US2335008A

US2335008A - Means for casting metals

Info

Publication number: US2335008A
Application number: US473834A
Authority: US
Inventors: Hubert V Hites
Original assignee: OHIO STEEL FOUNDRY CO
Current assignee: OHIO STEEL FOUNDRY CO
Priority date: 1943-01-28
Filing date: 1943-01-28
Publication date: 1943-11-23
Anticipated expiration: 1960-11-23

Description

Nov. 23, 1943. H. v. HlTES MEANS FOR CASTING METALS Filed Jan.v 28, 1943 Patented Nov. 23, 1943 UNITED STATES PATENT OFFICE MEANS FOR CASTING METALS Hubert V. Bites, Springfield, Ohio, assignor to The Ohio Steel Foundry Company, Lima, Ohio, a corporation of Ohio Application January 28, 1943, Serial No. 473,834

i" Claims. 101221-134) This invention relates to the casting of metals, and particularly steel, by the blind head method, wherein the feed metal for shrinkage in the casting is contained in a so-called blind head or riser and atmospheric pressure is admitted to the interior of the molten head metal to relieve a vacuum therein so that proper feed of metal to the casting to compensate for shrinkage may take place.

While the exact cooling action of molten metal in a blind head during a casting operation is not known, it is reasoned from experience that as the molten metal rises in a blind head its speed de-- pends on both the size of the casting cavity to be filled and that of the head cavity, which are proportional in size, andthat the larger the size the slower the speed of rise. Also, that the factors tending to cause chilling of the head metal and the forming of an air tight skin on its top surface, which prevents proper shrinkage feed, include the volume of air in the blind head cavity which must be expelled through the head wall as the metal rises in and fills the cavity; the area of wall exposed to the cavity; the condition of such wall, i. e., dry or green, and if the latter the extent of greenness, and the speed of rising movement of the metal in the cavity. These factors are all present to a greater extent in connection with the making of large castings than with small, so that apparently the tendency to chill and form an air tight skin on the top surface of the head metal increases substantially in proportion to the size.

It is also found in practice that fairly good but notentirely dependable results in maintaining the necessary shrinkage feed in the making of small castings, for instance, those employing blind heads of, or up to, approximately four inches indiameter, have been obtained by the use of a combustible disk-like chill retarding member in the top wall of the blind head cavity with a substantially flat face thereof exposed to the interior of the cavity and flush with its wall, but that when a similar chill retarding means is used in connection with the top walls of blind Other objects and advantages of the invention will be apparent from the following detailed description, and from the accompanying. drawing,

in whichi Figure 1 is a central vertical fragmentary sectional view of a mold of the blind head type embodying the invention, with the molten metal at the stage in its upward movement in the blind head cavity where it first contacts the chill retarding means; Fig. 2 is a view similar to Fig. 1, showing the blind head metal as it appears after complete shrinkage feed has taken place; Fig. 3

is a top plan view of the blind head metal after being shaken out from a mold and with the portion of the chill retarding means, which remains after combustion has taken place, removed from the head, and Figs. 4 and Sam different enlarged perspective views of a chill retarding unit embodying, the invention.

Referring to the drawing, I is a conventional showing of a blind head type of sand mold com-- monly used in the casting of metals and which has the customary blind head cavity 2 and the communicating casting cavity 3. Pouring of molten metal into the mold may be effected heads of larger diameter, the results are not satisfactory. It has also been found that such results have not been materially improved and as to project a distance into the blind head cavity so that the upper end of the blind head metal vrising in the blind head during casting will first have contact with the protuberant nature of the combustible chill retarding member before com-- through a gate 4 opening into the blind head cavity 2.

In carrying out the present invention, a core member 6 is mounted in the top wall of the blind head cavity 2 in exposed relation to theinterior of such cavity. This core is a unit separate from the mold body and comprises a disk-like .body part 1 having a substantially flat surface 8 from the central portion of which, in spaced relation to its edge, projects a small lug 9, which is preferably but not necessarily circular in cross-section and outwardly tapered. The side edge or peripheral wall of the core is preferably tapered with its large end uppermost to'facilitate retaining the core in place when the mold wall sand is packed therearound. A core which has been found very satisfactory in practice for use in connection with both small and large casting molds has its body 1 approximately two inches in diameter and fiveei'ghths of an inch thick with the projection 9 approximately one-half inch long and one-half inch in diameter at its lower end. The free radial space from the inner end of the projection to the side edge of the disk is approximately onehalfinch. It will be understood, however, that while specific dimensions are given, these are merely for the purpose of illustration. and not limitation.

The core 6 may be composed of any suitable material which will ignite and burn below the temperature of molten metal, and both coke powder and anthracite coal powder of a finely coarse ground nature packed and bound together in a shape retaining mass have been found to be very satisfactory for the purpose. The combustible material may comprise from 30 to 100 per cent of the mass, and this maybe boundtogether by a suitable binder, such, for instance, as oil, a-

cereal binder, and water. If the core contains less than 100% of the combustible material, the remainder may be of sand. The best results are ordinarily obtained, however, by using the full, or substantially the full, percentage of combustible material. The core material is pressed in a fairly loose manner so as to have a gas permeable characteristic greater than that of the mold sand to facilitate the passage of air under atmospheric pressure therethrough, and this characteristic is increased as combustion of the material takes place.

In use, a core 6 is set into the top wall of a blind head cavity when the mold is made, with the surface 8 of the core body I exposed to the interior of the cavity and substantially flush with its wall and with the lug or protuberant part 9 projected into the cavity towards the bottom. The usual ventmay be provided from, the top of the head cavity 2 through the mold wall, as shown at III by dotted lines, or suchvent may be and preferably is through an angular passage ll wholly or partiallyin the core 6, and thence through an upward passage l2 therefrom in the mold wall. In. the latter case, the passage I2 is offset from the entrance oftlie passage II to the head cavity so that any loose sand or other matter falling into the p'assagewill be caught by the core 6 and not fall into the head cavity. A small core-vent I3 is. also provided in'the mold I wall from the core to the outside so as to admit air under atmospheric pressure to the core and through it to the interior of "the head metal in the blind head cavity.

When molten metal is poured through the gate 4-it fills the casting cavity 3 and at the same time rises in the blind head cavity 2, so that the two are filled at, approximately the same time, the full condition of the mold being indicated by molten metal popping out of the vent 12, as well understood in the art. By the time the head metal I 4 has risen to near the top of the head cavity, an air tight skin has begun to form on its exposed top surface and has ordinarily proinvention the top surface of the head metal first strikes the projected end of the lug 9, causing ignition of the combustible material thereof, and

' as the metal continues to rise around the burning lug, the surface skin is stretched and heated thereby and caused to be punctured to provide an air passage into the interior of the head metal from the outside. As the metal rises into engagement with the top wall of the blind cavity, it makes contact with the larger bottom surface 8 of the core body in surrounding relation to the lug 9 so that the entire core is then ignited and caused to give off heat'to the contacting metal surface to not only retard further solidifying or skin forming action, but also to render the skin in contact with the surface 8 porous so as to better facilitate the admission of atmospheric pressure to the head metal. I

gressed to an extent that, unless a puncturing In Fig. 2, I5 designates a cavity formed in the head metal by admission of atmospheric pressure thereto and indicates that the necessary shrinkage feed of the head metal has taken place, while in Fig. 3, l6 designates the hole in the metal skin formed by the lug 9, and i1 designates the porous condition of the thin shell portion of the head immediately around the hole l6 and indicates the effect of the burning contacting core body thereon. It will be understood that atmospheric pressure is supplied to the head metal through the core-vent l3 and core 6.

It is found in practice, for some reason not fully understood, that desirable results, not possible by the use alone of a combustible projecting of the surface metal and render it porous or pervious to the passage of air therethrough.

I wish it understood that my invention is not limited to any specific construction, arrangement or form of the parts, as it is capable of numerous modifications and changes without departing from the spirit of the claims.

Having thus described my invention, what I claim as new, and desire to secure by United States Letters Patent, isr

1. A metal casting mold having a casting cavity and a communicating blind head cavit a core member having a gas permeable characteristic greater than'that of ordinary molding sand and including a combustible ingredient which burns upon. contact of molten metal therewith, said core having abody part set into the top portion of the head cavity wall and forming a part of the inner surface of such wall and having a relatively small central projection therefrom with which molten metal rising in the head cavity first contacts causing ignitionof the core material and penetration of the head metal skin before the rising metal makes contact with said exposed inner surface of the core body, said head member in the wall surface. With the present 76 wall having provision for admitting air under atmospheric pressure to said core member.

2. A combination as called for in claim 1 wherein the core body is of substantially fiat disklike form with the central projecting portion forming an abrupt angle with the face of the body exposed to said cavity and spaced from its edge.

wardly from the top wall of the cavity and being of stepped form to provide difierent surface areas which successively contact the top surface of metal rising in the upper portion of the cavity and ignite and burn upon contact therewith, the first step serving to puncture the metal skin to admit atmospheric pressure through the core to the interior molten metal of the head and the final step being substantially flush with and forming a continuation of the cavity wall, said head wall having provision for admitting air under atmospheric pressure to the core.

HUBERT V. HI'I'ES.