US3456712A

US3456712A - Centrifugal casting method

Info

Publication number: US3456712A
Application number: US525435A
Authority: US
Inventors: Arthur E Schuh
Original assignee: United States Pipe and Foundry Co LLC
Current assignee: United States Pipe and Foundry Co LLC
Priority date: 1966-02-07
Filing date: 1966-02-07
Publication date: 1969-07-22
Anticipated expiration: 1986-07-22
Also published as: GB1120155A; CH463712A; BR6786668D0; FR1508748A; BE692741A; ES334523A1; DE1558333A1; FI47289C; FI47289B; SE339979B; NL6700879A

Description

July 22, 1969 A. E. SCHUH CENTRIFUGAL CASTING METHOD 3 Sheets-Sheet 1 Filed Feb. 7, 1966 FIGJ FIGZ

I N VENT OR ATTORNEY Ari/H1! Sc/mh BY Ed 9. W

y 2, 1969 A. E. SCHUH 3,456,712

CENTRIFUGAL CASTING METHOD Filed Feb. 7, 1966 3 Sheets-Sheet 2 INVENTOR Arthur E. Sc/w/u BY p W ATTORNEY y 22, 1969 v A. E. SCHUH 3,456,712

CENTRIFUGAIJ CASTING METHOD Filed Feb. 7, 1966 3 Shets-Sheet 5 FIG? Arthur E. Sc/vuh ATTORNEY IN VENTOR 3,456,712 CENTRIFUGAL CASTING METHOD Arthur E. Schuh, Riverton, N.J., assignor to United States Pipe and Foundry Company, Birmingham, Ala., a corporation of New Jersey Filed Feb. 7, 1966, Ser. No. 525,435 Int. Cl. B22d 13/02, 13/10; B22c 3/00 US. Cl. 164-72 4 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to the manufacture of tubular metal castings, and more particularly is concerned with the manufacture of cast iron pipe having bell and spigot ends in permanent metal molds rotated substantially horizontally.

It is well known to cast pipe in permanent metal molds, such methods having been practiced extensively in this country for many years. Present methods comprise the use of cylindrical metal molds mounted on rollers in a water jacket and adapted to be rotated at suitable speeds. The water jacket is mounted on a carriage that can be moved by means of a hydraulic cylinder in the direction of the longitudinal axis of the mold on a fixed bed inclined slightly from the horizontal. The molten iron is fed into the mold through a trough similarly inclined. In casting, a ladle containing molten iron is tilted at a uniform rate to maintain a constant pouring rate. When the mold is at the extreme upper end of the fixed bed, it is ready for casting at which time the trough extends down the barrel of the mold for nearly its full length. After the casting ladle has been filled by the transfer ladle, the machine operator brings the bold up to speed and actuates the mechanism controlling the tilting of the ladle. In a few seconds the iron has filled the bell space at which time the operator starts moving the mold carriage longitudinally down the bed. The stream of iron discharged from the trough fiows onto the surface of the mold, where it is held in place by centrifugal force and forms the pipe.

Early in the development of such machines it was discovered that far better results are obtained if, instead of pouring the iron onto the bare mold, a dry unbonded powdery material such as ferro-silicon is applied on the inner mold surface just ahead of the iron steam. While constituting a definite improvement, the use of such linings neverthless does not result in completely acceptable pipe, there always being so-called pinholes or laps or cold shuts.

Perhaps the greatest stride in overcoming these disadvantages of casting pipe in permanent metal molds was the invention described in Schuh et a1. Patent No. 2,399,606 and known in the art as wet spray. Briefly stated, that invention comprises spraying the inner surface of the metal mold with a liquid suspension of a powdered refractory material and a binder to form'incrementally an insulating coating adherent to the mold and having a multiplicity of spaced protuberances von its inner face.

One of the distinct advantages of using permanent metal molds is the speed with which a great number of pipes can be cast, as compared to other methods such as pit casting and centrifugal casting in sand lined molds. Maxinited States Patent mum casting speeds have not been attained, however, due to the necessity of moving the mold through two twoway strokes for each pipe cast. One two-way stroke is required for pouring the metal throughout the length of the mold, while moving the mold relative to the pouring trough, and extracting the cast pipe by return of the mold to casting position. An additional two-way stroke is required to apply the wet spray mold coating and to posirtion the mold in a convenient position for setting the bell core. It has not previously been considered possible to use wet spray coatings except in a four stroke cycle when using the retractive pour method.

It is, accordingly, the principal object of the present invention to provide a casting procedure or method for producing pipe by the retrac-tive pour method wherein only one two-way stroke of the mold is required for the production of each pipe and a wet spray coating is used.

Another object of the invention is the provision of a casting method whereby pipe can be made in a permanent metal mold without the necessity of a separate two-way traverse of the mold for insertion of a bell core or for applying a mold coating.

Still a further object is to provide a method for casting metal pipe in a permanent mold in which the mold is moved in one direction along its horizontal axis to form the pipe and is moved in the opposite direction to extract the pipe and put the mold in position for another cycle.

Still another object is the provision of a method for casting metal pipe in a permanent metal mold in a shorter time than heretofore considered possible.

This invention has other objects that will be apparent from a consideration of the method described herein and of the specific embodiment shown in the drawings accompanying and forming part of the present specification. Such form will now be described in detail to illustrate the general principles of the invention, but it is to be understood that such detailed description is not to be taken in a limiting sense, since the scope of the invention is defined by the-claims appended hereto. In the drawings:

FIGURE 1 is a top view in cross section of a pipe casting machine suitable for practicing the process of illustrating the position of the machine components at the start of a casting cycle.

FIGURE 2 illustrates the position of the machine components at an intermediate stage in the casting cycle.

FIGURE 3 illustrates the position of the machine components at the end of a casting cycle.

FIGURES 4-7 illustrate suitable positions for the spraying nozzle with respect to the spout end of the pouring trough.

The present process can be carried outwith any retractive pour casting machine and, accordingly, only a brief. description of a representative casting machine is given. Turning to FIGURES 1-3, such a machine comprises a Water box 1 which is mounted on wheels 2 riding on tracks 3. Rotatably mounted on rollers 4 within the water box is mold 5 which is driven by motor 6 through poly-Y in the mold and secures it in place while the pipe is belt 7. At one end of the carriage a puring. trough 8 is,

mounted with its longitudinal axis substantially coaxial with the axis of the mold so that its pouring spout 9 traverses the length of the mold 4 when water box 1 is moved by means of hydraulic. cylinder 10. Adjacent the fixed end of trough 8 there is tiltably mounted a machine ladle 11 which can be tilted at a uniform rate by con-v ventional drive means, not shown. 7

In order to permit the attainment of the full benefit of the process of the present invention, the casting machine is preferably provided with a core setting mechanism which holds a core in position outside the mold until the proper time in the casting cycle when it quickly seats the core being cast. This core setting apparatus comprises an arm 12 which is secured to a shaft 13 and on its free end it is provided with a bearing support 14 in which a boss is rotatably mounted. Core 15 is seated on the boss and is backed up by flange 16 secured to the boss. Shaft 13 extends through a sleeve 17 and is secured to the rod of a fluid cylinder 18 by means of coupler 19. Sleeve 17 is provided with a slot 20 into which pin 21 projecting from shaft 13 extends. Slot 20 as illustrated consists of a helical portion with a longitudinal portion at each end. In FIGURE 1, pin 21 is positioned in the slot 20 so that core 15 is seated in the end of the mold. When the rod of the fluid cylinder is extended as shown in FIGURE 2, pin 21 is moved from one longitudinal portion of the slot, through the helical portion of the slot, and into the opposite longitudinal portion of the slot. In so doing shaft 13 is moved longitudinally and rotated so that the free end of arm 12 is moved away from and clear of the end of the mold. A new core 15 is placed on the core setter and held in position until the movement of the fluid cylinder 18 is reversed and it is thereby moved into alignment with and seated in the end of the mold.

In order to carry out the present process, it is necessary to provide a spray nozzle 23 near the end of the pouring trough. This nozzle is fed by means of fluid lines 24 which are secured to the side of trough 8i and covered with shield 25. In addition, since the spray nozzle 23 must be positioned away from the pouring spout 9 of the trough, it cannot provide an adequate coating in the bell cavity of the mold, therefore, spray nozzle 26 is mounted on the end of swinging arm 27. This arm swings into the position shown in FIGURE 3 at the end of a casting cycle to spray the bell caviy before core 15 is seated in the mold at the start of a new casting cycle.

The series of steps comprising the casting process of the present invention will now be described with particular reference to FIGURES 1-3 which depict diagrammatically the operations performed and the positions of the components of the apparatus at different stages of the casting cycle. In the first position, FIGURE 1, the mold surrounds the pouring trough. As was explained above, the bell end of the mold was coated at the end of the extraction stroke in the previous casting cycle, and the core was seated in the end of the mold by moving shaft 13 toward cylinder 18. As the shaft rotates due to pin 21 moving through the helical part of slot 20 the core 15 is moved into alignment with the end of the mold 5, and as the pin then moves along the longitudinal portion of the slot the core is seated in the mold.

Ladle 11 is tilted at a uniform rate causing a stream of metal to flow down trough 8 into the spinning mold. Preferably, ladle dump is actually started before the core is set in place so that there will be very little delay between the time the core is set in the mold and metal first starts to pour into the mold. When metal fills up the bell cavity, cylinder is activated to withdraw the mold 5 from trough 8, and :a fan spray of coating is applied to the mold simultaneously through nozzle 23. As a result, coating material and molten metal are applied along the length of the mold, the leading edge of the spray being only a short distance ahead of the leading edge of the molten metal at all times, e.g. three or four inches.

When the mold is completely withdrawn from trough 8 and positioned with its bell end adjacent bumping block 28 as shown in FIGURE 2, spinning of the mold is contintued until the pipe is at the proper temperature for pulling. Spinning of the mold is then stopped, and the core setting mechanism is withdrawn from the core in the formed pipe and moved away from the end of the mold by extending the rod of cylinder 18. A new core is immediately seated on the boss of the core setting mechanism, and pipe pulling apparatus 29 is moved into the end of the pipe in the mold. The pipe pulling mechanism has an expandable head that grips the inside surface of the pipe and holds the pipe against movement as the travel of cylinder 10 is reversed and the mold 5 is again moved over trough 8 resulting in the extraction of the pipe from the mold.

When the Water box reaches a point where the pipe is free and the pipe has been rolled clear of the end of the mold, arm 27 swings into the position shown in FIGURE 3 and spray coating is applied to the mold by spray nozzle 26. Arm 27 immediately swings clear of the mold, while cylinder 18 is activated to move core 15' into position in the end of the mold. At this point the machine is ready to start through another casting cycle. I

It is important that the spray nozzle 23 be positioned to give complete and uniform coverage of the mold. If the nozzle is too far from the end of the trough, it does not adequately spray the mold in the area behind the bell cavity, and-this area cannot be sprayed by a bell spray such as nozzle 26. The presence of the trough in the mold while nozzle 26 is spraying makes it impossible to spray any appreciable part of the mold bore by spraying from the bell end. On the other hand, if the nozzle 23 is too close to the end of trough 8 it will spray into the metal which is in the mold, onto the mold at a point which is too close to the area of metal impingement to permit the moisture to dry out of the coating slurry or down the barrel of the pipe being cast.

It is essential to direct the spray onto the mold so as to obtain complete coverage of a uniform coating having the desired wet spray coating characteristics. An air atomized fan spray system such as is commonly used for applying wet spray coatings to molds is satisfactory. Those skilled in the art will recognize that proper gun distance and slurry atomization must be maintained and space limitations make this difiicult in smaller size molds, however, methods have been devised to overcome this problem. When casting large pipe where there is adequate space in the mold to accommodate the spray head in almost any position, the spray head can be mounted at an angle so as to give spray in which the fan is directed down at an angle of about 45 (see FIGURE 5).

In smaller pipe molds, there is little room for the spray nozzle and it is more difficult to obtain complete, uniform coverage of the mold. For example, in an eight inch mold the spray nozzle is not spaced far enough from the mold surface to permit the nozzle to be pointed downward. However, it has been found that if the spray gun is mounted at approximately 14" from the end of the pouring trough with its axis in the horizontal plane parallel to the longitudinal axis of the mold and in the vertical plane at an angle of about 7 to the longitudinal axis of the mold (see FIGURE 4), a uniformcoating having the desired characteristics can be obtained. This arrangement has also been found to be satisfactory for casting 12" pipe.

In casting 6" and 8" pipe, desirable results have been obtained by mounting the spray gun with is axis parallel to the axis of the mold and providing a large air hole in the air cap on the side next to the trough whereby the spray fan is deflected away from the trough and onto the mold (see FIGURE 6).

In practicing the present invention, the best results are obtained when rapid casting rates are maintained with maximum delays. This results in a mold temperature that is hot enough to assure that the coating will dry almost instantly and that the metal solidification next to the coating will be delayed sufficiently to permit the escape of gases through the molten metaLWhenever a delay occurs at the end of a casting cycle, the mold should be retracted-from the trough and the coating applied even though metal is not being poured into the mold. When this is done, the coating will dry satisfactorily and the mold will be properly coated when casting is resumed.

I claim:

1. Method for making tubular metal castings by retractive casting in a substantially horizontal mold comprising; positioning the mold and trough so that the trough is within the mold, providing the end portion of the mold adjacent the spout of the trough with a wet spray coating, securing an end forming means in the end of the mold adjacent the spout end of the trough, rotating the mold, appying a helical spiral of molten metal along the length of the mold and simultaneously spraying from a nozzle positioned near the spout end of the trough a wet spray coating onto the mold a short distance ahead of the leading edge of the helical spiral of molten metal by providing relative longitudinal movement between the trough and mold, and extracting the pipe from the mold after solidification.

2. Method according to claim 1 wherein the molten metal and wet spray coating are distributed along the mold by retracting the mold from the trough.

3. Method according to claim 1 wherein the pipe is extracted from the mold by securing the pipe in a stationary position and withdrawing the mold from the pipe while simultaneously moving it over the trough.

4. Method according to claim 3 wherein the end of the mold adjacent the spout end of the trough is sprayed at the end of the extraction stroke of the mold.

References Cited UNITED STATES PATENTS I. SPENCER OVERHOLSER, Primary Examiner US. Cl. X.R.