US1903906A - Centrifugal molding apparatus - Google Patents

Description

April 18, 1933. H. M. NAUGLE ET AL. 1,903,905

CENTRIFFUGAL MOLDING APPARATUS Filed Feb. 18, 1950 2 Sheets-Sheet 1 gwmow HMNau yZe Q .AJDw/m/zd W v M a April 18, '1933- v I H. M. NAUGLE ET AL 15903806 CENTRIFUGAL MOLDI NG APPARATUS Filed Feb. 18, 1930 2 Sheets-Sheet 2 I}? J gram stow EMA/angle mm m AJYZwnJ'e/ d Patented Apr. 18, 1933 UNITED STATES PATENT OFFICE HARRY M. NAUGLE AND ARTHUR J'. TOWNSEND, OF CANTON, OHIO, ASSIGNORS TO NAUG-LE & TOWNSEND, INC., 013 WILMINGTON, DELAWARE, A CORPORATION OF DELAWARE CENTRIFUGAL 'MOLDIING AIPPARAT'OS Application filed February 18, 1830. Serial No. 429,359.

The invention relates to apparatus for making steel blooms, slabs, billets and the like directly from molten metal poured from a ladle or the like; and the object ofthe improvement is to provide apparatus for producing such semi-finished products on a large commercial scale, without the preliminary production of ingots with the attending difliculties and defects.

According to common practice, in order that the large bodies of metal refined at one time by the various methods of steel making may be obtained in a convenient shape for rolling, it is necessary that these large bodies be divided into smaller ones, called ingots, of a uniform shape and size. These conditions are obtained by pouring the metal while .it is still molten into molds of the desired dimensions, where it may be allowed to solidify in part or in whole before the mold is removed.

As a preliminary step toward forming steel into the various sections which its many uses require, the heavy ingots, except in certain plate mills and some large shape mills, are first roughly reduced, in mills especially designed for the purpose, to much lighter but still very simple sections, as the round, the square and the rectangle.

When the ingot has been reduced to the dimensions of a square between one and onefourth inches and six inches, it is cut into convenient lengths calledbillets; if these pieces are six inches square or larger, they are known as blooms; and if reduced to rectangular formsbut with widths which are less than twice the thickness and within the dimensions specified for the square, the same names apply. But if the width far exceeds the thickness of the rectangular section, then it is called a slab.

A prerequisite to faultlessly finished material is perfect ingots, and by a perfect ingot is meant one free from all cavities or openings. and made up of material that is homogeneous throughout. Unfortunately, the natural laws that govern the solidification of liquid metal operate against both of these requirements. and develop the well known natural defects in ingots called piping, blow holes, segregation and crystallization. Added to these are other defects, both incidental and accidental, such as checking, scabs, and slag inclusions.

Accordingly, the preliminary casting of ingots and the attendant defects are avoided, by pouring molten metal directly into a rapid- 1y rotating mold wherein it is thrown by centrifugal force and molded into a homogeneous, uniform, compact, substantially rectangular section body in the form of a preferably continuous ring, which may be straightened after solidifying either before or after completely cooling, thereby making blooms, slabs, or billets directly from molten metal without producing the defects in a preliminary ingot, which must be eliminated before a perfect bloom, slab or billet can be pro-o duced.

In order to obtain practical and commercial advantages from the centrifugal method of making steel rings for subsequently rolling into finish ed products, it is necessary to treat, handle and deal with very large masses of metal at one time, because the steel is melted and made in large units of seventy-five or more tons, which must necessarily be tapped at one time, and in order to retain the initial heat and maintain a uniform quality, it is practically necessary to mold it in semifinished form as quickly as possible.

- Moreover, when very large masses of metal are utilized in producing a massive ring having a cross sectional area of sixteen or more square inches and having a diameter of eight or more feet, the time required for filling the mold cavity is appreciable. Accordingly, the metal first thrown by centrifugal action into the mold cavity following the tapping of the ladle becomes materiallv cooler than the metal later introduced into the mold cavity for completely filling the same, not only because of the fact that the mold is much cooler than the molten metal and consequently immediately absorbs heat from the metal first poured, but also because of the rapid transfer of heat from the molten metal to the air because of the high peripheral speeds dt-vr ped in satisfactorily utilizing centrifugal action.

of the rapid loss of heat therefrom to the mold proper and to the surrounding atmosphere, to permit the entrapped and evolved gasesto escape from the body of metal being formed before the metal reaches the plastic condition during solidification; with the result that voids and gas pockets are formed and exist within the body of solidified metal,

which produce imperfections in the molded ring, defeating the advantages of centrifugally molding the same.

On the other hand, if metal is heated to above 2600 F., and if the heated molten metal which is poured from the ladle has a' temperature of 2600 F. and upwards during the entire pouring and mold filling operation, the molten metal remains sufliciently fluid, while the mold cavity is being completely filled, to prevent the formation of voids and gas pockets in the body ofmetal, because the same are squeezed out of the fluid mass by the action of centrifugal force.

Moreover, the metal is sufficiently fluid at temperatures above 2600 F. so as to respond to the pressure created by centrifugal force for forming a uniformly sound, dense and compact resulting product. If the temperature is below 2600 F. then the metal is not sufliciently fluid to respond to the pressure created by centrifugal force, and the resulting product does not have the desired uniform soundness. It is pointed out that the steel while being poured, after having attained in all or in part, the velocity of the-mold, is subjected to two differently directed forces, namely: that of gravity and that of centrifugal force; so that if the viscosity of metal is too high while the mold cavity is being filled, the effect of centrifugal force is lost. In other words the benefits resulting from the utilization of centrifugal force are largely dependent upon the fluidity of the metal during the pouring operation, and the fluidity is in turn dependent upon the initial pouring and mold filling temperatures of the molten metal, which must be 2600 F. and upwards.

The well known shrinkage of metalwhen cooling from aplastic condition to a solid state, which may be some three-sixteenths of an inch per foot is negligible when centrifugally molding comparatively small sections, lengths and masses of metal; but such shrinkage must be provided for' in centrifugally molding larger sections, lengths and masses of metal, with which the present improvement is directed, to avoid a granular disintegration of the metal when cooling, which will occur if the metal is not permitted to shrink in accordance with its natural law.

' Accordingly it is an object of the present invention to provide rotary centrifugal 'molding, apparatus, the use of which will meet and satisfy all of the above requirements. Such apparatus includes a mold having upper, lower and side walls forming an annular mold cavity mounted for rotary movement, preferably on a vertical axis, so that the effect of the force of'gravity on the metal being introduced into and contained within the mold cavity is constant and acts in one direction during rotation of the mold. This rotation is accomplished by providing preferably an electric motor drive for the mold. The motor is preferably of a variable speed type so thatthe mold may be rotated at different peripheral speeds for carrying out the centrifugal molding method.

It is essential in order that the mold fill- I ing temperature of the metal may be maintained at 2600 F. and upwards, that the molten metal be quickly introduced into the mold cavity from the. ladle without loss of time, Such loss of time may be partially avoided by providing for the introduction of the molten metal into the mold cavity from a ladle, without requiring the ladle to be accurately located at a particular position.

Moreover, it is desirable to introduce the molten metal into the mold cavity formed by upper, lower and side walls,,by flowing the same substantially tangentiallyof the mold cavity in the. direction of rotation thereof.

Thus, the only metal utilized will be that required for filling the mold cavity; and a loss of metal is obviated, which would occur if the metal were introduced vertically downward into a mold cavity extension where some of the molten metal will solidify. Moreover, such solidified molten metal in a mold cavity extension prevents a ready and easy removal of the molded annular ring from the mold and must later be severed from the molded annular ring to which it adheres.

It is also desirable to introduce the molten metal into the rotating annular mold at a point near the upper wall of the mold cavity so as to assist the action of centrifugal force in completely filling the mold cavity and more particularly the upper regions thereof adjacent the upper wall.

These requirements are taken care of by our improved apparatus by providing a pouring runner for receiving the molten metal from the ladle. The runner is preferably provided with a pouring spout directed substantially tangentially with the rotatable mold and located adjacent the upper region of the mold cavity and adjacent the upper wall thereof. Y Moreover, it is an object of the present improvement to provide a mold from which the molded annular. ring may be readily, quickly and easily removed without loss of time so that the advantages of production methods may be obtained in utilizing the apparatus, and so that the molded annular ring will retain sufficient heat for carrying out subsequent rolling operations without reheating the same. The apparatus therefore includes a mold, split circumferentially, with the partinggline preferably at a lower circumferential corner of the ring molded therein.

A preferred form of apparatus in which blooms, slabs, billets and the like may be centrifugally molded, is illustrated in the accompanying drawings in which Figure 1 is an axial section through the mold and central vertical bearing, showing the motor drive, the ladle, and the improved pouring runner in elevation;

Fig. 2 is a plan view of the mold and improved runner in pouring position;

3 is an enlarged fragmentary section through a portion of the mold and pouring runner taken on the line 33, Fig. 2;

Fig. 4 is an enlarged fragmentary section through a portion of the mold and pouring runner taken on the line 4-4, Fig. 2; and Fig. 5 is a fragmentary plan view of the lmproved pouring runner.

Similar numerals refer to similar parts throughout the drawings.

A billet 6,'in the form of a preferably continuous ring, may be made in an annular mold cavity formed by upper, lower and side walls. The ring plate bottom 7 forms the lower wall of the mold cavity, while the i11- turned L-shaped rim 8, rabbeted on the bottom plate 7, forms the upper and side walls of the mold cavity. The bottom plate7 and L-shaped rim 8 are both mounted on a bed plate disk 9, having a central hub 10, and a depending vertical axial shaft 11, journaled in a vertical bearing 12, mounted in a casing 13, supported on a central pier 14, of a con-. crete foundation 15.

The Weight of the mold is preferably supported by an annular flange 16, depending from the bed plate disk 9 and. riding on rollers 17, having axles 18, journale d in horizontal bearings 19, mounted on a supporting framework 20, located on the annular pier 21 of the concrete foundation 15.

The mold may be rotated at any desired peripheral speed by the motor 22, driving the shaft 23, having a bevel pinion 24, meshing with a master gear 25, keyed to the depending axle shaft 11 freely above the vertical bearing 12. there being means, not shown. for controlling the starting,' stopping, and change of speed of the motor 22.

The-ring plate bottom 7 of the mold is preferably provided with an upright flange 26, on its inner edge, and its under face,

may be provided with a series of grooves 27 for registering with projections or ribs 28 formed in the upper surface of the bed plate disk 9. The registry of the grooves 27 and ribs 28 is arranged so that there may be relative movement between the members 7 and 9 because of expansion or contraction due to changing temperatures of the members 7 and 9 during operation.

The outer edge of the ring plate bottom 7 is preferably notched at 29 for receiving the coacting notched portion 30 of the L-shaped rim 8, and these notched portions 29 and 30 are likewise arranged so that there may be relative movement between the members 7 and 8 due to expansion or contraction.

The L-shaped rim 8 also hasa downturned annular flange 31 which is received in a recess 32 in the bed plate disk 9.

Clamping rods 33 are pivotally mounted at 34 on the bed plate disk 9 for cooperating with their cross bars 35, to engage the notched ears 36, protruding from the L-shaped rim 8, to securely clamp the ring plate bottom 7 and L-shaped rim 8 to the bed plate disk 9 at a plurality of places around the periphery of the members 8 and 9 as well shown in Fig. 2 of the drawings.

The L-shaped rim 8 which forms the upper and outer side walls of the mold may thus,

be quickly released from the ring plate 7 and bed plate 9 by swinging the clamping rods 33 outwardly and lifting the L-shaped rim upwardly by attaching a crane hoist to the ears 37.

It is pointed out that the molded ring 6 Will shrink circumferentially during cooling, with the result that the L-shaped rim 8 may be readily removed therefrom as above de scribed. The mold cavity having upper, lower and side walls formed by the ring plate 7 and L-shaped rim 8 may thus be divided at a circumferential line 38 located at the lower outside annular corner of the molded metal ring 6, whereby upon removal of the rim 8, the molded ring 6 may be readily lifted away from the ring plate bottom 7 by a crane and removed to other equipment for being subsequently worked.

A supporting standard 39 is located adjacent the rotatable mold in which is journaled the vertical shaft 40, carrying the framework 41, extending preferably horizontally inward over the outer peripheral portion of the mold; and the framework 41 has mounted thereon a pouring runner; or receptacle generally indicated at 42 which may comprise a metal box 43 having an inner refractory lining 44, forming a cavity 45 trapezoidal in shape in vertical section as shown in Fig. 3, and in plan as shown in Figs. 2 and 5, and rectangular in shape in vertical section as shown in Fig. 4.

An outlet or spout 46 located adjacent a lowermost portion of the cavity 45 permits egress of molten metal contained in the pouring runner cavity.

Suitable levers and appliances 47 and 48 are provided on the standard 39 for raising the framework 41 and rotating the same so that the pouring runner 42 may be turned to a position such as shown in dotted lines in Fig. 2 from above the rotatable mold for permitting removal of the rim 8.

The operation of the apparatus is as follows: 4

The pouring runner or receptacle 42 is positioned as shown in Figs. 1, 2 and 3 above the mold with its outlet orspout 46 located adjacent the upper region and upper wall of the mold cavity and with the axis of the spout located substantially in a horizontal plane nearer to the upper mold wall than to the lower Wall thereof, as well shown in Figs. 1, 3 and 4. In this position, the axis of the outlet or spout 46 is directed substantially tangentially with the rotatable mold.

The motor 22 is started so as to revolve the mold through the shaft 23 and gearing 24-25 at a high peripheral speed, whereupon a ladle 49 containing molten metal having a temperature materially above 2600 F. is located with its spout 50 above the pouring runner cavity 45.

the mold shown by the arrows in Figs. 2 and 4 until sufiicient metal has been introduced into the rotating mold to produce the ring 6. Meanwhile the temperature of the metal is always above 2600 F. so that the metal will remain sufficiently fluid in order to respond to the pressure created by centrifugal force for forming the uniformly sound, dense and compact molded ring 6.

Thus the pressure created by centrifugal force presses the fluid metal very compactly and densely into the mold and squeezes and eliminates therefrom all gases while the molten metal is still at a temperature of 2600 F. and upwards. The rotary speed of the mold is maintained at a maximum rate until the metal has cooledfrom a fluid condition into a sufliciently plastic condition to sustain its own shape, whereupon the speed of rotation may be reduced to decrease the force of centrifugal action to permit the continuous ring to shrink freely away from the mold, after which the molded ring 6 may be removed from the mold by removal of the L-shaped rim 8 as above described.

It is pointed out that the particular location of the pouring runner 42 and its nozzle opening 46 permits the fluid metal to be introduced as nearly as possible to final position within the rotatable mold; and the location of the nozzle opening 46 adjacent the upper region and upper wall of the mold cavity as shown in' Figs. 3 and 4 materially assists the action of centrifugal force in locating the metal in the upper region of the mold cavity.

Upon the removal of the ring bloom 6 from the mold, it may be severed or cut at one or more places and then straightened by rolling or otherwise into a straight billet. Although the present apparatus has been shown and described for use in making a four by four inch section, it will be understood that the L-shaped rim 8 may be varied to form a mold cavity so as to make a ring, bloom or billet having a cross sectional area of more. than sixteen square inches, or a ring slab having a similar cross sectional area.

It is not bommercially practical to make rings, blooms, billets orslabshaving a cross sectional area less than sixteen square inches because the tonnage per cast would be too small. Moreover, sections smaller than sixteen square inches will cool excessively before the ring straightening operations are completed. On the other hand, sections of sixteen square inches and upwards can readily be reduced in size during the straightening operation without the production costs. And finally'the surface per unit of weight is much smaller in the case of large sections, thus reducing the proportionate cleaning charges.

Although a ring diameter of not less than eight feet has been described, it will be understood that rings, blooms, slabs and billets having a diameter of say twenty-five to thirty feet are preferable. In utilizing such large ring diameters, the tonnage per cast is of suflicient magnitude to enable great economies to be secured. Moreover, the freezing troubles encountered with the frequent opening of ladle valves in successively tapping small quantities of metal are obviated. And finally, the pouring of a large number of small diameter rings instead of a small number of large diameter rings requires so much time that the temperature of the metal in the ladle will fall below 2600 F., thus making centrifugal molding commercially impractical.

It is pointed out that it is most desirable if not necessary that the molding apparatus be operated so as to form the molded ring in a horizontal plane. In other words the shaft about which the centrifuge operates must be vertical so that the effect of the force of gravity on the metal is constant and in one direction during the operation of the apparatus.

Moreover, the use of a Vertical axis of rotation for molding a ring in a horizontal plane obviates the difficulties encountered when large quantities of metal are introduced into a rotating mold. Thus if the axis of rotation is horizontal, when metal is inmaterially adding to r troduced into a rotating mold, the combined forces of gravity and centrifugal force are unequal around the periphery of the mold and cause the metal introduced to be unequally distributed therein, which results in an eccentric operation of the mold producing vibration of the component parts and consequent excessive wearing of moving parts; while excessive vibration during solidification may produce a coarse crystalline structure in the metal.

Prior methods of producing blooms, slabs and billets including the ingot casting, soaking, and blooming mill operations provide substantially a yield of to while the production of blooms, slabs and billets by centrifugally molding the same in an apparatus such as herein disclosed, a yield of from to results. Moreover, the soaking and blooming mill operations are eliminated thus cutting out attendant investment in equipment, fixed charges, maintenance and labor. And finally, the time element involved in producing blooms, slabs and billets by utilizing apparatus such as disclosed herein is much less than when other forms of apparatus are used, because of the improved pouring runner, and the construction of the particular metal mold construction.

Accordingly the increase in yield, the elimination of operations, and the savings in time result in greatly reducing the cost of production of blooms, slabs and billets; and the resulting product has a superior quality free from defects.

The method of making blooms, slabs and billets described butnot claimed herein is claimed in our copending application for making blooms, slabs and billets, filed July 2, 1930, Serial No. 465,303, Patent No. 1,882,516, dated October 11, 1932.

We claim:

In rotary centrifugal molding apparatus, a bed plate disk rotatable about a vertical axis, an annular mold including upper, lower and outer side metal walls forming an annular mold cavity, said mold including a ring plate forming the bottom wall of-the mold, and an L-shaped annular rim rabbeted to the ring plate forming the side and top walls of the mold, and means engagingvthe rim for cllamping the rim and ring plate to the bed p ate.

In testimony that we claim the above, we have hereunto subscribed our names.

HARRY M. NAUGLE. ARTHUR J. TOWNSEND.

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