DE102020211426A1 - Process for the production of a hot-formed and press-hardened sheet steel part - Google Patents

Abstract

The invention relates to a method for producing a hot-formed and press-hardened sheet steel part (1), which has at least one material-thick sheet metal area (7) with locally increased sheet thickness (s1) and at least one material-thin sheet metal area (9) with locally reduced sheet thickness (s2), which method has the following process steps: a heat treatment step (ΔtW), in which a still unhardened blank (19) is heated to above the material-specific austenitization temperature (Ac3); an insertion step (te), in which the blank (19) is inserted into a forming tool (13) in the hot state, the material-thick sheet metal area (7) and the material-thin sheet metal area (9) each having a local insertion temperature (ϑe1, ϑe2); a press-hardening step (ΔtP), in which the blank (19) placed in the forming tool (13) is hot-formed and press-hardened, to be precise with the formation of the steel sheet part (1), the material-thick sheet metal area (7) and the material-thin sheet metal area (9) each have a local extraction temperature (ϑa1, ϑe2); and a removal step in which the steel sheet part (1) is removed from the forming tool (13). According to the invention, a pre-cooling step takes place between the heat treatment step (ΔtW) and the press hardening step (ΔtP), in which the material-thick sheet metal area (7) is locally cooled down to a local insertion temperature (ϑe1), whereby a temperature offset (ΔTE) between the local insertion temperature (ϑe1) of the material-thick sheet metal area (7) and the local insertion temperature (ϑe2) of the material-thin sheet metal area (9) is reduced, compared to hot forming without pre-cooling.

Description

The invention relates to a method for producing a hot-formed and press-hardened sheet steel part according to the preamble of claim 1, a process arrangement according to claim 10 and a sheet steel part according to claim 11.

A generic hot-formed and press-hardened sheet steel part has a carrier board with at least one patch board fixed thereon, which acts as a local component reinforcement. In the prior art, such a patch-reinforced sheet steel part is produced in a process sequence in which a carrier board pre-material and a patch board pre-material are coated on both sides with anti-scale layers in a coating process step. In a subsequent board cut, the carrier board and the patch board are cut to size. This is followed by a joining process step in which the patch board is joined to the carrier board in the cold, unhardened state, for example by spot welding. In a subsequent heat treatment process step, the composite component consisting of the carrier board and patch board fixed on it is heated to above the material-specific austenitization temperature, for example in a roller hearth furnace. The heat-treated composite component is placed in a tool cavity between tool parts of a forming tool in the hot state. There, a press hardening step takes place to form the sheet steel part.

The locally increased sheet thickness in the patch area (hereinafter generally referred to as the material-thick sheet area) of the formed sheet steel part inevitably leads to an inhomogeneous removal temperature from the forming tool, since a thicker blank area cools down significantly more slowly (or more volume energy has to be dissipated in the form of heat) than a thinner carrier blank area (hereinafter generally referred to as the material-thick sheet metal area). An inhomogeneous extraction temperature can cause temperature-related residual stresses in the formed sheet steel part. The patch board literally distorts the sheet steel part, which leads to positioning inaccuracies on the laser mount downstream of the hot forming tool. In addition, manufacturing and component tolerances cannot be reliably maintained. An increased holding time of the forming tool in order to bring thick component areas to the removal temperature also leads to geometric distortions, since the carrier board is also brought significantly below the removal temperature as a result of the full-form formation of the punch and die. A process-reliable production of dimensionally stable hot-formed components with reinforced areas may not be possible without further ado, depending on the component construction/design. In this context, particular mention should be made of large jumps in thickness as well as high component complexity and susceptibility to torsion. In particular, long, narrow and thin components are very susceptible.

In the prior art, the closing time in the forming tool can be increased in order to reduce component distortion. However, this is disadvantageous for reasons of efficiency. In addition, the component complexity or construction can be restricted. Here, however, disadvantages in component performance (lightweight construction, rigidity, crash resistance, energy absorption) must be made. In addition, thermal component distortion can be compensated to a certain extent. However, the compensation of the formed sheet steel part is a relatively error-prone process and is subject to a large number of variables.

From the U.S. 2004/0060623 A1 a method for the production of sheet steel parts of different ductility is known. From the US 2013/0312474 A a forming tool is known in which induction heating is used. From the DE 10 2009 051 822 B3 a method and a device for the production of shaped sheet metal parts is known.

The object of the invention is to provide a method for producing a hot-formed and press-hardened sheet steel part in which component distortion after removal from the forming tool is reduced in a simple manner in terms of process technology compared to the prior art.

The object is achieved by the features of claim 1, claim 10 and claim 11. Preferred developments of the invention are disclosed in the dependent claims.

According to the characterizing part of claim 1, a pre-cooling step takes place between the heat treatment step and the press-hardening step. During the pre-cooling step, the material-thick sheet metal area is cooled down to a local storage temperature. As a result, a temperature offset between the local insertion temperature of the material-thick sheet metal area and the local insertion temperature of the material-thin sheet metal area is reduced in comparison to hot forming without pre-cooling.

Depending on the jump in sheet thickness, the area of the board with increased sheet thickness can have a comparable temperature to the temperature of the thinner area of the board. Compared to the Warm according to the invention, the temperature offset between the areas of the blank is smaller if the blank is not pre-cooled.

An example is described below in order to illustrate the facts according to the invention: Thus, without pre-cooling, the blank can have a homogeneous temperature of 950° C. after hot forming. When placed in the tool, the thin blank area can have a temperature of 750°C and the thick blank area can have a temperature of 850°C.

The following situation arises with the pre-cooling according to the invention. After hot forming, the blank can have a homogeneous temperature of 950°C. When placed in the tool, the thin blank area can have a temperature of 730°C and the thick blank area can have a temperature of 750°C. This is a possible scenario where the temperature of the thick area of the board is still higher than the temperature of the thin area of the board.

In an optional process control, the pre-cooling step is designed as follows: In the pre-cooling step, the thick-material sheet metal area can be cooled down to a local insertion temperature that is lower than the local insertion temperature of the thin-material sheet area. The insertion temperature of the material-thick sheet metal area has cooled down to such a temperature level that the local extraction temperatures of the material-thin and material-thick sheet metal areas of the formed steel sheet adjust to one another. The ideal case would be that the withdrawal temperatures are identical. However, this cannot be reliably guaranteed for process-related reasons. Both the insertion temperature of the material-thick sheet metal area and the insertion temperature of the material-thin sheet metal area of the blank are preferably above a martensite start temperature in order to enable press hardening of both sheet metal areas.

It should be emphasized that the description of the invention only refers to patch boards as an example. The explanations also apply analogously to TWB/TRB or otherwise produced graded sheet thicknesses.

The invention envisages the process described below: First, a conventional blank production takes place in hot forming (either tool cutting or laser). Here, 22MnBS with an AISi anti-scale protection (AS60/60), which has proven itself in large series, is preferably used. Graduated sheet thicknesses can then be achieved with the following processes/technologies: Tailored Rolled Blank boards, Tailored Welded Blank boards and/or patch boards (it is irrelevant here how the form fit between the patch board and the carrier board takes place). The heating can be carried out conventionally in a roller hearth furnace. Instead, other methods can also be used (cf. induction, conduction, contact, NIR, etc.). After reaching the heating temperature (and the end of the diffusion time), the blanks are conveyed out of the oven. Here, the blanks are conveyed out on a relatively long (approx. 3 m) centering table in rapid traverse.

The invention relates to the following situation: Nozzles are attached to the centering table in the end position of the patch board (e.g. between the outfeed rollers), which pre-cool the patch board by means of convection during the release time of the feeder device (robot, linear feeder, etc.) (the nozzles can already cool before reaching the end position or before centering). In particular, there are several nozzles in the patch area (i.e. sheet metal area with a thick material) as well as in adjacent molded blank areas (i.e. sheet metal area with a thick material) in order to minimize the temperature gradient, which leads to unwanted heat conduction in the patch area. The nozzles can be charged with compressed air, among other things. This leads to local component cooling in the partially reinforced area of the blank (hereinafter referred to as the thicker sheet metal area). Accordingly, less heat has to be dissipated in this area within the tool and the amount of heat in the thin and thick area approaches significantly. The temperature reached after pre-cooling in the patch area should not fall below the martensite start temperature in order to be able to continue to guarantee good formability in the subsequent forming step.

In addition (and/or on their own), air nozzles can be attached to the feeder unit or feeder spider, which cool the component or the separate component area from above. Depending on the transfer time, between 5 and 10 seconds of increased convection cooling are possible.

The circuit board is inserted with a partially pre-cooled patch area (i.e. sheet metal area thick with material). A local insertion temperature should be achieved at which the volumetric amount of heat Qpatch area (volume of patch area*temperature or thermal energy) in the sheet metal area thick with material is as equal as possible to the volumetric amount of heat in the carrier area Qcarrier board (i.e. in the sheet metal area with thin material).

This is followed by conventional hot forming or press hardening of the blank to a removal temperature of <290°C. Here is im Compared to conventional solutions, the gradient between the patch board and the carrier board is reduced - due to the upstream reduction in the amount of heat.

All other process steps correspond to the state of the art (heat trimming, laser trimming, hard trimming, removal of waste from the tool, punching in the tool, different storage of the semi-finished parts on scaffolding or in boxes, etc.).

Aspects of the invention are highlighted again in detail below: In a technical implementation, the heat treatment step can take place in a heat treatment device. This can be implemented, for example, as an induction heating system, as a roller hearth furnace or as a conductive heating system. The blank heat-treated in the heat-treatment device can be conveyed to a centering station via an outlet section downstream of the furnace. In the centering station, the heat-treated blank is positioned in a predefined removal position, in which process-reliable gripping of the blank by a transfer unit is guaranteed. The transfer unit can, for example, be a feeder device (robot, linear feeder, etc.). With the help of the transfer unit, the blank is transferred from the centering station to the forming tool and inserted there.

It should be emphasized that all methods of "tailored tempering" can be used in the form of furnace technology. This includes, among other things, "thermal printing in the oven", in which different temperature ranges are deliberately set in the circuit board. Or the "hangout" method, in which part of the circuit board "hangs out of the oven". Pre-cooling according to the invention can also take place in these cases.

The pre-cooling step according to the invention does not take place in a separate pre-cooling process station that is positioned between the heat treatment device and the forming tool. Such a separately interposed pre-cooling process station would require additional process time. Rather, the pre-cooling according to the invention of the material-thick sheet metal area is preferably carried out along the outlet section, in the centering station and/or in the transfer unit. For example, the pre-cooling step can be carried out by contact cooling, for example by plate pre-cooling. Alternatively, the pre-cooling step can be implemented by convection using air nozzles (compressed air). Non-contact cooling using nozzles is preferred, as this can be implemented with existing plant and feeder technology. There is also no need to integrate an explicit intermediate station for pre-cooling. Furthermore, with contact cooling there are challenges in terms of wear of the contact plates, especially with contact with a liquid or semi-viscous layer made of ZnFe or Al/AIFe, for example.

In the pre-cooling step, a blank area is locally pre-cooled, which not only includes the material-thick sheet metal area of the blank, but also an overhang that protrudes beyond the edge of the material-thick sheet metal area. In this way, the temperature gradient, which leads to unwanted heat conduction in the sheet metal area that is thick with material, can be minimized.

In a first embodiment variant, the circuit board can be a patch circuit board, which is formed from a carrier circuit board and from at least one patch circuit board joined thereto. The material-thick area is thus realized by a double layer of carrier board and patch board, while the material-thin sheet metal area is realized exclusively by the carrier board. As an alternative to this, the circuit board can also be implemented as a tailored rolled blank or as a tailored welded blank.

It is preferred if the hot-formable blank is coated with an anti-scale layer, specifically in contrast to an uncoated hot-forming material, in which air cooling would lead to severe scale formation. In contrast to a Zn/ZnFe coating, the scale protection layer can advantageously be an AlSi layer.

Exemplary embodiments of the invention are described below with reference to the accompanying figures.

• 1 ein schematisches Schliffbild eines warmumgeformten und pressgehärteten Stahlblechteils;
• 2 eine Anlagenskizze, anhand der eine Prozessabfolge zur Herstellung des warmumgeformten und pressgehärteten Stahlblechteils veranschaulicht ist;
• 3 ein Zeit-Temperatur-Profil, das den zeitlichen Temperaturverlauf im materialdicken Blechbereich und im materialdünnen Blechbereich der Platine während des Warmumformprozesses zeigt;
• 4 in einer schematischen Teil-Perspektivansicht den Vorkühlschritt;
• 5 eine Platinenbeladespindel für eine Transfereinheit; und
• 6 eine Ansicht entsprechend 3, die ein Zeit-Temperatur-Profil gemäß dem Stand der Technik zeigt.

Show it:

• 1 a schematic micrograph of a hot-formed and press-hardened sheet steel part;
• 2 a plant sketch, on the basis of which a process sequence for the production of the hot-formed and press-hardened sheet steel part is illustrated;
• 3 a time-temperature profile that shows the temperature profile over time in the material-thick sheet metal area and in the material-thin sheet metal area of the blank during the hot forming process;
• 4 in a schematic partial perspective view, the pre-cooling step;
• 5 a board loading spindle for a transfer unit; and
• 6 a view accordingly 3 , which shows a time-temperature profile according to the prior art.

In the 1 a roughly schematic micrograph of a hot-formed and press-hardened sheet steel part 1 is shown. The sheet steel part 1 has a carrier plate 3 with a reinforcement plate 5 fixed thereon, which acts as a local component reinforcement and is materially connected to the carrier plate 3 (for example via welds that are not shown). In the 1 the steel sheet part 1 is divided into a material-thick sheet metal area 7 and a material-thin sheet metal area 9 . The material-thick sheet metal area 7 is formed by the double layer of carrier plate 3 and reinforcement plate 5 , while the material-thin area 9 is formed exclusively by the carrier plate 3 . The material-thick sheet metal area 7 has a locally increased sheet thickness s ₁ , while the material-thin sheet metal area 9 has a sheet metal thickness s ₂ that is reduced in comparison. In the figures, the sheet thicknesses s ₁ , s ₂ are exaggerated.

The hot-formed and press-hardened sheet steel part 1 is in a 2 shown system can be produced. The facility is in the 2 described only to the extent necessary for an understanding of the invention. Tool components that are not required for understanding the invention are in the 2 omitted. As a heat treatment device 11, the system has a roller hearth furnace, a downstream forming tool 13 for hot forming and press hardening of sheet steel parts 1, and a storage station 15 in which the sheet steel parts 1 produced are temporarily stored. The sheet steel parts 1 temporarily stored in the storage station 15 can be fed to a post-processing station (not shown), in which the sheet steel parts 1 are laser-cut, for example.

The Indian 2 The system shown is preceded by a joining process step (not shown), in which the reinforcing board 5 and the carrier board 7 (in the cold, unhardened state) are first joined by spot welding to form a composite component (hereinafter referred to as patch board 19). The patch board 19 is transferred to the heat treatment device 11 . There the patch board 19 is in a heat treatment phase Δt _w ( 3 ) heat-treated to above the material-specific austenitization temperature Ac3. After the end of the heat treatment phase Δt _w , a transfer phase Δt _T follows. In the transfer phase Δt _T , the heat-treated patch board 19 is conveyed via an oven outlet section a by means of outlet rollers 21 to a centering station 23, in which the patch board 19 is positioned in a predefined removal position. In the removal position, process-reliable gripping of the patch board 19 is ensured by means of a transfer unit 25, which loads the patch board 19 in an insertion step (time t _e in the 3 ) in an open tool cavity of the forming tool 13 inserts. Then follows a press hardening phase Δt _P ( 3 ), in which the tool cavity of the forming tool 13 is closed and the patch board 19 is formed in a press-hardening step, with the formation of the sheet steel part 1. The press-hardening phase Δt _P is followed by a removal step in which the formed sheet steel part 1 is removed from the forming tool at a removal temperature 13 is taken.

The core of the invention consists in the fact that a pre-cooling device 26 is provided in the system, by means of which a local pre-cooling of the material-thick sheet metal area 7 of the patch board 19 takes place before the press-hardening phase Δt _P . The pre-cooling device 26 works with convection. For this purpose, the pre-cooling device 26 has compressed air nozzles 27 which are in the 2 or 4 are positioned along the outlet section a and in the area of the centering station 23 .

The mode of operation of the pre-cooling device 26 is explained below using the temperature-time profile from FIG 3 described. In the temperature-time profile, the temperature profile over time ϑ ₁ (t) of the local process temperature ϑ ₁ in the thick sheet metal area 7 (with a dashed line) and the temperature profile over time ϑ ₂ (t) of the local process temperature ϑ ₂ in the sheet metal area 9 with the thin material (with solid line) is shown. Consequently, the two local process temperatures θ ₁ , θ ₂ are identical during the heat treatment phase Δt _W . In the subsequent transfer phase Δt _W , as a result of the local pre-cooling carried out with the pre-cooling device 26, the cooling rate in the material-thick sheet metal area 7 (i.e. temperature profile ϑ ₁ (t)) is significantly greater than the cooling rate in the material-thin sheet metal area 9 (i.e. temperature profile ϑ ₂ (t) ). Accordingly, in the deposit step (time t _e in the 3 ) the local insertion temperature ϑ _e1 in the material-thick sheet metal area 7 is reduced by the temperature offset ΔT _E compared to the local insertion temperature ϑ _e2 . In the following press hardening phase Δt _P , less heat has to be dissipated in the sheet metal area 9 with the thick material within the forming tool 13, so that the amount of heat in the area 7 with the thick material and the amount of heat in the area 9 with the thin material converge significantly.

With the help of the pre-cooling device 26, the material-thick sheet metal area 7 is locally cooled to a local insertion temperature ϑ _e1 , which is lower by the temperature offset ΔT _E than the local insertion temperature ϑ _e2 of the thin material sheet area 9. The temperature offset ΔT between the The local insertion temperature ϑ _e1 in the material-thick sheet metal area 7 and the local insertion temperature ϑ _e2 in the material-thin sheet metal area 9 is dimensioned such that after the press hardening phase Δt _P the local removal temperatures ϑ _a1 , ϑ _e2 of the material-thin and material-thick sheet metal areas 7, 9 of the formed sheet steel part 1 are different adjust. In the 3 the local removal temperatures θ _a1 , θ _a2 of the material-thin and material-thick sheet metal areas 7, 9 of the sheet steel part 1 are identical, for example.

As can be seen from the temperature-time profile of the 3 shows that both the local insertion temperature ϑ _e1 of the material-thick sheet metal area 7 and the local insertion temperature ϑ _e2 of the material-thin sheet metal area 9 of the patch board 19 are a temperature offset above the martensite start temperature Ms in order to enable press hardening of the patch board 19.

In the 4 the furnace outlet section a at the transition to the centering station 23 is shown in a perspective detailed view. The heat-treated patch board 19 is conveyed on the outfeed rollers 21 to the centering station 23 . By means of the compressed air nozzles 27 of the pre-cooling device 25, a board area Z (indicated by a dot-dash line) is locally pre-cooled along the outlet section a and at the centering station 23, which not only includes the material-thick sheet metal area 7 of the patch board 19, but also an overhang 29, which protrudes beyond the edge of the material-thick sheet metal area 7 of the patch board 19 transversely to the sheet metal thickness direction. In this way, a temperature gradient that leads to unwanted heat conduction in the material-thick sheet metal area 7 can be minimized.

In the 5 a circuit board loading spider 31 of the transfer unit 25 is shown. Accordingly, the circuit board loading spider 31 has grippers 33 . These can be brought into engagement with the patch board 19 for a transfer. In addition, additional compressed air nozzles 27 of the pre-cooling device 26 are integrated in the blank loading spider 31 . With the help of the material-thick metal plate 7 of Patschplatine 19 can be pre-cooled, as an alternative or in addition to in the 2 shown compressed air nozzles 27.

In the 6 shows a temperature-time profile according to the prior art, in which in the transfer phase Δt _T there is no local pre-cooling according to the invention of the sheet metal area 7 that is thick with material, but only a transfer-related cooling of both the sheet metal area 7 with the thick material and the sheet metal area 9 with the thin material.
Accordingly, in the 6 in the transfer phase Δt _w the cooling rate in the material-thick sheet metal area 7 (ie temperature profile θ ₁ (t)) is significantly smaller than the cooling rate in the material-thin sheet metal area 9 (ie temperature profile θ ₂ (t)). Accordingly, in the deposit step (time t _e in the 6 ) the local insertion temperature ϑ _e1 in the material-thick sheet metal area 7 is greater than the local insertion temperature ϑ _e2 in the material-thin sheet metal area 9.
In the following press hardening phase Δt _P , more heat has to be dissipated in the material-thick sheet metal area 7 than in the material-thin sheet metal area 9. This inevitably leads to an inhomogeneous removal temperature, since the material-thick sheet metal area 7 cools down significantly more slowly (or more volume energy has to be dissipated in the form of heat ) than the material-thin sheet metal area 9.

The inhomogeneous removal temperature is in the 6 illustrated by the temperature offset ΔT _A between the local extraction temperature θ _1a in the sheet metal area 7 with the thick material and the local extraction temperature θ _2a in the sheet metal area 9 with the thin material. Such an inhomogeneous removal temperature leads to temperature-related residual stresses. The material-thick sheet metal area 7 literally distorts the sheet steel part 1, resulting in positional inaccuracies in the post-processing station (laser recording). Manufacturing and component tolerances cannot be reliably adhered to either.

Reference List

1

sheet steel part

3

carrier board

5

reinforcement board

7

material-thick sheet metal area

9

material-thin sheet metal area

11

heat treatment device

13

forming tool

15

drop station

19

patch board

21

exit rollers

23

centering station

25

transfer unit

26

pre-cooling device

27

compressed air nozzles

29

Got over

31

blank loading spindle

33

gripper

s1, s2

sheet thicknesses

a

outlet section

Z

board area

ϑe1, ϑe2

local deposit temperatures

ϑa1, ϑa2

local extraction temperatures

Ms

martensite start temperature

Mf

martensite finish temperature

Δtw

heat treatment phase

ΔtT

transfer phase

ΔtP

press hardening phase

te

insertion time

Ac3

austenitization temperature

ΔTE

Temperature offset between the local insertion temperatures ϑ _e1 , ϑ _e2

ΔTA,

Temperature offset between the local extraction temperatures ϑ _a1 , ϑ _e2

ϑ1(t)

Temporal temperature curve of the process temperature in the material-thick sheet metal area

ϑ2(t)

Temporal temperature curve of the process temperature in the material-thin sheet metal area

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• US 2004/0060623 A1 [0005]
• US 2013/0312474 A [0005]
• DE 102009051822 B3 [0005]

Claims (12)

Method for producing a hot-formed and press-hardened sheet steel part (1), which has at least one material-thick sheet metal area (7) with locally increased sheet thickness (S ₁ ) and at least one material-thin sheet metal area (9) with locally reduced sheet thickness (S ₂ ), which method has the following Process steps has: - a heat treatment step (Δt _W ), in which a still unhardened blank (19) is heated to above the material-specific austenitization temperature (Ac3), - an insertion step (t _e ), in which the blank (19) in the hot state in a forming tool (13) is inserted, with the material-thick sheet metal area (7) and the material-thin sheet metal area (9) each having a local insertion temperature (ϑ _e1 , ϑ _e2 ), - a press-hardening step (Δt _P ), in which the material in the forming tool ( 13) inserted board (19) is hot-formed and press-hardened, namely to form the steel sheet part (1), wherein the material-thick sheet metal area (7) and the m Material-thin sheet metal area (9) each have a local removal temperature (ϑ _e1 , ϑ _e2 ), and - a removal step in which the sheet steel part (1) is removed from the forming tool (13), characterized in that between the heat treatment step (Δt _w ) and the press hardening step (Δt _P ) is followed by a pre-cooling step, in which the material-thick sheet metal area (7) is locally cooled down to a local insertion temperature (ϑ _e1 ), whereby a temperature offset (ΔT _E ) between the local insertion temperature (ϑ _e1 ) of the material-thick sheet metal area (7) and the local insertion temperature (ϑ _e2 ) of the material-thin sheet metal area (9) is reduced, compared to hot forming without pre-cooling. procedure after claim 1 , characterized in that the pre-cooling step is designed in such a way that the local insertion temperature (ϑ _e1 ) of the material-thick sheet metal area (7) is lower by a temperature offset (ΔT _E ) than the local insertion temperature (ϑ _e2 ) of the material-thin sheet metal area (9). procedure after claim 1 or 2 , characterized in that the local insertion temperatures (ϑ _e1 , ϑ _e2 ) of the material-thick sheet metal area (7) and the material-thin sheet metal area (9) of the blank (19) are above the martensite start temperature (Ms). procedure after claim 1 , 2 or 3 , characterized in that the heat treatment step (Δt _W ) takes place in a heat treatment device (11), such as an induction heating system, a roller hearth furnace or a conductive heating system, and in that the blank (19) heat-treated in the heat treatment device (11) is discharged via a furnace outlet section (a) is conveyed up to a centering station (23), in which the circuit board (19) is positioned in a predefined removal position, in which a process-reliable gripping of the circuit board (19) by a transfer unit (25) is ensured, by means of which the circuit board (19) is transferred to the forming tool (13) and inserted there. procedure after claim 4 , characterized in that the pre-cooling step takes place along the furnace outlet section (a), in the centering station (23) and/or in the transfer unit (25). Method according to one of the preceding claims, characterized in that the pre-cooling step takes place by contact cooling, for example plate pre-cooling, and/or by convection by means of air nozzles (27), in particular compressed air nozzles. Method according to one of the preceding claims, characterized in that in the pre-cooling step, a blank area (Z) is locally pre-cooled, which not only includes the material-thick sheet metal area (7) of the blank (19), but also an overhang (29) that extends transversely protrudes beyond the edge of the material-thick sheet metal area (7) in the sheet thickness direction, in order to minimize a temperature gradient that leads to unwanted heat conduction in the material-thick sheet metal area (7). Method according to one of the preceding claims, characterized in that the board (19) is a patch board, which is formed from a carrier board (3) and at least one reinforcing board (5) joined thereto, and that the material-thick sheet metal area (7) is formed by a Double layer of carrier board (3) and reinforcement board (5) is formed, and that the material-thin sheet metal area (7) is formed exclusively by the carrier board (3). Method according to one of the preceding claims, characterized in that the hot-workable blank (19) is coated with an anti-scale layer, and in that in particular the anti-scale layer is an AlSi layer. Procedure according to one of Claims 1 until 9 , characterized in that the circuit board (19) is implemented as a tailored rolled blank (TRB) or as a tailored welded blank (TWB). Process arrangement for carrying out a method according to one of Claims 1 until 9 . Sheet steel part (1) in a method according to any one of Claims 1 until 10 is made.

Images