US1882516A - Making blooms, slabs and billets - Google Patents

Description

Oct. 11, 1932.

H. M. NAUGLE ET AL MAKING BLOOMS, SLABS, AND BILLETS 7 Filed July 2, 1950 2 Sheets-Sheet 1 AJTalumend 01:1. 11, 1932. "H. M. IQNAUGLE ET AL 1,882,516

MAKING BLOOMS, SLABS, AND BILLETS Filed July 2, 19:50 2 Sheets-Sheet 2 E & mm EMA ally]? ill Patented Oct. 11, 1932 UNITED STATES PATENT OFFICE HARRY M. NA'U'GLE AND ARTHUR J. TOWNSEND, OF CANTON, OHIO, ASSIGNOBS TO NAUGLE & TOWNSEND, INC A CORPORATION OF DELAWARE MAKING BLOOMS, SLABS AND BILLETS Application filed Iu1y 2, 1930, Serial No. 465,303, and in Canada Ian: 4, 1830.

The invention relates to methods for making steel blooms, slabs, billets and the like directly from molten metal poured from a ladle or the like, this application being a. continuation of the common subject matter of our copending applications filed respectively October 16, 1928, Serial No. 312,802, and J anuary 18, 1930, Serial No. 421,844; and the obj ect of the improvement is to produce such semi-finished products on large commercial scale, without the preliminary production of ingots with the attending difiiculties 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.

its a preliminary step toward forming steel into the various sections which its many uses require, theheavy 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.

hen 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, called billets; if these pieces are six inches square or larger, they are known as blooms; and if reduced to rectangular forms but with widths which are less than twice the thickness andwithin 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 perfect ingot is required to produce a faultlessly fini hed material; 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 the liquid metal operateagainst both these 1 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 slaginclusions.

According to the present improvement, the preliminary molding of ingots and the necessary elimination of their inherent defects is avoided, by pouring molten metal directly into a rapidly 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 continuous or discontinuous 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 produced by that method.

In order to obtain practical and commercial advantages from the centrifugal method of molding steel rings, for subsequently rolling into finished products, it is necessary to treat, handle and deal with very large masses of metal at one time; because steel is melted and made in large units of seventy-five and 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 semi-finished form as quickly as possible, in a ring having a cross section of from sixteen square inches and upwards with a minimum dimension of say three inches, referred to herein as a massive ring.

Various methods have been proposed for the centrifugal molding of so-called ingots in the form of rings, and then opening and straightening the same, but those methods have been used for producing comparatively small cross sections, short lengths and limited masses of the material, for drawing or rolling the same directly into wire,'sheets, light rails and other light products; but such lighter operations do not develop difficulties which attend the making of massive rings.

In the first place, massive rings cannot be made with the uniformly compact and homogeneous structure throughout by centrifugal molding in the annular molds of small diameters, because of the substantial difference between the pressure of centrifugal action in the outer side of the ring as compared with the inner side thereof; and for the pur ose of the present invention, it is practica ly necessary to use an annular mold of such a large diameter that the difference in pressure of centrifugal force produced directly by rotation, between the outer and inner sides of the ring is so small as to be negligible, as, for instance, a diameter of at of a ring being molded by centrifugal action;

when a 4" x 4" ring is formed in a mold having a diameter of two feet, the centrifugal force produced directly by rotation at the inner face of the ring is only 66 of the centrifugal force produced directly by rotation at the outer face thereof; while if a 4 x 4" ring is formed in a mold having a diameter of eight feet, the centrifugal force produced directly by rotation at the inner face of the ring is 91%% of the centrifugal force produced directly by rotation at theouter face thereof.

In the first instance, the centrifugal force in the inner portion of the ring is so much less than in the outer portion thereof, that there is an objectionable, if not a prohibitive difference in the structure of the metal in the inner portion of the ring, as compared with the outer portion thereof; while in the second Instance, the difference in centrifugal force is so slight as to be substantially negligible.

An increase in the radial thickness of the ring as compared with the diameter of the mold, will, of course, increase the difference between the centrifugal force produced directly by rotation at the inner face and the outer face of the ring; but in all cases, the

centrifugal force produced directly by rotation at the inner face of the ring should be not less than say 85% of the centrifugal force produced directly by rotation at the outer face hereof, for the purposes of the present improvement.

In referring to and comparing/pressures exerted by particular particles resulting from centrifugal force produced directly by rotation of the mold, it is not intended to include the cumulative pressures of other particles exerted against the particular particles referred to or compared.

In the next place, the time element involved in carryin out previous methods of centrifugal mol ing rings having comparatively small cross sections and limited masses-0f metal, is not appreciable, because the mass of molten metal and sometimes the thickness thereof, is comparatively small, and the mold cavity is filled almost instantaneously upon the tapping of the ladle; but when larger masses of metal are molded for producing massive rings, having a cross sectional area of sixteen or more square inches, with a length of twenty-five or more feet, and weighing nearly'one ton or more, the time required for filling the mold cavity requires modifications of method and apparatus for successful quantity production of the massive rings, so that the molded material will be substantially uniform in density, strength and other characteristics throughout the length and breadth of the ring.

In molding massive rings, the molten metal first flowing by centrifugal action into the mold cavity, following the tapping of the ladle, tends to become materially cooler than the metal later flowing into the mold cavity for completely filling the same; not only because of the cooling effect of the mold itself, which immediately absorbs heat from the metal first flowing into it, but because of the rapid tranfer of heat from the molten metal to the air, resulting from the high peripheral speeds required for satisfactory centrifugal action.

It has been found that when molten metal is poured into a rapidly rctating mold, at a temperature less than 2600 F., to produce rings having cross sectional areas of sixteen or more square inches, with lengths of twentyfive or more feet; that the molten metal introduced into'the mold cavity is not sufficiently fluid, because of the rapid loss of heat therefrom to the mold proper and to the surrounding atmosphere, to permit the entrapped and evolved gases to escape from the body of metal being formed before the metal reaches the plastic condition during solidification, with a 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 centrifugal molding the same. \A further feature of the present improvement is to heat the molten metal and from the ladle at a temperature 0 from 2600 F. and upwards during the entire mold filling operation, so that the molten metal remains sufficiently fluid to squeeze gas pockets out of the fluid mass by action of centrifugal force and prevent the formation of voids in the body of the metal; and so that the metal will respond to the pressure created by centrifugal force and will form a uniformly sound, dense, and compact product.

It is pointed out that the steel while being poured, after having attained in all or in our it part the velocity of the mold, is subjected to two differently directed forces, namely that of gravity and that of centrifugal force, when the axis of rotation of the mold is vertical, so that if the viscosity of the metal is too high while the mold cavity is being filled,

the full effect of centrifugal force is lost.

In other words, the benefits resulting from the utilization of centrifugal force are lar ely dependent upon-the fluidity of the metal uring the pourm operation, and the fluidity-is in turn depen ent upon the initial pouring and mold filling tem erature of the molten metal, which should e at 2600 F. and upwards. e

Even though the diameter of the mold is large enough to avoid an objectionable difference' in pressure between the inner and outer sides of the ring, and even though the molten metal is suflicientl fluid to completely fill the mold before it comes too viscous; it is desirable, if not necessary, to limit the dimension of the ring either radially or axially to- 1 say not less than three inches, so as to maintaln a. substantial thickness in the body of the metal in all directions for retaining the temperature longer with greater fluidity, and:

with a resulting increase in'the effectiveness of the centrifu al force, thereby insuring a.

substantial uni ormity in the cooling of the metal and in the resulting texture of its structure.

And finally, the well known shrinkageo'f metal when coolin from a plastic condition to a solid state, which may be some three six-. teenths 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 metals, 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.

One method by which this requirement may be met and satisfied by the present improvement, is to reduce the speed of the rotary mold at or about the time the metal cools from a liquid state to a plastic condition, so as to reduce the pressure due to centrifugal force to such an extent as will permit the ring to shrink, by a further cooling of the metal from a plastic condition to a solid state, without any granular disintegration thereof.

This method may be sup lemented, and in some cases may be replace by forming the mold to make or mold a discontinuous ring which may shrink without much, if any, reduction in the centrifugal pressure'to avoid a granular disintegration of the metal; and again, the-mold may be made to produce a weakened place at one place in the ring, so as to pernut a ready rupture thereof at such .Fig. 2.

mold. l

The improved method may be carried out in the apparatus illustrated in the accompanying drawings forming part hereof, in which- Figure 1 is an axial section of one form of centrlfugal moldin which the improved out;

Fig. 2, a plan view of the same; Fig. 3, a fragmentary section on line 3-- 3, Fig. 2; and

Fig. 4, a fragmentary section on line 4-4,

Similar numerals refer to similar parts throughout the drawings. 7

A billet 5, in the form of a continuous or apparatus bymeans of method may be carried discontinuous ring, may be made in an annular mold composed of a ring plate bottom '6 with an inturned -L-shaped rim 7 rabbetecl thereon mounted on a bed plate disk 8 having a central hub 9 and a depending axle shaft 10 journaled in a vertical bearing 11 mounted on a supporting pedestal 12.

The inside diameter of the rim of the mold should be at least eight feet, and the weight of the mold ispreferably supported by an annular flange 13 depending from the bed plate disk and riding on rollers 14, having axles 15 journaled in horizontal bearings 16 mounted on supporting pedestals 17.

The mold may be rotated by a horizontal shaft 18 driven by suitable power, having a beveled pinion 19 meshing with a master gear 20 keyed to the depending axle shaft 10 freely above the vertical bearing 11, there being means, not shown, for controlling or stopping the application of the power and the speed of the rotation.

The ring plate bottom 6 of the mold is preferably provided with an upright flange 21 on its inner edge, and the molten metal 22 which has been heated to a temperature above 2600 F., may flow from a nozzle 23 of a ladle 24 when the same is tapped into a pour-- ing basin 24a and thence from the angularly and substantially tangentially directed noze zle 24b thereof into the mold which is rotated to move the peripheral parts thereof at a high rate of speed, which may be' upwards of 3500 to 4000 feet per minute, for some four 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; and the impurities being much lighter than the metal,

may form a thin coating on the inner surface of thering, whence the same can be readily removed by subsequent operations, if necesor desirable.

sar I X block may be positioned in the moldat one pointin its periphery to serve as ,a partition for making a discontinuous rin if it is desired to do so, an'dupon'the coo ing and solidification of the ring, .it ma be released from the mold by detaching -c amping bolts 26 and removing the L-rim 7 of the mold. from the ring plate bottom 6 thereof,

which can readily be done by lifting means ap lied to hooks 27 on the rim.

ccording to the improved method, the rotaryspeed of the mold is maintained at a maximum rate to maintain the centrifugal pressureresulting therefrom ata maximum ring at that point may be so lessened and .weakened that the ring will readily rupture at this point by the shrinkage of the metal during the rapid operation of the mold, thus automatically producing a discontinuous ring.

Upon the removal'of the ring bloom from the mold, it may be severed or'cut at one place, or if it is a discontinuous ring, may be merely opened up and straightened by rolling or otherwise into a straight billet, from which any impurities which may coat the original inner surface may be removed by any well known means.

-Although the present improvement has been described as making a four by four inch sectiomit will be understood that the L-shaped' rim may be varied to make a ring, bloom or billet having a cross sectional area of more than sixteen 'squareinches, or a ring slab having a similar cross sectional area, with a minimum dim'ension'of say three inches.

1 It is not commercially practical to make rings, blooms, billets or slabs having a cross sectional area less than sixteen square inches I because the tonnage per ring would be too small. Moreover, sections smaller than. sixteen square inches will cool excessively before i the ring straightening operations I are completed. On the other hand, sections of sixteen square inches and upwards can readily be reduced in size during the straightening opera on without materially adding to the production costs. And finally, the surface per unit of weight is much smaller in the case of large 1,sea,51e

sections, thus reducing the proportionate cleaning-charges. I

Althou a ring diameter of not less than eight feet as been described, it will be understood that rings, blooms, slabs and billets having larger diameters are contemplated. In utilizing such larfger ring diameters, the tonnage per ring is o suflicient magnitude to enable great economies to be secured. More- .over, 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 quires 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 ismost desirable if not necessary that the molding apparatus beoperated so as to form the molded ring in a' horizontal plane. In other words the shaft about which the centrifuge operates must he vertical so that the efiect of the force of grav- .of a small number of large diameter rings rej 'ity 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 of larger diameter in a horizontal plane obviates the difliculties encountered when large quantities of metal are introduced into a rotating mold. Thus if the axis ofrotation is'horizontal, or the. di-

ameter of the mold issmall, when metal is introduced 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.

Under old methods of producing blooms,

slabs and billets including the ingot casting,

soaking and blooming mill'operations there.

is a yield of to while in carrying out the present method of, making blooms, slabs-and billets by centrifugally molding the same, a yield of from to results.

Moreover, the soaking and blooming mill."

operati us are eliminated,' thus cutting out the attendant investment in equipment, fixed charges. maintenance and labor.

And finally,'the t me element involved in producing blooms, slabs and billets under the present methods is much less than under old methods. I

Thus the increase in yield, the elimination of operation. and the savings in time result in greatly reducing the cost of production of blooms. slabs and billets by utilizing the present method; and the product resulting therei metals.

from has a superior quality free from defects. ing

as well be used for aluminum, and other The apparatus shown and described but not claimed herein has been made the subject matterof our copending application for centrifugal casting apparatus, filed February 18, 1930, Serial No. 429.359.

We claim:

1. The method of making a massive ring bloom, slab, billet and the like having a cross sectional area of sixteen square inches and upwards with a minimum dimension of three inches and a circumferential length of twenty-five feet and u wards directly from molten metal, which includes flowing and compressing the molten metal by centrifugal force into a rotating annular mold to form a ring, maintaining fluidity of the molten metal during the flowing and compressing operation, maintaining the centrifugal pressure at a maximum until the metal has cooled to a self sustaining plastic condition, and then reducing the centrifugal pressure.

2. The method of making a massive ring bloom, slab, billet and the like having a cross sectional area of sixteen square inches and upwards with a minimum dimension of three inches and a circumferential length of twenty-five feet and upwards directly from molten metal, which includes flowing and compressing the molten metal by centrifugal force into a rotating annular mold to form a ring, maintaining fluidity of the molten metal during the flowing and compressing operation, maintaining the 'centrifu al pressure at a maximum until the metal as cooled to a self sustaining plastic condition with the centrifugal pressure due directly to rotation at the inner face of the ring not less than 85% of the centrifugal pressure due directly to rotation at the outer face thereof, and then reducing the centrifugal pressure.

3. The method of making massive blooms, slabs, billets and the like directly from molten metal, which includes flowing and compressing the molten metal by centrifugal force into an annular mold to form a ring, maintaining the centrifugal pressure at a maximum until the metal has cooled to a selfsustaining plastic condition, then reducing the centrifugal pressure, and then maintaining the reduced centrifugal pressure until the metal has further cooled to permit the ring thus formed to shrink without a granular disintegration of the metal.

4. The method of making massive blooms, slabs, billets and the like directly from molten metal which includes flowing and compressthe molten metal by centrifugal force into an annular mold to form a discontinuous ring, maintaining the centrifugal pressure at a maximum until the metal has cooled to a selfisustaining plastic condition, and then controlling the centrifugal pressure in reduced amount to permit the ring thus formed to shrink without a granular disintegration of the metal.

5. The method of making massive blooms, slabs, billets and the like directly from molten metal, which includes heating metal to a temperature above 2600 F., rotating an annular mold at a high rateof speed, pouring. flowing and compressing the metal into the annular mold by centrifugal force while the temperature of the metal is 2600 F. and .upwards, and then maintaining the rotary speed of the mold at a maximum to maintain the centrifugal pressure at a maximum until the'metal has cooled to a self-sustaining plastic condition.

6. The method of making massive blooms, slabs, billets and the like directly from molten metal, which includes heating metal to a temperature above 2600 F., rotating an annular mold about a vertical axis, pouring flowing and compressing the metal into the rotating annular mold by centrifugal force .while the temperature of the metal is 2600 F. and upwards, and then maintaining the centrifugal pressure at a maximum until the metal has cooled to a self-sustaining plastic condition.

7. The method of making massive blooms, slabs, billets and the like directly from molten metal, which includes heating metal. to a temperature above 2600 F., pouring, flowing and compressing the metal into'an an nular mold by centrifugal force while the temperature of the metal is 2600 F. and upwards, maintaining the centrifugal pressure until the metal has cooled to a self-sustaining plastic condition, and then reducing the centrifugal pressure'to permit the ring thus formed to shrink without a granular disintegration of the metal.

8. The method of making massive blooms, slabs, billets and the like directly from molten metal, which includes heating the metal to a temperature above 2600 F., pouring, flowing and compressing the metal into \an annular mold by centrifugal force while the temperature of the metal is 2600 F. and upwards, maintaining the centrifugal pressure until the metal has cooled to a self-sustaining plastic condition, reducing the centrifugal pressure, and then controlling the reduced centrifugal pressure to permit the ring thus formed to shrink without disintegration of the metal.

9. The method of making blooms, slabs, billets and the like having lengthsof twentyfive feet and upwards and cross sectional areas of sixteen square, inches and upwards directly from molten metal, which includes heating metal to a temperature above 2600 F., pouring, flowing and compressing the metal into an annular mold by centrifugal force while the temperature of the metal is 2600 F. and upwards, and then maintaining the centrifugal pressure at a maximum until the metal has cooled to a self-sustaincontaminating gases, which uards to squeeze the ing plastic condition.

10. The method of making blooms, slabs, billets and the like having lengths of twentyfive feet and upwards and cross sectional areas of sixteen square inches and upwards free from defects from molten metal having includes heating metal to a fluid state at a temperature above 2600 F., rotating an annular mold about a vertical axis, pouring, flowing and compressing the .fluid 'metal into the rotating annular mold by centrifugal force while the temperature of the metal is 2600 F. and upgases out of the body of metal, maintaining the centrifugal pressure until the metal has cooled to a self-sustaining plastic condition to form an annular ring, removing the ring from the mold, and then straightening the ring.

In testimony that We claim the above, We

have hereunto subscribed our names.

HARRY M. N AUGLE. ARTHUR J. TOWNSEND.

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