Hot formed pre-coated steel part
A hot formed pre-coated steel part includes a steel sheet precoated with a metallic coating and hot formed, the 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 being aluminum, unavoidable impurities and residual elements resulting from feeding ingots or from a passage of the steel sheet in a molten bath; and a ratio Al/Zn by weight greater than 2.9, where a microstructure in the steel after said hot forming being martensitic or martensitic-bainitic or made of at least 75% of equiaxed ferrite, 5 to 20% of martensite and bainite in an amount less than or equal to 10%.
1. A hot formed pre-coated steel part, comprising a steel sheet precoated with a metallic coating and then hot formed into the hot formed pre-coated steel part, the coating including:
2.0 to 24.0% by weight of zinc;
1.1 to 7.0% by weight of silicon;
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 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
a ratio Zn/Si by weight between 2.9 and 8;
a microstructure in the steel sheet after hot forming being martensitic or martensitic-bainitic or made of at least 75% of equiaxed ferrite, 5 to 20% of martensite and bainite in an amount less than or equal to 10%,
wherein a thickness of the coating is between 10 and 50 μm, and the coating is free from magnesium.
2. The hot formed pre-coated steel part according to claim 1 , wherein the coating comprises at least one of the additional elements chosen from Pb, Ni, Zr, or Hf.
3. The hot formed pre-coated steel part according to claim 1 , wherein the ratio Al/Zn is between 5 and 9.
4. The hot formed pre-coated steel part according to claim 1 , wherein the coating comprises from 2.0 to 4.0% by weight of silicon.
5. The hot formed pre-coated steel part according to claim 4 , wherein the coating comprises from 2.0 to 3.5% by weight of silicon.
6. The hot formed pre-coated steel part according to claim 4 , wherein the coating comprises from 5.0 to 10.0% by weight of zinc.
7. The hot formed pre-coated steel part according to claim 1 , wherein the coating comprises from 2.1 to 4.9% by weight of silicon.
8. The hot formed pre-coated steel part according to claim 1 , wherein the coating comprises from 1.5 to 3.5% by weight of silicon.
9. The hot formed pre-coated steel part according to claim 8 , wherein the coating comprises from 5.0 to 10.0% by weight of zinc.
10. The hot formed pre-coated steel part according to claim 1 , wherein the coating comprises from 5.0 to 19.0% by weight of zinc.
11. The hot formed pre-coated steel part according to claim 1 , wherein the coating comprises from 5.0 to 15.0% by weight of zinc.
12. The hot formed pre-coated steel part according to claim 1 , wherein the coating comprises from 5.0 to 10.0% by weight of zinc.
13. The hot formed pre-coated steel part according to claim 1 , wherein the coating comprises greater than 71% by weight of aluminum.
14. The hot formed pre-coated steel part according to claim 1 , wherein the coating comprises greater than 76% by weight of aluminum.
15. The hot formed pre-coated steel part according to claim 1 , wherein a thickness of the coating is between 12 and 50 μm.
16. The hot formed pre-coated steel part according to claim 15 , wherein the thickness is between 10 and 35 μm.
17. The hot formed pre-coated steel part according to claim 15 , wherein the thickness is between 12 and 18 μm.
18. The hot formed pre-coated steel part according to claim 15 , wherein the thickness is between: 26 and 31 μm.
19. The hot formed pre-coated steel part according to claim 1 , wherein the coating does not comprise any of Cr, Mn, Ti, Ce, La, Nd, Pr, Bi, In, Sn and Sb.
20. The hot formed pre-coated steel part according to claim 1 , wherein the coating does not include In and the coating does not include Sn.
21. The hot formed pre-coated steel part according to claim 1 , wherein the microstructure of the metallic coating comprises an interdiffusion layer Fe+Fe 3 Al, AlFe intermetallic phases containing dissolved Si and Zn, binary Zn-Al and Si-rich phases.
22. The hot formed pre-coated steel part according to claim 21 , wherein the microstructure of the metallic coating comprises at least one of a Zn 2 Mg phase or a Mg 2 Si phase.
23. The hot formed pre-coated steel part according to claim 1 , wherein the part is a press hardened steel part having a variable thickness.
24. The hot formed pre-coated steel part according to claim 23 , wherein the variable thickness is produced by a continuous flexible rolling process.
25. The hot formed pre-coated steel part according to claim 1 , wherein the part is a tailored rolled blank.
26. The hot formed pre-coated steel part according to claim 1 wherein the part is a front rail, a seat cross member, a side sill member, a dash panel cross member, a front floor reinforcement, a rear floor cross member, a rear rail, a B-pillar, a door ring or a shotgun.
27. The hot formed pre-coated steel part according to claim 1 wherein the steel sheet has a base made of 22MnB5 steel.
28. The hot formed pre-coated steel part according to claim 1 wherein the steel sheet has a base with a composition by weight percentage including: 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.
29. The hot formed pre-coated steel part according to claim 1 , 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.
30. The hot formed pre-coated steel part according to claim 1 , wherein the steel sheet has a base with a composition by weight percentage including: 0.03%≤C≤0.50%; 0.3%≤Mn≤3.0%; 0.05%≤Si≤0.8%; 0.015%≤Ti≤0.2%; 0.005%≤Al≤0.1%; 0%≤Cr≤2.50%; 0%≤S≤0.05%; 0%≤P≤0.1%; 0%≤B≤0.010%; 0%≤Ni≤2.5%; 0%≤Mo≤ 0.7%; 0%≤Nb≤0.15%; 0%≤N≤0.015%; 0%≤Cu≤0.15%; 0%≤Ca≤0.01%; 0%≤W≤0.35%, a balance of the steel sheet base composition being iron and unavoidable impurities from the manufacture of steel.
31. The hot formed pre-coated steel part according to claim 1 , wherein the coating after hot forming and subsequent cooling has no cracks.
32. An automotive vehicle comprising the part according to claim 1 .
33. The hot formed pre-coated steel part according to claim 1 , wherein the coating does not include Ca.
34. The hot formed pre-coated steel part according to claim 1 , wherein the ratio Al/Zn is 5.6 or less.
35. The hot formed pre-coated steel part according to claim 1 , wherein the coating includes 10 to 15% zinc, 2 to 5% silicon, a ratio Al/Zn between 5.3 and 8.8%; and a ratio Zn/Si by weight between 3 and 7.5.
36. The hot formed pre-coated steel part according to claim 1 , wherein the coating includes, by weight, 10%<zinc≤24%.
37. The hot formed pre-coated steel part according to claim 1 , wherein the coating includes 1.1 to 4.9% by weight of silicon.
38. The hot formed pre-coated steel part according to claim 1 , wherein the coating includes 1.1 to 2% by weight of silicon, or 15 to 24.0% by weight of zinc.
39. A hot formed pre-coated steel part, comprising a steel sheet precoated with a metallic coating and then hot formed into the hot formed pre-coated steel part, the coating including:
2.0 to 24.0% by weight of zinc;
1.1 to 7.0% by weight of silicon;
0 to 3.0% by weight of magnesium, with the proviso that the coating includes from 0.5 to 3.0% by weight of magnesium when the amount of silicon is between 1.1 and 4.0%,
and at least one 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 being aluminum, unavoidable impurities and residual elements resulting from feeding ingots or from a passage of the steel sheet in a molten bath; and
a ratio Al/Zn by weight between 8.6 and 9; and
a ratio Zn/Si by weight between 2.9 and 8, wherein the microstructure in the steel sheet after hot forming is made of at least 75% of equiaxed ferrite, 5 to 20% of martensite and bainite in an amount less than or equal to 10%, and a thickness of the coating is between 10 and 50 μm.
40. The hot formed pre-coated steel part according to claim 39 , wherein the coating comprises from 0.5 to 3.0% by weight of magnesium.
41. The hot formed pre-coated steel part according to claim 40 , wherein the coating comprises from 5.0 to 10.0% by weight of zinc.
42. The hot formed pre-coated steel part according to claim 41 , wherein the coating comprises greater than 71% by weight of aluminum.
43. The hot formed pre-coated steel part according to claim 41 , wherein the coating comprises greater than 76% by weight of aluminum.
44. The hot formed pre-coated steel part according to claim 39 , wherein the coating comprises from 1.0 to 2.9% by weight of magnesium.
45. The hot formed pre-coated steel part according to claim 39 , wherein the coating comprises from 1.5 to 3.5% by weight of silicon, from 5.0 to 10.0% by weight of zinc, and 1.0 to 2.9% by weight of magnesium.
46. The hot formed pre-coated steel part according to claim 45 , wherein the coating comprises greater than 71% by weight of aluminum.
47. The hot formed pre-coated steel part according to claim 45 , wherein the coating comprises greater than 76% by weight of aluminum.
48. A hot formed pre-coated steel part, comprising a steel sheet precoated with a metallic coating and then hot formed into the hot formed pre-coated steel part, the coating including:
2.0 to 24.0% by weight of zinc;
1.1 to 7.0% by weight of silicon;
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 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;
a ratio Zn/Si by weight between 2.9 and 8;
a microstructure in the steel sheet after hot forming being made of at least 75% of equiaxed ferrite, 5 to 20% of martensite and bainite in an amount less than or equal to 10%,
wherein a thickness of the coating is between 10 and 50 μm, and the coating is free from magnesium.
49. The hot formed pre-coated steel part according to claim 48 , wherein the coating includes 1.1 to 2% by weight of silicon, or 15 to 24.0% by weight of zinc.
50. A hot formed pre-coated steel part, comprising
a steel sheet precoated with a metallic coating and then hot formed into the hot formed pre-coated steel part, the coating including:
2.0 to 24.0% by weight of zinc;
1.1 to 7.0% by weight of silicon;
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 being aluminum, unavoidable impurities and residual elements resulting from feeding ingots or from a passage of the steel sheet in a molten bath; and
a ratio Al/Zn by weight greater than 2.9;
a microstructure in the steel sheet after hot forming being martensitic or martensitic-bainitic or made of at least 75% of equiaxed ferrite, 5 to 20% of martensite and bainite in an amount less than or equal to 10%, wherein the steel sheet has a base with a carbon content by weight of between 0.24% and 0.38%,
wherein a thickness of the coating is between 10 and 50 μm, and the coating is free from magnesium.
51. The hot formed pre-coated steel part according to claim 50 , wherein the coating includes 1.1 to 2% by weight of silicon, or 15 to 24.0% by weight of zinc.
52. A hot formed pre-coated steel part, comprising
a steel sheet precoated with a metallic coating and then hot formed into the hot formed pre-coated steel part, the coating including:
2.0 to 24.0% by weight of zinc;
1.1 to 7.0% by weight of silicon;
at least one 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 being aluminum, unavoidable impurities and residual elements resulting from feeding ingots or from a passage of the steel sheet in a molten bath; and
a ratio Zn/Si by weight is between 7.5 and 8;
a microstructure in the steel sheet after hot forming being made of at least 75% of equiaxed ferrite, 5 to 20% of martensite and bainite in an amount less than or equal to 10%, wherein the steel sheet has a base with a carbon content by weight of between 0.24% and 0.38%, wherein a thickness of the coating is between 10 and 50 μm, and the coating includes 0.5≤Mg≤3.0%.
53. The hot formed pre-coated steel part according to claim 52 , wherein the coating includes 1.1 to 2% by weight of silicon, or 15 to 24.0% by weight of zinc.
54. A hot formed pre-coated steel part, comprising a steel sheet precoated with a metallic coating and then hot formed into the hot formed pre-coated steel part, the coating including:
2.0 to 24.0% by weight of zinc;
1.1 to 7.0% by weight of silicon;
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 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
a ratio Zn/Si by weight between 2.9 and 8;
a microstructure in the steel sheet after hot forming being martensitic or martensitic-bainitic or made of at least 75% of equiaxed ferrite, 5 to 20% of martensite and bainite in an amount less than or equal to 10%; and
wherein the hot formed pre-coated steel part exhibits no microcracks having a depth greater than 50 μm; and
wherein a thickness of the coating is between 10 and 50 μm, and the coating is free from magnesium.
55. The hot formed pre-coated steel part according to claim 54 , wherein the coating includes 10 to 15% zinc, 2 to 5% silicon, a ratio Al/Zn between 5.3 and 8.8%; and a ratio Zn/Si by weight between 3 and 7.5.
56. A hot formed pre-coated steel part, comprising a steel sheet precoated with a metallic coating and then hot formed into the hot formed pre-coated steel part, the coating including:
5 to 10% by weight of zinc;
2 to 5% by weight of silicon;
at least on 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 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 between 5.3 and 8.8%; and
a ratio Zn/Si by weight between 3 and 7.5;
a microstructure in the steel sheet after hot forming being at least 75% of equiaxed ferrite, 5 to 20% of martensite and bainite in an amount less than or equal to 10%; and
wherein the hot formed pre-coated steel part exhibits no microcracks having a depth greater than 50 μm, wherein a thickness of the coating is between 10 and 50 μm, and the coating includes more than 0 and less that 3.0% by weight of magnesium, with the proviso that the coating includes from 0.5 to 3.0% by weight of magnesium when the amount of silicon is between 1.1 and 4.0%.
57. The hot formed pre-coated steel part according to claim 56 , wherein the coating includes 1.1 to 4.9% by weight of silicon.