EP0739262A1 - Abrasive grinding wheels - Google Patents

Abrasive grinding wheels

Info

Publication number
EP0739262A1
EP0739262A1 EP95916737A EP95916737A EP0739262A1 EP 0739262 A1 EP0739262 A1 EP 0739262A1 EP 95916737 A EP95916737 A EP 95916737A EP 95916737 A EP95916737 A EP 95916737A EP 0739262 A1 EP0739262 A1 EP 0739262A1
Authority
EP
European Patent Office
Prior art keywords
grinding wheel
wheel according
fibers
metallic
volume
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP95916737A
Other languages
German (de)
French (fr)
Inventor
Bernard Buffat
Patrick Micheletti
Michel Bousquet
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Saint Gobain Abrasifs SA
Original Assignee
Norton SA France
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Norton SA France filed Critical Norton SA France
Publication of EP0739262A1 publication Critical patent/EP0739262A1/en
Withdrawn legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
    • B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
    • B24D3/34—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents characterised by additives enhancing special physical properties, e.g. wear resistance, electric conductivity, self-cleaning properties
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
    • B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
    • B24D3/02—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent
    • B24D3/20—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents the constituent being used as bonding agent and being essentially organic
    • B24D3/28—Resins or natural or synthetic macromolecular compounds
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
    • B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
    • B24D3/34—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents characterised by additives enhancing special physical properties, e.g. wear resistance, electric conductivity, self-cleaning properties
    • B24D3/342—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents characterised by additives enhancing special physical properties, e.g. wear resistance, electric conductivity, self-cleaning properties incorporated in the bonding agent
    • B24D3/344—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents characterised by additives enhancing special physical properties, e.g. wear resistance, electric conductivity, self-cleaning properties incorporated in the bonding agent the bonding agent being organic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
    • B24D7/00—Bonded abrasive wheels, or wheels with inserted abrasive blocks, designed for acting otherwise than only by their periphery, e.g. by the front face; Bushings or mountings therefor
    • B24D7/02—Wheels in one piece
    • B24D7/04—Wheels in one piece with reinforcing means

Definitions

  • the invention relates to abrasive wheels, and more precisely to abrasive wheels with organic agglomerating, used in particular for refining, grinding, surfacing, deburring or more generally the various usual types of machining.
  • Abrasive wheels consist of abrasive particles embedded in a matrix based on an organic resin, for example of the phenolic or polyimide type.
  • the matrix is generally reinforced by means of glass fibers.
  • heating of the grinding wheel due to friction can cause degradation of the organic resin which, at least on the surface, is no longer able to retain the abrasive particles.
  • the diameter of the wheel decreases little by little until the replacement of the wheel is necessary.
  • the object of the present invention is to provide abrasive wheels with organic agglomeration, the life of which is improved.
  • the invention relates to an abrasive wheel comprising abrasive particles embedded in an organic binder, and which further comprises a reinforcement in the form of metallic fibers.
  • metallic fibers can be used in conjunction with traditional reinforcing fibers such as glass fibers.
  • the metallic reinforcing fibers advantageously replace the glass fibers and confer significantly improved mechanical properties with an equivalent quantity of fibers.
  • this type of reinforcement is a good thermal conductor, which allows good heat dissipation over the entire volume of the grinding wheel and thus reduces the risk of degradation of the organic matter.
  • the nature of the electrical conductor of the metal reinforcement makes it possible to control the wear of the wheel by means of contactless sensors.
  • the metallic fibers have the following dimensional characteristics: a length of 5 to 30 mm, preferably from 10 to 20 mm.
  • they are chosen in the form of ribbons, presenting, in particular, a width of 0.5 to 7 mm, in particular from 1 to 5 mm, and a thickness of less than 5 / 10ths of a mm, in particular of the order of 2 to 3/10 th of a mm.
  • these metallic fibers or ribbons can be chosen from metallic “glass”.
  • This term denotes a metallic material frozen in the vitreous state, which can be obtained in particular by a process called hyperhardening.
  • patent FR-2,486,838 corresponding to American patents US-4,520,859 and US-4,562,877. It is in fact a question of suddenly cooling a jet of molten metal coming out of an ejection orifice above which is a strip moving at high speed.
  • one of the faces of said strip and in the vicinity of the impact zone of the metal or of the alloy or of the molten metal is disposed at least one box comprising at least one fluid ejection orifice under pressure, preferably at low temperature, creating between the strip and the box a fluid cushion keeping it without friction on the box.
  • the molten metal or alloy comes into contact with the strip, it undergoes what is called hyperhardening, and it freezes to form a metallic ribbon in the vitreous state.
  • amorphous metallic ribbons have quite interesting properties, they are in particular particularly ductile and “flexible” while being particularly resistant on the mechanical level. Any other tempering process which makes it possible to obtain such metallic “glasses” can of course be used.
  • the metallic glasses used in the context of the invention can be based on alloys of the AxB ⁇ type where A consists of one or more transition metals (Fe, Cr, Ni, Mn, Co, ...) and B of one or more metalloids (P, C, Si, B, ...) and where x, which is the atomic fraction of A, can in particular be of the order of 0.8. It can also be, for example, amorphous cast iron.
  • Metallic fibers or ribbons are generally used at a volume of between 1 to 4% of the total volume of the manufactured wheel.
  • the mechanical resistance increases with the quantity of fibers used; however, the volume of the grinding wheel before forming by pressing the mixture and polymerizing the resin also increases, so that the molding and demolding operations can become critical beyond a certain volume of fibers or ribbons.
  • Very satisfactory results are obtained with a volume of fibers or ribbons representing approximately 1.2% to 4% of the total volume of the manufactured grinding wheel, and more generally of the order of 2 to 3% of the total volume of the grinding wheel.
  • the organic binder used to manufacture the grinding wheels according to the invention is preferably based on phenolic resins and / or polyimides.
  • the abrasive particles which are embedded in this agglomerant are, in known manner, preferably of ceramic material of the alumina type, which can also include a low level of impurities or "dopants", in particular traces of metals of the Zr or Fe type.
  • abrasive particles advantageously correspond to a volume of 40 to 70% of the total volume of the grinding wheel, in particular to approximately 50 to 65% of said volume. This proportion of particles can in fact be modulated as a function of the abrasive power of the grinding wheel sought.
  • these abrasive particles are grains, in the form of particles or sticks, having an average diameter (respectively a length) of 1 / 10th of mm to 3 mm, in particular of approximately 1.5 mm.
  • the size of the grains will be selected according to the use of the grinding wheel, in particular the degree of polish of the part to be obtained.
  • FIG. 1 comparative curves illustrating the mechanical properties of a grinding wheel according to the prior art and of grinding wheels according to the invention
  • Abrasive wheels with organic bonding agent are obtained by kneading the abrasive grains with a bonding agent, here a phenolic resin, and reinforcing fibers or tapes.
  • a bonding agent here a phenolic resin
  • the distribution of reinforcing fibers should be as homogeneous as possible.
  • the mixture ready, it is weighed and poured into a pressing mold.
  • the grinding wheel is then driven, in a heating press and then in an oven where the resin is polymerized at a temperature of the order of 180 ° C., for an average duration of approximately 24 to 36 hours.
  • the reinforcing fibers used are preferably ribbons of thin metallic glass, tempered by casting on a cold substrate - generally a wheel - continuously traveling.
  • these are ribbons of amorphous cast iron obtained by hyper quenching, as can be obtained by the process described in the aforementioned patents. They have a length of about 1 5 mm, a width of about 2 to 3 mm and a thickness of 2 to 3/10 mm.
  • the metal ribbons are preferably added at the rate of a fraction of the volume of the variable manufactured grinding wheel and between 1 and 4%, as explained later.
  • the volume of the mixture before cooking undergoes a relatively large swelling which can cause some problems during the filling of the mold, before the pressing operation, and later, during the demolding. This is why it is preferable to limit oneself to volumes of metallic ribbons of at most 4%. It may further be noted that a homogeneous mixture is all the easier to prepare the smaller the amount of fibers.
  • the pressing operation and the long and flat shape of the ribbons having a sufficiently large length / width ratio result in the preferred alignment of the ribbons in the plane perpendicular to the axis of the grinding wheel.
  • the radial arrangement of the reinforcing fibers which results from it favors the propagation of heat towards the central part of the grinding wheel, so that the heat is dissipated on the whole of the grinding wheel.
  • the abrasive particles are here in alumina, in the form of grains with an average diameter of approximately 1.5 mm, and they are incorporated into the agglomerating agent in an amount corresponding to approximately 62% of the total volume of the grinding wheel.
  • the grinding wheels according to the invention were tested from the point of view of their mechanical behavior and their thermal behavior, by comparing the results with that of reference grinding wheels, of the same dimensions and of an identical composition except for the nature reinforcing fibers and possibly their quantity.
  • the reference wheel contains 4% by volume of so-called reinforcing glass fibers.
  • the wheels tested have the form of cylindrical rings with an outside diameter of 61 0 mm, an inside diameter of 203 mm and a height of 76 mm. Grinding wheels of this type are used at a peripheral speed generally between 60 and 80 m / s; however, as a safety measure, it is desirable that the burst speed be greater than 150 m / s.
  • the reference wheel explodes at 5380 revolutions / minute, or 1 71 m / s.
  • the superior mechanical behavior of the grinding wheels according to the invention also emerges very clearly from the following rupture test: a full cylindrical wheel 26 mm in diameter for a height of 20 mm is pinched, on its edge, between two jaws, that the we just tighten until the part is broken.
  • the rupture obtained is, paradoxically, a failure similar to a failure in traction and therefore is very significant of the actual behavior of an abrasive wheel.
  • FIG. 1 the values of the compression at break measured on a series of 8 test pieces arbitrarily numbered from 1 to 8 are plotted for each series.
  • the first series corresponds to test tubes corresponding to the reference composition, that is to say a reinforcement by 4% of glass fibers.
  • the other two series, bearing for legend test n ° 1 or test n ° 2 correspond to compositions according to the invention, namely 1.41% by volume of metal ribbons for test n ° 1 and 4% by volume of ribbons for the test n ° 2.
  • the average gain compared to the reference wheel is 8% for the test n ° 1 series and 24% for the test n ° 2 series.
  • the thermal behavior of the grinding wheels was tested by placing between two platens of a press, heated to about 170 ° C, a first control bar whose composition corresponds to the reference grinding wheel and a second bar whose composition corresponds to that of the grinding wheel of test n ° 1. Bar temperatures are measured every minute using two thermocouples. The values are shown in Figure 2 (the circles corresponding to the temperature of the reference bar and the squares under test n ° 1). After a period of about a quarter of an hour, the temperature of the bars stabilizes, at a value of about 55-56 ° C for the bar according to the invention.
  • the bar corresponding to a grinding wheel according to the invention therefore heats up significantly more than the bar corresponding to the reference grinding wheel, which indicates that it has lost a good part of its insulating character.
  • the temperature rise of the bar according to the invention is a little faster, which is more especially advantageous. The effect of the metallic character of the ribbons is thus clearly demonstrated.
  • the quantity of metal present in the grinding wheels according to the invention is large enough to allow continuous monitoring using non-contact sensors, this for example to systematically check the value of the outside diameter of the grinding wheel and therefore its state of wear.
  • the grinding wheels according to the invention not only are more solid mechanically, but also make it possible to increase the quality of the machining of the ground parts: the fact that the grinding wheels according to the invention promote rapid heat dissipation prevents the ground parts from blackening or "burning" by excessive heating.

Abstract

Abrasive grinding wheels comprising an organic binder and reinforcing metallic fibres. Preferably, said fibres are glass metallic strips. The wheels of the invention have a long service life and are conductive.

Description

MEULES ABRASIVES ABRASIVE WHEELS
L'invention concerne des meules abrasives, et plus précisément les meules abrasives à agglomérant organique, utilisées notamment pour l'affinage, la rectification, le surfaçage, l'ébardage ou plus généralement les différents types usuels d'usinage.The invention relates to abrasive wheels, and more precisely to abrasive wheels with organic agglomerating, used in particular for refining, grinding, surfacing, deburring or more generally the various usual types of machining.
Il est connu des meules abrasives constituées par des particules abrasives noyées dans une matrice à base d'une résine organique, par exemple du type résine phénolique ou polyimide. Pour conférer une bonne tenue mécanique à ces meules, la matrice est généralement renforcée au moyen de fibres de verre. Au cours des opérations de meulage, échauffement de la meule dû aux frottements peut provoquer la dégradation de la résine organique qui, du moins en surface, n'est plus en mesure de retenir les particules abrasives. Le diamètre de la meule décroît ainsi petit à petit jusqu'à nécessiter le remplacement de la meule.Abrasive wheels are known which consist of abrasive particles embedded in a matrix based on an organic resin, for example of the phenolic or polyimide type. To give good mechanical strength to these wheels, the matrix is generally reinforced by means of glass fibers. During grinding operations, heating of the grinding wheel due to friction can cause degradation of the organic resin which, at least on the surface, is no longer able to retain the abrasive particles. The diameter of the wheel decreases little by little until the replacement of the wheel is necessary.
La présente invention a pour but des meules abrasives à agglomérant organique dont la durée de vie est améliorée. L'invention a pour objet une meule abrasive comprenant des particules abrasives noyées dans un agglomérant organique, et qui comporte en outre un renfort sous forme de fibres métalliques.The object of the present invention is to provide abrasive wheels with organic agglomeration, the life of which is improved. The invention relates to an abrasive wheel comprising abrasive particles embedded in an organic binder, and which further comprises a reinforcement in the form of metallic fibers.
Compte tenu de leur prix de revient légèrement plus élevé, les fibres métalliques peuvent être utilisées conjointement avec des fibres traditionnelles de renforcement telles que les fibres de verre. D'une part, les fibres métalliques de renforcement se substituent avantageusement aux fibres de verre et confèrent des propriétés mécaniques nettement améliorées à quantité équivalente de fibres. D'autre part, ce type de renfort est un bon conducteur thermique, ce qui permet une bonne dissipation de la chaleur sur l'ensemble du volume de la meule et diminue ainsi les risques de dégradation de la matière organique. Avantageusement, en outre, le caractère de conducteur électrique du renfort métallique permet de contrôler l'usure de la roue au moyen de capteurs sans contact.Given their slightly higher cost price, metallic fibers can be used in conjunction with traditional reinforcing fibers such as glass fibers. On the one hand, the metallic reinforcing fibers advantageously replace the glass fibers and confer significantly improved mechanical properties with an equivalent quantity of fibers. On the other hand, this type of reinforcement is a good thermal conductor, which allows good heat dissipation over the entire volume of the grinding wheel and thus reduces the risk of degradation of the organic matter. Advantageously, moreover, the nature of the electrical conductor of the metal reinforcement makes it possible to control the wear of the wheel by means of contactless sensors.
De préférence, les fibres métalliques présentent les caractéristiques dimensionnelles suivantes : une longueur de 5 à 30 mm, de préférence de 10 à 20 mm. Avantageusement, on les choisit sous forme de rubans, présentant, notamment, une largeur de 0,5 à 7 mm, notamment de 1 à 5 mm, et une épaisseur inférieure à 5/10ème de mm, notamment de l'ordre de 2 à 3/1 0ème de mm.Preferably, the metallic fibers have the following dimensional characteristics: a length of 5 to 30 mm, preferably from 10 to 20 mm. Advantageously, they are chosen in the form of ribbons, presenting, in particular, a width of 0.5 to 7 mm, in particular from 1 to 5 mm, and a thickness of less than 5 / 10ths of a mm, in particular of the order of 2 to 3/10 th of a mm.
Avantageusement, ces fibres ou rubans métalliques peuvent être choisies en « verre » métallique. Sous ce terme, on désigne un matériau métallique figé à l'état vitreux, que l'on peut obtenir notamment par un procédé appelé hypertrempe. Pour plus de détails sur cette technique, on pourra se reporter notamment au brevet FR-2 486 838 correspondant aux brevets américains US-4 520 859 et US-4 562 877. Il s'agit en fait de refroidir brusquement un jet de métal fondu sortant d'un orifice d'éjection au- dessus duquel se trouve une bande défilant à grande vitesse. En regard de l'une des faces de ladite bande et au voisinage de la zone d'impact du métal ou de l'alliage ou du métal fondu, est disposé au moins un caisson comportant au moins un orifice d'éjection d'un fluide sous pression, de préférence à basse température, créant entre la bande et le caisson un coussin fluide la maintenant sans frottement sur le caisson. Quand le métal ou l'alliage fondu entre au contact de la bande, il subit ce qu'on appelle une hypertrempe, et il se fige pour former un ruban métallique à l'état vitreux.Advantageously, these metallic fibers or ribbons can be chosen from metallic “glass”. This term denotes a metallic material frozen in the vitreous state, which can be obtained in particular by a process called hyperhardening. For more details on this technique, reference may be made in particular to patent FR-2,486,838 corresponding to American patents US-4,520,859 and US-4,562,877. It is in fact a question of suddenly cooling a jet of molten metal coming out of an ejection orifice above which is a strip moving at high speed. Opposite one of the faces of said strip and in the vicinity of the impact zone of the metal or of the alloy or of the molten metal, is disposed at least one box comprising at least one fluid ejection orifice under pressure, preferably at low temperature, creating between the strip and the box a fluid cushion keeping it without friction on the box. When the molten metal or alloy comes into contact with the strip, it undergoes what is called hyperhardening, and it freezes to form a metallic ribbon in the vitreous state.
Ces rubans métalliques amorphes ont des propriétés tout-à-fait intéressantes, ils sont notamment particulièrement ductiles et « souples » tout en étant particulièrement résistants sur le plan mécanique. Tout autre procédé de trempe permettant d'obtenir de tels « verres » métalliques peut bien sûr être utilisé.These amorphous metallic ribbons have quite interesting properties, they are in particular particularly ductile and “flexible” while being particularly resistant on the mechanical level. Any other tempering process which makes it possible to obtain such metallic “glasses” can of course be used.
Les verres métalliques utilisés dans le cadre de l'invention peuvent être à base d'alliages du type AxB^ où A est constitué d'un ou plusieurs métaux de transition (Fe, Cr, Ni, Mn, Co, ...) et B d'un ou plusieurs métalloïdes (P, C, Si, B, ...) et où x, qui est la fraction atomique de A, peut être notamment de l'ordre de 0,8. Il peut aussi s'agir, par exemple, de fonte amorphe.The metallic glasses used in the context of the invention can be based on alloys of the AxB ^ type where A consists of one or more transition metals (Fe, Cr, Ni, Mn, Co, ...) and B of one or more metalloids (P, C, Si, B, ...) and where x, which is the atomic fraction of A, can in particular be of the order of 0.8. It can also be, for example, amorphous cast iron.
Les fibres ou rubans métalliques sont généralement utilisés à raison d'un volume compris entre 1 à 4 % du volume total de la meule manufacturée. La résistance mécanique croît avec la quantité de fibres utilisée ; toutefois, le volume de la meule avant le formage par pressage du mélange et polymérisation de la résine croît également, de sorte que les opérations de moulage et démoulage peuvent devenir critiques au-delà d'un certain volume de fibres ou rubans. Des résultats très satisfaisants sont obtenus avec un volume de fibres ou rubans représentant environ 1 ,2 % à 4 % du volume total de la meule manufacturée, et plus généralement de l'ordre de 2 à 3 % du volume total de la meule. L'agglomérant organique utilisé pour fabriquer les meules selon l'invention est de préférence à base de résines phénoliques et/ou polyimides. Les particules abrasives qui sont noyées dans cet agglomérant sont, de manière connue, de préférence en matériau céramique du type alumine, pouvant également comprende un faible taux d'impuretés ou de « dopants », notamment des traces de métaux du type Zr ou Fe.Metallic fibers or ribbons are generally used at a volume of between 1 to 4% of the total volume of the manufactured wheel. The mechanical resistance increases with the quantity of fibers used; however, the volume of the grinding wheel before forming by pressing the mixture and polymerizing the resin also increases, so that the molding and demolding operations can become critical beyond a certain volume of fibers or ribbons. Very satisfactory results are obtained with a volume of fibers or ribbons representing approximately 1.2% to 4% of the total volume of the manufactured grinding wheel, and more generally of the order of 2 to 3% of the total volume of the grinding wheel. The organic binder used to manufacture the grinding wheels according to the invention is preferably based on phenolic resins and / or polyimides. The abrasive particles which are embedded in this agglomerant are, in known manner, preferably of ceramic material of the alumina type, which can also include a low level of impurities or "dopants", in particular traces of metals of the Zr or Fe type.
Ces particules abrasives correspondent avantageusement à un volume de 40 à 70 % du volume total de la meule, notamment à environ 50 à 65 % dudit volume. Cette proportion de particules peut en fait être modulée en fonction du pouvoir abrasif de meule recherché.These abrasive particles advantageously correspond to a volume of 40 to 70% of the total volume of the grinding wheel, in particular to approximately 50 to 65% of said volume. This proportion of particles can in fact be modulated as a function of the abrasive power of the grinding wheel sought.
De même, ces particules abrasives sont des grains, sous forme de particules ou bâtonnets, ayant un diamètre (respectivement une longueur) moyen(ne) de 1 /10ème de mm à 3 mm, notamment d'environ 1 ,5 mm. La taille des grains sera à sélectionner en fonction de l'utilisation de la meule, notamment du degré de poli de la pièce à obtenir.Likewise, these abrasive particles are grains, in the form of particles or sticks, having an average diameter (respectively a length) of 1 / 10th of mm to 3 mm, in particular of approximately 1.5 mm. The size of the grains will be selected according to the use of the grinding wheel, in particular the degree of polish of the part to be obtained.
D'autres détails et caractéristiques avantageuses de l'invention ressortent de la description faite ci-après en référence aux dessins annexés qui représentent :Other details and advantageous characteristics of the invention emerge from the description given below with reference to the appended drawings which represent:
* figure 1 : des courbes comparatives illustrant les propriétés mécaniques d'une meule selon l'art antérieur et de meules selon l'invention,FIG. 1: comparative curves illustrating the mechanical properties of a grinding wheel according to the prior art and of grinding wheels according to the invention,
* figure 2 : des courbes comparatives de la conductivité thermique de meules selon l'art antérieur et selon l'invention.* Figure 2: comparative curves of the thermal conductivity of grinding wheels according to the prior art and according to the invention.
Les meules abrasives à agglomérant organique sont obtenues en malaxant les grains d'abrasif avec un agglomérant, ici une résine phénolique, et des fibres ou rubans de renforcement. La répartition des fibres de renforcement doit être aussi homogène que possible. Le mélange prêt, il est pesé et versé dans un moule de pressage. La meule est alors conduite, sous presse chauffante puis dans un four où la résine est polymérisée à une température de l'ordre de 180°C, pendant une durée moyenne d'environ 24 à 36 heures.Abrasive wheels with organic bonding agent are obtained by kneading the abrasive grains with a bonding agent, here a phenolic resin, and reinforcing fibers or tapes. The distribution of reinforcing fibers should be as homogeneous as possible. The mixture ready, it is weighed and poured into a pressing mold. The grinding wheel is then driven, in a heating press and then in an oven where the resin is polymerized at a temperature of the order of 180 ° C., for an average duration of approximately 24 to 36 hours.
Les fibres de renforcement utilisées sont de préférence des rubans de verre métallique minces, trempés par coulée sur un substrat froid - en général une roue - défilant en continu. Ici, il s'agit de rubans de fonte amorphe obtenus par hypertrempe, tels qu'on peut les obtenir par le procédé décrit dans les brevets précités. Ils ont une longueur d'environ 1 5 mm, une largeur d'environ 2 à 3 mm et une épaisseur de 2 à 3/1 0ème de mm.The reinforcing fibers used are preferably ribbons of thin metallic glass, tempered by casting on a cold substrate - generally a wheel - continuously traveling. Here, these are ribbons of amorphous cast iron obtained by hyper quenching, as can be obtained by the process described in the aforementioned patents. They have a length of about 1 5 mm, a width of about 2 to 3 mm and a thickness of 2 to 3/10 mm.
Les rubans métalliques sont ajoutés de préférence à raison d'une fraction du volume de la meule manufacturée variable et comprise entre 1 et 4 %, comme explicité ultérieurement. Le volume du mélange avant cuisson subit un gonflement relativement important ce qui peut poser quelques problèmes lors du remplissage du moule, avant l'opération de pressage, et ultérieurement, lors du démoulage. C'est pourquoi il est préférable de se limiter à des volumes de rubans métalliques d'au plus 4 %. Il peut de plus être noté qu'un mélange homogène est d'autant plus facile à préparer que la quantité de fibres reste petite.The metal ribbons are preferably added at the rate of a fraction of the volume of the variable manufactured grinding wheel and between 1 and 4%, as explained later. The volume of the mixture before cooking undergoes a relatively large swelling which can cause some problems during the filling of the mold, before the pressing operation, and later, during the demolding. This is why it is preferable to limit oneself to volumes of metallic ribbons of at most 4%. It may further be noted that a homogeneous mixture is all the easier to prepare the smaller the amount of fibers.
Du point de vue de la présente invention, il est important de souligner que, de plus, l'opération de pressage et la forme longue et plate des rubans présentant un ratio longueur/largeur suffisamment important ont pour conséquence l'alignement privilégié des rubans dans le plan perpendiculaire à l'axe de la meule. Comme la meule travaille sur sa tranche, la disposition radiale des fibres de renforcement qui en résulte favorise la propagation de la chaleur vers la partie centrale de la meule, de sorte que la chaleur est dissipée sur l'ensemble de la meule. Les particules abrasives sont ici en alumine, sous forme de grains de diamètre moyen d'environ 1 ,5 mm, et elles sont incorporées dans l'agglomérant en une quantité correspondant à environ 62 % du volume total de la meule.From the point of view of the present invention, it is important to emphasize that, moreover, the pressing operation and the long and flat shape of the ribbons having a sufficiently large length / width ratio result in the preferred alignment of the ribbons in the plane perpendicular to the axis of the grinding wheel. As the grinding wheel works on its edge, the radial arrangement of the reinforcing fibers which results from it favors the propagation of heat towards the central part of the grinding wheel, so that the heat is dissipated on the whole of the grinding wheel. The abrasive particles are here in alumina, in the form of grains with an average diameter of approximately 1.5 mm, and they are incorporated into the agglomerating agent in an amount corresponding to approximately 62% of the total volume of the grinding wheel.
Les meules selon l'invention ont été testées du point de vue de leur comportement mécanique et de leur comportement thermique, en comparant les résultats avec celui de meules de référence, de mêmes dimensions et d'une composition identique à l'exception de la nature des fibres de renforcement et éventuellement, de leur quantité. La meule de référence comporte 4 % en volume de fibres de verre dites de renforcement. Les meules testées ont la forme d'anneaux cylindriques avec un diamètre extérieur de 61 0 mm, un diamètre intérieur de 203 mm et une hauteur de 76 mm. Des meules de ce type sont utilisées à une vitesse périphérique généralement comprise entre 60 et 80 m/s ; toutefois, par mesure de sécurité, il est souhaitable que la vitesse d'éclatement soit supérieure à 1 50 m/s. La meule de référence éclate à 5380 tours/minute, soit 1 71 m/s. Une meule selon l'invention avec un pourcentage de fibres métalliques de 2 % éclate à 5000 tours/minute, soit une vitesse de 1 60 m/s. La meule selon l'invention, à 4 % de fibres métalliques, a supporté sans dégradation apparente une rotation à 5400 tours/minute. La supériorité du comportement mécanique des meules selon l'invention ressort également très clairement du test de rupture suivant : une roue cylindrique pleine de 26 mm de diamètre pour une hauteur de 20 mm est pincée, sur sa tranche, entre deux mâchoires, que l'on vient serrer jusqu'à obtenir le bris de la pièce. La rupture obtenue est, paradoxalement, une rupture analogue à une rupture en traction et de ce fait, est très significative du comportement réel d'une meule abrasive. Sur la figure 1 , on a reporté les valeurs de la compression à la rupture mesurées sur une série de 8 éprouvettes arbitrairement numérotées de 1 à 8 pour chaque série. La première série correspond à des éprouvettes répondant à la composition de référence, soit un renforcement par 4 % de fibres de verre. Les deux autres séries, portant pour légende essai n° 1 ou essai n° 2 correspondent à des compositions selon l'invention, soit 1 ,41 % en volume de rubans métalliques pour l'essai n° 1 et 4% en volume de rubans métalliques pour l'essai n° 2. Le gain moyen par rapport à la meule de référence est de 8% pour la série essai n ° 1 et de 24% pour la série essai n° 2.The grinding wheels according to the invention were tested from the point of view of their mechanical behavior and their thermal behavior, by comparing the results with that of reference grinding wheels, of the same dimensions and of an identical composition except for the nature reinforcing fibers and possibly their quantity. The reference wheel contains 4% by volume of so-called reinforcing glass fibers. The wheels tested have the form of cylindrical rings with an outside diameter of 61 0 mm, an inside diameter of 203 mm and a height of 76 mm. Grinding wheels of this type are used at a peripheral speed generally between 60 and 80 m / s; however, as a safety measure, it is desirable that the burst speed be greater than 150 m / s. The reference wheel explodes at 5380 revolutions / minute, or 1 71 m / s. A grinding wheel according to the invention with a percentage of metallic fibers of 2% bursts at 5000 revolutions / minute, that is to say a speed of 1 60 m / s. The grinding wheel according to the invention, with 4% of metallic fibers, supported without apparent degradation a rotation at 5400 revolutions / minute. The superior mechanical behavior of the grinding wheels according to the invention also emerges very clearly from the following rupture test: a full cylindrical wheel 26 mm in diameter for a height of 20 mm is pinched, on its edge, between two jaws, that the we just tighten until the part is broken. The rupture obtained is, paradoxically, a failure similar to a failure in traction and therefore is very significant of the actual behavior of an abrasive wheel. In FIG. 1, the values of the compression at break measured on a series of 8 test pieces arbitrarily numbered from 1 to 8 are plotted for each series. The first series corresponds to test tubes corresponding to the reference composition, that is to say a reinforcement by 4% of glass fibers. The other two series, bearing for legend test n ° 1 or test n ° 2, correspond to compositions according to the invention, namely 1.41% by volume of metal ribbons for test n ° 1 and 4% by volume of ribbons for the test n ° 2. The average gain compared to the reference wheel is 8% for the test n ° 1 series and 24% for the test n ° 2 series.
D'autre part, le comportement thermique des meules a été testé en plaçant entre deux plateaux d'une presse, chauffés à environ 1 70°C, une première barre témoin dont la composition correspond à la meule de référence et une seconde barre dont la composition correspond à celle de la meule de l'essai n° 1 . Toutes les minutes, les températures des barres sont mesurées à l'aide de deux thermocouples. Les valeurs sont reportées à la figure 2 (les ronds correspondant à la température de la barre de référence et les carrés à l'essai n° 1 ). Après une durée d'environ un quart d'heure, la température des barres se stabilise, à une valeur d'environ 55-56°C pour la barre selon l'invention. La barre correspondant à une meule selon l'invention s'échauffe donc significativement plus que la barre correspondant à la meule de référence, ce qui indique qu'elle a perdu une bonne partie de son caractère isolant. De plus, on peut observer sur cette figure 2 que la montée en température de la barre selon l'invention est un peu plus rapide, ce qui est plus spécialement avantageux. L'effet du caractère métallique des rubans est ainsi clairement démontré.On the other hand, the thermal behavior of the grinding wheels was tested by placing between two platens of a press, heated to about 170 ° C, a first control bar whose composition corresponds to the reference grinding wheel and a second bar whose composition corresponds to that of the grinding wheel of test n ° 1. Bar temperatures are measured every minute using two thermocouples. The values are shown in Figure 2 (the circles corresponding to the temperature of the reference bar and the squares under test n ° 1). After a period of about a quarter of an hour, the temperature of the bars stabilizes, at a value of about 55-56 ° C for the bar according to the invention. The bar corresponding to a grinding wheel according to the invention therefore heats up significantly more than the bar corresponding to the reference grinding wheel, which indicates that it has lost a good part of its insulating character. In addition, it can be observed in this FIG. 2 that the temperature rise of the bar according to the invention is a little faster, which is more especially advantageous. The effect of the metallic character of the ribbons is thus clearly demonstrated.
Par ailleurs, la quantité de métal présente dans les meules selon l'invention est suffisamment importante pour autoriser un contrôle en continu à l'aide de capteurs sans contact, ceci par exemple pour vérifier systématiquement la valeur du diamètre extérieur de la meule et donc son état d'usure.Furthermore, the quantity of metal present in the grinding wheels according to the invention is large enough to allow continuous monitoring using non-contact sensors, this for example to systematically check the value of the outside diameter of the grinding wheel and therefore its state of wear.
En dernier lieu, il est important de souligner que les meules selon l'invention, non seulement sont plus solides sur le plan mécanique, mais en outre permettent d'augmenter la qualité de l'usinage des pièces meulées : le fait que les meules selon l'invention favorisent une rapide évacuation de la chaleur évite que les pièces meulées ne noircissent ou ne « brûlent » par échauffement excessif. Finally, it is important to emphasize that the grinding wheels according to the invention, not only are more solid mechanically, but also make it possible to increase the quality of the machining of the ground parts: the fact that the grinding wheels according to the invention promote rapid heat dissipation prevents the ground parts from blackening or "burning" by excessive heating.

Claims

REVENDICATIONS
I . Meule abrasive comprenent des particules abrasives noyées dans un agglomérant organique, caractérisée en ce qu'elle comporte également un renfort sous forme de fibres métalliques. I. Abrasive wheel include abrasive particles embedded in an organic binder, characterized in that it also includes a reinforcement in the form of metallic fibers.
2. Meule selon la revendication 1 , caractérisée en ce que les fibres métalliques ont une longueur de 5 à 30 mm, de préférence de 1 0 à 20 mm.2. Grinding wheel according to claim 1, characterized in that the metallic fibers have a length of 5 to 30 mm, preferably from 1 0 to 20 mm.
3. Meule selon la revendication 1 ou la revendication 2, caractérisée en ce que les fibres métalliques se présentent sous forme de rubans.3. Grinding wheel according to claim 1 or claim 2, characterized in that the metal fibers are in the form of ribbons.
4. Meule selon la revendication 3, caractérisée en ce que les rubans métalliques ont une épaisseur inférieur à 5/10ème de mm, notamment entre4. Grinding wheel according to claim 3, characterized in that the metal strips have a thickness of less than 5 / 10ths of a mm, in particular between
2/1 0 et 3/10ème de mm.2/1 0 and 3 / 10th of mm.
5. Meule selon la revendication 3 ou 4, caractérisée en ce que les rubans métalliques ont une largeur de 0,5 à 7 mm, notamment de 1 à 5 mm.5. Grinding wheel according to claim 3 or 4, characterized in that the metal strips have a width of 0.5 to 7 mm, in particular from 1 to 5 mm.
6. Meule selon l'une des revendications précédentes, caractérisée en ce que les fibres métalliques sont en « verre » métallique, notamment obtenu par hypertrempe d'un jet de métal fondu sur un substrat défilant en continu.6. Grinding wheel according to one of the preceding claims, characterized in that the metallic fibers are made of metallic "glass", in particular obtained by hyper-tempering a jet of molten metal on a continuously moving substrate.
7. Meule selon l'une des revendications précédentes, caractérisée en ce que les fibres métalliques sont à base de fonte amorphe.7. Grinding wheel according to one of the preceding claims, characterized in that the metal fibers are based on amorphous cast iron.
8. Meule selon l'une des revendications précédentes, caractérisée en ce que les fibres métalliques sont ajoutées à raison d'un volume de 1 à 4 % du volume total de la meule, notamment 2 à 3 % dudit volume.8. Grinding wheel according to one of the preceding claims, characterized in that the metal fibers are added at a rate of 1 to 4% of the total volume of the grinding wheel, in particular 2 to 3% of said volume.
9. Meule selon l'une des revendications précédentes, caractérisée en ce que l'agglomérant organique est à base de résines phénoliques et/ou polyimides. 9. Grinding wheel according to one of the preceding claims, characterized in that the organic binder is based on phenolic resins and / or polyimides.
1 0. Meule selon l'une des revendications précédentes, caractérisée en ce que les particules abrasives sont en céramique du type alumine, éventuellement avec des traces de métaux type Zr, Fe.1 0. Grinding wheel according to one of the preceding claims, characterized in that the abrasive particles are made of ceramic of the alumina type, possibly with traces of metals of the Zr, Fe type.
I I . Meule selon l'une des revendications précédentes, caractérisée en ce que les particules abrasives correspondent à un volume de 40 à 70 % du volume total de la meule, notamment d'environ 50 à 65 % dudit volume.I I. Grinding wheel according to one of the preceding claims, characterized in that the abrasive particles correspond to a volume of 40 to 70% of the total volume of the grinding wheel, in particular approximately 50 to 65% of said volume.
1 2. Meule selon l'une des revendications précédentes, caractérisée en ce que les particules abrasives sont des grains, sous forme de particules ou bâtonnets, ayant un diamètre moyen de 1 /10ème de mm à 3 mm, notamment d'environ 1 ,5 mm. 1 3. Meule selon l'une des revendications précédentes, caractérisée en ce que les fibres métalliques de renfort on un alignement privilégié dans un plan perpendiculaire à l'axe de la meule. 1 2. Grinding wheel according to one of the preceding claims, characterized in that the abrasive particles are grains, in the form of particles or sticks, having an average diameter of 1 / 10th of mm to 3 mm, in particular of approximately 1, 5 mm. 1 3. Grinding wheel according to one of the preceding claims, characterized in that the reinforcing metal fibers have a preferred alignment in a plane perpendicular to the axis of the grinding wheel.
EP95916737A 1994-04-12 1995-04-11 Abrasive grinding wheels Withdrawn EP0739262A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
FR9404303 1994-04-12
FR9404303A FR2718380B3 (en) 1994-04-12 1994-04-12 Abrasive wheels.
PCT/FR1995/000461 WO1995027593A1 (en) 1994-04-12 1995-04-11 Abrasive grinding wheels

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EP0739262A1 true EP0739262A1 (en) 1996-10-30

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JP (1) JPH08511481A (en)
KR (1) KR960703051A (en)
CN (1) CN1126964A (en)
AU (1) AU2311795A (en)
BR (1) BR9506150A (en)
CA (1) CA2164612A1 (en)
FR (1) FR2718380B3 (en)
PL (1) PL311955A1 (en)
TW (1) TW273525B (en)
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BR9506150A (en) 1996-04-16
KR960703051A (en) 1996-06-19
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JPH08511481A (en) 1996-12-03
AU2311795A (en) 1995-10-30
CN1126964A (en) 1996-07-17
PL311955A1 (en) 1996-03-18
FR2718380A1 (en) 1995-10-13
TW273525B (en) 1996-04-01
ZA953012B (en) 1996-01-05
CA2164612A1 (en) 1995-10-19
FR2718380B3 (en) 1996-05-24
MX9505205A (en) 1998-03-31
US5695394A (en) 1997-12-09

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