EP2264193A1 - Production of a partially press-hardened metal sheet component - Google Patents

Abstract

The method comprises transforming raw sheet metal material to a sheet metal mold part, pre-hardening the raw sheet metal material and heating the sheet metal mold part partially in a furnace in such a way that the area to be hardened is covered and is subjected to the press hardening. The non-covered area of the sheet metal mold part is heated in the furnace at above 900[deg] C. The mold formation of the sheet metal mold part corresponds to the vehicle body component. The raw sheet metal material is a coated steel plate. The method comprises transforming raw sheet metal material to a sheet metal mold part, pre-hardening the raw sheet metal material and heating the sheet metal mold part partially in a furnace in such a way that the area to be hardened is covered and is subjected to the press hardening. The non-covered area of the sheet metal mold part is heated in the furnace at above 900[deg] C. The mold formation of the sheet metal mold part corresponds to the vehicle body component. The raw sheet metal material is a coated steel plate. The degree of a thermal shielding of the relevant area is adjusted through the choice of the cover, a covering material, character of the covering material and/or arrangement on the sheet metal mold part. The covering is carried out by two shell molds that are arranged in relevant area on both sides at the sheet metal mold part. The shell mold is formed from a heat-resistant fiber material, a ceramic material, a metallic material or material composite. The shell mold is laid out not directly on the sheet metal mold part. Independent claims are included for: (1) a covering device; and (2) a vehicle body component.

Description

The invention relates to a method for producing a partially press-hardened sheet metal component according to the preamble of claim 1. The invention further relates to a cover device for producing a partially press-hardened sheet metal component and a motor vehicle body comprising a partially press-hardened sheet metal component.

The press-hardening of sheet-metal components, in particular of a steel sheet material, is well known from the prior art. Representative is in this regard on the GB 1 490 535 from the year 1974. In press-hardening, the strength and / or hardness of a sheet material is increased by a heat treatment and final cooling in a press-hardening tool. The increase in strength and / or hardness (hardening) of the sheet material is based essentially on a structural transformation.

In the DE 103 41 867 A1 Among other things, a method for producing a press-hardened sheet metal component is described, which has various areas which have a different degree of hardness. For this purpose, a sheet metal component intermediate form produced in a first method step is heated in an oven to the required hardening temperature and then subjected in a press hardening tool a partially different cooling, for which a variety of tool concepts are known from the prior art. A disadvantage is the sometimes very high tooling effort. Another disadvantage is a difficult process management.

An object of the invention is to provide an improved method for producing such sheet metal components, which requires in particular a lower tooling complexity. Furthermore, an object of the invention to specify a body that can assist in the implementation of the procedure.

This object is achieved by a method according to the features of claim 1 and by a covering device according to the features of the independent claim. Preferred and advantageous developments are the subject of the respective dependent claims. The invention also extends, according to a further independent claim, to a vehicle body, in particular a passenger power unit, which comprises at least one sheet metal component produced by this method and / or by using such a cover device.

The inventive method is used to produce a partially press-hardened sheet metal component, wherein the starting sheet material is first formed into a sheet metal part and this forming is followed by a press hardening, for which this sheet metal part is partially heated in an oven, such that at least one not to harden or less to harden Covered area and / or shielded and thereafter the press hardening takes place.

A sheet metal component has a spatial shape design. A partially press-hardened sheet-metal component is a sheet-metal component which has various regions (at least two) in which the sheet-metal material has a strength and / or hardness which can be differentiated from one another. In particular, it is provided that the sheet-metal component produced by the method according to the invention has at least one region in which the strength and / or hardness of the sheet metal material remains substantially unchanged relative to the starting sheet material. In essence, this means that due to various effects, even in such an area quite a slight increase in strength and / or hardening of the sheet material may occur, which, however, in the result significantly below that of the other area or the other area.

An "area" may be determined spatially and / or areally. "Strength" is understood to mean a material property of the sheet material which describes the mechanical resistance which the material of the sheet material brings about for plastic deformation or also for a separation. Under "hardness" is understood a material property, which describes the mechanical resistance, which opposes the material of the sheet material of an external mechanical action. Strength and hardness can be correlated according to common material models. Curing can also influence the ductility of the material.

The invention is based on the idea to achieve a partial press-hardening of the sheet metal component by a different, partial heating of the sheet material, wherein the not to be hardened or less hardened area is covered and this covered and / or shielded area in the oven not on the required Hardening temperature can heat and / or the required hardening temperature in this range can not be maintained for a sufficient period of time. Covering virtually results in thermal shielding of the covered area. Simply put, the press-hardened sheet-metal component acquires locally different properties due to the different insertion temperatures in the press-hardening tool, which primarily includes hardness, strength and / or ductility.

In accordance with the method according to the invention, initially a deformation of the starting sheet material into a sheet metal shaped part takes place, by which is meant a sheet metal part intermediate shape. This can be done in a single-stage or multi-stage deep drawing process. This is preferably a cold forming.

Subsequently, a partial heating of this sheet metal part takes place in an oven. For this purpose, at least one area of the sheet metal part which is not to be hardened or less hardened is covered and thermally shielded. The partially covered and / or shielded sheet metal part is placed as a whole in the oven. Such a furnace is preferably a continuous furnace. In the oven, a protective gas atmosphere may be formed. Furthermore, such an oven may have different temperature zones.

Then, if necessary, after removing the covers, the press hardening of the partially heated sheet metal part in a press-hardening tool. In this press hardening tool, a uniform and / or partially differentiated cooling of the sheet metal material can take place, whereby defined the hardening and / or increase in strength of the sheet material occurs.

The method according to the invention can be supplemented by intermediate steps, further steps and / or further partial steps, some of which are the subject of preferred developments.

The invention provides i.a. the advantage that even existing press hardening plants can be converted easily and at relatively low cost to a partial press hardening. Another advantage is in particular the possibility of partial press hardening coated steel materials, as explained in more detail below.

A sheet metal component produced by the method according to the invention is, in particular, a body component of a motor vehicle (motor vehicle body component). This may be a structural part, e.g. a B-pillar part, or an attachment part, such as a bumper reinforcement. However, in the case of the sheet metal component, it may be e.g. also act as a chassis member, such as e.g. an axle carrier.

According to a preferred embodiment, it is provided that the uncovered and / or shielded region of the sheet metal part is heated in the oven to above 900 ° C. The aim is that, in a steel material, this range will reach the austenitizing temperature required for press hardening and that this range will be maintained in the oven for a sufficiently long time at this austenitizing temperature, e.g. is adjustable in the oven by the residence time of the sheet metal part. In contrast, austenitizing in the covered and thermally shielded area is wholly or at least partially prevented by the partial covering, whereby in this area no or only a lower quench hardening during press hardening is possible.

According to a preferred embodiment, it is provided that the shape of the formed sheet metal part, ie the sheet metal component intermediate form, substantially already corresponds to that of the partially press-hardened sheet metal component to be produced. During press hardening, therefore, no further shaping is required or only a very small shaping (eg in the region of component radii), which is indicated by the expression "substantially". This is particularly advantageous with regard to the surface of the sheet metal component to be produced, even if the sheet metal material optionally has a coating.

Preferably, it is further provided that the press-hardened sheet-metal component subsequently no longer has to be trimmed. This can be achieved by a corresponding trimming the sheet metal part, which is less expensive. Furthermore, even before the press hardening, possibly also directly into the output board, holes and recesses can be introduced.

According to a preferred embodiment, it is provided that the starting sheet material is a coated steel sheet. The coating serves e.g. as corrosion protection. Such a coating is in particular a zinc-containing coating, which is in particular essentially formed from zinc, and which has preferably already been applied by the manufacturer. Compared to the prior art, the use of zinc-coated starting sheet materials is largely unproblematic. As steel sheet material in particular a steel material of the type 22MnB5 or 16MnB5 is provided.

According to a preferred embodiment, it is provided that the degree of thermal shielding of a relevant area to be covered is adjusted by the choice of the cover, a cover material, its nature and / or its arrangement on the sheet metal part. As cover, e.g. Blankets, reusable cover devices (as explained in more detail below) or specifically applied cover materials into consideration. The degree of thermal shielding may be e.g. be measured in percent. A 100% thermal shield can be considered as a thermal insulation, which substantially prevents heating of the sheet material during the residence time in the oven in the shielded area. A lower thermal shield leads to heating of the shielded area and a corresponding increase in strength and / or hardening of the sheet material during the press hardening, which is significantly lower than that of the other, uncovered area. As a result of the degree of thermal shielding, the strength and / or hardness of the sheet metal material that results during press hardening can thus be adjusted in a targeted manner.

According to a preferred embodiment, a plurality of regions of the sheet metal part are covered so that different degrees of thermal Shielding result. This makes it possible to produce (in a single pass) a press-hardened sheet-metal component with a wide variety of strength and / or hardness ranges. Such a component may be referred to as a complex press-hardened sheet metal component.

According to a preferred embodiment it is provided that the covering takes place by means of at least two shell molds, which are applied on both sides of the sheet metal part in the area concerned. It is preferably provided that an inner contour of such a shell mold corresponds to the spatial contour of the sheet metal part in the area to be covered or this is approximated. A mold shell can be flexible or rigid. On a sheet metal part several shell molds of different design can be arranged.

According to a preferred embodiment, it is provided that such a mold shell is essentially formed from a heat-resistant fiber material. Preferably, this fiber material is pressed and used in particular compression molded. A heat-resistant fiber material is in particular a rock wool, a silicate wool, an asbestos material or an asbestos substitute material.

According to a preferred embodiment, it is provided that a mold shell is formed from a ceramic material. Preferably, a mold shell is formed from a ceramic foam material.

According to a preferred embodiment, it is provided that a mold shell is formed from a metallic material. In particular, a mold shell is formed from a sheet metal material. In such a shell mold, it may be e.g. to act a section of an identical sheet metal part, one of which is placed in the area to be covered on the sheet metal part and placed under.

According to a preferred embodiment, it is provided that a mold shell is formed from a composite material. Such a composite material may for example be formed of several of the aforementioned materials, which are arranged for example in a sandwich structure.

According to a preferred embodiment, it is provided that a mold shell does not essentially rest directly on the sheet metal molding. Rather, a spacing or a spacing gap is provided between the surface of the sheet metal part and the inner surface of the mold shell to allow a relative thermal movement to each other and the surface of the sheet metal part and possibly their coating to protect against damage. By means of such a spacing, the degree of thermal shielding can also be changed. However, the mold shell and the sheet metal part can touch one another in a punctiform manner, which is indicated by the phrase "essentially".

According to a preferred development, it is provided that a heat-resistant material is arranged at least in sections between a mold shell, in particular a metallic or ceramic shell mold, and the sheet metal molded part. Such a material may be e.g. to be one of the aforementioned materials or a composite material formed therefrom, e.g. in the form of a flexible mat or a flexible braid is available.

The covering device according to the invention serves to cover a region which is not to be hardened or less hardened during the heating of a press-hardening sheet metal part in an oven. In particular, it is a reusable cover, whereby costs can be reduced.

It is preferably provided that the covering device is designed as a unit which is designed to completely receive the area of the press-hardening sheet-metal shaped part which is not to be hardened or less hardened.

According to a preferred embodiment, it is provided that the covering device comprises at least one mold shell according to the above statements, which in particular rigid, i. dimensionally stable, is formed.

According to a preferred development, it is provided that the covering device has at least one means for automated attachment and / or removal on or from the press-hardening sheet-metal shaped part. This will be explained in more detail below in connection with the figures.

The method according to the invention is preferably carried out using at least one covering device according to the invention.

Fig. 1

ein erfindungsgemäßes Verfahren in einer schematischen Übersicht;

Fig. 2

am Beispiel einer B-Säule einen erfindungsgemäß abzudeckenden Bereich, in einer perspektivischen Ansicht;

Fig. 3

eine wiederverwendbare Abdeckeinrichtung in einer schematischen Schnittansicht und Detailansicht; und

Fig. 4

eine alternative Ausführungsmöglichkeit einer Abdeckeinrichtung in einer schematischen Schnittansicht.

The invention will be explained in more detail by way of example with reference to FIGS. Show it:

Fig. 1

a method according to the invention in a schematic overview;

Fig. 2

the example of a B-pillar according to the invention to be covered area, in a perspective view;

Fig. 3

a reusable cover device in a schematic sectional view and detail view; and

Fig. 4

an alternative embodiment of a covering device in a schematic sectional view.

Fig. 1 shows the inventive method for producing a partially press-hardened sheet metal component according to a preferred embodiment in a schematic overview. The illustrated method comprises six steps I to VI, wherein further steps and / or sub-steps may be provided, such as a Entgraden or cleaning, which are not listed in detail.

The method begins in step I with the provision of a sheet of hardenable steel sheet material. This board is formed in step II in the cold state to form a sheet metal part. The forming takes place in particular by deep drawing. In step III, individual areas of this sheet metal part, ie at least one area covered, which should not be cured in a subsequent press hardening or only to be less hardened. In step IV, the partially covered sheet metal part, together with the covers, is placed in an oven. In the oven, the uncovered areas are heated to austenitizing temperature (> 900 ° C, sometimes up to 950 ° C) and kept at this temperature level over a defined period of time. Depending on the cover, the covered areas are not heated at all or only slightly heated, as long as the residence time in the furnace is not too long and / or the temperature in the furnace is not too high. Subsequently, the partially heated sheet metal part from the Removed oven and placed after removing the covers in a press hardening tool. The press hardening tool is arranged in a closing device, in particular a press. In step V, the press-hardening tool is closed by means of the closing device, whereby the heated sheet-metal molding sections are quenched and hardened in the cooled press-hardening tool (quench hardening). This quench hardening in the press hardening tool takes place under a simultaneous shaping or shape retention, for which purpose the press hardening tool remains closed under the action of force. In step 6, the press-hardened sheet metal component is removed from the press-hardening tool to be subsequently processed further.

Fig. 2 shows the inner reinforcement part 10 of a B-pillar for a motor vehicle body. This is a press-hardened sheet metal component made of a steel sheet material. The internal reinforcement stiffener 10 has a longitudinal web 13, which merges at its lower longitudinal end into a transverse web 12, which is provided for connection to a side sill, and which merges at its upper longitudinal end into a transverse web 11, which is provided for connection to a roof construction is. The longitudinal web 13 has two connection points 14 and 15 for the door hinges of a vehicle door.

In the hatched area 17, which comprises the lower connection point 15, the press-hardened inner reinforcement part 10 should have a lower strength and / or hardness, possibly also ductility, than in the other areas. To achieve this, the press-hardened internal reinforcement part 10 is produced by the process according to the invention, as explained above. The specified range 17 is for explanation only. Also, several such areas may be provided.

To cover the area 17, a covering device according to the invention can be used, such as one below in connection with FIG Fig. 3 is explained by way of example.

Fig. 3a shows a reusable cover 20 in a schematic sectional view. The cover device 20 is designed as a multi-part unit, in which the inner reinforcement part 10 is received with the region 17 and protrudes by way of example on the right side. The covering device 20 comprises a lower part 21 and an upper part 22, which are each rigidly formed. The lower part 21 has a sandwich structure which is formed from an outer shell 23 and an inner shell 24. The upper part 22 also has a sandwich structure, which is likewise formed from an outer shell mold 25 and from an inner mold shell 26.

The outer shell molds 23 and 25 are e.g. formed of a metal material or a ceramic material, which is advantageous in particular with regard to the shielding of thermal radiation in the furnace and the mechanical strength and stability of the covering device 20. The inner shell molds 24 and 26 are e.g. formed of a heat-resistant and heat-insulating fiber material, as explained above. The thickness and / or nature (e.g., density) of the inner shell molds 24 and 26 may include i.a. the thermal shield can be adjusted.

According to a preferred embodiment, the inner mold shells 24 and 26 are flexible and are supported by the outer mold shells 23 and 25. Alternatively it can be provided that the inner shell molds 24 and 26 are formed dimensionally stable, which is e.g. can be achieved by an in-molding Pessen the fiber material in conjunction with additives. The inner shell molds 24 and 26 may themselves be constructed in multiple layers. Here, e.g. As a result, a very good thermal insulation can be achieved by a different fiber orientation in the individual layers. The outer shell molds 23 and 25 may be fixedly connected to the inner shell molds 24 and 26. Alternatively, the inner shell molds 24 and 26 can be loosely inserted into the outer shell molds 23 and 25, whereby a slight interference effect is possible by a slight oversize. A modular design proves to be particularly advantageous in case of repair of the thermally highly stressed cover 20.

The upper part 22 and the lower part 21 are hingedly connected to each other via at least one hinge 28. In the example shown, the cover device 20 can be scissor-like around an unspecified hinge point for attaching and removing, or for inserting and removing the internal reinforcement part 10, to open. The opening can be done, for example, by applying a force F to the actuator arm 29, which is located on the left side of the hinge 28 and which belongs to the upper part 22. The closing of the cover 20 is preferably carried out automatically, in particular by gravity. This makes it very easy to automate the attachment and / or removal of the cover 20. The hinge 28 is designed heat-resistant and formed, for example, as a ceramic bearing.

It is preferably provided that the inner mold shells 24 and 26 do not rest directly on the inner reinforcement part 10. Rather, a spacing in the form of a spacing gap 30 is provided between the surface of the inner reinforcement part 10 and the inner shell molds 24 and 26. this shows Fig. 3b which has an enlarged section of the Fig. 3a reproduces. Such a spacing gap 30 may, inter alia, enable a relative thermal movement and protect the surface of the inner reinforcement part 10 from damage. The spacing gap 30 can be very small and is preferably less than the sheet thickness of the inner reinforcement part 10.

Fig. 4 shows an alternative embodiment of a covering device 20a in a schematic sectional view. The main difference to the possibility of execution of Fig. 3 is that the inner, formed from a fiber material mold shells 24 and 26 are included. For this purpose, inner support shells 41 and 42 are provided, which bear against the inner reinforcement part 10 directly or even spaced. These inner support shells 41 and 42 are formed, for example, of a metal material or a ceramic material and may, like the outer shell molds 23 and 25 also, be one or more parts.

In a simple embodiment of the in Fig. 4 shown covering means 20a, the outer shell molds 23 and 25, and the inner support shells 41 and 42 are formed by component cutouts, which are spaced apart by an insulating material.

Production of a partially press-hardened sheet-metal component

10

partially press-hardened sheet metal component; Internal reinforcement B-pillar

11

crosspiece

12

crosspiece

13

longitudinal web

14

Connection point for door

15

Connection point for door

17

area to be covered; Area with less hardening

20, 20a

cover

21

lower part

22

top

23

outer shell (lower part)

24

inner shell (lower part)

25

outer shell (upper part)

26

inner shell (upper part)

28

Hinge; joint

29

actuating arm; Means for automated attachment and / or removal

30

Beabstandungsspalt

I to VI

steps

F

Force, force

Claims (15)

A method for producing a partially press-hardened sheet metal component (10), in particular a body component, wherein the starting sheet material is first formed into a sheet metal part and this forming followed by a press hardening, for which the sheet metal part is partially heated in an oven, such that at least one not to hardening or less hardening area (17) is covered, and thereafter the press hardening takes place. Method according to claim 1,
characterized in that
the uncovered area of the sheet metal part in the oven is heated to over 900 ° C. Method according to claim 1 or 2,
characterized in that
the shape of the sheet metal part substantially already corresponds to that of the sheet metal component (10) to be produced. Method according to one of the preceding claims,
characterized in that
the starting sheet material is a coated steel sheet. Method according to one of the preceding claims,
characterized in that
the degree of thermal shielding of the relevant area (17) is adjusted by the choice of the cover, a cover material, its nature and / or its arrangement on the sheet metal part. Method according to one of the preceding claims,
characterized in that
the covering takes place by means of at least two shell molds, which are applied in the relevant area (17) on both sides of the sheet metal part. Method according to claim 6,
characterized in that
a mold shell is formed essentially of a heat-resistant fiber material. Method according to claim 6,
characterized in that
a mold shell is formed substantially of a ceramic material. Method according to claim 6,
characterized in that
a mold shell is formed essentially of a metallic material. Method according to claim 6,
characterized in that
a mold shell is formed from a composite material. Method according to one of claims 6 to 10,
characterized in that
a mold shell is not substantially rests directly on the sheet metal part. Covering device (20, 20a), in particular a reusable covering device, for covering a region which is not to be hardened or less hardened during the heating of a press-hardened sheet metal part in an oven. Covering device (20, 20a) according to claim 12 comprising at least one mold shell according to one of claims 7 to 10. Covering device (20, 20a) according to claim 12 or 13,
characterized in that
Means (29) for automated attachment and / or removal are included on or from the press-hardened sheet metal part. Vehicle body comprising at least one press-hardened sheet metal component (10) produced by a method according to one of claims 1 to 11 and / or using a covering device (20, 20a) according to one of claims 12 to 14.

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