JPH0428467B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an apparatus for producing a casting from an alloy having a casting temperature higher than 1400°C and which is easily oxidized in the molten state, and more particularly, The present invention relates to an apparatus for manufacturing thin or thick cast members having a somewhat complicated shape and used under large thermal stress. The target parts are mainly superalloy parts with an iron content of less than 20%, and heat-resistant alloy or high-alloy steel parts with an iron content of more than 20%. These superalloys are chromium alloys that are nickel-based, cobalt-based, or nickel- or cobalt- and iron-based, such as iron-nickel-chromium, iron-nickel-chromium-cobalt. It is an alloy that

The invention also relates to the casting of parts of low alloy steel and parts of ordinary steel. These steels are also extremely susceptible to oxidation in the molten state.

[Prior Art] Superalloys and high-alloy steels are sometimes used in hot working parts (metallurgical furnaces, machines, turbine rotors, on rails and on roads) in fields such as the metal machinery industry, the aviation industry, and the aerospace industry. used in the manufacture of moving vehicles).

Alloy steel is also called "special steel" or "refined steel."

One known method for manufacturing such members is to prepare an alloy (superalloy, high-alloy special steel, or low-alloy special steel) in an electric melting furnace such as an induction furnace, and then cast it into a mold using gravity. ing.

The main advantages of induction furnaces are that there is no carburizing atmosphere;
Extremely high temperatures can be obtained, which is an advantage for special steels. However, since this furnace stirs the metal, there is a risk of gaseous inclusions being generated. This is disadvantageous for superalloys or high temperature alloys. Additionally, current manufacturing methods sometimes result in a high percentage of cast products being discarded due to defects such as oxidation and voids. Furthermore, gravity filling increases the risk of oxidation and void formation, and also has the disadvantage that the alloy casting efficiency is not very high. By "efficiency" we mean the ratio between the net weight of the cast product and the total weight of the alloy introduced into the mold. This inefficiency is due to the weight of the chute and sprue, which must be separated from the cast product, and the presence of a heavy feeder, which also must be separated. Although this riser is intended to avoid the formation of cavities to the maximum extent possible, it does not always give satisfactory results.

Also, alloys with very high casting temperatures (approximately 1400°C) are highly susceptible to oxidation in the molten state. It is therefore necessary to avoid the formation of pouring alloys and oxidation during pouring. Furthermore, if we are to avoid any solidification during casting of this type of alloy and the formation of cavities in the cast product, we must avoid any agitation that would cause turbulence in the molten metal.

The applicant has already filed the
French Patent Application No. 21 May 1979 and 2 May 1979
No. 7442713 (Publication No. 2295808), No. 7708364 (Publication No. 2384568) and No. 7911067 (Publication No.
2455491) have provided various low pressure mold filling methods. In these methods, the mold is connected to a vertical conduit in order to prevent the formation of cavities when the part to be cast is thick, to improve the efficiency of the cast metal, and to produce products of more or less complex shapes without damage. The metal is supplied from the bottom to the top under pressure by placing the metal in close contact with the spout. However, these methods do not take into consideration the case where alloys that are easily oxidized are cast.

[Problems to be Solved by the Invention] An object of the present invention is to solve the problems of the prior art as described above.

That is, an object of the present invention is to produce and cast an alloy that has a casting temperature higher than 1400°C and is easily oxidized in the molten state, using a closed or nearly closed container, while avoiding oxidation, and under as low pressure as possible. The object of the present invention is to provide an apparatus for producing castings from easily oxidized alloys at high casting speeds.

[Means for Solving the Problems] The apparatus of the present invention produces the above-mentioned alloy in a closed electric furnace equipped with galafite bars, places this metal bath under the pressure of inert gas in the furnace, and molds the metal bath. is placed in close contact with the outlet of the melting furnace, and is fed directly from the melting furnace to the mold under the inert gas compression motrice so as to feed the molten alloy from bottom to top into the mold under low pressure. In this way, the assembly of the melting furnace and the mold is used as a closed container that is placed under inert gas pressure during casting.

The apparatus of the invention is used for producing alloys containing metals selected from chromium, nickel, cobalt and iron as basic constituents.

The present invention provides an apparatus for producing castings from alloys that have casting temperatures higher than 1400° C. and are susceptible to oxidation in the molten state. The device of the present invention includes:
The furnace comprises a melting furnace and a mold which can be combined with each other to form a sealed closed vessel low pressure casting assembly, the furnace having a sealable charging port, a graph for heating the molten alloy in the furnace by radiation. of the tiltable electric furnace type, comprising an inert bar and a conduit for introducing a flow of inert gas into the furnace, said mold being connected to the tap of the furnace through an inlet of the mold in a sealing fit; The channel is connected to the mold and has at least one small-diameter pipe or channel for discharging gas in the mold during casting, and one end of the channel is connected to the inner space of the channel. connected by a tapping trough of annular cross section, the other free end of which communicates with the mold and forms a tap opening, and further includes an annular tap trough for blowing inert gas at least around the tap tap. It is characterized by having a ring.

According to one embodiment of the invention, the furnace is supported by rollers mounted on bearings in the underframe, one of the rollers being driven by a geared electric motor, so that the previous After pouring, the furnace is tilted so that the tapping trough faces upward.

According to another embodiment of the invention, the mold comprises:
By applying thrust with a perforated plate attached to the tip of a piston rod placed on the upper surface of the mold, the piston rod is brought into sealing contact with the outlet of the furnace through the casting spout of the mold.

According to a further embodiment, the mold is placed in a sealed manner under an exhaust bell, on the top of which a suction tube is attached.

Other characteristics and advantages of the invention will become apparent from the following description of non-limiting embodiments based on the accompanying drawings, in which: FIG.

According to the embodiment of FIGS. 1 and 2, the apparatus of the invention essentially consists of a melting furnace 1 and a mold 2, which together form a sealable closed vessel casting assembly. .

More specifically, the melting furnace 1 is an electric furnace and is tilted via an arcuate curved table 3 supported by rollers 4 mounted on bearings 5 of the underframe. One of the rollers 4 is a drive roller and has a geared electric motor (reduction device).
Rotate by 6. The furnace 1 is of the reflection type and heated by radiation from a horizontal graphite bar 7.
The arch of the furnace 1 reflects the radiant heat onto the metal bath. The furnace 1 has a charging opening 8 which can be closed by a removable door or lid 9 and a tap trough 10 with a closed or tubular cross section. One end of the tapping gutter communicates with the internal space of the furnace, the other end is a free end, and a tap spout 11 preferably in the shape of a truncated cone is provided on the upper surface of the gutter.
is formed. This tap 11 is hermetically connected to the pouring port of the mold 2, as will be described later. The tube 12 communicates with the interior space of the furnace 1 and introduces a pressurized inert gas flow above the liquid level N of the metal bath M. This inert gas is preferably argon. On the tube 12,
A pressure regulating device 13 equipped with a measuring plate for measuring the pressure in the furnace space above the metal bath M is mounted. This pressure adjustment requires a pressure drop (mise a′ la de′charge).
Also included. In FIGS. 1 and 2, the adjusting and measuring device is shown in a simplified manner. In this specific example, mold 2 (Fig. 1) is a sand mold made by densely packing sand hardened with a molding binder inside the frame, but it is also possible to use a punched frame sand mold without a frame.
Plastic sand casting masks with fillers in the frame, metal cold molds covered or uncovered with sand, or graphite molds, etc. may be used.

In the embodiment shown, the mold 2 consists of two parts and has a core 14 made of compacted sand, since it is used for the production of hollow rotary bodies. The molding cavity 15 is thus constituted by the annular space between the outer suitable mold 2 and the core 14. A syringe or molten alloy feed channel 16 communicates with the lower part of the molding cavity 15, following the axis X--X of the rotary member. The feed channel 16 communicates with the bottom of the mold 2 via an opening 17, which has the shape of a truncated cone, for example, and which is connected to the outlet 11 of the tap trough 10 of the furnace 1 via a sealing ring 18 of a suitable material. are hermetically joined by a method known to those skilled in the art.

In order to facilitate the discharge of gas by suction during casting and to promote the introduction of the molten alloy M into the cavity 15 of the mold, the cavity is constructed of a pipe or passage with a small diameter, such as a needle hole. It is connected to the upper surface of the mold 2 via a groove 19.

In order to bring the mold 2 into close contact with the spout 11 so as to crush or at least compress the seal ring 18, a jack (not shown) has an axis X-X provided at the tip of the piston rod 21. A perforated plate 20 is pressed against the upper surface of the mold 2 by pressure.

When the mold 2 is brought into contact with the outlet 11 of the tap trough 10 in this way, the trough itself also rests on the support member 22 on the ground.
Being forced by others. This support member 22, also called be'quille in French, has a fixed height in this embodiment, but may also be adjustable in height, for example by means of a screw-nut system and a handle. The mold 2 is placed under an exhaust bell 23, which essentially covers the upper surface of the mold 2 and the perforated plate 20, and is provided with an annular packing 24 at the lower end that abuts against the side surface of the mold 2. . The packing 24 may be annular if the periphery of the mold is circular, or it may be a single lip packing or a skirt having a circular, square, rectangular, etc. shape depending on the outer circumference of the sides of the mold. A pipe 25 is provided at the top of the exhaust bell 23 and extends above the perforated plate 20 and is connected to a vacuum source (not shown). This pipe 25 is a suction pipe and is used to connect the lift 19 with the hole in the plate 20 during casting so that gas can easily flow out of the mold 2. The jack 21 is placed on a mold 2 moving device (not shown).

The invention also uses a blow ring 26 for blowing an inert gas, such as argon, around the tap 11 and also around the charging port 8 of the furnace 1 when the door 9 is open.

[Example] Method for manufacturing a cast product using the apparatus of the present invention In order to explain in more detail the structure, usage, action, and effect of the apparatus of the present invention, a casting method using the apparatus of the present invention will be described.

In the casting method using the apparatus of the present invention, first a part of the alloy composition is made of the most difficult to oxidize component (particularly nickel,
The previously mentioned Increases the melting rate of the alloy.

In this way, the solid charge is essentially melted by immersion in a metal bath previously introduced into the furnace, while the heating of the graphite bars by radiation serves to raise the temperature of said bath. fulfill.

As already mentioned, the applicants have already filed their respective documents in 1974.
French Patent Application No. 7442713 (Publication No. 2295808) of December 24, March 21, 1977 and May 2, 1979;
No. 7708364 (publication number 2384568) and No. 7911067
(Publication No. 2455491), various low pressure molding methods have been provided. In these methods,
The mold is tightly attached to the outlet of the vertical conduit in order to prevent the formation of cavities when the part to be cast is thick, to improve the efficiency of the casting metal, and to produce products with more or less complex shapes without damage. The metal is fed from the bottom to the top under pressure. However, these methods do not take into consideration the case where alloys that are easily oxidized are cast.

In the casting method using the apparatus of the present invention, as a measure to prevent oxidation during mold filling, the driving pressure of the blown active gas in the melting furnace is changed in a plurality of stages as described below during the casting cycle into the mold.

- “low pressure value” or “pre′pression value”
- a preliminary step of introducing the alloy in the vicinity of the tap opening using a pressure value called - a first step of rapidly increasing the pressure from said low pressure value or pre-pressure value to a high pressure value in order to fill the mold with the alloy; - in the mold; a second stage of maintaining said high pressure value finally obtained in the first stage for a significantly longer time than the first stage in order to calm the movement of the molten alloy introduced into the flow; - to completely eliminate the turbulence; In order to prevent this and obtain the boiling water effect,
That is, in order to maintain the alloy at the tap level in a molten state, the pressure is increased more slowly than in the first stage over a longer period of time than in the first stage, and the maximum value is an excess pressure value that is considerably redder than the above-mentioned high pressure value of the first stage. a third stage for the rise of pressure and the generation of a feeder effect in order to obtain - the maximum excess of pressure obtained in the third stage for a considerable time compared to the total time of the casting cycle until only the parts in the mold are fully solidified; a fourth stage of maintaining the inert gas pressure at said maximum overpressure value within a short period of time, in order to at least partially empty the casting channel without emptying the mold in which the alloy is solidifying; The fifth step is to lower the pressure from the pressure to the initial low pressure value or pre-pressure value.

By varying the pressure travel during the casting cycle in this way, turbulence of the alloy in the mold and therefore the inflow of oxidizing gases into the interior or surface of the forming cavity is completely avoided and no cavities are formed. An intact casting is obtained without any hardening (bouchon or carotte,
In other words, no solidified alloy is formed.

In the present invention, such casting measures are taken in addition to the selection of a melting furnace with graphite bars that completely avoids turbulence in the bath during the production of the cast alloy.

An annular rotating member having an axis X--X, for example a rotor of a turbine, is cast in a mold 2 having a molding cavity 15.

As an example, a superalloy (nickel-chromium-cobalt alloy) having the following composition (unit: weight %) is produced in the melting furnace 1. The produced superalloy is placed in metal bath M
used as.

- Chromium...7-15% - Cobalt...5-40% - Titanium and aluminum...7-10.5%, the ratio between titanium and aluminum is 0.6-1.4 - Boron...0.005-0.1% - Carbon...0.05-0.5% - Silicon ...0 to 0.8% - Manganese...0 to 1% - Iron...0 to 10% - Zirconium...0 to 0.2% - The rest, other than impurities, consists of nickel (14 to
75%) This alloy has high fracture strength when pressure is applied at high temperatures, and has a casting temperature of approximately 1600℃.

As another example, a heat-resistant alloy steel for forming parts to be used at temperatures between 500 and 900 degrees Celsius is melted in a melting furnace.
Generate with . The composition of this alloy steel (chromium-nickel-cobalt alloy containing iron) is as follows (wt%).

- Chromium...13-23% - Nickel...13-28% - Cobalt...22-28% - Boron...0.001-0.5% - Tungsten...0-5% - Molybdenum...0-5% - Niobium...0-5% - Tantalum...0 to 5% - Titanium...0 to 5% - Vanadium...0 to 5% - Carbon...0.05 to 0.45% - Manganese...up to 2% - Silicon...up to 1% - Iron and impurities...remaining (less than 50%) ) The casting method using the apparatus of the present invention involves producing this alloy (the superalloy or the heat-resistant alloy steel), casting the alloy using a closed container formed by combining the furnace 1 and the mold 2, and casting the alloy. The aim is to completely avoid oxidation due to the inflow of air into the container and turbulence of the molten alloy during melting and casting. Therefore, in this casting method, a melting furnace 1 equipped with a graphite bar that can be heated by radiation and sealed is used, and the melting furnace 1 is equipped as disclosed in patent application No. 8216427 filed by the applicant on September 28, 1982. The liquid charge and the solid charge are sequentially charged into the furnace 1 using a charging means, that is, a charging means which is deeply inserted into the interior of the furnace 1, and the argon (or nitrogen as the case may be) in the furnace 1 is removed. Adjust the pressure appropriately using the method described below to place the molten alloy M in the mold.
and promptly replace the mold. Further, the blowing annular ring 26 is used to appropriately protect the opening of the furnace 1 and the opening of the mold 2 during charging into the furnace 1, during casting, and when replacing the mold 2.

This casting method is carried out in more detail as follows.

(1) Charging into the melting furnace 1 (Fig. 2) Assuming that some bath remains at the bottom of the furnace 1 after the previous casting, the gutter 10 is tilted upward. As a result, the furnace 1 is tilted so that the alloy M is lowered below the tap 11. In this way, direct contact between the surface of alloy M and air is avoided. In this case, the argon blowing ring 26 is used to close the outlet 11 with an argon film, so that the problem can be more completely avoided. Furthermore, the means disclosed in French patent application no. Electrical heating means on the outside of the gutter -
is used to maintain the casting temperature of alloy M throughout the tapping trough 10 at 1600°C, thus avoiding solidification of the alloy within the tapping trough 10. After opening the door 9 and, if necessary, creating a circular protective layer of argon using the blow ring 26 placed at the entrance of the charging port 8, the above-mentioned French patent application no.
A liquid charge and a solid charge are introduced sequentially by the means described in No. 8216427. This means is simply shown in FIG. 2 as a single charging trough 27 to simplify the drawing.

The free end of the charging trough 27 must be inserted as deep as possible into the cavity of the melting furnace 1 in order to completely avoid contact with the outside air. An argon (or nitrogen) atmosphere is blown into the space above the liquid level N of the bath M in the furnace 1 through the conduit 12.

(a) Charge of Liquid Charge This liquid charge contains components other than the least oxidizable components of the superalloy or alloy steel, namely chromium, titanium, aluminum, manganese and carbon. This liquid charge accounts for 73 to 86% by weight of the total charge in the case of superalloys, and if the capacity of the furnace for multiple casting cycles is, say, 500 kg, then 400% of the total charge of 500 kg is
It will occupy Kg.

In the case of the aforementioned heat-resistant alloy steels, the liquid charge accounts for 70 to 86% by weight of the total charge, for example 350 kg compared to a total charge of 500 kg.

(b) Charge of the solid charge The solid charge accounts for about 14 to 27% by weight of the total charge in the case of the superalloys, and is therefore considerably less than the liquid charge, and is the most susceptible to oxidation. It contains the components chromium, titanium, aluminum, manganese and carbon, and corresponds to, for example, 100 kg if the total charge is 500 kg.

In the case of the above-mentioned heat-resistant alloy steel, the total charge is 14 to
It accounts for 30% by weight, for example 150 kg, and contains the most easily oxidized components, namely chromium, carbon, as well as all or part of tungsten, all or part of manganese, and all or part of silicon. The operation of sequentially charging liquid and solid charges is described in the aforementioned French Patent Application No. 8216427 by the applicant.

It is assumed that the melting furnace 1 was hot from the beginning because some amount of the bath M still remained, and after a certain period of time, all the charged materials become molten. The solid charge dissolved into the liquid charge much faster than by radiant heat from the graft bar 7 alone. Furthermore, heating by the graphite bar 7 prevented stirring of the metal bath M at all during melting. Meanwhile, an atmosphere under a predetermined prepressure was established in the furnace 1 by blowing pressurized argon through the conduit 12, and the alloy was raised to the level of the tap 11.

After the alloy is completely melted and before being poured into the mold 2, the bath M can be deoxidized as follows by utilizing the hermeticity of the melting furnace 1.
Conduit 12 is connected to a suction source to place the interior space of furnace 1 under vacuum or negative pressure. In this way,
The bath M is deoxidized by a chemical reaction between the carbon contained therein and the oxygen in the bath: C+O ₂ →CO ₂ .

The carbon dioxide gas generated is discharged via conduit 12.

(2) Mold arrangement and casting (Figures 1 and 3) After the melting time has elapsed and the entire bath M becomes a liquid with a temperature considerably higher than 1400°C, casting is performed.

The mold 2 is quickly introduced by a moving device carrying a jack 21, and then the perforated plate 2
0 to tightly press the mold 2 onto the tap 11.

If the exhaust bell 23 is not placed in place when the mold 2 is introduced, the exhaust bell 23 is inserted through the packing 24 after the seal ring 18 is inserted between the tapping port 11 and the casting port 17 of the mold. Cover the mold 2 to ensure a tight seal, and open the tap water gutter 10.
While continuing to press the mold 2 onto the spout 11 with pressure until it abuts on the support member 22,
The furnace 1 is tilted on rollers by a geared electric motor 6. The mold is then filled without turbulence by a method known per se but theoretical, taking into account the cooling sequence of the superalloy or refractory metal in order to completely avoid cavities. The casting cycle is carried out as follows. The alloy that is introduced first and is to be cooled first is introduced at the top of the cavity 15, i.e. in the part furthest from the supply pipe or channel 16, and is to be solidified last and therefore maintains the highest temperature for the longest time. The alloy portion in question must occupy the lowest part of the forming cavity 15, i.e. the part closest to the feed channel 16.

The casting temperature is higher than 1400℃, e.g. 1420℃
and the maximum may be, for example, 1650°C. Therefore, in the case of superalloys and heat-resistant alloy steels,
There is a gap between the lowest pouring temperature, which can be 1400°C, and the highest pouring temperature, which can be 1700°C. Exceeding this maximum temperature not only wastes energy but also slows solidification in the mold. In addition, in the supply path 16 of the mold below the minimum temperature, or even around the outlet 11 of the tap trough 10 of the furnace,
There is a risk that it will already solidify.

Therefore, the casting temperature is set to a value within the above-mentioned range.

Casting cycle (Fig. 3) - Preliminary stage OA: Introducing alloy near the tap 11 At the time when the mold 2 is pressed tightly onto the tap 11 of the tap trough 10, argon is introduced through the conduit 12. Therefore, a preload pressure P1, that is, a low pressure, is maintained in the internal space of the furnace 1.
This value P1 is obtained by appropriate adjustment of the pressure regulator 13. When the pressure is set to this value P1, the liquid metal flows to the outlet 1 of the outlet trough 10.
This is because the atmospheric pressure is higher than the pressure P1 inside the furnace 1. This value P1 is, for example, 0.15 bar.

- 1st stage AB: Filling the mold 2 In order to fill the mold, the pressure inside the furnace 1 must be
Change P1 to pressure P2. value P2 is greater than P1,
For example 0.4 bar. The time required for the pressure to rise from the value P1 to the value P2 (t2 - t1), that is, the time between A and B of the line indicating the extension of the casting cycle, is:
This pressure change must be short enough to completely avoid premature solidification in the feed channel 16 and the forming cavity 15, but this pressure change must ensure that the alloy flows laminarly into the forming cavity without turbulence. It must not flow too quickly into the section 15. Of course, the rate of pressure rise will be determined for obvious reasons on the production pitch. The time (t2 - t1) also depends on the amount of alloy to be introduced into the mold 2.

-Second stage BC: Maintaining pressure The metal is sufficiently filled throughout the molding cavity 15, even for a short time, and even at the top, which is farthest from the introduction path 16 and the casting port 17. , the time significantly longer than the time of the first stage (t3
−t2) to maintain high pressure journey P2. horizontal part
Maintaining pressure P2 for the time indicated by BC,
The alloy begins to solidify at least in the upper portion of the molding cavity furthest from the pour port 17. However, the alloy M is still in a molten state at the lowest part closest to the pouring port 17. This liquid state will be maintained in the next step as well.

- Third stage CD: pressure rise and riser effect As in the past, holes or cavities occur in the lowest part, which is still in a molten state when the solidifying top part furthest from the casting spout is supplied, i.e., the part closest to the casting spout. is easily formed. In order to fill these holes or voids, the present invention instead of providing the mold with a reservoir, pocket or riser for replenishing the "hot" molten alloy, the pressure is increased from a high pressure value P2 to a maximum value P3 from time t3 to t4. rise between. This value P3 is 0.7 bar in the specific example, and from t3
The time until t4 is a value determined based on experiments in order to completely avoid turbulence. When such a feeder effect is provided, high-temperature molten metal is supplied to the lower part of the mold under pressure, and as a result, the molten metal is finally fed into the supply furnace 16 from the topmost part farthest from the pouring port 17. While the solidification progresses gradually toward the lowest part, that is, the part closest to the casting opening 17, where it solidifies to the level above the casting opening 17, a perfect filling condition throughout the molding cavity 15 is ensured. It will be done. This is the result to be obtained in the next step.

- 4th stage DE: Maintaining the maximum pressure - Solidification This stage is carried out without reducing the maximum pressure P3, and it takes time (t5 - t4) until the casting is completely solidified.
This will be carried out over the following period. This time depends on the amount of alloy introduced into the mold and the difficulty of completely filling the entire mold.

This solidification must be gradual and slow, particularly from the top to the bottom. That is, it is necessary to proceed downward from the uppermost part of the molding cavity 15, which is the furthest away to be solidified first, to the lowest part, that is, the part closest to the casting port 17, which is to be solidified last.
At time t5, the solidification has progressed to the level of 1/2 of the height of the supply channel 16, that is, below the molding cavity 15. By maintaining the pressure P3 for the above-mentioned period of time in this way, a high-quality member without cavities can be obtained, and then the excess molten metal that is not used in the molding cavity 15 can be quickly lowered. It should be noted here that the more complex the shape of the molding cavity 15 or the greater the number of concave shapes in the molding cavity to manufacture multiple parts at once, the more the time between t4 and t5 increases. The pressure P3 maintenance time becomes longer. That is, this maintenance time (t5−t4)
depends on the difficulty of filling the entire molding cavity and the difficulty of solidifying it completely without cavities within the cavity.

- 5th stage FE: pressure reduction and molten metal fall. When time t5 is reached, the casting is ensured to be completely solidified. At this point, the pressure in the furnace 1 is rapidly lowered to a low pressure value P1, which is the preload pressure. At this time as well, the pressure regulator 13 described above is used. P3
This pressure drop from P1 to P1 may remain in the feed furnace 16, but will of course quickly force downwards all of the molten metal present outside the forming cavity 15, where the metal is in a fully solidified state. In order to return to , it will be carried out in an extremely short period of time from t5 to t6. This rapid pressure drop from P3 to P1 is important in improving the yield of cast metal. This yield is the ratio of the weight of the metal constituting the so-called casting to the total weight of the metal solidified in the mold 2 and thus in the forming cavity 15 and part of the feed channel 16.

At the same time, when the electric motor 6 is operated to tilt the furnace 1 to the position shown in FIG. 2, the tapping trough 10 is tilted downward toward the internal space of the furnace 1, so that the metal bath M can easily be poured into the internal space. The bath liquid level easily falls below the tapping port 11. The mold 2, which is still covered with the exhaust bell 23, is moved upward at time t6 and removed in order to demold the cast product. After time t6,
Another mold 2 covered with an identical exhaust bell 23 must be placed in the position of the previously cast mold. It is advantageous to spray the tap 11 with argon by means of the blow ring 26 during the idle time between the transfer of the finished mold and the introduction of a new mold.

Of course, the seal ring 18 is replaced when a new mold is introduced. In the first stage AB, which fills the mold, and the final stage EF, which empties a portion of the supply path 16, the times t2-t1 and t6-t5 are extremely short, but the pressure rises and drops too rapidly. It must not be so short as to cause
This is to avoid any outflow, discharge or mold splicing from the mold on the tap spout 11 of the tap trough 10 of the furnace. In fact, the tap hole 11 always receives the seal ring 18, which should be placed on the top surface of the tap gutter 10, where molten metal leaks and solidified material adheres, every time the mold is replaced. Must be clean.

[Operations and Effects] From the above explanation, it seems that the method of use and the operations and effects of the device of the present invention have become clear. Here, the structure of the device of the present invention and its functions and effects will be summarized.

A sealed closed vessel casting assembly, formed by the melting furnace and the mold joining together during casting, can avoid oxidation of the alloy caused by air entering the vessel, and prevents oxidation of the alloy during melting and casting. Turbulence of the molten alloy at times can be completely avoided.

By using a tiltable electric furnace with a sealable charging port, direct contact of the surface of the alloy bath M with air can be avoided.

By radiant heating of the molten alloy in the furnace with a graphite bar, stirring and oxidation of the bath M during melting can be completely avoided.

A conduit for introducing an inert gas into the furnace, which can be brought into sealing contact with the outlet of the furnace through the pouring port, and has one end communicating with the interior space of the furnace and the other free end communicating with the mold. and a mold, which may be connected to said furnace by means of a tapping trough of annular cross-section forming a tapping spout, in cooperation with each other under pressure (though of course below atmospheric pressure) from the bottom of the mold to the top. It performs the function of supplying molten metal to the destination, and as a result,
Even when the part to be cast is thick, the formation of cavities is prevented, the efficiency of the casting metal is increased, and products of more or less complex shapes can be produced without damage.

The small diameter ridge provided in the mold facilitates the discharge of gas by suction during casting and facilitates the introduction of molten alloy into the mold cavity.

An annular ring for blowing inert gas at least around the tap opening allows for the opening of the mold and (in some cases) the opening of the furnace, especially when inserting and pouring molten alloy into the mold, and also when changing the mold. Opening can be avoided.

These effects will be comprehensively explained in detail.

(1) Prevention of oxidation of superalloy The following oxidation prevention measures are taken in the apparatus of the present invention.

Preventing the inflow of air, the opening of the furnace 1, sometimes the charging port 8 and the outlet 11 of the mold 2, especially the pouring port 17.
Maintains hermeticity. Therefore, by applying thrust by the plate 20 facing the support member 22 through the seal ring 18, the mold 2
is pressed against the tapping spout 11 in a sealed manner to form a closed container consisting of an assembly of the furnace 1 and the mold 2.

Argon is introduced into the space inside the furnace 1 above the liquid level N of the metal bath, so that the entire space not occupied by molten metal is filled with argon, so that any air that may be present inside, and therefore oxygen, is removed from the exhaust bell 2.
3, perforated plate 20 and lift 19. If necessary, argon may be sprayed by means of a blow ring 26 to inject the inlet of the charging port 8 during charging, and the pouring port 17, especially the tap port 11, during pouring of molten metal into the mold, even when the mold is still in contact with the mold. If not, the above-mentioned preventive measures are reinforced by forming a protective film above the tap hole 11 (FIG. 2).

When the casting alloy is low metal steel, the step of blowing argon into the charging port 8 and the tap port 11 using the blow ring 26 described above may be omitted.

(2) Precautions to avoid turbulence in the alloy and cavities in the molded alloy Since a radiant heat furnace with graphite bar 7 is used, agitation of the bath M in the furnace is completely avoided.

Since the pressure is varied during the casting cycle, especially during stage AB when filling the mold, it is possible to fill the mold in a laminar flow without turbulence.

The device according to the invention has these advantages as its characteristic, so that even in a slow melting furnace it is possible to obtain components of good quality as quickly and economically as possible, and which are therefore extremely susceptible to oxidation in the molten state.
Problems due to the composition of the alloy with a casting temperature higher than 1400°C and problems due to the somewhat complex shape of the forming cavity 15 with a thin or, conversely, thick thread thickness, e.g. up to 2 mm, i.e. pressing. Problems requiring the hot water effect are solved.

[Brief explanation of drawings]

FIG. 1 is a simplified cross-sectional view showing the combined melting furnace and mold of the present invention, FIG. 2 is a cross-sectional view similar to FIG. 1 showing the melting furnace during charging of one component of the molten alloy, and FIG. The figure is a graph showing the change in the inert gas pressure P in the melting furnace as a function of time t during the casting cycle. 1...Melting furnace, 2...Mold, 4...Roller, 6
...Electric motor with gears, 7...Graphite bar, 8
...charging inlet, 10...outlet gutter, 11...outlet,
12... Conduit, 17... Casting port, 19... Lifting, 20... Perforated plate, 21... Piston rod, 25... Suction pipe, 26... Blow ring.

Claims (1)

[Scope of Claims] 1. Apparatus for producing castings from alloys susceptible to oxidation in the molten state with a casting temperature higher than 1400°C, which can be joined together to form a hermetically closed vessel-like low-pressure casting assembly. The furnace consists of a melting furnace and a mold, the furnace having a sealable charging port, a graphite bar for heating the molten alloy in the furnace by radiation, and introducing an inert gas flow into the furnace. The mold is of a tiltable electric furnace type and is equipped with a conduit for the purpose of discharging the gas in the mold during casting. said furnace and said mold have one end communicating with the interior space of the furnace and the other free end communicating with the mold. An apparatus characterized in that the apparatus is connected by a tapping trough with an annular cross section forming a tap opening, and further comprising an annular ring for blowing inert gas at least around the tap opening. 2. The furnace is supported by rollers mounted on bearings in the underframe, one of the rollers being driven by a geared electric motor, so that the furnace is tilted after the previous casting. 2. A device according to claim 1, characterized in that the tapping trough is oriented in the upward direction. 3. The mold is brought into sealing contact with the outlet of the furnace through the casting opening of the mold by applying thrust with a perforated plate attached to the tip of a piston rod placed on the upper surface of the mold. An apparatus according to claim 1 or 2, characterized in that: 4. The mold according to any one of claims 1 to 3, characterized in that the mold is disposed in a sealed manner under an exhaust bell to which a suction pipe is attached to the upper part of the mold. Device.