EP2398606B1 - Method for producing a press-quenched metal component - Google Patents

Description

The invention relates to a method for producing a press-hardened metal component made of steel or a steel alloy, in which a printed circuit board or a semifinished product is press-hardened in a forming tool. The invention also relates to a press-hardened metal component made of steel or a steel alloy, in particular for a motor vehicle, which is not press-hardened in at least one partial area.

For the production of motor vehicle bodies or housings components of high hardness are usually required. For components made of steel or a steel alloy, a very high strength and a very high hardness can be achieved by the process of press hardening. In this method, a board or a semi-finished product is hot-worked in a tool at temperatures above the austenitizing temperature and then cooled abruptly in the same tool. The austenitic structure of the component during hot forming is converted into a martensitic structure of high strength and hardness by the rapid cooling process. Depending on the expected load in a vehicle body or in a housing, it is necessary for some components that they have no continuous hardness, but areas with a lower hardness or with an increased elongation at break. This can be achieved in particular by the fact that the components should not be press-hardened in those areas where they should have lower hardness.

For the production of such components is from the, WO 2006/038868 A1 a method is known in which the die used for the press hardening in the areas in which the component to be produced is to have a lower hardness has recesses on the surface. This ensures that the board does not bear against the die during press hardening in the region of the recesses, but an air gap between the die and the board is formed. In this way, the board is cooled more slowly in this area, so that the hardness and thus the strength after the press-hardening of the component in this area is lower.

However, the method described has the disadvantage that the provided with the recesses dies are expensive to manufacture. Furthermore, it is for the production in principle of similar components, which should have only other areas with reduced hardness, it is necessary to have a separate die for each component. As a result, the cost of producing such components are greatly increased. The recesses in the tool can also lead to deformations in the component, so that an accurate shaping of the component with this method is difficult and sometimes even impossible.

From the EP 1 655 207 A2 In addition, the production of a B-pillar by means of press hardening is known, wherein different sheet thicknesses are provided by tailored-rolled blanks.

The EP 2 108 467 A2 describes a method for producing highly dimensional half shells by drawing, in which a previously introduced into the sheet material reserve in the form of bulges to improve the forming behavior. The finished product accordingly has a uniform material thickness.

According to WO 2008/024042 A1 If sheets with different curing behavior can be welded together, so that an overlap area with greater thickness can arise. Subsequent press hardening leads to areas with different hardness properties in the component. However, these areas, which are not to be cured, are adjusted by a specific selection of the materials intended for these areas. So different materials have to be combined.

Based on this prior art, the present invention seeks to provide a simple and inexpensive method for producing a press-hardened metal component and a press-hardened metal component made of steel or a steel alloy, in which the disadvantages of the prior art are avoided.

This object is achieved by a method having the features according to patent claim 1 and with a metal component having the features of patent claim 3.

According to the invention, the printed circuit board or the semi-finished product has partial regions with a reduced wall thickness, the partial regions having a reduced wall thickness not being press-hardened.

As a result of the reduced wall thickness, the board or the semifinished product in the corresponding subregions does not lie directly against the wall of the tool used for reshaping, so that air gaps form between this subarea of the board or semifinished product and the wall of the tool. During cooling of the component in the press-hardening process, the heat transfer from the blank or semi-finished product to the tool is reduced through the air gaps, so that slower cooling rates occur. The component is thus not press-hardened in these areas. This has in particular the consequence that only a small or even no martensitic microstructure can form in these subregions and the hardness in these areas is thus lower and the elongation at break value greater.

The advantage of this method lies in the fact that it is possible in this way with a regular press-hardening tool to produce a component having portions with a lower hardness or a higher elongation at break value. It is therefore not necessary in particular to design the tool in the non-press-hardened sub-areas. In this way, the cost of production is significantly reduced.

According to the invention, the subregions are provided with reduced wall thickness by embossing the blank or semifinished product prior to press hardening. By embossing the depressions can be produced in a particularly simple manner. For this purpose, in particular an embossing punch or an embossing roll, which is particularly advantageous in the embossing of large areas, can be used.

In a further embodiment of the method, a "tailored blank" is press-hardened.

"Tailored blanks" are individual blanks that are welded together using a joining technique to form a single board. As a result, for example, blanks with the same materials, but different sheet thicknesses or different materials with the same or different sheet thickness can be welded to form a board.

The use of tailored blanks in the process is advantageous because in this way components with complex shapes and variable material properties can be produced. Furthermore, the reductions in the wall thicknesses in the subregions can be achieved in a very simple and flexible manner.

The tailored blank preferably has at least one board without embossing and at least one board with embossing. Alternatively, the tailored blank has at least two embossed boards of different thickness.

In the case of the so-called "tailored rolled blanks", a material is rolled to different thickness over its length using a flexible rolling process. This allows a reduction in thickness in the workpieces with a continuous material transition, so that hardness edges are avoided in the transition to the non-press-hardened portions of the component. Preferably, a tailored rolled blank is press-hardened from previously embossed starting material.

In the case of the press-hardened metal component according to the invention made of steel or a steel alloy, in particular for a motor vehicle, at least one non-press-hardened partial region has a reduced wall thickness compared with the press-hardened partial regions. The metal component is preferably produced by a method according to the invention.

Due to the reduced wall thickness is achieved in a simple manner that the corresponding portions are not press-hardened after the press-hardening of the metal component. Such metal components can be used advantageously, for example, for motor vehicle bodies or housing, since they meet the variable material properties required there and are also inexpensive to manufacture.

A flexible adaptation of the metal components to the load requirements is achieved according to a further embodiment in that the non-press-hardened portions of the metal component are arranged load. Since in this case only the subregions with a reduced wall thickness have to be arranged correspondingly, without an adaptation of the tool required for the manufacture being required, the production of such a component can be carried out simply and inexpensively. The non-press-hardened portions of the metal component are preferably arranged in areas in which the metal component should have an increased elongation at break.

A particularly high hardness or strength of the metal component is achieved in a further embodiment in that the metal component consists of a manganese-boron steel, preferably of a steel type 22MnB5.

According to the invention, the subareas of the press-hardened metal component with reduced wall thickness are formed by embossing. In this way, the portions of reduced wall thickness are particularly easy to manufacture and flexible to arrange.

Another preferred embodiment of the press-hardened metal component is given by the fact that the embossments are formed strip-shaped. This is particularly advantageous, for example, if the metal component is to have edges of lesser hardness, for example predetermined bending edges.

A more even hardness distribution can be achieved in a further embodiment in that the stampings are formed point or rectangular. Under a punctiform embossment is understood, for example, a circular embossing, but also generally a stamp with a small aspect ratio.

In a further embodiment of the press-hardened metal component, the stampings are of a similar design and / or uniformly distributed in the non-press-hardened partial areas. In this way, areas with a uniform average hardness can be achieved. The training uniform or evenly distributed Stamping is also easier and less expensive. Thus, the embossing of the semifinished product for the production of the metal component can take place before the press hardening, for example with the aid of an embossing roller.

By not identically designed or not uniformly distributed stampings, however, can be achieved very flexible average hardness properties of the metal component. In this way, for example, a medium hardness gradient can be formed.

A press-hardened metal component with a total average hardness between a press-hardened and a non-press-hardened component can be achieved in a further preferred embodiment by virtue of the metal component having embossings substantially over its entire surface.

A further embodiment of the press-hardened component is given by the fact that the metal component is produced from a composite sheet which has at least two sinkers and one of the sinkers has deformations in order to provide partial regions of reduced wall thickness. This is advantageous because the board with the recesses and / or stampings can be produced separately. Furthermore, a large influence on the material properties of the metal component is possible by the choice of different materials for the boards.

A particularly flexible and cost-effective production is especially in complex press-hardened metal components possible in that the metal component is made of a tailored blank, a tailored strip or a tailored rolled blank. In the case of a tailored blank or a tailored strip, blanks of different steels in particular can be used.

Furthermore, it is preferred that the metal component was produced from a tailored blank made from at least two embossed blanks of different sheet thickness or that the metal component was produced from a tailored blank or a tailored strip made from joined blanks of different sheet thickness.

Furthermore, it is preferred that the metal component has been produced from a tailored rolled blank of previously embossed starting material.

Further features and advantages of the invention can be taken from the following description of exemplary embodiments. Reference is made to the attached drawing.

Fig. 1a-c

ein Ausführungsbeispiel eines erfindungsgemäßen Verfahrens,

Fig. 2a-d

vier Ausführungsbeispiele eines Halbzeugs mit Teilbereichen reduzierter Wanddicke zur Herstellung von Metallbauteilen,

Fig. 3a-b

zwei Ausführungsbeispiele eines erfindungsgemäßen Metallbauteils,

Fig. 4a-b

zwei weitere Ausführungsbeispiele eines erfindungsgemäßen Metallbauteils und

Fig. 5a-b

ein weiteres Ausführungsbeispiel eines erfindungsgemäßen Metallbauteils.

In the drawing show

Fig. 1a-c

an embodiment of a method according to the invention,

Fig. 2a-d

Four embodiments of a semifinished product with partial regions of reduced wall thickness for the production of metal components,

Fig. 3a-b

two embodiments of a metal component according to the invention,

Fig. 4a-b

two further embodiments of a metal component according to the invention and

Fig. 5a-b

a further embodiment of a metal component according to the invention.

In the FIGS. 1a to 1c an embodiment of a method according to the invention is shown. Fig. 1a shows a board 2, which has a reduced wall thickness in partial areas 4. The reduction of the wall thickness was achieved in the board 2 by stampings 6 on the upper side 8 of the board 2. As a result, the board 2 on its upper side 8 elevations 10. The board 2 consists of a steel or a steel alloy, preferably of a manganese-boron steel, in particular of a steel 22MnB5 type. The stampings 6 may have been introduced into the board 2, for example by means of an embossing roll. Fig. 1b shows a tool 12 for press hardening with an upper tool 14 and a lower tool 16. The inner surface 18 of the upper tool 14 and the inner surface 20 of the lower tool 16 are adapted to the contour of the component to be produced. To produce the component 22, the upper tool 14 and the lower tool 16 are moved apart. The board 2 is then positioned between the upper tool 14 and the lower tool 16, and the upper tool 14 and the lower tool 16 then go back together. Upon collapse, the board 2 is hot-worked at temperatures which are preferably above the austenitizing temperature. At the end the hot forming process, the elevations 10 are applied directly to the inner surface 18 of the upper tool 14, while the board 2 are spaced in the partial regions 4 with reduced wall thickness by the Verprägungen 6 of the inner surface 18 of the upper tool 14. As a result, an air gap 24 is formed in each case between the plate 2 and the inner surface 18 of the upper tool 14 in the region of the stampings 6. To harden the formed blank 2, it is quenched in the tool 12. Due to the direct contact of the elevation 10 with the inner surface 18 of the upper tool 14, the cooling of the board 2 in this area is very fast, so that there is a martensite of the material. In the partial regions 4 with reduced wall thickness, the cooling takes place more slowly due to the air gap 24, so that only little or no martensite occurs in these regions. After completion of the cooling process, the upper tool 14 and the lower tool 16 are moved apart again and removed from the board 2 and press-hardened component 22 removed. The finished component 22 is in Fig. 1c displayed. It has a high hardness in the area of the elevations 10, while the hardness in the partial areas 4 is lower. Instead, the sections 4 have an increased elongation at break value. Are subregions 4 with reduced wall thickness as in the component 22 in Fig. 1c shown evenly distributed over the component 22, the result is a component having an average hardness, which is between the hardness of a fully press-hardened component and a non-press-hardened component.

In the FIGS. 2a to 2d exemplary embodiments of semi-finished products with partial regions of reduced wall thickness are shown. This in Fig. 2a not shown inventive Semifinished product 30 consists of a board 32, have been applied to the patches 34. The patches 34 are connected to the board 32 preferably cohesively. The wall thickness of the semifinished product 30 is locally increased by the patches 34, so that partial areas 36 with a smaller wall thickness relative to the areas with the patches 34 result between the patches. When press-hardening the vehicle 30, the patches 34 are applied directly to the tool, while an air gap is formed in the partial regions 36. The advantage of using patches 34 is that the change in wall thickness of the semifinished product 30 can be achieved in a very simple and flexible manner.

In Fig. 2b a semifinished product 40 according to the invention is shown, which is designed as a composite sheet. It has a first circuit board 42 and a second circuit board 44, which is arranged above it and is connected to the first circuit board 42, preferably in a materially bonded manner. The second board 44 has embossments 46, so that the wall thickness of the semifinished product 40 is reduced in these areas. The stampings 46 may be inserted into the second board 44, for example, before the second board 44 is connected to the first board. In this way, it is possible, for example, to produce the second circuit board 44 in advance and emboss and apply it as needed on first boards 42, which should not have press-hardened portions. Furthermore, by using different materials for the first board 42 and the second board 44, it is possible to flexibly influence the material properties of the resulting semi-finished product 40.

This in Fig. 2c shown semifinished product 50 is also made as a composite sheet of a first board 52 and a second board 54. Unlike the in Fig. 2b shown semifinished product 40, the second board 54 of the semifinished product 50 has no stampings, but continuous recesses 56. The recesses 56 may be in the form of bores, for example. Alternatively, the recesses 56 may be provided by punching the second board 54. Preferably, a conventional perforated plate made of steel or a steel alloy can be used as the second circuit board 54, since this is particularly cost-effective and thus the wall thickness-reduced areas of the semifinished product 50 can be provided in a simple and favorable manner.

The semi-finished products or blanks are not limited to provide the portions of reduced wall thickness by one-sided provision of recesses or stampings. This is how the in Fig. 2d Semifinished product 60 shown on a board 62, in which stampings 64 have been introduced from both sides. In this way, the hot-formed semi-finished product 60 has an air gap to the upper or lower tool on both sides in the thickness-reduced subregions. This is particularly advantageous when both the upper and the lower tool are actively cooled during press hardening. As a result, a particularly slow cooling process is possible in these subareas, so that the material has essentially no martensite in this area.

In the FIGS. 3a and 3b two embodiments of the press-hardened metal component are shown. This in Fig. 3a shown metal component 70 was made of a locally stamped Board made. The metal component 70 thus has a first region 72 and a second region 74. Rectangular depressions 76 were introduced into the first region 72 before the press-hardening. The second region 74 has no such depressions. During the press-hardening process, the metal component 70 was made of a board, for example the one in FIG Fig. 1a shown board 2, first in the in Fig. 3a hot-formed form and then quenched in the tool. While the metal component 70 in the second region 74 was in direct contact with the tool surfaces over the entire surface, the first region 72 had air gaps on the rectangular stampings 76, so that the component 70 was not press-hardened at these locations. The second region 74 of the component 70 is thus completely press-hardened and accordingly has a high hardness, while the first region 72 of the component 70 has a lower hardness due to the non-press-hardened partial regions in the depressions 76 on average. Such areas with lower average hardness are preferably arranged according to load. Thus, the arrangement is particularly advantageous in those places where high elongation at break values are required.

This in Fig. 3b Metal component 80 shown differs from metal component 70 Fig. 3a in that the metal component 80 is designed as a composite metal sheet. The first region 82 and the second region 84 of the metal component 80 were each press-hardened separately and then joined together at the seam 86 by a joining process.

The stampings 76, 88 of the components 70, 80 are not limited to a rectangular shape, but can also in any other shapes, such as circular, be designed as a polygon or strip-shaped.

So shows Fig. 4a a further embodiment of a press-hardened metal component 90, which was produced from a locally stamped board. Analogous to in Fig. 3a shown component 70, the component 90 has a first region 92 with Verprägungen 94 and a second region 96 without stampings. Accordingly, the component 90 is not press-hardened in the region of the stampings 94, which in this case are strip-shaped, so that the first region 92 has a lower average hardness than the second region 96 Fig. 4b The metal component 100 shown differs from the metal component 90 Fig. 4a in that it has been produced from tailored blanks or tailored strips with different sheet thicknesses. To produce the metal component 100, a tailored blank 102 and two tailored strips 104, 106 with the same thickness and two tailored strips 108, 110 with a smaller thickness were added to a semifinished product and then press-hardened. During press hardening, an air gap was arranged between the semifinished product and the tool in the area of the tailored strips 108, 110 with a smaller wall thickness. As a result, the metal component 100 is not press-hardened in the area of the tailored strips 108, 110 with a smaller thickness.

Fig. 5a and Fig. 5b show a further embodiment of a press-hardened metal component. This in Fig. 5b The metal component 111 shown here consists of a lower metal component 112 and an upper metal component 114. The lower metal component 112 and the upper metal component 114 are identical in construction and independent of each other in one Press hardening process produced. In this case, the two metal components 112, 114 each have honeycomb-shaped recesses on one side, in the region of which there was no direct contact with the tool during the press-hardening. The metal components 112, 114 are therefore not press-hardened in these areas. After press-hardening, the metal components 112, 114 with sides having depressions are joined together, preferably welded. The resulting composite sheet 111 has on average by the stampings of the metal components 112, 114 lower hardness than a fully press-hardened composite sheet. As a result of the metal components 112, 114 being connected to one another on the sides having the embossing, the composite metal sheet 111 advantageously has smooth outer surfaces 118, 120.

Also conceivable would be an application, not shown, in which the metal components 112, 114 are first joined together with the recesses having sides, and then press-hardened, optionally also a corresponding shape can be provided. Also in this example, the force gap between the sheets causes an average reduced hardness as a fully press-hardened composite sheet.

It will be apparent to those skilled in the art that the invention is not limited to the described embodiments, but that in particular all combinations of the embodiments are possible. The properties of the press-hardened metal components can be generally improved by the fact that the blanks, semi-finished or finished metal components by one or more typical metallic or non-metallic coating concepts are coated. In all composite sheets, tailored blanks and tailored strips, it is basically possible and may be advantageous to use different steel materials.

Claims (10)

1. A method of producing a press-hardened metal component of steel or a steel alloy,

   - in which a blank (2) or a semi-finished product (30, 40, 50, 60) is press hardened in a forming tool (12),

   characterised in that

   - the blank (2) or the semi-finished product (30, 40, 50, 60) comprises partial areas (4, 36) with a reduced wall thickness,

   - the partial areas (4, 36) with a reduced wall thickness are produced through embossing the blank (2) or the semi-finished product (30, 40, 50, 60) before press hardening and,

   - the partial areas (4, 36) with a reduced wall thickness are not press hardened.
2. The method according to claim 1,
   characterised in that
   a composite sheet (40, 50) is press hardened, wherein the composite sheet (40, 50) comprises at least two blanks (42, 44, 52, 54) and one of the blanks (44, 54) has stampings (46) for providing partial areas with a reduced wall thickness.
3. A press-hardened metal component of steel or a steel alloy, more particularly for a motor vehicle, manufactured with a method according to one of claims 1 or 2,

   - which in at least one partial area (4, 36) is not press-hardened,

   characterised in that

   - at least one non-press-hardened partial area (4, 36) has a reduced wall thickness compared with the press-hardened partial area, and

   - the partial areas (4, 36) with a reduced wall thickness are formed by stampings (46, 64, 76, 94).
4. The press-hardened metal component according to claim 3,
   characterised in that
   the non-press-hardened partial areas (4, 36) of the metal component (22, 70, 80, 90, 100, 111) are arranged so as to be adapted to loading.
5. The press-hardened metal component according to claim 3 or 4, characterised in that
   the metal component (22, 70, 80, 90, 100, 111) is made of manganese-boron steel, preferably a steel of type 22MnB5.
6. The press-hardened metal component according to any one of claims 3 to 5, characterised in that
   the stampings (94) are configured in the form of strips.
7. The press-hardened metal component according to any one of claims 3 to 6, characterised in that
   the stampings (46, 64, 76) are punctiform or rectangular.
8. The press-hardened metal component according to any one of claims 3 to 7, characterised in that
   the stampings (46, 64, 76, 94) are configured similarly and/or are uniformly distributed in the non-press-hardened partial areas.
9. The press-hardened metal component according to any one of claims 3 to 8, characterised in that
   the metal component (22, 70, 80, 90, 100, 111) exhibits stampings (46, 64, 76, 94) substantially over its entire surface.
10. The press-hardened metal component according to any one of claims 3 to 9, characterised in that
    the metal component (22, 70, 80, 90, 100, 111) is produced from a composite sheet (40, 50) which comprises at least two blanks (42, 44, 52, 54) and one of the blanks (44, 54) has stampings (46) for the provision of partial areas with a reduced wall thickness.

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