Classifications

• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
  • C22C33/0207—Using a mixture of prealloyed powders or a master alloy
  • C22C33/0214—Using a mixture of prealloyed powders or a master alloy comprising P or a phosphorus compound
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/12—Both compacting and sintering
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C33/00—Making ferrous alloys
  • C22C33/02—Making ferrous alloys by powder metallurgy
  • C22C33/0257—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements
  • C22C33/0278—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5%
  • C22C33/0285—Making ferrous alloys by powder metallurgy characterised by the range of the alloying elements with at least one alloying element having a minimum content above 5% with Cr, Co, or Ni having a minimum content higher than 5%
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/10—Ferrous alloys, e.g. steel alloys containing cobalt
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
  • B22F2005/001—Cutting tools, earth boring or grinding tool other than table ware
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
  • B22F2998/10—Processes characterised by the sequence of their steps

Definitions

• the invention relates to the field of pre-alloyed metal powders, from which diamond cutting tools such as segments for saws and beads for the production of yarns for cutting hard materials such as granite are produced.
• the metal powders used to make diamond beads are usually made from granules containing about 20% tungsten carbide and about 80% cobalt. These granules are mixed with diamonds and compressed in the form of rings, and the green parts are sintered according to two possibilities.
• a natural sintering, also called “free sintering", (without mold) of the raw parts with their steel sheaths is carried out in a static or scrolling oven. But after this sintering, the cobalt and tungsten carbide beads are not sufficiently densified.
• a second heat treatment is essential, which must be carried out in a furnace operating at a high pressure of between 1500 and 2000 bar, to achieve hot isostatic pressing of the beads. This oven is expensive to buy and maintain.
• the object of the invention is first and foremost to provide pre-alloyed metal powders whose cost would be relatively moderate, and which would be compatible with processes for manufacturing diamond beads that are substantially less expensive than the existing processes, in particular because natural sintering , realized without mold, would nevertheless make it possible to obtain sufficiently powerful products, in particular for the cutting of the granite. Also, these powders should be compatible with the manufacture of other types of cutting tools for less demanding applications.
• the Fisher diameter of its particles is 1 to 3 ⁇ m.
• It is preferably constituted by a mixture of such a powder and of at least one sintering aid additive in a proportion of 80 to 90% by weight of powder and 10 to 20% by weight of additive.
• the sintering aid additive is preferably a phosphide of iron, nickel, copper or cobalt, or a mixture of at least two of these phosphides, or a mixed phosphide of at least two of these metals.
• the Fisher diameter of the particles of the first powder is 0.8 to 1.5 ⁇ m
• the Fisher diameter of the particles of the second powder is 3.0 to 4.0 ⁇ m
• the Fisher diameter of the powder. obtained after mixing is 1 to 3 ⁇ m.
• the subject of the invention is also a process for manufacturing a diamond cutting tool, comprising a step of mixing a pre-alloyed metal powder and diamonds, a cold pressing step of the mixture and a sintering step to said compressed mixture. characterized in that said metal powder is of the preceding type.
• Sintering is preferably natural sintering.
• Said tool can be a cutting segment for diamond saw.
• Said tool can be a diamond bead for cutting wire.
• Said powder may be of the aforementioned type.
• the invention also relates to a diamond saw of the type comprising cutting segments fixed on the periphery of a metal disk, characterized in that said segments were obtained by the above method.
• the invention also relates to a cutting wire of the type comprising diamond beads threaded on a cable, characterized in that said beads were obtained by the above method.
• the invention is based on the use of a prealloyed powder of precise composition, based on iron, cobalt and copper. It turns out that this powder, which does not involve very expensive elements in high proportions, makes it possible to produce diamond cutting tools (saws and beads) very powerful by simple natural sintering, so by an economical process and can be run with high productivity.
• a process for obtaining the powder, making it possible to obtain sintered products of particularly high characteristics from said powder, is also proposed.
• the prealloyed powder according to the invention must in particular meet the following requirements.
• the relative density of the raw parts obtained with it must be at least 60% for a maximum cold pressure of 700 MPa.
• the relative density of the part obtained must preferably be at least 97 %.
• the powder must be able to be used to manufacture parts whose hardness after sintering would be at least 220 HB, so that they can be used for cutting granite.
• the mean Fisher diameter of the particles is preferably from 1 to 3 ⁇ m.
• Its typical theoretical density is preferably 8.4 g / cm 3 .
• the ratio between the iron and cobalt contents is deliberately adjusted so as to avoid forming a hard and weak ⁇ 'phase, which is formed when the mass ratio Fe / (Fe + Co) is between 30 and 70%. According to the invention, this ratio is between 72 and 78%, and the ⁇ 'phase is avoided.
• the amount of copper added is that which is sufficient to provide good sintering.
• the oxygen content is maintained at 1.2% maximum to avoid the presence of oxides that would not be reduced in total by hydrogen during natural sintering.
• Such unreduced oxides would reduce the sinterability of the green parts, cause heterogeneities in the structures of the sintered parts, increase the hardness, therefore the fragility of the parts and react with the diamonds by destroying them at least on the surface. This would reduce the cutting performance of the tools.
• This powder can be obtained in particular in two different ways.
• a powder having the desired composition and morphology characteristics is prepared directly by the conventional hydrometallurgical route.
• x, y and z are in ratios corresponding to the atomic ratios which one wishes to find on the final powder between the respective contents in Cu, Fe, Co.
• Solid-liquid separation is then carried out followed by washing the hydroxide cake with deionized water to remove NaCl.
• the cake is then passed through a dryer to obtain a co-precipitated hydroxide powder with a residual water content of a few%.
• the hydroxide powder is reduced, in order to be transformed into a pre-alloyed metal powder.
• This reduction is preferably carried out in a scroll oven and under H 2 according to: Cu x Fe y Co z (OH) + H 2 ⁇ Cu x + Fe y + Co z + H 2 O.
• the pre-alloyed powder is ground under an inert gas in a mill, then sieved at 90 ⁇ m.
• the powder according to the invention is produced by mixing two powders of different compositions, also obtained separately by hydrometallurgy.
• Table 1 shows the compositions of the two powders to be used: ⁇ u> Table 1 ⁇ / u>: characteristics of the powders I and II used.
• a mixture of the powders I and II in relative proportions of 60 - 40% by weight approximately makes it possible to manufacture the powder according to the invention.
• the powder according to the invention After obtaining the powder according to the invention, it can be used directly or granulated by a conventional method that will now be described. These granules can then be used to make specific diamond tools, such as diamond threads and thin diamond segments.
• the prealloyed powder to be granulated is mixed with an organic binder powder at 2 to 3% by weight of the amount of powder to be granulated and an organic solvent in a high shear granulator. After the granulation step, the solvent is removed by evaporation.
• the granules are sieved continuously on vibrating screens comprising two superposed canvases, openings of different mesh (450 microns for the first, 63 microns for the second for example). The fraction of diameter between 63 ⁇ m and 450 ⁇ m is thus selected. The finer and coarser granules are recycled during the next granulation operation.
• additives known for this purpose such as tungsten carbide
• tungsten carbide have proved to be ineffective in the context of the invention because they decreased the densification during sintering, and thus the hardness of the pieces, the opposite result of what was desired.
• the tungsten carbide is insoluble in the powder according to the invention and therefore does not metallurgically bind to the metal matrix.
• iron phosphide makes it possible to obtain remarkable results from this point of view; the phosphides of nickel, copper and cobalt are also interesting.
• the powder obtained by mixing (“powder mixture”) was in a blender previously put under CO 2 , from 60% of powder I and 40% of powder II, these powders having been previously prepared separately by hydrometallurgy. The mixing operation lasted 50 minutes.
• the "direct” and “mixing" powders were then compressed to 200 MPa in order to produce PS 21 pieces, whose raw density was calculated from their dimensions and their weight.
• the direct powder had a density equal to 58.0% of the theoretical density, the powder mixes a density equal to 55.2% of its theoretical density.
• the PS21 parts are parallelepipedal pieces obtained by cold compression at 200 MPa of 6 g of powder in a steel matrix of dimensions 24.48 x 7.97 mm.
• the height of the green part obtained depends on the compressibility of the powder, and is generally of the order of 5 to 6 mm.
• the mixed powder has the best sintering densification and the best hardness after sintering.
• the hierarchy of performances between the direct powders and additive mix with FeP is the same as for pure powders (not additive).
• the mixed powder has the best results after sintering.
• the additivation makes it possible to obtain sintered pieces having a hardness substantially higher than that of the parts obtained under the same conditions from non-additive powders, as can be seen by comparing the results of Tables 2 and 3.
• the additive NiP under the conditions that have been said also provides outstanding results in terms of density and hardness sintered parts.
• the additivation can also be carried out using copper phosphide or cobalt. Also, a mixture of at least two of iron, nickel, copper and cobalt phosphides or a mixed phosphide of at least two of these metals can be used.
• the segments made with the reference powder and with the powder of the invention were sintered by natural sintering in a rolling oven at 940 ° C. for the powder of the invention and 980 ° C. for the reference powder, and then brazed. on 500 mm diameter steel discs to form the saws. Granites of different categories were then cut with saws. For each type of powder, three types of diamond mixtures were tested, made from diamonds of the company ELEMENT SIX whose references will be indicated.
• the saw of the invention had a service life of 4.8 m 2 / mm and a cutting speed of 620 cm 2 / min.
• the reference saw was unable to cut the granite.
• the saw of the invention had a life of 3 m 2 / mm and a cutting speed of 620 cm 2 / min.
• the reference saw had a service life of 4.1 m 2 / mm and a cutting speed of 600 cm 2 / min.
• the saw of the invention had a service life of 6.7 m 2 / mm and a cutting speed of 900 cm 2 / min.
• the results of tests of the saws of the invention are excellent in absolute value, and systematically better in every respect than those of the reference saws.
• the debinding, sintering and brazing operations were carried out in an oven under H 2 .
• the beads obtained were threaded onto steel cables at the rate of 37 beads / linear meter, then the assembly was plasticized to stiffen it.
• the powder according to the invention used pure, has good cold compressibility and densifies very well from 900 ° C. (97% of its theoretical density), in particular when it is obtained by mixing the powders I and II as previously defined.
• the hardness obtained after sintering can be considered insufficient for granite cutting, but would be sufficient for cutting marble.
• the addition of 15% iron phosphide or nickel increases the densification and hardness of the sintered parts in a way that makes them perfectly suitable for cutting granite.
• a "mixture 1" mixture under CO 2 was prepared for 50 min from commercial Fe, Co and Cu powders as shown in Table 6: ⁇ u> Table 6 ⁇ / u>: characteristics of the mixture 1 Element Fisher average particle size ⁇ Fis ( ⁇ m) Percentages by weight Iron (%), 4 50 Cobalt (%) 1.5 15 Copper (%) 3 35 Oxygen (%) - 0.8 ⁇ Fis ( ⁇ m) of Mixture 1 - 3.46
• the weight percentages of metals are expressed excluding oxygen content.
• This composition is in the middle of the range of the pre-alloyed powder according to the invention.
• the weight percentages of metals and phosphorus are expressed excluding oxygen content.
• PS21-type parts were compressed at 200 MPa.
• the powder according to the invention in particular in its additive version, is easily granular, which makes it possible to produce thin segments and diamond threads by inexpensive methods. It is easily sinterable in the presence of diamonds, whether in a static oven or in a scrolling oven, both in powder form and in the form of granules. It responds very well to the problems posed.
• powder according to the invention could also be used with advantage for making cutting tools by methods other than those described.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Powder Metallurgy (AREA)
• Polishing Bodies And Polishing Tools (AREA)

Priority Applications (1)

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Publications (2)

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• 2006
  • 2006-10-04 FR FR0608709A patent/FR2906739B1/fr active Active
• 2007
  • 2007-10-04 KR KR1020097006955A patent/KR20090060330A/ko active Search and Examination
  • 2007-10-04 PT PT78483187T patent/PT2082072T/pt unknown
  • 2007-10-04 CN CN2007800426962A patent/CN101541990B/zh active Active
  • 2007-10-04 ES ES07848318.7T patent/ES2663267T3/es active Active
  • 2007-10-04 HU HUE07848318A patent/HUE036676T2/hu unknown
  • 2007-10-04 PL PL07848318T patent/PL2082072T3/pl unknown
  • 2007-10-04 DK DK07848318.7T patent/DK2082072T3/en active
  • 2007-10-04 EP EP07848318.7A patent/EP2082072B1/fr active Active
  • 2007-10-04 WO PCT/FR2007/001622 patent/WO2008040885A2/fr active Application Filing

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