US2663921A - Method for the centrifugal casting of metal parts - Google Patents

Description

Dec. 29, 1953 C. C|T0 2,663,921

METHOD FOR THE CENTRIEUGAL CASTING OF METAL PARTS Filed June 8, 1949 Caz/mozzo Czlto.

Patented Dec. 29, 1953 y :MEtnHonFoR THE CENTRIFUGAL 'CASTING-QF METAL A:Paars camino citoyAUvccle, Belgium, assigmr fo'hf'aus- .losoaroh Laboratory 11.112-, .Bhladolliliif I Aeilioation: Juno 8, 1949, VSerial No- .37H88 2.01am. l(c1. 22-2095).

VThe present invention relates Ito, amethodfor the centrifugal casting ofmetal partsof annular Shapefina vrotary mould.l

-The structural claims originally embodedin thisapplicaton havebeendivided andare ineluded in divisionaly application SerialNo. 153,365, nowabandoned, ledApril 1, 1.950, for`Ins/talla.- tiongfor the CentrifugalCasting of a Metal Ingot oiGen'eral IA'nnuIar Shape.

The annular castingshitherto obtained by this method hadcraclis orfother faults on the cylindricaliperiphery, which mustbeattrilouted to the high co-eflicient of heatitransmission-of thewalls i` the cylindrical mould,` and alsoirequently, lacked homogeneity, which Wasessentially. dueto irregularities in thetenperatures of castingand cooling'heretoforeused The Arn'esent invention has'forfts-object to obtain by centrifugal casting annular metalparts offhomogeneous structure, without cracks, ssures orany solid and/orv gaseous inclusions.

According' to the invention, the centrifugal casting of the annular part is. eiected under thermal conditions that prevent a substantial accumulation of heat in thewalls of,y the mould, and which are such that the solidification bycoolng on said walls, fromfthe outside towards thenside, caribe varied, onthe onehand inrelation to the mass of metal being treated, and'on the other hand irl-relation to the. speedof rotation useclin the centrifugal casting operation, Yit being possible for said speed andsaid cooling also to be varied at yevery instantr in relation tothe increase in the'mass being cast loluringtloe process of casting and forming the saidpart.

This centrifugal castingaccordingvto the invention can be'effected abouta horizontal axis and the said thermal conditions canbe obtained lovV means thatcomprisean internal or axial heating and an external cooling .of the mass, which is dependent from the speed of rotation of `the. mass being treated, whichdetermines its, centrifugal force, and from zin-adjustable stream of cooling airv applied to the external periphery-of a oylindrcalimould, the wallsof which have only a slight-,.caloric inertia, sothat it is possible to reduce and/or adiustat will the lossof heat of.

said mould.

The invention thus ,provides in the virst place,

annexed to the v'present.specilcation and .whichV show .anfequprnent' intended Aforli-he manufacture of annular ingots with .a cylindricalperiphern In these drawings:

Fiel shows ,afolovatiooal .vewvof 'thofooiliaf ment withl portions broken away; .and

Fig. v2 is asection-through the vertical plane II--II of Fig. 1,y showingr :also Lthe; means Vfor-,cooling and rotating thetrotaly mould, Mid valso the casting operation, Y y

The equipment shown .i 'comprises a cylindrical Inouldv'Z which is;adaptedto'loerotatedabout a horizontal axial-I. .The mould. is provdedfat both itsfen'dswith ,cheells andfwhichllim fthe width of the ingot andare engaged over Ya -cylin. dricaldrum. or wall`5 Awhich is `vof, only y coin-'paratively small thickness. This cylindrical' Wal15,is provided; on the. outside with 'hns .6l which, areat right angles'to theaxis of rotation I-I and are arranged evenly andparalllto one another between the cheeks `3j' `and4,i1which"rest on four, rollers 'l andf8"mountedrespectivelyon shafts "9 and I El. The shaft 9 isthie' driven ,shaftj ot aspeed variator vIljfor the'motor l2. Iffitb'elassumed that the shaft i9 rotates in "the'drectionofgthe arrow X, the mould, lthereforerotates int l 1e,di.

rection'of thedarrow ,'Afan :|:j3the vrotor of, which isdriven, for l example, i loyi means 0f av belt m running .on 'apulley jliolffthe, 'shaft aoro'es airthrough anne, l rim ,tothe ons .ofintreoirecf tionof thearrowjz; .Thepipe I'Bjisjthereforefso loo/ated that vthe iet off.. @what issues/therefrom isj dreetedin the opposite directiongto the diret.,-l tion ofrotaton of tho-mould? A valve Ilv isttedgonthedelvery'pipefl'fto enable `the, quantity :of .air lolownilonto the to be. adiustod oventirolo?thej Spoed of. rotation ofthe rollers remains unchanged.

.The m0..-11.d.2 .is furthelmme quppedwthfa Sooroeofihoatn'itsjoontreljaone. Thesaiidfsourgoe ofV heatV is "shown A,nftliefform of 'twoj'carbon Velec-r trodes,I8-. I"8 betweeniwhichfan electric arenan loel struck 'to ,heatIk the inside. lof, thesmould.

'In o'derto 'Gastffr example, a mild steel ingt eooolina,starting-from'thererinhery n 3 in the plant which has just been described, it is advantageous to proceed as follows:

To avoid direct contact of the metal to be cast with the thin cylindrical wall 5 of the mould, the inside of the mould may be coated with milk of silica and bentonite or it is possible to distribute the refractory layer I 9 to be formed by centrifugal action and gradual heating. At the same time,

the joints formed between the cylindrical wall 5,.

and the cheeks 3 and 4 have thus been filled, whereby subsequent stripping is facilitated.

After having heated the inside of the mould 2 so as to raise it to a temperature of about 400 C., the casting operation is started, for example by quickly pouring into said mould from a Crucible 20 a mass of steel in quantity sufficient for it not to solidify and subjecting it to centrifugal action. The steel is poured at a temperature that may advantageously be between l,500 and 1,600 C. 'IVhe steel is then poured as slowly as possible, so that the layers of liquid which form are as thin as possible. lThis greatly facilitates the evenness of the settling and the elimination of the gases and impurities, while during the solidiflcation of the ingot it is important to control the speed of 4rotation of the mould in order to obtain a satisfactory homogenization during cooling. Thiscooling does not only vary with the speed of rotation of the mould, but also depends on the position of the valve i1. The orientation of the delivery pipe I6 for the air in the opposite direection to the direction of rotation of the fins 6 enhances the cooling, since the relative speed is equal to the sum of the linear speeds of the air stream and of said fins, so that the temperature of the mould may advantageously be maintained at a maximum value of about 550 to 600 C. In this manner, owing to the low calorific inertia of the mould and the possibility of adjusting the loss of heat, it ispossible to keep said loss of heat at a low value during the casting operation and for some time after the completion of same, and this adjustment can also be used toincrease said loss subsequently to such a degree that the temperature of the mould does not greatly exceed about 550 C.

It should be noted in particular that with this method of the invention, the value of the loss of heat in the mould, which can be varied at will, can be expressed by the formula: a=2|10\/1 J wherein u is the relative peripheral speed of the air with respect to the rotating mould.

In the case, for example, of an annular mild steel ingot of about fifty kg. the casting in a mould of suitable size is effected as follows:

During a first phase that corresponds to the beginning of the casting operation, the heated mould is rotated at such an angular speed that the centrifugal force developed is at least twice that necessary for the molten metal to assume the shape of a ring in contact with the mould. The approximate peripheral speed V of the mould at this point may be expressed as V2=2gr2/1" where y is the acceleration of gravity, r is the y radius of the inside of the mould and r' is the radius of the inside of the ingot. This rst phase may be completed in about ten minutes, while the casting has been effected after about two minutes.

During a second phase, the supply of heat is cut down and the above-mentioned'peripheral speed is reduced to a speed such that the centrifugal force is approximately that necessary to 4cause the uid metal to take the form of a ring elimination of the last traces of gases. The centrifugal force that acts during this third and final phase, which may last one hour and a half, is therefore about three times that required for the molten metal to assume the shape of a ring in contact with the mould. The peripheral speed V2 at this point is expressed as V22=3gr2/r'.

When the centrifugal action has been stopped, one of the two side cheeks is removed. The annular ingot can then be readily removed owing to the contraction of the metal, and it is allowed to cool slowly for about forty-eight hours, covered with hot ashes.

When examined under the microscope, it was observed that the ingot had a totally different molecular structure from that of steel cast in the ordinary manner. Whereas the normal molecularV structure of a well refined good cast steel is in the form of distinctly visible grains of ferrite surrounded by grains of pearlite, the steel which has been cast by the method according to the invention, on the contrary, shows under the microscope a structure almost similar to that of forged steel, without segregations of impurities and without blow-holes.

The invention is not restricted to the manu-r facture of ingots of annular shape with a cylindrical outer surface, but can also be applied to parts such as gears or the like, the outer periphery of which departs from the cylindrical shape. In this case, a rotary mould or drum may be used, the inner contour of which corresponds to the shape of the desired part, without exceeding the scope of the following claims.

What I claim is:

l. The process of -centrifugally casting a rnetallic ringlike ingot, using a metallic mould having a thin wall, which comprises rotating the thin walled metallic mould about its own axis in a horizontal position of the axis at an approximate minimum peripheral speed V expressed as V2=2g12/ r where y is the acceleration of gravity, r is the radius of the inside of the mould and r' is the radius of the inside of the ingot, preheating the interior of the mould to a temperature of about 400 C., coolingY the periphery of the mould be a stream of air directed on the outside of the mould, pouring molten metal into the preheated mould and forming the molten metal into a ring in contact with the inside of the mould, continuing the heating of the interior of the mould to heat the metal during the pouring and at least until the entirety of the molten metal cast has taken the ring form in the mould, subsequently stopping interior heating of the mould, subsequently reducing the approximate peripheral speed of the mould to a new value V1 expressed as V12=gr2/r and for a time at least equal to that of the pouring operation, then increasing the approximate peripheral speed of the mould to a new value V2 expressed as and further regulating the cooling rate so that the temperature of the mould does not exceed about 550 C.

2,. The process of centrifugally casting a mehorizontal position of the axis at an approxi.

mate minimum peripheral speed V expressed as V2=2gr2/r' where g is the acceleration of gravity, 1' is the radius of the inside of the mould and r is the radius of the inside of the ingot, preheating the interior of the mould to about 400 C., cooling the outside of the mould by a stream of air, pouring the molten metal into the preheated mould and forming the molten metal into a` ring in contact with the inside of the mould, continuing the heating of the interior of the mould to heat the metal during the casting and at least until all the molten metal to be cast has taken-the ring form on the inside of the mould, subsequently stopping the heating of the inside of the mould, reducing the approximate peripheral speed of the mould to a new Value V1 expressed as V12=yr2/r' and for a time of about one and one-half times the time which elapsed since the beginning of the pouring, then increasing the approximate peripheral speed of the mould to a new value V2 expressed as V22=3gr2/1" and regulating the cooling by regulating the air stream in a direction opposite to the direction of rotation in order to maintain the temperature in the mould not exceeding 550 C.

CAMILLO CITO.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 644,018 Lilienberg Feb. 20, 1900 1,277,543 Carney Sept. 3, 1918 1,349,416 Eynon Aug. 10, 1920 1,436,305 Cammen Nov. 21, 1922 1,573,089 Rice Feb. 16, 1926 1,698,623 Dale Jan. 8, 1929 1,698,624 Dale Jan.. 8, 1929 1,783,094 Moore et al Nov` 25, 1930 1,882,516 Naugle et al Oct. 11, 1932 1,957,718 Naugle et al May 8, 1934 1,993,774 De Bats Mar. 12, 1935 2,087,347 Larsen July 20, 1937 2,252,219 Trotzke Aug. 12, 1941 FOREIGN PATENTS Number Country Date 871,918 France Jan. 22, 1942 OTHER REFERENCES The Iron Age, page 81, May 26, 1949.

Claims (1)

1. THE PROCESS OF CENTRIFUGALLY CASTING A METALLIC RINGLIKE INGOT, USING A METALLIC MOULD HAVING A THIN WALL, WHICH COMPRISES ROTATING THE THIN WALLED METALLIC MOULD ABOUT ITS OWN AXIS IN A HORIZONTAL POSITION OF THE AXIS AT AN APPROXIMATE MINIMUM PERIPHERAL SPEED V EXPRESSED AS V2=2GR2/R'' WHERE G IS THE ACCELERATION OF GRAVITY, R IS THE RADIUS OF THE INSIDE OF THE MOULD AND R'' IS THE RADIUS OF THE INSIDE OF THE INGOT, PREHEATING THE INTERIOR OF THE MOULD TO A TEMPERATURE OF ABOUT 400* C., COOLING THE PERIPHERY OF THE MOULD BE A STREAM OF AIR DIRECTED ON THE OUTSIDE OF THE MOULD, POURING MOLTEN METAL INTO THE PREHEATED MOULD AND FORMING THE MOLTEN METAL INTO A RING IN CONTACT WITH THE INSIDE OF THE MOULD, CONTINUING THE HEATING OF THE INTERIOR OF THE MOULD TO HEAT THE METAL DURING THE POURING AND AT LEAST UNTIL THE ENTIRETY OF THE MOLTEN METAL CAST HAS TAKEN THE RING FORM IN

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