US2962278A

US2962278A - Holding apparatus for molten metals

Info

Publication number: US2962278A
Application number: US692335A
Authority: US
Inventors: Goetz Walter; Buhrer Erwin
Original assignee: Georg Fischer AG
Current assignee: Georg Fischer AG
Priority date: 1956-10-29
Filing date: 1957-10-25
Publication date: 1960-11-29
Anticipated expiration: 1977-11-29

Description

Nov. 29, 1960 w. GOETZ ETAL HOLDING APPARATUS FOR MOLTEN METALS 3 Sheets-Sheet 1 Filed 001;. 25, 1957 R a PM 3 El UN HR NE Nov. 29, 1960 w. GOETZ EI'AL 2,962,278

HOLDING APPARATUS FOR MOLTEN METALS Filed Oct. 25, 1957 3 Sheets-Sheet 2 Fig; 2

INVENTORS 1 WM. TER 6 72 ERrw/v EUHAE'K Nov. 29, 1960 w. GOETZ ETAL momma APPARATUS FOR MOLTEN METALS a Sheet-Sheet 3 Filed Oct. 25, 1957 U it The present invention relates to a process and a plant for melting iron, and more particularly to such process or plant wherein the molten iron is supplied to a mixer.

It is a known method in foundries to connect mobile or stationary reverberatory furnaces, which may be rotary or fixed, to the outlet side of cupola furnaces. It has also been proposed to connect electric furnaces to the outlet side of one or several cupola furnaces. Such melting plants are termed duplex melting plants. They are designed either to melt low-carbon or other special cast iron or merely to overheat liquid iron.

It has also been proposed to employ cupola furnaces with induction heated circulation channels or induction heated lower hearths or with induction heating furnaces continuously communicating with the iron in a forehearth to overheat liquid iron. A further group of proposals comprises the flow overheaters in the shape of induction heated circulation channel, induction are or resistance heated units arranged downward of a cupola furnace. All these proposals have the object in common of heating liquid iron above the temperature normally.

obtainable in cupola furnaces.

Recent molding or foundry developments enable molds to be produced automatically, i.e. in certain cycles, the range of applications of a plant not being dependent on the shape of patterns or, within certain limits, on the size of patterns, or on the number of castings required per pattern unit, or on variations in the wall thicknesses. This development therefore enables a varied range of castings to be made in automatic continuous operation. However, this development results in demands for the melting field which are not met by the conventional plant. During operation of such a foundry it may be come necessary, even where production is carefully planned, to vary the quantity of liquid iron delivered to a degree far exceeding present facilities. This is necessary because on the one hand the weight of liquid iron may change substantially per mold and on the other hand because no molds ready for casting can be stacked. A further requirement is that when casting is started, the first batch of liquid iron must be supplied at the perfect temperature. This is necessary because such a plant can no longer provide the possibility of casting the first, so-called cold batch in molds particularly easy to cast.

A further justified requirement is that the diflerence in the analysis of liquid iron melted in cupola furnaces be largely reduced.

In order to meet all the said requirements, it was particularly proposed to build a mixer with or without heating facilities, which cooperates with several melting units for the liquid metal and which is equipped with two pouring lips and two inlets for the metal. It was also proposed, for collecting the metal tapped from various cupola furnaces, to employ a heated mixer, a particular melting chamber being provided and heated by the Waste heat of the associated mixer and, possibly, by a special supplementary burner so that additions to the metal in the mixer can be melted down.

Neither the methods and devices cited at the beginning nor the above mixers meet the requirements created by the new developments in casting in a manner which is technically satisfactory or economically admissible.

States Patent and ICC

It is therefore an object of the present invention to pro vide for a process of melting iron and discharging molten iron in accordance with predetermined requirements.

A further object of the present invention is to provide a process of treating molten iron subsequently to the dis charge thereof from a melting furnace so as to influence the properties thereof with respect to analysis and temperature.

Another object of the present invention is the provision of a process in which the molten iron is preheated subsequently to its discharge from a melting station and to the removal of slag therefrom.

Still a further object of the present invention is to provide for the reheating of molten iron subsequently to its discharge from a melting station and previously to its accumulation at a mixing station.

It is a further object of the present invention to provide for the reheating of molten iron previously to its accumulation at a mixing station in a manner avoiding the necessity of removal of slag from reheated molten iron, subsequently to its reheating or accumulation at a mixing station.

Still another object of the present invention is the provision of a melting process permitting to deliver molten iron to the molds at a predetermined constant temperature throughout an operation period of a foundry and avoiding the supply of molten iron having reduced tem perature at the outset of this operation period. I

A further object of the present invention is the provision of a process for melting iron, in which the differences of composition or analysis in the molten iron, due

to the melting thereof in cupola furnaces, may be avoided,

Another object of the present invention is the provision:

of a process which permits to influence the properties of molten iron in a technically satisfactory and economically sound manner.

A further object of the present invention is the provision of means intermediate a melting station and a mixing station which permit to reheat the molten iron, subsequently to its discharge from the melting station and previously to its accumulation at the mixing station.

A further object of the present invention is the provisionof means permitting to vary the temperature of molten iron supplied to a mixer in a predetermined manner and to thereby influence the temperature of the molten iron discharged from this mixer.

A further object of the present invention is the provision of means arranged intermediate a melting station and a mixing station for the molten iron supplied from the melting station which permit to remove slag from the molten iron, previously to the accumulation thereof at said mixing station.

A further object of the present invention is the provision of a melting plant wherein the outlet for molten iron of a melting furnace is connected to a mixer via asiphon and wherein intermediate the siphon and the mixer section, while the mixer is shown partly in section and partly in elevation; v

Fig. 2 is a section taken along line li -II in Fig. 1,

Fig. 3 is a section taken along line III-III in Fig. 1.

Referring now particularly to the drawing, the reference numeral 1 designates a cupola furnace of standard design which is located above the floor 2 of the melting shop at a height depending on the discharging conditions of the mixer 3. A siphon 4 arranged adjacent the cupola furnace 1, is sealed by means of a cover 5, equipped with an opening 6 for the insertion of a burner prior to starting operation, and an observation aperture 7. As will be seen from Fig. 2, there is arranged in the side wall of siphon 4 a taphole 8 with a slag spout 9 and a second taphole 10 with an attachable trough 11. A connecting channel 12 connects the interior of the cupola furnace 13 with the slag chamber 14 and the iron chamber 15 beneath it. A ceramic tube 16 around which an induction heating coil 17 is arranged leads from the iron chamber 15 to an outlet tube 18 through which the liquid iron can enter the interior 19 of the mixer.

In order to increase the efiiciency of the induction heating coil 17 and to avoid excessive heating of the iron members, either all iron parts in the range of the magnetic field must be antimagnetic and preferably formed of austenite sheets, or these sheet members must be equipped with a lining, e.g. of copper sheet. The induction heating coil 17 is not provided with a closed magnetic core for the magnetic field since this would have to be designed with water cooling and cause electrical short circuits owing to the unavoidable formation of condensate. The induction heating coil 17 is advantageously located freely in a space 36 which is so connected with the outside by an opening 37 that condensate can drain through the latter. This opening 37 has the further advantage that the liquid iron can drain freely if the ceramic tube 16 should break owing to defective quality or defective installation.

The mixer 3 includes a mixing container 3a which is provided with a closure plug 41 for insertion of a burner designed to preheat this container and with a removable closure member 42 enabling the chamber 19 of the container to be inspected. The spout 38 is connected to the container so as to be removable therefrom in a known manner. The container 311 rests on a frame 22 via two runners and four rollers 21. A drive means 23 and the reduction gear 24 and a gear 25 meshing with a rack 26 enable the mixer to be pivoted or tilted mechanically between a plurality of angular positions. A platform 27 on which the pouring vessels or ladles 34 can be placed is hingedly connected to the runners 20 by means of the pivots 28. Each of the two pivots 28 carries a segment member 48 rigidly connected to platform 27. A rope 29 is connected to each of the two segments; the ropes being guided over rollers 30 and wound on the drums 31. The drums 31 are in driving engagement with an electric motor 23, and are rotated by the latter during the tilting movement of the mixer. Rotation of the drums is effected in such a manner that a length of rope 29 is unwound from, or wound on the drums corresponding to the tilting movement carried out by the mixer, so that the platform 27 is held horizontally over the whole range of tilting movement. Since the mixer spout 38 will maintain the same relative position with respect to the inlet opening of the pouring vessel 34 and, since the pivoting axis of the platform extends immediately adjacent to the mixing spout, it will be insured that the molten iron flowing from the mixer will be caught by the pouring vessel in all tilting positions of the mixer. Consequently, a sliding displacement of the pouring vessel, relative to the mixer, will be unnecessary. The frame 22 rests on four rollers 32 which can be swivelled about a vertical axis by 90 so that the mixer may be moved both towards and away from the cupola furnace, and in a direction normal thereto. The outlet tube 18 is provided with a water cooling system 33 of known design.

The process according to this invention is carried out as follows: s

When the melting unit is started, taphole 10 is open and taphole 8 closed. Experience has shown that when a cupola furnace is started, liquid slag is first discharged. As soon as liquid iron flows from the furnace, the taphole 10 is closed. The iron chamber 15 and the ceramic tube 16 rapidly fill with liquid iron, the slag in the slag chamber 14 floating above the iron in iron chamber 15. Since both the iron and slag chambers (14, 15) and the interior of the ceramic tube 16 are well preheated by a burner (not shown) inserted in the opening 6 and removed prior to starting the cupola furnace, there is practically no danger that the iron will solidify on its way into the interior 19 of the mixer.

The induction heating coil 17, which is connected with a source of three-phase current (not shown) advantageously operating in such cases with medium frequencies of approximately 4,000 cycles per second, heats the iron flowing through the ceramic tube 16 and the outlet tube 18 into the interior 19 of the mixer. As the medium frequency source and the power control of the induction heating coil 17 are designed according to known principles, they are not shown and their operation is not described. The power for the induction heating coil 17 is such that a given tapping temperature of the liquid iron is obtained and the preheating temperature of the mixer 3 after filling is allowed for. In normal cases a power of 15-30 kw.h. per ton liquid iron will be required during the starting cycle, which lasts about one hour. When the liquid iron charge in mixer 3 has reached the level 43 indicated in Fig. 3, liquid iron can be discharged therefrom for casting. When the same tapping temperature is to be maintained, experience shows that the heating power can be reduced to 0-5 kw.h. per ton liquid material within 1 to 2 hours depending on conditions.

The embodiment shown in the drawing for the design of the siphon 4 is particularly applicable to smaller cupola furnaces. In this case, the slag is allowed to rise to a certain level, so that it depresses the iron level in the iron chamber 15 while the slag rises into the interior 13 of the cupola furnace. When the slag in the slag chamber 14 has reached a certain level, it is removed through taphole 8, which is then closed again until the next tapping. Where the cupola furnace is larger, the taphole 8 with the slag spout 9 may be dispensed with. In the latter case, the slag is continuously removed from the cupola furnace via a slag opening 35, indicated in dash and dot lines in Fig. 1.

When liquid iron is poured into a casting vessel 34 from the mixer 3, the said vessel is placed on the platform 27 by a crane (not shown) prior to tilting the mixer. The platform 27, which is held horizontal during the tilting process, has the advantage that the flow of liquid iron from the mixer spout 38 always reaches the casting vessel 34 over the shortest distance in any tilting position of the mixer. The platform 27 has the further advantage that the casting vessel can be swung directly below the mixer 3 when the latter is emptied, which would be impossible if it were suspended from the crane. In order to avoid heat losses in the mixer and reactions of the atmospheric oxygen with the liquid iron as far as possible, the outlet portion of the siphon 4 opposite the inlet portion of the mixer 3 is sealed by asbestos braids 39. When slag is formed in the interior 19 of the mixer after several days, which does not emerge through the spout 38 of the mixer when it is tilted, the mixer spout 38 can be removedso as to render the larger opening 44 behind it accessible. This large opening 44 enables slag to be removed in the known manner. After removal, the mixer spout 38 is again connected.

When the cupola furnace is stopped, the residual iron and the residual slag are removed through the taphole 10 and the removable-trough 11 fromthe iron chamber 15 and the slag chamber 14. This will also empty the ceramic tube 16. The moulding operation is discontinued only when the mixer 3 is completely empty. After emptying, the mixer is removed from the cupola furnace. The inlet opening of the mixer and the spout 38 are closed, which enables the mixer to be started on the following day without supplementary heating. The siphon 4 is separated from the cupola furnace at the separating plane 40 while cooling of the induction heating coil 17 is continued, and taken to a cooling location by means of a hoisting device (not shown) where it is inspected and, if necessary, repaired.

The process according to this invention enables the design of the mixer to be selected independently of the heating, i.e. the mixer may have its interior design approaching a cylinder with a minimum surface for a predetermined volume. This in turn permits to employ also with large melting plants a tiltable mixer holding a quantity of approximately a one-hour output. As the inner surface of the mixer has a minimum area, there is a minimum of waste heat that passes through the mixer lining. Since the mixer is not heated during operation, the openings can be limited to the inlet and outlet openings for the liquid iron. This condition permits the heat losses so far caused by radiation from the interior of the mixer and the air flowing through the mixer openings to be practically eliminated. As no heating is required for the mixer, the interior temperature of the mixer will never exceed the temperature of the liquid iron. For this reason, and because practically no slag is formed in such a mixer, the life of the mixer lining greatly exceeds that of a heated mixer.

The process described in the foregoing enables the quantity of liquid iron produced to be adjusted to the casting requirements because technically satisfactory and economically admissible mixers of sufficient size may be built. For the same reason, analysis fluctuations in the liquid iron caused by the operation of the cupola furnace can be substantially reduced. If silicon or other accompanying metals still vary to an excessive degree in exceptional cases, these accompanying metals may be kept below average by appropriate selection of the charge and subsequently be added to the mixer through a separate additional opening (not shown) in liquid or solid form as high percentage ferro-alloys.

The method renders it possible to operate, during the starting cycle (for about one hour), with substantial superheating in the flow heater before liquid iron is discharged from the mixer, i.e. supplied for pouring of molds and thereby ensure that already the first batch cast possesses the desired temperature.

Various changes and modifications may be made without departing from the spirit and scope of the present invention and it is intended that such obvious changes and modifications be embraced by the annexed claims.

Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent, is:

1. A mixer for mixing and storing molten metal and discharging it into a pouring vessel, comprising movable supporting means, a mixing container for said molten metal having spout means and arranged on said supporting means for pivoting movement about an axis extending through said container, to thereby discharge said molten metal when in said container through said spout means, drive means on said supporting means operatively connected with said container for pivoting the latter about said axis, platform means hingedly connected to said container for supporting said pouring vessel in a substantially horizontal position below said spout means, and transmission means interconnecting said drive means with said platform means for tilting of said platform means relative to said container during pivoting movement thereof and commensurate with said pivoting movement, to thereby maintain said pouring vessel when supported on said platform means in said horizontal 6 position during said pivoting movement of said container whereby discharge of said molten metal into said pouring vessel is ensured.

2. In a melting plant for producing molten iron of substantially uniform analysis, a mixer for mixing, storing and discharging said molten iron into a ladle, comprising supporting means, having wheels for moving the latter, a mixing container for said molten metal having spout means and an inlet opening arranged on said supporting means for pivoting movement between a plurality of angular positions about an axis extending through said container and coaxially with said inlet opening, to thereby discharge said molten metal when in said container through said spout means, drive means on said supporting means operatively connected with said container for pivoting the latter about said axis, platform means hingedly connected to said container for support ing said ladle in a substantially horizontal position below said spout means, and transmission means interconnecting said drive means with said platform means for imparting parallel displacement to the latter during pivot- I ing movement of said container and commensurate therewith to thereby maintain said ladle when supported on said platform means in said horizontal position in all of said angular positions of said container whereby discharge of said molten metal into said pouring vessel is ensured.

3. The mixer according to claim 2, said spout means being of tubular shape and removably connected with said container.

4. A mixer for mixing and storing molten metal and discharging it into a ladle, comprising supporting means having wheels, a mixing container for said molten metal having tubular spout means, an inlet opening arranged on said supporting means for pivoting movement through a plurality of angular positions about an axis extending through said container and coaxially to said inlet opening, to thereby discharge said molten metal when in said container through said spout means, drive means on said supporting means operatively connected with said container for pivoting the latter about said axis, platform means hingedly connected to said container for supporting said ladle in a substantially horizontal position below said spout means, drum means supported by said supporting means and in driven engagement with said drive means, flexible transmission means wound on said drum means and operatively interconnecting the latter with said platform means for tilting of said platform means relative to said container during pivoting movement thereof and commensurate with said pivoting movement, to thereby maintain said ladle when supported on said patform means in said horizontal position in all of said angular positions of said container.

5. A mixer according to claim 4, wherein said wheels are pivotable about respective vertical axis intersecting the axis of rotation of said wheels at right angles.

References Cited in the file of this patent UNITED STATES PATENTS 38,513 Stileman et al May 12, 1863 980,369 Walker Jan. 3, 1911 1,133,317 Rice Mar. 30, 1915 2,071,890 McWane Feb. 23, 1937 2,339,337 Hulme Jan. 18, 1944 2,406,147 Hopkins Aug. 20, 1946 2,842,354 Hohne July 9, 1958 FOREIGN PATENTS 446,686 Great Britain May 5, 1936 1,019,121 France Jan. 16, 1953 OTHER REFERENCES Stoughton, The Metallurgy of Iron and Steel, 3rd edition, McGraW-Hill Book (10., Inc., New York, N.Y. (1923) (page 89 relied upon).