EP2323770A1

EP2323770A1 - Composite impactor for percussion crushers

Info

Publication number: EP2323770A1
Application number: EP09814104A
Authority: EP
Inventors: Guy Berton
Original assignee: Magotteaux International SA
Current assignee: Magotteaux International SA
Priority date: 2008-09-19
Filing date: 2009-08-26
Publication date: 2011-05-25
Anticipated expiration: 2029-08-26
Also published as: AU2009294782B2; WO2010031663A1; CA2735877A1; CA2735877C; MX2011003028A; US8651407B2; PT2323770E; BRPI0913717A2; CL2011000576A1; PL2323770T3; KR101621996B1; EG26800A; JP2012502789A; US20110226882A1; CN102176973A; DK2323770T3; EP2323770B1; BRPI0913717B1; ES2449440T3; BE1018129A3

Abstract

The invention relates to a composite impactor for percussion crushers, said impactor comprising a ferroalloy which is at least partially reinforced with titanium carbide in a defined shape, said reinforced part comprising an alternate macro-microstructure of millimetric areas concentrated with micrometric globular particles of titanium carbide, which are separated by millimetric areas essentially free of micrometric globular particles of titanium carbide, the areas concentrated with micrometric globular particles of titanium carbide forming a microstructure wherein the micrometric gaps between the globular particles are also filled by the ferroalloy.

Description

COMPOSITE IMPACTOR FOR PERCUSSION CRUSHERS

Object of the invention

The present invention relates to a composite impactor for impact crushers. Percussion crushers grouping crushing machines for rocks and hard materials such as hammer crushers, crushers, vertical axis crushers, etc. These machines are used extensively in the first and second stages of a production line designed to drastically reduce the dimension of rock in the extractive industries

(mines, quarries, cement plants, ...) and recycling.

Definition

The expression "impactor for impact crushers" is to be interpreted in the broad sense, namely a composite wear part whose function is to be in direct contact with the rock or the material to be grinded during the first phase. process where these rocks and materials are subjected to extremely violent impacts intended to fragment them.

These wear parts must therefore show great resistance to impact and they are often called hammers, beaters or impactors. The term "impactor" therefore includes hammers and beaters but also fixed armor plates undergoing the impacts of materials projected against them. State of the art

Few means are known to change the hardness and impact resistance of a foundry alloy in depth "in the mass". The known means generally concern surface modifications of shallow depth (a few mm). For wear parts made in the foundry, reinforcing elements must be present in depth in order to withstand significant and simultaneous localized stress in terms of mechanical stress, wear and impact and also because, in general, it is a significant proportion of the volume (or weight) of the piece that is consumed during its lifetime. The document LU 64303 (Joiret) describes a method of manufacturing hammers that implements two different materials, one harder to achieve the head, subjected to abrasion, the other more resilient that guarantees the resistance against breakage. EP 0 476 496 (Guerard) proposes the use of a hard insert mechanically crimped into a hammer body made of a ductile steel. EP 1 651 389 (Mayer) also discloses a hammer making technique employing two different materials, one being arranged in the form of a prefabricated insert disposed in the other material at the place where the piece is the most solicited. Document US 2008/041993 (Hall) proposes the use of inserts very hard material, fixed to the hammer on its working side. US 6,066,407 (Getz) discloses a reinforced composite impactor with carbides. However, it does not disclose a reinforcing structure with spheroidal titanium carbide particles surrounded by the infiltration alloy or any hierarchical microscopic geometry in the reinforced part. The common point of all these techniques of reinforcing parts used in crushing processes by percussion is obviously the difficulty of ensuring, in production and in service, a perfect and durable connection between the two materials used.

OBJECTS OF THE INVENTION [0010] The present invention discloses a composite impactor for impact 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 in fine micrometric globular particles of metal carbides with zones that are practically free of them within the metallic matrix. of the impactor. The present invention also provides a method for obtaining said reinforcement structure.

SUMMARY OF THE INVENTION [0012] The present invention discloses a composite impactor for impact crushers, said impactor comprising a ferrous alloy reinforced at least in part with titanium carbide according to a defined geometry, wherein said reinforced portion comprises a macro- alternating microstructure of millimetric zones of millimetric zones concentrated in micrometric globular particles of titanium carbide separated by millimetric zones substantially free of micrometric globular particles of titanium carbide, micrometrically concentrated micrometric micrometric particles of micrometric titanium carbide particles in which the micrometric interstices between said globular particles are also occupied by said ferrous alloy.

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

said concentrated millimetric zones have a concentration of titanium carbides greater than 36.9% by volume;

said reinforced portion has an overall titanium carbide content of 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 have a size of less than 20 μm;

said zones concentrated in globular particles of titanium carbide comprise 36.9 to 72.2% by volume of titanium carbide;

said millimetric zones, which are concentrated in titanium carbide, have a size ranging from 1 to 12 mm;

said millimetric zones, which are concentrated in titanium carbide, have a size ranging from 1 to 6 mm;

said concentrated zones made of titanium carbide have a dimension varying from 1.4 to 4 mm.

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

- Provision of a mold having the imprint of the impactor with a predefined reinforcement geometry; introducing, into the part of the impression of the impactor intended to form the reinforced part (5), a mixture of compacted powders comprising carbon and titanium in the form of millimetric granules precursors of titanium carbide;

casting a ferrous alloy in 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 impactor, 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 zones millimeters substantially free of micrometric globular particles of titanium carbide, said globular particles being also separated within said millimetric zones of concentrated titanium carbide micrometric interstices;

infiltration of the millimetric and micrometric interstices by said high-temperature ferrous casting alloy, subsequent to the formation of globular globular particles of titanium carbide.

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

compacted powders of titanium and carbon comprise a powder of a ferrous alloy;

said carbon is graphite.

The present invention also discloses a composite impactor obtained according to the method of any one of claims 11 to 13. Brief description of the figures

[0017] Figure 1 shows a horizontal axis crusher in which the impactors of the present invention are used. [0018] Figure 2 shows a vertical axis crusher in which the impactors of the present invention are also used.

Figure 3 shows an impactor / hammer of the prior art without reinforcement. Figures 4a and 4b show a hammer with two types of reinforcement possible. This reinforcing geometry is of course not limiting.

Figure 5a-5h shows schematically the method of manufacturing a hammer according to the invention. step 5a shows the device for mixing the titanium and carbon powders;

Step 5b shows the compaction of the powders between two rollers followed by crushing and sieving with recycling of the fine particles; FIG. 5c shows a sand mold in which a dam has been placed to contain the granules of compacted powder at the location of the reinforcement of the impactor (hammer);

FIG. 5d shows an enlargement of the reinforcement zone in which the compacted granules comprising TiC precursor reactants are found;

Step 5e shows the casting of the ferrous alloy in the mold;

- Figure 5f shows schematically the hammer which is the result of the casting;

FIG. 5g shows an enlargement of the zones with a high concentration of TiC nodules; FIG. 5h shows an enlargement within the same zone with a high concentration of TiC nodules. The micrometric nodules are individually surrounded by the casting metal. FIG. 6 shows a binocular view of a polished, unengaged surface of a section of the reinforced portion of an impactor according to the invention with millimetric zones (in light gray) concentrated in titanium carbide. micrometric globular (nodules of TiC). The dark part represents the metal matrix (steel or cast iron) filling at the same time the space between these concentrated micrometric globular titanium carbide zones but also the spaces between the globules themselves. Figures 7 and 8 show SEM electron microscope views of micrometric globular titanium carbide on polished and untouched 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. FIG. 9 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.

[0025] FIG. 10 schematically represents the zones of reinforcement on a hammer impactor. The reinforced corners are similar to those of FIG. 4b and the diagrammatic enlargement of the reinforcement zones makes it possible to show the reinforcement macro-microstructure according to the invention. Legend

I. millimetric zones concentrated in micrometric globular particles (nodules) of titanium carbide 2. millimeter gaps filled by the casting alloy globally free of micrometric globular particles of titanium carbide 3. micrometric interstices between TiC nodules also infiltrated by l casting alloy 4. micrometric globular titanium carbide in concentrated areas of titanium carbide

5. titanium carbide reinforcement

6. gas defects

7. hammer / impactor 8. mixer of Ti and C powders

9. hopper

10. roll

II. crusher

12. output grid 13. sieve

14. recycling of fine particles to the hopper

15. sand mold

16. dam containing compacted granules of Ti / C mixture 17. ladle

18. impactor (schematic)

Detailed description of the invention

In materials science, SHS reaction or "self-propagating high temperature synthesis", a self-propagating high temperature synthesis reaction where reaction temperatures are generally higher than 1500 ^° C., or even 2000, are reached. ⁰ C. for example, the reaction between the titanium powder and the powder carbon 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 reactive powder mixtures comprise carbon powder and titanium powder and are compressed into plates and then crushed in order to obtain granules whose size varies from 1 to 12 mm, preferably from 1 to 12 mm. 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 FIG. 3a-3h constitute the precursors of the titanium carbide to be created and make it possible to easily fill mold parts of various or irregular shapes. 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 impactor according to the present invention has a reinforcing macro-microstructure that can also be called alternating structure of concentrated zones in micrometric globular particles of titanium carbide separated by zones which are practically free. 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 reaction of self-propagating synthesis 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. 5g & 5h). By increasing the wettability, the infiltration can be done on any thickness or depth of reinforcement of the impactor. It advantageously makes it possible, after SHS reaction and infiltration by an external casting metal, to create one or more reinforcement zones on the impactor comprising a high concentration of micrometric globular particles of titanium carbide (which could also be called clusters). 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 were also 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 impactor; this allows a total freedom of choice of the casting metal. In the impactor finally obtained, the reinforcement zones with a high concentration of titanium carbide are composed of globular micrometer particles of TiC in significant percentage (between about 35 and about 70% by volume) and the ferrous alloy infiltration.

By micrometric globular particles are meant globally spheroidal particles which have a size ranging from microns to a few tens of microns at most, the vast majority of these particles having a size of less than 50 microns, and even at 20 microns. or even 10 μm. We also call them TiC globules. This globular form is characteristic of a method for obtaining titanium carbide by self-propagating SHS synthesis (see Fig. 8).

Obtaining pellets (Ti + C version) for reinforcing the impactor

The process for obtaining the granules is illustrated in Figure 5a-5h. 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. We get at the exit a band of material compressed which is then crushed 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 therefore 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 pressure applied (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 bands of 90% of the theoretical density is obtained, ie an apparent 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 size fractions are recycled at will (see Fig. 3b). The granules obtained overall 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 impactor according to the invention

The granules are made as described above. To obtain a three-dimensional structure or superstructure / macro-microstructure with these granules, they are placed in the areas of the mold where it is desired to reinforce the workpiece. 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.

During the reaction Ti + C -> TiC, there is a volumetric contraction of about 24% when passing reagents to the product (contraction from the difference in density between the reagents and 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

In the examples which follow, the following raw materials were used:

titanium, H. C. 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.

The reinforcement was carried out by placing granules in a metal container, which is then judiciously placed in the mold where the impactor is likely to be reinforced. Then we cast the steel or cast in this mold. Example 1

In this example, it is intended to achieve an impactor whose reinforced areas include a percentage by volume of TiC total 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% space between the granules + 15% 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) is 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 are obtained, ie 42% by global volume of TiC in the reinforced part of the impactor.

Example 2 [0044] In this example, it is intended to provide an impactor whose reinforced zones comprise an overall volume percentage of TiC of approximately 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 about 1.4 g / cm ³ (45% of space between the granules + 30% of porosity in the granules) is obtained. The granules are available in the section strengthen 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 is obtained, ie approximately 30% by global volume of TiC in the reinforced part of the impactor.

Example 3 [0045] In this example, it is intended to provide an impactor whose reinforced zones comprise an overall volume percentage of TiC of about 20%. For this purpose, a band is made by compaction at 60% 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 concentrated zones with approximately 45% of globular titanium carbide is obtained, ie 20% by global volume of TiC in the reinforced part of the impactor.

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 an impactor 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 mm. 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 compound, are obtained in the reinforced part. impactor.

The following tables show the many possible combinations.

Table 1 (Ti + 0.98 C) [0048] Overall percentage of TiC obtained in the reinforced macro-microstructure after reaction Ti + 0.98 C in the reinforced part of the impactor

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 impactor ranging from 45 to 70% by volume. (ratio of the total volume of granules 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 65% of filling, or 70% compaction and 55% filling, or 85% compaction and 45% 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.

Table 2

Relationship between the level of compaction, the theoretical density and the percentage of TiC obtained after reaction in the granule

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.

Table 3 [0050] Bulk Density of Pellet Stack

Compaction 55 60 65 70 75 80 85 90 95

Filling of part 70 1 .4 1 .6 1 .7 1 .8 2 2 1 2 2 2.4 2 5 reinforced part in% vol 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 impactor and which, as a result, determines the filling level and the compaction of the granules that he will use. The same tables were made for a mixture of Ti + C + Fe powders.

Ti + 0.98 C + Fe [0051] 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: 4.25 g / cm ³ Volumetric shrinkage during the reaction: 21%

Table 4 [0052] Overall percentage of TiC obtained in the reinforced microstructure after reaction Ti + 0.98 C + Fe in the reinforced part of the impactor

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%. % of compaction and 65% of filling, or 70% compaction and 55% filling, or 85% compaction and 45% filling.

Table 5

Relationship between the level of compaction, the theoretical density and the percentage of TiC, obtained after reaction in the granule taking into account the presence of iron

10

Table 6

[0054] Bulk Density of the Pellet Stack

(Ti + C + Fe)

Compaction 55 60 65 70 75 80 85 90 95

Filling of part 70 1 .6 1 .8 1 .9 2 .1 2.2 2.4 2.5 2 7 2 8 reinforced part in% vol. 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

15 (*) 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 millimeter porous granules which are crimped in the alloy

25 metal infiltration. These millimetric granules are themselves composed of microscopic particles of TiC globular tendency also crimped in the alloy metallic infiltration. This system makes it possible to obtain an impactor with a reinforcement 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 impactor comprises small globular particles of titanium carbide, hard and finely dispersed in a metal matrix which surrounds them, makes it possible to prevent the formation and propagation of cracks (see FIG. 4 & 6). There is thus a double dissipative system of cracks.

The cracks generally originate at the most fragile places, which are in this case 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 compaction level of the granules, two parameters can be varied 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 one wishes to give to reinforcement, given the design of the impactor and the place you want to strengthen, the use of pellets allows more opportunities and adaptation.

Manufacturing Advantages [0060] The use as reinforcement of a stack of porous granules, has certain advantages in terms of manufacture:

- less gassing,

- less susceptibility to the crack, - better localization of reinforcement in the impactor. 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 crack during the manufacture of the impactor 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: approximately 12.0 10-6 / 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 this In the invention, a small proportion of TiC reinforcement (less than 50% by volume) is used, resulting in less stress in the workpiece. 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 maintenance of the reinforcement in the impactor In the present invention, the boundary between the reinforced part and the unreinforced part of the impactor is not abrupt because there is a continuity of the metal matrix between the part reinforced and the unreinforced part, which allows to protect against a complete tearing of the reinforcement.

Test results

Three tests were carried out with hammer type impactors of the type shown in Figure 4b and Figure 10 over a weight range of 30 to 130 kg.

Test 1 weight hammers: 30 to 70 kgs crushed material: cement clinker increase the life of the hammer compared to a hardened steel hammer: 200%

Test 2 weight hammers: 70 to 130 kgs crushed material: limestone rock stage: primary increase in the life of the hammer compared to a hardened steel hammer: 100 to 200%

Test 3 hammer weights: 30 to 80 kgs crushed material: limestone stage: secondary increase in service life of the part: 100 to 200%

Claims

A composite impactor for impact crushers, said impactor 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 millimeter zones (1) concentrated in micrometric globular particles of titanium carbide (4) separated by millimetric areas (2) substantially free of micrometric globular particles of titanium carbide (4), said zones concentrated in micrometric globular particles of titanium carbide

(4) forming a microstructure in which the micrometric interstices (3) between said globular particles (4) are also occupied by said ferrous alloy.

An impactor according to claim 1, wherein said concentrated millimeter regions have a concentration of micrometric globular particles of titanium carbide (4) greater than 36.9% by volume.

An impactor according to any one of claims 1 or 2, wherein said reinforced portion has an overall titanium carbide content between 16.6 and 50.5% by volume.

4. Impactor according to any one of the preceding claims, wherein the micrometric globular particles of titanium carbides (4) have a size less than 50 .mu.m.

An impactor according to any one of the preceding claims, wherein the major part of the globular micrometric particles of titanium carbides (4) is less than 20 μm in size.

An impactor according to any one of the preceding claims, wherein said zones Concentrates of titanium carbide globular particles (1) comprise 36.9 to 72.2% by volume of titanium carbide.

An impactor according to any one of the preceding claims, wherein said concentrated areas of titanium carbide (1) have a size ranging from 1 to 12 mm.

8. An impactor according to any one of the preceding claims, wherein said concentrated areas of titanium carbide (1) have a size ranging from 1 to 6 mm.

9. An impactor according to any one of the preceding claims, wherein said concentrated areas of titanium carbide (1) have a dimension ranging from 1.4 to 4 mm.

10. A method of manufacturing by casting of a composite impactor according to any one of claims 1 to 9, comprising the following steps:

- provision of a mold having the imprint of the impactor with a predefined reinforcement geometry;

- introducing, into the part of the impression of the impactor 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 in 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 part (5) of the impactor of an alternating macro-microstructure of concentrated millimetric zones (1) into globular particles micrometric titanium carbide (4) at the location of said precursor granules, said zones being separated from each other by millimetric zones (2) essentially free of micrometric globular particles of titanium carbide (4), said globular particles (4) being also separated within said concentrated millimetric zones (1) of titanium carbide by micrometric interstices

(3); - infiltration of millimetric (2) and micrometer (3) interstices by said ferrous alloy casting at high temperature, 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 one of claims 10 or 11, wherein said carbon is graphite.

13. Impactor obtained according to any one of claims 10 to 12.