ES3018153T3 - One-step pretreatment method of metallic substrates for metal cold forming - Google Patents

Abstract

The present invention relates to a method for the pretreatment of a metal substrate for a subsequent cold metal forming process. Said method comprises at least steps (1) and (2) and optionally step (3), namely providing at least one substrate with at least one surface composed at least partially of at least one metal (1), contacting the at least one surface of the substrate provided in step (1) with an aqueous lubricant composition (A) with a pH value of less than 2.0 and comprising, in addition to water, oxalate anions (a1), thiosulfate anions (a2), chloride anions (a3), at least one film-forming polymer (a4), which is a homopolymer and/or copolymer that is prepared by the polymerization of at least one ethylenically unsaturated monomer, at least one wax (a5) and fluoride anions and/or bifluoride anions (a6), and optionally drying the coating film obtained after having carried out step (2), a pretreated metal substrate obtainable by the aforementioned inventive method, a method of cold forming a metal substrate including a step of subjecting the invention to a pretreated metal substrate through a cold forming process, an aqueous lubricant composition (A) as defined above, and a master batch for preparing the aqueous composition (A). (Automatic translation with Google Translate, no legal value)

Description

DESCRIPTION

One-step pretreatment method of metal substrates for cold forming of metals

The present invention relates to a method for the pretreatment of a metallic substrate for a subsequent metal cold forming process, this method comprising at least steps (1) and (2) and optionally step (3), namely providing at least one substrate having at least one surface at least partially made of at least one metal (1), contacting the at least one surface of the substrate provided in step (1) with an aqueous lubricant composition (A) having a pH value of less than 2.0 and comprising, in addition to water oxalate anions (a1), thiosulfate anions (a2), chloride anions (a3), at least one film-forming polymer (a4), which is a homopolymer and/or copolymer that is prepared by polymerization of at least one ethylenically unsaturated monomer, at least one wax (a5) and fluoride anions and/or bifluoride anions (a6), and optionally drying the coating film obtained after having carried out step (2), a substrate pretreated metal obtainable by the aforementioned inventive method, a method of cold forming a metal substrate including a step of subjecting the inventive pretreated metal substrate to a cold forming process, an aqueous lubricant composition (A) as defined above and a master batch for preparing the aqueous composition (A).

Background of the invention

Cold forming of metallic workpieces is conventionally achieved by rolling, such as thread rolling, drawing, in particular slip drawing or deep drawing, pressing, draw forming, and/or cold upsetting of the workpieces to transform them into articles having a desired shape. Cold forming usually takes place at temperatures below the recrystallization temperature of the metallic material of the workpiece subjected to cold forming, such as at temperatures below and up to 450°C. No external heat source is used in the cold forming method. Instead, any heat development or temperature increase is generally caused solely by the frictional forces between the metallic workpiece and the working tools used during forming and by internal frictional forces generated by the material flow in the workpiece. Cold forming usually results in an increase in pressure, for example, for steel, in the range of 200 MPa to 1 GPa and sometimes even up to 2 GPa. The temperature of the workpieces to be cold formed is initially at room temperature, i.e., approximately 10 to 32°C. If the workpieces are preheated before forming, for example, to a temperature in the range of 650 to 1250°C, the forming process is no longer a "cold forming" process, but rather a "semi-hot" forming, hot forming, or forging process.

If metal workpieces are cold-formed into shaped articles with a comparatively low degree of deformation, only fairly low forces are required for the cold-forming process to take place. For this purpose, conventionally non-reactive forming oils are applied to the workpieces. However, at higher degrees of deformation, at least one coating film, such as a conversion coating film, is usually applied to the workpieces before the cold-forming process. This film acts as a separating layer between the workpiece and the tools used to prevent cold welding during cold-forming. The conversion coating film used as a separating layer in this case can also act as a lubricating film if no additional coating film is applied to it. These processes are described, for example, in DE 1 179 437, DE 1 196 467 and EP 0233 503 A1: DE 1 179 437 relates to a pretreatment of iron or steel wires for subsequent cold forming. An oxalate coating is applied to the wires for this purpose. The coating is obtained using a solution containing, inter alia, oxalic acid and an alkenylphosphonic acid such as vinylphosphonic acid in monomeric form.

Document DE 1 196 467 also relates to a pretreatment of metal substrates for subsequent cold forming. For this purpose, an oxalate coating is applied to the wires. The coating is obtained using a solution containing, among other things, oxalic acid and polyvinylphosphonic acid and/or a copolymer comprising vinylphosphonic acid in the form of monomer units.

EP 0233503 A1 relates to a pretreatment method for facilitating subsequent cold forming of stainless steel substrates. For this purpose, an oxalate coating is applied to the substrate. The coating is obtained using an aqueous solution containing, among other things, oxalic acid, fluoride and nitrate anions, as well as a water-soluble polymer. The solution used is essentially free of any chloride anions and preferably free of thiosulfate anions, as the presence of these anions is undesirable according to EP 0233503 A1.

Alternatively, it is also possible and known in the prior art that not only can the conversion coating film applied onto the metal substrates be used solely at the same time as the lubricating film, but rather that an additional lubricating composition is also applied over the conversion coating film to form a lubricating film on this film in order to (further) reduce the frictional resistance between the workpiece surface and the tools and prevent the occurrence of cold welding. Different types of conversion coating films can be used for this purpose, in particular phosphate or oxalate coating films, which are applied from aqueous acidic compositions containing corresponding phosphate or oxalate. Furthermore, different types of lubricating compositions are known in the prior art. For example, aqueous lubricating compositions such as soaps or soap solutions, for example based on alkali metal or alkaline earth stearate, polymer dispersions, solid lubricants such as MoS<2> and/or graphite, and/or oil-based lubricants can be used to form the corresponding lubricating films. Processes of this type are described, for example, in EP 0 232 929 A1, WO 94/16119 A1, WO 2009/095373 A1, WO 2009/095375 A1, WO 2009/095374 A1 and JP S5672090 A.

EP 0232 929 A1 relates to a two-step pretreatment method for facilitating subsequent cold forming of stainless steel substrates. In a first step, an oxalate coating is applied to the substrate using a solution containing, among other things, oxalic acid, hydroxylammonium sulfate, and a water-soluble polymer. EP 0232929 A1 teaches that the use of chloride and fluoride anions in oxalation solutions should be avoided. In a second step, a lubricant is then applied over the oxalate coating. Metal soaps are named as suitable lubricants in EP 0 232 929 A1.

WO 94/16119 A1 describes a liquid aqueous composition for forming a conversion coating on metal surfaces in a first step for a subsequent cold forming process. The composition comprises an organic cationic polymer and may further comprise oxalate anions. In a second step, a lubricating film may be applied over the conversion film using, among others, oil-based lubricants and/or soaps.

WO 2009/095373 A1 describes a two-step pretreatment method for facilitating subsequent cold forming of metal substrates. In a first step, a phosphate layer is formed on the workpiece surface using an aqueous acid phosphating solution containing Ca, Mg, and/or K cations. In a second step, an aqueous alkaline lubricant composition containing organic polymers is applied.

Documents WO 2009/095375 A1 and WO 2009/095374 A1 describe a method for preparing metallic workpieces for cold forming. A lubricating coating layer is applied onto the metallic surface of the workpieces which optionally has a conversion coating layer as a separating layer by contacting the surface with an aqueous lubricating composition comprising at least one water-soluble, water-containing or water-binding oxide and/or silicate and an organic polymer in the case of WO 2009/095375 A1 or by contacting the surface with an aqueous lubricating composition comprising at least two waxes and an organic polymer in the case of WO 2009/095374 A1.

JP S5672090 A relates to a two-step pretreatment method for facilitating subsequent cold forming of steel substrates. For this purpose, an oxalate coating is applied to the substrates in a first step. The oxalate coating is obtained using a solution containing, among other things, oxalic acid and a water-soluble organic titanium compound, as well as polyvinylpyrrolidone. In a second step, a lubricant is applied over the oxalate coating. Metal soaps and solid lubricants are named as suitable lubricants in JP S5672090 A.

However, there are several drawbacks to the processes known in the prior art. First, both for ecological reasons and to avoid the formation of unwanted phosphorus-induced delta ferrite on the substrate, it is desirable not to use phosphate coating films as conversion coating films, such as the conversion coating films applied in the process described in WO 2009/095373 A1, but rather to use only phosphate-free systems. Regarding the lubricant compositions known in the prior art, oil-based lubricant compositions generally lead to a higher VOC content, since considerable amounts of oil can evaporate during use. Furthermore, oil-based lubricant systems can raise safety concerns, since they are flammable and must be stored at flash points >150° C as hazardous materials. For these reasons, the use of oil-based lubricant formulations is not desirable. Solid lubricants, such as MoS<2>- and/or graphite-based lubricants, are only suitable for heavy cold forming with large deformation ranges, and are therefore of limited use. Furthermore, the sulfur present in these lubricant films often has a detrimental effect, particularly on stainless steel. Therefore, the use of aqueous lubricant compositions is more desirable than solid and/or oil-based lubricants for both ecological and economic reasons.

Conventional aqueous lubricating compositions of the prior art are, however, usually alkaline compositions such as the (metallic) soaps and soap solutions described in EP 0232 929 A1, WO 2009/095373 A1, WO 2009/095375 A1, WO 2009/095374 A1 and JP S56 72090 A, which are based, for example, on alkali metal or alkaline earth metal stearate. These baths of alkaline lubricating composition often have only comparatively short service lives and must therefore be renewed quite frequently. This is, of course, disadvantageous both from an ecological point of view (larger amounts of water and of the constituents present in the compositions must be used) and from an economic point of view (higher energy costs and changeover time). In contrast to these aqueous alkaline lubricating compositions used to provide a lubricating layer on the conversion coating layer before it is applied, the compositions used to generate this aforementioned conversion coating layer are acidic compositions, as already mentioned above. To carry out this two-step pretreatment process, two different open treatment baths are usually employed, in which the metal workpieces are immersed, namely, a first bath containing the aqueous acidic conversion coating composition and a second bath containing the aqueous alkaline lubricating composition. However, it is essential to include a rinsing and/or neutralization step between these two immersion steps to remove any excess acid present on the workpiece after removing it from the first acidic bath and before immersing it in the second alkaline bath, in order to preserve the life of the two baths, and in particular, of the second bath, as long as possible. However, it is disadvantageous for economic and ecological reasons to necessarily have to carry out this rinsing and/or neutralization step. It is not possible to mix or blend conventional aqueous acidic compositions, such as phosphate and/or oxalate compositions, to provide the conversion coating layer with conventional aqueous alkaline compositions to provide the lubricating layer, since these compositions are not miscible with each other and, consequently, undesired phase separation would occur. Furthermore, most of the known organic polymer dispersions used to prepare conventional aqueous alkaline lubricating compositions are unstable in an acidic environment. Therefore, it is not always possible to simply use acidic versions of the known aqueous alkaline lubricating compositions.

EP 3290544 A1 relates to a water-based acidic lubricating coating agent having a pH value of 2.0 to 6.5, which contains, inter alia, a chemical conversion component such as oxalic acid and a lubricating component such as a lipophilic lubricating component including an oil or a soap. The coating agent may further comprise a water-based resin as a binder component. EP 3290 544 A1 further describes a method for one-step pretreatment of metal substrates for subsequent cold forming.

JP S545847 A relates to a lubricant composition for facilitating the cold forming of metals. The lubricant contains oxalic acid and at least one component selected from water-soluble organic titanium compounds, vinylpyrrolidone homopolymers, and vinylpyrrolidone copolymers. The lubricant composition may also contain a lubricating auxiliary.

Furthermore, conventional pretreatment processes for cold forming known in the prior art do not always result in a sufficiently high coating weight of the lubricant layer formed on the workpiece or, if a separating layer such as a conversion coating layer is also present beneath the lubricant layer, in a sufficiently high coating weight of the lubricant layer and this separating layer combined. This may result in insufficient adhesion properties of the layer(s) to the metal substrate. Furthermore, this may result in ineffective removal of the tool from the workpiece after and during cold forming and in an ineffective reduction of the coefficient of friction or even in undesired cold welding, since an insufficiently high amount of the coating layer(s), measured by their coating weight, remains present on the workpieces during the cold forming process.

Therefore, there is a need to simplify conventional surface pretreatment processes for cold forming of metals that make use of aqueous lubricant compositions for both economic and ecological reasons, in particular to provide an improved technology for water-based pretreatment of metal substrates for the cold forming process that requires fewer treatment steps and makes use of aqueous acidic lubricant compositions. At the same time, this simplified pretreatment must still lead to sufficiently high coating weights of the coating layer(s) formed on the metal substrates to ensure good adhesion to the substrate and an effective reduction of the coefficient of friction during cold forming and to prevent cold welding.

Problem

Therefore, an object underlying the present invention has been to provide a simplified surface pretreatment method for cold forming of metals that makes use of an aqueous lubricant composition for both economic and ecological reasons, in particular to provide an improved technology for the water-based pretreatment of metal substrates for the cold forming process that requires fewer treatment steps and makes use of aqueous acidic lubricant compositions. At the same time, however, this simplified pretreatment must still lead to sufficiently high coating weights of the coating layer(s) formed on the metal substrates to ensure good adhesion to the substrate and an effective reduction of the coefficient of friction during cold forming and to prevent any cold welding.

Solution

This object has been solved by the subject matter of the claims of the present application, as well as by the preferred embodiments thereof disclosed in this specification, that is, by the subject matter described herein.

A first object of the present invention is a method for the pretreatment of a metallic substrate for a subsequent cold forming process of metals, this method comprises at least steps (1) and (2) and optionally step (3), namely

(1) providing at least one substrate having at least one surface at least partially made of at least one metal,

(2) contacting the at least one surface of the substrate provided in step (1) with an aqueous lubricating composition (A) having a pH value of less than 2.0, wherein the aqueous lubricating composition (A) further comprises water

(a1) oxalate anions,

(a2) thiosulfate anions,

(a3) chloride anions,

(a4) at least one film-forming polymer, which is a homopolymer and/or copolymer that is prepared by polymerization of at least one ethylenically unsaturated monomer,

(a5) at least one wax, which is different from constituent (a4), and

(a6) fluoride anions and/or bifluoride anions,

and

(3) optionally drying the coating film obtained after performing step (2).

A further object of the present invention is a pretreated metal substrate obtainable by the inventive method.

A further object of the present invention is a method for cold forming a metal substrate, characterized in that it comprises a step of subjecting the pretreated metal substrate of the invention to a cold forming process.

A further object of the present invention is an aqueous lubricant composition (A) as defined hereinabove in relation to the inventive pretreatment method.

A further object of the present invention is a masterbatch for producing the inventive aqueous composition (A) by diluting the masterbatch with water and, if appropriate, adjusting the pH value.

It has surprisingly been found that all constituents present in the aqueous lubricating composition (A) can be formulated as and in an acidic composition at a pH value of less than 2.0. In particular, it has surprisingly been found that the composition (A) is stable under these acidic conditions and that, in particular, the at least one film-forming polymer present in the composition (A) is stable in this acidic environment. This surprisingly has the advantage that the composition (A) can be used in the inventive method both as a lubricating composition and as a conversion coating composition in a single step and that, consequently, it is not necessary to apply any conversion coating composition or any lubricating coating composition in an additional step and that it is also not necessary to carry out a rinsing step after step (2). The method can therefore be simplified, which has economic and ecological advantages.

It has also been surprisingly found that baths containing the acidic aqueous lubricating composition (A) have comparatively long service lives, in particular longer than baths containing conventional alkaline aqueous lubricating compositions. This, of course, has economic and ecological advantages.

Furthermore, it has been surprisingly found that the coating layer obtained by applying the composition (A) adhered firmly to the substrate and exhibited good lubricating properties. Therefore, the substrate pretreated by the inventive method can subsequently be subjected to a metal cold forming process, in particular with high-speed drawing. In the cold forming of substrates such as stainless steel, it has been found that a coating layer obtained from the application of the composition (A) to the substrate can be efficiently subjected to a drawing step in order to cold form the metal.

Furthermore, it has been surprisingly found that the coated metal substrates obtained by the inventive method have a sufficiently high coating weight of the coating layer(s) formed on the metal substrates obtained by applying the composition (A). The resulting coating layer(s) are homogeneous, thick, and adhere firmly to the substrate surface. It has been found that such a high coating weight not only ensures good adhesion to the substrate, but also an effective reduction of the coefficient of friction during cold forming and to prevent any cold welding. It has been surprisingly found that, among other things, selecting a pH value of the composition (A) below 2.0 results in the formation of a comparatively thick conversion coating layer, which in turn is advantageous for the subsequent cold forming process of the metal. This applies in particular to metal substrates, which are at least partially made of stainless steel. In the case of higher pH values, the conversion coating layers formed are not thick enough.

It has also been surprisingly found that the conversion coating layers formed are homogeneous, particularly when using metallic substrates made at least partially of stainless steel. It has been found, among other things, that the presence of fluoride and/or bifluoride anions, chloride and thiosulfate anions is advantageous in this regard.

Furthermore, it has been surprisingly found that the coated metal workpieces obtained using the inventive method have good corrosion resistance. Furthermore, it has been found that no stable foams have formed during the inventive surface treatment process.

Furthermore, it has been further found that the coating film obtained after step (2) or optionally after step (3) is a combined lubricant and conversion coating film. The coating film obtained therefore combines the properties of a conversion layer and a lubricant layer. The lubricant coating film can be present on top of the conversion coating film. Surprisingly, the combined layers can be separated and partly adjusted. For example, a longer treatment time in step (2) results in a thicker conversion layer, i.e., a greater layer thickness of the conversion layer, calculated as coating weight, while a higher concentration of the at least one wax (a5) and optionally of the at least one constituent (a4) leads to a thicker lubricant layer, i.e., a greater layer thickness of the lubricant layer, calculated as coating weight. In this way, a combined lubricant and conversion layer adapted to the respective cold forming conditions can be produced.

Detailed description of the invention

The term "comprising" within the meaning of the present invention, in particular in relation to the inventive method, the inventive composition (A) and the masterbatch used to prepare the composition (A), preferably has the meaning "consisting of". In this case, for example, with respect to the inventive composition (A), in addition to the mandatory constituents therein (constituents (a1) to (a6) and water), one or more of the additional optional components mentioned below may be contained in the composition. The same principle applies with respect to the composition (A) used in the inventive method and the masterbatch. All components/constituents may be present in each case in their preferred embodiments mentioned below. The same applies to the additional materials of the present invention.

Inventive pretreatment method

The inventive method is a method for pretreating a metal substrate for a subsequent cold forming process of the metal. The inventive method comprises at least steps (1) and (2) and optionally additionally step (3). The inventive method may further comprise one or more additional steps.

Step (1)

In step (1) of the inventive method, at least one substrate is provided having at least one surface at least partially made of at least one metal.

The surface of the substrate used is made at least partially of at least one metal, i.e., at least one region of this surface is made of at least one metal. The surface may consist of different regions comprising different metals. Preferably, the entire surface of the substrate is made of at least one metal. More preferably, the substrate consists of at least one metal.

Preferably, the at least one metal is selected from the group consisting of aluminum, aluminum alloys, zinc, steel including cold-rolled steel, hot-rolled steel, galvanized steel (zinc-galvanized steel) including hot-dip galvanized steel (hot-dipped zinc steel) or electrolytically galvanized steel, stainless steel, steel alloys including stainless steel alloys, magnesium and/or zinc-magnesium alloys and/or zinc-iron alloys, and mixtures thereof. In particular, the metal is ferrous and more preferably is steel. Most preferred is stainless steel and/or its alloys.

Preferably, the at least one surface of the substrate is at least partially made of stainless steel, more preferably the substrate itself is made of stainless steel.

Substrates that can be used include, for example, strips, foils, bales, wires, wire coils, more complicated shaped parts, sleeves, profiles such as hollow or solid profiles, tubes, discs, disks, rods, bars, or cylinders.

Optional steps (1a) and (1b)

The surfaces that will be substrates provided in step (1) may be cleaned by means of an acidic, alkaline or pH neutral cleaning composition and/or etched before treatment with the acidic aqueous composition (A) in step (2) as will be described below: Before step (2) of the inventive method, one or more of the following optional steps may be performed, preferably in this order:

Step (1a): cleaning, preferably using an alkaline aqueous cleaning composition, and optionally subsequently rinsing the surface of the substrate provided in step (1), and

Step (1b): Subject the substrate surface to acid pickling, i.e. etching, and subsequently rinse the substrate surface.

Preferably, both steps (1a) and (1b) are performed. The rinsing included in step (1a) is preferably carried out with deionized water or tap water. Preferably, acid pickling is carried out using hydrochloric acid, hydrofluoric acid, sulfuric acid, nitric acid, and/or phosphoric acid.

More preferably, at least step (1b) is performed, in particular by making use of hydrofluoric acid and/or nitric acid for pickling, in particular when the substrate is at least partially made of stainless steel.

Step (2)

In step (2) of the inventive method, the at least one surface of the substrate provided in step (1) is brought into contact with, preferably immersed in, an aqueous lubricating composition (A) having a pH value of less than 2.0, wherein the aqueous lubricating composition (A) comprises in addition to oxalate anions water as constituent (a1), thiosulfate anions as constituent (a2), chloride anions as constituent (a3), at least one film-forming polymer as constituent (a4), which is a homopolymer and/or copolymer that is prepared by polymerization of at least one ethylenically unsaturated monomer, at least one wax as constituent (a5) and fluoride anions and/or bifluoride anions as constituent (a6).

The treatment method according to step (2), i.e., "contacting," may, for example, include a spray coating process and/or a dip coating process. Composition (A) may also be applied by flooding the surface or by roller coating, or even manually by wiping or brushing. However, dipping is preferred. In this case, the substrate used is immersed in a bath containing composition (A).

Preferably, the contacting step (2) is carried out by at least partially immersing the substrate in a bath containing the aqueous lubricating composition (A) having a bath temperature in the range of 20 to 95° C, preferably 30 to 90° C, in particular 45 to 85° C, more preferably 50 to 75° C.

The treatment time, i.e. the period of time in which the surface is brought into contact with the aqueous composition (A) used in step (2) is preferably from 15 seconds to 20 minutes, more preferably from 30 seconds to 10 minutes, and most preferably from 45 seconds to 5 minutes, such as from 1 to 4 minutes.

Preferably, no rinsing step is performed after step (2) has been carried out.

Composition (A)

The term "aqueous" with respect to composition (A) within the meaning of the present invention preferably means that composition (A) is a composition containing at least 50% by weight, preferably at least 60% by weight, more preferably at least 70% by weight, in particular at least 80% by weight, more preferably at least 90% by weight or 95% by weight or 98% by weight or 99% by weight or even 100% by weight of water, based on its total content of organic and inorganic solvents, including water. Therefore, composition (A) may contain at least one organic solvent in addition to water, however, in an amount significantly lower than the amount of water present. Preferably, composition (A) is free of organic solvents. Therefore, preferably water is the only solvent/diluent present.

Preferably, the composition (A) contains water in an amount of at least 50% by weight, more preferably at least 60% by weight, even more preferably at least 70% by weight and even more preferably at least 80% by weight, in each case based on the total weight of the composition (A).

Preferably, the composition (A) has a pH value of less than 1.9, preferably less than 1.7, in particular a pH value in a range of 0.1 to 1.5, more preferably in a range of 0.5 to 1.5.

Preferably, the composition (A) is present in the form of a solution or dispersion, in particular in the form of a solution, preferably at a temperature of at least 40° C, in particular at least 50° C.

Preferably, composition (A) is free of phosphate anions. This means that, at least intentionally, no phosphate is added to composition (A). In the case of post-heat treatment of sensitive components, such as the hardening and tempering of screws, phosphorus-induced delta-ferrite may otherwise form, which can lead to disadvantageous material properties.

Preferably, composition (A) is silicone-free, i.e., free of siloxanes and/or polysiloxanes. This means that, at least intentionally, no silicone is added to composition (A). The presence of silicone can be disadvantageous when coating materials such as paint are applied to the substrate after subsequent cold forming.

Preferably, the composition (A) has a solids content in the range of 0.1 to 25% by weight, more preferably in the range of 0.2 to 20% by weight, even more preferably in the range of 0.3 to 15% by weight, still more preferably in the range of 0.4 to 12% by weight, in each case based on the total weight of the composition (A).

The sum of all components/constituents present in composition (A) adds up to 100% by weight.

Since the composition (A) comprises (a1) oxalate anions, it represents an oxalate composition, which is suitable for forming a conversion coating on the surface of a substrate. Since the composition (A) also comprises (a5) at least one wax and at least one film-forming polymer (a4), it also represents a lubricating composition, which is suitable for forming a lubricating coating on the surface of a substrate.

Constituents (a1), (a2) and (a3)

Preferably,

the oxalate anions (a1) are present in the composition (A) in an amount in the range from 2 to 500 g/l, more preferably from 5 to 100 g/l, in particular from 10 to 50 g/l of oxalic acid, calculated in each case as oxalic acid dihydrate, and/or

The thiosulfate anions (a2) are present in the composition (A) in an amount in the range from 0.01 to 25 g/l, more preferably from 0.5 to 10 g/l, in particular from 1.0 to 5.0 g/l, calculated in each case as sodium thiosulfate.

The chloride anions (a3) are present in the composition (A) in an amount in the range from 0.1 to 25 g/l, preferably from 0.5 to 10 g/l, in particular from 1.0 to 5.0 g/l, calculated in each case as sodium chloride.

For the purposes of the present invention, "oxalic acid" also means the singly and doubly deprotonated forms of oxalic acid. Similarly, for the purposes of the present invention, "oxalate" also means the singly and doubly protonated forms thereof, the doubly protonated form being oxalic acid. Preferably, oxalic acid dihydrate is used, as it is inexpensive and less hygroscopic.

If, in relation to weight concentrations (e.g. g/l), the term "calculated as X" is used, where X is a specific, specified chemical compound, this shall be understood as follows: If an alternative chemical compound (not X) is to be used in a molar concentration as calculated for X, taking into account its molar mass, from the specific weight concentration (e.g. g/l) stated in each case.

The content of the cations and anions mentioned herein relative to composition (A) can be monitored and determined by means of ICP-OES (inductively coupled plasma optical emission spectroscopy). This method is described in detail below. However, the content of free fluoride anions is determined by means of a fluoride electrode.

Constituent (a4)

The composition (A) comprises at least one film-forming polymer, which is a homopolymer and/or copolymer that is prepared by polymerization of at least one ethylenically unsaturated monomer as constituent (a4), which is different from constituent (a5).

Preferably, the at least one film-forming polymer is water-soluble or water-dispersible, more preferably water-soluble. Preferably, the at least one film-forming polymer is soluble or dispersible, more preferably soluble, in the composition (A).

Preferably, the at least one film-forming polymer (a4) is a homopolymer and/or copolymer, said homopolymer and/or copolymer being prepared at least from at least one monomer carrying at least one vinyl group, preferably selected from the group consisting of vinyl amine, vinyl alcohol, vinyl formamide, vinyl pyrrolidone, vinyl caprolactam, vinyl acetate and vinyl imidazole, preferably from at least one monomer selected from the group consisting of vinyl pyrrolidone and vinyl acetate, in particular from at least vinyl pyrrolidone. Exemplary polymers are Sokalan® K 17P from BASF SE, Germany and Lupamin® 9030 from BASF SE, Germany.

Most preferred are homopolymers of polyvinylpyrrolidone and copolymers of vinylpyrrolidone and vinyl acetate.

In case the at least one film-forming polymer (a4) is a copolymer, at least one additional monomer carrying at least one ethylenically unsaturated group and which is different from the monomers defined above can be used to prepare the constituent (a4). Preferably, these additional monomers have at least one (meth)acrylic group. (Meth)acrylic groups include, for example, (meth)acrylate groups and (meth)acrylic acid groups. The additional monomer can be an ionomer. The additional monomer can also be ethylene, propylene, butylene, styrene, etc. The term "(meth)acrylic" means "acryl" and/or "methacrylic". Similarly, "(meth)acrylate" means acrylate and/or methacrylate.

Preferably, the at least one film-forming polymer (a4) has a weight average molecular weight (Mw) in the range from 1,000 to 100,000 g/mol, more preferably from 3,000 to 75,000 g/mol, even more preferably from 5,000 to 50,000. The determination of the Mw is carried out by gel permeation chromatography (GPC).

Preferably, the at least one film-forming polymer (a4) is present in the composition (A) in an amount in the range of 0.05 to 20% by weight, more preferably in the range of 0.10 to 15% by weight, even more preferably in the range of 0.15 to 10% by weight, still more preferably in the range of 0.20 to 7.5% by weight, in particular 0.25 to 5.0% by weight, in each case based on the total weight of the composition (A).

Constituent (a5)

The composition (A) comprises at least one wax as constituent (a5), which is different from constituent (a4).

As the term "wax" already implies, the at least one wax is a solid substance at room temperature (23 °C). A person skilled in the art is familiar with the term "wax". This term is defined, for example, by the German Society for Fat Science (DGF) within the DGF standard method M-I 1 (75) (2015). Preferably, the at least one wax used as constituent (a5) satisfies this definition of a wax. Waxes according to this definition are kneadable at 20 °C, have a firm (solid) to brittle hardness, have a coarse to fine crystalline structure, are translucent to opaque in color but not vitreous or glass-like, melt without decomposition at temperatures above 40 °C, are slightly liquid above their melting point and have a low viscosity above their melting point, have a highly temperature-dependent consistency and solubility, and can be polished under slight pressure. Preferably and according to the DGF definition (DGF standard method M-I 1 (75)), a substance is not a wax if it does not meet more than one of the above properties.

Preferably, the at least one wax (a5) is water-soluble or water-dispersible, more preferably water-dispersible. Preferably, the at least one wax (a5) is soluble or dispersible in the composition (A).

Preferably, the composition (A) can be obtained by using an aqueous dispersion or solution of the at least one wax (a5) for its preparation.

Preferably, the at least one wax (a5) has a melting point in the range of 40 °C to 170 °C, more preferably in the range of 50 °C to 160 °C, especially preferred in the range of 50 °C to 140 °C.

The composition (A) preferably comprises more than one wax as constituent (a5). Preferably, the composition (A) comprises at least two, more preferably at least three different waxes as constituents (a5). Preferably, the at least two or at least three different waxes differ from one another at least in their melting temperature (melting point). Preferably, the difference between the melting points of at least two of the waxes is at least 20°C.

Preferably, the at least one wax (a5) is present in the composition (A) in an amount in the range of 0.1 to 20% by weight, more preferably in the range of 0.5 to 15% by weight, even more preferably in the range of 0.75 to 12.5% by weight, still more preferably in the range of 1.0 to 10.0% by weight, in particular 1.5 to 9.0% by weight, most preferably in the range of 2.0 to 7.5% by weight, in each case based on the total weight of the composition (A).

Preferably, the at least one wax (a5) is selected from the group consisting of cationic waxes, cationically stabilized waxes, and non-ionic waxes. A "cationically stabilized wax" is preferably a wax that is stabilized by cationic groups in an acidic medium, as in composition (A), or is stabilized by at least one cationic surfactant.

Preferably, the at least one wax (a5) is stabilized by at least one emulsifier. For example, the at least one wax (a5) may be stabilized by a cationic emulsifier (cationically stabilized) or may be stabilized by a non-ionic emulsifier (non-ionically stabilized). Examples of cationic emulsifiers are alkoxylated emulsifiers such as ethoxylated stearylamine and/or polyalkoxylated emulsifiers such as polyethoxylated tallow amine. Examples of non-ionic emulsifiers are alcohols including, for example, diethylaminoethanol.

Preferably, the at least one wax (a5) is selected from the group consisting of polyolefin waxes (including polyethylene waxes, in particular HDPE (high-density polyethylene) and/or polypropylene waxes, natural waxes including vegetable and animal waxes such as montan waxes, beeswaxes and/or carnauba waxes, paraffin waxes (petroleum-derived waxes) and mixtures thereof.

In this context, the term "olefin" primarily refers to the usual alkenes of polyolefins, preferably alkenes with 2 to 8, especially alkenes with 2 to 6 and especially alkenes with 2 to 4 carbon atoms, especially those with a terminal double bond. In the context of the present invention, preferred representatives are ethylene, propylene, 1-butene and isobutene. Ethylene and propylene are particularly preferred olefin monomers in the context of this invention. The term "polyolefin" is generally understood to mean homopolymers of a single type of olefin monomer (e.g., ethylene homopolymers) or copolymers of at least two olefin monomers (e.g., blend polymers comprising or consisting of ethylene, propylene, 1-butene and/or isobutene). Polyolefins therefore contain one or more types of olefin monomers and are therefore homopolymers or copolymers. However, they may also additionally contain one or more ethylenically unsaturated monomers other than olefin monomers, in particular ethylenically unsaturated monomers bearing carboxylic acid groups, polymerized or grafted. If various ethylenically unsaturated monomers bearing carboxyl groups or carboxylic acid anhydride groups are used for the purpose of polymerizing or grafting the olefin monomers, this is done in an amount such that the polyolefin wax as constituent (a5) containing carboxyl groups has an acid number in the range of 3 to 50, preferably 5 to 40, particularly preferably 8 to 35, very particularly preferably 10 to 25, and particularly preferably 13 to 20 mg Koh/g. The polyolefin waxes are preferably selected from the group consisting of oxidized polyethylene waxes, oxidized polypropylene waxes, oxidized poly(ethylene-co-propylene) waxes and oxidized ethylene-olefin copolymers, ethylene-(meth)acrylic acid copolymers and ethylene and/or propylene polymers other than the aforementioned copolymers, which have been grafted, for example, with maleic anhydride (converted to the hydrolyzed form and carrying free COOH groups). Of course, other ethylenically unsaturated acids, such as acrylic acid, can also be used for grafting.

The paraffin waxes used are preferably microcrystalline.

Examples of waxes that are commercially available and can be used are, for example, Aquacer® 1041 from BYK Chemie, Germany, Aquacer® 561 from BYK Chemie, Aquacer® 517 from BYK Chemie, Wükonil® O-33a from Münzing Chemie and Licowax® KST from Clariant, Germany.

Constituent (a6)

The composition (A) further comprises at least one of fluoride anions and bifluoride anions as constituent (a6). Preferably, the composition (A) comprises fluoride anions as constituent (a6), more preferably in combination with bifluoride anions.

The fluoride anions and/or the bifluoride anions are present in the composition (A) in each case independently of one another in an amount in the range from 0.01 to 25 g/l, preferably from 0.5 to 10 g/l, in particular from 1.0 to 5.0 g/l calculated as sodium fluoride in the case of the fluoride anions and as sodium bifluoride in the case of the bifluoride anions.

Optional additional constituents

Optionally, the composition (A) may comprise at least one additional constituent (a7). Said at least one additional constituent (a7) is preferably selected from the group consisting of thickeners, pigments, fillers, corrosion inhibitors, antifoams, surfactants and mixtures thereof. The constituent(s) (a7) may be present in an amount of 0.01 to 10% by weight in the composition (A), based on the total weight of the composition (A).

Examples of antifoams are polymer-based and silicone-free antifoams. If an antifoam is present, which is preferred, the amount of the at least one antifoam in composition (A) is preferably in a range of 0.01 to 3% by weight, based on the total weight of composition (A).

Examples of corrosion inhibitors are morpholine, benzylamine, butynediol, diisopropylamine nitrite, morpholine nitrite, 2-(2-heptadec-8-enyl-2-imidazolin-1-yl)ethanol, dicyclohexylamine nitrite, cyclohexylamine benzoate, dicyclohexylamine caprylate, guanadine chromate, hexamethyleneimine benzoate, dicyclohexylamine benzoate, ethylaniline, mercaptobenzotriazole, pyridine, rosin amine, phenylacridine, hexamethylenetetramine, nonylphenoxyacetic acid, succinic acid half ester and butynediol. If a corrosion inhibitor is present, the amount of the at least one corrosion inhibitor in the composition (A) is preferably in a range of 0.01 to 3% by weight, based on the total weight of the composition (A).

Examples of thickeners are polysaccharide, polysiloxane, polyvinylamide, polyacrylamide, and polyglycol.

Examples of pigments and fillers are boron nitride, graphite, and molybdenum sulfide. However, since graphite and molybdenum sulfide in particular are solid lubricants and their use is associated with disadvantages as described in the introduction, these pigments, in particular neither graphite nor molybdenum sulfide, are preferably present in composition (A).

Examples of surfactants are fatty alcohol alkoxylates and especially fatty alcohol ethoxylates.

Optional step (3)

The optional step (3) of the inventive method is a step, wherein the coating film obtained after step (2) is optionally dried.

The drying step (3) may preferably be carried out, for example, at a temperature in the range of 15 °C to 100 °C, more preferably at a temperature in the range of 18 °C to 95 °C, in particular at a temperature in the range of 20 °C to 90 °C.

Inventive pretreated substrate

A further object of the present invention is a pretreated metal substrate obtainable by the inventive method.

All preferred embodiments described above in connection with the inventive pretreatment method are also preferred embodiments of the pretreated substrate. The same applies, of course, to the embodiments of the substrate as described above in connection with step (1) of the inventive method.

The coating film obtained after step (2) or optionally after step (3) is a combined conversion and lubricant coating film. Therefore, the coating film obtained combines the properties of a conversion layer and a lubricant layer.

Preferably, the pretreated metal substrate obtainable by the inventive method contains a conversion coating film obtained by performing step (2) and further contains a lubricious coating film on top of said conversion coating film also obtained by performing step (2). However, it is also possible that the coating film obtained after step (2) or optionally after step (3) is chemically heterogeneous.

Preferably, the coating film present on the surface of the substrate after performing step (2) and optionally step (3) has a coating weight in a range of 1.0 to 40.0 g/m2, preferably in a range of 5.0 to 35.0 g/m2, more preferably in a range of 10.0 to 30.0 g/m2. The method for determining the coating weight is described in the examples section.

Inventive cold forming method

A further object of the present invention is a method of cold forming a metal substrate, characterized in that it comprises a step of subjecting the inventive pretreated metal substrate according to a cold forming process, preferably by stretching.

All possible cold forming processes known in the prior art can be carried out, in particular rolling, such as thread rolling or beating, for example, for nut or bolt blanks, drawing, in particular slip drawing (tensile compression forming), for example, of welded or seamless tubes, hollow sections, solid sections, wires or rods, for example, during wire drawing or tube drawing, or deep drawing, for example, of strips or sheet metal, pressing, such as cold extrusion (pressure forming), for example, of hollow or solid bodies, draw forming (forming to calibrate the final block/size) and/or cold upsetting, for example, from wire sections to fasteners such as nuts.

The most common shaped bodies to be formed from the inventive pretreated metal substrates are strips, sheets, bales, wires, wire coils, more complicated shaped parts, sleeves, profiles such as hollow or solid profiles, tubes, discs, disks, rods, bars or cylinders.

Preferably, the cold-formed substrate obtained after the cold-forming process still carries at least part of the coating film obtained after having carried out step (2) and optionally step (3): Due to the amount of the coating weight of the coating film obtained after step (2) or optionally step (3) present on the pretreated substrate, said coating film "survives" conventional cold-forming processes. For example, this leaves at least 10%, preferably at least 15%, particularly preferred at least 20% of the coating weight on a pretreated and cold-formed substrate after cold-forming, in particular if the substrate has been subjected to stretching. However, the coating film can be removed from the cold-formed substrate, for example, by using an aqueous cleaning composition. Therefore, after the cold forming process, the obtained substrate is preferably cleaned, in order to remove the conversion coating film and lubricant from the substrate, for example, by means of alkaline or acidic cleaners or pickling agents.

Inventive composition (A)

A further object of the present invention is an aqueous lubricant composition (A) as defined hereinabove in relation to the inventive pretreatment method.

All preferred embodiments described hereinbefore in relation to the inventive method and the composition (A) used in step (2) thereof and the constituents contained therein are also preferred embodiments of the inventive composition (A).

Inventive Master Batch

A further object of the present invention is a masterbatch for producing the inventive aqueous composition (A) by diluting the masterbatch with water and, if appropriate, adjusting the pH value.

All preferred embodiments described herein above in relation to the inventive methods and the inventive composition (A) and the constituents contained therein are also preferred embodiments of the inventive masterbatch.

If a masterbatch is used to produce the aqueous composition (A) according to the present invention, the masterbatch typically contains the constituents of the aqueous composition (A) to be produced in the desired proportions, but at a higher concentration. Such a masterbatch is preferably diluted with water to the constituent concentrations described above to form the aqueous composition (A). If necessary, the pH value of the aqueous composition (A) can be adjusted after dilution of the masterbatch. Of course, it is also possible to further add any of the optional components to the water, wherein the masterbatch is diluted, or to add any of the optional components after diluting the masterbatch with water. However, it is preferred that the masterbatch already contains all the necessary components.

Preferably, the masterbatch is diluted with water and/or an aqueous solution in the ratio of 1:5,000 to 1:5, more preferred 1:1,000 to 1:10, more preferred in the ratio of 1:300 to 1:10 and even more preferred 1:150 to 1:50 to produce composition (A).

Methods

1. Total acid (TA)

Total acid (TA) is the sum of the divalent cations present, as well as the free and bound oxalic acids (the latter being oxalates). It is determined by the consumption of 0.1 M NaOH using 10 to 15 drops of aqueous phenolphthalein solution as a test indicator. For this, 10 ml of the composition is pipetted into a suitable container, for example, a 300 ml Erlenmeyer flask and diluted with 50 ml of deionized water. It is then titrated with 0.1 M NaOH until a color change to red has occurred. The consumption in ml per 10 ml of the diluted composition corresponds to the total acid (TA) score.2

2. Solid content

The non-volatile fraction (solids or solid content) is determined according to DIN EN ISO 3251 (date: June 2019). This involves weighing 1 g of sample onto a pre-dried aluminum pan, drying the pan with the sample in a drying cabinet at 130°C for 60 minutes, cooling it in a desiccator, and then reweighing it. The residue, relative to the total sample quantity used, corresponds to the non-volatile fraction. 3. ICP-OES

The quantities of certain elements in a sample under analysis are determined using inductively coupled plasma atomic emission spectrometry (ICP-OES) in accordance with DIN EN ISO 11885 (date: 1 September 2009).

Examples

The following examples further illustrate the invention, but should not be construed as limiting its scope.

1. Inventive lubricating composition

Inventive Example 11

An acid-stable aqueous polymer lubricant composition l1 was prepared in a high-speed agitated mixer. The composition of this lubricant is given in Table 1.

T l 1: m i i n l l ri n m l l1

Polymer 1 is a polyvinylpyrrolidone homopolymer. A commercially available product from BASF SE was used.

Aqueous wax dispersion 1 contains a polypropylene wax, which is commercially available from BYK Chemie. Aqueous wax dispersion 2 contains a microcrystalline wax, which is commercially available from Michelman. Wax 3 is a montan wax, which is dispersible in aqueous media.

The composition has a pH value below 2.0.

Comparative example C1

The commercially available product Gardobond® AS 4200, which is an oxalation treatment solution containing oxalic acid, chloride and/or fluoride anions and sodium thiosulfate, has been used as comparative composition C1.

Comparative examples C2, C3, C4 and C5

Several additional comparative compositions were prepared, namely, compositions C2, C3, C4, and C5. Composition C2 was identical to Lubricant Example 11, but sodium chloride was not used in its preparation. Composition C3 was identical to Lubricant Example 11, but sodium thiosulfate was not used in its preparation. Composition C4 was identical to Lubricant Example I1, but neither sodium chloride nor sodium thiosulfate was used in its preparation. Composition C5 was identical to Lubricant Example I1, but its pH was adjusted to be >3.

2. Inventive method

2.1 Oxalation treatment and lubrication treatment in a single step by using the inventive composition 11

The following substrate S1 was used as the metal workpiece:

Sheet made of 1.0 mm stainless steel (material-No.: 1.4571).

The workpiece was immersed in a cleaning bath containing a 50 g/L aqueous cleaning solution of Gardoclean® 351 available from Chemetall GmbH at 90 °C for 10 min and then rinsed with cold tap water for 1 min. The surface-cleaned workpiece was then pickled using an aqueous solution containing 20 wt.% nitric acid and 4 wt.% hydrofluoric acid at room temperature (23 °C) for 1 min and subsequently rinsed with cold tap water for 1 min.

Then, in a single step, the workpiece was immersed in a bath containing lubricant example I1 at 65°C for 10 min.

Finally, the obtained coated workpiece was air dried at 85°C.

No solid foams formed during this process. The resulting sludge in the reaction bath of I1 was powdery and similar to the sludge formed in an oxalation bath containing Gardobond® AS 4200 from Chemetall GmbH (composition C1, cf. section 2.2) and could be easily removed from the reaction bath.

2.2Treatment with commercially available C1 oxalation solution in a single step

Substrate S1 as described above was used as the workpiece.

The workpiece was treated as follows:

The workpiece was immersed in a cleaning bath containing a 50 g/L aqueous cleaning solution of Gardoclean® 351 available from Chemetall GmbH at 90 °C for 10 min and then rinsed with cold tap water for 1 min. The surface-cleaned workpiece was then pickled using an aqueous solution containing 20 wt.% nitric acid and 4 wt.% hydrofluoric acid at room temperature (23 °C) for 1 min and subsequently rinsed with cold tap water for 1 min.

Then, in a single step, the workpiece was immersed in a bath containing Gardobond® AS 4200 at 65°C for 10 min.

Finally, the obtained coated workpiece was air dried at 85°C.

2.3Treatment using comparative compositions C2, C3, C4 and C5

A substrate S1 was treated in the same manner as described above in section 2.1, except that one of the compositions C2, C3, C4 and C5 was used instead of I1.

3. Properties of coated substrates

3.1 Coated substrate obtained from the 1-step process as described in point 2.1

The coating layer resulting from the coated workpiece is homogeneous, thick, and adheres firmly to the treated workpiece surface. The upper coating layer formed by the method is a polymer lubricant layer, and the lower coating layer formed is an oxalate coating layer. The properties of the coating layers are observed using SEM technology. It was shown that the lower oxalate coating layer on the stainless steel surface is a sufficiently closed coating layer on the metal workpiece surface.

The coating weights on the substrate were determined using the following test method: The coated workpiece was weighed. The polymer lubricant coating layer was then washed with boiling xylene to separate it, followed by boiling water. The workpiece was then dried and weighed. The oxalate coating layer was washed with an alkaline solution containing NaOH, triethylamine, and EDTA (PL 83 from Chemetall GmbH) to separate it. Finally, the workpiece was rinsed with water, dried, and weighed again.

The resulting coating weights are listed in Table 2.

Table 2: Coating weights on substrate surfaces S1 in /m2

The coated substrate exhibits very good lubricating properties and is well suited for cold forming, even at high draw speeds, and for cold extrusion. The coating layers adhere firmly to the metal surface of the substrates, even after cold forming.

After cold forming of the metal, the remaining coating still adhered firmly to the metal surface and the remaining coating layer can be washed off using an aqueous alkaline cleaner, e.g. Gardoclean® S 5171 with Gardobond® Additive H 7375 from Chemetall GmbH, or an aqueous acidic cleaner, e.g. Gardobond® Additive H 7132 with Gardobond® Additive H 7390 from Chemetall GmbH.

3.2 Coated substrate obtained from the 1-step process as described in point 2.2

The resulting oxalate coating layer on stainless steel is closed and homogeneous.

The weight of the coating on the substrate was determined using the following test method:

The oxalated workpiece was weighed. The oxalate coating layer was washed with an alkaline solution containing NaOH, triethylamine, and EDTA (PL 83 from Chemetall GmbH) to separate it. Finally, the workpiece was rinsed with water, dried, and weighed again. The resulting oxalate coating weight was 10 g/m2.

The coated substrate exhibits no lubricating properties at all and is therefore unsuitable for cold forming. To achieve this, the oxalate-coated stainless steel substrate must be lubricated in an additional process step.

3.3 Coated substrates obtained from 1-step processes as described in point 2.3

When using comparative composition C2, the coating layer resulting from the coated workpiece was found to have a lower homogeneity compared to the coated workpiece obtained using composition I1. Even lower homogeneity was observed when using comparative composition C3. When using comparative examples C4 and C5, no coating layer was found to have formed on the substrate.

Claims (15)

1. A method for pretreating a metal substrate for a subsequent cold metal forming process, said method comprising at least steps (1) and (2) and optionally step (3), namely (1) providing at least one substrate having at least one surface at least partially made of at least one metal, (2) contacting the at least one surface of the substrate provided in step (1) with an aqueous lubricating composition (A) having a pH value of less than 2.0, wherein the aqueous lubricating composition (A) further comprises water (a1) oxalate anions, (a2) thiosulfate anions, (a3) chloride anions in an amount in the range of 0.1 to 25 g/l, calculated as sodium chloride, (a4) at least one film-forming polymer, which is a homopolymer and/or copolymer that is prepared by polymerization of at least one ethylenically unsaturated monomer, (a5) at least one wax, which is different from constituent (a4), and (a6) fluoride anions and/or bifluoride anions in each case independently of each other in an amount in the range from 0.01 to 25 g/l, calculated as sodium fluoride in the case of fluoride anions and as sodium bifluoride in the case of bifluoride anions, and (3) optionally drying the coating film obtained after performing step (2). 2. The method according to claim 1, characterized in that the composition (A) has a pH value of less than 1.9, preferably less than 1.7, in particular a pH value in a range of 0.1 to 1.5. 3. The method according to claim 1 or 2, characterized in that the at least one film-forming polymer (a4) is a homopolymer and/or copolymer, said homopolymer and/or copolymer being prepared at least from at least one monomer selected from the group consisting of vinyl amine, vinyl alcohol, vinyl formamide, vinyl pyrrolidone, vinyl caprolactam, vinyl acetate and vinyl imidazole, preferably from at least one monomer selected from the group consisting of vinyl pyrrolidone and vinyl acetate, in particular from at least vinyl pyrrolidone. 4. The method according to any of the preceding claims, characterized in that the at least one film-forming polymer (a4) is present in the composition (A) in an amount in the range of 0.05 to 20% by weight, more preferably in the range of 0.10 to 15% by weight, in each case based on the total weight of the composition (A). 5. The method according to any of the preceding claims, characterized in that the at least one wax (a5) is selected from the group consisting of polyolefin waxes, preferably polyethylene waxes and polypropylene waxes, paraffin waxes and natural waxes, preferably montan waxes, beeswaxes and carnauba waxes, and mixtures thereof. 6. The method according to any of the preceding claims, characterized in that the at least one wax (a5) is present in the composition (A) in an amount in the range of 0.1 to 20% by weight, more preferably in the range of 0.5 to 15% by weight, in each case based on the total weight of the composition (A). 7. The method according to any of the preceding claims, characterized in that the oxalate anions (a1) are present in the composition (A) in an amount in the range from 2 to 500 g/l, more preferably from 5 to 100 g/l, in particular from 10 to 50 g/l of oxalic acid, calculated in each case as oxalic acid dihydrate, and/or the thiosulfate anions (a2) are present in the composition (A) in an amount in the range from 0.01 to 25 g/l, more preferably from 0.5 to 10 g/l, in particular from 1.0 to 5.0 g/l, calculated in each case as sodium thiosulfate, and/or Chloride anions (a3) are present in the composition (A) in an amount in the range of 0.5 to 10 g/l, in particular 1.0 to 5.0 g/l, calculated in each case as sodium chloride. 8. The method according to any of the preceding claims, characterized in that the composition (A) comprises at least one of the fluoride anions and the bifluoride anions as constituent (a6) in each case independently of each other in an amount in the range of 0.5 to 10 g/l, in particular 1.0 to 5.0 g/l, calculated in each case as sodium fluoride in case of fluoride anions and as sodium bifluoride in case of bifluoride anions.9 9. The method according to any of the preceding claims, characterized in that the contacting step (2) is carried out by at least partially immersing the substrate in a bath containing the aqueous lubricating composition (A) having a bath temperature in the range of 20 to 95° C, preferably 30 to 90° C, in particular 45 to 85° C. 10. The method according to any of the preceding claims, characterized in that the at least one surface of the substrate is at least partially made of stainless steel, preferably in that the substrate as such is made of stainless steel. 11. A pretreated metal substrate obtainable by the method according to any one of claims 1 to 10. 12. The pretreated metal substrate according to claim 11, characterized in that the coating film present on the surface of the substrate after having performed step (2) and optionally step (3) has a coating weight in a range of 1.0 to 40.0 g/m2, preferably in a range of 5.0 to 35.0 g/m2, more preferably in a range of 10.0 to 30.0 g/m2. 13. A method of cold forming a metal substrate, characterized in that it comprises a step of subjecting the pretreated metal substrate according to claim 11 or 12 to a cold forming process, preferably by drawing. 14. An aqueous lubricating composition (A) as defined in any one of claims 1 to 8. 15. A masterbatch for producing the aqueous composition (A) according to claim 14 by diluting the masterbatch with water and, if appropriate, adjusting the pH value.