Method for solving undercasting of annular thin-wall investment casting

Abstract

The invention belongs to the technical field of precision investment casting, and relates to a method for solving the insufficient casting defect of an annular thin-wall investment casting, which comprises the following steps: arranging a process patching cavity on an outer ring of an annular thin-wall part of a wax mold, and connecting the process patching cavity with the annular thin-wall part through symmetrically arranged connecting rods; a wax mold with a process patch is adopted for pressing the wax mold; the wax mold is sequentially subjected to combination, shell making, dewaxing and smelting pouring, and an annular thin-wall investment casting is obtained; and the annular thin-wall investment casting is polished and polished, and the investment casting is obtained. The solidification time difference is shortened, the problem of insufficient casting of the annular thin-wall investment casting is solved, the metallurgical quality of the annular thin-wall investment casting is improved, the annular thin-wall part and the process patching cavity are connected through the connecting rod, the contact area between the annular thin-wall part and a workpiece is reduced, the casting repair amount after casting is reduced, and the casting quality of the annular thin-wall investment casting is improved. Deformation of thin-wall parts of castings is avoided, and part waste loss is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of investment precision casting, and relates to a method for solving the under-casting defect of annular thin-wall investment castings. Background Art

[0002] Investment casting, also known as "lost-wax casting", uses soluble materials to make investment patterns and assemble the pattern modules. Then, multiple layers of refractory materials are coated on the surface of the pattern modules. After drying and curing, a mold shell is formed. The mold shell is heated to melt out the pattern material, and then molten metal is poured in after high-temperature roasting to obtain investment castings.

[0003] Like other casting methods, investment casting inevitably produces various defects on the castings, such as under-casting, cold shut, porosity, slag inclusion, cracks, etc. Among them, the under-casting defect usually occurs in thin-wall castings, and its typical feature is local lack of material at the thin walls of the casting or far from the ingate, and its edge is arc-shaped. The reasons for its occurrence are as follows: 1. The pouring temperature of the molten metal and the mold temperature are low; 2. The pouring speed is slow or the ingate is set unreasonably, and the metal flow path is too long; 3. The wall thickness of the casting is too thin, and the flow of the molten metal is poor; 4. The pouring is interrupted during pouring.

[0004] For the reasons for the occurrence of the under-casting defect, the following control measures can be taken: 1. Increase the pouring temperature of the molten metal and the mold temperature; 2. Increase the pouring speed or increase the number or area of the ingates to reduce the metal flow path; 3. Increase the pressure head of the riser and prevent the pouring from being interrupted during pouring.

[0005] From the reasons for the occurrence of the under-casting defect and the control measures above, except for the reason of the thin wall thickness of the casting, the other reasons have corresponding control measures. This is because the wall thickness of investment castings is almost all non-machined parts, which are directly formed by casting. The size of the wall thickness is directly given by the design unit according to the use requirements of the product, and some wall thickness sizes are less than 1 mm. Such thin-wall castings are extremely prone to under-casting defects during pouring, resulting in the scrapping of the castings.

[0006] During the actual production process, to prevent the occurrence of under-casting defects in thin-walled castings, in addition to adopting the above control measures as appropriate, it is also possible to increase an overall process allowance at the thin-walled part to artificially increase the size at the thin-walled part to reduce under-casting defects. After pouring and forming, the process allowance is removed by manual grinding; or methods such as adding vent rods at local parts prone to under-casting are used. These methods are applicable to castings with low surface quality requirements. For castings with high surface quality requirements, especially the surface through which the air flows, manual grinding cannot ensure a smooth transition on the casting surface. When the gas passes through, turbulent flow or eddy current phenomena are likely to occur. At the same time, large-area manual grinding is also likely to cause deformation of the thin-walled part of the casting, affecting the effectiveness of product use.

[0007] In the invention and creation with the publication number CN104325079A (Title: A Method for Solving Under-Casting of Precision Castings), a method for solving under-casting of precision castings is disclosed. This invention pre-presses an exhaust wax mold rod of a certain size, welds the exhaust wax mold rod on the wax mold at the part prone to under-casting. When casting the casting, the shell cavity formed by the exhaust wax mold rod plays a role in drainage, thus solving the under-casting defect of the casting to a certain extent.

[0008] This patent is a general method for solving the under-casting defect of castings. Different from the annular thin-walled castings claimed in this project, the structure of the annular casting has no directionality and belongs to a centrosymmetric structure, making it impossible to pre-judge the part prone to under-casting defects in advance; moreover, when casting the casting at the part where the exhaust rod is added, due to the pulling force of the alloy liquid at the exhaust rod, local deformation of the annular part is also likely to occur, so it is not applicable to this project.

[0009] In the invention and creation with the publication number CN102441642A (Title: A Method for Preventing Under-Casting of Blades of a High-Temperature Alloy Integral Turbine Impeller), a method for preventing under-casting of blades of a high-temperature alloy integral turbine impeller is disclosed. This invention bonds a wax sheet with a certain shape and size at the blade tip part of the wax mold of the integral turbine impeller, so that after the shell making and dewaxing of the integral turbine impeller wax mold are completed, a "gas storage bag" shell cavity is formed in the integral shell. When casting the casting, the shell cavity formed by the "gas storage bag" plays a role in drainage, thus solving the under-casting defect of the casting to a certain extent.

[0010] This patent solves the under-casting defect of the casting by adding an overall process allowance at the thin-walled part of the casting. After pouring and forming, the process allowance is removed by manual grinding or machining. It is not applicable to the annular casting with a wall thickness of less than 1 mm claimed in this project because adding an overall process allowance to such an annular casting with such a wall thickness is extremely likely to cause deformation of the thin-walled part of the casting whether by manual grinding or machining after pouring, so it is not applicable to this project. Summary of the Invention

[0011] The purpose of the present invention is to provide a method for solving the undercast defect of annular thin-walled investment castings, so as to solve the problem that the metallurgical quality cannot be guaranteed in the prior art while effectively solving the undercast defect of annular thin-walled investment castings.

[0012] In order to achieve the above object, the present invention adopts the following technical solutions: The present application discloses a method for solving the undercast defect of annular thin-walled investment castings, comprising the following steps: S1: A process subsidy cavity is provided on the outer ring of the annular thin-walled portion of the wax mold, and the process subsidy cavity is connected to the annular thin-walled portion via symmetrically arranged connecting rods; S2: Using a wax mold with process subsidies to press the wax model; S3: The wax pattern is assembled, shelled, dewaxed, and melted and poured in sequence to obtain an annular thin-walled investment casting; S4: Grinding and polishing the annular thin-walled investment casting to obtain an investment casting.

[0013] Preferably, the size of the process subsidy cavity is 9-12 mm larger than the diameter of the provided portion.

[0014] Preferably, the cross-section of the process subsidy cavity is circular, and the diameter of the circle is 2-3 mm.

[0015] Preferably, four connecting rods are symmetrically arranged.

[0016] Preferably, the cross section of the connecting rod is circular or square.

[0017] Preferably, when the cross-section of the connecting rod is circular, its diameter is 2-3 mm.

[0018] Preferably, when the cross-section of the connecting rod is a square, the side length thereof is 2-3 mm.

[0019] Preferably, in said S4, the four connecting rods at the annular thin-walled portion of the annular thin-walled investment casting are ground and polished.

[0020] Preferably, the annular thin-walled investment casting has a uniform wall thickness of less than 1 mm.

[0021] The present application also discloses an annular thin-walled investment casting, which is produced by any of the methods described above.

[0022] Compared with the prior art, the present invention has the following beneficial effects: A method for solving the under-casting defect of a ring-shaped thin-walled investment casting. When designing the wax mold, a process compensation cavity is additionally designed in a circle outside the ring-shaped thin-walled part in advance, which shortens the solidification time difference, thereby solving the under-casting problem of the ring-shaped thin-walled investment casting, improving the metallurgical quality of the ring-shaped thin-walled investment casting. And in this application, a connecting rod is used to connect the ring-shaped thin-walled part and the process compensation cavity, reducing the contact area with the workpiece, thereby reducing the amount of grinding and repair after casting, avoiding deformation of the thin-walled part of the casting, and reducing the loss of defective parts. At the same time, the production cost is greatly reduced, and the metal loss is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and therefore should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is a schematic flow chart of the method of the present invention; Figure 2 It is a schematic diagram of a mold with a process compensation cavity according to an embodiment of the present invention; Figure 3 It is a schematic diagram of the casting structure according to an embodiment of the present invention.

[0025] Among them: 1 - process compensation cavity; 2 - connecting rod; 3 - ring-shaped thin wall. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0026] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. Usually, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0027] Therefore, the following detailed description of the embodiments of the present invention provided in the drawings is not intended to limit the scope of the claimed present invention, but merely represents the selected embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0028] It should be noted that: similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings.

[0029] In the description of the embodiments of the present invention, it should be noted that if terms such as "upper", "lower", "horizontal", "inner", etc. are used to indicate the orientation or positional relationship, it is based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed during use. This is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation to the present invention. In addition, terms such as "first", "second", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.

[0030] In addition, if the term "horizontal" appears, it does not mean that the component is required to be absolutely horizontal, but it can be slightly inclined. For example, "horizontal" only means that its direction is more horizontal relative to "vertical", and does not mean that the structure must be completely horizontal, but it can be slightly inclined.

[0031] In the description of the embodiments of the present invention, it should also be noted that unless otherwise clearly specified and limited, if terms such as "set", "installed", "connected", "connected" are used, they should be understood in a broad sense. For example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be directly connected, or indirectly connected through an intermediate medium, and it can be the communication inside two components. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific situations.

[0032] The present invention will be further described in detail below with reference to the drawings: See Figure 1 , the present invention provides a method for solving the under-casting defect of a ring-shaped thin-wall investment casting, improving the metallurgical quality of the ring-shaped thin-wall investment casting, reducing the grinding and polishing amount after casting, and reducing the waste loss of parts. The method specifically includes the following steps: S1: A process subsidy cavity is arranged on the outer ring of the ring-shaped thin-wall part of the wax mold die, and the process subsidy cavity is connected to the ring-shaped thin-wall part through symmetrically arranged connecting rods; S2: Press the wax mold with the wax mold die with the process subsidy; S3: Combine, shell, dewax and melt and pour the wax mold in sequence to obtain a ring-shaped thin-wall investment casting; S4: Grind and polish the ring-shaped thin-wall investment casting to obtain an investment casting.

[0033] The present invention is a process method adopted to solve the under-casting defect of annular thin-walled investment castings. This process method is to additionally design a ring of process subsidy cavities on the outer ring of the annular thin-walled part during the design of the wax mold die. The process subsidy cavities are connected to the annular thin-walled part of the part wax mold through symmetrically arranged connecting rods; after the part wax mold is pressed and formed, a ring of annular process subsidy is attached to the outer ring of the annular thin-walled part (see Figure 2 ). After normal investment casting shell making, dewaxing, melting and pouring, as long as the four symmetric connecting rods exist, even if the annular process subsidy is not poured and formed, the under-casting defect of the annular thin-walled investment casting can be solved.

[0034] In some embodiments, a method for solving the under-casting defect of annular thin-walled investment castings includes the following steps: S1: Set process subsidy cavities on the outer ring of the annular thin-walled part of the wax mold die. The process subsidy cavities are connected to the annular thin-walled part through symmetrically arranged connecting rods; the size of the process subsidy cavities is 9 - 12 mm larger than the diameter of the set part.

[0035] S2: Press the wax mold using the wax mold die with process subsidies. S3: Combine, make the shell, dewax and melt and pour the wax mold in sequence to obtain the annular thin-walled investment casting. S4: Grind and polish the annular thin-walled investment casting to obtain the investment casting.

[0036] In some embodiments, in S1, process subsidy cavities are set on the outer ring of the annular thin-walled part of the wax mold die. The cross-section of the process subsidy cavities is circular, and the diameter of the circle is 2 - 3 mm.

[0037] In some embodiments, a method for solving the under-casting defect of annular thin-walled investment castings includes the following steps: S1: Set process subsidy cavities on the outer ring of the annular thin-walled part of the wax mold die. The process subsidy cavities are connected to the annular thin-walled part through symmetrically arranged connecting rods. S2: Press the wax mold using the wax mold die with process subsidies. S3: Combine, make the shell, dewax and melt and pour the wax mold in sequence to obtain the annular thin-walled investment casting. S4: Grind and polish the annular thin-walled investment casting to obtain the investment casting.

[0038] In S1, a process subsidy cavity is arranged on the outer ring of the annular thin-wall part of the wax mold die. The process subsidy cavity is connected to the annular thin-wall part through symmetrically arranged connecting rods; there are four symmetrically arranged connecting rods. The cross-section of the connecting rod is circular or square. When designing the wax mold die, a circle of process subsidy cavity is additionally designed in advance on the outer ring of the annular thin-wall part, shortening the solidification time difference, thus solving the problem of under-casting of the annular thin-wall investment casting, improving the metallurgical quality of the annular thin-wall investment casting. Moreover, in this application, the connecting rod is used to connect the annular thin-wall part and the process subsidy cavity, reducing the contact area with the workpiece, thereby reducing the grinding and polishing amount after casting the casting, avoiding the deformation of the thin-wall part of the casting, and reducing the waste loss of parts. At the same time, the production cost is greatly reduced, and the metal loss is reduced.

[0039] Further preferably, a method for solving the under-casting defect of an annular thin-wall investment casting includes the following steps: S1: A process subsidy cavity is arranged on the outer ring of the annular thin-wall part of the wax mold die. The process subsidy cavity is connected to the annular thin-wall part through symmetrically arranged connecting rods; when the cross-section of the connecting rod is circular, its diameter is 2 - 3 mm. When the cross-section of the connecting rod is square, its side length is 2 - 3 mm.

[0040] S2: Press a wax mold using the wax mold die with a process subsidy. S3: Assemble, shell, dewax, and melt and pour the wax mold in sequence to obtain an annular thin-wall investment casting. S4: Grind and polish the annular thin-wall investment casting to obtain an investment casting.

[0041] In some embodiments, a method for solving the under-casting defect of an annular thin-wall investment casting includes the following steps: S1: A process subsidy cavity is arranged on the outer ring of the annular thin-wall part of the wax mold die. The process subsidy cavity is connected to the annular thin-wall part through symmetrically arranged connecting rods. S2: Press a wax mold using the wax mold die with a process subsidy. S3: Assemble, shell, dewax, and melt and pour the wax mold in sequence to obtain an annular thin-wall investment casting. S4: Grind and polish the annular thin-wall investment casting to obtain an investment casting.

[0042] In S4, grind and polish the four connecting rods of the annular thin-wall part of the annular thin-wall investment casting. Slightly grind and polish the four connecting rods of the annular thin-wall part of the casting after pouring, and then an investment casting meeting the requirements can be obtained, reducing the grinding and polishing amount after casting the casting, avoiding the deformation of the thin-wall part of the casting, and reducing the waste loss of parts. At the same time, the production cost is greatly reduced, and the metal loss is reduced.

[0043] In some embodiments, a method for solving the under-casting defect of a ring-shaped thin-walled investment casting is as follows: The first step: When designing the wax mold die, a process compensation cavity is pre-added to the outer ring of the ring-shaped thin-walled part. The process compensation cavity is connected to the ring-shaped thin-walled part of the part wax mold by four symmetric connecting rods.

[0044] The second step: Use the wax mold die with the process compensation to press the wax mold.

[0045] The third step: Carry out normal combination, shell-making, dewaxing and melting and pouring of the wax mold.

[0046] The fourth step: Carry out micro-grinding and polishing on the four connecting rods of the ring-shaped thin-walled part of the casting after pouring, and a qualified investment casting can be obtained. It avoids the deformation of the thin-walled part of the casting, reduces the waste loss of parts. At the same time, it greatly reduces the production cost and reduces the metal loss.

[0047] The present application also discloses a ring-shaped thin-walled investment casting prepared by using the method described in any one of the above.

[0048] In summary, for the method for solving the under-casting defect of a ring-shaped thin-walled investment casting disclosed in the present application, a process compensation cavity is pre-added to the outer ring of the ring-shaped thin-walled part during the design of the wax mold die, which shortens the solidification time difference, thereby solving the under-casting problem of the ring-shaped thin-walled investment casting and improving the metallurgical quality of the ring-shaped thin-walled investment casting. And the present application uses connecting rods to connect the ring-shaped thin-walled part and the process compensation cavity, reducing the contact area with the workpiece, thereby reducing the amount of polishing after casting of the casting, avoiding the deformation of the thin-walled part of the casting, and reducing the waste loss of parts. At the same time, it greatly reduces the production cost and reduces the metal loss.

[0049]

Embodiment

[0050] For a ring investment casting with an integral thin wall, when designing the wax mold, a process compensation cavity is additionally designed in a circle on the outer ring of the thin-wall part of the ring in advance. The process compensation cavity is connected to the thin-wall part of the ring of the part wax mold by four symmetric connecting rods; after the part wax mold is pressed and formed, a ring-shaped process compensation is attached to the outer ring of the thin-wall part of the ring. After normal investment casting shell-making, dewaxing, melting and pouring, as long as the four symmetric connecting rods exist, even if the ring-shaped process compensation is not poured and formed, the undercasting defect of the thin-wall ring investment casting can be solved.

[0051] The specific process of a method for solving the undercasting of a thin-wall ring investment casting according to the present invention is as follows: The first step: When designing the wax mold, a process compensation cavity is additionally designed in a circle on the outer ring of the thin-wall part of the ring in advance. The size of the process compensation is increased by about 10 mm on the basis of the diameter size of the part of the part body that needs to be compensated (i.e., the part prone to undercasting). The cross-sectional shape of the process compensation is approximately a circle with a diameter of Φ2 mm. The process compensation cavity is connected to the thin-wall part of the ring of the part wax mold by four symmetric connecting rods, and the cross-sectional shape of the connecting rods is approximately a circle with a diameter of Φ2 mm or a square with a size of about 2 mm × 2 mm.

[0052] The second step: Press the wax mold using the wax mold with the process compensation.

[0053] The third step: Normally assemble, make the shell, dewax, melt and pour the wax mold.

[0054] The fourth step: Slightly grind and polish the four connecting rods at the thin-wall part of the ring of the cast part after pouring, and a qualified investment casting can be obtained.

[0055] In this embodiment, by using the method of additionally designing a ring of process compensation on the outer ring of the thin-wall part of the ring in advance when designing the wax mold, the undercasting problem of the thin-wall ring investment casting is solved, the metallurgical quality of the thin-wall ring investment casting is improved, the amount of polishing after casting is reduced, and the waste loss of parts is reduced.

[0056] The above is only the preferred embodiment of the present invention and is not used to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for solving the under-casting defect of a ring-shaped thin-walled investment casting, characterized in that, It includes the following steps: S1: A process subsidy cavity is arranged on the outer ring of the annular thin-wall part of the wax mold die. The process subsidy cavity is connected to the annular thin-wall part through symmetrically arranged connecting rods; S2: Press a wax mold using the wax mold die with the process subsidy; S3: Assemble, shell, dewax, and melt and pour the wax mold in sequence to obtain an annular thin-wall investment casting; S4: Grind and polish the annular thin-wall investment casting to obtain an investment casting.

2. A method for solving the under-casting defect of a ring-shaped thin-walled investment casting according to claim 1, characterized in that, The size of the process subsidy cavity is 9 - 12 mm larger than the diameter of the set part.

3. A method for solving the under-casting defect of a ring-shaped thin-walled investment casting according to claim 1, characterized in that, The cross-section of the process subsidy cavity is circular, and the diameter of the circle is 2 - 3 mm.

4. A method for solving the undercasting defect of a ring-shaped thin-walled investment casting according to claim 1, characterized in that, Four connecting rods are symmetrically arranged.

5. A method for solving the under-casting defect of a ring-shaped thin-walled investment casting according to claim 1, characterized in that, The cross-section of the connecting rod is circular or square.

6. A method for solving the under-casting defect of a ring-shaped thin-walled investment casting according to claim 5, characterized in that, When the cross-section of the connecting rod is circular, its diameter is 2 - 3 mm.

7. A method for solving the under-casting defect of a ring-shaped thin-walled investment casting according to claim 5, characterized in that, When the cross-section of the connecting rod is square, its side length is 2 - 3 mm.

8. A method for solving the under-casting defect of a ring-shaped thin-wall investment casting according to claim 1, characterized in that, In S4, grind and polish the four connecting rods of the annular thin-wall part of the annular thin-wall investment casting.

9. A method for solving the under-casting defect of a ring-shaped thin-walled investment casting according to claim 1, characterized in that, The wall thickness of the annular thin wall of the annular thin-wall investment casting is uniform and less than 1 mm.

10. A ring-shaped thin-walled investment casting, characterized in that, It is obtained by using the method described in any one of claims 1 - 9.

Images