A method for producing low-cost and high-uniformity titanium alloy ingots

Abstract

The invention discloses a method for producing a titanium alloy ingot with low cost and high uniformity. The method uses 100% VAR titanium alloy ingot complete riser as raw material, firstly controls the riser diameter and deflection degree, and adopts a vacuum electron beam welding machine to weld it into a consumable electrode, and then puts it into a vacuum consumable arc furnace, respectively performs primary smelting and finished product smelting, and strictly regulates the smelting current, speed, voltage, arc stabilization current and other related parameters during the smelting process, and finally obtains the finished ingot. The invention eliminates the pickling and alkali washing process of the material head, and avoids environmental pollution; in addition, by controlling the riser specifications and welding methods, the welding quality is guaranteed while the production efficiency is improved; in addition, by controlling the smelting parameters, it is possible to avoid accidents such as cracking of the weld during the primary smelting of the riser, the riser breaking and falling into the molten pool, etc., which affect the smelting safety, and promote the uniformity of the distribution of each element in the finished ingot, and greatly reduce the manufacturing cost of the titanium alloy ingot.

Description

Technical Field

[0001] The invention belongs to the technical field of nonferrous metal processing, and in particular relates to a production method of a low-cost and high-uniformity titanium alloy ingot. Background Art

[0002] Titanium and titanium alloy materials have the advantages of low density, high specific strength, low thermal expansion coefficient, good corrosion resistance, high compatibility, and easy welding. They are widely used in aerospace, automobile and shipbuilding, petrochemical, biomedicine, and marine engineering. At present, the processing cycle of titanium alloy products is long and the process loss is serious, resulting in high costs, which limits its further promotion and application. For this reason, countries that are in the leading position of material technology, such as the United States, China, and Europe, are committed to developing new titanium alloy processing technologies to reduce costs and expand the application of titanium alloys.

[0003] Among them, the use of titanium alloy material recycling is one of the most effective methods to reduce the comprehensive cost of titanium alloy products. At present, many scientific research institutions and production units at home and abroad have carried out research on titanium alloy waste recycling methods, including the use of returned chips and blocks mixed with normal materials, through EB smelting, EB + VAR, VAR + EB smelting and other methods, to produce TC4, TC11, TC18 and other grades of alloy products, realizing the industrial production of titanium alloy waste recycling. However, the existing technology is mainly based on chips and block scraps generated during the titanium alloy processing process. There is no efficient and economical recycling method for the large amount of riser waste generated during the titanium alloy ingot production process.

[0004] Due to the influence of ingot solidification shrinkage, even after the shrinkage compensation link during the smelting process, the riser of titanium alloy ingot still shows the characteristic of concave center. In addition, the average unit weight of the riser often exceeds 100kg. The conventional welding method is used for welding and smelting, which has the risks of difficult to ensure welding quality, insufficient strength of consumable electrode, and breakage of consumable electrode during smelting process. Some technical attempts are to saw the riser of the ingot, then use tungsten inert gas welding for dislocation welding, and fill the welding gap with the same grade of acid and alkali washed material heads, and then smelt to prevent the instability of the smelting process. However, in the production process of this method, in order to deal with the block production waste, hot alkali washing, acid washing and other steps need to be introduced, which will inevitably cause unavoidable environmental pollution. In addition, the risers are cut, staggered and assembled, and smaller block materials are filled in the joint gaps. Tungsten inert gas welding is used. Not only is the processing flow complicated, the specifications of the recovered ingots are small, and the production efficiency is extremely low, which is difficult to meet the needs of industrial production, but there is also a risk of tungsten inclusions introduced into the titanium alloy ingot by the tungsten electrode, which affects the uniformity of the chemical composition of the ingot, making it difficult to guarantee the quality of the recovered ingot.

[0005] In summary, there is no efficient and economical recycling measure at home and abroad for the large amount of riser waste generated in the production process of titanium alloy ingots. In view of this, this invention is specially proposed. Summary of the invention

[0006] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a low-cost and high-uniformity production method of titanium alloy ingots, which is mainly used to solve the problems of difficulty in recovering titanium alloy risers in the prior art, complex recovery process, high recovery cost, low efficiency, poor stability of riser welding quality, risk of breakage in the smelting process and poor uniformity of chemical composition of the recovered ingots, and at the same time solve the environmental pollution problem caused by recovering risers in the prior art.

[0007] The purpose of the present invention is to be solved by the following technical solutions:

[0008] The present invention provides a method for producing a low-cost and high-uniformity titanium alloy ingot, which specifically comprises the following steps:

[0009] Step 1: assemble multiple titanium alloy risers in a head-to-tail arrangement;

[0010] Step 2: Using a vacuum electron beam welder, perform girth welding on the titanium alloy riser assembled in step 1 under set parameters;

[0011] Step 3: Use the titanium alloy riser welded in step 2 as a consumable electrode, place it in a crucible with the bottom facing downward and the head facing upward, and then put it into a vacuum consumable arc furnace. After the pre-vacuum and the leak rate reach the set requirements, start the arc for one smelting to obtain an ingot;

[0012] Step 4: Turn the primary ingot obtained in step 3 around, and perform smelting in a manner with the head facing downward and the tail facing upward to obtain a finished ingot;

[0013] Step 5: Conduct transverse chemical composition analysis on the head, middle and tail of the ingot obtained in step 4.

[0014] Furthermore, when a plurality of titanium alloy risers are assembled in step 1, the diameter difference of the titanium alloy risers is controlled to be ≤15 mm, and the deflection degree of the sawing surface between the assembled titanium alloy risers is controlled to be ≤3 mm / m.

[0015] Furthermore, when the assembled titanium alloy riser is ring-welded in step 2, the welding parameters are set as follows: welding current is 300mA-450mA, focusing current is 700mA-1200mA, welding voltage is 60kV-65kV, and angular velocity range is 20° / min-50° / min.

[0016] Furthermore, after the assembled titanium alloy riser is circumferentially welded in step 2, it is cooled in a vacuum electron beam welding machine in a vacuum manner, and the cooling time t≥D / (5-7);

[0017] Wherein, D is the diameter of the welding titanium alloy riser, in mm; the unit of cooling time t is min.

[0018] Furthermore, in the step three, a smelting is performed when the pre-vacuum is ≤0.8Pa and the leakage rate is ≤0.5Pa / min.

[0019] Furthermore, the parameters of the first smelting in step three are set as follows: the smelting current during the normal smelting period is 15kA-19kA, the smelting voltage is 29V-32V, the arc stabilizing magnetic field adopts a DC arc stabilizing current, and the arc stabilizing current is 15A-20A.

[0020] Furthermore, the parameters for melting the finished product in step 4 are set as follows: pre-vacuum ≤ 0.8 Pa, leakage rate ≤ 0.5 Pa / min, melting speed during normal melting period is 20 kg / min to 30 kg / min, melting voltage is 34 V to 36 V, arc stabilization current adopts AC arc stabilization, and the arc stabilization current is 18 A to 25 A, and the arc stabilization period is 15 s to 20 s.

[0021] Furthermore, during the smelting of the finished product in step 4, when there are 2 to 4 titanium alloy risers remaining in the consumable electrode or the corresponding consumable electrode weight remains 200kg to 400kg, the current is gradually reduced to compensate for the shrinkage.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] 1. The production method provided by the present invention uses 100% VAR titanium alloy ingot complete risers as raw materials, and its specific production process is as follows: first, the diameter and deflection degree of the titanium alloy risers are controlled during assembly, and a vacuum electron beam welder is used to directly weld multiple complete risers into a consumable electrode; then the consumable electrode obtained by welding is loaded into a vacuum consumable arc furnace for a smelting, and during the smelting process, the smelting current, voltage, arc stabilizing current and other related parameters are strictly controlled; finally, in the finished product smelting process, the smelting speed, smelting voltage, arc stabilizing current and other related parameters are further adjusted to finally obtain the target titanium alloy ingot. Compared with the prior art, the production method of the present invention eliminates the pickling and alkali washing processes of the material head from the source, thus avoiding harm to the environment; in addition, by controlling the diameter and deflection of the riser during assembly and using a vacuum electron beam welder for ring welding, the welding quality is guaranteed while improving the production efficiency; in addition, by controlling and adjusting the relevant parameters of the primary smelting and the finished product smelting, it can avoid accidents such as cracking of the weld during the primary smelting of the riser, breakage of the riser and falling into the molten pool, which affect the smelting safety, and promote the uniform distribution of the elements in the finished ingot, and greatly reduce the manufacturing cost of the titanium alloy ingot. At the same time, the production method of the present invention can be applied to the preparation of titanium alloy ingots of different specifications and grades. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The accompanying drawings are incorporated in and constitute a part of this specification and, together with the description, serve to explain the principles of the present invention.

[0025] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0026] Figure 1 It is a flow chart of the production method of the present invention;

[0027] Figure 2 1 is a schematic diagram of the quality of riser welding in Example 1 of the present invention;

[0028] Figure 3 This is a composition detection diagram of the target TC4 titanium alloy ingot obtained in Example 1 of the present invention;

[0029] Figure 4 Schematic diagram of riser welding quality in Example 2 of the present invention;

[0030] Figure 5 This is a composition detection diagram of the target TB6 titanium alloy ingot obtained in Example 2 of the present invention;

[0031] Figure 6This is a composition detection diagram of the target TC21 titanium alloy ingot obtained in Example 3 of the present invention;

[0032] Figure 7 This is a schematic diagram of the quality of the riser after conventional vacuum plasma welding, which is used as the control group of Example 1;

[0033] Figure 8 This is a schematic diagram of a smelting process of a control group of Example 2;

[0034] Fig. 9 It is used as the control group of Example 3, and the ingot composition detection diagram is finally obtained. DETAILED DESCRIPTION

[0035] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Instead, they are merely examples consistent with some aspects of the present invention as detailed in the appended claims.

[0036] In order to enable those skilled in the art to better understand the technical solution of the present invention, the present invention is further described in detail below with reference to the accompanying drawings.

[0037] Before applying for the present invention, the technicians of the present invention tried to weld multiple titanium alloy ingot integral risers by vacuum plasma welding, but found in the process of the experiment that vacuum plasma welding is excellent for electrode blocks composed of loose sponge titanium and intermediate alloy, and the welding pool depth can be ≥30mm, but for dense titanium alloy ingot risers, it is very easy to crack after welding. The most serious thing is that the welding pool depth is obviously insufficient, only about 10mm, resulting in obviously insufficient welding strength and serious smelting safety risks. The technicians of the present invention have been committed to exploring and using simple and efficient production methods to achieve the goal of high quality and high quality recovery of titanium alloy ingot risers.

[0038] In order to solve the problem of difficulty in welding titanium alloy risers as a whole, the technicians of the present invention have conducted a large number of exploratory experiments and for the first time adopted vacuum electron beam welding of the whole riser. By controlling parameters such as welding current, welding voltage, and welding angular velocity, the molten pool depth of the weld can be effectively controlled, thereby improving the welding strength. On the basis of controlling the welding molten pool depth, the consumable electrode weld cracking problem after the whole riser welding can be effectively prevented by jointly controlling the welding angular velocity and the post-weld cooling time.

[0039] However, obtaining an integral riser consumable electrode with good welding quality is only the basis for using risers to produce low-cost titanium alloy ingots. If the smelting process is not set properly, there are also major hidden dangers that threaten the safety of smelting, such as the premature melting of the weld at the weld, which causes the consumable electrode to break, and the consumable electrode falls into the molten pool as a whole. Even if the safety problem of smelting is solved, since the risers are all shrinked by low current and long-term insulation, the components in the center of the riser often have a common phenomenon that the content of volatile elements such as Al and Sn is significantly lower than that of the edge. If the smelting process is unreasonable, the consumable electrode composed of multiple risers will inevitably have a significant component segregation phenomenon, which is difficult to meet the subsequent high-quality application requirements.

[0040] In order to solve the major quality and safety hazards such as cracking and breaking of the riser during the melting process after welding and falling into the molten pool, the solution proposed in the present invention is: first, the problem of melting and falling blocks is controlled by setting the relevant parameters of the primary melting, and then the problem of uniformity of the recovered components of the riser is solved by setting the relevant parameters of the secondary melting.

[0041] Specifically, in order to solve the problem of block falling during primary smelting, the technicians of the present invention have found through a large number of exploratory experiments that the melting current during the normal melting period of a primary smelting should be controlled at 15kA to 19kA. Due to the influence of the arc stabilizing magnetic field during the melting process, the consumable electrode during the melting process is always in a slight swinging state. If the melting current is lower than 15kA, the melting time will be significantly prolonged, thereby increasing the overall swinging time of the consumable electrode in the later stage, aggravating the block falling in the later stage of melting; however, if the melting current is higher than 19kA, the overall temperature of the molten pool will be increased due to the increase in melting power, aggravating the baking effect on the titanium alloy riser weld, and also increasing the probability of block falling during the primary melting of the riser. On the basis of controlling the melting current, the control of the melting voltage is equally important. In order to avoid the problem of falling blocks caused by the first melting of the titanium alloy riser weld, a lower voltage should be used during the melting process. If the voltage is higher than 32V, the arc distance will be lengthened, which will increase the probability of the edge weld melting first. If the weld melts first and the riser loses connection, the probability of falling blocks will increase. If the melting voltage is lower than 29V, serious splashing will occur during the melting process, affecting the stability of the melting. Therefore, the reasonable range of the melting voltage is 29V to 32V. In terms of the technology of controlling the melting current and voltage, since the riser as a whole has the characteristics of low center and high edge, the control of arc stabilization is also crucial. If the arc stabilization current is too small, it is difficult to effectively constrain the arc to be in the center of the consumable electrode to protect the quality of the weld. If the arc stabilization current is too large, the swing problem of the consumable electrode in the melting process will be aggravated due to the increase in the arc stabilization magnetic field strength, which will also bring major hidden dangers to the melting safety. The reasonable arc stabilization current range is 15A to 20A.

[0042] In addition, due to the influence of the shrinkage feeding process, the core of the riser of the titanium alloy ingot has always been the area with the worst composition. For the consumable electrode formed by the assembly of multiple risers, one smelting can only achieve the purpose of preliminary alloying. In order to avoid block falling, the large DC arc stabilizing current used in one smelting further aggravates the tendency of element segregation. Therefore, the finished product smelting process is very important. The technicians of the present invention have found through a large number of experiments that, unlike the finished product smelting of conventional titanium alloy ingots that have been fully alloyed, the finished product smelting process parameter range is narrower when the titanium alloy riser is used for one-time recovery smelting, and is sensitive to changes in process parameters. The reasonable melting speed range in the normal melting period is 20kg / min to 30kg / min. If the melting speed is too low, the melting time will be prolonged, further increasing the volatilization loss of Al elements in the axial center of the ingot. If the melting speed is too high, the depth of the molten pool will be deepened, which is not conducive to further homogenization of the composition. The reasonable range of melting voltage is 34V to 36V. If it is lower than 34V, it will cause serious splashing during the melting process. If it is higher than 36V, the consumable electrode will be seriously burned in the later stage of melting, which is not conducive to the shrinkage compensation process. The arc stabilization current adopts AC arc stabilization, the size is 18A to 25A, and the arc stabilization period is 15s to 20s. If the arc stabilization current or stirring period is too small, the stirring effect of the melting process is limited, affecting the distribution uniformity of the elements in the transverse section of the ingot. If the arc stabilization current or stirring period is too large, it will also aggravate the segregation tendency of the elements. On the basis of the above experiments, a large number of experiments were further conducted to obtain the technical solution of the present invention.

[0043] See also Figure 1 The present invention provides a method for producing a low-cost and high-uniformity titanium alloy ingot, which specifically comprises the following steps:

[0044] Step 1: assemble multiple titanium alloy risers in a head-to-tail arrangement;

[0045] Step 2: Using a vacuum electron beam welder, perform girth welding on the titanium alloy riser assembled in step 1 under set parameters;

[0046] Step 3: Use the titanium alloy riser welded in step 2 as a consumable electrode, place it in a crucible with the bottom facing downward and the head facing upward, and then put it into a vacuum consumable arc furnace. After the pre-vacuum and the leak rate reach the set requirements, start the arc for one smelting to obtain an ingot;

[0047] Step 4: Turn the primary ingot obtained in step 3 around, and perform smelting in a manner with the head facing downward and the tail facing upward to obtain a finished ingot;

[0048] Step 5: Conduct transverse chemical composition analysis on the head, middle and tail of the ingot obtained in step 4.

[0049] Among them, when multiple titanium alloy risers are assembled in step one, the diameter difference of the titanium alloy risers is controlled to be ≤15mm, and the deflection degree of the sawing surface between the assembled titanium alloy risers is controlled to be ≤3mm / m. When the assembled titanium alloy risers are ring-welded in step two, the welding parameters are set as follows: the welding current is 300mA~450mA, the focusing current is 700mA~1200mA, the welding voltage is 60kV~65kV, and the angular velocity range is 20° / min~50° / min; at the same time, after the ring welding, it is required to be cooled in a vacuum electron beam welding machine by vacuum, and the cooling time t≥D / (5~7), where D is the diameter of the welded titanium alloy riser, in mm; the cooling time t is in min. In step 3, when the pre-vacuum is ≤0.8Pa and the leakage rate is ≤0.5Pa / min, a smelting is performed, and the parameters for the first smelting are set as follows: the smelting current during the normal smelting period is 15kA-19kA, the smelting voltage is 29V-32V, the arc stabilizing magnetic field adopts a DC arc stabilizing current, and the arc stabilizing current is 15A-20A. The parameters for the finished product smelting in step 4 are set as follows: the pre-vacuum is ≤0.8Pa, the leakage rate is ≤0.5Pa / min, the smelting speed during the normal smelting period is 20kg / min-30kg / min, the smelting voltage is 34V-36V, the arc stabilizing current adopts an AC arc stabilizing current, and the arc stabilizing current is 18A-25A, and the arc stabilizing period is 15s-20s; at the same time, when there are 2-4 titanium alloy risers remaining in the consumable electrode or the corresponding consumable electrode weight is 200kg-400kg, the current is gradually reduced for shrinkage.

[0050] In order to further verify the efficacy of the present invention, the present invention technicians conducted the following specific experiments:

[0051] Example 1 (Target Preparation of TC4 Titanium Alloy Ingot)

[0052] The specific production process is as follows:

[0053] 1) Assemble multiple TC4 type 920mm titanium alloy risers in a head-to-tail arrangement, control the riser diameter difference to be ≤15mm during the assembly process, and control the sawing surface deflection between the assembled risers to be ≤3mm / m;

[0054] 2) placing the titanium alloy riser assembled in step 1) in a vacuum electron beam welding machine, and performing electron beam welding on the weld position under the condition of pre-vacuum ≤0.8Pa and leakage rate ≤0.5Pa / min. The specific welding parameters are set as follows: welding current is 400mA-450mA, focusing current is 1000mA-1200mA, welding voltage is 63kV-65kV, angular velocity range is 20° / min-30° / min; cooling time after welding is t≥D / 5=920 / 5=184min, where D is the diameter of the welded titanium alloy riser, in mm, and the quality of the riser after welding is as follows: Figure 2 As shown;

[0055] 3) The TC4 titanium alloy riser welded in step 2) is used as a consumable electrode, and is loaded into a crucible with a specification of Φ1020 mm in a manner of bottom downward and head upward, and then the whole is placed in a vacuum consumable arc furnace. When the pre-vacuum is ≤0.8Pa and the leakage rate is ≤0.5Pa / min, the arc is started for a single smelting. During the single smelting process, the smelting current in the normal smelting period is set to 17kA-19kA, the smelting voltage is set to 32V, the arc stabilizing magnetic field adopts a DC arc stabilizing current, and the arc stabilizing current is set to 20A;

[0056] 4) After removing the head flash from the primary ingot obtained in step 3), the ingot is loaded into a crucible with a specification of 1120 mm in a manner of head downward and bottom upward, and placed in a vacuum consumable arc furnace for finished product smelting. The parameters for finished product smelting are set as follows: pre-vacuum ≤ 0.8 Pa, leakage rate ≤ 0.5 Pa / min, smelting speed during normal smelting period is 30 kg / min, smelting voltage is 36 V, arc stabilization current adopts AC arc stabilization, arc stabilization current is 25 A, and arc stabilization period is 20 s. When there are 4 risers remaining on the consumable electrode or the corresponding weight is 400 kg, the current is reduced step by step for shrinkage compensation.

[0057] 5) The finished ingot obtained after the finished product smelting in step 4) is tested. 20mm thick sample pieces are taken from the head, middle and tail of the finished ingot, and the chemical composition is tested at nine points in the horizontal direction. The test results are as follows: Figure 3 shown.

[0058] By observing the quality of the riser welding obtained in Example 1 Figure 2 It can be seen that the welding molten pool is full and there is no cracking. By checking the first smelting process of this embodiment 1, the smelting process is smooth without abnormal conditions such as falling blocks and breaking of consumable electrodes falling into the molten pool. Finally, according to the sampling and analysis results of the finished ingots obtained in this embodiment 1, Figure 3 It can be seen that the elements in the entire ingot are evenly distributed, the extreme difference of Al element is 1300ppm, and the extreme difference of V element is 900ppm, which fully meets the requirements of TC4 titanium alloy ingot for high uniformity.

[0059] Example 2 (Target Preparation of TB6 Titanium Alloy Ingot)

[0060] The specific production process is as follows:

[0061] 1) Assemble multiple TB6 titanium alloy risers of 520 mm in size in a head-to-tail arrangement, and control the diameter difference of the risers to be ≤10 mm during the assembly process, and control the deflection of the sawing surface between the assembled risers to be ≤2 mm / m;

[0062] 2) placing the titanium alloy riser assembled in step 1) in a vacuum electron beam welding machine, and performing electron beam welding on the weld position under the condition of pre-vacuum ≤0.8Pa and leakage rate ≤0.5Pa / min, and the welding parameters are specifically set as follows: welding current is 300mA-350mA, focusing current is 700mA-800mA, welding voltage is 60kV-63kV, angular velocity range is 40° / min-50° / min; cooling time after welding is t≥D / 7=520 / 7=74min, where D is the diameter of the welded titanium alloy riser, in mm, and the quality of the riser after welding is as follows: Figure 4 As shown;

[0063] 3) The TB6 titanium alloy riser welded in step 2) is used as a consumable electrode, and is loaded into a crucible with a specification of Φ640 mm in a manner of bottom downward and head upward, and then placed as a whole in a vacuum consumable arc furnace. When the pre-vacuum is ≤0.8Pa and the leakage rate is ≤0.5Pa / min, the arc is started for a single smelting. During the single smelting process, the smelting current in the normal smelting period is set to 15kA-17kA, the smelting voltage is set to 29V, the arc stabilizing magnetic field adopts a DC arc stabilizing current, and the arc stabilizing current is set to 15A;

[0064] 4) After removing the flash from the head of the primary ingot obtained in step 3), the ingot is loaded into a crucible with a specification of 720 mm in a manner of head downward and bottom upward, and placed in a vacuum consumable arc furnace for finished product smelting. The parameters for finished product smelting are set as follows: pre-vacuum ≤ 0.8 Pa, leakage rate ≤ 0.5 Pa / min, smelting speed during normal smelting period is 20 kg / min, smelting voltage is 34 V, arc stabilization current adopts AC arc stabilization, arc stabilization current is 18 A, and arc stabilization period is 15 s. When there are 2 risers left on the consumable electrode or the corresponding weight is 200 kg, the current is reduced step by step for shrinkage compensation.

[0065] 5) The finished ingot obtained after the finished product smelting in step 4) is tested. 20mm thick sample pieces are taken from the head, middle and tail of the finished ingot, and the chemical composition is tested at nine points in the horizontal direction. The test results are as follows: Figure 5 shown.

[0066] By observing the quality of the riser welding obtained in Example 2 Figure 4 It can be seen that the welding molten pool is full and there is no cracking. By checking the first smelting process of this embodiment 2, the smelting process is smooth without abnormal conditions such as falling blocks and breaking of consumable electrodes falling into the molten pool. Finally, according to the sampling and analysis results of the finished ingots obtained in this embodiment 2, Figure 5 It can be seen that the elements in the entire ingot are evenly distributed, the Al element range is 1200ppm, the V element range is 1000ppm, and the Fe element range is 1100ppmn, which fully meets the requirements of TB6 titanium alloy ingot for high uniformity.

[0067] Example 3 (Target Preparation of TC21 Titanium Alloy Ingot)

[0068] The specific production process is as follows:

[0069] 1) Assemble multiple 720mm TC21 titanium alloy risers in a head-to-tail arrangement, control the riser diameter difference to be ≤10mm during the assembly process, and control the sawing surface deflection between the assembled risers to be ≤2mm / m;

[0070] 2) placing the titanium alloy riser assembled in step 1) in a vacuum electron beam welding machine, and performing electron beam welding on the weld position under the condition of pre-vacuum ≤0.8Pa and leakage rate ≤0.5Pa / min, and the welding parameters are specifically set as follows: welding current is 380mA-420mA, focusing current is 900mA-1100mA, welding voltage is 62kV-64kV, and angular velocity range is 35° / min-45° / min; cooling time after welding t≥D / 5=720 / 6=120min, where D is the diameter of the welded titanium alloy riser, in mm;

[0071] 3) The TC21 titanium alloy riser welded in step 2) is used as a consumable electrode, and is loaded into a crucible with a specification of Φ820 mm in a manner of bottom downward and head upward, and then the whole is placed in a vacuum consumable arc furnace. When the pre-vacuum is ≤0.8Pa and the leakage rate is ≤0.5Pa / min, the arc is started for a single smelting. During the single smelting process, the smelting current in the normal smelting period is set to 16kA-18kA, the smelting voltage is set to 30V, the arc stabilizing magnetic field adopts a DC arc stabilizing current, and the arc stabilizing current is set to 18A;

[0072] 4) After removing the flash from the head of the primary ingot obtained in step 3), the ingot is loaded into a crucible with a specification of 920 mm in a manner with the head facing downward and the bottom facing upward, and placed in a vacuum consumable arc furnace for finished product smelting. The parameters for finished product smelting are set as follows: pre-vacuum ≤ 0.8 Pa, leakage rate ≤ 0.5 Pa / min, smelting speed during normal smelting period is 25 kg / min, smelting voltage is 35 V, arc stabilization current adopts AC arc stabilization, the arc stabilization current is 20 A, and the arc stabilization period is 18 s. When there are 3 risers remaining on the consumable electrode or the corresponding weight remains 300 kg, the current is reduced step by step for shrinkage compensation.

[0073] 5) The finished ingot obtained after the finished product smelting in step 4) is tested. 20mm thick sample pieces are taken from the head, middle and tail of the finished ingot, and the chemical composition is tested at nine points in the horizontal direction. The test results are as follows: Figure 6 shown.

[0074] After checking the quality of the riser welding of Example 3, the welding molten pool was full and there was no cracking; then by checking the primary smelting process of Example 3, the smelting process was smooth without any abnormal conditions such as falling blocks and breaking of the consumable electrode falling into the molten pool; finally, according to the sampling and analysis results of the finished ingot obtained in Example 1, Figure 6 It can be seen that the elements in the whole ingot are evenly distributed, with the Al element range of 1500ppm, the Mo element range of 1000ppm, the Nb element range of 900ppm, the Sn element range of 1100ppm, the Zr element range of 900ppm, and the Cr element range of 800ppm, which fully meets the high uniformity requirements of TC21 titanium alloy ingots.

[0075] Comparative Example 1

[0076] The difference between Comparative Example 1 and Example 1 is only that: Step 2) during the welding of the titanium alloy riser after assembly, a vacuum plasma welding box is used for welding, the welding current is 300A to 800A, the welding voltage is 40V to 90V, the welding cooling time is 45min, and the other steps are exactly the same.

[0077] Comparative Example 1 The riser morphology after welding is as follows Figure 7 As shown, it can be seen through observation that the titanium alloy riser welded with a vacuum plasma welding box has serious cracking. Further dissection of the weld position revealed that the cracked weld is less than 10 mm deep and subsequent smelting is impossible.

[0078] Comparative Example 2

[0079] The difference between Comparative Example 2 and Example 2 is that: in step 3), during the primary smelting process, the smelting current during the normal smelting period of the primary smelting process is set to 20kA~25kA, the smelting voltage is set to 34V, the arc stabilization current is set to 12A, and the remaining steps are exactly the same as in Example 2.

[0080] However, in the first smelting process of Comparative Example 2, when the smelting reached 200 kg, the egg dropped, and the titanium alloy riser consumable electrode broke and fell into the molten pool as a whole, with a morphology as shown in FIG. Figure 8 As shown, subsequent smelting is not possible.

[0081] Comparative Example 3

[0082] The only difference between Comparative Example 3 and Example 3 is that: in step 4), during the smelting process of the finished product, the parameters of the smelting of the finished product are set as follows: the melting rate in the normal smelting period is 15 kg / min, the smelting voltage is 37 V, the arc stabilization current is 15 A, the stirring period is 10 s, and when the consumable electrode has 200 kg remaining, the current is gradually reduced for shrinkage compensation, and the remaining steps are exactly the same.

[0083] In the process of finished product smelting, due to the high voltage, the consumable electrode was severely burned in the late stage of smelting, resulting in serious shaking of the molten pool and incomplete reserved shrinkage feeding disc. After the finished product was smelted, 20mm thick test pieces were taken from the head, middle and tail of the prepared titanium alloy ingot for transverse chemical composition testing. The test results are as follows: Fig. 9 Shown: From Fig. 9 It can be seen that the uniformity of element distribution throughout the ingot is poor, with the extreme values ​​of Al element being 5200ppm, Mo element being 1500ppm, Nb element being 1800ppm, Sn element being 3500ppm, Zr element being 1100ppm, and Cr element being 1300ppm, and the minimum values ​​of Al and Sn elements being lower than the standard requirements.

[0084] The above description is only a specific embodiment of the present invention, so that those skilled in the art can understand or implement the present invention. 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 invention.

[0085] It should be understood that the present invention is not limited to what has been described above and that various modifications and changes may be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for producing a low-cost and high-uniformity titanium alloy ingot, characterized in that: The specific steps include: Step 1: assemble multiple titanium alloy risers in a head-to-tail arrangement; Step 2: Using a vacuum electron beam welder, perform girth welding on the titanium alloy riser assembled in step 1 under set parameters; Step 3: Use the titanium alloy riser welded in step 2 as a consumable electrode, place it in a crucible with the bottom facing downward and the head facing upward, and then put it into a vacuum consumable arc furnace. After the pre-vacuum and the leak rate reach the set requirements, start the arc for one smelting to obtain an ingot; Step 4: Turn the primary ingot obtained in step 3 around, and perform smelting in a manner with the head facing downward and the tail facing upward to obtain a finished ingot; Step 5: Performing lateral chemical composition analysis on the head, middle and tail of the finished ingot obtained in step 4; When the plurality of titanium alloy risers are assembled in step 1, the diameter difference of the titanium alloy risers is controlled to be ≤15 mm, and the deflection degree of the sawing surface between the assembled titanium alloy risers is controlled to be ≤3 mm / m; When the assembled titanium alloy riser is subjected to ring welding in the step 2, the welding parameters are set as follows: the welding current is 300mA-450mA, the focusing current is 700mA-1200mA, the welding voltage is 60kV-65kV, and the angular velocity range is 20° / min-50° / min; after the assembled titanium alloy riser is subjected to ring welding, it is cooled in a vacuum electron beam welding machine by vacuum, and the cooling time t≥D / (5-7); Wherein, D is the diameter of the titanium alloy riser for welding, in mm; the cooling time t is in min; The parameters of the first smelting in step 3 are set as follows: the smelting current in the normal smelting period is 15kA-19kA, the smelting voltage is 29V-32V, the arc stabilizing magnetic field adopts a DC arc stabilizing current, and the arc stabilizing current is 15A-20A; The parameters for melting the finished product in step 4 are set as follows: pre-vacuum ≤ 0.8 Pa, leakage rate ≤ 0.5 Pa / min, melting speed during normal melting period is 20 kg / min to 30 kg / min, melting voltage is 34 V to 36 V, arc stabilization current adopts AC arc stabilization, and the arc stabilization current is 18 A to 25 A, and the arc stabilization period is 15 s to 20 s.

2. The method for producing a low-cost and high-uniformity titanium alloy ingot according to claim 1, characterized in that: In the step three, a smelting is performed when the pre-vacuum is ≤0.8Pa and the leakage rate is ≤0.5Pa / min.

3. The method for producing a low-cost and high-uniformity titanium alloy ingot according to claim 1, characterized in that: During the smelting of the finished product in step 4, when there are 2 to 4 titanium alloy risers remaining on the consumable electrode or the corresponding consumable electrode weight remains at 200 kg to 400 kg, the current is gradually reduced to compensate for the shrinkage.

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