EP2995674A1 - Use of a sulfate and a process for the production of a steel component by forming in a machine - Google Patents

Abstract

The invention proposes as coating compositions which, with minimized lubricant requirement, on the one hand enable optimized tribological conditions in the forming of flat steel products and on the other hand are harmless in terms of their effect on the environment, the use of a sulfate from the group "aluminum sulfate, ammonium sulfate, iron Sulfate, magnesium sulfate "before. With this coating composition, a steel component can be produced by forming a flat steel product in a forming machine by providing a flat steel product having a tribologically active layer on at least one of the surfaces of the flat steel product or the forming machine used for forming by coating with a Coating agent from the group "aluminum sulfate, ammonium sulfate, iron sulfate, magnesium sulfate" is produced, that the flat steel product is inserted into the forming tool and that the inserted into the forming machine flat steel product is formed into the component.

Description

The invention relates to a use of a sulfate from the group "aluminum sulfate, ammonium sulfate, iron sulfate, magnesium sulfate".

Likewise, the invention relates to a method for producing a component by forming a flat steel product in a forming machine.

For forming into a component, the steel flat product to be formed in each case is placed in a forming machine and then shaped by the machine into the respective component. The transformation can be carried out as cold forming, that is to say as forming at temperatures below the recrystallization temperature of the respective steel of the flat steel products, or as hot forming, that is to say as forming at working temperatures which are above the recrystallization temperature.

A typical example of such a forming process is deep-drawing, in which the flat steel product to be formed is pressed by means of a punch into a die. The The shape of die and punch determine the shape that the flat steel product receives through the forming process.

With each forming operation, relative movements occur between the forming tool used for the shaping and the product to be formed. At the same time there is contact between the surfaces of the product and their associated surfaces of the forming tool. The resulting tribological system between the tool and the product to be formed is determined by the material properties of the product to be formed and the tool as well as by existing between the product to be formed and the tool media. As a result of the relative movement between the forming tool and the forming product touching the reshaping formed product friction.

This friction can be very different locally, especially during the forming of flat steel products, because the material of the flat steel product is deformed differently in sections as part of the forming and thus the material of the flat steel product flows locally as differently at the deformation. It is therefore precisely in the production of complex-shaped components by deep drawing or comparable cold forming processes, which are usually achieved in large degrees of deformation and complex shapes are displayed, dynamically changing frictional conditions in which static and sliding friction can occur alternately.

The frictional forces occurring in particular during cold forming can be so high that they cause the Interrupt continuous flow of the molding process and can cause a faulty impression of each component to be molded. At the same time, the unavoidable friction causes considerable tool wear.

In this context, flat steel products, in which a protective coating based on zinc or aluminum, which protects against corrosion or other environmental influences, prove particularly critical in the case of the actual flat steel product.

In order to reduce the negative effects caused by friction in the forming, in practice, the surfaces coming into contact with one another during the forming process are coated with lubricants. By using suitable coating agents, the forming tools can be protected and thus significantly increase tool life. For this purpose, the lubricant can be applied both to the flat steel product to be formed and to the surfaces of the tool which come into contact with the flat steel product.

Usually, as lubricants for cold forming lubricants based on mineral oil are used, which can be added to optimize their lubricating effect various additives, such as sulfur-containing, phosphorus-containing or chlorine-containing additives. A detailed explanation of the tribology in forming technology can be found in Chapter 2.8 of Volume 4 "Reshaping" of the Compendium "Production Processes" by Prof. Dr.-Ing. Fritz Klocke, Prof. em. Dr.-Ing. Dr. hc mult. Wilfried König, 5th ed., 2006, Springer-Verlag Berlin Heidelberg ,

Examples of cold-working coating compositions based on mineral oil or similar hydrocarbons are disclosed in U.S.P. DE 101 15 696 A1 described. These coating agents include paraffinic or naphthenic based lubricants or vegetable or animal based ester oils.

In the DE 10 2008 016 348 A1 Furthermore, a lubricating varnish based on graphite in mineral oil intended for application to the steel flat product to be formed is described. This bonded coating is intended to ensure a good sliding of the metal between the processing tools at high processing temperatures.

From the DE 100 07 625 A1 Coating agents based on carbonic acid esters are known. The coating compositions contain one or more components selected from the group of mono- and / or diesters of mono- or oligophosphoric acids, triglycerides and fatty acid methyl esters. These components are intended to serve primarily as a substitute for hydrocarbons of mineral oil or other petroleum distillates.

In the DE 699 06 555 T1 Finally, a method for applying a layer of zinc hydroxysulphate on galvanized steel sheet is described. The layer is applied as a solution to the flat steel product whose pH is greater than or equal to 12 but less than 13. The solution is made by anodic polarization of the surface applied to the galvanized surface of the flat steel product. The layer thus produced consists of zinc hydroxysulfate, also called "basic zinc sulfate".

Against the background of the prior art, the object of the invention was to provide coating compositions which, with minimized lubricant requirement, on the one hand enable optimized tribological conditions in the forming of flat steel products and on the other hand are harmless in terms of their effect on the environment.

Similarly, a process should be specified, with the components of flat steel products can be produced with high efficiency and minimized environmental impact by cold forming.

With respect to the coating agent, this object is achieved by the use of a sulfate selected from the group consisting of "aluminum sulfate, ammonium sulfate, iron sulfate, magnesium sulfate" as a coating agent for improving the tribological behavior of a flat steel product Forming has been solved in a forming machine.

The inventive solution of the above-mentioned with respect to the method task is that in the production of a steel component, the steps specified in claim 4 are completed.

Advantageous embodiments of the invention are specified in the dependent claims and are explained below as the general inventive concept in detail. The term "flat steel product" according to the understanding of the invention, all rolled products whose length is much greater than their thickness. These include steel strips and sheets as well as blanks and blanks derived from them.

In particular, so-called thin sheets, that is to say thin sheets, fall under the steel flat products to be cold-formed according to the invention. H. Sheets with a thickness of less than 4 mm, in particular 0.4-3.5 mm, typically 0.5-3 mm, which can be formed into a component in the cold or hot rolled state. An overview of typically provided as fine bleaching for cold forming steel flat products of the type in question are the DIN EN 10130 (uncoated thin sheets) and DIN EN 10346 (provided with a corrosion protection coating fine sheets). To name a few, here are the soft steels for forming with the material numbers 1.0226, 1.0350, 1.0355, 1.0306, 1.0322, 1.0853.

Surprisingly, it has been shown that the sulfates provided according to the invention as coating agents for flat steel products lead to a significant improvement of the tribological conditions during the forming of flat steel products. Thus, with the sulfates selected according to the invention for use as coating compositions, it is possible to achieve lubricating properties which are equivalent to the properties achieved with conventional lubricants of the type described above. This effect is fundamentally independent of whether the forming is carried out as cold or hot forming. Particularly effective prove the invention as Coating agents used sulfates in the cold forming of flat steel products.

In this case, the sulfates used according to the invention as a coating material to improve the friction conditions during forming are distinguished by a good environmental compatibility and can be applied in a simple manner to the respective flat steel product.

Because of their solubility in water, the sulfates used according to the invention can be removed just as easily from the steel components obtained after the forming process after the deformation. In the process, coating residues remaining on the steel component interfere at most insignificantly with the processes usually carried out after the forming in the further processing of steel components.

Specifically to call concrete sulfate according to the invention particularly suitable for practical use are the sulfates from the group "aluminum-III-sulfate, ammonium sulfate, ferrous sulfate, ferric sulfate, magnesium sulfate".

As a result, with the use according to the invention of sulphates from the group "aluminum sulphate, ammonium sulphate, iron sulphate, magnesium sulphate", a coating agent with optimum processing and use properties is available, which provides problems in a sufficient quantity and at low cost can be.

• Bereitstellen des Stahlflachprodukts;
• Erzeugen einer tribologisch wirksamen Schicht auf mindestens einer der sich bei der Umformung berührenden Flächen des Stahlflachprodukts oder der zum Umformen eingesetzten Umformmaschine durch Beschichten mit einem Beschichtungsmittel aus der Gruppe "Aluminium-Sulfat, Ammonium-Sulfat, Eisen-Sulfat, Magnesium-Sulfat";
• Einlegen des Stahlflachprodukts in das Umformwerkzeug;
• Umformen des in die Umformmaschine eingelegten Stahlflachprodukts zu dem Bauteil.

The inventive method for producing a steel component by forming a flat steel product in a forming machine accordingly comprises the following steps:

• Providing the flat steel product;
• Producing a tribologically active layer on at least one of the contacting during forming surfaces of the flat steel product or the forming machine used for forming by coating with a coating agent selected from the group "aluminum sulfate, ammonium sulfate, iron sulfate, magnesium sulfate";
• Inserting the flat steel product into the forming tool;
• Forming the inserted into the forming machine flat steel product to the component.

Owing to their ease of application, the sulfates provided according to the invention for use as coating agents in a process of the type according to the invention are suitable for coating the surfaces of the respective tool with which the flat steel product to be formed comes into contact during the forming process. Thus, the sulfates used in the invention can be sprayed as an aqueous solution to the respective critical surfaces of the forming tool, painted or applied in other already known in practice for this purpose manner.

As particularly advantageous in the industrial application of the invention, it turns out, if the respective Flat steel product is coated in the course of its production with the coating agent. Here, the ease of application and the good adhesion of the sulfates used according to the invention have a particularly positive effect on the surface of the flat steel product to be coated. The sulfates which are proposed according to the invention for use as lubricants can also be applied to the respective flat steel product to be shaped using conventional coating systems, such as are commonly available for applying organic or inorganic layers to flat steel products of the type in question. Thus, the respective sulfate can be applied as a coating agent by dipping, spraying, coating or brushing on the flat steel product.

The order of the sulfates according to the invention used as a coating agent to improve the state of friction in the deformation of flat steel products is particularly simple, that these sulfates wet well each surface to be coated and form correspondingly uniform layers, without requiring special precautions. In particular, it is not necessary to temper the particular aqueous solution particularly. Rather, the order of the present invention for use provided sulfate containing aqueous solution can be carried out at room temperature.

The application of the sulfates used according to the invention as coating agents is particularly simple when they are applied as an aqueous solution. After a subsequent drying process, there is a dense, uniformly distributed thin sulfate layer on the respective flat steel product, which ensures optimum deformation behavior during a forming process, in particular a cold forming operation.

This shows that there are no additives, such as those required in the prior art, for example, to set a specific pH, in order to ensure a good coverage of each surface to be coated with the coating composition used in the respective coating process. Thus, it has proved to be sufficient if the aqueous solution consists of two components, of which one component is water as a solvent and the other component is the respective sulfate as a tribologically active ingredient. If distilled water is used as the solvent, this has the advantage that it can not interfere with the function of the coating by foreign ions.

A sufficiently thick and dense tribologically effective coating for the purposes of the invention on the respective surface to be coated of flat steel products or forming tools results when the content of the tribologically active sulfate component in the aqueous solution 0.2 to 1 mol / l (based on the SO ₄ ^2- ion concentration) is, with good effective coatings in practice then arise reliable, if the content of the present invention provided sulphate component of the aqueous solution 0.4 to 0.7 mol / l (based on the SO ₄ ^{2 -} ion concentration) is.

It is also possible to apply mixtures of the sulfates provided according to the invention as coating agents to the flat steel product in the manner according to the invention.

In order to ensure a safe action of the sulphate coating agent intended for use according to the invention under operating conditions, the layer formed from the respective coating agent on the flat steel product or the surface of the forming tool to be coated can be applied with a coating weight of 5 to 50 mg / m ² , Optimal effects occur when the occupational weight is 10 - 30 mg / m ² .

In order to ensure optimum adhesion of the coating composition according to the invention for use on the respective surface, the surface in question can be cleaned alkaline prior to application of the coating composition.

By applying the sulfates provided according to the invention for the purpose of improving the tribological properties, the coefficient of friction of the respective coated surface is markedly improved. Thus, by a layer formed from the sulfates used according to the invention for use, the friction coefficient of the respective coated surface is regularly reduced to ≦ 0.15.

This success sets in particular when the flat steel product for protection against corrosion, in particular by hot dip coating, with a protective coating coated on the basis of zinc. The Zn-based coating can be applied in a conventional manner as a pure zinc layer, as a zinc alloy layer containing Mg, Al or Si, for example electrolytically or by hot dip coating on the respective steel substrate. It is also possible to coat flat steel products with Al-based coatings in accordance with the invention in order to improve their forming behavior during cold or hot forming.

Without having to accept the disadvantages of the conventional means, such as potentially environmentally damaging constituents, complex application methods and the like, coatings produced by the coating compositions selected according to the invention thus achieve frictional properties which are certainly consistent with the frictional properties of coatings consist of conventional, commonly used to improve the tribological properties means.

Fig. 1

ein Diagramm, in dem die Entwicklung des Reibungskoeffizienten der Oberfläche eines mit einer Ammonium-Sulfat-Schicht beschichteten verzinkten Feinblechs während des Streifenziehversuchs über die jeweilige Flächenpressung aufgetragen ist;

Fig. 2

ein Diagramm, in dem die Entwicklung des Reibungskoeffizienten der Oberfläche eines unbehandelten verzinkten Feinblechs während des Streifenziehversuchs über die jeweilige Flächenpressung aufgetragen ist;

Fig. 3

ein Diagramm, in dem die Entwicklung des Reibungskoeffizienten der Oberfläche eines mit einer Eisen-II-Sulfat-Schicht beschichteten verzinkten Feinblechs während des Streifenziehversuchs über die jeweilige Flächenpressung aufgetragen ist

Fig. 4

ein Diagramm, in dem die Entwicklung des Reibungskoeffizienten der Oberfläche eines mit einer Aluminium-Sulfat-Schicht beschichteten verzinkten Feinblechs während des Streifenziehversuchs über die jeweilige Flächenpressung aufgetragen ist.

The invention will be explained in more detail by means of exemplary embodiments. Show it:

Fig. 1

a diagram in which the development of the coefficient of friction of the surface of a coated with an ammonium sulfate layer galvanized sheet during the strip pulling test is plotted on the respective surface pressure;

Fig. 2

a diagram in which the evolution of the coefficient of friction of the surface of a untreated galvanized sheet is applied during the strip pulling test on the respective surface pressure;

Fig. 3

a diagram in which the development of the coefficient of friction of the surface of a coated with an iron-II sulfate layer galvanized sheet during the strip pulling test is plotted on the respective surface pressure

Fig. 4

a diagram in which the development of the coefficient of friction of the surface of a galvanized sheet coated with an aluminum sulfate layer during the strip pulling test is plotted over the respective surface pressure.

The curves of the coefficients of friction reproduced in the figures were determined in the strip pulling test, which is described, for example, in Section 2.8.7.4 of Volume 4 of the 5th edition of the compendium "Manufacturing Process 4" by Fritz Klocke and Wilfried König, Springer-Verlag Berlin Heidelberg, 2006 (ISBN-13 978-3-540-23650-4 ) is explained.

Trial 1

On a conventional flat steel product in the form of a Zn-coated sheet steel strip, a tribologically active ammonium sulfate layer has been applied.

For this purpose, an aqueous solution was prepared in which 90 g of ammonium sulfate ((NH ₄ ) ₂ SO ₄ ) in 1 l of water (dist.) Was dissolved, so that the ammonium sulfate content of the aqueous solution at 90 g / l was. The native pH of the resulting solution was 5.3.

The aqueous solution thus obtained has been applied at room temperature to the previously alkaline-cleaned steel flat product sheet by means of a so-called "chemcoater" which is customary in industry.

A "chemcoater" is a part of the plant used in the steel industry for applying chemical substances to be applied as an aqueous solution to galvanized flat carbon steel. In particular, such coaters are used for the application of water-soluble media, which serve for the pretreatment of the respective flat steel product for a subsequent coating or film coating or to improve the corrosion protection. Various treatment chemicals can be applied via rollers to the flat steel product to be coated in each case. Subsequently, the coated steel flat product passes through an oven in which the coating is dried.

The parameters set during the application of the ammonium sulphate solution are given in Table 1.

In order to determine the development of the cold - forming tool (stamp / die) of a cold forming machine, which is crucial for the behavior during cold forming (deep - drawing) To determine coefficients of friction over the surface pressure are samples of the thus obtained, with the ammonium sulfate layer occupied and in addition with a conventional oil, which is a conventional, under the name PL 3802-39S offered barium-free, thixotropic corrosion inhibitor with good Forming properties had been subjected to a strip tightening test with a coating weight of 1.5 g / m ² oily flat steel product. In this test, the samples were placed at room temperature between two uncoated brake shoes consisting of steel number 1.2379, which had a surface pressure of up to 100 MPa against the samples. The measuring section was 500 mm / min at a test speed of 60 mm / min. The contact area between the tool and the sample surface was 600 m ² . The result of this test is in Fig. 1 played.

For comparison, an untreated sample of the same flat steel product has also been subjected to a streaking test under the same conditions as the previously examined sample. The determined course of the friction coefficient over the surface pressure is in Fig. 2 specified. The course reproduced there shows that the substrate surface of the untreated sample shows the so-called "slip-stick effect" very early on. In the Fig. 2 Curve shown breaks off because the attempt has been canceled to avoid damage to the tool. The slip-stick effect is the phenomenon of stick slip. This occurs when the static friction is greater than the sliding friction. At the same time, dampened coupled surface parts practice a very fast Sequence of sticking, twisting, separating and slipping off. The effect disappears as soon as the friction partners are separated by a lubricant. The sulfates selected according to the invention each turn out to be like the comparison of Fig. 2 With Fig. 1 or the one explained below FIGS. 3 and 4 occupied, here as particularly effective.

Trial 2

On a conventional flat steel product, also in the form of a Zn-coated thin sheet metal strip, a tribologically active iron (II) sulfate layer has been applied.

For this purpose, 189 g of ferrous sulfate (FeSO ₄ ) was dissolved in 1 1 of fully demineralized water, so that the iron sulfate content of the aqueous solution was 189 g / l. The native pH of the resulting solution was 2.2.

The aqueous solution was applied as in Experiment 1 at room temperature by means of the coater already described above to the previously alkaline-cleaned steel flat product. The application parameters are also given in Table 1.

Samples of the thus obtained steel flat product coated with the ferrous sulfate layer have also been subjected to a streaking test under the conditions already explained above. The result of this test is in Fig. 3 played. It can be seen that the ferrous sulfate layer was the same as that tested in experiment 1 Ammonium sulphate layer at higher surface pressures certainly friction coefficients of less than 0.15 reach.

Trial 3

A conventional flat steel product, also in the form of a Zn-coated thin sheet metal strip, has been coated with a tribologically active aluminum sulphate layer.

For this purpose, 240 g of aluminum sulfate (Al ₂ (SO ₄ ) ₃ ) was dissolved in 1 l of distilled water, so that the aluminum sulfate content of the aqueous solution was 240 g / l. The native pH of the resulting solution was 2.1.

The aqueous solution has also been applied in this case at room temperature by means of the coater already described above on the previously alkaline-cleaned steel flat product. The application parameters are also given in Table 1. In this case, the term "setting dipping and application roller" designates the extent to which the nip between the dipping and the application roller is smaller than the thickness of the processed flat steel product. With "PMT" at the same time the so-called "peak metal temperature" is designated.

Samples of the resulting flat steel product coated with the aluminum sulphate layer were again subjected to a streaking test. The result of this test is in Fig. 4 played. It was confirmed here that the aluminum sulfate layer as well as the Experiment 1 investigated ammonium sulfate layer and the investigated in Experiment 2 iron II layer at higher surface pressures certainly friction coefficient of less than 0.15 reach.

The tribologically active layers, which consist of the sulfates proposed according to the invention for use, thus achieve the same effect as the conventional coatings consisting for example of ZnSO ₄ . Table 1 attempt Operation of the coater peripheral speeds Setting dipping and application roller Thickness of steel product Gap width between dipping and application roller bearing weight drying oven PMT applicator roll dipping roller transport roller temperature dwell [M / min] [M / min] [M / min] [.Mu.m] [Mm] [.Mu.m] [mg / m ² ] [° C] [S] [° C] 1 Reverse 30 10 25 -400 1 0.9 30 100 100 71 2 Reverse 25 10 23 -500 1 0.9 30 100 100 71 3 Mitläufig 30 10 40 -400 1 0.9 30 100 35 71

Claims (15)

Use of a sulfate, selected from the group "aluminum sulfate, ammonium sulfate, iron sulfate, magnesium sulfate", as a coating agent for improving the tribological behavior of a flat steel product during forming in a forming machine. Use according to claim 1, characterized in that the sulfate is selected from the group "aluminum-III-sulfate, ammonium sulfate, ferrous sulfate, ferric sulfate, magnesium sulfate". Use according to one of the preceding claims, characterized in that the layer produced from the coating agent is water-soluble. Method for producing a steel component by forming a flat steel product in a forming machine comprising the following steps: Providing the flat steel product, - Generating a tribologically active layer on at least one of the contacting in the forming surfaces of the flat steel product or the forming machine used for forming by coating with a coating agent selected from the group "aluminum sulfate, ammonium sulfate, iron sulfate, magnesium sulfate"; - inserting the flat steel product into the forming tool; - Forming of the inserted into the forming machine flat steel product to the component. A method according to claim 4, characterized in that the sulfate is selected from the group "aluminum-III sulfate, ammonium sulfate, ferrous sulfate, ferric sulfate, magnesium sulfate". Method according to one of claims 4 or 5,
characterized in that s is executed as a forming cold forming. Method according to one of claims 4 to 6,
characterized in that the tribologically active layer is produced on the flat steel product. Method according to one of claims 4 to 7,
characterized in that the coating agent is applied as an aqueous solution. A method according to claim 8, characterized in that the aqueous solution consists of two components, of which one component is water as a solvent and the other component is the respective sulfate as a tribologically active ingredient. A method according to claim 9, characterized in that the solvent is distilled water. A method according to claim 9 or 10, characterized in that the content of the tribologically active ingredient in the aqueous solution is 0.2 to 1 mol / l (based on the SO4 ^2- ion concentration). Method according to one of claims 4 to 11,
characterized in that the sulfur content of the tribologically active layer produced on the flat steel product is 5-50 mg / m ² . Method according to one of claims 4 to 12,
characterized in that the friction coefficient of the flat steel product after coating with the tribologically active layer is at most 0.15. Method according to one of claims 4 to 13,
characterized in that the flat steel product is coated with a corrosion protection layer and that the tribologically active layer is applied to the corrosion protection layer. Method according to one of claims 4 to 14,
characterized in that the tribologically active layer is applied at ambient temperature.

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