Metal suspension smelting die-casting manufacturing method

Abstract

The invention belongs to the technical field of metal die-casting, and particularly relates to a metal suspension smelting die-casting manufacturing method which is characterized in that metal suspension smelting die-casting manufacturing is completed by using suspension smelting equipment through the steps of vacuumizing, charging, die heating, heating, feeding, operation before pressurization, pressurization operation and cooling. According to the technical scheme, under the condition that the advantages of the suspension smelting technology are fully exerted, the low-melting-point metal extrusion casting and continuous casting liquid core pressing technology is used for reference, and the suspension smelting pressure casting technology is creatively provided so as to improve the performance of the cast ingot. The suspension induction melting can adapt to forming of most alloy materials in extrusion casting, and has the characteristic of wide adaptability; and meanwhile, the alloy has absolute advantages in high-temperature materials, can be used for smelting metal materials at the temperature of 3000 DEG C or above, and has absolute advantages in the aspect of forming refractory metal and special metal.

Description

Technical Field

[0001] The present invention belongs to the technical field of metal die casting, and particularly relates to a method for manufacturing metal suspension melting die casting. Background Art

[0002] With the development of society, people's requirements for the performance of materials are getting higher and higher. Traditional casting processes are accompanied by a series of defects, such as shrinkage cavities, porosity, gas holes, and coarse dendrites. Especially for some metals and alloys with poor fluidity, there is not enough time for feeding between dendrite gaps, which is extremely likely to generate a large amount of internal porosity, shrinkage cavities, and holes, seriously affecting the properties of the ingot.

[0003] As an advanced precision forming technology for non-ferrous alloys in the manufacturing industry, squeeze casting is being more and more widely used in the development trend of products towards precision, lightweight, energy-saving, and green. The demand for die-castings has also been continuously increasing. However, existing squeeze casting processes generally can only be applied to low-melting-point metal materials, such as aluminum alloy die casting and magnesium alloy die casting, and are not suitable for high-melting-point materials. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for manufacturing metal suspension melting die casting. By using the suspension melting equipment previously applied by the applicant (application number CN202520230665.5), and adopting the method of high-temperature pressurized melting and die casting, squeeze casting is carried out when the material is in a state between melting and solidification, so as to solve the problems mentioned in the above background art.

[0005] To achieve the above purpose, the present application is realized through the following technical solutions:

[0006] A method for manufacturing metal suspension melting die casting, using a suspension melting equipment, and adopting the following steps:

[0007] S1. Perform a vacuum pumping treatment on the inside of the melting furnace to make the working vacuum degree inside the melting furnace ≤ 6.7×10 -3 Pa;

[0008] S2. Add the material to be die-cast into the crucible inside the melting furnace;

[0009] S3. Heat the mold, control the temperature rise rate to be 30°C / h - 1200°C / h, and the final heating temperature to be 400°C - 2000°C;

[0010] S4. Heat the material to be die-cast in the crucible until it is completely melted, and keep it for 1 - 30 minutes;

[0011] S5. Transfer the melted material in the crucible to the mold heated in step S3 through a transfer device;

[0012] S6. Start the oil cylinder to push the pressure head to the pressurizing position. At this time, the material is in a semi-solid state in the mold.

[0013] S7. The pressure head continues to press down to perform pressure die-casting on the material in the mold. When the pressure die-casting starts, the surface temperature of the material is 20 - 500 °C below its solidification point. At this time, the material in the mold is still in a semi-solid state.

[0014] S8. After the die-casting is completed, retract the pressure head. The die-cast workpiece cools to room temperature in the mold and is demolded, thus completing the die-casting operation.

[0015] Furthermore, the suspension melting equipment includes a furnace frame, a melting furnace and an oil pressure system. The melting furnace and the oil pressure system are both arranged on the furnace frame.

[0016] The melting furnace includes a vacuum chamber, which is divided into a main vacuum chamber and a pre-chamber of the melting furnace that are connected to each other. The crucible is installed in the main vacuum chamber, the mold is installed in the pre-chamber of the melting furnace, and a transfer device is arranged between the crucible and the mold.

[0017] The oil pressure system includes an oil pressure system support, an oil cylinder, a piston rod and a pressure head. The oil pressure system support is installed on the furnace frame, the oil cylinder is installed on the oil system support, the piston rod is installed in the oil cylinder, the piston rod extends into the interior of the pre-chamber of the melting furnace from the top of the pre-chamber of the melting furnace, and the pressure head is arranged at the lower end of the piston rod. The mold is arranged below the pressure head.

[0018] Furthermore, in step S1, after evacuating the interior of the melting furnace, an inert gas is filled into the melting furnace, and the internal pressure of the melting furnace after filling the inert gas is 0.02 - 0.08 MPa.

[0019] Furthermore, the inert gas is argon.

[0020] Furthermore, in step S3, the temperature rise rate is 30 - 1200 °C / h.

[0021] Furthermore, in step S6, when pushing the pressure head to the pressurizing position, the pressure head pressing time is 2 - 5 s.

[0022] Furthermore, in step S7, the pressure head continues to press down to perform pressure die-casting on the material in the mold, which includes two stages. In the first stage, the stroke of the pressure head is 2 - 100 mm, the running time is 2 - 25 s, and the pressure is maintained for 5 - 600 s. In the second stage, the pressure head continues to press down to the size of the part and the pressure is maintained for 5 - 300 s. And the total stroke of the pressure head in the two stages does not exceed 200 mm.

[0023] Furthermore, the die-casting speed of the pressure head in the first stage is less than that in the second stage.

[0024] Further, in step S7, the ram continues to press down to apply pressure die-casting to the material in the mold. The ram stroke is 2 - 200 mm, the ram running time is 2 - 50 s, and it is directly die-cast into the part size, with a holding pressure for 5 - 900 s.

[0025] Further, in step S8, the die-cast workpiece cools to room temperature in the mold, including natural cooling or controlling the mold temperature through a heating device and slow cooling.

[0026] The beneficial effects of the present invention are:

[0027] Under the condition of giving full play to the advantages of the levitation melting technology, the present invention draws on the low-melting-point metal squeeze casting and continuous casting liquid core reduction technologies, and creatively proposes the levitation melting pressure casting technology to improve the properties of the ingot. Levitation induction melting can adapt to the forming of most alloy materials in squeeze casting, with the characteristic of wide adaptability; at the same time, it has an absolute advantage in high-temperature materials, can melt metal materials with a temperature of 3000 °C and above, and has an absolute advantage in the forming of refractory metals and special metals. Brief Description of the Drawings

[0028] Figure 1 It is a front view structural schematic diagram of the levitation melting equipment used in the present invention.

[0029] Figure 2 It is a side view structural schematic diagram of the levitation melting equipment used in the present invention.

[0030] Figure 3 It is a structural schematic diagram of the stamping part of the levitation melting equipment used in the present invention.

[0031] Figure 4 It is a schematic cross-sectional view of a typical casting structure, including a surface fine-grained equiaxed zone, an intermediate columnar crystal zone, and a central coarse equiaxed crystal zone.

[0032] Figure 5 It is a schematic cross-sectional view of the casting structure with a large cooling temperature gradient in the traditional casting process or for some metal alloys, with only a surface fine-grained equiaxed zone and an intermediate columnar crystal, and the central equiaxed crystal zone disappearing.

[0033] Figure 6 It is a schematic cross-sectional view after the weak dendrites are broken during die-casting.

[0034] Figure 7 It is a schematic diagram of the solidified structure of the cross-section after die-casting.

[0035] Figure 8 It is a schematic longitudinal section view of a typical casting structure.

[0036] Figure 9 It is a schematic diagram of the solidified structure of the longitudinal section after die-casting.

[0037] Description of the reference numerals in the drawings:

[0038] 1. Furnace frame column; 2. Furnace frame plate; 3. Furnace bottom; 4. Furnace body; 5. Furnace cover; 6. Furnace door; 7. Press machine column; 8. Upper plate of the press frame; 9. Crucible; 10. Oil cylinder; 11. Piston rod; 12. Press head; 13. Sealing ring; 14. Front chamber of the melting furnace; 15. Mold; 16. Hydraulic station. Detailed implementation manners

[0039] The technical solutions of the present invention will be described in detail below with reference to the accompanying drawings. The following embodiments are merely exemplary and can only be used to explain and illustrate the technical solutions of the present invention, rather than being construed as a limitation to the technical solutions of the present invention.

[0040] As Figures 1 to 9 shown, this application utilizes a suspension melting equipment (specifically see the applicant's patent, application number CN202520230665.5, a suspension melting equipment), and this technical solution is a die-casting manufacturing method developed using this equipment.

[0041] As Figures 1 to 3 shown, the suspension melting equipment involved in this application includes a furnace frame, a melting furnace, and an oil pressure system. In this application, the suspension melting furnace equipment also includes conventional feeding equipment, a power supply for the crucible and the mold, corresponding power equipment, and internal and external heat insulation devices of the melting furnace, etc., which are all prior arts and are not described in the technical solutions of this application. However, it does not mean that the suspension melting equipment of this application does not include corresponding supporting equipment. Those skilled in the art can make conventional configurations according to actual needs.

[0042] The furnace frame includes a furnace frame column 1 and a furnace frame plate 2, the furnace frame plate 2 is fixedly installed on the furnace frame column 1, and plays an overall supporting role. The melting furnace includes a furnace bottom 3, a furnace body 4, a furnace cover 5 and a furnace door 6. The furnace bottom 3 is installed on the furnace frame plate 2, the furnace body 4 is installed on the furnace bottom 3, and the furnace cover 5 is fixedly installed on the top of the furnace body 4, so as to form an overall melting furnace structure. The interior of the melting furnace is a vacuum chamber. In the present application, the vacuum chamber inside the melting furnace is divided into a main vacuum chamber and a furnace front chamber 14 that are interconnected. The crucible 9 is installed in the main vacuum chamber. The oil pressure system is fixedly installed in the furnace front chamber 14. The oil pressure system includes an oil cylinder 10, a piston rod 11 and a pressure head 12. A press column 7 is fixedly installed on the furnace frame plate 2, and the top of the press column 7 is fixed. A press frame upper plate 8 is installed, and the press frame upper plate 8 is located above the furnace front chamber 14. The oil cylinder 10 is fixedly installed on the press frame upper plate 8, and the piston rod 11 is installed in the oil cylinder 10. A sealing ring 13 is installed on the top of the furnace front chamber 14. The piston rod 11 is inserted in the sealing ring 13. The piston rod 11 extends into the front chamber 14 from the sealing ring 13. A pressure head 12 is fixedly installed at the bottom of the piston rod 11, a mold 15 is arranged on the furnace bottom 3, and a transfer device is arranged between the crucible and the mold. The mold 15 is arranged below the pressure head 12. The oil pressure system also includes a hydraulic station 16, which is connected to the oil cylinder 10. In the present application, the hydraulic station 16 is arranged on the furnace frame plate 2 to save space as much as possible.

[0043] The mold comprises a mold body and a ceramic heating plate arranged outside the mold body, and the ceramic heating plate is used to heat the mold.

[0044] An induction heating coil is arranged on the outer wall of the crucible, and the material inside the crucible is heated by the induction heating coil of the crucible itself until it is completely melted.

[0045] The bottom height of the oil cylinder 10 is 900 mm, that is, the distance between the bottom of the oil cylinder 10 and the top of the furnace bottom 3 is 900 mm. The stroke of the oil cylinder 10 is greater than or equal to 600 mm, and the pressure generated by the oil cylinder 10 is greater than or equal to 50 tons.

[0046] The hovering height of the pressure head 12 before working is 600mm (corresponding to the attached Figure 3 The distance between the bottom surface of the pressure head 12 and the top surface of the furnace bottom 3 is 600 mm. The height of the pressure head 12 before pressurization is 200-400 mm (corresponding to the attached Figure 3 At the middle position B), the pressing distance of the pressure head 12 after pressurization is 2~200mm (corresponding to the attached Figure 3 middle position C).

[0047] like Figures 1 to 9 As shown, the present application provides a metal suspension smelting die casting manufacturing method, using the above-mentioned suspension smelting equipment, and adopting the following steps:

[0048] S1. Vacuum the furnace to make the internal working vacuum less than or equal to 6.7×10 -3 Pa, usually the working vacuum is 7.0×10 -3 Pa; in the present application, the furnace works in a vacuum environment. In specific implementation, after evacuation, an inert gas protection (preferably argon) can be filled into the furnace. The internal pressure after filling with the inert gas is 0.02 MPa-0.08 MPa, preferably 0.06 MPa.

[0049] S2. Add TC4 (i.e. Ti6Al4V) material into the crucible. In other embodiments of the present application, corresponding materials are added according to the actual casting and the required amount is generally 5-50 kg, usually about 15-20 kg.

[0050] S3. Heat the mold with a ceramic heating plate, control the temperature rise rate to 30°C / h-1200°C / h, and the final heating temperature to 400°C-2000°C. In this embodiment, the average temperature rise rate is 500°C / h, and the final heating temperature is 1200°C.

[0051] S4. Using the induction heating coil of the crucible itself to heat the material inside the crucible until it is completely melted, the power is maintained for 1-30 minutes. In this embodiment, the power is maintained for 10 minutes.

[0052] S5. Transfer the molten material in the crucible into the mold through the transfer device. At this time, the mold has been preheated to the set temperature value in step S3 and maintained at the set temperature value.

[0053] S6, start the oil cylinder and push the pressure head to the pressurizing position (i.e. Figure 3 At position B), the pressure head presses down for 2-5s. During this process, the material is naturally cooled in the mold. At this time, the material is in a semi-solidified state, that is, a solidified shell is formed on the surface and the core is in a liquid state.

[0054] S7. The oil cylinder pushes the punch to continue pressing down, performing pressure die-casting on the material in the mold. When the pressure die-casting starts, the surface temperature of the material is 20°C - 500°C below its solidification point, usually around 100°C below the solidification point, and the material is in a semi-solid state. In this application, there are two process methods during the pressure operation: The first method: The stroke of the first stage of the punch is 2mm - 100mm. During this process, the center gradually solidifies until it is completely solidified, and the running time is 2s - 25s (the die-casting speed in this stage is relatively slower than that in the second stage to prevent the surface solidified shell from breaking), and the holding pressure is 5s - 600s, usually 30s. In the second stage, the stroke continues to press down to the size of the part (the die-casting speed is faster than that in the first stage, equivalent to vacuum hot pressing), and the maximum total stroke of the two stages does not exceed 200mm. The second method: The stroke of the punch is 2mm - 200mm at one time, and the running time is 2s - 50s to directly die-cast into the part size, and the holding pressure is 5s - 300s, usually 20s.

[0055] S8. After the die-casting is completed, the punch is retracted, and the mold heating device is turned off. The die-cast workpiece cools naturally (or the mold temperature is controlled by the mold heating device and cooled slowly) in the mold to room temperature, and then demolding is carried out, thus completing the operation.

[0056] Please refer to the attached Figure 6 Attachments Figure 7 And the attached Figure 9 Technical principle description of pressure die-casting (liquid core reduction): Pressure die-casting (liquid core reduction) technology is such that the surface of the material is in a solidified state while the core is in a liquid or paste state. Due to the existence of external pressure, a strong hydrostatic pressure will be generated in the core. Under the action of the hydrostatic pressure, a large number of weak secondary and tertiary dendrite arms in the columnar crystal region near the wall surface are broken. On the one hand, it can greatly improve the problem of coarse dendrites. On the other hand, these broken dendrites are brought into the molten liquid in the core that has not yet solidified, and these broken dendrites can act as crystal nuclei, expanding the equiaxed crystal region in the core and refining the grain size. For the gaps left by the already solidified dendrites, under the action of the hydrostatic stress, they can be fully compensated, making the internal structure dense and reducing composition segregation. After the core is completely solidified, at this time, the casting is still at a high temperature, so it has good plasticity and can continue plastic deformation (equivalent to vacuum hot pressing), which can weld the residual pores and looseness. Combined with the subsequent cooling process, it is possible to greatly reduce shrinkage cavities, pores, and looseness. In summary, using pressure die-casting (liquid core reduction) technology can greatly improve the structure of the ingot and enhance the performance of the ingot. From the perspective of technical feasibility and actual application requirements, it is very necessary to develop suspension melting pressure die-casting (liquid core reduction) technology.

[0057] Although embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, and the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A metal suspension smelting die casting manufacturing method, using a suspension smelting device, characterized in that: Use the following steps: S1. Vacuum the furnace to make the working vacuum degree ≤6.7×10 -3 Pa; S2, adding the material to be die-cast into the crucible in the furnace; S3, heating the mold, controlling the temperature rise rate to 30℃ / h-1200℃ / h, and the final heating temperature to 400℃-2000℃; S4, heating the material to be die-cast in the crucible until it is completely melted, and maintaining it for 1-30 minutes; S5, transferring the molten material in the crucible into the mold heated in step S3 through a transfer device; S6, start the oil cylinder and push the pressure head to the pressure position. At this time, the material is in a semi-solidified state in the mold; S7, the pressure head continues to press down to pressurize the material in the mold for die casting. When the pressure die casting starts, the surface temperature of the material is 20-500℃ below its solidification point. At this time, the material is still in a semi-solidified state in the mold; S8. After die casting is completed, the pressure head is retracted, the die-casting workpiece is cooled to room temperature in the mold, and demolded, thus completing the die casting operation.

2. The metal suspension melting and die casting manufacturing method according to claim 1, characterized in that: The suspension smelting equipment comprises a furnace frame, a furnace and an oil pressure system, wherein the furnace and the oil pressure system are both arranged on the furnace frame; The furnace includes a vacuum chamber, which is divided into a main vacuum chamber and a furnace front chamber connected to each other, the crucible is installed in the main vacuum chamber, the mold is installed in the furnace front chamber, and a transfer device is provided between the crucible and the mold; The hydraulic system includes a hydraulic system bracket, a cylinder, a piston rod and a pressure head. The hydraulic system bracket is installed on the furnace frame, the cylinder is installed on the oil system bracket, the piston rod is installed in the cylinder, the piston rod extends from the top of the furnace front chamber into the interior of the furnace front chamber, the pressure head is arranged at the lower end of the piston rod, and the mold is arranged below the pressure head.

3. The metal suspension melting and die casting manufacturing method according to claim 1, characterized in that: In step S1, after the interior of the furnace is evacuated, an inert gas is filled into the furnace. The internal pressure of the furnace after the inert gas is filled is 0.02-0.08 MPa.

4. The metal suspension melting and die casting manufacturing method according to claim 3, characterized in that: The inert gas is argon.

5. The metal suspension melting and die casting manufacturing method according to claim 1, characterized in that: In step S3, the temperature rise rate is 30-1200°C / h.

6. The metal suspension melting and die casting manufacturing method according to claim 1, characterized in that: In step S6, the pressure head is pushed to the pressure-applying position, and the pressure head is pressed down for 2-5 seconds.

7. The metal suspension melting and die casting manufacturing method according to claim 1, characterized in that: In step S7, the ram continues to press down to pressurize the material in the mold for die-casting, which includes two stages. The ram stroke in the first stage is 2-100mm, the running time is 2-25s, and the pressure is maintained for 5-600s. The second stage is that the ram continues to press down to the size of the part, the pressure is maintained for 5-300s, and the total ram stroke of the two stages does not exceed 200mm.

8. The metal suspension melting and die casting manufacturing method according to claim 7, characterized in that: The die-casting speed of the ram in the first stage is lower than the die-casting speed of the ram in the second stage.

9. The metal suspension melting and die casting manufacturing method according to claim 1, characterized in that: In step S7, the ram continues to press down to pressurize the material in the mold for die-casting. The ram stroke is 2-200 mm, the ram operation time is 2-50 s, and the part is directly die-cast into the size, and the pressure is maintained for 5-900 s.

10. The metal suspension melting and die casting manufacturing method according to claim 1, characterized in that: In step S8, the die-cast workpiece is cooled to room temperature in the mold, including natural cooling or slow cooling by controlling the mold temperature through a heating device.

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