Vacuum suspension smelting method and device for refractory metal high-entropy alloy

Abstract

The invention discloses a vacuum suspension smelting method of a refractory metal high-entropy alloy, which is characterized by comprising the following steps of: 1, adding a small amount of one, two or more components with the lowest melting point into one, two or more components with the highest melting point in the high-entropy alloy to form a primary intermediate alloy with a lower melting point; 2, adding one, two or more components with lower melting points into the primary intermediate alloy to obtain a secondary intermediate alloy with a further lower melting point; thirdly, intermediate alloys with the melting points reduced in sequence are formed in sequence in the same manner; and fourthly, the last intermediate alloy and the remaining metal are mixed and smelted, and the refractory metal high-entropy alloy with the components meeting the requirements is obtained. According to the process, the refractory metal high-entropy alloy is smelted through the technology that the intermediate alloy with the gradually-reduced melting point is smelted step by step, and the technical difficulty brought to the smelting process by the contradiction that the superheat degree of suspension smelting is small and the melting point difference of components of the alloy is large is effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of high entropy alloy material preparation, and in particular to a vacuum suspension melting method and device for a refractory metal high entropy alloy. Background Art

[0002] High entropy alloy is a high-end alloy material newly developed in the past 20 years. This material is an alloy of multi-component metals with equal atomic ratios, and the number of members is mostly quaternary or quinary. The characteristics of this alloy are that it can maintain a single-phase structure under multi-component conditions, and can concentrate the properties of the component metals to obtain excellent comprehensive properties.

[0003] Refractory metal high entropy alloys are high entropy alloys with refractory metals as components. Since there are many components and each component is a high melting point metal, it is very technically difficult to melt refractory metal high entropy alloys. Although electron beam melting can produce very high melting temperatures, it has the problem of prefabricating multiple metal components into raw material rods required for electron beam melting. In addition, how to make the components with different melting points in the molten pool uniform, how to ensure that the components with lower melting points and boiling points do not produce serious volatilization losses, so as to ensure that the composition of the alloy does not deviate seriously, these problems are technically difficult for electron beam melting.

[0004] Suspension smelting technology can also produce a higher melting temperature, which is an effective technical means for melting high entropy alloys of refractory metals. However, there are also technical difficulties in melting high entropy alloys of refractory metals using suspension smelting technology.

[0005] First, the melting point of the component with the highest melting point is close to the highest temperature that can be produced by suspension melting, so it is difficult to melt this component; second, the melting points of the components in high-entropy alloys are very different. If they are mixed together for melting, after the components with lower melting points are melted, the components with higher melting points are difficult to melt in the molten pool with lower temperature. Moreover, in the process of suspension melting, once the metal forms a molten pool, it is difficult to increase the temperature. Even if the heating power is increased, the overheating degree is only more than 100 degrees at most; third, suspension melting uses a water-cooled copper crucible, and most of the energy of the heating power is taken away by the cooling water, resulting in high energy consumption, especially when melting the metal component with the highest melting point. Long-term melting consumes a lot of energy. Summary of the invention

[0006] In view of the shortcomings of the prior art, the present invention proposes a technical measure for melting intermediate alloys with gradually lowered melting points in steps. The present invention sets a non-consumable melting electrode on the suspension melting equipment, and further reduces the technical difficulty of melting high-melting-point metals by using the arc discharge method. In view of the characteristics of many alloy components and large density differences of the components, a pulse power transmission function is set for the induction power supply, so that the intensity of the electromagnetic field changes dramatically, and a strong stirring effect is generated on the molten pool.

[0007] The present invention provides a vacuum suspension melting method for a refractory metal high entropy alloy, comprising the following steps:

[0008] The first step is to add a small amount of one, two or more components with the lowest melting point to form a primary intermediate alloy with a lower melting point.

[0009] The second step is to add one, two or more components with the second lowest melting point to the primary master alloy to obtain a secondary master alloy with a further lower melting point;

[0010] The third step is to form intermediate alloys with successively lower melting points in a similar manner;

[0011] The fourth step is to mix the final intermediate alloy with the remaining metal and smelt it to obtain a refractory metal high entropy alloy with the required composition.

[0012] Furthermore, during the smelting process from step 1 to step 3, the liquid volume Vh of the high melting point material is greater than the volume Vd of the low melting point material.

[0013] Furthermore, Vh / Vd>2.

[0014] Furthermore, during the smelting process from the second step to the fourth step, the intermediate alloy ingot is first turned over in the water-cooled copper crucible; preferably, the alloy obtained in the fourth step needs to be turned over and remelted once or several times.

[0015] Furthermore, when the metal components are being smelted and unmelted metal blocks are found in the molten pool, an auxiliary electrode is used to start arc discharge close to the material, and the high temperature of the arc is used to quickly melt the unmelted material.

[0016] Furthermore, the induction power supply has the function of pulse power transmission, and the period of the induction power supply pulse is T, T=T1+T2;

[0017] T1 is the high current time period in a pulse, A1 is the peak value of the high-frequency current in the T1 period, T2 is the low current time period in a pulse, A2 is the peak value of the high-frequency current in the T2 period;

[0018] Among them, T=1~100sec, T1 / T2=1~20, A2 / A1=0~30.

[0019] Furthermore, during the smelting process, the pulse power supply mode is not used in the heating and melting stage, and the pulse mode is only started in the homogenization stage after the material is melted.

[0020] The present invention also provides a vacuum suspension melting device for refractory metal high entropy alloys, which is applied to the above method and includes a vacuum melting chamber and a water-cooled copper crucible installed in the vacuum melting chamber. The current input by the induction power supply generates an electromagnetic field in the induction coil surrounding the water-cooled copper crucible.

[0021] Furthermore, a DC arc discharge device is arranged on the upper side of the vacuum melting chamber, and the DC arc discharge device includes a DC power supply, a cable, a conductive rod, a sealing structure and an electrode;

[0022] The positive electrode of the DC power supply is connected to the vacuum melting chamber and the water-cooled copper crucible, and the negative electrode thereof is connected to the upper end of the conductive rod located above the vacuum melting chamber through a cable;

[0023] The conductive rod extends into the interior of the vacuum melting chamber through the sealing structure and is located directly above the water-cooled copper crucible;

[0024] An electrode is installed at the lower end of the conductive rod, and the electrode is made of metal tungsten.

[0025] Furthermore, the conductive rod is a rod for transmitting electric current, and a cooling water path is also provided inside the conductive rod;

[0026] The main body of the sealing structure is configured as a stainless steel bellows, the lower end of which is installed on the chamber cover of the vacuum melting chamber, and the upper end is installed into the conductive rod in an insulated manner through a sealing interface.

[0027] The advantages of the present invention compared with the prior art are:

[0028] 1. In the smelting process, the component with the highest melting point among the components of the high entropy alloy is melted with the component with the lowest melting point to form an intermediate alloy. The melting point of this alloy is significantly lower than that of the high melting point component, thereby solving the biggest problem of melting this alloy - the difficulty of melting the component with the highest melting point requires very large power; compared with the prior art, the melting point of this alloy is still very high, the difficulty of melting is still very large, and the melting point difference between the component with the highest melting point and the component with the second highest melting point is often also very large. After the two are mixed, the molten pool formed by the melting of the component with the second highest melting point first may not be able to melt the component with the highest melting point;

[0029] 2. A method is proposed to solve the technical difficulties of smelting components with very different melting points: the ratio of the volume Vd of the low melting point component to the volume Vh of the high melting point component is Vd≤0.5Vh. In this case, the high melting point component will not be unable to melt in the molten pool of the low temperature component;

[0030] 3. The combination of high melting point components and a small amount of low melting point components can accelerate the melting process. The power required to melt the high melting point components is the highest and the time is the longest. However, once a small amount of liquid phase appears, the power of melting can be reduced and the time is not long. The small molten pool formed by the melting of the low melting point components can infiltrate the high melting point components in contact with it to form a low melting point alloy liquid. This alloy liquid then infiltrates the high melting point components in contact with it and forms a slightly higher melting point alloy liquid with more high melting point components, and so on, until all high melting point components form alloys with low melting point components.

[0031] 4. The technology of using DC arc to assist in melting high melting point metals is beneficial for promoting the complete melting of high melting point components in the process of melting refractory metal high entropy alloys, and for reducing the energy consumption and time of the melting process;

[0032] 5. Provide pulse heating current to the molten pool, so that the direction and intensity of the electromagnetic field change dramatically, causing strong vibration and agitation in the molten pool, which is of great significance for the homogenization of the composition of multi-component alloys composed of components with large density differences;

[0033] 6. The suspension melting technology eliminates the contamination of the crucible material, can achieve very high melting temperatures, and has the effect of electromagnetic stirring. These characteristics provide favorable conditions for melting refractory metal high-entropy alloys with high melting temperatures, large differences in component melting points and densities, and a large number of components. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Schematic diagram of suspension smelting in a water-cooled copper crucible;

[0035] Figure 2 This is a diagram of an arc discharge device installed on a suspension smelting device;

[0036] Figure 3 This is a current pulse diagram of the induction power supply in pulse power supply mode.

[0037] Figure numerals: 01 - water-cooled copper crucible, 02 - vacuum melting chamber, 03 - induction coil, 04 - molten pool, 05 - suspension force, 06 - DC power supply, 07 - cable, 08 - conductive rod, 09 - sealing structure, 10 - electrode, 11 - cooling water channel, 12 - sealing interface. DETAILED DESCRIPTION

[0038] Combined with Figure 1-3 As shown, this embodiment provides a vacuum levitation melting method for refractory metal high entropy alloys, and adopts levitation melting equipment as a device for melting refractory metal high entropy alloys.

[0039] Key References Figure 1The water-cooled copper crucible 01 of the suspension smelting equipment is installed in the vacuum smelting chamber 02, and the current input by the induction power supply generates an electromagnetic field in the induction coil 03 surrounding the water-cooled copper crucible 01. It can be understood that the water-cooled copper crucible 01 used in the suspension smelting technology has a structure with axial petals, and the electromagnetic field passes through the side wall of the water-cooled copper crucible 01 to heat the material in the crucible, and generates a suspension force 05 perpendicular to the axis direction of the water-cooled copper crucible 01 on the molten pool 04, so that the molten pool 04 is separated from the inner wall of the crucible under the action of the suspension force 05.

[0040] It is understandable that the suspension smelting technology eliminates the contamination of the molten pool 04 by the water-cooled copper crucible 01 material during the smelting process, which provides a guarantee for the purity of the material; the suspension smelting technology also eliminates the limitation of the crucible material in its ability to withstand high temperatures, so it can be applied to very high smelting temperatures; the suspension smelting uses an electromagnetic field to heat the molten pool 04, which has the effect of electromagnetic stirring, which also provides an important role for smelting high-entropy alloys with large differences in melting points and densities and many components. Suspension smelting has no restrictions on the shape and size of the smelting material, and can also use different casting techniques to directly prepare products of various shapes after smelting. These advantages make the suspension smelting technology an effective means of smelting refractory metal high-entropy alloys.

[0041] It should be noted that, as shown in Table 1 below, refractory metals include elements such as tungsten, rhenium, tantalum, molybdenum, niobium, hafnium, and vanadium, which not only have high melting points but also high densities. Refractory metal high entropy alloy is a multi-component alloy with equal atomic ratios, whose components are mainly the refractory metal elements in Table 1, and may also contain a small amount of non-refractory metal elements. High entropy alloys generally contain 4 to 5 components. In this embodiment, the first component with the highest melting point is recorded as M1, the second component with the second highest melting point is recorded as M2, the third component with the third highest melting point is recorded as M3, ..., and the component with the lowest melting point is recorded as Mi. It can be understood that i is greater than or equal to 4.

[0042] It is worth noting that the refractory metal high entropy alloy may also contain some trace elements. In this embodiment, the trace elements are not referred to as components.

[0043] Table 1 - Basic data of refractory metal elements

[0044]

[0045]

[0046] However, there are also important technical difficulties in melting refractory metal high entropy alloys using suspension melting technology. The reason is that the melting point of the component with the highest melting point in this alloy is close to the highest temperature that can be achieved by suspension melting. For example, the melting points of tungsten, rhenium and tantalum are close to or exceed 3000°C, and melting these metals has very high requirements for suspension melting equipment. The difficulty also lies in the fact that in refractory metal high entropy alloys, the melting points of the components have a very large gap. For example, the melting point of tungsten is 1500°C higher than that of vanadium. When various components with very different melting points are mixed together for melting, it is difficult to heat up the molten pool 04 after the component with the lower melting point is melted, and the components with high melting points in the molten pool 04 are difficult to melt.

[0047] In order to eliminate the above problems, the vacuum levitation melting method of the refractory metal high entropy alloy of this embodiment includes the following steps:

[0048] The first step is to add a small amount of one, two or more components with the lowest melting point to form a primary intermediate alloy with a lower melting point.

[0049] The second step is to add one, two or more components with the second lowest melting point to the primary master alloy to obtain a secondary master alloy with a further lower melting point;

[0050] The third step is to form intermediate alloys with successively lower melting points in a similar manner;

[0051] The fourth step is to mix the final intermediate alloy with the remaining metal and smelt it to obtain a refractory metal high entropy alloy with the required composition.

[0052] During the smelting process from the second step to the fourth step, the intermediate alloy ingot is first turned over in a water-cooled copper crucible. The alloy obtained in the fourth step needs to be turned over and remelted once or several times to make the alloy composition uniform.

[0053] Specifically, taking a five-element high entropy alloy as an example, first all of M1, or all of M1 with all or part of M2, and all or part of M5 are mixed and smelted to obtain a first intermediate alloy Z1 with a lowered melting point; then, Z1 is mixed with all or part of the remaining M2 and M3 and smelted to obtain a second intermediate alloy Z2 with a further lowered melting point; and so on, intermediate alloys with lower and lower melting points are obtained; finally, the finally formed intermediate alloy is mixed with the remaining metal raw materials and smelted to obtain a high entropy alloy that meets the composition requirements.

[0054] In this embodiment, during the smelting process of step 1 to step 3, the liquid volume Vh of the high melting point material must be significantly greater than the volume Vd of the low melting point material, preferably, Vh / Vd>2. Thus, the difficulty that the high melting point material is not melted due to the high melting point material being soaked in the molten pool of the low melting point material and the smelting temperature is no longer increased can be eliminated; and the problem that once the metal forms a molten pool during the suspension smelting process, the temperature is difficult to increase, and even if the heating power is increased, the superheat degree is only more than 100 degrees at most can be solved.

[0055] In this embodiment, during the smelting process from the second step to the fourth step, the intermediate alloy ingot is first turned over in the water-cooled copper crucible 01 to improve the uniformity of the alloy composition after smelting.

[0056] It should be noted that the use of suspension smelting technology to melt refractory metals requires a lot of power and a long time, and consumes a lot of energy. In order to reduce the difficulty and energy consumption of smelting, in this embodiment, a DC arc discharge device is arranged on the top of the smelting equipment.

[0057] Specifically, see Figure 2 The DC arc discharge device includes a DC power supply 06, a cable 07, a conductive rod 08, a sealing structure 09 and an electrode 10. The positive electrode of the DC power supply 06 is connected to the vacuum melting chamber 02 and the water-cooled copper crucible 01, and the negative electrode thereof is connected to the upper end of the conductive rod 08 located above the vacuum melting chamber 02 through the cable 07; the conductive rod 08 is a rod for transmitting current, and a cooling water path 11 is also provided inside the conductive rod 08; the conductive rod 08 extends into the interior of the vacuum melting chamber 02 through the sealing structure 09, and is located directly above the water-cooled copper crucible 01.

[0058] Preferably, the main body of the sealing structure 09 is configured as a stainless steel bellows, the lower end of which is mounted on the chamber cover of the vacuum melting chamber 02, and the upper end is mounted in an insulated manner into the conductive rod 08 through the sealing interface 12. Thus, the conductive rod 08 has the ability to rise and fall through the sealing interface 12 of the sealing structure 09, and the soft structure of the bellows also enables the conductive rod 08 to swing. The lower end of the conductive rod 08 is mounted with an electrode 10, and the electrode 10 is made of metal tungsten.

[0059] Therefore, during the smelting process, especially when smelting metal components with high melting points and when unmelted metal blocks are found in the molten pool, the DC power supply 06 is started, and the conductive rod 08 is lowered, so that the electrode 10 is close to the material to start arc discharge, and the high temperature of the arc is used to quickly melt the unmelted material. Through the above arrangement, the smelting time of the alloy can be greatly shortened, the energy consumption of the smelting process can be reduced, and a reliable guarantee is provided for the complete melting of the alloy components to obtain materials with components that meet the requirements.

[0060] It is understandable that the density difference of each component of the refractory metal is also very large (see Table 1). In the molten pool 04, due to the density difference, a state of high-density components being concentrated at the bottom of the molten pool 04 is formed. Although the electromagnetic field of the suspension smelting has a certain electromagnetic stirring effect, the intensity of its effect often cannot meet the requirement of making the molten pool 04 completely uniform.

[0061] In order to solve this difficulty, the present embodiment provides a pulse power transmission function for the induction power supply, so that the high-frequency electromagnetic field in the molten pool 04 changes in a periodic manner. Therefore, in each cycle, the sudden increase and decrease, or sudden generation and disappearance of the electromagnetic field will cause a drastic change in the electromagnetic field intensity, causing the molten pool 04 to produce very strong oscillations and agitation, which has a significant improvement effect on homogenization.

[0062] Specifically, see Figure 3 The period of the induction power pulse is T, T=T1+T2. T1 is the high current time period in a pulse, A1 is the peak value of the high-frequency current in the T1 segment, T2 is the low current time period in a pulse, A2 is the peak value of the high-frequency current in the T2 segment. T, T1, T2, A1, and A2 can all be set. Preferably, T=1~100sec, T1 / T2=1~20, and A2 / A1=0~30 are set.

[0063] It is worth noting that during the smelting process, the pulse power supply mode is not used in the heating and melting stage, and the pulse mode is only started in the homogenization stage after the material is melted.

[0064] At the end of the smelting process, at the moment of stopping the power supply, the high-temperature molten pool 04 suddenly falls to the bottom of the water-cooled copper crucible 01, which will burn the bottom of the crucible. In this embodiment, the power supply is slowly reduced at the end of the smelting process to keep the molten pool 04 in a suspended state and solidify. Therefore, when the power is further reduced, the material is already in a solid state when it falls to the bottom of the crucible, and in this state, the water-cooled copper crucible 01 is generally not burned.

[0065] The present invention also provides some specific embodiments to better understand the present invention:

[0066] Embodiment 1:

[0067] In this embodiment, 5 kg of WTaMoNbV high entropy alloy was smelted, and the components were composed according to equiatomic ratios, and the mass ratios were 30.40% W, 29.93% Ta, 15.87% Mo, 15.37% Nb, and 8.43% V. According to this composition, the masses of the components in the alloy were 1520 g of W, 1496.5 g of Ta, 793.5 g of Mo, 768.5 g of Nb, and 421.5 g of V.

[0068] In the suspension melting device, the first master alloy is melted with 1520g of W and 200g of V. Since the density of V is only 1 / 3 of that of W, the volume of these V is equivalent to 2 / 5 of that of W. From the phase diagram, the liquidus melting point of this WV master alloy is about 3000℃.

[0069] An ingot of WV master alloy with a mass of 1720 g was turned over in a crucible, and 1496.5 g of Ta (melting point 2996° C.) was added to smelt to obtain 3216.5 g of W-Ta-V master alloy with a melting point below 3000° C.

[0070] The W-Ta-V master alloy ingot was turned over in the crucible, and 793.5g of Mo was added for mixed melting to obtain 4010g of W-Ta-V-Mo master alloy. After turning the master alloy over in the crucible, 768.5g of Nb and the remaining 221.5g of V were added to finally obtain 5kg of WTaMoNbV high entropy alloy. The alloy was turned over and remelted once more to make the alloy composition uniform.

[0071] During each smelting process of the intermediate alloy and the final high entropy alloy, the power of the power supply is slowly reduced during the cooling process at the end of the smelting process to allow the alloy molten pool to solidify in a suspended state.

[0072] Embodiment 2:

[0073] This embodiment still uses a suspension smelting device to smelt 5kg of WTaMoNbV high entropy alloy, and the process route of the smelting process is the same as that of Example 1. The difference from Example 1 is that a DC arc discharge device is provided for the vacuum melting chamber. The device consists of a DC power supply, a cable, a conductive rod, a sealing structure and an electrode. The positive electrode of the DC power supply is connected to the melting chamber and the crucible, and its negative electrode is connected to the upper end of the conductive rod located above the melting chamber through a cable. The conductive rod is a rod for transmitting current, and a cooling water circuit is also provided inside it. The conductive rod extends into the interior of the melting chamber through a sealing structure and is located directly above the crucible. The main body of the sealing structure is a stainless steel bellows, the lower end of which is mounted on the chamber cover of the melting chamber, and the upper end is insulated by the conductive rod through a sealing interface. The conductive rod has the ability to rise and fall through the sealing interface of the sealing structure, and the soft structure of the bellows also enables the conductive rod to swing. The lower end of the conductive rod is equipped with an electrode, which is made of metal tungsten.

[0074] In the process of smelting the first master alloy WV master alloy and the second master alloy W-Ta-V master alloy, since the melting points of W and Ta are very high, an arc discharge device is used to assist the smelting process. The method is to start the DC power supply of the device during the heating process, lower the conductive rod, make the tungsten electrode contact the material to start the arc, and then slightly raise the electrode to maintain the arc between the electrode and the material, and use the arc to heat the material, so that the melting process is accelerated. In the process of using this device, the DC current provided by the power supply is maintained in the range of 600 to 800A. In the subsequent smelting process, due to the low melting point of the material, this arc discharge device can be omitted.

[0075] Embodiment 3:

[0076] This embodiment also uses a suspension smelting device to smelt 5kg of WTaMoNbV high entropy alloy, and the process route of the smelting process is the same as that of Embodiment 1. The difference from Embodiment 1 is that this embodiment sets a pulse power transmission mode for the induction power supply. During each smelting process, when the material in the crucible is melted, the power transmission mode of the power supply is changed to pulse power transmission. This power transmission mode generates a violent electromagnetic stirring effect in the molten pool, which promotes the homogenization of the composition of the molten pool.

[0077] The pulse period is T, T=T1+T2. T1 is a high current segment with a current intensity of A1, and T2 is a low current segment with a current intensity of A2. In this embodiment, T=3 sec, T1 / T2=5, and A2 / A1=0.1 are set.

[0078] Embodiment 4:

[0079] In this embodiment, 5 kg of TaMoNbHf quaternary high entropy alloy is planned to be smelted, and each component is composed according to an equiatomic ratio, and the mass ratio is 33.00% Ta, 17.50% Mo, 16.95% Nb, and 32.55% Hf. According to this composition, the mass of each component in the alloy is 1650 g Ta, 875 g Mo, 847.5 g Nb, and 1627.5 g Hf.

[0080] In the suspension smelting equipment, the first master alloy is smelted by combining 1650g of Ta and 550g of Hf. In this alloy, the volume of Hf is equivalent to 2 / 5 of Ta, and the liquidus melting point of the alloy is about 2700°C, which is close to the melting point of Mo.

[0081] The ingot of Ta-Hf master alloy with a mass of 2200g was turned over in the crucible, and 847.5g of Mo (melting point 2610°C) was added to smelt to obtain 3075g of Ta-Mo-Hf master alloy with a melting point below 2500°C. The Ta-Mo-Hf master alloy ingot was turned over in the crucible, 847.5g of Nb and the remaining 1077.5g of Hf were added to mix and melt, and then the ingot was turned over and remelted to obtain 5000g of Ta-Mo-Nb-Hf high entropy alloy.

[0082] Embodiment 5:

[0083] This embodiment plans to melt 5kg of WReTaMoNbV hexavalent high entropy alloy, and the components are composed according to the same atomic ratio, and the mass ratios are 23.25% W, 23.55% Re, 22.89% Ta, 12.13% Mo, 11.75% Nb, and 6.44% V. According to this composition, the masses of the components in the alloy are 1162.5g W, 1177.5g Re, 1144.5g Ta, 606.5g Mo, 587.5g Nb, and 322g V.

[0084] In the suspension smelting equipment, the first master alloy is smelted with 1162.5g of W, 1177.5g of Re and 322g of V to obtain a W-Re-V master alloy. After the master alloy is turned over, 606.5g of Mo and 587.5g of Nb are added for mixed smelting and then turned over and remelted to obtain a WReTaMoNbV high entropy alloy.

[0085] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A vacuum levitation melting method for refractory metal high entropy alloys, characterized in that: The steps include: The first step is to add a small amount of one, two or more components with the lowest melting point to form a primary intermediate alloy with a lower melting point. The second step is to add one, two or more components with the second lowest melting point to the primary master alloy to obtain a secondary master alloy with a further lower melting point; The third step is to form intermediate alloys with successively lower melting points in a similar manner; The fourth step is to mix the final intermediate alloy with the remaining metal and smelt it to obtain a refractory metal high entropy alloy with the required composition.

2. The method according to claim 1, characterized in that During the smelting process from step 1 to step 3, the liquid volume Vh of the high melting point material is greater than the volume Vd of the low melting point material.

3. The method according to claim 2, characterized in that Vh / Vd>2.

4. The method according to claim 1, characterized in that: During the smelting process from the second step to the fourth step, the intermediate alloy ingot is first turned over in a water-cooled copper crucible; preferably, the alloy obtained in the fourth step needs to be turned over and remelted once or several times.

5. The method according to claim 1, characterized in that: When smelting metal components and when unmelted metal blocks are found in the molten pool, an auxiliary electrode is used to start arc discharge close to the material, and the high temperature of the arc is used to quickly melt the unmelted material.

6. The method according to claim 1, characterized in that The induction power supply has the function of pulse power transmission. The period of the induction power supply pulse is T, T=T1+T2; T1 is the high current time period in a pulse, A1 is the peak value of the high-frequency current in the T1 period, T2 is the low current time period in a pulse, A2 is the peak value of the high-frequency current in the T2 period; Among them, T=1~100sec, T1 / T2=1~20, A2 / A1=0~30.

7. The method according to claim 6, characterized in that During the smelting process, the pulse power supply mode is not used in the heating and melting stage, and the pulse mode is only started in the homogenization stage after the material is melted.

8. A vacuum levitation melting device for refractory metal high entropy alloys, characterized in that: The method as claimed in any one of claims 1 to 7 comprises a vacuum melting chamber and a water-cooled copper crucible installed in the vacuum melting chamber, wherein the current input by the induction power supply generates an electromagnetic field in the induction coil surrounding the water-cooled copper crucible.

9. The device according to claim 8, characterized in that A DC arc discharge device is arranged on the upper side of the vacuum melting chamber, and the DC arc discharge device comprises a DC power supply, a cable, a conductive rod, a sealing structure and an electrode; The positive electrode of the DC power supply is connected to the vacuum melting chamber and the water-cooled copper crucible, and the negative electrode thereof is connected to the upper end of the conductive rod located above the vacuum melting chamber through a cable; The conductive rod extends into the interior of the vacuum melting chamber through the sealing structure and is located directly above the water-cooled copper crucible; An electrode is installed at the lower end of the conductive rod, and the electrode is made of metal tungsten.

10. The device according to claim 9, characterized in that The conductive rod is a rod that transmits current, and a cooling water circuit is also provided inside it; The main body of the sealing structure is configured as a stainless steel bellows, the lower end of which is installed on the chamber cover of the vacuum melting chamber, and the upper end is installed into the conductive rod in an insulated manner through a sealing interface.

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