WO2015173604A1 - Pièce se sûreté de masselotte de matrice - Google Patents

Pièce se sûreté de masselotte de matrice Download PDF

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Publication number
WO2015173604A1
WO2015173604A1 PCT/IB2014/001749 IB2014001749W WO2015173604A1 WO 2015173604 A1 WO2015173604 A1 WO 2015173604A1 IB 2014001749 W IB2014001749 W IB 2014001749W WO 2015173604 A1 WO2015173604 A1 WO 2015173604A1
Authority
WO
WIPO (PCT)
Prior art keywords
riser
ceramic
breaker insert
metal
riser breaker
Prior art date
Application number
PCT/IB2014/001749
Other languages
English (en)
Inventor
Donald B. Craig
Christopher J. Mann
David P. Haack
James R. SCHMAHL
Original Assignee
Porvair Plc
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 Porvair Plc filed Critical Porvair Plc
Publication of WO2015173604A1 publication Critical patent/WO2015173604A1/fr

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C21/00—Flasks; Accessories therefor
    • B22C21/12—Accessories
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/08—Features with respect to supply of molten metal, e.g. ingates, circular gates, skim gates
    • B22C9/084—Breaker cores
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D29/00—Removing castings from moulds, not restricted to casting processes covered by a single main group; Removing cores; Handling ingots

Definitions

  • Metal solidification rates are determined by the rate of heat extraction of the mold and the section modulus of the casting.
  • the section modulus and/or the heat extraction rate is carefully calculated and controlled for each casting design.
  • the modulus of the connection area between the riser and the casting is critical to the production of a defect free casting. A section modulus that is too small will result in premature solidification of the riser contact, creating a shrinkage defect due to insufficient feed metal, whereas a section modulus that is too large will result in the inability of the riser to be removed from the casting or a fracture plane that penetrates into the casting, resulting in a scrap casting.
  • a dense ceramic core will withstand the thermal exposure, but tends to increase the thermal extraction rate in the riser connection area, requiring an increase in the riser connection area.
  • Woven refractory cloths are not rigid, which makes them difficult to place in a sand mold and this lack of rigidity creates an opportunity for potential movement or dislodgement from the original position within the mold due to the pressure of the flowing metal.
  • a significant issue with the current state of the art is the removal of the risers from the casting after the casting has been removed from the molding sand.
  • Direct impact can be accomplished using either kinetic energy with a hammer strike or pulsed energy from a hydraulic wedge. Both of these impact methods are effective and cost efficient.
  • the problems with the impact method arises when the section modulus of the connection area is too large to remove the riser by impact without creating a fracture plane that penetrates into the casting body, resulting in mechanical damage, which makes the casting unsuitable for its intended use.
  • the required section size of the riser connection combined with the ductility of the cast iron make it impossible for the riser to be removed from the casting using impact without breaking the casting itself.
  • An additional problem with mechanical break off of the risers in many foundries is the ergonomic and safety issues associated with the use of the large sledge hammers required to deliver the manual impact needed to break the risers free of the castings. Any feature added to the contact area between riser and casting that reduces the impact required to separate the riser from the casting will result in improved ergonomics and reduced safety risk for this manual task.
  • a particular feature of the invention is the ability to provide preferential breakage due to a decrease in metal within a region without detrimental loss of thermal energy. [0012] A particular feature of the invention is the ability to refine the art of casting in a manner which was previously unavailable.
  • riser breaker insert inserting a riser breaker insert between the mold and the riser wherein the riser breaker insert comprises voids
  • Fig. 1 is a cross-sectional schematic view of an embodiment of the invention.
  • Fig. 3 is a cross-sectional schematic view of an embodiment of the invention.
  • Fig. 4 is a top schematic view of an embodiment of the invention.
  • Fig. 8 is a cross-sectional schematic view of an embodiment of the invention.
  • the present invention is directed to an improved riser breaker insert and an improved method for casting metal. More specifically, the present invention is related to an improved riser breaker insert which allows metal to flow there through with minimal loss of thermal energy wherein the riser breaker insert forms a plane which is more easily severed, thereby separating the cast from the waste.
  • FIG. 1 a casting system, 10, is illustrated in cross-sectional schematic view.
  • a mold, 12, with a cavity defining the intended shape of the eventual cast is filled with liquid metal, 14, which eventually takes on the shape of the interior of the cavity.
  • a riser, 16, provides a reservoir of molten metal, 18, wherein the molten metal in the riser remains liquid until after the molten metal in the mold is frozen, thereby providing a reservoir of molten metal from the riser which flows into the cavity to account for shrinkage as the molten metal in the cast solidifies.
  • the riser and mold are removed resulting in a blank, 22, comprising a cast, 24, and waste, 26, with a riser breaker insert, 20, embedded in frozen metal there between.
  • the cast has the shape of the interior of the mold.
  • a fracture plane, 28, passes through the region of the blank containing the riser breaker insert.
  • a kinetic breaker, 29, impacts the blank in the vicinity of the fracture plane to cause fracture at a fracture plane, thereby separating the cast from the waste at the riser breaker insert.
  • the frozen metal flows through the riser breaker insert and therefore the cross-section containing the riser breaker insert will include ceramic portions and metal portions wherein the metal portions are metal pillars extending from the waste to the cast. The combination of ceramic portions and metal portions provide an easily broken weak zone. The breakage occurs by fracturing the ceramic
  • FIG. 3 An embodiment of the invention is illustrated in Fig. 3 after fracturing at the fracture plane illustrated in Fig. 2 wherein the cast, 14, has a neck, 30, which is extraneous to the cast, 14, and is removed, typically by grinding, to provide a finished cast.
  • the neck is preferably as small as possible to minimize the grinding necessary; however, a small neck is preferable to insure that the bulk of the intended cast is not breached by the grinding process and that no portion of the riser breaker insert remains in the finished cast.
  • the neck may include some insert remnant, 31 , which is a portion of the riser breaker insert which remains adhered to, attached to or integral to the neck. It is therefore preferable to err on the side of some neck for quality assurance purposes.
  • the example illustrated comprises multiple structural rings, 38, of solid filament with solid filament forming an upper serpentine, 48, supported by the structural rings on one side and solid filament forming a bottom serpentine, 50, on the opposite side without limit thereto.
  • Fired clay, mullite, alumina, zirconia-toughened alumina, zirconia-toughened mullite, silicon carbide, silica-bonded mullite, and silica-bonded silicon carbide are examples of materials.
  • the cross-sectional shape of the solid filament is not particularly limited herein with triangular, rectangular, trapezoidal and higher polygonal shapes suitable. Round, oval or obround are particularly preferred due to the ease of extruding cross- sectional shapes without edges and the decreased probability of breakage at an edge during use.
  • Theoretical density of all of the ceramic parts is not easily achieved in practice and pore formers are often incorporated in the ceramic precursor to purposely add microporosity thereby decreasing the ceramic density. Adding microporosity to the ceramic matrix could reduce the strength of the breaker insert thereby weakening the zone surrounding the breaker insert and making it easier to remove the riser from the casting. It is preferable that the ceramic density of the solid filaments be at least
  • the second density is bulk density, which is the total percent volume of ceramic, including its intergranular porosity volume, as a function of total volume of the breaker insert.
  • the bulk density of ceramic as more specifically set forth in Fig. 8 wherein illustrated is a cross-sectional schematic view of a riser breaker insert.
  • the bulk density of ceramic is defined as the ratio of ceramic volume to the ratio of void volume, or non-ceramic volume, within the area bound by a tangent plane to the inner boundary, PL1 , a tangent plane to the outer boundary, PL2, a tangent plane to the furthest exterior extent of the top filaments, PL3, and a tangent plane to the furthest exterior extent of the bottom filaments, PL4.
  • the bulk density of the breaker insert is preferably at least 10 vol% to no more than 50 vol%. More preferably, the bulk density is at least 20 vol% to no more than 40 vol%. Below about 10 vol%, the strength of the breaker insert is insufficient and the breaker insert is susceptible to breakage during the pour. Above about 50 vol%, the flow of molten metal through the breaker insert may be insufficient to allow the riser to function properly.
  • the cross-sectional size of the solid filament, or strut is selected to provide sufficient ceramic area to provide a clean break in the metal, yet small enough to allow adequate flow of molten metal though the voids in the riser breaker insert.
  • the cross-sectional size the solid filament must be sufficiently large to be self-supporting during formation and firing of the riser breaker insert which depends, in part, on the material used.
  • a solid filter equivalent diameter of 0.5 mm to 5.0 mm is preferable. Below about 0.5 mm the ceramic may not be sufficiently self- sustaining. Above about 5.0 mm equivalent diameter the number and arrangement of voids becomes limited. More preferably the solid filament has an equivalent diameter of 0.75-mm to 2.5-mm and most preferably 1 -mm to 2-mm. Equivalent diameter is the diameter of a circle having the same cross-sectional surface area as the solid filament.
  • the gross shape is selected based on the orientation of the mold and riser and is not limited by the ability to design the riser breaker insert.
  • the instant invention allows for great flexibility in gross shape with the current limit being installed equipment and the typical desire to match the disposable riser breaker insert with existing equipment and processes.
  • a particular advantage of the instant invention is the ability to design the gross shape in concert with design of the mold thereby providing optimizations which were previously not considered. Based on current molds and risers available in the art, a gross shape of round is preferable since this matches the design criteria established by most existing equipment. With optimization, the gross shape may become trigonal, rectangular or may be the shape of a higher level polygon wherein flow dynamics can be altered as desired by the design.
  • the riser breaker insert can be manufactured in multiple geometric shapes, including but not limited to circles, ovals, squares, rectangles and
  • the cross sectional design of the matrix riser breaker insert can be engineered to provide the foundry with the required reductions in fracture resistance and concentration of mechanical force.
  • An example of a wedge shaped, circular matrix riser breaker insert is shown in Figs. 4-7 to illustrate this concept.
  • the cross section of the matrix riser breaker insert will utilize, but is not limited to, a wedge shape created by stacking beads of ceramic material one on top of another on the perimeter of the insert to form structural rings and symmetrically lowering the number of beads, or rings, stacked upon one another towards the center of the insert. This stacking is illustrated in Figs. 6 and 7, wherein three rows are illustrated as forming the outer boundary and one row forms the inner boundary thereby roughly defining a trapezoidal cross-section.
  • the riser breaker insert can be thicker at the outer boundary and thinner at the inner boundary to minimize the impact of flow restriction inherent in the design of the riser.
  • the cross-sectional shape can be used to increase flow restrictions in certain regions of the flowing metal if so desired based on flow dynamics of the metal and shape of the riser and related components.
  • the major void and minor void sizes and positions are chosen to allow optimum flow through the riser breaker insert, yet with the desire to minimize the columns of metal passing there through.
  • the size and shape of the major void is preferably large enough to minimize flow restriction since this represents the maximum flow rate, yet it must be sufficiently small to minimize the cross-sectional area of the pillar formed therein upon freezing of the metal contained in the major void.
  • the major void is too large, the pillar formed therein is large which makes severing the waste from the cast more difficult, thereby limiting the value provided by the riser breaker insert. If the major void becomes too small, the flow is restricted which may be a disadvantage. With prior art inserts this was a conundrum, yet with the instantly claimed invention the minor voids may be large, particularly closest to the inner boundary, thereby providing sufficient flow while minimizing the size of the central pillar formed in the major void. In one embodiment, the major void is the same size as a minor void, thereby eliminating the large pillar completely. Graduated void sizes, preferably with the largest voids towards the center, are particularly preferred in some embodiments.
  • Chemically reactive suspensions can be used to form the extruded material.
  • Chemically reactive suspensions employ two fluids in separate containers which are fed into a cylindrical mixing chamber. The two liquids are mixed and deposited from the mixing chamber onto a platform that moves relative to the mixing chamber to form the riser breaker insert. The mixture gels shortly after being deposited.
  • the platform may be stationary and the mixing chamber can move to form the pattern.
  • the slurry can be extruded into a bath containing solution, solvent or oil with high concentration of acid, base or salt that induces flocculation of the particles within the slurry.
  • the rate at which the slurry flocculates can be controlled by the concentration of acid, base or salt relative to the slurry and the materials used.
  • the extruded material may eventually be dried, if necessary, to remove any volatile components which is referred to herein as a green riser breaker insert.
  • the green riser breaker insert is then heated to a temperature necessary to sinter the ceramic precursor thereby forming a ceramic riser breaker insert.
  • a porous ceramic riser breaker insert will maintain the desired section modulus of the contact area between the riser and the casting, while creating an accompanying fracture plane and a smaller solid metal interface at the riser connection.
  • Cast iron is a natural composite material consisting of a controlled mixture of graphite particles intermingled with iron crystals.
  • the graphite particles generally crystallize out of the liquid metal simultaneously with the formation of iron crystals during the solidification of the casting.
  • the shape of these graphite crystals can be flakes/planes, tubes or spheroids depending upon how the molten metal is chemically modified by the foundry.
  • the molten metal is chemically modified to produce a spheroidal graphite shape which increases the elongation and tensile strength of the metal.
  • the formation of the spheroidal graphite is highly desirable in the casting, it makes the removal of the feed riser significantly more difficult to remove from the casting, particularly using direct impact. It is documented in the literature that a fracture propagates along the boundary between the iron matrix and the graphite crystals. In grey iron, the graphite crystals are flakes / planes and both the impact resistance and tensile strength are governed by the flake length. Longer flakes result in lower impact resistance and tensile strength. In ductile iron, the impact resistance and tensile strength are significantly increased through the modification of the graphite shape from interconnected flakes and planes to discontinuous spheroids of graphite.
  • a weak boundary needs to be created to allow the iron to fracture readily with reduced impact loads.
  • Ceramic materials used to filter ductile iron are known to have limited wettability with molten iron. This limited wettability between ceramic filament and molten iron creates the weak bond required to reduce the impact resistance at the riser connection area.
  • the filament length of the ceramic insert will be orders of magnitude greater than the length of the boundary between the graphite spheroids and the iron matrix. This significant increase in the length of the weak boundary area in the iron will significantly reduce the impact resistance of the metal in the contact area between the casting and the riser.
  • a design of the matrix breaker insert can be created for each casting application to further reduce the impact resistance in the iron by concentrating the impact force in a smaller area. This tailoring of the geometrical shape of the breaker insert will provide the foundry with the reduction in cast metal fracture resistance required to allow for removal of the riser with available impact force.
  • the artisan can use smaller risers with larger contact areas to feed molten metal into the casting without creating the risk of casting damage during riser removal.
  • the artisan can more readily use the direct impact method for riser removal, which is preferable.
  • the artisan is also now provided with the tools to re-evaluate the long stagnant art of molding and particularly the use of insulated/exothermic riser sleeves to maintain the liquid path between the riser and the casting.
  • incorporation of the riser breaker insert technology into the foundry process will provide opportunities to reduce cost by reducing riser size, utilizing the direct impact riser removal method and
  • shapes such as polygonal, round, obround, oblong, etc. refer to the general shape with the understanding that deviations from the shape may occur during the treatment process due to flow and the like.
  • a round extrusion for example, may be partially altered at one face, such as flattened, due to the material contouring to a surface upon which the round filament is placed and is therefore still considered to be a round filament even though there are perturbations to the extruded shape.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)
  • Manufacture Of Alloys Or Alloy Compounds (AREA)

Abstract

L'invention concerne un système de coulée pour le moulage de métal. Le système de coulée possède un moule comportant une cavité ayant une forme prédéfinie. Une masselotte est en communication fluidique avec le moule, la masselotte fournissant un métal fondu à ladite cavité lorsque le métal fondu se fige. Une pièce de sûreté est située entre le moule et la masselotte, la pièce de sûreté comportant des vides. Une alimentation en métal fondu est fournie, celle-ci pouvant remplir le moule et les vides de ladite pièce de sûreté de masselotte et au moins partiellement la masselotte.
PCT/IB2014/001749 2013-05-24 2014-10-31 Pièce se sûreté de masselotte de matrice WO2015173604A1 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US201361827065P 2013-05-24 2013-05-24
US14/279,817 2014-05-16
US14/279,817 US20140348693A1 (en) 2013-05-24 2014-05-16 Matrix Riser Breaker Insert

Publications (1)

Publication Number Publication Date
WO2015173604A1 true WO2015173604A1 (fr) 2015-11-19

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WO (1) WO2015173604A1 (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106187075A (zh) * 2016-07-11 2016-12-07 雷春生 一种发热保温真空冒口套的制备方法

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN104646632A (zh) * 2015-02-11 2015-05-27 宝鸡华光铸造材料科技有限公司 一种铸造用发热保温冒口套及湿法制备工艺

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1918578A1 (de) * 1968-04-12 1969-10-30 Michel Figueras Verfahren zur Herstellung von Gussstuecken sowie Vorrichtung zur Durchfuehrung dieses Verfahrens
US4141406A (en) * 1977-03-01 1979-02-27 Foseco Trading Ag. Breaker cores
EP0934785A1 (fr) * 1993-04-22 1999-08-11 Foseco International Limited Matériaux réfractaires et calorifuges comprenant des microbilles creuses d'aluminosilicate et leur utilisation dans la fonderie et les moules de coulée
US8187500B2 (en) 2008-10-17 2012-05-29 The Board Of Trustees Of The University Of Illinois Biphasic inks

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2561062A (en) * 1948-09-27 1951-07-17 Walter R Ling Pressure casting apparatus
US4188010A (en) * 1977-08-26 1980-02-12 General Foundry Products Corporation Casting risers
US4526338A (en) * 1984-04-23 1985-07-02 General Foundry Products Corporation High pressure molding riser
US5476135A (en) * 1994-06-06 1995-12-19 Volkmann; Adolf P. E. Mold box for forming sand pouring basins

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE1918578A1 (de) * 1968-04-12 1969-10-30 Michel Figueras Verfahren zur Herstellung von Gussstuecken sowie Vorrichtung zur Durchfuehrung dieses Verfahrens
US4141406A (en) * 1977-03-01 1979-02-27 Foseco Trading Ag. Breaker cores
EP0934785A1 (fr) * 1993-04-22 1999-08-11 Foseco International Limited Matériaux réfractaires et calorifuges comprenant des microbilles creuses d'aluminosilicate et leur utilisation dans la fonderie et les moules de coulée
US8187500B2 (en) 2008-10-17 2012-05-29 The Board Of Trustees Of The University Of Illinois Biphasic inks

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106187075A (zh) * 2016-07-11 2016-12-07 雷春生 一种发热保温真空冒口套的制备方法

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