US2824348A - Method of casting metals - Google Patents

Description

Feb. 25, 1958 J. c. WILLIAMS I METHOD OF CASTING METALS Filed mmn 1a. 1954 F/8POU5 COPE I /Pf MOLD v W J 4? United States Patent F METHOD on CASTING METALS John C. Williams, St. Charles, 11]., assignor to Hawley Products Company, St. Charles, 111., a corporation of Delaware Application March 18, 1954, Serial No. 417,020

9 Claims. (Cl. 22-2005) This invention relates to a new and improved method of casting metals and more particularly to a method of castmg metals which utilizes a porous core of preformed fibrous, heat resistant material.

One of the objects of the invention is to provide a method of casting metals which makes use of an inexpensive, light weight core of readily available materials.

Another object is to provide a new and improved method of casting metals by a process which is relatively simple and inexpensive.

Still a further object of the invention is to provide a method of casting metals employing a porous core of preformed fibrous heat resistant material from which the casting can readily be removed.

Still another object of the invention is to provide a casting method which eliminates sandblasting and wheel abrading.

An additional object of the invention is to provide a method of casting metals on a fibrous core which is heat resistant and sufliciently porous to let gas escape during the casting operation and, at the same time, sufficiently strong to retain its shape and remain substantially infusible at casting temperatures.

A further object of the invention is to provide a new and improved method for casting pipe ends.

Other objects and advantages of the invention will be apparent by reference to the following description in conjunction With the following drawings in which:

Fig. 1 is a perspective view of a fibrous molded core which can be employed in the practice of the invention;

Fig. 2 is a cross-sectional View taken along the lines 2, 2 of Fig. 1;

Fig. 3 is a plan view of the fibrous molded core shown in Fig. 1, and

Fig. 4 is an elevational view showing diagrammatically the manner in which the fibrous core is mounted on the end of a mandrel and a metal is cast thereon.

In the practice of the invention the metal, instead of being cast on a sand core in the customary manner, is cast on a preformed core made of fibrous, heat resistant material which is sufficiently dense, strong and smooth surfaced to maintain the shape of the casting but at the same time porous enough to let gases escape during the casting operation. The invention is especially suitable for the casting of pipe ends, for example, in the manufacture of cast iron or cast steel soil pipe. The preformed fibrous core is preferably placed over the end of a mandrel and the molten metal to be cast is flowed over and around the fibrous core. After the metal is cooled, the cast pipe is removed from the mandrel. The casting has no substantial tendency to fuse to the preformed fibrous core and the preformed fibrous core has no substantial tendency to adhere to the mandrel. Moreover, the preformed fibrous core has sufficient structural strength to withstand the temperature of the molten metal until it has set.

The core employed in practice of the present invention is composed of non-combustible intermingled and inter- 2,824,348 Patented Feb. 25, 1958 ice laced fibrous materials that have been accreted into a hollow shaped body which is light in weight but which has sufiicient strength to resist distortion during a casting operation. The method employed in the accretion molding of these cores is simple and readily adaptable to a mass production operation. A casting prepared on one of these cores is comparable in all respects to a product made according to the conventional sand core process. At the temperatures usually encountered in metal casting operations, e. g., 2500 F., the present molded fibrous core will withstand the temperature of the molten metal for a period long enough to cause the metal to assume the desired shape. Following the casting operation the core may be easily removed from the cast article and the fibrous material may be recovered and reused. 'While the article is referred to as a core it is also adaptable for use as the outside mold in a metal casting process.

The drawings represent one form of molded fibrous core which may be prepared according to the invention. It will be understood that the invention contemplates the preparation of cores of any size or shape that can be accreted or molded according to the method hereinafter described. In the drawings the molded fibrous core is illustrated as being composed of a body portion 1, a base 2 and an annular flange portion 3. The slope of the body portion from the flange 3 to the base 2 is exaggerated in the drawings for illustrative purposes, and it will be understood that in practice the taper of the body portion 1 will be slight. The object of the taper is to facilitate the removal of the core from the cast article.

The particular core illustrated herein is suitable for use in the casting of the flanged end on a section of cast soil pipe. In this respect the slight taper of the body portion 1 of the core will provide a tapered portion in the soil pipe which will facilitate the joining of pieces of pipe. For the same reason the raised portion 4 of the body 1 is provided. Between the base 2 of the core and the body portion 1 is provided an annular ring 5 which has a considerably greater slope than the body portion 1. The base 2 lends strength and rigidity to the core but the core may be molded Without said base. In such case the core will have an open end at this place.

The thickness of the core as illustrated in Fig. 2 is somewhat exaggerated for illustrative purposes. According to the invention the thickness of the core may be varied to suit the strength requirements for any individual situation. For ordinary purposes the molded core may be thin and light in Weight since it inherently possesses considerable structural strength. The combination of structural strength and light weight in the object greatly increases its utility and constitutes one of the important advantages of the invention.

The invention contemplates the use of any type of noncombustible fibrous material which is capable of withstanding the temperatures ordinarily encountered in metal casting operations. Glass fibers and asbestos fibers are illustrative of this class of materials. It is contemplated that the accretion molding of cores according to the invention may take place by slurrying a mass of fibrous materials of the class described above in a substantial quantity of water. The fiber and water slurry is then Water laid onto a porous former according to well known methods which are described in detail in numerous patents, for example, U. S. 1,872,583 issued August 8, 1932 and U. S. 1,952,168 issued March 27, 1934. Since the particular method of accretion molding is well known it is not deemed necessary to describe the method and apparatus in great detail here.

The fibrous materials described above may be employed in any combination which will give the desired structural strength and porosity to the finished core.

The strength and detail of the finished core may be improved by the addition of a setting material such as a thermosetting resin or an inorganic hydrosetting material of the Portland cement or plaster of Paris type. The phenolic resins are particularly adaptable to this type of core but the invention also contemplates the use of other thermosetting resins, such as urea resins and the melamine resins. The addition of setting material assists in binding the fibers together into a porous, accreted article having substantial structural strength. The resin may be applied by dipping the accreted article into a solution of .the resin or by precipitating the dissolved resin onto the slurried fibers according to well known methods.

The quantity of non-combustible fibers present in the preformed core is sufiicient to maintain the structural shape of the core during casting and the quantity of resin is sufiicient to bind the 'fibers together but insuflicient to destroy the porosity of the core during casting.

In order to provide a complete disclosure of the invention the following description of one embodiment of the invention will be given. It will be understood that the invention is not intended to be limited by the details of this description.

Example I Four and one-half pounds of milled glass fibers averaging one half inch in length are slurried in water along with one-half pound of African asbestos. The fiber mixture is suitably dispersed in the water by heating in the ordinary paper stock beater. The use of too much glass is undesirable because the accreted article will then be too free and will not form a good mat on the former. On the other hand, if too much asbestos is employed the accreted article will be too tight and it will be impossible to get the desirable thickness.

A satisfactory dispersion is made by employing from about 1% to 2% of total fiber on the weight of the water. The slurry may be maintained at approximately room temperature or the temperature may be raised to about 180 F. prior to the addition of resin to the slurry.

Approximately 20% by weight of resin (Resinox 615, a synthetic phenol-formaldehyde condensation product) on the weight of the fiber is thereafter dissolved in the slurry. The resin is preferably premixed with 2 parts L of water per part of resin and A. part of caustic .per part of resin prior to the addition to the slurry. Beating of the slurry is continued for a period of time sufiicient to insure thorough dispersion of the resin throughout the slurrry and then the pH is lowered to about 6 by the addition of hydrochloric acid. At this pH the resin precipitates on the surface of the fibers in a more or less uniform coating. Thereafter it may be desirable to add /2 pound of Carbowax 4000 which is a water soluble polyethylene glycol and which assists in causing the resin to adhere to the fibers.

The slurry is thereafter felted on conventional felting apparatus in any suitable'form such as the form shown in the attached drawings. Since the felting apparatus and method are well known in the art it is not deemed necessary to repeat such description. When an article of sufficient thickness has been felted, it is taken off of the former and put on a drying form where it is dried by blowing hot air through the porous accreted article at a temperature high enough to set the thermosetting resin. For example, hot air is drawn through the article at 250 F. for 20 minutes or at 300 F. for 3 minutes. In addition to setting the thermosetting resin and in creasing the structural strength of the article, drawing hot air through it dries it out and increases the porosity of the article so that gases may escape through it during the casting operation.

The molded article is thereafter employed in casting operations. For instance, to cast pipe ends, the fibrous mold or core shown in the drawings is placed over the end of a mandrel as shown in Fig. 4 and steel cast therearound. In practice, the arrangement shown in Fig. 4 can be varied substantially. For example, the mandrel or the pipe mold can be shaped to back up or support the exterior of the flange 3 of the core 1. Also, the base 2 of the core 1 can be cut out and the mandrel allowed to project therethrough. After the metal has cooled the cast pipe is removed from the mandrel. The fibrous core is easily removed from the mandrel and the casting because it has no tendency to fuse to either. No sandblasting or wheel abrading is necessary to smooth the casting or mandrel. The fibrous core has sufiicient structural strength to withstand the temperature of the molten metal until it has set in the shape dictated by the mold. The resin is at least partially destroyed by the high temperatures encountered in the casting operation and the strength of the fibrous core is correspondingly lessened. The core may then be easily removed from the cast piece and, if desired, the fibers may be reused in making up a slurry at the beginning of the cycle. However, the fibrous cores are so inexpensive and their use results in such an overall savings in finishing costs that theiruse results in a net savings in the cost of the casting even if they are thrown away.

From the foregoing disclosure it will be apparent that the present invention provides a new and improved disposable molded fibrous core for use in casting operations. The molded fibrous core has many advantages over the previously employed sand core in that it is light in weight, infusible, strong enough to resist distortion by ordinary handling, and inexpensive to make both from a material and labor standpoint.

It should be understood that variations may be made in the practice of the invention Without departing from the spirit of the invention. Thus a fiber such as asbestos may be used without the glass fiber provided it is of the type which is relatively free and does not pack too tightly. Some South African fibers have this freeness characteristic. Other heat resistant fibers can be employed in making the core, e. g., Fiberfrax (Carborundum Company) and Kaowool (Babcock & Wilcox Company). The resin may be applied not only by precipitation on the fiber as described in the illustrated example but also by a clipping process. Other variations will be apparent to those skilled in the art.

This application is a continuation-in-part of my copending application Serial No. 161,787, filed May 13, 1950, and now abandoned, wherein the preformed molded cores are claimed as new articles of manufacture.

The invention is hereby claimed as follows:

1. A method of casting metals which comprises casting molten metals around a preformed fibrous core comprising a major proportion of heat resistant, substantially non-combustible fibrous materials and a minor proportion of a thermosetting resinous binder, said thermosctting resinous binder being at least partially destroyed at the high temperatures employed in said metal casting.

2. A method of casting metals which comprises casting a molten metal on a preformed core consisting essentially of a major proportion of fibers which are non-combustible during the casting operation and a minor proportion of a resinous thermosetting binder disposed on said fibers and in the interstices between said fibers, said fibers being present in said core in sufiicient quantity to provide a core which will maintain its structural strength during casting and the quantity of said resin being sutficient to bind said fibers together but insutficicnt to destroy the porosity of said core during casting, said resinous thermosetting binder being at least partially destroyed at the high temperatures employed in said metal casting.

3. A method of making pipe ends which comprises placing a preformed tapered hollow shaped core consisting essentially of a major proportion of non-combustible intermingled and interlaced fibrous materials and a minor proportion of a thermosetting resinous binder over a mandrel, casting a molten metal on said fibrous core such that said thermosetting resinous binder is at least partially destroyed during said casting, cooling the cast metal and removing it from said fibrous core.

4. A method of casting metals which comprises casting a molten metal on a hollow, relatively thin shaped porous substantially rigid body comprising a major proportion of intermingled and interlaced fibers of non-combustible material and a minor proportion of a thermosetting resinous material adapted to bind said fibers together, said thermosetting resinous material being at least partially destroyed at the temperatures employed in said metal casting, cooling the cast metal and separating said hollow body therefrom.

5. A method of casting metals which comprises casting a molten metal on a hollow, relatively thin shaped porous substantially rigid body comprising a major proportion of intermingled and interlaced glass fibers and asbestos fibers and a minor proportion of a thermosetting resinous material adapted to bind said fibers together, said thermosetting resinous material being at least partially destroyed at the temperatures employed in said metal casting, cooling the cast metal and separating said hollow body therefrom.

6. A method of casting metals which comprises casting a molten metal on a hollow, relatively thin shaped porous substantially rigid body comprising a major proportion of heat resistant, substantially non-combustible fibers which have been intermingled and interlaced by water-laying accretion on a porous former and a minor proportion of a thermosetting resinous material adapted to bind said fibers together, said thermosetting resinous material being at least partially destroyed at the temperatures employed in said metal casting, cooling the cast metal, separating said hollow body therefrom and recovering said fibers from said hollow body for reuse.

7. A method of casting metals which comprises casting a molten metal on a hollow, relatively thin shaped porous substantially rigid body consisting essentially of a major proportion of glass fibers and asbestos fibers which have been intermingled and interlaced by water-laying accretion on a porous former and a minor proportion of a thermosetting resinous material adapted to bind said fibers together, said thermosetting resinous material being at least partially destroyed at the high temperatures em ployed in said metal casting, cooling the cast molten metal to set in the desired shape upon said hollow body within a period during which said hollow body contains sufficient structural strength to withstand said molten metal, and separating said hollow body from said cast metal.

8. A method of casting metals which comprises casting a molten metal on a hollow, relatively thin shaped porous substantially rigid body comprising a water-laid, accreted mixture of about nine parts by weight of glass fibers, about one part by weight of asbestos fibers, said glass fibers and said asbestos fibers together constituting a major portion of said hollow body, and about two parts by weight of a thermosetting resin adapted to bind said fibers together, said thermosetting resin being at least partially destroyed at the high temperatures employed in said metal casting, cooling the cast metal and separating said hollow body therefrom.

9. A method of casting metals which comprises casting a molten metal on a hollow, relatively thin shaped porous substantially rigid body consisting essentially of a water-laid, accreted mixture of about nine parts by weight of glass fibers, about one part by Weight of asbestos fibers, and a binding agent for said fibers consisting of about two parts by weight of a phenol-aldehyde resin and about one part by weight of a polyethylene glycol, said binding agent being at least partially destroyed at the high temperatures employed in said metal casting, cooling the cast metal and separating said hollow body therefrom.

References Cited in the file of this patent UNITED STATES PATENTS 342,906 Gartside June 1, 1886 1,281,679 Smith Oct. 15, 1918 1,486,631 Byers Mar. 11, 1924 2,162,386 Neuhof June 13, 1939 2,411,557 Schuh Nov. 26, 1946 2,509,599 Hollenberg May 30, 1950 2,633,433 Hollenberg Mar. 31, 1953 2,688,780 Anderson Sept. 14, 1954 FOREIGN PATENTS 200,730 Switzerland Jan. 2, 1939

Claims (1)

1. A METHOD OF CASTING METALS WHICH COMPRISES CASTING MOLTEN METALS AROUND A PREFORMED FIBROUS CORE COMPRISING A MAJOR PROPORTION OF HEAT RESISTANT, SUBSTANTIALLY NON-COMBUSTIBLE FIBROUS MATERIALS AND A MINOR PROPOR-

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