US2668774A

US2668774A - Mold surface coating

Info

Publication number: US2668774A
Application number: US184523A
Authority: US
Inventors: Louis H Heyl
Original assignee: Individual
Current assignee: Individual
Priority date: 1950-09-12
Filing date: 1950-09-12
Publication date: 1954-02-09
Anticipated expiration: 1971-02-09

Description

surfaces.

Patented Feb. 9, 1954 OFFICE MOLD SURFACE COATING Louis H. Heyl, Rocky River, Ohio No Drawing. Application September 12, 1950,

Serial No. 184,523

I 4 Claims. r 1 This invention relates to the casting of metals and more particularly to a method and coating for cores, molds, and chills preparatory to metal casting. v I

Those skilled in the art are familiar with the use of refractory compounds used for coating sand cores and molds. Such coatings have been developed from basic refractory materials for coating cores, molds and chills, as well as for patching cores or molds to produce pattern-true castings efficiently and with minimum loss and breakage, or surface damage caused by removing cores from castings or molding sand from outer Although satisfactory for some purposes, such refractory materials, as have been used inthe prior art, have certain limitations when applied as coatings inv the art of casting metals;

These limitations, which are inherent in the properties of the refractory coating materials, relate principally to lack of elasticity, flexibility and Viscosity. When metals are cast against such coated surfaces the thermal shock of the molten metal causes greater expansion of the core or mold than of the surface coating, and produces fine hairline cracking, and spalling, with resultant adherence or fusion of the sand to the casting, or adherence or fusion of the casting to a chill or tea metal mold.

These detrimental effects present serious problems in the art of casting metals. The fusion of the cast metal to a metal mold frequently results in broken or severely damaged metal molds. Likewise, the lack of proper viscosity at useable graviti'es of solution causes streaking or running of the coating and non-uniformity in application, Dipping, brushing, swabbing or spraying aqueous solutions of such coatings result in streaks and runs which form undesirable teardrops. In like manner, brushing of the coatings leaves brush marks and such imperfections are reproduced in the cored or molded surface of a metal casting.

' It is an object of this invention to provide a new and improved core, mold, or chill coating for casting metal and the like, which will result in pattern-true castings having a minimum loss and breakage, and easier cleaning of sand from the core or molded surface, thus producing castings which are not mutilated by excessive chipping; sand, or shot blasting, and which will result in a great saving of time and labor.

Another object of this invention is to provide a n w and improved core, mold, or chill coating composition for the casting of metals which will 2 have the desired degree of elasticity, flexibility, and viscosity to enable production of patterntrue castings.

A further object of this invention is to provide a method of making a new and improved core, mold, or chill coating for use in the casting of metals.

Briefly, in accordance with this invention, I provide a method of making a new and improved type of core, mold, or chill coating which includes the addition to refractory minerals and materials, of certain emulsions having the desired viscosity building character and to act as a binder of an elastic and flexible nature, then adding sufiicient water to make the composition have a putty-like consistency. Thereafter, in use at the foundry, more water is added to obtain a solution of the desired gravity, and then the solution is applied to a mold or core surface which is then dried or baked in an oven at elevated temperatures.

This invention also includes a resultant refractory compound which provides a newand improved coating for cores, molds and chills in the casting of metals.

I have found that the desired properties of optimum elasticity, flexibility and viscosity, as well as adherence of the coatings to a core or mold may be obtained with conventional refractory compounds by the addition to such compound of certain elastic emulsions. In accordance with this concept I have found that any of the conventional refractory compounds can be improved by the addition of these emulsions in the proper manner to act as a binder of an elastic and flexible nature, as well as a viscosity building element.

I carry out the present invention by making a homogeneous composition of a refractory ma terial and a binder. The refractory may comprise material, such as graphite, of both the amorphous and crystalline flake types, talc, carbon, soapstone, silica and the like which are mixed usually in pulverized form. The binder may comprise any one of the following: an emulsified asphalt, an emulsified rosin, such as is shown in United States patent to Kirschbraun, No. 1,615,303, issued January 25, 1927, a gilsonite emulsion or a liquid resin, such as a phenolic resin currently sold by Monsanto Chemical Company of Springfield, Mass. under the trade-name Resinox 4846 as illustrated in their circular designated Resinox 4846 Foundry Core Binder Resin published October 20, 1949. If desired. a stabilizing agent, such as bentonite, may be formed by the action of chemical agents on natural resins, such as rosin or colophony, and the natural rosin itself also have an inherent plasticity which renders such products suitable for use as an elastic and flexible binder. I have found that when any of these materials are mixed. with a conventional refractory coating material theyintroduce a viscosity building characteristic to the material which causes the final usable aqueous solution to lack mobility of flow and yet retain the desired. elasticity and flexibility.

Where a refractory and a binder are used, the ingredients may vary within the following proportions by weight:

Per cent Refractory '75 to 90 Binder to 25 A satisfactory formula utilizing a refractory and binder embodies the ingredients by weight as follows:

, Per cent Amorphous graphite 85 Asphalt emulsion Stabilizing agent /2 of 1% to 10%. Binder 2% to 50%. Refractory material Balance to make 100 A satisfactory formula for a composition embodying a refractory material, a stabilizing agent, and a binder may be obtained by using ingredients in the following proportions by weight:

Per cent Amorphous graphite 79.5 Bentonite 6.5 Asphalt emulsion 14 If desired, a mixture of refractories may be used such as graphite and talc or soapstone and the like, but the total amount of refractory should be kept within the limits specified for the refractory material in the aforementioned formula.

The refractory material and the stabilizin material, after being pulverized, are thoroughly mixed in a wet mixing machine of the muller type, putty chaser type, or dough mixer type, and then the binder after having been made in accordance with the disclosure in United States patent to Kirschbraun, No. 1,615,303, aforesaid, is added to the batch, with sufilcient water to result in a homogeneous completely kneaded putty-like composition. Thereafter, in use at the foundry, more water is added to produce a solution having a gravity of 32 degrees Baum. The solution thus produced will have a relative viscosity of approximately three times that of 4 compositions heretofore used for core or mold washing purposes.

The addition of these materials in the above described manner operates as a viscosity-building agent in the core or mold coating refractory compound which results in an aqueous solution having the desirable properties so as to lack mobility of flow and achieve optimum viscosity for a uniform smooth application of thecoating to a core or mold surface. These improved properties eliminate teardropping, running, streaking, brush marking, and other detrimental limitations which are inherent in conventional coating compounds. They also develop in the final coating a degree of elasticity and flexibility, as well as adher'ence, which will present a smooth and uniform refractory surface to which cast metals will lay readily as well as separate readily from a sand core, or a sand or metal mold or chill. The resulting coating containing the emulsion of asphalt, rosin, gilsoniteor synthetic resin firmly bonds itself to the core, to prevent spalling, peeling, or cracking and thereby eliminates the many undesirable limitations encountered in the use of conventional refractory coatings otherwise produced.

After having applied the coating to a mold or core surface by brushing, spraying, swabbing, or dipping, the coating is finally prepared for casting by subjecting it to temperatures of about 250 to 400 F. Highly elevated temperatures are not detrimental to my improved coating, and I have found that this coating will withstand temperatures up to 3300 F. without danger of charring, cracking, spalling or burning.

It is to be understood that this invention is not limited to any or all of the aforementioned ingredients, inasmuch as any refractory minerals may be used in combination with any of the elastic binding emulsions mentioned and with or without the stabilizing agent (bentonite) to obtain the useful and improved results. My inventive concept relates principally to the introduction of such emulsified binders in mixed form with conventional or other proposed refractory coating compounds. As a result of the introduction of such emulsions in core or mold refractory coating compounds, I have been able to build up the viscosity of the final solution and thereby successfully abate the detrimental effects of teardropping, running, streaking, brush marking, and non-uniformity of coating surface as well as to increase the elasticity of the coated surface to prevent spalling, cracking, cutting or washing of dirt into such cuts when encountered by hot flowing metal at temperatures up to 3300513. The coating will withstand any normal metal casting temperature, thereby leaving the casting surfaces readily freeable of sand and eliminating the adherence or fusion of cast metals to sand or metal molds, chills or sand cores. This new and improved coating with its distinctive features and properties may also be successfully used for mudding or patching of cores or dry sand molds, as well as for coating cores, molds and chills.

I have shown and described what I consider to be the preferred embodiments of my invention along with similar modified forms and suggestions, and it will be obvious'to those skilled in the art that other changes and modifications may be made without departing from the scope claims.

Per cent Amorphous graphite 79.5 Asphalt emulsion 14 Bentonite 6.5

Water in sufiicient quantity to impart to the composition a putty-like consistency.

2. A coating composition for core or mold surfaces used in the art of metal casting, consisting essentially of a refractory material, a binding material consisting of an aqueous asphalt emulsion, the binder being present in a proportion between 2% and 50% by weight and water in suflicient quantity to make the composition have a putty-like consistency.

3. A coating composition for core or mold surfaces used in the art of metal casting, consisting essentially of a refractory material, a stabilizing agent, a binder, the stabilizing agent being in the proportion of at least one-half of 1% to 10% by weight, and the binder consisting of an aqueous 6 asphalt emulsion in the proportion between 2% and 50% by weight, and water in suflicient quantity to impart to the composition a putty-like consistency.

4. A coating composition for core or mold surfaces used in the art of metal casting, consisting essentially of a refractory material, a binding material consisting of an aqueous asphalt emulsion, the binder being present in a proportion between 2% and 50% by weight, and water being added in sufiicient quantity to make a solution having a gravity of substantially 32 degrees Baum.

LOUIS H. HEYL.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,620,899 Kirschbra Mar. 15, 1927 2,159,952 Jones May 23, 1939 2,270,770 Ray Jan. 20, 1942 2,348,155 Shanley May 2, 1944 2,502,473 Napier Apr. 4, 1950 2,525,175 Keyser Oct. 10, 1950

Claims

4. A COATING COMPOSITION FOR CORE OR MOLD SURFACES USED IN THE ART OF METAL CASTING, CONSISTING ESSENTIALLY OF A REFRACTORY MATERIAL, A BINDING MATERIAL CONSISTING OF AN AQUEOUS ASPHALT EMULSION, THE BINDER BEING PRESENT IN A PROPORTION BETWEEN 2% AND 50% BY WEIGHT, AND WATER BEING ADDED IN SUFFICIENT QUANTITY TO MAKE A SOLUTION HAVING A GRAVITY OF SUBSTANTIALLY 32 DEGREES BAUME.