EP2361687B1 - Method for manufacturing a tube mill - Google Patents

Abstract

The method involves selecting a fully hardened plate material as source material for a slotted plate (5). The outer contour of the slotted plate is cut and slots are introduced in the plate material using a non-thermal cutting process. Some of the slotted plates are provided with slots arranged asymmetrically to the longitudinal central axis of the slotted plate. The hardness of the source material is so selected that it corresponds to the hardness of the manufactured slotted plate.

Description

The invention relates to a method for producing a tube mill, equipped with at least one intermediate or discharge wall, preferably a plurality of intermediate walls, which are equipped with a plurality of slotted plates. Furthermore, the invention relates to a slot plate and a tube mill, which are produced by this method. An example of this is from the DE 19638698 A1 known.

Tube mills serve to shred lumpy material and are used, for example, in cement production. In an often used embodiment of the tube mill, this has at least two grinding chambers, which are separated by an intermediate wall, one being used as a coarse grinding chamber and the other as a fine grinding chamber. In the two grinding chambers grinding balls are provided, which perform the crushing work. The intermediate wall is provided with a plurality of slit plates, which allow shredded material from the coarse grinding chamber enters the fine grinding chamber. The slit plates are designed so that they pass the sufficiently shredded material while the grinding balls are retained.

Due to the material to be crushed and the grinding balls, the slotted plates are exposed to a very large stress and must therefore be designed to wear resistant. The production of slotted plates is therefore associated with a lot of effort.

Currently slotted plates for tube mills are manufactured according to two different manufacturing processes, on the one hand the production by rolled steel and on the other hand the production by a casting process are used.

In the production by rolled steel, first produced by special rolling plates are selected, tested and an autogenous incision assembled. Subsequently, the slots are pre-milled on a machining center, in order to then obtain a concrete recognition for the conical, CNC-controlled main slot (oxy-fuel cutting). After this processing, the plate is subjected to an intermediate inspection and cleaned for the hardening process. Pre-forming must counteract the plate distortion that occurs during the hardening process so that the distortion is within an acceptable range. The hardening process requires in particular also precautions in the area of the fixing holes in order to avoid a "over hardening". After hardening, re-tempering is required to set the plate for practical use.

A major disadvantage of this method is that the original structure of the starting material is changed by the oxy-fuel cuts and must be readjusted by the subsequent annealing process (hardening + annealing) for each plate. For the slotted plates thus no consistent structure over the entire slotted plate delivery can be guaranteed, as it may come through different processes to inequalities. These processes may include a non-uniform temperature of quench media for curing, a non-uniform hardening temperature, and a non-uniform precaution to prevent over-hardening of the mounting holes. Furthermore, the hardening depth is limited so that only plate thicknesses of max. 50 mm can be used.

Another disadvantage of this method is seen in the limitation of the slot arrangement. Due to the hardening process minimum distances of the slots are prescribed to each other in order to preclude a later breaking of the plates. In addition, always equal distances of the slots to each other and to the edges must be adhered to in order to avoid different depths of hardening of the slot webs. If the distance of the slots from one another were to vary greatly, the narrower webs would break during overheating during operation.

Furthermore, it is necessary that the slotted plates are made symmetrical to avoid excessive distortion of the plates during curing. If plate distortions nevertheless exist, they can lead to considerable tension when installing the slotted plates, as the screw connections must be tightened to a minimum torque in order to avoid screw loosening during operation.

Alternatively, therefore, many use manufacturing by a casting process. However, this method requires that a casting model and the appropriate melt be provided for each slot plate. After the casting process, the plate must be cleaned, sprue surfaces removed and inspected for cracks. The casting process also requires a subsequent heat treatment. Furthermore, the back of the plate must be ground to ensure a flat plate support on the support frame.

Even with these slit plates, therefore, the original structure of the cast material must be adjusted by the subsequent heat treatment for each plate. The plate manufacturer can thus guarantee a consistent structure on the entire slotted plate delivery, since this in turn can lead to the above-mentioned irregularities.

From the casting technology point of view, a minimum plate thickness must still be maintained. Corresponding restrictions also arise with the distances between the slots and the entire slot arrangement. Particularly complex is also the grinding of the backs of the plates to ensure a sufficient plate support on the support frame. Otherwise, a plate break can not be ruled out. Compared to slit plates made of rolled steel, considerably greater residual wall thicknesses of the cast plate must be maintained in order to rule out plate fractures.

From the DE 196 38 698 a mill separation wall is known, which consists of circular segment-like partition plates, which are fastened by means of terminal strips to a wall scaffold, wherein the partition wall plates have formed by burnout Kantenausnehmungen.

Furthermore, in the DE 10 2007 046 193 a plate described as armor or wearing part for a screw flight, are cut out in the production of a coated metallic carrier sub-segments by means of water jet cutting.

The invention is therefore based on the object of specifying a new method for producing a tube mill with an existing of a plurality of slotted intermediate or discharge wall, with the production of slotted plates is characterized by a consistent structure of the entire slotted plate delivery and allows a variable design.

According to the invention, this object is solved by the features of claim 1.

1. a. Auswahl eines durchgehärteten Plattenmaterials als Ausgangsmaterial für die Schlitzplatten und
2. b. Schneiden der äußeren Kontur der Schlitzplatten und Einbringen von Schlitzen in das Plattenmaterial mittels eines nichtthermischen Schneidverfahrens, insbesondere mittels Wasserstrahlschneiden.

In the method according to the invention for producing a tube mill with at least one intermediate or discharge wall consisting of a multiplicity of slotted plates, the slotted plates are produced in accordance with the following method steps:

1. a. Selection of a hardened plate material as a starting material for the slotted plates and
2. b. Cutting the outer contour of the slit plates and introducing slots into the plate material by means of a non-thermal cutting method, in particular by means of water jet cutting.

By a non-thermal cutting process, the original structure of the starting material is not changed. In this respect, no subsequent hardening of the slotted plates is required. This does not lead to unwanted delays the slotted plates, so that no longer has to be paid to a symmetrical design of the plates. This results in completely new design possibilities.

According to the invention can be made of plate material, which is produced directly in the steelworks under optimal, always consistent and constantly monitored conditions of a production line (including hardening). As a result, the material properties are documented and proven for all batches. Uncertainties regarding the structure can thus be virtually ruled out.

Further embodiments of the invention are the subject of the dependent claims.

The possible use of a hard, yet ductile material for the through-hardened plate material provides more freedom in terms of design. Now plates can be produced which have an optimum tube mill process technology for the slot arrangement. This arrangement is completely independent of the symmetry, since no downstream curing process is required and no consideration for casting restrictions are required. Therefore, in particular slots can be avoided, which are unnecessary due to the formation of the framework.

According to a preferred embodiment of the invention, therefore, at least some of the slit plates are provided with slots arranged asymmetrically to the longitudinal central axis of the slit plate. Furthermore, some of the slit plates can be made with slits having different distances from each other. It is also conceivable that more slots per plate can be provided, which would improve the function of the intermediate or discharge wall.

After no additional curing step is required, the desired hardness of the slotted plates can be set very precisely by selecting a suitable starting material with the desired hardness.

By the non-thermal method of inserting the slots, the method is nearly independent of plate thickness. Theoretically, plates with at least 40 mm to, for example, 100 mm can now be realized. By a stronger plate material, the service life of the slotted plates can be influenced accordingly positive.

Since the non-thermal cutting process requires no subsequent curing, the material is insensitive to breakage, especially in the field of mounting holes. This allows an optimized execution of the plate attachment. Thus, a plurality of mounting holes formed as through holes can be drilled in the slotted plates, which are provided with an enlarged diameter blind bore.

The invention further relates to a slit plate produced by the method described above, and to a ball mill having an intermediate or discharge wall consisting of a multiplicity of such slotted plates.

Further embodiments and advantages of the invention are explained in more detail below with reference to the description and the drawing.

Fig. 1

eine schematische Seitenansicht einer Rohrmühle,

Fig. 2

eine Ansicht auf die Schlitzplatten eines Segments der Zwischenwand,

Fig. 3

eine Ansicht auf ein Segment des Traggerüsts der Zwischenwand und

Fig. 4

eine Schnittdarstellung im Bereich einer Befestigungsbohrung längs der Linie A-A der Fig. 2.

In the drawing show

Fig. 1

a schematic side view of a tube mill,

Fig. 2

a view of the slotted plates of a segment of the intermediate wall,

Fig. 3

a view of a segment of the framework of the partition and

Fig. 4

a sectional view in the region of a mounting hole along the line AA of Fig. 2 ,

In the Fig. 1 shown tube mill 1 consists essentially of a coarse grinding chamber 2 and a fine grinding chamber 3, which are separated by an intermediate wall 4 from each other. The intermediate wall 4 has a support frame 6 and a plurality of slot plates 5 attached thereto. Furthermore, a discharge device 8 is provided with a discharge wall 8a.

The tube mill 1 has a cylindrical outer wall and is suitably rotatably mounted in bearings 9 and 10 about an axis 11. Both grinding chambers 2, 3 are charged with suitable grinding balls, wherein the material supplied via a feed device 7 is first comminuted in the coarse grinding chamber 2. The sufficiently comminuted material passes through the slotted plates 5 in the fine grinding chamber 3 to be further crushed there. About the discharge wall 8a and the discharge 8, the ground material is discharged.

The intermediate wall 4 and the discharge wall 8a may be constructed similarly, so that the formation of the slotted plates will be explained below only with reference to the intermediate wall 4.

Fig. 2 shows a segment of the intermediate wall 4, as it is seen from the view of the coarse grinding chamber 2. The plurality of slit plates 5 are arranged concentrically about the axis 11 and cover substantially the entire intermediate wall. There are only in the middle no slotted plates provided. This area can be used as a passage for an air flow.

Each mounted slotted plate is defined by two radially aligned side edges and upper and lower arcuate boundary edges. The Outer contour is formed symmetrically with respect to a (radially aligned) longitudinal central axis 5b. The slit plate is further provided with a plurality of slits 5a, each terminating at a distance from the lateral boundary edges and are preferably aligned perpendicular to the longitudinal central axis 5b.

A corresponding segment of the support frame 6 is off Fig. 3 The support frame 6 is used for fastening the slotted plates 5 and has in the region of each slit plate 5 has a recess 6a which is formed so that in the view according to FIG Fig. 3 all slots 5a of the slot plate 5 mounted on the other side are visible. The contour of the recess 6a of the support frame 6 is adapted to the procedural sequence in the tube mill. In the illustrated embodiment, the recesses 6a and the associated slotted plates 5 are arranged on three circular rings arranged concentrically with each other, wherein the contours of the recesses 6a and the slot arrangement of the associated slotted plates 5 differ from each other in the various circular arrays. Even in a certain annulus are always two adjacent recesses 6a and the associated slot arrangement of the slotted plates 5 arranged in mirror image to each other.

The slotted plates 5 are usually screwed to the support frame 6. For this purpose, the slotted plates 5 are provided with corresponding through-holes 5 c, which according to the enlarged view of the slot according to Fig. 4 additionally provided with an enlarged diameter blind bore 5d. In the support frame 6 holes 6b are provided at the appropriate location, so that the slotted plates can be fixed with suitable screws / nuts on the support frame. On the one hand, the blind bores 5d allow a secure hold of the slotted plates and, on the other hand, prevent the screw head from protruding beyond the slot wall and being exposed to wear.

In the manufacture of the slotted plates 5, a suitable, cured plate material is first selected as the starting material. The starting material is selected immediately in the hardness desired for the finished slit plates. For this example, wear plates with a hardness of at least 500HV into consideration.

Subsequently, the outer contour of the slit plates 5 and the slits 5a are cut by means of a non-thermal cutting method, in particular by means of a water jet. By this non-thermal cutting process, there is no structural change, so that no subsequent hardening of the slotted plates is required.

In the hitherto known production methods for the slotted plates, it was necessary for the slits to extend symmetrically with respect to the longitudinal central axis 5b, since otherwise an additional distortion during hardening could not be avoided. Since no additional hardening is required with the non-thermal cutting method, the slots may also extend asymmetrically with respect to the longitudinal central axis 5b, as is apparent from most of the in FIGS Fig. 2 shown slotted plates immediately apparent. The recesses 6a have always been designed to be optimized in terms of process engineering and, for most slotted plates, have an asymmetrical contour relative to the longitudinal central axis 5b. As a result, part of the slots would not have been released through the recesses in the past and would therefore be unnecessarily longer. With the new method, according to which no consideration has to be given to any symmetries, it is possible to adapt the slots directly to the recesses of the support frame, thus avoiding unnecessarily long cuts.

A further advantage of the non-thermal cutting method is that the slots 5a of a slotted plate can also be arranged at different distances from each other and thus designed optimized in terms of process technology can be. The different distances are particularly evident in the radially arranged at the center slotted plates.

The plate thickness of the slotted plates has a decisive influence on the service life of the slotted plates. Thicker plates thus have a longer life before they have to be replaced. Due to the required in the previous manufacturing process subsequent curing process, the thickness was limited to about 50mm. Now also plate material with thicknesses of 40 to 100mm or even more can be used.

The new manufacturing process is thus characterized by greater freedom in the arrangement and design of the slots.

Claims (9)

1. Method for the manufacture of a tube mill (1) having at least one partition or discharge wall (4, 8a) comprising a plurality of slotted plates (5), wherein the slotted plates (5) are manufactured in accordance with the following process steps:

   a. selecting a fully hardened plate material as the starting material for the slotted plates (5) and

   b. cutting the outer contour of the slotted plates (5) and introducing slots (5a) into the plate material by means of a non-thermal cutting process.
2. Method according to claim 1, characterised in that at least some of the slotted plates (5) are provided with slots (5a) arranged asymmetrically relative to the longitudinal centre axis (5b) of the slotted plate.
3. Method according to claim 1, characterised in that at least some of the slotted plates (5) have slots (5a) arranged with different spacings from each other.
4. Method according to one or more of the preceding claims, characterised in that the slotted plates (5) are manufactured from the selected plate material without an additional hardening step.
5. Method according to one or more of the preceding claims, characterised in that the hardness of the starting material is so selected that it corresponds to the desired hardness of the slotted plates (5) to be manufactured.
6. Method according to one or more of the preceding claims, characterised in that a plate material having a plate thickness of at least 40 mm is used.
7. Method according to one or more of the preceding claims, characterised in that several drilled fastening holes which are in the form of drilled through-holes (5c) and which are provided with a blind drilled hole (5d) of enlarged diameter are drilled into the slotted plates (5).
8. Slotted plate (5), manufactured in accordance with the method according to one or more of the preceding claims.
9. Tube mill (1) having at least one partition or discharge wall (4, 8a) comprising a plurality of slotted plates (5), wherein the slotted plates (5) are manufactured in accordance with the method according to one or more of the preceding claims 1 to 7.

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