Lubricant for metal forming, in particular for forming steel, and method for producing the lubricant

Abstract

The invention relates to a forming lubricant for ferrous materials, in particular for forming steel. According to the invention, the forming lubricant comprises at least one mineral having a layered structure and an agent for modifying the layered structure. Advantageously, the mineral is swollen, delaminated, and / or exfoliated by means of the modifying agent. The modifying agent is or preferably comprises a surfactant, which preferably comprises a soap and / or an amine. In one embodiment of the invention, the surfactant is a water-soluble soap, preferably an alkali or alkaline earth salt of a fatty acid, which preferably has a chain length of at least ten carbon atoms. The mineral is advantageously a layered silicate, preferably kaolin or a mineral of the mica group. The invention further relates to a process for producing the forming lubricant and a molded body coated with the forming lubricant.

Description

[0001] The invention relates to a lubricant for metal forming, in particular for forming steel, which contains at least one mineral having a layered structure and an agent for modifying the layered structure.

[0002] The invention further relates to a method for producing the forming lubricant and a metal body coated with the forming lubricant.

[0003] In the forming of ferrous materials, different forming lubricants, known from previous use, are employed depending on the forming temperature. A distinction is made between cold forming, in which the workpieces to be formed are usually inserted into the forming tool at room temperature; semi-warm forming, in which the workpieces are preheated to approximately 600–900 °C before forming; and hot forming, in which the workpieces are preheated to approximately 900–1200 °C.

[0004] Furthermore, for some years now, a warm forming process has been discussed in which the workpieces are preheated to approximately 200 - 500 °C before forming, whereby component temperatures of more than 500 °C can occur during manufacturing.

[0005] During cold forming, workpieces can heat up to temperatures exceeding 400 °C. In many cases, such heating is desirable because higher temperatures reduce the strength of the formed parts. However, a problem arises because conventional lubricants, such as soaps or waxes, lose their properties required for forming at these higher temperatures. The load-bearing capacity drops abruptly when forming temperatures approach the melting point of the forming lubricant.

[0006] Semi-hot forming and hot forming processes typically use graphite, molybdenum disulfide or metal powder lubricants.

[0007] Currently, no suitable forming lubricants exist for the aforementioned warm forming process. Lubricants commonly used for cold forming are unsuitable due to their low thermal resistance. Therefore, it is necessary to use lubricants already employed for warm or semi-warm forming. However, these lubricants are rarely used in temperature ranges below 600 °C because undesirable adhesion to the tooling and corrosion occur during processing in presses. Furthermore, molybdenum disulfide and graphite contaminate the entire working environment and are comparatively expensive.

[0008] A lubricant of the type mentioned above is known from GB 1 322 838 A, which describes a lubricant for cold forming containing a mixture of soaps and lignosulfate as well as mica.

[0009] WO 2012 / 086564 A1 discloses a lubricant for the plastic machining of metallic materials, which contains an organically modified clay mineral, which contains a cationic-organic compound between layers of a layered clay mineral in a solid content of 5 - 95 wt.%.

[0010] US 6,194,357 B1 describes a water-based lubricant containing a water-soluble inorganic salt, a homogeneously dispersed solid lubricant, a surfactant, water, and at least one homogeneously emulsified substance consisting of mineral oils, animal or vegetable oils, fats, and / or synthetic oils.

[0011] CN 107502420 A describes a powder used for wire drawing. The powder contains dibutyltin dimaleate, oil, 2,4-dimethyl-6-tert-butylphenol, NPE, glycine, betaine, mica powder, titanyl sulfate, zinc stearate, calcium stearate, nano-zirconium oxide, and deionized water.

[0012] The invention is based on the objective of creating a forming lubricant suitable for cold forming that can be used at higher temperatures than known forming lubricants.

[0013] According to the invention, this problem is solved by the forming lubricant containing a polymeric ionic film former which has a volatile amine as a counterion, wherein the modifying agent is or contains a surfactant which has a water-soluble soap comprising an alkali or alkaline earth salt of a fatty acid.

[0014] By modifying the layer structure, particularly through swelling, delamination, and / or exfoliation, it becomes possible to create a comparatively large number of individual, mutually displaceable layers within the mineral, thus giving the forming lubricant exceptionally good sliding properties. Due to the mineral's temperature resistance and pressure stability, the forming lubricant is also stable at temperatures above 400 °C, exhibits good coefficients of friction, and can therefore be used for both cold and hot forming processes.

[0015] The invention is explained in more detail below with reference to the accompanying drawings. These show: Figs. 1 and 2 schematically show the structure of a layered silicate, Fig. 3 the result of a DSC measurement of the forming lubricant, Fig. 4 chemically the structure of the forming lubricant, Fig. 5 schematically the arrangement of the forming lubricant according to the invention on a surface of a metallic workpiece, and Fig. 6 the forming behavior of the forming lubricant and of comparison materials.

[0016] In one embodiment of the invention, the mineral is a phyllosilicate, preferably kaolin or a mineral of the mica group. The phyllosilicates of the smectite, pyrophyllite, vermiculite, and mica groups have proven to be particularly suitable. Phyllosilicates are also known as sheet silicates or phyllosilicates.

[0017] Microscopically, minerals, especially phyllosilicates, are particles composed of a multilayered arrangement (stack) of individual mineral platelets and / or layers, particularly silicate platelets and / or layers. These individual mineral platelets and / or layers are, as Fig. 1 shows that they are each connected to each other by ionic interactions.

[0018] Ions are arranged between the mineral platelets, and these ions can be exchanged through suitable chemical treatment. This exchange of ions, known as intercalation, can increase the distances between the mineral platelets ("swelling") and / or, as in Fig. 2As shown, individual mineral platelets are completely detached and rearranged. The detachment of the mineral platelets is called delamination. Exfoliation occurs when, preferably at least in a proportion > 30%, particularly preferably 50%, stacks of mineral platelets have been delaminated.

[0019] The mineral, in particular the layered silicate, is advantageously produced synthetically or obtained from natural deposits. It can advantageously be formed from naturally occurring weathering products, which are found, for example, as components of various clay minerals. The average particle size of the mineral is advantageously 0–30 µm, preferably with an average particle size < 15 µm. Particle sizes between 0.1 µm and 5 µm have proven to be particularly advantageous for the formation of the forming lubricant.

[0020] In one embodiment of the invention, the aforementioned layered silicates are compounds of the oxides, hydroxides and / or hydrates of aluminium and / or magnesium with silica, wherein aluminium and magnesium can wholly or partially replace each other in these compounds.

[0021] Such layered silicates can be described with the following basic formula: xAl 2 O 3 •yMgO•zSiO 2 •nH 2 O

[0022] Examples of layered silicates that are particularly well suited for the production of forming lubricants are: Kaolinite Al 4 [(OH) 8 | Si 4 O 10 ] (2Al 2 O 3 •4SiO 2 •4H 2 O) Pyrophyllite Al 2[ (OH) 2 | Si 4 O 10 ] (2Al 2 O 3 •4SiO 2 •H 2 O) Talk Mg 3 Si 4 O 10 (OH) 2 (3MgO•4SiO 2 •H 2 O)

[0023] According to the invention, the surfactant comprises a water-soluble soap, which includes an alkali or alkaline earth salt of a fatty acid, preferably having a chain length of at least ten carbon atoms. Advantageously, the surfactant comprises an amine.

[0024] Through modification, in particular through swelling, delamination and / or exfoliation, the layers of the mineral are coated with fatty acids or other long-chain carboxylic acids (≥ C10).

[0025] Salts of palmitic acid (hexadecanoic acid, C16) or stearic acid (octadecanoic acid, C18) are well suited and cost-effective, for example.

[0026] In a preferred embodiment of the invention, the soaps are at least partially soaps of divalent metals. Suitable examples include soaps of magnesium, calcium, and / or zinc. The forming lubricant could also comprise soaps of other divalent metal ions such as Sr²⁺, Ba²⁺, Pb²⁺, and Cd²⁺.

[0027] In one embodiment of the invention, the forming lubricant comprises a metal soap, preferably calcium and / or magnesium stearate, as well as at least one stearate of monoethanolamine, triethanolamine, isopropanolamine, and / or isobutanolamine (2-amino-2-methyl-1-propanol). Unreacted, and in particular unbridged, stearate residues remaining in the coating can react with any remaining amine residues during subsequent drying (> 100 °C) to form amides. The amides have higher melting points than the originally present, unreacted stearate components.

[0028] In addition to stabilizing the exfoliated mineral platelets, the metal soap also acts as a lubricant, the lubricating function of which is caused in particular by the fatty or carboxylic acid components.

[0029] It has surprisingly been found that sufficiently good friction coefficients can be achieved even with a comparatively low metal soap content of < 20 wt.%, preferably < 15 wt.%. Furthermore, the typical melting points of the metal soaps are surprisingly not observed in the forming lubricant, presumably due to the exfoliated layered silicate, even at higher concentrations. For example, as shown in more detail below, this is illustrated by the following: Fig. 3 As shown in the DSC measurement, a film of the forming lubricant with a calcium stearate content of 30% no longer exceeds the typical melting point for calcium stearate of approximately 160 °C. From this, it can be concluded that the calcium stearate is completely or at least largely adsorbed by the exfoliated silicate components or is present in a bridging form. A corresponding chemical arrangement is shown schematically in Fig. 4 shown.

[0030] In one embodiment of the invention, the metal soap content is 10 - 35 wt.%, preferably 15 - 25 wt.%.

[0031] In one embodiment of the invention, the polymeric film former is present as a solution or dispersion. Besides its function as a lubricant, the film former imparts chemical and / or physical properties to the forming lubricant such that it forms a film on the metal, creating a coating. This is achieved, among other things, by the formation of chemical bonds at the interface with the metal. The film former is advantageously formed by at least one water-soluble and / or dispersible polymer derived from the monomers of the vinyl group, in particular by at least one polymer or copolymer of at least one ethylene, one vinyl alcohol, one styrene, and / or one acrylic acid in the form of the free acid, its alkyl esters, or its alkylene esters. The film former is preferably present as a microdispersion. It is particularly well suited for bonding the forming lubricant to a steel surface, preferably a phosphated one.

[0032] Advantageously, the polymer dispersion contains a polyethylene-acrylic copolymer and / or, to increase the hardness of the forming lubricant when applied to the ferrous material, especially steel, an acrylate. The acrylate can be present in unesterified, partially esterified, or fully esterified form, e.g., as methyl ethyl, propyl, and / or (iso)butyl esters.

[0033] It has proven particularly advantageous to provide the polyethylene-acrylic copolymer as a mixture with an acrylate dispersion, as this results in an additional interaction and thus stabilization with swollen, delaminated and / or exfoliated mineral platelets.

[0034] Furthermore, the acrylate can influence the adhesion and hardness of a layer formed by the forming lubricant on the ferrous material at low temperatures ("initial hardness"). The same applies to the hardness and toughness of the forming lubricant at higher temperatures ("final hardness").

[0035] High initial hardness can be achieved, for example, by adding a styrene-acrylic copolymer. High final hardness or toughness can be achieved, for example, by adding an acrylo-butadiene copolymer, which tends to undergo spatial cross-linking at higher temperatures. A similar effect can be achieved with other cross-linkable acrylic derivatives or copolymers that contain, for example, propylene, butylene, or isobutylene components.

[0036] The film-forming agent, which preferably bears carboxyl groups, can be in ionic and / or non-ionic form. It can be synthesized using alkali hydroxide and / or at least one amine.

[0037] In one embodiment of the invention, the ionic film-forming agents have ammonia as the counterion. Preferably, the amine used is at least a short-chain alkyl or alkanol derivative of ammonia with at most four linear carbon units (≤ C4). Monoethanolamine, triethanolamine, isopropanolamine, and / or isobutanolamine have proven to be particularly suitable for this purpose.

[0038] In a particularly preferred embodiment of the invention, the forming lubricant contains a polymer powder exhibiting particularly high hardness and / or a particularly high molecular weight (M ≥ 1,000,000). The polymer is incorporated into the coating film formed on the metal by the forming lubricant and is particularly advantageous at low to medium temperatures ≤ 400 °C.

[0039] To achieve high hardness, a powder, preferably a micropowder, consisting of various non-aromatically substituted polyamides, such as polyamide 6, polyamide 66, or polyamide 12, is suitable, preferably comprising spherical particles. For particularly demanding applications, aromatically substituted polyamides can be used, which exhibit even higher melting points and / or temperature resistance. The preferred particle size of the micropowders is approximately 0–30 µm, with a particle size of 0.1 to max. 10 µm being particularly desirable.

[0040] As a micropowder with a particularly high molecular weight (M ≥ 1,000,000), the forming lubricant expediently comprises a, preferably spherical, polyethylene micropowder, wherein, due to the better temperature stability, polyethylene with a linear (= unbranched) structure is particularly preferred, for example LLDPE (Linear Low Density Polyethylene) or UHMWPE (Ultra High Molecular Polyethylene).

[0041] The particle size of the powder is suitably 0–30 µm, with a particle size of 0.1 to max. 15 µm being preferable.

[0042] In one embodiment of the invention, the forming lubricant contains a preservative, preferably a biocide, an antifoaming agent, and / or a stabilizing agent, particularly to prevent sedimentation of components of the forming lubricant. Suitable biocides include, for example, isothiazolinone derivatives, methylisothiazolinone (MIT), chloromethylisothiazolinone (CMIT), and / or benzisothiazolinone (BIT). The antifoaming agent is preferably formed by polyether-modified siloxanes or polydimethylsiloxanes. The forming lubricant may contain alkyl or alkanol ammonium salts of long-chain acrylic acid derivatives as stabilizing agents.

[0043] In the preferred embodiment of the invention, the forming lubricant is present as a coating on the metal body.

[0044] In one embodiment of the invention, the forming lubricant contains the mineral in a proportion of 2 to 70 wt.%, preferably 10 to 50 wt.%, particularly preferably 20 to 40 wt.%.

[0045] Advantageously, it contains the modifying agent in a proportion of 5 to 50 wt.%, preferably 10 to 35 wt.%, particularly preferably 15 to 25 wt.%.

[0046] In one embodiment of the invention, the forming lubricant comprises the film former in a proportion of 10 to 60 wt.%, preferably 15 to 50 wt.%, and particularly preferably 20 to 45 wt.%. The film former is expediently composed of at least 1 / 4 wt. of polyacrylate, at least 1 / 4 wt. of polyethylene-acrylic copolymer, and / or at least 1 / 4 wt. of polyamide.

[0047] Advantageously, the ratio of the weight fractions of the mineral, in particular the layered silicate, and of the modifying agent, in particular the metal soap, is between 0.2 : 1 and 1.8 : 1, preferably between 0.4 : 1 and 0.8 : 1.

[0048] The forming lubricant expediently contains the aforementioned powder in a proportion of 0 to 50 wt.%, preferably 5 to 40 wt.%, particularly preferably 10 to 30 wt.%.

[0049] In one embodiment of the invention, the forming lubricant is formulated as a liquid coating agent intended for application to the metal body, preferably to form a coating on the body, and preferably being a dispersion of the forming lubricant. The coating agent, preferably liquid, expediently contains the forming lubricant in a concentration of 2 to 70 wt.%, preferably 5 to 60 wt.%. The continuous phase of the coating agent is expediently formed by an aqueous liquid, preferably water, or an organic liquid.

[0050] It has proven advantageous to provide the coating material with a forming lubricant concentration of 2 to 10 wt.%, preferably 4 to 8 wt.%, when the metal is to be sprayed with or immersed in the coating material. At these concentrations, the coating material expediently has a pH value of 8.4 to 10.5, particularly preferably 8.7 to 9.5.

[0051] If the metal is coated with the forming lubricant during drawing in a die, it has proven advantageous to provide the coating agent in a forming lubricant concentration of at least 10 wt.%, preferably at least 15 wt.%. In this case, the coating agent expediently has a pH value of 10.0–13.0, and particularly preferably 10.5–11.5.

[0052] Advantageously, the metallic body is immersed in a bath of the coating material, particularly the aqueous solution, to form the forming lubricant as a coating. Alternatively or additionally, the metallic body can be sprayed or misted with the coating material, particularly the aqueous solution.

[0053] The forming lubricant according to the invention can be applied directly to the metal, in particular steel. If the forming lubricant is applied directly to a, preferably bare, i.e., uncoated, metallic surface, it has proven advantageous to clean the surface before applying the forming lubricant using an abrasive, preferably spherical, such as abrasive grains.

[0054] However, it has been shown that the best forming results are achieved when the metal has been phosphated beforehand. For this purpose, the workpieces in question are first phosphated in a commonly used phosphating solution containing zinc, calcium, magnesium and / or manganese, with a phosphate layer thickness of 6–10 g / m² being particularly preferable.

[0055] The workpieces phosphated in this way are then immersed in the aqueous dispersion of the coating according to the invention. After drying in air or in a dryer, a firmly adhering and water-resistant, thin film remains.

[0056] In the preferred embodiment of the invention, the film is formed with a coating of at least 0.25 g / m². Particularly good forming results can be achieved with a film coating of 0.5–2.5 g / m², preferably 1.0–2.0 g / m².

[0057] The production of the forming lubricant according to the invention is explained in more detail below using examples. Option A:

[0058] A mixture is prepared from 500 ml water and 500 g kaolin and / or sand-free, powdered clay. The pH of the mixture is adjusted to pH ≥ 11 using ethanolamine, and the mixture is stirred at room temperature for at least 24 hours. After adding 250 g powdered calcium stearate and approximately 0.25 g of surfactant mixture (anionic / nonionic), the mixture is kneaded and / or stirred for a further 24 hours at room temperature or at a temperature between 50 and 75 °C. The surfactant mixture is a mixture of alkali soaps and / or alkyl sulfonates and / or ethoxylates with the structural formula RO(CH₂CH₂O)xH (where R = C₁₆C₁₈ fatty alcohol, x = 18–25). Option B:

[0059] The pH of a commercially available calcium stearate dispersion, stabilized by an anionic or nonionic surfactant mixture, is adjusted to ≥ 11 by adding ethanolamine, and a sand-free, powdered clay is stirred into the calcium stearate dispersion. The dispersion is kneaded or stirred for 12 hours at room temperature or at a temperature between 50 and 75 °C.

[0060] In both variants, a surface-modified layered silicate is formed, which can be used to produce a forming lubricant, as in the examples explained below. Example 1:

[0061] An aqueous agent for forming a coating is produced from the forming lubricant, which has the following composition in wt.%: Surface modified layered silicate (kaolin / clay) 1,5 % Polyacrylate (as aqueous dispersion) 1,0 % Ethylene-acrylic copolymer (as aqueous dispersion) 1,0 % Calcium stearate 1,5 %

[0062] Ethanolamine is used to adjust the pH to 8.7–9.5, and the total solids content, or working concentration, is 5.0%. The coating compound is poured into a tray suitable for holding ring-wound, phosphated steel wire. The coating compound is heated to 50 °C. The ring to be coated can have either a bare or a phosphated surface. The bare surface can be cleaned with abrasive particles before applying the forming lubricant. The steel wire is immersed in the coating compound, then removed, and excess coating compound is allowed to drip off. It is then dried in ambient air or, preferably, in a dryer at a temperature of at least 100 °C. The forming lubricant then forms a coating on the steel wire.

[0063] The structure of a formed coating on a previously phosphated steel surface is shown schematically in cross-section in Fig. 5 shown. Exfoliated and stearate-modified layered silicate platelets 1 are embedded in a polymeric matrix 2 over the phosphate layer 3 of the steel 4.

[0064] In the case of coating a metallically bare, non-phosphated ring, the phosphate layer 3 is missing and the matrix 2 with the layered silicate platelets is arranged directly on the steel 4.

[0065] The forming lubricant formed on the wire contains 30 wt.% layered silicate, 30 wt.% calcium stearate, 20 wt.% polyacrylate and 20 wt.% ethylene-acrylic copolymer. Example 2:

[0066] The coating agent according to the invention of the first example is sprayed onto the ring of the first example using a spray nozzle in such a way that its surface is completely wetted. The excess coating agent is allowed to drip off. The workpieces or the rings are dried as in the first example. Example 3:

[0067] An aqueous coating agent with the following composition in wt.% is formed, to which a polymeric micropowder is added. Surface modified layered silicate (kaolin / clay) 3,0 % Polyacrylate (as aqueous dispersion) 2,0 % Ethylene-acrylic copolymer (as aqueous dispersion) 2,0 % Calcium stearate (as aqueous dispersion) 1,5 % Polyamide (as micro-powder) 1,5 %

[0068] The pH value of the coating agent is adjusted to pH 8.7 - 9.5 using isobutylamine; the effective concentration (total solids content) is 10.0%.

[0069] The coating material is heated to ≥ 65 °C and a wire wound into rings, as in Example 1 or Example 2, is coated. The wire can then be processed on a multi-stage press either immediately afterwards or at a later time. The forming lubricant according to this example is particularly well suited for multi-stage production at medium to high temperatures and high pressing pressures.

[0070] The forming lubricant formed on the wire contains 30 wt.% layered silicate, 15 wt.% calcium stearate, 15 wt.% polyamide, 20 wt.% polyacrylate and 20 wt.% ethylene-acrylic copolymer. Example 4:

[0071] A coating agent concentrate with the following composition in wt.% is formed, from which the coating agent according to the invention listed in the first example can be produced by dilution. Surface modified layered silicate (kaolin / clay) 12,0 % Polyacrylate (as aqueous dispersion) 8,0 % Polyethylene-acrylic copolymer (as aqueous dispersion) 8,0 % Calcium stearate (as aqueous dispersion) 12,0 %

[0072] The coating concentrate has a total solids content of 40%, although a solids content of 30–50% has proven particularly advantageous in terms of space-saving storage and ease of application. The pH value of the coating concentrate is 10.5–11.0 and is adjusted using a mixture of ethanolamine and isobutylamine.

[0073] Seven parts water are added to one part of the coating concentrate. This achieves the solids content of 5.0% specified in the first example. The pH value is checked and, if necessary, adjusted to pH 8.7–9.5 using ethanolamine. Coating and drying are carried out as in the first example.

[0074] The forming lubricant formed on the wire contains 30 wt.% layered silicate, 30 wt.% calcium stearate, 20 wt.% polyacrylate and 20 wt.% ethylene-acrylic copolymer. Example 5:

[0075] A coating agent concentrate with a solids content of 40% is prepared, to which a polymeric micropowder with a comparatively large molecular mass has also been added (values ​​in wt.%). Surface modified layered silicate (kaolin / clay) 16,0 % Polyacrylate (as aqueous dispersion) 5,0 % Acrylate styrene copolymer (as aqueous dispersion) 5,0 % Calcium stearate 8,0 % UHMW polyethylene micro-powder 6,0 %

[0076] The pH value of the coating concentrate is adjusted to 10.5–11.0 using a mixture of ethanolamine and isobutylamine. Other added additives include a preservative and a silane-based anti-setting agent at a maximum of 0.5% (based on the concentrate).

[0077] Four parts water are added to one part of the coating concentrate. The pH value is checked and adjusted to pH 8.7–9.5 using ethanolamine. This results in a solids content of 8% and the following composition in wt.%. Surface modified layered silicate (kaolin / clay) 3,2 % Polyacrylate (as aqueous dispersion) 1,0 % Acrylate styrene copolymer (as aqueous dispersion) 1,0 % Calcium stearate 1,6 % UHMW polyethylene (as micro-powder) 1,2 %

[0078] The coating and drying process is carried out as described above for the first example, whereby this composition is particularly suitable for preheating in an oven (hot forming) and for forming processes where particularly high pressure is used. Example 6:

[0079] An aqueous coating agent of the following composition in wt.% is formed, to which a polymeric micropowder and a stearic acid amide have been added. Surface modified layered silicate (kaolin / clay) 1,0 % Polyacrylate (as aqueous dispersion) 0,8 % Polyethylene-acrylic copolymer (as aqueous dispersion) 0,8 % Calcium stearate 1,0 % Distearylethylenediamide 1,8 % UHMW polyethylene micro-powder 0,6 %

[0080] The coating has a solids content of 6%. pH adjustment, coating, and drying are carried out as described for the first example.

[0081] The coating exhibits good sliding properties and enables good forming results. At low and medium temperatures, a significant reduction in the required pressing pressures can be achieved. Characterization of the forming lubricant

[0082] a) The thermal stability and melting behavior of the forming lubricant, the formation of which was described in Example 1, were tested using differential scanning calorimetry (DSC). The measurement was performed under a temperature gradient of 10 °C / min. Accordingly, the coating was heated from 25 °C to 600 °C over a period of one hour (58 min).

[0083] The DSC measurement, the result of which is in Fig. 4 The following was shown: 1. The coating remains stable up to 300 °C. A slightly negative heat signature, shown at a, is due to the glass transition temperature (Tg) of one of the film-forming agents used. A slightly positive heat signature is due to crosslinking reactions. 2. The melting points of the metal soap used (calcium stearate: at approximately 140–160 °C) and the polymeric film-forming agents (acrylate and PE-acrylic copolymer: at approximately 125–150 °C) cannot be identified or are completely unavailable. 3. A heat signature from > 300 °C to approximately 400 °C is due to the incipient decomposition of individual components of the forming lubricant, with pronounced decomposition phenomena at approximately 500–550 °C, shown at b. 4. Decomposition is not yet complete at the end of the measurement at 600 °C, marked c. 5.After the measurement, a dark grey residue of pyrolysis products remains, containing graphite and the platelets of the layered silicate.

[0084] With further temperature increases (> 600 °C), only graphite and the layered silicate remain. In this temperature range, graphite takes over the main role as a lubricant during forming, as it exhibits its optimal lubricating properties at this temperature. The thermal stability of the layered silicates exceeds 1000 °C, thus ensuring emergency or reserve lubrication even at these temperatures.

[0085] Consequently, the forming lubricant achieves sufficient lubrication in all relevant temperature ranges.

[0086] b) Forming tests have shown that the coating according to the invention, made from the forming lubricant according to the first example, has excellent sliding properties, especially under cold forming conditions, i.e. at low temperatures, and is noticeably superior to commercially available products.

[0087] The behavior was measured by forming or reducing reference test specimens at room temperature. For this purpose, previously phosphated test specimens (material: 23MnB4, as milled) coated with the inventive coating were reduced from Ø 18 mm to Ø 15 mm over a length of 100 mm. In addition to the forming lubricant according to the invention, oil / drawing grease, sodium stearate (reactive soap), and a commercially available polymer-wax forming lubricant were tested as comparison lubricants.

[0088] How Fig. 6As can be seen, it has been shown that the forming forces measured when using the forming lubricant according to the invention as described in the first example are about 30% lower than those of a drawing grease, about 20% lower than those when using sodium stearate, and at least 10% lower than those when using the commercially available polymer-wax forming lubricant.

[0089] Possible manufacturing processes extend to various applications in the field of cold and / or hot forming, and in particular to: Pulling from: Wire, tubes, hollow or solid profiles Rolling or deep drawing of: Band and sheet metal Extrusion, upsetting of: Wire or rod sections for: bolts, screws, nuts as well as more complex components such as steering columns, gears, etc.

Claims

1. Lubricant for metal forming, in particular for forming steel, comprising at least one mineral having a layer structure and an agent for modifying the layer structure, characterized in that the forming lubricant comprises a polymeric ionogenic film former having a volatile amine as counterion, where the modifying agent is or comprises a surfactant comprising a water-soluble soap comprising an alkali metal or alkaline earth metal salt of a fatty acid.

2. Forming lubricant according to Claim 1, characterized in that the mineral is swollen, delaminated or / and exfoliated by means of the modifying agent.

3. Forming lubricant according to Claim 1 or 2, characterized in that the fatty acid has a chain length of at least ten carbon atoms.

4. Forming lubricant according to any of Claims 1 to 3, characterized in that the mineral is a sheet silicate, preferably kaolin or a mineral of the mica group.

5. Forming lubricant according to any of Claims 1 to 4, characterized in that the surfactant includes an amine.

6. Forming lubricant according to any of Claims 1 to 5, characterized in that the polymeric film former is present in the form of a solution or a dispersion, where the polymer dispersion more preferably comprises a polyethylene-acrylic copolymer in order to adjust the adhesion of the mineral to the metal and / or an acrylate in order to increase the hardness of the forming lubricant.

7. Forming lubricant according to any of Claims 1 to 6, characterized in that the forming lubricant contains at least one polymeric powder, preferably microscale powder, having a proportion of 0% to 50% by weight, preferably 5% to 40% by weight.

8. Body made of metal, in particular steel, coated with the forming lubricant according to any of Claims 1 to 7.

9. Use of the forming lubricant according to any of Claims 1 to 7 for forming a metal body, in particular steel.

10. Use according to Claim 9, characterized in that the surface of the body is covered with an agent for forming a coating from the forming lubricant, preferably by dipping the body into the coating agent or / and spraying the body with the coating agent, and the forming lubricant, after application to the body, preferably forms a solid coating on the body.

11. Process for producing a forming lubricant, in particular the forming lubricant according to any of Claims 1 to 7, where a mineral having a layer structure is mixed with an agent for modifying its layer structure, characterized in that the forming lubricant is provided with a polymeric ionogenic film former having a volatile amine as counterion, where the modifying agent is or comprises a surfactant comprising a water-soluble soap comprising an alkali metal or alkaline earth metal salt of a fatty acid.

12. Process according to Claim 11, characterized in that the mineral is exfoliated by means of the modifying agent, preferably by mechanical processing, in particular under shear, preferably by kneading or / and stirring.

13. Process according to Claim 11 or 12, characterized in that the mineral is a sheet silicate, preferably kaolin or a mineral of the mica group.

14. Process according to any of Claims 11 to 13, characterized in that the mineral is a sheet silicate, preferably kaolin or a mineral of the mica group.

15. Process according to any of Claims 11 to 14, characterized in that the surfactant includes an amine.

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