An electron beam melting method for removing inclusions from high-aluminum and titanium superalloy return materials

Abstract

This invention discloses an electron beam melting method for removing inclusions from high-alumina and titanium superalloy recycled materials. The invention employs electron beam droplet melting technology, where a high-energy electron beam bombards the surface of the raw material to completely melt it. Under high vacuum and high-temperature irradiation in the melting furnace, impurities such as alumina on the surface of the molten droplets undergo in-situ decomposition reactions. Utilizing the unique flow field generated during electron beam droplet melting, combined with the electromagnetic field generated by beam spot stirring, undecomposed refractory inclusions are separated from the melt and concentrated at the beam spot irradiation site on the melt surface. This solves the problem of poor removal efficiency of numerous fine refractory inclusions distributed in high-alumina and titanium superalloy recycled materials using vacuum induction remelting, enabling large-scale industrial ultra-pure melting. The resulting electron beam ingots contain ≤0.3 (cm³) of inclusions such as alumina and titanium nitride. 2 / kg), which helps to realize the industrial-scale same-level recycling of a large amount of high-alumina and titanium casting high-temperature alloy return materials, and reduce the waste of my country's strategic metal resources.

Description

Technical Field

[0001] This invention relates to the field of metallurgical technology, specifically to an electron beam melting method for removing inclusions from high-alumina and titanium high-temperature alloy return materials. Background Technology

[0002] Cast superalloys, with their excellent high-temperature strength and good resistance to fatigue and oxidation corrosion, have become irreplaceable key materials for hot-end components of aerospace gas turbine engines. Al and Ti are the main forming elements of the γ' strengthening phase in nickel-based superalloys. As their content increases, the volume fraction of the γ' phase in the alloy also increases, thereby enhancing high-temperature performance. To improve the thrust-to-weight ratio of aero-engines, operating temperatures are increasing, placing higher demands on the material strength of hot-end components. Therefore, most of the hot-end components of advanced aero-engines use high-alumina and high-titanium nickel-based superalloys, with Al and Ti contents in single-crystal cast superalloys even exceeding 6%. However, the material utilization rate of cast superalloy parts is usually only 10-20%, and my country generates thousands of tons of recycled cast superalloys annually. Due to the high-temperature remelting casting process during the production of cast superalloy parts, the alloy melt reacts with the crucible, mold, etc., leading to a significant increase in the content of inclusions such as alumina in the recycled material. This significantly reduces the high-temperature plasticity and fatigue service life of the alloy, requiring strict purification processes before recycling can be considered. However, the current recycling rate of high-temperature alloys from casting in China is very low, especially the recycling of directional alloys and single-crystal alloys, which have not been formally applied, resulting in a serious waste of strategic metal resources such as Ni, Co, Cr, W, Mo, Ta, Hf, and Re.

[0003] In high-alumina and titanium casting superalloys, elements such as Al and Ti interact strongly with impurity elements during the smelting and casting process. Therefore, the inclusions in recycled materials mainly consist of fine, refractory inclusions, which cannot be effectively removed using traditional smelting processes such as vacuum induction remelting. Electron beam melting technology uses a high-energy electron beam generated by a high-voltage electric field as a heat source to bombard the raw materials, causing them to melt. Its high vacuum and high energy density characteristics result in a higher purification rate than other vacuum melting equipment. This technology is mainly applied in the smelting of refractory metals and alloys, and the preparation of high-purity titanium alloys. Currently, patented technologies for purifying superalloys using electron beam melting are mainly small-scale cold hearth furnace refining at the laboratory level, which cannot achieve large-scale continuous melting of recycled materials. Furthermore, existing patents for removing refractory inclusions all involve bombarding the melt surface with a high-energy beam during the refining process to decompose them in situ. However, increasing the refining steps and time, and pursuing the bombardment and decomposition of inclusions by the high-energy beam, leads to severe volatilization of the main elements in the recycled materials, significantly increasing the cost of recycling and hindering large-scale industrial application. Therefore, how to effectively and continuously purify high-alumina and titanium casting high-temperature alloy return materials and ensure ultra-low content control of refractory inclusions remains a challenge for the same-level reuse of return materials. Summary of the Invention

[0004] To address the aforementioned technical problems in high-alumina and titanium superalloy return materials containing fine refractory inclusions, which cannot be effectively removed by traditional smelting processes such as vacuum induction remelting, and where electron beam cold bed refining technology leads to severe volatilization of major elements in the return material, significantly increasing the cost of return material reuse and hindering large-scale continuous smelting, this invention provides an electron beam melting method for removing inclusions from high-alumina and titanium superalloy return materials. This invention uses a high-energy electron beam to bombard the surface of the raw material, causing complete melting. Under high vacuum and high-temperature irradiation in the melting furnace, impurities such as alumina on the surface of the molten droplets undergo in-situ decomposition. Utilizing the unique flow field generated during electron beam droplet melting, combined with the electromagnetic field generated by beam spot stirring, undecomposed refractory inclusions are separated from the melt and concentrated at the beam spot irradiation site on the melt surface. This solves the problem of poor removal efficiency of fine refractory inclusions widely distributed in high-alumina and titanium superalloy return materials using vacuum induction remelting, and avoids the problems of severe main element loss and significantly increased smelting costs caused by pursuing complete in-situ decomposition of inclusions. This invention provides an electron beam melting method for removing inclusions from high-aluminum and titanium superalloy return materials. Its advantage lies in its ability to achieve large-scale industrial-scale ultra-pure melting, yielding materials with an inclusion content ≤0.3 (cm³). 2 Electron beam casting of ingots ( / kg) can achieve deep removal of fine refractory inclusions in recycled master alloy ingots, which helps to realize the industrial-scale recycling of large quantities of high-temperature alloy recycled materials and reduce 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 electron beam melting method for removing inclusions from high-alumina and titanium superalloy recycled materials utilizes electron beam droplet melting technology to cause in-situ decomposition reactions of impurities (such as alumina) on the surface of molten droplets. Furthermore, the flow field generated during droplet melting, combined with an electromagnetic field, separates and enriches refractory inclusions from the melt, achieving deep removal of fine refractory inclusions from the interior of the recycled material, resulting in an inclusion content ≤0.3 (cm³). 2 The method comprises the following steps: ( / kg) of recycled ingots from recycled materials.

[0007] S1. After surface treatment, the high-aluminum and titanium high-temperature alloy return material is vacuum induction remelted 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 to the ingot lifting system and adjust it to the bottom of the water-cooled copper crucible. Turn on the electron beam melting equipment for preheating and vacuuming. After the vacuum degree of the melting chamber and electron gun chamber reaches the required level and remains stable, turn on the electron gun to start melting. Adjust the electron beam spot focus to the center of the crucible and slowly feed the raw material into the electron beam bombardment zone. After the raw material melts, the molten liquid drips into the water-cooled copper crucible. Operate the ingot lifting system to descend at a certain speed and adjust the electron beam melting power and feeding speed to keep the molten pool in the crucible at a certain height. Gradually pull the ingot, which has been rapidly cooled and solidified by the water-cooled copper crucible, out of the bottom of the molten pool from the bottom of the crucible. Maintain this state and continue melting until the raw material rod is completely melted. Gradually reduce the melting power to zero. After the furnace body cools, take out the ingot and cut off the top inclusion-rich area to obtain a high-purity, high-aluminum, and titanium return material electron beam regenerated ingot.

[0009] Further, in step S2, the inner diameter D of the water-cooled copper crucible is 150-320 mm, and the descent speed V of the ingot lifting system satisfies the following relationship with the inner diameter D of the water-cooled copper crucible: V = 1 × 10 5 / D 2 ~3×10 5 / D 2 mm / min.

[0010] Furthermore, in step S2, the melting power of the electron beam melting furnace during the melting process is P = 20~40kW, the height of the molten pool in the crucible is H = 5~20mm, and P, V and H satisfy the following relationship: 15≤P-0.93*H-1.32*V≤20.

[0011] Studies have found that when P - 0.93 * H - 1.32 * V < 15, the beam irradiation energy decreases, and the melting rate is too fast, leading to a weakening of the flow field stirring effect in the molten pool. Some undecomposed refractory inclusions precipitate to the bottom of the molten pool and remain inside the ingot after solidification, resulting in poor removal of fine refractory inclusions. When P - 0.93 * H - 1.32 * V > 20, the melt is exposed to high-energy beam irradiation for too long, resulting in severe volatilization of the main elements and a significant increase in smelting costs.

[0012] Furthermore, in step S1, the diameter of the raw material rod used for electron beam melting is in the range of 120 to 300 mm.

[0013] Furthermore, the inner diameter of the water-cooled copper crucible is not less than the diameter of the raw material rod used for electron beam melting.

[0014] Further, in step S2, the electron beam melting equipment is turned on for preheating and vacuuming. After the vacuum levels in the melting chamber and electron gun chamber reach the required level and remain stable, the electron gun is turned on to begin melting. The vacuum level in the melting chamber reaches less than 5 × 10⁻⁶. -2 The requirement is that the vacuum level of the electron gun chamber must be less than 1 × 10⁻⁶ Pa. -2 Pa's requirements.

[0015] Furthermore, in step S2, the bottom ingot fixed to the ingot lifting system is obtained by machining from a high-temperature alloy of the same grade.

[0016] Furthermore, in step S2, the thickness of the inclusion-rich area at the top of the electron beam melting ingot is 5-10 mm.

[0017] The embodiments of the present invention have the following advantages:

[0018] 1. The present invention provides an electron beam melting method for removing inclusions from recycled high-alumina and titanium superalloy materials. This method innovatively applies electron beam droplet melting technology to the ultrapure melting of recycled materials such as gating systems, risers, and scrap parts of high-alumina and titanium superalloy castings, achieving an inclusion content ≤0.3 (cm³). 2 Electron beam casting with a yield of / kg enables ultra-low control of fine refractory inclusions, allowing the purity of recycled high-aluminum and titanium casting high-temperature alloys to reach the level of virgin materials, promoting the same-level recycling of recycled materials, and reducing the waste of my country's strategic metal resources.

[0019] 2. This invention employs electron beam melting technology, using a high-energy electron beam to bombard the surface of the raw material, causing it to completely melt. Under the high vacuum and high-temperature irradiation within the melting furnace, impurities such as alumina on the surface of the molten droplets undergo in-situ decomposition reactions. The unique flow field generated during electron beam droplet melting, combined with the electromagnetic field generated by beam spot stirring, allows undecomposed refractory inclusions to separate from the melt and accumulate at the beam spot irradiation site on the melt surface. This solves the problem of poor removal efficiency of numerous fine refractory inclusions distributed in high-alumina and titanium recycled materials using vacuum induction remelting. Furthermore, it utilizes high-energy beam spot irradiation during the refining process. Compared with electron beam cold bed refining technology, which decomposes oxides in situ by bombarding the surface of the melt with long-term irradiation, the inclusion removal mechanism adopted in this invention, in addition to in-situ decomposition, also utilizes the enrichment effect of flow field combined with electromagnetic field. This ensures the deep removal of fine inclusions and avoids the problems of severe volatilization of main elements and significant increase in equipment energy consumption costs under long-term high-energy irradiation of the melt. Moreover, the process steps are less complex, enabling large-scale industrial ultrapure smelting and obtaining ultrapure high-alumina and titanium return material recycled ingots of more than 100 kilograms, which has significant advantages of high efficiency and low cost. Attached Figure Description

[0020] 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.

[0021] Figure 1 The electron beam regenerated ingot of high-alumina, titanium-cast high-temperature alloy K417 obtained by electron beam melting is provided in Embodiment 1 of the present invention. Detailed Implementation

[0022] 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.

[0023] Example 1

[0024] This embodiment provides an electron beam melting method for removing inclusions from high-aluminum and titanium superalloy return materials:

[0025] (1) After sandblasting and pickling the surface of the high-alumina and titanium casting high-temperature alloy K417 return material, vacuum induction remelting is performed to obtain a raw material bar for electron beam melting with a diameter of 230 (mm) and a length of 1 (m).

[0026] (2) A 230 mm diameter electron beam melting raw material bar is placed in the feeding system of the electron beam melting equipment. Melting is carried out using a water-cooled copper crucible with an inner diameter of 250 mm. The K417 master alloy is processed into a bottom ingot using induction melting. During the electron beam melting process, the vacuum degree of the melting chamber reaches 1.8 × 10⁻⁶. -2 (Pa), the vacuum degree of the electron gun chamber reaches 9.5×10 -3 (Pa), operate the ingot lifting system to descend at a speed of 4 (mm / min), use electron beam melting power of 30 (kW), maintain the height of the molten pool in the crucible at about 10 (mm), continuously melt until the raw material bar is completely melted, gradually reduce the melting power to zero, and remove the ingot after the furnace body cools. Figure 1 As shown, after removing the inclusion-rich region with a top thickness of 10 mm, a high-purity K417 return material electron beam regenerated ingot is obtained.

[0027] The K417 high-temperature alloy recycled ingot provided in this embodiment of the invention has a slag content reduced to 0.28 (cm³) using the electron beam button ingot method. 2 / kg), the total weight of the recycled ingot is 322 (kg), achieving ultra-low content control of fine refractory inclusions in high-aluminum and titanium casting high-temperature alloy return materials of more than 100 kg.

[0028] Example 2

[0029] This embodiment provides an electron beam melting method for removing inclusions from high-aluminum and titanium superalloy return materials:

[0030] (1) After sandblasting the high-alumina, titanium casting high-temperature alloy Mar-M246 return material, vacuum induction remelting was carried out to obtain a raw material bar with a diameter of 120 (mm) for electron beam melting.

[0031] (2) Place the 120 mm diameter electron beam melting raw material bar into the feeding system of the electron beam melting equipment. Melting is carried out using a water-cooled copper crucible with an inner diameter of 150 mm. The bottom ingot is processed by induction melting of Mar-M246 master alloy. The vacuum degree of the melting chamber is less than 1.5 × 10⁻⁶ mm. -2 (Pa), electron gun chamber vacuum level is less than 8.0×10 -3After (Pa), electron beam melting is carried out. The ingot lifting system is operated to descend at a speed of 12 (mm / min). The electron beam melting power is 38 (kW). The height of the molten pool in the crucible is maintained at about 6 (mm). The melting is continued until all the raw material rods are melted. The melting power is gradually reduced to zero. After the furnace body is cooled, the ingot is taken out. After removing the inclusion-rich area with a thickness of 8 (mm) at the top, a high-purity Mar-M246 return material electron beam regenerated ingot is obtained.

[0032] The Mar-M246 high-temperature alloy recycled ingot provided in this embodiment of the invention has a slag content of no more than 0.20 (cm³) as detected by the electron beam button ingot method. 2 / kg), the removal rate of oxide inclusions after smelting reaches more than 80%, realizing the ultra-low content control of fine refractory inclusions in the return material of high-alumina and titanium casting high-temperature alloys.

[0033] Comparative Example 1

[0034] This comparative example provides an electron beam melting method for removing inclusions from high-aluminum and titanium superalloy return materials:

[0035] (1) After sandblasting the high-alumina and titanium casting high-temperature alloy K417 return material, vacuum induction remelting was carried out to obtain a raw material bar with a diameter of 150 (mm) for electron beam melting.

[0036] (2) A 150 mm diameter electron beam melting raw material bar is placed in the feeding system of the electron beam melting equipment. Melting is carried out using a water-cooled copper crucible with an inner diameter of 180 mm. The ingot is processed using induction melting of K417 master alloy. The vacuum degree of the melting chamber reaches 2.5 × 10⁻⁶. -2 (Pa), the vacuum degree of the electron gun chamber reaches 9.5×10 -3 After (Pa), electron beam melting is carried out. The ingot lifting system is operated to descend at a speed of 15 (mm / min). The electron beam melting power is 20 (kW). The height of the molten pool in the crucible is maintained at about 20 (mm). The melting is continued until all the raw material rods are melted. The melting power is gradually reduced to zero. After the furnace body is cooled, the ingot is taken out. After removing the inclusion-rich area with a thickness of 5 (mm) at the top, K417 return material electron beam regenerated ingot is obtained.

[0037] The electron beam regenerated ingot of K417 high-temperature alloy provided in Comparative Example 1 of this invention has a slag content of 0.72 (cm³) as detected by the electron beam button ingot method. 2 / kg), because the descent speed of the ingot lifting system during the smelting process does not satisfy V=1×10 5 / D 2 ~3×10 5 / D 2The high melting speed (mm / min) and the low P-0.93*H-1.32*V < 15 result in reduced beam spot irradiation energy, preventing the in-situ decomposition of refractory inclusions such as alumina on the surface of the molten droplets. Furthermore, the excessively fast melting speed weakens the stirring effect of the flow field in the molten pool, causing some undecomposed refractory inclusions to precipitate to the bottom of the molten pool and remain inside the ingot after solidification. This results in limited removal of fine refractory inclusions, making it impossible to achieve ultra-low content control of inclusions in K417 return material.

[0038] 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. An electron beam melting method for removing inclusions from a high-aluminum, titanium high-temperature alloy return material, characterized by, The surface impurities of the molten droplets are decomposed in-situ by using electron beam droplet melting technology; and the flow field generated during the droplet melting process is combined with the electromagnetic field to separate and enrich the refractory inclusions from the melt, so as to achieve the effect of deeply removing the small refractory inclusions inside the return material, and obtain the return material regeneration ingot with the inclusion content ≤0.3 (cm 2 / kg). The method comprises the following steps: S1, the high aluminum, titanium high-temperature alloy return material is subjected to surface treatment, and then vacuum induction remelting is adopted to obtain a raw material rod with a proper size for electron beam melting; S2, the raw material rod for electron beam melting is placed in a feeding system of an electron beam melting device, a bottom ingot is fixed to an ingot lifting system and adjusted to the bottom of a water-cooled copper crucible, the electron beam melting device is started to preheat and vacuumize, the vacuum degree of the melting chamber and the electron gun chamber reaches the requirement and is kept stable, then the electron gun is opened to start melting, the electron beam spot focus is adjusted to be aligned with the center of the crucible, the raw material is slowly fed into the electron beam bombardment area, the raw material is melted, the molten liquid drops into the water-cooled copper crucible, the ingot lifting system is operated to be lowered at a certain speed, the electron beam melting power and the feeding speed are adjusted, the molten pool in the crucible is kept at a certain height, the bottom of the molten pool is rapidly cooled and solidified by the water-cooled copper crucible, the ingot is gradually pulled out from the bottom of the crucible, and the state is kept to continuously melt until the raw material rod is completely melted, the melting power is gradually reduced to zero, the ingot is taken out after the furnace body is cooled, and the top inclusion enrichment area is cut off, thereby obtaining a high-purity high-aluminum and titanium return material electron beam regenerated ingot; In step S2, the water-cooled copper crucible has an inner diameter D of 150-320 mm, and the lowering speed V of the ingot lifting system and the inner diameter D of the water-cooled copper crucible satisfy the following relationship: V=1×10 5 / D 2 ~ 3×10 5 / D 2 mm / min. In step S2, the melting power P of the electron beam melting furnace during the melting process is 20-40 kW, the height H of the molten pool in the crucible is 5-20 mm, and P, V and H satisfy the following relationship: 15≤P-0.93*H-1.32*V≤20.

2. The electron beam melting method for removing inclusions from a high-aluminum, titanium high-temperature alloy return material according to claim 1, characterized by, In step S1, the diameter of the raw material rod for electron beam melting is 120-300 mm.

3. The electron beam melting method for removing inclusions from a high-aluminum, titanium high-temperature alloy return material according to claim 1, characterized by, The inner diameter size of the water-cooled copper crucible is not less than the diameter size of the raw material rod for electron beam melting.

4. The electron beam melting method for removing inclusions in a high-aluminum, titanium high-temperature alloy return material according to claim 1, characterized by, In step S2, the electron beam melting device is started for preheating and vacuumizing, and the vacuum degree of the melting chamber and the electron gun chamber reaches the requirement and is kept stable, then the electron gun is opened to start melting, wherein the vacuum degree of the melting chamber reaches less than 5×10 -2 Pa, and the vacuum degree of the electron gun chamber reaches less than 1×10 -2 Pa.

5. The electron beam melting method for removing inclusions from a high-aluminum, titanium high-temperature alloy return material according to claim 1, characterized by, In step S2, the bottom ingot fixed to the ingot lifting system is obtained by machining the same brand high-temperature alloy.

6. The electron beam melting method for removing inclusions in a high-aluminum, titanium high-temperature alloy return material according to claim 1, characterized by, In step S2, the thickness of the top inclusion enrichment area of the electron beam melting ingot which is cut off is 5-10 mm.

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