Hot-rolled and coated steel sheet for hot-stamping, hot-stamped coated steel part and methods for manufacturing the same
A method for manufacturing a hot-rolled and coated steel sheet having a thickness between 1.8 mm and 5 mm. The method contains the steps of: providing a semi-product having a composition containing: 0.04%≤C≤0.38%, 0.40%≤Mn≤3%, 0.005%≤Si≤0.70%, 0.005%≤Al≤0.1%, 0.001%≤Cr≤2%, 0.001%≤Ni≤2%, 0.001%≤Ti≤0.2%, Nb≤0.1%, B≤0.010%, 0.0005%≤N≤0.010%, 0.0001%≤S≤0.05%, 0.0001%≤P≤0.1%, Mo≤0.65%, W≤0.30%, Ca≤0.006%, hot-rolling with a final rolling temperature FRT, to obtain a hot-rolled steel product having a thickness between 1.8 mm and 5 mm, then cooling down to a coiling temperature T coil satisfying: 450° C.≤T coil ≤T coilmax with T coilmax=650−140×fγ , T coilmax being expressed in degrees Celsius and fγ designating the austenite fraction just before the coiling, and coiling to obtain a hot-rolled steel substrate, pickling and coating the hot-rolled steel substrate with Al or an Al alloy by continuous hot-dipping in a bath, to obtain a hot-rolled and coated steel sheet containing a hot-rolled steel sheet and an Al or an Al alloy coating, having a thickness between 10 and 33 μm, on each side of the hot-rolled steel sheet.
1 . A hot-rolled and coated steel sheet, comprising:
(i) a hot-rolled steel sheet having a thickness between 1.8 mm and 5 mm, the hot-rolled steel sheet not being cold-rolled, the hot-rolled steel sheet being made of a steel having a composition comprising, by weight percent:
0.04%≤C≤0.38%,
0.40%≤Mn≤3%,
0.005%≤Si≤0.70%,
With Si/Mn≤0.22,
0.005%≤Al≤0.1%,
0.001%≤Cr≤2%,
0.001%≤Ni≤2%,
0.001%≤Ti≤0.2%,
Nb≤0.1%,
B≤0.010%,
0.0005%≤N≤0.010%,
0.0001%≤S≤0.05%,
0.0001%≤P≤0.1%,
Mo≤0.65%,
0.001%≤W≤0.30%,
Ca≤0.006%,
a balance of the composition consisting of iron and unavoidable impurities resulting from smelting,
said hot-rolled steel sheet having a depth of intergranular oxidation of less than 4 μm, said hot-rolled steel sheet having a structure consisting of ferrite and pearlite, and
(ii) an Al or an Al alloy coating, having a thickness between 10 and 33 μm, on each side of the hot-rolled steel sheet.
2 . The hot-rolled and coated steel sheet according to claim 1 , wherein the composition comprises, by weight percent:
0.04%≤C≤0.38%,
0.40%≤Mn≤3%,
0.005%≤Si≤0.70%,
0.005%≤Al≤0.1%,
0.001%≤Cr≤2%,
0.001%≤Ni≤0.1%,
0.001%≤Ti≤0.2%,
Nb≤0.1%,
B≤0.010%,
0.0005%≤N≤0.010%,
0.0001%≤S≤0.05%,
0.0001%≤P≤0.1%,
Mo≤0.65%,
W≤0.30%
Ca≤0.006%,
the balance of the composition consisting of iron and unavoidable impurities resulting from the smelting.
3 . The hot-rolled and coated steel sheet according to claim 2 , wherein the composition comprises, by weight percent:
0.04%≤C≤0.38%,
0.5%≤Mn≤3%,
0.005%≤Si≤0.5%,
0.005%≤Al≤0.1%,
0.001%≤Cr≤1%,
0.001%≤Ni≤0.1%,
0.001%≤Ti≤0.2%,
Nb≤0.1%,
B≤0.010%,
0.0005%≤N≤0.010%,
0.0001%≤S≤0.05%,
0.0001%≤P≤0.1%,
Mo≤0.10%,
Ca≤0.006%,
the balance of the composition consisting of iron and unavoidable impurities resulting from the smelting.
4 . The hot-rolled and coated steel sheet according to claim 1 , wherein the composition comprises, by weight percent: 0.075%≤C≤0.38%.
5 . The hot-rolled and coated steel sheet according to claim 1 , wherein the composition comprises, by weight percent:
0.040%≤C≤0.100%,
0.80%≤Mn≤2.0%,
0.005%≤Si≤0.30%,
0.010%≤Al≤0.070%,
0.001%≤Cr≤0.10%,
0.001%≤Ni≤0.10%,
0.03%≤Ti≤0.08%,
0.015%≤Nb≤0.1%,
0.0005%≤N≤0.009%,
0.0001%≤S≤0.005%,
0.0001%≤P≤0.030%,
Mo≤0.10%,
Ca≤0.006%,
the balance of the composition consisting of iron and unavoidable impurities resulting from the smelting.
6 . The hot-rolled and coated steel sheet according to claim 1 , wherein the composition comprises, by weight percent:
0.062%≤C≤0.095%,
1.4%≤Mn≤1.9%,
0.2%≤Si≤0.5%,
0.020%≤Al≤0.070%,
0.02%≤Cr≤0.1%,
wherein 1.5%≤(C+Mn+Si+Cr)≤2.7%,
3.4×N≤Ti≤8×N,
0.04%≤Nb≤0.06%,
wherein 0.044%≤(Nb+Ti)≤0.09%,
0.0005%≤B≤0.004%,
0.001%≤N≤0.009%,
0.0005%≤S≤0.003%,
0.001%≤P≤0.020%,
and optionally 0.0001%≤Ca≤0.006%,
the balance of the composition consisting of iron and unavoidable impurities resulting from the smelting.
7 . The hot-rolled and coated steel sheet according to claim 1 , wherein the composition comprises, by weight percent:
0.15%≤C≤0.38%,
0.5%≤Mn≤3%,
0.10%≤Si≤0.5%,
0.005%≤Al≤0.1%,
0.01%≤Cr≤1%,
0.001%≤Ti≤0.2%,
0.0005%≤B≤0.010%,
0.0005%≤N≤0.010%,
0.0001%≤S≤0.05%,
0.0001%≤P≤0.1%,
the balance of the composition consisting of iron and unavoidable impurities resulting from the smelting.
8 . The hot-rolled and coated steel sheet according to claim 1 , wherein the hot-rolled and coated steel sheet further comprises, on each side, a Zn coating having a thickness lower than or equal to 1.1 μm.
9 . The hot-rolled and coated steel sheet according to claim 1 , wherein the depth of intergranular oxidation is lower than 3 μm.
10 . The hot-rolled and coated steel sheet according to claim 1 , wherein the depth of intergranular oxidation is 2 μm or less.
11 . The hot-rolled and coated steel sheet according to claim 1 , wherein the hot-rolled steel sheet has no intergranular oxidation.
12 . The hot-rolled and coated steel sheet according to claim 1 , wherein the composition of the steel comprises, by weight percent 0.15%≤C≤0.38%.
13 . The hot-rolled and coated steel sheet according to claim 12 , wherein the composition of the steel comprises, by weight percent 0.40%≤Mn≤1.9%.
14 . The hot-rolled and coated steel sheet according to claim 1 , wherein the composition of the steel comprises, by weight percent 0.40%≤Mn≤1.9%.
15 . The hot-rolled and coated steel sheet according to claim 1 , wherein the composition comprises, by weight percent 0.36%≤Si≤0.70%.
16 . The hot-rolled and coated steel sheet according to claim 1 , wherein the composition of the steel comprises, by weight percent 0.027%≤Cr≤0.354%.
17 . The hot-rolled and coated steel sheet according to claim 1 , wherein a surface percentage of porosities in the coating is lower than or equal to 3%.
18 . The hot-rolled and coated steel sheet according to claim 1 , wherein an intermetallic layer of the coating has a thickness of less than 15 μm.
19 . The hot-rolled and coated steel sheet according to claim 1 , wherein the composition of the steel comprises, by weight percent 0.15%≤Mo≤0.25%.
20 . The hot-rolled and coated steel sheet according to claim 1 , wherein the composition of the steel comprises, by weight percent 0.541%≤Si≤0.70%.
21 . The hot-rolled and coated steel sheet according to claim 1 , wherein the composition of the steel comprises, by weight percent 0.111%≤Cr≤2%.
22 . The hot-rolled and coated steel sheet according to claim 1 , wherein the composition of the steel comprises, by weight percent 0.111%≤Cr≤0.354%.
23 . The hot-rolled and coated steel sheet according to claim 1 , wherein the composition of the steel comprises, by weight percent 0.25%≤Ni≤2%.
24 . The hot-rolled and coated steel sheet according to claim 1 , wherein the composition of the steel comprises, by weight percent Nb≤0.01%.
25 . The hot-rolled and coated steel sheet according to claim 1 , wherein the depth of intergranular oxidation is of 2 μm or more and 4 μm or less.
26 . The hot-rolled and coated steel sheet according to claim 1 , wherein the depth of intergranular oxidation is of 2 μm or more and 3 μm or less.
27 . A hot-rolled and coated steel sheet, comprising:
(i) a hot-rolled steel sheet having a thickness between 1.8 mm and 5 mm, the hot-rolled steel sheet not being cold-rolled, the hot-rolled steel sheet being made of a steel having a composition comprising, by weight percent:
0.15%≤C≤0.38%,
0.40%≤Mn≤3%,
0.005%≤Si≤0.70%,
With Si/Mn≤0.22,
0.005%≤Al≤0.1%,
0.001%≤Cr≤2%,
0.001%≤Ni≤2%,
0.001%≤Ti≤0.2%,
Nb≤0.1%,
B≤0.010%,
0.0005%≤N≤0.010%,
0.0001%≤S≤0.05%,
0.0001%≤P≤0.1%,
Mo≤0.65%,
W≤0.30%,
Ca≤0.006%,
a balance of the composition consisting of iron and unavoidable impurities resulting from smelting,
said hot-rolled steel sheet having a depth of intergranular oxidation of less than 4 μm, said hot-rolled steel sheet having a structure consisting of ferrite and pearlite, and
(ii) an Al or an Al alloy coating, having a thickness between 10 and 33 μm, on each side of the hot-rolled steel sheet.
28 . A hot-rolled and coated steel sheet, comprising:
(i) a hot-rolled steel sheet having a thickness between 1.8 mm and 5 mm, the hot-rolled steel sheet not being cold-rolled, the hot-rolled steel sheet being made of a steel having a composition comprising, by weight percent:
0.04%≤C≤0.38%,
0.40%≤Mn≤3%,
0.005%≤Si≤0.36%,
0.005%≤Al≤0.1%,
0.001%≤Cr≤2%,
0.001%≤Ni≤2%,
0.001%≤Ti≤0.2%,
Nb≤0.1%,
B≤0.010%,
0.0005%≤N≤0.010%,
0.0001%≤S≤0.05%,
0.0001%≤P≤0.1%,
Mo≤0.65%,
0.001%≤W≤0.30%,
Ca≤0.006%,
a balance of the composition consisting of iron and unavoidable impurities resulting from smelting,
said hot-rolled steel sheet having a depth of intergranular oxidation of less than 4 μm, said hot-rolled steel sheet having a structure consisting of ferrite and pearlite, and
(ii) an Al or an Al alloy coating, having a thickness between 10 and 33 μm, on each side of the hot-rolled steel sheet.