Preparation method of low-cost high-quality titanium ingot

Abstract

The invention relates to a preparation method of a low-cost high-quality titanium ingot. The method comprises the following steps that raw materials including 20%-30% of new materials (titanium sponge, aluminum-vanadium intermediate alloy, aluminum shots and aluminum plates) and 70%-80% of recycled materials (TC4 blocky recycled materials and TC4 scrap-shaped recycled materials) are prepared, and the recycled materials are treated; mixing the materials and pressing a titanium alloy lump; material distribution is conducted, specifically, the titanium alloy lumps, the recycled materials and the aluminum plates are evenly stacked in an electron beam cold bed furnace (EB furnace) for drying treatment; eB is smelted to obtain an EB cast ingot; performing end flattening treatment on the EB cast ingot; and the EB cast ingot serves as a consumable electrode and is subjected to secondary smelting in a vacuum consumable electric arc furnace (VAR furnace), and finally the finished TC4 titanium alloy cast ingot with uniform cast ingot components is obtained. The method effectively utilizes the recycled materials, reduces the production cost, improves the ingot casting quality, and is suitable for preparing high-performance titanium alloy materials for aviation, aerospace and the like.

Description

Technical Field

[0001] The invention relates to the technical field of titanium alloy smelting, in particular to a method for preparing low-cost and high-quality titanium ingots. Background Art

[0002] Titanium alloy materials are widely used in aerospace, marine engineering, military equipment and other fields due to their excellent properties such as high strength, low density and strong corrosion resistance. Among them, TC4 titanium alloy (Ti-6Al-4V), as a typical α-β type titanium alloy, has been widely used in aircraft fuselage structure, engine components and ship armor due to its good comprehensive performance. However, the production cost of TC4 titanium alloy is relatively high, mainly due to the expensive raw materials, complex manufacturing process and difficult processing. In particular, a large amount of residual waste (such as peeling scraps, head and tail sawing materials, processing scraps, etc.) will be generated during the production process. How to efficiently use these recycled materials is one of the important ways to reduce production costs.

[0003] At present, there are two main methods for recycling and smelting titanium alloys: vacuum consumable arc furnace (VAR) smelting and electron beam cold bed (EB) smelting. However, VAR smelting cannot effectively remove high and low density inclusions when processing titanium alloys, and because the recycled materials have different shapes, it is difficult to weld them into consumable electrodes. This limits the processing capacity of VAR smelting for recycled materials, resulting in the inability to smelt a large amount of recycled materials, increasing production costs. At the same time, although EB smelting can process a large amount of recycled materials and has a certain refining and impurity removal ability, due to the shallow depth of the molten pool, the material lacks effective electromagnetic stirring during the smelting process, resulting in segregation of easily segregated elements during the smelting process, affecting the quality of the ingot.

[0004] In summary, in order to meet the requirements of efficient recycling and high-quality ingots at the same time, a new smelting method is urgently needed that can make large-scale use of recycled materials while ensuring the composition uniformity and high quality of the ingots. Summary of the invention

[0005] Based on the above problems, the present invention proposes a method for preparing low-cost and high-quality titanium ingots, aiming to solve the problems existing in the prior art that a large amount of titanium alloy recycled materials cannot be melted back and the ingot composition has poor uniformity. The specific technical solution is as follows:

[0006] A method for preparing a low-cost, high-quality titanium ingot comprises the following steps:

[0007] (1) Raw material preparation:

[0008] The raw materials used include new materials and recycled materials, of which new materials account for 20% to 30% and recycled materials account for 70% to 80%. New materials include sponge titanium, AlV 55The raw materials of master alloy, aluminum bean and aluminum plate are as follows: titanium sponge 16.6%~24.9%, aluminum bean 1.86%~2.79%, AlV 55 The intermediate alloy is 1.51% to 2.265%, and the aluminum plate is 0.0375% to 0.125%. The recycled materials include TC4 block recycled materials and TC4 chip recycled materials, and the proportion of each component is: block recycled materials 59.5% to 73%, and chip recycled materials 7% to 10.5%.

[0009] (2) Mixing and pressing:

[0010] The titanium sponge, aluminum-vanadium master alloy and aluminum beans in the new materials are mixed with the TC4 chips in the recycled materials and pressed into titanium alloy lumps.

[0011] (3) EB smelting:

[0012] The titanium alloy lump, the TC4 block recycled material in the recycled material, and the aluminum plate in the new material are sent to the EB melting furnace for primary melting to obtain the EB ingot.

[0013] (4) VAR smelting:

[0014] The EB ingot is used as a consumable electrode and is melted once in a VAR melting furnace to obtain a finished TC4 titanium alloy ingot.

[0015] Furthermore, the above step (1) also includes the processing of recycled materials:

[0016] The recycled materials are processed, wherein the TC4 block-shaped recycled materials are subjected to sand blasting and pickling, and the TC4 chip-shaped recycled materials are subjected to cleaning, drying, crushing and magnetic separation.

[0017] Furthermore, the mixing pressing method in the above step (2) is to press titanium sponge, aluminum beans, AlV 55 The intermediate alloy and TC4 chip-like recycled materials are mixed several times and pressed into multiple titanium alloy lumps.

[0018] Furthermore, before the EB smelting in the above step (3), the titanium alloy lumps, TC4 block recycled materials and aluminum plates need to be evenly stacked in the EB furnace feed box, and the materials in the feed box are dried. Specifically, the titanium alloy lumps are stacked on the lower layer of the EB furnace feed box, and the TC4 block recycled materials are stacked on the upper layer. The aluminum plates can be stacked vertically on one side of the titanium alloy lumps or horizontally in the middle of the titanium alloy lumps and the TC4 block recycled materials.

[0019] Furthermore, in the above step (3), the radius of the EB ingot obtained by pulling the ingot in the EB smelting furnace is 25 to 30 mm smaller than the inner diameter of the consumable crucible of the VAR smelting furnace.

[0020] Furthermore, before the VAR smelting in the above step (4), the EB ingot needs to be flattened.

[0021] Furthermore, the components in the new material: the content of sponge titanium is: O content is 0.028wt%, N content is 0.002wt%, Fe content is 0.037wt%, C content is 0.008wt%, H content is 0.001wt%, and the balance is Ti;

[0022] AlV 55 The composition content of the intermediate alloy is: the content of V is 55.0% to 65.0wt%, the content of Al is 34.47wt% to 44.47wt%, and the content of impurities is 0.53wt%;

[0023] The purity of aluminum beans is greater than 99.6wt%.

[0024] Further, the composition of the recycled material: the Al content in the recycled material is between 6.0% and 6.3%, and the O content is between 0.17% and 0.25%;

[0025] The components of TC4 chip-like recycled material are as follows: Ti content 89.7wt%, Al content 6.030wt%, V content 4.1wt%, Fe content 0.084wt%, O content 0.25wt%;

[0026] The composition contents of TC4 block recycled material are: Ti content 89.74wt%, Al content 6.030wt%, V content 4.1wt%, Fe content 0.084wt%, O content 0.15wt%.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] The method for preparing low-cost, high-quality titanium ingots using TC4 recycled materials proposed in the present invention can utilize the respective smelting advantages of the EB furnace and the VAR furnace, while solving the problems that the traditional smelting method cannot melt back a large amount of titanium alloy recycled materials (block-shaped recycled materials and chip-shaped recycled materials) and the poor uniformity of the ingot composition.

[0029] The present invention can effectively process a large amount of recycled materials through one smelting through the EB smelting process, achieve efficient utilization of resources, and reduce production costs. The obtained EB ingot is smelted twice through the VAR smelting process, and the advantages of deep molten pool and electromagnetic stirring are utilized to homogenize the composition of the titanium alloy ingot and improve the ingot quality.

[0030] The titanium alloy ingot obtained by melting by the dual process of "electron beam cold hearth melting furnace + vacuum consumable melting furnace" has good uniformity of alloy element distribution, high cleanliness and excellent metallurgical quality, meeting the requirements of national standards GB / T 3620.1-2016 and GB / T 5193-2007. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a process flow chart in an embodiment of the present invention. Figure 2 Schematic diagram of the stacking of titanium alloy lumps and TC4 block-shaped recycled materials in the feed box of an EB furnace in step 3 of an embodiment of the present invention. DETAILED DESCRIPTION

[0032] The following will clearly and completely describe the technology in the embodiments of the present invention in conjunction with the accompanying drawings; it is obvious that the described embodiments are only part of the embodiments of the present invention, not all of the embodiments; based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work should fall within the scope of protection of the present invention. It should be noted that the embodiments of the present invention and the features in the embodiments can be combined with each other without conflict.

[0033] Embodiment 1:

[0034] Reference Figure 1 This embodiment provides a method for preparing a low-cost, high-quality titanium ingot, which includes the following steps:

[0035] Step 1: Prepare the ingredients

[0036] The raw materials used include new materials and returned materials. New materials include sponge titanium, aluminum-vanadium master alloy, aluminum beans, and aluminum plates, which account for a total of 20%; classification and processing of TC4 titanium alloy returned materials. Returned materials can be divided into two categories according to their physical state: block returned materials (large pieces of waste) and chip returned materials (fine debris or powdered waste).

[0037] Since there are large differences in oxygen content in return materials of different states, different process measures need to be taken to control the oxygen content. Since the behavior of block materials and chips in the subsequent electron beam cooling furnace smelting process is different, different compensation materials and cloth forms need to be used. Therefore, in order to ensure the stability of the smelting process and the quality of the finished product, block return materials and chip return materials need to be collected, recycled and remelted in a classified manner.

[0038] TC4 chip-shaped return materials must be processed due to their low stacking density and poor cleanliness. The processing process is as follows: cleaning, drying, crushing, and magnetic separation. The surface of the processed chips has no obvious oxidation and oil stains, and the length of the chips is ≤10mm; while the TC4 block-shaped return materials mainly include material heads and die forging scraps, and the surface of the materials needs to be processed by sandblasting, pickling, etc.

[0039] The chemical composition of the processed block and chip recycled materials is sampled and tested at a rate of 10% to ensure that the composition of the recycled materials is clear and the main element composition meets the requirements of aluminum content of 6.0-6.3% and oxygen content of 0.17-0.25%, which provides strong support for subsequent ingredient calculation and raw material preparation.

[0040] In this embodiment, the percentage of metal materials required for the raw material batching is: 16.6wt% of titanium sponge, 1.86wt% of Al bean alloy, 1.51wt% of AlV55 master alloy, 7wt% of TC4 chip-shaped recycled material, 73wt% of TC4 block-shaped recycled material, and 0.025wt% of aluminum plate;

[0041] The purity of aluminum beans is greater than 99.6wt%; the composition content of sponge titanium is: O content is 0.028wt%, N content is 0.002wt%, Fe content is 0.037wt%, C content is 0.008wt%, H content is 0.001wt%; AlV 55 The composition contents of the intermediate alloy are as follows: the content of V is 55.0% to 65.0wt%, the content of Al is 34.47wt% to 44.47wt%, and the content of impurities is 0.53wt%; the composition contents of the TC4 chip-like recycled material are as follows: the content of Ti is 89.7wt%, the content of Al is 6.030wt%, the content of V is 4.1wt%, the content of Fe is 0.084wt%, and the content of O is 0.25wt%; the composition contents of the TC4 block-like recycled material are as follows: the content of Ti is 89.74wt%, the content of Al is 6.030wt%, the content of V is 4.1wt%, the content of Fe is 0.084wt%, and the content of O is 0.15wt%.

[0042] Weigh a total of 9521.352 kg of raw materials according to the above proportions and store them separately.

[0043] 2. Mixing and pressing titanium alloy lumps:

[0044] The titanium sponge, aluminum-vanadium master alloy and aluminum beans in the new materials are mixed with the TC4 chips in the recycled materials and pressed into titanium alloy pellets. The specific steps include:

[0045] Add 2562.24kg of titanium sponge, aluminum bean alloy, AlV55 master alloy, and TC4 chip-like recycled materials into different silos of the compounding equipment;

[0046] Mix 15.5kg of titanium sponge, 1.71kg of aluminum bean alloy, 1.41kg of AlV55 master alloy, and 6.5kg of TC4 chip-like recycled material, and weigh them using a high-precision electronic scale to ensure a weighing accuracy of ±0.2g;

[0047] After each weighing, the material was transported to the mixer and mixed for 2 minutes, and then poured into the mold cavity of an 80MN hydraulic press for pressing;

[0048] After three mixings, a total of 75.36 kg of material was pressed into titanium alloy lumps with a size of 380 mm x 120 mm x 58 mm. The above steps were repeated to press 2562.24 kg of material into 34 titanium alloy lumps.

[0049] 3.Material preparation:

[0050] The titanium alloy lumps, TC4 block recycling materials in the titanium alloy return materials, and aluminum plates in the new materials are evenly stacked in the EB furnace feed box. The specific steps include:

[0051] The 34 blocks (titanium alloy lumps) pressed in step 2 are evenly stacked in the EB furnace feed box. Two small boxes and two large boxes are used for stacking. The lower layer is stacked with titanium alloy lumps, and the upper layer is stacked with block-shaped recycled materials. There are 2 blocks in each row of the lower layer (placed on both sides, and block-shaped recycled materials can be placed in the middle). In this way, each short box is placed in 3 rows, and each long box is placed in 5 rows. When stacking block-shaped recycled materials on the upper layer, try to increase the density to reduce the material height.

[0052] Among them, the stacking method of small material boxes is as follows: two pieces of alloy titanium lumps are stacked in a single row on the lower layer (6 pieces / box), and 1228kg of TC4 block recycled materials are stacked between the upper layer and the alloy titanium lumps. The length of the materials after stacking is consistent with the stacking length of the alloy titanium lumps. One piece of alloy titanium lumps is stacked horizontally on the lower layer at the front end of the small material box, and the length after stacking is 580mm. Three aluminum plates are stacked at 0-250mm in front of the alloy titanium lumps. 205kg of TC4 block recycled materials are stacked on the upper layer.

[0053] The stacking method of large material boxes: two pieces of alloy titanium lumps (10 pieces / box) are stacked in a single row on the lower layer, and 2045kg of TC4 recycled materials are stacked between the upper layer and the alloy titanium lumps. The length of the stacked materials is consistent with the stacking length of the alloy titanium lumps. An aluminum plate is stacked horizontally in the middle position between the titanium lumps and the residual materials at the rear end of the two large material boxes as the rear row material, and the aluminum plate is stacked at 0-190mm on the upper layer of the rear end of the two alloy titanium lumps.

[0054] The four bins were weighed and recorded. The weighed and checked materials were hoisted to the drying box by a crane and dried at 120°C for 4 hours.

[0055] 5. Electron beam melting:

[0056] The dried material in step 4 is sent to an electron beam cooling furnace for smelting, and a TC4 titanium alloy ingot is obtained through one smelting. The vacuum degree in the electron beam cooling furnace is higher than 5.0×10 -3 Torr, use a helium mass spectrometer leak detector to check the furnace for leaks, and the furnace leakage rate should be less than 2.0 Torr / min. The specific steps include:

[0057] First check the electron beam cooling furnace, including:

[0058] Check the filling hydrogen and oxygen gas pressure to ensure that the pressure is sufficient;

[0059] Check the cooling water of the power cabinet to ensure it is correct;

[0060] Turn on the power cabinet and set the voltage of the power cabinet to 30KV;

[0061] Confirm that the oxygen regulating valve switch valve is in the closed state, and turn down the fine-tuning valve by 1 / 5 to 1 / 4 turn to ensure that the initial O2 intake does not cause oxidation of the cathode surface of the electron gun.

[0062] Start-up of electron beam cooling furnace, including:

[0063] Start the 1#, 2#, 3#, 4#, 6#, and 7# electron guns, set the electron gun current values, and record them;

[0064] Start the 1#-4# electron guns first to melt the condensation shell surface in the cooling bed. During the startup process, expand the scanning track area as the current increases to avoid local overheating.

[0065] Start the 6# and 7# electron guns, adjust the scanning trajectory, increase the current to heat the ingot bottom support in the crystallizer, avoid quenching and splashing, and record the current value.

[0066] Normal smelting, including:

[0067] 1# to 4# electron guns ensure that the material is melted normally, 5# electron gun ensures that the material flows into the crystallizer through the runner, and 6# and 7# electron guns melt the surface of the molten pool in the crystallizer;

[0068] The power of the material melting area (1# to 4# electron guns) accounts for 65% of the total power, the power of the refining area (5# electron gun) accounts for 10%, and the power of the crystallization area (6# and 7# electron guns) accounts for 25%;

[0069] Push the material steadily at a feeding speed of 6-7mm / min. When the pushing is completed, the feeding time difference between the left and right sides cannot exceed 10 minutes. After the material is melted, turn off the 1~7# electron guns immediately.

[0070] After smelting, the obtained ingot is taken out from the EB furnace pulling system. The radius of the EB ingot is 25-30 mm smaller than the inner diameter of the consumable crucible of the VAR furnace to ensure the distance from the inner wall of the crucible when the EB ingot is used as a consumable electrode.

[0071] 6. Ingot processing

[0072] The EB ingot obtained by electron beam cold bed melting was flattened and the chemical composition was tested. The chemical composition of the TC4 titanium alloy ingot obtained after EB melting is shown in Table 1:

[0073] Table 1 Chemical composition of EB ingot in Example 1

[0074]

[0075] 7.VAR smelting:

[0076] The flattened EB ingot is used as a consumable electrode and sent to a VAR furnace for a second smelting to obtain a finished TC4 titanium alloy ingot. The specific steps include:

[0077] The EB ingot is placed in the crucible of the VAR furnace, and the auxiliary electrode and the consumable electrode are welded after the furnace is sealed. The furnace is evacuated to a vacuum degree of less than 0.3Pa and a gas leakage rate of ≤1Pa / min.

[0078] Check whether the electrode welding is normal, ensure that the consumable electrode is 25-30mm away from the inner wall of the crucible, and put sponge particles at the bottom of the crucible for arc starting.

[0079] Arc melting is carried out, and the consumable electrode is fed when the remaining weight is 150kg. After melting, the ingot is cooled for 6 hours.

[0080] The smelted ingot is taken out from the VAR furnace and quality inspected.

[0081] Finally, 9330.925 kg of finished TC4 titanium alloy ingot was obtained. After chemical composition detection and quality inspection, its chemical composition and quality parameters are shown in Table 2.

[0082] Embodiment 2:

[0083] The method steps provided in this embodiment are the same as those in Example 1, except that the raw materials used are 25% new materials and 75% recycled materials, as follows:

[0084] The new material contains 20.75wt% titanium sponge, 2.325wt% aluminum beans, 1.8875wt% AlV55 master alloy, and 0.03125wt% aluminum plate; the recycled material contains 8.75wt% TC4 chip-like recycled material and 66.25wt% TC4 block-like recycled material.

[0085] The chemical composition and quality parameters of the finished TC4 titanium alloy ingot obtained by the above raw materials through the same steps as in Example 1 are shown in Table 2.

[0086] Embodiment 3:

[0087] The method steps provided in this embodiment are the same as those in the above-mentioned embodiments 1 and 2, except that the raw materials are 30% new materials and 70% recycled materials, as follows:

[0088] The new material contains 24.9wt% titanium sponge, 2.79wt% aluminum beans, 2.265wt% AlV55 master alloy, and 0.0375wt% aluminum plate; the recycled material contains 10.5wt% TC4 chips and 59.5wt% TC4 block recycled materials.

[0089] The chemical composition and quality parameters of the finished TC4 titanium alloy ingot obtained by the above raw materials through the same steps as the above embodiment are shown in Table 2.

[0090] Table 2 Comparison of finished TC4 titanium alloy ingots in various embodiments

[0091]

[0092] In combination with Examples 1 to 3, the method provided by the present invention uses 20% to 30% of new materials (including 83% of sponge titanium, 9.3wt% of Al bean alloy, and 7.55wt% of AlV55 master alloy) and 70% to 80% of recycled materials (including 7% to 10.5% of TC4 chip-shaped recycled materials and 59.5% to 73% of TC4 block-shaped recycled materials) as raw materials to produce low-cost, high-quality TC4 titanium alloy ingots, wherein the comprehensive volatilization of the Al element is controlled below 14.8%, and the composition uniformity of the obtained ingot is excellent and meets the following table:

[0093]

Claims

1. A method for preparing low-cost and high-quality titanium ingots, characterized in that: The steps include: (1) Raw material preparation, wherein the raw materials include new materials accounting for 20% to 30% and recycled materials accounting for 70% to 80%, wherein the new materials include titanium sponge, AlV55 master alloy, aluminum beans, and aluminum plates, and the proportion of each raw material in the new materials is 16.6% to 24.9% titanium sponge, 1.86% to 2.79% aluminum beans, 1.51% to 2.265% AlV55 master alloy, and 1.51% to 2.265% aluminum plates. 0.0375-0.125%; the recycled materials include TC4 block recycled materials and TC4 chip recycled materials, among which TC4 block recycled materials account for 59.5%-73% and TC4 chip recycled materials account for 7%-10.5%; (2) Mixing and pressing, the titanium sponge and AlV 55 The master alloy, aluminum beans, and TC4 chip-like recycled materials are mixed and pressed into titanium alloy lumps; (3) EB smelting, feeding the titanium alloy lump described in step (2) and the aluminum plate and TC4 block recycled material in step (1) into an EB smelting furnace for one smelting to obtain an EB ingot; (4) VAR smelting: using the EB ingot described in step (3) as a consumable electrode, smelting it once in a VAR smelting furnace to obtain a finished TC4 titanium alloy ingot.

2. The method for preparing a low-cost, high-quality titanium ingot according to claim 1, characterized in that: Step (1) also includes processing the recycled materials, wherein the TC4 block-shaped recycled materials are subjected to sandblasting and acid washing, and the TC4 chip-shaped recycled materials are subjected to washing, drying, crushing and magnetic separation.

3. The method for preparing a low-cost, high-quality titanium ingot according to claim 1, characterized in that: In step (2), titanium sponge, aluminum beans, AlV 55 The intermediate alloy and TC4 chip-like recycled materials are mixed several times and pressed into multiple titanium alloy lumps.

4. The method for preparing a low-cost, high-quality titanium ingot according to claim 1, characterized in that: Before step (3), the method also includes evenly stacking the titanium alloy lumps, TC4 block-shaped recycled materials and aluminum plates in the EB furnace feed box, and drying the materials in the EB furnace feed box.

5. The method for preparing a low-cost, high-quality titanium ingot according to claim 4, characterized in that: The lower layer of the EB furnace feed box is stacked with titanium alloy lumps, and the upper layer is stacked with TC4 block recycled materials. The aluminum plate can be stacked vertically on one side of the titanium alloy lumps or horizontally in the middle of the titanium alloy lumps and the TC4 block recycled materials.

6. The method for preparing a low-cost, high-quality titanium ingot according to claim 6, characterized in that: The radius of the EB ingot obtained by pulling the ingot from the EB smelting furnace is 25 to 30 mm smaller than the inner diameter of the consumable crucible of the VAR smelting furnace in step (4).

7. The method for preparing a low-cost and high-quality titanium ingot according to claim 1, characterized in that: Before step (4), the EB ingot is also subjected to flattening treatment.

8. The method for preparing a low-cost, high-quality titanium ingot according to claim 1, characterized in that: The composition content of the titanium sponge described in step (1) is: 0.028wt% of O, 0.002wt% of N, 0.037wt% of Fe, 0.008wt% of C, 0.001wt% of H, and the balance is Ti; The AlV 55 The composition content of the intermediate alloy is: V content is 55.0% to 65.0wt%, Al content is 34.47wt% to 44.47wt%, and impurity content is 0.53wt%; The purity of the aluminum beans is greater than 99.6 wt %.

9. The method for preparing a low-cost, high-quality titanium ingot according to claim 1, characterized in that: The Al content in the recycled material in step (1) is between 6.0 and 6.3%, and the O content is between 0.17 and 0.25%.

10. The method for preparing a low-cost, high-quality titanium ingot according to claim 6, characterized in that: The components of the TC4 chip-like recycled material are as follows: Ti content is 89.7wt%, Al content is 6.030wt%, V content is 4.1wt%, Fe content is 0.084wt%, and O content is 0.25wt%; The components of the TC4 block recycled material are as follows: Ti content is 89.74wt%, Al content is 6.030wt%, V content is 4.1wt%, Fe content is 0.084wt%, and O content is 0.15wt%.

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