EP0153432A1 - Künstliches Stuckatierungsmaterial,Verfahren zu seiner Herstellung und seine Verwendung - Google Patents

Künstliches Stuckatierungsmaterial,Verfahren zu seiner Herstellung und seine Verwendung Download PDF

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Publication number
EP0153432A1
EP0153432A1 EP84102138A EP84102138A EP0153432A1 EP 0153432 A1 EP0153432 A1 EP 0153432A1 EP 84102138 A EP84102138 A EP 84102138A EP 84102138 A EP84102138 A EP 84102138A EP 0153432 A1 EP0153432 A1 EP 0153432A1
Authority
EP
European Patent Office
Prior art keywords
stucco
binder
refractory
shell
mixture
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.)
Ceased
Application number
EP84102138A
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English (en)
French (fr)
Inventor
Claude Watts
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.)
Dentsply Sirona Inc
Original Assignee
Dentsply International Inc
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 Dentsply International Inc filed Critical Dentsply International Inc
Priority to EP84102138A priority Critical patent/EP0153432A1/de
Priority to JP4373684A priority patent/JPS60187445A/ja
Publication of EP0153432A1 publication Critical patent/EP0153432A1/de
Ceased legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/02—Sand moulds or like moulds for shaped castings
    • B22C9/04—Use of lost patterns
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C1/00—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds
    • B22C1/16—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents
    • B22C1/165—Compositions of refractory mould or core materials; Grain structures thereof; Chemical or physical features in the formation or manufacture of moulds characterised by the use of binding agents; Mixtures of binding agents in the manufacture of multilayered shell moulds

Definitions

  • This invention relates to the art of investment casting, and more particularly to new and novel compositions and combinations of shell building materials to provide an improved shell mold.
  • the finished shell mold is dried thoroughly, usually overnight. This is followed by the usual steps of dewaxing, firing, casting, cooling, knock-out, salt bath, cut-off, sand blasting and other necessary after cast operations all well known in the art.
  • the ceramic shell mold becomes very hard after firing and casting.
  • the removal of the ceramic mold material to recover the metal castings becomes very difficult and expensive.
  • a pneumatic hammer is usually employed to remove as much refractory shell material as possible from the cast tree. In some instances the mechanical vibration is so severe that the metal castings are cracked or otherwise damaged.
  • caustic soda sodium hydroxide
  • the caustic soda soon becomes neutralized or spent and will no longer remove the shell material from the casting.
  • the salt bath must be cleaned and rejuvenated by removing the sludge and discarding a portion of the spent salt, so that fresh_sodium hydroxide can be added. This is a hot, dirty, and hazardous operation.
  • the safe disposal of the spent caustic soda is now an increasingly serious environmental problem.
  • A-high permeability is needed to permit the hot gases in the mold to escape as the molten metal is cast into the mold.
  • Still another area for improvement is in the combination of a shell mold with extremely high permeability together with very good strength characteristics.
  • An intermediate layer or layers such as this bound only with an organic binder will revert to a loose, free flowing powder after heating to a high enough temperature to burn off and remove the organic binder.
  • This approach does indeed improve the ease with which the bulk of the ceramic shell material is removed by mechanical vibration after casting.
  • it is not entirely satisfactory.
  • One difficulty is that the one r two primer coats that are applied prior to the intermediate coats containing the organic binder polyvinyl alcohol are not attached to the back-up coats.
  • there is a loosely filled space or gap in the mold Many times the force or weight of the molten metal will cause the first two coats (precoat layers) to buckle into the gap or space left by the intermediate layer. This results in a defective casting.
  • the overall strength of the shell mold is reduced because the intermediate layer produces a laminating effect with no bond between the prim- layers and the back-up players.
  • stucco materials such as Molochite, Calamo, Flintgrain, Mulgrain, and fused silica have been widely used for he production of ceramic shell molds.
  • Molochite, Calamo, Flint- rain and Mulgrain * are all trade names for refractory materials nd stuccoes that can be described chemically as calcined alumino-silicates. They have found widespread use because they are highly refractory and they have a fairly low and uniform coefficient of thermal expansion.
  • a typical example of the linear thermal expansion of a built-up shell mold comprising seven slurry oats and seven stucco layers will show an approximately straight Line curve from room temperature to 2000° F and an increase in
  • Molochite is prepared from a source of very pure clay mined in England and is available in this country from Casting Supply House in New York.
  • Calamo and Flintgrain are available from H arbison Walker Refractories, I nc. and Mulgrain Stuccoes are products of C.E. Minerals and are available from Pre-Vest, Inc. Cleveland, Ohio. length of about 0.4%.
  • This low and uniform thermal expansion is very desirable in shell molding because it minimizes cracking f the shell mold during the firing cycle due to possible differential thermal expansion.
  • Quartz occurs naturally in large quantities in the United States. Also, there are large deposits of very pure, igh grade quartz. And it is very economical.
  • Another object of my invention is to provide a stucco which if desired may be used to produce shell molds with both high permeability and good strength.
  • a further object of my invention is to provide a stucco which is as easy to use as stuccoes previously known but has the desirable qualities above listed.
  • Yet another object of my invention is to provide a stucco with favorable thermal expansion properties, but which can be made of economical raw materials which themselves do not possess such favorable properties.
  • the concept of this invention involves the use of commonly used primer and back-up slurries using the high temperature silica sol or ethyl silicate binder in each of the slurry dips.
  • Standard stuccoes are also used for the primer coat or first two coats if desired and also for some of the back-up coats.
  • the invention resides in the composition, preparation and use of special stucco for intermediate coats.
  • Stuccoes in general use by the investment casting in- ustry heretofore have consisted of solid grains of refractory particles of certain specified particle sizes. Furthermore these grains are substantially unaffected in either size, shape, or hardness by the firing cycle.
  • my invention is an different artificial stucco type material.
  • This artificia stucco is made using a refractory powder (200 to 325 mesh particle ize) mixed into a suitable condition with a water solution of an binder such as polyvinyl acetate emulsion.
  • an binder such as polyvinyl acetate emulsion.
  • Other organic binders such as polyvinyl alcohol, various gums, or starches ay also be used, but polyvinyl acetate is a preferred organic binder.
  • a blend of refractory particles including some as coarse as 100 mesh may also be used.
  • Suitable refractory powders include the group of silica flour, zirconium silicate, aluminum oxide, fuse silica and calcined alumino-silicate.
  • the refractory powder may be any cne of the above, or a mixture of two or more. These materials are thoroughly mulled so that all surfaces of the refractory powder are completely wetted by the binder to provide a strong bond between the particles on drying.
  • the mulled material is pellitized in equipment such as that manufactured by the California Pellet Mill Co., Crawfordsville, Indiana.
  • the pellets are then dried, crumbled and screened to provide an artificial stucco of the desired grain size distribution.
  • This artificial stucco is then used in place of the customarily used stucco for one or more of the intermediate slurry dips.
  • the organic binder is burned off during the firing cycle leaving a stucco shaped particle comprising a powdered refractory and voids left by the space occupied by the organic binde
  • the fired particle has very little strength and is easily crushed although there may be sufficient strength for the particles to maintain their shape.
  • the cross section of this improved shell mold before firing can be described as a honeycomb structure comprising artificial stucco particles having an organic binder surrounded by a thin layer or web of hardened refractory slurry containing a high temperature binder.
  • the very low strength of the artificial stucco particles is such that shell removal after casting is easily accomplished by mechanical vibration. This greatly reduces the danger of damaging or cracking the metal casting, because the degree of mechanical vibration required is greatly reduced. Also the amount of shell material removed by the knock-out operation is substantially increased, thereby reducing the volume of ceramic material that must be removed by the salt bath.
  • the article size of the major portion of the stucco grains should be finer - in the range of through a 50 mesh to on a 120 mesh, U.S. screen. This would provide a shell mold with a major portion consisting of the honeycomb type structure providing a fairly strong old combined with an exceptionally high degree of permeability.
  • One of the unique physical characteristics of the product f this invention is that an artifical stucco made using silica flour, bonded with an organic binder such as vinyl acetate and rocessed to form an artificial stucco granule, will not have a igh thermal expansion.
  • the reason for this desirable result is as ollows:
  • silica flour Because of the negligible thermal expansion when the stucco is made with silica flour, it can be used satisfactorily in combination with other low expanding refractory materials com- only used as the filler in the slurries containing the high temperature binders. Of course, other refractory powders than silica flour may be used, but the economy and convenience of the silica flour makes it a preferred constituent.
  • This mixture produced a damp powder, which when squeezed in the hand tended to stick together.
  • Polyco 117 SS is a vinyl acetate homopolymer emulsion made by the Borden Chemical Co.
  • test No. 1 the artificial stucco was used to stucco slurry dip number and 4.
  • Test No. 2 the artificial stucco was used for slurry ip numbers 3, 4, 5 and 6.
  • Test No. 3 was a control test for com- arison purposes. Standard refractory slurries, stuccoes, and binders in common use for at least the last 10 years were used for this control test. They are also the materials used on a produc- ion basis at the precision casting foundry where these tests were conducted.
  • wax centre tree was 2 inches in diameter by 15 inches long.
  • a metal hook for handling purposes was embedded in the pouring cup.
  • Three wax patterns identified as gun receiver parts were wax welded to the centre tree at the end opposite the pouring cup.
  • Eight wax patterns identified as carrier parts were wax welded at the pouring cup.end of the tree.
  • Nyacol 1430; DCH-10; Victawet 12 and Ranco-Sil #4 are all trade names of materials available from the Ransom and Randolph Co., Toledo, Ohio.
  • the above materials were mixed in a suitable container and in sufficient quantities to provide enough slurry for dipping purposes. They were mixed with a Lightnin Type mixer until the entrained air was eliminated. The viscosity was adjusted by adding either liquid or refractory powder to give a 14 second reading using a #4 Zahn cup.
  • Ranco-Sil #2 is the trade name of a fused silica powder available from the Ransom and Randolph Co., Toledo, Ohio.
  • test shells were thoroughly washed to remove dirt and traces of mold lubricant by immersing with agitation in a container of Ultrawash Solution available from Marketeers, Inc., Cleveland, Ohio. The set-ups were thoroughly dried for one hour using forced air.
  • the shell mold for each test set-up was prepared by dipping, draining, stuccoing and drying according to the following scheduled.
  • Ranco-Sil "B” is a fused silica stucco material available from the Ransom and Randolph Co., Toledo, Ohio.
  • Test No. 1 Knocked out using a pnematic hammer for 25 seconds. Practically all of the shell material was removed from all external surfaces including the center tree. The artificial stucco applied to slurry coats 3 and 4 had deteriorated in strength sufficiently so that substantially all of the back-up coats on both interior and exterior surfaces were removed by the mechanical vibration. There was some shell material consisting of the first two primer coats still remaining on internal surfaces. The results are considered to be excellent. It is estimated that 90 to 95% f the shell material was removed. Further vibration did not remove any additional shell material.
  • Test No. 2 The results for test No. 2 are exactly the same as for Test No. 1. No improvement in knock-out could be seen when using the artificial stucco for back-up coats 3, 4, 5 and 6 compared to Test No. 1 where the artificial stucco was used for only coat numbers 3 and 4.
  • Test No. 3 Knocked-out using a pneumatic hammer for seconds. There was a great difference in the amount of shell material removed comparing test numbers 1 and 2 with the control Test No. 3. It is estimated that 90 to 95% of the shell material as removed for tests 1 and 2 while only 50 to 60% was removed or Test No. 3. Very little shell material was removed around he center tree as well as on the internal surfaces. Additional vibration failed to remove any substantial addition of shell material.
  • the materials for the prime coat were added to a suitable container, and the materials for the back-up coat added to a second container.
  • the materials in each container were mixed thoroughly using a Lightnin Type Mixer. Mixing was continued for about 2 hours until the entrained air was eliminated.
  • Nyacol 1430, DCH-10, Victawet 12, Ranco-Sil #4, Ranco-Sil #2, and Zircon Flour are all available from the Ransom and Randolph Company, Toledo, Ohio.
  • the thermal expansion test specimen for Test No. 1 was prepared using #7 quartz silica available from Pre-Vest, Cleveland Ohio as the stucco material and having the following sieve analysis:
  • the thermal expansion test specimen for Test No. 2 was prepared using the artificial stucco of this invention using 200 mesh silica flour bonded with Polyco 117 SS as described above.
  • the particle size was through a U.S. 18 mesh screen and on a U.S. 50 mesh screen.
  • Two wire rods about 3/32 inches in diameter by 8 inches long were prepared for forming the test specimens by applying a thin film of wax.
  • test specimens were allowed to dry overnight. The following morning the ceramic shell test specimens prepared by repeated dipping, draining, stuccoing and drying of the wax coated metal rods were placed in an oven at 150° F for 15 minutes. The melted wax permitted easy removal of the metal rod. In this manner two ceramic shell test specimens about 3 inches long by 1/2 inch in diameter were prepared for running thermal expansion tests.
  • the specimens were placed in a recording diliatometer and the temperature increased from room temperature to 1800° F over a period of 90 minutes.
  • the maximum linear expansion for Test No. 1 at 1800° F was 1.60% where the quartz granules were used as stucco.
  • FIGURE 2 demonstrates that the maximum linear thermal expansion for Test No. 2 at 1800° F was 0.60%, where the artificial stucco of this invention was used.
  • the stucco of my invention may be manufactured in other ays than the pelletizing and crumbling process described herein. or example, the refractory powder, binder and any necessary solvent may be mixed to a paste and extruded, then permitted to dry. The dried extrusions are then crumbled and sieved as before. This process requires more solvent than pelletizing, which can be an dvantage for certain binders, such as the starches and gums. It is also clear that by adjusting the proportions of organic binder to refractory powder, a greater or lesser friability of the fired stucco is obtained. The strength needed in a particular application will be balanced against the necessary permeability and removability of the shell. Other factors which can be varied are mesh size and size distribution of the refractory powder and he stucco size.
  • binders may be employed. For example, a solution of about 5% by weight of cornstarch in water is effective as will be seen below and so are many gelatin and mucilag solutions.
  • the binder it is necessary that the binder be one which remains effective during and after the drying of the pellets, to bind the refractory powder together enough so that the pellets may be crumbled into stucco-sized particles without disintegrating further.
  • the binder must be suffi- burned or destroyed by 1600° F temperatures to no longer ind the refractory powder.
  • the solvent for the binder can be any liquid which dissolves the binder without reacting with it or the efractory powder, and which volitalizes smoothly during the drying process. It is used in whatever proportion is sufficient for pelletizing.
  • the solution of corn starch was made by adding the orn starch to cold water, then heating the water to boiling with onstant stirring. Heating and stirring was continued until all the corn starch was dissolved. The solution was then allowed to cool to room temperature.
  • the resulting stucco material was somewhat softer than he material produced according to the formula on page 11, but it is still considered to be suitable for use as'an artificial stucco.
  • Another example is the following formula which uses a combination of a solution of pure corn starch in water with Polyco 117SS.
  • the resulting stucco material was substantially harder than the formula using corn starch alone and is considered to be satisfactory in every respect to be used as an artificial stucco.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Materials Engineering (AREA)
  • Mold Materials And Core Materials (AREA)
EP84102138A 1984-02-29 1984-02-29 Künstliches Stuckatierungsmaterial,Verfahren zu seiner Herstellung und seine Verwendung Ceased EP0153432A1 (de)

Priority Applications (2)

Application Number Priority Date Filing Date Title
EP84102138A EP0153432A1 (de) 1984-02-29 1984-02-29 Künstliches Stuckatierungsmaterial,Verfahren zu seiner Herstellung und seine Verwendung
JP4373684A JPS60187445A (ja) 1984-02-29 1984-03-06 焼流し精密鋳造法ならびにそのためのスタツコ材料

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
EP84102138A EP0153432A1 (de) 1984-02-29 1984-02-29 Künstliches Stuckatierungsmaterial,Verfahren zu seiner Herstellung und seine Verwendung

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EP0153432A1 true EP0153432A1 (de) 1985-09-04

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EP84102138A Ceased EP0153432A1 (de) 1984-02-29 1984-02-29 Künstliches Stuckatierungsmaterial,Verfahren zu seiner Herstellung und seine Verwendung

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5159970A (en) * 1989-07-20 1992-11-03 Societe Nationale D'etude Et De Construction De Moteurs D'aviation "S.N.E.C.M.A." Method of making shell moulds for casting
GB2369594A (en) * 2000-10-16 2002-06-05 Howmet Res Corp Making investment casting molds; heated hopper
WO2005075130A1 (en) * 2004-02-05 2005-08-18 The University Of Birmingham Improved investment casting process
CN115846593A (zh) * 2022-11-28 2023-03-28 洛阳航辉新材料有限公司 一种熔模精密铸造用脱蜡设备

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP6095935B2 (ja) * 2012-10-09 2017-03-15 三菱日立パワーシステムズ株式会社 精密鋳造用鋳型の製造方法

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2912729A (en) * 1956-07-24 1959-11-17 John M Webb Refractory molds
US3367393A (en) * 1964-09-04 1968-02-06 Howe Sound Co Thermally insulated shell mold and method for making same
US3903950A (en) * 1973-12-26 1975-09-09 Howmet Corp Sandwich structure mold

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2912729A (en) * 1956-07-24 1959-11-17 John M Webb Refractory molds
US3367393A (en) * 1964-09-04 1968-02-06 Howe Sound Co Thermally insulated shell mold and method for making same
US3903950A (en) * 1973-12-26 1975-09-09 Howmet Corp Sandwich structure mold

Cited By (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5159970A (en) * 1989-07-20 1992-11-03 Societe Nationale D'etude Et De Construction De Moteurs D'aviation "S.N.E.C.M.A." Method of making shell moulds for casting
GB2369594A (en) * 2000-10-16 2002-06-05 Howmet Res Corp Making investment casting molds; heated hopper
US6749006B1 (en) 2000-10-16 2004-06-15 Howmet Research Corporation Method of making investment casting molds
GB2369594B (en) * 2000-10-16 2004-09-22 Howmet Res Corp Method of making investment casting molds
WO2005075130A1 (en) * 2004-02-05 2005-08-18 The University Of Birmingham Improved investment casting process
CN100409972C (zh) * 2004-02-05 2008-08-13 伯明翰大学 制作壳模的方法及利用该方法制作的壳模
CN115846593A (zh) * 2022-11-28 2023-03-28 洛阳航辉新材料有限公司 一种熔模精密铸造用脱蜡设备
CN115846593B (zh) * 2022-11-28 2023-10-20 洛阳航辉新材料有限公司 一种熔模精密铸造用脱蜡方法

Also Published As

Publication number Publication date
JPS60187445A (ja) 1985-09-24

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