METHOD FOR MODIFYING FINISHED SURFACES WITH THE AIM OF IMPROVED SURFACE PROPERTIES

Abstract

The present disclosure relates to a method for producing a semifinished product with modified surface, comprising at least one method step of at least regionally modifying the surface of a coated, skin-pass-rolled, oiled, cleaned metallic steel substrate via low-pressure or atmospheric-pressure plasma treatment of said surface regions with oxygen, argon or a mixture of oxygen and argon as process gas. The present disclosure further relates to the accordingly produced semifinished products and/or flat steel products, optionally formed semifinished products and/or flat steel products, and also to their use.

Claims

1. A method for producing a semifinished product with modified surface, comprising the following method steps: I. providing a striplike or sheetlike steel substrate, II. at least regionally applying a double-sided metallic coating based on zinc by hot-dip coating, III. skin-pass-rolling the metallically coated substrate from step II, IV. oiling the skin-pass-rolled, metallically coated substrate from step III, V. at least regionally cleaning the substrate, VI. at least regionally modifying the surface of the cleaned substrate from step V via low-pressure or atmospheric-pressure plasma treatment of said surface regions with oxygen, air, argon, forming gas or a mixture of oxygen and argon, oxygen and air as process gas.

2. A method for producing a semifinished product with modified surface, comprising the following method steps: I. providing a striplike or sheetlike steel substrate, II. skin-pass-rolling, at least regionally, the metallic substrate from step I, III. at least regionally applying a double-sided metallic coating based on zinc by electrolysis, IV. oiling the skin-pass-rolled, metallically coated substrate from step III, V. cleaning, preferably in the oiled region, the oiled, skin-pass-rolled, metallically coated substrate, VI. at least regionally modifying the surface of the cleaned substrate from step V via low-pressure or atmospheric-pressure plasma treatment of said surface regions with oxygen, air, argon, forming gas or a mixture of oxygen and argon, oxygen and air as process gas.

3. The method as claimed in claim 1 wherein steel substrate is coated with a metallic coating, based on Zn, ZnMg, ZnAl and/or ZnMgAl.

4. The method as claimed in claim 1 wherein the striplike substrate after at least one of the steps I, skin-pass rolling II or III, IV, V and/or VI, is wound up to form a coil, for supply to or is supplied to the downstream working step(s).

5. The method as claimed in claim 1 wherein the method after oiling step IV comprises an aging step IV.B.

6. The method as claimed in claim 5 wherein after the modifying of the surface in step VI, a further surface treatment step VII is carried out.

7. The method as claimed in claim 6, further comprising: further surface treatment step VII-i, including a coil-coating method is carried out.

8. The method as claimed in claim 7, wherein after step VI, first a pretreatment for coil coating, as step VII-i-a, and subsequently the coil-coating method, as step VII-i-b, are carried out.

9. The method as claimed in claim 6 wherein after the skin-pass rolling in step III, modification of the surface of the skin-pass-rolled substrate from step III is carried out via at least regional plasma treatment of the surface in a step III-ii-a and optionally a step III-ii-b of pre- and/or aftertreament.

10. The method as claimed in claim 6 wherein before the cleaning in step V (now V-ii-b), at least one step V-ii-a is carried out, selected from the group of the methods consisting of cutting, forming, joining, degreasing, activating, phosphating, cathodic dip-painting, and painting.

11. The method as claimed in claim 10, wherein a further surface treatment step VII-ii-a, activation of the surface is carried out.

12. The method as claimed in claim 11, wherein a further surface treatment step VII-ii-b, phosphating of the surface is carried out.

13. The method as claimed in claim 12 wherein the relative concentrations of C, O, Mg and/or Zn in a surface-bordering layer of the metallic coating, with a thickness equal to the typical XPS information depth, are substantially the same after between step III and after step VI.

14. (canceled)

15. A semifinished product produced in a method as claimed in claim 13.

16. The method as claimed in claim 2 wherein the steel substrate is coated with a metallic coating, based on Zn, ZnMg, ZnAl and/or ZnMgAl.

17. The method as claimed in claim 2 wherein the striplike substrate after at least one of the steps I, skin-pass rolling II or III, IV, V and/or VI, is wound up to form a coil, for supply to or is supplied to the downstream working step(s).

18. The method as claimed in claim 2 wherein the method after oiling step IV comprises an aging step IV.B.

19. The method as claimed in claim 18 wherein after the modifying of the surface in step VI, a further surface treatment step VII is carried out.

20. The method as claimed in claim 19, further comprising: further surface treatment step VII-i, including a coil-coating.

21. The method as claimed in claim 20, further comprising: further surface treatment step VII-i, including a coil-coating and wherein after step VI, first a pretreatment for coil coating, as step VII-i-a, and subsequently the coil-coating method, as step VII-i-b, are carried out.

Description

EXAMPLES

Example 1

[0083] A skin-pass-rolled substrate coated on a ZnMgAl basis as described above was produced and was degreased using organic solvent (combination of n-heptane with isopropanol, n-heptane with ethanol or ethanol with isopropanol). Plasma treatment took place with oxygen as process gas as described in table 1 for increasing the water wettability. Wettability was determined via the contact angle of water and diiodomethane; the control (K) used was an identically prepared metal sheet, but without plasma treatment.

TABLE-US-00001 TABLE 1 Sample Degreasing Plasma treatment P1 n-heptane, isopropanol f = 15 sccm, L = 50 W, t = 15 min P2 n-heptane, isopropanol f = 15 sccm, L = 50 W, t = 5 min P3 n-heptane, ethanol f = 15 sccm, L = 50 W, t = 5 min P4 n-heptane, ethanol f = 15 sccm, L = 50 W, t = 10 min

[0084] The results are represented in FIG. 1. From this it is clear that the plasma treatment significantly increases the wettability. The plasma treatment generally increases the wettability significantly, in other words not only for water. This means that the modification of the surface by plasma leads to a surface which is wettable effectively by polar liquids. Since the effect occurs even after the shortest treatment time of 5 min, meaning that the carbon-containing residual coverings are completely ablated, there is no difference in wettability achievable by longer treatment time.

[0085] The water contact angle of P1 was measured immediately after plasma treatment (P1-0), after 1 day (P1-1), 2 days (P1-2) and after 2 weeks (P1-3).

[0086] The results are represented in FIG. 2.

[0087] From this it is clear that through environmental contact and renewed soiling of the surface, the effect of the plasma treatment is reduced again.

Example 2

[0088] A coated substrate skin-pass-rolled as described above and galvanized on the basis of Zn (Z1) or ZnMgAl (ZM1 and ZM2) and also electrolytically (ZE1) was oiled with the anticorrosion oil PL3802-39S from Fuchs and subjected to alkaline degreasing with Ridoline 1340 from Henkel. Plasma treatment took place with argon or oxygen-argon mixture as process gas, as described above, for increasing the wettability. The wettability was determined via the contact angle with water and diiodomethane immediately after plasma treatment; serving as control (K) was an identically prepared metal sheet, but without.

[0089] The precise parameters are summarized in table 2:

TABLE-US-00002 Base pressure p Test pressure P q Ar q O2 L t Sample Cleaning [10{circumflex over ()}?4 mbar] [10{circumflex over ()}?2 mbar] [sccm] [sccm] [kW] [sec] ZM1 Mild 3 to 6 4 200 400 0.5 60 Z1 alkaline ZE1 ZM2 600 0

[0090] The results are represented in FIG. 3. From this it is clear that the plasma treatment generally increases the wettability significantly and that not only argon but also oxygen-argon mixtures are suitable for conditioning the wettability. For Zn and ZnMgAl coatings, an improvement in wettability in analogy to the pure oxygen plasma treatment is evident.

Example 3

Investigating the Effect of the Plasma Treatment on Coil-Coating Process

[0091] 15 respective substrates skin-pass-rolled as described above and coated on a ZnMgAl basis were produced and were oiled with the anticorrosion oil PL3802-39S from Fuchs. Of these substrates, 10 were degreased using alkali and 5 with MEK (methyl ethyl ketone). Additionally, five of the substrates degreased with alkali underwent plasma treatment with oxygen-argon mixture as process gas, as described above, for increasing the wettability. Parameters: base pressure between 3 and 6*10{circumflex over ()}?4 mbar, test pressure 4*10{circumflex over ()}?2 mbar, qAr 200 sccm, q O2 400 sccm, L=0.5 kW, treatment time 60 s.

[0092] Via a coil-coating line, all of the substrates were coated as pretreatment with an adhesion promoter (adhesion promoter GBX 4537).

[0093] A thermal imaging camera was used to represent the wet film of the pretreatment solution directly after coating.

[0094] In the case of the semifinished products without plasma treatment, the wet film extensively appeared to be regular, but fine transverse streaks were observed in the wet film, which remained after drying.

[0095] The uniformity of the layer of adhesion promoter was assessed by giving it a dark staining with copper sulfate solution. In the case of the semifinished products without plasma treatment, wetting defects were observed.

[0096] The semifinished products subjected to plasma treatment produced a unitary, full-area, homogeneous wetting without defects.

[0097] Evaluation took place visually.