EP3713673A1

EP3713673A1 - Pinned disc mill comprising discs with pins

Info

Publication number: EP3713673A1
Application number: EP18812097.6A
Authority: EP
Inventors: Holger Lieberwirth; Christos Aneziris; Christian Weigelt; Tim Hühnerfürst
Original assignee: Technische Universitaet Bergakademie Freiberg
Current assignee: Technische Universitaet Bergakademie Freiberg
Priority date: 2017-11-23
Filing date: 2018-11-23
Publication date: 2020-09-30
Also published as: WO2019101907A1; DE102017010910A1

Abstract

The invention relates to pinned disc mills comprising discs with pins. The pinned disc mills are characterized in particular by being usable in particular even under high mechanical loads. For this purpose, the discs consist of a fine-grain ceramic or a metal/ceramic composite material with a high degree of strength, and the pins consist of a metal/ceramic composite material with a high degree of hardness.

Description

Pin mill with slices with pins

The invention relates to pin mills with discs with pins.

In the field of mineral processing, in addition to the specific energy consumption, wear is a decisive influencing factor for the selection of efficient processing machines for pulping and the related process technology. For example, new wear-optimized solutions are constantly being sought and implemented in the most diverse processing plants.

Particularly high wear occurs in the comminution of abrasive, for example, highly quartz-containing materials such as quartz sands or quartz-containing ores. High stress rates, for example, to ensure full digestion in the finest area, let the wear grow exponentially beyond. For innovative processes such as selective comminution, impact stresses are particularly advantageous for high recycling of waste with a low specific energy requirement. However, the required high rates of wear and the associated wear made the process for materials with high abrasiveness considered uneconomical.

The requirements for corresponding impact loads can be fulfilled particularly effectively by the use of pin mills. Although jet mills produce a comparable grinding result, due to the high specific energy requirement of this type of mill and the resulting energy inefficiency in material shredding, jet mills can only be used economically for the comminution of very high-grade materials.

Pin mills are characterized by the fact that the materials bounce off the pins as they flow through the pin rows of the pin mill and are smashed.

For example, EP 0 200 003 A2 discloses a mixer with a pin mill. Pin mills are primarily used in the food, building materials and chemical industries. In these mills, loading speeds of up to approximately 200 m / s are achieved. Already at these speeds, abrasive grinding material causes high wear on the grinding tools. Both the particularly high hardness of the abrasive materials and the sharp-edged shapes of the individual particles play a decisive role here for the significant increase in wear. At high Stress rates of up to 400 m / s, which may be required for certain ores for an energy-efficient digestion of particle sizes <100 pm, the wear is on the order of magnitude, making the process uneconomical.

By the document DE 10 2014 101 786 A1 a counter-rotating pin mill is known, wherein increased stress rates is achieved by an opposing rotation system of stator and rotor.

Due to the high wear stresses during grinding operation, it is necessary to protect tools and other mill components accordingly. For this example, protective layers can be applied to the body of a steel material. These are, for example, ceramic protective layers in conjunction with a frictional material coupling to the base material. However, it has been shown that even small flaking of the applied wear protection layers in a short time lead to damage of the rest of the grinding body and the attached pins.

However, a monolithic production of the entire rotor or stator component from a purely ceramic wear protection material is not an alternative. Basically, the production of the entire component rotor or stator from such a wear material due to the increased material prices for wear-resistant materials hardly economically feasible. In addition to problems with the necessary balancing of fast-running, purely ceramic rotors, it should be noted that the particularly hard materials are subjected to high impact stresses during the grinding process, which leads increasingly to the formation of cracks in the rotor and / or stator when the material brittleness is simultaneously critical.

The publication CH 360 014 A discloses a ceramic composite body, in particular for mechanical engineering and a method for its production. The ceramic composite body consists of fired mineral substances and deposits, which are at least predominantly within the ceramic base material. The fired ceramic material is biased in the unloaded state by pressure, that the deposits whose material has a greater cooling-contraction coefficient than the ceramic material, are biased to train. The inserts are rods or wires with axial alignment. The composite body realized in this way is a material composite. The document US 2005/0 211 810 A1 discloses a rotor centrifugal crusher. The main focus is on increasing the hardness of the impact-loaded surfaces of the rotor centrifugal crusher.

The document US 5,845,856 A shows a technically complex pin mill with changeable wear-resistant pin elements. For mills with an existing high dynamics such a construction is not very suitable.

Cermets, which consist of a metallic and a ceramic phase, are characterized by particularly high hardness and wear resistance. Due to their lower bending strength, these materials are limited in use.

Cermets are known to be produced by powder metallurgy. They can be obtained according to the document GB 21 48 270 A but also by infiltration of porous SiC ceramic with molten aluminum at 700 ° C and a pressure of 46 MN / m2.

The document DE 39 14 010 C2 discloses a method for the production of metal-ceramic composite materials in which a porosity of defined porosity of a plurality of layers is infiltrated with molten aluminum.

The indicated in claim 1 invention has for its object to provide pin mills for high mechanical stresses easy.

This object is achieved with the features listed in claim 1.

The pin mills are characterized in particular by the fact that they can be used in particular even under high mechanical stresses. In the outer rows of pins of these mills realized stress rates of well over 100 m / s and with increasing tendency, the dynamic stresses in the impact even small Mahlgutpartikel are very high.

For this purpose, the disc of a fine-grained ceramic or a metal-ceramic composite material of high strength and the pins of a metal-ceramic composite material high hardness. The pin mills are not exclusively a combination of ceramic particles with a metal matrix in a composite material with corresponding increased strength values and hardness values. In the case of impact-stressed components, not only a high strength of the components ensures a longer service life. Only the appropriate toughness in combination with high strength prevents the formation of flakes in a component subject to impact. Components which are provided in particular with a wear protection material on the surface, are predestined for forming flaking of the cover layer at the interface between the base body and the applied wear protection layer. The pin mills are advantageously characterized by a cohesive connection between the base body and the protective layer, wherein ceramic wear protection layers are applied to the fast-rotating mill components. Only by this fact are extremely high adhesive strengths of the cover layer and a high strength at the same time high toughness of the entire component produced. Thus, surface ceramic coated components can be used for use as high speed components.

Advantageously, a composite material of ceramic and steel is used for the production of the stator and the rotor, wherein a homogeneous distribution of ceramic particles in the initial powdery matrix of the steel is present as a second material. This is not a composite of materials such as fibers, wires, rods or plates embedded in a matrix, for example. The steel matrix of the composite ensures sufficient toughness of the mill components as well as the possibility of mechanical post-processing for balancing and prevents tearing of the stator or rotor under impact loading. Ceramic particles with particularly high hardness are embedded in the steel matrix. These ensure increased wear resistance of the stator and the rotor. Thus, the components of the pin mill and in particular advantageously the rotating disc and / or the pins mounted thereon consist of a composite material of metal and ceramic. Furthermore, of course, the stator may be formed according to the rotor as a disc with the pins.

Furthermore, it must be pointed out that strength (in this case high strength of the disk) and hardness (in this case high hardness of the pins) are two different material parameters, which are not permanently in the same ratio. The strength describes the resistance to deformation and breakage. The hardness is defined as the resistance of a material to the penetration of a foreign body. Already from these definitions, the differences in the determination of these two different material parameters open up. While the strength with tensile tests or Pressure tests can be determined, the hardness is determined only with penetration tests (Brinell, Vickers or Rockwell method).

Thus, in the proposed configuration, the pin mill is particularly advantageously also suitable for disintegration comminution in ore processing, wherein these can be used in processing plants that are optimized for wear. Thus, abrasive, for example, highly quartz-containing materials such as ore-containing quartz sands or quartz-containing ores can be crushed. This can also be done at high strain rates, so that a full digestion in the finest possible range is guaranteed. The predominant in selective crushing impact loads are particularly advantageous for a high recycling material with low specific energy consumption.

Advantageous embodiments of the invention are specified in the subclaims.

The ceramic of the composite is optionally a fine and / or coarse-grained ceramic.

The grain size of the coarse-grained ceramic is optionally equal to / greater than 100 pm and less than or equal to 6 mm. Furthermore, the coarse fraction of the ceramic is equal to / greater than 5 vol .-% and less than or equal to 30 vol .-% of the composite material. This provides improved wear resistance with high toughness.

The composite material optionally consists of equal to or greater than 30% by volume and less than or equal to 90% by volume of ceramic. In particular, this is advantageous for the disc of the pin mill. The detachment of already a few millimeters large particles can have fatal consequences in view of the high dynamics of the mill and lead to the sudden failure of all pens. The components used do not necessarily have similar melting points. At 30 vol.% Of a reinforcement phase (ceramic) in the matrix (metal), the formation of a continuous ceramic phase within the matrix is not expected. Therefore, the metallic character of the composite dominates with respect to mechanical properties (fracture toughness, tensile strength and so on) and is improved by the embedded ceramic particles in terms of wear resistance.

The metal of the composite is optionally a powder having particles of size equal to / greater than 0.05 pm and less than or equal to 100 pm. This concerns the metal powder mixtures as starting materials. The steel powders used are known to be produced by gas atomization from the melt and have a spherical particle shape. Furthermore, these primary particles are not modified by milling processes or the like in their morphology.

The disk and / or pins optionally include or have at least one layer of a ceramic or a metal or a metal-ceramic composite. The layer is for this purpose applied by flame spraying or plasma spraying or soldering or build-up welding or cold spraying and subsequent sintering layer. The superficial layer is a coating or a material composite and not a composite material. This does not result in a combination of properties of the components, but rather for (local) utilization of the respective properties of the individual materials. Ceramic protective coatings are excellently suitable as a wear-resistant coating due to their particularly high strengths. With the soft / tough metal matrix of the metal-ceramic composite material, it is possible to finish the produced discs, pins or discs with the pins as components before coating or to balance for the highly dynamic rotary motion. Another advantage is the interlocking of the phase boundary between the layer and the disc and / or pins. The advantageous material approach involves the production of ceramic-coated composite material, which gives the ductile metal matrix with embedded hard ceramic particles sufficient toughness and wear resistance and high damage tolerance. Any necessary balancing of the rapidly rotating parts by mechanical post-processing is still possible due to the toughness of the matrix body. By combining fine-grained and coarse-grained particles, the machinability, the mechanical properties and the wear resistance are adjustable for the respective application. The disc and / or the teeth can be materially bonded by one or more coatings (ceramic / metallic / metalloceramic) by means of, for example, flame spraying with the metal-ceramic composite material. This method enables the processing of various metal-ceramic mixtures and the targeted application of variable material composites. Due to the material similarities between the base body and wear protection layer highest bond strengths are achieved. Thus, in the field of ceramic wear protection materials, sufficient toughness is possible for use in the event of impact stresses occurring. In addition, the excellent wear properties of the ceramics used can be used under conditions of wear, abrasion, adhesion, high temperature and corrosion. By adapting the ceramic content of the base material, the outstanding adhesive strength of the protective layer can be adapted and the toughness of the coated composite material adjusted individually. It can be a wide range of applications in a variety of areas are made possible. That can be advantageously achieved by a similar ceramic in the composite material and in the applied metallo-ceramic protective layer, with an above-average adhesion between the layer and disc and / or pins can be achieved. The otherwise recorded early flaking at a typical function load can be prevented. Due to the high wear resistance of ceramics, particularly wear-resistant mill bodies can also be realized in applications, for example, in the chemical industry, the pharmaceutical industry or in food processing. In particular, the high adhesive strength of the applied wear protection layer allows economical comminution with fast rotating parts in many abrasive products such as rice husks and color pigments.

For better adhesion, the disc and / or the pins can be processed mechanically or chemically or electrochemically, so that the ceramic or metallic or metalloceramic coating adheres well to the processed composite material.

The pins are optionally applied to the disc or with an end portion inserted into the disc pins, wherein the disc and / or the pins are not sintered or sintered and the pins are joined by gluing, soldering, welding, a subsequent firing or a combination thereof , The pins are so applied or introduced pins and thus both the disc both sintered and not sintered, for example, before a subsequent fire occurs. The application or introduction can be done so universally. The parts as a disc / pin made of different materials are glued. Advantageously, by a sintering of the metal-ceramic components, a positive connection and material connection between pin and disc can be present. This allows a mechanically reliable connection even under harsh conditions. The joining compound is formed during sintering (above 1300 ° C) and is thus stable even when heated by the grinding process.

The pins are optionally inserted directly after the original molding without sintering in a non-sintered disc and subsequently sintered with the non-sintered disc. This can be advantageously saved energy costs.

The pins are optionally inserted as sintered pins in a non-sintered disc. This disc with these pins are sintered together. The method of installation and thus the anchoring of the pins in the disc are decisive for the overall performance of the pin mill and therefore characteristic of the proposed variant. By prior sintering of the pins, for example, a material-appropriate sintering of the pins at be realized with respect to the disk sintering temperature higher temperature. This makes it possible to optimize the density, strength, hardness and thus the wear resistance of the pins. The connection then takes place in the downstream sintering process of both components. If both components (pin / disc) are made of identical material, they can also be sintered together immediately. By a prior sintering of the pins they can also be shrunk into the disc by the changed Sinterschwindung for better mechanical anchoring.

The ceramic may each be at least one carbide, a nitride, a boride, an oxide or a mixture with a combination thereof.

The ceramic of the layer may each be at least one carbide, a nitride, a boride, an oxide or a mixture with a combination thereof.

The ceramics of the disc, the pins and the layer may be alumina, zirconia, magnesia aluminate spinel, titania, silica, silicon nitride, silicium carbide, boron carbide, tungsten carbide, sialones, MAX phases or a mixture with a combination thereof.

The metal of the disc and pins may be steel, nickel, cobalt, chromium, manganese, titanium, iron, silicon, tungsten, zirconium, niobium, tantalum, aluminum, magnesium, an alloy thereof or a mixture thereof.

The composite optionally has carbon which may be present as an alloying element in the metal or for the in situ formation of phases, for example of carbides, or also freely for the purpose of defusing impact sensitivity.

The pin mill is further characterized by the fact that powder from primary processes, for example by atomization or melt synthesis with grinding, used, mixed and processed into moldings or semifinished and used by thermal spraying for surface coating of a part.

An embodiment of the invention is illustrated in principle in the drawings and will be described in more detail below.

Show it:

1 is a disc with pins of a pin mill, Fig. 2 shows a pin in a sectional view and

Fig. 3 is a pin in a disk in a sectional view.

A pin mill essentially has discs 1 with pins 2.

Fig. 1 shows a disc 1 with pins 2 of a pin mill in a schematic representation.

The disc 1 consists of a fine-grained ceramic or a metal-ceramic composite material of high strength. The pins 2 are made of a metal-ceramic composite material of high hardness. Fig. 1 shows a schematic plan view of a disc 1 with pins 2, wherein only a limited number of pins 2 are shown. In such an embodiment, the pins 2 are spaced apart in three circles. Fig. 1 shows here only by way of example from inside to outside two, four and nine pins 2 per circle. There may be recesses between the three annular surfaces with the pins 2.

The ceramic of the composite material is a coarse-grained ceramic with a grain size equal to or greater than 100 pm. The coarse fraction of the ceramic is at least 5 vol .-% of the composite material. Furthermore, the composite consists of at least 30 vol .-% ceramic.

The pins 2 may be in a first embodiment, applied to the disc 1 or introduced with an end portion in the disc 1 pins 2, wherein the disc 1 and / or the pins 2 are not sintered or sintered and the pins 2 by gluing, soldering, Welding, a subsequent fire or a combination thereof are joined.

The pins 2 can be inserted in a second embodiment, directly after the original molding without sintering in a non-sintered disc 1 and subsequently sintered with the non-sintered disc 1.

The pins 2 may be inserted as sintered pins 2 in a non-sintered disc 1 in a third embodiment, and this disc 1 may be sintered with these pins 2.

2 shows a pin 2 in a schematic sectional view.

In a further embodiment, the disc 1 and / or the pins 2 may have at least one layer 3 made of a ceramic or a metal or a metal-ceramic composite, the layer 3 being a flame-spraying or Plasma spraying or soldering or build-up welding or cold spraying and subsequent sintering applied layer 3 is.

Fig. 3 shows a pin 2 in a disc 1 in a schematic sectional view.

The disc 1 and the pin 2 consist for example of a metal-ceramic composite material. The ceramic of the pin 2 has a coarse-grained ceramic 4 and a fine-grained ceramic 5 in a fine-grained matrix 6. The pin 2 has, for example, by means of flame spraying applied ceramic and / or metallic and / or metallo-ceramic layers 3a to 3c.

The ceramic is in each case at least one carbide, a nitride, a boride, an oxide or a mixture with a combination thereof. For this purpose, the ceramic may be alumina, zirconia, magnesia aluminate spinel, titania, silica, silicon nitride, silicium carbide, boron carbide, tungsten carbide, sialones, MAX phases, or a mixture with a combination thereof.

The metal is steel, nickel, cobalt, chromium, manganese, titanium, iron, silicon, tungsten, zirconium, niobium, tantalum, aluminum, magnesium, an alloy thereof, or a mixture thereof.

In a further embodiment, the composite material may comprise carbon.

In a further embodiment, the pin 2 is machined from a compact material. The basis for this is a particle size optimized offset of 90% by volume of aluminum oxide (up to and including 3 mm) and 10% by volume of a high-alloyed steel powder (up to and including 100 μm), which is dewatered as an aqueous slip in a pressure slip casting plant at 20 bar and is heat treated by a heater. The pin 2 has a coated wear protection layer of pure aluminum oxide, wherein the order takes place with a rotating pin 2 by means of flame spraying. LIST OF REFERENCE NUMBERS

1 slice

2 pen

3 layer

4 coarse-grained ceramics

5 fine-grained ceramics

6 matrix

Claims

claims

A pin mill with discs (1) with pins (2), characterized in that the disc (1) is made of a fine-grained ceramic or a metal-ceramic composite of high strength and the pins (2) of a metal-ceramic composite material higher Hardness exist.

2. pin mill according to claim 1, characterized in that the ceramic of the composite material is a fine and / or coarse-grained ceramic.

3. pin mill according to claim 2, characterized in that the grain size of the coarse-grained ceramic is equal to / greater than 100 pm and less than / equal to 6 mm and that the coarse fraction of the ceramic equal to / greater than 5 vol .-% and less than / equal to 30 vol. % of the composite material.

4. pin mill according to one of the claims 1 to 3, characterized in that the composite material consists of equal / greater than 30 vol .-% and less than or equal to 90 vol .-% ceramic.

5. pin mill according to one of the claims 1 to 4, characterized in that the metal of the composite material is a powder with particles of size equal to / greater than 0.05 pm and less than or equal to 100 pm.

6. pin mill according to one of the claims 1 to 5, characterized in that the disc (1) and / or the pins (2) has or possess at least one layer (3) of a ceramic or a metal or a metal-ceramic composite material wherein the layer (3) is a layer (3) applied by flame spraying or plasma spraying or brazing or build-up welding or cold spraying and subsequent sintering.

7. pin mill according to one of the claims 1 to 6, characterized in that the pins (2) on the disc (1) applied or with an end portion in the disc (1) introduced pins (2), wherein the disc (1) and / or the pins (2) are not sintered or sintered and the pins (2) are joined by gluing, soldering, welding, a subsequent firing or a combination thereof.

8. pin mill according to claim 7, characterized in that the pins (2) are inserted directly after the original molding without sintering in a non-sintered disc (1) and subsequently sintered with the non-sintered disc (1).

9. pin mill according to one of the claims 1 to 8, characterized in that the pins (2) are inserted as sintered pins (2) in a non-sintered disc (1) and this disc (1) with these pins (2) are sintered ,

10. pin mill according to one of the claims 1 to 9, characterized in that the ceramic is in each case at least one carbide, a nitride, a boride, an oxide or a mixture or a combination thereof.

1 pin mill according to claim 6, characterized in that the ceramic of the layer is in each case at least one carbide, a nitride, a boride, an oxide or a mixture or a combination thereof.

A pin mill according to claim 10 or 11, characterized in that the ceramic is alumina, zirconia, magnesia, titanium dioxide, silica, silicon nitride, silicon carbide, boron carbide, tungsten carbide, sialons, MAX phases, or a mixture or combination thereof.

13. pin mill according to one of the claims 1 to 12, characterized in that the metal steel, nickel, cobalt, chromium, manganese, titanium, iron, silicon, tungsten, zirconium, niobium, tantalum, aluminum, magnesium, an alloy thereof or a Mixture of it is.

14. pin mill according to one of the claims 1 to 13, characterized in that the composite material comprises carbon.