CN201201039Y - Casting device for large hollow steel ingot with low segregation - Google Patents

Abstract

The utility model relates to the casting technology of a large hollow steel ingot, in particular to a casting device for a large hollow steel ingot with low segregation. It is suitable for the manufacturing process of large hollow steel ingots of various materials, models and specifications below 250 tons. The casting device is equipped with a lower chassis, an upper chassis, a steel ingot mold, and an inner core body. The upper chassis is placed on the lower chassis. The core body, the inner core body is a concentric cylinder formed by nesting the outer steel plate and the inner steel plate, there is a gap between the outer steel plate and the inner steel plate, and the cavity between the ingot mold and the inner core body forms a hollow steel ingot. The utility model solves the problems that the core is not easy to take out and the inner core body is deformed in the manufacturing process of the large hollow steel ingot, and at the same time alleviates the problem of segregation of the large hollow steel ingot.

Description

Casting device for large hollow steel ingot with low segregation

technical field

The utility model relates to the casting technology of a large hollow steel ingot, in particular to a casting device for a large hollow steel ingot with low segregation. It is suitable for the manufacturing process of large hollow steel ingots of various materials, models and specifications below 250 tons.

Background technique

The amount of hollow forgings such as large-scale hydrogenation reactors, nuclear power main pipelines, and pipe molds is increasing. In particular, the demand for large hollow forgings used in the chemical and energy industries has doubled in recent years, and the use of hollow steel ingots to forge large hollow forgings can achieve twice the result with half the effort, so the demand for large hollow steel ingots continues unabated. The manufacturing level of large hollow steel ingots in my country is not high, and the output is still very limited. The market for large hollow steel ingots is in short supply.

In the world, companies manufacturing super-large hollow steel ingots mainly include French Crusoe Company and Japanese Kawasaki Company. Crusoe Company has successfully poured 200 tons of hollow steel ingots. The hollow steel ingots produced are mainly used to produce hydrogenation reactors, while Kawasaki Company has successfully poured 200 tons of hollow steel ingots. The company has successfully poured 250 tons of hollow steel ingots, which are mainly used to produce forgings such as large pipe molds.

The difficulty in manufacturing large hollow steel ingots mainly lies in the control of the segregation position and segregation degree of the steel ingot. Segregation problems exist in large steel ingots, and all segregation makes the structure and composition of steel ingots uneven. Some micro-segregation can be eliminated in the forging process, and some may be alleviated, while the macro-segregation cannot be eliminated in the forging process, which seriously affects the quality of forgings. One of the main causes of segregation is the long solidification time of the steel ingot and the enrichment of low melting point substances. At the same time, the segregation of impurity elements also aggravates the segregation of the main elements, which increases the degree of segregation of the steel ingot. Since the hollow steel ingot adopts the method of simultaneous cooling of the steel ingot mold and the core, the degree of segregation of the steel ingot is small, but the control of the position of segregation still needs to be studied.

Some enterprises use solid steel ingots to forge hollow forgings. The A-type segregation zone of solid steel ingots is not easy to remove when forging hollow forgings. The segregation zone is just on the inner surface of the hollow forgings, and the main working surface of large hollow forgings is often the inner surface. This affects the use of forgings. Some hollow forgings require stainless steel surfacing welding on the inner surface. Due to the serious segregation of impurity elements or carbon elements on the inner surface of the forging, it brings great difficulties to the welding process. If the impurity elements are too high, even if the stainless steel surfacing process is completed, the surfacing layer will easily peel off during use, which will affect the service life of the components. Using hollow steel ingots to forge hollow parts can ensure that the inner surface of the forging does not appear segregation phenomenon, reduce welding difficulty and improve the service life of parts.

For some large key hollow forgings, the design company requires that they must be forged with hollow steel ingots. And it is required that the segregation of the hollow steel ingot must be far away from the inner surface of the steel ingot, especially during the forging process of a super-large steel ingot, the segregation zone moves to the inner surface as the forging progresses, if the segregation zone of the steel ingot is not far enough from the inner surface, during the forging process , the surface will still be exposed. Therefore, controlling the segregation position of steel ingot is another key to the production of hollow steel ingot.

In this case, the utility model adopts computer simulation technology, first predicts the possible location of segregation, and then uses large air volume cooling technology, steel structure nested core hole forming technology, metal liquid early covering technology, gas protection injection technology The segregation position and degree of segregation have been effectively controlled, and the new hollow steel ingot preparation technology has made it possible to manufacture large hollow steel ingots with low segregation.

Utility model content

The purpose of this utility model is to provide a casting device for large hollow steel ingot with low segregation, so that the core is not easy to take out and the deformation of the inner core body is solved during the manufacturing process of large hollow steel ingot, and at the same time the problem of segregation of large hollow steel ingot is alleviated, so that the hollow The segregation position of steel ingot has been controlled.

The technical scheme of the utility model is:

A casting device for large hollow steel ingots with low segregation. The casting device is equipped with a lower chassis, an upper chassis, a steel ingot mold, and an inner core body. The upper chassis is placed on the lower chassis. The inner core body of the hollow steel ingot is formed by nesting two layers of steel plates. The inner core body is a concentric cylinder formed by nesting the outer steel plate and the inner steel plate. There is a gap between the outer steel plate and the inner steel plate. The ingot mold and the inner The cavity between the cores forms a hollow ingot.

In the casting device for large hollow steel ingots with low segregation, the inside of the inner steel plate communicates with the gas inlet pipe, and the gap between the outer steel plate and the inner steel plate communicates with the inner side of the inner steel plate.

In the casting device for large hollow steel ingots with low segregation, the outer steel plate of the inner core body is 5-25 mm thick, the inner steel plate is 5-25 mm thick, the gap between the steel plates is 5-60 mm, the steel plates are supported by steel pipes, and the steel pipes are 4-25 mm thick. 60 pieces, the diameter of the steel pipe is 5-50mm.

In the casting device for a large hollow steel ingot with low segregation, the covering agent placed in a packaging bag is suspended in the cavity between the steel ingot mold and the inner core body.

In the casting device of the low-segregation large-scale hollow steel ingot, the covering agent is divided into 4 to 6 bags and suspended evenly in the steel ingot mold. The covering agent is suspended in two layers, the first layer is close to the bottom surface, and the second layer is close to the Mouth, the covering agent is 300-500mm high from the bottom surface of the cavity.

The casting device for large hollow steel ingots with low segregation is also provided with a gating system. The gating system is composed of a sprue cup, a sprue, a runner, and an inner runner. The lower chassis is provided with a runner, and the upper chassis is provided with a horizontal The sprue is connected to the sprue, and the sprue cup is connected to the runner through the sprue.

In the casting device for large hollow steel ingots with low segregation, an argon gas inlet pipe is arranged on the top of the sprue cup, and the argon gas inlet pipe is an annular gas protection cover. Air holes are opened inside the gas protection cover, and the outside is connected to the gas source through the intake pipe.

In the casting device for a large hollow steel ingot with low segregation, a thermal insulation board is placed around the riser at the top of the cavity between the steel ingot mold and the inner core body.

The manufacturing method of the utility model low-segregation large-scale hollow steel ingot mainly refers to that in the preparation process of the low-segregation large-scale hollow steel ingot, the steel structure nested core hole-forming technology, large air volume cooling technology, metal liquid early covering technology and gas protection injection flow are adopted. Technology controls the location and degree of segregation.

1. Steel structure nested core hole forming technology

(1) Technical features: Two layers of steel plates are mainly used to nest each other to form the inner core body of a hollow steel ingot. During the pouring and solidification process of the steel ingot, the inner core body is in the center of the steel ingot to form the central hole of the steel ingot.

(2) Structural features: the inner core body is composed of inner and outer steel plate cylinders, the inner and outer steel plate cylinders are two concentric cylinders of different sizes, the inner steel plate is embedded in the outer steel plate, and there is a certain gap between the steel plates , The gap between the steel plates is 5-60m, and the steel plates are supported by steel pipes. The inner and outer steel plates are welded together with steel pipes to form a cylindrical inner core. Among them, the outer steel plate is 5-25mm thick, the inner steel plate is 5-25mm thick, and there are 4-60 supporting steel pipes with a diameter of 5-50mm. The upper end of the inner steel plate cylinder is sealed with a steel plate, and an air hole is opened on the upper end, and the compressed air enters through the air hole on the upper end, and is discharged from the bottom through the inner and outer steel plates, forming an open circuit.

(3) Main function: During the pouring process, the steel plate on the outer layer of the inner core is in contact with the molten metal, which acts as a chill and resists the thermal shock of the molten steel. Compressed air passes through the middle of the inner steel plate, and the compressed air cools the outer steel plate through the gap between the inner and outer steel plates, reduces the temperature of the outer steel plate, and maintains the strength and rigidity of the outer steel plate. The inner steel plate plays the role of conveying compressed air and supporting, and the steel pipe mainly plays the role of supporting.

(4) How to use: After the inner core is manufactured, it is assembled with the steel ingot mold, upper chassis and lower chassis to form a hollow steel ingot cavity. The inner core is fixed on the upper chassis, and the steel ingot mold is set on the outside of the inner core, and the two are kept concentric. During pouring, molten steel solidifies between the inner core and the ingot mold to form a hollow ingot.

2. Large air volume cooling technology

(1) Technical features: During the pouring process of the steel ingot, the hollow steel ingot is cooled by compressed air through the inner core body. During the cooling process, a large amount of compressed air passes through the inner core body, and the heat is taken away from the steel ingot. By controlling the pressure and strength of the compressed air, the cooling capacity is adjusted to control the solidification process of the steel ingot.

(2) Main function: The large air volume can make the gas circuit of the entire inner core body have a greater pressure, so that the gas has a strong contact with the inner surface of the outer layer steel plate of the inner core, increase the heat exchange intensity, and increase the cooling effect of the gas. In addition, a large amount of gas flows through the inner core body, which ensures that the temperature of the gas in the inner core body will not rise too high, and also effectively increases the cooling capacity of the gas.

(3) How to use: During the pouring process, after the pouring is completed, the compressed air is introduced; the pressure of the compressed air is 0.2-0.8MPa, the gas intake is 50-400m ³ /min, and the ventilation time is 2-8h. In the process of feeding compressed air, the temperature of the outer steel plate of the inner core can be tracked. If the temperature of the outer steel plate is found to be too low, the air volume can be reduced, and if the temperature rises, the air volume can be increased.

3. Early metal liquid covering technology

(1) Technical features: The early covering technology of molten metal is to place the covering agent at a predetermined position. When the molten metal enters the cavity, the surface of the molten metal will be evenly covered with the covering agent at the first time to protect and purify the molten steel. effect.

(2) Main function: evenly suspend the covering agent in the cavity of the hollow steel ingot. When the molten steel enters the cavity, the covering agent will automatically fall when heated and cover the surface of the molten metal to protect the molten metal. While the covering agent protects the molten steel from oxidation, it also has a purification effect on the molten steel. The inclusions in the molten steel float up, combine with the mold slag in the covering agent, and enter the mold slag, so that the purity of the molten steel is improved.

(3) How to use: The covering agent can be suspended in two layers, the first layer is close to the bottom surface, and the second layer is close to the riser. When the molten metal enters the cavity, the first layer of covering agent is the first choice to play a protective role; when When the molten metal continues to rise, the surface covering agent moves downward along with the molten metal along the inner wall of the ingot mould, and the surface covering agent is gradually consumed. At this time, the heat of the molten steel causes the upper layer of covering agent to fall to continue to protect the molten steel from oxidation.

4. Gas protection injection technology

(1) Technical features: The high-temperature molten metal is in contact with the air in a large area during the pouring process, which is prone to secondary oxidation. The gas protection technology uses inert gas to separate the molten metal flow from the air, reducing the contact between the molten metal and the air, thereby controlling the oxidation of the molten metal.

(2) Main function: The gas protection cover is an annular cover with multiple air outlets on the inside and connected to the intake pipe on the outside. The use of the gas protection cover can make the inert gas more concentrated around the molten metal flow, reducing the impact of air flow on the protection Effect of gas. After the metal liquid flow is covered by a protective cover, an inert gas is introduced into the protective cover, and the inert gas forms a gas layer, and the metal liquid flow is wrapped in it, thereby preventing oxidation of the metal liquid.

(3) How to use: Before pouring, put the gas shield on the sprue cup so that the gas shield is concentric with the gate of the ladle. After the pouring starts, the inert gas is introduced into the gas shield through the inlet pipe, and the inert gas is evenly discharged through the gas outlet holes, forming a gas protective layer around the metal liquid flow.

In the utility model, the hollow steel ingot refers to a large hollow steel ingot of 30 to 250 tons.

The utility model has the following beneficial effects:

1. This utility model is suitable for the manufacturing process of large hollow steel ingots of various grades, models and types below 250 tons, and this technology can be used for the development of large hollow steel ingots.

2. The utility model adopts large air volume cooling technology and steel structure nested core forming technology, which makes it difficult to take out the core and the deformation of the inner core during the manufacture of large hollow steel ingots, and at the same time alleviates the problem of segregation of large hollow steel ingots , so that the segregation position of the hollow steel ingot is controlled, the operability of the casting process is guaranteed, the segregation position of the steel ingot is controlled, the shrinkage cavity and loose defects are reduced, and the utilization rate of the hollow steel ingot is improved.

3. The utility model adopts the early metal liquid covering technology and the gas protection injection technology, so that the large hollow steel ingot can be filled smoothly during the pouring process, the secondary oxidation inclusion is reduced, the purity of the steel ingot is improved, and the The application range of hollow steel ingots makes it possible for hollow steel ingots to be produced in more enterprises.

Description of drawings:

Fig. 1 is a schematic diagram of a casting device for a large hollow steel ingot with low segregation;

Among them: 1—lower chassis; 2—upper chassis; 3—steel ingot mold; 4—covering agent; 5—outer steel plate; 6—inner steel plate; 7—insulation board; 8—gas inlet pipe; 9—metal liquid ; 10—argon gas into the pipeline; 11—sprue cup; 12—sprue; 13—runner; 14—inner sprue.

Fig. 2 Simulation results of temperature field during solidification;

Fig. 3 simulation results of shrinkage cavity distribution;

Fig. 4 adopts the blank prepared by the method of the utility model.

Detailed ways

Describe the utility model in detail below in conjunction with accompanying drawing and embodiment.

As shown in Figure 1, the casting device of the present invention includes a lower chassis 1, an upper chassis 2, an ingot mold 3, a covering agent 4, an outer steel plate 5, an inner steel plate 6, a heat preservation plate 7, a gas inlet pipe 8, a metal Liquid 9, argon gas inlet pipe 10, sprue cup 11, sprue 12, runner 13, ingate 14, upper chassis 2 is placed on lower chassis 1, top of upper chassis 2: steel ingot mold is set on the outer ring 3. The inner ring is provided with a hollow steel ingot inner core body formed by nesting two layers of steel plates. The inner core body is a concentric cylinder formed by nesting outer steel plates 5 and inner steel plates 6. The outer steel plates 5 and the inner steel plates 6 There is a gap between them, the cavity between the steel ingot mold 3 and the inner core body forms a hollow steel ingot, and the insulation board 7 is placed around the riser at the top of the cavity between the steel ingot mold 3 and the inner core body. The gating system is composed of sprue cup 11, sprue 12, runner 13, and ingate 14. The lower chassis 1 is provided with a runner 13, and the upper chassis 2 is provided with an ingate 14 communicating with the runner 13. The sprue 11 is connected to the runner 13 through the sprue 12, and the top of the sprue 11 is provided with an argon gas inlet pipe 10, and the molten metal 9 passes through the sprue cup 11, the sprue 12, the runner 13, and the inflow Road 14 enters the mold cavity for filling.

The outer steel plate of the inner core body is 5-25mm thick, the inner steel plate is 5-25mm thick, the gap between the steel plates is 5-60mm, and the steel plates are supported by steel pipes. There are 4-60 steel pipes with a diameter of 5-50mm.

The inner side of the inner steel plate 6 communicates with the gas inlet pipe 8, the compressed air enters the inner steel plate 6 through the gas inlet pipe 8, and the inner core body is air-cooled by compressed air, and the compressed air enters from the inner steel plate 6 in the middle of the inner core body , The upper end of the inner steel plate cylinder is sealed with a steel plate, the upper end of the steel plate is ventilated, the compressed air enters through the vent hole on the upper end, and is discharged from the bottom between the inner and outer steel plates, forming an open circuit. Compressed air is ejected from between the outer steel plate 5 and the inner steel plate 6 to cool the outer layer of the core. The pressure of the compressed air is 0.2~0.8MPa, the gas flow rate is 50~400m ³ /min, and the ventilation time is 2~8h.

The covering agent 4 placed in the packaging bag is suspended in the cavity between the ingot mold 3 and the inner core body. Before the molten metal is poured, the covering agent 4 is suspended in the ingot mold 3. During the rising process of the molten metal, the metal The heat of the liquid melts the packaging bag of the covering agent, so that the covering agent can be evenly sprinkled on the surface of the molten metal as early as possible to ensure that the surface of the molten metal is not oxidized. The covering agent is divided into 4-6 bags, and evenly suspended in the ingot mold. The covering agent is suspended in two layers. The first layer is close to the bottom surface, and the second layer is close to the riser. The covering agent is 300-500mm high from the bottom of the cavity. .

The top of the sprue cup 11 is provided with an argon gas inlet pipe 10, which is an annular gas shield with air holes on the inside and connected to the gas source through the inlet pipe on the outside. During the pouring process, the molten metal flow flows through the center of the ring sleeve of the annular gas protection cover, the argon gas enters from the outer inlet of the ring sleeve, and is blown out from multiple outlets on the inner side, forming a gas protective layer around the molten steel flow. It achieves the effect of protecting the metal liquid flow and preventing oxidation.

Example 1

As shown in Figure 1, the weight of poured molten metal is 40 tons, the pouring speed is 5 tons per minute, and the material is No. 25 steel.

The implementation of the utility model is as follows: the process design is carried out by adopting the gas protection technology of the metal liquid surface, the design technology of the smooth filling pouring system, and the advanced computer simulation technology. technology, metal liquid early covering technology, gas protection injection technology, etc.

The advanced computer simulation technology ensures the rationality of the process design. The steel structure nested core hole forming technology and the large air volume cooling technology are used to complete the sequential solidification of the steel ingot and control the segregation position.

In this embodiment, the outer steel plate is 15 mm thick, the inner steel plate is 5 mm thick, the gap between the two steel plates is 15 mm, and the steel plates are supported by steel pipes. 15mm.

In this embodiment, the pressure of the compressed air is 0.3 MPa, the gas flow rate is 100 m ³ /min, and the ventilation time is 8 hours.

The first pouring was successful, the molten steel rose steadily, and there was no entrainment phenomenon. After blowing compressed air for 8 hours, the blank prepared by the method of the utility model is used to forge the large hollow steel ingot into a pipe die forging.

As shown in Figure 2, during the solidification process, the simulation results of the temperature field show that the solidification time of the hollow steel ingot is 4.5 hours, the complete solidification time of the steel ingot is 6 hours, the temperature distribution of the hollow steel ingot is uniform, and the sequential solidification of the steel ingot is beneficial to the metal of the steel ingot. Liquid does not shrink.

As shown in Figure 3, the simulation results of shrinkage cavity distribution show that the shrinkage cavity and porosity of the steel ingot are mainly concentrated in the riser, the size of the riser and the selected insulation material meet the requirements, and the porosity of the steel ingot is mainly distributed in the middle part of the riser of the steel ingot. It is consistent with the hollow steel ingot blank (Fig. 4), indicating that the defect location of the steel ingot is well controlled.

In the present utility model, "stable filling pouring system design technology" can refer to the Chinese invention patent application (publication number: CN1552542A), which mentions a non-air gap stable filling pouring design method and the pouring system used.

In the utility model, a steel ingot mold and a pouring system are rationally designed by means of computer simulation. "Computer simulation technology" can be found in: a method for simulating the filling process of castings mentioned in the Chinese invention patent application (publication number: CN 1388444A). And, a visual casting method mentioned in the Chinese invention patent application (publication number: CN 1631579A). And, a kind of integral casting method of cast steel support roll mentioned in Chinese invention patent application (publication number: CN1597180A).

Example 2

As shown in Figure 1, the weight of poured molten metal is 43 tons, the pouring speed is 7 tons per minute, and the material is No. 25 steel.

The implementation of the utility model is as follows: the process design is still carried out by adopting the metal liquid surface gas protection technology, the design technology of the smooth filling pouring system, and the advanced computer simulation technology, mainly adopting the large air volume cooling technology, the steel structure nested core Pore forming technology, early metal liquid covering technology, gas protection injection technology, etc.

In this embodiment, the outer steel plate is 25 mm thick, the inner steel plate is 25 mm thick, the gap between the two steel plates is 60 mm, and the steel plates are supported by steel pipes. 50mm.

In this embodiment, the pressure of the compressed air is 0.8MPa, the gas flow rate is 400m ³ /min, and the ventilation time is 5h.

The second pouring was successful, and the pouring was completed within the stipulated time. The large-scale hollow steel ingots produced were forged into pipe die forgings according to the requirements. No defects beyond the standard were found in the forgings after flaw detection, which met the flaw detection standards.

Example 3

As shown in Figure 1, the weight of poured molten metal is 45 tons, the pouring speed is 6 tons per minute, and the material is No. 25 steel.

The implementation of the utility model is as follows: the process design is still carried out by using the metal liquid surface gas protection technology, the design technology of the smooth filling pouring system, and the advanced computer simulation technology, and mainly adopts the technology of forming holes with steel structure nested cores, large temperature difference Cooling technology, narrow gap molding sand technology, pouring dispersed gate drainage technology, thick and large chassis forced cooling technology, etc.

In this embodiment, the outer steel plate is 20 mm thick, the inner steel plate is 10 mm thick, the gap between the two steel plates is 30 mm, and the steel plates are supported by steel pipes. 30mm.

In this embodiment, the pressure of the compressed air is 0.5 MPa, the gas flow rate is 200 m ³ /min, and the ventilation time is 6 hours.

The third pouring was successful, and the entire pouring task was completed within the specified time. The produced large hollow steel ingots were forged into hollow steel ingots, and no defects exceeding the standard were found after flaw detection, which met the flaw detection standards. It shows that the riser feeding capacity of the steel ingot has met the design requirements, and there are no large shrinkage cavities and porosity defects.

The utility model work process and result:

Utilizing the utility model in the casting process of the large hollow steel ingot, the large air volume cooling technology and the steel structure nested core hole forming technology are adopted to effectively control the segregation, so that the segregation zone of the steel ingot is in the middle position. Utilizing early metal liquid covering technology, gas protection injection technology, thick and large chassis forced cooling technology, etc., the pouring of large hollow steel ingots is completed, which ensures the solidification of steel ingots, reduces oxidation inclusions, and makes the performance, composition and structure of steel ingots reach the highest level. design requirements. The flaw detection results prove that the large hollow steel ingot has no defects such as excessive inclusions. The forgings forged from hollow steel ingots have reached the national standard, and the forgings have been found to have good performance after use.

comparative example

Traditional hollow steel ingot casting process: the sprue is made of steel pipe bricks with the same upper and lower diameters, and a right-angle transition is adopted at the junction of the sprue and the runner, and there are two runners with the same diameter. The unreasonable core design is not conducive to heat transfer, resulting in insufficient cooling strength of compressed air, and obvious segregation bands appear.

The disadvantages of this design are: (1) The gating system cannot be filled, and there is a large space for the molten metal to flow in the runner, which is easy to cause air entrainment and inclusions. The pouring flow protection technology is not strictly adopted, so that the inclusions of the steel ingot exceed the standard and cannot be processed. Forging of high precision forgings. (2) The cooling strength of the inner core is not enough, and the segregation of the steel ingot is obvious. The segregation appears on the inner subsurface of the steel ingot, and the segregation band appears on the inner surface of the forging after forging, which affects the use of the steel ingot. (3) The cooling strength of the inner core of the steel ingot is not enough, the temperature of the inner core rises, the strength decreases, the outer steel plate of the inner core is seriously deformed, and the inner core is not taken out smoothly.

Claims (8)

1. A casting device for a large hollow steel ingot with low segregation, characterized in that: the casting device is provided with a lower chassis (1), an upper chassis (2), a steel ingot mold (3), an inner core body, and the upper chassis (2) is placed On the lower chassis (1), on the top of the upper chassis (2): the outer ring is provided with a steel ingot mold (3), and the inner ring is provided with a hollow steel ingot inner core formed by nesting two layers of steel plates. The inner core is an outer steel plate (5 ), the inner steel plate (6) is a concentric cylinder formed by nesting each other, there is a gap between the outer steel plate (5) and the inner steel plate (6), and the cavity between the ingot mold (3) and the inner core body is formed Hollow ingot. 2. The casting device for large hollow steel ingots with low segregation according to claim 1, characterized in that: the inside of the inner steel plate (6) communicates with the gas inlet pipe (8), and the outer steel plate (5) and the inner steel plate ( 6) The gap between them communicates with the inner side of the inner layer steel plate (6). 3. The casting device for large hollow steel ingot with low segregation according to claim 1, characterized in that: the outer steel plate of the inner core body is 5-25 mm thick, the inner steel plate is 5-25 mm thick, and the gap between the steel plates is 5-60 mm. The steel plates are supported by steel pipes, there are 4 to 60 steel pipes, and the diameter of the steel pipes is 5 to 50mm. 4. The casting device for large hollow steel ingot with low segregation according to claim 1, characterized in that the covering agent placed in the packaging bag is suspended in the cavity between the ingot mold and the inner core body. 5. The casting device for large hollow steel ingot with low segregation according to claim 4, characterized in that the covering agent is divided into 4 to 6 bags and evenly suspended in the steel ingot mold, the covering agent is suspended in two layers, the first layer is close to On the lower bottom surface, the second layer is close to the riser, and the covering agent is 300-500mm high from the bottom surface of the cavity. 6. The casting device for large hollow steel ingots with low segregation according to claim 1, characterized in that: a pouring system is also provided, and the pouring system consists of sprue cup (11), sprue (12), runner (13 ), an inrunner (14), the lower chassis (1) is provided with a runner (13), the upper chassis (2) is provided with an inrunner (14) communicating with the runner (13), and the sprue cup (11 ) is connected to the runner (13) through the sprue (12). 7. The casting device for large hollow steel ingot with low segregation according to claim 6, characterized in that an argon gas inlet pipe (10) is arranged on the top of the sprue cup (11), and the argon gas inlet pipe (10) is an annular gas In the protective cover, air holes are opened on the inner side of the gas protective cover, and the outer side is connected with the gas source through the intake pipe. 8. The casting device for large hollow steel ingot with low segregation according to claim 1, characterized in that: a thermal insulation board is placed around the riser at the top of the cavity between the steel ingot mold and the inner core body.

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