EP3619182A1 - Grain abrasif céramique moulé ainsi que procédé pour la fabrication d'un grain abrasif céramique moulé - Google Patents

Grain abrasif céramique moulé ainsi que procédé pour la fabrication d'un grain abrasif céramique moulé

Info

Publication number
EP3619182A1
EP3619182A1 EP18720236.1A EP18720236A EP3619182A1 EP 3619182 A1 EP3619182 A1 EP 3619182A1 EP 18720236 A EP18720236 A EP 18720236A EP 3619182 A1 EP3619182 A1 EP 3619182A1
Authority
EP
European Patent Office
Prior art keywords
shaped ceramic
abrasive grain
abrasive
grain
ceramic abrasive
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.)
Pending
Application number
EP18720236.1A
Other languages
German (de)
English (en)
Inventor
Moritz Oldenkotte
Andreas Harzer
Georg Hejtmann
Jiri MISAK
Petra Stedile
Stefan Fuenfschilling
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.)
Robert Bosch GmbH
Original Assignee
Robert Bosch GmbH
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 Robert Bosch GmbH filed Critical Robert Bosch GmbH
Publication of EP3619182A1 publication Critical patent/EP3619182A1/fr
Pending legal-status Critical Current

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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/10—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
    • C04B35/111—Fine ceramics
    • C04B35/1115—Minute sintered entities, e.g. sintered abrasive grains or shaped particles such as platelets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B24—GRINDING; POLISHING
    • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
    • B24D11/00—Constructional features of flexible abrasive materials; Special features in the manufacture of such materials
    • C—CHEMISTRY; METALLURGY
    • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
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    • C04B35/00—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products
    • C04B35/01—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics
    • C04B35/10—Shaped ceramic products characterised by their composition; Ceramics compositions; Processing powders of inorganic compounds preparatory to the manufacturing of ceramic products based on oxide ceramics based on aluminium oxide
    • C04B35/111—Fine ceramics
    • C04B35/117—Composites
    • C04B35/119—Composites with zirconium oxide
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
    • C09K3/00—Materials not provided for elsewhere
    • C09K3/14—Anti-slip materials; Abrasives
    • C09K3/1409—Abrasive particles per se
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Definitions

  • the invention relates to a shaped ceramic abrasive grain, an abrasive article, and a method of making a shaped ceramic abrasive grain.
  • Shaped ceramic abrasive grains based on alpha-A 03 are known from the prior art. Shaped abrasive grains are abrasive grains having a defined shape and size. The abrasive grains receive their defined shape and defined size due to a defined shaping process.
  • WO 2014/020075 A1 describes various advantageous geometries for ceramic abrasive grains.
  • non-shaped or irregularly shaped abrasive grains are known from the prior art, which are also referred to as broken abrasive grains. The advantage of shaped ceramic abrasive grains is their higher grinding performance over non-shaped or irregularly shaped abrasive grains.
  • alpha-A Os is known from the prior art. If alpha-A 03 is used as the starting material, the so-called slip process is particularly suitable for the production of the abrasive grains. It is also known from the prior art to use precursor products of the alpha-A Os, which are first converted into alpha-A Os in the production of the abrasive grains, as starting material for the preparation.
  • Suitable precursor products are the alumina hydroxides Boehmite (gamma-AIO (OH)) and diaspore (alpha-AIO (OH)) as well as the aluminum orthohydroxides gibbsite (gamma-Al (OH) 3) and bayerite (alpha-Al (OH) 3).
  • the so-called sol-gel process is used, which produces abrasive grains of very fine microstructure.
  • the invention is based on a shaped ceramic abrasive grain based on alpha-A 03 (alpha-alumina). According to the invention, it is provided that the shaped ceramic abrasive grain based on alpha-A 03 contains a proportion of ZrCh (zirconium oxide) of 5% by weight to 30% by weight, based on the total weight of the shaped ceramic abrasive grain.
  • the alpha-A 03 has an average crystallite grain size of from 0.5 ⁇ m to 3 ⁇ m, preferably from 0.6 ⁇ m to 2 ⁇ m, and the ZrCh has an average crystallite grain size of from 0.25 ⁇ m to 8 ⁇ m, preferably from 0.3 ⁇ to 1.5 ⁇ .
  • the ZrCh is present at a level of from 10% to 25% by weight, more preferably from 15% to 22% by weight. It was found that an increased amount of ZrCh on the grinding performance of
  • Abrasive articles which are equipped with the abrasive grains according to the invention advantageously affects. It is believed that the increased level of ZrCh achieves a continuous, microcrystalline degradation of the abrasive grains which continuously releases new and sharp cutting edges. An increased amount of ZrCh could be associated with an increased number of weak spots in the structure of the abrasive grains, which have a positive effect on the abrasive properties of the abrasive grains.
  • An abrasive grain containing alpha-A 03 and ZrC ⁇ is also called a biphasic abrasive grain.
  • an abrasive grain having a defined geometry Under a shaped abrasive grain is understood in the context of the present invention, an abrasive grain having a defined geometry.
  • a shaped one Abrasive grain of defined geometry has a defined three-dimensional shape of defined size.
  • the defined shape of defined size is obtained by a defined shaping process in the production of the abrasive grain.
  • the defined geometry of the shaped abrasive grain should be reproducible.
  • the shaped abrasive grain should be repeatedly and selectively produced in the desired defined geometry.
  • a shaped abrasive grain is in particular not a broken or partially broken abrasive grain, which can be produced by crushing, in particular breaking.
  • geometric bodies which have two or more surfaces, one or more edges and one or more corners and / or tips.
  • One or more surfaces of the geometric bodies may be planar or curved.
  • a curved surface may be concave or convex.
  • One or more edges and / or one or more corners and / or one or more tips may be sharp or rounded.
  • One or more edges may have a chamfer.
  • geometric bodies suitable for shaped abrasive grains are polyhedra, for example tetrahedra, pentahedra, hexahedra and others.
  • rotating bodies for example cones, cylinders and others, are also suitable for shaped abrasive grains.
  • the geometric body of the shaped abrasive grain may in particular be a prism, a pyramid, a cylinder or a cone.
  • the shaped abrasive grain has at least one base surface which may be polygonal, for example triangular or quadrangular, or non-angular or curved, for example round or oval. For a base with multiple corners, one or more side edges may be straight or curved.
  • the geometric body also has in particular at least one side surface. If the ceramic abrasive grain has at least one base surface, at least one side surface and at least one tip, then it may be shaped in the manner of a cone.
  • the geometric body may in particular have a base surface and a plurality of side surfaces and at least one tip. Such an abrasive grain may be shaped like a pyramid.
  • the at least one side surface may form a lateral surface.
  • the geometric body of the shaped abrasive grain may have at least one cover surface, which may be polygonal, for example triangular or quadrangular, or non-angular or curved, for example round or oval.
  • cover surface may be polygonal, for example triangular or quadrangular, or non-angular or curved, for example round or oval.
  • one or more side edges may be straight or curved.
  • the at least one cover surface and the at least one base surface may have the same geometric shape or different geometric shapes.
  • the top surface and the bottom surface may be arranged substantially parallel to each other. However, they can also be arranged at an angle to each other.
  • the area of the base and the top surface may be substantially equal or different in size.
  • the at least one cover surface is connected to the base surface via at least one side surface.
  • the at least one side surface form a lateral surface between the base surface and the top surface.
  • the base surface and the top surface are each formed by a polygon with a number n of corners, the shaped abrasive grain may, for example, have n side surfaces.
  • the geometric body may be shaped in the manner of a prism having a base surface and a top surface and a plurality of side surfaces.
  • the geometric body may also be shaped in the manner of a cylinder with a base surface and a top surface and a side surface.
  • the geometric body with a base and a top surface and a plurality of side surfaces may also be shaped in the manner of a truncated pyramid.
  • the geometric body with a base surface and a top surface and a side surface may also be shaped in the manner of a truncated cone.
  • the at least one base surface and / or top surface may be formed, for example, by an equilateral and equiangular polygon, in particular an equilateral and equiangular triangle or quadrilateral.
  • the at least one base surface may also be formed by a non-equilateral polygon.
  • straight or oblique geometric bodies are suitable.
  • the shaped abrasive grain may be a straight or oblique prism, a straight or oblique pyramid, a straight or oblique cylinder, or a straight or slate cone.
  • the body of the abrasive grain is preferably flat.
  • a flat geometric body is considered a body whose at least one base and / or Deck surface one, in particular maximum extent which is many times greater than a, in particular maximum extent between the base and the top surface along the one or more side surfaces.
  • the extent of the base surface and / or top surface can be defined, for example, by a length of a side edge of the base surface and / or top surface.
  • the extent between the base surface and the top surface along a side surface may be defined by a thickness of the body.
  • the ratio of extension of the base surface and / or top surface to extension between the base surface and top surface of the geometric body can be, for example, in a range of 2 to 10, in particular in a range of 2 to 5.
  • the ratio of side edge length to thickness of the geometric body is from 2 to 10, in particular from 2 to 5.
  • the shaped abrasive grain of defined geometry may also be formed by any three-dimensional shape that can be made reproducible.
  • An arbitrary three-dimensional reproducible form is to be understood as meaning a form in which several surfaces together form a three-dimensional body in free form.
  • the defined three-dimensional shape of the ceramic abrasive grain may be a regular three-sided straight prism.
  • Abrasive grain has a base and a top surface, which are each formed by three side edges of equal length.
  • the base area and the top surface are essentially the same size.
  • the base surface and the top surface are arranged substantially parallel to each other.
  • the base surface and the top surface are spaced apart by three substantially equal side surfaces, which form a lateral surface of the prism.
  • the regular three-sided straight prism is particularly flat.
  • the ratio of side edge length to thickness of the prism is for example in a range of 2 to 10, in particular in a range of 2 to 5, more particularly in a range of 2.75 to 4.75.
  • deviations from an ideal or exact geometric body can occur in the case of a real shaped abrasive grain as a result of the production.
  • different degrees of deviation occur.
  • one or more surfaces, for example a ground, top or side surface, of the geometric body may irregularly have unevenness. These can be formed for example by air bubbles. Deformations can also occur, for example, through a drying process.
  • alpha-A 03 As starting material for the production of the ceramic abrasive grain according to the invention alpha-A 03 is used.
  • Alpha-A G ⁇ is known per se to the person skilled in the art and is commercially available, for example in powder form. In the context of the present invention, therefore, alpha-A 03 itself is used as starting material.
  • no precursor product of the alpha-A Os such as boehmite (gamma-AIO (OH)
  • boehmite gamma-AIO (OH)
  • ZrCh is also used as a starting material for the production of the ceramic abrasive grain according to the invention.
  • ZrCh is also known per se to the person skilled in the art and is commercially available, for example in powder form.
  • an average crystallite grain size is meant here the grain size of the alpha-A Os or ZrG crystallite grain in the shaped ceramic abrasive grain. It has been found within the scope of the present invention that a low mean crystallite grain size achieves a higher material removal than a larger average crystallite grain size.
  • An average crystallite grain size means that a mean value is formed from a certain number of measured values for the crystallite grain size.
  • the crystallite grain size can be determined by methods known per se, such as, for example, SEM or XRD analysis. For example, the images of a SEM analysis can be evaluated using the line-cut method.
  • the line-cutting method (also referred to as line method) is known per se to the person skilled in the art from the structural analysis. In this case, an average value of all measured sectional segment lengths is formed for the determination of the grain size. If necessary, a correction factor can be taken into account when determining the mean value.
  • a ratio of the average crystallite grain size of the alpha-A Os to the average crystallite grain size of the ZrCh is from 0.4 to 7.
  • the abrasive grain contains a stabilizer for stabilizing the ZrÜ2 with a maximum proportion of 20 wt.%
  • the stabilizer a Oxide of the metals yttrium, magnesium, calcium or cerium or a mixture of two or more of these oxides.
  • Particularly suitable stabilizers are Y 2 O 3, CeO 2, MgO, CaO.
  • Such ZrÜ2 is also referred to as stabilized ZrÜ2.
  • the stabilization causes the ZrÜ2 to remain in the tetragonal phase during cooling and not into the monoclinic phase.
  • the stabilization can also cause the ZrÜ2 to remain in the cubic phase on cooling and not transition into the tetragonal phase.
  • a stabilized ZrO 2 is understood to mean not only a completely stabilized or substantially completely stabilized ZrO 2, but also a partially stabilized ZrO 2.
  • a partially stabilized on cooling at least partially in the tetragonal phase.
  • the ZrÜ2 should at least be stabilized to such an extent that it does not or not completely change into the monoclinic phase on cooling.
  • the abrasive grain preferably contains MgO with a proportion of at most 0.5% by weight, in particular 0.02% by weight to 0.4% by weight.
  • MgO can serve as a means of inhibiting grain growth.
  • MgO is known per se to the person skilled in the art and commercially available, for example, in powder form.
  • the shaped ceramic abrasive grain further preferably contains S1O2 at a level of from 0.01% to 2% by weight, more preferably from 0.015% to 1% by weight, most preferably from 0.02% to 0.5% by weight .%.
  • S1O2 has the effect of preventing or reducing giant grain growth in the microstructure and thus improving the grinding performance.
  • the shaped ceramic abrasive grain contains Na 2 O at a level of from 0.01% to 0.5% by weight, preferably from 0.015% to 0.2% by weight.
  • a low content of Na2O can cause or inhibit giant grain growth in the microstructure and thus improve the grinding performance.
  • the shaped ceramic abrasive grain contains CaO in a proportion of 0.01% by weight to 0.03% by weight. Also, a low proportion of CaO can in particular cause a large grain growth in the structure is prevented or reduced, and thus the grinding performance is improved.
  • Fe 2 O 3 is contained in a proportion of 0.01% by weight to 0.2% by weight.
  • a low content of Fe 2 O 3 causes or prevents a growth of giant grains in the microstructure and thus improves the grinding performance.
  • the shaped ceramic abrasive grain has a density which is from 92% to 99.9%, in particular from 96% to 99.9%, of the theoretical density.
  • a high density causes a greater strength of the abrasive grains and is associated with a smaller number of pores.
  • the density of the abrasive grain can be determined by methods known per se, for example mercury porosimetry. It has been found that a high number of pores is undesirable. It is assumed that, in the case of a high number of pores, when grinding a workpiece with the shaped ceramic abrasive grain, rounding occurs at the cutting edges and metallic grinding dust is introduced into the pores.
  • the invention further relates to an abrasive article containing shaped ceramic abrasive grains based on alpha-A 03 with a content of ZrCh of 5 wt.% To 30 wt.%, Wherein the alpha-A 03 has an average crystallite grain size of 0.5 ⁇ has up to 3 ⁇ , and the ZrCh has a mean crystallite grain size of 0.25 ⁇ to 8 ⁇ .
  • abrasive grains and / or partially shaped abrasive grains are contained in addition to the shaped ceramic abrasive grains. These non-shaped abrasive grains and / or partially shaped abrasive grains serve as supporting grains, for example.
  • the proportion of shaped ceramic abrasive grains is for example at most 80%, in particular from 50% to 80%, very particularly from 60% to 70%, based on the total amount of abrasive grains.
  • Non-formed ceramic abrasive grains unlike shaped ceramic abrasive grains, have no defined geometry. They do not have a defined three-dimensional shape of defined size.
  • Unformed abrasive grains are of irregular shape and are randomly shaped. They can be made by crushing, for example by breaking, whereby the crushing takes place in a random manner, so that the abrasive grains are formed by fragments.
  • Such non-shaped, especially broken abrasive grains are well known to those skilled in the art. Their preparation is described for example in EP 947485 AI.
  • Partially shaped ceramic abrasive grains unlike shaped ceramic abrasive grains, do not have a completely defined geometry.
  • Partially shaped abrasive grains, unlike non-shaped abrasive grains sometimes have a defined geometry with a partially defined three-dimensional shape of partially defined size.
  • partially shaped abrasive grains have at least one defined side surface, in particular at least two defined side surfaces, and / or at least one defined edge, in particular at least two defined edges.
  • Partially shaped abrasive grains have at least one random shaped side surface and / or at least one random shaped edge.
  • Such abrasive grains can be prepared, for example, by first shaping to a precursor product and then comminuting the precursor product. Thus, for example, first a layer with two substantially plane-parallel side surfaces can be formed. This layer can then be crushed in a random manner, resulting in irregularly shaped break edges.
  • Such partially shaped abrasive grains are described for example in DE 102015108812 Al.
  • the abrasive article in addition to the two-phase shaped ceramic abrasive grains with a proportion of ZrCh of 5 wt.% To 30 wt.% also comprises single-phase shaped ceramic abrasive grains based on alpha-A Os.
  • a single-phase abrasive grain is understood to mean an abrasive grain of alpha-As with a content of ZrC ⁇ of substantially 0% by weight. Accordingly, a single-phase abrasive grain essentially has no share in ZrCh. A single-phase abrasive grain is essentially free of ZrCh.
  • the abrasive article comprises a blend of biphasic shaped ceramic abrasive grains and single-phase shaped ceramic abrasive grains. Based on the total amount of shaped ceramic abrasive grains of such an abrasive article, the proportion of single-phase ceramic abrasive grains formed is at most 80%, more preferably greater than 0% and maximum of 80%, more preferably at least 5% and maximum of 50% over the proportion of two-phase molded ceramic grains abrasive grains.
  • the two-phase and one-phase shaped ceramic abrasive grains may be included non-shaped, in particular broken, abrasive grains and / or partially shaped abrasive grains. These act, for example, as supporting grains.
  • an abrasive article comprising a mixture of single-phase shaped ceramic abrasive grains and two-phase shaped ceramic abrasive grains also provides increased grinding performance.
  • Such an abrasive article has the advantage over a two-phase shaped abrasive grain abrasive article having no proportion of single-phase shaped abrasive grains that the abrasive article is less expensive.
  • the abrasive article is in particular a coated abrasive article.
  • the abrasive article comprises in particular a flexible base with at least one layer, in particular of paper, cardboard, vulcanized fiber, foam, a plastic, a textile structure, in particular a woven, knitted, knitted, braided, nonwoven, or a combination of these materials, in particular paper and Fabric, in one or more layers.
  • the flexible backing gives the abrasive properties specific properties in terms of adhesion, elongation, tear and tensile strength, flexibility and stability.
  • the abrasive grains adhere to the flexible backing, in particular by means of a base binder.
  • the abrasive grains are prefixed in particular in the desired position and distribution on the substrate.
  • Suitable base binders for applying abrasive grains to a flexible backing of the prior art are well known to those skilled in the art. known. Synthetic resins, such as, for example, phenolic resin, epoxy resin, urea resin, melamine resin, polyester resin, are particularly suitable as basic binders.
  • the abrasive article may comprise at least one size coat, for example two size coat binders.
  • the coat binder (s) are applied in particular layer by layer to the base binder and the abrasive grains.
  • Suitable size coat binders are well-known in the art for suitable size coat binders. Synthetic resins, for example phenolic resin, epoxy resin, urea resin, melamine resin, polyester resin, are particularly suitable as capping agents.
  • binders and / or additives may be provided to impart specific properties to the abrasive article. Such binders and / or additives are familiar to the person skilled in the art.
  • abrasive articles such as bonded abrasive articles
  • Bonded abrasive articles are, in particular, synthetic resin-bonded release and roughing disks which are familiar to the person skilled in the art.
  • resin-bonded cutting and grinding discs a mass is mixed from abrasive minerals and fillers, powder resin and liquid resin, which are then pressed into cutting and grinding discs in different thicknesses and diameters.
  • the abrasive article may be in various shapes, for example, as a grinding wheel or as an abrasive belt, as a bow, rolls or strips.
  • the invention also relates to a process for the production of shaped ceramic abrasive grains, which comprises the following steps:
  • a solids content of the abrasive grain precursors is from 85% to 99.9% by weight; d) removing the abrasive grain precursors from the wells; e) sintering the abrasive grain precursors into abrasive grains based on alpha-A 03 with a content of ZrCh of 5 wt.% To 30 wt.% And a density of 92% to 99.9% of the theoretical density, wherein the alpha-A 03 an average crystallite grain size of 0.5 ⁇ m to 3 ⁇ m, and the ZrCh has an average crystallite grain size of 0.25 ⁇ m to 8 ⁇ m.
  • the method according to the invention is based on the slip method.
  • the preparation of the shaped ceramic abrasive grains according to the invention does not take place according to the sol-gel process which is well known from the literature. The individual process steps are explained in more detail below.
  • a slurry of at least one alpha-A Os powder, a ZrC ⁇ powder and a dispersant is prepared.
  • dispersing agent is particularly suitable water.
  • commercially available alpha-A Os powder and commercial ZrC ⁇ powder of the desired purity can be used.
  • the preparation of the slip can be carried out in particular in a dissolver.
  • the slip prepared according to step a) has a solids content of 50% by weight to 90% by weight and an average particle size of 0.1 ⁇ m to 8 ⁇ m.
  • the mean particle size of the solids content in the slurry can be in particular from 0.1 ⁇ m to 4 ⁇ m, very particularly from 0.1 ⁇ m to 2 ⁇ m, and furthermore in particular from 0.1 ⁇ m to 1 ⁇ m. It has been found that this small average particle size of the solids content in the slurry favors the formation of abrasive grains having a relatively low average crystallite grain size. As already mentioned, a relatively small mean crystallite grain size has an advantageous effect on the grinding performance.
  • the step a) of the method may also comprise a grinding process.
  • the grinding process is carried out in a mill, for example a ball mill.
  • the grinding process can be carried out after the dispersion of the pulverulent fractions of the alpha-A Os and ZrCh in the dispersion medium.
  • a binder is added to the slip.
  • Suitable binders are familiar to the person skilled in the art. For example, various polysaccharides and oligomers are particularly suitable.
  • the finished slurry contains in particular a proportion of binder of 0.1 wt.% To 2 wt.%.
  • the binder causes a higher strength of the abrasive grain precursor, so the unsintered abrasive grain, and thereby facilitates handling, for example, during the removal of the abrasive grain precursor from the mold.
  • a moisturizing agent is added to the slip.
  • Glycerin is particularly suitable as humectant.
  • the finished slip contains in particular a content of humectants of 0.2% by weight to 10% by weight, in particular 0.5% by weight to 8% by weight, very particularly 1% by weight to 6% by weight.
  • the humectant favors the subsequent drying process according to step c) and prevents the abrasive grain precursor from becoming too dry and thus brittle.
  • step a) of the method further additives can be added to the slurry.
  • a dispersant may be added.
  • the amount of the dispersing agent added is, for example, from 0.1% by weight to 2% by weight.
  • a wetting agent for example a polyglycol ether
  • the amount of wetting agent added is, for example, from 0.05% by weight to 2% by weight from 0.1% by weight to 0.6% by weight.
  • step b) the slip is filled into depressions of a casting mold, the depressions having a defined geometry.
  • This process step is used to shape the slurry to form shaped ceramic abrasive grains.
  • the slip is introduced into wells of defined geometry.
  • the mold contains a plurality of wells into which the slurry is poured.
  • the recesses have a defined geometry that defines the geometry of the shaped ceramic abrasive grains.
  • the wells of defined geometry form the negative molds for the production of the shaped ceramic abrasive grain.
  • a defined geometry of the depressions is understood to mean a defined three-dimensional shape of defined size in the context of the present invention.
  • the plurality of wells of the mold have all the same defined geometry to produce a plurality of shaped ceramic abrasive grains of the same geometry in one operation.
  • the mold may also have recesses of different defined geometry to produce shaped ceramic abrasive grains of different geometry in one operation.
  • the recesses are provided in particular on the upper side of the casting mold and are designed to be open towards the upper side of the casting mold, so that the slurry can be introduced into the recesses from above.
  • the filling can be done without pressure.
  • excess slurry can be removed from the surface of the mold by means of a squeegee.
  • the mold may be formed of a metal, for example aluminum, or of a plastic, for example silicone, polyurethane or polyvinyl chloride.
  • the drying of the slip according to step c) is preferably carried out at a temperature of 25 ° C to 60 ° C, in particular from 30 ° C to 50 ° C. Drying is preferably carried out in a drying oven. During drying, at least a portion of the dispersant is removed. The drying in particular lasts from 5 minutes to 4 hours, more particularly from 20 minutes to 40 minutes. If the drying takes place at too high a temperature within a relatively short time, shrinkage leads to deformations of the abrasive grain precursors, which are generally undesirable
  • abrasive grain precursors are formed, which have a solids content of 85 wt.% To 99.9 wt.%.
  • the abrasive grain precursors are removed from the wells.
  • This process step of demoulding the abrasive grain precursors can be done in different ways.
  • the abrasive grain precursors may be removed from the wells by gravity.
  • the removal can be done by deflecting the mold around a relatively narrow radius. Removal may be assisted by additional tools such as brushes, compressed air, vacuum and / or vibration.
  • the abrasive grain precursors are sintered.
  • the sintering of the abrasive grain precursors takes place in particular at a temperature of 1300 ° C to 1700 ° C, in particular from 1450 ° C to 1600 ° C.
  • abrasive grains based on alpha-A 03 are formed with a content of ZrCh of 5 wt.% To 30 wt.% And a density of 92% to 99.9% of the theoretical density, wherein the alpha-A 03 an average crystallite grain size from 0.5 ⁇ to 3 ⁇ and the ZrCh has a mean crystallite grain size of 0.25 ⁇ to 8 ⁇ .
  • the invention also relates to shaped ceramic abrasive grains which are produced by the process according to the invention.
  • the invention also relates to an abrasive article comprising shaped ceramic abrasive grains made by the process of the invention.
  • Figure 1 is a schematic view of one embodiment of the shaped ceramic abrasive grain of the invention.
  • Figure 2 is a detail of a schematic sectional view of an embodiment of the abrasive article according to the invention.
  • FIG. 3 is a diagram illustrating the grinding performance of the abrasive article according to FIG. 2
  • FIG. 4 shows a flow chart for illustrating the method steps for producing the shaped ceramic abrasive grain.
  • FIG. 1 schematically shows an exemplary embodiment of a shaped ceramic abrasive grain 10 according to the invention.
  • the geometric shape of the abrasive grain 10 is formed by a regular three-sided straight prism having the side edges 12 and the height 14.
  • the base 16 and the top surface 18 are accordingly each formed by three equal side edges 12.
  • the base 16 and the top surface 18 are the same size and are spaced apart by the height 14.
  • the three side surfaces 17 are formed by rectangles and are the same size.
  • the side edges 12 have a length of 1400 ⁇ .
  • the height 14 is 410 ⁇ .
  • the length of the side edge 12 may also be 1330 ⁇ and the height 14 400 ⁇ .
  • FIG. 2 shows a section of an exemplary embodiment of an abrasive article 50 according to the invention with abrasive grains 10 in a schematic sectional view.
  • the abrasive article 50 in the illustrated embodiment is a coated abrasive article 50 having a carrier element 52 of vulcanized fiber.
  • the vulcanized fiber support element 52 serves as a flexible support for the abrasive grains 10.
  • Vulcanized fiber is a composite of pulp, particularly cotton or cellulose fibers, and is well known to those skilled in the art as a flexible support for prior art abrasive articles.
  • the abrasive grains 10 are fixed on the support element 52 by means of a base binder 54, for example of phenolic resin.
  • the layer of base binder 54 and abrasive grains 10 is coated with a capping agent 56, for example, phenolic resin.
  • the process according to the invention for the production of shaped ceramic abrasive grains is explained in more detail with reference to the flowchart according to FIG.
  • the manufacturing method 100 includes the following steps.
  • a first step 110 the production of a slip from at least one alpha-A Os powder, a ZrCh powder and a dispersing agent, wherein in the slurry, a solids content of 50 wt.% To 90 wt.% And a mean particle size of 0 , 1 ⁇ is up to 8 ⁇ .
  • the filling of the slip takes place in depressions of a casting mold, wherein the depressions have a defined geometry.
  • abrasive grain precursors are removed from the wells.
  • a fifth step 150 the sintering of the abrasive grain precursors into alpha-A03-based abrasive grains having a ZrCh content of 5 wt% to 30 wt% and a density of 92% to 99.9% of the theoretical density is performed in which the alpha-A Os has an average crystallite grain size of 0.5 ⁇ m to 3 ⁇ m and the ZrCh has an average crystallite grain size of 0.25 ⁇ m to 8 ⁇ m.
  • Figure 3 is a graph showing the grinding performance of different abrasive articles made with shaped ceramic abrasive grains having different amounts of ZrO2. In the diagram is on the y-axis as a measure of the
  • an abrasive article having single phase shaped ceramic abrasive grains containing no ZrO 2 (0 wt% ZrCh) (hereinafter also referred to as Variant A) was used.
  • the abrasive grains of variants AZ22, AZ16 and A were prepared as follows. First, a slurry was prepared for each of the variants AZ22, AZ16 and A (see Figure 4, step 110).
  • the amounts listed in Table 1 of water as a dispersant and Dolapix as a dispersant with the amounts listed in Table 1 of powdered alpha-A Os, powdered ZrÜ2 (for the variants AZ22, AZ16) and powdered MgO were homogenized in a dissolver.
  • the powdered ZrO2 was partially stabilized ZrO2 (containing 3 mol% of Y2O3 stabilized ZrCh).
  • the slip was further followed by the other amounts listed in Table 1 of the organic additives Optapix AC 112 as a binder, Glydol N109 as a network medium and glycerol added as a humectant. Subsequently, the slurry was ground in a ball mill. The finished slip had an average particle size of 0.2 ⁇ m.
  • the finished slip was filled into depressions of a casting mold for each of the three variants AZ22, AZ16 and A in a subsequent step, the depressions having a defined geometry (compare FIG. 4, step 120).
  • the Schlickers were filled into the wells manually by means of a hand doctor blade.
  • the mold was in the form of a 3 mm thick plate and was made of silicone.
  • the mold had a multiplicity of depressions of the same geometry.
  • the cavities in the mold were formed as negative molds of a regular three-sided straight prism having an edge length of 1.7 mm and a depth of 0.5 mm.
  • the slip was dried in the depressions of the casting mold (compare FIG. 4, step 130).
  • the drying was carried out at a temperature of 40 ° C for a period of about 1 hour.
  • abrasive grain precursors having a solids content of, for example, 96% by weight could be obtained.
  • the abrasive grain precursors were removed from the wells of the mold (see Figure 4, step 140).
  • the mold was a tight Radius deflected.
  • the demolding was also mechanically supported by a brush.
  • the abrasive grain precursors were sintered into abrasive grains (see Figure 4, step 150).
  • the sintering was carried out at a temperature of 1530 ° C for a duration of 120 minutes for the variants AZ16 and AZ22 and at a temperature of 1560 ° C for a duration of 180 minutes for the variant A.
  • the abrasive grains had a density of 98% (variant AZ22), 97% (variant AZ16) and 95% (variant A95) of the theoretical density.
  • the abrasive grains had a ZrCh content of 16% by weight (variant AZ16, inventive example 1), 22% by weight (variant AZ22, inventive example 2) and 0% by weight (variant A, comparative example).
  • the average crystallite grain size of the alpha-A Os was 1.28 ⁇ m
  • the mean crystallite grain size of the alpha-A Os was 1.39 ⁇ m.
  • the average crystallite grain size of the ZrCh was 0.61 ⁇ in the variant AZ22 and 0.57 ⁇ in the variant AZ16.
  • the respective abrasive articles 50 in the form of abrasive wheels made with abrasive grains AZ22, AZ16 and A were constructed as follows (see Fig. 2).
  • As the support member 52 a fiber disk made of vulcanized fiber having a diameter of 180 mm and a thickness of 0.8 mm was used, respectively.
  • As the base binder 54 a mixture of phenolic resin (35-50 wt.%) And chalk (30-45 wt.%) was used.
  • the amount of base binder used was 100-120 g / m 2 in the wet state.
  • the amount of abrasive grains 10 applied to the backing member 52 with base binder 54 was 640-740 g / m 2 .
  • the cap binder 56 employed for the AZ22 and AZ16 variants was a mixture of phenolic resin (20-30% by weight), chalk / kaolin mixture 1: 1 (30-40% by weight) and cryolite (5-20% by weight) ,
  • a mixture of phenolic resin (20-30% by weight), chalk (35-45% by weight) and cryolite (5-20% by weight) was used as the capping agent 56.
  • the amount of capping agent used was 760-950 g / m 2 in the wet state.
  • the respective grinding wheel was driven at a speed of 4181 rpm and the workpieces were fed past the grinding wheel at a feed rate of 1.5 mm / s.
  • the workpieces were pressed with a weight of 6 kg to the grinding wheel.
  • the graph of FIG. 3 shows a significantly increased grinding performance for the two abrasive grains AZ22 and AZ16 compared to the single-phase abrasive grain A. Further, the graph shows a higher grinding performance for the abrasive grain AZ22 compared to the abrasive grain AZ16 in a first phase of the grinding test (FIGS about 35 plates) and vice versa a higher grinding performance for the abrasive grain AZ16 compared to the abrasive grain AZ22 in a second phase of the grinding test (from about 35 plates to 80 plates). In the first phase of the grinding test, the wear of the abrasive grains is less than in the second phase (from about 35 plates to 80 plates).

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Abstract

L'invention concerne un grain abrasif céramique moulé, à base d'alpha-Al2O3, ayant une teneur en ZrO2 allant de 5 % en poids à 30 % en poids, l'alpha-Al2O3 présentant une taille moyenne de grains cristallins allant de 0,5 µm à 3 µm et le ZrO2 une taille moyenne de grains cristallins allant de 0,25 µm à 8 µm, ainsi qu'un article abrasif comprenant de tels grains abrasifs et un procédé pour la production de tels grains abrasifs.
EP18720236.1A 2017-05-02 2018-04-25 Grain abrasif céramique moulé ainsi que procédé pour la fabrication d'un grain abrasif céramique moulé Pending EP3619182A1 (fr)

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DE102017207322.5A DE102017207322A1 (de) 2017-05-02 2017-05-02 Geformtes keramisches Schleifkorn sowie Verfahren zur Herstellung eines geformten keramischen Schleifkorns
PCT/EP2018/060598 WO2018202507A1 (fr) 2017-05-02 2018-04-25 Grain abrasif céramique moulé ainsi que procédé pour la fabrication d'un grain abrasif céramique moulé

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DE102017210799A1 (de) 2017-06-27 2018-12-27 Robert Bosch Gmbh Geformtes keramisches Schleifkorn sowie Verfahren zur Herstellung eines geformten keramischen Schleifkorns
DE102018212732A1 (de) 2018-07-31 2020-02-06 Robert Bosch Gmbh Geformtes keramisches Schleifkorn, Verfahren zur Herstellung eines geformten keramischen Schleifkorns und Schleifartikel
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EP2692813A1 (fr) * 2012-08-02 2014-02-05 Robert Bosch Gmbh Grain abrasif avec soulèvements de différentes hauteurs
WO2014020075A1 (fr) * 2012-08-02 2014-02-06 Robert Bosch Gmbh Grain abrasif contenant une première face sans angle et une seconde face avec angle
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DE102016100196A1 (de) * 2015-02-06 2016-08-11 Center For Abrasives And Refractories Research & Development C.A.R.R.D. Gmbh Geformte Sinterschleifkörner auf Basis von Aluminiumoxid mit Anteilen an mineralogischen Phasen bestehend aus Mullit, Tialit und/oder Armalcolit und Baddeleyit und/oder Srilankit sowie ein Verfahren zu ihrer Herstellung
DE102015108812A1 (de) 2015-06-03 2016-12-08 Center For Abrasives And Refractories Research & Development C.A.R.R.D. Gmbh Plättchenförmige, zufällig geformte, gesinterte Schleifpartikel sowie ein Verfahren zu ihrer Herstellung
DE102016109254B4 (de) * 2016-05-19 2018-08-09 Refratechnik Holding Gmbh Zur Elastifizierung von grobkeramischen Feuerfesterzeugnissen geeignetes feuerfestes Spinellgranulat, Verfahren zu dessen Herstellung, Feuerfesterzeugnis mit dem Spinellgranulat, Verwendung des Feuerfesterzeugnisses, Auskleidung eines Industrieofens mit dem Feuerfesterzeugnis

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US20200140338A1 (en) 2020-05-07
WO2018202507A1 (fr) 2018-11-08
CN110891919A (zh) 2020-03-17

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