CA1186475A - Semicontinuous casting apparatus - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A semicontinuous casting apparatus comprises a holding furnace connected through a closed metal feeding system to a metal supply means having a metal supply duct. Mounted on the metal supply means is a mould provided with a cooling system and having a dummy bar placed in its upper part and connected with a casting withdrawal system. The mould cooling system is provided with a device for forcing out a liquid coolant from the mould by means of compressed gas. The dummy bar has a central head which accom-modates a heating element and an adjustable valve for admitting an inert gas into the casting being formed. The casting withdrawal system has two casting withdrawal mechanisms alternately co-operating with the dummy bar and of which one is used for pulling out the casting from the mould for a distance not smaller than the length of the casting minus the length of the mould, and the other one is effective to pull out the casting from the mould for a distance not smaller than the length of the mould. The invention is preferably utilized in the production of solid and hollow castings by a semicontinuous casting process in which such castings are drawn up from a mould.

Description

The present invention relates to casting machines, ancl more particularly, to apparatus for the semicontinuous casting of metal.
The invention is preferably used for the semicontinuous casting of metal in the production of solid or hollow castings by drawing up.
Continuous and semicontinuous casting machines are now finding an ever greater application in the metallurgical industry throughout the world.
10 The introduction of such machines makes it possible to substantially reduce the production cycle as compared to conventional techniques used in foundry practice. In addition~ these types of machines allow a considerable saving in time and labour, an 15 extra gain in yield, enhanced production efficiency, as well as improved working conditions. The castings produced by such machines have uniform structure and good properties.
Japanese Pat. No. 45-39345 describes a 20 machine for continuous casting by drawing~up, which comprises a sealed chamber for molten metal, a water-cooled mould immersed in the molten metal, a dummy bar incorporated in a casting withdrawal mechanism.
The above-described machine is constructed so as to permit the production of hollow castings by uphill casting of molten metal into the mould cavity. This being the case, a solidified layer and a semisolid layer contiguous thereto are formed on the working surface of the mould (a solid-liquid phase). When the two above-mentioned layers reach a given thickness, the metal meniscus is brought down to be level with the lower end of the mould.
Thereafter, upon complete solidification of the ~l~8~ 5 semisolid layer, the lower end of the solidified section is brought up to the top end of the mould and the metal meniscus is brought down to be level with the lower end of the solidified section.
The mould cooling system in the above machine is not provided with a device for forcing out a liquid coolant from the mould which, con-sequently, makes it impossible to control the casting skin formation conditions. Furthermore, the machine has no device for improving quality of the inner surface of the casting being produced.
U. S. Pat. No. 3,302,252 discloses a machine for continuous casting of metal by drawing-up, which comprises a device for feeding a molten metal to an air-operated metal supply means having a metal supply duct. Mounted on the metal supply means is a mould provided with a cooling system and having a dummy bar placed on its upper part and operably connec-ted with a castiny withdrawal mechanism. There is also provided an appliance for building up pressure in the metal supply means and a metal oscillating device.
The pipe casting produced by the machine has its wall formed on the working surface of the mould after it is filled with molten metal. The casting being formed is continuously withdrawn upwardly from the mould by means of a dummy bar operably connected to the casting withdrawal mechanism. In the process of casting formation the level of molten metal in the mould cavity is raised and lowered by means of the metal oscillating device.
The above-described machine has no means for introducing an inert gas into the interior of 1~8~75 the casting being formed. The conditions causing the molten metal to move in the mou]d cavity may bring about oxidation of the inner surface of ~he solidified layer, as a result of which -the newly forming layer will fail to adhere to the casting skin during subsequent rise of the metal meniscus.
This, in turn, will impair the quality of the cast product and, in the event of casting aluminium alloys, will lead to defective products.
An object of the present invention is to ensure stability of the semicontinuous casting process.
Another object of the invention is to improve quality of the cast products.
The foregoing objects of the invention are attained in a semicontinuous-casting apparatus com-prising a holding furnace connected through a closed metal feeding system to an air-operated metal supply means having a rnetal supplyduct, a mould with a cooling system arranged on the metal supply means, and a dummy bar placed on the upper part of the mould and operably connected to a casting withdrawal system, wherein, according to the :invention, the mould cooling system is provided with a device for forcing out a liquid coolant from the mould by means of compressed gas, the dummy bar having a central head adapted to accommodate a heating element and an adjustable valve for admitting an inert gas into the interior of the casting being formed, the casting withdrawal system having two casting withdrawal mechanisms for alter-nate cooperation with the dummy bar, of which one mechanism is operated to pull out the casting from the mould for a distance not smaller than the length 9L7~

of withdrawal of the casting minus the length of the mould, and the other casting withdrawal mechanism is effective to pull out the casting from the mould for a distance not smaller than the length of the mould.
Such apparatus construction makes it possible to produce castings of uniform structure and good surface quality.
One of the casting withdrawal mechanisms is preferably provided with a movable platform having a lever through which the platform is oper-ably connected with the dummy bar, and a drive; the other casting withdrawal mechanism is preferably provided with a movable bar slided in roller guides, a toothed rack and a member for engagement with the dummy bar, and a drive.
Such structural arrangement of the casting withdrawal mechanisms makes it possible to create favourable casting withdrawal conditions and to shorten intervals between the casting cycles.
Where hollow castings are to be produced, the semicontinuous casting apparatus is preferably provided wlth a device for broaching and sizing the interior of the cast product, which device is made in the forrn of a broaching and sizing tool located in the lower part of the central head, and a drive which may be the actuator used to driving one of the casting withdrawal mechanisms.
The use of such device allows the production of quality castings with adequately sized inner surfaces.
~he invention will now be described, b~ way of example only, with reference to the accompanying drawings, wherein . , --FIG. 1 is a general view of a semicontinuous-casting apparatus according to the invention;
FIG. 2 shows a central head of a dummy bar, FIG. 3 is a top view oE the dummy bar;
FIG. 4 shows slewing sections of a secondary-cooling chamber;
FIG. 5 shows a closed system through which a molten metal is fed from a holding furnace to an air-operated metal supply means;
FIG. 6 shows a system through which a coolant is fed to the mould;
FIG. 7 is a cross-section on line VII-VII
of FIG. 3; and FIG. 8 shows a dummy bar with a broaching and sizing tool.
Referring now to the drawings in detail, and to Figure 1 in particular, a semicontinuous-casting apparatus comprises a holding furnace 1 which is connected to an air-operated metal supply means 2 through a closed metal feeding system 3.
The mctal supply means 2 is connected to a compressed gas feeding system 4. Mounted on the top cover of the metal supply means 2 is a metal supply duct 5 with a flange being heated. Connected to the flange of the metal supply duct 5 is a cooled mould 6 having a cooling system with a coolant source 7 and a device 8 for forcing out a liquid coolant from the mould 6 by means of compressed gas.
The apparatus incorporates at least two dummy bars 9 w'nich, when required~ are mounted on the mould 6 prior to starting the next casting cycle.

The dummy bar 9 has a central opening adapted to receive a central head 10. The central head 10 has a heating element 11 (FIG. 2) and an adjustable valve 12. The body of the head 10 is formed with the holes through which it communicates with an inert gas supply system 13 (FIG. 1).
Mounted on the dummy bar 9 are two legs 14 formed with holes (FIGS. 1,3) through which the dummy bar 9 cooperates with a casting withdrawal mechanism 15 or 16 (FIG. 1). ~hen the dummy bar 9 cooperates with the casting withdrawal mechanism 15, pins 17 of a lever 18 are introduced into the holes fitted in the legs 14. If, however, the dummy bar 9 is asso-ciated with the casting withdrawal mechanism 16, the holes in the legs 14 receive pins 19 (FIG. 3) of a movable spring-loaded bracket 20 with a slot 21. The pins 19 of the bracket 20 and its slot 21 are aligned so that the pins 19 are permitted to enter into the holes provided in the legs 14 of the dummy bar 9, while the bracket 20 per se, or rather its section formed with the slot 21, is accommodate~ in the openings formed in a member of the casting withdrawal mechanism 16 (FIG. 1). The casting withdrawal mechanisms 15 and 16 make up a casting withdrawal system.
The casting withdrawal mechanism 15 in-corporates a drive (not shown), a feed screw 22 and a platform 23. The platform 23 bears against the feed screw 22 and is movable relative to stationary mounted guide columns (not shown). Movably mounted on the platform 23 is-the lever 18 with the pins 17.
The casting withdrawal Inechanism i6 is placed on a trolley 24 for movement along stationary mounted beams 25 located above the apparatus.

Disposed above the mould 6 within a length corresponding to the length of withdrawal of a cast-ing 26 from the mould 6 is a secondary-cooling zone 27 defined by twin slewing sections made in the form of at least two shoes 28 (FIG. 4) secured to arms 29.
The shoes 28 are smaller in length than the mould 6 (FIG. 1) and are preferably equal in length to the maximum di.stance for which the casting 26 is with-drawn in a single cycle.
The apparatus of the invention has the following structural features.
The closed metal feeding system 3 intended for feedi.ng molten metal from the holding furnace 1 to the air-operated metal supply means 2 has a tap closing appliance which is accommodated ln a chamber 30.
The closed metal feeding system 3 comprises a tap 31 (FIG. 5) which is formed in a refractory block 32 and is closed by a gate 33 placed in a holder 34 through which the gate 33 is pressed against the refractory block 32. The gate 33 with the holder 34 is forced against khe refractory block 32 by means of a connecting rod 35. The holder 34 is connected with a lever 36 resting on a pivot 38 fixed in stands 37, and driven by an actuator 39 located externally of the chamber 30.
~itted in the wall of the metal supply duct 5 (FIG. 1) below its heated flange is a hole connected to a tube 40 which communicates with the compressed gas supply system 4 and has a shutoff valve 4].. The tube 40 has one of its ends flaring up towa.rd the metal duct 5. The inner wall of this part of the tube 40 has a protective casting preventing adhesion of the cast metal to the walls of the tube 40. The tapered end of the tube 40 and the protective coating facilitate the return of metal r which can penetrate into the tu~e in the course of operation.
The mould cooling system with the coolant supply source 7 (FIG. 1) and device 8 for forced dis-charge of coolant from the mould includes a valve 42 (FIG. 6) for feeding compressed air to the mould 6, set in a pipeline 43 through which the coolant is delivered from the mould 6 to the coolant vessel 7.
Set in a pipeline 44, through which a coolant is delivered from the container 7 to the mould 6, and arranged in series therein are a relief valve 45 intended to return a liquid coolant to the container 7, and a closed vessel 46 provided with an indicator 47 of the coolant level in the closed vessel 46.
Interposed between the coolant container 7 and the relief valve 45 is a tube 48 for returning a liquid coolant.
The casting withdrawal mechanisms 15 (FIG. 1) and 16 are well adapted for rapid alternate cooperation with the dummy bar 9 in a required sequence. The first to associate with the dummy bar 9 (FIG. 7) having the legs 14 with holes 49, is the mechanism 15 (FIG. 1) which is brought in cooperation with the dummy bar 9 through the pins 17 fixed in the gu:ide-slided lever 1~ of the movable platform 23. The movable platform 23 is permitted to travel for a distance equal at least the length of the casting 26 minus the length of the mould 6.
The casting withdrawal mechanism 16, mounted on the trolley 24, is constructed so as to permit the casting 26 to be pulled out for a length not smaller than that of the mould 6. The mechanism 16 has, slidably mounted on roller guides 50, bars 51 with a pair of toothed racks 52 fixed thereon and engaged with a pair of driven pinions 53. The lower end of the bar 51 carries a member 54 with openings through which the bar 51 is connected with the bracket 20 ( FIG. 3) mounted on the dummy bar 9.
Where the casting 26 is to be made hollow, the semicontinuous-casting apparatus of the invention is provided with a device for broaching and sizing the interior of the casting 26. The device in question is made in the form of a broaching and sizing tool 55 (FIG. 8) located in the lower part of the central head 10, and a drive, which may be an actuator 56 (FIG. 1) incorporated in the casting withdrawal mechanism 16.
The member 54 of the bar 51 is readily con-nected and disconnected from a shank 57 (FIG. 8) of the broaching and sizing tool 55, with the bar 51 (FIG. 1) being made of sufficient length to permit the central head 10 to travel over the entire length of the casting 26 being produced.
The central head 10 (F~G. 8) has a valve 58 by means of which an inert gas is fed into the interior of the castiny 26. The valve 58 is operably connected with a piston 59. The central head 10 has two radial ho],es 60 and 61 fitted in the middle part thereof. The hole 60 is connected to a chamber 62 accornmodating the slidable piston 59, and the hole 61 communicates with a chamber 63 accommodating the valve 58.
The central head 10 is received in an opening 64 in the dummy bar 9 and is held in place by means of rods 65 and 66 which are fitted into sleeves 67 and 68. The rods 65 and 66 have radial and a~ial holes. A radial hole 69 in the rod 65 communicates with a radial hole 70 in the rod 65, then with a hole 71 in the leg 14 of the dummy bar ,~
, - ", 9, and further with a radial hole 72 ( FIGS. 7 and 8) as well as with an axial hole 73 in the pin 17 of the casting withdrawal mechanism 15 (FIG. 1).
Connected to the hole 73 ( FIG. 7) at the end of the pin 17 is a nipple 74 having a flexible hose 75 coupled thereto for supplying compressed gas.
An axial hole 76 (FIG. 8) in the rod 66 communicates with a radial hole 77 in the rod 66, then with a hole 78 in a support stand 79 of the dummy bar 9, further with a radial hole 80 and a radial hole 81 in a pin 82 of the casting withdrawal mechanism 15 (FIG. 1). Connected to the hole 81 (FIG. 8) at the end of the pin 82 is a hose (not shown) for feeding inert gas.
When used for producing round castings, the apparatus of the inventin is operated in the following manner.
After preparatory operations, the metal duct 5 ( FIG. 1) is heated to a temperature close to the melting temperature of the metal being cast.
Next, the dummy bar 9 is placed on top of the mould 6 and then i9 connectd to the casting with-drawal mechanism 15 by means of the pins 17.
Then, the ai.r-operated metal supply means

2 and the chamber 3() of the closed metal supply system 3 are blown through with an inert gas, such as argon, to produce inert atmosphere therein.
This being done, the tapping hole 31 (FIG. 5) is opened as the holder 34 with the gate 33 are moved upwardly through the agency of the lever 36 to permit a required amount of molten metal to be poured from the holding furnace 1 (FIG. 1) into the metal supply means 2.

Although the amount of molten metal fed to the air-operated metal supply means 2 usually corres-ponds to the weight of the casting 26 being produced, it may be more or less than this weight.
After the metal supply means 2 has been filled with metal up to a preset level, the tapping hole 31 is closed by the gate 33 and superpressure is built up in the chamber 30 and in the metal supply means 2 with the aid of the compressed gas supply system 4 (FIG. 1), whereupon the molten metal is caused to pass through the metal supply duct 5 into the mould 6, whereby raising the level of metal (meniscus) until it comes in contact with the lower end of the dummy bar 9. Gas can be Ereely discharged from the cavity of the mould 6 through the central head 10 of the dummy bar 9. In this case the valve 12 (FIG. 2) does not close the outlet 83. However, in certain cases it may be advantageous for the molten metal to be fed into the mould 6 with super-pressure acting on the raising metal meniscus. To this end, the valve 12 is forced against the outlet at a preset pressure so as to ensure a required pressure of gas on the raising metal meniscus.
Normally it takes not more than 3 to 5 sec to fill the mould 6 with molten metal.
Once the mould 6 is filled with molten metal and the outlet 83 in the central head 10 is closed, a skin of the casting 26 to be produced is formed to a preset thickness under conditions close to those obtained in permanent-mold casting with superpressure acting from the side of molten metal.
To fulfill this condition, immediately after filling the mould 6 (FIG. 1) with molten metal or prior to feeding the molten metal thereinto, depending on the '7~

possibilities of the mould 6, a coolant is removed from the cooling channels of the mould 6 with the aid of the compressed gas ~air) supply system 8. Due to the heat liberated in the course of metal solidifi-cation, the walls of the mould 6 are heated to a required temperature, for example, of 150 to 250C
where aluminum alloys are cast.
Although the liquid coolant continues to be fed from the coolant supply source 7 at the time when compressed air is introduced into the channels of the mould 6, it is immediately recycled to the supply source 7 through the relief valve 45 (FIG. 6).
The initial formation of the skin of the casting 26 is carried out in the preheated mould 6 at a preset superpressure. This pressure may be in the range of 0.5 to 6 ato and over. ~ required pressure is mounted by means of a compressed inert gas fed through the compressed gas supply system 4 (FIG. 1).
The casting 26 is formed in the preheated mould 6 until the skin thereof reaches a thickness of about 10 to 30 mm, whereupon compressed gas is discharged from the channels of the mould 6 and a liquid coolant, such as water, is introduced at a temperature close to ambient temperature. The rate of heat removal from the casting 26 is stepped up.
This being done by lowering the temperature of the walls of the mould 6 and by reason of the fact that with the supply of coolant the mould 6 is substan-tially reduced in size and its walls come i.nto closer contact with the casting 26. In the given case, it is possible to create conditions under which the solidified skin of the casting 26 will undergo external stresses, from the side of the walls of 4~7~

the mould 6, and internal stresses acting from the side of molten metal. The following example is given below to emphasize the importance of taking into account the expansion of the mould 6 caused by high temperatures of its walls. In the event of producing a round-shaped casting 500 mm in dia in the mould 6, formed of aluminium alloy with a hard-anodized work-ing surface, with the coefficient of linear expansion of this alloy being 24~10 6 in the temperature range of 20 to 300C, the inner diameter of the mould 6 will change by 2.4 mm with the change of temperature of the walls of the mould 6 by 200C. Obviously, such substantial change in the size of the mould 6 should be given due consideration and should be used to good advantage.
Further, with the superpressure still acting on the skin of casting being formed, its formation continues until it reaches 40 to 60 mm in thickness.
Once the skin of the casting 26 is formed to a preset thickness, the superpressure acting on the molten metal through the compressed gas supply system 4 is released and the liquid coolant is COII-currently discharged from the channels of the mould 6, whereby it becomes possible to ensure some expansion of the mould 6 due to its heating. Thus, favourable conditions are created to enable effective withdrawal of the casting 26 from the mould 6.
Next, the solidified skin of the casting 26, the upper part of which is reliably connected with the dummy bar 9, is rapidly withdrawn (for 3 to 3 sec) upwardly from the mould 6 by beams of the withdrawal mechanism 15 for a length not exceeding that of the mould 6. After the casting 26 has been withdrawn from the mould 6, the levers 29 (FIG. 4) with the ` s~
/ .,, shoes 28 are rotated about their axes so as to be tightly pressed against the casting 26, enveloping its entire outer surface.
As the casting 26 is withdrawn from the mould 6, an inert gas is concurrently introduced into the interior of the casting 26 through the head 10 (FIG. 1) by means of the inert gas supply system 13.
It is possible due to the fact that in the course of initial formation of the casting 26 the temperature in the central end part of the casting 26 was main-tained higher than that of the cast metal by meansof the heater 11 ~FIG. 2) accommodated in the central head 10.
If the pressure in the metal supply means 2 (FIG. 1) is close to air pressure, then with an inert gas being introduced into the interior of the casting 26, the molten metal will be rapidly discharged from the casting interior and it may be completely removed from the cavity of the mould 6. Therefore, it will be disadvantageous to bring down the metal level below the lower end of the mould 6. Ilhus, after introducing gas into the interior of the casting 26 being formed, the metal meniscus is first brought down, but not lower than the lower end of the casting 26. Further, 2S by producing a required superpressure in the metal supply means 2, the metal meniscus is maintained at this level and, as the casting 26 is withdrawn from the mould 6, the metal meniscus is again raised at the speed not lower than that at which the casting 26 is withdrawn from the mould.
On completion of the casting withdrawal operation, the metal meniscus in the interior of the casting 26 continues to be raised until it reaches a preset uppermost position, while inert gas is dis-charged from the casting 26 through the central head10 of the dummy bar 9.
/

s In certain cases, after the casting 26 has been withdrawn from the mould 6 for a given distance, it can be pulled slightly backward to make up for the linear shrinkage of the newly forming casting 26.
The skin formation process in the newly formed casting 26 is carried out in the cavity of the mould 6 as described above with reference to the initial skin formation procedure, i.e. with super-pressure acting from the side of molten metal and with the walls of the mould 6 being first heated and then cooled. The heating of the walls of the mould 6, i.nitiated still before withdrawing the casting 26 from the mould 6, is continued until the walls are heated to a preset tempera-ture and after the casting 26 has been withdrawn from the mould 6 when the skin of the casting 26 is still thin. Then, at a preset time a coolant is again introduced into the mould 6.
Starting from the formation of the second portion of the casting 26, in the interval between withdrawing cycles, the molten metal is continuously brought up and down in the interior of the casting 26 being formed at a preset rate, for example, at the rate of 0.5 to 2.0 m/sec. During the above-mentioned up and down cycles~ an inert gas is di.s-charged and introduced through the central head 10 in the dummy bar 9. These gas discharging and feed-ing steps could be carried out with a required super-pressure being built up on the metal meniscus.
If, for instance, continuous movement of metal relative to the solidified skin is to be carried out during initial formation of the casting 26, an inert gas is introduced before the moment of initial withdrawal of the casting 26 from the mould 6, where-upon the above-mentioned conditions will be made possible.

After the second withdrawal cycle, the second pair of the slewing sectlons of the secondary-cooling chamber 27 is operated and the entire production cycle is repeated until the casting 26 is pulled out to a preset height.
Further, the skin formation process is carried on until the casting 26 is completely formed in the mould 6 without being withdrawn therefrom.
From this moment on, the casting 26 is being formed until it becomes solid in cross section or until a preset thickness of its wall under conditions of con-tinuous up-and-down movement of molten metal inside the casting 26. It permits the casting 26 being pro-duced to have sound structure and uniform chemical composition.
If stringent requirements are not imposed on the quality of the casting 26, the up-and--down movement of metal inside the casting 26 is not com-pulsory to carry out in the course of its formation to preset si~es.
Where a sound solid casting 26 is required, the movement of molten metal inside the casting 26 is discontinued toward the end of the solidification process and, maintaining the superpressure acting from the side of the metal supply duct 5, the solidi-fication of the casting 26 is completed.
The casting 26 is intermittently withdrawn from the mould 6 for a given distance by means of the dummy bar 9 in conjunction with the casting withdrawal mechanism 15. At the end of the withdrawal operation, the casting withdrawal mechanism 15 is disenaaged from the dummy bar 9 while the casting withd,rawal mechanism 16 is concurrently connected thereto. The platform 23 of the casting withdrawal mechanism 15 ~ t7 is brought down to permit its rapid connection (for 10-15 sec) with the next dummy bar 9.
The casting withdrawal mechanisms 15 and 16 are connected to and disconnected from the dummy bar 9 simultaneously. This is carried out as follows.
The pins 17 are brought out of the holes in the legs 14 of the dummy bar 9, and the pins 19 ~FIG. 3) of the bracket 20 are automatically received in the same holes of the legs 14. As this happens, the bracket 20 formed with the slot 21 is received in the grooves provided in the member 54 (~IG. 1) secured to the bar 51 of the casting withdrawal mechanism 16. In this way, the dummy bar 9 is disengaged from the casting withdrawal mechanism 15 so as to cooperate with the casting withdrawal mechanism 16.
With the aid of the mechanism 16, the cast-ing 26 is completely withdrawn from the mould 6 and then is conveyed along the guides 25 by the trolley 24 to a special storage.
To enable easy disengagement of the lower end of the solid casting 26 Erom the molten metal during its withdrawal from the mould 6, an inert gas is fed to the place of disengagement throuyh the tube 40 from the system 4 via the valve 41.
As soon as the casting 26 has been withdrawn from the mould 6, a new dummy bar 9 is mounted on the mould 6 for cooperation with the casting withdrawal mechanism 16. Simultaneously, a new portion of molten metal is fed from the holding furnace 1 to the air-operated metal supply means 2.
The metal supply means 2 may be replenished with molten metal during the casting cycle at a time when the gas pressure in the metal supply means 2 is released.

If a hollow casting 26 is to be produced, then on withdrawi~g the casting 26 for z given length, the skin formation process lasts until the skin of the casting 26 reaches a required thickness over the full vertical extent thereof. Thereafter, the broach-ing and sizing operations are carried out. To this end, the rods 65 and 66 (FIG. 8) are retracted from the central head 10 so as to be disengaged from the sleeves 67 and 68.
Next, the drive 56 (FIG. 1) is operated to bring down the bars 51 and, on connecting the member 54 with the shank 57 (FIG. 8), the central head 10 is introduced into the interior of the casting 26.
Here, the tool 55 is brought into use to cut off a part of the solidified metal from the inside walls of the casting 26 (broaching) and to effect sizing of the opening to the diameter of the tool 55.
The cut-off metal is returned to the metal supply means 2 (FIG. 2) to be melted down therein.
In the course of broaching, the opening in the casting 26 is not made through but stops 20 to 30 mm short of the lowerend thereof, whereupon the central head 10 is disengaged from the bar 51 an~
the lat-ter is then lifted and held in place to permit the slots in the member 54 to be in opposite space relationship with the slot 21 (FIG. 3) in the bracket 20. Next, the dummy bar 9 is connected with the cast-ing withdrawal mechanism 16 while the casting with-drawal mechanism 15 is disengaged therefrom.
Further, the drive 56 is operated to effect withdrawal of the casting 26 from the mould 6, and the platform 23 ~.7ith the leuer 23 is brought down to the lower position so as to be connected by means of the pins 17 with the new dummy bar 9 mounted on the mould 6.

,.

t7~i ~ Once Ollt of the mould 6, the casting 26 is conveyed by the trolley 24 to a specially designed place where final broaching of its opening is carried out and the central head 10 is removed therefrom.
As soon as the casting 26 is brought away from the casting line, the ne~ dummy bar 9 is placed on the mould 6 for cooperation with the casting ~ith-drawal mechanism 15 while the central head 10 is connected by means of the rods 65 and 66 (FI~. 8) with the compressed gas supply system 13 (FIG. 1).
When all the above-mentioned operations are completed, a new casting cycle is started.
The semicontinuous-casting apparatus of the invention makes it possible to produce castings of good surface and structural quality and of uniform chemical composition.
In addition, the apparatus is suitable for the production of hollow castings with a presized inner surface of high quality.
As a result, it becomes possible to reduce expenses required for the further mechanical treat-ment of castings, to diminish the number of defective castings, and to improve performance characteristics of the finished products manufactured from the cast-ings produced by the apparatus of the invention.
l'he production capacity of the semi-continuous-casting apparatus can be increased 3-to 6-fold per one strand as compared to conventional machines of similar type now in use (depending on the size of the casting being produced and the amount of metal pouredj. Consequently, a higher yield is possible with a fewer number of machines, ~hich afford a substantial reduction in capital investments and operational costs.

Claims (3)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:-

1. Apparatus for semicontinuous casting of metal, comprising: a holding furnace; a molten metal closed supply system having its one end connected to said holding furnace; an air-operated metal supply means having a metal supply duct and con-nected to the other end of said closed metal supply system; a mould with a cooling system mounted on said metal supply means; a device for forcing out a liquid coolant from the mould; a dummy bar mounted in the upper part of said mould, a central head provided in said dummy bar and adapted to accommo-date a heating element and an adjustable valve for admitting an inert gas into the interior of a casting being formed; a casting withdrawal system made up of two casting withdrawal mechanisms alter-nately cooperating with said dummy bar and of which one is used to pull out the casting from the mould for a distance not smaller than the length of the mould and the other one is effective to withdraw the casting from the mould for a distance not smaller than the length of said mould.

2. Apparatus as claimed in claim 1, wherein one of said casting withdrawal mechanisms comprises a movable platform with a lever for cooperation with said dummy bar and a drive, and the other said casting withdrawal mechanism comprises a bar moved in roller guides with toothed racks and a member for connection with said dummy bar, and a drive.

3. Apparatus as claimed in claim 1, wherein a device is provided for broaching and sizing the interior cavity of a casting, said device being made in the form of a broaching and sizing tool located in the lower part of the central head, and a drive which may be the actuator used for driving one of said casting withdrawal mechanisms.