A super-pure smelting method of DZ125 directional high-temperature alloy return material

Abstract

The embodiment of the application discloses a kind of ultra-pure smelting methods of DZ125 directional high-temperature alloy return material.The molten droplet formed by high-energy beam spot bombardment carries out rapid degassing reaction at gas-liquid interface, and the total content of oxygen and nitrogen in the ingot obtained is not more than 10 ppm, realizing the ultra-low content control of impurity elements;Without the need for cold bed refining step, the continuous smelting is carried out by operating the ingot lifting system, which greatly improves the ultra-pure smelting efficiency of high-temperature alloy return material, solves the problem that the traditional single vacuum induction remelting method cannot achieve the deep removal effect of impurity elements such as oxygen and nitrogen, and can realize large-scale industrial ultra-pure smelting, which is helpful for the same grade recycling of directional high-temperature alloy return material and avoids the waste of strategic metal resources.

Description

Technical Field

[0001] This invention relates to the field of alloy smelting technology, specifically to an ultrapure smelting method for DZ125 directional high-temperature alloy return material. Background Technology

[0002] Directional solidification casting superalloys possess excellent comprehensive performance at medium and high temperatures, superior fatigue resistance, and good casting properties. They are primarily used to manufacture rotor blades and guide vanes for aerospace gas turbine engines. With the rapid development of aerospace technology, the demand for directional superalloys is increasing. Directional superalloys typically contain strategic metals such as Ni, Co, Cr, W, Mo, Ta, and Hf. However, due to the complex design of the gating system and the inherent scrap rate of the blades, the material utilization rate of alloy parts is usually only 10-20%, resulting in a large amount of recycled material. Because the casting process involves high-temperature remelting, the alloy melt reacts with the crucible and mold shell to form non-metallic impurities, mainly in the form of oxygen-nitrogen complexes, in the recycled material. This significantly increases the oxygen and nitrogen content in the alloy, resulting in a substantial reduction in high-temperature plasticity and fatigue life. Strict purification processes are necessary before recycling is even considered. Currently, China lacks recycled material purification and recycling technologies that meet the requirements for equivalent use. Therefore, recycled directional superalloys are not formally used domestically, leading to a serious waste of strategic metal resources.

[0003] DZ125 directional casting superalloy contains hafnium, which interacts strongly with impurity elements during smelting and casting. Therefore, the recycled material contains high levels of gaseous impurities such as oxygen and nitrogen, and the occurrence state of these impurities also changes. Traditional single-stage vacuum induction remelting processes cannot achieve deep removal. Electron beam melting technology, with its high vacuum and high energy density, is mainly used for smelting refractory metals and alloys, and its purification rate is significantly higher than other vacuum melting equipment. Currently, the main process for purifying multi-element alloys using electron beam melting is cold hearth furnace refining. However, electron beam refining suffers from the loss of main elements. Simply increasing the refining temperature and time to achieve high-energy beam irradiation of the melt to generate large superheat and promote impurity volatilization will also lead to severe volatilization of main elements in the recycled material, resulting in low melting efficiency and significantly increased recycling costs. Therefore, how to efficiently and quickly purify directional solidification casting superalloy recycled material and achieve ultra-low content control of impurities such as oxygen and nitrogen remains a challenge for the same-level reuse of directional alloy recycled material. Summary of the Invention

[0004] To address the aforementioned technical problems of high oxygen and nitrogen content in returned materials of directional casting superalloys, and the altered occurrence states of these impurities, traditional single-stage vacuum induction remelting processes cannot achieve deep removal, while electron beam cold-bed refining suffers from low melting efficiency and significantly increased recycling costs, this invention provides an ultra-pure melting method for DZ125 directional superalloy returned materials. This invention employs electron beam droplet melting technology, where molten droplets formed by high-energy beam bombardment undergo rapid degassing at the gas-liquid interface. The resulting ingot contains no more than 10 ppm of total oxygen and nitrogen, achieving ultra-low impurity content control. Furthermore, it eliminates the need for a cold-bed refining step, allowing for continuous melting via an ingot lifting system, thus significantly improving the ultra-pure melting efficiency of the directional superalloy returned materials. The present invention provides an ultrapure smelting method for DZ125 directional high-temperature alloy return material. Its advantage lies in solving the problem that traditional single-stage vacuum induction remelting methods cannot achieve deep removal of impurity elements such as oxygen and nitrogen. It can realize large-scale industrial ultrapure smelting, which is conducive to the same-level recycling of directional high-temperature alloy return material and reduces the waste of my country's strategic metal resources.

[0005] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0006] An ultrapure smelting method for DZ125 directional superalloy return material employs electron beam droplet melting technology. Molten droplets formed by high-energy beam bombardment undergo rapid degassing at the gas-liquid interface, resulting in an ingot with a total oxygen and nitrogen content not exceeding 10 ppm. This achieves ultra-low content control of impurity elements in the return material, solving the problem that traditional single-stage vacuum induction remelting methods cannot achieve deep removal of impurity elements such as oxygen and nitrogen. This method enables large-scale industrial ultrapure smelting. The method includes the following steps:

[0007] S1. Vacuum induction remelting is performed on the DZ125 directional high-temperature alloy return material to obtain a raw material bar with suitable size for electron beam melting.

[0008] S2. Place the raw material rod for electron beam melting into the feeding system of the electron beam melting equipment, fix the bottom ingot into the ingot lifting system and adjust it to the bottom of the water-cooled copper crucible, and turn on the electron beam melting equipment for preheating and vacuuming.

[0009] S3. After the vacuum levels in the melting chamber and electron gun chamber reach the required level, the electron gun is turned on, and the electron beam melting power and beam size are adjusted before melting. The high-energy beam bombards the surface of the raw material bar. After the raw material melts, it forms molten droplets that undergo rapid degassing in a high vacuum and superheat environment and drip into a water-cooled copper crucible. At the same time, the ingot lifting system is operated to slowly pull out the ingot that has been rapidly solidified in the water-cooled copper crucible at a certain melting speed. This state is maintained and melting is continued until the raw material bar is completely melted. The melting power is gradually reduced to zero.

[0010] S4. After the furnace body cools down, the ingot is removed, and the top impurity-rich area is cut off to obtain an electron beam ingot of directional alloy return material with ultra-low impurity element content control.

[0011] Further, in step S2, the inner diameter D1 of the water-cooled copper crucible is 50–300 mm; in step S3, the electron beam melting power P is 25–65 kW; and the ingot melting speed V is 25–200 cm⁻¹. 3 / min, and D1, P and V satisfy the following relationship: 0≤0.24*D1+0.16*VP≤10.

[0012] Through extensive experimental research, the inventors discovered that the parameters of the melting power are directly related to the inner diameter of the water-cooled copper crucible and the melting speed. Using different crucible inner diameters alters the heat radiation area during the melting process, while different melting speeds change the cooling loss value. When D1, P, and V satisfy the above relationship, it ensures that the DZ125 recycled material achieves deep removal of impurity elements during electron beam melting while controlling the burn-off of active main elements. When the value of 0.24*D1+0.16*VP is less than 0, the burn-off of main elements is severe; when the value of 0.24*D1+0.16*VP is greater than 10, the impurity removal effect decreases.

[0013] Further, in step S1, the diameter of the raw material rod for electron beam melting is D2 = 20~250mm, and D1 and D2 satisfy the following relationship: 1.2*D2≤D1≤1.6*D2.

[0014] Furthermore, in step S3, the diameter of the electron beam spot ranges from 40% to 80% of the inner diameter of the water-cooled copper crucible.

[0015] Further, in step S2, the electron beam melting equipment is turned on for preheating and vacuuming, and the vacuum degree of the melting chamber reaches less than 2 × 10⁻⁶. -2 The requirement is that the vacuum degree of the electron gun chamber should be less than 8 × 10⁻⁶ Pa. -3 After Pa's request, the electron gun was turned on to begin melting.

[0016] Furthermore, in step S2, the bottom ingot fixed to the ingot lifting system is obtained by machining from the same grade of oriented high-temperature alloy.

[0017] Furthermore, in step S4, the thickness of the impurity-rich region at the top of the electron beam melting ingot is 5-20 mm.

[0018] The embodiments of the present invention have the following advantages:

[0019] 1. The present invention provides an ultrapure smelting method for DZ125 directional high-temperature alloy return material, which innovatively applies electron beam drip melting technology to the ultrapure smelting of return materials such as directional high-temperature alloy gatings, risers, and scrap parts. It solves the problem that traditional single-stage vacuum induction remelting methods cannot achieve deep removal of impurity elements such as oxygen and nitrogen. It can realize efficient and rapid industrial continuous smelting, and the total oxygen and nitrogen content in the ingot can be reduced to below 10 (ppm), achieving ultra-low content control of impurity elements. This makes the purity of the return material reach the level of virgin material, promotes the same-level recycling of directional alloy return material, and reduces the waste of my country's strategic metal resources.

[0020] 2. This invention employs a high-energy electron beam to bombard oriented high-temperature alloy return material bars, forming molten droplets that undergo rapid degassing at the gas-liquid interface, achieving ultra-low content control of impurities such as oxygen and nitrogen. Since electron beam melting is a centralized heating method, in cold-bed melting processes, larger melts can only be removed through localized overheating combined with scanning mode adjustments, and impurities such as nitrides may diffuse and dissolve into the melt. This invention eliminates the need for a cold-bed refining step. In a high-vacuum, high-superheat furnace environment, the large specific surface area of ​​the molten droplets ensures sufficient degassing and decomposition reactions at the interface. Simultaneously, a suitable melting speed is matched with the ingot lifting system for continuous melting, significantly improving the ultra-pure melting efficiency of oriented high-temperature alloy return material. This invention provides an ultra-pure melting method for oriented high-temperature alloy return material, with simple process steps, high efficiency, and the ability to achieve large-scale industrial ultra-pure melting. Attached Figure Description

[0021] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0022] Figure 1 This is a photograph of molten droplets during the electron beam melting process of DZ125 directional high-temperature alloy return material provided in Embodiment 1 of the present invention;

[0023] Figure 2 The photograph shows an actual scene of the electron beam melting process of DZ125 directional high-temperature alloy return material provided in Comparative Example 1 of this invention, in which a jamming phenomenon occurred, leading to the termination of the melting process. Detailed Implementation

[0024] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Example 1

[0026] This embodiment provides a method for ultrapure smelting of DZ125 directional superalloy return material, including the following steps:

[0027] (1) Vacuum induction remelting of waste parts of directional high temperature alloy DZ125 was carried out to obtain a raw material bar for electron beam melting with a diameter of 60 (mm);

[0028] (2) Place the raw material rod for electron beam melting into the feeding system of the electron beam melting equipment, use induction melting to process the DZ125 alloy ingot, use a water-cooled copper crucible with an inner diameter of 90 (mm), and turn on the electron beam melting equipment for preheating and vacuuming.

[0029] (3) The vacuum degree of the melting chamber reaches 7.9×10 -3 (Pa), the vacuum degree of the electron gun chamber reaches 2.3×10. -3 (Pa) Turn on the electron gun, adjust the electron beam melting power to 36 kW, adjust the beam diameter to 50 mm, and begin melting. Simultaneously, operate the ingot lifting system to move the ingot 150 cm... 3 The raw material bar is pulled out at a melting speed of ( / min) and continuously melted until it is completely melted, and the melting power is gradually reduced to zero.

[0030] (4) After the furnace body is cooled, the ingot is taken out and the impurity enrichment area with a thickness of 6 (mm) on the top is cut off to obtain DZ125 directional high temperature alloy return material electron beam ingot.

[0031] This invention uses a high-energy electron beam to bombard a returning material bar, forming a structure like... Figure 1 As shown, impurity elements in the molten droplets can undergo rapid degassing and decomposition reactions at the gas-liquid interface, achieving ultra-low content control of impurity elements such as oxygen and nitrogen. The total oxygen and nitrogen content in the electron beam casting of the DZ125 directional high-temperature alloy return material provided in this embodiment is 6 ppm, achieving deep impurity removal from the return material. Simultaneously, it effectively avoids excessive burning loss of active main elements such as Cr, with an actual Cr burning loss rate not exceeding 1.5 wt%. The actual Cr content after smelting is >8.65 wt%, meeting the composition requirements of the DZ125 alloy.

[0032] Example 2

[0033] This embodiment provides a method for ultrapure smelting of DZ125 directional superalloy return material, including the following steps:

[0034] (1) Vacuum induction remelting of waste parts of directional high temperature alloy DZ125 was carried out to obtain a raw material bar for electron beam melting with a diameter of 100 (mm);

[0035] (2) Place the raw material rod for electron beam melting into the feeding system of the electron beam melting equipment, use induction melting to process the DZ125 alloy ingot, use a water-cooled copper crucible with an inner diameter of 120 (mm), and turn on the electron beam melting equipment for preheating and vacuuming.

[0036] (3) The vacuum degree of the melting chamber reaches 1.0×10⁻⁶. -2 (Pa), the vacuum degree of the electron gun chamber reaches 4.5×10 -3 (Pa), turn on the electron gun, adjust the electron beam melting power to 27 (kW), adjust the beam diameter to 90 (mm), and begin melting. Simultaneously, operate the ingot lifting system to move the ingot at a height of 30 (cm). 3 The raw material bar is pulled out at a melting speed of ( / min) and continuously melted until it is completely melted, and the melting power is gradually reduced to zero.

[0037] (4) After the furnace body is cooled, the ingot is taken out and the impurity enrichment area with a thickness of 10 (mm) on the top is cut off to obtain DZ125 directional high temperature alloy return material electron beam ingot.

[0038] The DZ125 directional high-temperature alloy return material electron beam casting provided in this embodiment has a total oxygen and nitrogen content of 8 (ppm) in the casting, which achieves the effect of deep impurity removal of the return material. At the same time, it effectively avoids excessive burning loss of active elements such as Cr. The actual Cr burning loss rate is 0.8wt%, and the actual Cr content after melting is 8.69wt%, which meets the composition requirements of DZ125 alloy.

[0039] Example 3

[0040] This embodiment provides a method for ultrapure smelting of DZ125 directional superalloy return material, including the following steps:

[0041] (1) Vacuum induction remelting was performed on the riser and gating part of the directional high temperature alloy DZ125 to obtain two raw material bars with a diameter of 160 (mm) and a length of 1.3 (m) for electron beam melting;

[0042] (2) Place two raw material bars for electron beam melting into the feeding system of the electron beam melting equipment, process the bottom ingot by electroslag remelting DZ125 alloy, use a water-cooled copper crucible with an inner diameter of 200 (mm), and turn on the electron beam melting equipment for preheating and vacuuming.

[0043] (3) The vacuum degree of the melting chamber reaches 1.3×10 -2 (Pa), the vacuum level of the electron gun chamber reaches 7.2×10⁻⁶. -3 (Pa), turn on the electron gun, adjust the electron beam melting power to 50 (kW), adjust the beam diameter to 80 (mm), and begin melting. Simultaneously, operate the ingot lifting system to move the ingot at a height of 40 (cm). 3 Pull out the melting speed of / min), operate the feeding system to continuously melt until both raw material bars are completely melted, and gradually reduce the melting power to zero.

[0044] (4) After the furnace body is cooled, the ingot is taken out and the impurity enrichment area with a thickness of 20 (mm) on the top is cut off to obtain DZ125 directional high temperature alloy return material electron beam ingot.

[0045] The DZ125 directional high-temperature alloy return material electron beam casting provided in this embodiment has a total oxygen and nitrogen content of 9 ppm. After ultra-pure melting, the total weight of the casting is 423 kg. This achieves ultra-low content control of impurity elements in directional high-temperature alloy return materials of more than 100 kg. At the same time, it effectively avoids excessive burning of active elements such as Cr. The actual Cr burning rate does not exceed 2.0 wt%, and the actual Cr content after melting is >8.60 wt%, which meets the composition requirements of DZ125 alloy.

[0046] Comparative Example 1

[0047] This comparative example provides a method for smelting DZ125 directional superalloy return material, including the following steps:

[0048] (1) Vacuum induction remelting of waste parts of directional high temperature alloy DZ125 was carried out to obtain a raw material bar for electron beam melting with a diameter of 100 (mm);

[0049] (2) Place the raw material rod for electron beam melting into the feeding system of the electron beam melting equipment, use induction melting to process the DZ125 alloy bottom ingot, use a water-cooled copper crucible with an inner diameter of 150 (mm), and turn on the electron beam melting equipment for preheating and vacuuming.

[0050] (3) The vacuum degree of the melting chamber reaches 1.5×10 -2 (Pa), the vacuum degree of the electron gun chamber reaches 7.0×10⁻⁶. -3 (Pa), turn on the electron gun, adjust the electron beam melting power to 25 (kW), adjust the beam diameter to 60 (mm), and begin melting. Simultaneously, operate the ingot lifting system to move the ingot at a height of 120 (cm). 3 The raw material bar is pulled out at a melting speed of ( / min) and continuously melted until it is completely melted, and the melting power is gradually reduced to zero.

[0051] (4) After the furnace body is cooled, the ingot is taken out and the impurity enrichment area with a thickness of 15 (mm) on the top is cut off to obtain the electron beam ingot of directional high temperature alloy DZ125 return material.

[0052] The DZ125 high-temperature alloy return material provided in this comparative example experienced ingot jamming during electron beam melting, leading to melting stoppage. Actual photos are shown below. Figure 2 As shown. In Comparative Example 1, due to the mismatch between the melting power and melting speed, the molten liquid level was difficult to control, causing the molten liquid to accumulate on the upper part of the crucible wall and gradually overflow, resulting in ingot jamming and halting the melting process. Furthermore, the comparative example includes the relationship between the electron beam melting power P, melting speed V, and the inner diameter D1 of the crucible, 0.24*D1+0.16*VP>10, indicating a significant decrease in impurity removal efficiency. Testing revealed that the DZ125 directional high-temperature alloy return ingot provided in this comparative example contained 10 ppm of oxygen and 6 ppm of nitrogen, failing to achieve the desired deep impurity removal effect.

[0053] Although the present invention has been described in detail above with general descriptions and specific embodiments, modifications or improvements can be made to it, which will be obvious to those skilled in the art. Therefore, all such modifications or improvements made without departing from the spirit of the present invention fall within the scope of protection claimed by the present invention.

Claims

1. A method for ultrapure smelting of DZ125 directional superalloy return material, characterized in that, The method includes the following steps: S1. Vacuum induction remelting is performed on the DZ125 directional high-temperature alloy return material to obtain a raw material bar with suitable size for electron beam melting. S2. Place the raw material rod for electron beam melting into the feeding system of the electron beam melting equipment, fix the bottom ingot into the ingot lifting system and adjust it to the bottom of the water-cooled copper crucible, and turn on the electron beam melting equipment for preheating and vacuuming. S3. After the vacuum levels in the melting chamber and electron gun chamber reach the required level, the electron gun is turned on, and the electron beam melting power and beam size are adjusted before melting. The high-energy beam bombards the surface of the raw material bar. After the raw material melts, it forms molten droplets that undergo rapid degassing in a high vacuum and superheat environment and drip into a water-cooled copper crucible. At the same time, the ingot lifting system is operated to slowly pull out the ingot that has been rapidly solidified in the water-cooled copper crucible at a certain melting speed. This state is maintained and melting is continued until the raw material bar is completely melted. The melting power is gradually reduced to zero. S4. After the furnace body cools down, the ingot is taken out and the top impurity enrichment area is cut off to obtain an electron beam ingot of directional alloy return material with ultra-low impurity element content control. The total oxygen and nitrogen content in the electron beam ingot of directional alloy return material does not exceed 10 ppm. In step S2, the inner diameter D1 of the water-cooled copper crucible is 50 ~ 300 mm. In step S3, the electron beam melting power P is 25 ~ 65 kW, and the ingot melting speed V is 25 ~ 200 cm. 3 / min, and D1, P and V satisfy the following relationship: 0≤0.24*D1+0.16*VP≤10; In step S1, the diameter of the raw material rod for electron beam melting is D2 = 20 ~ 250 mm, and D1 and D2 satisfy the following relationship: 1.2*D2≤D1≤1.6*D2.

2. The ultrapure smelting method for DZ125 directional superalloy return material according to claim 1, characterized in that, In step S3, the diameter of the electron beam spot ranges from 40% to 80% of the inner diameter of the water-cooled copper crucible.

3. The ultrapure smelting method for DZ125 directional superalloy return material according to claim 1, characterized in that, In step S2, the electron beam melting equipment is turned on for preheating and vacuuming, and the vacuum degree of the melting chamber reaches less than 2×10⁻⁶. -2 The requirement is that the vacuum degree of the electron gun chamber should be less than 8 × 10⁻⁶ Pa. -3 After Pa's request, the electron gun was turned on to begin melting.

4. The ultrapure smelting method for DZ125 directional superalloy return material according to claim 1, characterized in that, In step S2, the bottom ingot fixed to the ingot lifting system is obtained by machining of the same grade of oriented high temperature alloy.

5. The ultrapure smelting method for DZ125 directional superalloy return material according to claim 1, characterized in that, In step S4, the thickness of the impurity-rich region at the top of the electron beam melting ingot is 5 to 20 mm.

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