weight of boric acid

10 parts by weight of hydroxyapatite

On a pilgrimage route for the production of seamless pipes, the pilgrim mandrels were sprayed with an aqueous suspension of the above-mentioned lubricant. The layer weight on the mandrel bar was 20 g / m ³ before the forming process started.

After the pilgrimage process, the mandrel bar was smooth and free of scale particles. The inner tube surface was also smooth. The internal roughness of the pipes had decreased significantly. The mean value was 10 μm.

In contrast, the surface of the mandrel bar was tainted with scale particles when using a known lubricant. These particles had to be ground by hand after twelve forming processes, which represents a considerable delay in production and is to be regarded as uneconomical. The mean value of the internal roughness of the pipes was 53 μm.

Claims

Patent claims

1. Lubricant containing 75 to 90% by weight of graphite, characterized in that it contains 1 to 10% by weight of phosphates.

2. Lubricant according to claim 1, characterized in that it contains 3 to 5% by weight of phosphates.

3. Lubricant according to claim 1 or 2, characterized in that it additionally contains 1 to 4, preferably 2 to 2.5 wt.% Alkali silicate.

4. Lubricant according to claim 3, characterized in that it contains sodium silicate as the alkali silicate, advantageously with a ratio of SiO ₂ : NagO of about 2.

5. Lubricant according to one of claims 1 to 4, characterized in that it additionally contains 1 to 10, preferably 4 to 6% by weight of bentonite.

6. Lubricant according to claim 5, characterized in that it contains a bentonite with a BET surface area of 6 m ² / g.

7. Lubricant according to one of claims 1 to 6, characterized in that it additionally contains 0.5 to 1, preferably 0.7 to 0.9% by weight of silicophosphate.

8. Lubricant according to claim 7, characterized in that it contains a silicophosphate with about 22% SiO ₂ and about 54% P ₂ O ₅ .

9. Lubricant according to one of claims 1 to 8, characterized in that it contains as graphite a natural or synthetic graphite with high crystallinity and an ash content below 5%.

10. Lubricant according to one of claims 1 to 9, characterized in that it contains a phosphate ischuπg from tetrasodium diphosphate, primary zinc orthophosphate, primary manganese orthophosphate, disodium dihydrogen diphosphate and potassium polyphosphate as phosphates.

11. Lubricant according to claim 10, characterized in that it contains a phosphate mixture containing 25 to 50, preferably 33 to 43% by weight of tetrasodium diphosphate, 1 to 20, preferably 3 to 11% by weight of primary zinc orthophosphate, 0.5 to 20, preferably contains 1 to 10% by weight of primary manganese orthophosphate, 2 to 25, preferably 5 to 15% by weight of disodium dihydrogen diphosphate and 8 to 35, preferably 15 to 25% by weight of potassium polyphosphate.

12. Lubricant according to claim 10 or 11, characterized in that the phosphate mixture additionally contains boric acid and / or hydroxylapatite.

13. Lubricant according to claim 12, characterized in that the phosphate mixture additionally contains 5 to 25, preferably 10 to 20% by weight of boric acid and / or 0.5 to 15, preferably 1 to 10% by weight of hydroxyapatite.

14. Lubricant according to one of claims 10 to 13, characterized in that the phosphate mixture about 38% by weight of tetrasodium diphosphate, about 7% by weight of primary zinc orthophosphate, about 5% by weight of primary manganese orthophosphate, about 10% by weight of disodium dihydrogen diphosphate, about 20% by weight % Potassium polyphosphate, about 15% by weight boric acid and about 5% by weight hydroxylapatite.

15. Lubricant according to one of claims 1 to 14, characterized in that it is in the form of an aqueous dispersion with a solids content of 20 to 40% by weight, preferably 24 to 35% by weight, the percentages of graphite, phosphates or phosphate mixture , Alkali silicate, bentonite and silicophosphate refer to the solids content of the aqueous dispersion.

16. Lubricant according to one of claims 1 to 15, characterized in that it additionally contains at least one solid lubricant, preferably in an amount of 1 to 5% by weight.

17. Lubricant additive, characterized by a phosphate mixture consisting of 25 to 50% by weight of tetrasodium diphosphate, 1 to 20% by weight of primary zinc orthophosphate, 0.5 to 20% by weight of primary manganese orthophosphate, 2 to 25% by weight of disodium dihydrogen diphosphate and 8 to 35 % By weight of potassium polyphosphate.

18. Lubricant additive according to claim 17, characterized in that it contains 33 to 43% by weight of tetrasodium diphosphate, 3 to 11% by weight of primary zinc orthophosphate, 1 to 10% by weight of primary manganese orthophosphate, 5 to 15% by weight of disodium dihydrogen diphosphate and 15 to 25% by weight % Contains potassium polyphosphate.

19. Lubricant additive according to claim 17 or 18, characterized in that it additionally contains 5 to 25% by weight of boric acid and / or 0.5 to 15% by weight of hydroxyapatite.

20. Lubricant additive according to claim 19, characterized in that it contains 10 to 20% by weight of boric acid and / or 1 to 10% by weight of hydroxyapatite.

21. Lubricant additive according to one of claims 17 to 20, characterized in that it consists of about 38% by weight of tetrasodium diphosphate, about 7% by weight of primary zinc orthophosphate, about 5% by weight of primary manganese orthophosphate, about 10% by weight of disodium dihydrogen diphosphate, about 20% by weight % Potassium polyphosphate, about 15% by weight boric acid and about 5% by weight hydroxylapatite.

22. Use of a lubricant according to one of claims 1 to 15 as a mandrel lubricant.