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.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Polishing Bodies And Polishing Tools (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=9461995

Family Applications (1)

Country Status (13)

Families Citing this family (11)

Family Cites Families (13)

• 1994
  • 1994-04-12 FR FR9404303A patent/FR2718380B3/fr not_active Expired - Fee Related
• 1995
  • 1995-04-11 AU AU23117/95A patent/AU2311795A/en not_active Abandoned
  • 1995-04-11 JP JP7526132A patent/JPH08511481A/ja active Pending
  • 1995-04-11 WO PCT/FR1995/000461 patent/WO1995027593A1/fr not_active Application Discontinuation
  • 1995-04-11 EP EP95916737A patent/EP0739262A1/fr not_active Withdrawn
  • 1995-04-11 BR BR9506150A patent/BR9506150A/pt not_active Application Discontinuation
  • 1995-04-11 KR KR1019950705605A patent/KR960703051A/ko not_active Withdrawn
  • 1995-04-11 US US08/549,818 patent/US5695394A/en not_active Expired - Fee Related
  • 1995-04-11 PL PL95311955A patent/PL311955A1/xx unknown
  • 1995-04-11 CN CN95190291A patent/CN1126964A/zh active Pending
  • 1995-04-11 CA CA002164612A patent/CA2164612A1/fr not_active Abandoned
  • 1995-04-12 ZA ZA953012A patent/ZA953012B/xx unknown
  • 1995-04-29 TW TW084104286A patent/TW273525B/zh active

Non-Patent Citations (1)

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