DE102011108912A1 - Segmented press hardening tool - Google Patents

Abstract

The invention relates to a press hardening tool (100) for producing hardened sheet metal parts from a sheet steel material (400), comprising at least two tool parts which are movable relative to one another in a working direction (D) and between which by applying a pressing force (F) acting in the working direction (D) ) a heated sheet steel material (400) can be formed and cooled and thereby hardened. It is provided that at least one of the tool parts (220) is formed segmented and at least a first segment (221) with a transversely to the working direction (D) extending mold portion and at least a second segment (223) with a steep to the working direction (D ), wherein the first segment (221) is movably disposed on the respective tool part (220) and can yield when exceeding a certain pressing force (F) against the applied pressing force (F) (A), thereby further moving the tool parts together and allowing associated increased pressure (B, C) of the second segment (223) on the steel sheet material (400).

Description

The invention relates to a press hardening tool for producing hardened sheet metal parts from a hardenable steel sheet material.

Press hardening tools for producing hardened sheet metal parts are known from the prior art. Such press hardening tools comprise at least two tool parts which are movable relative to one another in a working direction and between which a heated sheet steel material is formed and, at the same time, cooled simultaneously under application of a pressing force, whereby an increase in strength occurs according to the known metallurgical mechanisms.

In order to achieve the best possible cooling and in a good shape retention, a full-surface concerns of the steel sheet material to the tool acting surfaces of the tool parts is required during the press hardening process. This full-surface concern is usually achieved by a complex incorporation of the press-hardening tool. In practice, however, despite this incorporation, a full-surface concerns of the steel sheet material on the tool effective surfaces, especially in steep areas (i.e., steep with respect to the working direction), can not be reliably guaranteed, which z. B. is due to increasing tool wear and / or irregular thickness distributions of the steel sheet material.

This problem is already in the WO 2006/015849 A2 explained. To solve this problem is in the WO 2006/015849 A2 proposed a press-hardening tool in which the steel sheet material is only partially clamped in relevant areas between the tool parts during press hardening, for which purpose the tool effective surfaces are formed with corresponding clamping webs (for example in the form of protrusions or oversizes). In the areas where the steel sheet material is not clamped in the press hardening process, this is spaced with an air gap to one or both tool effective surfaces.

A disadvantage of the in the WO 2006/015849 A2 However, the proposed press hardening tool is that the steel sheet material in the non-clamped areas undergoes no or only a relatively smaller increase in strength due to the lower cooling rate. The sheet metal part produced thus has different strength properties. However, such a sheet metal part is not suitable for all uses.

It is therefore an object of the present invention to provide a press-hardening tool that does not have the abovementioned disadvantages or at least only to a lesser extent.

This object is achieved by a press-hardening tool according to the invention having the features of claim 1. The features and feature combinations specified in the dependent claims relate to preferred refinements and developments of the press-hardening tool according to the invention.

The press-hardening tool according to the invention comprises at least two tool parts which are movable relative to one another in a working direction and between which a heated steel sheet material is formed by application of a pressing force acting in the working direction (shaping of the sheet steel material is understood as forming and / or holding, as explained in more detail below). and cooled and this can be cured in a known manner. According to the invention, at least one of the tool parts is formed at least partially segmented and has at least a first segment with a transverse to the working direction extending form portion and at least a second segment with a steeply extending to the working direction form portion, wherein the first segment movable on the respective tool part is arranged and give in against a given pressing force against this applied pressing force or can retreat, thereby enabling further movement of the tool parts and a concomitant increased pressing of the second segment to the steel sheet material. The press-hardening tool according to the invention can be designed for the simultaneous production of a plurality of hardened sheet-metal shaped parts. Furthermore, the production of partially hardened sheet-metal shaped parts is also possible with the press-hardening tool according to the invention.

In order to accomplish the cooling of the steel sheet material during the press hardening process, it is preferably provided that at least one tool part and in particular also the segmented tool part is designed as a coolable tool part, for which purpose this tool part is equipped with at least one cooling device for cooling or at least partially cooling the tool effective surface. In particular, at least one second segment is formed with at least one cooling device (eg cooling channels).

The segments of a segmented trained tool part each have a mold section. A molding section is understood to mean a surface area belonging to a tool effective area, which is directly connected to the steel sheet material during the press hardening process Contact touch arrives. This shape portion may be flat or formed with a spatial shape. A form section extending transversely to the working direction is understood to mean, in particular, a surface section (the tool active surface) which extends substantially perpendicularly to the working direction. Under a steeply extending to the working direction of the mold section is in particular a surface portion (the tool acting surface) understood, which extends substantially at an angle of 0 ° to 15 ° to the working direction. To assess the extension or alignment of a mold section, a mathematical compensation surface for the surface section in question may be considered. The segments of a segmented tool part are preferably designed and arranged such that their mold sections form a substantially gap-free tool effective area at each point in time of the press hardening process.

By at least a first segment yielding or shrinking against this applied pressing force in the press hardening process when exceeding a certain or defined pressing force, the tool parts of the press-hardening tool according to the invention (without appreciable increase of the applied pressing force) can be moved even further together (in the order of a few hundredths or tenths of a millimeter), whereby in the steep areas, the surface portions of the opposing or corresponding tool acting surfaces are moved towards each other in the working direction. By means of the tool-making measures according to the invention, it is thus also possible to provide the sheet-metal material to be hardened with sufficient force to mold and cool in the areas steep to the working direction (for example in the frame areas) with a high surface pressure (in particular in relation to conventional press-hardening tools). be achieved.

In contrast to that from the WO 2006/015849 A2 Known press hardening tool, the tool parts of the press-hardening tool according to the invention are preferably designed such that the steel sheet material over the entire surface can rest against the tool-working surfaces of these tool parts. With appropriate design of the cooling devices in this case a uniform cooling and good shape retention can be achieved over the sheet metal part. Irrespective of this, the press hardening tool according to the invention can also be designed in such a way that the steel sheet material to be hardened rests only in regions on the tool acting surfaces during the press hardening process.

It is preferably provided that both the first segment and the second segment are fastened to a base plate belonging to the respective tool part, wherein the first segment (which has a form section extending transversely to the working direction) is supported directly or indirectly resiliently on this base plate. Due to the resilient support of the first segment to a base plate extending transversely to the direction of the mold section remains permanent, d. H. in particular also during the further movement of the tool parts, with the steel sheet material in touching contact and also brings a defined compressive force or surface pressure on the steel sheet material. Furthermore, locally occurring excessive pressing forces can be reduced, which could lead to sheet metal molding errors and / or damage to the press hardening tool.

The resilient support of a first segment can, for. B. by mechanical springs, such as. Belleville springs, be accomplished. Particularly preferably, it is provided that the resilient support of a first segment is accomplished by at least one gas spring and in particular by at least one nitrogen spring. Such gas springs or nitrogen springs are available as purchased parts. The maximum travel of a first segment relative to the base plate may be between 0.5 mm and 1.5 mm, and in particular approximately 1.0 mm. The maximum travel can be limited in both directions by a mechanical stop.

It is particularly preferred that at least one second segment (which has a steeply extending to the working direction mold section) is designed as a slide, which is designed as a slide second segment is moved during further movement of the tool parts in a direction transverse to the direction and this quasi active is pressed against the steel sheet material reinforced. As a result, the sheet steel material is pressed locally in this area reinforced to the corresponding tool effective surface of the opposite tool part, which can be achieved for shaping and cooling optimal surface contact of the sheet steel to be hardened material to the mold surfaces with an associated herewith optimal surface pressure. The case taking place slide stroke z. B. in the range of a few hundredths to several tenths of a millimeter.

For the mechanical actuation of a second segment designed as a slide, the relevant tool part can have at least one driver. This driver can be designed as a driver block, directly or indirectly on the tool base plate of the relevant tool part is attached. In particular, it is provided that the driver or driver block and formed as a slider second segment are formed with corresponding inclined surfaces, which slide on each other when moving the tool parts of the press hardening tool, about which in a known manner the displacement of the slider formed as a second segment is accomplished.

Furthermore, it is preferably provided that the second segment designed as a slide has at least one cooling device. Such a cooling device can, for. B. be incorporated in the second segment cooling channels, which can be traversed by a cooling medium. By this measure, an optimal cooling of the steel sheet material during press hardening process can be accomplished even in steep areas.

A particularly preferred embodiment of the press-hardening tool according to the invention provides that only one tool part and in particular only the die is segmented. Such a press-hardening tool will be explained in more detail below in connection with the figures.

Further features and advantages of the invention will become apparent in a non-restrictive manner from the following exemplary description with reference to the schematic figures.

1 shows a sectional view of an inventive press hardening tool.

2 shows in a sectional view a press hardening process with the press hardening tool of FIG 1 ,

1 shows a press hardening tool according to the invention 100 for producing hardened sheet metal parts. The press hardening tool 100 includes a first upper tool part 200 and a second lower tool part 300 , As shown, the press hardening tool is located 100 in an open state. To close the press hardening tool 100 is the upper part of the tool 200 in the direction of work specified with D relative to the lower tool part 300 moveable, including the press hardening tool 100 is installed in a forming press, not shown.

The upper tool part (upper tool) 200 has an upper base plate 210 on top of which is a chilled die 220 is constructed. The matrix 220 is segmented and includes a first middle segment 221 , which has a substantially horizontally and perpendicular to the working direction D extending form portion 222 and a plurality of second lateral segments 223 immediately adjacent to the first segment 221 are arranged and extending steeply to the working direction D form sections 224 exhibit. The steeply aligned to the direction D mold sections 224 the second segments 223 extend at an angle y of about 15 ° to the working direction D, which is the second segment shown on the right 223 is illustrated with dashed lines (the oblique line represents a compensating surface for the mold section 224 ). The mold sections 222 and 224 form a closed die-side tool effective area. With 230 Cooling channels are designated for cooling the die-side tool effective surface or the mold sections 222 and 224 be traversed by a cooling medium.

The first segment 221 is over several gas springs 260 directly on the upper base plate 210 supported and can by compression of these gas springs 260 move back against the direction of work D. To limit the travel, optional is a spacer 225 intended. Due to the number and design of the gas springs 260 can one on the first segment 221 effective spring force can be adjusted.

The second segments 223 are designed as slides, which can be moved transversely to the working direction D. The displacement of the slide formed as a second segments 223 done by the Treiberklötze 240 , which is directly on the upper base plate 210 are attached. The driver pegs 240 and formed as a slider second segments 223 have corresponding oblique surfaces when moving the upper tool part 200 can slide on each other in the working direction D, which in a known manner, the shifting of the second segments designed as a slide 223 transversely to the working direction D is accomplished. In addition, not shown actuators (eg. Hydraulic Kurzhubzylinder) in the upper part of the tool 200 be installed. At the inclined surfaces of the driver pads 240 are sliding plates 250 attached. Also on the corresponding inclined surfaces of the slide formed as a second segments 223 Sliding plates or the like may be attached. Means for resetting the second segments designed as slides 223 are not shown. The reset could z. B. by spring elements (such as, for example, gas springs) accomplished.

The lower tool part (lower tool) 300 has a lower base plate 310 on top of which a chilled stamp 320 is constructed. The Stamp 320 is designed as a rigid punch and has a closed punch-side tool acting surface. The Stamp 320 can also be of a different design. Corresponding to the die-side tool acting surface, the punch-side tool acting surface comprises an area (or area). Mold section) 322 which extends substantially perpendicular to the working direction D, and a plurality of regions (or mold sections) 324 , which extend steeply to the working direction D. With 330 Cooling channels are referred to, which are flowed through by a cooling medium for cooling the punch-side tool effective area. The lower tool part 300 may further comprise a hold-down (not shown) or blank holder. This is preferably a cooled down holder which has a corresponding cooling device (such as, for example, cooling channels).

To produce a hardened sheet metal part, a heated sheet steel material is introduced into the opened press hardening tool 100 inserted. Typically, the sheet steel material to be cured becomes prior to loading into the press hardening tool 100 heated to a temperature of more than 900 ° C. In a first variant of the method, the steel sheet material to be hardened, when placed in the press-hardening tool, can be in the form of a flat sheet-metal blank (direct press-hardening method, wherein the press-hardening tool has a deforming function). In a second variant of the method, the steel sheet material to be hardened when inserted into the press hardening tool may have the form of an already cold preformed sheet metal part or intermediate molded part (indirect press hardening, wherein the press hardening tool has a reshaping or shape-retaining function). After inserting a heated sheet steel material, the press hardening tool becomes 100 for performing a press hardening operation by moving the upper tool part 200 closed in working direction D.

2 shows the press hardening tool 100 in the closed state. Between the matrix 220 and the stamp 320 is a hardened steel sheet material 400 when closing the press hardening tool 100 was shaped according to the punch and die contour and rests widely on the tool effective surfaces. The matrix 220 is located as a whole in a lower end position and can no longer be moved in the working direction D.

Is the matrix located 220 in the illustrated lower end position of the forming press is required for press hardening pressing force F on the press hardening tool 100 applied what is through the on the upper base plate 210 directed force arrow F is illustrated. The applied pressing force F leads to an increase in pressure in the gas pressure springs 260 when closing the press hardening tool 100 initially served only for power transmission. When exceeding a certain or defined by design pressing force F, the gas springs 260 which in this case is synonymous with a yielding of the first segment 221 against the applied pressing force F, at least until this to the optional spacer element 225 abuts (as in 2 shown). By the compression of the gas springs 260 can the tool parts 200 and 300 continue driving together (or the upper tool part 200 can continue in the working direction D on the lower tool part 300 be approached), this collapse is accomplished by the effective pressing force F.

The further movement of the tool parts 200 and 300 goes hand in hand with an analog compression of the gas springs 260 , This compression of the gas springs 260 requires a continuous yielding of the first segment 221 , This yielding may be considered a retraction of the first segment, which in and of itself remains stationary 221 within the upper part of the tool 200 be understood, in which the first segment 221 , as illustrated by the movement arrow A, almost to the upper base plate 210 too moved, although the upper base plate 210 actually on the first segment 221 too moved. The gas springs 260 also cause the first segment 221 or its shape section 222 at any time of the press hardening process with the steel sheet material 400 remains in touch, with a specific one of the gas springs in the area in question 260 generated compressive force (which optionally with a on the spacer 225 transferred compressive force superimposed) on the steel sheet material 400 is applied, resulting in a flat concern of the sheet steel material to be hardened 400 at the mold sections 222 and 322 leads with a defined surface pressure.

Furthermore, it comes because of by compression of the gas springs 260 enabled further collision of the tool parts 200 and 300 to one through the Treibklötze 240 initiated displacement of the slide formed as a second segments 223 in the direction of the stamp 320 so these segments 223 as illustrated with the movement arrows B, reinforced in the steep areas with a certain compressive force against the steel sheet material 400 be pressed. This leads to a flat and especially large-area concerns of the sheet steel material to be hardened even in the steep areas 400 at the corresponding tool effective surfaces or at the corresponding mold sections 224 and 324 with a relatively high surface pressure. This allows a quick and uniform cooling of the steel sheet material 400 even in the steep areas, resulting in an optimal increase in strength in sheet steel material 400 is brought about. Regardless of this, the second segments designed as slides have 223 also a forming (ie transforming or at least shape-preserving) function. With regard to this formative function also larger displacement movements or slide strokes can be provided, which exceed the above-mentioned orders of magnitude in the range of a few hundredths to several tenths of a millimeter, in which case preferably also the maximum travel or travel of a first segment relative to the base plate more than 1.5 mm can amount.

Incidentally, the sliding movement B of the second segments designed as slides superimposed 223 with the movement of the upper tool part 200 in the working direction D during further movement of the tool parts 200 and 300 , By appropriate design of the driver 240 and / or designed as a slide. second segments 223 can advantageously a substantially perpendicular to the punch-side Werkzeugwirkflächebereich 324 directional slider movement are generated, which is exemplary of the right side second segment 223 with the arrow C is illustrated.

After cooling the steel sheet material 400 What is done while maintaining the pressing force F, the press hardening tool 100 by moving the upper part of the tool 200 open against the direction of D and the hardened sheet metal part can be removed. The hardened sheet metal part is, for. B. to a vehicle tunnel for a motor vehicle body, which by design has steep area.

LIST OF REFERENCE NUMBERS

100

Press hardening tool

200

upper tool part (upper tool)

210

upper base plate

220

die

221

first segment

222

Molding section (first segment)

223

second segment / slider

224

Molding section (second segment)

225

spacer

230

Cooling device, cooling channels

240

driver

250

sliding plate

260

Gas spring

300

lower tool part (lower tool)

310

lower base plate

320

stamp

330

Cooling device, cooling channels

400

Steel sheet material

A

Back-off movement (of the first segment)

B

Movement movement (of the second segment)

C

resulting slider movement

D

working direction

F

pressing force

y

angle

QUOTES INCLUDE IN THE DESCRIPTION

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

Cited patent literature

• WO 2006/015849 A2 [0004, 0004, 0005, 0012]

Claims (9)

Press hardening tool ( 100 ) for producing hardened sheet metal parts from a steel sheet material ( 400 ), comprising at least two tool parts ( 200 . 300 ) which are movable relative to one another in a working direction (D) and between which a heated steel sheet material (in which a pressing force (F) is applied in the working direction (D) is applied). 400 ) can be formed and cooled and thereby hardened, characterized in that at least one of the tool parts ( 200 . 300 ) is formed segmented and at least a first segment ( 221 ) with a transverse to the working direction (D) extending form portion ( 222 ) and at least one second segment ( 223 ) with a steeply extending to the working direction (D) form section ( 224 ), wherein the first segment ( 221 ) movable on the relevant tool part ( 200 . 300 ) is arranged and upon exceeding a certain pressing force (F) against the applied pressing force (F) can yield, thereby further collapse of the tool parts ( 200 . 300 ) and a concomitant increased pressure of the second segment ( 223 ) to the steel sheet material ( 400 ). Press hardening tool ( 100 ) according to claim 1, characterized in that the tool parts ( 200 . 300 ) are formed such that the steel sheet material ( 400 ) over the entire surface of the tool areas of these tool parts ( 200 . 300 ) may be present. Press hardening tool ( 100 ) according to claim 1 or 2, characterized in that both the first segment ( 221 ) as well as the second segment ( 223 ) at one of the relevant tool part ( 200 ) belonging base plate ( 210 ), the first segment ( 221 ) resiliently on this base plate ( 210 ) is supported. Press hardening tool ( 100 ) according to claim 3, characterized in that the resilient support of the first segment ( 221 ) on the base plate ( 210 ) by at least one gas spring ( 260 ) is accomplished. Press hardening tool ( 100 ) according to claim 3 or 4, characterized in that the maximum spring travel of the first segment ( 221 ) relative to the base plate ( 210 ) is between 0.5 mm and 1.5 mm and in particular approximately 1.0 mm. Press hardening tool ( 100 ) according to one of the preceding claims, characterized in that at least one second segment ( 223 ) is designed as a slide, this designed as a slider second segment ( 223 ) during further movement of the tool parts ( 200 . 300 ) is displaced in a direction (B) transversely to the working direction (D) and thereby reinforced against the steel sheet material ( 400 ) is pressed. Press hardening tool ( 100 ) according to claim 6, characterized in that the relevant tool part ( 200 ) at least one driver ( 240 ) for the mechanical actuation of the second segment designed as a slide ( 223 ) having. Press hardening tool ( 100 ) according to claim 6 or 7, characterized in that the slide formed as a second segment ( 223 ) at least one cooling device ( 230 ) having. Press hardening tool ( 100 ) according to one of the preceding claims, characterized in that only one tool part ( 200 ) and in particular only the die ( 220 ) is formed segmented.

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