WO2006029934A2

WO2006029934A2 - Lubricant for lubricating heated metal objects

Info

Publication number: WO2006029934A2
Application number: PCT/EP2005/053631
Authority: WO
Inventors: Norbert Aurin; Steffen Bugner; Bernd Schneider
Original assignee: Chemische Fabrik Budenheim Kg
Priority date: 2004-09-17
Filing date: 2005-07-26
Publication date: 2006-03-23
Also published as: DE102004045128A1; WO2006029934A3

Abstract

The aim of the invention is to obtain a lubricant containing a graphite and a phyllosilicate for lubricating two heated metal objects, in mutual contact through their surfaces, moving in relation to each other. Said lubricant contains, in relation to the solid material content, at least 5 wt. % of phyllosilicate containing water but free of alkali.

Description

Lubricant for lubricating heated metal objects

The present invention relates to a lubricant for lubricating two surface-contacting heated metal objects, which perform a relative movement to each other, wherein the lubricant has a content of graphite and a content of at least one sheet silicate. Moreover, this invention relates to the use of such a lubricant in the hot deformation of metals and in particular in the manufacture of seamless pipes.

In the shaping processing of metals, in some cases considerable pressures occur on the surfaces of the metal to be processed and of the processing tool. Correspondingly high are the restraining forces of two such surface-contacting heated metal objects which perform a relative movement to one another. These restraining forces define the friction conditions between the two metal objects and significantly influence the durability of the processing tools. In addition, the friction conditions ultimately determine the surface quality of the products produced.

In the production of seamless pipes, for example, a solid steel block is heated to a specific forming temperature and rolled out into a short, thick-walled hollow body, the pipe core. This tube blank is inserted via a tool, the mandrel, and extended or forged over the mandrel without additional heat supply.

There is therefore a general need for lubricants for lubricating two heated metal objects in contact with each other in terms of area, such as, for example, a mandrel and a tube. Various lubricant compositions are known from the state of the art, which are basically suitable for lubricating two hot metal objects contacting each other in a planar manner. A large proportion of these lubricants contain graphite as an ingredient, which is also well-known as a lubricant for metal objects at ordinary ambient temperatures. A disadvantage of graphite-containing lubricants is that, in particular at high processing temperatures, carburization frequently takes place, the graphite occupying outer grid positions of the B-scale crystal (iron carbide formation), which can lead to partial embrittlement. In the further processing of the workpiece by pulling, stretching, bending, etc., the brittle material breaks at this point, and the part is unusable. The reject rate is increased, which is economically unsustainable. - -

Graphite-containing lubricants are known from the prior art, which additionally have a content of alkali-containing phyllosilicates. Thus, EP 0 745 661 discloses a graphite-containing lubricant which has a proportion of one or more clay minerals from the class of smectites. In addition, these lubricants either have a content of silica sol or potassium aluminosilicate. According to EP 0 745 661, such lubricants can largely overcome the disadvantage of the Aufkoh¬ ment of graphite-containing lubricants at relatively high operating temperatures.

Although lubricants containing both graphite and alkali-containing phyllosilicate may have less carburization in metalworking, they often require improvement in the friction ratios between the metal surfaces in order to improve the durability of the tooling tools, e.g. the mandrel rods, extend.

The object underlying this invention is therefore to provide a graphite-containing lubricant which has no carburization when lubricating two heated metal objects which contact one another in a planar manner and which move relative to one another, and the restraining forces occurring between the surfaces of the metal objects reduced in comparison to corresponding lubricants from the prior art, so as to extend the durability of the very expensive tools (eg mandrel bars).

This object is achieved by a lubricant of the type mentioned, which is additionally da¬ characterized in that the lubricant, based on the solids content, at least 5 wt .-% alkali-free hydrous sheet silicate has.

The group of alkali-free hydrous sheet silicates has the common feature that these phyllosilicate minerals are substantially free of alkali. The group of alkali-free wasserhal¬ term sheet silicates includes, inter alia, the minerals kaolinite, antigorite, halloysite, greenalite, pyrophyllite, talc, margarite, vermiculite, sudoite and chlorite.

In the context of the development work on the present invention, it has surprisingly been shown that the addition of alkali-free hydrous sheet silicate to graphite-containing lubricants positively influences the friction conditions between two heated metal objects touching each other in a planar manner, which move relative to one another, by the retention forces between the two Metal objects are reduced. This advantage is achieved from a proportion of alkali-free hydrous phyllosilicate of at least 5 wt .-%, based on the solids content of the lubricant. The reduction of the restraint forces achieved as a result was on average about 10% compared to conventional lubricants. This substantial reduction in restraining forces had an impact on the durability of the machining equipment. - -

so positive that the life of these tools increased by an average of about 20-25%.

Although it is known to add phyllosilicates to graphite-containing lubricants, only alkaline-containing mica or mica-type phyllosilicates with alkali component have hitherto been used for this purpose. The mica or micaceous sheet silicates are among the three-layer silicates. The group of three-layer silicates includes e.g. the frequently used alkaline-containing smectites (inter alia montmorillonite), which are contained, inter alia, in the bentonites as main minerals.

In preferred embodiments of the present invention, the lubricant contains at least 30% by weight of graphite, based on solids content. The graphite used can be of synthetic as well as natural origin. Preferably, the graphite content of a lubricant according to the invention is in a range of 30-90% by weight, and more preferably the graphite content is 50-80% by weight, based on the solids content. It is astonishing that even with lubricants according to this invention with relatively high graphite content no carburization could be detected on the surface of the machined metal objects. Thus, no signs of carburisation (eg cracks in the inner surface, partial embrittlement) were found on the inner surface of tubes which were processed on a mandrel which had been provided with a lubricant according to the invention, even after stretching during further processing ,

In preferred embodiments of the present invention, the lubricant comprises at least 10% by weight of phyllosilicate based on solids content. The lubricant preferably comprises 10-50% by weight of phyllosilicate, and phyllosilicate fractions, based on the solids content, of 20-40% by weight are particularly preferred. It should be noted that in some embodiments the proviso only applies that the proportion of alkali-free hydrous sheet silicate in the Gesamtschichtsili¬ catgehalt of the lubricant is at least so high that the proportion of alkali-free hydrous sheet silicate, based on the solids content of the total lubricant, at least 5 wt. -% is. In preferred embodiments, the proportion of alkali-free hydrous sheet silicate, based on the solids content of the lubricant, at least 10 wt .-%. Vor¬ preferably comprises the lubricant, based on the solids content 10-90 wt .-% alkali-free hydrous sheet silicate, wherein the lubricant particularly preferably 20-60 wt .-% alkali-free hydrous sheet silicate comprises.

According to this invention, preference is given to the alkali-free hydrous sheet silicates which have single-component single layers, for example kaolinite, antigorite and halloysite. Further preferred alkali-free hydrous sheet silicates selected from the group of non-hydrated alkali-free hydrous phyllosilicates. Particularly preferred alkali-free hydrous sheet silicates - -

are the non-hydrated two-layered single layer phyllosilicates of the kaolinite-antigorite family, such as the kaolinite. Particularly preferred among the sheet silicates from the kaolinite family, the clay mineral kaolinite, an aluminum hydrosilicate of the general formula AI ₂ [Si ₂ O ₅ (OH) ₄ ]. Kaolinite is white, soft and flaky in its purest form. The two-layered kaolinite layers are not hydrated and are unfolded. Particularly characteristic of kaolinite is the great tendency for intercalation of chemical substances between the individual kaolinite layers. As a result of the condensation of the Al (OH) ₃ layers, the unfolded silicate layers are particularly stabilized. In this case, the hydrated aluminum ions act in principle as very large ions.

Kaolinite is obtained either by slaking the clay kaolin or synthetically from polysilicic acid and aluminum hydroxide. Since kaolins consist predominantly of the mineral kaolinite (about 88%), kaolin is used instead of pure kaolinite in some embodiments, i. that the proportion of kaolinite, based on the solids content, is achieved by a correspondingly higher addition of kaolin. In other embodiments, both kaolinite and kaolin are used in appropriate amounts. The same applies to synthetically produced kaolinite, i. in that preferred lubricants according to the present invention are additionally characterized by comprising kaolin or synthetically produced kaolinite. The advantage of using the kaolin clay is the lower cost of the raw material. In contrast, the higher purity of the mineral kaolinite or the highest possible purity of the synthetically produced kaolinite may be desired for the purpose of a more exact reproducibility of products of uniform quality. In particularly preferred embodiments, the lubricant according to the invention comprises both kaolin and synthetically produced kaolinite.

Further embodiments of the invention are additionally characterized in that they comprise at least one thickener. Preferably, the at least one thickener is a bentonite, among which particularly smectites are preferred among the bentonites, and montmorillonite is particularly preferred among the smectites. The proportion of the thickener or the thickener to the lubricant, based on the solids content, preferably about 1-10 wt .-%.

A particularly preferred specific embodiment of the present invention comprises, based on the solids content, at least 50-79% by weight of graphite, 20-40% by weight of kaolinite and 1-10% by weight of thickener.

In addition, preferred embodiments of the invention comprise at least one alkali metal thophosphate, particular preference being given to those alkali metal phosphates which are selected from trisodium, tripotassium or trilithium orthophosphate. The addition of alkali orthophosphates is well known in the art, and for the purposes of this invention, preferably comprises 0.5-15% by weight, based on the solids content of the lubricant. Particularly preferred is the - -

Alkali orthophosphate content in the range of 1-10% by weight, based on the solids content of the lubricant, and more preferably in the range of 1-7.5% by weight. These proportions in specific embodiments of various alkali metal orthophosphate zusammenset¬ zen.

The lubricants according to the invention can be used wherever, at high temperatures, two metal objects in contact with one another flatly make a relative movement relative to one another. These include e.g. also roller cages for plain bearings, where elevated temperatures can occur. However, the lubricants according to the invention are preferably used in contact with one another on flat metal objects, one of which is a tool and another is a workpiece. For this purpose, it is particularly expedient if the lubricant according to the invention is in the form of an aqueous solution or dispersion or suspension. The solids content of such a solution or dispersion / suspension is preferably 25-35% by weight.

The aqueous preparation of a lubricant according to the invention can, for example, be applied to the tool (for example a mandrel bar), the lubricant forming a fine separating and lubricant film after evaporation of the water.

Basically, the inventive concept is suitable for the lubrication of any metal objects, but is preferably used in the hot deformation of metals, preferably at working temperatures of about 700-1300 ⁹ C. Particularly preferred lubricants according to the invention for lubricating mandrel bars or lumps in the production of seamless Metal tubes used. Under metal pipes are understood here, for example, tubes made of non-ferrous metals, aluminum or the like. Particularly preferred is the use of lubricants according to the invention in the production of seamless steel tubes at working temperatures of about 1000-1300 ⁰ C.

A lubricant according to the present invention is particularly useful in the processing of heated metal articles in an Assel mill as well as in the impact bench process and in the processing with a pilger skeleton. Even when continuous rolling clear advantages in terms of surface quality, the service life of the mandrels and the force between the Walzgerü¬ costs achieved, it is irrelevant whether the rolls with free thorns, according to the "semi-floating" principle, the MPM Method (MPM = Multiple Purpose MiII) or the PQF method (PQF = Premium Quality Finishing).

Further advantages and features of the present invention will become apparent from the following examples. - -

EXAMPLE 1

From a lubricant of the composition

60% by weight graphite

36% by weight of kaolinite

4% by weight ⁽ % thickener

A 30% aqueous suspension was prepared. The graphite used in this example was a natural graphite having a purity of> 98% and an average particle size of 6 μm. The kaolinite used was obtained by kaolin slurry (kaolin EGS 80, Erbslöh). The thickener used was a modified bentonite (Optigel WM, Süd-Chemie).

The 30% aqueous suspension of the above composition was sprayed on the about 80 ⁹ C hot mandrels of a MPM (Multiple Purpose MiII). After evaporation of the carrier liquid, the tubes were rolled. The case determined restraining forces were 85 to at a 1150 ⁰ C block temperature. The durability of the spikes was 2000 pipes.

EXAMPLE 2

From a lubricant of the composition

60% by weight of graphite

31% by weight of kaolin

4% by weight of thickener

5% by weight K ₃ PO ₄

a 30% aqueous suspension was prepared. The graphite used and the thickener used corresponded to the substances mentioned in Example 1. The kaolin used was a white kaolin with a kaolin content of 88% by weight (kaolin EGS 80, Erbsloh). K ₃ PO ₄ was from Chemische Fabrik Budenheim KG.

A 30% aqueous suspension of the above composition was sprayed onto the approximately 80 ° C mandrels of a Multiple Purpose MiII (MPM). After evaporation of the carrier liquid, the tubes were rolled. The retention forces were 80 to 1 150 ⁹ C. The durability of the spikes was 2050 tubes.

COMPARATIVE EXAMPLE 1 (Prior Art)

From a lubricant according to EP 0 745 661 with the composition

60% by weight graphite 36% by weight potassium aluminosilicate (Mica G, Aspanger), particle size d ₅₀ = 6.5 μm)

4% by weight of thickener

A 30% aqueous suspension was prepared. The graphite used and the thickener used corresponded to the substances mentioned in Example 1.

The inventive 30% aqueous suspension of the above composition was sprayed onto the about 80 ⁹ C hot mandrels of a MPM (Multiple Purpose MiII). After evaporating the carrier liquid, the tubes were rolled. The retention forces determined in this case were 95 tons at a 1 150 ° C block temperature. The durability of the spikes was 1775 tubes.

Claims

- PATENT APPLICATIONS

1 . Lubricating agent for lubricating two heated metal objects contacting each other in a planar manner, which move relative to each other, wherein the lubricant has a content of graphite and a content of at least one sheet silicate, characterized in that the lubricant, based on the solids content, has at least 5 wt .-% alkali-free hydrous sheet silicate.

2. Lubricant according to claim 1, characterized in that, based on the solids content, at least 30% by weight of graphite, preferably 30-90% by weight of graphite and particularly preferably 50-80% by weight of graphite includes.

3. A lubricant according to claim 1 or 2, characterized in that it, based on the solids content, at least 10 wt .-% phyllosilicate, preferably 10 - 50 wt .-%

Phyllosilicate, and more preferably 20-40% by weight of phyllosilicate.

4. A lubricant according to any one of claims 1 to 3, characterized in that it, based on the solids content, at least 10 wt .-%, preferably 10 - 50 wt .-% and particularly preferably 20 - 40 wt .-% alkali-free hydrous phyllosilicate comprises.

5. A lubricant according to any one of claims 1 to 4, characterized in that it wenig¬ least one alkali-free hydrous sheet silicate from the group kaolinite, antigorite, Halloy- sit, greenalite, pyrophyllite, talc, margarite, vermiculite, sudoite and chlorite, preferably kaolinite and / or antigorite.

6. A lubricant according to any one of claims 1 to 5, characterized in that at least one alkali-free hydrous sheet silicate from the group of alkali-free hydrous sheet silicates is selected with a single-layer and / or at least one alkali-free hydrous sheet silicate from the group of non-hydrated alkali-free wasserhal¬ selected phyllosilicates is selected.

7. A lubricant according to any one of claims 1 to 6, characterized in that it additionally comprises at least one thickener, wherein the at least one thickener is preferably a bentonite, particularly preferably a smectite, and particularly preferably montmorillonite and, based on the solids content, is preferably contained in a content of about 1-10% by weight in the lubricant. - -

8. A lubricant according to any one of claims 1 to 7, characterized in that it comprises, based on the solids content, at least 50 - 79 wt .-% graphite, 20 - 40 wt .-% kaolinite and 1 - 10 wt -.% Thickener ,

9. Lubricant according to one of claims 1 to 8, characterized in that it additionally comprises at least one alkali metal phosphate, preferably at least one alkali metal orthophosphate and particularly preferably comprises at least one alkali metal phosphate selected from trisodium, tripotassium or trilithium orthophosphate ,

10. A lubricant according to claim 9, characterized in that, based on the solids content, a content of 0.5 to 15 wt .-%, preferably from 1 to 10 wt .-% and particularly preferably from 1 - 7.5% by weight alkali phosphate.

1 1. Lubricant according to one of claims 1 to 10, characterized in that it is in the form of an aqueous suspension, preferably having a solids content of 20-35

% By weight.

12. Use of a lubricant according to any one of claims 1 to 1 1 in the Heißverfor¬ tion of metals, preferably at working temperatures of about 700-1300 ° C, and more preferably at operating temperatures of about 1000 - 1300 ° C.

13. Use of a lubricant according to any one of claims 1 to 12 for lubricating mandrel bars or billets in the manufacture of seamless metal pipes, preferably in the manufacture of seamless steel pipes.