EP2326738B1 - Milling cone for a compression crusher - Google Patents

Abstract

The present invention discloses a composite milling cone for compression crushers, said milling cone comprising a ferrous alloy at least partially reinforced with titanium carbide according to a defined geometry, in which said reinforced portion comprises an alternating macro-microstructure of millimetric areas concentrated with micrometric globular particles of titanium carbide separated by millimetric areas (2) essentially free of micrometric globular particles of titanium carbide, said areas concentrated with micrometric globular particles of titanium carbide forming a microstructure in which the micrometric interstices between said globular particles are also filled by said ferrous alloy.

Description

Object of the invention

The present invention relates to a composite grinding cone for compression crushers in the field of rock crushing in extractive industries such as mines, quarries, cement plants, etc., but also in the recycling industry, etc., as well as than a method of manufacturing such cones.

Definition

In this document, we mean by "compression crusher", cone crushers or gyratory crushers equipped with grinding cones constituting the main wear part of these machines.

Cone crushers or gyratory crushers have a cone-shaped wear part called the grinding cone. This type of cone is the subject of this patent application. The cone has the function of being in direct contact with the rock or the material to be ground during the process phase, where very high compressive stresses are applied to the material to be crushed.

Compression crushers are used in the early stages of the production line to drastically reduce the size of the rock, in the extractive industries (mines, quarries, cement plants, ...) and recycling.

State of the art

Few means are known for modifying the hardness and compressive strength of a foundry alloy at depth "in the mass". The known means generally concern surface modifications of shallow depth (a few mm). For foundry parts, reinforcing elements must be present in depth in order to withstand significant and simultaneous localized stress in terms of mechanical stress (wear, compression, impact) to limit wear and therefore the consumption of the part during its lifetime.

The document US5,516,053 (Hannu ) describes a method of improving the performance of grinding cones for cone crushers, based on a reloading technique using hard particles such as tungsten carbide; this technique produces its effects only on the surface and on a relatively limited thickness.

The document JP 53 17731 proposes a solution that consists of alternating zones that are more resistant and less resistant to wear, in the direction of the generator of a grinding cone. This technique has the effect of generating on the surface of the cone a relief that would be favorable to the extension of the service life of the part.

The document US 6,123,279 (Stafford ) proposes to reinforce the surfaces of manganese steel cones and jaws by means of tungsten carbide inserts which are introduced and mechanically fixed in housings provided for that purpose; this solution results in a discontinuous reinforcement of the surface of the workpiece.

The document WO 2007/138162 (Hellman ) describes a method of making a cone using composite materials.

The document US 2008/041995 (Hall ) plans to reinforce the working surface of a cone with inserts made of hard materials.

Goals of the invention

The present invention discloses a composite grinding cone for compression crushers having improved wear resistance while maintaining good impact resistance. This property is obtained by a composite reinforcement structure specifically designed for this application, a material that alternates on a millimeter scale dense zones into fine micrometric globular particles of metal carbides with zones that are practically free of them within the metal matrix. grinding cone.

The present invention also provides a method for obtaining said reinforcing structure.

Summary of the invention

The present invention discloses a composite grinding cone for compression crushers, said grinding cone comprising a ferrous alloy reinforced at least in part with titanium carbide according to a defined geometry, wherein said reinforced portion comprises an alternating macro-microstructure of zones millimeters millimeter areas concentrated in micrometric globular particles of titanium carbide separated by millimetric areas essentially free of micrometric globular particles of titanium carbide, said zones concentrated in micrometric globular particles of titanium carbide forming a microstructure in which the micrometric interstices between said globular particles are also occupied by said ferrous alloy.

• lesdites zones millimétriques concentrées ont une concentration en carbures de titane supérieure à 36.9 % en volume ;
• ladite partie renforcée a une teneur globale de carbure de titane entre 16.6 et 50.5 % en volume ;
• les particules micrométriques globulaires de carbure de titane ont une taille inférieure à 50µm ;
• la majeure partie des particules micrométriques globulaires de carbure de titane a une taille inférieure à 20 µm ;
• lesdites zones concentrées en particules globulaires de carbure de titane comportent 36.9 à 72.2 % en volume de carbure de titane ;
• lesdites zones millimétriques concentrées en carbure de titane ont une dimension variant de 1 à 12 mm ;
• lesdites zones millimétriques concentrées en carbure de titane ont une dimension variant de 1 à 6 mm ;
• lesdites zones concentrées en carbure de titane ont une dimension variant de 1.4 à 4 mm.

According to particular embodiments of the invention, the composite grinding cone comprises at least one or a suitable combination of the following characteristics:

• said concentrated millimeter areas have a concentration of titanium carbides greater than 36.9% by volume;
• said reinforced portion has an overall titanium carbide content between 16.6 and 50.5% by volume;
• the micrometric globular particles of titanium carbide have a size of less than 50 μm;
• most of the micrometric globular particles of titanium carbide has a size less than 20 microns;
• said zones concentrated in globular particles of titanium carbide comprise 36.9 to 72.2% by volume of titanium carbide;
• said millimetric areas of concentrated titanium carbide have a size ranging from 1 to 12 mm;
• said millimetric zones concentrated in titanium carbide have a dimension ranging from 1 to 6 mm;
• said concentrated areas of titanium carbide have a dimension ranging from 1.4 to 4 mm.

• mise à disposition d'un moule comportant l'empreinte du cône de broyage avec une géométrie de renforcement prédéfinie ;
• introduction, dans la partie de l'empreinte du cône de broyage destiné à former la partie renforcée (5), d'un mélange de poudres compactées comportant du carbone et du titane sous forme de granulés millimétriques précurceurs de carbure de titane ;
• coulée d'un alliage ferreux dans le moule, la chaleur de ladite coulée déclenchant une réaction exothermique de synthèse auto-propagée de carbure de titane à haute température (SHS) au sein desdits granulés précurseurs ;
• formation, au sein de la partie renforcée du cône de broyage composite d'une macro-microstructure alternée de zones millimétriques concentrées en particules globulaires micrométriques de carbure de titane à l'emplacement desdits granulés précurseurs, lesdites zones étant séparées entre elles par des zones millimétriques essentiellement exemptes de particles globulaires micrométriques de carbure de titane, lesdites particules globulaires étant également séparées au sein desdites zones millimétriques concentrées de carbure de titane par des interstices micrométriques ;
• infiltration des interstices millimétriques et micrométriques par ledit alliage ferreux de coulée à haute température, consécutive à la formation de particules microscopiques globulaires de carbure de titane.

The present invention also discloses a method of manufacturing the composite grinding cone according to any one of claims 1 to 9 comprising the following steps:

• providing a mold having the impression of the grinding cone with a predefined reinforcement geometry;
• introducing, into the portion of the cavity of the grinding cone for forming the reinforced portion (5), a mixture of compacted powders comprising carbon and titanium in the form of millimetric granules precursors of titanium carbide;
• casting a ferrous alloy into the mold, the heat of said casting triggering an exothermic reaction of self-propagating synthesis of high temperature titanium carbide (SHS) within said precursor granules;
• forming, within the reinforced portion of the composite grinding cone, an alternating macro-microstructure of millimetric zones concentrated in micrometric globular particles of titanium carbide at the location of said precursor granules, said zones being separated from each other by millimetric zones essentially free of micrometric globular particles of titanium carbide, said globular particles being also separated within said millimetric areas of concentrated titanium carbide by micrometric interstices;
• infiltration of the millimetric and micrometric interstices by said high-temperature ferrous casting alloy, subsequent to the formation of microscopic globular particles of titanium carbide.

• les poudres compactées de titane et de carbone comportent une poudre d'un alliage ferreux ;
• ledit carbone est du graphite.

According to particular embodiments of the invention, the method comprises at least one or a suitable combination of the following characteristics:

• the compacted powders of titanium and carbon comprise a powder of a ferrous alloy;
• said carbon is graphite.

The present invention also discloses a composite grinding cone obtained by the method of any one of claims 11 to 13.

Brief description of the figures

The Figures 1 and 2 show an overall three-dimensional view of the different types of machines in which grinding cones according to the present invention are used.

The figure 3 shows a three-dimensional view of a grinding cone and how the reinforcement (s) can be arranged to achieve the desired purpose. (reinforcement geometry)

• l'étape 4a montre le dispositif de mélange des poudres de titane et de carbone ;
• l'étape 4b montre la compaction des poudres entre deux rouleaux suivie d'un concassage et d'un tamisage avec recyclage des particules trop fines ;
• la figure 4c montre un moule de sable dans lequel on a placé un barrage pour contenir les granulés de poudre compactée à l'endroit du renforcement de la barre de blindage pour le concasseur à mâchoire ;
• la figure 4d montre un agrandissement de la zone de renforcement dans laquelle se trouvent les granulés compactés comportant les réactifs précurseurs du TiC ;
• l'étape 4e montre la coulée de l'alliage ferreux dans le moule ;
• la figure 4f montre schématiquement un cône de broyage qui est le résultat de la coulée ;
• la figure 4g montre un agrandissement des zones à forte concentration en nodules de TiC ;
• la figure 4h montre un agrandissement au sein d'une même zone à forte concentration en nodules de TiC. Les nodules micrométriques sont individuellement entourés par le métal de coulée.

The figure 4a-4h schematically represents the process for manufacturing a cone according to the invention.

• step 4a shows the device for mixing titanium and carbon powders;
• step 4b shows the compaction of the powders between two rollers followed by crushing and sieving with recycling of the fine particles;
• the figure 4c shows a sand mold in which a dam has been placed to contain the compacted powder granules at the reinforcement point of the armor bar for the jaw crusher;
• the figure 4d shows an enlargement of the reinforcement zone in which the compacted granules comprising TiC precursor reactants are located;
• step 4e shows the casting of the ferrous alloy in the mold;
• the figure 4f schematically shows a grinding cone that is the result of casting;
• the figure 4g shows an enlargement of areas with high concentrations of TiC nodules;
• the figure 4h shows an enlargement within the same zone with a high concentration of TiC nodules. The micrometric nodules are individually surrounded by the casting metal.

The figure 5 represents a binocular view of a polished, unengaged surface of a section of the reinforced portion of a cone according to the invention with millimetric zones (in light gray) concentrated micrometric globular titanium carbide (TiC nodules) ). The dark part represents the metal matrix (steel or cast iron) filling at the same time the space between these concentrated zones in micrometric globular titanium carbide but also the spaces between the globules themselves.

The figures 6 and 7 represent electron SEM microscopic views of micrometric globular titanium carbide on polished and unattacked surfaces at different magnifications. We see that in this particular case most of the globules of titanium carbide have a size less than 10 microns.

The figure 8 represents a view of micrometric globular titanium carbide on a fracture surface taken by SEM electron microscope. It can be seen that the globules of titanium carbide are perfectly incorporated in the metal matrix. This proves that the casting metal completely infiltrates (impregnates) the pores during casting once the chemical reaction between titanium and carbon is initiated.

Legend

1. 1. Millimeter areas concentrated in micrometric globular particles (nodules) of titanium carbide
2. 2. millimetric interstices filled with the casting alloy generally free of micrometric globular particles of titanium carbide
3. 3. micrometric interstices between TiC nodules also infiltrated by casting alloy
4. 4. micrometric globular titanium carbide, in the concentrated areas of titanium carbide
5. 5. titanium carbide reinforcement
6. 6. gas defects
7. 7. cone with reinforcement according to the invention
8. 8. mixer of Ti and C powders
9. 9. hopper
10. 10. roll
11. 11. crusher
12. 12. exit grid
13. 13. sieve
14. 14. recycling of fine particles to the hopper
15. 15. sand mold
16. 16. dam containing the compacted granules of Ti / C mixture
17. 17. ladle
18. 18. cone (schematic)

Detailed description of the invention

In materials science, the term SHS or "self-propagating high temperature synthesis" reaction is a self-propagating, high temperature synthesis reaction in which reaction temperatures are generally higher than 1500 ° C or even 2000 ° C. For example, the reaction between titanium powder and carbon powder to obtain titanium carbide TiC is highly exothermic. Only a little energy is needed to initiate the reaction locally. Then, the reaction will spontaneously propagate to the entire mixture of reagents thanks to the high temperatures reached. After initiation of the reaction, there is a reaction front which propagates spontaneously (self-propagated) and which makes it possible to obtain titanium carbide from titanium and carbon. The titanium carbide thus obtained is said to be "obtained in situ because it does not come from the cast ferrous alloy.

The reactant powder mixtures comprise carbon powder and titanium powder and are compressed into plates and then crushed to obtain granules ranging in size from 1 to 12 mm, preferably from 1 to 6 mm, and particularly preferably from 1.4 to 4 mm. These granules are not 100% compacted. They are generally compressed between 55 and 95% of the theoretical density. These granules allow easy use / handling (see Fig. 3a-3h).

These millimetric granules of mixed carbon and titanium powders obtained according to the diagrams of figure 4a-4h are the precursors of the titanium carbide to be created and make it easy to fill mold parts of various shapes or irregular. These granules can be held in place in the mold 15 by means of a dam 16, for example. The shaping or assembly of these granules can also be done using an adhesive.

The composite grinding cone according to the present invention has a reinforcing macro-microstructure which may alternatively be called an alternating structure of concentrated micrometric globular particles of titanium carbide separated by zones which are substantially free of it. Such a structure is obtained by the reaction in the mold of the granules comprising a mixture of powders of carbon and titanium. This reaction is initiated by the heat of casting of the cast iron or steel used to pour the whole piece and thus both the unreinforced part and the reinforced part (see Fig. 3e). The casting therefore triggers an exothermic synthesis reaction self-propagated at high temperature of the mixture of powders of carbon and titanium compacted in the form of granules (self-propagating high-temperature synthesis - SHS) and previously placed in the mold 15. The reaction then has the distinction of continuing to spread as soon as it is initiated.

This high temperature synthesis (SHS) allows easy infiltration of all millimetric and micrometric interstices by cast iron or casting steel ( Fig. 4g & 4h ). By increasing the wettability, the infiltration can be done on any thickness or depth of reinforcement of the grinding cone. It advantageously makes it possible, after SHS reaction and infiltration by an external casting metal, to create one or more reinforcement zones on the grinding cone comprising a high concentration of micrometric globular particles of titanium carbide (which could also be called clusters of nodules), which areas have a size of the order of a millimeter or a few millimeters, and which alternate with areas substantially free of globular titanium carbide.

Once these granules have reacted according to an SHS reaction, the zones of reinforcement where these granules were found show a concentrated dispersion of micrometric globular particles 4 of TiC carbide (globules) whose micrometric interstices 3 have also been infiltrated by the casting metal. which is here cast iron or steel. It is important to note that the millimetric and micrometric interstices are infiltrated by the same metal matrix as that which constitutes the unreinforced part of the grinding cone; this allows a total freedom of choice of the casting metal. In the grinding cone finally obtained, the reinforcement zones with a high concentration of titanium carbide are composed of globular micrometric particles of TiC in significant percentage (between about 35 and about 70% by volume) and the ferrous alloy infiltration.

Micrometric globular particles are understood to mean globally spheroidal particles having a size ranging from a few μm to a few tens of μm at the most, the vast majority of these particles having a size of less than 50 μm, and even 20 μm, or even less than 10 μm. We also call them TiC globules. This globular form is characteristic of a method for obtaining titanium carbide by self-propagating synthesis SHS (see Fig. 7 ).

Obtaining pellets (Ti + C version) for reinforcing the grinding cone

The process for obtaining the granules is illustrated in figure 4a-4h . The granules of carbon / titanium reagents are obtained by compaction between rollers 10 in order to obtain strips that are then crushed in a crusher 11. The mixture of the powders is made in a mixer 8 consisting of a tank equipped with blades , to promote homogeneity. The mixture then passes into a granulation apparatus through a hopper 9. This machine comprises two rollers 10, through which the material is passed. Pressure is applied to these rollers 10, which compresses the material. A strip of compressed material is obtained at the outlet, which is then crushed in order to obtain the granules. These granules are then sieved to the desired particle size in a sieve 13. An important parameter is the pressure applied to the rollers. At most this pressure is high, the more the band, and therefore the granules will be compressed. It is thus possible to vary the density of the strips, and consequently the granules, between 55 and 95% of the theoretical density which is 3.75 g / cm ³ for the stoichiometric mixture of titanium and carbon. The apparent density (taking into account the porosity) is then between 2.06 and 3.56 g / cm ³ .

The degree of compaction of the bands depends on the applied pressure (in Pa) on the rollers (diameter 200 mm, width 30 mm). For a low level of compaction, of the order of 10 ⁶ Pa, we obtain a density on the bands of the order of 55% of the theoretical density. After passing through the rollers 10 to compress this material, the apparent density of the granules is 3.75 x 0.55, ie 2.06 g / cm ³ .

For a high level of compaction, of the order of 25 × 10 ⁶ Pa, a density on the strips of 90% of the theoretical density is obtained, ie a bulk density of 3.38 g / cm ³ . In practice one can go up to 95% of the theoretical density.

Therefore, the granules obtained from the raw material Ti + C are porous. This porosity varies from 5% for highly compressed granules, to 45% for slightly compressed granules.

In addition to the level of compaction, it is also possible to adjust the granulometric distribution of the granules and their shape during the operation of crushing strips and sieving Ti + C granules. Unwanted particle size fractions are recycled at will (see Fig. 4b ). The granules obtained generally have a size between 1 and 12 mm, preferably between 1 and 6 mm, and particularly preferably between 1.4 and 4 mm.

Realization of the reinforcement zone in the composite grinding cone according to the invention

The granules are made as described above. To obtain a three-dimensional structure superstructure / macro-microstructure with these granules, they are available in the areas of the mold where it is desired to reinforce the part. This is achieved by agglomerating the granules either by means of an adhesive, or by confining them in a container, or by any other means (dam 16).
The bulk density of the stack of Ti + C granules is measured according to ISO 697 and depends on the level of compaction of the bands, the granulometric distribution of the granules and the crushing mode of the bands, which influences the shape of the granules .
The bulk density of these Ti + C granules is generally of the order of 0.9 g / cm ³ to 2.5 g / cm ³ depending on the level of compaction of these granules and the density of the stack.

Before reaction, there is therefore a stack of porous granules composed of a mixture of titanium powder and carbon powder.

• la porosité microscopique présente dans les espaces à forte concentration en carbure de titane, dépendant du niveau de compaction initial de ces granulés ;
• les espaces millimétriques entre les zones à forte concentration en carbure de titane, dépendant de l'empilement initial des granulés (densité en vrac) ;
• la porosité venant de la contraction volumétrique lors de la réaction entre Ti + C pour obtenir le TiC.

During the Ti + C → TiC reaction, there is a volumetric contraction of about 24% when passing reagents to the product (contraction coming from the density difference between the reagents and the products). Thus, the theoretical density of the Ti + C mixture is 3.75 g / cm ³ and the theoretical density of the TiC is 4.93 g / cm ³ . In the final product, after the reaction to obtain TiC, the casting metal will infiltrate:

• the microscopic porosity present in spaces with a high concentration of titanium carbide, depending on the initial level of compaction of these granules;
• the millimeter spaces between the zones with a high concentration of titanium carbide, depending on the initial stacking of the granules (bulk density);
• the porosity coming from the volumetric contraction during the reaction between Ti + C to obtain the TiC.

Examples

• titane, H.C. STARCK, Amperit 155.066, moins de 200 mesh,
• carbone graphite GK Kropfmuhl, UF4, > 99.5 %, moins de 15 µm,
• Fe, sous la forme Acier HSS M2, moins de 25 µm,
• proportions :
  • Ti + C 100 g Ti - 24.5 g C
  • Ti + C + Fe 100 g Ti - 24.5 g C - 35.2 g Fe Mélange 15 min dans mélangeur Lindor, sous argon.

La granulation, a été effectuée avec un granulateur Sahut-Conreur.
Pour les mélanges Ti+c+Fe et Ti+C, la compacité des granulés a été obtenue en faisant varier la pression entre les rouleaux de 10 à 250.10⁵ Pa.
Le renforcement a été effectué en plaçant des granulés dans un container métallique, qui est ensuite judicieusement placé dans le moule à l'endroit où le cône de broyage est susceptible d'être renforcé. Ensuite on coule l'acier ou la fonte dans ce moule.In the examples that follow, the following raw materials were used:

• titanium, HC STARCK, Amperit 155.066, less than 200 mesh,
• graphite carbon GK Kropfmuhl, UF4,> 99.5%, less than 15 μm,
• Fe, in the form of HSS M2 steel, less than 25 μm,
• proportions:
  • Ti + C 100 g Ti - 24.5 g C
  • Ti + C + Fe 100 g Ti - 24.5 g C - 35.2 g Fe Mix 15 min in Lindor mixer, under argon.

Granulation was carried out with a Sahut-Conreur granulator.
For the Ti + c + Fe and Ti + C mixtures, the compactness of the granules was obtained by varying the pressure between the rolls by 10 to 250 × 10 ⁵ Pa.
Reinforcement has been done by placing granules in a metal container, which is then conveniently placed in the mold where the grinding cone is likely to be reinforced. Then we cast the steel or cast in this mold.

Example 1

In this example, it is intended to provide a grinding cone whose reinforced areas comprise an overall volume percentage of TiC of about 42%. For this purpose, a band is produced by compaction at 85% of the theoretical density of a mixture of C and Ti. After crushing, the granules are sieved to obtain a pellet size of between 1.4 and 4 mm. A bulk density of the order of 2.1 g / cm ³ (35% of space between the granules + 15% of porosity in the granules) is obtained.

the granules are placed in the mold at the location of the part to be reinforced, which thus comprises 65% by volume of porous granules. A chromium cast iron (3% C, 25% Cr) was then cast at about 1500 ° C in a non-preheated sand mold. The reaction between Ti and C is initiated by the heat of melting. This casting is done without a protective atmosphere. After reaction, in the reinforced part 65% by volume of zones with a high concentration of approximately 65% of globular titanium carbide is obtained, ie 42% by global volume of TiC in the reinforced part of the grinding cone.

Example 2

In this example, it is intended to achieve a grinding cone whose reinforced areas comprise a global volume percentage of TiC of about 30%. For this purpose, a 70% compaction band is made of the theoretical density of a mixture of C and Ti. After crushing, the granules are sieved to obtain a pellet size of between 1.4 and 4 mm. A bulk density of the order of 1.4 g / cm ³ (45% of space between the granules + 30% of porosity in the granules) is obtained. The granules are placed in the part to be reinforced, which thus comprises 55% by volume of porous granules. After reaction, in the reinforced part, 55% by volume of zones with a high concentration of approximately 53% of globular titanium carbide, ie approximately 30% by volume of TiC in the reinforced portion of the grinding cone, are obtained.

Example 3

In this example, it is intended to provide a grinding cone whose reinforced areas comprise a global volume percentage of TiC of about 20%. At this In the end, a 60% compaction band is made of the theoretical density of a mixture of C and Ti. After crushing, the granules are sieved so as to obtain a granule size of 1 and 6 mm. A bulk density of the order of 1.0 g / cm ³ (55% of space between the granules + 40% of porosity in the granules) is obtained. The granules are placed in the part to be reinforced, which thus comprises 45% by volume of porous granules. After reaction, in the reinforced part 45% by volume of zones concentrated to about 45% of globular titanium carbide are obtained, ie 20% by global volume of TiC in the reinforced part of the grinding cone.

Example 4

In this example, it was sought to attenuate the intensity of the reaction between carbon and titanium by adding a ferrous alloy powder. As in Example 2, it is intended to provide a grinding cone whose reinforced zones comprise a global volume percentage of TiC of about 30%. For this purpose, a compaction band is produced at 85% of the theoretical density of a mixture by weight of 15% of C, 63% of Ti and 22% of Fe. After crushing, the granules are sieved to obtain a granule size between 1.4 and 4 min. A bulk density of the order of 2 g / cm ³ (45% of space between the granules + 15% of porosity in the granules) is obtained. The granules are placed in the part to be reinforced, which thus comprises 55% by volume of porous granules. After reaction, 55% by volume of zones with a high concentration of approximately 55% of globular titanium carbide, ie 30% by volume of global titanium carbide in the reinforced macro-microstructure of the grinding cone, are obtained in the reinforced part. .

The following tables show the many possible combinations.

<b><u> Table 1 </ u> (Ti + 0.98 C) </ b> Overall percentage of TiC obtained in the reinforced macro-microstructure after Ti + 0.98 C reaction in the reinforced part of the grinding cone Compaction of the granules (% of theoretical density which is 3.75 g / cm ³ ) 55 60 65 70 75 80 85 90 95 Filling the reinforced part of the part (% vol.) 70 29.3 31.9 34.6 37.2 39.9 42.6 45.2 47.9 50.5 65 27.2 29.6 32.1 34.6 37.1 39.5 42.0 44.5 46.9 55 23.0 25.1 272 29.3 31.4 33.4 35.5 37.6 39.7 45 18.8 20.5 22.2 23.9 25.7 27.4 29.1 30.8 32.5 This table shows that with a compaction level ranging from 55 to 95% for the strips and therefore the granules, it is possible to practice filling levels in granules in the reinforced part of the grinding cone ranging from 45 to 70% by volume ( ratio between the total volume of pellets and the volume of their confinement). Thus, to obtain an overall concentration of TiC in the reinforced portion of about 29% vol. (in bold letters in the table), we can proceed to different combinations such as for example 60% of compaction and 55% of filling, or 70% of compaction and 55% of filling, or else 85% of compaction and 45% of filling . To obtain granular filling levels in the reinforced portion up to 70% by volume, it is necessary to apply a vibration to compact the granules. In this case, the ISO 697 standard for measuring the degree of filling is no longer applicable and the quantity of material in a given volume is measured.

<b><u> Table 2 </ u></b> Relationship between the compaction level, the theoretical density and the percentage of TiC obtained after reaction in the granule Compaction of granules 55 60 65 70 75 80 85 90 95 Density in g / cm ³ 2.06 2.25 2.44 2.63 2.81 3.00 3.19 3.38 3.56 TiC obtained after reaction (and concentration) in% vol. in the granules 41.8 45.6 49.4 53.2 57.0 60.8 64.6 68.4 72.2 Here we have represented the density of the granules as a function of their level of compaction and deduced the volume percentage of TiC obtained after reaction and thus contraction of about 24% vol. Granules compacted to 95% of their theoretical density thus make it possible to obtain after reaction a concentration of 72.2% vol. in TiC.

<b><u> Table 3 </ u></b> Bulk density of the stack of pellets compaction 55 60 65 70 75 80 85 90 95 Filling the reinforced part of the part in% vol 70 1.4 1.6 1.7 1.8 2 2.1 2.2 2.4 2.5 65 1.3 * 1.5 1.6 1.7 1.8 2.0 2.1 2.2 2.3 55 1.1 1.2 1.3 1.4 1.5 1.7 1.8 1.9 2.0 45 0.9 1.0 1.1 1.2 1.3 1.4 1.4 1.5 1.6 (*) Bulk density (1.3) = theoretical density (3.75 g / cm ³ )) x 0.65 (filling) x 0.55 (compaction) In practice, these tables are used by the user of this technology, which sets a global percentage of TiC to be produced in the reinforced part of the grinding cone and which, as a result, determines the level of filling and the compaction of the elements. granules that he will use. The same tables were made for a mixture of Ti + C + Fe powders.

Ti + 0.98 C + Fe

• Nous entendons par poudre de fer : fer pur ou alliage de fer.
• Densité théorique du mélange : 4.25g/cm³
• Retrait volumétrique lors de la réaction : 21 %

Here, the inventor has targeted a mixture to obtain 15% by volume of iron after reaction. The proportion of mixture that has been used is:
100g Ti + 24.5g C + 35.2g Fe

• We mean by iron powder: pure iron or iron alloy.
• Theoretical density of the mixture: 4.25g / cm ³
• Volumetric shrinkage during the reaction: 21%

<b><u> Table 4 </ u></b> Overall percentage of TiC obtained in the reinforced macro-microstructure after reaction Ti + 0.98 C + Fe in the reinforced part of the grinding cone Compaction of the granules (% of theoretical density which is 4.25 g / cm ³ ) 55 60 65 70 75 80 85 90 95 Filling the reinforced part of the part (% vol) 70 25.9 28.2 30.6 32.9 35.5 37.6 40.0 42.3 44.7 65 24.0 26.2 28.4 30.6 32.7 34.9 37.1 39.3 41.5 55 20.3 22.2 24.0 25.9 27.7 29.5 31.4 33.2 35.1 45 16.6 18.1 19.6 21.2 22.7 24.2 25.7 27.2. 28.7 Again, to obtain an overall concentration of TiC in the reinforced part of about 26% vol (in bold letters in the table), one can proceed to different combinations such as for example 55% compaction and 70% filling, or 60%. % compaction and 65% filling, or 70% compaction and 55% filling, or 85% compaction and 45% filling.

Table 5 Relationship between the compaction level, the theoretical density and the percentage of TiC, obtained after reaction in the granule taking into account the presence of iron Compaction of granules 55 60 65 70 75 80 85 90 95 Density in g / cm ³ 2.34 2.55 2.76 2.98 3.19 3.40 3.61 3.83 4.04 TiC obtained after reaction (and contraction) in% vol. in the granules 36.9 40.3 43.6 47.0 50.4 63.7 57.1 60.4 63.8

Table 6 Bulk density of the stack of pellets (Ti + C + Fe) compaction 55 60 65 70 75 80 85 90 95 Filling the reinforced part of the piece in% vol. 70 1.6 1.8 1.9 2.1 2.2 2.4 2.5 2.7 2.8 65 1.5 * 1.7 1.8 1.9 2.1 2.2 2.3 2.5 2.6 55 1.3 1.4 1.5 1.6 1.8 1.9 2.0 2.1 2.2 45 1.1 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.8 (*) Bulk density (1.5) = theoretical density (4.25) x 0.65 (filling) x 0.55 (compaction)

Advantages

The present invention has the following advantages over the state of the art in general:

Better shock resistance

With the present process, there are porous millimetric granules which are crimped into the metal infiltration alloy. These millimetric granules are themselves composed of microscopic particles of globular TiC also crimped in the metal alloy infiltration. This system makes it possible to obtain a grinding cone with a reinforcing zone comprising a macrostructure within which there is an identical microstructure on a scale approximately a thousand times smaller.

The fact that the reinforcing zone of the grinding cone comprises small globular particles of titanium carbide, hard and finely dispersed in a metal matrix around them, avoids the formation and propagation of cracks (see Fig. 4 & 6 ). There is thus a double dissipative system of cracks.

Cracks generally originate at the most fragile places, which in this case are the TiC particle or the interface between this particle and the infiltration metal alloy. If a crack originates at the interface or in the micrometric particle of TiC, the propagation of this crack is then impeded by the infiltration alloy which surrounds this particle. The toughness of the infiltration alloy is greater than that of the TiC ceramic particle. The crack needs more energy to pass from one particle to another, to cross the micrometric spaces that exist between the particles.

Maximum flexibility for implementation parameters

In addition to the level of compaction of the granules, it is possible to vary two parameters which are the granulometric fraction and the shape of the granules, and therefore their bulk density. On the other hand, in an insert reinforcement technique, it is only possible to vary the level of compaction thereof in a limited range. In terms of the shape that we want to give the reinforcement, given the design of the grinding cone and the place that we want to strengthen, the use of granules allows more opportunities and adaptation. (see figure 3 )

Advantages in manufacturing

• moins de dégagement gazeux,
• moindre susceptibilité à la clique,
• meilleure localisation du renforcement dans le cône de broyage.

La réaction entre le Ti et le C est fortement exothermique. L'élévation de température provoque un dégazage des réactif, c'est-à-dire des matières volatiles comprises dans les réactifs (H₂O dans le carbone, H₂, N₂ dans le titane). Au plus la température de réaction est élevée, au plus ce dégagement est important. La technique par granulés permet de limiter la température, de limiter le volume gazeux et permet une évacuation plus facile des gaz et ainsi de limiter les défauts de gaz. (voir Fig. 9 avec bulle de gaz indésirable).The use as reinforcement of a stack of porous granules, has certain advantages at the level of manufacture:

• less gassing,
• less susceptibility to the clique,
• better localization of the reinforcement in the grinding cone.

The reaction between Ti and C is strongly exothermic. The rise in temperature causes degassing of the reagents, that is to say volatile materials included in the reagents (H ₂ O in carbon, H ₂ , N ₂ in titanium). The higher the reaction temperature, the greater this clearance is important. The granular technique makes it possible to limit the temperature, to limit the gaseous volume and allows an easier evacuation of the gases and thus to limit the gas defects. (see Fig. 9 with unwanted gas bubble).

Low susceptibility to cracking during the manufacture of the grinding cone according to the invention

The coefficient of expansion of the TiC reinforcement is lower than that of the ferrous alloy matrix (TiC expansion coefficient: 7.5 × 10 ^-6 / K and the ferrous alloy: about 12.0 × 10 ^-5 / K). This difference in the expansion coefficients has the consequence of generating tensions in the material during the solidification phase and also during the heat treatment. If these voltages are too great, cracks may appear in the room and lead to scrapping it. In the present invention, a small proportion of TiC reinforcement (less than 50% by volume) is used, resulting in less stress in the part. In addition, the presence of a more ductile matrix between the micrometric globular particles of TiC in alternating zones of low and high concentration makes it possible to better manage any local voltages.

Excellent retention of reinforcement in the grinding cone

In the present invention, the boundary between the reinforced portion and the unreinforced portion of the grinding cone is not abrupt since there is a continuity of the metal matrix between the reinforced portion and the unreinforced portion, which allows protect it against a complete tearing of the reinforcement.

Test results

Three tests were carried out with cones of the type represented in figure 3 .

Test 1 secondary crusher

Crushed material: aggregates, high abrasiveness increased life of reinforced cone compared to a manganese steel cone: 50%

Test 2 secondary crusher

crushed material: aggregates, medium abrasiveness increase in the life of the reinforced cone compared to a manganese steel cone: 130%

Test 3 secondary crusher

crushed material: aggregates, average abrasiveness increase in the life of the reinforced cone compared to a manganese steel cone: 170%

Claims (13)

1. A composite milling cone for compression crushers, said milling cone comprising a ferrous alloy at least partially reinforced (5) with titanium carbide according to a defined geometry, wherein said reinforced portion (5) comprises an alternating macro-microstructure of millimetric areas (1) concentrated with micrometric globular particles of titanium carbide (4) separated by millimetric areas (2) essentially free of micrometric globular particles of titanium carbide (4), said areas concentrated with micrometric globular particles of titanium carbide (4) forming a microstructure in which the micrometric interstices (3) between said globular particles (4) are also filled by said ferrous alloy.
2. The milling cone according to claim 1, wherein said millimetric concentrated areas have a concentration of micrometric globular particles of titanium carbide (4) greater than 36.9% by volume.
3. The milling cone according to any of claims 1 or 2, wherein said reinforced portion has a global titanium carbide content between 16.6 and 50.5% by volume.
4. The milling cone according to any of the preceding claims, wherein the micrometric globular particles of titanium carbide (4) have a size of less than 50µm.
5. The milling cone according to any of the preceding claims, wherein the major portion of the micrometric globular particles of titanium carbide (4) has a size of less than 20 µm.
6. The milling cone according to any of the preceding claims, wherein said areas concentrated with globular particles of titanium carbide (1) comprise 36.9 to 72.2% by volume of titanium carbide.
7. The milling cone according to any of the preceding claims, wherein said areas concentrated with titanium carbide (1) have a dimension varying from 1 to 12 mm.
8. The milling cone according to any of the preceding claims, wherein said areas concentrated in titanium carbide (1) have a dimension varying from 1 to 6 mm.
9. The milling cone according to any of the preceding claims, wherein said areas concentrated in titanium carbide (1) have a dimension varying from 1.4 to 4 mm.
10. A method for manufacturing by casting a composite milling cone according to any of claims 1 to 9, comprising the following steps:

    - providing a mold comprising the imprint of the milling cone with a predefined reinforcement geometry;

    - introducing, into the portion of the imprint of the milling cone intended to form the reinforced portion (5), a mixture of compacted powders comprising carbon and titanium in the form of millimetric granules precursor of titanium carbide;

    - casting a ferrous alloy into the mold, the heat of said casting triggering an exothermic self-propagating high temperature synthesis (SHS) of titanium carbide within said precursor granules;

    - forming, within the reinforced portion (5) of the milling cone, an alternating macro-microstructure of millimetric areas concentrated (1) with micrometric globular particles of titanium carbide (4) at the location of said precursor granules, said areas being separated from each other by millimetric areas (2) essentially free of micrometric globular particles of titanium carbide (4), said globular particles (4) being also separated within said millimetric areas concentrated (1) with titanium carbide by micrometric interstices (3);

    - infiltration of the millimetric (2) and micrometric (3) interstices by said high temperature cast ferrous alloy, following the formation of microscopic globular particles of titanium carbide (4).
11. The manufacturing method according to claim 10, wherein the mixture of compacted powders of titanium and carbon comprises a powder of a ferrous alloy.
12. The manufacturing method according to any of claims 10 or 11, wherein said carbon is graphite.
13. The milling cone obtained according to any of claims 10 to 12.

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