US3164871A

US3164871A - Centrifugal casting apparatus and the method of making the same

Info

Publication number: US3164871A
Application number: US149621A
Authority: US
Inventors: Paul F Haughton
Original assignee: Combustion Engineering Inc
Current assignee: Combustion Engineering Inc
Priority date: 1961-11-02
Filing date: 1961-11-02
Publication date: 1965-01-12
Anticipated expiration: 1982-01-12
Also published as: GB977808A

Description

Jan. 12, 1965 P. F. HAUGHTON 3,164,871 CENTRIFUGAL CASTING APPARATUS AND THE METHOD OF MAKING THE SAME Filed Nov. 2, 1961 3 Sheets-Sheet 1 INVENTOR. PAUL F HAUGHTON 1965 v I P. F. HAUGHTON 3,

CENIRIFUGAL CASTING APPARATUS AND THE METHOD OF MAKING THE SAME Filed Nov. 2, 1961 3 Sheets-Sheet 2 INVENTOR. PAUL F HAUGHTON Jan. 12, 1965 P. F. HAUGHTON 3,164,871

CENTRIFUGAL CASTING APPARATUS AND THE METHOD OF MAKING THE SAME Filed Nov. 2, 1961 3 Sheets-Sheet 3 INVENTOR: PAUL F. HAUGHTON URE 1;

United States Patent Office 3,164,37l Patented Jan. 12, 1965 Paul F. Haughton, Ringgold, Ga., assignor to Combustion Engineering, Inc., Windsor, Cnn., a corporation of Delaware Filed Nov. 2, 1961, Ser. No. 149,621 4 Claims. (Cl. 2265) This invention relates to apparatus for the centrifugal casting of metal, and the method of making the same.

One method used today for making metal tubing or pipes is to centrifugally casthollow cylindrical castings by pouring a molten metal into a mold rotating at high speeds. The inner and outer surfaces of the so-formed castings are then machined to form smooth, flawless cylindrical surfaces. These machined pieces or hollows can thereafter be passed through a reducing machine which will reduce the diameter of such pieces, thereby extending the length, if desired.

The centrifugal casting apparatus presently in use today will not always produce perfect castings. A large percentage of such castings contain flaws such as porous areas, laps, or cracks which require considerable grinding, machining, and, sometimes the necessity of cutting off the central openings are removably secured, for example by.

bolts, to flanges 38 and 40 during the casting process to prevent moltenmetal from being spun out of the ends of mold 10.

' Molten metal which is melted in an electric induction furnace (not shown) is transferred into pouring ladle 46, and from there it is poured into boot 48 and flows from boot 48 into the hollow interior 62 of mold 10 by means of spout 50. Gas burners 52 are used to preheat the mold to a temperature of from 400-500 F. during the casting process. As illustrated in FIGURES 1 and 2, a thin layer of a suitable lining maerial 60 is formed on the inner surface of mold 10 to prevent the molten metal being cast from coming in contact with and becoming fused to the interior of mold 10. This lining material must completely cover the inner surfaceof mold 10, for

'if the molten metal were to come in'contact with mold end portions of such castings. Such flaws or imperfections ing, the effect of which is to pump the molten metal into a circular orbit rather than to allow it to freely run down the mold, so that the molten metal moves along the length of the mold in a solid front.

Other objects and advantages will become apparent from the following description taken in conjunction with the accompanying drawings wherein:

FIGURE 1 is a side view of a centrifugal casting apparatus utilizing my invention;

FIGURE 2 is a plan view taken on line 22 of FIG- URE l; V v t FIGURE 3 is an end view taken on line 3 3. of FIG- FIGURE 4 is a cross section of the mold used in FIG- URE l; I v

FIGURE 5 is an enlarged partial cross section taken on line 5-5 of FIGURE 4;

FIGURE 6 shows a partial casting made in accordance with my invention;

FIGURE 7 shows a partial casting made by conventional casting apparatus.

Looking now to FIGURES 1-3 of the drawings, mold means are shown comprising a'mold 10 and a mold lining 60, to be used for thecentrifugal casting of the hollow cylindrical metallic castings. This mold is rotated during the casting process by means of a motor 12, which rotates or drives pairs of rollers or hearing 20 and 22 secured on shaft 18 by means of drum 14 and belt 16.

Members

24 and 26 which are fixed or secured in a suitable manner support the rotating shaft 18. The other side of mold 10 is supported by pairs of rollers or

bearings

28 and 30 which are rotatable along with the shaft 32. Fixed

members

34 and 36 support the shaft 32.

The left and right ends of. mold 10 contain

flanges

38 and 40 respectively, and

end cores

42 and 44 containing depth of the first coating of lining material.

' has a lining thereon.

in the spiral groove will thus only be half that covering in even in a few small spots, the fusion formed thereby. would be suflicient to prevent the later removal of the casting from the mold.

FIGURE 4 illustrates one form of the configurations or irregularities that can be'formed on the inner surface of the mold or the mold lining which allows more perfect castings to be consistently made in accordance with my invention. As illustrated in FIGURE 4 a plurality of spiral grooves 70. are formed, which grooves will pump the molten metal into a circular orbit when the mold is rotated, thus making the molten metal move along the length of the mold in a solid front. These grooves are spiraled from the right end of the mold to the left end so that they tend to slow up, or retard, the flow of molten metal which moves from left to right down the length of the mold when it is rotated counterclockwise as shown by the arrows in FIGURE 4.

The preferred method of forming these grooves 70 will now be described. A spray nozzle is moved through the mold while the mold isrotating, to spray a thin coating of a suitable lining material of even thickness on the inner surface of the mold it). Next a member containing a plurality of prongs or fingers is pushed longitudinal- -ly through the mold while it is rotating very slowly. The

prongs or fingers are in engagement with the inner surface of the mold, and thus will remove a' portion of the lining, forming the spiral grooves 70 as illustrated. The prongs will cut grooves which extend through the entire Since the lining material is cosiderably softer than the metal of the permanent-mold 10, the forming of the grooves is easily accoplished. After this step the spraynozzle is again passed through the mold, spraying on a second coating of lining material so that the entire inner surface of the mold The depth of the lining material the rest of the inner surface of the mold, as seen in FIG. 5. After this has been done

end cores

42 and 44 containing central openings areinserted and'the apparatus is ready for a cast-ing to be poured.

It is not necessary to form. the grooves such as illustrated in FIGURES .4 and 5 on the lining material itself. Instead it would be possible to form the grooves in the metal of the mold itself, and thereafter spray on the lining material. In the case of the spirial configuration formed in the mold itself, it would be necessary to have the mold slightly tapered from one end to the other in order to permit the casting to be withdrawn therefrom. The space between the grooves, the angle of the spiral, and the width of the grooves is not critical, and any dimensions can be used.

Obviously, by decreasing the rpm. of the mold, or

increasing the speed at which the pronged member is moved through the mold during the grooving operation, the axial distance between each coil can be increased.

An example of a suitable distance between coils of the spiral would be one inch. This could be formed by rotating the mold at twenty r.p.m. while moving the pronged member therethrough at a speed of ten feet per minute, if the pronged member contained six equally spaced prongs or fingers, all of which engaged the inner surface of the mold.

. The optimum method of forming, the configurations or irregularties from tests run was found to be as follows: 1) first a coating of lining-material approximately .02 to .03 inch thick was sprayedonto the'inner surface of the mold; (2) a plurality of spiral grooves were scratched into the lining material by pushing a member containinga plurality of fingersthereon through the mold while it was rotating very slowly; and (3) spraying in .02 to .03 inch of a second coating of the lining material. The thickness of the lining is not overly critical, as long as itis sufficient to prevent fusing of the molten metal with the mold. Also, the lining could be formed in a manner other than by spraying it on. Any suitable lining material can be used. A semi-permanent lining, such as a rammed refractory lining, can be used if desired. In the above described operation a mixture of diatomaceous earth containing a small percentage of bentonite clay and sodium silicate as a binder was used. A new lining of this material is formed after each casting.

FIGURE 6 illustrates the manner in which the forward portion of the advancing molten metal moves along the length of the mold in a solid front when utilizing a grooved lining. FIGURE -7 illustrates how the forward portion of the advancing molten metal moves in a casting made by conventional casting apparatus having a smooth lining therein. A small charge of molten metal insuflicient to form a whole or complete casting was poured under like conditions into a rotating mold to form each of these pieces illustrated in FIGURES 6 and 7, so that the advancing portion of the molten metal froze or solidified in the shapes shown. As can be seenin FIGURE 6 where a spiral groove was formed in the lining, the molten metal moved along the mold in a solid front. As

shown in FIGURE 7 the molten metal poured in a mold containing a smooth lining moved along the mold in the form of a long, lazy spiral. Not shown in the figure but quite important is the cross section of the two pieces. The piece in FIGURE 6 will have a uniform wall thickness on the advancing edge while that in FIGURE 7 will have a tapered cross section varying from 6. to /4".

The use of the spiral grooves results in many advantages. With standard pouring techniques utilizing a smooth mold, excessive laps, cracks, and porous areas are frequently found in the castings. The results of a test comparing castings made'utilizing a standard smooth lin ing as against utilizing a spiral grooved lining showed three times as many castings required repair after ma;-

chining when using a smooth lining as when using a grooved lining, all other factors constant.

When utilizing a standard smoothlining, it is necessary to rotate the mold below a predetermined maximum rpm. in order to-prevent hoop stress cracking, which are longitudinal cracks in the castings which form when too high a r.p.m. is used. When using a smooth lining, hoopstress cracks usually start to appear when approximately 1300 rpm. is exceeded. When utilizing the grooved lining in accordance with my invention, it is possible to rotate the mold at 1650 rpm. or even higher without encountering any hoop stress cracking. One advantage of using a high rpm. is that it aids the molten metal in going into orbit sooner and prevents raining,

which is droplets of molten metal falling down into the central portion of the casting when the centrifugal force is. not sufiiciently high. Another advantage is that the casing is more free of inclusions. A further advantage of using a grooved lining is that the pouring time is not as critical when using the grooved lining, and less flaws are formed when too fast or too slow a pour is made than is formed when using a smooth lining.

The optimum pouring time when utilizing my invention for a 460 pound casting poured into a mold a little over 10 feet long and 4% inches in diameter is seconds. The casting formed has a wall thickness of approximately 1.125 inches. After the casting has cooled sufficiently in the mold, the end core 44 isremoved', and the casting can be pulled out of the mold. The inner and outer surfaces of the casting are then machined to form perfectly smooth, flawless, cylindrical surfaces. Such machining will remove the small irregularities from the outer surface of the casting caused by the grooves in the mold means, either the mold or the mold lining.

It is possible to cast most any type of metal or alloy with my above described apparatus. Many types have been already cast, including, ferritic steels such as T2, T311, T9, T11, and T22; austenitic steels such as TP304, TP316 and TP347; Cu-Mo alloys; Inconel; and many others.

While I have shown and described the preferred embodiments of the invention it is to be understood that the invention is not limited thereto but may be otherwise variously embodied and practiced within the scope of the following claims.

What I claim is:

1. Apparatus to be used for centrifugal casting including a mold, a layer of lining material on the inside of said mold, said mold having a first, pouring end, and a second, nonpouring end, means for pouring molten material at the pouring end only, means for rotating said mold in one preselected direction, spiral groove means formed in the inner surface of said lining material, said spiral groove means extending in one direction only, from the pouring end toward the nonpouring end in a direction opposite to said preselected direction of rotation.

2. Apparatus to be used for centrifugal metal casting including a mold, said mold having a first, pouring end, and a second, nonpouringend, means for pouring molten metal at the pouring end only, means for rotating the mold in one preselected direction, lining means covering the inner surface of said mold for preventing the casting from becoming fused to the mold, and a spiral irregularity in the inner surface of said lining means for causing the'molten metal being cast to be pumped into a circular orbit, so that it moves along the length of the mold in a solid front, said spiral irregularity extending in one direction only, from the pouring end toward the nonpouring end in a direction opposite to said preselected direction of rotation.

3. Apparatus to be used for centrifugal metal casting including a mold, said mold having a first, pouring end, and a second, nonpouring end, means for pouring molten metal at the pouring end only, means for rotating said mold in one preselected direction, lining means coating the inner surface of said mold for preventing the casting from becoming fused to the mold, a spiral groove formed on the inner surface of the lining means for causing the molten metal to be pumped into a circular orbit as the mold rotates, so that'it moves along the length of the mold in a solid front, said spiral groove ext-ending in one direction only, from the pouring end toward the nonpouring end in a direction opposite to said preselected direction of rotation.

4. Apparatus to be used for centrifugal metal casting including a substantially hollow cylindrical mold, said mold having a first pouring end and a second, nonpouring end, means for pouring molten metal at the pouring end only, means for rotating the mold in one preselected direction, lining means covering the inner surface of the mold for preventing the casting from becoming fused to the mold, and a spiral irregularity in the inner surface of said lining means for causing the molten metal being cast to be pumped into a circular orbit, so that it moves along the length of the mold in a solid front, said spiral irregularity extending throughout substantially the entire length 2,339,141 Brown J an. 11, 1944 of the mold in one direction only, from the pouring end 2,399,666 Schu-h et al Apr. 30, 1946 toward the nonpouring end in a' direction opposite to said 2,513,101 Olsen et al June 27, 1950 preselected direction of rotation. 2,543,332 Olsen et a1. Feb, 27, 1951 2,577,423 Ludwig et a1. Dec. 4, 1951 References Cited in the file of this patent 2,681,260 Kistler June 15, 1954 UNITED STATES PATENTS 2,752,651 Seeba et al July 3, 1956 1,573,566 Nichols Feb. 16, 1926 FOREIGN PATENTS 2,095,573 Rldley et 1937 11 340 Gmat Britain N01 23 1912 2,124,445 Carrington July 19, 1938 10

Claims

1. APPARATUS TO BE USED FOR CENTIFUGAL CASTING INCLUDING A MOLD, A LAYER OF LINING MATERIAL ON THE INSIDE OF SAID MOLD, SAID MOLD HAVING A FIRST, POURING END, AND A SECOND, NONPOURING END, MEANS FOR POURING MOLTEN MATERIAL AT THE POURING END ONLY, MEANS FOR ROTATING SAID MOLD IN ONE PRESELECTED DIRECTION, SPIRAL GROOVE MEANS FORMED IN THE INNER SURFACE OF SAID LINING MATERIAL, SAID SPIRAL GROOVE MEANS EXTENDING IN ONE DIRECTION ONLY, FROM THE POURING END TOWARD THE NONPOURING END IN A DIRECTION OPPOSITE TO SAID PRESELECTED DIRECTION OF ROTATION.