EP1462195A1 - Process for the manufacture of hollow grinding members and grinding members thus obtained - Google Patents

Abstract

Preparation of hollow grinding bodies for material to be ground (MG) including a casting mold with a hollow space, arrangement of the casting core in the hollow space to give an intermediate space for the MG, introduction of casting core holding elements, application of an envelope to each of these, casting of the MG in the hollow space, where the envelopes consist of a metallic material which can be melted with the MG. An independent claim is included for a grinding body such that an intermediate layer is formed between the envelopes and holding elements (6).

Description

The invention relates to a method for producing hollow Comprehensive grinding media for the grinding of grinding materials a mold with a cavity, placing a mold core in the cavity, so that a bowl-like space for Cast material is created, introducing holding elements for the Core, applying a covering to the holding elements and Pour the casting material into the space.

It is known for grinding cement clinker, cement raw material, To use coal and similar ground material which are hollow. The hollow design of the grinding media brings the advantage over considerable weight savings massive grinding media with itself. One disadvantage is that with hollow bodies due to the limited thickness of the shell Wear is a bigger problem than with solid grinding media is. So that there is no unnecessarily high wear, So the grinding media are made so that they are as possible are low wear. A known from obvious prior use Manufacturing process for such hollow grinding media is composite casting, a casting mold is used for casting has an inner cavity in which a cast core is arranged is that there is a gap. In this space casting material is poured so that after solidification a bowl-like body is created. Here is now the difficulty that the casting core in the inner cavity the mold must be fixed. Furthermore, from the core escaping gases are removed. It is known about this Purpose the core by means of a steel pipe Keep core shoring. The steel tubes are hollow, so that gases can be removed from the core through them. To avoid unwanted interactions between the core shoring and the Preventing casting material are from apparent prior use The following methods for protecting the core shoring are known:

In a first method, the core is covered with ceramic Material wrapped. To the core shoring from the grinding media to be able to remove after the casting solidifies created several holes in the bowl of the grinding media. By this becomes the core shoring together with its ceramic cladding away. The holes created in this way are proportionate large diameter. Obstruct in grinding operation the edges of these holes unroll the grinding media. It comes to the so-called edge wearing. This leads to increased Loads on the grinding media, so that it is at these points subject to increased wear. Especially in the case of brittle Existing grinding media easily flake off in this area, which eventually led to failure of the grinding media.

In a second process, the tubes of the core shoring not covered with ceramic in the area of the intermediate space, but remain unprotected. In the casting process, they are Cast material immediately exposed. As a result, it during the casting process at least partially for fusing of the casting material with the surface of the pipes of the core shoring comes. The core shoring is therefore after solidification the cast material is not removed. They remain in the grinding media. It is true that edges are carried during operation, however, it occurs due to the fact that it is fused as in composite casting Core pipes no longer cause flaking in this Area. The disadvantage of this method is that the core shoring not removed due to the melted core tubes can become and is lost.

The invention has for its object a method of type mentioned and a grinding media produced therewith provide with the disadvantages mentioned above be reduced or avoided.

The solution according to the invention lies in the features of the independent Expectations. Advantageous embodiments are the subject of the dependent claims.

According to the invention in a method for producing Hollow grinding media for the grinding of grinding materials a mold with a cavity, placing a mold core in the cavity, so that a bowl-like space for Cast material is created, introduction of holding elements for holding of the core, applying a covering to the holding elements and pouring the casting material into the space provided that at least in the area of the space for the wrapping a metallic material is used, which with the Casting material melts.

The invention is based on the idea that the holding elements for the cast core (usually these are pipes) with a protective Wrapping provided from a metallic material exists so that it can fuse with the casting material. The holding elements themselves, on the other hand, because they are protective covering are protected against melting, be removed. This accomplishes two things. On the one hand are the result of removing the holding elements Holes are relatively small because only the holding elements themselves and not also to have their wrapping removed needs. Reduce through the smaller size of the holes the negative effects of wearing edges. additionally arises from the melting of the protective covering made of metallic material a good transition in the area of the holes, so that even with particularly brittle materials flaking does not occur. In the result you get one particularly good load-bearing behavior of the grinding media and thus one low wear with smooth running. By using metallic material for the wrapping can thus be on surprisingly simple way to take advantage of a protective Envelope with regard to removability of the holding elements that of waiving the wrapping and thereby composite casting-like melting.

It has been shown that a particularly good protective effect on the one hand and a particularly good melting behavior on the other can be achieved in that the strength of the metallic Wrapping is varied depending on the location. This can an adaptation to location-dependent different parameters of the Solidification and cooling process can be carried out. On this way a particularly good, largely error-free Fusion of the casing with the casting material can be achieved.

It is expedient to use the metallic sheath over such Apply length so that they are in the area of the casting core and / or the protruding projection protruding. By the Wrapping metallic material not only on the area the gap, d. H. the later fusion zone with the Casting material, is limited, is achieved that just in a good melting result in the particularly critical surface area is achieved. The flawlessness of the merger increases so that the wear behavior of the grinding media further improved. It turned out to be useful if the protrusion is between one and two thirds of the diameter the holding elements is.

In a particularly preferred embodiment, before Apply an insulating intermediate layer to the metallic covering generated. With such intermediate insulation will have better thermal separation between the metallic Wrapping and the holding element itself, reached. Thereby it is simplified to the method according to the invention cause the metallic cladding to be flawless with the casting material melts and that on the other hand the holding element can be removed as easily as possible. In addition, the insulating intermediate layer has the advantage that during the casting process occurring significant temperature changes only to a lesser extent Act circumference on the holding elements so that the Danger is counteracted by thermally induced Changes in length of the holding elements tensions in the solidifying Casting material can be introduced. This improves the shape accuracy of the manufactured with the inventive method Refining body.

The insulating interlayer can also be formed in this way be that the metallic sheathing loose on the Holding elements sits. In this case, air acts as a special simple and effective isolator.

The cross section of the holding elements is expediently like also the wrapping chosen to be as small as possible. This allows it, the holes created after removing the holding elements to keep it as small as possible.

Preferably, in the method according to the invention Melting of the metallic covering with the casting material through known ultrasound methods for error-free being checked. This enables particularly good control the process parameter of the manufacturing process. This allows all parameters of the manufacturing process including the dimensions of the holding elements and the metallic Wrapping can be optimized.

The invention also extends to a grinding media for Crushing ground material, which is designed as a hollow body and openings for holding elements for holding in its shell of a cast core, with envelopes of the holding elements the openings are melted down, and the sealed envelopes made of metallic material. The grinding media according to the invention has due to the melted Enclosures made of metallic material a composite casting Structure in the area of the openings. This gives advantageous properties with regard to edge wearing in the area of the openings and from chipping in the area of the openings resulting in danger to operational safety of the grinding media.

Fig. 1

einen Querschnitt durch eine für das erfindungsgemäße Verfahren verwendete Gußform;

Fig. 2

eine vergrößerte Detailansicht der Oberfläche eines erfindungsgemäß hergestellten Mahlkörpers mit einer Öffnung im Bereich eines Halteelements im verschmolzenen Zustand; und

Fig. 3a, b

Detailansichten der erfindungsgemäßen Umhüllung mit Halteelement im unverschmolzenen Zustand.

The invention is explained below using an exemplary embodiment with reference to the accompanying drawings. In it show:

Fig. 1

a cross section through a mold used for the inventive method;

Fig. 2

an enlarged detail view of the surface of a grinding body produced according to the invention with an opening in the region of a holding element in the fused state; and

3a, b

Detailed views of the casing according to the invention with the holding element in the unmelted state.

To explain the method according to the invention, first described the mold used. The mold 1 has one inner cavity 2, which is spherical. The The cavity is connected to the surroundings via a plurality of through bores 3 the mold 1 in connection. There is also an inlet (not shown) provided for pouring casting material.

Within the cavity 2 there is a spherical one Cast core 4. It is arranged in the cavity 2 that between the surface of the casting core 4 and the surface of the spherical cavity 2, an intermediate space is formed Every point has the same width. The gap 5 thus takes the form of a spherical shell.

To hold the casting core 4 in position within the spherical cavity 2, a core shoring 6 is provided. The core shoring 6 consists of several tubes 61, 62, 63 which are inserted in the cast core 4 and in the holes 3 of the Mold 1 are supported. The pipes 61, 62, 63 meet in the center of the spherical core 4. So that the core 4 can be degassed, the tubes 61, 62, 63 are hollow executed. The dimensions of the tubes 61, 62, 63 are 75 mm for the outside diameter and 25 mm for the inside diameter.

The tubes 61, 62, 63 are in the region of the intermediate space 5 provided with a covering 71, 72, 73 made of metallic material. The metallic material can be, for example to various well-known structural steel or boiler plate qualities act. The enveloped area is chosen so that it is not only over the area of the interspace 5 runs, but also in each case over a certain distance the mold core 4 and the mold 1 extends. The length of this also referred to as the protrusion distance in the illustrated Embodiment about a third of the outer diameter of tubes 61, 62, 63.

In Fig. 3a is the example of the tube 62 with the casing 72 gives an enlarged view. The envelope 72 encloses the tube 62 like a ring. It can be taut on the pipe 62 sit or with a certain game. In the latter case is located over a wide range of circumference Air gap between the outer surface of the tube 62 and the Envelope 72. This air gap has a thermally insulating effect. This ensures that the metallic casing 72 is free of defects with the casting material introduced into the intermediate space 5 can merge without the risk that the Pipe 62 warmed too much and also melted. Thereby it is ensured that the tube 62 is slightly out the solidified casting material can be removed. To achieve this Effect is not absolutely necessary to the metallic Envelope 72 by means of an air gap from the core tube 62 isolate. It can also be provided that an insulating material as an intermediate layer 8 in the area between the outer surface of the tube 62 and the metallic sheath 72 ' is applied. This is shown in Fig. 3b. Here too this results in the advantageous thermal decoupling of the metallic sheath 72 'from the core tube 62.

To produce the grinding media, after the casting core 4 in the mold 1 introduced and in the right place by means of of the core structure 6 is positioned and the tubes 61, 62, 63 of the core shoring with the metallic sheath according to the invention 71, 72, 73 are provided, molding material through the inlet (not shown) in the spherical shell-shaped space 5 filled until it completely fills it. The casting material cools down in mold 1 and solidifies. Here comes it fuses with the metallic material of the Envelopes 71, 72, 73 in such a way that around the core tubes 61, 62, 63 a compound zone is created. The core tubes 61, 62, 63 themselves do not melt. You can after solidification of the casting material is removed from the resulting grinding media become.

2 is an enlarged section of the outer surface of the Grinding body 9 produced according to the invention is shown. you recognizes an opening 11 through which one of the core tubes 61, 62, 63 has been removed. In the surrounding the opening 11 Area is shown schematically an annular zone, in which the metallic sheath 71, 72, 73 with the Cast material is fused. This composite casting zone is with designated by the reference numeral 10. The opening 11 is thanks to the Invention quite small, it only needs to be so big that it is sufficient for the passage of the core tube 61, 62, 63. The sheath 71, 72, 73 surrounding the core tube does not need to be removed, it is in accordance with the invention fused the casting material. Thanks to the small dimensions the opening 11 occurs anyway only to a small extent Edge support. It also comes thanks to the created according to the invention Compound zone 10 even with particularly brittle materials hardly any flaking. This achieves the invention Grinding ball 9 excellent operating and wear properties.

Claims (13)

A process for the production of hollow grinding media (9) for comminuting grinding materials, comprising
a casting mold (1) with a cavity (2),
Arranging a casting core (4) in the cavity (2) so that a shell-like intermediate space (5) for casting material is created,
Introduction of holding elements (6) for holding the cast core (4),
Applying a covering (71, 72, 73) to the holding elements (6),
Pouring the casting material into the intermediate space (5),
characterized in that
at least in the area of the intermediate space (5) for the covering (71, 72, 73) a metallic material is used which melts with the casting material. A method according to claim 1, characterized in that the thickness of the metallic casing (71, 72, 73) is varied depending on the location. Method according to one of the preceding claims, characterized in that the metallic covering (71, 72, 73) is applied over such a length that a protrusion projects into the area of the casting core (4) and / or the casting mold (1). Method according to claim 3, characterized in that the protrusion is between one and two thirds of the diameter of the holding elements (6). Method according to one of the preceding claims, characterized in that an insulating intermediate layer (8) is produced under the metallic covering (71, 72, 73). A method according to claim 5, characterized in that an air layer is used as the insulating intermediate layer. Method according to one of the preceding claims, characterized in that structural steel or boiler plate is used as the metallic material. Method according to one of the preceding claims, characterized in that spherical grinding media are produced. Grinding body for comminuting grinding material, which is designed as a hollow body and has in its shell openings (11) for holding elements (6) for holding a cast core (4), envelopes (71, 72, 73) of the holding elements (6) opening ( 10) are melted around the edges,
characterized in that
the melted envelopes (10) consist of metallic material. Grinding body according to claim 9, characterized in that the thickness of the casing (71, 72, 73) is location-dependent. Grinding body according to claim 9 or 10, characterized in that an intermediate layer (8) is arranged between the casing (71, 72, 73) and the holding elements (6). Grinding body according to one of claims 10 to 11, characterized in that structural steel or boiler plate is used as the metallic material. Grinding body according to one of claims 9 to 12, characterized in that it is designed as a grinding ball (9).

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