EP2387621A1

EP2387621A1 - Method and device for the heat treatment of components by plasma fire

Info

Publication number: EP2387621A1
Application number: EP10701214A
Authority: EP
Inventors: Harry Kroetz; Inga Rudolph; Juergen Hackenberg
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2009-01-15
Filing date: 2010-01-13
Publication date: 2011-11-23
Also published as: WO2010081827A1; DE102009000238B3

Abstract

The invention relates to a method for the heat treatment of components (5; 8), wherein a voltage source (15) is electrically connected to a tool (17; 30) as one pole and to the component (5; 8) or a secondary electrode (25) as the other pole, and the tool (17; 30) and the component (5; 8) or the secondary electrode (25) are interconnected via an electrolyte (12) in an electroconductive manner. In a first process step, the voltage source (15) is used to ignite a plasma (19) in the area of at least one cavity (1; 2) of the component (5; 8) which cavity has one or several sides, especially a bore, by applying a voltage (U) to the voltage source (15), and at least part of the surface of the cavity (1; 2) is heated. In a second process step, the voltage (U) is reduced and the plasma (19) is extinguished so that the electrolyte (12) reaches the surface of the cavity (1; 2). The method according to the invention allows bores (1; 2) to be hardened with relatively little input of power.

Description

description

METHOD AND DEVICE FOR HEAT TREATMENT OF COMPONENTS BY PLASMA HEATING

State of the art

The invention relates to a method for heat treatment of components according to claim 1 and an apparatus according to claim 5.

In particular, when hardening holes in components that have a relatively small diameter, it is very difficult to target the surface of the hole! Oka! to announce. Therefore, in practice often the entire component! heat treated, which represents a relatively high energy consumption and procedurally extends the process.

There is already a known Ve driving, in which a plasma on the surface of a

Component is ignited for the purpose of heating the component surface, wherein the component is in an electrolyte. Furthermore, it is known, for example by means of so-called induction hardening or by means of Laserstrahlhär- teπ edge layers of a component to harden. However, these methods are only used to a very limited extent when hardening bores, which for example have a diameter of less than 2 mm. This is due to the fact that, for example, it is very difficult to redirect a laser or Elektronenstrahiung targeted at small holes or so small inducers manufacturing technology previously not be produced.

Disclosure of the invention

The invention is therefore based on the object to provide a method that allows a heat treatment of holes in components that requires a low energy input and a relatively low process time. This object is achieved in terms of the method with the features of claim 1. Advantageous developments of the method and an apparatus for performing the method and its advantageous developments are specified in the subclaims, in the context of the invention düng fall all combinations of at least two of the description, the claims and / or figures disclosed Merkmaien. To avoid repetition, features disclosed apparatus according soüen as claimable proceed according o ^f fenbart shall apply. Likewise, according to the method offer bare features are considered to be disclosed according to the device and claimable.

The invention is based on the idea that a piasrna is ignited in the region of a bore, wherein the bore is then quenched by the electrolyte after curing of the plasma and thus hardened. By the method according to the invention it is therefore only necessary to use the relatively small size

To heat area of the hole itself. Due to the relatively low energy required hierfü ^* this is done relatively quickly, leaving only a short process time is required.

It is advantageous that the method can be carried out both using a DC voltage, as well as a pulsed DC voltage or an AC voltage, whereby it can be optimally adapted to existing devices and thus possibly requires only small additional investment costs.

It is also particularly advantageous that the method can be combined with other thermochemical, thermal or electrochemical treatments of the bore of the component. As a result, the material properties or the topographic properties can be influenced in a desired manner with relatively little additional effort in a relatively short time.

A device zι m performing the method advantageously has a pin-shaped Fo ^r m on. This allows the hole over the entire depth schnei! and it is conceivable to influence the energy input into the surface of the bore in a simple manner by a suitable choice of the diameter of the tool. For better and uniform supply of the bore with the electrolyte, or one of the Äussildυng the plasma serving medium is proposed in an advantageous Ausführurgsform to equip the tool with at least one supply line, such as a bore, which at the required Stelien the bore of the Bauteiis empties.

To reduce the amount of energy required, it is also advantageous to provide an auxiliary tool with a reservoir for the electrolyte. As a result, only energy is released into a relatively small amount of electrolyte via the plasma.

Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings.

These show in:

Fig. 1 to Hg. 4 each have a simplified schematic representation of different

Votrichtungen for carrying out the method according to the invention for the heat treatment of a bore of a component.

in the figures sine the same components and components with the same function with the same Bezuqszeichen.

In Fig. 1 is a device 10 for heat treatment, in particular for hardening a hole! represented in a component 5. The device 10 comprises a container 11 which is filled with an electrolyte 12 (or an electrolyte solution), the bore 1 being completely in contact with the electrolyte 12. The negative terminal of a voltage channel 15, in the illustrated embodiment of a ballast terminal, is electrically connected via a first line 16 to a pin-shaped tool 17, which thus forms a cathode. The tool 17 penetrates the bore 1 completely. Furthermore, the positive pole of the voltage source 15 is electrically connected via a second line 18 to the component 5, which thus forms an anode. After applying a voltage U to the voltage source 15, an electric current flows! Due to the electrolysis of water, hydrogen is formed on the surface of the tool 17 at the surface of the bore 1 to form oxygen. Thereupon, the electric wide ^{r is} due to the formation of Gaspoϊsters between the bore 1 and the / Verkzeug 17. If the voltage U at the voltage source 15 is high enough (eg greater than 80V depending on the type of electrolyte used and the components geornetrieπ), there is an ionization of the gas and a breakdown in the form of a spark, through which a plasma 19 is formed, which surrounds the tool 17 in the electrolyte 12 and extends to the surface of the bore 1. This plasma 19 thus heats the surface of the bore 1 within the component 5. Once the surface of the bore 1 is heated to the desired depth to the required extent, the voltage U at the voltage source 15 can be reduced or turned off again, so that the plasma 19 goes out. Thereupon, the (relatively cold) electrolyte 12 comes into contact with the upper surface of the bore 1, whereby the surface of the bore 1 quenched and thus cured in the desired manner.

In addition, it is mentioned that the polarity of the applied voltage U can also be reversed. In this case! oxygen then forms on the tool 17 and hydrogen on the component 5 or the bore 1. The basic hardening process, however, otherwise proceeds identically.

Furthermore, it is also possible to use an AC voltage or an AC voltage source in the event of a dc voltage or a Gteich voltage source. When using a DC voltage source, it is also possible to use a pulsed DC voltage. Essential is only the at least temporary formation of a plasma 19 for heating the bore. 1

In the first Ausfüh -ungsbeispsei gernäß Fig. 1, the energy supply is stopped by switching off or reducing the voltage U after reaching the desired temperature in the surface of the bore 1. In the case of the last-mentioned possibilities, the energy transmission into the component 5 can be controlled, for example, via the pulse / pause ratio in the case of a pulsed DC voltage. Other ways of regulating the energy supply exist by an adjustable current limit, a limitation of the magnitude of the voltage amplitude of the type or the composition of the electrolyte 12 or an influence on the distance between the tool 17 and the surface of the bore 1. In the latter case, this can be done in a simple manner by an appropriate choice the diameter of the tool 17 done. The energy supply can also be effected by selective heat treatment of at least areas of the component 5, in particular by a locally different energy supply, for example by bending electrodes or a distance regulation.

In the second embodiment shown in FIG. In the case of an otherwise identical structure, the component 5 is galvanically isolated from the voltage source 15 in comparison with the first exemplary embodiment. While the tool 17 is in turn connected to the negative pole of the voltage source 15, the plus pole via a line 22 is electrically connected to a tubular grid electrode 25, which acts as a positive electrode. Also in the second Ausführungsbeispie! the plasma 19 again forms on the surface of the tool 17 and, due to its small distance from the bore 1, heats the surface of the bore 1, but in this case no current flows through the component 5.

In addition, it is mentioned that the hip electrode does not necessarily have to be in the bore 1, but it can also be located outside the bore 1 at any point in the electrolyte 12. This leads to gas formation in the bore 1 and subsequently to the formation of a plasma 19th

At the third exit ^: 3, the electrical circuit between Spannungser Spannungsqueile 15 and the tool 17 and the component 5 of the device 10 according to the first embodiment of Fig. 1. In contrast, however, a Hiffswerkzeug 27 is provided, which is in contact with the bottom 6 of the Component 5 is. In the exemplary embodiment, the auxiliary tool 27 has a hemispherical recess 28, which is arranged in extension or in alignment with the bore 1 of the component 5. The recess 28 serves as a reservoir for the electrolyte 12. In order for a plasma 19 to form, it is merely necessary here for there to be sufficient electrolyte 12 in the region of the recess 28 and the bore 1. With this As a result of the small amount of heated electrolyte 12, therefore, less heat is dissipated to the environment, so that relatively little energy is required for heat treatment of the component 5.

In the fourth embodiment according to FIG. 4, a component 8 is a

Sackiochbohrung 2 hardened. In this case, the electrical circuit of the component 8 and of the tool 30 corresponds in principle to the first embodiment of FIG. 1. In order to ensure electrolyte supply in the blind bore 2, the tool 30 has a passage hole in its longitudinal axis

10 31, which opens at the bottom of the tool 30, and which is connected to a, not shown, pressurized ElektroiytquelSe. Additionally or alternatively, from the through hole 31 and radially arranged Spritzbohru igen 33 may be provided, wherein only two spray holes 33 are shown in Fig. 4 by way of example. A corresponding order

15 tion of such Spriϊzbohrungen 33 thus relatively hard to reach places in the blind hole 2 (or possibly other wärmezu- treatedSnden points of components) with electrolyte 12 can be supplied. Instead of the electrolyte 12, it is also possible to supply a suitable gas or gas mixture which controls the formation of the plasma 19. z

In addition, it is mentioned that in addition to the described with reference to the four Ausführungsbeϊspiete martensitic hardening Bohrunger bore 1, 2, the described method can also be used in other processing methods au'weisen at least one heat treatment step. These include in particular

25 re and thus not aa thermo-chemical heat treatment processes such as nitriding, nitrocarbonating, boriding, chromating or carburizing. In these methods, the corresponding substances are added to the electrolyte 12. Thus, in the case of carburizing, the carbon may be supplied to the electrolyte 12 in the form of graphite powder. Also, the use of a

30 Emulsion of electrolyte and oil conceivable. The oil decomposes in this case caused by the plasma 19 high temperatures and thus provides the required Kohlensioff. Alternatively, it is also conceivable to use a graphite electrode (ais tool 17) that degrades in plasma 19 and thus provides the benötig ^¬ th carbon.

35 A further variant of heat treatments of the bore 1, 2 is the so-called Aniassen mentioned, in which the bore 1, 2 is heated to a certain temperature over a defined period of time. Furthermore, the method described can also be used as part of several processing steps, in which the Oberfiächentopologse during or subsequent to the

Hardening by Pfasmaätzen or other electrochemical machining with possibly temporally adjusted heat treatments of the Bauteiis 5, 8 or the hardened bore 1, 2 ir the same setting can be further influenced.

The invention has been described by way of example with reference to a component 5, 8, which has a bore 1 or a blind bore 2 aulweist. Of course, the inventive method is not limited only to such holes. Rather, it is applicable to all single or multi-sided cavities in components 5, 8. Ms examples of such cavities his exemplary rotationally symmetrical Bauteiiführungen profiled component guides (for example, conically extending guides), chambers, bags o.a. called. Also, the method can be applied to areas between high pressure and low pressure areas, for example, injectors.

Claims

claims

1. A process for the heat treatment of components (5, 8), in which a stress creep (15) with a tool (17, 30) as a butt! and the component (5, 8) or a hip electrode (25) as a different Po! are electrically connected and the tool (17; 30) and the component (5; 8) or the hip electrode (25) via an electrolyte (12) are electrically conductively connected to each other, wherein by means of the voltage source (15) in a first method step Applying a voltage (U) to the Spannungsquefte (15) a plasma (19) in the region of at least one one-sided or mehrseitig formed cavity (1; 2) of the component (5; 8), in particular a bore, is ignited, wherein at least a portion of the surface of the cavity (1; 2) is heated, and wherein in a second process step, the voltage (U) is reduced, whereupon the plasma (19) goes out, so that electrolyte (12) to the surface of the cavity (1; 2).

2. The method according to claim 1, characterized in that as voltage (U) a DC voltage, an AC voltage or a pulsed G eichspannung is used.

3. The method according to claim 2, characterized in that the energy supply into the surface of the cavity (1; 2) by regulating the height of the voltage (U), the pulse / break ratio of the voltage (U), a current limit , a limitation of the magnitude of the voltage amplitude, the At of the electrolyte (12) or a regulation of the distance between the tool (17; 30) and the cavity (1; 2) is controlled.

4. The method according to any one of claims 1 to 3, characterized that the cavity (1, 2) is subsequently subjected to a thermochemical, a thermal or an electrochemical treatment during or after the first two process steps by at least one further process step.

5. The method according to claim 4, characterized in that additives in the electrolyte (12) are provided, which during the first and the second Verfahrensschrits diffusion processes in the surface of the component (5; 8), in particular Bornseren, chromating, nitriding or carburizing errnglgli - chen.

6. Apparatus for carrying out a method according to one of claims 1 to 5, with a Spannungsqueile (15), whose one Po! with a tool (17, 30) and at the other pole is connected to a component (5, 8) or a help electrode (25), characterized in that the tool (17, 30) is pin-shaped.

7. The device according to claim 8, characterized in that the tool (30) has at least one supply line (31, 33) connected to an electrode, which in an arrangement of the tool (30) in the cavity (2) in the region of the cavity ( 2) of the component (5, 8) opens and supplies them with electrolyte (12).

8. Apparatus according to claim 6 or 7, characterized in that a memory for the electrolyte (12) exhibiting element is provided, which mt the component (5) is connectable, wherein the cavity (1) of the component (5) in conjunction is arranged with the memory.

9. Apparatus according to claim 6, characterized in that the tool (17) consists at least partially of graphite.