CN117047034A - Loosening and shrinkage cavity control method for large-size equiaxed crystal superalloy castings - Google Patents
Loosening and shrinkage cavity control method for large-size equiaxed crystal superalloy castings Download PDFInfo
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- CN117047034A CN117047034A CN202311092881.XA CN202311092881A CN117047034A CN 117047034 A CN117047034 A CN 117047034A CN 202311092881 A CN202311092881 A CN 202311092881A CN 117047034 A CN117047034 A CN 117047034A
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- 238000005266 casting Methods 0.000 title claims abstract description 86
- 238000000034 method Methods 0.000 title claims abstract description 45
- 229910000601 superalloy Inorganic materials 0.000 title claims abstract description 22
- 239000013078 crystal Substances 0.000 title claims abstract description 15
- 244000035744 Hura crepitans Species 0.000 claims abstract description 31
- 230000007547 defect Effects 0.000 claims abstract description 27
- 238000003723 Smelting Methods 0.000 claims abstract description 13
- 230000015572 biosynthetic process Effects 0.000 claims abstract description 9
- 238000012546 transfer Methods 0.000 claims abstract description 8
- 230000004048 modification Effects 0.000 claims abstract description 3
- 238000012986 modification Methods 0.000 claims abstract description 3
- 230000008569 process Effects 0.000 claims description 23
- 229920000742 Cotton Polymers 0.000 claims description 16
- 238000004321 preservation Methods 0.000 claims description 10
- 229910045601 alloy Inorganic materials 0.000 claims description 9
- 239000000956 alloy Substances 0.000 claims description 9
- 230000009466 transformation Effects 0.000 claims description 6
- 238000001816 cooling Methods 0.000 claims description 4
- 238000005520 cutting process Methods 0.000 claims description 4
- 238000000465 moulding Methods 0.000 claims description 4
- 238000010583 slow cooling Methods 0.000 claims description 3
- 241001062472 Stokellia anisodon Species 0.000 claims description 2
- 238000005495 investment casting Methods 0.000 abstract description 2
- 239000011257 shell material Substances 0.000 description 41
- 238000007711 solidification Methods 0.000 description 19
- 230000008023 solidification Effects 0.000 description 19
- 239000010425 asbestos Substances 0.000 description 9
- 229910052895 riebeckite Inorganic materials 0.000 description 9
- 229910000831 Steel Inorganic materials 0.000 description 6
- 239000010959 steel Substances 0.000 description 6
- 230000000694 effects Effects 0.000 description 4
- 238000007689 inspection Methods 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 230000017525 heat dissipation Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 239000000463 material Substances 0.000 description 2
- 238000005272 metallurgy Methods 0.000 description 2
- 238000012797 qualification Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 238000005336 cracking Methods 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000013461 design Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000001917 fluorescence detection Methods 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 238000009413 insulation Methods 0.000 description 1
- 229910052742 iron Inorganic materials 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 235000011837 pasties Nutrition 0.000 description 1
- 238000005488 sandblasting Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
- 230000007704 transition Effects 0.000 description 1
- 238000011179 visual inspection Methods 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/02—Sand moulds or like moulds for shaped castings
- B22C9/04—Use of lost patterns
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C21/00—Flasks; Accessories therefor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C21/00—Flasks; Accessories therefor
- B22C21/12—Accessories
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22C—FOUNDRY MOULDING
- B22C9/00—Moulds or cores; Moulding processes
- B22C9/12—Treating moulds or cores, e.g. drying, hardening
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D15/00—Casting using a mould or core of which a part significant to the process is of high thermal conductivity, e.g. chill casting; Moulds or accessories specially adapted therefor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D27/00—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting
- B22D27/04—Influencing the temperature of the metal, e.g. by heating or cooling the mould
- B22D27/045—Directionally solidified castings
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
- B22D46/00—Controlling, supervising, not restricted to casting covered by a single main group, e.g. for safety reasons
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
The invention discloses a loosening and shrinkage cavity control method for a large-size equiaxed crystal superalloy casting, and belongs to the technical field of investment precision casting. The method comprises the following steps: (1) Performing asbestos-wrapping modeling on a large-size casting shell, and then placing the asbestos-wrapping shell into a sand box, wherein the sand box is subjected to targeted modification according to the cotton-wrapping modeling technological condition of the casting; (2) Smoothly loading the sand box with the molded shell into a muffle furnace for presintering the molded shell; (3) Transferring the shell to an ingot mould chamber of vacuum smelting equipment for smelting by using a mould shell transfer trolley, and pouring to obtain the large-size isometric crystal superalloy casting. The method reduces or eliminates the formation tendency of loose and shrinkage cavity metallurgical defects by controlling the temperature field of the sand box and the shell transfer time.
Description
Technical Field
The invention relates to the technical field of precision investment casting, in particular to a loosening and shrinkage cavity control method for a large-size equiaxed crystal superalloy casting.
Background
Compared with turbine blades of an aeroengine, the hot end components (including turbine blades and guard rings) of the high-power industrial gas turbine are larger in size and heavier in weight, and the remarkable difference has a great influence on the preparation process of large-size high-temperature alloy castings, particularly the control of metallurgical defects. In the manufacture of the large-size equiaxed crystal superalloy casting, the traditional equiaxed crystal superalloy casting preparation process is adopted, so that metallurgical defects such as looseness, shrinkage cavity and the like are very easy to occur, the qualification rate of the casting is greatly reduced, the manufacturing cost of the large-size superalloy hot end part is greatly increased, and the wide application of the large-size superalloy casting in an industrial gas turbine is limited.
Basic conditions for forming metallurgical defects such as looseness, shrinkage cavity and the like of castings include: (1) a broad range of alloy crystallization temperatures; (2) The molten steel temperature difference of different parts of the casting in the solidification process is small, namely the solidification temperature gradient is small, the solidification area is wider, the metallurgical defects such as looseness, shrinkage cavity and the like tend to be solidified in a volume (pasty) mode, and the formation tendency of the metallurgical defects is large. In general, the basic principle of porosity and shrinkage cavity metallurgical defect control is to realize sequential solidification by establishing temperature gradients of different parts of a casting, so that the metallurgical defects such as porosity, shrinkage cavity and the like are transferred to a feeding head. In the solidification process of the large-size casting, especially in the solidification process of solid castings with equal wall thickness and large wall thickness (such as guard rings and large tenon parts of large-size blades), metallurgical defects such as looseness, shrinkage cavity and the like are very easy to generate. The establishment of the temperature gradient by external means is a main method for realizing sequential solidification and reducing or eliminating the defects of loosening and shrinkage cavity. In industrial production, the mould shell is shaped in a targeted way by utilizing heat-insulating effect of asbestos or heat-conducting materials such as chill, so that gradient heat dissipation conditions and temperature gradients are formed. However, the temperature gradient formed only by the molding process such as asbestos or mounting chill has limited control effect on the loosening and shrinkage defects of high-temperature alloy castings with equal wall thickness and large wall thickness.
Disclosure of Invention
Aiming at the defects in the preparation of the large-size superalloy castings of the heavy-duty gas turbine, the invention aims to provide the loosening and shrinkage cavity control method of the large-size isometric crystal superalloy castings, and the method reduces or eliminates the formation tendency of the loosening and shrinkage cavity metallurgical defects of the castings by further improving the temperature gradient, so that the qualification rate and the metallurgical quality of the large-size superalloy castings are improved.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a loose and shrinkage cavity control method of large-size equiaxed crystal superalloy castings is characterized in that in the process of preparing superalloy castings, the formation tendency of loose and shrinkage cavity metallurgical defects is reduced or eliminated by controlling the temperature field of a sand box and the shell transfer time; the method comprises the following steps:
(1) Carrying out asbestos-wrapping modeling on a large-size casting shell, and then placing the asbestos-wrapped shell into a sand box;
(2) The sand box with the molded shell is stably arranged in a muffle furnace, so that shaking is avoided; presintering the shell;
(3) After the presintering of the shell reaches the requirement of the specified time, transferring the shell into an ingot mould chamber of vacuum smelting equipment by using a mould shell transfer trolley to smelt, and then pouring to obtain the large-size isometric crystal superalloy casting.
In the step (1), the sand box is modified in a targeted manner according to the cotton wrapping molding process condition of the casting, specifically: cutting and windowing reconstruction is carried out on the sand box in the area (such as the area without cotton wrapping and the chill area) of the casting needing rapid cooling so as to achieve the purpose of increasing the cooling rate of the casting in the area; meanwhile, in the area (such as a shell cotton-covering area, particularly a feeding head area) where the casting needs slow cooling control, the sand box is subjected to heat preservation transformation, and the inner wall and the outer wall of the sand box are subjected to cotton pasting heat preservation treatment.
In the step (3), the time for transferring the shell from the muffle furnace to the ingot mould chamber of the vacuum smelting equipment is controlled to be 2.5-4 min, and the shell is required to be taken and put lightly in the transferring process, so that shaking is avoided.
The design mechanism and the beneficial effects of the invention are as follows:
1. according to the invention, the temperature gradient of the sequential solidification part of the casting in the solidification process of the high-temperature alloy molten steel is improved by the sand box transformation means, so that the sequential solidification feeding capability of the casting is effectively improved, and the formation tendency of the loose and shrinkage metallurgical defects of the large-size casting is reduced or eliminated.
2. The invention controls the time for transferring the shell from the muffle furnace to the ingot mould chamber of the vacuum smelting equipment to be more than 2.5min, so that the area (such as a non-cotton-covered area and a cold iron area) of the casting needing to be cooled sufficiently is cooled, and the cotton-covered area (especially the cotton-covered area with thicker casting feeding head) of the shell has much smaller heat loss than the shell material due to the good heat preservation effect of the asbestos material, therefore, the temperature gradient of the area needing to be cooled rapidly and the cotton-covered area (especially the cotton-covered area with thicker casting feeding head) can be increased when the time for transferring the shell from the muffle furnace to the ingot mould chamber of the vacuum smelting equipment is more than 2.5min, the sequential solidification feeding capacity of the casting is effectively improved, and the formation tendency of loose and shrinkage cavity metallurgical defects of the large-size casting is reduced or eliminated. The purpose of controlling the time for transferring the shell from the muffle furnace to the ingot mould chamber of the vacuum smelting equipment to be within 4 minutes is to prevent the problems of metallurgy, dimensional deformation and the like of castings caused by too fast solidification of high-temperature alloy molten steel due to great reduction of the temperature of the shell and excessive dissipation of heat at a heat insulation cotton part of the shell.
Drawings
FIG. 1 is a schematic illustration of a common metallurgical defect of a large-size superalloy grommet casting; wherein (a) and (b) are defects at different locations.
FIG. 2 is a schematic diagram of a flask temperature field modification of the present invention.
FIG. 3 is a third stage grommet casting for a heavy duty gas turbine made by the process of the present invention.
FIG. 4 is an X-ray film of a third stage grommet casting of a heavy duty gas turbine manufactured by the process of the present invention.
FIG. 5 is a fluorescence detection image of a third stage guard ring of a heavy duty gas turbine prepared by the process of the invention.
Detailed Description
For a further understanding of the present invention, the present invention is described below with reference to the examples, which are only illustrative of the features and advantages of the present invention and are not intended to limit the scope of the claims of the present invention.
Example 1:
the embodiment is a loosening and shrinkage cavity control method for a third-stage guard ring casting of a heavy-duty gas turbine, and aims to solve the problems of loosening and shrinkage cavity defects on the surface of a large-size superalloy guard ring casting. FIG. 1 is a schematic view of a typical metallurgical defect of a front shroud that is not treated with this embodiment.
In the embodiment, in the process of preparing the high-temperature alloy casting, the formation tendency of loose and shrinkage cavity metallurgical defects is reduced or eliminated by controlling the temperature field of a sand box and the shell transfer time; the method comprises the following steps:
1. according to the structural characteristics of the large-size third-stage guard ring casting and the cotton wrapping molding process, the sand box is subjected to structural and temperature field transformation (see fig. 2), the sand box is subjected to cutting and windowing transformation in the area (the area without cotton wrapping at the lower section of the casting) where the casting needs to be quickly solidified, the heat dissipation efficiency is improved, and the solidification rate of molten steel in the area is improved. And thickening cotton pasting heat preservation treatment is carried out on the inner wall area and the outer wall area of the sand box corresponding to the riser position of the shell, wherein the cotton pasting thickness of the inner wall area and the outer wall area is 20mm (the total thickness of the inner wall and the outer wall is 40 mm). The method improves the temperature gradient of the sequential solidification part of the casting in the solidification process of the high-temperature alloy molten steel by the sand box transformation means, effectively improves the sequential solidification feeding capability of the casting, and reduces or eliminates the formation tendency of the defects of loose, shrinkage cavity and shrinkage crack metallurgy of the large-size casting.
Wherein: according to the structure and solidification characteristics of the third-stage guard ring casting, a modeling process of gradient cotton wrapping is developed, and the specific modeling process is as follows: the lower section of the casting exposes the shell, the middle section is wrapped with heat preservation asbestos with the thickness of 10mm, the upper section is wrapped with heat preservation asbestos with the thickness of 20mm, and the riser area is wrapped with heat preservation asbestos with the thickness of 40 mm.
2. After the large-size casting shell is subjected to asbestos wrapping modeling according to a technical specification, the shell is placed into a sand box, and the upper end of the sand box is covered with asbestos 40mm later. And the sand box with the molded shell is stably arranged in the muffle furnace, so that shaking is avoided.
3. After the presintering of the shell reaches the requirement of the specified time, transferring the presintering shell to a casting process by using a mould shell transfer trolley, wherein the time for transferring the shell from a muffle furnace to an ingot mould chamber of vacuum smelting equipment is controlled to be 2.5-3.5 min, and the shell is required to be taken and put lightly in the process of transferring the shell, so that shaking is avoided. The purpose of controlling the time for transferring the shell from the muffle furnace to the ingot mould chamber of the vacuum smelting equipment to be more than 2.5min is to enable the area (such as a bare shell area and a corresponding sand box windowing area) of the casting to be sufficiently cooled, while the shell cotton covering area (a thick cotton covering area and a sand box cotton covering area corresponding to a casting feeding riser) is much smaller than the heat dissipated by the shell material and the sand box windowing area due to good heat preservation effect of asbestos materials, so that the temperature gradient between the area (such as a bare shell area and a corresponding sand box windowing area) which is required to be rapidly solidified can be increased when the time for transferring the shell from the muffle furnace to the ingot mould chamber of the vacuum smelting equipment to be more than 2.5min, the sequential solidification feeding capacity of the casting is effectively improved, and the tendency of large-size castings, shrinkage cavities and shrinkage metallurgical defects (such as loose riser and shrinkage cavity defects) are reduced or eliminated. The purpose of controlling the time for transferring the shell from the muffle furnace to the ingot mould chamber of the vacuum smelting equipment to be within 3.5min is to prevent the problems of metallurgical and dimensional deformation and the like caused by the too fast solidification of high-temperature alloy molten steel due to the large reduction of the temperature of the shell and the excessive dissipation of heat of a heat-insulating cotton part of the shell due to the large reduction of the temperature gradient.
The casting temperature, casting speed and other technological parameters are carried out according to the special technological requirements of the casting, vacuum is broken after casting for 4min, then the casting vehicle is withdrawn, and the casting is taken down after being placed on the casting vehicle for 10 min. The cast casting is placed in a casting placing area, the placing time is at least longer than 4 hours, and the processes of shell cleaning, riser cutting and sand blasting are carried out after the casting is completed.
The castings prepared by the process of the steps are subjected to visual inspection, X-ray inspection and fluorescent inspection, and the inspection results show that: after the process of the steps is adopted, the surface loosening, shrinkage cavity and shrinkage cracking defects of the surface of the casting (particularly the connection transition area of the casting and the feeding head) are thoroughly overcome, the loosening grade in the casting is greatly reduced, and the surface defect control is obviously improved, as shown in figures 3, 4 and 5.
Claims (4)
1. A loose and shrinkage cavity control method for a large-size equiaxed crystal superalloy casting is characterized by comprising the following steps: in the process of preparing the high-temperature alloy casting, the formation tendency of loose and shrinkage cavity metallurgical defects is reduced or eliminated by controlling the temperature field of a sand box and the shell transfer time; the method comprises the following steps:
(1) Carrying out asbestos-wrapping modeling on a large-size casting shell, and then placing the asbestos-wrapped shell into a sand box;
(2) The sand box with the molded shell is stably arranged in a muffle furnace, so that shaking is avoided; presintering the shell;
(3) After the presintering of the shell reaches the requirement of the specified time, transferring the shell into an ingot mould chamber of vacuum smelting equipment by using a mould shell transfer trolley to smelt, and then pouring to obtain the large-size isometric crystal superalloy casting.
2. The method for controlling the porosity and shrinkage cavity of a large-size equiaxed crystal superalloy casting according to claim 1, wherein the method comprises the following steps: in the step (1), according to the cotton wrapping molding process condition of the casting, the sand box is subjected to targeted modification, specifically: cutting and windowing reconstruction is carried out on the sand box in the area of the casting needing rapid cooling so as to achieve the purpose of increasing the cooling rate of the casting in the area; meanwhile, the sand box is subjected to heat preservation transformation in the area where the casting needs slow cooling control, and the inner wall and the outer wall of the sand box are subjected to cotton pasting heat preservation treatment.
3. The method for controlling the porosity and shrinkage cavity of a large-size equiaxed crystal superalloy casting according to claim 2, wherein the method comprises the following steps: the area of the casting, which needs to be rapidly cooled, comprises a cotton-free area and a chill area; the area of the casting, which needs slow cooling control, comprises a shell cotton wrapping area and a feeding head area.
4. The method for controlling the porosity and shrinkage cavity of a large-size equiaxed crystal superalloy casting according to claim 1, wherein the method comprises the following steps: in the step (3), the time for transferring the molded shell from the muffle furnace to the ingot mould chamber of the vacuum smelting equipment is controlled to be 2.5-4 min, and the molded shell is required to be taken and put lightly in the transferring process, so that shaking is avoided.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311092881.XA CN117047034A (en) | 2023-08-29 | 2023-08-29 | Loosening and shrinkage cavity control method for large-size equiaxed crystal superalloy castings |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202311092881.XA CN117047034A (en) | 2023-08-29 | 2023-08-29 | Loosening and shrinkage cavity control method for large-size equiaxed crystal superalloy castings |
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| Publication Number | Publication Date |
|---|---|
| CN117047034A true CN117047034A (en) | 2023-11-14 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202311092881.XA Pending CN117047034A (en) | 2023-08-29 | 2023-08-29 | Loosening and shrinkage cavity control method for large-size equiaxed crystal superalloy castings |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN117047034A (en) |
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2023
- 2023-08-29 CN CN202311092881.XA patent/CN117047034A/en active Pending
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