WO2002079360A1 - Lubricant blend and use of the same - Google Patents

Abstract

The invention relates to a lubricant blend containing, a) between 40 and 99.6 wt % of an oil that is liquid at room temperature or of a blend of different oils and b) between 0.4 and 10 wt. % of a wax or a blend of several waxes, the sum of the constituents totalling 100 wt. % and a residual amount, which consists of additional active ingredients or auxiliary agents, making up the 100 wt. %. The lubricant blend preferably contains a) between 40 and 84.6 wt. % of an oil that is liquid at room temperature or of a blend of different oils, b) between 0.4 and 10 wt. % of a wax or a blend of several waxes, c) between 1 and 25 wt. % of fatty acid esters and/or d) between 1 and 25 wt. % lubricant additives, whereby constituent(s) c) and/or d) together amount to at least 15 wt. %, the sum of all components does not exceed 100 wt. % and a residual amount, which consists of additional active ingredients or auxiliary agents, makes up the 100 wt. %. The invention also relates to the use of said lubricant blend for the forming, in particular the hydroforming of metal workpieces.

Description

'Lubricant mixture and its use'

The invention relates to a lubricant mixture which can preferably be used for lubrication between the workpiece and the tool in the non-cutting forming of workpieces from metals. In particular, it is suitable for external lubrication in internal high-pressure forming.

When metal workpieces are formed without cutting, a force is exerted on the workpiece, which leads to the deformation of the metal by flow processes. Examples of this are forming by pressing, cold extrusion, drawing, deep drawing and hydroforming, English called "hydroforming". (In the following, the hydroforming is abbreviated to "IHU".) These processes result in friction between the surface of the workpiece and the tool used, for example dies, stamps, drawing dies, drawing rings or drawing dies or the hollow shape at the IHU. This friction must be reduced by using suitable lubricants, as otherwise damage to the tool and workpiece, for example due to cold welding, can occur. In addition, the lubricant reduces the force and thus the energy required for the forming process.

The IHU, for which the lubricant according to the invention is particularly suitable, is a forming process in which hollow sheet metal parts are formed in a mold using a liquid medium (“pressure medium”). (See for example: Lecture by Dieter Brans: "Tribological aspects of hydroforming", Lecture event "Metalworking today and tomorrow" by the Lubricant Industry Association, Frankfurt / Main, November 2nd and 3rd, 1998, and Christian Busch, Rainer Dörfler, Wolfgang Büß and Christoph Metz: "Lubrication concepts for hydroforming workpieces and pressure fluids for the hydroforming process", lecture at the automotive working group for forming, Bad Nauheim, November 30, 1999, as well as the literature cited there. The IHU and an external lubricant that can be used for this purpose are also the subject of WO00 / 13814.)

At the IHU, a liquid pressure medium is used to build up an internal pressure in the workpiece as a hollow body. Depending on the part geometry, material properties and material thicknesses, the pressure can be between approximately 800 and approximately 10,000 bar. In addition to the pressure medium, other mechanical forces can be used, which cause additional workpiece material to flow into the forming zone. These additional forces can act in the axial or radial direction and are of the order of about 800 to about 3000 bar.

The IHU usually proceeds in the following steps (see also the lecture by Dieter Brans cited above):

1. The workpiece is placed in the open mold,

2. the hydraulic cylinders are docked,

3. the workpiece is filled with the pressure medium on the inside and then vented,

4. The required internal pressure for the forming is built up via pressure intensifiers.

5. Once the near-net shape has been reached, the internal pressure is increased to "calibration pressure" (for example up to 8000 bar), whereby the workpiece completely rests on the hollow shape of the tool;

6. The pressure is then released and the pressure medium is discharged.

During this forming, there is a relative movement between the tool and the workpiece and thus a friction between their surfaces. It is therefore necessary to apply a lubricant between the workpiece and the tool. This is also called "external lubrication" or "external lubricant" (in English as "the side lube"), while the pressure medium is also called "pressure side lube". Hydraulic oils (use limited to pressures below approximately 1500 bar because of their compressibility) or aqueous media based on water-miscible mineral oil-containing products or synthetic solutions, as are also known in the field of cooling lubricants, are suitable as pressure media.

In contrast, the present invention relates to a lubricant mixture that can be used for external lubrication. Up to now, external lubrication is known (compare the literature cited above):

1. drawing oils and drawing greases,

2. soaps on conversion layers such as phosphating or oxalizing layers,

3. sliding varnishes with graphite, molybdenum sulfide or Teflon,

4. waxes,

5. Pull foils.

These products each have different disadvantages: drawing greases can only be applied manually and are therefore not very suitable for series production. In the case of soap-covered conversion layers, a cost-intensive conversion treatment is required and the foaming behavior deteriorates when the soaps are introduced into the printing medium. Sliding varnishes lead to considerable contamination and are very difficult to remove. Wax particles can get into the print medium and block fine filters on the pressure intensifiers. Drawing films have to be applied manually and removed again and disposed of after each use and are therefore not suitable for series production due to cost reasons. Removing the external lubricant after the forming process has ended can generally be problematic.

When choosing the pressure medium and the lubricant for the external lubrication, it should be noted in particular that in practice there is an entry of external lubricants into the pressure medium and / or one Contamination of the external lubricant with the pressure medium can occur. The latter must not lead to the lubricating effect becoming insufficient. It is therefore desirable in practice if, in the event of a mixing of the pressure medium and the external lubricant, these two media separate again quickly and independently. This makes it possible to reuse the pressure medium and, if necessary, the external lubricant separately, thereby reducing costs.

The object of the present invention is to provide a new lubricant mixture which can be used in particular as external lubrication at the IHU, but also for other non-cutting forming processes. The lubricant mixture should be easy to apply and easy to remove after use by aqueous cleaners. When pressure medium is introduced into the lubricant mixture or vice versa, the two media should quickly separate from one another so that they can be used separately.

The present invention relates to a lubricant mixture comprising a) 40 to 99.6% by weight of an oil which is liquid at room temperature or a mixture of different oils and b) 0.4 to 10% by weight of a wax or a mixture of several waxes, the sum of the constituents being 100% by weight and a remaining remainder consisting of 100% by weight of further active ingredients or auxiliaries.

An “oil” is understood here to mean a substance which is liquid at room temperature, the viscosity of which is higher than that of water under the same conditions and which does not mix with water. Examples of these are mineral oils based on paraffin or naphthenic or ester oils based on natural (ie vegetable or animal) or synthetic. Mineral oils are particularly suitable. The oils preferably have a viscosity in the range from 2 to 500 mm ² / second measured at 20 ° C. according to DIN 53211. The lubricant mixture preferably contains no less than 55% by weight, in particular not less than 60% by weight and particularly preferably not less than 70% by weight of oil.

Natural waxes, modified waxes or synthetic waxes can be used as waxes. Examples are montan wax, carnauba wax or polyethylene wax. The lubricant mixture preferably contains not less than 0.4% by weight and in particular not less than 0.6% by weight of wax. The upper limit for the wax content is preferably 5% by weight, in particular 3% by weight. It can be particularly advantageous to use different wax types together, for example montan wax together with polyethylene wax.

The waxes are liquefied by the oil under the stated proportions. They improve the lubricating effect of the oil and lead to a very low coefficient of friction. Because of the liquefaction by the oil, the waxes together with the oil can be easily removed from the surfaces covered with them by conventional aqueous cleaners. In the event of accidental, but often unavoidable, entry into the print medium, there is no risk of the fine nozzles becoming blocked.

In addition to oil and wax, the lubricant mixture according to the invention preferably additionally contains one or more further components selected from fatty acid esters and lubricating additives. A preferred lubricant mixture is characterized in that it additionally contains at least one of the following two components: c) 1 to 25% by weight of fatty acid ester and / or d) 1 to 25% by weight of lubricant additives, the sum of all components being 100 Does not exceed wt .-% and a remaining remainder consists of 100 wt .-% of other active ingredients or auxiliaries.

Preferred lubricating additives are, in particular, high-performance lubricating additives (so-called “EP additives” according to the English expression “extreme pressure” additives "), which can be selected, for example, from sulfur or phosphorus-containing EP additives. Examples of these are sulfurized fatty acid esters, dialkyl trisulfides, dialkyl pentasulfides, for example" di-tert-dodecyl polysulfide ", which mainly appears to be the trisulfide, and neutralized phosphoric acid esters. Instead of these lubricating additives or together with these, the lubricant mixture can additionally contain esters if the oils mentioned above are not already ester oils. These esters can in particular be selected from fatty acid esters (where the fatty acids can have 8 to 22 carbon atoms, in particular 12 to 18 carbon atoms and can be vegetable or animal fatty acids or fatty acid mixtures) with mono- or polyvalent, in particular with polyvalent, Alcohols with 2 to 6 carbon atoms. Glycerol, trimethylolpropane or pentaerythritol are particularly suitable as alcohol components, although not every alcohol group has to be esterified. Examples include trimethylolpropane trioleate, glycerol tricaprylate and dipentaerythritol fatty acid ester.

The total amount of the fatty acid esters and / or the lubricating additives is preferably at least 15% by weight, based on the total lubricant mixture. An even more preferred lubricant mixture is thus characterized in that it a) 40 to 84.6% by weight of an oil which is liquid at room temperature or a mixture of different oils, b) 0.4 to 10% by weight of a wax or a mixture several waxes, and at least one of the following two components: c) 1 to 25% by weight of fatty acid ester and / or d) 1 to 25% by weight of lubricating additives, components c) and / or d) together comprising at least 15 Make up wt .-%, the sum of all components does not exceed 100 wt .-% and a remaining remainder consists of 100 wt .-% of other active ingredients or auxiliaries.

The lubricant mixture is preferably low in water and in particular water-free. This means that preferably no water is intentionally added to the lubricant mixture. In practice, there is a limited However, water intake cannot always be avoided. However, the lubricant mixture should not contain more than 5% by weight, preferably not more than 1% by weight and in particular not more than 0.5% by weight of water.

The lubricant mixture is preferably low in and in particular free of emulsifiers, that is to say of compounds with surface-active properties such as soaps, alkyl sulfates or sulfonates or alkoxylation products of alcohols, amines or carboxylic acids with more than six carbon atoms in the alkyl radical. Under practical conditions, this means that the lubricant mixture contains no more than 1% by weight, preferably no more than 0.5% by weight and in particular no more than 0.1% by weight of emulsifiers. In particular, no emulsifiers are preferably intentionally added to the lubricant mixture. This poverty or freedom from emulsifiers helps to ensure that the pressure medium, which in practice is frequently added to the external lubricant, is quickly separated from the lubricant mixture. This allows the lubricant mixture to be separated and the pressure medium to be recycled. Lubricant mixture entering the pressure medium does not impair its foaming behavior.

The lubricant mixture preferably contains both fatty acid esters c) and lubricating additives d). In this case, it is further preferred to limit the individual proportions of fatty acid esters and lubricating additives to the range from 5 to 20% by weight.

A very particularly preferred lubricant mixture is therefore characterized in that it a) 50 to 84.6% by weight of an oil which is liquid at room temperature or a mixture of different oils, b) 0.4 to 10% by weight of a wax or a mixture several waxes, c) 5 to 20 wt .-% fatty acid esters and d) 5 to 20 wt .-% lubricating additives, the components c) and d) together making up at least 15 wt .-%, the sum of all components 100 wt. -% does not exceed and a remaining remainder to 100 wt .-% consists of other active ingredients. With a suitable choice of oil (example a) to c)), this fulfills the criterion that the coefficient of friction (measured according to the example part) after contact with the “pressure side fluid” is less than or equal to 0.010.

The lubricant mixture can essentially only consist of these components, at least when used for the first time. After contact with the pressure medium, it cannot be ruled out that components of the pressure medium may get into the lubricant mixture.

The viscosity of the lubricant mixture can be adjusted over a wide range, so that the lubricant mixture can be liquid or pasty at room temperature (15 to 25 ° C). This makes it easier to apply to a workpiece or tool. For example, the viscosity at 20 ° C., measured according to DIN 53211, can be in the range from 10 to 5000, in particular in the range from 20 to 2000 mm ² / second. Viscosities in the range from 10 to 200 mm ² / second are preferred for spray applications. Highly viscous lubricant mixtures can be applied to the workpiece using application aids.

The lubricant mixture is preferably used for lubrication between the workpiece and the tool in the non-cutting forming of metal workpieces. In particular, the lubricant mixture is used for internal high-pressure forming as external lubrication, that is, for lubrication between the tool and the workpiece. Due to its favorable viscosity, the lubricant mixture can be applied very easily to the tool and / or the outside of the workpiece, for example by spraying, so-called "airless spraying" (i.e. spraying without the use of compressed air), dipping, rolling or brushing. It is therefore suitable for use in series production.

Should a mixture of a liquid, water-based pressure medium and the lubricant mixture occur during or after the hydroforming, the pressure medium and the lubricant mixture separate quickly and independently again from each other and can be used / reused separately. Accordingly, a preferred use is that the hydroforming is carried out using a liquid, water-based pressure medium and that after the shaping process has ended, a phase separation is carried out between the lubricant mixture mentioned and the pressure medium.

The lubricant mixture adhering to the surfaces of the tool and / or workpiece can be removed by a technically customary water-based cleaning medium after the shaping process has ended.

Table 1a:

Examples of particularly preferred lubricant mixtures according to the invention (can be produced by mixing the individual components together in the order given)

Table 1b: Examples of further lubricant mixtures according to the invention

Die Ermittlung des Coefficient of friction erfolgt nach dem sogenannten Zylindertest: Ein Zylinder (Durchmesser: 5 cm, Länge: 12 cm, Material: Stahl St 35), auf den der Kühlschmierstoff aufgetragen (manuell durch Wischen) wird, wird unter einem Druck von 800 bar 7,5-12 cm durch ein Rohr gleichen Durchmessers (Werkzeugstahl Nr. 12379) geschoben. Die resultierende Reibkraft F_r wird als Funktion der Bewegung gemessen, sie korreliert linear mit dem Reibkoeffizient (Coefficient of friction).

The coefficient of friction is determined according to the so-called cylinder test: a cylinder (diameter: 5 cm, length: 12 cm, material: steel St 35), to which the cooling lubricant is applied (manually by wiping), is under a pressure of 800 bar 7.5-12 cm through a tube of the same diameter (tool steel No. 12379). The resulting friction force F _r is measured as a function of the movement, it correlates linearly with the coefficient of friction.

F _r = CoF x R x Pi x I xp

C.o.F .: Coefficient of friction

Pi: 3.14159 ...

R: radius

I: length

print

Table 2 shows the Cof measured at half the path length. When trying to come into contact with a pressure-side lube, a dilute solution of a pressure-side lube is sprayed onto the wax-containing die-side lubes in order to simulate practical conditions.

Table 2a:

Friction coefficient of preferred lubricant mixtures according to the invention (particularly preferred: examples a) to c))

Table 2b:

Friction coefficient of the other lubricant mixtures according to the invention

Die Separierung von Die-side lube und Pressure-side lube wird in Anlehnung an DIN 51599 in Verbindung mit dem Bewertungssystem der Firma Hans Schmidt Gleittechnik („Demulgierverhalten von Bettbahnölen und Kühlschmierstoffen", erhältlich von Hans Schmidt Gleittechnik GmbH. & Co. KG, Schloßgrund 15, 96472 Rödental, Deutschland) durchgeführt. Die Ergebnisse sind in Tabelle 3 dargestellt.

The separation of die-side lube and pressure-side lube is based on DIN 51599 in connection with the evaluation system of the company Hans Schmidt Gleittechnik ("demulsification behavior of bed sheet oils and cooling lubricants", available from Hans Schmidt Gleittechnik GmbH. & Co. KG, Schloßgrund 15, 96472 Rödental, Germany) The results are shown in Table 3.

^■ Pressure-side lubes: (5% solutions each) P3-multan ^® 70-40 semi-synthetic cooling lubricant with emulsifiers (anionic / non-ionic)

P3-multan ^® 61-2 DF fully synthetic cooling lubricant without non-ionic surfactants

(The products mentioned are commercial products from Henkel KGaA)

Die-side lubes (= external lubricant): according to the invention and emulsifier-free: examples a, b and c

contains emulsifier: (not according to the invention)

Michem ^® Lube 160 (carnauba wax with emulsifier, commercial product of the company

Michelman Inc., Cincinnati, Oh, USA)

Experimental procedure:

4 parts by weight of the pressure-side lube were shaken vigorously 10 times in a test tube with 1 part by weight of the die-side lube and then left to stand.

Rating:

1: complete phase separation 2: almost complete phase separation : 3 phases: oil, aqueous solution and foam: oil and foam phase: no phase separation

Table 3: Results of the phase separation experiments

The results show that aqueous wax emulsions containing emulsifiers are unsuitable as die-side lubes and semi-synthetic cooling lubricants are less suitable than fully synthetic cooling lubricants for pressure-side lubes.

The removability was checked with cleaners in the following way: 0.2 ml each of examples a, b, c were applied to an iron strip with a surface area of 30 cm ² and stored in a drying cabinet at 65 ° C. for 24 hours. The strips were then placed in a 10 I-spray booth with 20 g / l P3-neutracare ^® 310 (Henkel KGaA), operating in water at a pressure of 2.5 bar cleaned at 65 ° C for 2 minutes and then rinsed with deionized water. The residual carbon content was less than 2 percent of the initial value in all three examples.

Claims

claims 1. Lubricant mixture containing a) 40 to 99.6% by weight of an oil which is liquid at room temperature or a mixture of different oils and b) 0.4 to 10% by weight of a wax or a mixture of several waxes, the sum of the Constituents make up 100 wt .-% and a remaining remainder consists of 100 wt .-% of other active ingredients. 2. Lubricant mixture according to claim 1, characterized in that it additionally contains at least one of the following two components: c) 1 to 25% by weight of fatty acid ester and / or d) 1 to 25% by weight of lubricant additives, the sum of all Components does not exceed 100 wt .-% and a remaining remainder consists of 100 wt .-% of other active ingredients or auxiliaries. 3. Lubricant mixture according to claim 2, characterized in that it a) 40 to 84.6 wt .-% of an oil liquid at room temperature or a mixture of different oils, b) 0, 4 to 10% by weight of a wax or a mixture of several waxes, and at least one of the following two components: c) 1 to 25% by weight of fatty acid ester and / or d) 1 to 25% by weight of lubricating additives, where the components c) and / or d) together make up at least 15% by weight, the total of all components does not exceed 100% by weight and a remaining remainder consists of 100% by weight of further active ingredients or auxiliaries. , Lubricant mixture according to one or more of claims 1 to 3, characterized in that it contains no more than 5% by weight of water. 5. Lubricant mixture according to one or more of claims 1 to 4, characterized in that it does not contain more than 1% by weight, preferably not more than 0.5% by weight and in particular not more than 0.1% by weight. Contains emulsifiers. 6. Lubricant mixture according to one or more of claims 1 to 5, characterized in that it contains both fatty acid esters c) and lubricating additives d). 7. Lubricant mixture according to claim 6, characterized in that it a) 50 to 84.6 wt .-% of an oil liquid at room temperature or a mixture of different oils, b) 0.4 to 10 wt .-% of a wax or a mixture several waxes, c) 5 to 20 wt .-% fatty acid esters and d) 5 to 20 wt .-% lubricating additives, the components c) and d) together making up at least 15 wt .-%, the sum of all components 100 wt. -% does not exceed and a remaining remainder to 100 wt .-% consists of other active ingredients. 8. Lubricant mixture according to one or more of claims 1 to 7, characterized in that it is liquid or pasty at room temperature. 9. Use of a lubricant mixture according to one or more of claims 1 to 8 for lubrication between workpiece and tool in the non-cutting forming of workpieces made of metal. 10.Use according to claim 9, characterized in that the non-cutting forming is an internal high pressure forming and that the lubricant mixture is used for lubrication between tool and workpiece. 11. Use according to one or both of claims 9 and 10, characterized in that the lubricant mixture is applied to the tool and / or to the outside of the workpiece by spraying, airless spraying, dipping, rolling or brushing. 12. Use according to claim 11, characterized in that the hydroforming is carried out using a liquid, water-based pressure medium and that after the shaping process has ended, a phase separation between said lubricant mixture and the pressure medium is carried out. 13. Use according to one or more of claims 9 to 12, characterized in that, after the shaping process has ended, said lubricant mixture is removed from the workpiece and / or the tool with the aid of a water-based cleaning medium.