EP1511939B1 - Production of machine parts provided with a mineral casting - Google Patents

Abstract

The invention relates to a method for the production of machine parts which are at least partially provided with a mineral casting. The mineral casting is carried out in a liquid state in at least one part of a housing element ( 1, 2 ) of the machine part acting as a casting mould, such that the mineral casting, after hardening, forms a lining element adapted to the inner contour of the housing element ( 1, 2 ). The aim of the invention is to enable the mineral cast lining elements ( 5 ) to be adapted as accurately as possible to the inner contour of the outer housing ( 1, 2 ) without any risk of destroying the mineral cast body ( 5 ) occurring when pumps are produced or operated. According to the invention, the inner surfaces of the housing element ( 1, 2 ) are treated with a separating means ( 3 ) prior to the casting out operation.

Description

The invention relates to a process for the preparation of at least partially with Mineral casting lined machine parts, wherein the mineral casting in the liquid Condition in at least one serving as part of a mold housing element of the machine part is poured, so that the mineral cast after curing a lining element adapted to the inner contour of the housing element forms.

High corrosion and wear resistant mineral casting for the production of monolithic Cast pump housings or pump parts, for example known from DE 43 43 547 C1.

From DE 297 23 409 U1 is a centrifugal pump for chemically aggressive, erosive or abrasive media known, according to the aforementioned method can be produced. In the prior art pump, the jacket housing itself used as part of the casting mold and poured out with the mineral casting. this has the advantage that the demolding is eliminated and the lining elements formed by the casting the pump housing in place in the housing part remain. In this way, a composite part of the metallic shell casing and formed of mineral casting lining element.

The production of mineral-lined machine parts according to the method proposed in DE 297 23 409 U1 has a number of Disadvantages. When curing the mineral casting, it is inevitable to reaction shrinkage, so that the solid with the metallic shell casing bonded mineral castings cracks due to its low tensile strength can. In case of thermosetting binders also exists the problem that with large dimensions of the shell or the Mineralgußkörpers due to the different thermal conductivity and the Thermal expansion coefficient Damage during cooling can arise. Comparable problems also arise in the operation of Centrifugal pumps of the known type, when there are expansions of the pump housing comes through dynamic stress. For larger pumps are expansions of several millimeters not uncommon, which inevitably leads to the fact that the brittle Mineralgußkörper firmly connected to the outer housing be destroyed.

The present invention is based on the task, the previously known Further develop a method such that eliminates the disadvantages mentioned become. In particular, a method is to be created by the invention, can be produced with the pump housing for centrifugal pumps, in which the made of mineral cast lining elements as exactly as possible to the inner Contour of the jacket are adapted without the risk that in the manufacture or operation of the pumps to destroy the Mineral casting comes.

This task is based on a method of the aforementioned Art solved by the fact that the inner surfaces of the housing element before the pouring be treated with a release agent.

The method according to the invention has the following advantages:

Thereby that due to the use of the release agent no solid connection between the lining element and the housing element, It can not destroy the mineral body by temperature differences come between the housing element and the lining element. The different caused by the temperature differences Thermal expansion may be due to the gap created by the release agent Housing element and lining element are added.

In addition, destruction due to possible expansion of the machine part avoided.

In the manufacture of pump housings for centrifugal pumps according to the invention Method is ensured by the release agent layer that from the medium no ions through the mineral cast in the housing material can diffuse. The diffusion of ions could occur in the housing material disadvantageously cause chemical reactions and by volume increase blow up the mineral casting layer or weaken the outer material.

When using the release agent is also ensured that the mineral casting during the casting process over the entire surface of the inner contour of the housing element adapts. Without any post-processing of the casting or the inner contour the housing element is a large-scale power transmission from the lining element ensured on the outer case.

The wall thickness of the lining element can in the method according to the invention usefully by a casting process in the housing element be set core. The as part of the mold too Insert coming core, which determines the inner contour of the lining element, is removed after hardening or hardening of the mineral casting.

Especially for machine parts that are resistant to abrasion, erosion or corrosion should be protected, as for example in centrifugal pumps for accordingly abrasive, erosive or corrosive media comes as mineral casting expediently a mixture of a binder with filler for Use, wherein the filler is a fine-grained wear and corrosion resistant Material, in particular silicon carbide, quartz sand, glass, Ceramic or a mixture of these materials. For optimization Chemical resistance and wear resistance should be the mixture contain as much filler and as little binder as possible.

It is advantageous in the inventive method as a binder under Heat supply hardening resin hardener system to use. To this Way, it is possible to influence the curing process targeted. The Mineral cast mixture may be sufficient during the mixing and casting process Cast metal mixture may be sufficient during the mixing and pouring process be kept liquid for a long time, then cured by selective heating to become. Suitable Kunsarz hardener systems are as commercial products available.

A useful development of the method according to the invention results, when the housing member in the mineral casting protruding anchoring means having. This is any kind of positive connection between the housing part and the lining element, by means of which, for example prevents the Mineralgußkörper from the housing part fall out. This can also be prevented by recesses in the housing part, in which the cast mineral casting anchors itself. So that Mineral casting still removable, the anchoring means, e.g. Also provided with a corresponding pocket wall element of the Housing part, detachable by means of suitable screwing of the housing part be designed.

As described above, the method according to the invention is particularly suitable Method for the manufacture of pump housings for centrifugal pumps. The housing element in this case is a jacket housing part a volute casing of a centrifugal pump.

It makes sense to proceed according to the following process steps:

First, at least two interconnected, on the inner surface shell parts treated with the release agent are poured out with the mineral casting, wherein inside the jacket housing parts is a core, which specifies the wall thickness of the lining element during the casting process. After hardening or hardening of the mineral casting, the jacket parts become separated from each other, whereupon that of the one-piece lining element destroyed and removed at least partially enclosed core can be. Finally, the jacket housing parts are joined together again. This approach has the advantage that the Mineralgußauskleidung the spiral housing is one-piece. A mutual sealing of the lining elements the respective housing parts is unnecessary. The disadvantage, however, is that the core, through which the shape of the impeller chamber of the centrifugal pump is specified after the casting is enclosed in the mineral casting, so that the core must be destroyed and can not be reused.

Alternatively, a procedure according to the following method steps offers At first, at least two on the inner surface with the release agent treated jacket housing parts individually poured with the mineral casting, wherein the wall thickness of the lining elements during the casting process respectively a core is given. After hardening or hardening of the mineral casting the core is taken. Then they are lined with the mineral casting Mantelgehäuseteile joined together, the sealing surfaces of the lining elements be sealed. In this way, the core can be multiply be used. For the sealing preferably elastic seals used.

Thereby that according to the last-described method, the jacket housing parts be poured individually, there is advantageously the possibility the formed by the shell housing parts and the respective core Mold form such that the lining elements in the Protruding sealing surfaces a few millimeters from the jacket housing parts. At the Assembly and screwing of the spiral housing parts produced according to the invention So can the sealing surfaces of the lining elements with large Force are pressed together. In addition, so are the lining elements firmly pressed from the inside to the shell housing parts, creating a good Power transmission ensured by the pumped fluid to the outer housing becomes.

Alternatively, the formed by the shell housing parts and the respective core Mold be formed such that the lining elements in the area the sealing surfaces behind the Verschraubungsbünden the casing housing parts lying back or flush with these. In this case will be only the forces caused by the elastic seals on the Transfer lining elements, which also ensures a safe application of the Mineral cast body ensures the inner surfaces of the casing housing parts can be.

According to the method described above, a centrifugal pump can be produced, the at least one impeller and at least one wheel chamber receiving the impeller which at least partially with lining elements is lined with mineral casting, wherein the lining elements of a metallic shell casing are enclosed, consisting of at least two jacket housing parts exists, in which the lining elements are shed. The centrifugal pump is according to the invention characterized in that between the outer surfaces of the lining elements and the inner surfaces of the Sheath housing parts a filled with a release agent gap exists.

Figur 1

schematische Darstellung der Herstellung eines Spiralgehäuses für eine Kreiselpumpe nach einer ersten Variante des erfindungsgemäßen Verfahrens;

Figur 2

schematische Darstellung der Herstellung eines Spiralgehäuses für eine Kreiselpumpe nach einer zweiten Variante des erfindungsgemäßen Verfahrens;

Figur 3

Querschnittdarstellung eines Spiralgehäuses einer erfindungsgemäßen Kreiselpumpe;

Figur 4

Draufsicht auf das Spiralgehäuse gemäß Figur 3.

Embodiments of the invention are explained below with reference to the figures. Show it:

FIG. 1

schematic representation of the production of a spiral housing for a centrifugal pump according to a first variant of the method according to the invention;

FIG. 2

schematic representation of the production of a spiral housing for a centrifugal pump according to a second variant of the method according to the invention;

FIG. 3

Cross-sectional view of a spiral housing of a centrifugal pump according to the invention;

FIG. 4

Top view of the spiral housing according to FIG. 3

The manufacturing process shown schematically in Figure 1 is based on two interconnected metallic shell housing parts 1 and 2 of a spiral housing a centrifugal pump. The inner surfaces of the housing elements 1, 2 are pretreated with a release agent. FIG. 1 shows a dashed line Release agent layer 3. In the manufacture of spiral housings for centrifugal pumps has in practice the use of a liquid release agent proven on a wax basis. For example, it is particularly suitable commercially Available "release agent T2" from Ebalta Kunststoff GmbH. Like in the Figure 1 is located in the interior of the connected jacket housing parts 1, 2 cavity formed a core 4. Figure 1a) shows the state through the interconnected jacket housing parts 1, 2 and the Core 4 formed mold before the casting process. According to the figure 1 b) is the Gap between the housing elements 1, 2 and the core 4 after the pouring process filled with mineral casting. The mineral body molds on the inner contour of the casing housing parts 1, 2 adapted lining element 5, whose inner contour is predetermined by the core 4. After the Anoder Curing the mineral casting, the core 4 is destroyed and removed. The figure 1c) shows the final state of the manufacturing process. After removing the Kerns 4 remains enclosed by the lining element 5 cavity 6th back, which forms the impeller chamber of the centrifugal pump. Through the between the jacket housing parts 1, 2 and the lining element 5 remaining Release agent layer 3 is ensured that the lining element. 5 not firmly connected to the outer housing. It can not be too Destruction of the lining element 5 by temperature differences come between the jacket housing parts 1, 2 and the lining element 5. The different caused by any temperature differences Thermal expansion can of a between the release agent layer 3 and the lining element 5 resulting gap or of the release agent layer 3 yourself. The described production process further ensures that without any finishing of the lining element 5 or the inner contour of the jacket housing parts 1, 2 a large area Power transmission from the lining element 5 through the jacket housing parts 1, 2 formed outer housing is ensured.

In the production method shown schematically in Figure 2 are two separate molds used, consisting of the upper shell housing part. 1 or the lower shell housing part 2 consist. The two jacket housing parts 1, 2 are each covered by a plate 7 and 8, to which each part of the core 4 is attached. Both jacket housing parts 1, 2 are pretreated on their inner surfaces with release agent. FIG. 2a) shows the molds with the release agent layer 3 before the casting process. The both jacket housing parts 1, 2 are poured out individually with mineral casting, in turn, the wall thickness of each formed by the mineral casting Lining element 5, as shown in Figure 2b), specified by the core 4 becomes. After hardening or hardening of the mineral casting are respectively the core 4, which is reusable in the process shown in Figure 2 is, and the plates 7, 8 removed. In this condition are those with mineral casting lined shell housing parts 1, 2 in Figure 2c). The sealing surfaces of the lining elements 5 of the lower shell housing part 2 are with sealed elastic sealing elements 9, so that the upper shell housing part 1 can be placed. FIG. 2 shows the final state of FIG mated jacket housing parts 1, 2 existing spiral housing. The Impeller chamber 6 is sealed from two against each other by means of the sealing elements 9 Lined lining elements 5, which due to the Release agent layer 3 is not fixed to the metallic shell housing parts 1, 2 are connected.

Figures 3 and 4 show a volute casing of a centrifugal pump, which consists of two metallic outer shell housing parts 1 and 2 consists. That in the figures not shown impeller of the centrifugal pump is received by the impeller chamber 6, partially lined with lining elements 5 of mineral casting is. Between the outer surfaces of the lining elements 5 and the Inner surfaces of the shell housing parts 1, 2 is shown in phantom in FIG Release agent layer 3 to see, which ensures that no firm connection between the jacket housing parts 1, 2 and the lining elements 5 exists. Between the sealing surfaces of the lining elements are sealing elements 9 arranged. At the same time, it can be seen in FIG. 3 that the lining elements 5 positively received in the shell housing parts 1, 2 are. FIG. 4 also shows gland collars 10, 11 of the jacket housing parts 1, 2 and a connecting flange 12 for the outlet of the centrifugal pump.

Claims (11)

1. A process for the production of machine parts which are at least partially lined with mineral casting, wherein the mineral casting is cast in the liquid condition into at least one housing element (1, 2) of the machine part, serving as part of a casting mould, so that after hardening the mineral casting forms a lining element (5) adapted to the internal contour of the housing element, characterised in that the inside surfaces of the housing element (1, 2) are treated prior to the pouring operation with a separating agent (3).
2. A process according to claim 1 characterised in that the wall thickness of the lining element (5) is predetermined by a core (4) disposed in the housing element (1, 2) in the casting operation.
3. A process according to claim 1 characterised in that the mineral casting used is a mixture of a binding agent with filler, wherein the filler is a fine-grain, wear-resistant and corrosion-resistant material such as in particular silicon carbide, quartz sand, glass, ceramic or a mixture of those materials.
4. A process according to claim 3 characterised in that the binding agent used is a synthetic resin-hardener system which hardens under the application of heat.
5. A process according to claim 1 characterised in that the housing element has anchoring means which project into the mineral casting or is otherwise connected in positively locking relationship to the lining element.
6. A process according to one of the preceding claims characterised in that the housing element is a peripheral housing portion of a spiral casing of a rotary pump.
7. A process according to claim 6 characterised by the following process steps:

   at least two peripheral housing portions (1, 2) which are connected together and which are treated at the inside surface with the separating agent (3) are filled with the mineral casting, wherein disposed in the interior of the peripheral housing portions is a core (4) which predetermines the wall thickness of the lining element (5) in the casting operation;

   after initial or final hardening of the mineral casting the peripheral housing portions (1, 2) are separated from each other;

   the core which is at least partly surrounded by the one-part lining element (5) is destroyed and removed; and

   the peripheral housing portions (1, 2) are assembled again.
8. A process according to claim 6 characterised by the following process steps:

   at least two peripheral housing portions (1, 2) which are treated at the inside surface with the separating agent (3) are individually filled with the mineral casting, wherein the wall thickness of the lining element (5) is predetermined in the casting operation by a respective core (4);

   after initial or final hardening of the mineral casting the core (4) is removed; and

   the peripheral housing portions (1, 2) lined with the mineral casting are assembled, with the sealing surfaces of the lining elements (5) being sealed off.
9. A process according to claim 8 characterised in that the casting mould formed by the peripheral housing portions (1, 2) and the respective core (4) are of such a configuration that in the region of the sealing surfaces the lining elements (5) project some millimetres out of the peripheral housing portions (1, 2).
10. A process according to claim 8 characterised in that the casting mould formed by the peripheral housing portions (1, 2) and the respective core (4) are of such a configuration that in the region of the sealing surfaces the lining elements (5) are disposed behind the screw flanges (10, 11) of the peripheral housing portions (1, 2) or terminate flush.
11. A rotary pump comprising at least one impeller and at least one impeller chamber (6) which accommodates the impeller and which is at least partially lined with lining elements (5) of mineral casting, wherein the lining elements (5) are enclosed by a metallic peripheral housing comprising at least two peripheral housing portions (1, 2) into which the lining elements (5) are cast, characterised in that a gap (3) filled with a separating agent exists between the outside surfaces of the lining elements (5) and the inside surfaces of the peripheral housing portions (1, 2).

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