Coated steel sheet and high strength press hardened steel part and method of manufacturing the same

Abstract

To provide a coated steel sheet serving as a material for a press hardened steel part having high strength and a high bending angle, and a press hardened steel part.SOLUTION: A coated steel sheet having a composition comprising, by weight percent: C0.26-0.40%, Mn0.5-1.8%, Si0.1-1.25%, Al0.01-0.1%, Cr0.1-1.0%, Ti0.01-0.1%, B0.001-0.004%, P≤0.020%, S≤0.010%, and N≤0.010%, the remainder of the composition being iron and unavoidable impurities resulting from processing, wherein the coated steel sheet comprises, from a bulk to a surface of the coated steel sheet: a bulk having a microstructure comprising, in surface fraction, from 60% to 90% of ferrite, the remainder being martensite-austenite islands, pearlite or bainite, the bulk being topped with a decarburized layer comprising, in upper part, a ferrite layer having a thickness from 1 μm to 100 μm; and a coating layer comprising aluminum or an aluminum alloy.SELECTED DRAWING: Figure 3a

Description

Technical Field

[0001] The present invention relates to a coated steel sheet and a high-strength press-hardened steel part having good bending properties.

Background Art

[0002] High-strength press-hardened parts can be used as structural elements of motor vehicles for intrusion prevention or energy absorption functions.

[0003] In such types of applications, it is desirable to manufacture steel parts having high mechanical strength, high impact resistance, and good corrosion resistance. Furthermore, one of the major challenges in the automotive industry is to reduce the weight of vehicles from the perspective of global environmental conservation without neglecting safety requirements in order to improve the fuel efficiency of vehicles.

[0004] This weight reduction can be achieved, in particular, by using steel parts having a martensite or bainite / martensite microstructure.

[0005] Publication WO 2016 / 104881 relates to hot press forming parts and a manufacturing method thereof, which are used as structural parts of vehicles and the like and require impact resistance characteristics, more specifically, having a tensile strength of 1300 MPa or more, and a method of heating a steel material to a temperature at which austenite single phase can be formed and quenching and hot forming using a mold. In order to obtain such characteristics, the mother steel sheet contains a thin ferrite layer with a thickness of less than 50 μm on the surface, and it is necessary to control the size and density of carbides. This ferrite layer in the substrate enables suppression of the propagation of fine cracks formed on the plating layer to the mother plate, but results in low bendability with a bend angle of less than 70°.

[0006] International Publication No. 2018 / 179839 relates to a hot-pressed component obtained by hot-pressing a steel sheet having a microstructure that varies in the thickness direction, the hot-pressed component comprising a soft layer made of at least 90% ferrite, a transition layer made of ferrite and martensite, and a hard layer mainly composed of martensite, and having both high strength and high bendability. To obtain such properties, the cold-rolled steel sheet is annealed in an atmosphere having a dew point temperature of 50°C to 90°C, which may be harmful to the aluminum alloy coating.

Prior Art Documents

Patent Documents

[0007]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] Therefore, an object of the present invention is to solve the above problems and provide a press-hardened steel component having a combination of high mechanical properties with a tensile strength TS of 1500 MPa or more and a bending angle greater than 70°. Preferably, the press-hardened steel component according to the present invention has a yield strength YS of 1250 MPa or more.

[0009] Another object of the present invention is to obtain a coated steel sheet that can be deformed into such a press-hardened steel component by hot forming.

Means for Solving the Problems

[0010] The object of the present invention is achieved by providing the steel sheet according to claim 1. Another object is achieved by providing the method according to claim 2. Another object of the present invention is achieved by providing the press-hardened steel part according to claim 3. The steel part can also include the characteristics according to any one of claims 4 to 6. Another object is achieved by providing the method according to claim 7.

[0011] Here, with reference to the accompanying drawings, the present invention will be described in detail and illustrated by examples without introducing any limitations.

Brief Description of the Drawings

[0012]

Figure 1a

Figure 1b

Figure 2a

Figure 2b

Figure 3a

Figure 3b

Figure 4a

Figure 4b

Figure 5a

Figure 5b

Modes for Carrying Out the Invention

[0013] Next, the composition of the steel according to the present invention will be described, and the contents are expressed in weight percent.

[0014] According to the present invention, the carbon content includes 0.26% to 0.40% in order to ensure satisfactory strength. If the carbon exceeds 0.40%, the weldability and bendability of the steel plate may decrease. When the carbon content is less than 0.26%, the tensile strength does not reach the target value.

[0015] The manganese content includes 0.5% to 1.8%. If the addition amount exceeds 1.8%, the risk of center segregation increases and the bendability is impaired. If it is less than 0.5%, the hardenability of the steel plate decreases. Preferably, the manganese content includes 0.5% to 1.3%.

[0016] According to the present invention, the silicon content includes 0.1% to 1.25%. Silicon is an element involved in the hardening in the solid solution. Silicon is added to limit the formation of carbides. If it exceeds 1.25%, silicon oxide is formed on the surface, impairing the coating property of the steel. Furthermore, the weldability of the steel plate may decrease. Preferably, the silicon content is 0.2% to 1.25%. More preferably, the silicon content is 0.3% to 1.25%. More preferably, the silicon content is 0.3% to 1%.

[0017] The aluminum content includes 0.01% to 0.1% because it is a very effective element for deoxidizing the steel in the liquid phase during refinement. When the titanium content is insufficient, aluminum can protect boron. The aluminum content is less than 0.1% to avoid oxidation problems and ferrite formation during press hardening. Preferably, the aluminum content includes 0.01% to 0.05%.

[0018] According to the present invention, the chromium content includes 0.1% to 1.0%. Chromium is an element involved in the hardening in the solid solution and must be higher than 0.1%. The chromium content is less than 1.0% to limit workability problems and costs.

[0019] The titanium content ranges from 0.01% to 0.1% to protect boron from forming BN. The titanium content is limited to 0.1% to avoid TiN formation.

[0020] According to the present invention, the boron content ranges from 0.001% to 0.004%. Boron improves the hardenability of steel. The boron content is 0.004% or less to avoid the risk of slab breakage during continuous casting.

[0021] Several elements can be optionally added.

[0022] Nickel can be added up to a maximum of 0.5% as an optional element because it can substantially reduce the sensitivity to delayed fracture.

[0023] The molybdenum content can be optionally added up to a maximum of 0.40%. Similar to boron, molybdenum improves the hardenability of steel. Molybdenum is 0.40% or less to limit costs.

[0024] According to the present invention, niobium can be optionally added up to a maximum of 0.08% to improve the ductility of steel. If the addition amount exceeds 0.08%, the risk of forming NbC or Nb(C, N) carbides increases and the bendability is impaired. Preferably, the niobium content is 0.05% or less.

[0025] Calcium can also be added up to a maximum of 0.1% as an optional element. The addition of Ca at the liquid stage enables the formation of fine oxides that promote the castability of continuous casting.

[0026] The remainder of the steel composition is iron and impurities resulting from refining. In this regard, P, S, and N are at least regarded as residual elements that are inevitable impurities. Their contents are less than 0.010% for S, less than 0.020% for P, and less than 0.010% for N.

[0027] Next, the microstructure of the coated steel sheet according to the present invention will be described.

[0028] The cross-section of the coated steel sheet of the present invention is schematically shown in FIGS. 3a and 4a. The coated steel sheet is covered on the upper part with a decarburized layer (3) including a ferrite layer (4) having a thickness of 1 μm to 100 μm, and includes a coating layer (1) and a bulk (2). Preferably, the thickness of the ferrite layer includes 20 μm to 100 μm. More preferably, the thickness of the ferrite layer is 25 μm to 100 μm. More preferably, the thickness of the ferrite layer is 30 μm to 80 μm.

[0029] The bulk (2) of the coated steel sheet contains 60% to 90% ferrite by surface fraction, and the remainder has a microstructure composed of island-like martensite-austenite, pearlite or bainite.

[0030] This ferrite is formed during the annealing in the transformation range of the cold-rolled steel sheet. The remainder of the microstructure is austenite at the end of soaking, which transforms into island-like martensite-austenite, pearlite or bainite during the cooling of the steel sheet.

[0031] The decarburized layer existing on the upper part of the bulk is obtained during the annealing of the cold-rolled steel sheet by controlling the atmosphere in the furnace so that the dew point temperature is strictly set higher than -10 °C and 20 °C or lower.

[0032] The coated steel sheet according to the present invention can be manufactured by any suitable manufacturing method, and those skilled in the art can define this. However, it is preferable to use the method according to the present invention including the following steps: Provide the above-described steel composition to a semi-finished product that can be further hot-rolled. Reheat the semi-finished product at a temperature including 1150 °C to 1300 °C.

[0033] Then, hot-roll the steel sheet at a finish hot-rolling temperature including 800 °C to 950 °C.

[0034] Next, the hot-rolled steel is cooled, coiled at a temperature Tcoil below 670°C, and optionally pickled to remove oxidation.

[0035] Next, the coiled steel sheet is optionally cold-rolled to obtain a cold-rolled steel sheet. The cold rolling reduction rate preferably includes 20% to 80%. If it is less than 20%, recrystallization during subsequent heat treatment is not preferable and may impair the ductility of the steel sheet. If it exceeds 80%, there is a risk of edge cracking during cold rolling.

[0036] Next, the steel sheet is annealed in an HNx atmosphere containing 0% to 15% H2 up to an annealing temperature T A including 700°C to 850°C, and held for a holding time t A including 10 seconds to 1200 seconds at the annealing temperature T A to obtain an annealed steel sheet. If it is less than 700°C, the formation rate of the decarburized layer is too slow and a ferrite layer cannot be obtained on top of it. The holding time t A is 10 seconds or more to enable the formation of the ferrite layer and 1200 seconds or less to limit the thickness of this ferrite layer.

[0037] During this annealing, the atmosphere in the furnace is precisely controlled to have a dew point temperature T DP1 higher than -10°C and lower than or equal to +20°C in order to form a decarburized layer according to the present invention. If T DP1 is -10°C or lower, the formation of the decarburized layer becomes slow and a ferrite layer is not formed on top of it. The bendability of the steel parts becomes too low. If T DP1 is higher than 20°C, the surface of the steel sheet is completely oxidized, which may impair the coating property and mechanical properties of the steel sheet.

[0038] In one embodiment of the present invention, the annealed steel sheet is heated to an annealing temperature T2 including 700°C to 850°C, maintained at the temperature T2 for a holding time t2 including 10 seconds to 1200 seconds, and the atmosphere has a dew point T DP2 precisely higher than -10°C and lower than or equal to +20°C.

[0039] Next, the steel sheet is coated with an aluminum alloy coating.

[0040] Next, the microstructure of the press-hardened steel part according to the present invention will be described. The cross-section of the press-hardened steel part is schematically shown in FIGS. 3b and 4b.

[0041] The steel part continuously has the following from the bulk to the surface of the steel part: - A bulk (7) having a microstructure containing more than 95% martensite and less than 5% bainite in surface fraction, - A ferrite interdiffusion layer (6), - An aluminum-based coating layer (5) is included.

[0042] During the heating of the steel blank cut out from the steel sheet according to the present invention, all the microstructure elements of the bulk transform into austenite, and the ferrite in the decarburized layer transforms into austenite having a grain size wider than that of the austenite in the bulk. After hot forming, the steel part is then die quenched. Since the interdiffusion layer grows from the former wide-grained austenite layer, it has a grain width larger than the original austenite grain size in the bulk. In order to improve the bendability of the steel sheet without degrading the mechanical properties, the ratio of the width GW of the ferrite grains in the interdiffusion layer to the original austenite grain size PAGS bulk in the steel sheet satisfies the following formula int for improving the bendability of the steel sheet without degrading the mechanical properties. The width of the ferrite grains is the average distance between two parallel grain boundaries of the interdiffusion layer, and the grain boundaries are oriented in the thickness direction of the steel sheet. The combination of the annealing temperature T (GW int / PAGS bulk ) - 1 ≧ 30% is satisfied.

[0043] This is for improving the bendability of the steel sheet without degrading the mechanical properties. The width of the ferrite grains is the average distance between two parallel grain boundaries of the interdiffusion layer, and the grain boundaries are oriented in the thickness direction of the steel sheet. The combination of the annealing temperature T A , the annealing time t A and the dew point temperature T DP1 results in a wide grain width GW intPromote the formation of. Furthermore, the heat treatment of the steel blank before press forming controls austenite grain growth and thus controls the PAGS in the bulk.

[0044] In one embodiment, the press-hardened steel part may further include a martensite layer having a carbon gradient between the bulk and the interdiffusion layer, as represented by (8) in FIG. 4b. During heating of the steel blank, carbon diffuses from the bulk to the surface. Then, the ferrite upper part of the decarburized layer transforms into a layer of austenite having a carbon gradient. During die quenching, this austenite layer having a carbon gradient transforms into a layer of martensite having a carbon gradient.

[0045] The press-hardened steel part according to the present invention has a tensile strength TS of 1500 MPa or more and a bending angle greater than 70°. The bending angle is determined in the press-hardened part according to the VDA238-100 bending standard (normalized to a thickness of 1.5 mm).

[0046] In a preferred embodiment of the present invention, the yield strength YS is 1250 MPa or more. TS and YS are measured according to the ISO standard ISO 6892-1.

[0047] The press-hardened steel part according to the present invention can be manufactured by any suitable manufacturing method, and those skilled in the art can define it. However, it is preferable to use the method according to the present invention including the following steps: Cut the coated steel sheet according to the present invention into a predetermined shape to obtain a steel blank. Then, heat the steel blank at a temperature including 880°C to 950°C for 10 seconds to 900 seconds to obtain a heated steel blank. Then, transfer the heated blank to a forming press before hot forming and die quenching.

[0048] Here, the present invention will be described by the following examples, which are by no means limiting.

Examples

[0049] Six grades whose compositions are summarized in Table 1 were cast into semi-finished products and processed into steel plates and then steel parts according to the processing parameters summarized in Table 2.

[0050] Table 1 - Composition The tested compositions are summarized in the following table, and the element contents are expressed in weight percent.

[0051]

Table 1

[0052] Table 2 - Processing Parameters The cast steel semi-finished products were reheated at 1200 °C, hot-rolled at a finishing hot-rolling temperature including 800 - 950 °C, coiled at 550 °C, and cold-rolled with a reduction ratio of 60%. Then, the steel plate was heated to temperature T A and maintained at said temperature for a holding time t A in an HNx atmosphere containing 5% H2 with a controlled dew point. Then, the steel plate was cooled to a temperature of 560 - 700 °C and then melt-coated with an aluminum-silicon coating containing 10% silicon.

[0053] Samples 1, 2, 5, and 6 were subjected to a second annealing at temperature T2 before coating, and the steel plates were maintained at said T2 temperature for a holding time t2 in an HNx atmosphere having 5% H2 and a controlled dew point. The following specific conditions were applied:

[0054]

Table 2

[0055] The coated steel plates were analyzed, and the corresponding characteristics of the decarburized layer were summarized in Table 3.

[0056] Table 3 - Characteristics of Decarburized Layer of Coated Steel Sheet

[0057]

Table 3

[0058] Subsequently, the coated steel sheet was cut to obtain a steel blank, heated at 900 °C for 6 minutes, and hot formed. The steel parts were analyzed for the corresponding microstructure, the width GW of the ferrite grains in the interdiffusion layer int and the prior austenite grain size PAGS in the bulk bulk are summarized in Table 4. The mechanical properties are summarized in Table 5.

[0059] Table 4 - Microstructure of Press-Hardened Steel Parts

[0060]

Table 4

[0061] The surface fraction, the width of the ferrite grains in the interdiffusion layer, and the PAGS are determined by the following method: A test piece is cut from the press-hardened steel part, polished, and etched with a reagent known per se to reveal the microstructure. Subsequently, the cross-section is examined using an optical microscope or a scanning electron microscope, for example, a scanning electron microscope equipped with a field emission electron gun (「FEG-SEM」) with a magnification exceeding 5000 times in combination with a BSE (backscattered electron) device.

[0062] Table 5 - Mechanical Properties of Press-Hardened Steel Parts The mechanical properties of the tested samples were measured and summarized in the following table:

[0063]

Table 5

[0064] The examples show that the steel parts according to the invention, namely Examples 1 to 2, are the only steel parts showing all the target properties thanks to their specific composition and microstructure.

[0065] Figure 3a represents a schematic cross-sectional view of the coated steel sheet of Test 2. The processing parameters of the present invention, the annealing temperature T A , the annealing time t A and the dew point temperature T DP1The combination enables the decarburized layer (3) with a ferrite layer (4) formed on the top to be obtained.

[0066] Next, the coated steel sheet is hot formed. Fig. 3b shows a schematic cross-sectional view of the press-hardened steel part of Test 2.

[0067] The width of the ferrite grains formed in the interdiffusion layer (5) is a legacy of the pure ferrite layer where austenite formation occurs during heating and has a larger grain size. The interdiffusion layer grows with this large austenite grain size. The width of the ferrite grains in the interdiffusion layer (6) is larger than the prior austenite grain size of the bulk (7) and has a bending angle larger than 70°, resulting in good bendability.

[0068] Fig. 4a shows a schematic cross-sectional view of the coated steel sheet of Test 1. The processing parameters of the present invention, annealing temperature T A , annealing time t A and dew point temperature T DP1 The combination enables the decarburized layer (3) with a ferrite layer (4) formed on the top, which is thicker than that of Test 1 due to a higher C content, to be obtained.

[0069] Next, the coated steel sheet is hot formed. Fig. 4b shows a schematic cross-sectional view of the press-hardened steel part of Test 1.

[0070] The width of the ferrite grains formed in the interdiffusion layer (6) is a legacy of the pure ferrite layer where austenite formation occurs during heating and has a larger grain size. The interdiffusion layer grows with this large austenite grain size. The width of the ferrite grains in the interdiffusion layer (6) is larger than the prior austenite grain size of the bulk (7) and has a bending angle larger than 70°, resulting in good bendability. Furthermore, the thick ferrite layer (4) in the coated steel sheet forms a martensite layer with a carbon gradient between the bulk and the interdiffusion layer in the press-hardened steel part, resulting in a tensile strength higher than 1500 MPa.

[0071] In Test 3, the coated steel sheet has a decarburized layer without a ferrite layer at its upper part, as schematically shown in Fig. 2a. The absence of the ferrite layer is due to the low dew point temperature T of -10 °C, which slows down the decarburization rate. DP1 This slows down the decarburization rate.

[0072] Next, the coated steel sheet is hot formed. Fig. 2b shows a schematic cross-sectional view of the press-hardened steel part from Test 3. Since there is no ferrite layer, the width of the ferrite grains in the interdiffusion layer (6) is equivalent to the prior austenite grain size of the bulk (7), resulting in a low bending angle of less than 70°.

[0073] In Test 4, a low dew point temperature T of -40 °C DP1 suggests that there is no decarburized layer and no ferrite layer in the coated steel sheet.

[0074] Fig. 1a shows a schematic cross-sectional view of the coated steel sheet of this test, which has a coating layer (1) and a bulk (2).

[0075] Next, the coated steel sheet is hot formed. Fig. 1b shows a schematic cross-sectional view of the press-hardened steel part from Test 4. Since there is no ferrite layer, the width of the ferrite grains in the interdiffusion layer (6) is equivalent to the prior austenite grain size of the bulk (7), resulting in a low bending angle of less than 70°.

[0076] In Test 5, the steel sheet is maintained at the soaking temperature for 10,800 seconds, whereby a thicker ferrite layer is formed in the coated steel sheet by the decarburized layer than in the previous tests. Fig. 5a shows a schematic cross-sectional view of the coated steel sheet of Test 5, which has a coating layer (1), a decarburized layer (3), a thicker ferrite layer (4) with a coarser grain size, and a bulk (2).

[0077] Next, the coated steel sheet is hot formed, and FIG. 5b shows a schematic cross-sectional view of the press-hardened steel part from Test 5. During heating of the steel part, the bulk microstructure is austenite, and the thick ferrite layer transforms into a layer of austenite with a carbon gradient. However, due to the thickness of the ferrite layer being greater than 100 μm, the ferrite layer remains present between the interdiffusion layer and the layer of austenite with a carbon gradient.

[0078] During the die quenching of the steel part, the ferrite layer still exists, and the layer of austenite with a carbon gradient transforms into a martensite layer with a carbon gradient, resulting in a multiphase layer. This causes a decrease in the yield strength.

[0079] In Test 6, the steel sheet has a low carbon level of 0.21%. This low carbon content, combined with the processing parameters, results in a decarburized layer of the coated steel sheet with a ferrite layer. Nevertheless, the yield strength and tensile strength of the press-hardened steel part are not achieved due to the low carbon level.

Claims

1. By weight percentage, as follows, C: 0.26 to 0.40% Mn: 0.5 to 1.8% Si: 0.1 to 1.25% Al: 0.01 to 0.1% Cr: 0.1 to 1.0% Ti: 0.01 to 0.1% B: 0.001 to 0.004% P ≤ 0.020% S ≤ 0.010% N ≤ 0.010% comprising, and optionally, by weight percentage, as follows, Ni ≤ 0.5% Mo ≤ 0.40% Nb ≤ 0.08% Ca ≤ 0.1% comprising one or more of the elements of, a coated steel sheet made of steel having the composition, with the balance of the composition being iron and unavoidable impurities resulting from refining, wherein the coated steel sheet has, from the bulk to the surface of the coated steel sheet, as follows, - a bulk having a microstructure containing 60% to 90% ferrite by surface fraction, the balance being island-like martensite-austenite, pearlite or bainite, - such bulk is covered with a decarburized layer containing a ferrite layer having a thickness of 1 μm to 100 μm at the top, - a coating layer made of aluminum or an aluminum alloy comprising, a coated steel sheet.

2. A method for manufacturing a coated steel sheet, comprising the following consecutive steps: - a step of casting a steel having the composition according to Claim 1 to obtain a slab, - a step of hot rolling the slab reheated at a finish hot rolling temperature including 800°C to 950°C - reheating the slab at a temperature T including 1100°C to 1300°C ｒｅｈｅａｔ ; and - optionally, a step of pickling the coiled steel sheet, - Winding temperature T less than -670°C ｃｏｉｌ The step of winding the hot-rolled steel sheet at this temperature to obtain a wound steel sheet - optionally, a step of cold rolling the coiled steel sheet to obtain a cold rolled steel sheet, - a step of cooling the annealed steel sheet in a temperature range of 560°C to 700°C, - Heating a hot-rolled steel sheet or a cold-rolled steel sheet to an annealing temperature T including 700 °C to 850 °C Ａ and maintaining the steel sheet at the temperature T for a holding time t including 10 seconds to 1200 seconds Ａ to obtain an annealed steel sheet, wherein the atmosphere contains 0% to 15% of H2 and has a dew point T strictly higher than -10 °C and lower than or equal to +20 °C Ａ ＤＰ１ step - a step of coating the annealed steel sheet with an aluminum or aluminum alloy coating - a step of cooling the coated steel sheet to room temperature comprising, a method.

3. A press-hardened steel part, by weight percentage, as follows, C: 0.26 to 0.40% Mn: 0.5 to 1.8% Si: 0.1 to 1.25% Al: 0.01 to 0.1% Cr: 0.1 to 1.0% Ti: 0.01 to 0.1% B: 0.001 to 0.004% P ≤ 0.020% S ≤ 0.010% N ≤ 0.010% comprising, and optionally, by weight percentage, as follows, Ni ≤ 0.5% Mo ≤ 0.40% Nb ≤ 0.08% Ca ≤ 0.1% comprising one or more of the elements of having the composition, with the balance of the composition being iron and unavoidable impurities resulting from refining, wherein the steel part has continuously, from the bulk to the surface of the steel part, as follows, ​ - A bulk having a microstructure containing more than 95% martensite and less than 5% bainite in terms of surface fraction, - A ferrite interdiffusion layer, - A coating layer based on aluminum, comprising, The width GW of ferrite grains in the interdiffusion layer with respect to the prior austenite grain size PAGS in the bulk ｂｕｌｋ satisfies the following formula ｉｎｔ for the ratio thereof (GW ｉｎｔ / PAGS ｂｕｌｋ ) - 1 ≥ 30% meeting the requirements, a press-hardened steel part.

4. The press-hardened steel part according to claim 3, comprising a layer of martensite having a carbon gradient between the bulk and the ferrite interdiffusion layer.

5. The press-hardened steel part according to claim 3 or 4, having a tensile strength TS of 1500 MPa or more and a bending angle greater than 70°.

6. The press-hardened steel part according to claim 5, having a yield strength YS of 1250 MPa or more.

7. A method for manufacturing the press-hardened steel part according to any one of claims 3 to 6, comprising the following consecutive steps: - Providing a steel sheet having the composition according to claim 1 or manufactured by the method according to claim 2; - Cutting the steel sheet into a predetermined shape to obtain a steel blank; - Heating the steel blank at a temperature including 880 °C to 950 °C for 10 seconds to 900 seconds to obtain a heated steel blank; - Transferring the heated blank to a forming press; - Hot-forming the heated blank in the forming press to obtain a formed part; - Die quenching the formed part comprising, a method.

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