PAINTED, HOT FORMED, COATED STEEL PART
A painted 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; and a paint layer.
1 . A painted steel part, comprising:
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; and
a paint layer.
2 . The painted steel part according to claim 1 , wherein a microstructure in the steel after said hot forming is 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%.
3 . The painted steel part according to claim 1 , wherein the paint layer includes an e-coating layer.
4 . The painted steel part according to claim 3 , wherein the painted steel part has a phosphate layer between said coating and said e-coating layer.
5 . The painted steel part according to claim 3 , wherein the paint layer further includes a further paint layer over the e-coating layer.
6 . The painted steel part according to claim 4 , wherein the paint layer further includes one or more further paint layers over the e-coating layer.
7 . The painted steel part according to claim 5 , wherein the one or more further paint layers include a primer coat layer, a base coat layer and a top coat layer.
8 . The painted steel part according to claim 1 , wherein the coating comprises the magnesium at 0.5 to 3.0% by weight and the silicon between 1.1 and 4.0% by weight.
9 . The painted steel part according to claim 1 , wherein the coating comprises at least one of the additional elements chosen from Pb, Ni, Zr, or Hf.
10 . The painted steel part according to claim 1 , wherein the ratio Al/Zn is between 5 and 9.
11 . The painted steel part according to claim 1 , wherein the coating comprises from 2.0 to 5.0% by weight of silicon.
12 . The painted steel part according to claim 1 , wherein the coating comprises from 2.1 to 4.9% by weight of silicon.
13 . The painted steel part according to claim 1 , wherein the coating comprises from 1.5 to 3.5% by weight of silicon.
14 . The painted steel part according to claim 11 , wherein the coating comprises from 2.0 to 3.5% by weight of silicon.
15 . The painted steel part according to claim 1 , wherein the coating comprises from 5.0 to 19.0% by weight of zinc.
16 . The painted steel part according to claim 1 , wherein the coating comprises from 5.0 to 15.0% by weight of zinc.
17 . The painted steel part according to claim 1 , wherein the coating comprises from 5.0 to 10.0% by weight of zinc.
18 . The painted steel part according to claim 11 , wherein the coating comprises from 5.0 to 10.0% by weight of zinc.
19 . The painted steel part according to claim 13 , wherein the coating comprises from 5.0 to 10.0% by weight of zinc.
20 . The painted steel part according to claim 1 , wherein the coating comprises from 0.5 to 3.0% by weight of magnesium.
21 . The painted steel part according to claim 1 , wherein the coating comprises from 1.0 to 2.9% by weight of magnesium.
22 . The painted steel part according to claim 18 , wherein the coating comprises from 1.0 to 2.9% by weight of magnesium.
23 . The painted steel part according to claim 19 , wherein the coating comprises from 1.0 to 2.9% by weight of magnesium.
24 . The painted steel part according to claim 1 , wherein the coating comprises greater than 71% by weight of aluminum.
25 . The painted steel part according to claim 1 , wherein the coating comprises greater than 76% by weight of aluminum.
26 . The painted steel part according to claim 1 , wherein a thickness of the coating is between 5 and 50 μm.
27 . The painted steel part according to claim 26 , wherein the thickness is between 10 and 35 μm.
28 . The painted steel part according to claim 26 , wherein the thickness is between 12 and 18 μm.
29 . The painted steel part according to claim 26 , wherein the thickness is between 26 and 31 μm.
30 . The painted steel part according to claim 1 , wherein the coating does not comprise elements selected among Cr, Mn, Ti, Ce, La, Nd, Pr, Ca, Bi, In, Sn and Sb or combinations thereof.
31 . The painted steel part according to claim 1 , wherein the coating does not include In and the coating does not include Sn.
32 . The painted 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.
33 . The painted steel part according to claim 32 , wherein the microstructure of the metallic coating comprises at least one of a Zn 2 Mg phase or a Mg 2 Si phase.
34 . The painted steel part according to claim 1 , wherein the part is a press hardened steel part having a variable thickness.
35 . The painted steel part according to claim 34 , wherein the variable thickness is produced by a continuous flexible rolling process.
36 . The painted steel part according to claim 1 , wherein the part is a tailored rolled blank.
37 . The painted 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.
38 . The painted steel part according to claim 1 wherein the steel sheet has a base made of 22MnB5 steel.
39 . The painted steel part according to claim 1 , wherein the steel sheet has a base with a carbon content by weight of between 0.24% and 0.38%.
40 . The painted steel part according to claim 1 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.
41 . The painted 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.
42 . The painted 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.
43 . The painted steel part according to claim 1 , 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.
44 . The painted steel part according to claim 22 , wherein the coating comprises greater than 71% by weight of aluminum.
45 . The painted steel part according to claim 23 , wherein the coating comprises greater than 71% by weight of aluminum.
46 . The painted steel part according to claim 22 , wherein the coating comprises greater than 76% by weight of aluminum.
47 . The painted steel part according to claim 23 , wherein the coating comprises greater than 76% by weight of aluminum.
48 . The painted steel part according to claim 1 , wherein the coating after hot forming and subsequent cooling has no cracks.
49 . An automotive vehicle comprising the part according to claim 1 .