US2426988A - Mold coating - Google Patents
Mold coating Download PDFInfo
- Publication number
- US2426988A US2426988A US465484A US46548442A US2426988A US 2426988 A US2426988 A US 2426988A US 465484 A US465484 A US 465484A US 46548442 A US46548442 A US 46548442A US 2426988 A US2426988 A US 2426988A
- Authority
- US
- United States
- Prior art keywords
- coating
- mold
- casting
- phosphate
- coatings
- 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 - Lifetime
Links
- 238000000576 coating method Methods 0.000 title description 89
- 239000011248 coating agent Substances 0.000 title description 65
- 238000005266 casting Methods 0.000 description 33
- 229910052751 metal Inorganic materials 0.000 description 30
- 239000002184 metal Substances 0.000 description 30
- 229910019142 PO4 Inorganic materials 0.000 description 28
- 235000021317 phosphate Nutrition 0.000 description 28
- 239000012212 insulator Substances 0.000 description 25
- 239000010452 phosphate Substances 0.000 description 25
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 25
- 239000011230 binding agent Substances 0.000 description 20
- 229910045601 alloy Inorganic materials 0.000 description 18
- 239000000956 alloy Substances 0.000 description 18
- 239000000463 material Substances 0.000 description 18
- 239000010410 layer Substances 0.000 description 17
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 14
- 229910052749 magnesium Inorganic materials 0.000 description 14
- 239000011777 magnesium Substances 0.000 description 14
- 239000001488 sodium phosphate Substances 0.000 description 9
- 229910000162 sodium phosphate Inorganic materials 0.000 description 9
- RYFMWSXOAZQYPI-UHFFFAOYSA-K trisodium phosphate Chemical compound [Na+].[Na+].[Na+].[O-]P([O-])([O-])=O RYFMWSXOAZQYPI-UHFFFAOYSA-K 0.000 description 9
- 230000006872 improvement Effects 0.000 description 7
- 238000000034 method Methods 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 239000002585 base Substances 0.000 description 5
- 230000003628 erosive effect Effects 0.000 description 4
- 239000010439 graphite Substances 0.000 description 4
- 229910002804 graphite Inorganic materials 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 3
- 239000002245 particle Substances 0.000 description 3
- 150000003013 phosphoric acid derivatives Chemical class 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 239000010455 vermiculite Substances 0.000 description 3
- 229910052902 vermiculite Inorganic materials 0.000 description 3
- 235000019354 vermiculite Nutrition 0.000 description 3
- 229910001018 Cast iron Inorganic materials 0.000 description 2
- 229910000861 Mg alloy Inorganic materials 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 229910052783 alkali metal Inorganic materials 0.000 description 2
- 150000001340 alkali metals Chemical class 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 239000010425 asbestos Substances 0.000 description 2
- 229910010272 inorganic material Inorganic materials 0.000 description 2
- 239000011147 inorganic material Substances 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 150000002739 metals Chemical class 0.000 description 2
- 229910052895 riebeckite Inorganic materials 0.000 description 2
- 239000002893 slag Substances 0.000 description 2
- 239000010959 steel Substances 0.000 description 2
- 229910000838 Al alloy Inorganic materials 0.000 description 1
- -1 Silocel Substances 0.000 description 1
- 239000004115 Sodium Silicate Substances 0.000 description 1
- 230000001464 adherent effect Effects 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000007900 aqueous suspension Substances 0.000 description 1
- 230000001680 brushing effect Effects 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000002845 discoloration Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000000395 magnesium oxide Substances 0.000 description 1
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 description 1
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000005058 metal casting Methods 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 238000010120 permanent mold casting Methods 0.000 description 1
- 239000002694 phosphate binding agent Substances 0.000 description 1
- 239000011241 protective layer Substances 0.000 description 1
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 description 1
- 229910052911 sodium silicate Inorganic materials 0.000 description 1
- 238000004901 spalling Methods 0.000 description 1
- 239000007921 spray Substances 0.000 description 1
- 238000005507 spraying Methods 0.000 description 1
Classifications
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
- Y10T428/00—Stock material or miscellaneous articles
- Y10T428/24—Structurally defined web or sheet [e.g., overall dimension, etc.]
- Y10T428/24273—Structurally defined web or sheet [e.g., overall dimension, etc.] including aperture
- Y10T428/24298—Noncircular aperture [e.g., slit, diamond, rectangular, etc.]
- Y10T428/24306—Diamond or hexagonal
Definitions
- This invention relates to methods of coating, and coatings for surfaces of mold cavities into which molten light metal, such as aluminum and aluminum alloys and magnesium and magnesium alloys, is to be cast. Such surfaces are usually composed of mold wall, cores and chills cooperating to form and define a cavity in the mold. While generally applicable to any mold, the invention has particular reference to molds of the permanent or semi-permanent type in which at least a portion of the mold cavity surface is composed of a relatively permanent material such as steel, cast iron or other metal. The invention is particularly useful in the casting of magnesium and alloys thereof and is specifically directed to the problems arising when that molten metal, or alloys containing substantial amounts thereof, contacts coatings provided on the surfaces of the mold cavity.
- Coatings are usually applied to the walls of a mold cavity, prior to casting molten metal therein, to prevent a sudden chilling of that portion of the metal which contacts the surfaces of the mold cavity, to prevent reaction between mold material and molten metal, to prevent cavity wall erosion and sticking of the metal casting to the mold Wall, and to serve other purposes, all of which are well known in the foundry art.
- the coating should have the required thermal characteristics, should provide a surface from which a casting of smooth clean surface may be obtained, should promote ready and exact filling of the mold cavity by the molten metal and should be resistant to the erosive or abrasive action of the incoming metal, as well as capable of preserving its physical integrity under the varying thermal conditions to which it is necessarily subjected during repeated casting operations. It is desirable that a balance of all of these qualities be obtained with the end in view of producing a sound satisfactory casting without constant expensive interruption of the casting process to renew the coating on the casting cavity.
- This invention is directed to that general object, its specific object being to provide coated molds, methods of casting and coatings which will meet the peculiar problems which occur in the casting of light metals and alloys.
- the invention provides coatings, methods of coating and coated molds which are particularly suited to the casting of magnesium and those alloys of magnesium which contain that metal in such amount as to lend to the alloy the well known reactive characteristics of that metal.
- the coatings of this invention are comprised of two general elements-binder and insulator or body material.
- the coatings are applied to the mold cavity surfaces by means of a carrier, liquid in character, which is usually water, although other liquids may be used.
- a carrier liquid in character, which is usually water, although other liquids may be used.
- the proportions or concentration of this carrier with respect .to the coating will depend upon the operator's needs and the manner in which the coating is to be applied, for instance, byspraying, brushing or the like.
- the insulator or body material may be one or more of many inorganic materials which are used to perform this function in mold coatings.
- colloidal graphite, furnace slag and vermiculite are particular insulators which are adapted to achieve optimum benefits and specific results in the practice of this invention, but other inorganic materials such as, for instance, other forms of graphite, magnesium oxide, diatomaceous silica, asbestos, soapstone, china clays, and the like, may also be used toward the obtainment of the general objects above stated. Any one or several of these and other insulators may be used in one coating.
- proportion of insulator to binder in the final coating is governed by considerations specific and immediate to the foundry conditions faced by the operator, and selection of specific proportions is governed by the intricacy and size of the mold cavity, the particular light metal or alloy being handled, the relative binding quality of the binder, the bulk and covering power of the insulator, the thickness of coating desired and other well known factors. In any event, absolute proportions are a matter of simple and routine selection.
- the binder promotes adherence of the particles of the insulator or body material to the mold wall and forms a matrix which gives continuity to the coating and may also serve toprotect the insulator particles against erosion or attack of the molten metal. Binders previously used for this purpose have not been entirely satisfactory in the casting of magnesium and its alloys. The problem has been to provide a binder which is not subject to attack by that highly reactive metal and which would also bind the insulator particles to the mold in the form of a continuous coating. Binders, such as sodium silicate, which 3 have previously been used forthis purpose have often been found to be inadequate. particularly as regards resistance to attack by the molten metal at elevated temperatures. The result has been that the coatings failed within a relatively short time, thus necessitating frequent interruption of the casting process in order to renew the coating.
- soluble stable phosphate is meant phosphates which are, initially, substantially soluble as such in the carrier and which do not melt or cease to exist as phosphate at the temperatures reached during the casting operations.
- soluble stable phosphates the phosphates of those alkali metals of atomic weight between 20 and 40 are preferred, the preferred results being obtained with sodium phosphate.
- a mold coating compounded in accordance with this invention will therefore comprise a binder of soluble phosphate, preferably sodium phosphate, and insulator or body material.
- a coating is particularly adapted to the casting of magnesium and those alloys which contain that reactive metal in such amounts as to cause similar reactive characteristics: in the alloy.
- the coating is substantially inert to the molten metal, as compared with previously used coatings, is hard and is relatively stable in the sense that it does not easily crack or spall under the conditions of casting. While the inorganic insulator or body material used in these coatings may be.
- the inert insulators vermiculite, furnace slag and colloidal graphite act with the soluble phosphate binder to produce superior coatings which are particularly adapted to the casting of magnesium and its alloys.
- these insulators are present in the coating, other insulators, an excellent example of which is the diatomaceous silica known as Silocel,'may advantageously he added to further vary the characteristics of the coating.
- a desirable property of the soluble stable phosphate-bound coatings which are the-subject of this-invention is their relative permanence under the conditions met in casting in permanent molds.
- permanent mold casting is a relatively continuous operation in which costs depend, to a substantial extent, upon lack of interruption of the casting routine.
- the molds used are. through one or several production days, permanent, and a continuous supply of molten metal to such molds is merely a matter of arrangement. Given good foundry conditions the casting routine can therefore proceed uninterrupted provided that the coating on the mold cavity surfaces does not fail and thus necessitate interruption of foundry procedure in order that it may be renewed.
- Mold cavity coatings for the casting of light metals and alloys thereof including the superior coatings compounded in accordance with the principles of this invention, do not achieve a permanence of the same character as that of the molds to which they are applied, and this is particularly true in the casting of magnesium and its alloys.
- a mold coating with a superflcial layer of soluble phosphate, preferably sodium phosphate.
- This layer is applied to the surface of the mold coating in any convenient manner as by spraying and when dried forms a hard surface which adds to the effective life of the mold coating without materially altering its functional characteristics. If sprayed while the mold surfaces are at elevated temperature, as is often the practice in applying mold coatings, drying will be substantially instantaneous. when applied to any mold coating, including the soluble phosphate-bound coatings which are the subject of this invention, as well as the coatings which they are designed to replace, this facing or layer of soluble stable phosphate serves to minimize reaction between molten magnesium or its alloys and the coating.
- the mold cavity is, at least in part, defined by a non-permanent material, such as a sand core
- a non-permanent material such as a sand core
- Aquadag cubic centimeters (colloidal graphite in water suspension, the water likewise acting as the carrier).
- the relative proportions of binder and insuiator in these particular coatings are adjusted for use in the casting of a magnesium base alloy in a permanent mold of relatively intricate cavity shape. Such specific proportions form no part of this invention and may be varied by the operator to meet specific conditions.
- the soluble stable phosphate is preferably present in amounts not less than bout 25 per cent by weight of the total weight of binder and insuiator but percentages expressed by weight are not necessarily significant since some insulators, such as Silocel, asbestos and others, have a very low weight per unit volume. Simple trial will indicate the amount of soluble phosphate necessary to bind the insulator to the mold and to produce the desirable continuity and thickness of coating.
- These coatings may be used as such, but in the preferred embodiment of the invention they are provided with the superficial layer of soluble phosphate above described.
- the mold coatings herein described may be applied directly to the surfaces of the mold cavity. In some instances it may be desirable to first wash the mold cavity surfaces with a preliminary wash or coating to obtain a surface to which the mold coating will more readily adhere.
- the use of such preliminary washes or base coat ings is well known. Their use is, of course, no part of this invention, and since they are completely covered by the mold coating applied thereon, they do not contact the molten metal poured into the mold cavity. Other similar steps such as are normally used in foundry practice may be undertaken in connection with the practice of the present invention.
- the mold used was made of cast iron. Steel cores were used.
- the molten metal cast into this mold was a magnesium base alloy containing about 90 per cent of magnesium.
- the metalreceiving surfaces of the mold cavity were first treated with a base wash to promote adherence of the mold coating.
- the mold cavity surfaces thus prepared were then coated with a mold coating composed of Grams Finely divided vermiculite 200 Sodium phosphate (NaaPO4J2HzO) 125 this coating being applied in a carrier consisting of one half liter of water.
- the coating thus formed was sprayed with an aqueous solution of soluble phosphate (100 grams of NaaPOa12HzO in 250 cubic centimeters of water) to form the superficial protective layer above described. Castings were then poured until the coating thus formed on the mold cavity surface failed. Failure as noted by discoloration of the casting or the coating or by spalling or cracking of the coating did not take place until 33 casts had been made as compared with a failure of previously used coatings after about 4 casts. Such a comparison in this particular instance is numerically indicative rather than absolute. In all cases, however, the coatings of the present invention have been observed to be superior to previously used coatings.
- the improvement consisting in providing on at least part of the meld. ear-its; surfaces a coating comprising a 6 binder of substantially soluble stable phosphate and inorganic insulator material and thereafter applying to the coating thus formed a superficial layer of substantially soluble stable phosphate.
- the improvement consisting in providing on at least part of the mold cavity surfaces a coating comprising a binder of substantially soluble stable phosphate and inorganic insulator material and thereafter applying to the coating thus formed a layer of a phosphate of an alkali metal of atomic weight between 20 and 40.
- the improvement consisting in providing on at least part of the mold cavity surfaces a coating comprising a binder of substantially soluble stable phosphate and inorganic insulator material and thereafter applying a solution of sodium phosphate to said coating to form thereon a superficial layer of said phosphate.
Description
Patented Sept. 9, i947 MOLD COATING Walter A. Dean, Lakewood, Ohio, asslgnor to Aluminum Company oi America, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application November 13, 1942,
Serial No. 465,484
9 Claims. (Cl. 22-189) This invention relates to methods of coating, and coatings for surfaces of mold cavities into which molten light metal, such as aluminum and aluminum alloys and magnesium and magnesium alloys, is to be cast. Such surfaces are usually composed of mold wall, cores and chills cooperating to form and define a cavity in the mold. While generally applicable to any mold, the invention has particular reference to molds of the permanent or semi-permanent type in which at least a portion of the mold cavity surface is composed of a relatively permanent material such as steel, cast iron or other metal. The invention is particularly useful in the casting of magnesium and alloys thereof and is specifically directed to the problems arising when that molten metal, or alloys containing substantial amounts thereof, contacts coatings provided on the surfaces of the mold cavity.
Coatings are usually applied to the walls of a mold cavity, prior to casting molten metal therein, to prevent a sudden chilling of that portion of the metal which contacts the surfaces of the mold cavity, to prevent reaction between mold material and molten metal, to prevent cavity wall erosion and sticking of the metal casting to the mold Wall, and to serve other purposes, all of which are well known in the foundry art. For
successful operation the coating should have the required thermal characteristics, should provide a surface from which a casting of smooth clean surface may be obtained, should promote ready and exact filling of the mold cavity by the molten metal and should be resistant to the erosive or abrasive action of the incoming metal, as well as capable of preserving its physical integrity under the varying thermal conditions to which it is necessarily subjected during repeated casting operations. It is desirable that a balance of all of these qualities be obtained with the end in view of producing a sound satisfactory casting without constant expensive interruption of the casting process to renew the coating on the casting cavity.
This invention is directed to that general object, its specific object being to provide coated molds, methods of casting and coatings which will meet the peculiar problems which occur in the casting of light metals and alloys. In achieving these objects, as hereinafter described, the invention provides coatings, methods of coating and coated molds which are particularly suited to the casting of magnesium and those alloys of magnesium which contain that metal in such amount as to lend to the alloy the well known reactive characteristics of that metal.
The coatings of this invention are comprised of two general elements-binder and insulator or body material. The coatings are applied to the mold cavity surfaces by means of a carrier, liquid in character, which is usually water, although other liquids may be used. The proportions or concentration of this carrier with respect .to the coating will depend upon the operator's needs and the manner in which the coating is to be applied, for instance, byspraying, brushing or the like. The insulator or body material may be one or more of many inorganic materials which are used to perform this function in mold coatings. Their specific selection may depend upon several factors, including the temperatures involved, the thermal characteristics required, the nature of the desired surface of the casting to be produced (smooth or rough) and, with regard to obtaining optimum coating quality and performance under particular molding conditions, the binder employed. As is later specifically noted, colloidal graphite, furnace slag and vermiculite are particular insulators which are adapted to achieve optimum benefits and specific results in the practice of this invention, but other inorganic materials such as, for instance, other forms of graphite, magnesium oxide, diatomaceous silica, asbestos, soapstone, china clays, and the like, may also be used toward the obtainment of the general objects above stated. Any one or several of these and other insulators may be used in one coating. The proportion of insulator to binder in the final coating is governed by considerations specific and immediate to the foundry conditions faced by the operator, and selection of specific proportions is governed by the intricacy and size of the mold cavity, the particular light metal or alloy being handled, the relative binding quality of the binder, the bulk and covering power of the insulator, the thickness of coating desired and other well known factors. In any event, absolute proportions are a matter of simple and routine selection.
The binder promotes adherence of the particles of the insulator or body material to the mold wall and forms a matrix which gives continuity to the coating and may also serve toprotect the insulator particles against erosion or attack of the molten metal. Binders previously used for this purpose have not been entirely satisfactory in the casting of magnesium and its alloys. The problem has been to provide a binder which is not subject to attack by that highly reactive metal and which would also bind the insulator particles to the mold in the form of a continuous coating. Binders, such as sodium silicate, which 3 have previously been used forthis purpose have often been found to be inadequate. particularly as regards resistance to attack by the molten metal at elevated temperatures. The result has been that the coatings failed within a relatively short time, thus necessitating frequent interruption of the casting process in order to renew the coating.
According to my invention I provide a binder of soluble stable phosphate which not only withstands the action of the molten metal to a remarkable degree, but also fulfills the other functions which are necessary to the provision of a relatively hard, adherent and continuous coating upon the mold cavity surfaces. By "soluble stable phosphate is meant phosphates which are, initially, substantially soluble as such in the carrier and which do not melt or cease to exist as phosphate at the temperatures reached during the casting operations. Of such soluble stable phosphates the phosphates of those alkali metals of atomic weight between 20 and 40 are preferred, the preferred results being obtained with sodium phosphate.
A mold coating compounded in accordance with this invention will therefore comprise a binder of soluble phosphate, preferably sodium phosphate, and insulator or body material. Such a coating is particularly adapted to the casting of magnesium and those alloys which contain that reactive metal in such amounts as to cause similar reactive characteristics: in the alloy. The coating is substantially inert to the molten metal, as compared with previously used coatings, is hard and is relatively stable in the sense that it does not easily crack or spall under the conditions of casting. While the inorganic insulator or body material used in these coatings may be.
chosen from the wide range of such materials available in order to meet the particular conditions of casting such as, for example, the thermal conditions, the type of coating surface desired, the complexity of the mold cavity and the particular light metal or alloy being cast, I have found that the inert insulators vermiculite, furnace slag and colloidal graphite act with the soluble phosphate binder to produce superior coatings which are particularly adapted to the casting of magnesium and its alloys. When these insulators are present in the coating, other insulators, an excellent example of which is the diatomaceous silica known as Silocel,'may advantageously he added to further vary the characteristics of the coating.
A desirable property of the soluble stable phosphate-bound coatings which are the-subject of this-invention is their relative permanence under the conditions met in casting in permanent molds. In large modern foundries permanent mold casting is a relatively continuous operation in which costs depend, to a substantial extent, upon lack of interruption of the casting routine. The molds used are. through one or several production days, permanent, and a continuous supply of molten metal to such molds is merely a matter of arrangement. Given good foundry conditions the casting routine can therefore proceed uninterrupted provided that the coating on the mold cavity surfaces does not fail and thus necessitate interruption of foundry procedure in order that it may be renewed. Mold cavity coatings for the casting of light metals and alloys thereof, including the superior coatings compounded in accordance with the principles of this invention, do not achieve a permanence of the same character as that of the molds to which they are applied, and this is particularly true in the casting of magnesium and its alloys.
To further increase the longevity of a mold coating I provide the mold coating with a superflcial layer of soluble phosphate, preferably sodium phosphate. This layer is applied to the surface of the mold coating in any convenient manner as by spraying and when dried forms a hard surface which adds to the effective life of the mold coating without materially altering its functional characteristics. If sprayed while the mold surfaces are at elevated temperature, as is often the practice in applying mold coatings, drying will be substantially instantaneous. when applied to any mold coating, including the soluble phosphate-bound coatings which are the subject of this invention, as well as the coatings which they are designed to replace, this facing or layer of soluble stable phosphate serves to minimize reaction between molten magnesium or its alloys and the coating. In applying this superficial layer of soluble phosphate, neither the manner of application nor the concentration of the phosphate in the solution is a critical factor. The concentration employed will govern the number of applications necessary to produce a superficial layer of a given thickness. A solution of 20 per cent by weight of sodium phosphate has given good results when applied by a spray. The desirable result is a well-dried continuous superficial hard layer of soluble stable phosphate imposed on the mold coating.
Where the mold cavity is, at least in part, defined by a non-permanent material, such as a sand core, no problem of permanence arises since the cavity is, to that extent, destroyed after each casting operation. However, the value of the superficial layer in decreasing the reaction of the molten metal on the core coating and in preventing erosion during casting is sumciently great as to justify its use in many cases.
As examples of mold coating compounded in accordance with the principles of this invention and particularly useful in the casting of magnesium and of alloys containing that metal may be cited the following:
Aquadag, cubic centimeters (colloidal graphite in water suspension, the water likewise acting as the carrier).
The relative proportions of binder and insuiator in these particular coatings are adjusted for use in the casting of a magnesium base alloy in a permanent mold of relatively intricate cavity shape. Such specific proportions form no part of this invention and may be varied by the operator to meet specific conditions. Usually the soluble stable phosphate is preferably present in amounts not less than bout 25 per cent by weight of the total weight of binder and insuiator but percentages expressed by weight are not necessarily significant since some insulators, such as Silocel, asbestos and others, have a very low weight per unit volume. Simple trial will indicate the amount of soluble phosphate necessary to bind the insulator to the mold and to produce the desirable continuity and thickness of coating. These coatings may be used as such, but in the preferred embodiment of the invention they are provided with the superficial layer of soluble phosphate above described.
The mold coatings herein described may be applied directly to the surfaces of the mold cavity. In some instances it may be desirable to first wash the mold cavity surfaces with a preliminary wash or coating to obtain a surface to which the mold coating will more readily adhere. The use of such preliminary washes or base coat ings is well known. Their use is, of course, no part of this invention, and since they are completely covered by the mold coating applied thereon, they do not contact the molten metal poured into the mold cavity. Other similar steps such as are normally used in foundry practice may be undertaken in connection with the practice of the present invention.
Following is a specific example of the practice of the invention herein described in its preferred form! The mold used was made of cast iron. Steel cores were used. The molten metal cast into this mold was a magnesium base alloy containing about 90 per cent of magnesium. The metalreceiving surfaces of the mold cavity were first treated with a base wash to promote adherence of the mold coating. The mold cavity surfaces thus prepared were then coated with a mold coating composed of Grams Finely divided vermiculite 200 Sodium phosphate (NaaPO4J2HzO) 125 this coating being applied in a carrier consisting of one half liter of water. The coating thus formed was sprayed with an aqueous solution of soluble phosphate (100 grams of NaaPOa12HzO in 250 cubic centimeters of water) to form the superficial protective layer above described. Castings were then poured until the coating thus formed on the mold cavity surface failed. Failure as noted by discoloration of the casting or the coating or by spalling or cracking of the coating did not take place until 33 casts had been made as compared with a failure of previously used coatings after about 4 casts. Such a comparison in this particular instance is numerically indicative rather than absolute. In all cases, however, the coatings of the present invention have been observed to be superior to previously used coatings.
While certain preferred embodiments of the invention, and specific examples thereof, have been described, it will be understood that such are by way of example only and that the invention may be otherwise practiced within the scope of the appended claims. It will also be understood that the mold cavity surfaces referred to in the appended claims may be originally bare or originally provided with a preliminary or base coating.
I claim: 7
i. In the coating of mold cavities into which molten light metal is to be cast, the improvement consisting in providing on at least part of the meld. ear-its; surfaces a coating comprising a 6 binder of substantially soluble stable phosphate and inorganic insulator material and thereafter applying to the coating thus formed a superficial layer of substantially soluble stable phosphate.
2. In the-coating of mold cavities into which molten light metal is to be cast, the improvement consisting in providing on at least part of the mold cavity surfaces a coating comprising a binder of substantially soluble stable phosphate and inorganic insulator material and thereafter applying to the coating thus formed a layer of a phosphate of an alkali metal of atomic weight between 20 and 40.
3. In the coating of mold cavities into which molten light metal is to be cast, the improvement consisting in providing on at least part of the mold cavity surfaces a coating comprising a binder of substantially soluble stable phosphate and inorganic insulator material and thereafter applying a solution of sodium phosphate to said coating to form thereon a superficial layer of said phosphate.
4. In the method of casting light metal into mold cavities at least a portion of the surfaces of which are provided with a coating containing a binder and inorganic insulator material, the improvement consisting in facing the coating with a layer of substantially soluble stable phosphate.
5. In the method of casting light metal into mold cavities at least a portion of the surfaces of which are provided with a coating containing a binder and inorganic insulator material, the improvement consisting in facing the coating with a layer of sodium phosphate. I I
6. In combination a mold cavity surface, a coating containing a binder and inorganic insulator material on said surface and a layer of substantially soluble stable phosphate on the surface of said coating.
'7. In combination a mold cavity surface, a coating composed of substantially soluble stable phosphate and inorganic insulator material on said surface and a layer of sodium phosphate on the surface of said coating.
8. In the casting of magnesium and alloys thereof in permanent molds at least part of the mold cavity surfaces of which are provided with a coating containing a binder and inorganic insulator material, the improvement consisting in applying to the outer surface of said coating a layer of substantially soluble stable phosphate.
. 9. In the casting of magnesium and alloys thereof in permanent molds the mold cavity surfaces of which are provided, at least in part, with a coating containing a binder and inorganic insulator material, the improvement consisting in applying to the outer surface of said coating a layer of sodium phosphate.
WALTER. A. DEAN.
asraannons crrnn The following references are of record in the file of this patent:
UNITED STATES PATENTS Number
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US465484A US2426988A (en) | 1942-11-13 | 1942-11-13 | Mold coating |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US465484A US2426988A (en) | 1942-11-13 | 1942-11-13 | Mold coating |
Publications (1)
Publication Number | Publication Date |
---|---|
US2426988A true US2426988A (en) | 1947-09-09 |
Family
ID=23847994
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
US465484A Expired - Lifetime US2426988A (en) | 1942-11-13 | 1942-11-13 | Mold coating |
Country Status (1)
Country | Link |
---|---|
US (1) | US2426988A (en) |
Cited By (7)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2618530A (en) * | 1949-06-18 | 1952-11-18 | Aluminum Co Of America | Mold coating |
US2716792A (en) * | 1950-10-05 | 1955-09-06 | Kroyer Karl Kristian Kobs | Method of cast-forging metals |
US3175931A (en) * | 1963-11-26 | 1965-03-30 | Carl A Burgess | Treatment of aluminum surfaces |
US3637412A (en) * | 1968-09-16 | 1972-01-25 | Combustion Eng | Ladle lining refractory |
US3735797A (en) * | 1968-03-27 | 1973-05-29 | Foseco Int | Process and apparatus for die-casting of ferrous metals |
US3761047A (en) * | 1971-08-09 | 1973-09-25 | Gould Inc | Mold coating |
WO2013155132A3 (en) * | 2012-04-12 | 2014-01-16 | Rel, Inc. | Method of casting composite articles |
Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1719276A (en) * | 1928-05-23 | 1929-07-02 | Western Gold & Platinum Works | High-temperature casting investment |
US1751482A (en) * | 1927-06-20 | 1930-03-25 | Emil L Leasman | Core and process of forming the same |
US1909819A (en) * | 1932-12-01 | 1933-05-16 | Armstrong Cork Co | Coating for molds and method of coating molds therewith |
US1960711A (en) * | 1933-02-20 | 1934-05-29 | Dow Chemical Co | Method of casting magnesium |
US2072212A (en) * | 1934-08-15 | 1937-03-02 | Winthrop Chem Co Inc | Embedding mass |
US2183424A (en) * | 1938-08-05 | 1939-12-12 | George C Clark | Mold material for casting metals |
US2209035A (en) * | 1938-11-26 | 1940-07-23 | Nobilium Products Inc | Refractory investment |
US2246463A (en) * | 1940-09-26 | 1941-06-17 | Ind Colloids Company | Treatment of mold surfaces |
-
1942
- 1942-11-13 US US465484A patent/US2426988A/en not_active Expired - Lifetime
Patent Citations (8)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US1751482A (en) * | 1927-06-20 | 1930-03-25 | Emil L Leasman | Core and process of forming the same |
US1719276A (en) * | 1928-05-23 | 1929-07-02 | Western Gold & Platinum Works | High-temperature casting investment |
US1909819A (en) * | 1932-12-01 | 1933-05-16 | Armstrong Cork Co | Coating for molds and method of coating molds therewith |
US1960711A (en) * | 1933-02-20 | 1934-05-29 | Dow Chemical Co | Method of casting magnesium |
US2072212A (en) * | 1934-08-15 | 1937-03-02 | Winthrop Chem Co Inc | Embedding mass |
US2183424A (en) * | 1938-08-05 | 1939-12-12 | George C Clark | Mold material for casting metals |
US2209035A (en) * | 1938-11-26 | 1940-07-23 | Nobilium Products Inc | Refractory investment |
US2246463A (en) * | 1940-09-26 | 1941-06-17 | Ind Colloids Company | Treatment of mold surfaces |
Cited By (10)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US2618530A (en) * | 1949-06-18 | 1952-11-18 | Aluminum Co Of America | Mold coating |
US2716792A (en) * | 1950-10-05 | 1955-09-06 | Kroyer Karl Kristian Kobs | Method of cast-forging metals |
US3175931A (en) * | 1963-11-26 | 1965-03-30 | Carl A Burgess | Treatment of aluminum surfaces |
US3735797A (en) * | 1968-03-27 | 1973-05-29 | Foseco Int | Process and apparatus for die-casting of ferrous metals |
US3637412A (en) * | 1968-09-16 | 1972-01-25 | Combustion Eng | Ladle lining refractory |
US3761047A (en) * | 1971-08-09 | 1973-09-25 | Gould Inc | Mold coating |
WO2013155132A3 (en) * | 2012-04-12 | 2014-01-16 | Rel, Inc. | Method of casting composite articles |
US9180511B2 (en) | 2012-04-12 | 2015-11-10 | Rel, Inc. | Thermal isolation for casting articles |
US10179364B2 (en) | 2012-04-12 | 2019-01-15 | Rel, Inc. | Thermal isolation for casting articles |
US10434568B2 (en) | 2012-04-12 | 2019-10-08 | Loukus Technologies, Inc. | Thermal isolation spray for casting articles |
Similar Documents
Publication | Publication Date | Title |
---|---|---|
US3450189A (en) | Process of coating metal castings | |
US3204303A (en) | Precision investment casting | |
US3243397A (en) | Mold and core coating composition from calcined hydrated aluminum silicate, mica, and bentonite | |
JPH0420686B2 (en) | ||
JP2014073504A (en) | Mold wash for casting | |
US2882568A (en) | Lining for ingot molds | |
US2426988A (en) | Mold coating | |
US2426987A (en) | Mold coating | |
CZ304714B6 (en) | Aqueous composition for the manufacture of insulating refractory material and article having a body of refractory material | |
US3184815A (en) | Metal casting process | |
US2973563A (en) | Lining for ingot molds and method of producing ingots | |
ES330507A1 (en) | Procedure to inhibit from the erosion the surface of molds for the foundry. (Machine-translation by Google Translate, not legally binding) | |
US3211560A (en) | Mold wash composition and casting mold coated therewith | |
US3184813A (en) | Metal casting process | |
US2090408A (en) | Mold coating | |
US3447936A (en) | Mold coating composition,particularly for centrifugal molds | |
JPS6318035A (en) | Pig iron material | |
US8833433B2 (en) | Foundry mold insulating coating | |
US8376024B1 (en) | Foundry mold insulating coating | |
CN110961570B (en) | Preparation method of zirconium oxide composite spray coating for metal mold casting | |
US5325907A (en) | Metallic mold for casting vehicle wheel | |
US3420644A (en) | Method for molding of glass and ceramic materials | |
US3770465A (en) | Mold wash composition | |
US1965949A (en) | Mold for casting ferrous metals | |
US1453593A (en) | Coating for metal molds |