阅读说明：本技术 一种去除高温合金中高密度夹杂物的方法 (Method for removing high-density inclusions in high-temperature alloy ) 是由 谭毅 游小刚 周海晶 孟凡国 王轶农 于 2020-12-28 设计创作，主要内容包括：本发明提供一种去除高温合金中高密度夹杂物的方法,包括如下步骤：S1、高温合金原材料的预处理；S2、电子束精炼去除高温合金中的高密度夹杂物,得到高纯度的DD406高温合金铸锭。本发明利用电子束精炼过程中的局部大过热环境实现熔体内部小尺寸高密度夹杂物的溶解去除,利用夹杂物与熔体的密度差以及马兰戈尼效应加速大尺寸夹杂物的沉降,进而通过凝壳捕获机制加以去除,从而达到全面去除合金中的高密度夹杂物的目的。(The invention provides a method for removing high-density inclusions in a high-temperature alloy, which comprises the following steps: s1, preprocessing a high-temperature alloy raw material; and S2, removing high-density inclusions in the high-temperature alloy by electron beam refining to obtain the high-purity DD406 high-temperature alloy ingot. The invention utilizes local large overheating environment in the electron beam refining process to realize the dissolution and removal of small-size high-density inclusions in the melt, accelerates the sedimentation of large-size inclusions by utilizing the density difference between the inclusions and the melt and the Marangoni effect, and further removes the large-size inclusions through a skull capturing mechanism, thereby achieving the purpose of comprehensively removing the high-density inclusions in the alloy.)

1. A method for removing high-density inclusions in a high-temperature alloy is characterized by comprising the following steps:

s1, pretreatment of the high-temperature alloy raw material:

s11, the raw material is DD406 alloy containing high-density inclusions;

s12, processing the raw materials to a proper size, wherein the raw materials can be placed into a water-cooled copper crucible for refining;

s13, polishing the processed raw material, and removing ceramic adhesion, an oxidation layer and processing traces on the surface to ensure that the alloy has no external pollutants;

s14, cleaning and drying the polished raw materials for later use;

s2, removing high-density inclusions in the high-temperature alloy through electron beam refining:

s21, cleaning the water-cooled copper crucible for electron beam refining and solidification: polishing, wiping with alcohol and drying to ensure that the water-cooled copper crucible is clean and pollution-free;

s22, cleaning pollutants on the furnace body and the furnace wall of the electron beam melting furnace, and avoiding the introduction of foreign impurities in the refining process;

s23, placing the pretreated raw material in a water-cooled copper crucible, and closing an electron beam melting furnace door after the raw material is determined to be ready and a furnace body is cleaned;

s24, pre-vacuumizing the electron beam smelting furnace and the electron gun body to reach the target vacuum degree; preheating the electron gun after the target vacuum degree is reached;

s25, after preheating, uniformly scanning by using a left-side electron gun to melt the raw materials;

s26, after the raw materials are completely melted, refining the raw materials for 10 min;

s27, performing electron beam refining for 10min, and then performing overheating treatment on the melt;

s28, after the melt is subjected to overheating treatment, continuously refining the raw material, and fully settling large-size high-density inclusions;

s29, after refining, instantly adjusting the beam current of the electron gun on the left side to 0mA, and simultaneously starting a melting crucible dumping mechanism to enable the melt refined in the water-cooled melting copper crucible to flow into the water-cooled solidifying copper crucible, and the skull in the water-cooled melting copper crucible is kept in the original crucible;

s210, uniformly scanning the high-temperature alloy melt in the water-cooled copper crucible for solidification by using the right-side electron gun to ensure that the surface of the melt in the water-cooled copper crucible for solidification is uniform;

s211, closing high voltage of the left electron gun and the right electron gun, increasing the beam current of the two electron guns to a certain value to reduce the high voltage value from 30kV to 0kV, and then closing the electron guns to fully solidify and cool the cast ingot in a water-cooled copper crucible for solidification;

s212, taking out the DD406 alloy ingot after the furnace body, the gun body and the ingot are fully cooled, and obtaining the high-purity DD406 high-temperature alloy ingot.

2. The method for removing high-density inclusions in the high-temperature alloy according to claim 1, wherein the specific steps of the step S14 are as follows:

and ultrasonically cleaning the polished DD406 alloy raw material by using deionized water and alcohol respectively, cleaning for three times by using the deionized water and the ultrasonic, placing the alloy into a drying box after cleaning, and drying at 30 ℃ for electron beam refining.

3. The method for removing high-density inclusions in the high-temperature alloy according to claim 1, wherein the specific steps of the step S24 are as follows:

opening electron beam refining equipment, and pumping the furnace body and the electron gun body of the electron beam smelting furnace to a target vacuum state, wherein the vacuum degree of the furnace body is required to be less than 5 multiplied by 10^-2Pa, the vacuum degree of the gun body is required to be less than 5 multiplied by 10^-3Pa, starting electron guns on the left and right sides after the target vacuum degree is reached, enabling the beam current size to be 120mA, and preheating for 12 minutes.

4. The method for removing high-density inclusions in the high-temperature alloy according to claim 1, wherein the specific steps of the step S25 are as follows:

after preheating is finished, adjusting the beam current of the electron guns on the left side and the right side to 0, starting high voltage, slowly increasing the beam current of the electron gun on the left side to 500mA after the high voltage reaches 30kV and is stable, wherein the radius of a beam spot is 20-25 mm, and uniformly scanning the DD406 alloy raw material in the water-cooled copper crucible to uniformly heat and melt the raw material.

5. The method for removing high-density inclusions in the high-temperature alloy according to claim 1, wherein the specific steps of the step S26 are as follows:

after the alloy is completely melted, the alloy is continuously refined for 10min in an electron beam annular scanning mode by keeping the parameters, so that volatile impurities in the high-temperature alloy melt are fully removed, and meanwhile, large-size high-density inclusions are gradually settled to the bottom of a molten pool and are captured by a skull.

6. The method for removing high-density inclusions in the high-temperature alloy according to claim 1, wherein the specific steps of the step S27 are as follows:

and after refining by electron beams for 10min, rapidly increasing the beam current of the electron beams on the left side to 800mA, keeping the radius of a beam spot unchanged, fixing the position of the beam spot to the center of the ingot after increasing to the specified power, and carrying out melt overheating treatment for 10min under the condition, so that small-size inclusions, carbides and the like in the melt are fully dissolved, and simultaneously promoting the vacuum degassing reaction of the high-temperature alloy melt.

7. The method for removing high-density inclusions in the high-temperature alloy according to claim 1, wherein the specific steps of the step S28 are as follows:

and (3) after the melt is subjected to overheating treatment, reducing the beam current to 500mA, and continuously refining the alloy for 10min to fully settle large-size high-density inclusions.

8. The method for removing high-density inclusions in the high-temperature alloy according to claim 1, wherein the specific steps of the step S210 are as follows:

increasing the beam current of the right-side electron gun to 400mA, adjusting the radius of the beam spot to 20-25 mm, keeping the parameters of the electron gun unchanged, uniformly scanning the high-temperature alloy melt in the water-cooled copper crucible for solidification for 5min, so that the surface of the melt in the water-cooled copper crucible for solidification is uniform, and then reducing the beam current of the right-side electron gun to 0 mA.

Technical Field

The invention relates to a method for removing high-density inclusions in a high-temperature alloy.

Background

A large amount of alloying elements can be added in the preparation process of the high-temperature alloy, so that the high-temperature alloy has good service performance, and with the continuous improvement of the use requirement of the alloy, some noble metal elements such as Ta, Hf, Re and the like are gradually added into the high-temperature alloy, particularly the oriented and single-crystal high-temperature alloy, so as to meet the performance requirement of long-term service. However, certain precious alloying elements (e.g., Hf, etc.) are highly reactive elements that react readily with crucibles, shells, and other refractories during melting to form fine, high density inclusions (e.g., HfO)₂Etc.) to contaminate the alloy melt, and removal of these high density inclusions is therefore required.

At present, the main way of removing the inclusion in the smelting process is to adopt foamed ceramic for filtration and promote the floating of the inclusion in a molten pool or adsorb the inclusion floating to the surface. However, high density inclusions in superalloys (e.g., HfO) have a relatively large specific gravity relative to the alloy melt₂Etc.) because the density is higher than the alloy matrix, it is difficult to create the floating condition in the smelting process, and the foam ceramic filtration only has better effect on large-size inclusions and very limited effect on removing small-size high-density inclusions, so the traditional inclusion removing method is difficult to realize the deep removal of high-density inclusions in the high-temperature alloy, and how to effectively remove the high-density inclusions in the high-temperature alloy (especially directional solidification and single crystal high-temperature alloy) is still a challenge at present.

Disclosure of Invention

High density inclusions (e.g., HfO) in superalloys based on the above teachings because of their relatively large specific gravity relative to the alloy melt₂Etc.) density is higher than that of alloy matrix, floating condition is difficult to create in smelting process, and the foamed ceramic filtering has good effect only on large-size inclusion and small-size high-density inclusionThe impurity removal effect is very limited, so the traditional impurity removal method is difficult to realize the technical problem of deep removal of high-density impurities in the high-temperature alloy, and the method for removing the high-density impurities in the high-temperature alloy is provided. The method mainly utilizes a local large overheating environment in the electron beam refining process to dissolve and remove small-size high-density inclusions in the melt, accelerates the sedimentation of large-size inclusions by utilizing the density difference between the inclusions and the melt and the Marangoni effect, and further removes the large-size inclusions through a skull capturing mechanism, thereby achieving the purpose of comprehensively removing the high-density inclusions in the alloy.

The technical means adopted by the invention are as follows:

a method for removing high-density inclusions in a high-temperature alloy comprises the following steps:

s1, pretreatment of the high-temperature alloy raw material:

s11, the raw material is DD406 alloy containing high-density inclusions;

s12, processing the raw materials to a proper size, wherein the raw materials can be placed into a water-cooled copper crucible for refining;

s13, polishing the processed raw material, and removing ceramic adhesion, an oxidation layer and processing traces on the surface to ensure that the alloy has no external pollutants;

s14, cleaning and drying the polished raw materials for later use;

s2, removing high-density inclusions in the high-temperature alloy through electron beam refining:

s21, cleaning the water-cooled copper crucible for electron beam refining and solidification: polishing, wiping with alcohol and drying to ensure that the water-cooled copper crucible is clean and pollution-free;

s22, cleaning pollutants on the furnace body and the furnace wall of the electron beam melting furnace, and avoiding the introduction of foreign impurities in the refining process;

s23, placing the pretreated raw material in a water-cooled copper crucible, and closing an electron beam melting furnace door after the raw material is determined to be ready and a furnace body is cleaned;

s24, pre-vacuumizing the electron beam smelting furnace and the electron gun body to reach the target vacuum degree; preheating the electron gun after the target vacuum degree is reached;

s25, after preheating, uniformly scanning by using a left-side electron gun to melt the raw materials;

s26, after the raw materials are completely melted, refining the raw materials for 10 min;

s27, performing electron beam refining for 10min, and then performing overheating treatment on the melt;

s28, after the melt is subjected to overheating treatment, continuously refining the raw material, and fully settling large-size high-density inclusions;

s29, after refining, instantly adjusting the beam current of the electron gun on the left side to 0mA, and simultaneously starting a melting crucible dumping mechanism to enable the melt refined in the water-cooled melting copper crucible to flow into the water-cooled solidifying copper crucible, and the skull in the water-cooled melting copper crucible is kept in the original crucible;

s210, uniformly scanning the high-temperature alloy melt in the water-cooled copper crucible for solidification by using the right-side electron gun to ensure that the surface of the melt in the water-cooled copper crucible for solidification is uniform;

s211, closing high voltage of the left electron gun and the right electron gun, increasing the beam current of the two electron guns to a certain value to reduce the high voltage value from 30kV to 0kV, and then closing the electron guns to fully solidify and cool the cast ingot in a water-cooled copper crucible for solidification;

s212, taking out the DD406 alloy ingot after the furnace body, the gun body and the ingot are fully cooled, thereby obtaining the high-purity DD406 high-temperature alloy ingot.

Further, the specific steps of step S14 are as follows:

and ultrasonically cleaning the polished DD406 alloy raw material by using deionized water and alcohol respectively, cleaning for three times by using the deionized water and the ultrasonic, placing the alloy into a drying box after cleaning, and drying at 30 ℃ for electron beam refining.

Further, the specific steps of step S24 are as follows:

opening electron beam refining equipment, and pumping the furnace body and the electron gun body of the electron beam smelting furnace to a target vacuum state, wherein the vacuum degree of the furnace body is required to be less than 5 multiplied by 10^-2Pa, the vacuum degree of the gun body is required to be less than 5 multiplied by 10^-3Pa, starting electron guns on the left and right sides after the target vacuum degree is reached, enabling the beam current size to be 120mA, and preheating for 12 minutes.

Further, the specific steps of step S25 are as follows:

after preheating is finished, adjusting the beam current of the electron guns on the left side and the right side to 0, starting high voltage, slowly increasing the beam current of the electron gun on the left side to 500mA after the high voltage reaches 30kV and is stable, wherein the radius of a beam spot is 20-25 mm, and uniformly scanning the DD406 alloy raw material in the water-cooled copper crucible to uniformly heat and melt the raw material.

Further, the specific steps of step S26 are as follows:

after the alloy is completely melted, the alloy is continuously refined for 10min in an electron beam annular scanning mode by keeping the parameters, so that volatile impurities in the high-temperature alloy melt are fully removed, and meanwhile, large-size high-density inclusions are gradually settled to the bottom of a molten pool and are captured by a skull.

Further, the specific steps of step S27 are as follows:

and after refining by electron beams for 10min, rapidly increasing the beam current of the electron beams on the left side to 800mA, keeping the radius of a beam spot unchanged, fixing the position of the beam spot to the center of the ingot after increasing to the specified power, and carrying out melt overheating treatment for 10min under the condition, so that small-size inclusions, carbides and the like in the melt are fully dissolved, and simultaneously promoting the vacuum degassing reaction of the high-temperature alloy melt.

Further, the specific steps of step S28 are as follows:

and (3) after the melt is subjected to overheating treatment, reducing the beam current to 500mA, and continuously refining the alloy for 10min to fully settle large-size high-density inclusions.

Further, the specific steps of step S210 are as follows:

increasing the beam current of the right electron gun to 400mA, adjusting the radius of a beam spot to 20-25 mm, keeping the parameters of the electron gun unchanged, uniformly scanning the high-temperature alloy melt in the solidification crucible for 5min to ensure that the surface of the melt in the solidification crucible is uniform, and then reducing the beam current of the right electron gun to 0 mA.

Compared with the prior art, the invention has the following advantages:

1. the method for removing the high-density inclusions in the high-temperature alloy provided by the invention creatively provides the method for removing the high-density inclusions in the high-temperature alloy by adopting an electron beam refining technology. The method is characterized in that the dissolution and removal of small-size high-density inclusions in a melt are realized by using a local large overheating environment in an electron beam refining process, the sedimentation of large-size inclusions is accelerated by using the density difference between the inclusions and the melt and the Marangoni effect, and then the large-size inclusions are removed by a skull capture mechanism, so that the aim of comprehensively removing the high-density inclusions in the alloy is fulfilled.

2. According to the method for removing the high-density inclusions in the high-temperature alloy, provided by the invention, the small-size high-density inclusions in the melt are dissolved and removed by increasing the overheating of the melt in the high-temperature high-vacuum electron beam refining process, and the large-size high-density inclusions in the melt are captured and removed by the adsorption effect of the skull at the bottom of the cast ingot on the large-size inclusions settled below a molten pool. Namely, the size and the number of the high-density inclusions in the high-temperature alloy ingot obtained by the method are obviously reduced, and a new method is provided for effectively removing the high-density inclusions in the high-temperature alloy ingot.

In conclusion, the technical scheme of the invention can solve the problem that high-density inclusions (such as HfO) in the high-temperature alloy have larger specific gravity relative to the alloy melt in the high-temperature alloy₂And the like) density is higher than that of an alloy matrix, floating conditions are difficult to create in the smelting process, the foamed ceramic filtering only has a good effect on large-size inclusions, and the effect on removing small-size high-density inclusions is very limited, so that the traditional inclusion removing method has the problem that the deep removal of high-density inclusions in the high-temperature alloy is difficult to realize.

For the reasons, the method can be widely popularized in the fields of removing inclusions in the alloy and the like.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.

FIG. 1 is a schematic diagram of an electron beam refining process of the present invention.

FIG. 2 is a schematic view of the casting process after electron beam refining according to the present invention.

FIG. 3 is a graph showing the Reynolds number of the relative motion between high-density inclusions and a fluid and the size of the inclusions according to the present invention.

FIG. 4 is a graph showing the relationship between the moving rate of high-density inclusions and the particle size of inclusions according to the present invention.

In the figure: 1. an oil diffusion pump; 2. a valve; 3. a mechanical pump; 4. local overheating areas of the melt; 5. an alloy melt; 6. condensing a shell layer; 7. water-cooling the copper crucible; 8. a melting crucible dumping mechanism; 9. cooling water; 10. an electron gun; 11. an electron beam; 12. a roots pump.

Detailed Description

It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict. The present invention will be described in detail below with reference to the embodiments with reference to the attached drawings.

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of exemplary embodiments according to the invention. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The relative arrangement of the components and steps, the numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless specifically stated otherwise. Meanwhile, it should be understood that the sizes of the respective portions shown in the drawings are not drawn in an actual proportional relationship for the convenience of description. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art may not be discussed in detail but are intended to be part of the specification where appropriate. Any specific values in all examples shown and discussed herein are to be construed as exemplary only and not as limiting. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, further discussion thereof is not required in subsequent figures.

As shown in FIG. 1, the present invention provides a method for removing high-density inclusions in a superalloy, comprising the steps of:

pretreatment of high-temperature alloy raw materials

1. Taking the DD406 alloy as an example, the raw material of the DD406 alloy containing high-density inclusions is processed to a suitable size so as to be put into a water-cooled copper refining crucible.

2. And polishing the processed DD406 alloy to remove ceramic adhesion, oxide layer, processing trace and the like on the surface, so that the alloy has no external pollutants.

3. And ultrasonically cleaning the polished DD406 alloy raw material by using deionized water and alcohol respectively, cleaning for three times by using the deionized water and the ultrasonic, placing the alloy into a drying box after cleaning, and drying at 30 ℃ for electron beam refining.

Secondly, electron beam refining is carried out to remove high-density inclusions in the high-temperature alloy

1. And cleaning (polishing, alcohol wiping and drying) the water-cooled copper crucible for electron beam refining and solidification so as to ensure that the water-cooled copper crucible is clean and pollution-free.

2. Cleaning furnace body and furnace wall pollutants, and avoiding the introduction of foreign impurities in the refining process.

3. The pretreated DD406 alloy raw material is placed in a water-cooled copper refining crucible, is determined to be ready, and a furnace door is closed after a furnace body is cleaned.

4. Opening electron beam refining equipment, and pumping the furnace body and the electron gun body of the electron beam smelting furnace to a target vacuum state, wherein the vacuum degree of the furnace body is required to be less than 5 multiplied by 10^-2Pa, the vacuum degree of the gun body is required to be less than 5 multiplied by 10^-3Pa, starting electron guns on the left and right sides after the target vacuum degree is reached, enabling the beam current size to be 120mA, and preheating for 12 minutes.

5. After preheating is finished, adjusting the beam current of the electron guns on the left side and the right side to 0, starting high voltage, slowly increasing the beam current of the electron gun on the left side to 500mA after the high voltage reaches 30kV and is stable, wherein the radius of a beam spot is 20-25 mm, and uniformly scanning the DD406 alloy raw material in the water-cooled copper crucible to uniformly heat and melt the raw material.

6. After the alloy is completely melted, the alloy is continuously refined for 10min in an electron beam annular scanning mode by keeping the parameters, so that volatile impurities in the high-temperature alloy melt are fully removed, and meanwhile, large-size high-density inclusions are gradually settled to the bottom of a molten pool and are captured by a skull.

7. After electron beam refining is carried out for 10min, the beam current of the electron beam on the left side is rapidly increased to 800mA, the radius of a beam spot is kept unchanged, the position of the beam spot is fixed to the center of an ingot after the beam spot is increased to a specified power, and melt overheating treatment is carried out for 10min under the condition, so that small-size inclusions, carbides and the like in the melt are fully dissolved, and meanwhile, the vacuum degassing reaction of the high-temperature alloy melt is promoted (figure 1).

8. And (3) after the melt is subjected to overheating treatment, reducing the beam current to 500mA, and continuously refining the alloy for 10min to fully settle large-size high-density inclusions.

9. After refining is finished, the beam current of the electron gun on the left side is instantly adjusted to 0mA, and meanwhile, the melting crucible dumping mechanism is started, so that the melt refined in the water-cooled copper crucible for melting flows into the water-cooled copper crucible for solidification, and the skull in the water-cooled copper crucible for melting is kept in the original crucible.

10. Increasing the beam current of the right-side electron gun to 400mA, adjusting the radius of the beam spot to 20-25 mm, keeping the parameters of the electron gun unchanged, uniformly scanning the high-temperature alloy melt in the water-cooled copper crucible for solidification for 5min, so that the surface of the melt in the water-cooled copper crucible for solidification is uniform, and then reducing the beam current of the right-side electron gun to 0 mA.

11. And (3) closing the high voltage of the left electron gun and the right electron gun, increasing the beam current of the two electron guns to a certain value to reduce the high voltage value from 30kV to 0kV, and then closing the electron guns to fully solidify and cool the cast ingot in the water-cooled copper crucible for solidification.

12. And taking out the DD406 alloy ingot after the furnace body, the gun body and the ingot are fully cooled, thereby obtaining the high-purity DD406 high-temperature alloy ingot.

Fig. 1 is a schematic view showing an electron beam refining process according to the present invention, and fig. 2 is a schematic view showing a casting process after electron beam refining according to the present invention. The invention adopts the equipment shown in figures 1 and 2 to remove high-density inclusions in the high-temperature alloy. The electron gun 10 is fixed at two side corners of the top of the electron beam melting furnace, the water-cooled copper crucible for melting 7 is placed in the electron beam melting furnace through the melting crucible dumping mechanism 8, the water-cooled copper crucible for solidification 7 is placed at the bottom of the electron beam melting furnace, and cooling water 9 is introduced. The DD406 alloy raw material is placed in a water-cooled copper crucible 7 for melting and is in the scanning range of an electron beam 11. The oil diffusion pump 1 is adjacent to the mechanical pump 3, and the communication relationship between the oil diffusion pump 1 and the mechanical pump is controlled by a valve 2; the roots pump 12 is adjacent to the furnace body mechanical pump 3, and the two are connected together. The alloy melt 5 is a molten metal material in a water-cooled copper crucible 12 and forms a local superheat zone 4 of the melt after melting. The melt refined in the water-cooled copper crucible for melting 7 flows into the water-cooled copper crucible for solidification 7, and the skull layer 6 in the water-cooled copper crucible for melting is retained in the original crucible.

The method provided by the invention realizes the dissolution and removal of small-size high-density inclusions in the melt by increasing the overheating of the melt in the high-temperature high-vacuum electron beam refining process, realizes the capture and removal of large-size high-density inclusions in the melt by the adsorption effect of the skull at the bottom of the ingot on the large-size inclusions settled below a molten pool, and further obtains a high-purity high-temperature alloy ingot by casting. The size and the number of the high-density inclusions in the high-temperature alloy ingot obtained by the method are obviously reduced, and a new method is provided for effectively removing the high-density inclusions in the high-temperature alloy ingot.

The mechanism for capturing the high-density inclusion skull is as follows:

HfO compared to the alloy melt₂The inclusions have a higher density, and in the melting phase, the high-density inclusions gradually sink to the bottom of the melt under the action of gravity, and the inclusions in the raw material have sufficient time to settle before the end of the refining phase, assuming that the inclusions are uniform spherical particles with a diameter d_pThe force was analyzed as follows:

the gravity borne by the inclusions is F_gComprises the following steps:

in the formula, ρ_pThe density of inclusions and g is the acceleration of gravity.

Buoyancy of inclusions in the melt F_b：

Wherein rho is the density of the alloy melt.

The inclusions are subjected to the resultant force of gravity and buoyancy:

density of inclusions ρ_pGreater than the rho of the alloy melt, so that the inclusions move downwards and gradually sink to the bottom of the molten pool, and the resistance F suffered by the inclusions in the process of sinking_rComprises the following steps:

in the formula, C_DIs a coefficient of drag (drag), A_pIs the projected area of the particle in the direction of the fluid, and u is the relative velocity of the fluid and the solid.

The comprehensive stress F of the inclusion particles is as follows:

F＝F_g-F_b-F_r (5)

according to newton's second law, the resultant force F in the above formula can be represented by the following formula, where a is the acceleration:

F＝ma (6)

at the moment when the inclusion begins to rise, its initial velocity u is zero and the resistance F is set_rZero, so the acceleration is at a maximum; the resistance of the inclusions increases with increasing speed u during the ascent, and the acceleration a correspondingly decreases, when the speed reaches a critical value u_tWhen the force is zero, the acceleration of the impurities is zero, and the speed u of the impurities is zero_tNo longer changed.

Because the specific surface area of the small particles is large, the resistance of the impurities in the particles in the extremely short time of rising of the particles is close to balance with the net gravity (namely gravity minus buoyancy) borne by the particles, and the accelerated rising of the impurities is usually negligible for the whole rising process. When a is 0, u is u_tAs can be seen from the formula (3-6),

coefficient of resistance C_DReynolds number Re which is the relative motion between the inclusions and the fluid_tFunction of Reynolds number Re_tIs defined as:

in the formula, μ is the viscosity Pa · s of the fluid.

Assuming that the inclusions are spherical particles having a maximum particle diameter of 100 μm, the precipitation behavior of the inclusions is in Re_t<1 hour obeys Stokes' law, coefficient of resistance C_DComprises the following steps:

the final velocity of the rise of the inclusions can be calculated by the formula (7-9):

reynolds number Re of the movement of inclusions in the melt_tCalculated from equations (8) and (10):

where ρ is_gAnd ρ are the density of the high density inclusions and the alloy melt, respectively. With HfO₂For example, the high density inclusion density was 9680kg/m³The density of the alloy melt is 8500kg/m³The viscosity mu range of the nickel-based alloy is about 0.005-0.01 Pa.s, and the gravity acceleration is 9.8m/s²Therefore, the Reynolds number Re of the relative motion of the inclusions and the fluid under different viscosities can be calculated_tThe relationship with the size of inclusions is shown in FIG. 3. As can be seen from FIG. 3, the Reynolds number Re of the relative motion between the inclusions and the fluid at different viscosities_tAre all less than 1, and therefore the sedimentation process of high density inclusions obeys Stokes law. The viscosity of the melt is calculated to be differentThe inclusion settling rate is related to the inclusion particle size as shown in fig. 4.

As can be seen from fig. 4, the lower the melt viscosity, the larger the size of the inclusions, and the faster the sedimentation rate. For example, when the melt viscosity is 0.007Pa.s and the size of the inclusions is 40 μm, the sedimentation rate is 1.47X 10^-4m.s^-1. During electron beam refining, high density inclusions can be sufficiently settled in the melt, 40 μm of high density inclusions move in the melt for a distance of 88.2mm when the refining time is 10min, and the distance of the settlement of the inclusions increases as the refining time increases. When the depth of the molten pool is less than the sediment distance of the inclusions, the inclusions can be captured by the skull layer at the bottom of the molten pool and then retained in the skull layer. After full sedimentation, high-density inclusions in the alloy are enriched in the solidified shell layer, and the high-purity alloy cast ingot can be obtained by pouring the residual alloy melt into a solidification crucible.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.