EP2680667A1 - Process for the preparation of a heating assembly and tool including the heating assembly - Google Patents

Abstract

The method involves inserting an insulated heating wire (4) directly into a groove (6) formed along the surface (3) of a base element (2). The groove comprising heating wire is filled with the consistent sealing material (7) by a cold gas spraying, and closed. The heating wire has a round cross section with a diameter of a preset value. A nut is arranged at the bottom of the heating wire. The individual layers (5) of the heating wire comprise different spacing. Independent claims are included for the following: (1) a heating assembly; and (2) a tool for shaping and/or heating up a component.

Description

The present invention relates to a method for producing a heating arrangement. Furthermore, the invention relates to a heating arrangement with an integrated heating element and a tool for forming and / or heating a component with the heating arrangement.

The technology of press hardening and hot forming of body components is increasingly finding its way into the automotive industry. In the case of form hardening or direct hot forming, a flat, glowing sheet metal blank is deep-drawn. In press hardening of steel, a preformed and trimmed body component is subsequently heated and hardened by quenching. Reasons for the application of these methods are the increasing requirements of the legislation on occupant protection and crash behavior with low weight. This demands new solutions from the automotive and supplier industry in lightweight steel construction, such as the structural components "sills" and the "reinforcement A and B pillars". Even the so-called "side impact protection" in the door, which forms a vital barrier between the outside and the passenger compartment during a side crash, is manufactured using this technology. This is achieved by the transformation of the glowing components made of specific material under high temperature or during the subsequent quench hardening of the finished components. A molded component or a circuit board is first converted by heating in the annealing furnace to about 870 ° C to 950 ° C in the austenitic region. The component is then placed in a water-cooled tool, reshaped or held and thus cooled down to about 200 to 100 ° C within a few seconds. This heat treatment results in a martensitic microstructure. This increases the strength of the component and allows a tensile strength of e.g. 1650 MPa. The hard components provide excellent crash performance for the vehicle. It turns out, however, that for optimal safety reserves in occupant protection and crash behavior of the body at certain points, depending on the vehicle concept, a mixed structure of martensite, austenite and ferrite is necessary.

It is an object of the present invention to provide a method for producing a heating arrangement with an integrated heating element, which at cost-effective production and low-maintenance operation allows a very precise and konturnahe heating of a component. Furthermore, it is an object of the invention to provide a corresponding heating arrangement and a tool for forming and / or heating of the component.

The object is achieved by the features of the independent claims. The dependent claims each have preferred developments of the invention to the subject.

Thus, the object is achieved by a method for producing a heating arrangement, comprising the following steps: (i) providing a base element with at least one groove in the surface of the base element, (ii) inserting at least one heating element into the groove, and (iii) cohesive Closing the groove and simultaneously enclosing the element by powder spraying, preferably cold gas spraying. In the groove so a heating element, preferably formed as insulated heating wire inserted. After insertion, the groove is closed by spraying powder. This ensures that the heating element is fully positively connected to the base element, so that an optimal heat transfer is ensured. The groove and the heating element can follow any path or any geometry in the surface of the base element and thus at certain, selected positions, the surface of the base element and thus also the surface-mounted component heat extremely konturnah.

The heating elements are in particular constructed in three parts. Inside there is a live wire. This wire is wrapped with insulation. The insulation in turn is covered with a metal sheath. This metal jacket allows the application of particular ductile materials, such as metal or polymers, preferably by the cold gas spraying process. The result is a cohesive connection for the optimum temperature transition, wherein the powder particles connect to the jacket of the heating element, without destroying the shell and in particular without the underlying insulation.

Preferably, after the application of the sprayed material, a heat treatment of the heating arrangement takes place in order to achieve strength values comparable to conventionally produced heating arrangements.

In a preferred embodiment it is provided that the groove over a certain, preferably its entire length is completely filled with the heating element and the injected material. There are thus no cavities within the groove after completion of the heating arrangement. By using the powder spray method, the heating element is completely enclosed by the material of the base element and by the injected material. Preferably, after the closing of the groove, the desired surface can be produced on the base element by a chip removing process.

Furthermore, it is preferably provided that is applied directly to the heating element, preferably by cold gas spraying. The groove occluding geometry is therefore not made separately, but injected directly into the groove and on the heating element.

In a preferred embodiment it is provided that the groove has a curved course and the heating element according to the groove is also curved. Advantage of the method used here is that the heating element, in particular designed as a heating wire, following almost any radii, can be installed extremely contour close to the surface of the base member. The course of the heating element is ultimately only limited by the minimum bending radius of the heating element. As a result, the contours near the heating element in a three-dimensional surface of the base element is possible. The advantage of the method used here is thus that the geometric shape of the heating element, in particular designed as a heating wire, apart from observance of a minimum bending radius is not subject to any restrictions. As a result, the contours near the heating element even on curved surfaces is possible.

In a preferred embodiment, it is provided that a plurality of individual heating elements are inserted into a groove. It is also possible that a plurality of individual grooves are introduced into the base element, in which case in each individual groove Heating elements are inserted. The individual grooves may have different distances to the surface of the base member and overlap each other. This results in several layers of heating elements. In particular, it is provided that a second groove is milled into the injected material, which is used to close a first groove. This second groove does not have to run parallel to the first groove, so that the second groove is only partially introduced into the sprayed material. In this second groove also at least one heating element is inserted. Subsequently, the second groove is closed by powder spraying, preferably cold gas spraying. This results in superimposed layers of heating elements.

In particular, it is provided that the heating elements have a round or polygonal cross section. The cross section of the heating element is preferably between 0.25 mm and 15 mm, with polygonal cross sections counting the largest cross section. The length of a single heating element is preferably between 10 mm and 20,000 mm. The operating temperature for the entire heating arrangement ranges from 0 to over 1000 ° C.

The method according to the invention has decisive advantages over conventional methods, for example with heating cartridges in bores. The powder spraying gives optimum heat transfer from the heating element to the base element. This also results in a uniform and well controllable heat input into the corresponding component. Even with three-dimensional surfaces on the base element, a very near contour heat transfer to the component can be achieved. In contrast to soldering or gluing, no foreign material is introduced by spraying. Rather, the same or a similar material may be used according to the base member. As a result, different length expansions in the heating arrangement are avoided and no low melting point, no low strength or no low heat transfer must be taken into account.

The invention further comprises a heating arrangement with a base element and at least one groove. In the groove at least one heating element is inserted and the groove is cohesively with a powdered, preferably cold-gas sprayed, Material sealed, at the same time the heating element is enclosed by the injected material. At least in a destructive examination of the heating arrangement can be seen whether the groove was closed by spraying or not.

The presented in the context of the method according to the invention advantageous embodiments and subclaims find correspondingly advantageous application to the heating arrangement according to the invention.

When forming and / or curing components, it is particularly advantageous to heat the component only partially or to heat at certain positions with different temperatures or to maintain appropriate temperatures. For this purpose, the heating arrangement according to the invention is particularly well suited because a contoured component can be heated. According to the invention therefore a tool for forming and / or heating a component is provided. This tool comprises at least one heating arrangement described above, wherein the surface of the base element is designed for supporting the component. The surface of the base member is the surface into which the grooves are inserted. The advantageous embodiments described in the context of the method according to the invention and in the context of the heating arrangement according to the invention and the corresponding subclaims find equally advantageous application to the tool according to the invention.

In particular, it is provided that the tool has a tool base body with a tool surface. This tool surface is designed to support the component, which is to be heated and / or reshaped. The tool surface is partially formed by the surface of the heater assembly. For this purpose, the heating arrangement is inserted into the tool base body, so that the surface of the heating arrangement partially forms the tool surface.

Particularly preferably, it is provided that a pressure plate and / or a thermal insulation are arranged between the tool base body and the heating arrangement. In particular, the pressure plate is located between the thermal insulation and the tool body. By the pressure plate is a uniform force transmission from the tool body via the heating arrangement on the component.

Furthermore, spring elements are preferably provided between the tool base body and the heating arrangement. The tool according to the invention or the heating arrangement can be operated at temperatures of more than 900 ° C. Due to corresponding temperature expansions, the heating arrangement can not be rigidly bolted to the tool body. Therefore, the spring elements, for example, designed as disc springs, provided. As a result, regardless of the length expansion, the heating arrangement always lies completely against the component due to the temperature.

For exact fixation and guidance of the heating arrangement on the tool body, preferably spacer elements and / or centering rods extend from the tool body in the direction of the heating arrangement. The spacer elements are in particular designed as spacer tubes. The spacer element and / or the centering stuck in recesses in the base element of the heating arrangement. By the spacer elements and / or centering and by the spring elements ensures that the heating assembly is fully applied to the component.

It is particularly preferred that both the upper and the lower die have a tool base body with integrated heating arrangement, as just described.

The technology of hot forming or press hardening described above makes the steel stronger (up to a tensile strength of 1650 MPa), but also more brittle, ie the elongation at break decreases. There is a requirement that some components in certain areas should be ductile or more plastic, since these components in the event of a crash, a higher energy absorption capacity is required. These body components are said to have the ability to absorb forces extremely quickly without tearing or breaking, even in a high velocity impact. Brittle materials can cause injury during rupture (crash) caused by flying parts. In practice, by introducing an additional process step, called annealing or tempering, the hardness of the component is reduced and set the desired performance characteristics (hardness, tensile strength and higher toughness) of the steel.

When tempering or tempering by conventional methods, the hardness or tensile strength can be adjusted only over the entire component. The tool according to the invention now makes it possible to adjust the characteristic of the service hardness and ductility only in a specific region of the component, for example an automobile body, in order to ensure a correct measure between high tensile strength and plastic deformability.

For this purpose, the heating arrangements, also referred to as inserts, preferably located in the upper and lower die of a tool. About the fixed heating elements, the heating arrangements are heated to a certain temperature, depending on the specification of the component properties. In particular, the heating elements can be introduced in several layers one above the other by means of the powder spraying process. As a result, the heating elements are materially connected to the structure of the base element, so that an optimal temperature transition with relatively short heating times to operating temperature, for example, in the setup process of a tool can be achieved. The entire system is electrically heated, controlled and regulated, and it can be integrated, for example, into an existing cold-forming, hot-forming, press-hardening, and magnesium or CFRP manufacturing line. With the method according to the invention and the tool according to the invention, individually ductile required areas can be produced partially to reach the austenitizing temperature (hardening). An annealing takes place during the cooling process at the same cycle time in the component pass.

Temperatures of 0 ° C to 1000 ° C are possible, so that very precise component properties can be set. The control and regulation of the system takes place, inter alia, with the aid of permanently integrated temperature sensors, which lie very close to the heating elements and in particular for each position of the Heating elements are arranged separately. Thus, it is possible to carry out an individual fine adjustment of the component properties during the process times via an external control unit. The process can be applied to all known Hot Forming Steels (MB, LA) and all tempered areas, including galvanized sheet metal, uncoated, plastic and CFRP materials. The tool according to the invention makes it possible to be used both for hot forming (direct process) of flat boards, and for the subsequent press hardening (indirect process) of molded components, as well as in various applications for plastic and CFRP. The geometric possibilities are unrestricted and it is possible to make a close contour. The connection of the heating arrangements with the tool body can be done as described above via spacers and spring elements. However, it is equally possible to use a corresponding spring-loaded screw connection, which allows at least a stroke of approximately 0.5 mm between the heating arrangement and the tool base body. The heating arrangements are manufactured and used individually for different requirements and different component geometries. Depending on the process application and material selection of the component to be processed, a differently adapted structure of the heating arrangements takes place in the tool. In addition, the heat transfer areas for cooling and the formation of mixed structures in the transition area via the air gap and elongation at a temperature for metallic and non-metallic component materials are taken into account. By setting a certain temperature, the cooling component is not cooled in the area of the heated heating arrangements in the tool and there is thus no structural transformation in the corresponding areas, so that set ductile areas. The heating elements are in particular multi-layer firmly integrated in the base element, so that a homogeneous temperature distribution is achieved. Depending on the application, conductive and non-conductive metal materials can be used for the production.

The heater assemblies of the present invention, due to the wide temperature range, can be used for all process techniques for materials that can deform under temperature or that require temperature to complete a geometry or property. So can the treated component For example, be made of steel, aluminum, magnesium, plastic or CFRP. By using the tool according to the invention in the hot-forming technology, the component properties can be controlled or adjusted differently during the hot-forming process or during the press-hardening. Since only energy or heat is introduced to the partially desired areas, there is an improved energy balance compared to conventional methods in which, for example, components are completely charged with heat or larger cross sections have to be heated. By firmly connected to the structure of the base element heating elements and thermocouples, which can be used contour and near the surface, very uniform temperature characteristics, and thus homogeneous ductile finely adjusted component properties can be produced. Uniform and rapid heating is a prerequisite for a uniform component structure. Exact heat transfer zones can be defined by the contours of the heating elements.

By certain temperatures, manufacturing parameters and settings, the process times for heating and cooling of a hot forming tool in the described invention with the specific heating arrangements can be exactly coordinated with each other, so that cycle time losses are approximately avoided. The heating arrangements described can be relatively easily integrated into the tool body, so that additional methods for improved component serviceability, in particular in automotive body construction, are not necessary. The areas of application are to be seen in particular on the A, B or C pillar or on the sill of an automobile body. Especially with these components, it is necessary that only certain sections are hardened and other sections remain ductile.

Figur 1

zwei Ansichten einer erfindungsgemäßen Heizanordnung gemäß einem ersten Ausführungsbeispiel,

Figur 2

eine Schnittansicht aus Figur 1,

Figur 3

die erfindungsgemäße Heizanordnung gemäß einem zweiten Ausführungsbeispiel, und

Figur 4

einen Schnitt durch ein erfindungsgemäßes Werkzeug gemäß einem dritten Ausführungsbeispiel.

Further details, features and advantages of the invention will become apparent from the following description and the figures. Show it:

FIG. 1

two views of a heating arrangement according to the invention according to a first embodiment,

FIG. 2

a sectional view FIG. 1 .

FIG. 3

the heating arrangement according to the invention according to a second embodiment, and

FIG. 4

a section through an inventive tool according to a third embodiment.

Based on Figures 1 and 2 the first embodiment of the heating arrangement 1 will be explained in detail. FIG. 1 shows in simplified representation on the left a plan view of the heating arrangement 1. Right side view of the heating arrangement 1 is shown. FIG. 2 shows the in FIG. 1 marked section AA.

The heating arrangement 1 comprises a base element 2, preferably made of metal. In this base element, a groove 6 is milled. The groove 6 meanders along a surface 3 of the base element 2.

In the groove 6, a heating element, designed as a heating wire, inserted so that the heating element 4 is bent and the meandering shape of the groove 6 follows.

The right representation in FIG. 1 shows that at least three layers of grooves 6 and heating elements 4 are arranged one above the other in the base element 2. The individual layers 5 have different distances to the surface 3. At least one groove 6 with at least one inserted heating element 4 is provided per layer 5.

FIG. 2 shows in detail the structure of the groove 6. The groove 6 is open to the surface 3 out. In the bottom of the groove, the heating element 4 is arranged. The heating element 4 here has a round cross-section with a diameter 10.

After inserting the heating element 4 in the groove 6, the complete, remaining free space of the groove 6 is filled with a molded material 7. For this purpose, a powder injection method, in particular a cold gas spraying method, is used. This ensures that the heating element 4 is fully connected in a form-fitting manner to the material of the base element 2 or to the sprayed material 7. The injected material 7 in turn is complete positively connected to the material of the base element 2. This ensures optimum heat transfer from the heating element 4 to the surface 3.

FIG. 3 shows a second embodiment of the heating assembly 1. The same or functionally identical components are provided in all embodiments with the same reference numerals. In the second embodiment, there are a plurality of juxtaposed grooves 6, each with at least one inserted heating element 4. According to this heating arrangement 1, it is possible to produce on the surface 3 most different temperatures, since each heating element 4 can be controlled separately. In addition, it is of course also possible to arrange a plurality of layers 5 in the second embodiment one above the other so as to make the temperature distribution on the surface 3 even more differentiated.

FIG. 4 shows according to a third embodiment, a tool 11. This tool 11 has a tool base 13. At least one heating arrangement 1 is inserted or integrated in the tool base body 13. The tool 11 is used for heating and / or forming a component. The component rests on a tool surface of the tool base body 13, whereby a part of the surface of the tool base body 13 is created by the heating arrangement 1 and thus by the surface 3 of the heating arrangement 1. For this purpose, it is provided in particular that in the surface 3 of the heating arrangement 1, a displacement surface 12 is formed for a possible deformation of the corresponding component.

At least one spacer element 17, designed as a spacer tube, and a centering device 18 extend from the tool base body 11. The heating arrangement 1, in particular the base element 2, is placed on the spacer element 17 and the centering device 18. On the underside of the heating arrangement 1, there is a laminar thermal insulation 14 arranged. Between the insulation 14 and the tool body 13 is a pressure plate 15 for uniform power transmission. Between the pressure plate 15 and the tool body 13, at least one spring element 16, designed as a plate spring, is arranged. Not shown is a possible screw connection between the heating arrangement 1 and Tool base 13, which allows a certain balance along the centering 18 and along the spacer 17.

For exact control of the temperature in the heating arrangement 1, at least one thermal sensor 19 is integrated into the base element 2. In particular, it is provided that at least one thermal sensor 19 is integrated into the base element 2 per layer 5 and / or per groove 6. In particular, the thermocouple 19 is inserted into a recess in the base element 2 and then enclosed by the powder injection method.

LIST OF REFERENCE NUMBERS

1

heating arrangement

2

base element

3

Surface of the base element

4

heating element

5

documents

6

groove

7

Injected material, in particular cold gas-sprayed material

10

Diameter of the heating element

11

Tool

12

Verdrängerfläche

13

Tool body

14

insulation

15

printing plate

16

spring elements

17

spacer

18

centering

19

thermocouple

Claims (14)

Method for producing a heating arrangement (1), comprising the following steps: Providing a base element (2) with at least one groove (6), - Inserting at least one heating element (4) in the groove (6), and - Cohesive closing of the groove (6) and simultaneous inclusion of the heating element (4) by powder spraying, preferably cold gas spraying. A method according to claim 1, characterized in that a heating wire, preferably an insulated heating wire, is used as the heating element. Method according to one of the preceding claims, characterized in that the groove (6) over a certain, preferably the entire length is completely filled with the heating element (4) and the injected material (7). Method according to one of the preceding claims, characterized in that injection is effected directly onto the heating element (4). Method according to one of the preceding claims, characterized in that the groove (6) is curved and the heating element (4) corresponding to the groove (6) is bent. A method according to claim 5, characterized in that heating element is bent three-dimensionally. Method according to one of the preceding claims, characterized by - introducing a further groove (6) at least partially into the sprayed material (7), - Inserting at least one further heating element (4) in the further groove (6), and - Cohesive closing of the further groove (6) and simultaneous inclusion of the further heating element (4) by powder spraying, preferably cold gas spraying. Heating arrangement (1), comprising: - A base element (2) with at least one groove (6), and at least one heating element (4) inserted in the groove (6), - Wherein the groove (6) is materially closed with a powder-sprayed material (7) and the heating element (4) by the powder-sprayed material (7) is included. Heating arrangement according to claim 8, characterized in that the heating element is a heating wire, preferably an insulated heating wire. Tool (11) for forming and / or heating a component, comprising: at least one heating arrangement (1) produced according to claims 1 to 8 or defined in claims 8 or 9, - Wherein the surface (3) of the base element (2) is designed to support the component. Tool according to claim 10, characterized by a tool base body (13) with a tool surface for supporting the component, wherein the at least one heating arrangement (1) is inserted into the tool surface. Tool according to claim 11, characterized in that a pressure plate (15) and / or a thermal insulation (14) are arranged between the tool base body (13) and the heating arrangement (1). Tool according to one of claims 11 or 12, characterized in that between the tool base body (13) and the heating arrangement (1) at least one spring element (16) is arranged. Tool according to one of claims 11 to 13, characterized in that extending from the tool base body (13) has a centering (18) and / or a spacer element (17) in a recess in the base element (2).

Images