EP0215783B1 - Coating for molds and expendable cores - Google Patents

Coating for molds and expendable cores Download PDF

Info

Publication number
EP0215783B1
EP0215783B1 EP19850902289 EP85902289A EP0215783B1 EP 0215783 B1 EP0215783 B1 EP 0215783B1 EP 19850902289 EP19850902289 EP 19850902289 EP 85902289 A EP85902289 A EP 85902289A EP 0215783 B1 EP0215783 B1 EP 0215783B1
Authority
EP
European Patent Office
Prior art keywords
coating
core
die casting
sand
binding agent
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.)
Expired
Application number
EP19850902289
Other languages
German (de)
English (en)
French (fr)
Other versions
EP0215783A4 (en
EP0215783A1 (en
Inventor
Charles J. Dybala
John J. Maczko
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.)
Doehler-Jarvis LP
Original Assignee
DOEHLER-JARVIS LP
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 DOEHLER-JARVIS LP filed Critical DOEHLER-JARVIS LP
Publication of EP0215783A1 publication Critical patent/EP0215783A1/en
Publication of EP0215783A4 publication Critical patent/EP0215783A4/en
Application granted granted Critical
Publication of EP0215783B1 publication Critical patent/EP0215783B1/en
Expired legal-status Critical Current

Links

Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/10—Cores; Manufacture or installation of cores
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C3/00—Selection of compositions for coating the surfaces of moulds, cores, or patterns

Definitions

  • the invention primarily relates to the art of die casting such metals as aluminum, zinc, magnesium, copper, iron and their alloys and to a solution to a long standing problem therein; i.e., the lack of a commercially feasible die casting technique to produce castings having undercut regions. More specifically, this invention relates to a coating composition useful on expendable die casting cores and particularly in pressurized die casting methods.
  • Sand cores have been employed for high pressure die castings and have been composed of sand mixed with a binding agent. The mixture is formed into the desired core shape and cured, bound together, by use of heat or chemical reaction. The cured core can then be used in the casting process.
  • Washout resistance is the ability of the core to withstand erosion from the high metal velocities that occur during injection of the molten metal. The washed out sand adversely affects tolerances on the finished part, since the sand may become embedded within the casting.
  • the strength of the core is determined mainly by the sand binder used. Therefore, suitable coating and compositions must be compatible with binders having desired strength.
  • US-A-4,096,293 discloses a core wash useful in pressurized die casting methods made of hydrocarbon solvent, fumaric resin, particulated calcium aluminate and a suspending agent.
  • the composition comprises 5 to 90 wt% solvent, o,5 to 5 wt% resin, 5 to 80 wt% calcium aluminate and 0,1 to 2 wt% suspending agent.
  • the fumaric resin is described as the reaction products of fumaric acid, gum rosin and pentaerythritol.
  • the suspending agents are disclosed to include high molecular weight polymers, polyacrylates, colloidal silicas, clay, vegetable gums and amine-treated bentonite.
  • Wetting agents are disclosed to include methyl alcohol, water and anionic and cationic surfactants.
  • the prior art is further illustrated by US-A-4,001,468 which discloses a wash coating useful for preventing core erosion.
  • the composition of the coating includes an organic vehicle, suspending agent, refractory material and an organic polymer or copolymer.
  • the organic vehicle is described as having a kauributanol value (ASTM D1133) of 36 or higher.
  • the suspending agent is described as including clay, vegetable gums and amine-treated bentonite in ratio of suspending agent to vehicle of between 1:80 and 1:250.
  • the refractory powder is described including graphite, coke, mica, silica, aluminium oxide, magnesium oxide, talc and zircon flour in a weight ratio of refractory to vehicle of between 1:2,5 and 1:3,5.
  • the organic polymer or copolymer can be vinyl toluene butadiene polymer, styrene/butadiene copolymer, vinyl toluene/acrylate copolymer, styrene/acetylene copolymer, acrylate homopolymer, and styrene/butadiene copolymer in weight ratios of polymer/copolymer to vehicle between 1:50 and 1:200.
  • Disadvantages of said US-A include use of an organic binder which when heated releases an outgas which causes pores in the casting and lost strength. Further, these coatings are typically powdery and have reduced scratch resistance or hardness. Hardness is an indication of resistance to metal penetration or metal burning and erosion.
  • US-A-4,342,597 discloses to use a die casting sand core with a single coating consisting of an inorganic binder.
  • US-A-4,298,951 discloses to use a die casting sand core with an undercut where two identical coatings are provided consisting of organic bound coatings.
  • the invention in a first aspect consists in a strong die casting sand core comprising:
  • the invention in a second aspect consists in a method of coating a bonded sand core comprising sand bound together by a binder, the coating steps comprising:
  • the invention in still another aspect consists in a method of forming a die casting having an undercut region comprising:
  • a core and first mold wash composition comprising:
  • this invention comprises a method of treating a foundry core or mold by coating the surface of the sand core or mold with a wash of the foregoing composition.
  • this invention comprises a mold and expendable core coated with the foregoing composition.
  • the first core wash coating of this invention comprises particulate refractory material, an inorganic binding agent and a liquid vehicle.
  • This coating is suitable for use on sand cores and molds which are useful in die casting as well as in gravity fed casting.
  • This invention meets the four core requirements through the use of a core system having a coating/binder system that enhances shakeouts, washout resistance and surface penetration resistance.
  • the wash coatings can also include such secondary components such as fungicides, wetting agents and defoaming agents.
  • the wash coatings are useful on uncoated inorganic and organic sand and binder agent cores which provide good shakeout characteristics but fall to have suitable washout surface penetration resistance and effect in strength.
  • the binder agent of the core is a organic resin. More preferably, the agent is an acid curable organic resin and oxidizing agent which is cured by exposure to sulfur dioxide.
  • Suitable refractory materials for this invention should not react with the binder agent and are graphite, mica, fused silica, aluminium oxide, magnesium oxide, carbon black and zircon flour.
  • the refractory material is selected from the group consisting of fused silica, zircon flour and aluminium oxide.
  • refractory material is fused silica.
  • the refractory material should preferably have a particle size ranging from about 1 to 100 microns. Fused silica having a particle size within the range of about 1 and about 45 microns is most preferred.
  • the fused silica is wet milled.
  • the first wash coating comprises an inorganic binding agent such as colloidal silica, clay, or amine-treated bentonite or a combination thereof.
  • the suspending agent is selected from a group consisting of colloidal silicas, clays and bentonite. More preferably, the agent is colloidal silica.
  • the liquid vehicle may be either aqueous or organic. Selection of the vehicle is usually based on the type of binder used to bind the sand of the foundry core and mold. If the core binder is aqueous, the vehicle for the coating should preferably be organic. If the core binder is organic, the vehicle for the coating should preferably be aqueous.
  • the composition of the core wash should range from about 30 to 80 wt % refractory material, from about 1 to about 25 wt % binder agent and from about 20 to 70 wt % liquid vehicle.
  • the more preferred composition ranges from about 50 to 70 wt % refractory material, about 5 to 12 wt % binder agent and about 25 to about 40 wt % liquid vehicle.
  • the most preferred composition is about 62 wt % refractory material, about 8 wt % binder agent and about 30 wt % liquid vehicle.
  • the wash coating should preferably form a coating on the sand core having a thickness ranging from about 250 to about 5000 microns.
  • the preferred range of thickness is between 1000 and about 3000 microns.
  • sand and binding agent are mixed and air blown or hand-packed into a core box having the desired shape of the core.
  • the core is cured by heating or passing a suitable gas through the core box.
  • the core is removed from the box as a solid mass.
  • the coating may then be applied to the core by conventional techniques such as dipping or spraying the core.
  • the coating may be applied as single or multiple coats.
  • the core and coating are then allowed to dry.
  • the coating of this invention is covered with a top wash coating containing a refractory material, binding agent, preferably suspending agent and a liquid vehicle.
  • the second coating improves protection of the core and facilitation of core removal from the casting.
  • the refractory material of the top wash coating is selected from the group consisting of fused silica, zircon flour and aluminium oxide.
  • the material is zircon flour.
  • the suspending agent of the top wash coating may be selected from a group consisting of high molecular weight polymers and copolymers, silicas, vegetable gums, clays and combination thereof.
  • the suspending agent of the top wash is selected from a group consisting of colloidal silicas, clays, and bentonite. More preferably, the agent is colloidal silica.
  • the binding agent of the top wash coating is organic and may be selected from suitable agents such as polymer resins.
  • the liquid vehicle of the top wash is organic. Selection of the vehicle is usually based on the type of binder used to bind the sand of the foundry core and mold as well as the first coating. It the binder is aqueous, the vehicle for the coating should preferably be organic. More preferably, the top coating comprises zirconium silicate, resin binder and isopropyl alcohol. The top wash coating should preferably form a cured coating on the sand core having a thickness ranging from about 100 to about 2000 microns and the preferred range is from about 250 to 1000 microns.
  • the second wash coating may be applied as single or multiple coats.
  • An expendable sand core was formed of 97.90 wt % silica foundry sand (AFS Fineness No. 65), 1.47 % furane and 0.59 wt % methyl ethyl ketone peroxide, and 0.04 wt % silane.
  • the core was treated with sulfur dioxide for two seconds at ambient temperature and pressure.
  • a core wash composition was prepared containing various levels of fused silica, colloidal silica and water, the fused silica particles ranging in size from 1 to 45 microns.
  • the composition was milled by introducing porcelain balls into a container of the composition and rotating the container for two to three hours to break up large agglomerated particles.
  • the milled composition was poured through a cloth paint strainer.
  • the specific gravity of the composition was then checked and adjusted by addition of fused silica or colloidal silica slurry until the Baume reading fell within the range of 56 and 62.
  • Approximately 10% by volume of methanol was added.
  • An additional amount of kaolin was added to the composition which was then stirred for a minimum of one hour. The composition was then allowed to stand for 24 hours.
  • the coated cured core was used to produce a complex aluminum alloy die casting having an undercut region.
  • the core was removed from the casting using conventional mechanical shakeout techniques.
  • the core and casting were tested for shakeout, washout and penetration and rated for each characteristic.
  • Example 1 A cured coated core of Example 1 was dipped in the core wash composition for approixmately ten seconds, removed and drained. The coat was allowed to dry. The dry coated core was dipped again in the core wash composition for about five seconds, drained and dryed in a circulating air oven at 175°F for at least three minutes. A casting was made using the core and both were rated as in Example 1.
  • Example 1 An uncoated expendable core was prepared as in Example 1, a casting prepared therefrom and the core and casting were tested and rated as in Example 1.
  • a coated expendable core was prepared as in Example 1. This core was cooled for at least two minutes and dipped in a top coating composition containing zirconium silicate, a resin binder, and isopropyl alcohol (Arcolite #412, Atlantic Richfield Co.) for two to three seconds. The core was drained and allowed to air dry for 30 minutes. A casting was made using the core.
  • a top coating composition containing zirconium silicate, a resin binder, and isopropyl alcohol (Arcolite #412, Atlantic Richfield Co.) for two to three seconds. The core was drained and allowed to air dry for 30 minutes. A casting was made using the core.
  • the double-coated core and the casting were rated for shakeout, washout and penetration.
  • Example 3 An uncoated expendable core as prepared as in Example 3 was dipped in the zirconium silicate/resin binder coating composition of Example 4 and allowed to dry. A casting was made of the coated core and casting were rated.

Landscapes

  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Mold Materials And Core Materials (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)
EP19850902289 1985-04-16 1985-04-16 Coating for molds and expendable cores Expired EP0215783B1 (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
PCT/US1985/000675 WO1986006012A1 (en) 1985-04-16 1985-04-16 Coating for molds and expendable cores

Publications (3)

Publication Number Publication Date
EP0215783A1 EP0215783A1 (en) 1987-04-01
EP0215783A4 EP0215783A4 (en) 1987-09-16
EP0215783B1 true EP0215783B1 (en) 1991-07-17

Family

ID=22188645

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19850902289 Expired EP0215783B1 (en) 1985-04-16 1985-04-16 Coating for molds and expendable cores

Country Status (4)

Country Link
EP (1) EP0215783B1 (enrdf_load_stackoverflow)
JP (1) JPS62502455A (enrdf_load_stackoverflow)
DE (1) DE3583505D1 (enrdf_load_stackoverflow)
WO (1) WO1986006012A1 (enrdf_load_stackoverflow)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EA027905B1 (ru) * 2015-06-12 2017-09-29 Белорусский Национальный Технический Университет Состав литейной краски для форм и стержней
CN113967720A (zh) * 2021-10-27 2022-01-25 安徽信息工程学院 一种镁铝合金涂料组合物及其制备方法
CN114231795A (zh) * 2021-12-23 2022-03-25 佛山市天禄智能装备科技有限公司 用于回转窑的耐高温合金的制备方法及回转窑窑体

Family Cites Families (13)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2426987A (en) * 1942-11-13 1947-09-09 Aluminum Co Of America Mold coating
GB919194A (en) * 1959-09-18 1963-02-20 British Steel Castings Res Ass Improvements in or relating to paints for foundry moulds and cores
US3216078A (en) * 1962-08-30 1965-11-09 Magnet Cove Barium Corp Process for casting steel and compositions of matter for use therein
US3436235A (en) * 1967-10-26 1969-04-01 Eutectic Eng Co Colloidal silica compositions containing set indicator
US3666531A (en) * 1970-07-16 1972-05-30 Nalco Chemical Co Metal casting process
US3802902A (en) * 1972-03-17 1974-04-09 Ti Tech Int Inc Method of making molds
US4001468A (en) * 1974-04-26 1977-01-04 Ashland Oil, Inc. Method for coating sand cores and sand molds
US4096293A (en) * 1977-09-06 1978-06-20 Ashland Oil, Inc. Mold and core wash
CA1144338A (en) * 1978-05-25 1983-04-12 Enno H. Page Expendable cores for die casting
AU539985B2 (en) * 1979-10-01 1984-10-25 Farley Metals Inc. Die casting core
US4413666A (en) * 1979-10-01 1983-11-08 Nl Industries, Inc. Expendable die casting sand core
US4319925A (en) * 1981-03-06 1982-03-16 Weston Research Corporation Coating compositions for metal casting molds
US4342597A (en) * 1981-03-06 1982-08-03 Weston Research Corporation Coating compositions for liners of molten metal troughs and ladles

Also Published As

Publication number Publication date
JPH0240412B2 (enrdf_load_stackoverflow) 1990-09-11
WO1986006012A1 (en) 1986-10-23
JPS62502455A (ja) 1987-09-24
DE3583505D1 (de) 1991-08-22
EP0215783A4 (en) 1987-09-16
EP0215783A1 (en) 1987-04-01

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