Method and production line for hot forming and press hardening a structural component

Abstract

Examples of methods of hot forming structural components are provided. The methods include heating a blank made from a press hardenable boron steel and forming the heated blank in a production line or multi-step apparatus. Examples of the present disclosure provide hot forming and cutting of a blank with a cycle time of 10 seconds or less for each of the tools.

Description

[0001] The present disclosure relates to methods for manufacturing hot formed structural components and uses of ultra-high strength steels in hot forming processes. More particularly the present disclosure relates to fast methods for hot forming and cutting structural components.BACKGROUND

[0002] In the field of vehicle construction, the development and implementation of lightweight materials or components is becoming more and more important in order to satisfy criteria for lightweight construction. The demand for weight reduction is especially driven by the goal of reduction of CO2 emissions. The growing concern for occupant safety also leads to the adoption of materials which improve the integrity of the vehicle during a crash while also improving the energy absorption.

[0003] A process known as Hot Forming Die Quenching (HFDQ) (also known as hot stamping or press hardening) uses e.g. boron steel sheets to create stamped components with Ultra High Strength Steel (UHSS) properties, with tensile strengths of e.g. 1.500 MPa or more. The increase in strength as compared to other material allows for a thinner gauge material to be used, which results in weight savings over conventionally cold stamped mild steel components.

[0004] In order to improve corrosion protection before, during or after a hot stamping process, coatings may be applied. For example the use of AI-Si coatings or Zn coatings is known.

[0005] Depending on the composition of the base steel material, blanks may need to be quenched (i.e. be cooled down rapidly) to achieve the high tensile strengths. In a well-known process, a blank that has been heated to e.g. 900°C or more is transferred to a press, in which it is deformed. At the same time, the blank is rapidly quenched to e.g. a temperature of around 200°C. The rapid quenching is done to obtain a fully martensitic microstructure which leads to high stiffness and strength.

[0006] Examples of steel materials which can harden by leaving them to cool to room temperature by air cooling with relatively low cooling speed are also known. These steels may be referred to as "air hardenable" steels.

[0007] The hot stamping process may be performed in a manner such that a blank to be hot formed is heated to a predetermined temperature e.g. to or above an austenization temperature by, for example, a furnace system so as to decrease the strength of the blank i.e. to facilitate the hot stamping process. The heated blank may be formed by, for example, a press system having a low temperature compared to the blank (e.g. room temperature) and a temperature control, thus a shaping process and a heat treatment using the temperature difference may be performed.

[0008] A hot stamping process may include a conveyor or a transferring device which transfers the heated blank from the furnace to a press tool which is configured to press the blank. Upstream from the furnace system, a cutting system for cutting blanks directly from a steel coil can be provided.

[0009] The use of multistep press apparatus for manufacturing hot formed elements is known. The multistep press apparatus may comprise a plurality of tools configured to perform different operations on different blanks simultaneously. With such arrangements, a plurality of blanks can undergo different manufacturing steps simultaneously during each stroke of the press apparatus. The efficiency and performance of a multistep apparatus may be higher than systems employing a plurality of different machines or apparatuses for different manufacturing steps, such as, laser trimming or hard cutting.

[0010] When zinc coated steel blanks are used, the blanks may need to be cooled down to a certain temperature before a hot forming process to reduce or minimize problems such as microcracks. Once the blank is cooled down, it is transferred from the external pre-cooling tool to the multistep press apparatus.

[0011] US 2022 / 0258223 discloses press apparatus and methods for manufacturing hot formed structural components. The apparatus comprises a fixed lower body, and a mobile upper body. The apparatus comprises a cooling tool and a press tool which is arranged downstream from the cooling tool, and a blank transfer mechanism to transfer the blank from the cooling tool to the press tool. The cooling tool has an upper gas cooling tool connected to the mobile upper body and / or a lower gas cooling tool connected to the fixed lower body. The press tool comprises an upper pressing die connected to the upper body and a lower pressing die is connected to the lower body.

[0012] EP3437750 A1 discloses examples of methods of hot forming structural components. The methods include heating a blank made of an Ultra High Strength Steel with an aluminum coating and forming the heated blank in a multi-step apparatus.

[0013] EP3067129 A1 discloses press systems for manufacturing hot formed structural components. The system comprises a fixed lower body, a mobile upper body and a mechanism configured to provide upwards and downwards press progression of the mobile upper body with respect to the fixed lower body. The system further comprises a cooling / heating tool configured to cool down and / or heat a previously heated blank having locally different microstructures and mechanical properties which comprises: upper and lower mating dies , and the upper and lower dies comprising two or more die blocks adapted to operate at different temperatures corresponding to zones of the blank having locally different microstructures and mechanical properties, and a press tool configured to draw the blank, wherein the press tool is arranged downstream the cooling / heating tool. This system is particularly aimed at creating "soft zones" in order to improve the ductility and energy absorption in specific areas of a component made from Usibor ®< 1500 (22MnB5). This use of 22MnB5 boron steel requires a specific temperature control between different die blocks of the cooling / heating tool and downstream post-processing tools to achieve the different microstructures and corresponding different characteristics.

[0014] EP3067128 A1 discloses a multistep press system for manufacturing hot formed structural components. The system comprises a fixed lower body, a mobile upper body and a mechanism configured to provide upwards and downwards press progression of the mobile upper body with respect to the fixed lower body. The system further comprises a cooling tool configured to cool down a previously heated blank which comprises: upper and lower mating dies, the lower die connected to the lower body with one or more lower biasing elements and / or the upper die connected to the upper body with one or more upper biasing elements. The system further comprises a press tool configured to draw the blank, wherein the press tool is arranged downstream from the cooling tool. This system is particularly aimed at the use of zinc coated ultra-high strength steels.

[0015] One disadvantage related to the use of zinc coated steels is that a zinc oxide layer can form on the blanks. In many applications, the zinc oxide layer needs to be removed or reduced after the manufacturing process. For example, shot blasting may be used to remove the zinc oxide layer partially or completely. Also, components with an AlSi coating can generally be welded better than components with a Zn coating.

[0016] The most commonly used steel in press hardening processes is coated 22MnB5 or similar. For example, Usibor ®< 1500 is commercially offered by ArcelorMittal ™< , MBW-W ®< 1500 is commercially offered by ThyssenKrupp, and other steel manufacturers offer further steels. After heating to above Ac3 temperature (e.g. after heating to about 900°C), a heated blank may be formed and quenched. Quenching may occur above a critical cooling rate of about 27°C / s to obtain a substantially fully martensitic microstructure and an ultimate tensile strength of about 1.500 MPa.

[0017] More recently, hot stamping of even higher grades of steel has been intensively investigated. E.g. 37MnB5 steels or similar have a higher carbon content than 22MnB5 and can achieve ultimate tensile strength after hot stamping of 2.000 MPa or even more. Usibor ®< 2000 which is commercially available from ArcelorMittal ™< and MBW-K ®< 1900 (a 34MnB4 steel) commercially available from ThyssenKrupp ™< are two of such steels.

[0018] Such steels may be called "second generation" press hardening steels. This newer generation of press hardening steels may herein be regarded boron-manganese steel suitable for hot stamping with a higher carbon content than 22MnB5, and which obtain an ultimate tensile strength of more than 1.500 MPa, specifically at least 1.700 MPa when fully martensitic after press hardening. The silicon content may typically be lower than for the first generation press hardening steels. Examples include 20MnCr, 28MnB5 steel (e.g. Docol PHS1800), 30MnB5 (e.g. SQ1800), 34MnB5 or 34MnB4 (e.g. MBW 1900), 37 MnB5 or 37 MnB4 (e.g. Usibor 2000 HPF 2000, Docol PHS2000, phs ultraform 2000). The new generation of steels may also be described as PHS 1.700 or higher, i.e. PHS 1.700, PHS 1.800, PHS 1.900 or PHS 2.000, more specifically PHS 1.900 or higher.

[0019] Another characteristic of such steels is however its brittleness and very low ductility after hot stamping. This means that post-processing operations including e.g. joining are more complicated and that energy absorption in case of an impact or crash is limited. This is one of the reasons why, in spite of the high tensile strength and potential to even further reduce the weight of automotive structures, these steels have actually had few practical applications in automotive structures to this day.

[0020] There is a tendency in the field to optimize the use of materials to the maximum extent possible. I.e. to use tailor welded blanks or other technologies to provide the precisely required mechanical characteristics in each area of the component.

[0021] There is furthermore a tendency in the field to provide hot stamping using larger blanks to obtain larger components, which require less joining operations after hot stamping. For example, it is known to manufacture a door ring including a portion of the rocker, the B-pillar, A-pillar, and hinge pillar in a single hot stamping operation. Prior to the hot stamping operation, several blanks (which may be of different thickness and / or different materials) are joined to each other to form a composite blank. The composite blank is subsequently heated and deformed. WO2020 / 002335 is a prior art document disclosing such door rings, and methods for manufacturing them.

[0022] A blank that is made up of different "sub-blanks" may be a so-called Tailor Welded Blank, i.e. the sub-blanks are joined in an edge-to-edge laser welding process. Alternatively, spot welding may be used.

[0023] Alternatively, such as illustrated e.g. in WO 2020 / 002335, blanks are partially overlapped with each other when joined together. The resulting composite blank has areas of increased thickness where the overlap was arranged. The local increase in thickness can be used to provide a local increase in stiffness and strength.

[0024] Finally, there is an ever increasing need to make manufacturing of automotive components as efficient and quick as possible to reduce cost of manufacturing. In particular, it would be desirable to provide an automotive component in a process including both hot stamping and cutting of the component with a cycle time of each of the tools of 10 seconds or less. Particularly, it would be desirable to have such a process and be able to provide an automotive component with intended mechanical characteristics in terms of ultimate tensile strength, yield strength and ductility.

[0025] The present disclosure seeks to provide improvements in hot stamping process of high grade steels, and specifically in multistep processes and apparatuses.SUMMARY

[0026] In a first aspect, a method for hot forming and press hardening a structural component in a production line comprising: a furnace, a press tool configured to deform blanks, and the press tool having an upper press die and a lower press die, a cutting tool arranged downstream from the press tool and configured to perform a cutting and restriking operation, and having an upper cutting tool die and a lower cutting tool die and a transfer system to transfer blanks from the furnace to the press tool and from the press tool to the cutting tool.

[0027] The method comprises providing a press hardenable boron steel blank, heating the blank to above an austenization temperature in the furnace, actively cooling or heating at least a selected portion of the blank, deforming and cooling the blank in the press tool, transferring the formed blank from the press tool to the cutting tool and cutting one or more areas of the formed blank and cooling the formed blank in the cutting tool. Herein a temperature of the blank before forming the blank is 600°C - 850°C, a temperature of the formed blank is cooled down to 400 - 600°C in the press tool and the formed blank is cooled down to 300°C, preferably 275°C, in the cutting tool.

[0028] In accordance with this aspect, an efficient method for manufacturing structural steel components is provided. The throughput of the production line may be increased or maximized. Furthermore, structural components with desirable mechanical properties may be obtained.

[0029] Methods provided herein can avoid deformations of the structural component after cutting. By lowering the temperature below 300°C, preferably below 275°C, and in specific examples lower than 200°C, while the component is in the restriking tool, subsequent deformation of the hot components due to the release of heat can be avoided. At the same time, hydrogen-induced delayed fracture (a known problem in hot stamping processes) can be avoided.

[0030] Cutting of the component can be carried out effectively at a temperature which is high enough (and thus the material is soft enough) to avoid microcracks in the cutting area, and thus reducing the risk of delayed fracture. In some steels, in order to avoid such a risk, cutting is preferably carried out around 400°C, whereas for some other steels cutting may be carried out at a temperature of around 200 °C without creating microcracks.

[0031] Throughout the present disclosure, cutting may be regarded as including to any process step, in which parts of the blanks are removed. Cutting may herein be regarded encompassing operations such as trimming and piercing.

[0032] Throughout the present disclosure, whenever reference is made to a temperature of a blank or component, the mentioned temperature refers to an average temperature of a "main portion" of the blank or component. I.e. it will be appreciated (and is also addressed herein) that a blank or component ay have a varying thickness and that temperature differences can occur within the same blank, particularly dependent on the local thickness. When addressing specific temperatures of a blank or component, the temperature refers to the average temperature of a portion of the blank that can be regarded as representative for the blank, e.g. the portion of the blank with the predominant thickness.

[0033] In specific examples, the blanks may be of a "second generation" press hardening steels as defined hereinbefore. In examples of the present disclosure, desirable mechanical characteristics of an ultimate tensile strength of more than 1.600 MPa e.g. 1.700 MPa - 1.900 MPa can be obtained, in combination with an A50 elongation of 5% or more, specifically an A50 elongation of 5 - 6%. The high ultimate tensile strength provides the potential for reducing thickness of the components and thereby their weight. The increased ductility as compared to conventional press hardening of such steels can improve the behaviour in the case of impact / crash and facilitate further post-processing.

[0034] Yield strength, ultimate tensile strength and A50 elongation may be measured in accordance with standard tensile strength test for metallic specimens as defined e.g. in ISO 6892-1. The A50 elongation refers to the elongation at break for a test specimen with an initial length of 50 mm (to be distinguished from e.g. A80).

[0035] In any of the herein disclosed examples, the press hardenable boron steel blank may be coated, specifically with an aluminum-silicon (AlSi) coating. Since an Ultra High Strength Steel blank with an aluminum silicon coating can be used, shot blasting to remove the zinc oxide layer partially or completely is not necessary. Other coatings, such as AlSi coatings with magnesium in the coating, or zinc (galvannealed or galvanized) may be used.

[0036] Reference is herein made to press hardenable boron steels, with a carbon content of 0.32 - 0.45 % by weight, specifically 0.32 - 0.4% of carbon by weight, and more specifically 0.32 - 0.38%, a content of manganese of 0.6 - 1.5%, specifically 0.6 - 1.4% and a boron content of 0.003 - 0.006% by weight, specifically 0.004 - 0.005% by weight. In practice, there may be slight variations between different coils of steels, even when made with the same manufacturing process by the same steel supplier. In practice, there may even be slight variations between blanks cut from the same steel coil. Suitable steels include e.g. 37MnB5 steel, 38MnB5 steel, 34MnB5 steel and 34 MnB4 steel.

[0037] One typical composition of a 34MnB4 steel that has been tested is summarized below in weight percentages (rest is iron (Fe) and impurities): Carbon (C) (%) 0.35 Silicon (Si) (%) 0.8 Manganese (Mn) (%) 0.96 Chromium (Cr) (%) 0.19 Molybdenum (Mb) (%) 0.18 Phosphor (P) 0.012% Sulphur (S) (%) 0.0002 Titanium (Ti) + niobium (Nb) 0.055% Aluminium (Al) 0.03% Boron (B) (%) 0.002% Nitrogen (N) 0.003% Nickel (Ni) 0.01%

[0038] Usibor ®< 2000 may be generally described as 37MnB5 steel. The composition of Usibor ®< 2000, is summarized below in weight percentages (rest is iron (Fe) and impurities): Maximum carbon (C) (%): 0.36 Maximum silicon (Si) (%): 0.8 Maximum manganese (Mn) (%): 0.8 Maximum phosphorus (P) (%): 0.03 Maximum sulphur (S) (%): 0.01 Aluminium (Al) (%): 0.01 - 0.06 Maximum titanium (Ti) (%): 0.07 Maximum niobium (Nb) (%): 0.07 Maximum copper (Cu) (%): 0.20 Maximum boron (B) (%): 0.005 Maximum chromium (Cr) (%): 0.50 Maximum molybdenum (Mb) (%): 0.50

[0039] MBW-K ®< 1900 may generally be described as a 34MnB4 steel. The composition of MBW-K ®< 1900 is summarized below in weight percentages (rest is iron (Fe) and impurities): Maximum carbon (C) (%): 0.38 Maximum silicon (Si) (%): 0.4 Maximum manganese (Mn) (%): 1.4 Maximum phosphorus (P) (%): 0.025 Maximum sulphur (S) (%): 0.01 Minimum Aluminium (Al) (%): 0.015 Maximum titanium (Ti) (%): 0.05 Maximum niobium (Nb) (%): 0.07 Maximum boron (B) (%): 0.005 Maximum chromium (Cr) + molybdenum (Mb) (%): 0.50

[0040] MBW ®< 1900 is another manganese-boron steel from ThyssenKrupp ™< which may have an ultimate tensile strength of 1900 MPa. It is commercially available with aluminium-silicon coatings and suitable for hot stamping and the methods disclosed herein. The chemical composition of MBW ®< 1900 is summarized below in weight in percentages (rest is iron (Fe) and impurities): Maximum carbon (C) (%): 0.38 Maximum silicon (Si) (%): 0.40 Maximum manganese (Mn) (%): 1.40 Maximum phosphor (P) (%): 0.025 Maximum sulphur (S) (%): 0.010 Minimum aluminium (Al) (%): 0.1 Maximum niobium (Nb) (%): 0.05 Maximum titanium (Ti) (%): 0.05 Maximum chromium and molybdenum (Cr + Mo) (%): 0.50 Maximum boron (B) (%): 0.005

[0041] B1800HS is yet another boron steel which may have an ultimate tensile strength of about 1800 MPa and suitable for hot stamping and the methods disclosed herein. The chemical composition of B1800HS is summarized below in weight in percentages (rest is iron (Fe) and impurities): Carbon (C) (%): 0.28 - 0.35 Maximum silicon (Si) (%): 0.5 Manganese (Mn) (%): 1.0 - 1.8 Maximum phosphor (P) (%): 0.025 Maximum sulphur (S) (%): 0.010 Aluminium (Al) (%): 0.01 -0.06 Maximum titanium (Ti) (%): 0.05 Maximum boron (B) (%): 0.0050 Maximum chromium and molybdenum and niobium (Cr + Mo + Nb) (%): 0.80

[0042] A further suitable steel is CR1900T-MB-DS. The chemical composition is summarized below in weight in percentages (rest is Fe and impurities): Carbon (C) (%): 0.30 - 0.38 Maximum silicon (Si) (%): 0.8 Manganese (Mn) (%): 2.0 Maximum chromium (Cr) : 0.25% Maximum phosphor (P) (%): 0.03 Maximum Molybdenum (Mo): 0.25 Maximum sulphur (S) (%): 0.005 Aluminium (Al) (%): 0.01 -0.08 Maximum Titanium (Ti) + Niobium (%): 0.20 Boron (B) (%): 0.0010 - 0.0050 Maximum nickel (Ni): 0.10 Maximum nitrogen (N): 0.01

[0043] In examples, the blank may be heated to above Ac3 temperature, and particularly to 870 - 930°C, more specifically 900 - 930°C. Heating may occur particularly in a furnace arranged upstream from the press tool and cutting tool in the production line.

[0044] In some examples, the obtained component may further be submitted to a bake hardening process. E.g. a structural component may be submitted to a temperature of about 180°C during about 20 minutes. A bake hardening process may further increase the yield strength of the obtained component, whereas ultimate tensile strength remains substantially the same.

[0045] In some examples, the production line comprises a multi-step tool comprising a fixed lower body, a mobile upper body, and a mechanism configured to provide upwards and downwards press progression of the mobile upper body with respect to the lower body, and wherein the upper press die is connected to the mobile upper body and the lower press die is connected to the fixed lower body, and the upper cutting die is connected to the mobile upper body, and the lower cutting die is connected to the fixed lower body.

[0046] With the integration of the tools in the same apparatus by connecting the upper dies of the press tool and the cutting tool to the mobile upper body, the transfer time from the press tool to the cutting tool may be reduced, thus the process may be optimized and the productivity may be improved. Also the temperature of the blanks during the different steps of the process can be improved.

[0047] In some examples, the dies of the press tool and / or of the cutting tool may comprise channels conducting cooling water. The dies of the cooling tool may alternatively or additionally comprise channels conducting air.

[0048] In some examples, a cycle time for each of the tools may be 12 seconds or less, specifically 10 seconds or less. The overall processing time from the moment of extraction from the furnace to the moment of extraction from the cutting and restriking tool may be e.g. 20 - 25 seconds.

[0049] Different types of blanks may be processed in examples of the present disclosure. In some examples, the blanks may have a uniform thickness. In other examples, the blanks may comprise different materials and / or different thicknesses. For example, Tailor Welded Blanks may be used. In other cases, sub-blanks which are partially overlapped with each other, or patches may be used to form the press hardenable boron steel blank.

[0050] In some examples, the press hardenable boron steel blank includes a first portion with a first thickness, and a second portion with a second thickness, wherein the second thickness is higher than the first thickness. In the fast forming process, it is important that the different portions of the blank follow a similar temperature profile (and obtain a similar microstructure at the end of the process), in spite of having different thicknesses.

[0051] In some examples, the second portion (of increased thickness) may be more actively cooled than the first portion prior to deforming. Alternatively or in addition, the first portion may be actively heated in the press tool and / or cutting tool.

[0052] In some examples, the press hardenable boron steel blank is made by joining two or more sub-blanks.

[0053] In yet a further aspect, a component obtainable by any of the methods herein disclosed is provided.

[0054] In a further aspect, a production line for hot forming and press hardening a structural component is provided. The production line comprises a furnace configured to heat a press hardenable boron steel blank to above an Ac1 temperature, particularly to above an Ac3 temperature, and a press tool arranged downstream from the furnace and configured to deform the heated blanks, and the press tool having an upper press die and a lower press die. The production line further comprises a first transfer system to transfer blanks from the furnace to the press tool and a cutting tool arranged downstream from the press tool and configured to perform a cutting and restriking operation, and having an upper cutting tool die and a lower cutting tool die. The production line further comprises a second transfer system to transfer blanks from the press tool to the cutting tool. In accordance with this aspect, the furnace and / or the first transfer system and / or the press tool comprises cooling elements for actively cooling at least a selected portion of the heated blank.

[0055] Restriking may herein be regarded as the re-application of pressure to the already deformed blank to achieve a higher-quality deformation. The restriking further allows the chance to further cool down the blank, or in general to provide further temperature control. The dies of the cutting tool may be mating, and the upper and / or lower die may include cooling channels to quickly cool down the blank.

[0056] In accordance with this aspect, a production line is provided which is configured specifically for quick forming and cutting processes.BRIEF DESCRIPTION OF THE DRAWINGS

[0057] Non-limiting examples of the present disclosure will be described in the following, with reference to the appended drawings, in which: Figure 1 schematically represents a production line according to an example; Figures 2A - 2D schematically illustrate a CCD diagram and a temperature profile of a blank as it undergoes a method of manufacturing according to examples of the present disclosure; Figure 3 schematically illustrates a press tool incorporating heating and cooling features according to an example; Figure 4 schematically illustrates a distribution of die blocks of a press tool according to an example; and Figure 5 schematically illustrates a multistep apparatus in accordance with an example of the present disclosure. DETAILED DESCRIPTION OF EXAMPLES

[0058] Figure 1 schematically represents a production line according to an example. An example of a method for hot forming a structural component in a production line is schematically illustrated in figure 1.

[0059] A steel coil 10 of a press hardenable boron steel is provided. Well known press hardenable boron steel blanks, such as 22MnB5 steels. In preferred examples, a second generation press hardenable boron steel having a composition by weight of 0.32 - 0.45% of carbon, a manganese content of 0.6 - 1.5%, and a boron content of 0.003 - 0.006% may be used.

[0060] A blanking apparatus 20 may cut suitably sized blanks from coil 100. The steel may or may not have a protective coating.

[0061] The blanks may have a thickness of 0,6 mm - 4 mm, specifically 1 - 3 mm. In some examples, the steel may be 34MnB4 of 37MnB5 steel.

[0062] In specific examples, the steel may have a content by weight of 0.34 - 0.4% carbon, specifically 0.34 - 0.39%, and more specifically 0.34 - 0.38%. The steel may further have a content of 0.8 - 1.4% of manganese. The steel may have a content by weight of boron of 0.003 - 0.005%, and specifically 0.004 - 0.005%. In specific examples, the steel may have a content by weight of 0.3 - 0.9%, specifically 0.4 - 0.8% of silicon.

[0063] The blanks may be provided to furnace 30. The blanks may be heated to above an austenization temperature, and in particular to above an Ac3 temperature. In specific examples, the blanks may be heated in the furnace for between 5 and 10 minute and may be heated to about 870 - 930°C, specifically 900 - 930°C.

[0064] Different furnace systems suitable for this purpose are known in the art. For example, a furnace may have a length of 30 - 50 meters. At the end of the furnace, a centering table may be provided.

[0065] After exiting the furnace 30, the heated blanks may be transferred to press tool 50 configured to deform or draw the blanks. A suitable press tool may e.g. have a press force of 1.400 or 2.000 Tn.

[0066] The press tool 50 comprises an upper press die 52 and a lower press die 54. A blank may be positioned in between the upper press die 52 and lower press die 54. The upper press die 52 may perform an upward-downwards progression with respect to lower press die 54 to deform the previously heated blank.

[0067] The production line 100 further comprises a cutting tool 60 arranged downstream from the press tool 50 and configured to perform a cutting and restriking operation on the formed blank (a blank that has undergone a drawing process in the press tool). The cutting tool comprises an upper cutting die 62 and a lower cutting die 64. The upper press die 52 and upper first post-press die 62 are configured to operate in unison. Particularly, the upwards-downwards movement of the upper first post-press die 62 may be synchronized with the upward-downwards movement of the upper press die 52.

[0068] The production line 100 further comprises a transfer system to transfer formed blanks from the press tool 50 to the first post-press tool 60. In this particular example, a plurality of transfer robots with grippers or suction units is provided. A transfer robot 44 may grip the deformed blank after it has undergone the drawing operation in press tool 50 and place it in the first post-press tool 60.

[0069] A further transfer robot 46 may grip the blank after the cutting and restriking operation and place the blank in a storage or rack for further processing. In some examples, a further laser cutting station may be provided. The deformed and cut blanks may be transported to the laser cutting station, where further cutting, trimming and trepanning may be carried out.

[0070] The capacity and throughput of the furnace and the tools arranged downstream may be adapted to each other. I.e. in one example, a furnace may be designed to convey pairs of blanks. In such a case, pairs of press tools and cutting tools may be arranged downstream from the furnace. In another case, half of the blanks of the pairs of blanks may be temporarily retained in the furnace (e.g. by lifting them) to allow the blanks to exit the furnace one by one.

[0071] In further examples, the furnace may convey multiple blanks (e.g. two or three or more) next to each other at the same time. Or two parallel furnaces may be provided, e.g. each having a length of about 30 - 50 meters. A plurality of blanks may thus be output at the same time. The plurality of blanks may be picked up by a gripper system, or multiple grippers moving in unison. The multiple grippers may be independent from each other, or may be coupled to each other to move in unison.

[0072] The plurality of blanks may be arranged next to each other in the same press tool. All blanks may be deformed to obtain the same shape (i.e. to form the same component), or each of the blanks may be deformed to obtain a different shape (i.e. to form different components). Such a setup may be useful for forming multiple components belonging to the same vehicle at the same time, e.g. multiple components of a vehicle door, or multiple components of a vehicle floor or of a battery support structure.

[0073] After the blanks have been cooled and deformed in the press tool, the plurality of blanks are transported in unison to the cutting tool. In the cutting tool, the plurality of blanks are cooled and cut at the same time as well. Then the plurality of formed components may be simultaneously extracted from the cutting tool as well.

[0074] The production line illustrated in figure 1 may be used for the manufacture of a variety of structural components. In particular examples, structural components with a length and width of more than 1 meter may be manufactured in such a production line. In some examples, unitary door rings (door rings made of a single integrally formed body) may be manufactured in such a production line. Unitary door rings may be e.g. a single door rings (extending from A-pillar to B-pillar, or from B-pillar to C-pillar) or double door rings (extending from A-pillar to C-pillar).

[0075] Further large structural components which may be manufactured in a production line 100 according to figure 1 include e.g. unitary roof rings, bumper beam assemblies including a bumper beam and a pedestrian beam, a unitary ring surrounding a battery box, a rear framework structure including rear rails and a transverse beam as a unitary structure and others.

[0076] Such large structural components may be manufactured efficiently in a hot stamping process. Due to the size of such components, the different tools are difficult to integrate in a single press apparatus. However, the methods and systems may also be used for other components that may be press formed e.g. B-pillar, A-pillar, hinge pillar, bumper crossbeams and others.

[0077] In some examples, a blank may be composed of multiple smaller blanks or sub-blanks. Some of the sub-blanks may be joined to other sub-blanks in a Tailor Welded Blank (TWB) edge-to-edge butt joint. Alternatively, or additionally, the sub-blanks may be partially overlapped with each other to form an overlapping region with an increased thickness compared to other areas. The areas of increased thickness may be selected to locally reinforce the structural component. The increased thickness in these areas may provoke an increased heating time in a furnace. In the drawing or deforming operation, and in subsequent processes, the overlapping areas may cool down more slowly unless specific measures are taken.

[0078] The method for hot forming a structural component comprises heating the blank to above an austenization temperature, particularly above an Ac3 temperature for the selected steel e.g. 890 - 930°C.

[0079] The method further comprises transferring the heated blank from the furnace to the press tool and deforming the heated blank in the press tool 50 and transferring the blank from the press tool 50 to the cutting tool 60. A temperature of the blank before forming the blank is 600°C - 850°C, and a temperature of the formed blank is cooled down to 400 - 600°C in the press tool. The formed blank is subsequently cooled down to 300°C or lower, preferably to 275°C or even lower in the cutting tool.

[0080] The method may further be illustrated with reference to a CCT diagram, such as illustrated in figure 2A. A Continuous Cooling Transformation (CCT) diagram is a chart that for a specific steel indicates the transformations that occur as it cools at different rates. CCT diagrams can be used to indicate how different cooling rates affect the microstructure and, ultimately, the mechanical properties of materials after heating.

[0081] Figure 2A indicates a CCT diagram for a typical boron steel. It will be clear that depending on the steel used, the CCT diagrams may look slightly different. Different areas in the CCT diagram indicate different microstructures. Herein, the letter A stands for austenite, M for martensite, B for bainite, P for pearlite, and F for ferrite. Further indicated in the CCT diagram are the martensite start temperature, Ms, and the martensite finish temperature Mf. In the CCT diagram, a maximum critical cooling rate and a minimum cooling rate are indicated which, for the given material indicate an upper and lower cooling rate to obtain a steel with mostly martensitic microstructure (and thus high ultimate tensile strength, and high yield strength) while avoiding hydrogen induced fracture.

[0082] In order to ensure that the blank is cooled at an appropriate rate, during transfer, deforming and cutting, active temperature control may be required.

[0083] In accordance with a first aspect of the disclosure, at least a selected portion of the blank (and potentially the whole blank) is actively cooled prior to deforming of the blank. Active cooling may herein be regarded as the use of specific cooling means to achieve a higher cooling rate than passive air cooling.

[0084] Figure 2B schematically indicates a first stage of cooling (interrupted line in figure 2B) which may be incorporated in examples of the present disclosure. In a first stage, the active cooling of at least the selected portion of the blank comprises active cooling in the furnace. That is, the entire blank or portions of the blank may be cooled with relatively cold air in the furnace. Thermal printing, as commercially offered by Shwartz ™< can create multiple regions of different strength and elongation behaviours in a single component. Similarly, Ebner ™< offers commercial solutions for (partial) cooling in the furnace. In furnace cooling may be used to cool down the blank to e.g. 900 - 650°C, particularly 850 - 700°C.

[0085] Additionally, or alternatively, the active cooling of at least the selected portion of the blank comprises active cooling during a transfer from the furnace to the press tool. The transfer mechanism used for transferring the blank from the furnace to the press tool may incorporate air knives or other active air cooling means to cool down (a part) of the blank, in particular parts of the blank with increased thickness. In examples, cooling during transfer may comprise cooling to 850 - 600°C (the dotted line in figure 2B).

[0086] Additionally, or alternatively, the active cooling of at least the selected portion of the blank comprises active cooling in the press tool prior to the deforming of the blank (indicated with a continuous line in figure 2B). Cooling in the press tool may be used to achieve temperatures of e.g. 800 - 550°C. In some examples (illustrated hereinafter), one or more die blocks of the press tool may include slots, through which pressurized cooling gas (e.g. air) may be ejected and impinge upon the blank.

[0087] During the deforming, the whole blank (or at least selected portions thereof) may be cooled down because of contact with cold die blocks. The upper and / or lower press die may include cooling channels conducting cooling liquid (e.g. water).

[0088] As illustrated in figure 2C, the temperature of the blank at the end of the press tool may be 600 - 400°C, specifically 500 - 400°C. The temperature should still be high enough to allow for effective cutting when the blank arrives at the cutting tool. Finally, as illustrated in figure 2D, the blank may be cut and further cooled down in the cutting tool to well below the martensite finish temperature, and specifically to below 275°C.

[0089] In preferred examples, the cycle time of each of the tools may be 12 seconds or less, specifically 10 seconds or less. The cycle in each of the tools may comprise 1 - 5 of effective cooling and forming or cutting, and 5-9 seconds to the transfer and positioning of the blanks. The transfer from the furnace to the press tool may take about 1- 3 seconds in an example.

[0090] As previously mentioned, different blanks of different materials, with different thicknesses and with or without coatings may be used in the herein disclosed examples. Depending on the material, thickness, etc. used, the process can be tailored to achieve satisfactory results.

[0091] Some suitable steels are mentioned in Table 1. Table 1: suitable steels. Mechanical properties refer to maximum obtainable mechanical properties if rapid cooling above the critical cooling rate is applied.Chemistry Final mechanical properties Supplier Commercial name Coating type Coating amount C Si Mn Cr Mo P S Ti Al B YS TS A50% A80% ThyssenMBW1900 ASPRGAlSi60 / 600,380,41,40,50,0250,010,050,0150,00512001900-4MBW1200 ASPROAlSi60 / 600,160,41,40,50,0250,010,050,0150,0059001200-5MBW500 ASPROAlSi60 / 600,10,351--0,030,0250,150,0150,005400550-17Arcelormittal Usibor2000AlSi60 / 600,360,80,80,50,50,030,010,070,01-0,060,0051400180055Ductibor1000AlSi60 / 600,10,61,80,2-0,030,010,050,01-0,10,005800100066Ductibor500AlSi60 / 600,10,51,70,2-0,030,0250,090,0150,0013505501414Voestalpine PHS Scalefree 2000GA / GI35 / 350,30 - 0,380,520,50,020,0050,20 (+Nb)0, 02 - 0, 080,002 - 0,005120019005-PHS Scalefree 1000GA / GI35 / 35PHS Scalefree 490GA / GI35 / 350,130,51,5--0,030,0250,15 (+Nb)0,015-40049016-Posco PET2000H-ALAlSi70~90g / m 2< 0,3-0,380,820,25-0,030,0050,20,01 - 0,080, 001-0, 0051100-14501750-21504-PET550H-ALAlSi70~90g / m 2< 0,10,51,5--0,030,0250,01-0,080,015-350-500450-65012-BaoSteel B1800HS+ASAlSi0,340,231,110,210,20,0130,0050,050,030,003138018504-B1200HS+ASAlSiB500HS+ASAlSiTagal TA-2000 AS EcoAlSi20 / 201200 - 15001800 - 21005-TA-1000 AS EcoAlSi20 / 20min 700min 1000-8TA-500 AS EcoAlSi20 / 20min 350min 500-17

[0092] It should be noted that in the table, mostly ultra-high strength steels are used, but also other steels suitable for hot stamping but are less stiff and strong (and rather more ductile) can be used as well. E.g. steels with an ultimate tensile strength of 500 MPa or 1.000 MPa after hot forming die quenching may be used as well, e.g. in parts of the blank. Examples of ductile steels include Ductibor ®< 500, Ductibor ®< 1000 and CRL-340LA.

[0093] Ductibor ®< is a steel material with much higher ductility than Usibor ®< materials, and components made of this material can be effective for absorbing energy during an impact. The yield strength of Ductibor ®< 500 may be 400 MPa or more, and the ultimate tensile strength of 550 MPa or more.

[0094] The composition of Ductibor ®< 500 is summarized below in weight percentages (rest is iron (Fe) and impurities): Maximum carbon (C) (%): 0.1 Maximum silicon (Si) (%): 0.5 Maximum manganese (Mn) (%): 1.7 Maximum phosphorus (P) (%): 0.03 Maximum sulphur (S) (%): 0.025 Aluminium (Al) (%): 0.015 - 0.2 Maximum titanium (Ti) (%): 0.09 Maximum niobium (Nb) (%): 0.10 Maximum copper (Cu) (%): 0.20 Maximum boron (B) (%): 0.001 Maximum chromium (Cr) (%): 0.20

[0095] The yield strength of Ductibor ®< 1000 may be 800 MPa or more, and the ultimate tensile strength of 1000 MPa or more. The composition of Ductibor ®< 1000 is summarized below in weight percentages (rest is iron (Fe) and impurities): Maximum carbon (C) (%): 0.10 Maximum silicon (Si) (%): 0.6 Maximum manganese (Mn) (%): 1.8 Maximum phosphorus (P) (%): 0.03 Maximum sulphur (S) (%): 0.01 Aluminium (Al) (%): 0.01 - 0.1 Maximum titanium (Ti) (%): 0.05 Maximum niobium (Nb) (%): 0.10 Maximum copper (Cu) (%): 0.20 Maximum boron (B) (%): 0.005 Maximum chromium (Cr) (%): 0.20

[0096] In examples, the press hardenable boron steel blank may have a uniform thickness, e.g. a thickness of 0.8 - 2mm. In other examples, the press hardenable boron steel blank may include a first portion with a first thickness, and a second portion with a second thickness, wherein the second thickness is higher than the first thickness. It should be clear that blanks with more that two different portions of differing thickness may also be used.

[0097] In examples, the second (thicker) portion is more actively cooled than the first portion prior to deforming. I.e. in the furnace, and / or during transfer, and / or when placed in the press tool, the thicker portion may be cooled more than the thinner portions. The objective is that, regardless of the local thickness, the entire blank undergoes a rather similar treatment, so that relatively homogeneous properties and microstructure are obtained.

[0098] In further examples, the first (thinner) portion may be actively heated in the press tool and / or cutting tool. Both the press tool and cutting tool may be generally cooled using cooling channels. In order to avoid the thinner portion cooling down too quickly, or much more quickly than a thick portion of the blank, the thinner portion may be heated in the press tool and / or the cutting tool.

[0099] Figures 3 and 4 illustrate examples of systems that may be used particularly for tailored cooling and / or heating.

[0100] Figure 3 illustrates a cross-section of a press tool, including an upper die 110 and a mating lower die 120. Further schematically illustrated is a press hardenable boron steel blank 130, including a first portion 132 with a first thickness 132, a second portion 134, with a second thickness and a third portion 136 with a third thickness. The third thickness is higher than the second thickness, which in turn is higher than the first thickness.

[0101] Although not illustrated in figure 3, the blank 130 may be supported on a blank holder.

[0102] As previously discussed, such a press hardenable boron steel blank with different thicknesses may be made by joining two or more sub-blanks. The press hardenable boron steel blank may be a Tailor Welded Blank combining sub-blanks of different thicknesses and / or different materials. In examples, at least one of the sub-blanks is made of a material having an ultimate tensile strength of 1.100 MPa or less, specifically 1.000 MPa or less.

[0103] E.g. if in a component a more ductile portion is desired, a sub-blank of Ductibor ®< 1000 MPa may be combined with a sub-blank of Usibor ®< 1500 or Usibor ®< 2000 to name just an example.

[0104] As previously disclosed, particularly for larger components, the press hardenable boron steel blank may be made by welding two or more sub-blanks which partially overlap with each other. When joining multiple sub-blanks by overlapping, the combined blank will have portions of different thickness as illustrated in figure 3. For example, for a unitary vehicle door ring, a blank of e.g. 1.6 mm may be overlapped with another blank of e.g. 1.2 mm in a specific area to form a local thickness of 2.8 mm.

[0105] When the blank has been placed in the press tool, selected portions of the blank may be cooled (e.g. thicker portion 136), whereas other selected portions of the blank may be heated to avoid them from cooling down too much (e.g. thin portion 132). To this end, the upper and / or lower die may include slots connected to pressurized air. The air may impinge on the thick portion 136 of the blank to locally cool down the blank. Other portions of the upper and / or lower die may include heaters 140, e.g. inductive or resistance heaters to heat thinner portions of the blank. In further examples, the composition of the die block may be different to retain heat. E.g. a die block may include a specific (ceramic) coating with a particularly low reflectance to retain heat. Such a die block may be heated to e.g. 300 - 550°C and since they dissipate little heat may stay close to such temperature in operation.

[0106] In some examples, biasing elements such as e.g. springs may be integrated in the upper and / or lower press dies such that certain mating die blocks of the press tool (a pair of a die block of the upper press tool and a die block of the lower press tool that face each other) enter into contact with the blank before other die blocks enter into contact. In other words, a selection of the die blocks maybe closed earlier than other die blocks.

[0107] In those die blocks wherein contact is established earlier, cooling down may start earlier, and may be quicker than in other die blocks. If overlapping regions are to be cooled down more quickly, a biased die block may be used for that area. Additionally, or alternatively, one or more die blocks may integrate heating means in order to avoid a too rapid cooling down.

[0108] In a further example, as illustrated in figure 4, an upper and / or lower die of the press tool may comprise multiple die blocks E1 - E8. Each of the individual blocks may include individual cooling or heating means and sensors 200 (such as thermocouples) to control the temperature in different parts of the blank.

[0109] Even though figures 3 and 4 illustrate the heating and cooling with respect to the press tool, it should be clear that similar features may be included in the cutting tool.

[0110] In some examples, the method may comprise cutting at least a portion of the press hardenable boron steel blank in the forming tool. I.e. the press tool may include cutting components to cut portions of the blank. Typically, in this case, a small part of the cutting, trimming and / or piercing operations may be carried out in the press tool whereas the major part of the cutting, trimming and / or piercing may be carried out in the cutting tool.

[0111] In examples, the method may further comprise later cutting the structural component in a laser cutting station. In some examples, directly downstream from the cutting tool, an active cooling tool may be provided to ensure further cooling and ensure dimensional stability of the components.

[0112] Figure 5 illustrates a further example of a press tool 350 and cutting tool 360 which may be used in examples of the present disclosure. The press tool 350 and the cutting tool 360 are integrated in the same press apparatus 300 in this example. The press apparatus 300 comprises a fixed lower body 320, a mobile upper body 310, and a mechanism configured to provide upwards and downwards press progression of the mobile upper body 310 with respect to the fixed lower body 320, and wherein the upper press tool die 352 and the upper cutting tool die 362 are connected to the moving upper body. The lower press tool die 354 and the lower cutting tool die 364 re connected to the fixed lower body 320.

[0113] With each upwards and downwards press progression, both the cutting tool and the press tool move upwards and downwards in unison. An aspect of using a single press apparatus incorporating both the press tool 350 and the cutting tool 360 is that transfer time may be reduced.

[0114] Schematically illustrated in figure 5 are a first component 374 after forming and cutting, a blank 372 which has been deformed (but not cut yet), and a blank 373 which still has to undergo both operations.

[0115] In some examples, the obtained structural component may further be submitted to a bake hardening process. A temperature of bake hardening may be between 170°C and 200°C, and a bake hardening time may be between 15 and 25 minutes.

[0116] With bake hardening, an increase in yield strength of the structural component may be obtained. Energy absorption and toughness of the material may thereby be increased. These results have been experimentally confirmed for the above-referenced steels.

[0117] The mechanism of the press may be driven mechanically, hydraulically or servo mechanically. The progression of the mobile upper body 310 with respect to the fixed lower body 320 may be determined by the mechanism. In this particular example, the press may be a servo mechanical press, thus a constant press force during the stroke may be provided. The servo mechanical press may be provided with infinite slide (ram) speed and position control. The servo mechanical press may also be provided with a good range of availability of press forces at any slide position, thus a great flexibility of the press may be achieved. Servo drive presses have capabilities to improve process conditions and productivity in metal forming. The press may have a press force of e.g. 2000 Tn.

[0118] In some examples, the press may be a mechanical press, thus the press force progression towards the fixed lower body 320 may depend on the drive and hinge system. Mechanical presses therefore can reach higher cycles per unit of time. Alternatively, hydraulic presses may also be used.

[0119] In some examples, one or more of the lower dies 354, 364 may be connected to the lower body 320 with a lower biasing element configured to bias the lower die to a position at a predetermined first distance from the lower body 320. In some examples, a single lower biasing element may be provided, or more than two lower biasing elements can be provided. The biasing elements may comprise, for example, a spring e.g. a mechanical spring or a gas spring although some other biasing elements may be possible e.g. hydraulic mechanism. The biasing elements ensure that the upper and / or lower dies are "closed" or enter into contact with the blank before reaching the bottom dead center of the press.

[0120] In some examples, one or more of the upper dies 352, 362 may also be connected to the upper body 310 with one or more upper biasing elements configured to bias the upper die in a position at a predetermined second distance from the upper body.

[0121] With the insertion of the upper and / or lower biasing elements, the contact time between the upper dies and the lower dies may be regulated and increased during a stroke cycle (up and down movement of the mobile upper body with respect to the lower body.

[0122] The use of such biasing elements allows the cooling tool to have a different cycle time than the other tools integrated in the same apparatus. This is explained in more detail in EP3067128. However, within the scope of the present disclosure, the use of biasing elements is merely optional. Depending on the steel of the blanks and their coating, biasing elements may not be needed at all. As mentioned herein, such biasing elements may be used for closing of complete tools or "dies". In examples, biasing elements may be used only for a selection of die blocks.

[0123] In examples, the press tool may be provided with a blank holder configured to hold a blank and to positioning the blank onto the lower die. The blank holder may also be provided with e.g. springs to bias the blank holder to a position at a predetermined distance from the lower die.

[0124] An automatic transfer device (not shown) e.g. a plurality of industrial robots or a conveyor, or beams with gripping elements may also be provided to perform the transfer of blanks between the tools. Since the transfer devices may be integrated in the same press system, there is less transfer time, and the temperature control is better.

[0125] In all examples, temperature sensors and control systems in order to control the temperature may be provided in any tools or in the transfer system. The tools may also be provided with further cooling systems, blanks holders, etc.

[0126] In some examples, a centering element e.g. pins and / or guiding devices may be provided upstream the cooling tool, thus the blank may be properly centered.

[0127] For reasons of completeness, various aspects of the present disclosure are set out in the following numbered clauses: Clause 1. A method for hot forming and press hardening a structural component in a production line comprising: a furnace; a press tool configured to deform blanks, and the press tool having an upper press die and a lower press die; a cutting tool arranged downstream from the press tool and configured to perform a cutting and restriking operation, and having an upper cutting tool die and a lower cutting tool die; a transfer system to transfer blanks from the furnace to the press tool and from the press tool to the cutting tool, and the method comprising: providing a press hardenable boron steel blank; heating the blank to above an austenization temperature in the furnace; actively cooling at least a selected portion of the blank; deforming and cooling the blank in the press tool; transferring the formed blank from the press tool to the cutting tool; cutting one or more areas of the formed blank and cooling the formed blank in the cutting tool, wherein a temperature of the blank before forming the blank is 600°C - 850°C, wherein a temperature of the formed blank is cooled down to 400 - 600°C in the press tool; and wherein the formed blank is cooled down to 300°C, preferably to 275°C in the cutting tool. Clause 2. The method according to clause 1, wherein the active cooling of at least the selected portion of the blank comprises active cooling in the furnace. Clause 3. The method of clause 1 or 2, wherein the active cooling of at least the selected portion of the blank comprises active cooling during a transfer from the furnace to the press tool. Clause 4. The method according to any of clauses 1 - 3, wherein the active cooling of at least the selected portion of the blank comprises active cooling in the press tool prior to the deforming of the blank. Clause 5. The method according to any of clauses 1-4, wherein the blank is heated to 890 - 930°C in the furnace. Clause 6. The method according to any of clauses 1-5, wherein the whole blank is heated to above an Ac1 temperature in the furnace, and specifically wherein the whole blank is heated to above an Ac3 temperature in the furnace. Clause 7. The method according to any of clauses 1-6, further comprises active cooling of the formed and cut blank after the cutting tool. Clause 8. The method according to any of clauses 1 - 7, wherein the press hardenable boron steel blank has a content by weight of 0.32 - 0.45%, a manganese content of 0.6 - 1.5%, and a boron content of 0.003 - 0.006%. Clause 9. The method according to clause 8, wherein the press hardenable boron steel blank has a content by weight of 0.32 - 0.4 %, a manganese content of 0.6 - 1.4%, specifically 0.8 - 1.4% and a boron content of 0.004 - 0.005%. Clause 10. The method according to clause 8 or 9, wherein the press hardenable boron steel blank has a content by weight of 0.3 - 0.9%, specifically 0.4 - 0.8% of silicon. Clause 11. The method according to any of clauses 1 - 10, wherein the press hardenable boron steel blank is coated. Clause 12. The method according to clause 11, wherein the press hardenable boron steel blank has an AlSi coating. Clause 13. The method according to clause 12, wherein the AlSi coating further comprises magnesium. Clause 14. The method according to clause 11, wherein the press hardenable boron steel blank has a zinc or zinc alloy coating. Clause 15. The method according to any of clauses 1 - 14, wherein a time from the moment of extracting a blank from the furnace to extracting the blank from the cutting tool is 20 - 25 seconds. Clause 16. The method according to any of clauses 1 - 15, wherein the press hardenable boron steel blank has a uniform thickness. Clause 17. The method according to any of clauses 1 - 15, wherein the press hardenable boron steel blank includes a first portion with a first thickness, and a second portion with a second thickness, wherein the second thickness is higher than the first thickness. Clause 18. The method according to clause 17, wherein the second portion is more actively cooled than the first portion prior to deforming. Clause 19. The method according to clause 17 or 18, wherein the first portion is actively heated in the press tool and / or cutting tool. Clause 20. The method according to any of clauses 1 - 19, wherein the press hardenable boron steel blank is made by joining two or more sub-blanks. Clause 21. The method according to clause 20, wherein the press hardenable boron steel blank is a Tailor Welded Blank. Clause 22. The method according to clause 20 or 21, wherein the press hardenable boron steel blank is made by welding two or more sub-blanks which partially overlap with each other. Clause 23. The method according to clause 20, 21 or 22, wherein the press hardenable boron steel blank is made by positioning a patch blank completely overlapping with another blank and joining the patch blank to the other blank. Clause 24. The method according to any of clauses 20 - 23, wherein the sub-blanks are made from the same material. Clause 25. The method according to any of clauses 20 - 23, wherein at least one of the sub-blanks is made of a material having a maximum ultimate tensile strength of 1.100 MPa or less, specifically 1.000 MPa or less. Clause 26. The method according to any of clauses 1 - 25, further comprising cutting at least a portion of the press hardenable boron steel blank in the forming tool. Clause 27. The method according to any of clauses 1 - 26, wherein an ultimate tensile strength of the structural component is 1.600 MPa or more, specifically 1.700 - 1.900 MPa. Clause 28. The method according to clause 27, wherein the structural component obtained has an A50 elongation of 5% or more. Clause 29. The method according to clause 27 or 28, wherein the structural component obtained has a yield strength of 1.000 MPa or more, specifically 1.100 - 1.300 MPa. Clause 30. The method according to any of clauses 1 - 29, further comprising transporting the component to a laser cutting station, and cutting the structural component in the laser cutting station. Clause 31. The method according to any of clauses 1 - 30, wherein the press tool and the cutting tool are integrated in the same press apparatus, the press apparatus comprising a fixed lower body, a mobile upper body, and a mechanism configured to provide upwards and downwards press progression of the mobile upper body with respect to the fixed lower body, and wherein the upper press tool die and the upper cutting tool die are connected to the moving upper body. Clause 32. The method according to clause 31, wherein an operational cycle of the press apparatus is less than 12 seconds, specifically about 10 seconds or less. Clause 33. The method according to any of clauses 1 - 32, wherein in the press tool and the cutting tool, a cooling time is 1 - 5 seconds, and a transfer time is 5 - 9 seconds. Clause 34. The method according to any of clauses 1 - 33, wherein a transfer time between the furnace and the press tool is between 1 and 3 seconds, specifically between 1,5 and 2,5 seconds. Clause 35. The method according to any of clauses 1 - 34, further comprising bake hardening the structural component obtained, wherein a temperature of bake hardening is between 170°C and 200°C, and wherein a bake hardening time is between 15 and 25 minutes. Clause 36. The method according to any of clauses 1 - 35, wherein a length of the structural component after forming is at least 1 meter, specifically 2 - 4 meters, and a width of the structural component after forming is at least 1 meter, specifically 1 - 2 meters. Clause 37. The method according to clause 36, wherein the structural component is a unitary door ring, and wherein the unitary door ring is one of a front door ring extending from hinge-pillar and A-pillar to B-pillar, a rear door ring extending from B-pillar to C-pillar or a double door ring extending from hinge-pillar and A-pillar to C-pillar. Clause 38. The method according to clause 36, wherein the structural component is a unitary roof ring, a bumper beam assembly including a bumper beam and a pedestrian beam, or a unitary reinforcement ring surrounding a battery box, or a rear framework structure including rear rails and a transverse beam as a unitary structure. Clause 39. The method according to any of clauses 1 - 38, wherein the press hardenable boron steel blank has a thickness of 0,6 mm - 4 mm, specifically 0,8 - 3, more specifically 1-2 mm, and more specifically 1 - 1.6 mm. Clause 40. The method according to any of clauses 1 - 39, wherein the press hardenable boron steel blank is made of 34MnB4, 34MnB5 steel, 37MnB5 or 37MnB4 steel. Clause 41. The method according to any of clauses 1 - 39, wherein the press hardenable boron steel blank is made of 22MnB8 steel, or 22MnSiB9-5. Clause 42. A structural component obtainable by any of the methods according to clauses 1-41. Clause 43. A production line for hot forming and press hardening a structural component comprising: a furnace configured to heat a press hardenable boron steel blank to above an Ac1 temperature, particularly to above an Ac3 temperature; a press tool arranged downstream from the furnace and configured to deform the heated blanks, and the press tool having an upper press die and a lower press die; a first transfer system to transfer blanks from the furnace to the press tool; a cutting tool arranged downstream from the press tool and configured to perform a cutting and restriking operation, and having an upper cutting tool die and a lower cutting tool die; a second transfer system to transfer blanks from the press tool to the cutting tool, wherein the furnace and / or the first transfer system and / or the press tool comprises cooling elements for actively cooling at least a selected portion of the heated blank. Clause 44. The production line of clause 43, wherein the furnace is configured for tailored tempering. Clause 45. The production line of clause 43 or 44, wherein the first transfer system is configured for tailored cooling of the selected portion of the heated blank. Clause 46. The production line of any of clauses 43 - 45, wherein the upper press die and / or the lower press die have cooling channels for conducting cooling liquid. Clause 47. The production line of clause 46, wherein the press tool comprises a plurality of die blocks. Clause 48. The production line of clause 47, wherein the press tool comprises one or more first die blocks with holes for ejecting cooling air to the selected portion of the heated blank. Clause 49. The production line of clause 47 or 48, wherein the press tool comprises one or more second die blocks configured for heating a portion of the blanks. Clause 50. The production line of clause 49, wherein the second die blocks configured for heating a portion of the blanks comprises an induction heater or a resistance heater. Clause 51. The production line of clause 49 or 50, wherein the second die blocks comprise a coating or cladding configured to retain heat. Clause 52. The production line of any of clauses 43- 51, wherein a cycle time from extracting a blank from the furnace to extracting the blank from the cutting tool is 12 seconds or less, specifically 10 seconds or less. Clause 53. The production line of any of clauses 43 - 52, wherein the press tool comprises one or more cutting element to partially cut the blanks. Clause 54. The production line of any of clauses 43 - 53, further comprising a laser cutting station arranged downstream from the cutting tool. Clause 55. The production line of any of clauses 43 - 54, wherein the first transfer system comprises a multi-axis robot with a gripper. Clause 56. The production line of any of clauses 43 - 55, wherein the press tool and the cutting tool are integrated in the same press apparatus, the press apparatus comprising a fixed lower body, a mobile upper body, and a mechanism configured to provide upwards and downwards press progression of the mobile upper body with respect to the fixed lower body, and wherein the upper press tool die and the upper cutting tool die are connected to the moving upper body. Clause 57. The production line of any of clauses 43 - 55, wherein the press tool and the cutting tool are separated press apparatus, and the second transfer system comprises a multi-axis robot with a gripper. Clause 58. The production line of any of clauses 43 - 57, further comprising a cooling tool arranged downstream from the cutting tool, and further comprising a third transfer system for transferring the blanks from the cutting tool to the cooling tool. Clause 59. The production line of any of clauses 43 - 58, wherein the press hardenable boron steel blank has a content by weight of 0.32 - 0.45%, a manganese content of 0.6 - 1.5%, and a boron content of 0.003 - 0.006%. Clause 60. The production line according to clause 59, wherein the press hardenable boron steel blank has a content by weight of 0.32 - 0.4 %, a manganese content of 0.6 - 1.4%, specifically 0.8 - 1.4% and a boron content of 0.004 - 0.005%. Clause 61. The production line according to clause 59 or 60, wherein the press hardenable boron steel blank has a content by weight of 0.3 - 0.9%, specifically 0.4 - 0.8% of silicon. Clause 62. The production line according to any of clauses 43 - 61, wherein the press hardenable boron steel blank is coated. Clause 63. The production line according to clause 62, wherein the press hardenable boron steel blank has an AlSi coating. Clause 64. The production line according to clause 63, wherein the AlSi coating further comprises magnesium. Clause 65. The production line according to clause 62, wherein the press hardenable boron steel blank has a zinc or zinc alloy coating. Clause 66. The production line of any of clauses 43 - 65, wherein the press hardenable boron steel blank has a uniform thickness. Clause 67. The production line according to any of clauses 43 - 65, wherein the press hardenable boron steel blank includes a first portion with a first thickness, and a second portion with a second thickness, wherein the second thickness is higher than the first thickness. Clause 68. The production line according to any of clauses 43 - 67, wherein the press hardenable boron steel blank is made by joining two or more sub-blanks. Clause 69. The production line according to clause 68, wherein the press hardenable boron steel blank is a Tailor Welded Blank. Clause 70. The production line according to clause 68 or 69, wherein the press hardenable boron steel blank is made by welding two or more sub-blanks which partially overlap with each other. Clause 71. The production line according to any of clauses 68 - 70, wherein the press hardenable boron steel blank is made by positioning a patch blank completely overlapping with another blank and joining the patch blank to the other blank. Clause 72. The production line according to any of clauses 68 - 71, wherein the sub-blanks are made from the same material. Clause 73. The production line according to any of clauses 43 - 71, wherein a length of the structural component after forming is at least 1 meter, specifically 2 - 4 meters, and a width of the structural component after forming is at least 1 meter, specifically 1 - 2 meters. Clause 74. The production line according to clause 73, wherein the structural component is a unitary door ring, and wherein the unitary door ring is one of a front door ring extending from hinge-pillar and A-pillar to B-pillar, a rear door ring extending from B-pillar to C-pillar or a double door ring extending from hinge-pillar and A-pillar to C-pillar. Clause 75. The production line according to clause 73, wherein the structural component is a unitary roof rings, a bumper beam assembly including a bumper beam and a pedestrian beam, or a unitary reinforcement ring surrounding a battery box, or a rear framework structure including rear rails and a transverse beam as a unitary structure. Clause 76. The production line according to any of clauses 43 - 75, wherein the press hardenable boron steel blank has a thickness of 0,6 mm -4 mm, specifically 0,8 - 3mm, more specifically 1-2 mm, and more specifically 1 - 1.6 mm Clause 77. The production line according to any of clauses 43 - 76, wherein the press hardenable boron steel blank is made of 34MnB4, 34MnB5, 37MnB5 or 37MnB4 steel. Clause 78. The production line according to any of clauses 43 - 76, wherein the press hardenable boron steel blank is made of 22MnB8 steel, or 22MnSiB9-5.

[0128] Although only a number of examples have been disclosed herein, other alternatives, modifications, uses and / or equivalents thereof are possible. Furthermore, all possible combinations of the described examples are also covered. Thus, the scope of the present disclosure should not be limited by particular examples, but should be determined only by a fair reading of the claims that follow.

Claims

1. A method for hot forming and press hardening a structural component in a production line comprising: a furnace; a press tool configured to deform blanks, and the press tool having an upper press die and a lower press die; a cutting tool arranged downstream from the press tool and configured to perform a cutting and restriking operation, and having an upper cutting tool die and a lower cutting tool die; a transfer system to transfer blanks from the furnace to the press tool and from the press tool to the cutting tool, and the method comprising: providing a press hardenable boron steel blank; heating the blank to above an austenization temperature in the furnace; actively cooling at least a selected portion of the blank; deforming and cooling the blank in the press tool; transferring the formed blank from the press tool to the cutting tool; cutting one or more areas of the formed blank and cooling the formed blank in the cutting tool, wherein a temperature of the blank before forming the blank is 600°C - 850°C, wherein a temperature of the formed blank is cooled down to 400 - 600°C in the press tool; and wherein the formed blank is cooled down to 275°C in the cutting tool.

2. The method according to claim 1, wherein the active cooling of at least the selected portion of the blank comprises active cooling in the furnace and / or active cooling of at least the selected portion of the blank comprises active cooling during a transfer from the furnace to the press tool.

3. The method according to claim 1 or 2, wherein the active cooling of at least the selected portion of the blank comprises active cooling in the press tool prior to the deforming of the blank.

4. The method according to any of claims 1-3, wherein the whole blank is heated to above an Ac3 temperature in the furnace.

5. The method according to any of claims 1 - 4, wherein the press hardenable boron steel blank has a content by weight of 0.32 - 0.45%, a manganese content of 0.6 - 1.5%, and a boron content of 0.003 - 0.006%.

6. The method according to any of claims 1-5, wherein the press hardenable boron steel blank is coated.

7. The method according to any of claims 1-6, wherein a cycle time from the moment of extracting a blank from the furnace to extracting the blank from the cutting tool is 12 seconds or less, specifically 10 seconds or less.

8. The method according to any of claims 1-7, wherein the press hardenable boron steel blank includes a first portion with a first thickness, and a second portion with a second thickness, wherein the second thickness is higher than the first thickness.

9. The method according to claim 8, wherein the second portion is more actively cooled than the first portion prior to deforming.

10. The method according to claim 8 or 9, wherein the first portion is actively heated in the press tool and / or cutting tool.

11. The method according to any of claims 1 - 10, wherein the press hardenable boron steel blank is made by joining two or more sub-blanks.

12. The method according to claim 11, wherein the press hardenable boron steel blank is a Tailor Welded Blank, or wherein the press hardenable boron steel blank is made by welding two or more sub-blanks which partially overlap with each other.

13. The method according to any of claims 1 - 12, further comprising cutting at least a portion of the press hardenable boron steel blank in the forming tool.

14. The method according to any of claims 1 - 13, further comprising later cutting the structural component in a laser cutting station.

15. A production line for hot forming and press hardening a structural component comprising: a furnace configured to heat a press hardenable boron steel blank to above an Ac1 temperature, particularly to above an Ac3 temperature; a press tool arranged downstream from the furnace and configured to deform the heated blanks, and the press tool having an upper press die and a lower press die; a first transfer system to transfer blanks from the furnace to the press tool; a cutting tool arranged downstream from the press tool and configured to perform a cutting and restriking operation, and having an upper cutting tool die and a lower cutting tool die; a second transfer system to transfer blanks from the press tool to the cutting tool, wherein the furnace and / or the first transfer system and / or the press tool comprises cooling elements for actively cooling at least a selected portion of the heated blank.

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