US3872913A

US3872913A - Continuous method and apparatus for upwards casting

Info

Publication number: US3872913A
Application number: US095038A
Authority: US
Inventors: Timo Jorma Juhani Lohikoski
Original assignee: Outokumpu Oyj
Current assignee: Outokumpu Oyj
Priority date: 1969-12-15
Filing date: 1970-12-04
Publication date: 1975-03-25
Anticipated expiration: 1992-03-25
Also published as: GB1328399A; DE2060451A1; FR2077552B1; FI46810C; DE2060451B2; FI46810B; FR2077552A1; CH521807A; JPS5027032B1; SE371379B

Abstract

Melt is continuously drawn upwards from a supply of the melt by suction through a vertical graphite nozzle the upper portion of which is cooled to solidify the melt enough in the nozzle to endure pulling the solidified product upwards through a cooler having a cross-section which is somewhat greater than that of the product. Attached to a support above the melt supply there is a support for a vertical cooler having three pipes defining a tortuous flow passage therebetween the ends of which are provided with an inlet and an outlet for passing e.g. cooling water through the passage. The innermost tube of the cooler through which the product is pulled is of somewhat greater diameter than the product and has an opening at the upper part thereof to create suction inside the apparatus. Coaxially attached to and partially surrounded by the lower part of the cooler there is a graphite nozzle the lower end of which is immersed in the melt supply.

Description

[ 1 Mar. 25, 1975 1 CONTINUOUS METHOD AND APPARATUS FOR UPWARDS CASTING [75] Inventor: Timo .lorma .luhani Lohikoski, Pori, Finland [73] As'signee: Outokumpu ()y,Outokumpu,

Finland [22] Filed: Dec. 4, 1970 [21] Appl. No.: 95,038

[30] Foreign Application Priority Data Dec. 15. 1969 Finland 3631/69 [52] US. Cl 164/64, 164/82, 164/253, 164/281. 164/283 R [51] Int. Cl .l B22d 11/12 [58] Field of Search 164/64, 82, 85, 253, 273 R, 164/281, 283

[56] References Cited I UNITED STATES PATENTS 1.088.171 2/1914 Pehrson 164/260 2.171.132 8/1939 Simons 164/64 2.667.673 2/1954 Harrison 164/283 X 2.837.791 6/1958 'lessmann... 164/89 X 3.099.053 7/1963 Eliot 164/89 X FOREIGN PATENTS OR APPLICATIONS 1.319.365 l/l963 France 164/283 intensively cooled 7on9 1,218,120 6/1966 Germany 164/82 Primary Examiner-R. Spencer Annear Attorney, Agent, or Firm-Brooks Haidt & Haffner [5 7] ABSTRACT Melt is continuously drawn upwards from a supply of the melt by suction through a vertical graphite nozzle the upper portion of which is cooled to solidify the melt enough in the nozzle to endure pulling the solidified product upwards through a cooler having a crosssection which is somewhat greater than that of the product.

Attached to a support above the melt supply there is a support for a vertical cooler having three pipes defining a tortuous flow passage therebetween the ends of which are provided with an inlet and an outlet for passing e.g. cooling water through the passage. The innermost tube of the cooler through which the product is pulled is of somewhat greater diameter than the product and has an opening at the upper part thereof to create suction inside the apparatus. Coaxially attached to and partially surrounded by the lower part of the cooler there is a graphite nozzle the lower end of which is immersed in the melt supply.

2 Claims, 2 Drawing lFigures Solldlhed Metal I 7 Molten Melol SHEET 10F 2 Molten Metol intensively coo\ed Zone CONTINUOUS METHOD AND APPARATUS FOR UPWARDS CASTING BACKGROUND OF THE INVENTION A. Field of the Invention The invention relates to the field of continuous up wards casting of profiled products as bars, plates, pipes and the like.

B. Description of the Prior Art In recent years, the continuous casting of metals and alloys has been the subject of keen development work.

One method for continuous casting uses a nozzle of solid graphite in which the melt is solidified and can be drawn out continuously through the nozzle. There are several casting machine types based on this principle. Two main types can be distinguished among them:

1. Vertical casting, in which the graphite nozzle with its cooler is attached to the bottom of the melt container (the furnace) and the drawing takes place vertically downward.

2. Horizontal casting, in which the nozzle with its cooler is attached to the side of the furnace and the drawing takes place respectively in a horizontal direction.

Excepting the drawing direction the two methods are similar. Each has a fire-resisting melt container (furnace), and the graphite nozzle must reach through the masonry work of the furnace. Consequently, there must be an opening corresponding to the nozzle in the masonry. This causes many difficulties in the applica tion of the method. Firstly, the nozzle and its cooler must be attached tightly to the wall of the melt container so that melt will not escape through any cracks. This requires demanding maintenance of the masonry openings. Secondly, the part of the melt container wall to which the nozzle is attached must be freed from melt when the nozzle is changed (the melt container must be either emptied or tilted). Consequently, when several nozzles are used they must all be changed at the same time, in which case the time/profit ratio of the nozzle remains unprofitable. In addition, in the case of a disturbance melt can discharge from the nozzle and harm both the equipment and the employees. Because the nozzle and the cooler must be attached tightly to the wall of the melt container, the task of directing the nozzle and the drawing machinery on line with one another is painstaking and exacting; it is made even more difficult by the movements caused by the heat expansion of the wall of the melt container.

The shape of the hole of the graphite nozzle determines the shape ofthe cross section of the casting. The shape can be round or in different profiles. Also, tubelike articles can be cast by providing the nozzle with a graphite core. However, in this case the casting is more difficult and the nozzle must be changed more often.

It is possible to place the casting equipment above the free surface of the melt so that the casting, or the drawing. takes place upward. In this case the difficulties enumerated above can be avoided.

An upward casting like this has been presented by A. Simons in the U.S. Pat. No. 2,] 7],l32 according to which melted metal is lifted with the help of suction to the cooling area where it solidifies and the formed bar can be continuously drawn upward.

According to Simons the cooling area is formed by a vertical tubelike piece; the inner diameter of this piece determines the diameter of the lbar to be cast. To the lower end of this tubelike piece is connected at continuation made of refractory material the purpose of which is to conduct melt from the melt container to the cool ing area, or to the tube mentioned above.

It is, however, very difficult to connect two pieces of different materials to each other so tightly that melted metal will not squeeze into any crack or hollow, espe cially as the temperatures of the pieces are different and they expand in heat in different ways. The melted metal squeezes into each small cavity, forced by its inner pressure, and solidifies there. The thin. solidifying outer surface of the drawn bar gets stuck to these solidified particles, and the result is at least cracking of the surface and probably interruption of the casting.

SUMMARY OF THE INVENTION According to the invention there is provided an improved method for upwards casting of profiled products, in which the upper portion of the nozzle is cooled so as to solidify the product, before it leaves the nozzle by pulling, enough to endure the pulling into the cooler where it is further cooled.

The invention now introduced is based on the idea that a nozzle, for example, a graphite nozzle. is placed above the free surface of the melt so that only the lower end of the nozzle is immersed in the melt and that the upper end is surrounded by a cooler and that melt is lifted to the cooled upper part of the nozzle with suction. The suction device is connected to the upper part of the cooler with a suction pipe. This pipe has three simultaneous functions: to support the nozzle and the cooler, to conduct cooling water to and from the cooler, and to aftercool the casting.

Several nozzles like this can be operated above the same melt container.

The following advantages will be gained with this arrangement:

1. Each casting nozzle can be changed and casting started or interrupted without disturbing the other nozzles. I

2. Melt can never accidentally discharge through the nozzle.

3. The size of the nozzle can be the smallest possible because of the elimination of the difficult passages through masonry with possible torsional stress and the dimensional requirements set by them. As a result, the use of expensive, wearing graphite is reduced to the minimum and the devices are small so that several of them can be fitted to the same melt container.

4. The maintenance of the holes for nozzles in the masonry is entirely eliminated.

5. The nozzle is always in line with the pulling devices because it can be connected to the latter with stiff structural parts and is independent from the structural parts of the furnace.

6. The furnace itself need not be tiltable and. consequently, its structure is simpler.

In addition, the following advantages are gained in the casting process:

I. The solidifying front. or the interface between the melt and the solid matter, is perpendicular to the longitudinal axis of the casting, while it forms an oblique angle in horizontal casting. This is clearly advantageous, especially when a pipe is being cast. because an oblique solidifying front around a conical core causes eccentricity in the pipe wall. In this respect, upward casting is comparable to downward vertical casting.

2. Likewise, in upward casting, gravity will not cause tighter pressing of the casting against the lower surface with resulting uneven wearing of the nozzle.

3. The melt in the furnace is always hotter and, consequently, also lighter than the melt along the solidifying front. These differences of density will cause flows in the melt so that, close to the nozzle walls, cooled melt will sink and, respectively, in the middle, hot melt will rise to sink to the walls along the solidifying surface. Thus, a continuous flow of fresh melt rinses the solidifying surface, preventing impurities (such as gases) from concentrating in front of the cooling surface and from thus causing flaws in the casting.

4. The metallostatic pressure prevailing inside the nozzle can be reduced more in upward casting than in other casting methods. In addition, the pressure is of the same magnitude around the entire nozzle, the case being the opposite in horizontal casting in which the pressure is greater on the lower surface than on the upper. The smallness of this pressure is an essential advantage because the pressure pushes the already solidified thin surface layer against the inner surface of the nozzle and thus creates frictional forces in proportion to the pressure.

The reduction of pressure reduces the frictional forces and, firstly, decreases the wearing of the graphite, and, secondly, limits the cracking of the thin solidified surface layer when it glides along the surface of the nozzle. Close to the melting point, metals are often fragile and do not endure the pulling strain caused by the frictional forces; the strain is the smallest possible in upward casting.

The size of the vacuum can be made large enough (for example, by lengthening the nozzle) to make the gases escape from themelt, causing a continuous vacuum casting.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. I is a cross-sectional side view of an apparatus according to the invention for continuous casting of bars and threads; and

FIG. 2 is a similar view of another apparatus for continuous upward vertical casting of pipes.

DESCRIPTION OF THE. PREFERRED EMBODIMENTS One application for the casting of solid thread or bar is shown in FIG. 1. Part 7 is the actual graphite nozzle, the lower end of which is immersed under the surface of the melt. Its upper end is surrounded by cooler 6.

Concentric pipes

3, 4, and together with frame part 2 form the supporting arm of the cooler. At the upper end of frame part 2 there is changeable part 1, which has an opening corresponding to the article to be cast and which serves as a packing sleeve against the pressure of the open air. A suitable underpressure is sucked into pipe 5 through opening C; the underpressure lifts melted metal to the cooling area of the nozzle. The lower end of pipe 4 has been soldered to cooler 6 and its upper end packed to frame part 2. Cooling water comes through opening A in frame part2, and runs first along the space between

pipes

3 and 4 to the lower part of cooler 6. There it moves to the narrow space between pipe 5 and the inner mantle of the cooler, where the cooling is particularly effective because of the increase of velocity, and from there on upward along the space between

pipes

4 and 5 to discharge opening B. At this time it simultaneously cools the casting product drawn upward inside pipe 4. Above part 1 there is, as usual, drawing equipment of continuous casting and, if necessary, cutting and reeling devices.

As indicated in the summary of the invention, the melt is cooled sufficiently as it passes through the nozzle 7 to solidify before leaving the nozzle to a sufficient extent that the product formed in the nozzle can be pulled upward out of the nozzle. In effect the nozzle structure acts as the mold for shaping the product which solidifies as the melt passes therethrough.

It is noteworthy that a device according to FIG. I can be used to cast bars of different size by only changing the nozzle and the packing sleeve at the upper end. The

illustrated device has been experimentally used to cast' products with diameters from 2 to 20 mm.

Even alloys difficult to cast (for instance, alloys that corrode the nozzle graphite) can be cast with the described method because the changing of the nozzle does not greatly disturb effective operation of the furnace.

If FIG. 1 is understood as a cross section of a longer. flat chill mold, it shows a device for the casting of platelike products.

FIG. 2 shows an application of the method for the casting of tubelike blanks. At the lower end of the device there is tubelike graphite outer part 9 of the nozzle the inner diameter ofthis part determining the outer diameter of the pipe to be cast; and also conical core 8 with its lower end connected to outer part 9 the core determining the inner diameter of the pipe and, thus, also the thickness of the pipe wall. In the core part there are channels to conduct melt to the ringlike nozzle cavity.

The cooling organs consist of frame part 3 to which are attached outer pipe 4, inner pipe 5, and intermediary pipe 6. The outer and inner pipes are connected at the lower end by nozzle cooler 7. Intermediary pipe 6 extends as far as the inside of the cooler and forms, to gether with the inner mantle of the cooler, a narrow space where the velocity of cooling water increases to make cooling more effective. Cooling water flows in through opening A in frame part 3. It flows along the space between

pipes

4 and 6 to the lower part of the nozzle cooler whence it flows through the narrow space mentioned above into the space between

pipes

5 and 6. There it flows upward, finally flowing out through opening B in the frame part. At the same time it cools the cast pipe moving upward inside pipe 5.

Frame part 3, as shown in FIG. 2, has been attached tightly with fastening corners to underpressure chamber 1 above it, in which the necessary underpressure is maintained with suitable suction, effected e.g. by a vac uum pump.

In the underpressure chamber there are also the necessary means for withdrawal and cutting of the cast product. The upward pulling of a cast bar or similar product may be effected by using rotating rollers or suitable jaws which are both well known in casting technique. Cutting may be effected with a saw. a face plate, etc.

Those of ordinary skill in this art will appreciate that means for moving a cast product into and through the sleeve I exist, for example, as shown in the aforementioned U.S. Pat. No. 2,l7l,l32.

The devices according to FIG. 1 were used to cast Tp 107 bar according to TES 437-74 with a diameter of 17 mm. The temperature of the melted metal was 1080-l 100. The underpressure prevailing in the chill mold was 500 mm standard pressure and the flowing velocity of cooling water l/min. In this case the production was 50 cm/min, or 60 kg/h per nozzle.

What is claimed is:

1. An improved continuous method of upwards casting of profiled products, such as bars, plates and pipes in which melt is sucked above the surface of the melt into a nozzle where it is solidified and then pulled upwards through a cooler to form a solidified product, the improvement comprising:

applying said upwards-directed suction on the melt through the nozzle which is partly immersed in the melt;

cooling the upper portion of the nozzle to solidify the product enough to endure pulling; further cooling the product in the cooler above the 5 ously upwards from a melt comprising:

a support above the melt;

a vertical cooler attached to the support and comprising three concentric pipes defining a passage therebetween having an inlet and an outlet for coolant medium, the innermost pipe having a greater cross-section than the product and an opening for creating suction inside said innermost pipe; and

a nozzle coaxially attached to and partially surrounded by the lower end of the cooler to cool the upper portion of the nozzle for conducting the metal from the melt and for forming a shaping sur- E NETED STATES PATENT OFFICE I .CERTEFiCATE OF CORRECTI PATENT-NU; 3,872,913 Q e DATED March 25, 1975 INVENYOMS) I Timo Jorma. Juhani Lohikoski it is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown beiow:

Col. -4, line 5, "of" should read -for-..

Signed and sealed this 20th day of May 1975.,

(SEAL) Attest:

C. MARSHALL DANN RUTH C. MASON Commissioner of Patents Attesting Officer and Trademarks

Claims

1. An improved continuous method of upwards casting of profiled products, such as bars, plates and pipes in which melt is sucked above the surface of the melt into a nozzle where it is solidified and then pulled upwards through a cooler to form a solidified product, the improvement comprising: applying said upwards-directed suction on the melt through the nozzle which is partly immersed in the melt; cooling the upper portion of the nozzle to solidify the product enough to endure pulling; further cooling the product in the cooler above the nozzle; and pulling the solidified product removed from the nozzle upwards by pulling means above the Cooler.

2. Apparatus for casting profiled products continuously upwards from a melt comprising: a support above the melt; a vertical cooler attached to the support and comprising three concentric pipes defining a passage therebetween having an inlet and an outlet for coolant medium, the innermost pipe having a greater cross-section than the product and an opening for creating suction inside said innermost pipe; and a nozzle coaxially attached to and partially surrounded by the lower end of the cooler to cool the upper portion of the nozzle for conducting the metal from the melt and for forming a shaping surface for solidification of the melt.