US1630045A

US1630045A - Centrifugal casting of metals

Info

Publication number: US1630045A
Application number: US726445A
Authority: US
Inventors: Lucien I Yeomans
Original assignee: AO Smith Corp
Current assignee: AO Smith Corp
Priority date: 1924-07-17
Filing date: 1924-07-17
Publication date: 1927-05-24
Anticipated expiration: 1944-05-24

Description

May 24. 1927.

1.. I. YEOMANS CENTRIFUGAL CASTING 0F METALS Filed Juiy 17, 1924 INVENTOR.

WTNESJ. v

' Z W lay g 6 I ATTORNEYS.

Patented May 24, 1927.

UNITED STATES PATENT OFFICE.

LUCIEN I. YEOMANS, OF CHICAGO, ILLINOIS, ASSIGNOR TO A. 0. SMITH CORPORATION, OF MILWAUKEE, WISCONSIN, A CORPORATION OF NEW YORK.

CENTRIFUGAL CASTING OF METALS.

' Application filed July 17,

The features residing in the invention will now be described, and the novelty thereof will be pointed out in the-appended claims.

The drawing herewith is merely illustra- 6 tive in a conventional manner of the uses of my invention, which latter it will be understood may be employed in connection with or applied to any type of centrifugal casting machine in which a rotating metal mold 10 is used. However, the invention is not to be limited in its application to that particular branch of the art, but may be employed as well in connection with metal molds used in ordinary casting processes.

In the drawing which accompanies this specification, Figure lshows a longitudinal, vertical sectional view, and Fig. 2. shows an end elevation, looking from the right of Fig. l, of a conventional centrifugal casting machine, provided with a tubular mold havingthe usual removableheads, one of which at least is formed with an enlarged central opening through which the molten metal used in casting may be introduced, and which may be removed'therefrom to permit the casting to Such a mold being old and well known,

specific description of its structural features is unnecessary .in the present instance.

It is recognized in the present art that the process of centrifugal casting with metal molds is particularly well adapted to the expeditious production of annular or tubular metal bodies, designed for and capable of various used, within'a limitedrange. Pespite the fact that the process of centrifugally casting metals has been known andoperated in various manners and with variously constructed machines for more than one hundred years, such process has not yet attained that high degree of erfection in its results that is greatly to be esired in an art so replete with dormant possibilities. The causes which have intervened to prevent the achievement 'of the results sought for are many, and have been the subject of much study and wide experimentation in the attempts of inventors to solve the problems which are involved.

Principal among these causes is the matter of the control of the thermal conditions attending the use of the metal mold during successive casting operations. To create and maintain a suitable thermal condition in the metal moldused in successive casting operof the casting.

peated use of the mold in successive casting-v be withdrawn from the mold.

1924. Serial ml 726,445.

as a normal condition, has proven a vex-atious problem. it has; been the subject of much theoretical work, only partially productive of the results which have been earnestly striven for.

In casting metal alloys which are susceptible to a quick chilling effect upon contact with the relatively cold surfaces of a metalmold, theheat is abstracted very rapidly from the casting after the freezing point of the metal alloy has been reached, very often to the deterioration of the quality On the other hand, the reoperations where rapid production is desired, has the effect of creating in the mold a temperature which becomes so high that it approachesthe fusion point of the metal'of which the mold is formed, and contacting portions of the molten metal which is poured into the mold will stick thereto, resulting in defective castings and renderingthe mold unscrviceable until it can be restored to prime condition. Again, such high temperature in the mold is a source of danger, -in that the cohesive nature of the metal of the mold is disturbed, and the latter is liable .to disruption under the centrifugal force generated inthe high speed rotatlon of the mold. The elimination of these adverse conditions is the purpose of my present invention.

I In making relatively thin castings of any metal by the centrifugal process, it is of material advantage to retard the cooling of the castingto an extent which will permit all gases and lighter impurities or other inclusions in the molten metal to escape with certaintybefore the metal congeals, and it has been found'that superior results may be obtained by retarding this chilling of the cast ing as much as possible and protracting the interval duringwhich a given amount of heat is transferred from the casting to the mold, or through the mold to the cooling media sometimes resorted to in conjunction therewith. 1 -Among the plans looking to that end, various metals have been used in the formation of the molds. Molds have been constructed, some of costly metals having a property of internal conductivity which is these molds of the better quality have been mold at the time ,found to conduce to the production of markedly superior results in the castings. By reason of such superiority, it has been found profitable to use such molds, although their first cost has been excessive, when compared with the cost of other metals having greater internal conductivity.

In my studies and tests along th1s lme, conducted with a view to the ascertainment. of a satisfactory solution of. the difliculties which have been encountered in so many instances in the ast, I have discovered that by a very simpl d rooedure the thermal condition ofa metal mold may be brought to such desired normal temperature as will be best 7 adapted for and conducive to the achievement of highly satisfactory results in. successive casting operations, and that such normaltemperature can be maintained efii ciently throughout the whole of the casting operations, by reducing to a predetermine degree the temperature of the mold, as by the abstraction therefrom of 'a' definite number of heat units transmitted to the mold by the molten metal in the casting operation.

This very desirable result is brought about by a. novel treatment applied to the mold in the interim of the casting operations. In such treatment, I find it entirely possible to control the rapidity with which the heat is.

abstracted from the casting 'metal" by 'the mold, when the molten metal used in cast-- ing is poured thereinto. -As hereinbefore indicate this state of affairs follows treatment of the mold after each casting operation, so that the temperature of the mold at the time of pouring the metal is maintained in such normal degree as will surround the casting operations with conditions contributing largely to the production of wholly satisfactory articles of uniform construction in the successive casting operations. The extent of the absorption by the mold of the heat of the cast 2: metal and the temperature which the mold can attain, are regulated with such substantial exactness that material variations in the temperature of the of casting are practically eliminated. Hence, the mold is uniformly conditioned at all times of casting, so that the transmutation of the molten metal into a casting is retarded in such degree as is necessary to Hermit its conversion into a solid state who y free from blow holes or impurities of any nature.

conditioning the mold so as 'to present a.

predetermined temperature reduction for the purposes of my invention, I use water as a temperature equalizer or quencher. But the manner of its application is distinctly novel, and the provision of special constructions 'for the circulation of water through or about the mold, or the submersion of the latter, as are sometimes resorted to, is rendered.

unnecessary. Thus, I am enabled to dispense with all of the usual extraneous water' cooling devices' and their connections, to-

gether with the costs required for their installation. Such special constructions as have been employed heretofore for the purpose of cooling the mold act with varying degrees of success,'and have not been effectlve 1n producing that normal condition in the temperature of the mold that is essential to the attainment of the highest results in casting.

4 By supplying a predetermined, -measured quantity of water to the interior of the mold a the water at the time of its introduction into .the mold to the boiling point, plus the latent heat to transform it from water at 212 F. to steam at 212 F.

An example of the application of my invention in a practical manner is illustrated in the following: In casting an annular body of steel having a wall thickness of one inch and a weight of one thousand pounds, for instance, a mold having a wall thickness of three inches and a weight of approximately three thousand pounds will be provided. The molten metal is cast at a temperature of about 2700 F., and it is desired to remove the casting fromthe mold after congelation at a' temperature of about 2000"F., 'or after a drop of about 700 F. in the temperature of the casting has taken place. The heat transferred from the cast metal to the mold may be represented, since the spegific heat of themetal may be assumed as .20,

'(60 1000)=200,000 B. t. u.

In the equation, the factor 60 is'the B. t. u. representing the latent heat of fusion of steel. This total of 200,000 B. t. u. is the equivalent in amount to that represented by the transformation or conversion of 179.3 pounds of water at 62 F. to steam at 212 F., or of 21.6 gallons of water at the same temperature so utilized, as follows:

approximately 233- F. .at this time. The

temperatures found to be suitable in the rotating mold after the cooling'operation and before casting, may range from 250 F. to 1100 F., butshould not be permitted to rise above the latter, in the interest of safety while the mold and its charge of molten metal are under rotation. In the present instance, a mold temperature of about 500 F. is suitable, and this is produced by treatment of the mold and maintained as-a normal.

Upon replacing the end plate of the mold after withdrawing the casting, water to the amount of 21.6 gallons will be poured into the rotating mold, and upon complete vaporization of the water, the temperature of the mold will have been reduced about 233 F., or to normal, due to the absorption of the heat from it necessary to heat and vaporize the water. After which the mold is ready for another casting operation.

These operations are repeated throughout the successive casting operations, with the result that castings of remarkable uniformity and perfection are produced. lVith these facts in mind, the efi'ect'of the intermitting or alternate casting and cooling of the mold to maintain the temperature of the latter at approximately a predetermined normal degree, and their eifect upon the castings produced, as well as upon the molds, are obvious.

I have found it very advantageous in the treatment of the mold incident to the cooling operation, to introduce a refractory material of suitable nature, for insulating purposes. Suchmaterial may be incorporated in the water used for cooling and be evenly deposited over the surface of the mold when the water is evaporated. Or it may be introduced into the mold as a spray over the surface thereof. The coating may be of a substance, graphite, for example, which will lower the melting point of the metal upon its first contact with the surface of the mold, so as to retard the cooling of the metal, and by alloying with the first. thin layer of the molten metal flowing into the mold, form' upon the casting a surface which will be free fromthe' cracks which are usually attendant upon'processes of casting in whichthe sudden chilling of the molten metal under such conditions is productive of or conducive to the production of shrinkage cracks which detract from the value of the product.

The mold should be pre-heatedto raise its temperature to normal, as a preliminary to the first casting operation. Such. preliminary heating may beefl'ected in various ways, as by placing themold in a heating furnace, or by subjecting it to a gas flame. Heating maybe eifected also by pouring into the mold a quantity of molten metal so as to transferthe heat therefrom to the mold, and such metal may be withdrawn from the mold and discarded when this has been done.

Having thus described my invention, what i prises the step of introducing into the mold after the casting has been willulraun a measured quantity of water which by its evaporation will'abstract from the mold the heat units imparted thereto by the [molten metal of which the casting is formed.

2. In n'ietal casting, the process of mold conditioning which comprises the sleps ol heating the mold preparatory to the first casting operation to impart a. normal tem: perature thereto, and after each casting operation introducing into the mold a measured quantity of water which in its evaporation will abstract from the mold the heat units imparted thereto by the molten metal, whereby such normal temperature is maintained;

3; In metal casting, the process of mold preparation which comprises-the operations of introducing into the mold a measured.

quantity of water which by its evaporation will abstract from the mold the heat units imparted thereto by the molten metal preof congelation, and restoring the normal temperature of the mold bythe application therein of a measured quantity of water which in its evaporation willabstract from the mold the heat units imparted thereto by the finolten metal.

5. In connection with the process recited inclaim 4, the step of rotating the mold during the operation of pouring the molten metal to form the casting.

6. The process of metal-casting, which comprises the operations of pre-heati-ng the mold to a pre-determined normal temperature, pouring molten metal into the mold, withdrawing the casting after the temperature has reached the point of congelation, and restoring the normal temperature of the mold by the application of a measured quantity of waterwhich in its evaporation will abstract from the mold the heat units imparted thereto by the'molten metal.

7. In connection with the process recited in claim 6, the step of rotating the mold during theoperation of pouring. the molten metal to form the casting.

8. The process of metal casting which comprises the o erations of pre-heating the mold to a pre-dhtermined normal temperature, coating the inside of the mold with a 5 material which will retard the cooling of the casting metal and form an alloy with the surface ofthe metal of which the casting is formed, pouring molten metal into the mold, withdrawing the casting when its 10 temperature reaches the point of congelation, and restorin the normal temperature of the mold by tlie application of a measured quantity of water which in its evaporation will abstract from the mold the heat units imparted thereto by the molten metal. ll

9. In connection with the process recited in claim 8, the step of rotating themold during the operation of pouring the molten metal to form the casting.

In testimony whereof, I have signed my 30 name at Milwaukee, Wisconsin, this 3d day of July, 1924.

LUCIEN I. YEOMANS.