Temporary corrosion protection layer

Abstract

A method for producing a component made of a steel product coated with an Al—Si protective coating, includes: providing a substrate consisting of a steel produced coated with an Al—Si protective coating, heating the substrate to a temperature T1 such that the Al—Si protective coating is only partially pre-alloyed with Fe of the steel product, cooling the pre-alloyed substrate to room temperature, applying a corrosion protection oil to the surface of the pre-alloyed substrate, wherein the oil consists of a composition containing fatty acid ester, transporting the pre-alloyed substrate to which the oil has been applied, heating the pre-alloyed substrate to which the oil has been applied to a temperature T2 such that the Al—Si protective coating is fully alloyed with Fe of the steel product and the oil is removed without leaving residue, and shaping the re-heated substrate to form the component.

Claims

1. Method for producing a component made of a steel product coated with an Al—Si protective coating, comprising: providing a substrate consisting of a steel product coated with an Al—Si protective coating, heating the substrate to a temperature T1 such that the Al—Si protective coating is only partially pre-alloyed with Fe of the steel product, cooling the pre-alloyed substrate to room temperature, applying a corrosion protection oil to the surface of the pre-alloyed substrate, wherein the corrosion protection oil contains fatty acid esters, transporting the pre-alloyed substrate to which the corrosion protection oil has been applied, heating the pre-alloyed substrate to which the corrosion protection oil has been applied to a temperature T2, wherein the corrosion protection oil is not removed from the substrate by cleaning the pre-alloyed substrate to which the corrosion protection oil has been applied before it is heated to T2 and the heating is carried out to T2 such that the Al—Si protective coating is fully alloyed with Fe of the steel product and the corrosion protection oil is removed without leaving residue, and shaping the re-heated substrate to form the component.

2. Method according to claim 1, wherein the heating to T2 takes place under a protective atmosphere.

3. Method according to claim 1, wherein the composition contains at least 98% by weight of the fatty acid esters.

4. Method according to claim 1, wherein the fatty acid esters is a C8-C16 compound.

5. Method according to claim 1, wherein the composition has a sulfur content in the range of 0.1-2% by weight.

6. Method according to claim 1, wherein the composition has a saponification number in the range of 150-265 mg KOH/g.

7. Method according to one of the preceding claim 1, wherein the corrosion protection oil is applied to the substrate in a quantity of 0.5 to 2 g/m2.

8. Method according to claim 1, wherein the temperature T2 corresponds to a temperature range of 850° C. to 1000° C.

9. Method according to claim 1, wherein the temperature T1 corresponds to a temperature range of 550° to 780° C.

10. Method according to claim 1, wherein the heating of the pre-alloyed substrate to which the corrosion protection oil has been applied to the temperature T2 comprises: heating the substrate to the temperature range T2 of 850° C. to 1000° C., holding the substrate in the temperature range T2, and cooling the substrate to a temperature range T3 of 550° C. to 750° C.

11. Method according to claim 8, wherein the temperature T2 corresponds to a temperature range of 880° C. to 930° C.

12. Method according to 8, wherein the temperature T1 corresponds to a temperature range of 600° to 700° C.

13. Method according to claim 10, wherein the temperature T2 is a temperature range of 880° C. to 930° C. and/or the temperature range T3 is a temperature range of 600° C. to 700° C.

14. Method according to claim 10, wherein the heating to T2 is 60 to 210 s.

15. Method according to claim 10, wherein the holding in the temperature range T2 is 30 to 600 s.

16. Method according to claim 10, wherein the cooling after the pre-alloying takes place occurs with a cooling rate in the range of 2 to 25 K/s.

17. Method according to claim 14, wherein the heating to T2 is 90 to 180 s.

18. Method according to claim 15, wherein the holding in the temperature range T2 is 30 to 120 s.

19. Method according to claim 16, wherein the cooling after the pre-alloying takes place occurs with a cooling rate in the range of 8 to 20 K/s.

Description

EXAMPLES

(1) The present disclosure will be explained in greater detail in the following based on examples.

(2) A substrate consisting of a steel sheet with a sheet thickness of 1.5 mm with quality 22MnB5 was provided with a 25 μm thick Al—Si protective coating in a hot-dip process. The protective coating contained 10% by weight Si, 3% by weight Fe and the remainder Al. The steel product coated with the Al—Si protective coating was pre-alloyed as a pre-assembled plate at 700° C. in a circulating air furnace. The Al—Si protective coating of the steel sheet that was pre-alloyed in this manner now contained 30% by weight Fe, 10% by weight Si and the remainder Al. Then 0.5 g/m.sup.2 of a corrosion protection oil was applied in a roller application process. The corrosion protection oil used in this case was a fatty acid derivative of a native oil, which does not contain any further additives or inhibitors. After transport and storage, these sheets were further processed at a site that is not protected from the weather. Prior to further processing, no changes to the surface or corrosion damage could be detected. The sheets were conveyed by means of industrial robots to a hot forming furnace for further processing and austenitized at 925° C. in 2.5 min enough that they could then be shaped and cured in a cooled mold. Measurements at the hot forming furnace showed no further emissions in the furnace atmosphere other than CO.sub.2, H.sub.2O and the furnace atmosphere that already existed beforehand in the form of nitrogen. No residues of the applied oil could be detected even on the press hardened component.

(3) It will be appreciated that various of the above-disclosed and other features and functions, or alternatives or varieties thereof, may be desirably combined into many other different systems or applications. Also that various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.