Thermoforming and pressure quenching tool and method of operating same

Abstract

The invention relates to a hot-forming and press-quenching tool (1) having an upper tool (2) and a lower tool (3) which can be moved in opposite directions in a press stroke direction (4), a mold cavity (10) being formed between the upper tool (2) and the lower tool (3) in the closed state, a cooling channel (13) for the passage of a cooling medium is formed in the upper tool (2) and / or in the lower tool (3), at least one cutting tool (7) is arranged on the upper tool (2), said cutting tool being movable relative to the upper tool (2). The cutting tool (7) has at least one cooling channel for temperature control and / or the cutting tool (7) has a forming surface (8) oriented in the pressing stroke direction (4) and a cutting edge (9) downstream of the forming surface and / or adjoining the forming surface (8) in the pressing stroke direction (4).

Description

Technical Field

[0001] The present invention relates to hot forming and press quenching tools.

[0002] The invention also relates to a method for producing hot-formed and press-quenched components on a hot-forming and press-quenching tool. Background Art

[0003] Hot forming and press quenching techniques are known in the prior art. For this purpose, particularly in the automotive industry, a steel sheet blank is used, which is heated to a temperature above the austenitizing temperature, that is, above the Ac3 temperature, which typically exceeds 900°C. The heated blank is placed in a hot forming tool and formed while still warm. This offers particularly good formability in terms of freedom of shape. Once the forming process is at least partially, or in particular completely, completed, the component produced in this manner remains in the hot forming tool and is further quenched. In this case, it is heated within a particularly short time to a temperature at which the austenite previously formed due to the austenitizing temperature at least partially transforms into martensite. In this way, tensile strengths Rm exceeding 1000 MPa, in particular exceeding 1250 MPa, and particularly preferably exceeding 1400 MPa, are achieved in the component. For example, a quenching temperature exceeding 27 K / s is selected. When the final temperature is reached, for example below 300°C, in particular below 200°C, the hard component produced in this manner is removed from the hot forming tool.

[0004] It is known from the prior art that these components can be processed mechanically or by separation techniques, for example, during hot forming and / or after the hot forming process or the press quenching process is completed.

[0005] For example, such a manufacturing method is known from DE 10 2011 116 714 A1. The forming process is carried out using forming tool segments. Subsequently, a separating slide is activated to separate the formed components in the closed hot forming tool. Summary of the Invention

[0006] The object of the present invention is to optimize the freedom of shaping and the finishing method compared to the prior art for large-scale production, in particular taking into account the heat losses during shaping.

[0007] The hot forming and press quenching tool consists of an upper tool and a lower tool. The upper tool and the lower tool are movable relative to each other in the direction of the pressing stroke. The pressing stroke direction corresponds essentially to the vertical direction. When closed, a mold cavity remains between the upper and lower tools. In this mold cavity, the previously inserted plate blank or steel sheet blank is subsequently formed into a component. The closed hot forming and press quenching tool with the upper and lower tools rests essentially completely on the formed component. In order to carry out the press quenching process after the hot forming process, cooling channels for the passage of a cooling medium are formed in the upper and lower tools. During the forming process or at the latest after the forming process is completed, a cooling medium is passed through the tools to quench and harden the formed component.

[0008] Furthermore, at least one cutting tool is arranged in the upper tool and is movable relative to the upper tool.

[0009] According to the present invention, the hot forming and press-hardening tool forming process is now characterized by the cutting tool itself having at least one cooling channel. This cooling channel is controlled separately from the cooling channels in the upper and lower tools. The at least one cooling channel allows for individual tempering of the cutting tool. Suitable supply and discharge lines are provided on the cutting tool. The present invention thus ensures that a temperature of between 500°C and 700°C is achieved at the component's cutting edge during the trimming process. Further cooling after trimming allows the trimmed edge on the component to be press-hardened accordingly.

[0010] Alternatively or additionally, the cutting tool has a forming surface oriented in the direction of the pressing stroke and a cutting edge located behind and / or adjacent to the forming surface in the direction of the pressing stroke. The cutting edge is thus formed on the cutting tool itself. Thus, when the hot forming and press hardening tools are closed in the direction of the pressing stroke, the steel sheet blank placed on the clamping device or on the lower tool is first formed by the forming surface of the cutting tool. In particular, due to the tempering of the cutting tool, no intense cooling occurs at the beginning of the forming process, and thus no press hardening occurs. The cutting movement is preferably performed only when the hot forming tool is at its bottom dead center. Another significant advantage is that the forming surface of the cutting tool itself provides greater precision for the cutting line or cutting contour to be created. Because of the concerns regarding the cutting tool, especially during the forming process itself, a precise geometric position relative to the cutting tool is optimal for finishing immediately after forming. The cutting tool can thus be pre-centered with respect to the cutting edge.

[0011] To this end, the cutting tool is designed specifically as a slender tool and is positioned specifically in the edge region of the upper tool. For example, particularly slender automotive components, such as motor vehicle pillars, such as A- or B-pillars, can be trimmed with the utmost precision, at least in sections. Simultaneously, thanks to the temperature control of the cutting tool and the ability to control microstructural transformations during the press-hardening process, not only the cutting geometry but also the desired material properties of the resulting cutting edge region on the component are optimized.

[0012] Furthermore, the lower tool is preferably formed with a cutting edge that corresponds to the cutting edge of the cutting tool and is trimmed by the relative movement of the cutting tool relative to the lower tool. In particular, the lower tool is securely connected to the lower press table. The cutting edge of the lower tool can be formed directly on the lower tool. However, the cutting edge of the lower tool can be designed as a blade or segment. For example, if the cutting edge of the lower tool becomes worn, it can be replaced, thereby achieving high-precision trimming of the edge.

[0013] The forming surface of the cutting tool itself is in particular a rounded edge. In particular, if the cutting tool is arranged on the outer edge area of ​​the upper tool, the edge area of ​​the component to be formed is bent corresponding to the lower tool according to the principle of deep drawing or bending. The forming surface can be designed to be variable over the length of the cutting tool, or to vary along the length of the cutting tool. Therefore, the forming surface is not a radius that extends constantly along the longitudinal direction of the cutting tool. Chamfers or forming surfaces of different radii can be formed on the forming surface of the cutting tool. This makes it possible to produce and subsequently trim components with complex three-dimensional shapes. The cutting edge itself does not have to be straight, but can have a variable direction to adapt to the shape geometry of the component to be produced later.

[0014] As the lowering motion continues until it reaches bottom dead center, a cavity is formed between the upper and lower tools. Once the forming process is complete, the forming surface of the cutting tool no longer forms part of the cavity. The separation operation then takes place. In this sense, the cutting edge of the cutting tool represents the outer boundary of the cavity. The cutting motion confines the cavity to the outside relative to the cutting edge created on the component.

[0015] The cutting tool itself is designed as a segment and is mounted in a floating manner on or in an upper tool.

[0016] The cutting tool preferably has an elongated extension. This elongated extension is particularly longer than 15 cm, particularly preferably longer than 20 cm, and in particular longer than 30 cm. Thus, the cutting tool according to the invention allows for highly precise trimming of particularly long cutting edges tailored to the geometry and material properties to be adjusted. The elongated extension of the cutting tool can then essentially correspond to the length of the cutting edge.

[0017] To enable the cutting tool to move relative to the upper tool, the cutting tool is preferably driven directly by an actuator. The actuator is preferably a hydraulic actuator, in particular a hydraulic cylinder. Preferably, a plurality of hydraulic cylinders are provided. These cylinders are then slid out in the direction of movement of the cutting tool.

[0018] If higher cutting forces are required, the cutting tool can preferably also be driven by a force converter, in particular in the form of a wedge-shaped slide. The wedge-shaped slide itself is then moved by an actuator.

[0019] The direction of movement of the cutting tool itself is substantially perpendicular to the direction of the pressing stroke. Specifically, the direction of movement of the cutting tool extends at an angle between 40° and 90°, particularly between 50° and 90°, and particularly preferably between 60° and 90°, between the direction of movement of the cutting tool and the direction of the pressing stroke of the thermoforming tool. The direction of the pressing stroke of the thermoforming tool is substantially vertically oriented. In simple terms, the direction of movement of the cutting tool can be substantially horizontal or extend at the aforementioned angle.

[0020] The cutting tool is further mounted in a floating manner on the upper tool. Specifically, for example, the predetermined cutting geometry of the resulting cutting edge of the formed component can be determined by the cutting edge of the lower tool. The floating bearing of the cutting tool then enables the cutting tool to move slightly laterally and / or vertically with respect to its actual direction of movement during the cutting movement, thereby optimally adjusting the cutting edge of the lower tool. This results in a particularly high precision of the cutting geometry. For example, the cutting tool itself is spring-elastically supported in the direction of the pressing stroke. For example, the cutting tool can have axial freedom in its direction of movement or be guided axially.

[0021] The present invention relates to a method for producing hot-formed and press-quenched components, in particular on the aforementioned hot-forming and press-quenching tool. The method is characterized by the following steps:

[0022] Heat the steel plate blank to above Ac3 temperature;

[0023] Insert into thermoforming tool and perform forming operation;

[0024] Reach bottom dead center;

[0025] After reaching bottom dead center, performing a separation operation by moving the cutting tool relative to the upper tool, wherein the temperature of the cutting edge is between 500° C. and 700° C. at the beginning of the separation operation and / or during the separation operation;

[0026] The formed component is quench-hardened and removed.

[0027] This means that a sheet steel blank made of a hardenable steel alloy (e.g., 22MnB5) is heated to above the Ac3 temperature. This temperature is above the austenitization temperature and typically exceeds 900°C. The thus-heated sheet steel blank is then placed in a combined hot forming and press quenching tool and the forming operation is carried out. An undesirable side effect is that the thus-heated sheet steel blank or the partially formed component cools down while the system and the tool face are in contact. However, this is negligible. Specifically, the forming operation is completed in just 3 seconds. Particularly preferably, the time between removal from the heating furnace, insertion into the hot forming tool, and completion of the forming operation is less than 10 seconds, for example.

[0028] The forming operation is performed in the direction of the pressing stroke until the upper and lower tools are in the so-called bottom dead center, i.e., there is no further relative movement between the upper and lower tools, and the sheet metal blank is completely formed into the desired component. According to the invention, in particular, part of the forming operation is performed by the cutting tool itself, in particular the forming surface of the cutting tool.

[0029] When or immediately after reaching the bottom dead center, a separation operation is performed on at least one edge of the component to be produced using the cutting tool according to the invention, thereby producing a cutting edge on the formed component. The cutting edge has a cutting edge length that corresponds in particular to at least 10% of the circumferential length of the formed steel sheet material. The cutting is carried out at the edge of the component and is an edge trimming. At the beginning of the separation operation and / or during the separation operation, the material temperature in the edge of the component (i.e. at the cutting edge produced) is between 500°C and 650°C. After the separation operation is completed, the temperature can still be within the above range. This is particularly possible because the cutting tool is tempered separately due to at least one cooling channel in the cutting movement. Immediately after the cutting operation is completed, the cooling of the cutting tool can also cause press quenching of the external cutting edge. Therefore, even in the area of ​​the cutting edge, the material structure that needs to be set can be produced reliably and in a manner suitable for large-scale production.

[0030] After completing the forming operation and / or finishing operation, the entire component is press-hardened in a hot forming and press-hardening tool. Here, a suitable cooling medium is guided through the upper tool and the lower tool so that the formed and finished component realizes at least partial, particularly complete, martensitic transformation.

[0031] The separation operation itself is preferably carried out completely. Partial separation is then achieved through appropriate waste disposal or treatment. However, according to the invention, the separation operation can also be carried out only partially. This means that at least 50% of the wall thickness of the molded component is cut through. In a subsequent processing step, the remaining wall thickness is cut off in a final separation operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Further advantages, features, characteristics and aspects are the subject of the following description. Preferred designs are shown in schematic diagrams. These help to make the invention easier to understand. In the accompanying drawings:

[0033] Figure 1 The hot forming and press-quenching tool according to the invention is shown in the open state with a sheet metal blank inserted therein;

[0034] Figure 2 The tool is shown in a partially closed state;

[0035] Figure 3 The tool is shown at bottom dead center;

[0036] Figure 4 The tool is shown at bottom dead center and performing a dressing motion;

[0037] Figure 5 An example of a thermoforming tool closing and performing a cutting motion is shown;

[0038] Figure 6 Different movements of the cutting tool achieved by direct actuators or wedge slides are shown;

[0039] Figure 7 Shown along Figure 6 Section line AA of the cutting tool according to the invention.

[0040] In the drawings, the same reference symbols are used to denote the same components even though repeated descriptions are omitted for simplicity.

[0041] List of reference numerals:

[0042] 1. Hot forming and press quenching tools; 2. Upper tool; 3. Lower tool; 4. Pressing stroke direction; 5. Cooling channels of 2 and 3; 6. Steel plate blank; 7. Cutting tool; 8. Forming surface of 7; 9. Cutting edge of 7; 10. Die cavity; 11. Movement direction of 7; 12. Cutting edge of 3; 13. Cooling channel of 7; 14. External part of 6; 15. Actuator; 16. Spring element; 17. Slide rail; 18. Wedge-shaped slider; 19. Upper slide rail; 20. Axial guide element; L, length; V, vertical direction; α, angle. DETAILED DESCRIPTION

[0043] Figure 1The hot forming and press hardening tool 1 according to the invention is shown in the open state. It comprises an upper tool 2 and a lower tool 3. The upper tool 1 is designed as a female tool, while the lower tool 3 is designed as a male tool. Therefore, relative to the vertical direction V, the lower tool 3 rises in the pressing stroke direction 4. However, within the scope of the invention, it is conceivable that the lower tool 3 is arranged fixedly, while the upper tool 2 is lowered onto or sunk into the lower tool 3.

[0044] This movement takes place in the pressing stroke direction 4. The upper tool 2 and the lower tool 3 each have a cooling channel 5.

[0045] The inserted steel sheet blank 6 (hereinafter also referred to as sheet blank) is placed on the lower tool 3. Cutting tools 7 according to the present invention are arranged on the left and right sides of the upper tool 2. The respective cutting tools 7 are arranged in the outer edge region of the upper tool 2. The cutting tools 7 have forming surfaces 8 pointing in the direction of the pressing stroke 4.

[0046] according to Figure 2 , the lower tool 3 has been raised along the pressing stroke direction 4. The blank is bent along the pressing stroke direction 4 around the forming surface 8 of the cutting tool 7, and then along Figure 4 By moving further together in the pressing stroke direction 4, then occupying Figure 3 The position shown. This is the bottom dead center. Thus, the upper tool 2 and the lower tool 3 are completely closed in the pressing stroke direction 4. This results in almost full-surface contact of the die cavity 10 and the blank (not shown in detail) within the die cavity 10. The cutting tool 7, in particular the forming surface 8 of the cutting tool 7, no longer rests on the blank (not shown in detail).

[0047] When or immediately after reaching the bottom dead center, the cutting tool 7 is moved in a movement direction 11. The movement direction 11 is arranged at an angle α of preferably 40° to 90° with respect to the pressing stroke direction 4.

[0048] The cutting edge 12 of the cutting tool 7 corresponds to the cutting edge 9 of the lower tool 3. As a result, a piece of the plate that protrudes relative to the cutting movement 11 or shearing movement is cut and thus severed.

[0049] Cooling channels 5 are provided within the cutting tool 7 itself. The presence of at least one cooling channel 5 allows the temperature of the cutting tool 7 to be regulated. The cutting tool 7 can, for example, have residual heat, so that before the start of the cutting process, the sheet metal blank resting against the cutting tool 7 is only slightly cooled, but in particular does not at least partially harden in this area, so that the cutting process can be carried out in soft or unhardened areas.

[0050] Figure 5 a to Figure 5 d shows again in detail Figures 1 to 4 According to the process. Figure 5 a, the steel sheet blank 6 is placed on the lower tool 3. Then, the lower tool 3 moves into the upper tool 2 along the pressing stroke direction 4, thereby starting the forming process, as shown in FIG. Figure 5 As shown in b. Then the outer part of the steel plate blank 6 is bent. Specifically, this occurs due to the contact of the system with the forming surface of the cutting tool 7. Figure 5 In Figure c, the forming process has ended. The upper tool 2 and the lower tool 3 are in contact with each other and are at the bottom dead center. In the case of the formed component, the outer part of the steel plate protrudes outward from the mold cavity 10.

[0051] according to Figure 5 d. The cutting tool 7 then moves in the direction of movement 11 and separates the outer part of the shaped component. A cutting movement is thus performed when the cutting edge 12 of the cutting tool 7 passes the cutting edge 12 of the lower tool 3, which occurs due to a corresponding cutting movement.

[0052] Figure 6 On the left side of the image plane is shown the cutting tool 7 which is driven directly by the actuator 15 and which is also Figures 1 to 4 . This can be, for example, a hydraulic cylinder. The actuator 15 moves the cutting tool 7 directly in the direction of movement 11. For this purpose, the cutting tool 7 is mounted floatingly on the upper tool 2. In the pressing stroke direction 4, the cutting tool 7 can be spring-loaded, for example, by means of a spring element 16, so that a certain amount of play can be achieved in the pressing stroke direction 4. As a result, in the subsequent cutting movement, in particular the cutting edge 12 of the lower tool 3 can pass with corresponding precision. When the bottom dead center is reached, the cutting tool 7 can rest on a lower slide 17, which can be fastened, for example, to a part of the lower tool 3, so that the cutting tool is guided on the slide 17 and on the upper side by the spring support.

[0053] If increased forming force is required, the motion can be switched to motion direction 11 by means of the wedge slide 18, so that a greater force can be applied for cutting. This can occur, for example, if the cutting edge extends more than 20 cm, and in particular more than 30 cm, into the image plane. The wedge slide 18 itself can also be driven by the actuator 15. However, due to the transmission between the wedge slide 18 and the cutting tool 7, a greater cutting force can be applied.

[0054] Within the scope of the invention, the two drive devices can also be combined, in particular if, for example, two cutting tools 7 are connected to the upper tool 2, and the cutting tools 7 need only exert a small cutting force due to the short cutting edge on the component. However, the other cutting tool 7 requires a greater cutting force, for example if the cutting edge is greater than 20 cm, in particular greater than 30 cm.

[0055] Figure 7 Shown along Figure 6 A sectional view along the section line AA of FIG. 1 shows the cutting tool 7, which has a corresponding length L. This length L corresponds to the length L of the cutting edge to be produced on the component and can be, for example, greater than 20 cm, in particular greater than 30 cm. The cutting tool 7 is mounted in the upper tool 2 in the direction of the pressing stroke via a spring device 16. The cutting tool 7 can also have an upper slide 19 between the spring device 16 and the upper tool 2. The cutting tool 7 is mounted on the corresponding slide 17 on the lower tool 3 and rests on the slide 17. Additional axial guide elements 20 can also be provided.

Claims

1. A hot forming and press hardening tool (1) comprising an upper tool (2) and a lower tool (3), said upper tool and lower tool being movable towards each other in a pressing stroke direction (4), wherein: In a closed state, a mold cavity (11) is formed between the upper tool (2) and the lower tool (3), and a cooling channel (5) for allowing a cooling medium to pass through is formed in the upper tool (2) and / or the lower tool (3), wherein at least one cutting tool (7) that can move relative to the upper tool (2) is arranged on the upper tool (2), characterized in that the cutting tool (7) has at least one cooling channel (13) for temperature control and / or the cutting tool (7) has a forming surface (8) oriented along the pressing stroke direction (4) and a cutting edge (9) located behind the forming surface and / or adjacent to the forming surface (8) along the pressing stroke direction (4).

2. The hot forming and press quenching tool (1) according to claim 1, characterized in that A cutting tool (7) is arranged in the edge region of the upper tool (2).

3. The hot forming and press quenching tool (1) according to claim 1 or 2, characterized in that A cutting edge (12) is formed on the lower tool (3), and the cutting edge performs a cutting movement together with the cutting tool (7).

4. Hot forming and press hardening tool (1) according to one of the preceding claims, characterized in that The profile surface (8) is a rounded edge, wherein in particular the profile surface changes in the longitudinal direction of the cutting tool (7).

5. Hot forming and press quenching tool (1) according to one of the preceding claims, characterized in that The cutting tool (7) is designed in a segmented manner, in particular having an elongated extension greater than 15 cm, in particular greater than 20 cm, in particular greater than 30 cm.

6. Hot forming and press quenching tool (1) according to one of the preceding claims, characterized in that The cutting tool (7) is driven directly by an actuator (15), or the cutting tool (7) is driven by a force converter (18), in particular in the form of a wedge mechanism.

7. Hot forming and press hardening tool (1) according to one of the preceding claims, characterized in that The direction of movement of the cutting tool (7) extends oriented at an angle to the pressing stroke direction, the angle being between 40° and 90°, in particular between 50° and 90°, particularly preferably between 60° and 90°.

8. Hot forming and press hardening tool (1) according to one of the preceding claims, characterized in that The cutting tool (7) is mounted floatingly on the upper tool (2).

9. Hot forming and press hardening tool (1) according to one of the preceding claims, characterized in that The cutting tool (7) is mounted in a spring-elastic manner in the pressing stroke direction (4).

10. A method for producing hot-formed and press-quenched components, in particular using a hot-forming and press-quenching tool (1) according to claim 1, characterized in that The method comprises the following steps: -Heat the steel plate blank to above Ac3 temperature, - inserting the hot forming and press quenching tool (1) and performing the forming operation, -reaching bottom dead center, - after reaching the bottom dead center, performing a separation operation by moving the cutting tool (7) relative to the upper tool (2), wherein at the beginning of the separation operation and / or during the separation operation, the temperature of the cutting edge is 500° C. to 700° C., The shaped component is at least partially quench-hardened and removed.

11. The method according to claim 10, characterized in that The separation operation is carried out completely or to at least 50%, based on the wall thickness of the component being formed.

12. The method according to claim 10, characterized in that After trimming, a tensile strength of more than 1350 MPa is set in the trimmed edge by cooling and press quenching.

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