Device and method for fixture hardening

Abstract

The present invention relates to a fixture hardening device comprising a hardening mandrel and a pressure-exercising element, wherein the device is designed to hold a component to be hardened between the hardening mandrel and the pressure-exercising element, the hardening mandrel and / or the pressure-exercising element having at least one internal cooling channel. The invention further relates to a fixture hardening method.

Description

[0001] The present invention relates to a device and a method for fixture hardening.

[0002] It is known according to the prior art that the quenching process in the press hardening process is carried out by means of a circulating oil to quench the workpiece and to reproducibly set a constant temperature of the tool at the beginning of the press hardening process.

[0003] Alternatively, the press hardening process can be carried out using a gaseous quenching medium under high pressure. The cooling medium comes into direct contact with the component and the tool. The contact of the hot component with the tool heats the tool, causing it to expand. Particularly with short cycle times, this can lead to the tool heating up, which is then cooled again by the circulating quenching medium.

[0004] Typically, short-term process adjustments in press hardening are achieved using hardening mandrels of different sizes. For example, if the dimensional accuracy of components needs to be improved without designing a new tool or fundamentally changing the process, several hardening mandrels with different dimensions are kept on hand. Another option is to machine the hardening mandrel to adjust its dimensions.

[0005] A particular disadvantage of the current state of the art is that a workpiece quenched with oil must be cleaned of excess oil in a washing system. Oxidation and oil residues create a surface layer of a few micrometers, which must be removed by a suitable process.

[0006] High-pressure gas quenching in a hardening press causes a significant disruption to the working environment due to gas escaping and loud pump motor noise.

[0007] The directional effect of the press hardening process arises from forces acting on the workpiece. The workpiece's formability is greater at high temperatures due to the temperature-dependent yield point. For optimal formability and thus dimensional accuracy of the workpiece, plastic deformation must occur at the highest possible temperature.

[0008] In current technology, the workpiece is cooled extremely rapidly by the strong quenching effect of oil or cooled gas under high pressure (high-pressure gas quenching). This rapid cooling results in a very short time frame in which the tool can plastically deform the workpiece, thus leading to insufficient utilization of the straightening potential of the press hardening process. Rapid cooling of the workpiece is associated with heating and expansion of the tool.

[0009] A hardening mandrel with internal cooling is considerably more expensive to manufacture, depending on the production method, and can only be dimensionally adjusted to a limited extent using the usual methods.

[0010] The choice of material and component geometry (diameter) and the resulting minimum required quenching effect limit the applicability of the press hardening process.

[0011] Against this background, the present invention aims to mitigate or even completely eliminate the disadvantages of the prior art.

[0012] A specific objective of the invention is to enable a press hardening and quenching process by means of contact cooling between the workpiece and the tool. It should be possible to implement both cooling in the internally cooled hardening press without contact between the workpiece and the quenching medium, and a combined process of internal cooling and direct quenching.

[0013] The aim is to improve the effectiveness of the straightening forces exerted by the press and thus the resulting dimensional accuracy of the workpiece. Furthermore, the process should be carried out in an oil-free tool or with a closed internal oil circuit to avoid the disadvantages of oil quenching.

[0014] The problem area is the process control and tool design of a press hardening and quenching tool. The problem area is the design of a split hardening mandrel including internal cooling.

[0015] This problem is solved by the subject matter of the independent claims. Advantageous embodiments of the invention are the subject matter of the dependent claims.

[0016] According to the invention, a press hardening process is to be carried out by cooling through contact between the workpiece and the tool. No cooling medium is to come into direct contact with the workpiece. The tool is purged with nitrogen to establish an inert atmosphere. The tool is to be kept at a nearly constant temperature by internal cooling and to dissipate heat from the workpiece. The internal cooling of the tool is optionally achieved with a liquid or gaseous medium.

[0017] The invention relates to a tool (in other words, a device) for carrying out a press hardening and quenching process for a workpiece (also referred to as a component), (of any geometry), wherein the quenching process preferably takes place by contact with the internally cooled tool instead of by direct exposure of the workpiece to the cooling medium.

[0018] According to the invention, a fixture hardening device is provided with a hardening mandrel and at least one pressure exertion element, wherein the device is designed to accommodate a component to be hardened between the hardening mandrel and the pressure exertion element, wherein the hardening mandrel and / or the pressure exertion element has at least one internal cooling channel.

[0019] The cooling medium therefore remains in the tool and does not reach the component.

[0020] The at least one cooling channel is preferably arranged adjacent to a contact surface of the hardening mandrel and / or the pressure application element, which is designed to come into contact with the component during fixture hardening. Several cooling channels may be present, for example, running parallel to each other.

[0021] The hardening mandrel can be made of one piece or multiple pieces. The same applies to the pressure-exerting elements.

[0022] For example, the hardening mandrel can be designed in at least two parts and have an inner part and an adapter detachably connected to the inner part, the adapter being designed to come into contact with the component.

[0023] The inner part can have a radially circumferential shoulder at one end, on which the preferably ring-shaped adapter can be detachably mounted.

[0024] The adapter can be free of cooling channels; in this case, the component is cooled by the cooling channels of the inner part of the hardening mandrel.

[0025] Differently designed adapters allow the same inner part of the hardening mandrel to be used for hardening various components with different geometries.

[0026] Furthermore, the present invention relates to a method for fixture hardening, wherein the method is preferably carried out using a device according to the invention.

[0027] In this process, a cooling and / or quenching process of a component to be hardened is carried out, preferably exclusively, by contact of the component with the hardening mandrel and / or the pressure exertion element of the device.

[0028] In a method according to the invention, the component is preferably not exposed to direct contact with the cooling medium, although this would be conceivable for additional cooling.

[0029] A method according to the invention can further include the following step: creating an inert environment in an area of ​​contact between the device and the component, preferably by flushing with gas, in particular inert gas, to prevent oxidation of the component.

[0030] Furthermore, the present invention relates to the use of a device and / or a method according to the invention for the manufacture of an aircraft, in particular an airplane, and / or a component thereof.

[0031] In other words, according to the invention, the technical problem is preferably solved by internal cooling of the tool and cooling by means of contact between the tool and the workpiece.

[0032] Parts of the tool that are in direct contact with the workpiece, in particular the hardening mandrel and the press segments, are cooled, for example, by means of a suitable cooling medium via internal channels. The cooling medium can be gaseous or liquid and preferably does not reach the surface of the component.

[0033] The tool is preferably additionally purged with a gas or an inert gas in the area where the component is inserted, in order to create constant conditions and reduce possible oxidation of the workpiece.

[0034] Preferably, no quenching medium is directed to the surface of the workpiece; cooling occurs mainly or entirely through contact between the workpiece and the tool.

[0035] According to the invention, two variants are provided for the hardening mandrel: 1. A one-piece hardening mandrel with internal cooling, 2. A hardening mandrel consisting of an inner adapter or receiver with internal cooling and an outer ring that is adapted to the specific component.

[0036] The second variant involves constructing a split hardening mandrel to allow internal cooling of the mandrel and to be able to work with different hardening mandrel attachments.

[0037] The split hardening mandrel has or consists of an adapter with internal cooling and a preferably ring-shaped attachment, which is designed in such a way that it comes into contact with the component when the component cools and whose dimensions are responsible for the straightening effect and the final dimensions of the component after cooling.

[0038] The present invention offers at least the following advantages: The directional effect of the hardening press is increased by the contact cooling, which is slower than the usual oil or gas quenching, thereby improving the dimensional accuracy of the component. The press hardening process using contact quenching offers the advantage of an oil-free tool and workpiece. This means that no oil vapors are produced during quenching, no combustion residues are generated, and the workpiece does not need to be cleaned of oil. Compared to high-pressure gas quenching, the advantage lies in a significantly quieter and energy-saving process.

[0039] The following advantages result from dividing the hardening mandrel into an internally cooled adapter and a hardening mandrel attachment: The internally cooled adapter can be manufactured from a different material and using different processes to realize and even enable the design. This allows for more flexible manufacturing.

[0040] The manufacturing costs for the attachments (material costs and heat treatment costs) are reduced compared to a one-piece hardening mandrel.

[0041] Such a two- or multi-part, internally cooled adapter can be used for multiple component geometries, as only the attachment needs to be changed. The split mandrel allows for faster mandrel changes during operation.

[0042] In a hardening process, the present invention allows the process sequence to be designed in such a way that no quenching medium comes into contact with the workpiece, but it is also possible to work with a combination of internal cooling and direct cooling.

[0043] The possibility of combining internal cooling and direct quenching offers an increase in the quenching effect and thus makes it possible to treat workpieces with larger diameters or with materials requiring particularly high quenching effect using the press hardening process.

[0044] It should be noted here that the terms "ein" and "eine" do not necessarily refer to exactly one of the elements, although this is a possible interpretation, but can also denote a plurality of elements. Likewise, the use of the plural also includes the presence of the element in question in the singular, and conversely, the singular also includes several of the elements in question.

[0045] Furthermore, all features of the invention described herein can be combined with one another or claimed separately from one another as desired.

[0046] Further advantages, features and effects of the present invention will become apparent from the following description of preferred embodiments with reference to the figure. Here, the figure shows... Fig. 1: a tool according to the invention for fixture hardening with internal cooling and a one-piece hardening mandrel; Fig. 2: a tool according to the invention for fixture hardening with internal cooling and a two-piece hardening mandrel, Fig. 3: a tool according to the invention for fixture hardening with internal cooling, all components of the tool are designed in two parts.

[0047] Fig. Figure 1 shows a sectional view through a hardening press with a ring-shaped component clamped between a hold-down device 1, the hardening mandrel 2 and a radially pressing segment 3.

[0048] The hardening mandrel 2 and the radially pressing segment 3 are each equipped with internal cooling channels 4. Several radially circumferential cooling channels, running parallel to each other, are present.

[0049] In the embodiment according to Fig. 2 The hardening mandrel 2 is designed in two parts and comprises an inner part 2a and an adapter 2b radially surrounding the inner part 2a.

[0050] The inner part 2a of the hardening mandrel 2 is equipped with cooling channels 4, which are arranged adjacent to the adapter 2b. The adapter 2b can be placed or plugged onto the inner part 2a and is preferably detachably held on the inner part 2a.

[0051] The inner part 2a forms a preferably radially circumferential shoulder 5 or step at its lower end, on which the adapter 2b rests in the state connected to the inner part 2a.

[0052] Adapter 2b is the one in Fig. In variant 2 shown, a large part of the contact area between the hardening mandrel 2 and the ring-shaped component is covered. Adapter 2b can, in principle, also cover the entire contact area between the hardening mandrel 2 and the component 1.

[0053] In the variant in Fig.3 are the hardening mandrel 2, the radially pressing segment 3 (also called the pressure jaw, of which any number may be present) and the hold-down device 1, which are formed in two parts and equipped with cooling channels 4.

[0054] The hardening mandrel therefore has parts 2a and 2b, the hold-down has parts 1a and 1b, and the pressing segment 3 has parts 3a and 3b.

Claims

[1] Fixture hardening device comprising a hardening mandrel and at least one pressure exertion element, wherein the device is designed to accommodate a component to be hardened between the hardening mandrel and the at least one pressure exertion element, wherein the hardening mandrel and / or the pressure exertion element has at least one internal cooling channel. [2] Device according to claim 1, wherein the at least one cooling channel is arranged adjacent to a contact surface of the hardening mandrel and / or the pressure exerting element, which is designed to come into contact with the component during fixture hardening. [3] Device according to claim 1 or 2, characterized by that the hardening mandrel is formed in one piece or in multiple pieces. [4] Device according to claim 3, characterized bythat the hardening mandrel and / or at least one pressure exertion element, preferably all pressure exertion elements, is designed in at least two parts and has an inner part and an adapter detachably connected to the inner part, which is designed to come into contact with the component. [5] Device according to claim 5, wherein the inner part has a radially circumferential shoulder at one end on which the preferably ring-shaped adapter is detachably mounted. [6] Device according to claim 4 or 5, wherein the adapter is free of cooling channels. [7] Method for fixture hardening, wherein the method is preferably carried out using a device according to claims 1 to 6, characterized by , that a cooling and / or quenching process of a component to be hardened is carried out, preferably exclusively, by contact of the component with the hardening mandrel and / or the pressure exertion element of the device. [8] Method according to claim 7, wherein the component is not exposed to direct contact with the cooling medium. [9] Method according to claim 7 or 8, further comprising the step of: creating an inert environment in an area of ​​contact between the device and the component, preferably by flushing with gas, in particular inert gas, to prevent oxidation of the component. [10] Use of a device according to any one of claims 1 to 6 and / or a method according to any one of claims 7 to 9 for the manufacture of an aircraft, in particular an airplane, and / or a component thereof.

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