A method for preparing low-cost high-quality TC21 titanium alloy ingot

Abstract

The application discloses a preparation method of low-cost high-quality TC21 titanium alloy ingot, and the method comprises the following steps: controlling the source of TC21 recycled materials and the adding proportion of various component materials, uniformly mixing, pressing into crumb-shaped alloy electrode blocks, arranging the crumb-shaped alloy blocks and other TC21 blocks in a multi-layer matching mode, combining with an EB smelting process to obtain an EB smelting ingot, sawing the bottom of the EB smelting ingot, turning the bottom, taking the bottom as a consumable electrode and then performing VAR smelting, and finally obtaining a TC21 titanium alloy ingot with uniform organization and chemical composition by adjusting and controlling smelting current, arc-stabilizing magnetic field stirring intensity, cooling heat exchange capacity and other parameters in the VAR smelting stage. The application solves the channel segregation problems of high-melting-point elements Mo and Nb and the volatilization loss problems of Al and Sn elements by adding types, proportions and arrangement modes of raw materials and combining with an EB+VAR double smelting process, and the manufacturing cost of the TC21 titanium alloy ingot is effectively reduced.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of non-ferrous metal processing, and particularly relates to a preparation method of low-cost high-quality TC21 titanium alloy ingot. BACKGROUND

[0002] Titanium alloy is a new type of metal material with high specific strength and good corrosion resistance, high temperature resistance, low density, non-magneticity and other characteristics, which was developed in the 1950s and 1960s of the 20th century. At the same time, it also has excellent biocompatibility, and is applied in various fields such as aviation, aerospace, ships, energy, chemical industry and the like, and plays an irreplaceable role in economy and national defense.

[0003] Among them, TC21 titanium alloy is an α / β type high-strength, high-toughness and high-damage tolerance titanium alloy developed by China, and the nominal composition is Ti-6Al-2Sn-2Zr-2Mo-1.5Cr-2Nb. The titanium alloy has good strength, plasticity and toughness, low crack propagation rate and excellent comprehensive performance, and is an important aviation and aerospace main load-bearing structural material. At present, the conventional TC21 titanium alloy product is generally obtained through the following steps: first, preparing an electrode from sponge titanium and intermediate alloy, then welding, melting, forging and machining, and the material utilization rate of the final part is less than 15%. The production process is seriously wasted, which leads to high cost of the TC21 product at the present stage, and high cost has become an important bottleneck restricting the popularization and application of the TC21 product.

[0004] In order to reduce the cost, the industry generally adopts the method of recycling and reusing titanium alloy scrap. For this reason, many scientific research institutions and production units at home and abroad have carried out research on the recycling method of scrap. However, at present, the research mainly focuses on the recycling of pure titanium and TC4 type products by using an EB furnace, and the recycling of multi-element titanium alloy products is relatively less, and the uniformity of the composition of the ingot after recycling and melting is not related. For example, the patent with the publication number CN113122726A discloses a TC18 titanium alloy scrap recycling and remelting process. Although the patent can efficiently recycle and remelt various types of TC18 titanium alloy scrap to realize the production of different shaped ingots, the patent does not involve the uniformity of the composition of the ingot after recycling and remelting. In addition, the patent with the publication number CN106756082A discloses a process for recycling and remelting TC11 scrap by using an electron beam cold bed furnace. By stacking TC11 scrap and Al plates, TC11 titanium alloy is obtained by one-time melting by using an electron beam cold bed furnace, which solves the demand for recycling and remelting processing of TC11 scrap which cannot be pressed into electrodes, but the problem of the uniformity of the composition of the melted ingot is not involved. In the EB melting process, with the increase of the size of the ingot, the problem of the deterioration of the uniformity of the composition of the ingot will inevitably be faced.

[0005] TC21 titanium alloy contains high specific gravity, high melting point Mo, Nb elements and volatile elements Al, Sn, compared with VAR smelting, in the process of EB smelting, the electron beam can produce high temperature of more than 3500 DEG C on the surface of raw materials and molten pool, which is much higher than the temperature of VAR smelting molten pool, resulting in serious volatilization of Al, Sn and other elements, and the channel segregation is intensified due to the settlement of high specific gravity Mo and Nb. Because it is difficult to control the uniformity of each element in the recovery process, the TC21 smelting and recovery technology has always been unable to break through in industrial production, and there is no related report on the smelting and recovery technology of TC21 titanium alloy product at home and abroad.

[0006] Therefore, the present application provides a preparation method of low-cost high-quality TC21 titanium alloy ingot to overcome the defects of the prior art. SUMMARY

[0007] The purpose of the present application is to overcome the defects of the prior art, provide a preparation method of low-cost high-quality TC21 titanium alloy ingot, and mainly solve the problems of high cost of existing TC21 products, excessive compensation of Al and Sn elements in the recovery process, and difficult composition control of high melting point Mo, Nb elements and volatile elements Al and Sn.

[0008] The purpose of the present application is to overcome the defects of the prior art, provide a preparation method of low-cost high-quality TC21 titanium alloy ingot, and mainly solve the problems of high cost of existing TC21 products, excessive compensation of Al and Sn elements in the recovery process, and difficult composition control of high melting point Mo, Nb elements and volatile elements Al and Sn.

[0009] A preparation method of low-cost high-quality TC21 titanium alloy ingot comprises the following steps:

[0010] Step one, clean TC21 scrap, titanium sponge, Al beans, Al70Cr, Ti80Sn and TiO2 are mixed according to the nominal composition of TC21, and then pressed into scrap alloy electrode block;

[0011] Step two, the scrap alloy electrode block obtained in step one is arranged with TC21 material head, TC21 strip material and TC21 riser material in a multi-layer arrangement manner;

[0012] Step three, after the vacuum degree and leakage rate meet the requirements, EB smelting is carried out, and EB ingot is obtained after EB smelting is completed;

[0013] Step four, the bottom of the EB ingot obtained in step three is sawed to a certain thickness, and the head is adjusted in the vacuum consumable arc furnace for VAR smelting, and the target TC21 titanium alloy ingot is obtained after VAR smelting is completed;

[0014] Step five, the TC21 titanium alloy ingot obtained in step four is subjected to chemical composition detection, and sampling is carried out from the head, middle and tail respectively for determining the quality of the TC21 titanium alloy ingot.

[0015] Further, in the step one, when the ingredients are prepared, the Al element is increased by 12% to 15% based on the reference value, the Sn element is increased by 10% to 16% based on the reference value, the Cr element is increased by 5% to 7% based on the reference value, the Zr element remains unchanged, the Mo element is reduced by 3% to 4% based on the reference value, and the Nb element is reduced by 4.5% to 5.5% based on the reference value.

[0016] Further, in the step one, when the scrap alloy electrode blocks are pressed, the total weight of a single scrap alloy electrode block is controlled to be 45 kg to 120 kg, and in each scrap alloy electrode block, the addition amount of TC21 scrap accounts for 60% to 65% of the total weight of the scrap alloy electrode block, the addition amount of Al70Cr accounts for 0.5% to 1.5% of the total weight of the scrap alloy electrode block, the addition amount of Al beans accounts for 2% to 5.5% of the total weight of the scrap alloy electrode block, the addition amount of Ti80Sn accounts for 1% to 3.2% of the total weight of the scrap alloy electrode block, the addition amount of TiO2 accounts for 0.0006% to 0.002% of the total weight of the scrap alloy electrode block, and the balance is sponge titanium.

[0017] Further, in the step one, when the scrap alloy electrode blocks are pressed, the thickness of the scrap alloy electrode block placed at the front end position of the material box is controlled to be 60 mm to 100 mm, and the thickness of the scrap alloy electrode block placed at the rear end position of the material box is controlled to be 40 mm to 80 mm.

[0018] Further, in the step two, when the materials are laid, a double-layer laying method is adopted, specifically:

[0019] The bottom layer is first laid with the scrap alloy electrode blocks, and then the TC21 head material, the TC21 strip material and the TC21 riser material are placed on the scrap alloy electrode blocks in sequence and uniformly; the top layer is also laid in the same way as the bottom layer, and the distribution thickness of the scrap material and the block material at the front end position of the material box is controlled to be 1:3, and the distribution thickness of the scrap material and the block material at the rear end position of the material box is controlled to be 1:4.

[0020] Among them, the scrap material refers to the scrap alloy electrode block, and the block material refers to the TC21 head material, the TC21 strip material and the TC21 riser material.

[0021] Further, in the step three EB smelting, when the vacuum degree of the feeding chamber is less than 0.8 Pa, the vacuum degree of the smelting chamber is ≤0.4 Pa, and the leakage rate is ≤0.4 Pa / min, the electronic guns of the melting zone, the refining zone and the crystallization zone are first started to preheat, then the smelting current is increased to build a shell and a bottom under the condition of constant voltage, and finally the smelting power is increased to perform normal smelting after the building of the shell and the bottom is completed.

[0022] In the preheating stage, the electron gun current of the melting zone is set to 2.3A-2.7A, the electron gun current of the refining zone is set to 2.5A, and the electron gun of the crystallization zone is set to 2.3A, and the total time of the preheating stage is controlled to be 40-60 minutes.

[0023] In the shell building and bottom forming stage, the electron gun current of the melting zone is set to 3.5A-5.8A, the electron gun current of the refining zone is set to 4.7A-5.0A, and the electron gun of the crystallization zone is set to 4.0A-5.0A.

[0024] In the normal melting stage, the power of the melting zone is controlled to be 1800kW-2100kW, the power of the refining zone is controlled to be 680kW-720kW, and the power of the crystallization zone is controlled to be 780kW-1120kW, and the melting power is kept unchanged at the end of the melting to directly trip, so that the element fluctuation of the ingot head can be avoided.

[0025] Further, in the EB melting in the third step, the parameters of the normal melting stage are set as follows: the pushing speed is 270mm / h-400mm / h, the melting speed is 16kg / min-22kg / min, the water inlet temperature in the cooling process is 25℃-27℃, the water outlet temperature is 28℃-30℃, and the water flow is 1500L / min-3000L / min.

[0026] Further, in the VAR melting in the fourth step, the gap between the electrode and the crucible is kept to be 40mm-100mm, and the normal melting stage is quickly entered after 10-15 minutes of arc striking, and in the normal melting stage, a melting mode of small current and large stable arc period is adopted to promote the homogenization of the EB ingot elements.

[0027] Further, in the VAR melting in the fourth step, the parameters of the normal melting stage are set as follows: the melting current is 20kA-24kA, the melting speed is 15kg / min-21kg / min, the stable arc current is 18A-25A, and the stable arc period is 20s-35s; the feeding process is entered when the consumable electrode height is 100mm-120mm from the bottom, the melting speed is gradually reduced in the feeding process, and the feeding is completed by tripping when the consumable electrode thickness is 30mm-40mm.

[0028] Further, in the VAR melting in the fourth step, in the normal melting stage, the heat exchange amount in the cooling process of the TC21 titanium alloy ingot is controlled to be 27000kJ / min-33600kJ / min.

[0029] Compared with the prior art, the application has the following beneficial effects:

[0030] The preparation method provided by the application, by controlling the source of TC21 recycled materials and the adding proportion of various component materials, uniformly mixing, pressing into a crumb alloy electrode block, and then combining the crumb alloy electrode block with other TC21 block materials in a multi-layer distribution manner, combining with EB smelting process control, first obtaining a TC21 titanium alloy EB ingot, then sawing and reversing the bottom of the EB ingot as a consumable electrode to perform VAR smelting, in the VAR smelting stage, by adjusting and controlling the smelting current, the arc stabilizing magnetic field stirring intensity, the cooling heat exchange capacity and other parameters, finally a high-quality TC21 titanium alloy ingot with uniform chemical composition and organization is obtained. Compared with the prior art, by controlling the adding type, proportion and distribution method of raw materials and combining the EB+VAR double smelting process, not only the channel segregation problem of Mo and Nb high-melting-point elements is solved, but also the volatilization loss problem of Al and Sn elements is solved. Therefore, the manufacturing cost of the TC21 titanium alloy ingot is effectively reduced, and after detecting the TC21 titanium alloy ingot produced by the application, the chemical compositions of each (head, middle and tail) position are uniform. BRIEF DESCRIPTION OF DRAWINGS

[0031] The accompanying drawings, which are incorporated into and form a part of the specification, are used to explain the principles of the application together with the specification and are used to further appreciate the advantages and features of the application.

[0032] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the accompanying drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, for those skilled in the art, other drawings can also be obtained based on these drawings without any creative labor.

[0033] Figure 1 is a flow chart of the TC21 titanium alloy ingot preparation method of the application;

[0034] Figure 2 is a schematic diagram of the crumb alloy electrode block of the application;

[0035] Figure 3 is a crumb alloy double-layer distribution actual photograph of the application;

[0036] Figure 4 is an EB material box distribution schematic diagram of the application.

[0037] Figure 5 is a distribution actual photograph of Comparative Example 1;

[0038] Figure 6 is a sampling position schematic diagram of the application;

[0039] Figure 7 is a component detection data diagram of Example 1 of the application;

[0040] Figure 8is the component detection data graph of Example 2 of the present application;

[0041] Figure 9 is the component detection data graph of Example 3 of the present application;

[0042] Figure 10 is the component detection data graph of Comparative Example 1 as a control group of Example 1.

[0043] Wherein, 1 is the chippings alloy electrode block; 2 is the TC21 head; 3 is the TC21 strip material; 4 is the TC21 riser material. DETAILED DESCRIPTION

[0044] The exemplary embodiments will be described in detail herein with reference to the attached drawings. In the following description, unless otherwise indicated, like numbers in the attached drawings refer to the same or similar elements. The following exemplary embodiments are not meant to represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus consistent with some aspects of the present application as detailed in the appended claims.

[0045] In order to make the skilled in the art better understand the technical scheme of the present application, the present application is further described in detail below in combination with the drawings and examples.

[0046] For the volatile elements in titanium alloy, additional compensation in the batching stage has become one of the general technologies of EB smelting. Before the present application, the inventors tried to use the element compensation method and smelting method of conventional EB smelting to recycle different forms of TC21 alloy materials. However, due to the presence of volatile elements Al and Sn and segregation-prone elements Cr, Mo and Nb in TC21, the extreme difference of EB ingot is more than 10,000 ppm by using the conventional method, which exceeds the standard requirement and is difficult to meet the use demand. Based on this, the inventors found through a large number of researches that different adding methods and adding sequences of the returned materials have a significant influence on the element volatilization in the EB smelting process. For the TC21 alloy returned materials, Al and Sn element compensation is carried out in the TC21 scrap material, which has the advantages that the TC21 returned scrap has been fully alloyed, and the overall element is uniform and controllable. Compared with directly using titanium sponge, Al beans and TiSn as raw materials for EB smelting, the volatilization loss of Sn element can be reduced by 40%, and the volatilization loss of Al element can be reduced by 25%. In addition, the inventors found through a large number of experiments that the material distribution method has a significant influence on the element volatilization and channel segregation in the smelting process. Even if TC21 scrap is used as the base material for Al and Sn element compensation, when the compensation amount exceeds 10%, Al and Sn elements also volatilize seriously and have large fluctuations. Based on this, the inventors propose a layered material distribution method, in which the volatile Sn and Al elements are mixed with Al beans, TiSn and TC21 returned scrap to press electrodes, and are placed in layers in the material bin, so as to be placed at the bottom and middle section positions in the height direction of the material bin, and the upper part is covered with TC21 material head and strip material. In this way, in the EB smelting process, the electron beam is irradiated on the material head and strip material, the material at this position is melted first, and the heat generated by melting can promote the rapid melting of the upper scrap electrode, which further promotes the rapid melting of the lower material head, strip material and bottom scrap electrode, which is beneficial to the rapid conversion of various types of returned materials into liquid state, reducing the risk of element loss in the melting zone.

[0047] In addition, the inventors precisely adjust the smelting power of each region of the electron gun in the EB smelting stage, combine the ingot pulling speed, material pushing speed and water cooling parameter control in the smelting process, and further promote the uniformity of the distribution of each element in the EB ingot.

[0048] On this basis, the inventors use the ingot prepared by EB melting as the consumable electrode of VAR melting, and then carry out VAR melting. This is because of the inherent characteristics of EB melting, that is, even if a large amount of compensating elements are added and the feeding sequence is adjusted, the element distribution of the bottom of the obtained EB ingot is still worse than that of the middle and upper parts. Based on this, the inventors find through a large number of researches and experiments that the tail part of the EB ingot with poor composition uniformity can be placed at the head part of VAR melting by using the method of reverse melting, and by controlling the height of the remaining consumable electrode entering the feeding and the remaining thickness of the consumable electrode at the time of tripping, the element distribution uniformity can be effectively improved. In addition, a smaller melting rate and a smaller current, a melting mode with a large stable arc period are used during VAR melting to realize strong stirring under a shallow bath depth, and the combination of a strong water cooling parameter heat exchange amount can effectively improve the distribution uniformity of the easily segregating elements Mo and Nb and the easily volatile elements Al and Sn, and the technical scheme of the present application is obtained through a large number of experiments.

[0049] See Figure 1 The present application provides a preparation method of low-cost high-quality TC21 titanium alloy ingot, comprising the following steps:

[0050] Step one, clean TC21 scrap, sponge titanium, Al beans, Al70Cr, Ti80Sn and TiO2 are dosed based on the nominal composition of TC21, and then mixed uniformly and pressed into scrap alloy electrode blocks;

[0051] Specifically, during dosing, the Al element is increased by 12% to 15% based on the reference value, the Sn element is increased by 10% to 16% based on the reference value, the Cr element is increased by 5% to 7% based on the reference value, the Zr element remains unchanged, the Mo element is reduced by 3% to 4% based on the reference value, and the Nb element is reduced by 4.5% to 5.5% based on the reference value.

[0052] During pressing of the scrap alloy electrode blocks, the total weight of a single scrap alloy electrode block is controlled to be 45kg to 120kg, and in each scrap alloy electrode block, the addition amount of TC21 scrap accounts for 60% to 65% of the total weight of the scrap alloy electrode block, the addition amount of Al70Cr accounts for 0.5% to 1.5% of the total weight of the scrap alloy electrode block, the addition amount of Al beans accounts for 2% to 5.5% of the total weight of the scrap alloy electrode block, the addition amount of Ti80Sn accounts for 1% to 3.2% of the total weight of the scrap alloy electrode block, the addition amount of TiO2 accounts for 0.0006% to 0.002% of the total weight of the scrap alloy electrode block, and the balance is sponge titanium. In addition, during pressing of the scrap alloy electrode blocks, the thickness of the scrap alloy electrode blocks placed at the front end position of the material box is controlled to be 60mm to 100mm, and the thickness of the scrap alloy electrode blocks placed at the rear end position of the material box is controlled to be 40mm to 80mm.

[0053] Step two, the crumb alloy electrode block obtained in step one is arranged with TC21 head, TC21 strip and TC21 riser material in a multi-layered manner;

[0054] In the present application, double-layer arrangement is adopted. Specifically, the crumb alloy electrode block is first laid on the bottom layer, and then the TC21 head, TC21 strip and TC21 riser material are evenly placed on the crumb alloy electrode block in sequence. The top layer is also arranged in the same manner as the bottom layer. The distribution thickness of the crumb material and the block material at the front end of the material box is controlled to be 1:3, and the distribution thickness of the crumb material and the block material at the middle and rear end of the material box is controlled to be 1:4. The crumb material refers to the crumb alloy electrode block, and the block material refers to the TC21 head, TC21 strip and TC21 riser material.

[0055] Step three, after the vacuum degree and the leakage rate meet the requirements, EB melting is carried out, and the EB ingot is obtained after the EB melting is completed.

[0056] Specifically, when the vacuum degree of the feeding chamber is less than 0.8 Pa, the vacuum degree of the melting chamber is less than or equal to 0.4 Pa, and the leakage rate is less than or equal to 0.4 Pa / min, the electron guns of the melting zone, the refining zone and the crystallization zone are first started to preheat. After the preheating is completed, the voltage is kept constant, then the melting current is increased to build the shell and the bottom, and finally the melting power is increased to carry out normal melting after the building of the shell and the bottom is completed. It should be noted that the voltage remains unchanged during the whole process from preheating to normal melting.

[0057] In the preheating stage, the electron gun current of the melting zone is set to 2.3A-2.7A, the electron gun current of the refining zone is set to 2.5A, and the electron gun of the crystallization zone is set to 2.3A. The total time of the preheating stage is controlled to be 40-60 min.

[0058] In the building of the shell and the bottom stage, the electron gun current of the melting zone is set to 3.5A-5.8A, the electron gun current of the refining zone is set to 4.7A-5.0A, and the electron gun of the crystallization zone is set to 4.0A-5.0A.

[0059] In the normal melting stage, the power of the melting zone is controlled to be 1800kW-2100kW, the power of the refining zone is controlled to be 680kW-720kW, and the power of the crystallization zone is controlled to be 780kW-1120kW. The melting power remains unchanged at the end of the melting stage to directly trip, which is used to avoid the element fluctuation of the ingot head.

[0060] In addition, the other parameters in the normal melting stage are set as follows: the pushing speed is 270mm / h-400mm / h, the melting speed is 16kg / min-22kg / min, the water inlet temperature during the cooling process is 25℃-27℃, the water outlet temperature is 28℃-30℃, and the water flow is 1500L / min-3000L / min.

[0061] Step four, the bottom of the EB ingot obtained in step three is sawed to a certain thickness, and is reversed to be subjected to VAR smelting in a vacuum consumable arc furnace, and a target TC21 titanium alloy ingot is obtained after the VAR smelting is completed;

[0062] Specifically, the gap between the electrode and the crucible is kept in the range of 40mm to 100mm when charging, and the normal smelting stage is quickly entered after 10min to 15min of arcing, and in the normal smelting stage, a smelting mode of small current and large stable arc period is adopted to promote the homogenization of the elements of the EB ingot. The parameters of the normal smelting stage are as follows: the smelting current is 20kA to 24kA, the smelting speed is 15kg / min to 21kg / min, the stable arc current is 18A to 25A, and the stable arc period is 20s to 35s, so as to realize strong stirring under a relatively shallow bath depth and promote the uniformity of element distribution; the feeding process is started at a position 100mm to 120mm from the bottom of the consumable electrode, the feeding process gradually reduces the melting speed, and when the thickness of the consumable electrode is 30mm to 40mm, the feeding process is completed by tripping.

[0063] In addition, in the VAR normal smelting stage, the heat exchange amount during the cooling process of the TC21 titanium alloy ingot is controlled in the range of 27000kJ / min to 33600kJ / min,

[0064] Step five, the TC21 titanium alloy ingot obtained in step four is subjected to chemical composition detection, and samples are taken from the head, middle and tail respectively for determining the quality of the TC21 titanium alloy ingot.

[0065] In order to further verify the efficacy of the preparation method of the application, the inventors carried out the following specific tests:

[0066] Example 1

[0067] 1) Clean TC21 scrap, titanium sponge, Al beans, Al70Cr, Ti80Sn and TiO2 are dosed based on the nominal composition of TC21, wherein the Al element is increased by 12% based on the reference value, the Sn element is increased by 10% based on the reference value, the Cr element is increased by 5% based on the reference value, the Zr element remains unchanged, the Mo element is reduced by 3% based on the reference value, and the Nb element is reduced by 4.5% based on the reference value.

[0068] 2) After mixing all raw materials in step 1) uniformly, press into crumb alloy electrode block, when pressing crumb alloy electrode block, the total weight of single crumb alloy electrode block is controlled to be 45 kg, and in each crumb alloy electrode block, the adding amount of TC21 crumb accounts for 60% of the total weight of the crumb alloy electrode block, the adding amount of Al70Cr accounts for 0.5% of the total weight of the crumb alloy electrode block, the adding amount of Al accounts for 2% of the total weight of the crumb alloy electrode block, the adding amount of Ti80Sn accounts for 1% of the total weight of the crumb alloy electrode block, the adding amount of TiO2 accounts for 0.002% of the total weight of the crumb alloy electrode block, and the balance is sponge titanium. In addition, when pressing the crumb alloy electrode block, the thickness of the crumb alloy electrode block placed at the front end position of the material box is controlled to be 60 mm, and the thickness of the crumb alloy electrode block placed at the rear end position of the material box is controlled to be 40 mm.

[0069] 3) The crumb alloy electrode block is arranged with TC21 head, TC21 strip and TC21 riser in a two-layer arrangement; specifically, the crumb alloy electrode block, TC21 head, TC21 strip and TC21 riser are placed on the crumb alloy electrode block in turn; the top layer is also arranged in the same way as the bottom layer, and the distribution thickness of the crumb and block materials at the front end position of the material box is controlled to be 1:3, and the distribution thickness of the crumb and block materials at the rear end position of the material box is controlled to be 1:4; wherein the crumb material refers to the crumb alloy electrode block, and the block material refers to the TC21 head, TC21 strip and TC21 riser. The specific arrangement structure is shown in Figure 3 、 4 .

[0070] 4) After the vacuum degree and leakage rate meet the requirements, EB melting is carried out. The crystallizer specification adopts a Φ720 mm specification circular crystallizer. When the vacuum degree of the feeding chamber is less than 0.8 Pa, the vacuum degree of the melting chamber is less than or equal to 0.4 Pa, and the leakage rate is less than or equal to 0.4 Pa / min, the electronic guns of the melting zone, the refining zone and the crystallization zone are respectively started to preheat, wherein the electronic gun current of the melting zone is set to 2.3 A-2.7 A, the electronic gun current of the refining zone is set to 2.5 A, and the electronic gun of the crystallization zone is set to 2.3 A. The total preheating time is controlled to be 40 min. After the preheating is completed, the melting current is increased to build the shell and the bottom, wherein the electronic gun current of the melting zone is set to 3.5 A-5.8 A, the electronic gun current of the refining zone is set to 4.7 A-5.0 A, and the electronic gun of the crystallization zone is set to 4.0 A-5.0 A. After the shell and the bottom are built, the melting power is increased (the voltage is unchanged during the whole process from preheating to melting) to carry out normal melting. During the normal melting stage, the power of the melting zone is controlled to be in the range of 1800 kW-2100 kW, the power of the refining zone is controlled to be in the range of 680 kW-720 kW, and the power of the crystallization zone is controlled to be in the range of 780 kW-1120 kW. The pushing speed during the normal melting stage is 270 mm / h-400 mm / h, the melting speed is 16 kg / min-22 kg / min, the water inlet temperature during the cooling process is 25°C, the water outlet temperature is 28°C, and the water flow is set to 1500 L / min. At the same time, in order to avoid the fluctuation of Al, Sn and other elements at the head of the ingot, the melting power is kept unchanged at the end of the ingot melting to directly trip.

[0071] 5) After the EB melting is completed, the bottom of the EB ingot is sawn to a thickness of 20 mm, and the head is adjusted to carry out VAR melting in a vacuum consumable arc furnace. During the VAR melting, a Φ820 mm specification is adopted for the crucible. After the arc is started, the normal melting stage is quickly entered at 10 min. During the normal melting stage, the melting current is in the form of a small current and a large stable arc period, which further promotes the element homogenization effect of the EB ingot. The melting current is controlled to be 20 KA, the melting speed is controlled to be 15 kg / min, the stable arc current is 18 A, the stable arc period is 20 s, and the heat exchange amount during the cooling process of the ingot is controlled to be 27000 kJ / min-33600 kJ / min. Strong stirring under a relatively shallow bath depth is realized to promote the uniformity of the element distribution. The ingot enters the feeding process at a distance of 100 mm from the bottom, the feeding process gradually reduces the melting speed, and when the remaining thickness of the consumable electrode is 30 mm, the feeding process is completed by tripping.

[0072] 6) After the VAR melting is completed, transverse samples are taken from the head, the middle and the tail of the ingot for chemical composition detection.

[0073] The sampling positions are as shown in Figure 6 , and the specific detection results are as shown in Figure 7 . According to Figure 7The test results show that the content of Al, Mo, Nb, Sn, Zr and Cr in the TC21 titanium alloy ingot prepared in Example 1 meets the requirements of the national standard and the national military standard composition range, and is uniformly distributed on the cross sections at different positions of the ingot, and the ranges of the 39 points (13 points for each of the head, middle and tail) are 0.10%, 0.07%, 0.08%, 0.12%, 0.11% and 0.09% respectively.

[0074] Example 2

[0075] 1) The clean TC21 scrap, titanium sponge, Al beans, Al70Cr, Ti80Sn and TiO2 are proportioned based on the nominal composition of TC21, wherein the content of Al is increased by 15% based on the reference value, the content of Sn is increased by 16% based on the reference value, the content of Cr is increased by 7% based on the reference value, the content of Zr remains unchanged, the content of Mo is reduced by 4% based on the reference value, and the content of Nb is reduced by 5.5% based on the reference value.

[0076] 2) After mixing all the raw materials in step 1) uniformly, the mixed alloy electrode block is pressed into a scrap state, and when the scrap alloy electrode block is pressed, the total weight of a single scrap alloy electrode block is controlled to be 120 kg, and in each scrap alloy electrode block, the addition amount of TC21 scrap accounts for 65% of the total weight of the scrap alloy electrode block, the addition amount of Al70Cr accounts for 1.5% of the total weight of the scrap alloy electrode block, the addition amount of Al accounts for 5.5% of the total weight of the scrap alloy electrode block, the addition amount of Ti80Sn accounts for 3.2% of the total weight of the scrap alloy electrode block, the addition amount of TiO2 accounts for 0.0006% of the total weight of the scrap alloy electrode block, and the balance is titanium sponge. In addition, when the scrap alloy electrode block is pressed, the thickness of the scrap alloy electrode block placed at the front end position of the material box is controlled to be 100 mm, and the thickness of the scrap alloy electrode block placed at the rear end position of the material box is controlled to be 80 mm.

[0077] 3) The scrap alloy electrode block is arranged with TC21 material head, TC21 strip material and TC21 riser material in a two-layer arrangement manner; specifically, the scrap alloy electrode block is laid at the bottom, and the TC21 material head, the TC21 strip material and the TC21 riser material are placed uniformly above the scrap alloy electrode block in sequence; the top layer is also arranged in the same way as the bottom layer, and the distribution thickness of the scrap and block materials at the front end position of the material box is controlled to be 1:3, and the distribution thickness of the scrap and block materials at the rear end position of the material box is controlled to be 1:4; wherein the scrap material refers to the scrap alloy electrode block, and the block material refers to the TC21 material head, the TC21 strip material and the TC21 riser material.

[0078] 4) After the vacuum degree and leakage rate meet the requirements, EB melting is carried out. The crystallizer specification adopts a Φ820 mm specification circular crystallizer. When the vacuum degree of the feeding chamber is less than 0.8 Pa, the vacuum degree of the melting chamber is less than or equal to 0.4 Pa, and the leakage rate is less than or equal to 0.4 Pa / min, the electronic guns of the melting zone, the refining zone and the crystallization zone are respectively started to preheat, wherein the electronic gun current of the melting zone is set to 2.3 A-2.7 A, the electronic gun current of the refining zone is set to 2.5 A, and the electronic gun current of the crystallization zone is set to 2.3 A. The total preheating time is controlled to be 60 min. After the preheating is completed, the melting power is increased to build the shell and the bottom, wherein the electronic gun current of the melting zone is set to 3.5 A-5.8 A, the electronic gun current of the refining zone is set to 4.7 A-5.0 A, and the electronic gun current of the crystallization zone is set to 4.0 A-5.0 A. After the shell building and the bottom building are completed, the melting power is increased (the voltage is unchanged during the whole process from preheating to melting) to carry out normal melting. During the normal melting stage, the power of the melting zone is controlled to be in the range of 1800 kW-2100 kW, the power of the refining zone is controlled to be in the range of 680 kW-720 kW, and the power of the solidification zone is controlled to be in the range of 780 kW-1120 kW. The pushing speed during the normal melting stage is 300 mm / h-400 mm / h, the melting speed is 20 kg / min-22 kg / min, the water inlet temperature during the cooling process is 27℃, the water outlet temperature is 30℃, and the water flow is set to 3000 L / min. At the same time, in order to avoid the fluctuation of Al, Sn and other elements at the head of the ingot, the melting power is kept unchanged at the end of the ingot melting to directly trip.

[0079] 5) After the EB melting is completed, the bottom of the EB ingot is sawed to a thickness of 20 mm, and the head is adjusted to carry out VAR melting in a vacuum consumable arc furnace. During the VAR melting, a Φ920 mm specification is used for the crucible. After the arc is started, the normal melting stage is quickly entered at 15 min. During the normal melting stage, the melting current is in the form of a small current and a large stable arc period, which further promotes the element homogenization effect of the EB ingot. The melting current is controlled to be 24 KA, the melting speed is controlled to be 21 kg / min, the stable arc current is 25 A, the stable arc period is 35 s, and the heat exchange amount during the cooling process of the ingot is controlled to be in the range of 30000 kJ / min-33600 kJ / min. Strong stirring under a relatively shallow bath depth is realized to promote the uniformity of the element distribution. The ingot enters the feeding process at a height of 120 mm from the bottom, the feeding process gradually reduces the melting speed, and when the remaining thickness of the consumable electrode is 40 mm, the feeding is completed by tripping.

[0080] 6) After the VAR melting is completed, transverse samples are taken from the head, the middle and the tail of the ingot for chemical composition detection.

[0081] The sampling positions are as shown in Figure 6 , and the specific detection results are as shown in Figure 8 . According to Figure 8The test results show that the content of Al, Mo, Nb, Sn, Zr and Cr in the TC21 titanium alloy ingot prepared in Example 2 meets the requirements of the national standard and the national military standard composition range, and is uniformly distributed on the cross sections at different positions of the ingot, and the ranges of the 39 points (13 points for each of the head, middle and tail) are 0.14%, 0.12%, 0.09%, 0.10%, 0.10% and 0.11% respectively.

[0082] Example 3

[0083] 1) The clean TC21 scrap, titanium sponge, Al beans, Al70Cr, Ti80Sn and TiO2 are proportioned based on the nominal composition of TC21, wherein the content of Al is increased by 13% based on the reference value, the content of Sn is increased by 13.5% based on the reference value, the content of Cr is increased by 7% based on the reference value, the content of Zr remains unchanged, the content of Mo is reduced by 3.5% based on the reference value, and the content of Nb is reduced by 5% based on the reference value.

[0084] 2) After mixing all the raw materials in step 1) uniformly, press into a scrap alloy electrode block, when pressing the scrap alloy electrode block, the total weight of a single scrap alloy electrode block is controlled to be 100 kg, and in each scrap alloy electrode block, the addition amount of TC21 scrap accounts for 65% of the total weight of the scrap alloy electrode block, the addition amount of Al70Cr accounts for 1.3% of the total weight of the scrap alloy electrode block, the addition amount of Al accounts for 5.2% of the total weight of the scrap alloy electrode block, the addition amount of Ti80Sn accounts for 3.0% of the total weight of the scrap alloy electrode block, the addition amount of TiO2 accounts for 0.001% of the total weight of the scrap alloy electrode block, and the balance is titanium sponge. In addition, when pressing the scrap alloy electrode block, the thickness of the scrap alloy electrode block placed at the front end position of the material box is controlled to be 80 mm, and the thickness of the scrap alloy electrode block placed at the rear end position of the material box is controlled to be 60 mm.

[0085] 3) The scrap alloy electrode block is arranged with TC21 material head, TC21 strip material and TC21 riser material in a two-layer arrangement; specifically, the scrap alloy electrode block is laid at the bottom, and the TC21 material head, TC21 strip material and TC21 riser material are placed uniformly above the scrap alloy electrode block; the top layer is also arranged in the same way as the bottom layer, and the distribution thickness of the scrap and block materials at the front end position of the material box is controlled to be 1:3, and the distribution thickness of the scrap and block materials at the rear end position of the material box is controlled to be 1:4; wherein the scrap material refers to the scrap alloy electrode block, and the block material refers to the TC21 material head, TC21 strip material and TC21 riser material.

[0086] 4) After the vacuum degree and leakage rate meet the requirements, EB melting is carried out. The crystallizer specification adopts a Φ920 mm specification circular crystallizer. When the vacuum degree of the feeding chamber is less than 0.8 Pa, the vacuum degree of the melting chamber is less than or equal to 0.4 Pa, and the leakage rate is less than or equal to 0.4 Pa / min, the electronic guns of the melting zone, the refining zone and the crystallization zone are respectively started to preheat, wherein the electronic gun current of the melting zone is set to 2.3 A-2.7 A, the electronic gun current of the refining zone is set to 2.5 A, and the electronic gun of the crystallization zone is set to 2.3 A. The total preheating time is controlled to be 60 min. After the preheating is completed, the melting current is increased to build the shell and the bottom, wherein the electronic gun current of the melting zone is set to 3.5 A-5.8 A, the electronic gun current of the refining zone is set to 4.7 A-5.0 A, and the electronic gun of the crystallization zone is set to 4.0 A-5.0 A. After the shell and the bottom are built, the melting power is increased (the voltage is unchanged during the whole process from preheating to melting) to carry out normal melting. During the normal melting stage, the power of the melting zone is controlled to be in the range of 1800 kW-2100 kW, the power of the refining zone is controlled to be in the range of 680 kW-720 kW, and the power of the solidification zone is controlled to be in the range of 780 kW-1120 kW. The pushing speed during the normal melting stage is 270 mm / h-400 mm / h, the melting speed is 16 kg / min-22 kg / min, the water inlet temperature during the cooling process is 26°C, the water outlet temperature is 29°C, and the water flow is set to be 1500 L / min. At the same time, in order to avoid the fluctuation of Al, Sn and other elements at the head of the ingot, the melting power is kept unchanged at the end of the ingot melting to directly trip.

[0087] 5) After the EB melting is completed, the bottom of the EB ingot is sawn to a thickness of 20 mm, and the head is adjusted to carry out VAR melting in a vacuum consumable arc furnace. During the VAR melting, a Φ1020 mm specification is adopted for the crucible. After the arc is started, the normal melting stage is quickly entered at 15 min. During the normal melting stage, the melting current is in the form of a small current and a large stable arc period, which further promotes the element homogenization effect of the EB ingot. The melting current is controlled to be 24 KA, the melting speed is controlled to be 20 kg / min, the stable arc current is 25 A, the stable arc period is 30 s, and the heat exchange amount during the cooling process of the ingot is controlled to be in the range of 32000 kJ / min-33000 kJ / min. Strong stirring under a relatively shallow bath depth is realized to promote the uniformity of the element distribution. The ingot enters the feeding process at a height of 120 mm from the bottom. The feeding process gradually reduces the melting speed. When the remaining thickness of the consumable electrode is 30 mm, the feeding is completed by tripping.

[0088] 6) After the VAR melting is completed, the transverse samples are taken from the head, the middle and the tail of the ingot for chemical composition detection.

[0089] The sampling positions are as shown in Figure 6 , and the specific detection results are as shown in Figure 9 . According to Figure 9The test results show that the contents of Al, Mo, Nb, Sn, Zr, and Cr in the TC21 titanium alloy ingot prepared in Example 3 all meet the requirements of the national and military standards for composition. Moreover, the contents are evenly distributed on different cross-sections of the ingot, with the ranges of 39 points (13 points each at the head, middle, and tail) being 0.15%, 0.08%, 0.09%, 0.10%, 0.12%, and 0.10%, respectively.

[0090] Comparative Example 1

[0091] The difference between Comparative Example 1 and Example 1 is that:

[0092] Step 2) During the electrode block pressing process, the amount of TC21 chips, Al70Cr, Al beads and Ti80Sn added is not controlled, and the thickness of the compensation electrode block at different positions is not controlled.

[0093] In step 3), the electrode block is placed at the bottom of the hopper. A double-layer material distribution method is not used; only the material head is ensured to evenly fill the gaps in the hopper. The specific material distribution is as follows: Figure 5 As shown.

[0094] The remaining steps are exactly the same as in Example 1.

[0095] Samples were taken from the head, middle, and tail sections of the TC21 titanium alloy ingot obtained in Comparative Example 1 for testing and analysis. The test results are as follows: Figure 10 As shown. According to Figure 10 The test results showed that the content of Al ranged from 5.37% to 6.12%, Mo from 1.92% to 2.52%, Nb from 1.76% to 2.32%, Sn from 1.60% to 2.13%, Zr from 1.77% to 2.23%, and Cr from 1.33% to 1.76%. Among these, Nb exceeded the upper limit of the standard by 2.25%, Sn was below the lower limit by 1.75%, and Cr exceeded the upper limit by 1.75%. Furthermore, the composition fluctuated greatly at different cross-sections of the ingot, with ranges of 0.75%, 0.60%, 0.56%, 0.53%, 0.46%, and 0.43% for 39 points, respectively.

[0096] Comparative Example 2

[0097] The difference between Comparative Example 2 and Example 2 is that:

[0098] In step 4), in the preheating stage, the electron gun current of the melting zone is set to 3.5A-4.2A, the electron gun current of the refining zone is set to 4.0A, and the electron gun of the crystallization zone is set to 4.5A; in the shell building and bottom making stage, the electron gun current of the melting zone is set to 6.2A, the electron gun current of the refining zone is set to 5.4A, and the electron gun of the crystallization zone is set to 5.8A; after the shell building and bottom making is completed, the smelting power is raised for normal smelting, in the normal smelting stage, the power of the melting zone is controlled within 2300kW, the power of the refining zone is controlled within 600kW, and the power of the solidification zone is controlled within 700kW, the smelting speed is 28kg / min, the water inlet temperature is set to 25℃, the water outlet temperature is set to 30℃, and the water flow is set to 1000L / min.

[0099] The remaining steps are completely the same as those in Example 2.

[0100] The head of the TC21 titanium alloy ingot finally obtained in the present comparative example 2 is detected and analyzed, and it is found that the Sn element content at the center of the head is only 1.52%, which seriously exceeds the lower limit of the standard, and the Al content is 5.45%, which is far lower than the target value 6.0%, so no other detection is performed.

[0101] Comparative Example 3

[0102] The difference between Comparative Example 3 and Example 3 is that:

[0103] In step 5), after the EB ingot bottom is sawn, no turning is performed, and direct VAR smelting is performed. After 30min of arc striking, the normal smelting stage is entered, the smelting current is 28KA, the smelting speed is controlled to be 25kg / min, the steady arc adopts 15A, the steady arc period is 10s, the heat exchange amount is not controlled in the ingot cooling process, the actual heat exchange amount is 12000kJ / min-15000kJ / min, the remaining 70mm of the consumable electrode enters the feeding, and the remaining 10mm trips.

[0104] The remaining steps are completely the same as those in Example 3.

[0105] The tail of the ingot finally obtained in the present comparative example 3 is detected and analyzed, and the Al content at the center of the tail is 5.07%, which exceeds the lower limit of the standard, the Sn content is 1.45%, which also exceeds the lower limit of the standard, the Nb content is 2.37%, which exceeds the upper limit of the standard, and only the Mo, Zr and Cr element contents meet the standard requirements.

[0106] The above description is only a specific embodiment of the present application, enabling those skilled in the art to understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application.

[0107] It should be understood that the application is not limited to what has been described hereinabove and that various modifications and changes can be made without departing from the scope of the application. The scope of the application is limited only by the claims that follow.

Claims

1. A method for preparing a low-cost, high-quality TC21 titanium alloy ingot, characterized in that, Includes the following steps: Step 1: Prepare clean TC21 chips, sponge titanium, Al bean, Al70Cr, Ti80Sn and TiO2 according to the nominal composition of TC21, mix them evenly and press them into chip-shaped alloy electrode blocks. When pressing the shaving alloy electrode blocks: the total weight of a single shaving alloy electrode block is controlled between 45kg and 120kg, and in each shaving alloy electrode block, the amount of TC21 shavings added accounts for 60% to 65% of the total weight of the shaving alloy electrode block, the amount of Al70Cr added accounts for 0.5% to 1.5% of the total weight of the shaving alloy electrode block, the amount of Al granules added accounts for 2% to 5.5% of the total weight of the shaving alloy electrode block, the amount of Ti80Sn added accounts for 1% to 3.2% of the total weight of the shaving alloy electrode block, the amount of TiO2 added accounts for 0.0006% to 0.002% of the total weight of the shaving alloy electrode block, and the balance is sponge titanium; the thickness of the shaving alloy electrode blocks placed at the front end of the material box is controlled between 60mm and 100mm, and the thickness of the shaving alloy electrode blocks placed at the rear end of the material box is controlled between 40mm and 80mm; Step 2: The alloy electrode chips obtained in Step 1 are combined with TC21 sprue, TC21 strip material and TC21 riser material in a multi-layered manner for material distribution; Step 3: After the vacuum degree and leakage rate meet the requirements, EB melting is carried out. After the EB melting is completed, EB ingots are obtained. In EB melting, when the vacuum degree of the feed chamber is less than 0.8Pa, the vacuum degree of the melting chamber is ≤0.4Pa, and the leakage rate is ≤0.4Pa / min, the electron guns of the melting zone, refining zone and crystallization zone are turned on for preheating. After preheating, under constant voltage conditions, the melting current is increased to build the shell and form the bottom. Finally, after the shell and bottom are built, the melting power is increased for normal melting. During the preheating stage: the electron gun current in the melting zone is set to 2.3A to 2.7A, the electron gun current in the refining zone is set to 2.5A, and the electron gun current in the crystallization zone is set to 2.3A. The total preheating time is controlled between 40 and 60 minutes. Shell-forming and bottom-forming stage: Electron gun current in melting zone is set to 3.5A~5.8A, electron gun current in refining zone is set to 4.7A~5.0A, and electron gun current in crystallization zone is set to 4.0A~5.0A; During normal smelting: the power in the melting zone is controlled at 1800kW~2100kW, the power in the refining zone is controlled at 680kW~720kW, and the crystallization rate is controlled within the range of 780kW~1120kW. Furthermore, the smelting power is kept constant and the circuit is tripped directly at the end of the smelting process to avoid fluctuations in the elements at the head of the ingot. The parameters for the normal smelting stage are set as follows: the feeding speed is 270 mm / h to 400 mm / h, the smelting speed is 16 kg / min to 22 kg / min, the inlet water temperature during the cooling process is 25℃ to 27℃, the outlet water temperature is 28℃ to 30℃, and the water flow rate is 1500 L / min to 3000 L / min. Step 4: Sawing the bottom of the EB ingot obtained in Step 3 to a set thickness, and turning it around to perform VAR melting in a vacuum arc remelting furnace. After VAR melting is completed, the target TC21 titanium alloy ingot is obtained. During VAR melting, the gap between the electrode and the crucible is maintained at 40mm to 100mm. After arc ignition, the process quickly transitions to the normal melting stage within 10 to 15 minutes. A melting method with low current and long arc stabilization period is adopted, with the following parameters set: melting current of 20kA to 24kA, melting speed of 15kg / min to 21kg / min, arc stabilization current of 18A to 25A, and arc stabilization period of 20s to 35s. The feeding process begins when the height of the consumable electrode is 100mm to 120mm from the bottom. The feeding process gradually reduces the melting speed and trips when the thickness of the consumable electrode is 30mm to 40mm to complete the feeding process, which promotes the homogenization of elements in the EB ingot. During the normal smelting stage, the heat exchange during the cooling process of TC21 titanium alloy ingots is controlled at 27000kJ / min~33600kJ / min; Step 5: Perform chemical composition analysis on the TC21 titanium alloy ingot obtained in Step 4. During the analysis, samples are taken from the beginning, middle, and end of the ingot to determine its quality.

2. The method for preparing low-cost, high-quality TC21 titanium alloy ingots according to claim 1, characterized in that, In step one, when preparing the ingredients, the Al element is increased by 12% to 15% from the baseline value, the Sn element is increased by 10% to 16% from the baseline value, the Cr element is increased by 5% to 7% from the baseline value, the Zr element remains unchanged, the Mo element is decreased by 3% to 4% from the baseline value, and the Nb element is decreased by 4.5% to 5.5% from the baseline value.

3. The method for preparing low-cost, high-quality TC21 titanium alloy ingots according to claim 1, characterized in that, In step two, when laying the fabric, a double-layer fabric method is used, specifically as follows: First, lay the chipped alloy electrode blocks at the bottom layer, and then place TC21 material heads, TC21 strips and TC21 risers evenly on top of the chipped alloy electrode blocks. The top layer is laid out in the same way as the bottom layer. The thickness of the chip and block materials at the front of the material box is controlled at 1:3, and the thickness of the chip and block materials at the rear of the material box is controlled at 1:

4. Among them, "chip material" refers to chip-shaped alloy electrode blocks, and "block material" refers to TC21 material heads, TC21 strip material, and TC21 riser material.

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