WO2019242901A1

WO2019242901A1 - Method for producing load-optimised sheet-metal components

Info

Publication number: WO2019242901A1
Application number: PCT/EP2019/058743
Authority: WO
Inventors: Martin Kibben; Lars Bode; Thomas Steier
Original assignee: Thyssenkrupp Ag; Thyssenkrupp Steel Ag
Priority date: 2018-06-19
Filing date: 2019-04-08
Publication date: 2019-12-26
Also published as: DE102018114653A1; EP3810349A1

Abstract

The invention relates to a method for producing sheet-metal components from a material, in particular for a car body, comprising the following method steps: pre-forming a workpiece to form a pre-formed component, wherein excess material is introduced into the pre-formed component at least in regions; and calibrating the pre-formed component to form an at least partially finally formed component using the excess material, wherein the pre-formed component is compressed in particular at least in sections, characterised in that the material has a yield strength Rp0.2 to tensile strength Rm ratio of Rp0.2 / Rm ≥ 0.53.

Description

Process for the production of load-optimized sheet metal components

The invention relates to a method for producing sheet metal components from a material, in particular for an automobile body, comprising the

Method steps: preforming a workpiece into a preformed component, excess material being introduced into the preformed component at least in regions, and calibrating the preformed component into an at least partially final molded component using the excess material, in particular wherein the preformed component is compressed at least in sections. In addition, the invention relates to the use of a sheet metal component.

Molded sheet metal components are used on an industrial scale, in particular

Half-shells, usually produced by a deep-drawing process (with and without hold-down devices) from sheet metal blanks, ie essentially flat sheets

Conventional deep drawing is a sheet metal blank formed into a half-shell by tensile pressure forming in accordance with DIN 8584. A hold-down device is used to prevent the board material from buckling and wrinkling when it flows into the die under the effect of the tangential compressive stress. The

The hold-down device presses on the edge of the sheet and this against the edge of the die, causing frictional tension between the edge of the sheet and the hold-down device. A disadvantage of this, however, is that the sheet-metal blank undergoes a strong deformation during deep drawing and the frictional stresses due to batch-dependent

Material deviations cannot always be carried out reliably.

Deep-drawn components, whether with or without the use of a hold-down device, generally require a final edge trimming in which excess areas of the deep-drawn component are cut off. In the case of parts with flanges, this can be done, for example, by one or more trimming tools, some or all of the flange from above or obliquely in the desired manner

trimming. With flangeless parts, on the other hand, trimming is already essential more complex, because it has to be cut off from the side, for example via a wedge gate valve. However, the trimming operations are disadvantageous in that the trimming usually requires one or even several separate operations, which often also require their own tool technology and their own logistics system. In addition, trimming operations often reduce that

Material utilization, which creates additional costs due to the high operating weight per sheet metal component.

In order to avoid, in particular, the batch-dependent dimensional accuracy and the high proportion of trimmings in the manufacture of sheet metal components,

described generic methods with preforming and calibration (the so-called reduced or free calibrating deep drawing) developed. In these, the inhomogeneous stress state of the preform induced by the preforming is realigned by calibration. This largely prevents undesired, batch-dependent springback of the component, which occurs in particular in the case of high-strength materials in combination with small sheet thicknesses.

However, this approach itself has some restrictions. For example, various boundary conditions must be observed when manufacturing the preform. In this way, too, the batch-dependent mechanical influences and changes

Material properties, friction and tool wear the lengths of the local cross-sectional developments, since the board is then stretched more or less. Such uncontrolled stretching of the material causes the

Adding material for the subsequent calibration step may leave the permissible, process-reliably controllable range of values.

This could be countered by facing one

conventional manufacturing by thermoforming dispenses with active, external sheet metal storage. When producing the preform, however, less plastic stretching occurs in particular in the component frames. The disadvantage here is that the reduced elongation of the material used, especially in the frames, less solidified than in deep-drawn components. Under solidification, one becomes

Understand the increase in the yield or yield point of a steel material as plastic deformation progresses. Another disadvantage is the lower plastic elongation which leads to a reduced decrease in sheet thickness. In addition, the

Sheet thickness of the component is increased when calibrating the preform. Because here the distributed material addition of the preform is compressed in the direction of the sheet plane, which leads to a further increase in the sheet thickness in the component. This leads to higher required forces and tool loads. Overall, this leads to an increased sheet thickness of the formed component compared to the conventional method.

With the conventional deep drawing described at the beginning, an increase in the yield or yield point can be achieved. This has for the conventional

Forming, however, means that the forming capacity of the high-strength material used is already largely consumed during the forming process and the finished component can therefore hardly bear any plastic deformation. For the load on the component, for example in the case of body components in the event of a crash, this can mean that the material fails when it is folded or buckled due to tearing, and the component therefore cannot withstand the required level of energy and force. Such failure thus has a negative impact on the deformation behavior of the components in the event of a crash and thus on vehicle safety. But also for

postforming operations that may be necessary, such as the so-called

Placing collars (e.g. for RPS holes) may no longer provide sufficient plastic forming capacity after the main shaping.

Starting from this prior art, the present invention has for its object to provide a method for producing sheet metal components, with which the advantages of the

Deep drawing and trimming-free calibrating deep drawing can be combined, that is to say in particular high-precision sheet metal components can be produced can, the at least similar advantageous mechanical properties [about consolidation) as appropriately dimensioned deep-drawn

Have sheet metal components and require the lowest possible operating weight.

In addition, the present invention is based on the object of specifying the use of a corresponding sheet metal component.

This object is achieved according to a first teaching of the present invention in a method for producing sheet metal components from a material, in particular for an automobile body, comprising preforming a workpiece into a preformed component, excess material being introduced into the preformed component at least in regions, and calibrating the preformed component to an at least partially final molded component using the

excess material, in particular wherein the preformed member is at least partially compressed, achieved in that the material has a ratio of yield strength R _p o, ₂ has to tensile strength R _m of R _p0, 2 / Rm> 0.53.

The preformed component can be formed in one or more steps using various shaping processes that can also be combined with one another

manufactured. The preforming can be, for example, deep-like

Forming step include. The sheet metal component can in particular be a flanged or flangeless half-shell. In the case of half-shells in particular, the preforming can also involve multi-stage shaping, for example embossing the base to be created and raising the frames to be created or optionally placing the flanges to be created. Special forms of deep drawing are also conceivable, such as combinations of folding and / or stamping. The preformed component obtained by the preforming can in particular be regarded as a near-net shape component which is the intended one

Finished part geometry taking into account given boundary conditions such as

Resilience and formability of the material used corresponds as well as possible. Calibration can be understood in particular to mean final shaping of the preformed component, which can be achieved, for example, by a pressing process. The final molded component can be essentially one

fully formed component can be understood. However, it is possible for the final molded component to still modify the component

Processing steps can be subjected, such as an insertion of connection holes. However, the aim is to design the calibration form in such a way that, if possible, no further shaping steps are necessary.

The workpiece is, for example, an essentially flat sheet metal blank. The material from which the workpiece is produced is in principle any material which has the ratio of yield strength to tensile strength according to the invention. However, the material is preferably a malleable metal, in particular a steel material, preferably a multi-phase steel.

With excess material there will at least be encores in the local

Cross-sectional lengths of the preformed sheet metal component referred to, that is, that at least locally more material is present than for the wall thickness or

Sheet thickness or the actually developed cross-sectional length of the finally formed sheet metal component would actually be necessary. This excess material is used for

Calibrated out. The excess material can be provided, for example, as a material reserve in the floor area, in the frame area, in the flange area and / or in a transition area between the flange and frame area or frame and floor area.

The yield strength R _p0 , 2 and the tensile strength R _m as well as other parameters described here, such as the elongation at break, are in the sense of the invention in particular in a tensile test according to DIN EN ISO 6892-1: 2017-02, z. B.

Method A, determined. WO 2019/242901 _ g. PCT / EP2019 / 058743

According to the invention, it was recognized _» that a generic method _» , in particular a trimmed or reduced-calibrating deep-drawing process (hereinafter also referred to as the “BKT method”), can be used in such a way that high-dimensional sheet metal components, in particular half-shells, that can produce similar have partly identical or even improved mechanical properties as appropriately dimensioned conventionally deep-drawn sheet metal components, but require a lower operating weight and can also be manufactured true to size and process reliably. It has been shown that the skillful selection of materials described achieves that the final molded component is at least similar or essentially identical mechanical

Has properties (in particular with regard to hardening) and wall thicknesses or sheet thicknesses like a correspondingly dimensioned deep-drawn one

Sheet metal component. This means that the selection of materials according to the invention means that sheet metal components can be provided, which on the one hand have dimensional accuracy familiar from the BKT process on the one hand, and on the other hand the usual low wall thicknesses and mechanical properties, such as the rest, that are familiar from conventional deep drawing (with or without the use of a hold-down device) - Formability (that is, the possibility of plastic deformation that a material can withstand without cracking, such as the elongation at break and the

Yield strength R _p o, ₂ and / or tensile strength R _m ). In some cases, these mechanical properties known from conventional deep drawing, such as the residual formability, can also be exceeded with the same starting material. The properties of the material described relate to the unformed state.

Embodiments of the B KT method attributed to the applicant are described, for example, in German Offenlegungsschriften DE 10 2007 059 251 Al, DE 10 2008 037 612 Al, DE 10 2009 059 197 Al, DE 10 2013 103 612 Al, DE 10 2013 103 751 Al , DE 10 2016 118 418 Al and DE 10 2016 118 419 Al, the content of which is incorporated by reference. The features of the BKT process have in common that in a first process step with a modified A preform is produced that comes as close as possible to the final shape or finished shape of the component, but with the difference that in the

Defined component sections such as flange, frame and / or floor

Excess material are introduced, which are shaped out again in a second method step by a special upsetting of the at least sectionally, in particular entire, preformed component during calibration.

In particular, as described in further details in DE 10 2007 059 251 A1, it can be provided that the entire cross section of the preformed component has excess board material due to its geometric shape, due to the excess material during the forming of the

preformed component in its final shape by at least one other

Pressing the entire cross-section is compressed to the final molded component and the final molded component has an increased wall thickness substantially over the entire cross section.

Likewise, as described in DE 10 2008 037 612 A1, it can be provided in further details that the preformed component has excess board material due to its geometric shape, the excess material during the shaping of the preformed component into its final shape by at least one further pressing process Component is compressed to the final molded component, the preformed component having the excess board material in the transition region between the frame region and the flange region.

Furthermore, as described in DE 10 2016 118 418 A1 in further details, it can be provided that a material quantity adjustment is set in the preformed component, the material quantity adjustment being set with a floor-specific, frame-specific, radius-specific and / or flange-specific material quantity adjustment. Finally, as described in DE 10 2016 118 419 A1 in further details, it can be provided that the bottom area of the preformed component essentially has the geometry and / or the local cross sections of the bottom area of the at least partially finished component.

Compared to conventional deep drawing, in which active, external hold-down can take place, less plastic expansion occurs in the manufacture of the preformed component, which in particular in the component frames, which is what

Residual forming capacity positively influenced. During the subsequent calibration, the introduced excess material is compressed in the direction of the sheet metal plane, which leads to the fact that the springback of the sheet metal components is essentially eliminated, since the introduced compressions overlap the springback forces or transform stresses in the sheet metal component that trigger a springback.

It has been shown that the reduction in plastic elongation and thus the lower increase in the yield strength of the material compared to

Conventional deep drawing can advantageously be compensated for by using a material with a higher yield point than the material used in conventional deep drawing. The final molded component can then have similar or essentially identical mechanical characteristics than if it had been thermoformed. The increased wall thickness or sheet thickness of the finally formed sheet metal component compared to sheet metal components produced by conventional deep drawing can also be advantageously used in such a way that a sheet metal blank of reduced thickness is now used. In particular with regard to a possible elimination of the edge trim, the operating weight can thus be reduced even further.

As a result, it was recognized that, through a skilful selection of materials, the described method can be used to provide components which, with a lower operating weight and less equipment, require high dimensional accuracy of a BKT method and still both a similar or essentially identical geometry as well as similar or essentially identical

mechanical properties to conventional deep-drawn sheet metal components

exhibit. At the same time, the outlay on equipment is reduced compared to classic deep drawing, and the lower degrees of forming also reduce the load on the tools and increase tool life.

According to a preferred embodiment of the method according to the invention, the preforming of the workpiece into the preformed component takes place essentially without holding. This is understood in particular to mean that the method is carried out with a distanced, with a non-force-loaded or even without hold-down or sheet holder. The workpiece is therefore preferably not clamped during preforming. This can be achieved by preforming, for example, using a special form of deep drawing, the so-called “crash forming” or “embossing with folding”.

According to a preferred embodiment of the method according to the invention, the material (in the _unformed state) has a ratio of yield strength R _p0.2 to strength R _m of> 0.56, preferably> 0.6, preferably> 0.62, particularly preferably> 0 , 64, more preferably from> 0.66, more preferably> 0.7. With materials that have a ratio of yield strength R _p0.2 to strength R _m of particularly preferably> 0.64, it is possible to _improve the material properties

adjust the final formed sheet metal component in such a way that they do not differ significantly from or exceed those of a conventionally deep-drawn sheet metal component of similar or essentially identical dimensions. This

Sheet metal components can, however, be manufactured more dimensionally than with conventional deep drawing. Another improvement in aligning the

Properties of the finally formed sheet metal component on a similarly or identically dimensioned conventionally deep-drawn sheet metal component result in particular at a ratio of yield strength R _p0.2 to strength R _m of> 0.66, preferably> 0.7. According to a further embodiment of the method according to the invention

Essentially the entire cross section of the preformed sheet metal component

excess material. As a result, the finally formed sheet metal components can be produced in a dimensionally stable form without excessive local loads

especially to provoke the tools.

In a further preferred embodiment of the method according to the invention, the sheet metal component is a half-shell-shaped sheet metal component, in particular an im

Cross section of U-shaped or hat-shaped sheet metal component. It has been shown that half-shell-shaped sheet metal components, and in particular U-shaped or hat-shaped sheet metal components in cross section, can be produced particularly dimensionally and with advantageous mechanical properties by means of the method according to the invention.

According to a preferred embodiment of the method according to the invention, the workpiece is a sheet metal blank. In particular, the sheet metal plate has a thickness of less than 3.5 mm, preferably less than 3 mm, particularly preferably less than 2.4 mm. For example, the sheet metal plate can have a thickness between 0.7 mm and 1.8 mm. The method according to the invention can be used particularly advantageously directly on sheet metal blanks, further preforming steps can thus be avoided.

According to a further embodiment of the method according to the invention, the material (in the non-deformed state) has a tensile strength R _m of at least 500 MPa, preferably at least 600 MPa, particularly preferably at least 700 MPa along and / or transversely to the rolling direction. For example, the material has a tensile strength R _m of at least 800 and / or at most 1250 MPa along and / or across the rolling direction. It has been shown that, in particular by using materials with a tensile strength in the specified range, it is possible to produce sheet metal components with shaped properties that are similar or identical to conventionally dimensioned, deep-drawn sheet metal components. The material preferably has a tensile strength R _m of 900 to 1200 MPa along and / or across the rolling direction. With such a material, a further improved adjustment of the properties of the finally formed sheet metal component to a similarly or essentially identically dimensioned conventionally deep-drawn sheet metal component can be achieved.

According to a further embodiment of the method according to the invention, the material has a yield strength R _p o _» z of at least 400 MPa, preferably at least 500 MPa, more preferably at least 600 MPa along and / or across

Rolling direction. For example, the material has a yield strength R _p0 , 2 of at least 700 and / or at most 950 MPa along and / or across the rolling direction. It has been shown that, in particular, by using such a material, a further improved matching of the properties of the finally formed sheet metal component to a similarly or essentially identically dimensioned conventionally deep-drawn sheet metal component can be achieved. At the same time, however, it has been shown that, despite the reshaping with a comparatively high yield strength compared to conventional deep drawing, a high degree of dimensional accuracy can be achieved, in particular due to the lower equipment expenditure and the reduced operating weight.

According to a further embodiment of the method according to the invention, the material has an elongation at break Aeo of less than 30%, in particular less than 25%, preferably less than 20%, preferably less than 15%, particularly preferably less than 10%.

In a further embodiment of the method according to the invention, the material is a steel, in particular a multi-phase steel, preferably a dual-phase steel. It was recognized that the method according to the invention can advantageously be used for the production of sheet metal components made of steel, in particular of multi-phase steel, preferably of dual-phase steel. In a further preferred embodiment of the method according to the invention, the material is a steel which has one or more (in particular all) of the following alloy components in percent by weight (% by weight):

0 _< c <0.115,

0 <Si <0.650,

0 <Mn <2.350,

0 <P <0.040,

0 <S <0.0050,

0.015 <Al <0.060,

0 <Cr + Mo <1,000%,

0 <Nb + Ti <0.120%,

0 <V <0.060%,

0 <B <0.0030%,

0 <Cu <0.350%, with the remainder Fe and unavoidable impurities. It has been shown that such steels are particularly suitable for the substitution of steels which are used in one

conventional technical methods for manufacturing similar or identical

dimensioned sheet metal components are used, and still in

Essentially the same mechanical properties as can be achieved with the deep-drawn sheet metal components. By combining the

Material according to the invention with the method steps according to the invention can thus be cost-effectively provided with sheet metal components with essentially identical properties as in conventional deep drawing.

According to a second teaching, the invention also relates to the use of a sheet metal component produced using a method according to the invention

Automotive body component, in particular as a component of a frame, a longitudinal or cross member, a column or a crash structure. In particular, it is a component that is relevant for crash safety. It has been shown that The sheet metal components produced according to the invention are optimally suited for use as an automotive body component. The car body components previously used by conventional deep drawing can thus be replaced by appropriate alternatives.

Furthermore, the invention will be explained in more detail using an exemplary embodiment.

The advantages of the method according to the invention are particularly evident in

Comparison to a corresponding conventional method, which will first be described. Conventional deep-drawing initially produces a sheet metal component from a flat sheet metal sheet of 1.5 mm thickness consisting of a dual-phase steel of the type CR330Y590T-DP with a yield strength of 330 MPa and an elongation at break Aeo of 18%. By using, for example, pressurized hold-down devices in combination with drawing beads during deep drawing to a sheet metal component with a medium wall thickness or

Sheet thickness of 1.35 mm, there is an average elongation of 10% during forming on the sheet metal component. Due to the expansion of the material and the simultaneous hardening, there is still a possible residual expansion of 8% in the sheet metal component before cracks occur, so that the forming capacity is limited accordingly. In addition, there is an increased yield strength of 700 MPa for this conventionally deep-drawn sheet metal component.

In order to use the method proposed according to the invention to produce a sheet metal component with similar or improved properties as by the previous deep drawing, a material is first selected which is a

Ratio of yield strength R _p0.2 to strength R _m of> 0.53, particularly preferably> 0.64 or even> 0.7. The material should have essentially the same mechanical properties after forming as the conventionally deep-drawn sheet metal component, a yield strength of 700 MPa and a minimum elongation at break of 8%. This is so that the final shape After forming, the component has essentially the same wall thickness or sheet thickness as the deep-drawn sheet metal component, a flat sheet metal plate with a thickness of 1.35 mm to 1.4 mm reduced compared to the deep drawing shown above is selected Thickness of 1.4 mm used, which has a ratio of yield strength R _p0.2 to strength R _m of particularly preferably> 0.64. The sheet metal blank made of this material is first preformed into a preformed component, excess material being introduced into the preformed component at least in some areas, and then the preformed component is calibrated to an at least partially finished component using the excess material. The final molded component produced in this way has a geometry that is essentially identical to that of the conventionally deep-drawn component, in particular an essentially identical wall thickness, and also has mechanical properties and crash properties similar to this, but could be produced reliably with high dimensional accuracy.

Claims

Patent claims

1. Process for the production of sheet metal components from one material,

in particular for an automobile body, comprising the process steps:

- Preforming a workpiece into a preformed component, wherein

excess material is introduced into the preformed component at least in regions, and

Calibrating the preformed component to form an at least partially finished component using the excess material, in particular wherein the preformed component is compressed at least in sections,

characterized in that

the material has a ratio of yield strength R _p o, 2 to tensile strength R _m of

Rp0.2 / Rm 5 0.53.

2. The method according to claim 1,

characterized in that

the preforming of the workpiece into the preformed component takes place essentially in a holding manner.

3. The method according to claim 1 or 2,

characterized in that

the material has a ratio of yield strength R _po , 2 to strength R _m of> 0.56, preferably> 0.6, preferably> 0.62, particularly preferably> 0.64, more preferably of> 0.66, more preferably > 0.7.

4. The method according to any one of claims 1 to 3,

characterized in that

essentially the entire cross section of the preformed sheet metal component has excess material.

5. The method according to any one of claims 1 to 4,

characterized in that

the component is a half-shell metal component, in particular an im

Cross section is U-shaped or hat-shaped sheet metal component.

6. The method according to any one of claims 1 to 5,

characterized in that

the workpiece is a sheet metal plate and the sheet metal plate has in particular a thickness of less than 3.5 mm, preferably less than 3 mm, particularly preferably less than 2.4 mm.

7. The method according to any one of claims 1 to 6,

characterized in that

the material has a tensile strength R _m of at least 500 MPa, preferably at least 600 MPa, particularly preferably at least 700 MPa along and / or transversely to the rolling direction.

8. The method according to any one of claims 1 to 7,

characterized in that

the material has a yield strength R _p o, 2 of at least 400 MPa, preferably at least 500 MPa, more preferably at least 600 MPa along and / or across the rolling direction.

9. The method according to any one of claims 1 to 8,

characterized in that that the material has an elongation at break Aeo of less than 30%, in particular less than 25%, preferably less than 20%, preferably less than 15%, particularly preferably less than 10%.

10. The method according to any one of claims 1 to 9,

characterized in that

the material is a steel, in particular a multi-phase steel, preferably a dual-phase steel.

11. The method according to any one of claims 1 to 10,

characterized in that

the material is steel, one or more of the following

Alloy components in percent by weight (% by weight) have:

0 <C <0.115,

0 <Si <0.650,

0 <Mn <2.350,

0 <P <0.040,

0 <S <0.0050,

0.015 <Al <0.060,

0 <Cr + Mo <1,000%,

0 <Nb + Ti <0.120%,

0 <V <0.060%,

0 <B <0.0030%,

0 <Cu <0.350%, with the remainder Fe and unavoidable impurities.

12. Use of a sheet metal component produced by a method according to one of claims 1 to 11 as an automobile body component, in particular as a component a frame, a longitudinal or cross member, a column or one

Crash structure.