Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
  • B22F3/12—Both compacting and sintering
  • B22F3/16—Both compacting and sintering in successive or repeated steps
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D18/00—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for
  • B24D18/0009—Manufacture of grinding tools or other grinding devices, e.g. wheels, not otherwise provided for using moulds or presses
• • 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
  • B24D3/04—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 inorganic
  • B24D3/06—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 inorganic metallic or mixture of metals with ceramic materials, e.g. hard metals, "cermets", cements
  • B24D3/10—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 inorganic metallic or mixture of metals with ceramic materials, e.g. hard metals, "cermets", cements for porous or cellular structure, e.g. for use with diamonds as abrasives
• • 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
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C1/00—Making non-ferrous alloys
  • C22C1/04—Making non-ferrous alloys by powder metallurgy
  • C22C1/0408—Light metal alloys
  • C22C1/0416—Aluminium-based alloys
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C21/00—Alloys based on aluminium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C26/00—Alloys containing diamond or cubic or wurtzitic boron nitride, fullerenes or carbon nanotubes
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
  • B22F2005/001—Cutting tools, earth boring or grinding tool other than table ware
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2301/00—Metallic composition of the powder or its coating
  • B22F2301/05—Light metals
  • B22F2301/052—Aluminium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2301/00—Metallic composition of the powder or its coating
  • B22F2301/05—Light metals
  • B22F2301/058—Magnesium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2301/00—Metallic composition of the powder or its coating
  • B22F2301/10—Copper
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2301/00—Metallic composition of the powder or its coating
  • B22F2301/30—Low melting point metals, i.e. Zn, Pb, Sn, Cd, In, Ga
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2302/00—Metal Compound, non-Metallic compound or non-metal composition of the powder or its coating
  • B22F2302/45—Others, including non-metals
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
  • B22F2998/00—Supplementary information concerning processes or compositions relating to powder metallurgy
  • B22F2998/10—Processes characterised by the sequence of their steps

Definitions

• the present invention refers, in general, to a process for obtaining a diamond tool for the working of ceramic. More particularly, the present invention refers to a process for making a grinding wheel for the squaring of ceramic.
• the grinding wheel in question is made of an aluminum-based material loaded with super abrasives.
• the present diamond tools are produced by using metal alloys based on iron so as to ensure a percentage of polluting metals less than 5%.
• the construction technique of said iron-based tools has allowed to produce grinding wheels with machining performance—in terms of processing quality, removal capacity and tool life—comparable to that of the conventional tools produced by using cobalt-based alloys or nickel-based alloys, when operating on wet processing lines, namely with use of water.
• the iron-based metal tools are no more performing, especially in terms of processing quality, removal capacity of the tool and ability to dissipate the heat generated during the processing.
• the so-obtained tools can not be used in any case on ceramic processing lines meeting the ecological standards required today.
• An object of the invention is to overcome the aforementioned drawbacks and others by providing a diamond tool, in particular a grinding wheel for working ceramic, which is environmentally friendly and allows to obtain non-polluting processing waste, such as sludges and powders.
• Another object of the invention is to provide a diamond tool so light to reduce the stress on the machine on which it is mounted and facilitate the transport and assembly operations.
• grinding wheel or “grinding wheels” is to be considered as a substitute for “tool” or “tools”.
• the process according to the invention comprises the following steps:
• the process according to the invention is characterized by the fact that the mixture of powders (I) includes the following components (percentages by weight):
• Said component (iii) is in the elementary state.
• the aluminum and the other metals are preferably in the form of powders.
• the aluminum powders typically have a size between 35 and 300 micrometers, with a maximum 3% of powders larger than 200 micrometers and 5% to 15% of powders smaller than 45 micrometers.
• the powers have preferably a size between 45 and 200 micrometers, more preferably between 60 and 150 micrometers.
• the process is characterized also by the fact that the copper is included in a quantity of 0.1% to 10%, preferably from 0.1% to 6%, more preferably from 0.1% to 3% by weight in the powder mixture (I).
• the mixture of powders (I) includes (percentages by weight):
• magnesium partly reduces alumina and activates sintering; in addition, magnesium improves the mechanical characteristics of the piece to be obtained.
• Zinc is very soluble in aluminum and is used as alloying element for high strength alloys. Zinc contributes to hardening by precipitation.
• Silicon improves wear resistance and hardness, as well as decreasing the thermal expansion coefficient.
• the step of pressing-sintering is performed by heating the semi-finished product at a temperature comprised between 530° C. and 650° C. for a time comprised between 15 min. and 60 min.
• the pressing-sintering step can be performed in pure nitrogen atmosphere.
• the semi-finished product is delubricated by heating it at a temperature comprised between 380° C. and 420° C. for a time comprised between 15 min. and 25 min.
• the finished piece may be subjected to at least one heat treatment in order to improve the mechanical characteristics.
• the heat treatments that may be performed on the finished piece are the following: sintering and cooling at ambient temperature; heating in air, subsequent rapid cooling in water and natural or artificial aging; hardening, cooling in water and artificial aging.
• the pressing-sintering of the semi-finished product may be performed directly on an aluminum support previously made.
• the same sectors are pressed-sintered in suitable graphite mold and then, they are welded to the base body.
• the molding step is very important which determines the dimensional goodness of the piece after sintering.
• DIM Diamond Injection Molding
• the mixture is molded by means of an injection molding machine. Then, the so-obtained piece must be suitably dewaxed before proceeding with the actual sintering phase. Also for this technology, the molding step is very important which determines the dimensional goodness of the piece.
• DMLS direct metal laser sintering
• SLM direct metal laser sintering
• the process according to the invention for obtaining a tool for working ceramic provides mainly to subject the powder mixture to pressing and, in case, to a subsequent de-lubrication. Subsequently, the sintering of the semi-finished product is carried out and finally, the finish of the product.
• thermal treatments can be carried out on the finished product.
• the aluminum powder is formed by air-atomized aluminum powder, irregularly shaped.
• the particles are covered by a very thin layer of oxide which can not be reduced in the classic sintering atmosphere.
• the powders have a size between 35 and 300 micrometers, with a maximum 3% of powders of a size greater than 200 micrometers, and from 5% to 15% of powders of a size lower than 45 micrometers.
• the powders have a size between 45 and 200 micrometers, and preferably between 60 and 150 micrometers.
• the powder mixtures ready for the use in the process according to the present invention, include not only aluminum but, in a minimum part, also other elements.
• the used elements may be magnesium, copper, zinc and silicon.
• Magnesium reduces partially alumina and activates the sintering; in addition, magnesium improves the mechanical characteristics of the piece to be obtained.
• Copper improves the washability of the liquid phase with respect to the aluminum and contributes to the hardening by precipitation.
• Zinc is very soluble in aluminum and is used as alloying element of high strength alloys. Zinc contributes to hardening by precipitation.
• Silicon improves wear resistance and hardness, as well as decreasing the thermal expansion coefficient.
• Said elements are soluble in aluminum so that during the sintering, said elements create liquid phases that are able to penetrate the oxide layer at the points where it has been broken during pressing and to spread and bind with aluminum.
• stearamide waxes are used in amounts usually between 0.5% and 2.5% by weight. These waxes do not leave residues and are effective.
• the compressibility of the aluminum-based mixtures is very good, much higher than that of iron-based mixtures and bronze-based mixtures; in fact, already at 200 MPa, 90% of the theoretical density is reached with resistances greater than 7 N/mm 2 .
• the usable material is high strength steel; in the case of large volumes, however, the use of hard metal is preferable, also for a better precision and a reduction of the necessary gaps.
• the oxide layer is broken and metal contacts are created which allow the subsequent sintering processes.
• the removal of the lubricant must be carried out at temperatures such as not to affect activation and diffusion in the liquid phase which in some mixtures takes place already at temperatures of 430°.
• mixtures can be delubricated directly by subjecting them to sintering temperatures, without any negative effect.
• the actual sintering takes place.
• the piece is heated in suitable molds.
• the sintering temperatures vary typically between 530 and 650° C. according to the type of alloy and mixture while the sintering time can vary between 15 and 60 min.
• the pressure is applied also in a second phase on an oleodynamic press after the mold has reached the desired temperatures.
• the high affinity of aluminum with oxygen is the main obstacle to be overcome in the sintering phase. It is also for this reason that the mixture has activating elements such as magnesium and the other previously described elements.
• the diffusion and allegation processes need accuracy in the uniformity of the powders used and in the control of sintering temperature and time.
• the piece is subjected to the finishing phase.
• the finishing phase considering the excellent plasticity of the so-obtained piece, it is possible to carry out a further thickening so as to improve the mechanical properties.
• the characteristics of sintered aluminum can be modified through heat treatments by natural or artificial aging.
• T1 sintering and cooling at ambient temperature without other processes
• T4 air heating at 500° C. for 30 minutes followed by rapid cooling and natural aging at ambient temperature for at least 30 days;
• T6 air heating at 500° C. for 30 minutes followed by rapid cooling in water and artificial aging at 160° C. for 18 hours;
• T76 quench hardening at 470° C., cooling in water and artificial aging at 130° C. for 24 hours.
• the properties of tensile strength of the sintered aluminum are comparable or better than those of bronze, brass and carbon steels of low and middle density.
• the properties of elongation are similar to those of bronze or stainless steel.
• a mixture of powders (I) is subjected to a process for obtaining a mold and consists of (percentages by weight):
• the mixture is put into a mold and the de-lubrication phase is performed at a temperature between 380° C. and 420° C., preferably at 400° C., for a time of 20 minutes.
• the sintering phase is performed at a temperature between 590° C. and 600° C. for a time of 20 minutes.
• the properties of the so-obtained article are the following: the density of the sintered aluminum is 2.52 g/cm 3 , the dimensional variation is ⁇ 0.4%, the tensile strength is 190 N/mm 2 for T1, 260 N/mm 2 for T4 and 320 N/mm 2 for T6, wherein the hardness is 60 HB, 75HB and 100 HB, and the elongation A5 is 5% for T1, 3% for T4 and 1% for T6, respectively.
• the so-obtained tool has a high mechanical resistance, a good dimensional stability and is suitable for the treatment of quench hardening and aging.
• Example 1 The procedure of Example 1 is repeated but the mixture of powders (I) consists of (percentages by weight):
• the de-lubrication phase is performed at a temperature between 380° C. and 410° C., preferably at 395° C., for a time of 20 minutes.
• the subsequent sintering phase is performed at a temperature between 630° C. and 635° C. for a time of 30 minutes.
• the properties of the so-obtained article are the following: the density of the sintered aluminum is 2.47 g/cm 3 , the dimensional variation is ⁇ 0.5%, the tensile strength is 140 N/mm 2 for T1 and 230 N/mm 2 for T6, wherein the hardness is 40 HB and 75 HB, and the elongation A5 is 5% for T1 and 3% for T6, respectively.
• the so-obtained tool has an excellent corrosion resistance, a good mechanical resistance and ductility, and is suitable for anodizing.
• Example 1 The procedure of Example 1 is repeated but the mixture of powders (I) consists of (percentages by weight):
• the de-lubrication phase is not performed because the sintering phase is performed at a temperature between 580° C. and 590° C. for a time of 60 minutes.
• the properties of the so-obtained article are the following: the density of the sintered aluminum is 2.78 g/cm 3 , the dimensional variation is ⁇ 1.5%, the tensile strength is 300 N/mm 2 for T1 and 450 N/mm 2 for T76, wherein the hardness is 100 HB and 150 HB, and the elongation A5 is 5% for T1 and 2% for T76, respectively.
• the so-obtained tool has a high mechanical resistance.
• Example 3 The procedure of Example 3 is repeated but the mixture of powders (I) consists of (percentages by weight):
• the de-lubrication phase is not performed because sintering occurs at a temperature between 580° C. and 590° C. for a time of 60 minutes.
• the properties of the so-obtained article are the following: the density of the sintered aluminum is 2.67 g/cm 3 , the dimensional variation is ⁇ 2.0%, the tensile strength is 200 N/mm 2 for T1 and 280 N/mm 2 for T6, wherein the hardness is 100 HB and 130 HB, and the elongation A5 is 1% for T1 and 0.5% for T6, respectively.
• the so-obtained tool has a good wear resistance and good mechanical characteristics up to 200° C., as well as a low coefficient of thermal expansion.
• the excellent properties of aluminum-based alloys enable to produce diamond tools of new concept which are ecological, light and performing.
• the grinding wheel obtained with the process according to the invention weighs about half in comparison to a conventional metal grinding wheel, with significant benefits.
• One of the main benefits is the lower stress on the mechanics of the machine that supports and moves the grinding wheel.
• the metal band is sintered on an iron ring and then, it is coupled to an aluminum body.
• the cutting part can be sintered directly on the aluminum body so as to avoid some steps of the working with the result of being much lighter.

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• Engineering & Computer Science (AREA)
• Chemical & Material Sciences (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Ceramic Engineering (AREA)
• Inorganic Chemistry (AREA)
• Powder Metallurgy (AREA)

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• 2017
  • 2017-07-26 IT IT102017000085373A patent/IT201700085373A1/it unknown
• 2018
  • 2018-07-25 WO PCT/IB2018/055553 patent/WO2019021213A1/en unknown
  • 2018-07-25 EP EP18756496.8A patent/EP3658333A1/en active Pending
  • 2018-07-25 US US16/631,621 patent/US20200180031A1/en not_active Abandoned
• 2023
  • 2023-04-11 US US18/298,733 patent/US20240075524A1/en active Pending

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