Method for improving yield and uniformity of electron beam cold bed smelted titanium alloy

Abstract

The invention discloses a method for improving the yield and uniformity of electron beam cold bed smelted titanium alloys, which comprises the following steps of: firstly, loading materials into a stock bin, firstly loading prepared raw materials into the stock bin during loading, and then supplementing lump materials into the head of the stock bin; charging the stock bin into a furnace after charging is completed, smelting to obtain a finished cast ingot, and monitoring and controlling parameters such as current and vacuum degree of an electronic gun in real time during smelting; and finally, the prepared cast ingot is subjected to saw cutting and aftertreatment. In order to solve the problems that the vacuum and current fluctuation at the initial stage of EB smelting is large and uneven bottom components are easily caused, the component fluctuation is intensively controlled in the area where the circulating materials are located by reasonably designing the adding mode of the circulating materials and the technological parameters of the gun starting and material drying stage, and the influence on the chemical uniformity of the newly-added raw material part is avoided. In addition, after smelting is finished, a circulating material part containing component fluctuation is integrally sawn and removed, on one hand, the yield of cast ingots is improved, and on the other hand, the uniformity of the cast ingots is guaranteed.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of metal smelting, and relates to electron beam smelting, in particular to a method for improving the yield and uniformity of titanium alloy products in electron beam cold hearth smelting. BACKGROUND

[0002] In the current titanium alloy manufacturing process, the electron beam cold hearth furnace (EBCHM) as an advanced smelting equipment has been maturely applied to produce high-quality titanium alloy ingots. Although EBCHM has significant advantages such as removing high and low density inclusions, the existing process still has deficiencies, which restricts its further promotion and application.

[0003] Among them, due to high vacuum and high smelting temperature, etc., when smelting high-saturation-vapor-pressure elements (such as aluminum, chromium, tin, etc.), there is a burnout volatilization associated with vacuum, which results in a lower yield than traditional vacuum consumable smelting (VAR). In addition, during the process of starting the gun and drying the material, the randomness of material outgassing and the large number of control variables of the electron gun make it difficult to accurately determine the specific weight and extent of the affected material. Even after sawing, there may still be incomplete sawing, which increases the risk of large composition fluctuations and uneven composition of the end of the finished ingot. These problems not only affect the quality consistency of the final product, but also increase the production cost and complexity. Although the smelting parameters can be adjusted or the equipment can be improved to some extent, due to the complex debugging process and high cost, these methods are difficult to be widely applied.

[0004] In summary, although the technology of smelting titanium alloy ingots by electron beam cold hearth furnace has made certain progress, there is still a lot of room for improvement in terms of yield and quality uniformity. In order to solve these problems, it is urgent to develop a new method to improve the yield of titanium alloy ingots while ensuring the uniformity of product quality. SUMMARY

[0005] In view of the deficiencies of the prior art, the purpose of the present application is to provide a method for improving the yield and uniformity of titanium alloy smelted by electron beam cold hearth, which solves the technical problem that the vacuum current fluctuates greatly in the early stage of smelting by electron beam cold hearth furnace, which easily leads to uneven composition at the bottom.

[0006] In order to solve the above technical problems, the technical scheme is adopted as follows: A method for improving the yield and uniformity of titanium alloy smelted by electron beam cold hearth, comprising the following steps: Step 1, material bin loading: Step 1.1, preparing raw materials; Step 1.2, loading the raw materials prepared in Step 1.1 into the material bin, and supplementing block materials to the head of the material bin.

[0007] Step two, after the completion of step one of the charge bin furnace, smelting after the preparation of finished ingot: Step 2.1, start the electron gun: the material bin is placed in the EB furnace, check no abnormality after sealing, then vacuum; when the vacuum value is less than or equal to 3.0 Pa and the leakage rate is less than or equal to 2.0 Pa / min, seven electron guns are started in turn, and the seven electron guns are recorded as 1# gun, 2# gun, 3# gun, 4# gun, 5# gun, 6# gun and 7# gun, wherein, 1# gun, 2# gun, 3# gun and 4# gun are main heating guns, 5# gun and 6# gun are auxiliary heating guns, and 7# gun is a refining gun; when the current of 1# gun to 5# gun is kept at 2-4 A, and the current of 6# gun and 7# gun is kept at 2 A, it is stable for more than 5 min.

[0008] Step 2.2, increase the current of all main heating guns and the first auxiliary heating gun to heat the material: Step 2.2.1, increase the current of the first auxiliary heating gun: turn on 5# gun and gradually increase the current of 5# gun; during the process of increasing the current of 5# gun, if the rising rate of vacuum value is too fast, the hydrogen of the electron gun is reduced synchronously; if the current of 5# gun is greater than 12 A, the electron gun is immediately closed, and the electron gun is restarted after the vacuum decreases.

[0009] Step 2.2.2, increase the current of the first main heating gun: when the vacuum value is less than or equal to 2.5 Pa, and the current of 5# gun is kept at 6 A for 6-10 min, reduce the current of 5# gun to 2-4 A, and turn on 1# gun at the same time, gradually increase the current of 1# gun to 4-6 A; during the process of increasing the current of 1# gun, if the vacuum value rises, the hydrogen of 1# gun and 5# gun is reduced synchronously; if the current of 1# gun is greater than 10 A, the electron gun is immediately closed, and the electron gun is restarted after the vacuum decreases; after the current of 1# gun is stable, adjust the current of 5# gun to 4-5 A.

[0010] Step 2.2.3, increase the current of the second main heating gun (the electron gun located in the diagonal direction of the first main heating gun): when the vacuum value is less than or equal to 2.0 Pa, and the current of 1# gun and 5# gun is kept at 4-6 A for 6-10 min, reduce the current of 1# gun and 5# gun to 2-4 A, and turn on 4# gun at the same time, gradually increase the current of 4# gun to 4-6 A; during the process of increasing the current of 4# gun, if the vacuum value rises, the hydrogen of 1# gun, 4# gun and 5# gun is reduced synchronously; if the current of 4# gun is greater than 10 A, the electron gun is immediately closed, and the electron gun is restarted after the vacuum decreases; after the current of 4# gun is stable, adjust the current of 1# gun and 5# gun to 5 A.

[0011] Step 2.2.4, increase the current of the remaining main heating guns: turn on gun #2 and gun #3 respectively, and wait for the vacuum to stabilize after the current of gun #2 and gun #3 stabilizes at 5A; the opening order of gun #1 / gun #4 and gun #2 / gun #3 can be changed; after two main heating guns have been turned on, if the vacuum fluctuation is large when the third main heating gun is started, turn off the already turned-on electron guns first, and turn the electron guns back on after the vacuum drops.

[0012] Step 2.3, start the second auxiliary heating gun and refining gun: when the vacuum value is ≤2.0Pa and the duration is 8-15min, turn on gun #6 and gun #7; operate gun #5 to open the overflow port, so that the titanium alloy molten liquid flows into the crystallizer; if the vacuum value rises during the process of opening the overflow port, reduce the current of part of the main heating gun or turn off the main heating gun, and restore it after the vacuum drops; use gun #6 and gun #7 to spread the titanium alloy molten liquid flowing into the crystallizer, and gradually cover the bottom of the entire crystallizer.

[0013] Step 2.4, adjust the current of all electron guns and carry out melting: when the vacuum value is ≤2.0Pa, adjust the current of guns 1 to 4 to 6 to 8.8A, and guns 5 to 7 to 4.5 to 7A, and start normal melting; after the material added to the head is completely melted, shrink the electron gun image at the edge of the crystallizer for 2 to 3 minutes, and then restore it to normal, so that the ingot will shrink at this point after cooling.

[0014] Step 3: The ingots obtained in Step 2 are sawed and post-processed.

[0015] The present invention also includes the following technical features: Specifically and optionally, in step 1.1, the titanium alloy is TC4 titanium alloy. The raw materials of TC4 titanium alloy include sponge titanium and intermediate alloy. The intermediate alloy includes vanadium aluminum, aluminum granules, iron granules and titanium dioxide.

[0016] When the titanium alloy is TC4 titanium alloy, step 1.2 specifically includes: pressing the raw materials into electrode blocks after mixing, and loading the electrode blocks into the hopper according to the loading requirements; placing the prepared clean EB semi-circular cut head blocks horizontally at the head of the hopper, with a 100mm semi-circular cut head placed as the first layer; placing two layers of aluminum plates above the semi-circular cut head, with lengths of 780, 600, 420, and 260mm respectively; after placing the aluminum plates, placing another 100mm thick semi-circular cut piece on top of them; replenishing the other hopper head is the same as the above process, with a total of 568kg of raw materials and 11.6kg of aluminum plates added to the two hoppers.

[0017] When the titanium alloy is TC4 and the ingot shape is φ920mm, step three specifically includes: after the ingot is cooled for 10 hours and then taken out of the furnace, the resulting shrinkage area is sawn; then the sawn round material is cut in half in the diameter direction, and then the material cut in half is sawn at 1 / 2 thickness in the thickness direction according to the horizontal laying requirements; finally, the surface needs to be cleaned to remove obvious oxidation or oil stains for subsequent recycling.

[0018] Specifically and optionally, in step 1.1, the titanium alloy is TA15 titanium alloy. The raw materials of TA15 titanium alloy include sponge titanium and master alloy. The master alloy includes vanadium aluminum, molybdenum aluminum, aluminum granules, sponge zirconium and titanium dioxide.

[0019] When the titanium alloy is TA15 titanium alloy, step 1.2 specifically includes: pressing the raw materials into electrode blocks after mixing, and loading the electrode blocks into the hopper according to the loading requirements; placing the prepared raw materials vertically at the head of the hopper to replenish the material, placing near-trapezoidal slices vertically at the bottom of the hopper, and placing aluminum plates on top of the near-trapezoidal slices. The aluminum plates are 625mm long and are placed in two rows and two layers; after the aluminum plates are placed, placing crescent-shaped slices on top of them; the replenishment process at the head of the other hopper is the same as above, and a total of 356kg of TA15 material and 7.1kg of aluminum plates are replenished into the two hoppers.

[0020] When the titanium alloy is TA15 and the ingot shape is φ750mm, step three specifically includes: after the ingot is cooled for 7 hours and then removed from the furnace, sawing is performed at the resulting shrinkage area; then the disc-shaped material that has been sawn off is cut in the middle of the diameter direction, and then the material that has been cut in the middle is cut at 1 / 3 of the radius parallel to the diameter direction according to the longitudinal placement requirements; finally, the surface needs to be cleaned to remove obvious oxidation or oil stains for subsequent recycling.

[0021] Specifically and optionally, in step 1.1, the titanium alloy is TB6 titanium alloy. The raw materials of TB6 titanium alloy include sponge titanium and master alloy. The master alloy includes vanadium aluminum, molybdenum aluminum, aluminum granules, sponge zirconium and titanium dioxide.

[0022] When the titanium alloy is TB6 titanium alloy, step 1.2 specifically includes: pressing the raw materials into electrode blocks after mixing, loading the electrode blocks into the silo according to the loading requirements; then placing 200kg of clean material of the same grade and the burn-off raw material to be replenished at the head of the silo as required, and calculating the replenishment of burn-off elements based on the weight of the same grade material.

[0023] When the titanium alloy is TB6 and the ingot shape is φ520mm, step three specifically includes: after the ingot has cooled for 5 hours and is removed from the furnace, sawing is performed at the resulting shrinkage area; then, the sawn disc-shaped material is cut in half along its diameter, and then the half-cut material is cut in the thickness direction or parallel to the previously cut diameter direction. The thickness direction sawing is performed at 1 / 3 to 1 / 2 of the thickness; the parallel diameter sawing is performed at 1 / 3 to 2 / 3 of the radius. Finally, the surface needs to be cleaned to remove obvious oxidation or oil stains for subsequent recycling.

[0024] The beneficial technical effects of this invention compared to the prior art are as follows: (I) This invention addresses the problem of large vacuum and current fluctuations in the initial stage of EB smelting, which easily leads to uneven composition at the bottom. By rationally designing the method of adding circulating materials and the process parameters during the start-up and drying stage, the composition fluctuations are concentrated and controlled in the area where the circulating materials are located, thus avoiding affecting the chemical homogeneity of the newly added raw materials. In addition, after smelting, the circulating material containing composition fluctuations is sawn off as a whole, which improves the yield of ingots and ensures the uniformity of ingots.

[0025] (II) This invention introduces a recycling mechanism, which uses the material with fluctuating composition cut off after the previous smelting as “recycled material” and puts it back into the next smelting, thus realizing the efficient reuse of waste. Attached Figure Description

[0026] Figure 1 This is a feeding cycle process for the head of electron beam cold hearth melting.

[0027] Figure 2 This is a schematic diagram of the horizontal feeding configuration at the head of an electron beam cold bed melting process.

[0028] Figure 3 This is a schematic diagram of the longitudinal placement of feed material at the head of an electron beam cold bed melting process.

[0029] Figure 4 This is a photograph of a horizontally positioned object used for feeding material at the head of an electron beam cold bed melting machine.

[0030] Figure 5 This is a photograph of a longitudinally placed feedstock at the head of an electron beam cold hearth melting process.

[0031] Figure 6 A schematic diagram of multi-point sampling for electron beam cold hearth melting of ingots.

[0032] Figure 7 This is a photograph of other feed materials at the head of an electron beam cold hearth melting machine.

[0033] Figure 8 The chemical composition uniformity of Example 1 and Comparative Example 1 was compared.

[0034] Figure 9 The chemical composition uniformity of Example 2 and Comparative Example 2 was compared.

[0035] The technical solution of the present invention will be further described below with reference to the embodiments. Detailed Implementation

[0036] It should be noted that, unless otherwise specified, all raw materials used in this invention are those known in the art.

[0037] Following the above technical solutions, specific embodiments of the present invention are given below. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0038] Example 1: This embodiment provides a method for improving the yield and uniformity of titanium alloys melted by electron beam cold hearth, such as... Figure 1 As shown, the method includes the following steps: Step 1: Loading materials into the hopper: Step 1.1, Prepare raw materials: The raw materials for TC4 titanium alloy include sponge titanium and intermediate alloys (vanadium aluminum, aluminum granules, iron granules, titanium dioxide), and recycled materials may also be included if necessary; The target composition of the smelted TC4 titanium alloy is: aluminum 6.5 wt%, vanadium 4.2 wt%, iron 0.18 wt%, oxygen 0.18 wt%, and the balance is titanium.

[0039] Step 1.2: Load the raw materials prepared in Step 1.1 into the hopper, and add block material to the head of the hopper: After the raw materials are mixed, they are pressed into electrode blocks, and the electrode blocks are loaded into the electron beam cold hearth furnace (EB furnace) hopper according to the loading requirements; such as Figure 2 As shown, the prepared clean EB semi-circular cut pieces are placed horizontally at the head of the hopper, with 100mm semi-circular cut pieces placed as the first layer. Two layers of aluminum plates are placed above the semi-circular cut pieces, with lengths of 780, 600, 420, and 260mm respectively. After the aluminum plates are placed, another 100mm thick semi-circular slice is placed on top of them. The material replenishment process at the head of the other hopper is the same as above. A total of 568kg of raw materials and 11.6kg of aluminum plates are added to the two hoppers. The planned diameter of the EB ingot to be smelted is 920mm, and the material input is 10,000kg.

[0040] Step two: After completing the loading in step one, the material is loaded into the furnace and smelted to obtain the finished ingot. Step 2.1, Start the electron guns: Place the hopper containing the raw materials into the EB furnace. After checking for any abnormalities, seal the furnace and turn on the vacuum pump group to evacuate the air. When the vacuum value is ≤3.0Pa and the leakage rate is ≤2.0Pa / min, start the seven electron guns sequentially (referred to as gun #1, gun #2, gun #3, gun #4, gun #5, gun #6, and gun #7) until the current of electron guns #1-5 is maintained at 4A and the current of electron guns #6-7 is maintained at 2A (do not reduce the size of the pattern to prevent melting the copper pad), and maintain this stable state for more than 10 minutes. During smelting, electron guns #1-4 serve as the main heating source (i.e., the main heating gun), ensuring uniform temperature distribution and promoting the flotation of inclusions and homogenization of composition; electron guns #5-6 provide auxiliary heating (i.e., the auxiliary heating gun), adjusting the temperature gradient at the edge of the molten pool to reduce segregation; electron gun #7 is used for fine-tuning and local reheating (i.e., the refining gun), ensuring the optimal state of the final ingot.

[0041] Step 2.2: Increase the current of all main heating guns and the first auxiliary heating gun to dry the material: Step 2.2.1, increase the current of the first auxiliary heating gun: turn on gun #5, widen the scanning image, and gradually increase the current of gun #5; at this time, as the furnace temperature rises and the vacuum value increases rapidly, the hydrogen in the electron gun needs to be reduced simultaneously to prevent the current from being too high; if the current exceeds 12A, the electron gun should be turned off immediately, and the electron gun should be turned on again after the vacuum drops. Step 2.2.2, increase the current of the first main heating gun: When the vacuum value is ≤2.5Pa and the current of gun #5 can be stabilized at 6A for about 10 minutes, reduce the current of gun #5 to 4A, and at the same time turn on electron gun #1, gradually increase the current of gun #1 to 6A; if the vacuum value rises, reduce the hydrogen gas in electron guns #1 and #5 simultaneously. If the current exceeds 10A, the electron gun should be turned off and the vacuum should be reduced; after gun #1 stabilizes, increase the current of gun #5 to 5A.

[0042] Step 2.2.3, increase the current of the second main heating gun: When the vacuum value is ≤2.0Pa, and the current of guns 1# and 5# can be stabilized at 6A for about 10 minutes, reduce the current of guns 1# and 5# to 4A, and at the same time turn on electron gun 4# (obliquely facing), gradually increase the current of gun 4# to 6A. If the vacuum value rises, reduce the hydrogen gas in electron guns 1#, 4#, and 5# simultaneously. If the current exceeds 10A, the electron gun should be turned off and wait for the vacuum to decrease. After gun 4# stabilizes, increase the current of guns 1# and 5# to 5A.

[0043] Step 2.2.4, increase the current of the remaining main heating guns: Refer to steps 2.2.2 and 3.2.3, turn on electron guns #2 and #3 respectively, and wait for the vacuum to stabilize after reaching 5A. The order of turning on electron guns #1 / #4 and #2 / #3 can be changed. If the vacuum fluctuates greatly when the third electron gun is started after two guns have been turned on, the electron gun that has already been turned on can be turned off first as appropriate.

[0044] Step 2.3: Start the second auxiliary heating gun and refining gun: When the vacuum value is ≤2.0Pa for 15 minutes, turn on electron guns #6 and #7; operate gun #5 to open the overflow port, allowing the titanium alloy melt to flow into the crystallizer; if the vacuum value rises, the current of some guns from gun #1 to #4 can be reduced or the electron gun can be turned off as needed, and restored after the vacuum drops; use guns #6 and #7 to spread the titanium alloy melt flowing into the crystallizer, gradually covering the bottom of the entire crystallizer.

[0045] Step 2.4: Adjust the current of all electron guns for melting: Once the vacuum value is ≤2.0Pa, adjust the current of guns #1 to #4 to 8.8A, and guns #5 to #7 to 7A, and begin normal melting. After the display shows that the material added to the head has been completely melted, shrink the electron gun image at the edge of the crystallizer for 3 minutes, then return to normal, allowing the ingot to cool and form a shrinkage at this point.

[0046] Step 3: Sawing and post-processing the ingot obtained in Step 2: After the ingot is cooled for 10 hours and removed from the furnace, it is sawn at the resulting shrinkage area. Then, the sawn round material is cut in half along the diameter direction. The material cut in half along the diameter direction is then cut at half the thickness according to the horizontal laying requirements. Finally, the surface needs to be cleaned to remove obvious oxidation or oil stains for subsequent recycling.

[0047] Verification of the effect of Example 1: The TC4 titanium alloy EB ingot produced using the process of Example 1 weighed 9648 kg after sawing, with a yield of 96.5%. A schematic diagram of the 13-point sampling at the sawn end is shown below. Figure 6 The specific test data are shown in Table 1. According to the test results, the average values ​​of the main components Al, V, O, and Fe are 6.54, 4.26, 0.193, and 0.174, respectively, close to the target values ​​of 6.5, 4.2, 0.18, and 0.18. Furthermore, the maximum values ​​of Al, V, O, and Fe are 6.58, 4.32, 0.209, and 0.187, respectively, while the minimum values ​​are 6.47, 4.18, 0.176, and 0.165, with ranges of 0.11, 0.14, 0.033, and 0.022. In conclusion, the chemical composition homogeneity in this area is considered to be good.

[0048] Table 1. Elemental distribution data of ingots obtained in Example 1

[0049] Example 2: This embodiment provides a method for improving the yield and uniformity of titanium alloys melted by electron beam cold hearth, such as... Figure 1 As shown, the method includes the following steps: Step 1: Loading materials into the hopper: Step 1.1, Prepare raw materials: The raw materials for TA15 titanium alloy include sponge titanium and master alloys (vanadium aluminum, molybdenum aluminum, aluminum granules, sponge zirconium, titanium dioxide), and recycled materials may also be included if necessary; The target composition of the smelted TA15 titanium alloy is: aluminum 6.8 wt%, molybdenum 1.7 wt%, vanadium 2.25 wt%, zirconium 2.25 wt%, oxygen 0.12 wt%, with the balance being titanium.

[0050] Step 1.2: Load the raw materials prepared in Step 1.1 into the hopper, and add block material to the head of the hopper: After the raw materials are mixed, they are pressed into electrode blocks, and the electrode blocks are loaded into the EB hopper according to the loading requirements; such as Figure 2 As shown, the prepared raw materials are placed vertically at the head of the silo to replenish the material. Near-trapezoidal slices are placed vertically at the bottom of the silo, and aluminum plates with a length of 625mm are placed on top of the near-trapezoidal slices, in two rows and two layers. After the aluminum plates are placed, crescent-shaped slices are placed on top of them. The replenishment process at the head of the other silo is the same as above. A total of 356kg of TA15 material and 7.1kg of aluminum plates are replenished into the two silos. The planned diameter of the smelting ingot is 750mm, and the feeding amount is 8800kg. Step two: After completing the loading in step one, the material is loaded into the furnace and smelted to obtain the finished ingot. Step 2.1, Start the electron guns: Place the hopper containing the raw materials into the EB furnace. After checking for any abnormalities, seal the furnace and turn on the vacuum pump group to evacuate the air. When the vacuum value is ≤3.0Pa and the leakage rate is ≤2.0Pa / min, start the seven electron guns (referred to as gun 1#, gun 2#, gun 3#, gun 4#, gun 5#, gun 6#, and gun 7# in sequence) until the current of electron guns 1#-5# is maintained at 4A and the current of electron guns 6#-7# is maintained at 2A (do not reduce the size of the pattern to prevent melting the copper pads). After stabilizing for 8 minutes, turn off the electron guns.

[0051] Step 2.2: Increase the current of all main heating guns and the first auxiliary heating gun to dry the material: Step 2.2.1, Increase the current of the first auxiliary heating gun: Turn on gun #5, widen the scanning image, and gradually increase the current of gun #5. At this time, as the furnace temperature rises and the vacuum value increases rapidly, the hydrogen gas in the electron gun needs to be reduced simultaneously to prevent excessive current; if the current exceeds 12A, the electron gun should be turned off immediately, and restarted after the vacuum drops. Step 2.2.2, increase the current of the first main heating gun: When the vacuum value is ≤2.5Pa and the current of gun #5 can be stabilized at 6A for about 8 minutes, reduce the current of gun #5 to 3A, and at the same time turn on electron gun #1, gradually increase the current of gun #1 to 5A; if the vacuum value rises, reduce the hydrogen gas in electron guns #1 and #5 simultaneously; if the current exceeds 10A, the electron gun should be turned off and wait for the vacuum to decrease; after gun #1 stabilizes, increase the current of gun #5 to 5A.

[0052] Step 2.2.3, increase the current of the second main heating gun: When the vacuum value is ≤2.0Pa, and the current of guns 1# and 5# can be stabilized at 5A for about 8 minutes, reduce the current of guns 1# and 5# to 3A, and at the same time turn on electron gun 4# (obliquely facing), gradually increase the current of gun 4# to 5A. If the vacuum value rises, reduce the hydrogen gas of electron guns 1#, 4#, and 5# simultaneously. If the current exceeds 10A, the electron gun should be turned off and wait for the vacuum to decrease. After gun 4# stabilizes, increase the current of guns 1# and 5# to 5A.

[0053] Step 2.2.4, Increase the current of the remaining main heating guns: Refer to steps 2.2.1 to 2.2.3, turn on electron guns #2 and #3 respectively, and wait for the vacuum to stabilize after reaching 5A. The order of turning on electron guns #1 / #4 and #2 / #3 can be interchanged; if two guns have already been turned on, the vacuum fluctuation is large when the third electron gun is started, and the already turned-on electron gun can be turned off first as needed.

[0054] Step 2.3: Start the second auxiliary heating gun and refining gun: When the vacuum value is ≤2.0Pa for 10 minutes, turn on electron guns #6 and #7; operate gun #5 to open the overflow port, allowing the titanium alloy molten liquid to flow into the crystallizer; if the vacuum value rises, the current of some guns from gun #1 to #4 can be reduced or the electron gun can be turned off as needed, and the vacuum value can be restored after it drops; use guns #6 and #7 to spread the titanium alloy molten liquid flowing into the crystallizer, gradually covering the bottom of the entire crystallizer.

[0055] Step 2.4: Adjust the current of all electron guns for melting: Once the vacuum value is ≤2.0Pa, adjust the current of guns #1 to #4 to 8A, and guns #5 to #7 to 6A, and begin normal melting. After the display shows that the material added to the head has been completely melted, shrink the electron gun image at the edge of the crystallizer for 3 minutes, then return to normal, allowing the ingot to cool and form a shrinkage at this point.

[0056] Step 3: Sawing and post-processing the ingot obtained in Step 2: After the ingot is cooled for 10 hours and removed from the furnace, it is sawn at the resulting shrinkage area. Then, the sawn round material is cut in half along the diameter direction. The material cut in half is then cut at 1 / 3 of the radius, parallel to the diameter direction of the cut material, according to the longitudinal placement requirements. Finally, the surface needs to be cleaned to remove obvious oxidation or oil stains for subsequent recycling.

[0057] Verification of the effect of Example 2: The TA15 EB ingot produced using the process of Example 2 weighed 8574 kg after sawing, with a yield of 97.4%. A schematic diagram of the 13-point sampling at the sawing end is shown below. Figure 6 The specific test data are shown in Table 2. According to the test results, the average values ​​of the main components Al, V, Mo, and Zr are 6.88, 2.35, 1.77, and 2.28, respectively, close to the target values ​​of 6.80, 2.25, 1.70, and 2.25. Furthermore, the maximum values ​​of Al, V, Mo, and Zr are 7.00, 2.41, 1.81, and 2.32, and the minimum values ​​are 6.75, 2.28, 1.73, and 2.22, with ranges of 0.25, 0.13, 0.08, and 0.10. In conclusion, the chemical composition homogeneity in this area is considered to be good.

[0058] Table 2. Elemental distribution data of ingots obtained in Example 2

[0059] Example 3: This embodiment provides a method for improving the yield and uniformity of titanium alloys melted by electron beam cold hearth, such as... Figure 1 As shown, the method includes the following steps: Step 1: Loading materials into the hopper: Step 1.1, Prepare raw materials: The raw materials for TB6 titanium alloy include sponge titanium and intermediate alloys (vanadium aluminum, molybdenum aluminum, aluminum granules, sponge zirconium, titanium dioxide), and recycled materials may also be included if necessary; The target composition of the smelted TB6 titanium alloy is: vanadium 10.00 wt%, aluminum 3.0 wt%, iron 2.0 wt%, oxygen 0.15 wt%, with the balance being titanium.

[0060] Step 1.2: Load the raw materials prepared in Step 1.1 into the silo and add block material to the head of the silo: After the raw materials are mixed, press them into electrode blocks. Load the electrode blocks into the EB silo according to the loading requirements. Then, place 200kg of clean material of the same grade and the raw material to be replenished (such as 4.5kg of aluminum) at the head of the silo as required (the aluminum raw material to be replenished is in the form of pure aluminum plate and covered). The replenishment of the burning loss element is calculated based on the weight of the material of the same grade. The planned melting and casting ingot diameter is 520mm and the feeding amount is 3000kg.

[0061] Step two: After completing the loading in step one, the material is loaded into the furnace and smelted to obtain the finished ingot. Step 2.1, Start the electron guns: Place the hopper containing the raw materials into the EB furnace. After checking for any abnormalities, seal the furnace and turn on the vacuum pump group to evacuate the air. When the vacuum value is ≤3.0Pa and the leakage rate is ≤2.0Pa / min, start the seven electron guns (referred to as gun 1#, gun 2#, gun 3#, gun 4#, gun 5#, gun 6#, and gun 7# in sequence) until the current of electron guns 1#-5# is maintained at 2A and the current of electron guns 6#-7# is maintained at 2A (do not shrink the pattern to prevent melting the copper pads). After stabilizing for 5-10 minutes, turn them off. Step 2.2: Increase the current of all main heating guns and the first auxiliary heating gun to dry the material: Step 2.2.1, Increase the current of the first auxiliary heating gun: Turn on gun #5, widen the scanning image, and gradually increase the current of gun #5. At this time, as the furnace temperature rises and the vacuum value increases rapidly, the hydrogen gas in the electron gun needs to be reduced simultaneously to prevent excessive current; if the current exceeds 12A, the electron gun should be turned off immediately, and restarted after the vacuum drops. Step 2.2.2, increase the current of the first main heating gun: When the vacuum value is ≤2.5Pa and the current of gun #5 can be stabilized at 4A for about 6 minutes, reduce the current of gun #5 to 2A, and at the same time turn on electron gun #1, gradually increase the current of gun #1 to 4A; if the vacuum value rises, reduce the hydrogen gas in electron guns #1 and #5 simultaneously. If the current exceeds 10A, the electron gun should be turned off and wait for the vacuum to decrease; after gun #1 stabilizes, increase the current of gun #5 to 4A.

[0062] Step 2.2.3, increase the current of the second main heating gun: When the vacuum value is ≤2.0Pa, and the current of guns 1# and 5# can be stabilized at 4A for about 6 minutes, reduce the current of guns 1# and 5# to 2A, and at the same time turn on electron gun 4# (obliquely facing), gradually increase the current of gun 4# to 4A. If the vacuum value rises, reduce the hydrogen gas in electron guns 1#, 4#, and 5# simultaneously. If the current exceeds 10A, the electron gun should be turned off and wait for the vacuum to decrease. After gun 4# stabilizes, increase the current of guns 1# and 5# to 5A.

[0063] Step 2.2.4, Increase the current of the remaining main heating guns: Refer to steps 2.2.1 to 2.2.3, turn on electron guns #2 and #3 respectively, and wait for the vacuum to stabilize after reaching 5A. The order of turning on electron guns #1 / #4 and #2 / #3 can be interchanged; if two guns have already been turned on, the vacuum fluctuation is large when the third electron gun is started, and the already turned-on electron gun can be turned off first as needed.

[0064] Step 2.3: Start the second auxiliary heating gun and refining gun: When the vacuum value is ≤2.0 Pa for 8 minutes, turn on electron guns #6 and #7. Operate gun #5 to open the overflow port, allowing the molten titanium alloy to flow into the crystallizer. If the vacuum value rises, reduce the current of some guns from #1 to #4 or even turn off the electron gun as needed. Restore the vacuum after it drops. Use guns #6 and #7 to spread the molten titanium alloy flowing into the crystallizer, gradually covering the entire bottom of the crystallizer.

[0065] Step 2.4: Adjust the current of all electron guns for melting: Once the vacuum value is ≤2.0Pa, adjust the current of electron guns 1-4 to 6A, and guns 5-7 to 4.5A, and begin normal melting. After the display shows that the material added to the head has been completely melted, shrink the electron gun image at the edge of the crystallizer for 2 minutes, then return to normal, allowing the ingot to cool and form a shrinkage at this point.

[0066] Step 3: Sawing and post-processing the ingot obtained in Step 2: After the ingot has cooled for 5-10 hours and is removed from the furnace, the resulting shrinkage area is sawn. Then, the sawn circular material is cut in half along its diameter. Next, the half-cut material is sawn in the thickness direction or parallel to the diameter direction. The thickness-direction sawing is done at 1 / 3 to 1 / 2 of the thickness; the parallel-diameter sawing is done at 1 / 3 to 2 / 3 of the radius. Finally, the surface must be cleaned to remove any obvious oxidation or oil stains for subsequent reuse.

[0067] Verification of the effect of Example 3: The TB6 EB ingot produced using the above process weighed 2812 kg after sawing, with a yield of 93.7%. Using the same amount of material and ingot shape, without head replenishment, the EB ingot was sawn to a thickness of 200 mm, weighing 170 kg. The weight of the sawn ingot was 2630 kg, with a yield of 87.7%. Compared to not sawing, the yield increased by 6%, a significant improvement.

[0068] Comparative Example 1: This comparative example provides a method to improve the yield and uniformity of titanium alloys melted by electron beam cold hearth. The method is basically the same as that in Example 1, except that head feeding is not performed.

[0069] In this comparative example, step one includes: TC4 titanium alloy raw materials include sponge titanium and intermediate alloys (vanadium aluminum, aluminum granules, iron granules, titanium dioxide), and recycled materials if necessary; the target composition of the smelted TC4 titanium alloy is: aluminum 6.5 wt%, vanadium 4.2 wt%, iron 0.18 wt%, oxygen 0.18 wt%, with the balance being titanium. The prepared raw materials are loaded into a silo, mixed, and pressed into electrode blocks. The electrode blocks are then loaded into the silo according to the loading requirements. The planned diameter of the smelted EB ingot is 920 mm, and the feed rate is 10,000 kg.

[0070] In this comparative example, steps two and three are exactly the same as steps two and three in Example 1.

[0071] Verification of the effect of Example 1: The TC4 titanium alloy EB ingot produced using the process of Comparative Example 1 had a sawn thickness of 200 mm and a weight of 570 kg. After sawing, the ingot weight was 9110 kg, with a yield rate of 91.1%. A schematic diagram of the 13-point sampling at the sawn end is shown below. Figure 6 The specific test data are shown in Table 3. According to the test results, the average values ​​of the main components Al, V, O, and Fe are 6.54, 4.38, 0.201, and 0.160, respectively, which are close to the target values ​​of 6.5, 4.2, 0.18, and 0.18. Furthermore, the maximum values ​​of Al, V, O, and Fe are 6.63, 4.46, 0.227, and 0.177, respectively, while the minimum values ​​are 6.20, 4.25, 0.171, and 0.147, with ranges of 0.43, 0.21, 0.056, and 0.03. In conclusion, the chemical composition homogeneity in this area is considered acceptable.

[0072] Table 3. Elemental distribution data of ingots obtained in Comparative Example 1

[0073] In comparison, Example 1 showed a significant increase in yield, from 91.1% to 96.5% compared to Comparative Example 1. Furthermore, the chemical composition uniformity of Example 1 and Comparative Example 1 was also compared. Figure 8 In Example 1, the uniformity of each control element is significantly better and closer to the target value, proving that Example 1 significantly improves the uniformity of the composition of the ingot end face.

[0074] Comparative Example 2: This comparative example presents a method for improving the yield and uniformity of titanium alloys melted by electron beam cold hearth. This method is essentially the same as that in Example 2, except that the initial lance warm-up process in step two is different. The method specifically includes the following steps: Step 1: Loading materials into the silo: In this comparative example, step 1 is exactly the same as step 1 in Example 2.

[0075] Step two: After completing the loading in step one, the material is loaded into the furnace and smelted to obtain the finished ingot. Step 2.1, Start the electron guns: Place the hopper containing the raw materials into the EB furnace. After checking for any abnormalities, seal the furnace and turn on the vacuum pump group to evacuate the air. When the vacuum value is ≤3.0Pa and the leakage rate is ≤2.0Pa / min, start the seven electron guns (referred to as gun 1#, gun 2#, gun 3#, gun 4#, gun 5#, gun 6#, and gun 7# in sequence) until the current of electron guns 1#-5# is maintained at 6A and the current of electron guns 6#-7# is maintained at 3A (do not reduce the size of the pattern to prevent melting the copper pads). After stabilizing for 6 minutes, turn them off.

[0076] Step 2.2: Increase the current of all main heating guns and the first auxiliary heating gun to dry the material: Step 2.2.1, Increase the current of the first auxiliary heating gun: Turn on gun #5, widen the scanning image, and gradually increase the current of gun #5; at this time, as the furnace temperature rises and the vacuum value increases rapidly, the hydrogen in the electron gun needs to be reduced simultaneously to prevent the current from being too high; if the current exceeds 14A, the electron gun should be turned off immediately, and the electron gun should be turned on again after the vacuum drops. Step 2.2.2, increase the current of the first main heating gun: When the vacuum value is ≤2.5Pa, and the current of gun #5 can be stabilized at 6A for about 6 minutes, reduce the current of gun #5 to 4A, and at the same time turn on electron gun #1, gradually increase the current of gun #1 to 6A; if the vacuum value rises, reduce the hydrogen gas in electron guns #1 and #5 simultaneously; if the current exceeds 12A, turn off the electron gun and wait for the vacuum to decrease; after gun #1 stabilizes, increase the current of gun #5 to 4A.

[0077] Step 2.2.3, increase the current of the second main heating gun: Increase the current of the second main heating gun: When the vacuum value is ≤2.0Pa, and the current of guns 1# and 5# can be stabilized at 6A for about 6 minutes, reduce the current of guns 1# and 5# to 4A, and at the same time turn on electron gun 4# (obliquely facing), gradually increase the current of gun 4# to 4A. If the vacuum value rises, reduce the hydrogen gas in electron guns 1#, 4#, and 5# simultaneously. If the current exceeds 10A, the electron gun should be turned off and the vacuum should be reduced. After gun 4# stabilizes, increase the current of guns 1# and 5# to 4A.

[0078] Step 2.2.4, Increase the current of the remaining main heating guns: Refer to steps 2.2.1 to 3.2.3, turn on electron guns #2 and #3 respectively, and wait for the vacuum to stabilize after reaching 4A. The order of turning on electron guns #1 / #4 and #2 / #3 can be interchanged; if the vacuum fluctuates greatly when the third electron gun is started after two guns have already been turned on, the electron gun that has already been turned on can be turned off first, depending on the situation.

[0079] Step 2.3: Start the second auxiliary heating gun and refining gun, then increase the current of all electron guns for melting: When the vacuum value is ≤2.0Pa for 10 minutes, turn on electron guns #6 and #7; operate gun #5 to open the overflow port, allowing the molten titanium alloy to flow into the crystallizer; if the vacuum value rises, reduce the current of some guns from #1 to #4 or even turn off the electron guns as needed, and restore them after the vacuum drops; use guns #6 and #7 to spread the molten titanium alloy flowing into the crystallizer, gradually covering the entire bottom of the crystallizer; when the vacuum value is ≤2.0Pa, adjust the current of guns #1 to #4 to 8-9A, and guns #5 to #7 to 5-7A, and start normal melting. After the display shows that the material added to the head has been completely melted, shrink the electron gun image scanning the edge of the crystallizer for 3 minutes, then return to normal, allowing the ingot to shrink at this point after cooling.

[0080] Step 3: Sawing and post-processing the ingot obtained in Step 2: In this comparative example, Step 3 is exactly the same as Step 3 in Example 2.

[0081] Verification of the effect of Comparative Example 2: The TA15 titanium alloy EB ingot produced using the process of Comparative Example 1 had a sawn thickness of 200 mm and a weight of 370 kg. After sawing, the ingot weighed 8182 kg, with a yield of 93.0%. A schematic diagram of 13 sampling points at the sawn end is shown below. Figure 6 The specific test data are shown in Table 4. According to the test results, the average values ​​of the main components Al, V, Mo, and Zr are 6.75, 2.37, 1.76, and 2.19, respectively, which are close to the target values ​​of 6.80, 2.25, 1.70, and 2.25. Furthermore, the maximum values ​​of Al, V, Mo, and Zr are 7.04, 2.48, 1.91, and 2.26, respectively, and the minimum values ​​are 6.42, 2.32, 1.59, and 2.16, respectively, with ranges of 0.62, 0.16, 0.32, and 0.10. In conclusion, the chemical composition homogeneity of this area is considered acceptable.

[0082] Table 4. Elemental distribution data of ingots obtained in Comparative Example 2

[0083] In comparison, Example 2 showed a significant increase in yield, from 93.0% to 97.4% compared to Comparative Example 2. Furthermore, the chemical composition uniformity of Example 2 and Comparative Example 2 was also compared. Figure 9 In Example 2, the uniformity of each control element is significantly better and closer to the target value, proving that Example 2 significantly improves the uniformity of the composition of the ingot end face.

Claims

1. A method for improving the yield and uniformity of titanium alloys melted by electron beam cold hearth, characterized in that, The method includes the following steps: Step 1: Loading materials into the hopper: Step 1.1, Prepare the raw materials; Step 1.2: Load the raw materials prepared in Step 1.1 into the silo and add block materials to the head of the silo; Step two: After completing the loading in step one, the material is loaded into the furnace and smelted to obtain the finished ingot. Step 2.1, Start the electron gun: Place the hopper containing the raw materials into the EB furnace, check for any abnormalities, seal the furnace, and then evacuate the vacuum. When the vacuum value is ≤3.0 Pa and the leakage rate is ≤2.0 Pa / min, start all the electron guns in sequence. The electron guns include multiple main heating guns, multiple auxiliary heating guns, and at least one refining gun. When the current of all main heating guns and at least one auxiliary heating gun is maintained at 2-4A, and the current of the remaining auxiliary heating guns and refining gun is maintained at 2A, it should be stable for at least 5 minutes. Step 2.2: Increase the current of all main heating guns and the first auxiliary heating gun to dry the material; Step 2.3: Activate the second auxiliary heating gun and refining gun; Step 2.4: Adjust the current of all electron guns to perform melting; Step 3: The ingots obtained in Step 2 are sawed and post-processed.

2. The method for improving the yield and uniformity of titanium alloys smelted by electron beam cold hearth as described in claim 1, characterized in that, Step 2.2 includes: Step 2.2.1, Increase the current of the first auxiliary heating gun: Turn on the first auxiliary heating gun and gradually increase the current of the first auxiliary heating gun; Step 2.2.2, Increase the current of the first main heating gun: When the vacuum value is ≤2.5Pa, and the current of the first auxiliary heating gun is stably maintained at 4-6A for 6-10 minutes, reduce the current of the first auxiliary heating gun to 2-4A, and at the same time turn on the first main heating gun, gradually increasing the current of the first main heating gun to 4-6A; after the current of the first main heating gun is stable at 4-6A, increase the current of the first auxiliary heating gun to 4-5A; Step 2.2.3, increase the current of the second main heating gun located diagonally opposite the first main heating gun: When the vacuum value is ≤2.0Pa, and the current of the first main heating gun and the first auxiliary heating gun is stably maintained at 4-6A for 6-10 minutes, reduce the current of the first main heating gun and the first auxiliary heating gun to 2-4A, and at the same time turn on the second main heating gun, gradually increase the current of the second main heating gun to 4-6A; after the current of the second main heating gun stabilizes at 6A, increase the current of the first main heating gun and the first auxiliary heating gun to 5A; Step 2.2.4, Increase the current of the remaining main heating guns: Turn on the remaining main heating guns respectively, and wait for the vacuum to stabilize after the current of the remaining main heating guns stabilizes at 5A.

3. The method for improving the yield and uniformity of titanium alloys smelted by electron beam cold hearth as described in claim 2, characterized in that, In step 2.2.1, if the vacuum value rises too quickly during the current increase process, the hydrogen in the electron gun is reduced simultaneously; if the current of the first auxiliary heating gun is greater than 12A, the electron gun is immediately turned off and restarted after the vacuum drops.

4. The method for improving the yield and uniformity of titanium alloys smelted by electron beam cold hearth as described in claim 2, characterized in that, In step 2.2.2, if the vacuum value increases during the process of increasing the current of the first main heating gun, the hydrogen in the electron gun of the first main heating gun and the first auxiliary heating gun will be reduced simultaneously; if the current of the first main heating gun is greater than 10A, the electron gun will be turned off immediately and restarted after the vacuum drops.

5. The method for improving the yield and uniformity of titanium alloys smelted by electron beam cold hearth as described in claim 2, characterized in that, In step 2.2.3, if the vacuum value increases during the process of increasing the current of the second main heating gun, the hydrogen in the electron guns of the first main heating gun, the second main heating gun, and the first auxiliary heating gun will be reduced simultaneously; if the current of the second main heating gun is greater than 10A, the electron gun will be turned off immediately and restarted after the vacuum drops.

6. The method for improving the yield and uniformity of titanium alloys smelted by electron beam cold hearth as described in claim 2, characterized in that, In step 2.2.4, if the vacuum fluctuation is large when the third main heating gun is started after the two main heating guns have been turned on, the electron gun that has already been turned on should be turned off first, and the electron gun should be turned on again after the vacuum drops.

7. The method for improving the yield and uniformity of titanium alloys smelted by electron beam cold hearth as described in claim 1, characterized in that, Step 2.3 includes: when the vacuum value is ≤2.0Pa and the duration is 8-15min, turn on the remaining auxiliary heating guns and refining guns; operate the first auxiliary heating gun to open the overflow port, so that the titanium alloy molten liquid flows into the crystallizer; if the vacuum value rises during the process of opening the overflow port, reduce the current of part of the main heating gun or turn off the main heating gun, and restore it after the vacuum drops; use the remaining auxiliary heating guns and refining guns to spread the titanium alloy molten liquid flowing into the crystallizer, and gradually cover the bottom of the entire crystallizer.

8. The method for improving the yield and uniformity of titanium alloys melted by electron beam cooling as described in claim 1, characterized in that, Step 2.4 includes: when the vacuum value is ≤2.0Pa, adjust the current of all main heating guns to 6-8.8A, and adjust the current of all auxiliary heating guns and refining guns to 4.5-7A, and start normal melting; after the material added to the head is completely melted, shrink the electron gun image of the edge of the crystallizer for 2-3 minutes, and then restore it to normal, so that the ingot will shrink at this point after cooling.

9. The method for improving the yield and uniformity of titanium alloys melted by electron beam cooling as described in claim 1, characterized in that, The titanium alloy mentioned is one of TC4 titanium alloy, TA15 titanium alloy and TB6 titanium alloy.

10. The method for improving the yield and uniformity of titanium alloys melted by electron beam cooling as described in claim 9, characterized in that, When the titanium alloy is TC4 titanium alloy, step 1.2 specifically includes: pressing the raw materials into electrode blocks after mixing, loading the electrode blocks into the hopper according to the loading requirements; placing the prepared clean EB semi-circular cut head blocks horizontally at the head of the hopper, with a 100mm semi-circular cut head placed as the first layer; placing two layers of aluminum plates above the semi-circular cut head, with aluminum plate lengths of 780, 600, 420, and 260mm respectively; after the aluminum plates are placed, placing another 100mm thick semi-circular cut piece on top of them; and replenishing the other hopper head in the same manner as above. When the titanium alloy is TA15 titanium alloy, step 1.2 specifically includes: pressing the raw materials into electrode blocks after mixing, loading the electrode blocks into the hopper according to the loading requirements; placing the prepared raw materials vertically at the head of the hopper to replenish the material, placing near-trapezoidal slices vertically at the bottom of the hopper, placing aluminum plates on top of the near-trapezoidal slices, the aluminum plates being 625mm in length, and placing them in two rows and two layers; after the aluminum plates are placed, placing crescent-shaped slices on top of them; the replenishment process at the head of the other hopper is the same as the above process. When the titanium alloy is TB6 titanium alloy, step 1.2 specifically includes: pressing the raw materials into electrode blocks after mixing, loading the electrode blocks into the silo according to the loading requirements; then placing clean materials of the same grade and the burn-off raw materials to be replenished at the head of the silo as required, and calculating the replenishment of burn-off elements based on the weight of the materials of the same grade.

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