CN116159983A

CN116159983A - Method for preparing high-purity ordered gradient superalloy by electron beam drop melting layer-by-layer casting technology

Info

Publication number: CN116159983A
Application number: CN202211527985.4A
Authority: CN
Inventors: 谭毅; 崔弘阳; 白如圣; 游小刚; 李鹏廷; 李毅
Original assignee: Dalian University of Technology
Current assignee: Dalian University of Technology
Priority date: 2022-11-30
Filing date: 2022-11-30
Publication date: 2023-05-26

Abstract

The invention provides a method for preparing high-purity ordered gradient superalloy by using an electron beam drop melting layer-by-layer casting technology, which comprises the following steps: s1, preprocessing raw materials; s2, electron beam drop melting; s3, dropwise dissolving the materials layer by layer. The invention realizes the high purification preparation of the high-temperature alloy, the size of the prepared cast ingot inclusion is small, the content of impurity elements is obviously reduced, and the hot processing performance of the high-temperature alloy can be further improved by introducing an ordered structure.

Description

Method for preparing high-purity ordered gradient superalloy by electron beam drop melting layer-by-layer casting technology

Technical Field

The invention relates to a method for preparing high-purity ordered gradient superalloy by using an electron beam drop melting layer-by-layer casting technology.

Background

The turbine disk is one of the most important core hot-end components of an aircraft engine, and its metallurgical quality and performance level are decisive for improving the reliability, safety life and performance of the engine and the aircraft. The service environment determines that the size of the inclusions in the alloy is as small as possible or even none. Thus, there is a need to prepare ultra-clean superalloy master alloys. And the difficult deformation degree of the alloy is continuously improved along with the continuous increase of the alloying proportion.

The traditional preparation method of the high-temperature alloy at present comprises the steps of smelting and preparing the high-temperature alloy by a vacuum induction and vacuum consumable duplex process. The decomposition of large-sized inclusions and the removal of impurity elements are limited. And the size of the cast alloy crystal grains is larger, which is unfavorable for the subsequent cogging and forging treatment. The electron beam drop melting process is to bombard the surface of the material with high energy electron beam, and is one kind of melting mode for smelting refractory metal and its alloy, titanium and titanium alloy and melting purified material. When the electron beam is used for melting, the high-temperature alloy raw material is gradually melted by adjusting the parameters such as the size of the electron beam current, the size of the electron beam spot and the like, and impurities in the high-temperature alloy are decomposed under the high-vacuum and high-superheat environment, so that impurity elements can be effectively removed. And then utilizing layer-by-layer induced solidification, and adding an ordered gradient structure in the middle of the cast ingot.

Disclosure of Invention

According to the traditional preparation method of the high-temperature alloy, which is proposed above, the high-temperature alloy is smelted and prepared by a vacuum induction and vacuum consumable duplex process, the decomposition of large-size inclusions and the removal of impurity elements are limited, and the size of cast alloy grains is large, so that the technical problems of follow-up cogging and forging treatment are not facilitated, and the method for preparing the high-purity ordered gradient high-temperature alloy by using the electron beam drop melting layer-by-layer casting technology is provided. The invention mainly induces inclusion to be concentrated at the alloy edge and sucks slag to treat at the end of electron beam drop melting, thereby achieving the purpose of preparing high-purity ordered gradient superalloy.

The invention adopts the following technical means:

a method for preparing high-purity ordered gradient superalloy by electron beam drop melting layer-by-layer casting technology comprises the following steps:

s1, pretreatment of raw materials:

s11, using a rod-shaped superalloy as a raw material;

s12, cutting, polishing, cleaning and drying the high-temperature alloy bar for later use;

s2, electron beam drop melting:

s21, cleaning the inside of a furnace body of the electron beam smelting furnace, and polishing and cleaning the water-cooled copper crucible;

s22, placing the pretreated high-temperature alloy right above a water-cooled copper crucible, cleaning the periphery of the crucible by adopting alcohol, wiping the crucible by using cotton cloth, and closing a furnace door after ensuring that the interior of the furnace body is clean and pollution-free;

s23, switching on power supplies of a cooling system and electron beam melting equipment, and vacuumizing a melting chamber and an electron gun chamber to achieve a target vacuum degree;

s24, after the vacuum degree of the smelting chamber and the electron gun chamber meets the requirement, starting a No. 1 electron gun to realize the drip smelting of the high-temperature alloy into the water-cooled copper crucible;

s25, after high-temperature alloy with certain mass is dripped, starting a No. 2 electron gun, and removing melt edge inclusions in the water-cooled copper crucible by using electron beams;

s3, dropwise dissolving layer by layer: and repeating the step S24 and the step S25 for a plurality of times to obtain the high-purity ordered gradient superalloy.

Further, in the step S11, the diameter of the rod-shaped superalloy is 20 to 100mm;

the specific steps of the step S12 are as follows:

s12, cutting the high-temperature alloy bar into a cylinder with the diameter phi of 20-100 mm and the length of 800-1000 mm, and polishing stains and oxide skin on the surface of the cylinder by using a handheld angle grinder;

s13, cleaning the polished alloy by deionized water and alcohol respectively, cleaning the alloy by an ultrasonic cleaner, drying the alloy by a blower, and dripping the alloy by an electron beam for use.

Further, in step S21, the surface of the water-cooled copper crucible is polished by a hand-held polisher, so that oxide skin and stains on the surface of the crucible are removed, and the surface of the crucible is ensured to be smooth; the polished crucible is cleaned by alcohol and is wiped clean by cotton cloth, so that the inside of the water-cooled copper crucible is kept clean and pollution-free.

Further, in the step S22, the pretreated superalloy rod is clamped at a feeding clamp, so that the superalloy cylindrical end face is located right above the water-cooled copper crucible.

Further, in the step S23, a low vacuum is drawn on the melting chamber and the electron gun chamber through a low vacuum system; when the vacuum degree reaches 0-5 Pa, the high vacuum system is started to make the vacuum degree of the smelting chamber smaller than 5 multiplied by 10 ^-2 Pa～8×10 ^-2 Pa, the vacuum degree of the electron gun chamber is less than 8×10 ^-3 Pa～9×10 ^-3 Pa。

Further, the specific steps of the step S3 are as follows:

s31, after the alloy in the step S25 is dripped for 20min, starting the 1# electron gun and the 2# electron gun again, repeating the step S24, dripping the high-temperature alloy with single-layer quality, and repeating the step S25 to remove the inclusion at the edge of the melt in the water-cooled copper crucible;

s32, repeating the step S31 for a plurality of times, and preparing the alloy ingot layer by layer in a semi-continuous mode for a plurality of times to reach the size of the required ingot, so as to obtain a high-purity low-segregation high-temperature alloy ingot with a certain size;

s33, turning off the high voltage of the electron beam, turning off the electron gun, and keeping the high vacuum state of the furnace body;

s34, after the smelting furnace is cooled for 60min, argon is introduced twice to continuously cool the furnace body, and after the furnace body is completely cooled, the high-purity ordered gradient superalloy is taken out.

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

after the vacuum degree of the smelting chamber and the electron gun chamber meets the requirement, starting the high voltage of the 1# electron gun, and setting the lower focusing current to 110mA after the voltage reaches 20kV and is stable for 1 min; irradiating the generated electron beam on the end face of the high-temperature alloy bar clamped by the feeding system, slowly increasing the beam current to 1200mA, starting to melt the bar, and gradually melting the high-temperature alloy drop by drop and falling into a water-cooled copper crucible; at the moment, the feeding mechanism uniformly pushes the high-temperature alloy bar forward, and the dripping end face is ensured to be right above the crucible.

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

adopting a No. 2 electron gun to perform spiral line scanning on the dripped high-temperature alloy raw material, controlling alloy in the water-cooled copper crucible to solidify in a mode of uniformly growing upwards from the bottom of the crucible, and driving the inclusion to the edge position of a molten pool; after the high-temperature alloy with one layer of quality is dripped, the No. 1 electron gun is closed; removing the inclusion at the edge of the melt in the crucible through a slag sucking system; and then uniformly reducing the beam current of the No. 2 electron gun to 0mA, so that a layer of high-purity superalloy is formed.

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

1. according to the method for preparing the high-purity ordered gradient superalloy by using the electron beam drop melting layer-by-layer casting technology, the aim of preparing the high-purity ordered gradient superalloy is achieved by inducing inclusion to be enriched at the edge of the alloy and performing slag absorption treatment at the end of electron beam drop melting.

2. According to the method for preparing the high-purity ordered gradient superalloy by using the electron beam drop melting layer-by-layer casting technology, when the electron beam drops are melted, the superalloy raw materials are gradually melted by adjusting the size of electron beam current, the size of electron beam spot and other parameters, and impurities in the superalloy are decomposed under the high-vacuum and high-superheat environment, so that impurity elements can be effectively removed. And then utilizing layer-by-layer induced solidification, and adding an ordered gradient structure in the middle of the cast ingot.

3. The method for preparing the high-purity ordered gradient superalloy by using the electron beam drop melting layer-by-layer casting technology provided by the invention realizes high purification preparation of the superalloy, the prepared cast ingot inclusion is small in size and the impurity element content is obviously reduced, and the hot processing performance of the superalloy can be further improved by introducing an ordered structure.

4. According to the method for preparing the high-purity ordered gradient superalloy by using the electron beam drop melting layer-by-layer casting technology, which is provided by the invention, the introduction of an ordered gradient structure is realized on the basis of refining the drop melting superalloy by using an electron beam, and the electron beam drop melting and layer-by-layer casting are combined, so that the high-purity ordered gradient superalloy ingot is effectively prepared. Further improving the metallurgical quality of the high-temperature alloy. The preparation yield of the alloy is improved to more than 85% from the traditional 60%.

In summary, the technical scheme of the invention can solve the problems that the prior conventional preparation method of the high-temperature alloy comprises a vacuum induction and vacuum self-consumption duplex process for smelting and preparing the high-temperature alloy, the decomposition of large-size inclusions and the removal of impurity elements are limited, and the size of the cast alloy crystal grain is larger, so that the follow-up cogging and forging treatment are not facilitated.

For the reasons, the invention can be widely popularized in the fields of high-temperature alloy preparation 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 that are required in the embodiments or the description of the prior art will be briefly described, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings may be obtained according to the drawings without inventive effort to a person skilled in the art.

FIG. 1 is a schematic diagram of an electron beam drop melt layer-by-layer casting apparatus of the present invention.

In the figure: 1. an electron gun; 2. a mechanical pump; 3. a flapper valve; 4. a diffusion pump; 5. an electron beam; 6. dripping and dissolving a crucible; 7. a diffusion pump; 9. a cooling water pipe; 10. a cooling water inlet; 11. and (5) dripping and dissolving a molten pool.

Detailed Description

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

For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are only some embodiments of the present invention, not all embodiments. The following description of at least one exemplary embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the 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 present invention. As used herein, the singular is also intended to include the plural unless the context clearly indicates otherwise, and furthermore, it is to be understood that the terms "comprises" and/or "comprising" when used in this specification are taken to specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof.

The relative arrangement of the components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present invention unless it is specifically stated otherwise. Meanwhile, it should be clear that the dimensions of the respective parts shown in the drawings are not drawn in actual scale for 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. In all examples shown and discussed herein, any specific values should be construed as merely illustrative, and not a limitation. Thus, other examples of the exemplary embodiments may have different values. It should be noted that: like reference numerals and letters denote like items in the following figures, and thus once an item is defined in one figure, no further discussion thereof is necessary in subsequent figures.

Based on the great advantage of electron beam technology in preparing high purity multielement alloy, the layer-by-layer casting technology can effectively introduce an interlayer interface. The patent provides a method for preparing high-purity ordered gradient superalloy by using an electron beam drop melting layer-by-layer casting technology, high purification preparation of superalloy is realized, the size of prepared cast ingot inclusion is small, the content of impurity elements is obviously reduced, and the hot processing performance of superalloy can be further improved by introducing an ordered structure.

The electron beam drop melting process is to bombard the surface of the material with high energy electron beam, and is one kind of melting mode for smelting refractory metal and its alloy, titanium and titanium alloy and melting purified material. When the electron beam is used for melting, the high-temperature alloy raw material is gradually melted by adjusting the parameters such as the size of the electron beam current, the size of the electron beam spot and the like, and impurities in the high-temperature alloy are decomposed under the high-vacuum and high-superheat environment, so that impurity elements can be effectively removed. And then utilizing layer-by-layer induced solidification, and adding an ordered gradient structure in the middle of the cast ingot.

The invention provides a method for preparing high-purity ordered gradient superalloy by electron beam drop melting layer-by-layer casting. And inducing inclusion to be enriched at the alloy edge at the end of electron beam drop melting and carrying out slag absorption treatment, thereby achieving the aim of preparing the high-purity ordered gradient superalloy.

The method comprises the following steps:

1. pretreatment of raw materials

1. The raw material is a bar-shaped high-temperature alloy with the diameter of 20-100 mm.

2. Cutting the high-temperature alloy bar into a cylinder with the diameter of 20-100 mm and the length of 800-1000 mm, and polishing stains and oxide skin on the surface of the cylinder by using a handheld angle grinder.

3. And cleaning the polished alloy with deionized water and alcohol respectively, cleaning the alloy by using an ultrasonic cleaner, drying the alloy by using a blower, and dripping the alloy by using an electron beam.

2. Electron beam drop melting

1. Cleaning the inside of the furnace body of the electron beam melting furnace. The surface of the water-cooled copper crucible is polished by a hand-held polisher, oxide skin and stains on the surface of the crucible are removed, and the surface of the crucible is ensured to be smooth. The polished crucible is cleaned by alcohol and is wiped clean by cotton cloth, so that the inside of the water-cooled copper crucible is kept clean and pollution-free.

2. And clamping the pretreated high-temperature alloy bar at the feeding clamp to enable the cylindrical end surface of the high-temperature alloy to be positioned right above the water-cooled copper crucible. And the periphery of the crucible is cleaned by adopting alcohol, and the crucible is wiped clean by cotton cloth, so that the furnace door is closed after the inside of the furnace body is clean and pollution-free.

3. And switching on the power supply of the cooling system and the electron beam melting equipment, and pumping low vacuum to the melting chamber and the electron gun chamber through the low vacuum system. When the vacuum degree reaches 0-5 Pa, the high vacuum system is started to make the vacuum degree of the smelting chamber smaller than 5 multiplied by 10 ^-2 Pa～8×10 ^-2 Pa, the vacuum degree of the electron gun chamber is less than 8×10 ^-3 Pa～9×10 ^-3 Pa。

4. After the vacuum degree of the smelting chamber and the electron gun chamber reaches the requirement, starting the high voltage of the 1# electron gun (namely the left side electron gun), and setting the lower focusing current to 110mA after the voltage reaches 20kV and is stabilized for 1 min. And irradiating the generated electron beam on the end surface of the high-temperature alloy bar clamped by the feeding system, slowly increasing the beam current to 1200mA, starting to melt the bar, and enabling the high-temperature alloy to be melted drop by drop and fall into a water-cooled copper crucible. At the moment, the feeding mechanism uniformly pushes the high-temperature alloy bar forward, and the dripping end face is ensured to be right above the crucible.

5. And adopting a No. 2 electron gun to perform spiral line scanning on the dripped high-temperature alloy raw material, controlling alloy in the water-cooled copper crucible to solidify in a mode of uniformly growing upwards from the bottom of the crucible, and driving the inclusion to the edge position of a molten pool. And after the high-temperature alloy with one layer of quality is dripped, the No. 1 electron gun is turned off. And removing the inclusion at the edge of the melt in the crucible through a slag sucking system. And then uniformly reducing the beam current of the No. 2 electron gun to 0mA, so that a layer of high-purity superalloy is formed.

By refining the alloy drop by drop, the large particles are excited and dissolved by electron beams, so that the inclusions are removed. The non-decomposed inclusions are controlled to float on the surface of the molten pool by a No. 2 electron beam gun, so that the inclusion removal is realized.

3. Drop-by-drop solution

1. After the alloy is dripped for 20min, the 1# electron gun and the 2# electron gun are started again, and the high-temperature alloy with single-layer quality is dripped according to the process of the electron beam dripping. By controlling the solidification process in a single layer, the microscopic segregation degree of the alloy is ensured, and the macroscopic segregation phenomenon (the element density in the alloy is different, so that the top and bottom elements are possibly uneven in the large-scale ingot) in the preparation process of the large-scale ingot is eliminated by accumulating layer by layer. The present invention includes, but is not limited to: 3kg, 5kg and 10kg of ingots can be designed according to the size of the crucible, and each layer can be controlled to be 500g or 800g. Different thicknesses can be prepared according to different requirements.

2. The high-purity low-segregation high-temperature alloy cast ingot with a certain size is obtained through repeated semi-continuous layer-by-layer preparation, and the size of the cast ingot is required.

3. At this time, the electron beam high voltage is turned off, the electron gun is turned off, and the high vacuum state of the furnace body is maintained.

4. And after the smelting furnace is cooled for 60min, argon is introduced into the furnace body for continuously cooling the furnace body twice, and the high-purity ordered gradient superalloy is taken out after the furnace body is completely cooled.

Fig. 1 is a schematic diagram of an electron beam drop-melting layer-by-layer casting device according to the invention, and the device shown in fig. 1 is adopted to prepare the high-purity ordered gradient superalloy. Two electron guns 1 are respectively fixed at two side angles at the top of the electron beam melting furnace, a water-cooled copper crucible (a drip-soluble crucible 6) is placed at the bottom of the electron beam melting furnace through a crucible bracket and is connected with a cooling water pipeline 9, and a cooling water inlet 10 is arranged at the side edge of the electron beam melting furnace. The superalloy is placed on the side wall of the water-cooled copper crucible 6 and dropped in the scanning range of the electron beam 5 of the electron gun # 1 (left side electron gun), the superalloy dropped into the water-cooled copper crucible 6 forms a dropping pool 11, and electron beam solidification is performed by the electron gun # 2 (right side electron gun). The diffusion pump 4 is adjacent to the mechanical pump 2, and the communication relationship between the two is controlled by the baffle valve 3; the diffusion pump 7 is adjacent to the mechanical pump 2, and the two are connected together.

The method realizes the introduction of the ordered gradient structure on the basis of refining the drop-melting superalloy by the electron beam, combines the drop-melting of the electron beam with the drop-melting of the layer by layer, and effectively prepares the high-purity ordered gradient superalloy cast ingot. Further improving the metallurgical quality of the high-temperature alloy. The preparation yield of the alloy is improved to more than 85% from the traditional 60%.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present invention, and not for limiting the same; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some or all of the technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit of the invention.

Claims

1. The method for preparing the high-purity ordered gradient superalloy by using the electron beam drop melting layer-by-layer casting technology is characterized by comprising the following steps of:

s1, pretreatment of raw materials:

s11, using a rod-shaped superalloy as a raw material;

s2, electron beam drop melting:

2. The method for preparing high-purity ordered gradient superalloy by using electron beam drop melting layer-by-layer casting technology according to claim 1, wherein in step S11, the diameter of the rod superalloy is 20-100 mm;

the specific steps of the step S12 are as follows:

3. The method for preparing the high-purity ordered gradient superalloy by using the electron beam drop melting layer-by-layer casting technology according to claim 1, wherein in the step S21, the surface of the water-cooled copper crucible is polished by a hand-held polisher, oxide skin and stains on the surface of the crucible are removed, and the smoothness of the surface of the crucible is ensured; the polished crucible is cleaned by alcohol and is wiped clean by cotton cloth, so that the inside of the water-cooled copper crucible is kept clean and pollution-free.

4. The method for preparing high-purity ordered gradient superalloy by using electron beam drop melting layer-by-layer casting technology according to claim 1, wherein in step S22, the pretreated superalloy rod is clamped at a feeding clamp, and the superalloy cylindrical end face is positioned right above a water-cooled copper crucible.

5. The method for preparing high-purity ordered gradient superalloy by using electron beam drop melting layer-by-layer casting technology according to claim 1, wherein in step S23, a low vacuum is applied to the melting chamber and the electron gun chamber by a low vacuum system; when the vacuum degree reaches 0-5 Pa, the high vacuum system is started to make the vacuum degree of the smelting chamber smaller than 5 multiplied by 10 ^-2 Pa～8×10 ^-2 Pa, the vacuum degree of the electron gun chamber is less than 8×10 ^-3 Pa～9×10 ^-3 Pa。

6. The method for preparing the high-purity ordered gradient superalloy by using the electron beam drop melting layer-by-layer casting technology according to claim 1, wherein the specific steps of step S3 are as follows:

7. The method for preparing the high-purity ordered gradient superalloy by using the electron beam drop casting technology according to claim 1 or 6, wherein the specific steps of step S24 are as follows:

8. The method for preparing the high-purity ordered gradient superalloy by using the electron beam drop casting technology according to claim 1 or 6, wherein the specific steps of step S25 are as follows: