DE102013002097B4 - Method for producing a coolable tool part for a molding tool for hot forming and / or press hardening, and a molding tool produced therewith - Google Patents

Abstract

Method for producing a coolable tool part (110; 120) for a molding tool (100) for hot forming and / or press hardening of workpieces made of sheet metal, with a tool active surface (112; 122) and with at least one cooling channel for active cooling of the tool active surface (112; 122), comprising the following steps: - producing a main body (111; 121) carrying the tool active surface (112; 122), the main body (111; 121) being formed with at least one cooling bore (115; 125); and introducing at least one insert tube (130), a jacket (131) of the insert tube (130) being provided with a longitudinal slot (135), by elastically compressing the insert tube (130) into at least one of the cooling bores (115; 125), wherein the insert tube (130) is formed, at least in sections, with an inner wall with inner fins (132) which increases the heat exchange capacity.

Description

The invention relates to a method for producing a coolable tool part for a molding tool for hot forming and / or for press hardening workpieces made of sheet metal.

The invention also relates to a coolable mold according to the preamble of claim 8 for hot forming and / or press hardening of workpieces made of sheet metal.

Hot forming is the forming of a metal sheet material above the recrystallization temperature. Press hardening refers to a cooling of the metal sheet material that takes place essentially simultaneously with the hot forming (or possibly only keeping in shape), whereby considerable increases in strength can be achieved. Press hardening can be seen as a special case of thermoforming. Sheet metal parts produced by thermoforming or press hardening are used in particular in automobile construction.

The hot forming or press hardening is typically carried out using a press-bound molding tool. Such a molding tool generally has a plurality of tool parts (for example the upper part of the tool and the lower part of the tool) which can be moved relative to one another, between which the metal sheet material or the workpiece is formed. The tool parts are designed with corresponding active tool surfaces. For active cooling of these active tool surfaces, cooling channels (or the like) which are arranged in the tool parts and through which cooling fluid can flow are provided. The design of such cooling channels, in particular with regard to optimal cooling or cooling performance, and their production is relatively complex and in practice is associated with many problems.

The state of the art is based on the patents WO 2011/110346 A2 and DE 10 2009 058 657 A1 directed.

In DE 10 2008 016 118 A1 describes a device for the production of molded components in manufacturing processes with a tool determining a contour and surface structure of the molded component, the tool having at least an upper tool half and a lower tool half and a device for tempering.

Out DE 10 2008 062 486 A1 a double wall tube heat exchanger is known. This has an outer tube and an inner tube. A distance between the outer tube and the inner tube and the inner region of the inner tube serves as corresponding coolant flow paths. The inner tube has a plurality of inner area fins formed on the inner peripheral surface thereof. The inner area fins protrude radially inwards; extend in a longitudinal direction of the inner tube; and are arranged at circumferential intervals. The inner tube has a plurality of elongated protrusions formed on the outer peripheral surface thereof. The elongated projections protrude radially outwards; extend in the longitudinal direction; and are arranged at circumferential intervals. The interior slats are larger in height than the elongated protrusions.

DE 10 2005 032 113 B3 relates to an apparatus and a method for hot forming and partial hardening of a component between two tool halves in a press. The tool halves are each divided into at least two segments that are separated from one another by thermal insulation. The two segments can be heated or cooled by a temperature control, so that different temperatures and thus cooling curves can be set in different areas of the component. This enables a component to be manufactured with areas of different hardness and ductility.

The invention has for its object to show a way in which at least one disadvantage associated with the prior art can be avoided or at least reduced when producing a coolable mold.

This object is achieved by an inventive method according to claim 1 for producing a coolable tool part for a molding tool for hot forming and / or press hardening with the features of claim 1. With a further independent claim, the solution to the problem also extends to using a coolable mold produced according to the method of the invention for hot forming and / or for press hardening. Preferred refinements and developments arise analogously for all subjects of the invention both from the respective dependent claims and from the following explanations.

• - Herstellen eines die Werkzeugwirkfläche tragenden Grundkörpers, wobei der Grundkörper mit wenigstens einer Kühlbohrung ausgebildet wird; und
• - Einbringen wenigstens eines Einsatzrohrs in wenigstens eine der Kühlbohrungen, wobei dieses Einsatzrohr zumindest abschnittsweise mit einer die Wärmetauschleistung steigernden Innenwandung mit Innenrippen ausgebildet ist ausgebildet ist,

wobei ein Mantel des Einsatzrohrs mit einem Längsschlitz versehen ist und dass das derart ausgebildete Einsatzrohr elastisch zusammengedrückt und in die betreffende Kühlbohrung eingebracht wird.The method according to the invention for producing a coolable tool part for a molding tool for hot forming and / or press hardening workpieces made of sheet metal, the tool part (at least) having a tool active surface and at least one cooling channel for actively cooling this tool active surface, comprises at least the following steps:

• - Producing a base body carrying the active tool surface, the base body being formed with at least one cooling hole; and
• Introducing at least one insert tube into at least one of the cooling bores, this insert tube being formed at least in sections with an inner wall with inner ribs which increases the heat exchange capacity,

wherein a jacket of the insert tube is provided with a longitudinal slot and that the insert tube formed in this way is elastically compressed and introduced into the relevant cooling hole.

The method according to the invention enables the simple and inexpensive production of a tool part with optimized cooling capacity, which can also be used to manufacture or to build a molding tool according to the invention for hot forming and / or press hardening of workpieces made of sheet metal.

The tool part can be, for. B. can be an upper tool part or a lower tool part of a molding tool. However, a tool part can also be a tool segment that belongs to an upper tool part or to a lower tool part.

The method according to the invention comprises the step: producing a base body carrying the active tool surface, the base body being formed with at least one cooling hole. It is preferably a metallic base body, in particular formed from tool steel. The active tool surface can be formed directly on the base body or on (at least) one shell element (or the like) which can be connected to the base body. A cooling hole can be formed in the base body, in particular close to the active surface, and / or in the connection area of the base body with a shell element. The cooling hole can be made by drilling, in particular deep hole drilling, and / or milling. Furthermore, the base body can be produced by casting while keeping the cooling hole clear (by means of a casting core) and machining. In particular, it is provided that the cooling bore has a smooth bore inner wall.

The method according to the invention further comprises the step: introducing at least one insert tube into at least one of the cooling bores. An insert tube is understood to be an elongated hollow body through which a cooling fluid can flow. Since the insert tube has a finite axial length, this can also be referred to as an insert tube piece or more generally as a tube piece. It is preferably provided that the insert tube or pipe section has a smooth outer wall, which can lie flush against the smooth inner wall of the cooling bore into which the insert tube is introduced. This insert tube has, at least in sections, an inner wall with inner fins which increases the heat exchange capacity (this is the transferable thermal energy per time). A higher heat exchange capacity leads to a higher cooling capacity. The cooling capacity can thus be increased locally and / or overall by means of at least one insert tube. By locally increasing the heat exchange capacity and the associated locally increasing cooling capacity, for example, depending on requirements, a homogeneous or inhomogeneous cooling characteristic (which in particular means the local distribution of the cooling rates that can be achieved over the active surface or surfaces) can be set in a targeted manner. Through an overall increased heat exchange capacity and the associated increase in the total cooling capacity, for. B. the output of the mold (number of pieces per time) can be increased.

An inner wall that increases the heat exchange capacity is characterized by suitable design features on the inner tube wall of the insert tube. Appropriate measures are taken to increase or increase the heat exchange capacity on the inner wall of the insert tube. This heat exchange performance can also be referred to as internal heat exchange performance. For example. it can be provided that the insert tube has an enlarged surface compared to a smooth inner wall (smooth tube), which is also larger in area than the inner wall of the cooling bore in the relevant section, so that there is virtually an increase in the surface area for the cooling fluid. As an alternative or in addition, it can be provided that the inner wall of the insert tube is formed with swirling elements in order to induce swirling or mixing of the cooling fluid, as a result of which the heat exchange performance can likewise be increased.

It is provided that the casing of the insert tube is provided with a longitudinal slot and that the insert tube designed in this way is elastically compressed and inserted or inserted into the cooling bore. The longitudinal slot, in particular straight or, for example, also helical, extends over the entire axial length of the insert tube, so that it can be compressed over its entire axial length, this compression bringing about a reduction in cross-section. It is preferably provided that the slotted insert tube (with respect to the cooling hole) is designed with an oversize, so that it expands elastically after insertion or insertion, which on the one hand causes the Insert tube fixed in the cooling hole and on the other hand, a flat heat transfer contact is brought about. Such an insert tube can advantageously be removed from the cooling bore relatively easily.

It is provided that the insert tube (at least in sections) is designed with inner fins and in particular with twisted inner fins. Tubes with inner fins are known from the prior art (but not for the intended use intended here), for example to the patent specification DE 100 38 624 A1 is referred. Due to the inner fins, the surface relevant for the internal heat transfer can be increased many times over compared to a smooth pipe (smooth pipe). By means of a twisted arrangement or formation of the inner fins, the heat exchange performance can be further increased by turbulence generated in the cooling fluid.

A preferred production step provides that an insert tube (undersized with respect to the cooling bore) is inserted or inserted into the cooling bore and then expanded by pressurization or by applying an internal pressure, as a result of which the outer wall of the insert tube lies flush against the inner wall of the cooling bore , As a result, the insert tube is fixed in the cooling bore on the one hand, and a flat heat transfer contact is brought about on the other hand.

With the above-described manufacturing steps, an insert tube can be introduced into a cooling hole with relatively little effort, it also being possible to reach locations or positions in the cooling hole that are difficult to access. Both of the options explained above can be implemented on a tool part to be produced.

It is preferably provided that the insert tube is formed from aluminum. Aluminum has a very good thermal conductivity. Furthermore, an insert tube made of aluminum can be installed very well in the manner explained above. Regardless of this, an insert tube can also be formed from other metallic materials (for example stainless steel, copper, brass and the like) or from non-metallic materials (for example plastic material or composite material).

Furthermore, it can be provided that the insert tube is formed from a flexible material or is formed like a hose. After being introduced into a cooling hole, widening and curing can take place, for example, by applying an internal pressure and supplying heat.

It is preferably provided that a heat-conducting paste (or the like) is used when inserting the insert tube into the cooling bore in order to reduce the frictional resistance during insertion and / or to improve the heat transfer after insertion. The thermal paste used can therefore have a double function. Another function of the thermal paste can be the prevention of corrosion (contact corrosion). As an alternative or in addition, it can be provided that the insert tube has an outer wall (i.e. on the outer wall) with a coating. Likewise, the insert tube can also be formed with a coating on the inside (i.e. on the inside wall) in order to avoid or at least reduce corrosion and / or erosion caused by the cooling fluid. Coatings can be produced, for example, by anodizing, painting, applying metals (copper, nickel and the like), applying nanostructures, applying plastic, etc.

The invention also relates to a method for producing a coolable molding tool for hot forming and / or for press hardening workpieces made of sheet metal, a tool part produced using the previously explained method according to the invention having at least one other tool part, in particular also using the previously explained method according to the invention is produced, is assembled into a mold according to the invention. This is the subject of a subsidiary claim.

The coolable molding tool according to the invention for hot forming and / or press hardening of workpieces made of sheet metal comprises a plurality of tool parts which can be moved relative to one another (for example the upper part of the tool and the lower part of the tool) and which are designed with corresponding active tool surfaces (between which the sheet metal material is formed), at least one of these tool parts also at least one cooling channel through which cooling fluid can flow is designed for active cooling of the associated active tool surface. It is provided that this molding tool or at least one tool part belonging to the molding tool has at least one cooling hole in which at least one insert tube is arranged, which at least in sections has an inner wall which increases the heat exchange performance. The molding tool and / or at least one tool part of this molding tool is produced in particular using a method according to the invention.

Otherwise, the preceding and / or following explanations regarding the method according to the invention apply analogously to the molding tool according to the invention and vice versa.

It is preferably provided that the molding tool according to the invention has a plurality of insert tubes which are arranged and / or configured differently in order to set a specific cooling characteristic at defined points or in defined positions (within a cooling bore or within different cooling bores), the different configurations having all structural properties an insert tube can include. So z. For example, it can be provided that insert tubes (ie at least one insert tube) are only arranged at locations or positions where a particularly high cooling capacity is required locally, the high cooling capacity then being improved by the heat exchange capacity with the insert tube (through an enlarged inner surface and / or is brought about by improved swirling of the cooling fluid). In this case, an individual adaptation of the insert tube can be provided with regard to the locally required heat exchange performance.

The invention comprises numerous other possibilities for an appropriate adaptation and in particular also for the local adaptation of the cooling capacity of a molding tool according to the invention. For example, several identical or differently designed insert tubes can be arranged in a cooling bore (or a cooling circuit). Furthermore, an insert tube can have differently shaped sections. Depending on the objective, it is therefore possible to achieve uneven or uniform (homogeneous) cooling within a cooling hole (or a cooling circuit). Uniform cooling can e.g. B. can be achieved in that by using an insert tube or several insert tubes the internal surface of the bore, which is relevant for the heat exchange performance, is increased continuously or stepwise with the flow length and / or by means of appropriate measures the swirling of the cooling fluid is increased continuously or stepwise, thereby the cooling potential (or the heat absorption capacity) of the cooling fluid. In this way, for example, the effect of a heat exchange performance decreasing over the flow length can also be compensated. It can also be provided that cooling bores are designed differently, in which case the insert tubes introduced into these different cooling bores can also be designed differently. This non-exhaustive list of possibilities makes it clear that within the scope of the invention, both the specific arrangement and configuration of the cooling bores and the specific configuration and arrangement of the insert tubes can be carried out optimally, depending on the individual case, with regard to a specific objective.

With the invention, the simple and inexpensive possibility is created to set the locally and / or overall required cooling capacity in the production of a mold for hot forming and / or press hardening of workpieces made of sheet metal as required. Furthermore, the cooling capacity can be increased with relatively little effort, in particular in comparison to other possibilities known from the prior art. The invention can also be applied to existing molds.

• 1 zeigt ein erfindungsgemäßes Formwerkzeug in einer perspektivischen Ansicht.
• 2 zeigt ein aufgeschnittenes Einsatzrohr in einer perspektivischen Ansicht.
• 3 zeigt ein geschlitztes und verbautes Einsatzrohr in einer Querschnittsdarstellung.

The invention is explained in more detail below by way of example and in a non-restrictive manner with reference to the schematic figures. The features shown in the figures and / or explained below can, regardless of specific combinations of features, be general features of the invention.

• 1 shows a molding tool according to the invention in a perspective view.
• 2 shows a cut insert tube in a perspective view.
• 3 shows a slotted and installed insert tube in a cross-sectional view.

1 shows a mold 100 , with an upper part of the tool 110 and a tool base 120 , for hot forming and / or press hardening of sheet metal workpieces. Between the tool parts 110 and 120 a metal sheet material (workpiece) can be hot formed and / or press hardened in a manner known per se, for which purpose the tool parts 110 and 120 corresponding tool effective surfaces 112 and 122 exhibit.

Both the top part of the tool 110 as well as the lower part of the tool 120 is with multiple cooling channels 115 and 125 in the form of elongated holes (deep holes). Through these cooling holes 115 and 125 can flow cooling fluid (cooling medium) to the tool effective surfaces 112 and 122 to actively cool. Connection means are not shown. With 111 and 121 are the base body formed from a solid metallic material, in which the cooling holes 115 and 125 are arranged.

According to the invention it is provided that when producing the molding tool 100 , or when manufacturing at least one of the tool parts 110 or 120 , in at least one of the previously in the main body 111 / 121 introduced cooling holes 115 / 125 at least one insert tube 130 is introduced, which has an inner wall increasing the heat exchange capacity. This is an example of the left cooling hole 125 on the lower part of the tool 120 shown. Also in the other cooling holes 115 / 125 can use one or more such insert tubes 130 be arranged, these insert tubes 130 can be identical or different. For example. can be provided that such insert tubes 130 be arranged where the heat exchange capacity and thus the cooling capacity is to be increased locally. It can further be provided that with such insert tubes 130 regarding the effective areas 112 / 122 an inhomogeneous or homogeneous cooling performance is to be brought about. Furthermore, reference is made to the explanations above.

2 shows an example of an insert tube 130 , The insert tube shown 130 shows several of the coat 131 inner ribs projecting radially inwards and evenly spaced apart in the circumferential direction 132 on, which also over the axial longitudinal extension of the insert tube 130 are twisted. Through the inner ribs 132 the surface relevant for the heat transfer into the cooling fluid is increased by a multiple compared to a smooth tube, whereby a multiplication of the heat exchange performance is achieved. In the center of the insert tube 132 there is a free flow cross-section 133 , which enables an unimpeded core flow. The free flow cross section 133 is in fluid communication with the individual through the inner ribs 132 formed outer flow chambers, so that the total flow of the cooling fluid through the insert tube 130 divided into partial streams. Due to the twisted design of the inner ribs 132 turbulence is brought about and the mixing of the partial flows is favored, whereby the achievable heat exchange performance is further increased.

Around the insert tube 130 in a cooling hole 115 / 125 To be able to introduce, it can be provided that this opposite the cooling hole in question 115 / 125 is formed with undersize and is expanded after being introduced by pressurization.

Another preferred option is for the coat 131 of the insert tube 130 with a longitudinal slit 135 is provided and that the insert tube formed in this way 130 elastically compressed and into the relevant cooling hole 115 / 125 is introduced or used. 3 shows in cross-section in this way in a cooling hole 115 / 125 inserted or inserted insert tube 130 , With 135 is the longitudinal slot in the jacket 131 designated. The insert tube designed with oversize with respect to the cooling bore cross section 130 is caused by elastic clamping forces in the cooling hole 115 / 125 fixed, the outer wall of the insert tube 130 in the radial direction against the inner wall of the cooling hole 115 / 125 suppressed. Between the outer wall of the insert tube 130 and the inner wall of the cooling hole 115 / 125 there is a thermal paste 140 to improve the heat transfer or reduce the heat transfer resistance. The thermal paste 140 can also reduce friction when inserting or inserting the insert tube 130 into the cooling hole 115 / 125 serve.

LIST OF REFERENCE NUMBERS

100

mold

110

Upper die

111

body

112

Tool effective area

115

cooling hole

120

Tool part

121

body

122

Tool effective area

125

cooling hole

130

insert tube

131

pipe casing

132

internal rib

133

free flow cross section

135

slot

140

Thermal Compounds

Claims (9)

Method for producing a coolable tool part (110; 120) for a molding tool (100) for hot forming and / or press hardening of workpieces made of sheet metal, with a tool active surface (112; 122) and with at least one cooling channel for active cooling of the tool active surface (112; 122), comprising the following steps: - Manufacture of a main body (111; 121) carrying the active tool surface (112; 122), the main body (111; 121) being formed with at least one cooling bore (115; 125); and - Introducing at least one insert tube (130), wherein a jacket (131) of the insert tube (130) is provided with a longitudinal slot (135), by elastically compressing the insert tube (130) in at least one of the cooling bores (115; 125), the Insert tube (130) is formed at least in sections with an inner wall with inner ribs (132) which increases the heat exchange capacity. Procedure according to Claim 1 , characterized in that the insert tube (130) is formed with twisted inner ribs (132) over the axial longitudinal extent. Procedure according to Claim 1 or 2 , characterized in that the insert tube (130) with undersize in the relevant cooling hole (115; 125) introduced and then expanded by pressurization. Procedure according to one of the Claims 1 to 3 , characterized in that the insert tube (130) is formed from aluminum. Procedure according to one of the Claims 1 to 3 , characterized in that the insert tube (130) is formed from a flexible material. Method according to one of the preceding claims, characterized in that when the insert tube (130) is introduced into the cooling bore (115; 125) in question, a thermal paste (140) is used. Method according to one of the preceding claims, characterized in that the cooling bore (115, 125) has a smooth bore inner wall and that the insert tube (130) has a smooth outer wall which lies flush with the shape of the smooth inner wall of the cooling bore (115, 125). Forming tool (100) for hot forming and / or press hardening of workpieces made of sheet metal, with a plurality of tool parts (110, 120) which are movable relative to one another and which are formed with corresponding tool active surfaces (112, 122), at least one of these tool parts (110; 120) being included at least one cooling channel (115; 125) for actively cooling the associated active tool surface (112; 122), characterized in that at least one of the tool parts (110; 120) with a method according to one of the Claims 1 to 7 was produced, which is why this molding tool (100) has at least one cooling bore (115; 125), in which at least one insert tube (130) is arranged, which at least in sections has an inner wall with inner ribs (132) which increases the heat exchange performance. Molding tool (100) after Claim 8 , characterized in that it has a plurality of insert tubes (130) which are arranged at defined positions and / or are configured differently to set a specific cooling characteristic.

Images