Hot-rolled coated steel sheet for hot stamping, hot-stamped coated steel part and method for producing same

Abstract

Abstract\n\n\nHot-rolled coated steel sheet for hot stamping, hot-stamped coated steel part and method for producing the same

Description

Hot-rolled coated steel sheet for hot stamping, hot-stamped coated steel piece and method for producing same The present invention relates to a hot-rolled coated steel sheet for hot stamping, which has a thickness of between 1.8 mm and 5 mm, and the adhesion of the coating after hot stamping is excellent. The invention also relates to a hot-stamped coated steel piece, at least a portion of which has a thickness of between 1.8 mm and 5 mm, and the adhesion of the coating is excellent. The invention also relates to a method for producing a hot-rolled coated steel sheet for hot stamping with a thickness of between 1.8 mm and 5 mm, and a method for producing a hot-stamped coated steel piece. With the increasing use of high-strength steel in the automotive industry, the need for steel that has both high strength and good ductility has increased. The increasing demand for weight reduction while increasing the safety factor of the vehicle has led to the creation of new concepts of steel in the automotive industry that can increase both strength and ductility as much as possible. Therefore, various types of steel with different degrees of strength have been offered to this industry. In recent years, the use of coated steel by hot stamping process for forming parts has become of particular importance, especially in the automotive industry. The steel sheets from which these parts are produced have a thickness that is mainly between 0.7 and 2 mm and are obtained through hot rolling and then cold rolling. In addition, the demand for hot stamping steel sheets with thicknesses exceeding 1.8 mm and even exceeding 3 mm to 5 mm is also increasing. Such sheets are used to manufacture chassis or suspension arm parts that have been produced by cold pressing until now, and to produce parts that are required by hot stamping of Chinese tailor rolled sheets (TRB). However, hot stamping coated steel sheet with a thickness of more than 3 mm cannot be produced by cold rolling. In fact, current cold rolling production lines are not designed to produce such cold rolled steel sheet. In addition, the production of cold rolled coated steel sheet with a thickness of 1.8 mm to 5 mm requires the use of a low cold rolling reduction ratio, which is incompatible with the recrystallization that occurs in the annealing step after cold rolling. Therefore, cold rolled coated steel sheet with a thickness of 1.8 mm to 5 mm will not have sufficient smoothness and will, for example, lead to shape and form defects during the welding process. Accordingly, it has been proposed to produce high-thickness steel sheets by hot rolling. For example, JP 2010-43323 discloses a process for producing hot-rolled steel sheets for hot stamping with a thickness of more than 1.6 mm. However, its inventors have found that when producing coated steel sheet by hot rolling, the adhesion of the coating on the surface of the steel piece that is then subjected to hot stamping is not very satisfactory. This causes poor paint adhesion on the hot stamped piece. For example, paint adhesion is evaluated through a wet paint adhesion test. In addition, in some special cases, the thickness of the coating before and after hot stamping cannot be precisely controlled, and the thickness of the coating obtained may be outside the target range. This target thickness range is mainly between 10 μm and 33 μm, for example, the range of 10-20 μm, the range of 15-33 μm or the range of 20-33 μm. This uncontrolled coating thickness leads to the weakening of weldability. Furthermore, as will be explained in more detail below, the inventors have found that the adhesion of the coating can be improved under certain conditions by slowing down the pickling process without the need for optimization in the control of the coating thickness. In these conditions, the control of the coating thickness, and consequently the weldability, also becomes worse and the productivity of the production line is reduced. Therefore, the object of the present invention is to provide a hot-rolled coated steel sheet with a thickness between 1.8 mm and 5 mm and a method for producing the same, which enables high adhesion of the coating after hot stamping to be achieved and at the same time enables control of the coating thickness of the hot-rolled coated steel sheet within a desired range, particularly within a range between 10 μm and 33 μm. Another object of the present invention is also to provide a hot stamped coated steel part, the thickness of at least a portion of which is between 1.8 mm and 5 mm, and the adhesion of the coating is increased, and a method for producing it. Finally, the object of the present invention is to provide a process in which the productivity of the pickling line is not reduced. To this end, the present invention relates to a method for producing hot-rolled coated steel sheet with a thickness between 1.8 mm and 5 mm, comprising the following steps: -Preparation of a semi-finished steel product that has the following compositions by weight: 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% The rest of the composition consists of iron and inevitable impurities resulting from smelting, -Hot rolling the semi-finished product with a final rolling temperature FRT so that a hot rolled steel product with a thickness between 1.8 mm and 5 mm is obtained, and then: -Cooling the hot-rolled steel product to the coiling temperature Tcoil and coiling the hot-rolled steel product at the said coiling temperature Tcoil, so that a layer of hot-rolled steel is obtained, the appropriate coiling temperature Tcoil is: 450°C ≤ Tcoil ≤ Tcoilmax, Where Tcoilmax means the maximum coiling temperature, which is calculated as follows: Tcoilmax is expressed in degrees Celsius and f indicates the amount of austenite present in the hot rolled steel product just before coiling. -Acid washing of hot rolled steel sheet -Coating the hot-rolled steel layer with Al or an Al alloy by continuous placement in a hot bath, so as to obtain a hot-rolled coated steel sheet whose coating is Al or Al alloy and whose thickness on each side of the hot-rolled steel sheet is between 10 and 33 µm. In one embodiment of the invention, the Ni content is at most 0.1%. In this case, the composition consists, by weight, of: 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 rest of the composition consists of iron and inevitable impurities resulting from smelting, It is better if the composition is as follows by weight: 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 rest of the composition consists of iron and inevitable impurities resulting from smelting, It is best if the final rolling temperature of FRT is between 840 and 1000°C. In one embodiment of the invention, the composition is such that 0.075% ≤ C ≤ 0.38%. In a specific case, steel has the following chemical composition by weight: 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 rest of the composition consists of iron and inevitable impurities resulting from smelting, In a particular embodiment of the invention, the steel has the following chemical composition by weight: 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% 1.5% ≤ (C + Mn +Si + Cr) ≤ 2.7% such that 3.4 x N ≤ Ti ≤ 8 x N 0.04% ≤ Nb ≤ 0.06% 0.044% ≤ (Nb+Ti) ≤ 0.09% such that 0.0005% ≤ B ≤ 0.004% 0.001% ≤ N ≤ 0.009% 0.0005% ≤ S ≤ 0.003% 0.001% ≤ P ≤ 0.020% 0.0001% ≤ Ca ≤ 0.006%, and if deemed appropriate The rest of the composition consists of iron and inevitable impurities resulting from smelting. According to another specific embodiment of the present invention, the steel has the following chemical composition by weight: 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 rest of the composition consists of iron and inevitable impurities resulting from smelting. According to another specific embodiment of the present invention, the steel has the following chemical composition by weight: 0.24% ≤ C ≤ 0.38% 0.40% ≤ Mn ≤ 3% 0.10% ≤ Si ≤ 0.70% 0.015% ≤ Al ≤ 0.070% 0.001% ≤ Cr ≤ 2% 0.25% ≤ Ni ≤ 2% 0.015% ≤ Ti ≤ 0.1% 0% ≤ Nb ≤ 0.06% 0.0005% ≤ B ≤ 0.0040% 0.003% ≤ N ≤ 0.010% 0.0001% ≤ S ≤ 0.005% 0.0001% ≤ P ≤ 0.025%, The amount of titanium and nitrogen must complete the following relationship: Ti / N > 3.42 The amount of carbon, manganese, chromium, and silicon must complete the following relationship: The chemical composition can also include one of the following elements, if desired: 0.05% ≤ Mo ≤ 0.65% 0.001% ≤ W ≤ 0.30% 0.0005% ≤ Ca ≤ 0.005%, The rest of the composition consists of iron and inevitable impurities resulting from smelting. It is preferable that the percentage of voids in the surface area of ​​the hot-rolled steel sheet after pickling and before coating is less than 30%. The surface area means the area starting from the top point of the surface of the hot-rolled steel sheet and extending 15 m from this top point into the depth. It is better that the intergranular oxidation depth of hot-rolled steel sheet is less than 4 μm. According to one embodiment of the invention, the pool contains 8 to 11% silicon and 2 to 4% iron by weight, with the remainder being aluminum or aluminum alloy and processing impurities. According to another embodiment of the invention, the pool contains, by weight, 0.1 to 10% magnesium, 0.1 to 20% aluminum, and the remainder is Zn or a Zn alloy, and, if desired, elements such as Si, Sb, Pb, Ti, Ca, Mn, Sn, La, Ce, Cr, Ni, Zr and / or Bi can also be added to it, and impurities resulting from processing are also present. According to another embodiment of the invention, the pool contains, by weight, 2 to 24 percent zinc, 7.1 to 12 percent silicon, optionally 1.1 to 8.0 percent magnesium, and optionally additional elements such as Pb, Ni, Zr, or Hf, with the amount of each of these additional elements being less than 0.3 percent, the remainder being aluminum and unavoidable impurities and precipitation factors, and the Al / Zn ratio being greater than 2.9. According to another embodiment of the invention, the pool contains, by weight, 4 to 20 percent zinc, 1 to 3.5 percent silicon, optionally 1 to 4 percent magnesium, and optionally additional elements such as Pb, Ni, Zr, or Hf, the amount of each of these additional elements being less than 0.3 percent, the remainder being aluminum and unavoidable impurities and precipitation factors, and the Zn / Si ratio being between 3.2 and 8. According to another embodiment of the invention, the pool contains, by weight, 2 to 24 percent zinc, 1.1 to 7 percent silicon, optionally 1.1 to 8.0 percent magnesium, if the silicon content is between 1.1 and 4.0 percent, and optionally additional elements such as Pb, Ni, Zr or Hf, the amount of each of these additional elements being less than 0.3 percent, the remainder being aluminum and unavoidable impurities and precipitation factors, and the Al / Zn ratio being greater than 2.9. According to an embodiment of the present invention, the method also includes, after coating the hot-rolled steel sheet with aluminum or aluminum alloy, the step of depositing a Zn coating on the Al or Al alloy through cementation, by electroplating or sonic vapor jet deposition, and the thickness of the Zn coating is less than or equal to 1.1 µm. It is best to do acid washing in an HCI bath for a period of time between 15 and 65 seconds. In one embodiment of the invention, the structure of the hot-rolled steel sheet contains ferrite and pearlite. The invention also relates to a method for producing hot-rolled coated steel sheet with a thickness between 1.8 mm and 5 mm, the method comprising the following steps: -Preparation of a semi-finished steel product with compositions that include the following by weight: or 0.24% ≤ C ≤ 0.38% and 0.40% ≤ Mn ≤ 3% 0.38% ≤ C ≤ 0.43% and 0.05% ≤ Mn ≤ 0.40% or 0.10% ≤ Si ≤ 0.70% 0.015% ≤ Al ≤ 0.070% 0.001% ≤ Cr ≤ 2% 0.25% ≤ Ni ≤ 2% 0.015% ≤ Ti ≤ 0.1% 0% ≤ Nb ≤ 0.06% 0.0005% ≤ B ≤ 0.0040% 0.003% ≤ N ≤ 0.010% 0.0001% ≤ S ≤ 0.005% 0.0001% ≤ P ≤ 0.025%, The amount of titanium and nitrogen must complete the following relationship: Ti / N > 3.42, The amount of carbon, manganese, chromium, and silicon must complete the following relationship: The chemical composition can also include one of several elements, if desired: 0.05% ≤ Mo ≤ 0.65% 0.001% ≤ W ≤ 0.30% 0.0005% ≤ Ca ≤ 0.005%, The rest of the composition consists of iron and inevitable impurities resulting from smelting, -Hot rolling of the semi-finished steel product at a final rolling temperature between 840 and 1000 degrees Celsius, to obtain a hot-rolled steel product with a thickness between 1.8 mm and 5 mm, and then: -Cooling the hot-rolled steel product to the coiling temperature Tcoil and coiling the hot-rolled steel product at the aforementioned coiling temperature Tcoil, so that a hot-rolled steel sheet is obtained, the appropriate Tcoil temperature is: 450°C ≤ Tcoil ≤ 495°C, -Acid washing of hot rolled steel sheet -Coating hot-rolled steel sheet with Al or an Al alloy by continuous placement in a hot bath, so as to obtain a hot-rolled coated steel sheet whose coating is Al or Al alloy and whose thickness on each side of the hot-rolled steel sheet is between 10 and 33 µm. It is preferable that the percentage of voids in the surface area of ​​the hot-rolled steel sheet after pickling and before coating is less than 30%. The surface area means the area extending from the top point of the surface of the hot-rolled steel sheet to a depth of 15 m from this top point. It is better that the intergranular oxidation depth of hot-rolled steel sheet is less than 4 μm. In one embodiment of the invention, the structure of the hot-rolled steel sheet contains ferrite and pearlite. The invention also relates to a hot-rolled coated steel sheet containing: -Hot-rolled steel sheet with a thickness between 1.8 mm and 5 mm, the composition of which, in terms of weight percentage, is as follows: 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%, The rest of the composition consists of iron and inevitable impurities resulting from smelting, The said hot-rolled steel sheet has an intergranular oxidation depth of less than 4 m, - An Al or Al alloy coating with a thickness between 10 and 33 µm on each side of the hot-rolled steel sheet. According to one embodiment of the invention, the composition is such that Ni ≤ 0.1%. In this case, the composition preferably comprises, by weight: 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 rest of the composition consists of iron and inevitable impurities resulting from smelting, According to one embodiment of the invention, the composition is such that 0.075% ≤ C ≤ 0.38%. According to a specific case, steel has the following composition by weight: 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 rest of the composition consists of iron and inevitable impurities resulting from smelting. According to another specific embodiment of the invention, the steel composition has the following elements by weight: 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% 1.5% ≤ (C + Mn +Si + Cr) ≤ 2.7% such that 3.4 x N ≤ Ti ≤ 8 x N 0.04% ≤ Nb ≤ 0.06% 0.044% ≤ (Nb+Ti) ≤ 0.09% such that 0.0005% ≤ B ≤ 0.004% 0.001% ≤ N ≤ 0.009% 0.0005% ≤ S ≤ 0.003% 0.001% ≤ P ≤ 0.020% 0.0001% ≤ Ca ≤ 0.006%, and if deemed appropriate The rest of the composition consists of iron and inevitable impurities resulting from smelting, According to another specific embodiment, the steel composition has the following elements by weight: 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 rest of the composition consists of iron and inevitable impurities resulting from smelting. According to another specific embodiment, the steel composition has the following elements by weight: 0.24% ≤ C ≤ 0.38% 0.40% ≤ Mn ≤ 3% 0.10% ≤ Si ≤ 0.70% 0.015% ≤ Al ≤ 0.070% 0.001% ≤ Cr ≤ 2% 0.25% ≤ Ni ≤ 2% 0.015% ≤ Ti ≤ 0.1% 0% ≤ Nb ≤ 0.06% 0.0005% ≤ B ≤ 0.0040% 0.003% ≤ N ≤ 0.010% 0.0001% ≤ S ≤ 0.005% 0.0001% ≤ P ≤ 0.025%, The amount of titanium and nitrogen must complete the following relationship: Ti / N > 3.42, The amount of carbon, manganese, chromium, and silicon must complete the following relationship: The chemical composition can also include one of the following elements, if desired: 0.05% ≤ Mo ≤ 0.65% 0.001% ≤ W ≤ 0.30% 0.0005% ≤ Ca ≤ 0.005%, The rest of the composition consists of iron and inevitable impurities resulting from smelting. It is preferable that the coating consists of an intermetallic layer with a maximum thickness of 15 μm, i.e. less than or equal to 15 μm. According to one embodiment of the invention, the hot-rolled coated steel sheet also includes, on each side thereof, a Zn coating with a thickness less than or equal to 1.1 μm. In one case, the hot-rolled steel sheet has a fritopoerlitic structure, that is, a structure containing ferrite and pearlite. The invention also relates to a hot-rolled coated steel sheet comprising: -Hot-rolled steel sheet with a thickness between 1.8 mm and 5 mm, the composition of which by weight includes the following: 0.24% ≤ C ≤ 0.38% and 0.40% ≤ Mn ≤ 3% or 0.38% ≤ C ≤ 0.43% and 0.05% ≤ Mn ≤ 0.40% or 0.10% ≤ Si ≤ 0.70% 0.015% ≤ Al ≤ 0.070% 0.001% ≤ Cr ≤ 2% 0.25% ≤ Ni ≤ 2% 0.015% ≤ Ti ≤ 0.1% 0% ≤ Nb ≤ 0.06% 0.0005% ≤ B ≤ 0.0040% 0.003% ≤ N ≤ 0.010% 0.0001% ≤ S ≤ 0.005% 0.0001% ≤ P ≤ 0.025%, The amount of titanium and nitrogen must complete the following relationship: Ti / N > 3.42, The amount of carbon, manganese, chromium, and silicon must complete the following relationship: The chemical composition can also contain one of the following elements, if desired: 0.05% ≤ Mo ≤ 0.65% 0.001% ≤ W ≤ 0.30% 0.0005% ≤ Ca ≤ 0.005%, The rest of the composition consists of iron and inevitable impurities resulting from smelting, The intergranular oxidation depth of the hot-rolled steel sheet is less than 4 μm. - An Al or Al alloy coating with a thickness between 10 and 33 µm on each side of the hot-rolled steel sheet. It is preferable that the coating consists of an intermetallic layer with a maximum thickness of 15 μm, i.e. less than or equal to 15 μm. According to one embodiment of the invention, the hot-rolled coated steel sheet also includes, on each side thereof, a Zn coating with a thickness less than or equal to 1.1 μm. In one case, the hot-rolled steel sheet has a fritopoerlitic structure, that is, a structure containing ferrite and pearlite. The invention also relates to a method for a hot-rolled coated steel sheet comprising the following steps: -Providing a hot-rolled coated steel sheet according to the present invention or produced in a manner consistent with the present invention. -Cutting hot-rolled coated steel sheet to create small sheets -Heating the raw part in a furnace at a temperature of Tc to obtain a heated raw part -Transferring the heated blank to the mold and hot stamping it in the mold, resulting in a hot stamped blank. -Cooling the heated stamped blank to a temperature below 400°C to obtain a heated stamped coated steel part. According to one embodiment of the invention, after cutting the hot-rolled coated steel sheet to obtain a blank and before heating the blank to a temperature of Tc, the blank is welded to another blank of steel with the following compositions in 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 ≤ 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% The rest of the composition consists of iron and inevitable impurities resulting from smelting. It is better if that other raw piece has a composition like this: Ni ≤ 0.1%. According to another embodiment of the invention, after cutting the hot-rolled coated steel sheet to obtain a blank and before heating the blank to a temperature Tc, the blank is welded to another blank of steel with the following compositions in weight percent: 0.24% ≤ C ≤ 0.38% and 0.40% ≤ Mn ≤ 3% or 0.38% ≤ C ≤ 0.43% and 0.05% ≤ Mn ≤ 0.40% or 0.10% ≤ Si ≤ 0.70% 0.015% ≤ Al ≤ 0.070% 0.001% ≤ Cr ≤ 2% 0.25% ≤ Ni ≤ 2% 0.015% ≤ Ti ≤ 0.1% 0% ≤ Nb ≤ 0.06% 0.0005% ≤ B ≤ 0.0040% 0.003% ≤ N ≤ 0.010% 0.0001% ≤ S ≤ 0.005% 0.0001% ≤ P ≤ 0.025%, The amount of titanium and nitrogen must complete the following relationship: Ti / N > 3.42, The amount of carbon, manganese, chromium, and silicon must complete the following relationship: The chemical composition can also contain one of the following elements, if desired: 0.05% ≤ Mo ≤ 0.65% 0.001% ≤ W ≤ 0.30% 0.0005% ≤ Ca ≤ 0.005%, The rest of the composition consists of iron and inevitable impurities resulting from smelting. The present invention also relates to a hot-rolled coated steel part, at least a portion of which has a thickness of between 1.8 mm and 5 mm, and the hot-stamped steel part comprises an Al or Al alloy coating, and the surface porosity percentage of the coating is less than or equal to 3%. According to one embodiment of the invention, the said section is made of steel whose composition by weight is as follows: 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%, The rest of the composition consists of iron and inevitable impurities resulting from smelting. According to one embodiment, the composition of the steel in said section can be such that Ni ≤ 0.1%. According to another version, the said part is made of steel whose composition by weight is as follows: 0.24% ≤ C ≤ 0.38% and 0.40% ≤ Mn ≤ 3% or 0.38% ≤ C ≤ 0.43% and 0.05% ≤ Mn ≤ 0.40% or 0.10% ≤ Si ≤ 0.70% 0.015% ≤ Al ≤ 0.070% 0.001% ≤ Cr ≤ 2% 0.25% ≤ Ni ≤ 2% 0.015% ≤ Ti ≤ 0.1% 0% ≤ Nb ≤ 0.06% 0.0005% ≤ B ≤ 0.0040% 0.003% ≤ N ≤ 0.010% 0.0001% ≤ S ≤ 0.005% 0.0001% ≤ P ≤ 0.025%, The amount of titanium and nitrogen must complete the following relationship: Ti / N > 3.42, The amount of carbon, manganese, chromium, and silicon must complete the following relationship: The chemical composition can also contain one of the following elements, if desired: 0.05% ≤ Mo ≤ 0.65% 0.001% ≤ W ≤ 0.30% 0.0005% ≤ Ca ≤ 0.005%, The rest of the composition consists of iron and inevitable impurities resulting from smelting. The invention also relates to the use of a hot stamped coated steel part according to the present invention or produced by a method according to the present invention for producing chassis or body parts or suspension arms for a vehicle. The invention will now be described in detail and will be fully illustrated by way of example and without limiting the scope of the invention, with reference to the accompanying drawings. The drawings are: -Figure 1: Cross-section of a hot-rolled coated steel piece showing the evaluation of coating adhesion after hot stamping. -Figure 2: Cross-section of hot-rolled steel sheet, prior to coating and hot stamping, showing the determination of the percentage of surface porosity on the surface of the hot-rolled steel sheet. The term "hot-rolled" steel product, sheet, layer, or piece means that the product, sheet, layer, or piece has been hot rolled, not cold rolled. The present invention relates to hot-rolled steel sheet that has not been cold-rolled. Hot-rolled sheets or layers differ from cold-rolled sheets or layers in the following characteristics: In general, the hot and cold rolling steps cause some damage to the second phase particles, which is due to the difference in the rheological behavior (the science of flow and deformation of flows that describes the interaction between forces, deformation and time) between the matrix and the second phase particles (oxides, sulfides, nitrides, carbides, etc.). In the case of cold rolling, voids can nucleate and grow around cementites, carbides or pearlites. In addition, the particles may disintegrate. This damage is observed in sheets that are cut and prepared by ion beam polishing. This method avoids manual human intervention due to the metal flow in mechanical polishing that can partially or completely fill the pores. Deeper observations of the presence of real pores are made by scanning electron microscopy.Compared to hot-rolled steel sheet rolled in the austenitic range, internal damage observed around or within cementite particles can be attributed to cold rolling because these particles are not present in the hot rolling stage. Therefore, damage observed around cementite, carbides, or pearlite in a rolled steel sheet is an indication that the steel sheet has been cold rolled. Furthermore, in the following, hot-rolled steel sheet means a hot-rolled steel product whose production method has been carried out before any coating step, and hot-rolled coated steel sheet means a product resulting from a production method including a coating step. Therefore, hot-rolled coated steel sheet is obtained as a result of coating hot-rolled steel sheet and includes a steel product with a coating on each side. In order to distinguish the hot-rolled coated steel sheet steel product (i.e. excluding its coating) from the hot-rolled steel sheet without coating, the hot-rolled coated steel sheet steel product will be hereinafter referred to as "hot-rolled steel sheet". Hot-rolled steel sheet is generally produced from semi-finished steel products that are heated, rolled to the desired thickness, cooled to the coiling temperature Tcoil, and then coiled and pickled at the same cooling temperature Tcoil to remove unwanted scales, waste, and protrusions. The hot-rolled steel sheet may then be coated to produce a hot-rolled coated steel sheet that must be cut, heated in a furnace, stamped, and cooled to ambient temperature to produce the desired structure. The inventors have investigated the problem of the lack of proper adhesion of the coating following hot stamping and have concluded that this lack of adhesion occurs mainly in the parts located in the center and longitudinal axis of the coil area during the coiling operation. Upon further investigation of this phenomenon, the inventors concluded that the lack of proper adhesion of the coating after hot stamping is due to intergranular oxidation that occurs during coiling. Steel, especially just before coiling, contains austenite. After coiling, some of this austenite transforms into ferrite and pearlite, generating heat. The heat generated leads to an increase in temperature in the coiled steel sheet, especially in the central and axial parts of the coil. The center of the coil is the part of the steel sheet that is located along the longitudinal axis of the sheet, from the starting point of the sheet, which is 30% of the total length of the sheet, to the end, which is 70% of the total length of the sheet. In addition, the axial region is the region in the center of the longitudinal axis of the sheet, the width of which is 60% of the total width of the sheet. In the central and axial areas, during coiling, the twisting operation is performed in close proximity and the local oxygen pressure is such that only elements that oxidize faster and easier than iron are oxidized, especially elements such as silicon, manganese or chromium. The iron-oxygen phase diagram in atmosphere 1 shows that iron oxide formed at high temperatures, for example, westite (FeO), is not stable at temperatures below 570°C and in thermodynamic equilibrium, it transforms into two other phases: hematite (Fe2O3) and magnetite (Fe3O4). In contrast, if the temperature increases in parts of the coil during coiling, especially in the central and axial regions of the coil, so that the temperature exceeds 570°C, hematite and magnetite transform into westite, one of the results of this decomposition is the formation of oxygen. The oxygen produced by this reaction combines with elements that are more easily oxidized than iron, especially silicon, manganese, and chromium, which are present on the surface of the steel sheet. Naturally, these oxides form at grain boundaries rather than being uniformly distributed throughout the matrix. As a result, oxidation is much more pronounced at grain boundaries. From now on, we will refer to this oxidation as intergranular oxidation. Therefore, at the end of the coiling operation, the coil contains intergranular oxidation at the surface and up to a certain point in depth, the height of which can reach up to 17 μm. The inventors found that a significant intergranular oxidation occurs in the hot-rolled steel sheet and consequently in its final product, which leads to a lack of proper adhesion of the coating after hot stamping. In fact, after coating, when the sheet is heated for hot stamping, carbon diffuses towards the coating and comes into contact with intergranular oxides, in particular manganese oxide and silicon. This carbon diffusion leads to reactions between SiO2 and C, between MnO and C and between Mn2SiO4 and C, forming carbon oxide. These carbon oxides are displaced and dissolve until the final hardening of the coating, which then leads to the formation of pores in the coating and, ultimately, to poor adhesion of the coating. The effect of intergranular oxidation on the adhesion of the coating is specific to hot-rolled steel sheets that are not subjected to cold rolling after coiling, just the opposite of cold-rolled steel sheets. In fact, during the production of these cold-rolled steel sheets, the intergranular oxidation that may exist in the surface layers before cold rolling, like the entire sheet, loses its thickness during cold rolling. As a result, the depth of intergranular oxidation of cold-rolled steel sheets before hot stamping is greatly reduced compared to the depth of intergranular oxidation in hot-rolled steel sheets. Intergranular oxidation can be reduced or even completely stopped before coating. This reduction or stopping can be achieved by intensive pickling of the steel sheet, for example, in an HCI bath for 375 seconds. However, intensive acid pickling requires a drastic reduction in production line speed, which is not in line with industry standards. In addition, the intense pickling results in the creation of a processed surface on the sheet. The processed surface is the entire surface area of ​​the steel sheet that comes into contact with the pool during coating. This processed surface leads to the dissolution of more iron than the surface of the sheet during coating in the pool and, as a result, the growth of the intermetallic layer, which ultimately leads to the coating not being limited to a specific area in the vicinity of the steel sheet coating but also reaching the surface of the coating. As a result of all these events, the thickness of the coating can no longer be controlled within the desired range. The intermetallic layer consists of a solid compound containing metal elements with a specific stoichiometry and has a crystal structure in such a way that the atoms are arranged in a specific position. The inventors have found that limiting or stopping intergranular oxidation during coiling makes it possible to produce hot-rolled coated steel sheet with a thickness of between 1.8 mm and 5 mm with good adhesion after hot stamping, while allowing the coating thickness to be controlled within the target range, particularly between 10 and 33 μm, while maintaining acceptable productivity in the pickling line. The steel composition is such that it can be hot stamped to produce a part with a tensile strength greater than or equal to 500 MPa or greater or equal to 1000 MPa or greater or equal to 1350 MPa or greater or equal to 1680 MPa. A steel composition according to the first aspect of the invention is disclosed below. In relation to the chemical composition of steel, carbon plays a very important role in hardenability and tensile strength after hot stamping, and the reason for this is the effect it has on the hardness of martensite. If its content is less than 0.04%, it is not possible to achieve a tensile strength of more than 500 MPa after stamping under any cooling conditions. If its content is more than 0.38%, in combination with other elements according to the first aspect, the adhesion of the coating after hot stamping will not be very satisfactory. Without wishing to be bound by any particular theory, a C content of more than 0.38% can lead to the formation of carbon oxide during the heating of the sheet before hot stamping, which will exacerbate the negative effect of intergranular oxidation on the adhesion of the coating. In addition, a content of more than 0.38% causes the steel to have a reduced crack resistance and hardness. The value of C depends on the desired tensile strength TS of the hot stamped part produced by hot stamping of sheet steel. In particular, for carbon contents in the range of 0.06% to 0.38% by weight, the tensile strength TS of hot stamped parts, produced by complete austenitization and stamping followed by martensitic quenching, depends practically and only on the carbon content and is related to the carbon content as follows: TS (MPa)=3220(C%)+908, In the equation above, C% means the weight percentage of carbon. According to one embodiment of the invention, the value of C is greater than or equal to 0.75%. Manganese, apart from its role in deoxidation, also has an important effect on quenching, especially when its content is at least 0.40% and the C content is at most 0.38%. At values ​​above 3%, the stabilization of austenite by Mn is very important and leads to the formation of a curved structure in the sheet which is easily visible. According to one embodiment, the Mn content is less than or equal to 2.0%. Silicon in an amount of at least 0.005% helps to deoxidize the liquid steel and also helps to harden the steel. However, its amount should be limited to prevent the formation of excess silicon oxide. In addition, the amount of silicon should be limited to prevent the stability of austenite, which is very important. Therefore, the amount of silicon is less than or equal to 0.70%, for example, less than or equal to 0.5%. Preferably, the Si amount is at least 0.10%. Aluminum can also be used as a deoxidizer. The Al content should be less than or equal to 0.1% and no more than 0.005%, and is often greater than or equal to 0.010%. It is preferable that the Al content be less than or equal to 0.070%. If desired, elements such as chromium, tungsten and / or boron can also be used in the compositions to increase the quenchability of the steel. In particular, Cr can be used to increase the quenching ability of steel, which also helps to achieve the desired TS tensile strength after hot stamping. When Cr is added to the composition, its amount should be greater than or equal to 0.01% to 2%. If Cr is not added, the amount of Cr initially present in the composition is equal to 0.001%. W can also be added to the composition to increase the quenching and hardenability of the steel by forming tungsten carbides. When W is added to the composition, its amount should be greater than or equal to 0.001% and less than or equal to 0.30%. When B is added to the composition, its amount should be greater than 0.0002%, and preferably greater than or equal to 0.0005% to 0.010%. It is more preferable that the amount of B is less than or equal to 0.005%. Up to 0.1% niobium and / or up to 0.2% titanium can also be added to the composition if desired to achieve precipitation hardening. When Nb is added to the composition, its amount should preferably be at least 0.01%. In particular, when the Nb amount is between 0.01% and 0.1%, grain-hardening carbonitride precipitates Nb(CN) are formed in austenite or ferrite during hot rolling. The Nb amount should preferably be less than or equal to 0.06%. Preferably, the Nb amount should be between 0.03% and 0.05%. When Ti is added to the composition, its amount should preferably be at least 0.015% to 0.2%. When the Ti amount is between 0.015% and 0.2%, precipitation occurs at a very high temperature in the form of TiN and then, at a lower temperature, in the form of TiC in austenite, which leads to hardening. In addition, when titanium is added to the composition in addition to boron, titanium prevents boron from combining with nitrogen, and nitrogen combines with titanium. As a result, it is preferable that the titanium amount is more than 3.42N. However, the Ti amount should be less than or equal to 0.2%, preferably less than or equal to 0.1%, to prevent the precipitation of coarse-grained TiN precipitates. If Ti is not added to the composition, the amount of Ti present as an impurity in the composition will be at least 0.001%. Molybdenum can be added to the composition at a maximum of 0.65%. When Mo is added to the composition, it is preferable that its amount is at least 0.05%, for example, less than or equal to 0.10%. It is preferable that Mo is added to the composition together with Nb and Ti to form co-precipitates that are very stable at high temperatures and prevent the growth of austenite grains during heating. The best effect is obtained when the amount of Mo is between 0.15% and 0.25%. Nickel is present as an impurity in a small amount, i.e. 0.001% and less than or equal to 0.1% in the composition. Sulfur, phosphorus, and nitrogen are also mainly present as impurities in the composition of steel. The nitrogen content is at least 0.0005%. The nitrogen content should be at most 0.010%, to avoid coarse-grained TiN deposits. If the amount of sulfur and phosphorus in the composition exceeds the permissible amount, the ductility will decrease. Therefore, their amount should be limited to 0.05% to 0.1%, respectively. It is better if the value of S is at most 0.30%. Achieving a very low value of S, i.e. less than 0.0001%, is very costly and not profitable. Therefore, the value of S is mostly greater than or equal to 0.0001%. It is preferable that the phosphorus content is at most 0.05%, and even better, that it is at most 0.025%. It is very expensive to achieve a very low P content, i.e. less than 0.0001%. Therefore, the P content is generally greater than or equal to 0.0001%. The steel may be processed to sulfite cyclic with calcium, which results in improved bend angles due to sulfite cyclic MnS. Therefore, the steel composition may contain at least 0.0001% to 0.006% Ca. The remainder of the steel composition consists of iron and inevitable impurities resulting from the smelting process. According to the first case, steel, by weight, has the following chemical composition: 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 remainder of the steel composition consists of iron and inevitable impurities resulting from the smelting process. With this combination, steel parts can be produced that have a tensile strength of at least 500 MPa after hot stamping. According to the second embodiment of the invention, the steel has the following chemical composition, by weight: 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% 1.5% ≤ (C + Mn +Si + Cr) ≤ 2.7% such that 3.4 x N ≤ Ti ≤ 8 x N 0.04% ≤ Nb ≤ 0.06% 0.044% ≤ (Nb+Ti) ≤ 0.09% such that 0.0005% ≤ B ≤ 0.004% 0.001% ≤ N ≤ 0.009% 0.0001% ≤ S ≤ 0.003% 0.0001% ≤ P ≤ 0.020% 0.0001% ≤ Ca ≤ 0.006%, and if deemed appropriate The remainder of the steel composition consists of iron and inevitable impurities resulting from the smelting process. With this combination, steel parts can be produced that have a tensile strength of at least 1000 MPa after hot stamping. According to the third embodiment of the invention, the steel has the following chemical composition, by weight: 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 ≤ 0.08% 0.0005% ≤ N ≤ 0.010% 0.0001% ≤ S ≤ 0.05% 0.0001% ≤ P ≤ 0.1% The remainder of the steel composition consists of iron and inevitable impurities resulting from the smelting process. With this combination, steel parts can be produced that have a tensile strength of at least 1350 MPa after hot stamping. Next, a steel composition is disclosed in accordance with a second aspect of the present invention. If the Mn content is between 0.40% and 3%, the C content is between 0.24% and 0.38%. Carbon plays an important role in the hardness and tensile strength after hot stamping, and the reason for this is the effect it has on the hardness of martensite. A content of at least 0.24% makes it possible to achieve a TS tensile strength of at least 1800 MPa after hot stamping without the need to add expensive elements. If the Mn content is between 0.40% and 3%, a carbon content of more than 0.38% leads to a decrease in crack resistance and a decrease in tensile strength. . If the Mn content is between 0.40% and 3%, it is better for the C content to be between 0.31% and 0.36%. A high C content of 0.38% to 0.43% can be used when the Mn content is reduced to a range of 0.05% to 0.40%. In this way, the reduction in Mn can be compensated by an increase in C, while still achieving good corrosion resistance. In addition to its role in deoxidation, manganese also has an important effect on quenching. When the C content is between 0.24% and 0.38%, the Mn content must be at least 0.40% and less than or equal to 3%. The Mn content of at least 0.40% is necessary to achieve a temperature Ms, which is the initial temperature of the austenite to martensite transformation during cooling, which is sufficient to achieve the desired strength (tensile strength TS of at least 1800 MPa in this embodiment of the invention). At values ​​above 3%, the stabilization of austenite by Mn is very important, leading to the formation of a visible bent structure. It is better if the Mn value is less than or equal to 2.0%. Alternatively, if the C content is increased to a range between 0.38% and 0.43%, the Mn content can be reduced to a range between 0.05% and 0.40%. Reducing the Mn content allows for greater corrosion resistance. It is better to express the amount of Mn and C as Cr. When the C content is between 0.32% and 0.36%, the Mn content is between 0.40% and 0.80%, and the Cr content is between 0.05% and 1.20%, it is possible to achieve greater resistance to cracking. When the C content is between 0.24% and 0.38%, and the Mn content is between 1.50% and 3%, the possibility of a healthy boiling point will be satisfactory to an acceptable extent. When the C content is between 0.38% and 0.43%, and the Mn content is between 0.05% and 0.40%, and preferably between 0.09% and 0.11%, the corrosion resistance is greatly increased. The change in the composition range allows for an Ms temperature of around 320 to 370°C, which ensures very high strength in the heated stamped parts. Silicon is added to the composition in an amount between 0.10% and 0.70% by weight. A minimum amount of 0.10% results in higher hardness and deoxidation of the liquid steel. However, its amount must be limited to prevent excessive formation of silicon oxide. In addition, the amount of silicon must be limited to prevent the stability of austenite, which is very important. Therefore, the amount of silicon should be less than or equal to 0.70%. When the C content is between 0.24% and 0.38%, it is better to have a silicon content of at least 0.50% to prevent hardening of fresh martensite, which may occur during the holding time of the steel in the mold and after martensitic transformation. As a deoxidizer, an amount of less than or equal to 0.070% or greater than or equal to 0.015% aluminum can be added to the composition. An amount greater than 0.070% may cause coarse aluminum grains to form during processing and reduce ductility. It is better if the amount of aluminum is less than 0.020% to 0.060%. If desired, the composition can also contain chromium and / or tungsten to increase the quenchability of the steel. Chromium increases the quenching ability of steel and helps to achieve the desired TS tensile strength after hot stamping. When Cr is added, its amount should be greater than or equal to 0.01% to 2%. If this amount is not added, the initial amount of Cr in the composition will be less than 0.001%. When the C content is between 0.24% and 0.38%, the Cr content is preferably between 0.30% and 0.50%. When the Mn content is between 1.50% and 3%, the addition of Cr is optional, and the quenching ability obtained through the addition of Mn is sufficient. When the C content is between 0.38% and 0.43%, it is better for the Cr content to be more than 0.5% and preferably between 0.950% and 1.050% to increase corrosion resistance. In addition to the conditions described above, the values ​​of C, Mn, Cr and Si must fulfill the following condition: In these conditions, the amount of martensite, which itself has hardened as a result of martensite hardening during the time the part is held in the mold, is very limited, such that a large amount of fresh martensite allows for a tensile strength of at least 1800 MPa to be achieved. W can be added to the composition to increase the quenching ability and hardness of the steel, which leads to the formation of tungsten carbide. When W is added to the composition, its amount should be greater than or equal to 0.001% and less than or equal to 0.30%. B is added to the composition in an amount of more than 0.0005% to 0.0040%. B increases the quenching ability. B prevents the intergranular segregation of P by diffusing at the grain boundaries. Up to 0.1% niobium and / or up to 0.2% titanium can also be added to the composition if desired to achieve precipitation hardening. When Nb is added to the composition, its amount should preferably be at least 0.01%. In particular, when the Nb amount is between 0.01% and 0.06%, grain-hardening carbonitride precipitates Nb(CN) are formed in austenite or ferrite during hot rolling. Therefore, Nb restricts the growth of austenite grains during pre-stamping heating. In any case, the Nb amount is less than or equal to 0.06%. In fact, an amount higher than 0.06% may increase the rolling load excessively. It is preferable that the Nb amount is between 0.03% and 0.05%. Ti can be added to the composition in an amount of at least 0.015% to 0.1%. When the Ti content is between 0.015% and 0.1%, precipitation occurs at very high temperatures in the form of TiN and then, at lower temperatures, in the form of TiC in austenite, which leads to hardening. In addition, titanium prevents the external combination with nitrogen, and nitrogen combines with titanium. As a result, it is better for the titanium content to be more than 3.42N. However, the Ti content should be less than or equal to 0.1% to prevent the precipitation of coarse-grained TiN precipitates. It is better for the Ti content to be between 0.020% and 0.040% to result in the formation of nitride grains that restrict the growth of austenite grains during the pre-stamping heating. Molybdenum can be added to the composition at a maximum of 0.65%. When Mo is added to the composition, it is better to add it to a minimum of 0.05%. It is better to add Mo together with Nb and Ti to form co-precipitates that are very stable at high temperatures and prevent the growth of austenite grains during heating. The best effect is achieved when the Mo content is between 0.15% and 0.25%. To increase the cracking resistance of steel, between 0.25% and 2% nickel can be added to the composition. The nitrogen content should be at least 0.003% to lead to precipitation of TiN, Nb(CN) and / or (Ti,Nb)(CN) and to limit the growth of austenite grains as described above. The nitrogen content should be at most 0.010% to prevent precipitation of coarse TiN grains. If the amount of sulfur and phosphorus in the composition exceeds the permissible amount, the ductility will decrease. Therefore, their amount should be limited to 0.005% to 0.025%, respectively. It is better to have a maximum S content of 0.005% to prevent sulfide precipitation. Achieving a very low S content, i.e. less than 0.0001%, is very costly and not profitable. Therefore, the S content is mostly greater than or equal to 0.0001%. It is better to keep the phosphorus content at a maximum of 0.025% to limit the segregation of P at the austenitic grain boundary. It is very expensive to achieve a very low P content, i.e. less than 0.0001%. Therefore, the P content is mostly greater than or equal to 0.0001%. The steel may be processed to sulfide cyclic with calcium, which results in improved bend angles due to sulfite cyclic MnS. Therefore, the steel composition may contain at least 0.0005% to 0.005% Ca. The remainder of the steel composition consists of iron and inevitable impurities resulting from the smelting process. As previously explained, the inventors found that the lack of proper adhesion of the coating in steel parts produced by hot stamping a hot-rolled coated steel sheet is due to intergranular oxidation existing on the surface of the hot-rolled coated steel sheet before hot stamping and at certain thicknesses. First, the inventors defined a standard that the hot-stamped coated steel piece had to meet to ensure proper adhesion of the coating. The inventors found that the quality of the coating's adhesion could be determined by determining the percentage of porosity on the coating's surface. The percentage of surface porosity of the coating can be determined on the hot stamped coated part, that is, after hot stamping and cooling to ambient temperature. The percentage of porosity of the coating surface was determined by observing five cross-sections of the sample under an optical microscope at a magnification of x1000. Each cross-section has a length lref that is specifically chosen to represent the coating. The length lref is taken to be 150 m. As can be seen in Figure 1, for each cross-section, an image analysis is performed using an image analyzer such as Olympus Stream Essentials® to determine the percentage of surface porosity in the coating in this cross-section. For this purpose, the upper and lower boundaries B1 and B2 belonging to the coating are determined. In particular, the upper boundary defines the boundary of the coating in contact with its surroundings and the lower boundary indicates the location of the separation of the steel material from the coating. Then, the total surface occupied by the coating, including the pores P, between the lower and upper boundaries is determined and the surface occupied by the pores that fall between the lower and upper boundaries is also evaluated (gray areas in Figure 1). Then, the percentage of surface porosity of the coating in the cross-section in question is calculated as the ratio between the surface occupied by the pores and the total surface occupied by the coating (multiplied by 100). Finally, the percentage of porosity of the coating surface is calculated as the average of the five values ​​obtained previously. If the percentage of porosity on the surface of the coating is less than or equal to 3%, the adhesion of the coating is acceptable. On the other hand, if the percentage of porosity on the surface of the coating is more than 3%, the adhesion of the coating will not be very satisfactory. In addition, the inventors have found two criteria that the hot-rolled steel product and the hot-rolled steel sheet must meet to ensure that the coating thickness will be controlled within the desired control range, particularly within the range of 20 to 33 μm or between 10 and 20 μm, and that the adhesion of the coating after stamping will be acceptable. The first criterion relates to the surface condition of the hot-rolled steel product, after pickling and before coating. As explained earlier, the processed surface of the hot-rolled steel product must be controlled just before coating to prevent excessive dissolution of iron from the steel surface and uncontrolled growth of the intermetallic layer upon entering the hot pool, as this would make it impossible to control the coating thickness within the appropriate range. In fact, the intergranular oxidation of the hot-rolled steel product is reduced by double and intense pickling, which will reduce the intergranular oxidation in the hot-rolled steel sheet. However, due to this double pickling, the surface condition of the product (i.e., the processed surface) will be such that the control of the coating thickness is lost. The inventors have found that in order to ensure that the coating thickness is controlled within the desired range of 10 to 33 μm, the thickness of the intermetallic layer formed during coating should remain less than 15 μm, and also in order to control the thickness of the intermetallic layer to remain at 15 μm, the percentage of surface porosity of the coating in the surface region of the hot-rolled steel product after any pickling and before coating should be less than 30%. The thickness of the intermetallic layer here means the thickness of the intermetallic layer of the hot-rolled coated steel sheet. The criterion of the percentage of porosity of the coating surface should be considered especially in the area of ​​the hot-rolled steel product that is located in the center and axis of the coil during the coiling operation. As shown in Figure 2, the surface area is the area extending from the top of the hot-rolled steel product to the depth and extending 15 μm from the top. The surface porosity percentage of this area is determined using 5 cross-sections representing the hot-rolled steel product, each cross-section having a length lref of 150 μm. It is preferable that the cross-sections are taken from samples located in the central and axial areas of the coil. In each cross-section, a surface area of ​​the sample is identified by image analysis tools such as Olympus Stream Essentials® as a rectangular area whose upper side reaches the two highest points Pt1 and Pt2 on the cross-section surface and whose lower side is 15 μm from the upper part. Therefore, each surface region of the sample has a length lref and a depth of 15 m. In each cross-section, the surface areas of the sample that are not steel are identified, and the total area of ​​such areas is determined. The percentage of surface porosity of the coating on the surface of the sample is then determined as the ratio of the total area of ​​the areas that are not steel to the total area of ​​the sample areas, then multiplied by 100. Finally, the percentage of surface porosity of the coating on the hot-rolled, pickling steel product is determined as the average of the five values ​​obtained previously. The second criterion is the maximum depth of intergranular oxidation in the hot-rolled steel sheet, or in other words, the steel product after coating. In fact, the inventors found that in order to achieve an acceptable level of surface adhesion after hot stamping, the depth of intergranular oxidation in the hot-rolled coated steel sheet should be less than 4 μm. This criterion must be met especially in the area of ​​the hot-rolled coated steel sheet that is located in the center and axis of the coil during the coiling operation. The depth of intergranular oxidation is determined on hot-rolled coated steel sheet, i.e. after coating. The depth of intergranular oxidation means the thickness of the area of ​​the hot-rolled steel sheet that includes the portion of the surface of the hot-rolled steel sheet (i.e., from the contact point between the coating and the hot-rolled steel sheet) toward the inside of the hot-rolled steel sheet, in the direction perpendicular and perpendicular to this surface, where intergranular oxidation occurs. Intergranular oxidation is observed in particular with an optical microscope at a magnification of x1000 on five different cross-sections, each with a length of lref of 150 m. The cross-sections are taken from a sample taken from the central and axial region of the coil. In each cross-section, the maximum depth of intergranular oxidation is measured. Finally, the intergranular oxidation depth is calculated as the average of the five values ​​obtained previously. Therefore, in order to ensure that the coating thickness can be controlled within the target range and that the adhesion of the coating after hot stamping will be acceptable, that is, the percentage of surface porosity of the coating will be less than 3%, the following two conditions must be met: -The percentage of surface porosity in the surface area of ​​the hot-rolled steel product, after pickling and before coating, must be less than 30%, and -The depth of intergranular oxidation in hot-rolled steel sheet after pickling and coating should be less than 4 μm. Hot rolled steel products can be produced by forging steel, the composition of which corresponds to the composition previously presented herein. In this way, a semi-finished steel product is obtained, which can be reheated at a Treheat temperature of between 1150°C and 1300°C. The reheated semi-finished product is then rolled at the final rolling temperature FRT to obtain a final hot rolled steel product. The Treheat temperature can be, for example, between 1150°C and 1240°C. The final temperature of FRT rolling is mainly set between 840 and 1000 degrees Celsius. In order to create a thickness between 1.8 mm and 5 mm, for example between 3 and 5 mm, in the final hot-rolled steel product, hot-rolling reduction is used. Then, the hot-rolled steel product is cooled on the exit table until it reaches the coiling temperature Tcoil and then coiled, resulting in a product called a hot-rolled steel substrate. The coiling temperature Tcoil is adjusted to prevent or at least reduce intergranular oxidation. The coiling temperature Tcoil should be specifically adjusted so that the intergranular oxidation depth in the hot-rolled steel layer is less than 5 μm. In fact, if the intergranular oxidation depth in the steel layer is less than 5 μm, the intergranular oxidation depth in the hot-rolled steel sheet after coating will remain less than 4 μm. It is best to select and adjust the coiling temperature Tcoil so that intergranular oxidation does not occur. Using a steel having a composition according to the first aspect of the present invention, the inventors have found that in order to achieve an intergranular oxidation depth in a hot rolled steel sheet of less than 4 μm, the coiling temperature Tcoil must be lower than the maximum coiling temperature Tcoilmax. The maximum coiling temperature depends on the amount of austenite just before coiling, which is indicated by f. In fact, a high amount of f austenite just before coiling leads to the transformation of a significant part of the austenite during coiling and, consequently, a significant increase in temperature, especially in the center and axis of the sheet in the coiling solution. On the contrary, if the amount of f austenite just before coiling is low, no transformation occurs during coiling or its extent will be limited and, consequently, the temperature increase of the sheet will be reduced. Therefore, the maximum coiling temperature Tcoilmax is a decreasing function of the austenite content f just before coiling. The inventors have found that in order to achieve an intergranular oxidation depth of less than 4 μm in hot rolled steel sheet, the maximum coiling temperature Tcoilmax should be as follows: In the above equation, Tcoilmax is expressed in degrees Celsius and f is the amount of austenite in the steel just before coiling, which is between 0 (meaning 0% austenite) and 1 (meaning 100% austenite). Therefore, the maximum coiling temperature Tcoilmax will be between 510 and 650 degrees Celsius. Therefore, the coiling temperature Tcoilmax must satisfy the following equation: The amount of austenite f in the steel just before coiling can be determined by a non-destructive, non-contact electromagnetic (EM) technique using an instrument for determining the magnetic properties of steel sheet. The principles of this technique, described, for example, in the document "Online electromagnetic monitoring of austenite transformation in hot strip rolling and its application to process optimization" by V. Marmulev et al., Revue de Métallurgie 110, pp.205-213 (2013), are based on the difference between the magnetic properties of austenite, which is paramagnetic, and those of ferrite, pearlite, bainite and martensite, which are ferromagnetic phases. For example, a device for determining the amount of austenite f is disclosed in US 2003 / 0038630 A1. The amount of austenite f just before coiling depends on the steel composition, especially the C value, the final rolling temperature FRT, and the cooling process between the final rolling temperature FRT and the coiling temperature Tcoil. More precisely, the higher the C value, the higher the austenite content f in the steel just before coiling. Therefore, all other parameters being equal, the higher the C value, the lower the maximum coiling temperature Tcoilmax. In particular, if the C value in the steel is greater than or equal to 0.075%, the austenite content in the layer will remain above 0.5, and thus the maximum coiling temperature Tcoilmax will be less than 580°C. For a steel of a given composition and thickness, on a given production line, and with a constant final rolling temperature FRT, the maximum coiling temperature Tcoilmax can be determined by determining the austenite content of the steel product during cooling from the final rolling temperature FRT, and by comparing the temperature T of the layer during cooling with the value f'(T), f'(T) 650-140, which is the austenite content of the layer at T during cooling. Maximum coiling temperature Tcoilmax is the temperature at which T = 650 -140 f'(T). Generally, it is best to keep the coiling temperature below 580°C and, best of all, below 570°C. However, the coiling temperature must remain above 450 degrees to avoid undesirable increases in the mechanical properties of the steel that result from low coiling temperatures. Under such conditions, intergranular oxidation in the hot-rolled steel layer is limited, and therefore, the intergranular oxidation depth of the hot-rolled steel sheet after coating will also be less than 4 μm. Using a steel having a composition according to the second aspect of the present invention, the inventors have found that in order to achieve an intergranular oxidation depth in the hot-rolled steel sheet of less than 4 μm, the coiling temperature Tcoil must be even more limited than in the compositions according to the first aspect of the invention, and the heat value must be less than or equal to 495 degrees Celsius. The conditions mentioned above for uniform adhesion and control of the coating thickness within the desired range must also be observed here. However, due to the presence of Ni in an amount greater than or equal to 0.25%, those amounts are not sufficient to provide adequate productivity in the pickling line. In fact, the inventors have found that the presence of Ni in an amount greater than or equal to 0.25% also leads to increased adhesion of irregularities (small, point-like protrusions - translator) in the hot rolling mill. The presence of such irregularities that have strong adhesion to the surface makes the coating of the sheet difficult and weakens it. These flakes and irregularities can be removed by double and intense pickling, but the productivity in the pickling line will be greatly reduced in this way. The inventors have found that reducing the coiling temperature to less than or equal to Tcoilmax=495°C can help reduce the roughness that occurs on the hot rolling mill exit table.Therefore, the metallic nickel formed at the contact point of the asperity and steel is reduced, which facilitates the breakdown of the asperity and the pickling operation in the pickling line, and consequently increases the productivity in the said line. After coiling, the hot-rolled steel layer is pickled. Since the depth of intergranular oxidation is small, the pickling conditions will not affect the adhesion of the coating after hot stamping or the thickness of the coating. To be more precise, even if a partial pickling is performed, due to the small depth of intergranular oxidation before pickling, the depth of intergranular oxidation in the hot-rolled steel sheet after pickling will also be small, and the coating will have a thickness of less than 4 μm in any case. Thus, little carbonic acid is formed during heating before hot forming, and the adhesion of the coating after hot stamping will not be a problem. In addition, even if severe pickling is carried out, due to the shallow depth of intergranular oxidation before pickling, the percentage of surface porosity on the surface of the hot-rolled steel layer after pickling will remain less than 30%. Therefore, severe dissolution of iron from the steel surface and uncontrolled growth of the intermetallic layer do not occur when the steel sheet is coated in the pool, and the coating thickness can be controlled within the desired range. Acid pickling, for example, can be carried out in an HCI bath for a period of between 15 and 65 seconds. The hot-rolled steel sheet that is pickled meets the first criterion defined above, that is, the percentage of surface porosity in the surface area is less than 30%. In addition, the hot-rolled and pickled steel sheet has no or very little intergranular oxidation, which means that the second criterion described above is met, that is, achieving an intergranular oxidation depth of less than 4 m in the hot-rolled steel sheet after coating. After pickling, the hot-rolled, pickling steel sheet can be oiled or an organic layer such as Easyfilm®HPE can be applied to temporarily protect the sheet surface. Then, the hot-rolled and acid-washed steel sheet is continuously immersed in the bath and coated with Al or Al alloy to obtain a hot-rolled coated steel sheet. For example, the coating can be Al-Si. A pool sample for an Al-Si coating contains, by weight, mainly 8 to 11% silicon, 2 to 4% iron, and the remainder is aluminum or aluminum alloy and unavoidable impurities from processing. Alloying elements present in aluminum include strontium and / or calcium in amounts between 15 and 30 ppm. As another example, the coating can be Zn-Al-Mg. A typical Zn-Al-Mg coating bath contains mainly 0.1% to 10% magnesium by weight, between 0.1% and 20% aluminum, and the remainder Zn or Zn alloy, to which elements such as Si, Sb, Pb, Ti, Ca, Mn, Sn, La, Ce, Cr, Ni, Zr and / or Bi can be added if desired, and of course, there are also unavoidable impurities resulting from processing. For example, suppose that the pool contains 0.5% to 8% aluminum, 0.3% to 3.3% magnesium, and the remainder is Zn or Zn alloy, with selected elements such as Si, Sb, Pb, Ti, Ca, Mn, Sn, La, Ce, Cr, Ni, Zr, and / or Bi, and unavoidable impurities from processing. As another example, the coating could be made of Al-Zn-Si-Mg. The first sample for the Al-Zn-Si-Mg pool contains by weight 2% to 24% zinc, 7.1% to 12.0% silicon, optionally 1.1% to 8.0% magnesium, and optionally additional elements such as Pb, Ni, Zr or Hf, the amounts of which should be less than 0.3%. The remainder consists of aluminum and unavoidable processing impurities and precipitated elements, and its Al / Zn ratio is greater than 2.9. The second sample of Al-Zn-Si-Mg pool contains by weight 4.0% to 20.0% zinc, 1% to 3.5% silicon, optionally 1.0% to 4.0% magnesium, and optionally additional elements such as Pb, Ni, Zr or Hf, the amounts of which should be less than 0.3%. The remainder consists of aluminum and unavoidable processing impurities and precipitated elements, and its Zn / Si ratio is between 3.2 and 8.0. The second sample of Al-Zn-Si-Mg pool contains by weight 2.0% to 24.0% zinc, 1.1% to 7.0% silicon, optionally 1.1% to 8.0% magnesium if the silicon content is between 1.1% and 4.0%, and optionally contains additional elements such as Pb, Ni, Zr or Hf, the amounts of these additional elements should be less than 0.3%. The remainder consists of aluminum and unavoidable processing impurities and precipitated elements, and its Al / Zn ratio is also greater than 2.9. After coating is applied through a hot bath, the coated steel sheet is usually exposed to gas spray nozzles on both sides and then the coated steel sheet is cooled. The hot-rolled coated steel sheet thus obtained consists of a hot-rolled steel sheet and Al or Al alloy coating on both sides. Hot-rolled steel sheet generally has a fritto-pearlitic structure, i.e. a structure consisting of ferrite and pearlite. The thickness of the Al or Al alloy coating on each side of the hot-rolled steel sheet is between 10 m and 33 m. According to the first embodiment of the invention, the thickness of the coating is controlled to be in the range between 20 μm and 33 μm. According to the second embodiment of the invention, the thickness of the coating is controlled to be in the range between 10 μm and 20 μm. According to the third embodiment of the invention, the thickness of the coating is controlled to be in the range between 15 μm and 25 μm. After coating, the depth of intergranular oxidation in the hot-rolled steel sheet due to pickling will be less than 4 μm and mostly less than 3 μm. This depth starts from the surface of the hot-rolled steel sheet (i.e. the surface separating the hot-rolled steel sheet from the coating) and goes into the inside of the steel sheet. Furthermore, due to the percentage of surface porosity in the surface area of ​​the hot-rolled steel layer before coating, even after pickling, the coating thickness will remain within the desired range, specifically between 10 μm and 33 μm on each side of the hot-rolled coated steel sheet and at any point on each side of the hot-rolled coated steel sheet. Now, the hot-rolled coated steel sheet is ready for hot stamping. For this purpose, the hot-rolled coated steel sheet is cut to obtain smaller sheets. If desired, this blank can be welded to another blank to obtain a tailor-made sheet (TWB), comprising a first sheet cut from a hot-rolled coated steel sheet according to the present invention and a second sheet. The second sheet can also be cut and used from a hot-rolled coated steel sheet according to the present invention or can be a sheet obtained from a cold-rolled coated steel sheet. The first sheet should in particular have a thickness of between 1.8 mm and 5 mm and can be welded to a second sheet of a different thickness and / or made of a different steel composition. It is preferable that the second blank is made of a steel whose composition by weight is as follows: 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% The rest of the composition consists of iron and inevitable impurities resulting from smelting. The second sheet can also be made of steel whose composition by weight is as follows: 0.24% ≤ C ≤ 0.38% and 0.40% ≤ Mn ≤ 3% or 0.38% ≤ C ≤ 0.43% and 0.05% ≤ Mn ≤ 0.40% or 0.10% ≤ Si ≤ 0.70% 0.015% ≤ Al ≤ 0.070% 0.001% ≤ Cr ≤ 2% 0.25% ≤ Ni ≤ 2% 0.015% ≤ Ti ≤ 0.1% 0% ≤ Nb ≤ 0.06% 0.0005% ≤ B ≤ 0.0040% 0.003% ≤ N ≤ 0.010% 0.0001% ≤ S ≤ 0.005% 0.0001% ≤ P ≤ 0.025%, The amount of titanium and nitrogen must complete the following relationship: Ti / N > 3.42 The amount of carbon, manganese, chromium, and silicon must complete the following relationship: The chemical composition can also include one of the following elements, if desired: 0.05% ≤ Mo ≤ 0.65% 0.001% ≤ W ≤ 0.30% 0.0005% ≤ Ca ≤ 0.005%, The rest of the composition consists of iron and inevitable impurities resulting from smelting. For ease of understanding, it is noted that the term "raw material" is used hereinafter to mean a sheet obtained from a hot-rolled coated steel sheet according to the present invention or a welded seam sheet containing this raw material. The blank is then heat treated in a furnace before hot stamping, and the stamp is heated to produce a hot stamped coated steel part. The blank is heated, in particular in a furnace, to a temperature Tc that allows at least partial transformation into austenite. This temperature is, for example, between 860 and 950 °C, and preferably between 880 and 950 °C. In this way, a heated blank is obtained. Then, the heated blank is taken out of the furnace and transferred to a mold where it is subjected to thermal deformation (hot stamping) to form the desired geometric shape and obtain a hot stamped blank. The hot stamped blank is cooled to a temperature of 400 degrees Celsius at a cooling rate Vr, which is preferably greater than 10°C / s, and more preferably greater than 30°C / s, thereby obtaining a hot rolled coated steel blank. The hot-rolled coated steel piece obtained in this way has very acceptable coating adhesion. In particular, the percentage of porosity on the coating surface of the hot-rolled coated steel piece is less than or equal to 3%. Furthermore, after painting, for example by spraying, the paint adhesion is also considerably satisfactory. Paint adhesion can be assessed by means of a wet paint adhesion test in accordance with ISO 2409:2007. If the wet paint adhesion test result is less than or equal to 2, adhesion is considered good, and if the wet paint adhesion test result is more than 2, adhesion is considered poor. Examples Hot-rolled coated steel sheets were produced by molding semi-finished products with the compositions by weight disclosed in Table 1: Table 1 Steel C (%) Mn (%) Si (%) Al (%) Cr (%) Ni (%) Ti (%) Nb (%) B (%) N (%) S (%) P (%) Mo (%) W (%) Ca (%) A 0.23 1.13 0.24 0.037 0.159 0.013 0.036 0.001 0.0016 0.005 0.0017 0.015 0.003 0.003 0.0016 B 0.06 1.64 0.022 0.024 0.027 0.016 0.067 0.048 - 0.005 0.004 0.016 0.003 0.002 0.0015 C 0.36 1.24 0.226 0.032 0.111 0.105 0.034 0.001 0.0032 0.006 0.0014 0.015 0.021 0.004 0.0021 D 0.344 0.61 0.541 0.030 0.354 0.417 0.034 0.038 0.0039 0.005 0.0004 0.008 0.205 0.003 0.0006 E 0.07 1.62 0.36 0.040 0.09 0.012 0.021 0.051 0.0030 0.006 0.0010 0.012 - 0.003 0.0004 The Ni content reported in Table 1 for steels A, B, and E is consistent with the presence of Ni in the form of precipitates (or impurities). The hot-rolled steel products were cooled to the coiling temperature Tcoil and coiled at the coiling temperature Tcoil to obtain hot-rolled steel sheets. The hot-rolled steel sheets were pickled in an HCI bath for tpickling time. After pickling, samples were taken from the axial and central regions of the hot-rolled steel sheets and for each sample, the percentage of surface porosity in the surface region was determined according to the method described earlier. Then, the hot rolled steel sheets were immersed in the bath and coated. Table 2 shows the bath compositions used for coating the samples. The target coating thickness was between 20 and 33 μm on both sides of the sheet. Table 2 Coating Si (%) Fe (%) Zn (%) Mg (%) Al (%) + impurities  9 3 <0.1 <0.1 88  3.4 1.4 15.6 1.8 77.8 After hot-dip coating, some hot-rolled coated steel sheets were subjected to 0.7 µm Zn coating on Al alloy via electrodeposition. After coating, samples were taken from the central and axial regions of the sheets and in each sample, the depth of intergranular oxidation was determined according to the method described earlier. In addition, the coating thickness and the thickness of the intermetallic layer were also determined. Hot-rolled coated steel sheets were cut to obtain blanks. Blanks were cut from the central and axial areas of the hot-rolled coated steel sheets and the coated steel sheets were heated in a furnace for a time tc and up to a temperature of 920°C. This time tc included the heating phase to the desired temperature and the holding phase at this temperature. The blanks were then transferred to the mold, the stamp was heated and cooled to ambient temperature. A sample was taken from each coated heated stamp piece and the adhesion of the coating was evaluated by determining the percentage of porosity of the coating surface as described previously. In addition, the coating thickness was also measured. Finally, a 20µm electroless coating was applied to one side of each piece and the paint adhesion to the piece was tested by the wet paint adhesion test according to ISO 2409:2007. If the wet paint adhesion test result was less than or equal to 2, adhesion was considered good and if the wet paint adhesion test result was more than 2, adhesion was considered poor. In all these examples, the sheet width was 1 m. The production conditions (steel composition, thickness th after hot rolling, final rolling temperature FRT, austenite content just before coiling f and maximum coiling temperature Tcoilmax, coiling temperature Tcoil, pickling time tpickling and heating time tc) for each piece are reported in Table 3. Table 3 Steel sample coated with Zn electroplating th (mm) FRT (°C) f  T coilmax (°C) T coil (°C) t pickling (s) t C (s) 1 A  No 3.3 875 0.65 559 585 25 600 2 A  No 3.3 875 0.65 559 655 45 600 3 A  No 3.3 875 0.65 559 585 45 600 4 A  No 3.3 875 0.65 559 585 375 600 5 A  No 3.3 850 0.61 565 540 375 600 6 A  No 3.3 850 0.59 567 515 16 600 7 A  No 3.3 850 0.59 567 515 21 600 8 A  No 3.3 885 0.87 528 520 28 600 9 A  No 3.3 885 0.87 528 520 35 600 10 A  No 3.3 905 0.88 527 510 26 600 11 A  No 3.3 905 0.88 527 510 23 600 12 A  No 3.3 865 0.61 565 533 63 600 13 A  No 3.3 905 0.87 528 519 22 600 14 A  No 3.3 904 0.87 528 515 15 600 15 A  No 3.3 867 0.64 560 554 52 600 16 A  No 3.3 861 0.64 560 548 24 600 17 A  No 3.3 851 0.85 531 476 45 600 18 A  No 3.3 857 0.83 534 504 60 600 19 B  No 2.6 845 0.1 636 655 41 520 20 B  No 2.6 905 0.1 636 555 25 520 21 B  No 2.6 845 0.1 636 555 60 520 22 C  No 3.2 905 0.8 538 655 21 600 23 D  No 3.2 875 0.9 495 531 28 600 24 D  No 3.2 872 0.9 495 495 38 600 25 D  No 3.2 874 0.9 495 581 20 600 26 E  No 3.3 880 0.5 580 545 24 600 27 A  No 3.1 885 0.65 559 655 25 600 28 A  No 3.1 885 0.84 532 515 21 600 29 A  Yes 3.3 862 0.62 563 515 22 600. In this table, the underlined values ​​do not correspond to the present invention. The characteristics of each hot-rolled steel layer, sheet or piece (percentage of porosity SVss, surface area of ​​hot-rolled steel layers, depth of intergranular oxidation DIO of hot-rolled steel sheet, coating thickness Ct, intermetallic layer thickness IMt, percentage of surface porosity of the coating in the hot-stamped piece coating SPcoating, and paint adhesion quality, good or bad) are presented in Table 4. Table 4 Sample SV SS (%) D IO (  m) C t (  m) IM t (  m) SP coating < 3%? Paint Adhesion 1 18.1 5 27.5 11.4 No Bad 2 17.1 10 30.52 8.6 No Bad 3 17.5 4 27.9 11.2 No Bad 4 37.1 NA 37.6 37.6 Yes Good 5 5.7 0 31.8 10.9 Yes Good 6 18.2 0 31.2 12.8 Yes Good 7 11 0 29 11 Yes Good 8 15.3 0 29.6 12 Yes Good 9 19.9 0 24.3 10.4 Yes Good 10 nd 2 23 10.4 Yes Good 11 11.5 2 21.3 11.7 Yes Good 12 10.8 0 21.9 10.3 Yes Good 13 14.2 2 26.9 12.6 Yes Good 14 14.4 0 28.4 10.5 Yes Good 15 20.2 0 23.5 10.2 Yes Good 16 13.9 0 22.7 10.9 Yes Good 17 13 0 26.5 9.9 Yes Good 18 16 0 27.2 11.1 Yes Good 19 nd 9 28.2 8.7 No Bad 20 nd 0 22.6 11.8 Yes Good 21 nd 0 26.8 10.3 Yes Good 22 nd 12 30 10 No Bad 23 nd 8 27.6 10.1 No Bad 24 nd 0 24.9 9.9 Yes Good 25 nd 9 28.4 11.5 No Bad 26 7.0 0 27.1 11 Yes Good 27 nd 13 23 7 No Bad 28 nd 2 28.1 10.7 Yes Good 29 nd 0 26.2 11.1 Yes Good In Table 4, nd means "not specified" and NA means "not applicable" (i.e., not applicable in that case - translator). Samples 1-4, 19, 22, 23, 25 and 27 were produced at coiling temperatures that were not in accordance with the invention. In particular, samples 1-4, 19, 22, 23, 25 and 27 were coiled at a temperature exceeding the maximum coiling temperature Tcoilmax, which resulted in a large depth of intergranular oxidation before pickling. Samples 1-3, 19, 22, 23, 25 and 27 were acid-pickled under normal conditions, i.e. for a period of between 15 and 65 seconds. As a result of the acid-pickling conditions and coiling temperature, the intergranular oxidation depth of the steel sheet (measured after coating) in samples 1-3, 19, 22, 23, 25 and 27 was greater than or equal to 4 µm, i.e. exceeding the maximum allowable depth for oxidation. Therefore, after hot stamping, the porosity percentage of the coating surface was more than 3% and, as a result, the paint adhesion was poor. In addition, sample 23, which was made of E-steel containing 0.471% Ni, was coiled at 531°C. As a result, a large portion of the roughness that had adhered to its surface was still present on it before and after pickling. Removing these roughnesses (fine, point-like protrusions - translator) required performing double and intense pickling, which in any case would have resulted in a decrease in the productivity of the pickling line. Similar results were obtained when coiling temperatures below 531°C but above 495°C were used. Sample 4 was subjected to double pickling for 375 seconds. As a result of the pickling conditions and coiling temperature, even though the hot-rolled steel sheet after coating was free of intergranular oxidation, the surface porosity percentage of the steel layer before coating was very high (37.1%). As a result, uncontrolled growth of the intermetallic layer occurred during hot coating, and it became impossible to control the coating thickness in the range of 20-33 μm. The coating thickness in sample 4 was 37.6 μm. In contrast, sample 5 was subjected to double pickling for the same duration as sample 4. However, unlike sample 4, it was produced at the coiling temperature according to the present invention. Therefore, before pickling, the hot-rolled steel layer contained no or very little intergranular oxidation. Thus, after pickling, unlike sample 4, the percentage of porosity in the surface region of the steel layer was small (5%). As a result, it was possible to control the coating thickness in the range of 20-33 m. Therefore, from the comparison of samples 4 and 5, we see that the production conditions according to the present invention allow achieving better adhesion of the coating after hot stamping and also increase the quality of paint adhesion while controlling the coating thickness within the desired range. In addition, a comparison of samples 5 and 6, which were either double (sample 5) or short (sample 6) pickling under conditions where the coiling temperature was in accordance with the conditions of the present invention, was made. The intensity of pickling had no effect on the adhesion of the coating and had no effect on the control of the coating thickness. The results indicate that in the process according to the present invention, the intensity of pickling can be reduced without causing problems in the adhesion of the coating after hot stamping. Therefore, the production according to the process according to the present invention does not require the implementation of double pickling. As a result, the process according to the present invention makes it possible to produce hot-rolled coated steel sheets with a thickness of between 1.8 mm and 5 mm with acceptable coating adhesion after hot stamping, and at the same time allows the control of the coating thickness of the hot-rolled coated steel sheets within the desired range, in particular in the range between 10 and 33 m without reducing the productivity of the pickling line. Examples 5 to 18, 20, 21, 24, 26, 28 and 29 show that if the hot-rolled coated steel sheet is produced according to the method of the present invention, the hot-rolled steel sheet will have no intergranular oxidation or its amount will be very small, so that the percentage of porosity of the SPcoating hot-stamped part coating will be low and the paint adhesion will be acceptable. In addition, the depth of intergranular oxidation before pickling is low and the percentage of surface porosity in the surface area of ​​the steel layer before pickling is also reduced. As a result, the coating thickness can also be controlled in the range of 20-33 m. Sample 24 is a special case made of D steel and its composition was in accordance with the second aspect of the present invention. Its coiling temperature was less than or equal to 495 degrees Celsius. As a result of using this coiling temperature, the hot-rolled steel sheet had no intergranular oxidation or had a very small amount. The surface porosity percentage of the SPcoated hot stamping part coating was also low, and the paint adhesion was also satisfactory. In addition, the depth of intergranular oxidation before pickling was also small, so that the surface porosity percentage in the surface region of the steel layer before coating was small. As a result, it was possible to control the coating thickness in the range of 20-33 m. In addition, it was possible to reduce the pickling time in order to achieve high efficiency in the pickling line.

Claims

Claims 1. A method for producing hot-rolled coated steel sheet with a thickness between 1.8 mm and 5 mm, comprising the following steps: -Providing a semi-finished steel product having the following compositions by weight: 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 rest of the composition also consists of iron and unavoidable impurities resulting from melting, - Hot rolling of the semi-finished product with a final rolling temperature FRT between 840 and 1000 degrees Celsius so that a hot rolled steel product with a thickness between 1.8 mm to 5 mm and then: - cooling the hot rolled steel product to the coiling temperature Tcoil and coiling the hot rolled steel product at the coiling temperature Tcoil, so that a hot rolled steel layer is obtained, the appropriate coiling temperature Tcoil is: 450°C ≤ Tcoil ≤ Tcoilmax, where Tcoilmax means the maximum coiling temperature, which is calculated as follows: Tcoilmax is expressed in degrees Celsius (same as Celsius - translator) and f also indicates the amount of austenite present in the hot rolled steel product, just before coiling - pickling the hot rolled steel sheet - coating the hot rolled steel layer with Al or an Al alloy by continuously placing it in a hot bath, so that a hot rolled steel sheet consisting of ferrite and pearlite with an Al or Al alloy coating with a thickness of between 10 and 33 µm on each side of the steel sheet Hot rolling is achieved.

2. A method for producing a hot-rolled coated steel sheet according to claim 1, such that its composition by weight is as follows: 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 remainder of the composition also consists of iron and unavoidable impurities resulting from melting. is, 3. A method for producing a hot-rolled coated steel sheet according to claim 1 or 2, such that 0.075% ≤ C ≤ 0.38%.

4. A method for producing a hot-rolled coated steel sheet according to any one of claims 1 or 2, such that its chemical composition in terms of weight percentage is as follows: 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 ≤ The remaining 0.006% of the composition consists of iron and unavoidable impurities resulting from smelting, 5. A method for producing a hot-rolled coated steel sheet according to any one of claims 1 or 2, such that its chemical composition in terms of weight percentage is as follows: 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% 1.5% ≤ (C + Mn + Si + Cr) ≤ 2.7% such that 3.4 x N ≤ Ti ≤ 8 x N 0.04% ≤ Nb ≤ 0.06% 0.044% ≤ (Nb+Ti) ≤ 0.09% such that 0.0005% ≤ B ≤ 0.004% 0.001% ≤ N ≤ 0.009% 0.0005% ≤ S ≤ 0.003% 0.001% ≤ P ≤ 0.020% 0.0001% ≤ Ca ≤ 0.006%, and if desired, the remainder of the composition consists of iron and unavoidable impurities resulting from smelting.

6. A method for producing a hot-rolled coated steel sheet according to any one of claims 1 or 2, such that its chemical composition in terms of weight percentage is as follows: 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 remainder of the composition also consists of iron and unavoidable impurities resulting from melting.

7. A method for producing hot-rolled coated steel sheet with a thickness between 1.8 mm and 5 mm, comprising the following steps: -Providing a semi-finished steel product having the following compositions by weight: 0.24% ≤ C ≤ 0.38% and 0.40% ≤ Mn ≤ 3% or 0.38% ≤ C ≤ 0.43% and 0.05% ≤ Mn ≤ 0.40% or 0.10% ≤ Si ≤ 0.70% 0.015% ≤ Al ≤ 0.070% 0.001% ≤ Cr ≤ 2% 0.25% ≤ Ni ≤ 2% 0.015% ≤ Ti ≤ 0.1% 0% ≤ Nb ≤ 0.06% 0.0005% ≤ B ≤ 0.0040% 0.003% ≤ N ≤ 0.010% 0.0001% ≤ S ≤ 0.005% 0.0001% ≤ P ≤ 0.025%, The amount of titanium and nitrogen must fulfill the following relationship: Ti / N > 3.42 The amount of carbon, manganese, chromium and silicon must fulfill the following relationship: The chemical composition can also include one of the following elements if desired: 0.05% ≤ Mo ≤ 0.65% 0.001% ≤ W ≤ 0.30% 0.0005% ≤ Ca ≤ 0.005%, The remainder of the composition also consists of iron and unavoidable impurities resulting from melting, - Hot rolling of the semi-finished steel product at a final rolling temperature between 840 and 1000 degrees Celsius, to a hot rolled steel product with a thickness between 1.8 mm to 5 mm, and then: - cooling the hot rolled steel product to the coiling temperature Tcoil and coiling the hot rolled steel product at the coiling temperature Tcoil, so that a hot rolled steel sheet is obtained, the appropriate Tcoil temperature is: 450°C ≤ Tcoil ≤ 495°C, - pickling the hot rolled steel sheet - coating the hot rolled steel sheet with Al or an Al alloy by continuously placing it in a hot bath, so that a hot rolled clad steel sheet is obtained, the coating being Al or an Al alloy and the thickness on each side of the hot rolled steel sheet being between 10 and 33 µm.

8. A method for producing a hot-rolled coated steel sheet according to any one of claims 1 to 7, such that after pickling and before coating, the percentage of porosity in the surface region of the hot-rolled steel sheet is less than 30%. The surface region means the region starting from the upper point of the surface of the hot-rolled steel sheet and extending from this upper point to a depth of 15 m.

9. A method for producing a hot-rolled coated steel sheet according to any one of claims 1 to 8, such that the intergranular oxidation depth of the hot-rolled steel sheet is less than 4 μm.

10. A method for producing hot-rolled coated steel sheet according to any one of claims 1 to 9, wherein the pool contains 8 to 11% silicon and 2 to 4% iron by weight, the remainder being aluminum or aluminum alloy and processing impurities.

11. A method for producing a hot-rolled coated steel sheet according to any one of claims 1 to 9, wherein the pool contains by weight from 2% to 24% zinc, from 7.1% to 12.0% silicon, optionally from 1.1% to 8.0% magnesium, and optionally additional elements such as Pb, Ni, Zr or Hf, the amounts of these additional elements being less than 0.3%. The remainder consists of aluminum and unavoidable processing impurities and precipitated elements, and the Al / Zn ratio is greater than 2.

9.

12. A method for producing a hot-rolled coated steel sheet according to any one of claims 1 to 9, wherein the pool contains by weight 4.0% to 20.0% zinc, 1% to 3.5% silicon, optionally 1.0% to 4.0% magnesium, and optionally additional elements such as Pb, Ni, Zr or Hf, the amounts of these additional elements being less than 0.3%. The remainder consists of aluminum and unavoidable processing impurities and precipitated elements, and the Zn / Si ratio is between 3.2 and 8.

0.

13. A method for producing a hot-rolled coated steel sheet according to any one of claims 1 to 9, wherein the pool contains by weight 2.0% to 24.0% zinc, 1.1% to 7.0% silicon, optionally 1.1% to 8.0% magnesium, where the silicon content is between 1.1% and 4.0%, and optionally additional elements such as Pb, Ni, Zr or Hf, the amounts of these additional elements being less than 0.3%. The remainder consists of aluminum and unavoidable processing impurities and precipitated elements, and the Al / Zn ratio is greater than 2.

9.

14. A method for producing a hot-rolled coated steel sheet according to any one of claims 1 to 13, wherein after coating the hot-rolled steel sheet with Al or Al alloy, it further comprises a step of depositing a Zn coating on the Al or Al alloy by cementation, by electroplating or by sonic vapor jet deposition, and the thickness of the Zn coating is less than or equal to 1.1 µm.

15. Hot-rolled coated steel sheet containing: - Hot-rolled steel sheet with a thickness between 1.8 mm and 5 mm, the composition of which is as follows in terms of weight percentage: 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%, remainder The remaining composition also consists of iron and unavoidable impurities resulting from melting, so that the intergranular oxidation depth of the hot-rolled steel sheet is less than 4 μm and the structure of the hot-rolled steel sheet contains ferrite and pearlite.- An Al or Al alloy coating with a thickness between 10 and 33 m on each side of the hot-rolled steel sheet.

16. Hot-rolled coated steel sheet according to claim 15, wherein the steel has the following composition by weight: 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 remainder of the composition also consisting of iron and impurities to be avoided. The insoluble is due to melting, 17. Hot-rolled coated steel sheet according to claim 15, wherein the steel has the following composition by weight: 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 remainder of the composition also consisting of iron and unavoidable impurities resulting from the smelting, 18. Hot-rolled coated steel sheet according to any one of claims 15 to 17 such that 0.075% ≤ C ≤ 0.38%.

19. Hot-rolled coated steel sheet according to any one of claims 15 to 17, such that the chemical composition of the steel by weight is as follows: 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% Remainder The compound also consists of iron and inevitable impurities resulting from smelting, 20. Hot-rolled coated steel sheet according to any one of claims 15 to 17, wherein the chemical composition of the steel by weight is as follows: 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% 1.5% ≤ (C + Mn +Si + Cr) ≤ 2.7% such that 3.4 x N ≤ Ti ≤ 8 x N 0.04% ≤ Nb ≤ 0.06% 0.044% ≤ (Nb+Ti) ≤ 0.09% such that 0.0005% ≤ B ≤ 0.004% 0.001% ≤ N ≤ 0.009% 0.0005% ≤ S ≤ 0.003% 0.001% ≤ P ≤ 0.020% 0.0001% ≤ Ca ≤ 0.006%, and if desired the remainder of the composition also consists of iron and unavoidable impurities resulting from smelting, 21. Hot-rolled coated steel sheet according to any one of claims 15 to 17, wherein the chemical composition of the steel is as follows by weight: 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 remainder of the composition also consisting of iron and unavoidable impurities resulting from melting, 22. Hot-rolled coated steel sheet comprising: - Hot-rolled steel sheet with a thickness between 1.8 mm to 5 mm whose compositions in terms of weight percentage are as follows: 0.24% ≤ C ≤ 0.38% and 0.40% ≤ Mn ≤ 3% or 0.38% ≤ C ≤ 0.43% and 0.05% ≤ Mn ≤ 0.40% or 0.10% ≤ Si ≤ 0.70% 0.015% ≤ Al ≤ 0.070% 0.001% ≤ Cr ≤ 2% 0.25% ≤ Ni ≤ 2% 0.015% ≤ Ti ≤ 0.1% 0% ≤ Nb ≤ 0.06% 0.0005% ≤ B ≤ 0.0040% 0.003% ≤ N ≤ 0.010% 0.0001% ≤ S ≤ 0.005% 0.0001% ≤ P ≤ 0.025%, amount Titanium and nitrogen must fulfill the following relationship: Ti / N > 3.42 The amount of carbon, manganese, chromium and silicon must fulfill the following relationship: The chemical composition may also include one of the following elements if desired: 0.05% ≤ Mo ≤ 0.65% 0.001% ≤ W ≤ 0.30% 0.0005% ≤ Ca ≤ 0.005%, the remainder of the composition also consists of iron and unavoidable impurities resulting from melting, such that the intergranular oxidation depth of the hot-rolled steel sheet is less than 4 m, - an Al or Al alloy coating with a thickness between 10 and 33 m on each side of the hot-rolled steel sheet.

23. A hot-rolled coated steel sheet according to any one of claims 15 to 22, wherein the coating has an intermetallic layer with a thickness of less than 15 μm.

24. A hot-rolled coated steel sheet according to any one of claims 15 to 23, wherein the hot-rolled coated steel sheet has a Zn coating on each side with a thickness of less than or equal to 1.1 μm.

25. A method for producing a hot-rolled coated steel part, comprising the following steps: - providing a hot-rolled coated sheet according to any one of claims 15 to 24 or carrying out the method according to any one of claims 1 to 14 and thereby obtaining a hot-rolled coated steel sheet by that method - cutting the hot-rolled coated sheet to obtain a blank - heating the blank in a furnace to a temperature Tc to obtain a heated blank - transferring the heated blank to a mold and hot stamping it in the mold and thereby obtaining a hot-stamped blank - cooling the heated blank to a temperature below 400°C to obtain a hot-stamped coated steel part 26. A method for producing a hot stamped coated steel part according to claim 25, wherein after cutting the hot rolled coated steel sheet to obtain a blank and before heating the blank to a temperature Tc, the blank is welded to another blank of steel with the following compositions in 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 ≤ 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 % The remaining composition of the alloy consists of iron and unavoidable impurities resulting from melting, 27. A method for producing a hot stamped clad steel part according to claim 25, wherein after cutting the hot rolled clad steel sheet to obtain a blank and before heating the blank to a temperature Tc, the blank is welded to another blank of steel with the following compositions in weight percent: 0.24% ≤ C ≤ 0.38% and 0.40% ≤ Mn ≤ 3% or 0.38% ≤ C ≤ 0.43% and 0.05% ≤ Mn ≤ 0.40% or 0.10% ≤ Si ≤ 0.70% 0.015% ≤ Al ≤ 0.070% 0.001% ≤ Cr ≤ 2% 0.25% ≤ Ni ≤ 2% 0.015% ≤ Ti ≤ 0.1% 0% ≤ Nb ≤ 0.06% 0.0005% ≤ B ≤ 0.0040% 0.003% ≤ N ≤ 0.010% 0.0001% ≤ S ≤ 0.005% 0.0001% ≤ P ≤ 0.025%, The amount of titanium and nitrogen must fulfill the following relationship: Ti / N > 3.42 The amount of carbon, manganese, chromium and silicon must fulfill the following relationship: The chemical composition can also include one of the following elements if desired: 0.05% ≤ Mo ≤ 0.65% 0.001% ≤ W ≤ 0.30% 0.0005% ≤ Ca ≤ 0.005%, The remainder of the composition also consists of iron and unavoidable impurities resulting from melting, 28. A hot-stamped coated steel part comprising at least one part with a thickness of between 1.8 mm and 5 mm, said hot-rolled coated steel part comprising an Al or Al alloy coating, and said coating having a porosity of less than or equal to 3%, and said part being made of steel having the following compositions by weight: 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%, the remainder of the composition consists of iron and unavoidable impurities resulting from melting.

29. A hot stamped coated steel part according to claim 28, wherein the composition of the steel in said part is such that Ni ≤ 0.1%.

30. A hot-rolled stamped coated steel part comprising at least one part with a thickness of between 1.8 mm and 5 mm, said hot-rolled coated steel part comprising an Al or Al alloy coating, and said coating having a porosity of less than or equal to 3%, and said part being made of steel having the following compositions by weight: 0.24% ≤ C ≤ 0.38% and 0.40% ≤ Mn ≤ 3% or 0.38% ≤ C ≤ 0.43% and 0.05% ≤ Mn ≤ 0.40% or 0.10% ≤ Si ≤ 0.70% 0.015% ≤ Al ≤ 0.070% 0.001% ≤ Cr ≤ 2% 0.25% ≤ Ni ≤ 2% 0.015% ≤ Ti ≤ 0.1% 0% ≤ Nb ≤ 0.06% 0.0005% ≤ B ≤ 0.0040% 0.003% ≤ N ≤ 0.010% 0.0001% ≤ S ≤ 0.005% 0.0001% ≤ P ≤ 0.025%, The amount of titanium and nitrogen must fulfill the following relationship: Ti / N > 3.42 The amount of carbon, manganese, chromium and silicon must fulfill the following relationship: The chemical composition can also include one of the following elements if desired: 0.05% ≤ Mo ≤ 0.65% 0.001% ≤ W ≤ 0.30% 0.0005% ≤ Ca ≤ 0.005%, The remainder of the composition also consists of iron and unavoidable impurities resulting from melting, 31. Use of a hot stamped coated steel part according to any one of claims 28 to 30 or produced by a method according to any one of claims 25 to 27 for producing chassis or unpainted parts of a vehicle body or vehicle suspension arms.

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