A casting method for a hundred-ton spent fuel container

Abstract

The invention discloses a casting forming method for a hundred-ton spent fuel container. Molten iron is simultaneously poured into a mold through a double-package double-pouring system. The pouring time is 90 - 120 s, it solidifies 2 h after pouring, and the spent fuel storage and transportation integrated metal container is obtained by opening the box 12 - 24 h later. The mold includes a metal mold fixed on a sand box and an internal furan resin sand core arranged inside the metal mold. A top furan resin sand core is arranged at the top of the metal mold, a graphite chill is arranged inside the top furan resin sand core, and an iron plate is arranged outside. Iron plate exhaust holes are evenly distributed on the iron plate. The invention can make the pressure of the molten iron in the cavity greater and obtain a ductile iron casting with a denser structure.

Description

Technical Field

[0001] The invention relates to a casting method for a hundred-ton spent fuel container, belonging to the field of casting. Background Art

[0002] The integrated metal container for spent fuel storage and transportation is a container specially used for the management, storage and transportation of spent fuel assemblies. It is required to be integrally cast, with a gross weight of 130t, a liquid iron volume of 160t, and a wall thickness of 500mm. It needs to pass the verification of four transportation accident conditions, including penetration test, drop test, high temperature burning resistance test and water immersion test. The various performance indicators are strictly required. Therefore, the production of integrated ductile iron containers for spent fuel storage and transportation requires the solution of the problems of spheroidization inoculation and anti-decay of thick and large-section ductile iron to maintain good performance requirements of castings.

[0003] The publication number is CN110014123B. It is a casting method for a 100-ton-class metal container for storage and transportation of spent fuel, specifically a molding process method and an iron sand combination mold for the 100-ton-class metal container for storage and transportation of spent fuel, especially a casting method and an iron sand combination mold for the 100-ton-class metal container for storage and transportation of spent fuel. The iron mold is cast with ductile iron, the outer mold is composed of multiple parts and a cover mold, the large clay core is a sand skeleton plus a chill, the chill is embedded in the molding sand, the bottom molding sand is furan resin sand, after the molding is completed, it is micro-vibrated and compacted, and then poured. This process has formulated special process parameters and process methods, using a pouring system and a filtration system to separate the primary oxidation slag in the molten iron, and reduce the chemical reaction of the molten iron with the air and the mold, reduce the secondary oxidation slag, so that the graphitization expansion of the casting during the solidification process fully offsets the liquid shrinkage and solidification shrinkage, and eliminates shrinkage cavities and shrinkage. However, it only relies on the large clay core as the sand skeleton and the cold iron structure for rapid cooling, and the solidification time is still relatively long, which is easy to form spheroidization decay, which is not conducive to the maintenance of graphite morphology; at the same time, the existence of the gas vent makes the rigidity of the casting insufficient, and during the solidification process, the graphite expands, which is not conducive to the formation of a dense casting structure. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a casting method for a 100-ton spent fuel container, so that the molten iron solidifies in 2 hours, solving the problem of graphite decay during the solidification of the ductile iron container, and at the same time making the prepared integrated metal container for spent fuel storage and transportation have uniform structure and good density, meeting the standards of flaw detection and mechanical properties.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0006] A casting method for a 100-ton spent fuel container, wherein molten iron is simultaneously poured into a mold through a double-bag double-pouring system, the pouring time is 90 to 120 seconds, solidifies 2 hours after pouring, and is unpacked 12 to 24 hours to obtain an integrated metal container for spent fuel storage and transportation;

[0007] The mold includes a metal mold fixed on a sand box and an internal furan resin sand core disposed inside the metal mold. A top furan resin sand core is provided at the top of the metal mold, and a graphite chill is disposed inside the top furan resin sand core and an iron plate is disposed outside. Iron plate exhaust holes are evenly distributed on the iron plate.

[0008] A further improvement of the technical solution of the present invention is that: a graphite chill is disposed on the outer surface of the internal furan resin sand core.

[0009] A further improvement of the technical solution of the present invention is that: the graphite chill is processed from high thermal conductivity carbon bricks, and a graphite chill gap of 30-50 mm is reserved between adjacent graphite chills, and the inside is filled with furan resin sand.

[0010] A further improvement of the technical solution of the present invention is that: a circulating water pipe is laid inside the internal furan resin sand core.

[0011] A further improvement of the technical solution of the present invention is that: after the molten iron pouring is completed, cooling water at 15-30 °C is introduced into the circulating water pipe, the water passing time is 12-24 h, and the water passing volume is 5-10 t / h.

[0012] A further improvement of the technical solution of the present invention is that: a seating weight is provided at the top of the iron plate during the molten iron pouring, and the weight of the seating weight is 2-3 times that of the poured molten iron, and the thickness of the iron plate is 100-200 mm.

[0013] A further improvement of the technical solution of the present invention is that: the material of the metal mold is ductile iron, and the thickness is 200-300 mm.

[0014] A further improvement of the technical solution of the present invention is that: the double-package double-pouring system includes two sets of pouring cups and a runner connecting the pouring cups and passing through the sand box until it is connected to the mold cavity opening.

[0015] A further improvement of the technical solution of the present invention is that: the spent fuel storage and transportation integrated metal container obtained by this method has uniform structure, good compactness and high strength.

[0016] Due to the adoption of the above technical solution, the technical progress achieved by the present invention is:

[0017] By double-package pouring in the present invention, 160 t of molten iron is poured within 90-120 s, with rapid filling, improving the uniformity of the molten iron in the mold; at the same time, the mold adopts measures of a metal mold on the outer wall, internal and upper graphite chills, and water cooling inside the resin sand core, which can ensure that the molten iron in the mold cavity solidifies rapidly and evenly within 2 hours (the solidification time of the patent with the publication number CN110014123B is basically 7-9 hours), solving the problem of graphite recession during the solidification of ductile iron containers.

[0018] A graphite chill and a furan resin sand core are arranged on the top of the casting mold of the present invention, and an iron plate with iron plate exhaust holes is arranged on the top of the furan resin sand core. Gas in the molten iron can escape from the graphite chill and the furan resin sand core. Compared with the patent with publication number CN110014123B, the molten iron inside the mold cavity will escape from the gas outlet after reaching a certain pressure. The present invention can make the pressure of the molten iron in the mold cavity higher and obtain a ductile iron casting with a denser structure.

[0019] Graphite chillers are made of high thermal conductivity carbon bricks. A 30-50mm gap should be reserved for the graphite chillers and filled with resin sand to ensure the yield of the mold and avoid shrinkage of the casting.

[0020] The 100-ton-class spent fuel storage and transportation integrated ductile iron container produced by the present invention can meet the requirements of special flaw detection standards through UT (ultrasonic) flaw detection. After anatomical inspection, there is no significant difference in graphite morphology and graphite grade between the inner and outer parts of the casting thickness, and the organization is uniform and the performance is good. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic diagram of the structure of the present invention;

[0022] Among them, 1. pouring cup, 2. pouring channel, 3. metal mold, 4. sand box, 5. iron plate, 6. iron plate exhaust hole, 7. top furan resin sand core, 8. graphite chill, 9. internal furan resin sand core, 10. graphite chill gap, 11. circulating water pipeline. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with embodiments:

[0024] like Figure 1 As shown, a mold for casting a 100-ton spent fuel container includes a sand box 4 filled with furan resin sand, a casting mold and a double-bag double-casting system are fixedly arranged on the top of the sand box 4, the double-bag double-casting system is separated on both sides of the casting mold and is used to pour molten iron into the casting mold, including two sets of pouring cups 1 and a runner 2 connecting the pouring cups 1 and the casting mold cavity, the runner 2 includes a straight runner, a horizontal runner and an inner runner, and the horizontal runner is located inside the sand box 4. The molten iron is poured into the casting mold simultaneously through the double-bag double-casting system, and the pouring time is 90 to 120 seconds.

[0025] The mold includes a metal mold 3 fixed on a sand box 4 and an internal furan resin sand core 9 arranged inside the metal mold 3. The material of the metal mold 3 is ductile iron with a thickness of 200 - 300 mm, and a top furan resin sand core 7 is arranged at the top of the metal mold 3; graphite chill irons 8 are respectively built on the inner side of the top furan resin sand core 7 and the outer surface of the internal furan resin sand core 9. The graphite chill irons 8 are processed from high thermal conductivity carbon bricks. A graphite chill iron gap 10 of 30 - 50 mm is reserved between adjacent graphite chill irons 8, and the graphite chill iron gap 10 is filled with furan resin sand. The gas in the molten iron inside the cavity escapes outward through the graphite chill irons and the furan resin sand.

[0026] An iron plate 5 is arranged on the outer side of the top furan resin sand core 7, and iron plate exhaust holes 6 are evenly distributed on the iron plate 5. The thickness of the iron plate 5 is 100 - 200 mm to ensure a certain strength. When pouring the molten iron, a seating weight is arranged on the top of the iron plate 5, and the weight of the seating weight is 2 - 3 times that of the poured molten iron to prevent the mold from expanding when the graphite expands.

[0027] A circulating water pipeline 11 is laid inside the internal furan resin sand core 9, and the circulating water pipeline 11 extends outside the sand box 4 and is connected to a cooling tower. After the molten iron is poured, cooling water at 15 - 30 °C is introduced into the circulating water pipeline 11, the water passing time is 12 - 24 h, and the water passing volume is 5 - 10 t / h.

[0028] Specifically, it includes the following steps:

[0029] S1. Prepare the sand box 4, use furan resin sand for molding, place the double-package double-pouring system in place according to the specific drawing requirements, fix the circulating water pipeline 11, fill the sand box 4 with furan resin sand, and tamp it with a special tamping tool.

[0030] S2. After the furan resin sand hardens, layer by layer build the inner wall graphite chill irons 8 according to the diameter and height requirements of the drawing. The graphite chill iron gap for each layer is 30 - 50 mm, and the inside and the gap are filled with furan resin sand.

[0031] S3. Preheat the metal mold 3 by baking with gas. When it reaches 110 - 130 °C, spray a special coating on the inner wall of the metal mold, and control the coating thickness to be 1.5 - 2.5 mm.

[0032] S4. The top furan resin sand core 7 is molded in a special core box. Place graphite chill irons inside the core box according to the drawing requirements, fill in furan resin sand, tamp it with a special tamping tool, and remove the mold after hardening for 12 hours.

[0033] S5. Spray a special coating on the bottom end face of the upper top furan resin sand core 7 and the outer wall of the inner wall graphite chill iron 8, with a thickness of 1.5 - 2.5 mm.

[0034] S6. Select refractory materials with appropriate diameters for the double-package double-pouring system 2, fill them with furan resin sand and ram them. Select a sprue cup 1 with appropriate specifications and build it with refractory materials.

[0035] S7. According to the equipment drawing, place the metal mold 3, the top furan resin sand core 7, the iron plate 5, the weights, the double-package double-pouring system 2, and the sprue cup 1 one by one, and connect the circulating water system to the cooling tower.

[0036] S8. According to the requirements of the smelting and pouring processes, prepare the ingredients and smelt to obtain molten iron. The molten iron is simultaneously poured into the mold through the double-package double-pouring system, and the pouring time is 90 - 120 s.

[0037] S9. After pouring, start the cooling water circulation pump for cooling, control the water temperature at 15 - 30 °C, open the box after 12 - 24 hours of water supply with a water flow rate of 5 - 10 t / h to obtain an integrated metal container for spent fuel storage and transportation.

Claims

1. A casting method for a hundred-ton spent fuel container, characterized in that: Molten iron is simultaneously poured into the mold through a double-package double-pouring system, the pouring time is 90 - 120 s, it solidifies 2 h after pouring, and the mold is opened 12 - 24 h later to obtain an integrated metal container for spent fuel storage and transportation; The mold includes a metal mold (3) fixed on a sand box (4) and an internal furan resin sand core (9) arranged inside the metal mold (3). A top furan resin sand core (7) is arranged at the top of the metal mold (3), and a graphite chill (8) is arranged inside the top furan resin sand core (7), and an iron plate (5) is arranged outside. Iron plate exhaust holes (6) are evenly distributed on the iron plate (5); Graphite chills (8) are arranged on the outer surface of the internal furan resin sand core (9); The graphite chills (8) are processed from high thermal conductivity carbon bricks, and a graphite chill gap (10) of 30 - 50 mm is reserved between adjacent graphite chills (8), and the inside is filled with furan resin sand; A circulating water pipe (11) is laid inside the internal furan resin sand core (9); After the molten iron is poured, cooling water at 15 - 30 °C is introduced into the circulating water pipe (11), the water passing time is 12 - 24 h, and the water passing rate is 5 - 10 t / h; When pouring the molten iron, a seating weight is arranged on the top of the iron plate (5), and the weight of the seating weight is 2 - 3 times that of the poured molten iron, and the thickness of the iron plate (5) is 100 - 200 mm; The double-package double-pouring system includes two pouring cups (1) and a runner (2) connecting the pouring cups (1) and passing through the sand box (4) until it is connected to the mold cavity opening; The integrated metal container for spent fuel storage and transportation obtained by this method has uniform structure, good compactness and high strength.

2. The casting method for a hundred-ton spent fuel container according to claim 1, characterized in that: The material of the metal mold (3) is ductile iron, and the thickness is 200 - 300 mm.

Images