METHOD FOR MANUFACTURE OF A PRE-COATED STEEL SHEET

1 . A method for manufacture of a pre-coated steel sheet, comprising:

providing a steel sheet, wherein the steel sheet has a base with a composition by weight percentage including 0.20%≤C≤0.25%; 0.15%≤Si≤0.35%; 1.10%≤Mn≤1.40%; 0%≤Cr≤0.30%; 0%≤Mo≤0.35%; 0%≤P≤0.025%; 0%≤S≤0.005%; 0.020%≤Ti≤0.060%; 0.020%≤Al≤0.060%; 0.002%≤B≤0.004%, a balance of the steel sheet base composition being iron and unavoidable impurities from the manufacture of steel; and

coating the steel sheet with a metallic coating, the metallic coating including:

2.0 to 24.0% by weight of zinc;

1.1 to 7.0% by weight of silicon;

optionally from 0.5 to 3.0% by weight of magnesium when the amount of silicon is between 1.1 and 4.0%,

and optionally additional elements chosen from Pb, Ni, Zr or Hf, a content by weight of each additional element being less than 0.3% by weight,

a balance of the metallic coating being aluminum, unavoidable impurities and residual elements resulting from feeding ingots or from a passage of the steel sheet in a molten bath;

a ratio Al/Zn by weight greater than 2.9, and

wherein the metallic coating does not include In and the metallic coating does not include Sn.

2 . A method for manufacture of a pre-coated steel sheet, comprising:

providing a steel sheet, wherein the steel sheet has a base with a composition by weight percentage including: 0.24%≤C≤0.38%; 0.40%≤Mn≤3%; 0.10%≤Si≤0.70%; 0.015%≤Al≤0.070%; 0%≤Cr≤2%; 0.25%≤Ni≤2%; 0.020%≤Ti≤0.10%; 0%≤Nb≤0.060%; 0.0005%≤B≤0.0040%; 0.003%≤N≤0.010%; 0.0001%≤S≤0.005%; 0.0001%≤P≤0.025%; it being understood that the contents of titanium and nitrogen satisfy Ti/N>3.42, and that the contents of carbon, manganese, chromium and silicon satisfy 2.6C+Mn/5.3+Cr/13+Si/15≥1.1%, the composition optionally comprising one or more of the following: 0.05%≤Mo≤0.65%; 0.001%≤W≤0.30%; 0.0005%≤Ca≤0.005%, a balance of the steel sheet base composition being iron and unavoidable impurities from manufacture; and

coating the steel sheet with a metallic coating, the metallic coating including:

2.0 to 24.0% by weight of zinc;

1.1 to 7.0% by weight of silicon;

optionally from 0.5 to 3.0% by weight of magnesium when the amount of silicon is between 1.1 and 4.0%,

and optionally additional elements chosen from Pb, Ni, Zr or Hf, a content by weight of each additional element being less than 0.3% by weight,

a balance of the metallic coating being aluminum, unavoidable impurities and residual elements resulting from feeding ingots or from a passage of the steel sheet in a molten bath;

a ratio Al/Zn by weight greater than 2.9, and

wherein the metallic coating does not include In and the metallic coating does not include Sn.

3 . A method for manufacture of a pre-coated steel sheet, comprising:

providing a steel sheet, wherein the steel sheet has a base with a composition by weight percentage including: 0.040%≤C≤0.100%; 0.80%≤Mn≤2.00%; 0%≤Si≤0.30%; 0%≤S≤0.005%; 0%≤P≤0.030%; 0.010%≤Al≤0.070%; 0.015%≤Nb≤0.100%; 0.030%≤Ti≤0.080%; 0%≤N≤0.009%; 0%≤Cu≤0.100%; 0%≤Ni≤0.100%; 0%≤Cr≤0.100%; 0%≤Mo≤0.100%; 0%≤Ca≤0.006%, a balance of the steel sheet base composition being iron and unavoidable impurities from manufacture; and

coating the steel sheet with a metallic coating, the metallic coating including:

2.0 to 24.0% by weight of zinc;

1.1 to 7.0% by weight of silicon;

optionally from 0.5 to 3.0% by weight of magnesium when the amount of silicon is between 1.1 and 4.0%,

and optionally additional elements chosen from Pb, Ni, Zr or Hf, a content by weight of each additional element being less than 0.3% by weight,

a balance of the metallic coating being aluminum, unavoidable impurities and residual elements resulting from feeding ingots or from a passage of the steel sheet in a molten bath;

a ratio Al/Zn by weight greater than 2.9, and

wherein the metallic coating does not include In and the metallic coating does not include Sn.

4 . The method of claim 1 , wherein the ratio is greater than or equal to 5.0.

5 . The method of claim 1 , wherein said coating comprises coating by hot-dip galvanization.

6 . The method of claim 1 , wherein said coating comprises coating by electrogalvanization.

7 . The method of claim 1 , wherein said coating comprises coating by physical vapour deposition.

8 . The method of claim 7 , wherein said physical vapour deposition is jet vapor deposition

9 . The method of claim 7 , wherein said physical vapour deposition is sputtering magnetron.

10 . The method of claim 1 , wherein said coating comprises hot-dip galvanization.

11 . The method of claim 10 , wherein said hot-dip galvanization includes dipping said steel sheet in a molten metal bath.

12 . The method of claim 11 , wherein the molten metal bath comprises zinc, silicon, and aluminum.

13 . The method of claim 12 , wherein the molten metal bath further comprises magnesium.

14 . The method of claim 12 , wherein the molten metal bath further comprises additional elements chosen from Pb, Ni, Zr, or Hf, the content by weight of each additional element being less than 0.3% by weight.

15 . The method of claim 12 , wherein the molten metal bath has a temperature between 580 and 660° C.

16 . The method of claim 1 , wherein after said coating, the method further includes wiping the coated steel sheet with nozzles ejecting gas on both sides of the coated steel sheet.

17 . The method of claim 1 , wherein after said coating and wiping, the method further includes cooling the coated steel sheet.

18 . The method of claim 1 , wherein after said coating, the method further includes cooling the coated steel sheet.

19 . The method of claim 18 , wherein the cooling is at a cooling rate equal or greater than 15° C.s −1 between the beginning of the solidification and the end of the solidification.

20 . The method of claim 19 , wherein the cooling rate is equal to or greater than 20° C.s −1

21 . The method of claim 18 , further including performing a skin-pass on said cooled, coated, steel sheet.

22 . The method according to claim 1 , wherein the metallic coating comprises the magnesium at 0.5 to 3.0% by weight and the silicon between 1.1 and 4.0% by weight.

23 . The method according to claim 1 , wherein the metallic coating comprises at least one of the additional elements chosen from Pb, Ni, Zr, or Hf.

24 . The method according to claim 1 , wherein the ratio Al/Zn is between 5 and 9.

25 . The method according to claim 1 , wherein the metallic coating comprises from 2.0 to 5.0% by weight of silicon.

26 . The method according to claim 1 , wherein the metallic coating comprises from 2.1 to 4.9% by weight of silicon.

27 . The method according to claim 1 , wherein the metallic coating comprises from 1.5 to 3.5% by weight of silicon.

28 . The method according to claim 25 , wherein the metallic coating comprises from 2.0 to 3.5% by weight of silicon.

29 . The method according to claim 1 , wherein the metallic coating comprises from 5.0 to 19.0% by weight of zinc.

30 . The method according to claim 1 , wherein the metallic coating comprises from 5.0 to 15.0% by weight of zinc.

31 . The method according to claim 1 , wherein the metallic coating comprises from 5.0 to 10.0% by weight of zinc.

32 . The method according to claim 25 , wherein the metallic coating comprises from 5.0 to 10.0% by weight of zinc.

33 . The method according to claim 27 , wherein the metallic coating comprises from 5.0 to 10.0% by weight of zinc.

34 . The method according to claim 1 , wherein the metallic coating comprises from 0.5 to 3.0% by weight of magnesium.

35 . The method according to claim 1 , wherein the metallic coating comprises from 1.0 to 2.9% by weight of magnesium.

36 . The method according to claim 32 , wherein the metallic coating comprises from 1.0 to 2.9% by weight of magnesium.

37 . The method according to claim 33 , wherein the metallic coating comprises from 1.0 to 2.9% by weight of magnesium.

38 . The method according to claim 1 , wherein the metallic coating comprises greater than 71% by weight of alum inum.

39 . The method according to claim 1 , wherein the metallic coating comprises greater than 76% by weight of aluminum.

40 . The method according to claim 1 , wherein a thickness of the metallic coating is between 5 and 50 μm.

41 . The method according to claim 40 , wherein the thickness is between 10 and 35 μm.

42 . The method according to claim 40 , wherein the thickness is between 12 and 18 μm.

43 . The method according to claim 40 , wherein the thickness is between 26 and 31 μm.

44 . The method according to claim 1 , wherein the metallic coating does not comprise elements selected among Cr, Mn, Ti, Ce, La, Nd, Pr, Ca, Bi, In, Sn and Sb or combinations thereof.

45 . The method according to claim 1 wherein the steel sheet has a base made of 22MnB5 steel.

46 . The method according to claim 1 , wherein the steel sheet has a base with a carbon content by weight of between 0.24% and 0.38%.

47 . The method of claim 36 , wherein the metallic coating comprises greater than 71% by weight of aluminum.

48 . The method of claim 36 , wherein the metallic coating comprises greater than 76% by weight of aluminum.