CN111112587A - Method for reducing secondary shrinkage cavity of high-temperature alloy master alloy - Google Patents
Method for reducing secondary shrinkage cavity of high-temperature alloy master alloy Download PDFInfo
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- CN111112587A CN111112587A CN201911387605.XA CN201911387605A CN111112587A CN 111112587 A CN111112587 A CN 111112587A CN 201911387605 A CN201911387605 A CN 201911387605A CN 111112587 A CN111112587 A CN 111112587A
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- 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
- B22D27/09—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure
- B22D27/13—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using pressure making use of gas pressure
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- 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
- B22D27/15—Treating the metal in the mould while it is molten or ductile ; Pressure or vacuum casting by using vacuum
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Abstract
The invention relates to the field of high-temperature smelting of high-temperature alloy master alloy, and discloses a method for reducing secondary shrinkage cavity of high-temperature alloy master alloy, wherein the method comprises the steps of carrying out vacuum overheating casting on the high-temperature alloy master alloy into a mold frame which is preheated, insulated and loaded into a mold car chamber, and rapidly sealing the mold car chamber; and then, filling gas into the sealed die car chamber within a preset time, pressurizing to a preset pressure, and carrying out hot isostatic pressing, wherein the pressure in the sealed die car chamber is increased due to the expansion of the gas caused by heating during the hot isostatic pressing, and when the pressure in the sealed die car chamber is reduced to the preset pressure again, the sealed die car chamber is decompressed to the atmospheric pressure, and then the die frame is moved out. The hot isostatic pressing treatment near the melting point is carried out by utilizing the high temperature of the melt casting and the external gas pressure, so that the effect similar to die casting is achieved, and the secondary shrinkage cavity of the high-temperature alloy master alloy is greatly reduced and even eliminated.
Description
Technical Field
The invention relates to the field of high-temperature smelting of high-temperature alloy master alloy, in particular to a method capable of effectively reducing or even eliminating secondary shrinkage cavity of cast high-temperature alloy master alloy.
Background
The vacuum induction smelting process of high temperature alloy mother alloy adopts mold casting process, and the mold is cast iron or No. 45 steel. In the process of casting and solidification, the position of final solidification is in the middle of the master alloy bar, and the master alloy bar cannot be supplemented by surrounding molten metal due to thermal expansion and cold contraction, so that a closed shrinkage cavity is formed, and the secondary shrinkage cavity is called as a secondary shrinkage cavity. The conventional pouring mode cannot eliminate secondary shrinkage cavities, and the secondary shrinkage cavities exist in the alloy ingot and are distributed continuously or discontinuously, so that the secondary shrinkage cavities cannot be cut off. For some precision casting applications, the remelting casting application is not influenced as long as the secondary shrinkage cavity is ensured not to expose. However, some remelting castings require cutting into short bars of the master alloy, which inevitably exposes shrinkage cavities and increases the risk of moisture and impurities. In the field of 3D printing, a plasma rotating electrode mode (PREP process) is adopted, and the rotating speed of the master alloy is up to 25000 r/min, so that the dynamic balance of the master alloy is seriously influenced by the existence of shrinkage cavities, the fine powder rate is low, and even precision equipment is damaged.
Solves the problem of shrinkage cavity, and has many beneficial explorations at home and abroad. Patent ZL200720065511.7 and patent ZL201110099504.x both achieve the purpose of greatly reducing shrinkage cavities by horizontal continuous casting. However, the horizontal continuous casting is high in cost at present, particularly, the patent zl201110099504.x belongs to vacuum horizontal continuous casting, the technical requirement is extremely high, the technology is still at the improvement stage at present, and the production cost is about 30% higher than that of the common die casting.
Patent ZL201611268089.5 has realized concentrating the secondary shrinkage cavity of inside under vacuum condition and has guided near the corner through setting up heating and water cooling plant to can conveniently excise, reduce inside secondary shrinkage cavity. This process is only suitable for die-casting production of a single die tube or a small number of die tubes with relatively large spacing. For the casting of master alloys of superalloys commonly used in industry, the mould tubes are generally of the order of 5 rows, at least 3 rows, and this heating and cooling arrangement cannot be achieved.
Patent ZL201410219670.2 was manufactured by uniformly brushing a first suspension of Al2O3, CaO, MgO (formulation A) onto the inner surface of a mold tube; uniformly brushing a second suspension (formula B) of Al2O3, CaO, TiO2 and floating beads on the inner surface of the 1/3-1/4 die cavity at the upper part of the die tube; the comprehensive characteristics that the heat conductivity of the formula A is low and the mixed aqueous solution coating is strong in adhesion with a casting mold after being dried are utilized, so that the surface finish of the cast ingot is improved; by utilizing the heat insulation and preservation of the floating beads in the formula B and the high coating property of the mixed suspension of the floating beads, Al2O3, CaO and TiO2, the upper part 1/3-1/4 of the casting mold has the function of a heat insulation riser at the cavity height, and the metal melt is slowly solidified at the cavity height to play a good feeding role and obviously reduce the shrinkage cavity depth. The process is simple and feasible, but the biggest problem is that the suspension liquid applied by the process pollutes the high-temperature alloy melt, the 400-mesh oxide adopted by the process corresponds to the particle size of 37.5 mu m, and the inclusion is carried out when the oxide is mixed into the molten steel (foreign matters larger than 1 mu m in the high-temperature alloy are considered as inclusion).
Patent ZL201811281133.5 also works by heating the mold tube in a vacuum chamber to create a temperature gradient and thereby reduce shrinkage porosity. Patent ZL201610232749.8 improves surface quality and internal shrinkage cavity by adding a water port pipe and a water port switch on a diverter plate and introducing the functions of stretching and vibrating to break dendrites. These operations are complex, are not easy to implement in mass production under vacuum, and may destroy the advantages of the existing casting processes.
Disclosure of Invention
The purpose of the invention is as follows: aiming at the problems in the prior art, the invention provides a method for reducing the secondary shrinkage cavity of a high-temperature alloy master alloy bar, which can economically and effectively reduce, even completely eliminate the secondary shrinkage cavity of the vacuum smelting high-temperature alloy master alloy bar.
The technical scheme is as follows: the invention provides a method for reducing secondary shrinkage cavity of a high-temperature alloy master alloy, which is characterized by comprising the following steps of: the method comprises the steps of carrying out vacuum overheating casting on high-temperature alloy master alloy to a mold frame which is preheated, insulated and loaded into a mold car chamber, then rapidly sealing the mold car chamber, then filling gas into the sealed mold car chamber within preset time, pressurizing to preset pressure, carrying out hot isostatic pressing, increasing the pressure in the sealed mold car chamber due to the fact that the gas is heated and expanded during the hot isostatic pressing, and when the pressure in the sealed mold car chamber is reduced to the preset pressure again, releasing the pressure in the sealed mold car chamber to atmospheric pressure, and then moving out the mold frame.
Preferably, the mold frame should be preheated to 750 ℃ and held for more than 4 hours.
Preferably, the gas filled into the sealed die car chamber within a preset time is high-pressure nitrogen or high-pressure carbon dioxide gas.
Preferably, the preset time is within 3 min.
Preferably, the preset pressure is 10-15 MPa, and the gas pressure in the sealed die car chamber during hot isostatic pressing is increased to 10-25 MPa due to thermal expansion.
Preferably, the casting temperature of the vacuum superheat casting is 150-200 ℃ higher than the melting point of the high-temperature alloy master alloy, and the vacuum condition is 1.3 Pa.
Preferably, the superalloy master alloy is a nickel-based superalloy or an iron-based superalloy.
Has the advantages that: the design principle of the invention is based on the fact that a master alloy rod has a temperature gradient from the core to the outer surface in the process of solidifying the high-temperature alloy from a molten liquid state (with zero strength) to a solid state, and the temperature and the strength of the master alloy rod are in inverse proportion. By utilizing the characteristic that the yield strength of the high-temperature alloy master alloy is close to zero in the initial melting state after the high-temperature alloy master alloy is subjected to vacuum overheating casting, high-pressure gas is quickly filled, the high-temperature master alloy rod is placed in a high-pressure gas atmosphere, and the hot isostatic pressing of the high temperature of the master alloy rod and the high pressure of the external gas is utilized, so that the effect similar to die casting can be achieved by adopting lower gas pressure, the secondary shrinkage cavity effect is greatly reduced, and even the internal shrinkage cavity is eliminated.
The yield strength of the iron-based high-temperature alloy at 1000 ℃ is from 40MPa to 150MPa according to the grades of different materials. Assuming 1480 ℃ is its melting temperature, then its corresponding hot isostatic pressing temperature should be controlled at 1337 ℃ to 1438 ℃ at a pressure of 12MPa. Under the same conditions, the hot isostatic pressing temperature can be reduced by 45 ℃ for every 5MPa increase of the pressure.
The yield strength of the nickel-based superalloy at 1000 ℃ is from 50MPa to 170MPa according to the grades of different materials. Assuming 1450 ℃ is its melting temperature, its corresponding hot isostatic pressing temperature should be controlled between 1343 ℃ and 1418 ℃ at a pressure of 12MPa. Under the same conditions, the hot isostatic pressing temperature can be reduced by 40 ℃ for every 5MPa increase of the pressure.
The invention has the advantages that:
1. the vacuum induction melting and hot isostatic pressing shrinkage cavity eliminating processes of the high-temperature alloy master alloy are organically combined, and the heat of the vacuum induction melting is utilized to directly pressurize to reduce or even eliminate shrinkage cavities;
2. and nitrogen or carbon dioxide is used as a pressurizing gas, and no additional heating source is needed, so that the cost is low.
Detailed Description
The present invention will be described in detail with reference to specific examples.
Embodiment 1:
the embodiment provides a method for reducing secondary shrinkage cavity of a K213 iron-based high-temperature alloy.
The grade of K213 iron-based high-temperature alloy is selected, and the initial melting temperature of K213 is 1300-1400 ℃. The specific component ranges and actual values are shown in the following table 1:
TABLE 1
Step 1, selecting mould pipes with the inner diameter of 80mm, the outer diameter of 100mm and the length of 700mm, and taking 15 mould pipes as a mould frame, wherein the mould frame is wrapped by heat-preservation cotton with the thickness of 28mm, so that heat loss is prevented;
and 2, baking the mould at 750 ℃, preserving heat for 4 hours, loading the mould into a mould car chamber 5 minutes before casting, quickly vacuumizing, and moving the mould into a smelting chamber.
And 3, selecting the casting temperature of 1580 ℃, and carrying out rapid casting (on the premise that molten steel does not overflow) under the condition that the vacuum degree is 1.3 Pa.
And 4, after the casting is finished, moving the mold car into a mold car chamber, sealing the mold car chamber, quickly pressurizing common nitrogen through a 3-way gas bottle, and quickly pressurizing the pressure in the mold car chamber to 12MPa within 2 minutes.
And 5, closing the furnace for hot isostatic pressing, wherein the pressure is raised to 18-20 MPa due to the thermal expansion of nitrogen. And then cooling the die car chamber along with the furnace until the pressure of the die car chamber returns to 12MPa again, slowly releasing the pressure and then discharging the die car chamber out of the furnace.
After this process, the internal shrinkage cavity of K213 is relieved from the continuous, central secondary shrinkage cavity of maximum size 8mm, to a central secondary shrinkage cavity of point-like and maximum size 3 mm.
Embodiment 2:
the present embodiment provides a method of mitigating K418 secondary shrinkage of a nickel-base superalloy.
The nickel-based high-temperature alloy with the mark number of K418 is selected, and the initial melting temperature of the K418 is 1250-1350 ℃. The specific component ranges and actual values are shown in the following table 2:
TABLE 2
Step 1, selecting mould pipes with the inner diameter of 80mm, the outer diameter of 100mm and the length of 700mm, and taking 15 mould pipes as a mould frame, wherein the mould frame is wrapped by heat-preservation cotton with the thickness of 28mm, so that heat loss is prevented;
and 2, baking the mould at 750 ℃, preserving heat for 4 hours, loading the mould into a mould car chamber 5 minutes before casting, quickly vacuumizing, and moving the mould into a smelting chamber.
And 3, selecting the casting temperature to be 1530 ℃, and carrying out rapid casting (on the premise that molten steel does not overflow) under the condition that the vacuum degree is 1.3 Pa.
And 4, after the casting is finished, moving the mold car into a mold car chamber, sealing the mold car chamber, quickly pressurizing common nitrogen through a 3-way gas bottle, and quickly pressurizing the pressure in the mold car chamber to 12MPa within 2 minutes.
And 5, closing the furnace for hot isostatic pressing, wherein the pressure is raised to 18-20 MPa due to the thermal expansion of nitrogen. And then cooling the die car chamber along with the furnace until the pressure of the die car chamber returns to 12MPa again, slowly releasing the pressure and then discharging the die car chamber out of the furnace.
After this process, the internal shrinkage cavity of K418 was relieved from the continuous, 6mm maximum central secondary shrinkage cavity to the very individual, 2mm maximum central secondary shrinkage cavity.
The above embodiments are merely illustrative of the technical concepts and features of the present invention, and the purpose of the embodiments is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.
Claims (7)
1. A method for reducing secondary shrinkage cavity of a high-temperature alloy master alloy is characterized by comprising the following steps: vacuum overheating casting the high-temperature alloy master alloy into a mold frame which is preheated, insulated and loaded into a mold car chamber, and rapidly sealing the mold car chamber; and then, filling gas into the sealed die car chamber within a preset time, pressurizing to a preset pressure, and carrying out hot isostatic pressing, wherein the pressure in the sealed die car chamber is increased due to the expansion of the gas caused by heating during the hot isostatic pressing, and when the pressure in the sealed die car chamber is reduced to the preset pressure again, the sealed die car chamber is decompressed to the atmospheric pressure, and then the die frame is moved out.
2. The method of reducing secondary shrinkage of superalloy master alloy as in claim 1, wherein the mold frame is preheated to 750 ℃ and held for more than 4 hours.
3. The method for reducing secondary shrinkage of superalloy master alloy as in claim 1, wherein the gas injected into the sealed die car chamber within a predetermined time is high pressure nitrogen or high pressure carbon dioxide gas.
4. The method of mitigating secondary shrinkage of a superalloy master alloy as in claim 1, wherein the predetermined time is within 3 minutes.
5. The method for reducing secondary shrinkage of a superalloy master alloy as claimed in claim 1, wherein the predetermined pressure is 10-15 MPa, and the gas pressure in the sealed die car chamber during hot isostatic pressing is increased to 10-25 MPa due to thermal expansion.
6. The method for reducing the secondary shrinkage cavity of the high-temperature alloy master alloy according to any one of claims 1 to 5, wherein the casting temperature of the vacuum superheat casting is 150-200 ℃ higher than the melting point of the high-temperature alloy master alloy, and the vacuum condition is 1.3 Pa.
7. The method of mitigating secondary shrinkage cavity of a superalloy master alloy as in any of claims 1 to 5, wherein the superalloy master alloy is a nickel-based superalloy or an iron-based superalloy.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911387605.XA CN111112587A (en) | 2019-12-30 | 2019-12-30 | Method for reducing secondary shrinkage cavity of high-temperature alloy master alloy |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112517862A (en) * | 2020-11-20 | 2021-03-19 | 中国科学院金属研究所 | Secondary hole shrinkage control method for large-size high-temperature alloy master alloy cast ingot |
| CN113714486A (en) * | 2021-09-01 | 2021-11-30 | 无锡天更蓝涡轮风机有限公司 | Device for forging liquid metal by using ultrahigh-pressure nitrogen |
Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0293960A1 (en) * | 1987-05-30 | 1988-12-07 | Ae Plc | Process and apparatus for metal casting |
| EP0293961A1 (en) * | 1987-05-30 | 1988-12-07 | Ae Plc | Casting method and apparatus therefor |
| EP0728546B1 (en) * | 1995-02-23 | 2000-04-26 | Howmet Corporation | Directionally solidified investment casting with improved filling |
| CN105834409A (en) * | 2016-05-20 | 2016-08-10 | 河南理工大学 | Integrated preparing and forming device for magnesium alloy thin-walled pieces |
| CN109848373A (en) * | 2019-04-01 | 2019-06-07 | 扬州峰明光电新材料有限公司 | The composite casting equipment and casting method of thick and large casting |
-
2019
- 2019-12-30 CN CN201911387605.XA patent/CN111112587A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0293960A1 (en) * | 1987-05-30 | 1988-12-07 | Ae Plc | Process and apparatus for metal casting |
| EP0293961A1 (en) * | 1987-05-30 | 1988-12-07 | Ae Plc | Casting method and apparatus therefor |
| EP0728546B1 (en) * | 1995-02-23 | 2000-04-26 | Howmet Corporation | Directionally solidified investment casting with improved filling |
| CN105834409A (en) * | 2016-05-20 | 2016-08-10 | 河南理工大学 | Integrated preparing and forming device for magnesium alloy thin-walled pieces |
| CN109848373A (en) * | 2019-04-01 | 2019-06-07 | 扬州峰明光电新材料有限公司 | The composite casting equipment and casting method of thick and large casting |
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112517862A (en) * | 2020-11-20 | 2021-03-19 | 中国科学院金属研究所 | Secondary hole shrinkage control method for large-size high-temperature alloy master alloy cast ingot |
| CN112517862B (en) * | 2020-11-20 | 2022-01-14 | 中国科学院金属研究所 | Secondary hole shrinkage control method for large-size high-temperature alloy master alloy cast ingot |
| CN113714486A (en) * | 2021-09-01 | 2021-11-30 | 无锡天更蓝涡轮风机有限公司 | Device for forging liquid metal by using ultrahigh-pressure nitrogen |
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Application publication date: 20200508 |