阅读说明：本技术 热成形材料，组件以及用途 (Thermoformed material, component and use ) 是由 延斯-乌尔里克·贝克尔 斯特凡·米斯洛维奇 于 2017-05-16 设计创作，主要内容包括：本发明涉及由三层材料复合物组成的热成形材料,包括一个由可淬火钢组成的核心层和两个材料配合地与该核心层连接的、由软性钢组成的覆盖层,且一层或双层地配有腐蚀保护涂层,尤其基于铝的涂层,所述可淬火钢在加压淬火状态下具有抗拉强度>1600MPa和/或硬度>490HV10,尤其抗拉强度>1700MPa和/或硬度>520HV10,所述软性钢的抗拉强度最高对应于所述核心层在加压淬火状态下的抗拉强度的四分之一。本发明还涉及组件以及对应的用途。(The invention relates to a hot-formed material consisting of a three-layer material composite, comprising a core layer consisting of a hardenable steel having a tensile strength of >1600MPa and/or a hardness of >490HV10, in particular a tensile strength of >1700MPa and/or a hardness of >520HV10 in the press-hardened state, and two cover layers consisting of soft steel, which are connected to the core layer in a material-fit manner and are provided with a corrosion-protective coating, in particular an aluminum-based coating, in one or two layers, wherein the tensile strength of the soft steel corresponds at most to one quarter of the tensile strength of the core layer in the press-hardened state. The invention also relates to an assembly and a corresponding use.)

1. A hot-forming material consisting of a three-layer material composite, comprising a core layer consisting of a hardenable steel having a tensile strength of >1600MPa and/or a hardness of >490HV10, in particular a tensile strength of >1700MPa and/or a hardness of >520HV10 in the press-hardened state, and two cover layers consisting of a soft steel, which are joined together in a material-fit manner to the core layer and are provided in one or two layers with a corrosion-protective coating, in particular an aluminum-based coating, the tensile strength of the soft steel corresponding at most to one quarter of the tensile strength of the core layer in the press-hardened state.

2. A hot-formed material according to claim 1, characterized in that the core layer consists of, in weight%, in addition to Fe and unavoidable impurities under production conditions:

C：0.27–0.8％，

si: up to 0.5% by weight,

mn: up to 2.0% by weight,

p: to the high extent of 0.06%,

s: to the maximum of 0.05 percent,

al: to the maximum of 0.2 percent,

cr + Mo: up to 1.0% by weight,

cu: to the maximum of 0.2 percent,

n: up to 0.01% by weight,

nb + Ti: to the maximum of 0.2 percent,

ni: up to 0.5% by weight,

v: to the maximum of 0.2 percent,

b: up to 0.01% by weight,

as: to the high extent of 0.02%,

ca: up to 0.01% by weight,

co: to the high extent of 0.02%,

sn: up to 0.05%.

3. A hot-formed material according to claim 1 or 2, characterized in that the covering layer consists, in weight%, in addition to Fe and inevitable impurities under production conditions, of:

c: to the high extent of 0.06%,

si: up to 0.6% by weight,

mn: up to 1.0% by weight,

p: to the maximum of 0.1 percent,

s: to the high extent of 0.06%,

al: to the maximum of 0.2 percent,

cr + Mo: up to 0.5% by weight,

cu: up to 0.3% by weight,

n: up to 0.01% by weight,

ni: up to 0.3% by weight,

nb + Ti: to the maximum of 0.25 percent,

v: to the maximum of 0.05 percent,

b: up to 0.01% by weight,

sn: to the maximum of 0.05 percent,

ca: up to 0.01% by weight,

co: up to 0.02%.

4. A thermoformed material according to any of the preceding claims, characterized in that the core layer has a C content of between 0.30-0.75 wt. -%, in particular between 0.35-0.68 wt. -%, preferably between 0.43-0.65 wt. -%, more preferably between 0.48-0.62 wt. -%, particularly preferably between 0.51-0.60 wt. -%.

5. A thermoformed material according to any of the preceding claims, characterized in that each cover layer has a material thickness of between 0.5% and 20%, in particular between 1% and 10%, based on the total material thickness of the thermoformed material.

6. A thermoformed material according to any of the preceding claims, characterized in that said material composite is manufactured by cladding or by casting.

7. A thermoformed material according to any of the preceding claims characterized in that the ratio of the C content of the core layer to the C content of the cover layer is >4, in particular >5, preferably >6, particularly preferably > 7.

8. The hot formed material according to any of the preceding claims, wherein the hot formed material satisfies the following relation in terms of a difference in bending angle (Δ BW) in a state with and without a corrosion protective coating, determined according to VDA238-100 in a three-point bending test:

Δ BW <17 °. F,. whereinAs a dimensionless strength relationship.

9. A hot-formed material according to any of the preceding claims, characterized in that the hot-formed material is a part of a customized product, in particular a part of a customized welded blank and/or a customized rolled blank.

10. A component manufactured by press quenching from a hot formed material according to any of the preceding claims.

11. Use of an assembly according to claim 10 in the body or chassis of a land-based vehicle.

Technical Field

The invention relates to a thermoformed material consisting of a three-layer material composite.

Background

New solutions to reduce the weight of vehicles and thus at the same time reduce fuel consumption are sought in the automotive industry. Where a lightweight construction is an important element to enable a reduction in vehicle weight.

This may additionally be achieved by using materials with increased strength. As the strength increases, generally its ability to bend decreases. In order to achieve not only increased strength of the lightweight construction but also to ensure the necessary occupant protection of the crash-relevant components, it is ensured that the materials used can convert the energy introduced by the crash by deformation. This is subject to a high level of deformability, in particular in crash-related components of the vehicle structure. One possibility to save weight is to design or construct the body and/or chassis of the land-based vehicle (Fahrwerk) even more lightweight, for example by means of innovative materials compared to conventionally used materials. This may replace the component-specific conventional material, for example by a material with a thinner wall thickness, having optimized properties. For example, a hot-formed steel, in particular a manganese boron steel, such as a 22MnB5 steel, is used, which in the press-quenched state has a tensile strength of about 1500MPa and a yield limit of about 1100 MPa. The potential is not far exhausted in terms of strength increase, so that the possibility exists that the tensile strength can be brought or adjusted up to 1900MPa and more by corresponding alloy design, or alternatively or additionally by optimizing the manufacturing route. Usually the hot formed steel is provided with a metallic coating based on zinc or aluminium for subsequent use or its working. With this as a condition, the properties (e.g., ductility) of the steel material in a state of press-quenching and forming for components may be negatively changed as compared with an uncoated steel material in a press-quenched state. The achievable lightweight construction potential is thereby reduced, since for example the loss of ductility must be compensated by a less pronounced reduction in material thickness in order to ensure a safe component behavior in the event of a crash as before.

In hot forming, a conventionally cut steel slab is heated to an austenitizing temperature so that it is subsequently hot formed and cooled simultaneously in a cooled mold. By intensive cooling, with a cooling rate of at least 27K/s being necessary for 22MnB5, for example, the structure is completely transformed from austenite to martensite, and the material to be worked into the component acquires its desired high strength in the press-quenched state. This method is also known in the art as the press quenching concept. The steels used here are usually provided with an aluminum-based coating, for example an AlSi coating, in order to avoid undesirable scale formation (Zunderbi ldung) when the steel sheet is heated to austenitizing temperature. This makes it possible that the assembly does not have to be freed of adhering scale, for example by spraying, for subsequent mounting on the vehicle structure (for example by resistance spot welding) and for adequate paint adhesion. In addition, the AlSi coating contributes to the protection of the component against corrosion under the conditions of use by means of a barrier action.

When heating a steel sheet to austenitizing temperature, two conditions are considered for the choice of, for example, the residence time of the steel sheet in the furnace. One of these must ensure complete penetration of the steel sheet and, on the other hand, complete and complete alloying of the AlSi coating.

The steel designed for hot forming has an alloy design based on carbon, manganese and boron. MBW1500 and MBW1900, offered under the applicant's trademark, reach tensile strengths of about 1500 or 1900MPa in the press quenched state. After press quenching, there is a residual difference in ductility between the uncoated and AlSi coated materials for both materials. Which can be demonstrated, for example, in a sheet bending test according to VDA238-100, in which the bending angle of the AlSi-coated material is reduced relative to the uncoated material. This is because less decarburization of the steel edge of the uncoated material can occur during the press quenching process. After cooling in the forming tool, therefore, in this decarburized edge layer, a lower hardness is provided locally than in the interior non-decarburized regions of the material, wherein a martensite or even bainite structure of lower hardness can be formed. The two structural shapes have a relatively higher residual ductility compared to martensite in the inner non-decarburized region, which has a smaller susceptibility to initial crack formation under bending load. This edge decarburization process does not occur, in particular in AlSi-coated materials, by the presence of the coating, so that the edge layer of the steel has a relatively higher susceptibility to cracking.

The difference in ductility between the uncoated and coated state (as manifested by the achievable bend angle) increases with increasing overall strength of the hot formed material. In addition to the basic tendency of ductility to decrease substantially with increasing strength, a state can be reached in which the hot-formed material only obtains mechanical property features favorable for light construction in the uncoated state.

Disclosure of Invention

The aim of the invention is to provide a hot-forming material which can be produced as a corrosion-protected, very high-strength component with a crack-insensitive edge layer.

This object is achieved by a hot-forming material having the features of claim 1.

In order to be able to use the lightweight construction potential of very high-strength hot-formed materials, in particular without having to take into account subsequent additional measures, such as spraying for scale removal, and to provide a certain barrier effect in terms of corrosion, it is proposed according to the invention to provide a hot-formed material consisting of a three-layer material composite comprising a core layer consisting of a quenchable steel having a tensile strength >1600MPa and/or a hardness >490HV10, in particular a tensile strength >1700MPa and/or a hardness >520HV10, preferably a tensile strength >1800MPa and/or a hardness >550HV10, more preferably a tensile strength >1900MPa and/or a hardness > HV 575HV10, even more preferably a tensile strength >2000MPa and/or a hardness >600HV10, even more preferably a tensile strength >2100MPa and/or a hardness >630HV10 in the press-quenched state, more preferably a tensile strength of >2200MPa and/or a hardness of >660HV10, especially a tensile strength of >2300MPa and/or a hardness of >685HV10, the tensile strength of the soft steel corresponding up to a quarter of the tensile strength of the core layer in the press-quenched state. The thermoformed material according to the invention is provided on one or both sides with a corrosion-protective coating, in particular an aluminum-based coating. Both cover layers are used only as surface-adjacent regions of the material composite to provide a crack-insensitive edge layer similar to edge decarburization, which compensates for the difference in bending angle between materials known from the overall very high-strength hot-formed steel (Rm >1600MPa), which are not coated and which are provided with a corrosion-protective coating, in particular an aluminum-based coating.

In the sense of the invention, the mild steel has a tensile strength of <600MPa and/or a hardness of <190HV10, in particular a tensile strength of <550MPa and/or a hardness of <175HV10, preferably a tensile strength of <450MPa and/or a hardness of <140HV10, particularly preferably a tensile strength of <380MPa and/or a hardness of <120HV 10. The soft steel has properties that are particularly positive for coating and/or deformability.

HV corresponds to Vickers hardness and is measured according to DIN EN ISO 6507-1: 2005 to-4: 2005.

The hot formed material according to the invention can thus be integrated in existing hot forming standard processes without having to make changes in the process chain. The coating tendency (Beschichtungsneigung) and/or deformability is determined to a large extent by the properties of the surface of the material composite, which surface is provided according to the invention by the cover layer as a similar functional layer.

The thermoformed material can be made in web, sheet or sheet form or provided in a subsequent process step.

According to a first embodiment of the hot-forming material, the core layer consists of the following, in weight%, in addition to Fe and unavoidable impurities under the production conditions:

C：0.27–0.8％，

si: up to 0.5% by weight,

mn: up to 2.0% by weight,

p: to the high extent of 0.06%,

s: to the maximum of 0.05 percent,

al: to the maximum of 0.2 percent,

cr + Mo: up to 1.0% by weight,

cu: to the maximum of 0.2 percent,

n: up to 0.01% by weight,

nb + Ti: to the maximum of 0.2 percent,

ni: up to 0.5% by weight,

v: to the maximum of 0.2 percent,

b: up to 0.01% by weight,

as: to the high extent of 0.02%,

ca: up to 0.01% by weight,

co: to the high extent of 0.02%,

sn: to the maximum of 0.05 percent,

c is an alloying element which increases the strength and contributes to the increase in strength with increasing content, so that a content of at least 0.27 wt.%, in particular at least 0.30 wt.%, preferably at least 0.35 wt.%, more preferably at least 0.43 wt.%, more preferably at least 0.48 wt.%, particularly preferably at least 0.51 wt.% is present in order to achieve or set the desired strength. Brittleness also increases with increasing strength, so that the content is limited to a maximum of 0.8 wt.%, in particular a maximum of 0.75 wt.%, preferably a maximum of 0.68 wt.%, more preferably a maximum of 0.65 wt.%, more preferably a maximum of 0.62 wt.%, particularly preferably a maximum of 0.60 wt.%, in order not to adversely affect the material properties and to ensure sufficient weldability.

Si is an alloying element which can contribute to the mixed crystal quenching and can actively contribute to the strength increase depending on the content, so that a content of at least 0.05 wt.% can be present. The alloying elements are limited to a maximum of 0.5 wt.%, in particular a maximum of 0.45 wt.%, preferably a maximum of 0.4 wt.%, in order to ensure sufficient rollability.

Mn is an alloying element which contributes to hardenability and can positively contribute to tensile strength, in particular for binding S to MnS, so that a content of at least 0.3 wt.% can be present. The alloying elements are limited to a maximum of 2.0 wt.%, in particular a maximum of 1.7 wt.%, preferably a maximum of 1.5 wt.%, in order to ensure sufficient weldability.

Al as an alloying element can contribute to the deoxidation, wherein a content of at least 0.01 wt.%, in particular 0.015 wt.%, can be present. The alloying elements are limited to a maximum of 0.2 wt.%, in particular a maximum of 0.15 wt.%, preferably a maximum of 0.1 wt.%, in order to substantially reduce and/or avoid precipitation in the material (in particular in the form of non-metallic oxide inclusions) which may negatively affect the material properties. The content may be set, for example, between 0.02 and 0.06 wt%.

Cr as an alloying element can also contribute to the adjustment of the strength, in particular positively to the quenchability, depending on the content, in particular at least 0.05 wt.%. The alloying elements are limited to a maximum of 0.8 wt.%, in particular a maximum of 0.6 wt.%, preferably a maximum of 0.4 wt.%, in order to ensure sufficient weldability.

B as an alloying element may contribute to quenchability (especially when incorporating N) and may be present in an amount of at least 0.0008 wt%. The alloying element is limited to a maximum of 0.01 wt.%, in particular to a maximum of 0.008 wt.%, since higher contents adversely affect the material properties and will lead to a reduction in the hardness and/or strength of the material.

Ti and Nb as alloying elements may be added to the alloy alone or in combination for grain refinement (Kornfeinung) and/or N bonding, especially when Ti is present in a content of at least 0.005 wt%. For complete binding of N, Ti will be provided in a content of at least 3.42 × N. The alloying elements are limited to a maximum of 0.2 wt.%, in particular a maximum of 0.15 wt.%, preferably a maximum of 0.1 wt.%, in combination, since higher contents adversely affect the material properties, in particular the toughness of the material.

Mo, V, Cu, Ni, Sn, Ca, Co, As, N, P or S are alloying elements, and when they are alloyed without setting the purpose of specific properties, they may be calculated As impurities alone or in combination. The content is limited to maximum 0.2 wt% Mo, maximum 0.2 wt% V, maximum 0.2 wt% Cu, maximum 0.5 wt% Ni, maximum 0.05 wt% Sn, maximum 0.01 wt% Ca, maximum 0.02 wt% Co, maximum 0.02 wt% As, maximum 0.01 wt% N, maximum 0.06 wt% P, maximum 0.05 wt% S.

Under the aluminum-based coating, the cover layer, due to its chemical composition, assumes the role of edge decarburization, wherein it forms a layer in the material composite which is less crack-sensitive than the core layer under the applied coating in the press-hardened state. The coating consists, in addition to Fe and unavoidable impurities under the production conditions, in% by weight:

c: to the high extent of 0.06%,

si: up to 0.6% by weight,

mn: up to 1.0% by weight,

p: to the maximum of 0.1 percent,

s: to the high extent of 0.06%,

al: to the maximum of 0.2 percent,

cr + Mo: up to 0.5% by weight,

cu: up to 0.3% by weight,

n: up to 0.01% by weight,

ni: up to 0.3% by weight,

nb + Ti: to the maximum of 0.25 percent,

v: to the maximum of 0.05 percent,

b: up to 0.01% by weight,

sn: to the maximum of 0.05 percent,

ca: up to 0.01% by weight,

co: up to 0.02%.

In order to increase the deformability and/or coatability, C is limited to a maximum of 0.06 wt.%, in particular a maximum of 0.05 wt.%, preferably a maximum of 0.035 wt.%, as alloying element, wherein C is present in a minimum of 0.001 wt.%.

Si is an alloying element that can contribute to the quenching of the mixed crystal and actively contributes to the strength improvement, so that a content of at least 0.01 wt.% may be present. The alloying elements are limited to a maximum of 0.6 wt.%, in particular a maximum of 0.5 wt.%, preferably a maximum of 0.4 wt.%, in order to ensure sufficient rollability and/or surface quality.

Mn is an alloying element which can contribute to quenchability and positively acts on tensile strength, in particular for binding S to MnS, so that a content of at least 0.1 wt.% can be present. The alloying elements are limited to a maximum of 1.0 wt.%, in particular a maximum of 0.95 wt.%, preferably a maximum of 0.9 wt.%, in order to ensure sufficient weldability.

Al as an alloying element can contribute to the deoxidation, wherein a content of at least 0.001 wt.%, in particular 0.0015 wt.%, can be present. Al is limited to a maximum of 0.2 wt.%, in particular a maximum of 0.15 wt.%, preferably a maximum of 0.1 wt.%, in order to substantially reduce and/or avoid precipitation in the material (in particular in the form of non-metallic oxide inclusions) which may negatively affect the material properties.

Cr as an alloying element can also contribute to the strength adjustment depending on the content and can be present in particular in a content of at least 0.01% by weight. Cr is limited to a maximum of 0.35 wt.%, in particular a maximum of 0.3 wt.%, preferably a maximum of 0.25 wt.%, in order to be able to ensure substantially complete coatability of the surface.

B as an alloying element may contribute to quenchability (especially when N is incorporated) and may especially be present in an amount of at least 0.0002 wt%. The alloying element is limited to a maximum of 0.01 wt.%, in particular a maximum of 0.005 wt.%, since higher contents adversely affect the material properties and will lead to a reduction in hardness and/or strength in the material.

Ti and Nb as alloying elements may be added to the alloy alone or in combination for grain refinement and/or N-bonding, in particular in a content of at least 0.001 wt% Ti and/or at least 0.001 wt% Nb. For complete binding of N, Ti will be provided in a content of at least 3.42 × N. The alloying elements are limited to a maximum of 0.25 wt.%, in particular a maximum of 0.2 wt.%, preferably a maximum of 0.15 wt.%, in combination, since higher contents adversely affect the material properties, in particular the toughness of the material.

Mo, V, Cu, Ni, Sn, Ca, Co, N, P or S are alloying elements, and when they are alloyed without setting the purpose of specific properties, they may be counted alone or in combination as impurities. The content is limited to maximum 0.15 wt% Mo, maximum 0.05 wt% V, maximum 0.3 wt% Cu, maximum 0.3 wt% Ni, maximum 0.05 wt% Sn, maximum 0.01 wt% Ca, maximum 0.02 wt% Co, maximum 0.01 wt% N, maximum 0.1 wt% P, maximum 0.06 wt% S.

According to a further embodiment of the thermoformed material, the cover layers each have a material thickness of between 0.5% and 20%, in particular between 1% and 10%, relative to the total material thickness of the thermoformed material. The cover layer should be dimensioned in terms of its material thickness such that the positive properties of the core layer are not significantly adversely affected, wherein the material thickness of the cover layer (per side) is limited to a maximum of 20%, in particular a maximum of 15%, preferably a maximum of 10%, particularly preferably a maximum of 4%, relative to the total material thickness of the thermoformed material, in order to ensure a lightweight construction potential resulting from this strength level, wherein it is intended to keep the material composite (total) strength as close as possible to the level of this extremely high-strength core material as a single piece of material. Furthermore, the core layer has a distance to the surface of the hot-formed material such that a layer which is less susceptible to cracks than the core layer can be provided, wherein the material thickness (per side) of the cover layer is at least 0.5%, in particular at least 1%, preferably at least 2%, relative to the total material thickness of the hot-formed material. The thermoformed material or the three-layer material composite has a total material thickness of between 0.6 and 8.0mm, in particular between 1.2 and 5.0mm and preferably between 1.5 and 4.0 mm.

According to a further embodiment of the hot-formed material, the material composite is produced by cladding, in particular by rolling, preferably hot-rolling, or by casting. The hot-formed material according to the invention is preferably manufactured by hot rolling a clad layer, as disclosed in e.g. german patent DE102005006606B 3. Reference is made to this patent and the contents thereof are hereby incorporated into the present application. Alternatively, the thermoformed material according to the invention can be manufactured by casting, and one possibility of its manufacture is disclosed in Japanese publication JP-A03133630. The manufacture of metal material composites is generally known from the prior art.

Due to the thermal loading, C diffusion in the direction from the core layer to the cladding layer occurs, for example during the production of the material composite, preferably during hot-rolling of the cladding layer and during press-quenching. The thinner the overlay, the more carburized can come out of the core to the surface of the hot formed material and result in an increase in the bend angle step. In order to keep the difference between the state with and without the corrosion protection coating as small as possible, according to a further embodiment of the hot-forming material, the C content of the core layer: the proportion of the C content of the cover layer is >4, in particular >5, preferably >6, in particular preferably >7, more preferably >8, in order to be able to achieve a smaller drop in the (overall) strength of the thermoformed material.

According to a further embodiment of the hot-formed material, the difference in bending angle (Δ BW), measured in a three-point bending test according to VDA238-100, with and without a corrosion protection coating, for which purpose the hot-formed material satisfies the following relationship.

To calculate the dimensionless strength relationship F, the tensile strength of the core layer in the three-layer thermoformed material was compared with that of a single-piece thermoformed steel (corresponding to the conventionally used 22MnB5 steel having a tensile strength of 1500 Mpa) used as a reference. The difference in bend angle of the target area of the thermally deformable material falls below 17 ° F in °. If the bending angle difference falls above 17 ° F, this means that the thermoformed material with the corrosion protection coating is too brittle compared to the unprotected material and thus does not offer a sufficient, economical, lightweight construction potential.

According to a second aspect, the invention relates to an assembly manufactured by press quenching from a hot-formed material according to the invention, in particular for manufacturing components for automotive construction, railway/ship construction or for aeronautics and astronautics. The formation of a crack insensitive layer by the cladding layer compared to the core layer enables an assembly provided with an aluminum based coating to have an improved bending angle compared to a single piece of thermoformed steel having the same alloy composition as the core layer of the thermoformed material according to the invention.

According to a third aspect, the invention relates to the use of an assembly made of a thermoformed material according to the invention in a body or chassis of a land-based vehicle. In this case, it is preferably a passenger motor vehicle, a commercial vehicle or a bus, which is a vehicle with an internal combustion engine, a purely electric drive or a hybrid drive. The assembly can be used as a longitudinal or transverse beam or column in land-based vehicles, for example, it is designed as a profile, in particular as a crash profile in bumpers, sills, side impact beams or areas requiring little deformation/intrusion in the event of a crash.

Drawings

The invention is further illustrated by the figures and examples which follow.

FIG. 1 shows the results of the sheet bending test on various samples according to VDA 238-100.

Detailed Description

Hot-formed materials with a three-layer material composite are produced from commercially available flat steel products by hot-rolling the cladding. The steels given in Table 1 were used as cladding layers D1-D3, and the steels given in Table 2 were used as core layers K1-K6. The tensile strengths listed in tables 1 and 2 are in the press-quenched state. A total of 24 different thermoformable materials (I-1 to IV-6) were arranged, see Table 3. Of the 18 of the thermoformed materials (I-1 to III-6), the individual cover layers have a material thickness of 10% per side, based on the total material thickness of the thermoformed material, while in the thermoformed materials (IV-1 to IV-6), the material thickness of the cover layers amounts to only 5% per side, based on the total material thickness of the thermoformed material.

In which two cover layers and a core layer arranged therebetween are stacked on top of one another to form individual sheet blanks (Blechzuschnitte), wherein the cover layers are joined to one another at least regionally along their edges in a material-fit manner, preferably by welding, to form a pre-composite (vorverbond). The pre-composite is brought to a temperature >1200 ℃ and hot rolled in several steps to a material composite with a total thickness of 3mm and further processed to a cold strip with a thickness of 1.5 mm. The material composite or the hot-forming material is coated on both sides with an aluminum-based coating (AlSi coating each having a layer thickness of 20 μm). The layer thickness may be between 5 and 30 μm.

The produced hot-formed materials (I-1 to IV-6) were divided into slabs. In addition to the hot-formed material, six AlSi-coated steels and six uncoated steels (corresponding to the compositions in table 2) were provided as controls, i.e. a core layer with a thickness of 1.5mm without a covering layer. Heating the flat blank and the coated and uncoated single piece steel to an austenitizing temperature, in particular above A_C3(with respect to the core layer) were each heated in an oven for about 6 minutes and thoroughly heated and then each thermoformed into the same assembly in a cooled mold and cooled. A cooling rate of>30K/s. The entire thickness of the core layer is substantially entirely composed of martensite, wherein the transition region to the cover layer may additionally contain ferrite and/or bainite portions. In the cover layer, a hybrid structure is provided, which has the following components: ferrite, bainite, and partial martensite.

Samples were cut from the press quenched assembly, which were subjected to a sheet bending test according to VDA 238-100. The results are collated in FIG. 1. FIG. 1 shows a graph in which the total tensile strength in [ MPa ] is recorded on the x-axis and the difference in bend angle in [ ° ] is recorded on the y-axis relative to the uncoated sample. It is evident that the press quenched sample of a single piece coated with an aluminum-based coating (AlSi) consisting of the core material shows the greatest difference in bending angle while at the same time having increased strength compared to the uncoated control. The values of the press quenched samples consisting of the hot formed material according to the invention are uniformly located below the single press quenched sample consisting of the core material. Embodiments I-1 to I-6 have too high a difference in bending angle that is too similar to the single-piece thermoformed material likewise displayed, since the cover layers of embodiments I-1 to I-6 have a C content > of 0.07% by weight. Due to the thermal load, C diffusion in the direction from the core layer to the cover layer occurs here and reduces the effect of the soft cover layer. In embodiments II-1 and IV-6, however, the C content of the coating is less than in embodiments I-1 to I-6, so that there is a higher probability of carburization in a buffering sense. Thereby creating a smaller difference in bending angle. The C content of the cover layer is at most 0.06 wt.%, in particular at most 0.05 wt.%. The thermoformed material according to the invention (see the region according to the invention in fig. 1) is distinguished from the embodiments not according to the invention by the following relationship.

The invention is not limited to the examples shown and the embodiments outlined. Conversely, a hot formed material according to the present invention may also be a part of a customized product, for example as a part of a customized welded blank and/or a customized rolled blank.

	C	Si	Mn	P	S	Al	Cr	Nb	Ti	B	Rm(Mpa)
												D3	0.003	0.02	0.13	0.01	0.012	0.325	0.05	0.005	0.007	0.0004	305
D2	0.0375	0.04	0.25	0.015	0.015	0.04	0.06	0.004	0.004	0.0006	319
												D1	0.07	0.205	0.8	0.02	0.006	0.04	0.075	0.02	0.004		458

TABLE 1

	C	Si	Mn	P	S	Al	Cr	Ni	Nb	Ti	V	B	Ca	Rm(Mpa)
															K1	0.35	0.25	1.3	0.01	0.0015	0.035	0.14		0.0015	0.0325		0.0028		1911
K2	0.42	0.225	1.3	0.02	0.003	0.035	0.35		0.003	0.0275		0.003	0.0013	2093
															K3	0.45	0.07	0.62	0.01	0.004	0.04	0.22		0.002	0.026		0.003		2304
K4	0.48	0.22	1.2	0.01	0.002	0.035	0.24		0.002	0.03		0.0032	0.002	2400
															K5	0.53	0.23	1.19	0.01	0.003	0.03	0.58	0.2	0.002	0.025	0.02	0.003		2518
K6	0.61	0.39	1.6	0.01	0.003	0.04	0.73		0.0025	0.03		0.0035	0.002	2731

TABLE 2

TABLE 3