WO2010091924A1

WO2010091924A1 - Method for producing a fitting, a lateral screen or a refining product carrier for high temperature applications and metal component

Info

Publication number: WO2010091924A1
Application number: PCT/EP2010/050690
Authority: WO
Inventors: Peter Jährling; Willi Grigat
Original assignee: Paul Hettich Gmbh & Co. Kg
Priority date: 2009-02-13
Filing date: 2010-01-21
Publication date: 2010-08-19
Also published as: DE102009008931A1

Abstract

A method relating to the production of a fitting, a lateral screen or a refining product carrier for high temperature applications comprises: producing a blank and applying a metal coating comprising at least one solid lubricant, and a metal component made of a blank and a metal coating comprising a solid lubricant.

Description

Method for producing a fitting, a side grille or a product carrier for high temperature applications and metallic component

The invention relates to a method for producing a fitting, a side rail or a product support according to the preamble of claim 1 and a metallic component for use in the high-temperature region, according to the preamble of claim 10.

When using components, in particular drawer guides, in ovens, there is the problem of the lubrication of moving parts. Fats and oils are unsuitable for ovens in pyrolysis at 500 ⁰ C. Thus, the use of solid lubricants is needed here. These include graphite, molybdenum disulfide, polytetrafluoroethylene and hexagonal boron nitride.

The application of these solid lubricants should be as even as possible. By frequent use of the extracts and sliding mechanisms can a

Removal of the solid lubricant can not be completely prevented. Already known are material-saving application methods in which the solid lubricant compound is applied in pasty or dissolved form or as a bonded coating. However, since the solid lubricants are applied only superficially to a component, it is currently often come into contact with the component to the contamination of hands and clothing. To counteract the removal of the solid lubricants, these were applied selectively on sliding surfaces of the corresponding components, while other areas of the components were exposed to the corrosive baking oven conditions.

EP 0 218 645 discloses a plating bath for co-depositing metal and a permanently lubricated solid lubricant, the plating bath comprising a specific water-soluble, cationic surfactant. DE 1 255 431 discloses the incorporation of dry lubricant particles into a metal coating. This takes place by means of storage in plastic bubbles in the form of microencapsulations.

The present invention therefore, starting from the previous methods of application of solid lubricants in the task of creating a component with a coating, which ensures a lower abrasion of the lubricants and also corrosion resistant and suitable for high temperature applications.

The present invention solves this object by a method and a metallic component by the features of the characteristics of claims 1 and 10.

The process for producing a fitting, a side rail or a product carrier for high-temperature applications involves two successive production steps. In a first step, a metallic blank is made or formed, and in a subsequent second step, a metallic coating is applied to the blank. In this metallic coating at least one solid lubricant is incorporated.

By direct incorporation of the solid lubricant in the metal layer of the metallic coating, there are two main advantages.

Solid lubricants predominantly have a layered structure. Their tribologically advantageous properties can be explained by a shift of the superimposed layers. This results in prolonged use to a sliding wear of the lubricant layer. Metal layers are both removed during friction and shifted to each other. If, however, the soft solid lubricants are incorporated in metal layers, then material factors such as Vickers hardness and friction coefficient can be optimized in such a way that significantly less abrasion of the coating material takes place. This lower abrasion is expressed in abrasion factors, which are four to five times lower than in pure metal coatings. Another advantage is that the solid lubricant can not be removed by mechanical cleaning of the sliding surface, but is firmly connected to the metal surface.

In the production according to the invention, moreover, the metallic luster of

Surface preserved even after the coating of the blank with the metallic coating. The surface can be additionally surface-treated by applying several types of metal.

Since the application of the metallic coating can be done both partially but completely over the entire surface of the blank, a corrosion protection by the metallic coating is possible. Therefore, it is no longer necessary, as before, to form the blank from stainless steel, which is cost and energy intensive.

In the method, it is advantageous if the solid lubricant is incorporated as boron nitride during application of the metallic coating in the metal structure. The excellent tribological properties of the boron nitride are additionally supplemented by the incorporation into the metallic coating. Hexagonal boron nitride retains its tribological properties at over 600 ^° C. as much as possible and is therefore particularly suitable as a lubricant for use in ovens and the like with pyrolysis operation. It is also extremely pressure-resistant, whereby the coefficient of friction under pressure load decreases even further, which corresponds to a thixotropic mode of action. By incorporating boron nitride into a metal structure, therefore, a hard, but lubricious layer on the surface of the

Blank are generated.

Depending on the type of metallic coating and the metallic blank, this coating can already be achieved in an advantageous manner by immersing a metallic raw part in a solution with dissolved metal ions. This occurs, for example, in the cementation of copper on iron fittings. - A -

In order to achieve a particularly firmly adhering metallic coating, an advantageous application of a metallic coating by means of electrochemical deposition can be effected by a galvanic process.

In an advantageous method, nickel plating of the metallic blank can take place with incorporation of solid lubricants. In the case of nickel plating, a large proportion of the supplied current is used for depositing the nickel on the metallic blank. Therefore, a nickel plating process is very energy efficient compared to other galvanic processes. The nickel coating is also chemically resistant to dilute acids and much of

Lyes, as used in aggressive chemical cleaning agents. In addition, nickel is not corrodible and resistant to water and air.

It is advantageous if the metallic blank after coating with a metallic coating passes through a tempering process, in which an additional curing of the coating takes place. Larger dislocations in the metal grid are eliminated and the stored solid lubricants are more firmly integrated into the metal structure. The heating process should be controlled slowly by a temperature gradient. Similarly, the cooling should be controlled by a gradient to avoid disorder due to different

To avoid thermal expansion coefficient of the individual components.

Preferably, the annealing process between 300 to 700 ⁰ C, preferably 400-600 ⁰ C operated. Higher degrees of hardness of the metal coatings with solid lubricant contents can be achieved in this area than is the case with comparable uncured metal coatings.

In order to obtain the most uniform possible deposition on the surface of the blank, it is advantageous to smooth the blank before applying the metallic excess.

For additionally reducing the abrasion indices and the surface roughness with additional fine distribution of some boron nitride particles on the surface of the layered blank is a post-processing after application of the metallic coating by smoothing the surface of advantage.

In addition, the aforementioned object is achieved by a metallic component according to the invention for use in the high-temperature range, in particular

Solved baking ovens, which provides a molded blank with a metallic coating, which additionally contains at least one solid lubricant.

Due to the nature of this component, it can be used wherever high-temperature friction occurs. This relates primarily to equipment for food preparation, but can also be used in appliances such as drying ovens, for example for drying chemical preparations, muffle ovens, vacuum ovens and the like, where pull-out guides or other fittings are used.

It is advantageous if the metallic coating contains boron nitride. Boron nitride in this case has excellent tribological properties, is also used in areas of about 300 ⁰ C and therefore can be subjected to a tempering s process to increase the coating hardness together with the metallic component.

Another advantageous solid lubricant which is present in or on the metallic coating of the component is polytetrafluoroethylene. This solid lubricant is characterized by its high availability and its small particle size. Due to this small particle size, the solid lubricant can be dissolved disperse in an electrolyte solution and then finely dispersed in the metallic coating to be stored.

Further advantageous solid lubricants, which may be present on or in the metallic coating, are molybdenum sulfide and graphite. These solid lubricants have a maximum operating range of 35O ⁰ C and 45O ⁰ C and can be used in these temperature ranges in ovens as solid lubricant additives in coatings. By using a cobalt-nickel alloy as a metallic coating with the aforementioned solid lubricants, the wear resistance of the coating can be increased again.

In the case of metallic coatings, a high boron nitride content usually also leads to a high phosphorus content, which is embedded in the metal structures. In a heat treatment sprozes s can advantageously be a hardening of the metallic coating by removal of phosphides from the metal structure.

The invention will be explained in more detail using an exemplary embodiment with reference to the accompanying drawings. They show:

Figure 1 is a front view and a perspective view of a pullout guide according to the invention;

Figure 2 is an exploded view of the pullout guide;

FIGS. 3a-f show several side views, a front view and a perspective view of a further embodiment of the invention; and

FIG. 4 shows a schematic temperature diagram for producing a coated component.

A pullout guide 1 for high-temperature applications, in particular for ovens, comprises a guide rail 2 and a guide rail 3 movable relative to the guide rail 2, between which a middle rail 10 is mounted. Furthermore, the pullout guide 1 can also have more than one middle rail. For the movable mounting of the middle rail 10 and the running rail 3 rolling elements 4, in particular made of ceramic, are provided. In this case, a plurality of raceways 6 for the spherical rolling elements 4 are provided on the guide rail 2, the middle rail 10 and the running rail 3 in each case. The rolling elements are arranged in a Wälzkörperkäfig. Other components of the pullout guide are a stopper 7, a stopper 10 a plurality of brackets 8 for fixing the pullout guide 1 and a diaphragm. 9

Another pullout guide 1 'for high temperature applications is shown in Figure 3 and shows a guide rail 2' and a movable relative to the guide rail track 3 ', which is mounted on the guide rail. For the movable mounting of the running rail 3 'rolling elements 4', in particular made of ceramic, are provided, which are guided in raceways 6 '. Other components such as a stop V, a plurality of brackets 8 'and a diaphragm 9' are mounted analogously to the previously described embodiment of the pullout guide.

The rails 1, 2, 3, 1 'and 2' are made for use in ovens from a stamped and bent sheet steel and provided with a coating. The components of the pullout guide, in particular the rails 1, 2, 3, 1 'and 2', are manufactured by the following steps:

First, the metallic blanks are produced by punching and bending a steel sheet. The blank can be machined.

Thereafter, a metal layer is electrodeposited on the surface of the blanks, wherein the electrolyte solution contains boron nitride or other solid lubricant, which is incorporated in the application deposited in the metal layer deposited on the blank.

In the galvanic process, mass transfer in a bath of electrolyte with two metal electrodes is achieved. The metal electrodes consist of different metals. At the anode metal ions are dissolved, which then migrate to the cathode, where they attach themselves. If there is a certain concentration of solid lubricant in the electrolyte bath, which is finely divided and dispersedly dissolved, then this can be incorporated into the metal structure during the deposition of the metal layer at the cathode.

In the deposited metal layer can be incorporated up to a volume fraction of 29% boron nitride, which is a boron nitride content of about 28-33 g / l in the electrolyte solution. Boron nitride is dispersed in the electrolyte solution. Other process parameters are the current density (at 4-6 A / dm ² ), the pH (at pH 2-4) and the electrolyte temperature (at 40-60 ⁰ C).

The coated blanks are then heated to a temperature of at least

400 ⁰ C heated and annealed for a predetermined period of time before they are cooled back to room temperature.

The hardness of the metallic coating can be three to four times harder (up to 630 HV) in the case of a NiBN layer (nickel boron nitride) than a normal nickel coating. In addition, there is a friction coefficient of about 0, 1 or less, less wear than pure nickel layers and low abrasion.

The abrasion was performed according to the Taber Abraser test according to existing DIN standards and gave a Taber Wear Index of 2.5 for a nickel coating with a boron nitride content of 29% and 3.5 for a boron nitride content of 12%, after three grinding cycles.

Another possibility of the coating consists in an autocatalytic chemical reduction process, wherein a phosphorus-containing NiBN layer is deposited on the metallic surface of the blank. Here, the phosphorus content increases with increasing proportion of boron nitride in the nickel. At the same time, the layer thickness decreases for the same duration of the deposition process.

Another possibility is the galvanic application of a mixture of several metals, in which also boron nitride molecules are incorporated during the deposition process. In this case, the metal mixture, for example a nickel-cobalt mixture, may also be phosphorus-containing.

An inventive phosphorus-containing nickel-cobalt coating consists of:

- Cobalt: mass fraction 0.20 - 0.25

- Phosphorus: mass fraction 0,06 - 0,08

Hexagonal boron nitride: mass fraction 0.03-0.04 nickel: mass fraction 0.63-0.71 The tempering can be carried out according to the annealing process shown in FIG.

FIG. 4 schematically shows a temperature diagram for the method of the temperature of galvanically coated fittings, side grilles and food carriers with boron nitride molecules embedded in the metallic coating for high-temperature applications. The coated blank is first heated from ambient temperature i3 _0th It starts with a temperature gradient of 8-15 K / min, in particular 10 K / min, starting from an initial temperature

⁰ C in a temperature gradient of 25 K / min over. When reaching a target temperature iϊ ₂ of 500 ⁰ C follows a temperature plateau over 30 min away. Finally, a cooling phase with 10-20 K / min, in particular 15 K / min back to

In the illustrated embodiment, a galvanically coated pullout guide has been described. Of course, it is also possible to provide other metallic components with a coating according to the invention. In particular, food supports, side rails, fittings or other usable in ovens components can be coated.

Additional dispersants which adsorb on the surface of the BN particles can additionally be introduced into the metal coating, for example to prevent agglomeration of the boron nitride particles. This can be done by charging the particles, which also builds electrostatic interactions with the metal substrate of the metallic coating, which facilitate Einlagerang and distribution of the dispersed boron nitride particles in the deposited metal coating.

Also possible is a Einlagerang of PTFE (polytetrafluoroethylene) in the electrodeposited metal coatings, but here a corresponding annealing step is omitted and the application of such a coated furnace part only a maximum of up to 25O ⁰ C, otherwise thermal decomposition of the PTFE is possible. Grandsätzlich comes by the application of a galvanic or chemical Metallic coating with the inclusion of other solid lubricants, also a use of graphite or molybdenum sulfide into consideration.

The lubricants used should also meet the hygiene requirements of the German version DIN EN ISO 21469: 2006.

LIST OF REFERENCE NUMBERS

pull-out guide

guide rail

runner

rolling elements

Rolling Element

career

attack

clip

cover

middle rail

attack

Claims

claims

1. A method for producing a fitting, a side rail or a product carrier for high-temperature applications, characterized by the following steps:

a) producing a blank; and b) applying a metallic coating containing at least one solid lubricant.

2. The method according to claim 1, characterized in that the solid lubricant is incorporated as boron nitride during application of the metallic coating in the metal structure.

3. The method according to claim 1 and 2, characterized in that the application of the metallic coating is carried out by electrochemical deposition of one or more metals on the surface of the metallic blank.

4. The method according to any one of the preceding claims, characterized in that the application of the metallic coating takes place by a galvanic process.

5. The method according to any one of the preceding claims, characterized in that a nickel plating of the metallic blank is performed.

6. The method according to any one of the preceding claims, characterized in that the metallic blank after the application of the metallic coating, which contains at least one solid lubricant, is annealed.

7. The method according to claim 6, characterized in that a heat treatment is controlled by a temperature program with at least two temperature gradients.

8. The method according to claims 6 and 7, characterized in that the Temperang at 300 to 700 ⁰ C, preferably 400 to 600 ⁰ C takes place.

9. The method according to any one of the preceding claims, characterized in that the surface of the blank is smoothed before and / or after the application of the metallic coating.

10. Metallic component for use in the high temperature range, in particular ovens, characterized in that the component comprises a metallic blank, which has a metallic coating, which additionally contains at least one solid lubricant.

11. Metallic component according to claim 10, characterized in that the metallic coating contains boron nitride as a solid lubricant.

12. Metallic component according to claim 10 or 11, characterized in that the metallic coating contains PTFE (polytetrafluoroethylene) as a solid lubricant.

13. Metallic component according to one of the preceding claims, characterized in that the metallic coating contains molybdenum sulfite (MoS ₂ ) and / or graphite as a solid lubricant.

14. Metallic component according to one of the preceding claims, character- ized in that the metallic coating contains a cobalt-nickel compound.

15. Metallic component according to one of the preceding claims, characterized in that the metallic coating is phosphorus-containing.