STEEL COMPONENT HAVING A METAL COATING PROTECTING IT AGAINST CORROSION

Abstract

The present invention relates to a method for producing a steel component comprising a substrate and a coating, to a corresponding sleet component and to the use thereof in the automotive sector.

Claims

1-13. (canceled)

14. A steel component comprising a steel substrate coated with a coating, wherein: the steel component has a rolling degree of from 0.5% to 75%, the rolling degree being a ratio of a decrease in thickness of the steel component due to rolling the steel substrate and the coating, to an initial thickness of the steel component before rolling the steel substrate and the coating; the steel component has a content of diffusible hydrogen Hdiff of up to 0.4 ppm, the steel substrate includes, by weight percentage (wt. %): 0.06 to 0.50 C, 0.50 to 3.0 Mn, 0.10 to 0.50 Si, 0.01 to 1.00 Cr, up to 0.20 Ti, up to 0.10 Al, up to 0.10 P, up to 0.1 Nb, up to 0.01 N, up to 0.05 S, up to 0.1 B, and remainder Fe and unavoidable impurities; and the coating includes, by wt. %: 3 to 15 Si, 1 to 3.5 Fe, 0.05 to 5.0 alkali and/or alkaline earth metals, and remainder Al and unavoidable impurities.

15. The steel component according to claim 14, wherein the steel component does not have a uniform thickness.

16. The steel component according to claim 15, wherein different regions of the steel component have different rolling degrees.

17. The steel component according to claim 16, wherein a first region of the steel component has a lower rolling degree than a second region of the steel component.

18. The steel component according to claim 14, wherein the content of diffusible hydrogen Hdiff is up to 0.3 ppm.

19. The steel component according to claim 14, wherein the content of diffusible hydrogen Hdiff is up to 0.1 ppm.

20. The steel component according to claim 14, wherein the rolling degree is from 2.5% to 60%.

21. The steel component according to claim 14, wherein the coating is a double sided coating with a coating weight of 20 to 240 g/m.sup.2.

22. The steel component according to claim 21, wherein the coating weight of 50 to 180 g/m.sup.2.

23. The steel component according to claim 14, further comprising a fully alloyed alloy layer in a thickness of from 5 μm to 60 μm arranged between the steel substrate and the coating.

24. The steel component according to claim 23, wherein the thickness of the fully alloyed alloy layer is from 10 μm to 45 μm.

25. The steel component according to claim 14, wherein the coating is a hot-dip coating.

26. The steel component according to claim 14, wherein the steel substrate is a hot rolled steel substrate or a cold rolled steel substrate.

27. The steel component according to claim 14, wherein: the steel substrate has a rolling degree to sheet thickness ratio (WGB) of greater than 0.8 to 200; the WGB is a dimensionless value being determined according to the following formula: $\mathrm{WGB}=1.5.Math.\frac{1+\mathrm{rolling}\mathrm{degree}.Math.100}{\frac{1}{2}.Math.\left(1+\sqrt{\mathrm{Sheet}\mathrm{thickness}}\right)}$ in said formula, the sheet thickness is in mm and is a final thickness of the steel substrate after rolling.

28. A bumper support/reinforcement, door reinforcement, B-pillar reinforcement, A-pillar reinforcement, roof frame, or body sill comprising the steel component according to claim 14.

29. The steel component according to claim 14, wherein the steel substrate includes, by wt. %: 0.06 to 0.50 C, 0.50 to 3.0 Mn, 0.10 to 0.50 Si, 0.01 to 1.00 Cr, up to 0.20 Ti, 0.01 to 0.05 Al, 0.00 to 0.05 P, 0.001 to 0.1 Nb, up to 0.01 N, 0.00 to 0.005 S, 0.001 to 0.05 B, and remainder Fe and unavoidable impurities.

30. The steel component according to claim 14, wherein the steel substrate includes, by wt. %: 0.06 to 0.50 C, 0.50 to 3.0 Mn, 0.10 to 0.50 Si, 0.01 to 1.00 Cr, up to 0.20 Ti, 0.02 to 0.05 Al, 0.00 to 0.02 P, 0.001 to 0.1 Nb, up to 0.01 N, 0.00 to 0.003 S, 0.002 to 0.0035 B, and remainder Fe and unavoidable impurities.

31. The steel component according to claim 14, wherein the steel substrate includes, in wt. %: 0.20 to 0.25 C, 0.50 to 3.0 Mn, 0.10 to 0.50 Si, 0.01 to 1.00 Cr, up to 0.20 Ti, up to 0.10 Al, up to 0.10 P, up to 0.1 Nb, up to 0.01 N, up to 0.05 S, up to 0.1 B, and remainder Fe and unavoidable impurities.

32. The steel component according to claim 14, wherein the steel substrate includes, in wt. %: 0.20 to 0.225 C, 0.50 to 3.0 Mn, 0.10 to 0.50 Si, 0.01 to 1.00 Cr, up to 0.20 Ti, up to 0.10 Al, up to 0.10 P, up to 0.1 Nb, up to 0.01 N, up to 0.05 S, up to 0.1 B, and remainder Fe and unavoidable impurities.

33. The steel component according to claim 14, wherein the coating includes, by wt. %: 9 to 10 Si, 2 to 3.5 Fe, 0.11 to 0.6 alkali and/or alkaline earth metals, and remainder Al and unavoidable impurities.

Description

DRAWINGS

[0094] FIG. 1 shows a graph in which the WOP value is plotted against the rolling degree to sheet thickness ratio. On said graph, the numbering means the following: [0095] 1 WOP value (hydrogen-related furnace parameter value) [0096] 2 WGB (rolling degree to sheet thickness ratio) [0097] 3 Partial surface “3” [0098] 4 Partial surface “4” [0099] 5 Partial surface “5”

[0100] FIG. 2 shows, by way of example, how the WOP value is determined with a known rolling degree to sheet thickness ratio according to the invention, and in this case the numbering means the following: [0101] E1 rolling degree 0.5%, starting sheet thickness 3.0 mm, rolling degree to sheet thickness ratio 1.6, resulting in WOP value of from 300 to 790. [0102] E2 rolling degree 2.5%, starting sheet thickness 3.0 mm, rolling degree to sheet thickness ratio 3.8, resulting in WOP value of from 300 to 780. [0103] E3 rolling degree 30%, starting sheet thickness 1.5 mm, rolling degree to sheet thickness ratio 41.8, resulting in WOP value of from 300 to 630. [0104] E4 rolling degree 50%, starting sheet thickness 1.98 mm, rolling degree to sheet thickness ratio 63.6, or rolling degree 47%, starting sheet thickness 1.5 mm, rolling degree to sheet thickness ratio 64.7, resulting in WOP value of from 200 to 600 in each case.

EXAMPLES

Example 1

[0105] The following embodiments serve to explain the invention in greater detail.

[0106] Blanks are used which have been obtained from melts having the alloy components according to Table 1.

TABLE-US-00001 TABLE 1 Melt composition of the flat steel products used Alloy component in wt. % Alloy elements Melt A Melt B Melt C Melt D C 0.224 0.212 0.219 0.212 to 0.225 Si 0.23 0.22 0.26 0.21 to 0.27 Mn 1.20 1.11 1.14 1.11 to 1.20 P 0.014 0.009 0.013 0.009 to 0.016 S 0.0029 0.0013 0.0023 0.0006 to 0.0029 Al total 0.035 0.027 0.032 0.026 to 0.038 Cr 0.190 0.187 0.183 0.180 to 0.190 Nb 0.001 0.001 0.001 0.001 to 0.001 Mo 0.0055 0.0018 0.0040 0.0016 to 0.0055 Ti 0.028 0.029 0.025 0.020 to 0.033 B 0.0022 0.0024 0.0026 0.0021 to 0.0028 All data in wt. %, remainder Fe and unavoidable impurities

[0107] The flat steel products used have a coating containing 9 to 10 wt. % Si, 2 to 3.5 wt. % iron, remainder aluminum and the amount of Mg set out in Table 2, The coating weight, the sheet thickness and the rolling degree of the flat steel products used are likewise set out in Table 2. The corresponding WOP value is then determined in the graph according to FIG. 1 by means of the rolling degree to sheet thickness ratio (formula 3), and T.sub.furnace, t.sub.furnace and T.sub.dew point of the furnace atmosphere are subsequently determined and set by means of formula (1). The thus heated flat steel product is then removed from the furnace and inserted into a mold after a transport time of 6 seconds. After insertion into the mold, this mold immediately closes and remains in the closed state for approx. 20 seconds, in order to thereby cool the component to <80° C. by contact with the cooled molds. Samples are taken from the manufactured steel components, which are analyzed with regard to the amount of diffusible hydrogen contained (H.sub.diff) by means of desorption mass spectrometry using heated samples (thermal desorption mass spectrometry (TDMS)).

TABLE-US-00002 TABLE 2 Se- Mg con- Coating weight Sheet Rolling rial tent on both sides thickness degree T.sub.furnace t.sub.furnace T.sub.dew point H.sub.diff WOP no. Melt [wt. %] [g/m.sup.2] [mm] [%] WGB [K] [h] [K] [ppm] value Region V1 A 0.3 80 1.50 0 1.3 1193.15 0.100 288.15 0.12 557 — V2 A 0.3 80 1.50 0 1.3 1193.15 0.167 288.15 0.17 584 — V3 A 0.3 140 1.50 0 1.3 1193.15 0.222 288.15 0.13 606 — V4 A 0.3 140 1.50 0 1.3 1193.15 0.100 288.15 0.14 557 — V5 A 0 140 1.50 0 1.3 1193.15 0.222 288.15 0.45 606 — 6 A 0.3 140 1.10 27 41.0 1193.15 0.100 248.15 0.07 129 A 7 A 0.3 140 1.10 27 41.0 1193.15 0.167 248.15 0.05 156 A 8 A 0.3 140 1.10 27 41.0 1193.15 0.222 248.15 0.05 177 A 9 A 0.3 140 1.10 27 41.0 1193.15 0.100 268.15 0.26 288 A 10 A 0.3 140 1.10 27 41.0 1193.15 0.167 268.15 0.14 315 B 11 A 0.3 140 1.10 27 41.0 1193.15 0.222 268.15 0.12 336 B 12 A 0.3 140 0.80 47 76.0 1193.15 0.100 248.15 0.15 129 A 13 A 0.3 140 0.80 47 76.0 1193.15 0.167 248.15 0.13 156 A 14 A 0.3 140 0.80 47 76.0 1193.15 0.222 248.15 0.05 177 A 15 A 0.3 140 0.80 47 76.0 1193.15 0.100 268.15 0.34 288 A 16 A 0.3 140 0.80 47 76.0 1193.15 0.167 268.15 0.29 315 B 17 A 0.3 140 0.80 47 76.0 1193.15 0.222 268.15 0.22 336 B V18 A 0.3 140 0.80 47 76.0 1193.15 0.222 288.15 0.89 606 — V19 C 0 140 1.50 0 1.3 1193.15 0.083 288.15 0.47 550 — V20 C 0 140 1.50 0 1.3 1193.15 0.167 288.15 0.59 584 — V21 C 0 140 1.50 0 1.3 1193.15 0.083 268.15 0.20 281 — V22 C 0 140 1.50 0 1.3 1193.15 0.083 248.15 0.10 122 — 23 B 0.4 140 1.35 30 43.0 1193.15 0.083 268.15 0.20 281 A 24 B 0.4 140 1.35 30 43.0 1193.15 0.167 268.15 0.17 315 B 25 B 0.4 140 1.35 30 43.0 1193.15 0.083 288.15 0.22 550 B 26 B 0.4 140 1.35 30 43.0 1193.15 0.167 288.15 0.31 584 B 27 B 0.4 140 1.00 50 76.5 1193.15 0.083 268.15 0.11 281 A 28 B 0.4 140 1.00 50 76.5 1193.15 0.083 268.15 0.13 281 A 29 B 0.4 140 1.00 50 76.5 1193.15 0.167 268.15 0.11 315 B 30 B 0.4 140 1.00 50 76.5 1193.15 0.167 268.15 0.12 315 B 31 B 0.4 140 1.00 50 76.5 1193.15 0.083 288.15 0.26 550 B 32 B 0.4 140 1.00 50 76.5 1193.15 0.167 288.15 0.28 584 B V33 D 0.3 140 1.50 0 1.3 1253.15 0.083 288.15 0.27 554 — V34 D 0.3 140 1.50 0 1.3 1153.15 0.167 288.15 0.27 579 — V35 D 0 140 1.50 0 1.3 1153.15 0.250 288.15 0.47 610 — 36 D 0 140 1.50 25 35.1 1193.15 0.083 268.15 0.29 281 V37 D 0 140 1.50 25 35.1 1193.15 0.050 288.15 0.52 536 — 38 D 0 140 1.50 25 35.1 1193.15 0.083 258.15 0.05 185 A 39 D 0 140 1.50 25 35.1 1193.15 0.167 258.15 0.22 219 A 40 D 0.5 140 1.00 0 1.5 1193.15 0.167 288.15 0.27 584 B 41 D 0.5 140 1.97 0 1.2 1193.15 0.083 288.15 0.10 550 B 42 D 0.5 140 1.97 0 1.2 1193.15 0.250 288.15 0.30 616 B V43 D 0 140 1.50 25 35.1 1193.15 0.083 288.15 0.85 550 — V44 D 0 140 1.50 25 35.1 1193.15 0.167 268.15 0.49 315 — 45 D 0.3 140 1.50 0 1.3 1193.15 0.083 298.15 0.24 718 B 46 D 0 140 1.30 30 43.5 1193.15 0.083 268.15 0.27 281 A 47 D 0 140 1.30 30 43.5 1193.15 0.083 268.15 0.27 281 A V48 D 0 140 1.30 30 43.5 1193.15 0.083 288.15 0.57 550 — V49 D 0 140 0.95 50 77.5 1193.15 0.083 268.15 0.58 281 — V50 D 0 140 0.95 50 77.5 1193.15 0.167 268.15 0.47 315 — V Comparative example

Example 2

[0108] Determination by way of example of allowable values for T.sub.furnace, t.sub.furnace and T.sub.dew point to maintain an H.sub.diff value of 0.4 ppm in produced components made of flat steel products.

[0109] Example E3 from FIG. 2:

[0110] h.sub.0=2.143 mm; h.sub.1=sheet thickness=1.5 mm; Δh=0.643 mm; coating with Mg 0.35 wt. %

[00005]$\mathrm{rolling}\mathrm{degree}=\frac{\Delta h}{h_0}=\frac{0.643\mathrm{mm}}{2.143\mathrm{mm}}=0\text{.3}=30\%$$\mathrm{WGB}=1.5.Math.\frac{1+\mathrm{rolling}\mathrm{degree}.Math.100}{\frac{1}{2}.Math.\left(1+\sqrt{\mathrm{Sheet}\frac{\mathrm{thickness}}{\mathrm{mm}}}\right)}=1.5.Math.\frac{1+0.3.Math.100}{\frac{1}{2}.Math.\left(1+\sqrt{\frac{1.5\mathrm{mm}}{\mathrm{mm}}}\right)}=41.8$

[0111] For the WGB value of 41.8, a WOP value of from 300 to 630 can be read out from FIG. 1 or calculated using the specified points. Now the three parameters T.sub.furnace, t.sub.furnace and T.sub.dew point can be set to result in a WOP value of: 300≤WOP≤630, for example: T.sub.furnace=930° C.=1203.15 K; t.sub.furnace=400 s=0.111 h; and T.sub.dew point=10° C.=283.15 K

[00006]$300\le \mathrm{WOP}\le 630$$\iff 300\le \frac{T_{\mathrm{furnace}}}{K}.Math.\log \left(\frac{t_{\mathrm{furnace}}}{h}+1.15\right)+{\left(\frac{T_{\mathrm{dew}\mathrm{point}}}{K}-243.15\right)}^{1.6}\le 630$$\iff 300\le \frac{1203.15K}{K}.Math.\log \left(\frac{0.111h}{h}+1.15\right)+{\left(\frac{283.15K}{K}-243.15\right)}^{1.6}\le 630$$\iff 300\le 487\le 630$$\iff \mathrm{true}\mathrm{statement}$

[0112] Since the calculated WOP value of 487 is between 300 and 630, the selected parameters allow a maximum H.sub.diff value of 0.4 ppm to be maintained in the component.

INDUSTRIAL APPLICABILITY

[0113] The steel component produced according to the invention has a low tendency toward hydrogen-induced fractures under load stresses and can therefore advantageously be used in the automotive sector, aircraft construction or rail vehicle construction.