ALUMINIUM-BASED COATING FOR STEEL SHEETS OR STEEL STRIPS AND METHOD FOR THE PRODUCTION THEREOF

Abstract

in an aluminium-based coating for steel sheets or steel strips, the coating includes an aluminium-based coat applied in a hot-dip coating method, a covering layer containing aluminium oxide and/or hydroxide being arranged on the coat. The covering layer is produced by plasma oxidation and/or hot water treatment at temperatures of at least 90 C., advantageously at least 95 C., and/or steam treatment at temperatures of at least 90 C., advantageously at least 95 C. Alternatively, the covering layer containing aluminium oxide and/or hydroxide can be produced by anodic oxidation, the coat being produced in a molten bath with a Si content of between 8 and 12 wt. %, and an Fe content of between 1 and 4 wt. %, the remainder being aluminium.

Claims

1.-21. (canceled)

22. A method for producing a press-hardened component of steel sheet or steel strip, said method comprising: applying an aluminium-based coat onto the steel sheet or steel strip in a hot-dipping process; subjecting the coated steel sheet or steel strip to plasma oxidation and/or a hot water treatment and/or steam treatment and/or anodic oxidation after the hot-dipping process to thereby form a cover layer containing aluminium oxide and/or aluminium hydroxide on a surface of the coat, while forming oxides or hydroxides; heating the steel sheet or steel strip for hardening to a temperature above Ac3 at least in a region thereof; forming the steel sheet or steel strip at the temperature; and cooling the steel sheet or steel strip at a rate which, at least in a region thereof, is above a critical cooling rate.

23. The method of claim 22, wherein the coat is produced in a melting bath with an Si content of 8 to 12 wt. %, an Fe content of 1 to 4 wt. %, with the remainder being aluminium.

24. The method of claim 22, wherein the hot water treatment or the treatment with steam is performed at a temperature of at least 90 C.

25. The method of claim 22, wherein the hot water treatment or the treatment with steam is performed at a temperature of at least 95 C.

26. The method of claim 22, wherein the cover layer is applied onto the surface of the coat in a continuous process.

27. The method of claim 22, wherein the cover layer is applied having an average layer thickness less than 4 m and greater than 0.05 m.

28. The method of claim 22, wherein the cover layer is applied having an average layer thickness less than 1.0 m and greater than 0.1 m.

29. The method of claim 22, wherein the anodic oxidation is effected in a medium on a basis of boric acid, citric acid, sulphuric acid, oxalic acid, chromic acid, alkyl sulphonic acids, carboxylic acids, alkali carbonates, alkali phosphates, phosphoric acid, hydrofluoric acid.

30. The method of claim 22, wherein anodisation is effected at a current density between 1-50 A/dm.sup.2 and a voltage of 10-120 V and an electrolyte temperature between 0-65 C.

31. The method of claim 22, further comprising introducing colour pigments and/or pigments into the cover layer for influencing a function of the cover layer after anodisation and/or plasma oxidation of the coat and prior to hot water treatment and/or steam treatment.

32. The method of claim 22, further comprising introducing an element influencing an electrical conductivity and/or an antibacterial property of the cover layer as a function-influencing pigment.

33. The method of claim 22, further comprising introducing conductive, metallic particles, fullerenes, nano-structured particles as function-influencing pigments.

34. A press-hardened component of steel sheet or steel strip, said press-hardened component comprising an aluminium-based coating, produced according to a method as set forth in claim 22.

35. The press-hardened component of claim 34, wherein the aluminium-based coating forms a cover layer containing aluminium oxide and/or aluminium hydroxide on a surface of the coating.

36. The press-hardened component of claim 35, wherein the cover layer has an average layer thickness less than 4 m and greater than 0.05 m.

37. The press-hardened component of claim 35, wherein the cover layer has an average layer thickness less than 1.0 m and greater than 0.1 m.

38. The press-hardened component of claim 35, wherein the cover layer includes colour pigments and/or pigments for influencing a function of the cover layer.

39. The press-hardened component of claim 35, wherein the cover layer includes an electrical conductivity influencing element and/or antibacterial property influencing element.

40. The press-hardened component of claim 35, wherein the cover layer includes conductive, metallic particles, fullerenes, nano-structured particles as function-influencing pigments.

Description

PROCESS EXAMPLE I

[0050] A) Hot-dip finishing (aluminium-based coat)

B) Anodisation

[0051] 1. Alkaline pre-treatment (with/without surfactants)
2. Acid deoxidation (e.g. sulphuric acid, nitric acid . . . )

3. Rinsing

[0052] 4. Anodisation process

5. Rinsing

[0053] 6. Colouring/application of functional pigments

7. Rinsing

[0054] 8. Thermal water/steam treatment process (compaction process)

9. Drying

[0055] C) Hot-forming process

PROCESS EXAMPLE II

[0056] A) Hot-dip finishing (aluminium-based coat)

B) Anodisation

[0057] 1. Alkaline pre-treatment (with/without surfactants)
2. Acid deoxidation (e.g. sulphuric acid, nitric acid . . . )

3. Rinsing

[0058] 4. Anodisation process

5. Rinsing

[0059] 6. Colouring I application of functional pigments

7. Rinsing

[0060] 8. Thermal water/steam treatment process (compaction process)

9. Drying

[0061] C) Cold-forming process

PROCESS EXAMPLE III

[0062] A) Hot-dip finishing (aluminium-based coat)
B) Plasma oxidation
1. Alkaline pre-treatment (with/without surfactants)
2. Acid deoxidation (e.g. sulphuric acid, nitric acid . . . )

3. Rinsing

4. Drying

[0063] 5. Plasma etching
6. Plasma oxidation process
C) Hot-forming process or cold-forming process

PROCESS EXAMPLE IV

[0064] A) Hot-dip finishing (aluminium-based coat)
B) Thermal water/steam treatment
1. Alkaline pre-treatment (with/without surfactants)
2. Acid deoxidation (e.g. sulphuric acid, nitric acid . . . )

3. Rinsing

[0065] 4. Thermal water/steam treatment process

5. Drying

[0066] C) Hot-forming process or cold-forming process