DE2011516A1 - Metal band grinding tools and manufacturing process - Google Patents

Description

-IT 605

Patent attorneys

Munich £ 7 P-. ', "' ^ • - ^jLa R

JS o r t on Company, v / orcester / Massachusetts (by SteV.A.).

Metal band grinding tools and manufacturing process

The invention relates to grinding tools with a metal bandage and in particular a method of making abrasive articles whose abrasive particles are relatively spaced apart show each other ».

So far, grinding tools with metal bandage 'after several Process produced, Of these processes, the cold pressing and sintering process is probably the most widespread found and primarily because of its economy. In this process, the abrasive particles are temporarily covered with a binding agent, after which a metal powder is added * The preliminary binder causes the metal powder to be delivered to the gun particles remain. This Öemieoh is then converted into a

appropriately designed form filled and under a pressure

2
compressed by for example 5500 kg / cm. The pressed grinding tool is then burned in a furnace at a temperature until the particles of the metal bandage are sintered, the burning preferably being carried out in an inert or non-oxidizing atmosphere. Such a process and the products produced thereby are described in US Pat. No. 2,737,454 (JGDanec).

Another method of making such abrasive tools is by hot pressing. In this procedure a mixture of abrasive particles, e.g. diamond particles, one preliminary binder and made from a metallic binder as in the method described above. This Mixture is then poured into a mold that is resistant to high temperatures and high pressures. Pure these forms thick-walled graphite molds are preferably used. The lorm containing the mixture is then used in a heating press a pressure and at a temperature at which (which) compresses the mixture to almost theoretical density and causing the metallic binder to be sintered. After the mold and its contents have cooled down, it remains dimensionally stable Grinding tool back, This process has not found as widespread use as the cold press sintering process because of the higher cost of hot pressing and more expensive equipment. The higher cost of the hot pressing process will be justified by the possibility of being able to produce somewhat more complicated grinding tools than with the Cold press-sintering process is possible. However, there are also design options for grinding tools in the hot pressing process somewhat limited.

An important contribution to the advancement of technology in the field of the manufacture of abrasive tools with a metal bandage was described some time ago in the American patent _{specification No. 3,316,073 (JG #} Kelso. The Kelso invention was one of the greatest! Advances in overcoming one of the major disadvantages of the two pressing methods mentioned, namely

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the difficulty in uniformly distributing the abrasive grains within the metal association when the volume ratio of the metal association to the abrasive grains is relatively large, ie approximately 1: 1 and more. KeIsο discovered. That with careful circulation of the abrasive grains in the presence of a finely divided metal binder, e.g. WO / Co, while simultaneously spraying with controlled amounts of a moistening agent, e.g. water, or a solution of shellac, dextrin, phenol-formaldehyde resin or the like, each Abrasive grain was coated by itself with a spherical coat of WO / Co powder. - The thickness of this coating may vary depending on the desired distance or the distribution of abrasive grains different in the 'final product are greatly generated. These abrasive grains provided with ™ a coating are then filled into a mold and either cold-pressed and sintered or hot-pressed in an inert atmosphere the metal powder and the abrasive grains have been mechanically bonded before the mixture is poured into the mold for pressing. The finished grinding tool is then largely improved with regard to the uniformity of the distribution of the sole grains. Although methods based on the combination of Kelso invention with the cold pressing and sintering or by hot pressing, M represent a significant advance in the art, have so ^ "these methods still lack on. Of these defects may be mentioned the circumstances that According to the Kelso patent, the abrasive grain size is 60 and more, and that although more complicated grinding tools can be produced by hot pressing, this possibility is limited.

The invention relates to an abrasive tool consisting of abrasive particles from a sintered metallic Material are surrounded, the metallic material consists of a sintered metal powder that the abrasive particles directly surrounds, as well as from a metallic binder, dae that of the abrasive grains and the layer of the metallic

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Material fills the unoccupied volume of the grinding tool.

The invention also provides a method for producing a grinding tool, wherein a powder of a metallic Material on each abrasive particle in the form of a porous Layer is applied, with individual grains containing the abrasive produced, which are filled into a mold after which the spaces between the grains with a metallic binders are filled in »Using heat and pressure, the grains and the binder are then filled with united

The method is particularly suitable for the manufacture of grinding tools, in which abrasive grains, for example from diamond, silicon carbide, boron carbide, boron nitride, aluminum oxide, aluminum oxide-zirconium oxide, zirconium oxide spinel and the like are first embedded in a porous layer of a powder made of a metallic material which is initially bonded to the abrasive grains by means of a temporary binder. The encapsulating layer can be produced to any desired thickness, from a thickness of 1 micron and even less if the grain size of the metal powder is less than 1 micron to a thickness of "5 ₉ Z mm and more if the Abrasive grain size, the dimensions of the grinding tool and the desired spacing of the abrasive grains from one another justify such a thick coating. The encapsulated abrasive particles are then preferably heated, wherein the preliminary binder decomposes and / or evaporates and the grains of metal powder are sintered from which the encapsulating layer If an abrasive with a grain size of 60 or more is used, the method described in the Kelso patent is preferably used, according to which the abrasive grains are embedded in a porous layer of a powder of a metallic material less than 60 on and in particular of 200 and finer, the fine grains are preferably made into a mixture with a sufficient amount of the preliminary binder and a metal powder which is moist to

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is paste-like, whereby the even distribution of the abrasive grains in the metal powder is facilitated, while in the conventional, relatively dry mixture, the abrasive grains seek to separate from the grains of metal powder. The mixture is then made using a grain size 60 corresponding Sieves sieved, whereby individual particles are formed, which can contain one or more grains of loaf, after which the sieved divided mixture is sintered and finally carefully broken open. However, sieving is not absolutely necessary. The moist mixture can be used without prior sieving are sintered, after which the sintered mass is broken up and is then sieved.

Regardless of whether it is spherical particles according to the Kelso invention or the irregularly shaped particles that are produced in the manner described above, the particles are filled into a correspondingly designed shape, and the spaces between the particles are filled with a metallic binder filled. There are basically two ways of doing this. A casting mold is preferably provided which consists of the actual mold chamber and a storage container which is connected to the mold chamber via a channel. After the mold chamber has been filled with the particles containing the abrasive, the reservoir is filled with a metallic binder, "after which the entire mold is assembled and placed in an oven heated to a temperature above the melting point of the metallic binder." Here, the metallic binder is liquefied, and since the storage container is located higher _; x * site as the actual mold chamber, the molten metallic binder flows due to its inherent gravity through the channels into the mold cavity and up through the particles, and fills the spaces between them exploited-t; but an external force can also be exerted on the molten metal, such as in the injection or die casting process. *

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According to another method, a conventional 3? Orm, for example of graphite, with the particles containing the abrasive together with a sufficient amount of one Powder filled with a metallic binder that fills the spaces between the particles. This mixture, can then cold-pressed and subjected to a heat treatment, the metallic material being sintered in the conventional manner or is melted, or the mixture can also be hot-pressed with simultaneous application of heat and pressure, to cause sintering or melting of the metallic binder and if the layer encapsulating the abrasive grains consists of the same material as the binding agent, sintering or melting also takes place,

Although not essential, heating should be used are preferably carried out in an inert or non-oxidizing atmosphere, e.g. in nitrogen, hydrogen, argon or the like in order to avoid oxidation of the metallic materials which comprise the encapsulating layer and the main connecting means form. Furthermore, an inert atmosphere is particularly desirable when diamond abrasive grains are used to create a to avoid decomposition of the diamond caused by oxidation at elevated temperatures.

A larger distance between the sole grains can through can be achieved that the abrasive grains with a very thick encapsulating layer of the powder of the metallic material be provided. For this purpose, you can also use the sole grains first a moderately thick encapsulating layer can be created, after which the spacing between the encapsulated grains is thereby created is increased that these are mixed with particles that consist of only sintered grains of the metal powder without sole grains or that even contain a secondary abrasive or filler material such as boron nitride, silicon carbide, tungsten carbide, Aluminum oxide, boron carbide, aluminum oxide-zirconium oxide, zirconium oxide spinel or mixtures of these substances. Using such secondary abrasives or general materials creates a harder and stronger connection than without these substances.

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The embodiment of the invention in which a molten metallic binder in a shaped bed of particles is poured, is in the lall of special value and use, when the metallic binder from the commonly used Bronze or silver solders. Since such binders do not wet diamonds, conventional manufacturing processes are used Diamond grains are produced with only a weak association. However, the abrasive grains are first turned into a porous one Powder embedded in a metallic material, and is a molten metallic binder is poured into the spaces between the encapsulated abrasive grains the encapsulating layer is impregnated with the molten metal ned, whereby the particles are permanently united with one another.

The invention will now be described in detail. In the attached drawing is the »

■■ ψ ' - - ■ "■

Fig! a partially | drawn as a section side view a grinding wheel used to grind the edge of a lens, the complex J-shape of part 14 the grinding wheel is shown,

Figo2 a. vertical section through a graphite mold to

. Enriched testify complicated grinding tools which is poured into the 3? grinding tool shown Ig.1, wherein a molten metallic binder in the intermediate spaces between the M rule encapsulated abrasive grains same,

Figure 3 is a section through an irregularly shaped encapsulated Abrasive particles made by the screening process described above, and the

4 shows a vertical section through a graphite mold with which at the same time the core or the core carrying the abrasive and the portion containing the abrasive of the grinding tool can be produced.

The invention relates to grinding tools, the volume wise $ 1 or more abrasives included.

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In order to be able to use the invention successfully, certain restrictions must be observed with regard to the fact which metallic encapsulating material powder is combined with which metallic binder, which substances the may have the same metallic composition or of must be different from one another, depending on which particular embodiment of the invention is used.

This can be done using the Kaptpress and sintering process encapsulating material and the binding agent consist of the same material, ZoB. made of tungsten carbide, or it can be different Materials are used, e.g. bronze and Y / olf ramkarbid, as long as both materials can be sintered at an achievable processing temperature.

With the simultaneous application of heat and pressure, the same or different materials of the type mentioned can be used are used «If the materials have the same composition, the selected material needs to be available for the standing hot pressing temperatures only to be meltable or sinterable. On the other hand, ground two different materials used, the metallic binder should melt or sinter at a temperature which is below the melting temperature of the encapsulating material.

Using the third and preferred embodiment of the invention is the choice of materials for the encapsulating Layer and even more limited for the binder. It is important here that the porous, encapsulating the abrasive grain Layer is impregnated by the metallic binder. For this purpose, the metallic binder must be melted or be liquefied at a temperature that is significantly below the softening temperature of the encapsulating material, the interstices between the particles with the binder having a relatively low melting point filled in and the pores in the encapsulating layer itself, the result is a powerful, dense grinding tool of high quality generated. With the help of this process, swash plates can be manufactured reliably and at low cost Abrasive surfaces have every degree of intricacy, like

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2011518

those grinding wheels that are used to grind carbide cutting tools, so that grinding wheels and grinding tools can now be produced in any Jorm for which a press form can be produced * 11g.1 shows an embodiment of a grinding wheel for grinding the edges of lenses, This grinding wheel has a solid core 10 with a mandrel hole 12 in the middle, with the grinding section 14 containing the abrasive being attached to the circumference of the core 10. A simple embodiment of a mold for öießen slices of grinding after lig.1 is shown as a section in the i _o ¹ ig 2 ·. The mold consists of the graphite sheet 16, which is split at 18 and has the recess 17 and contains the lower part of the cylindrical 'G-raphite bushing 20 and the sraphite supply container 22. The storage container 22 is provided with a projection 24 which fits into the recess 17 in the middle of the sapphite crucible 16 and serves to center the storage container 22 in the graphite crucible 16. The lower part of the reservoir 22 is provided with a series of holes 26 "concentric with the extension 24" and through which the molten metallic material 40 can flow into the channel 28 and ultimately into the cavity 30 The storage container forms the inner wall of the 'mold cavity 30 and, together with the bottom of the crucible 1.6, the channel 28,: ■ - .-. ■■■. ■ - ■ - .: - ■■' ■ '-

- To use this shape, parts 1: 6 ^r and 16 ^st; of the crucible 16 attached to one another, for example by means of a steel band, after which the storage container 22 is inserted into the crucible 16 and ^; with Ml # e of the attachment 24 and the recess 17 in the crucible emif ^ e ^^ wir'd ". A previously calculated volume of encapsulated abrasive grains 52 is poured into the lörmhohlraum 30. Then ifi * ¹ 'socket' 20 is inserted and The storage container 22 is filled with the metallic binding agent, after which the entire "arrangement" is heated to a temperature above the melting point of the binding agent. The force exerted by the head of the 'melted metallic' binder 40 pushes the liquid into the porous cavity 40, which forms the intermediate spaces 38

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between the encapsulated particles 32 and into the Pores of the encapsulating layer 36 on which the abrasive grains penetrate. After that, the whole thing is cooled, after which the arrangement is disassembled without difficulty and the generated Grinding wheel ring can be easily removed.

Another advantage of the device according to the invention is to see that the core together with the section of the grinding wheel containing the abrasive grains in one operation can be made so that the two parts do not need to be attached to each other in a further operation. For this purpose a shape according to FIG. 4 can be used. This shape is similar to the shape according to FIG. 2 in that it has the same graphite crucible 16 split at 18 with the parts 16 'and 16 ", which has the! Mold cavity 30 for the manufacture of the grinding section, as well as the recess 17 on the inner bottom surface of the crucible. In this embodiment of the mold, however, there is still a plug 46 with a T-shape Channel 48 is provided, which establishes a connection between the part of the mold cavity provided for the core of the grinding wheel and the lower part of the reservoir 52 »The Storage container 52 is designed so that it fits well into the Crucible 16 fits into it and is provided with an opening 54 into which the plug 46 fits so that the complete Mold cavity consists of the part 50 for shaping the grinding wheel core and the part 30 for shaping the grinding section.

For the simultaneous casting of the core and the grinding section, the two parts 16 ¹ and 16 ^{n of} the crucible 16 are assembled and connected to one another by a metal band, after which the plug 46 is inserted into the recess 17. Thereafter, a thin walled hollow cylinder 56 is centered in the mold and the appropriate volume of encapsulated abrasive grain 32 is poured into the space between the cylinder 56 and the portion 30 of the mold cavity. Thereafter, porous metallic particles 58 with or without secondary abrasives or fillers are filled into the part 50 of the mold provided for the production of the grinding wheel core. The thin-walled cylinder 56 is then removed. The storage container 52 is at the loading

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-U-

The right place is inserted into the mold, with which the construction of the mold is finished solid metallic binder filled, and the whole arrangement is heated to the melting point of the metallic binder 40, so that the binder becomes liquid and through the channel 48 flows into the mold cavity and fills the spaces between the particles in the two parts 50 and 30 of the mold. After the mold has cooled down, it is taken apart so that the complete grinding wheel consisting of the core and the grinding section can be removed.

If the grinding tool to be produced has a relatively simple shape, then the one containing the abrasive can Part and the core of the grinding tool made in the way be that the spaces between the particles be filled with a powder of a metallic binder, after which the whole is cold-pressed and sintered or hot-pressed is described as frosted.

Instead of the encapsulated spherical one shown Particles 32 can be the irregularly shaped particles produced by the method described above and are shown in FIG. In the case of these particles, the encapsulating coating 42 has an irregular shape Form and contains one or more abrasive grains 44. This special type becomes important when using abrasive grains with the grit 60 and finer can be used.

The grinding tools produced by this process differ significantly from those produced by the processes already known manufactured products insofar as when examining a grinding section with a microscope, the encapsulated particles are clearly against the metallic binder lift up. This is especially noticeable when using the casting process This also applies if the cold press-sintering process is used or the hot pressing process is used, and when the encapsulating metallic material has a different particle size and a different chemical composition than the metallic binder * V / iron the two metallic materials the same particle size and the same chemical

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Composition, so they are not so easily distinguishable from the metallic binder.

Some examples of the application of the invention are described below.

Example I.

A metal-bonded cylindrical section containing diamond splits, which is attached to a drive means and together with this constitutes a core drill, was produced in such a way that first the volume of the diamond split section and then the amount of diamond chip required in this volume was calculated, which calculation is to a diamond concentration of 100 (25 vol. $), ie the ratio is 10 cnr to 2.5 cnr - 8.775 grams). The 8.775 gram batch of 46 grit diamond split was encapsulated in a layer of powder composed of $ 90 tungsten carbide and 10 ^ lobalt by weight as taught in the Kelso patent. The Wu / Go sheet was made to a thickness such that the volume of the Wu / Oo light was approximately equal to the volume of the abrasive. The encapsulated abrasive grains then had a true volume of 5 cm. In the same method, an amount of 20 cm and of Wu / Co-free particles were made of abrasive grains of essentially the same size as the abrasive grains containing the particles. A sufficient length of these particles was mixed with the diamond split containing the particles to give a loose amount of 10 cm. These were then heated for 30 minutes in nitrogen at 55O ⁰ O to the preliminary binder to be removed, followed by heating to 95O ⁰ C in nitrogen was carried out, wherein the Wu / Co powder was sintered. To a small extent, there was sintering between the particles themselves; however, the agglomerations could easily be broken open with the fingers. A mold with a simple, smooth-walled cylinder instead of the specially designed molding 30 according to Pig.2 was partially assembled, and the 10 cm iOrm hollow was filled with 10 cm loosely packed encapsulated diamond split and WC / Go particles, after which the mold was completely was put together. The reservoir was filled with pure bronze powder made by weight

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_-; / - 13 - 20-1 ί-51.6; "

$ 20 tin and $ 80 copper. The entire arrangement was then placed in an oven and heated to 1050 ^ 0 for 30 minutes in a hydrogen atmosphere. Here was the bronze powder melted and flowed in the lorm because of the higher altitude into the Jorm cavity, the spaces between filled with the particles and the porous, encapsulating WC / Cosciiicht around the diamond grains and the WC / Co particles with the bronze were impregnated. The Eorm was out of the oven taken out, cooled and taken apart, so that the diamond section could be removed. This was then with Help a silver solder and a flux on one with one Adapting piece equipped steel pipe soldered on, one of which Core drill was created that attached to "a! Propellant." can be.

Besides the used WC / Co, other carbides, such as Wp-.Q> BC or the like or one of the many Disen-iFiekel carbon _e nstoff alloys for the present purpose suitable, requiring only that for encapsulating the abrasive grains metallic material used and the material used for the split-free particles has a melting point which is above the melting point of the metallic binder. For the same reason, a bronze was used as the binder, however, other metallic materials such as silver solder, brass and the like can and are also used

B e is "ρ 1 e 1 II

As described in Example I in the same manner, a grinding wheel after the Mg ₀ 1 was prepared "with the exception that in this! 'All the diamond Split having the grain 100, the method described above in the preparation of the baths / Co encapsulated abrasive grain containing particles and the abrasive grain free particles was applied The diamond containing particles were prepared in such a way that equal real volume parts of diamond grit and WC / Co powder with about 5% by weight of a 10% solution by weight of paraffin were thoroughly mixed in 1,1,1-trichloroethane, creating a moist mixture that passed through a sieve

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was sieved with a mesh size of 240 microns, producing a small amount of individual, irregularly shaped particles, as shown in the jig x 3. These particles were then treated with heat as described in Example I, after which the agglomerate was carefully broken up. A length of split-free Wo / Co particle was prepared in the same manner. All diamond-containing particles were mixed with a sufficient amount of split-free particles, which mixture had an apparent total volume of 10 cm. This mixture was poured into a mold according to FIG. The procedure described in Example I was otherwise used. The intricately shaped Diaaiant section was soldered with silver to a steel disk with the appropriate dimensions, whereby a grinding wheel shown in Fig. 1 was produced, which can be used for grinding the edges of ceramic plates and other artifacts,

Example III

A diamond core drill was completely bonded with Y / C / Co, but in the design according to Example I was produced in such a way that diamond-containing and diamond-free particles were first produced in the exact amounts given in Example I and in the same way. Instead of filling the total amount of 10 cm of split-containing and split-free particles into a casting mold, the particles were mixed with approximately 14 grams of a powder mixture of 75 ι 25 wt, $ WO / Go and poured into a conventional graphite mold. The mold was then heat-pressed at a temperature of 1200 G for about 15 minutes under a pressure of 472 kg / cm.

In this case, 14 grams fill dec, _fa eainberfcen YC / ΰο powder aiu the interstices between the particles; instead of the molten bronze, as in Examples I and II.

Example IY

A diamond core drill according to Example I was used in dor Manufactured from the diet split encapsulated in WC / Go and the aplit-free particles were prepared in the manner described in Example II, after which the 10 cm split-containing and

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split-free particles. with §, 6 grams of a G-emiseh.es of 80: wt. & Cu / Sn were mixed. Thereafter, the mixture was poured into a steel mold of conventional design and under a Druck.von about 5500 kg / cm pressed, and finally, the cold-pressed diamond portion was sintered 30 minutes at a temperature of 900 ⁰ C long.

In this embodiment of the invention, the fill 8.6 g of the sintered bronze powder instead of the sintered WO / Co according to the example III.

Claims

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Claims (1)

Claims Abrasive tool with abrasive particles from a sintered metallic material, characterized in that the metallic material consists of a powder a sintered metallic material which immediately surrounds the particles of the abrasive material, and that the volume of the grinding tool not occupied by the grinding material and the layer of metallic material a metallic binder is filled. Grinding tool according to claim 1, characterized in that the metallic binder consists of another metallic Material exists as the sintered metal. 5. Grinding tool according to claim Z _1, characterized in that the sintered metallic material is impregnated with particles of the abrasive material which are coated with a sintered metal, and that the particles are connected to one another by a molten metallic binder. 4ο grinding tool according to claim 3, characterized in that that the sintered metal consists of a metal carbide, and the metallic binder of bronze, brass or Silver solder is made. 5. Grinding tool according to claim 1 or Z, characterized in that the sintered material consists of a coating on the abrasive containing grains, which grains are connected to one another by a sintered uetallic binder. 009837/1589 6 _β grinding tool according to claim 5, characterized in that said coating as well as the metallic binder consists essentially of tungsten carbide-cobalt or of iron-nickel-carbon alloys. 7. Process for producing grinding tools with an IVletail bond, wherein a powder of a metallic material is applied to abrasive particles, which material in is subjected to a form of the action of heat and pressure, characterized in that a powder of a metallic material is formed on each abrasive particle a porous layer is applied, with grains that contain the abrasive that the coated abrasive grains into a corresponding designed lOrmhohlrauin that the Gaps between the said grains are filled with a metallic binder, and that the Grains and the binder are permanently combined with one another using heat and pressure » 8. The method according to any one of claims 1 to 7> characterized in that that the porous particles ,. made from the powder of a metallic material and free of abrasives are mixed with the particles containing the abrasive in such proportions that a Grinding tool is generated, as a minimum in terms of volume 1j6 contains abrasive split. _ ' 9 · Method according to one of claims 1 and 2, 7 and 8, characterized in that the metallic material powder has a higher melting point than the metallic Binder, and that the binder is added in the molten state under pressures that either come from the Head of the molten metal and / or from the outside exerted pressures exist. , 009837/1589 - I ο - 10. The method according to any one of claims 1 and 2 and 7 and 8, characterized in that the metallic binder consists of a powder that the heat is supplied from an external heat source and that the pressure is mechanical is exercised. 1. The method according to any one of claims 1-4 and 7-10, characterized in that the abrasive grains with the Abrasive material along with one to moisten the mixture Sufficient amount of preliminary binder to be mixed in that the moist mixture passes through a sieve is driven, the meshes of which are larger than the ± Yorns of the abrasive material, with a plurality of irregular formed composite particles, and that the resulting particles are heated to remove the preliminary binder and the metallic Sintering material powder. 12. The method according to any one of claims 1-4 and 7-10, characterized characterized in that the abrasive grains together with the metallic fluid powder and a temporary binder are circulated, forming a plurality of spherical particles containing the abrasive will. 13. The method according to any one of claims 6-12, characterized in, that the spherical and the abrasive containing Particles are heated to remove the preliminary binder and to turn the metal before material powder sinter. 009837/1589