USE OF A SULPHATE, AND METHOD FOR PRODUCING A STEEL COMPONENT BY FORMING IN A FORMING MACHINE

Abstract

Coating materials with minimized lubricant demand enable optimized tribological conditions in forming flat steel products and are also unobjectionable in relation to their effects on the environment. With such coating materials, steel components can be produced by forming flat steel products in forming machines. For example, a tribologically-active layer may be produced on at least one surface of a flat steel product or a forming machine used to form the flat steel product, wherein the at least one surface comes into contact with the opposing component during forming. The tribologically-active layer may be formed by coating the at least one surface with a coating material from a group consisting of aluminum sulfate, ammonium sulfate, iron sulfate, and magnesium sulfate. The flat steel product may be inserted into the forming machine to be formed into the steel component.”

Claims

1.-15. (canceled)

16. A flat steel product configured to be formed by a forming machine, the flat steel product comprising a coating material that includes a sulfate from a group consisting of aluminum sulfate, ammonium sulfate, iron sulfate, and magnesium sulfate, wherein the coating material improves a tribological characteristic of the flat steel product relative to a tribological characteristic of a flat steel product without the coating material.

17. The flat steel product of claim 16 wherein the group consists of aluminum(III) sulfate, ammonium sulfate, iron(III) sulfate, iron(II) sulfate, and magnesium sulfate.

18. The flat steel product of claim 16 wherein the coating material forms a water-soluble layer.

19. A forming machine for forming a flat steel product, the forming machine comprising a coating material that includes a sulfate from a group consisting of aluminum sulfate, ammonium sulfate, iron sulfate, and magnesium sulfate, wherein the coating material improves a tribological characteristic of the forming machine relative to a tribological characteristic of a forming machine without the coating material.

20. The forming machine of claim 19 wherein the group consists of aluminum(III) sulfate, ammonium sulfate, iron(III) sulfate, iron(II) sulfate, and magnesium sulfate.

21. The forming machine of claim 19 wherein the coating material forms a water-soluble layer.

22. A method of producing a steel component by forming a flat steel product in a forming machine, the method comprising: providing the flat steel product; producing a tribologically-active layer on at least one surface of the flat steel product or of the forming machine by coating the at least one surface with a coating material from a group consisting of aluminum sulfate, ammonium sulfate, iron sulfate, and magnesium sulfate; inserting the flat steel product into the forming tool; and forming the flat steel product to create the steel component, wherein during forming the at least one surface of the flat steel product comes into contact with the forming machine, or the at least one surface of the forming machine comes into contact with the flat steel product.

23. The method of claim 22 wherein the group consists of aluminum(III) sulfate, ammonium sulfate, iron(II) sulfate, iron(III) sulfate, and magnesium sulfate.

24. The method of claim 22 wherein the forming of the flat steel product is performed as cold forming of the flat steel product.

25. The method of claim 22 wherein the tribologically-active layer is produced on the flat steel product.

26. The method of claim 25 wherein a sulfur fraction of the tribologically-active layer produced on the flat steel product is 5-50 mg/m.sup.2.

27. The method of claim 25 wherein a coefficient of friction of the at least one surface of the flat steel product after the tribologically-active layer is produced is not more than 0.15.

28. The method of claim 22 wherein the coating material is applied as an aqueous solution.

29. The method of claim 28 wherein the aqueous solution consists of a first component and a second component, wherein the first component is water as a solvent and the second component is the respective sulfate as a tribologically-active constituent.

30. The method of claim 29 wherein the first component is distilled water as the solvent.

31. The method of claim 29 wherein an amount of the tribologically-active constituent in the aqueous solution is 0.2-1 mol/l based on a SO.sub.4.sup.2-ion concentration.

32. The method of claim 22 wherein the flat steel product includes a anticorrosion control coat, wherein the tribologically-active layer is produced on the anticorrosion control coat.

Description

[0044] The invention is elucidated in more detail below with working examples. In the drawing:

[0045] FIG. 1 shows a diagram in which the development of the coefficient of friction of the surface of a galvanized thin sheet coated with an ammonium sulfate layer, during the strip-drawing test, is plotted against the respective contact pressure;

[0046] FIG. 2 shows a diagram in which the development of the coefficient of the surface of friction of an untreated galvanized thin sheet, during the strip-drawing test, is plotted against the respective contact pressure;

[0047] FIG. 3 shows a diagram in which the development of the coefficient of friction of the surface of a galvanized thin sheet coated with an iron(II) sulfate layer, during the strip-drawing test, is plotted against the respective contact pressure

[0048] FIG. 4 shows a diagram in which the development of the coefficient of friction of the surface of a galvanized thin sheet coated with an aluminum sulfate layer, during the strip-drawing test, is plotted against the respective contact pressure.

[0049] The coefficient of friction profiles reproduced in the figures were determined in a strip-drawing test, which is explained, for example, in section 2.8.7.4 of volume 4 of the 5.sup.th edition of the “Fertigungsverfahren 4” [Fabrication methods 4] compendium by Fritz Klocke and Wilfried König, Springer-Verlag Berlin Heidelberg, 2006 (ISBN-13 978-3-540-23650-4).

[0050] Experiment 1

[0051] A tribologically active ammonium sulfate layer was applied to a conventional flat steel product in the form of a thin sheet strip provided with a Zn coating.

[0052] This was done by preparing an aqueous solution where 90 g of ammonium sulfate ((NH.sub.4).sub.2SO.sub.4) were dissolved in 1 l of water (distilled), giving the aqueous solution an ammonium sulfate content of 90 g/l. The native pH of the resulting solution was 5.3.

[0053] The aqueous solution thus constituted was applied at room temperature to the thin sheet flat steel product, subjected beforehand to alkaline cleaning, by means of a “Chemcoater” which is customary in the industry.

[0054] A “Chemcoater” is a plant component which is used in the steel industry for applying chemical substances, for application in the form of an aqueous solution, to galvanized quality flat steel. Such coaters are used in particular for applying water-soluble media which serve to pretreat the respective flat steel product for a subsequent varnish or film coating or for improving the corrosion control. It allows different treatment chemicals to be applied via rollers to the particular flat steel product to be coated. The flat steel product furnished with the coating subsequently travels through an oven, in which the coating is dried.

[0055] The parameters set when applying the ammonium sulfate solution are reported in table 1.

[0056] In order to determine the development of the coefficient of friction against the contact pressing, which is decisive for the characteristics on cold forming (deep drawing) in the cold-forming tool (punch/die) of a cold forming machine, samples of the resulting flat steel product, coated with the ammonium sulfate layer and additionally oiled with a conventional oil, which was a conventional, barium-free, thixotropic anticorrosion agent with good forming properties, available under the name PL 3802-39S, the oiling taking place with an add-on weight of 1.5 g/m.sup.2, were subjected to a strip-drawing test. In this test, the samples were disposed at room temperature between two uncoated braking jaws consisting of the steel with material number 1.2379, which acted with a contact pressure of up to 100 MPa against the samples. The measuring distance was 500 mm/min at a testing speed of 60 mm/min. The contact area between tool and sample surface was 600 m.sup.2. The result of this test is shown in FIG. 1.

[0057] For comparison, an untreated sample of the same flat steel product was likewise subjected to a strip-drawing test under the same conditions as the sample investigated before. The profile of the coefficient of friction against the contact pressure, determined in this case, is reported in FIG. 2. The profile reproduced there shows that the substrate surface of the untreated sample exhibits the “slip-stick” effect already at a very early stage. The plot shown in FIG. 2 runs out, since the experiment was discontinued in order to avoid damage to the tool. This slip-stick effect is a phenomenon which occurs when the static friction is greater than the sliding friction. In this case, surface parts coupled in a damped manner perform a very rapid sequence of sticking, bracing, separating, and gliding. The effect disappears as soon as the friction partners are separated by a lubricant. The sulfates selected in accordance with the invention prove particularly effective here, as demonstrated by a comparison of FIG. 2 with FIG. 1 or with FIGS. 3 and 4, which are elucidated below.

[0058] Experiment 2

[0059] A tribologically active iron(II) sulfate layer is applied to a conventional flat steel product likewise in the form of a thin sheet strip provided with a Zn coating.

[0060] For this purpose, 189 g of iron(II) sulfate (FeSO.sub.4) were dissolved in 1 l of fully demineralized water, giving the aqueous solution an iron sulfate content of 189 g/l. The native pH of the resulting solution was 2.2.

[0061] As in the case of experiment 1, the aqueous solution was applied at room temperature, using the coater already described above, to the flat steel product, which had undergone alkaline cleaning beforehand. The application parameters are again reported in table 1.

[0062] Samples of the flat steel product furnished with the layer of iron(II) sulfate were likewise subjected to a strip-drawing test under the conditions already elucidated above. The result of this test is shown in FIG. 3. It is apparent that, just like the ammonium sulfate layer investigated in experiment 1, the iron(II) sulfate layer reliably achieves coefficients of friction of less than 0.15 with relatively high contact pressures.

[0063] Experiment 3

[0064] A tribologically active aluminum sulfate layer is applied to a conventional flat steel product likewise in the form of a thin sheet strip provided with a Zn coating.

[0065] For this purpose, 240 g of aluminum sulfate (Al.sub.2(SO.sub.4).sub.3) were dissolved in 1 l of fully demineralized water, giving the aqueous solution an aluminum sulfate content of 240 g/l. The native pH of the resulting solution was 2.1.

[0066] In this case as well, the aqueous solution was applied at room temperature, using the coater already described above, to the flat steel product, which had undergone alkaline cleaning beforehand. The application parameters are again reported in table 1. In the table, the indication “Setting of dip roll and application roll” identifies the degree by which the squeeze-off gap present between the dip roll and application roll is smaller than the thickness of the processed flat steel product. At the same time, “PMT” refers to the “Peak Metal Temperature”.

[0067] Samples of the resulting flat steel product coated with the aluminum sulfate layer were again subjected to a strip-drawing test. The result of this test is shown in FIG. 4. Here as well it was confirmed that, just as for the ammonium sulfate layer investigated in experiment 1 and the iron(II) layer investigated in experiment 2, the aluminum sulfate layer reliably achieves coefficients of friction of less than 0.15 at relatively high contact pressures.

[0068] The tribologically active layers which consist of the sulfates proposed for use in accordance with the invention therefore achieve the same effect as the conventional coatings consisting, for example, of ZnSO.sub.4.

TABLE-US-00001 TABLE 1 Gap width Setting of between dip Peripheral speeds dip roll and Thickness roll and Drying oven Mode of Application Transport application of flat steel application Add-on Residence operation roll Dip roll roll roll product roll weight Temperature time PMT Experiment of coater [m/min] [m/min] [m/min] [μm] [mm] [μm] [mg/m.sup.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 co-rotating 30 10 40 −400 1 0.9 30 100  35 71