A smelting method for improving the quality of the bottom of a titanium alloy ingot

Abstract

The application discloses a smelting method for improving the quality of the bottom of a titanium alloy ingot, and the process route is: electrode preparation, primary smelting, secondary smelting, tertiary smelting and finished ingot; the current system during the tertiary smelting is set as (KA / min): 4 / 1~A→(2B / 3) / 2~(2~3)→(B+0.5~1) / (3~5)→B; wherein, A is the time for the current to rise to 2 / 3 of the stable stage current at a current rising speed of 1.5 KA / min, B represents the stable stage current, and the arc stabilizing during the arc starting stage is direct current, and the stable stage is alternating current. The titanium alloy ingot prepared through the method has a machining amount of the bottom within 10 mm, the machining workload is reduced, the yield is improved, and the composition of the bottom of the ingot is uniform.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy ingot preparation technology, specifically relating to a smelting method for improving the bottom quality of titanium alloy ingots. This method can improve the bottom quality of titanium alloy ingots of commonly used industrial specifications (Φ630~Φ720mm). Background Technology

[0002] Titanium alloys are widely used in aviation, aerospace, shipbuilding and medical fields due to their high specific strength, good high temperature performance, good corrosion resistance, and good shape memory, fatigue strength and fracture toughness.

[0003] Currently, the mainstream preparation method for titanium alloy ingots is the vacuum arc remelting (VAR) method, and ingots with high requirements for compositional uniformity generally require three melting processes. The final melting process can be divided into three stages: arc initiation, melting, and feeding. To prevent safety accidents caused by arcing and crucible breakdown, a small current is used for arc initiation. To quickly establish a molten pool, the small current is maintained for a certain period of time, and then the current is rapidly increased to complete the arc initiation until a stable melting stage is reached.

[0004] However, the traditional method described above uses a small current at the start of the arc. After the arc is started, one side produces and fills with molten metal, while the other side only begins to produce and fill with molten metal after a period of time, until a complete molten pool is achieved. Throughout this process, the side that first produces and fills with molten metal solidifies first due to the lower temperature at the bottom of the crucible. Furthermore, the final arc stabilization is typically done using AC melting, causing subsequent molten metal to cover the already solidified side, resulting in a cold shut at the bottom. The larger the crucible diameter, the more severe this one-sided filling and solidification becomes. Typically, industrially common titanium alloy ingots (Φ630~Φ720mm) will have a large area of ​​defects at the bottom 1 / 2R, with a depth of 20~30mm. Completely removing these metallurgical defects requires extensive turning or even sawing, leading to a decrease in ingot yield. Simultaneously, due to the rapid solidification of the alloy molten metal on one side, alloying elements fail to diffuse sufficiently, resulting in poor alloy uniformity at the bottom. In addition, for titanium alloy smelting, the bottom of the crucible is prone to deformation due to heat and gravity, resulting in an uneven crucible bottom. In this case, the molten liquid will flow to one side more obviously, and the bottom quality will be worse.

[0005] In view of this, the inventors propose a smelting method to improve the bottom quality of titanium alloy ingots, thereby overcoming the shortcomings of the prior art. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a smelting method to improve the bottom quality of titanium alloy ingots, thereby solving the problems of large bottom processing amount, low yield and poor composition uniformity of titanium alloy ingots prepared by traditional smelting methods.

[0007] The objective of this invention is achieved through the following technical solution:

[0008] A smelting method for improving the bottom quality of titanium alloy ingots specifically includes the following steps;

[0009] Step 1: Electrode Preparation

[0010] Weigh the raw materials of the target titanium alloy ingot and mix them evenly. First, press the electrode blocks, and then weld the pressed electrode assembly into an electrode.

[0011] Step 2: First Melting

[0012] The electrode obtained in step one is used as a consumable electrode and smelted in a vacuum consumable arc furnace to obtain a primary ingot.

[0013] Step 3: Secondary Smelting

[0014] The primary ingot obtained in step two is used as a consumable electrode in a vacuum consumable arc furnace for secondary melting to obtain a secondary ingot. When loading the furnace, the primary ingot must be inverted (head down).

[0015] Step 4: Three-stage smelting

[0016] The secondary ingot obtained in step three is used as a consumable electrode and is smelted three times in a vacuum consumable arc furnace. In the later stage of smelting, the ingot is fed back to obtain a tertiary ingot.

[0017] Step 5: Casting the finished ingot

[0018] The three ingots obtained in step four are subjected to peeling, sampling, flaw detection, and sawing of risers to obtain the target titanium alloy ingot.

[0019] Furthermore, in step two, during the first melting stage, the melting current is set to 15.0–20.0 kA, the melting voltage is set to 28.0–37.0 V, and the arc stabilizing current is DC 10.0–20.0 A.

[0020] Furthermore, during the secondary melting in step three, the melting current is set to 18.0–25.0 kA, the melting voltage is set to 29.0–38.0 V, the arc stabilization current is AC 10.0–20.0 A, and the stirring cycle is 15–60 s.

[0021] Furthermore, in step four, during the three melting processes, the arc-starting current is set to 4.0 kA, the melting current is set to 19.5–28.5 kA, the melting voltage is set to 30.0–40.0 V, the arc-stabilizing current is set to 15.0–25.0 A, and the stirring cycle is set to 15–60 s.

[0022] Furthermore, during the three melting processes in step four, the current regime is as follows: 4 / 1~A→(2B / 3) / 2~(2~3)→(B+0.5~1) / (3~5)→B;

[0023] Where A represents the time it takes for the current to rise from 4KA to 2 / 3 of the current in the smelting stage, with the time unit being min and the current rising rate being 1.5KA / min; and B represents the smelting current in the smelting stage, with the current unit being KA.

[0024] Furthermore, during the three melting processes in step four, the arc-stabilizing current during the arc-starting stage is DC, and the arc-stabilizing current during the melting stage is AC.

[0025] Furthermore, the smelting method is used to prepare titanium alloy ingots with dimensions of Φ630~Φ720mm.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The smelting method provided by this invention generally adopts a three-stage VAR smelting method. However, compared with the traditional smelting method, in the third smelting stage, the current regime during the smelting process is adjusted to maximize the heat at the bottom of the crucible before the molten pool is formed, shortening the time from the start of molten pool formation to its completeness (before solidification), and avoiding the situation where one side solidifies while the other side does not produce molten liquid. During the arc stabilization stage, DC current is used to ensure that molten liquid continuously flows through the side where molten liquid is formed first, preventing premature solidification, thereby reducing or eliminating the formation of cold shuts at the bottom of commonly used industrial ingot sizes (Φ630~Φ720mm). Practical verification shows that the machining allowance at the bottom of the ingot obtained using this smelting method can be controlled within 10mm, reducing machining workload and improving yield. At the same time, because the molten pool can be maintained to a fully complete state, the various elements in the titanium alloy can diffuse fully, thus achieving uniformity in composition, including at the bottom of the ingot. Attached Figure Description

[0028] The accompanying drawings are incorporated in and form part of this specification, and together with the description serve to explain the principles of the invention.

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, those skilled in the art can obtain other drawings based on these drawings without creative effort.

[0030] Figure 1 This is a flowchart of the smelting method for improving the bottom quality of titanium alloy ingots according to the present invention;

[0031] Figure 2This is a schematic diagram of a horizontal sample taken from the bottom of a titanium alloy ingot prepared by the smelting method of this invention.

[0032] Among them, 1 represents the heart; 2 represents 1 / 3R; 3 represents 2 / 3R; and 4 represents the periphery. Detailed Implementation

[0033] Exemplary embodiments will now be described in detail, examples of which are illustrated in the accompanying drawings. When the following description relates to the drawings, unless otherwise indicated, the same numerals in different drawings denote the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with the present invention. Rather, they are merely examples of apparatuses consistent with some aspects of the invention as detailed in the appended claims.

[0034] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments.

[0035] Please see Figure 1 The present invention provides a smelting method for improving the bottom quality of titanium alloy ingots, the smelting method specifically including the following steps;

[0036] Step 1: Electrode Preparation

[0037] Weigh the raw materials (including sponge titanium, master alloy, etc.) of the target titanium alloy ingot and mix them evenly. First, press the electrode blocks, and then weld the pressed electrode assembly into an electrode.

[0038] Step 2, First Melting:

[0039] The electrode obtained in step one is used as a consumable electrode and smelted in a vacuum consumable arc furnace to obtain a primary ingot. The specific smelting parameters are set as follows: the arc ignition current is 4.0 kA, the smelting current is 15.0 to 20.0 kA, the smelting voltage is 28.0 to 37.0 V, and the arc stabilization current is DC 10.0 to 20.0 A.

[0040] Step 3: Secondary Smelting

[0041] The primary ingot obtained in step two is used as a consumable electrode in a vacuum consumable arc furnace for secondary melting to obtain a secondary ingot. When loading the furnace, the primary ingot must be inverted, i.e., head down. The specific melting parameters are set as follows: the arc ignition current is set to 4.0KA, the melting current is set to 18.0~25.0KA, the melting voltage is set to 29.0~38.0V, the arc stabilization current is AC 10.0~20.0A, and the stirring cycle is 15~60s.

[0042] Step 4: Three-stage smelting

[0043] The secondary ingot obtained in step three is used as a consumable electrode and smelted three times in a vacuum consumable arc furnace. Feeding is performed in the later stage of smelting to obtain a tertiary ingot. The specific smelting parameters are set as follows: the arc-starting current is set to 4.0 kA, the smelting current is set to 19.5–28.5 kA, the smelting voltage is set to 30.0–40.0 V, the arc-stabilizing current is 15.0–25.0 A, and the stirring cycle is 15–60 s. The arc-stabilizing current in the arc-starting stage is DC, and the arc-stabilizing current in the smelting stage is AC.

[0044] Furthermore, the current regime during the three melting processes is as follows (KA / min): 4 / 1~A→(2B / 3) / 2~(2~3)→(B+0.5~1) / (3~5)→B; where A is the time it takes for the arc-starting current of 4KA to rise to 2 / 3 of the melting current in the melting stage, and its current rise rate is 1.5KA / min, and B represents the melting current in the melting stage.

[0045] Step 5: Casting the finished ingot

[0046] The three ingots obtained in step four are subjected to peeling, sampling, flaw detection, and sawing of risers to obtain the target titanium alloy ingot.

[0047] To further verify the effectiveness of the smelting method of the present invention, the inventors conducted the following specific embodiments:

[0048] Example 1

[0049] Preparation of 630mm TC4 titanium alloy (nominal composition Ti-6Al-4V) ingots

[0050] 1) Electrode preparation

[0051] Titanium sponge, aluminum-vanadium master alloy, aluminum granules, and titanium dioxide are weighed according to the mass percentage, mixed evenly, and then the electrode blocks are pressed. The pressed electrode assemblies are then welded into electrodes.

[0052] 2) One-time smelting

[0053] The electrode obtained in step 1) is used as a consumable electrode and smelted in a vacuum consumable arc furnace to obtain a primary ingot with a diameter of 500mm. During the smelting stage, the smelting current is 15.0~18.0KA, the smelting voltage is 28.0~35.0V, and the arc stabilizing current is DC 10.0~20.0A.

[0054] 3) Secondary smelting

[0055] The primary ingot obtained in step 2) is used as a consumable electrode and then remelted in a vacuum consumable arc furnace to obtain a secondary ingot with a diameter of 560mm. When loading the furnace, the electrode should be inverted, i.e., head down. During the remelting stage, the remelting current is 18.0~24.0KA, the remelting voltage is 29.0~36.0V, the arc stabilizing current is AC 10.0~20.0A, and the stirring cycle is 15~60s.

[0056] 4) Three-stage smelting

[0057] The secondary ingot obtained in step 3) was used as a consumable electrode and subjected to tertiary melting in a vacuum consumable arc furnace to obtain a 630mm tertiary ingot. The arc-starting current was set to 4.0KA, the melting current was set to 19.5KA, the melting voltage was set to 30.0~40.0V, and the arc-stabilizing current was set to AC. 15.0~25.0A, stirring cycle 15~60s; wherein, the arc stabilizing current during the arc ignition stage is DC, and the melting current regime (KA / min) from arc ignition to melting stage is: 4.0 / 1~6→13.0 / 2~2→20.5 / 5→19.5 (that is, the time taken to rise to 2 / 3 of the melting current in the melting stage is 6min. Since the current rising rate is 1.5KA / min, the total current rise in 6 minutes is 6*1.5=9. Adding the 4KA for arc ignition, the 2 / 3 of the melting current in the melting stage should be 13KA. Therefore, the melting current B in the melting stage is 19.5KA). When the melting current rises to 20.5KA, the arc stabilizing current changes from DC to AC.

[0058] 5) Finally, the bottom of the triple-layer ingot obtained in step 4) is machined by turning, with a machining allowance of approximately 5-6 mm, to completely remove metallurgical defects such as cold shuts and porosity. Simultaneously, samples are taken from the bottom, including chip samples from the core, 1 / 3R, 2 / 3R, and edges, for transverse chemical composition analysis. See the attached diagram for sampling locations. Figure 1 The results of the cross-sectional chemical composition test are shown in Table 1 below.

[0059] Table 1. Horizontal chemical composition at the bottom of the ingot

[0060]

[0061] Example 2

[0062] Preparation of 630mm TA15 titanium alloy (nominal composition Ti-6.5Al-1Mo-1V-2Zr) ingots

[0063] 1) Electrode preparation

[0064] Titanium sponge, aluminum-vanadium master alloy, aluminum-molybdenum master alloy, aluminum granules, sponge zirconium, and titanium dioxide are weighed according to the mass percentage, mixed evenly, and then the electrode blocks are pressed. The pressed electrode assemblies are then welded into electrodes.

[0065] 2) One-time smelting

[0066] The electrode obtained in step 1) is used as a consumable electrode and smelted in a vacuum consumable arc furnace to obtain a primary ingot with a diameter of 500mm. During the smelting stage, the smelting current is 15.0~18.0KA, the smelting voltage is 28.0~35.0V, and the arc stabilizing current is DC 10.0~20.0A.

[0067] 3) Secondary smelting

[0068] The primary ingot obtained in step 2) is used as a consumable electrode and then remelted in a vacuum consumable arc furnace to obtain a secondary ingot with a diameter of 560mm. When loading the furnace, the electrode should be inverted, i.e., head down. During the remelting stage, the remelting current is 18.0~24.0KA, the remelting voltage is 29.0~36.0V, the arc stabilizing current is AC 10.0~20.0A, and the stirring cycle is 15~60s.

[0069] 4) Three-stage smelting

[0070] The secondary ingot obtained in step 3) was used as a consumable electrode and smelted three times in a vacuum consumable arc furnace to obtain a 630mm tertiary ingot. The arc-starting current was set to 4.0KA, the smelting current was 22.5KA, the smelting voltage was 30.0~40.0V, the arc-stabilizing current was AC 15.0~25.0A, and the stirring cycle was 15~60s. Among them, the arc-stabilizing current in the arc-starting stage was DC, and the smelting current regime (KA / min) from arc-starting to smelting stage was: 4.0 / 1~7→15.0 / 2~3→23.0 / 4→22.5. When the smelting current rose to 23.0KA, the arc-stabilizing current was changed from DC to AC.

[0071] 5) Finally, the bottom of the triple-layer ingot obtained in step 4) is machined by turning, with a machining allowance of approximately 7-8 mm, to completely remove metallurgical defects such as cold shuts and porosity. Simultaneously, samples are taken from the bottom, including chip samples from the core, 1 / 3R, 2 / 3R, and edges, for transverse chemical composition analysis. See the attached diagram for sampling locations. Figure 1 The results of the cross-sectional chemical composition test are shown in Table 2 below.

[0072] Table 2. Horizontal chemical composition at the bottom of the ingot

[0073]

[0074]

[0075] Example 3

[0076] Prepare TC11 titanium alloy (nominal composition Ti-6.5Al-3.5Mo-1.5Zr-0.3Si) ingots with a diameter of 630mm.

[0077] 1) Electrode preparation

[0078] Titanium sponge, aluminum-molybdenum master alloy, aluminum granules, sponge zirconium, titanium-silicon alloy, and titanium dioxide are weighed according to the mass percentage, mixed evenly, and then the electrode blocks are pressed. The pressed electrode assemblies are then welded into electrodes.

[0079] 2) One-time smelting

[0080] The electrode obtained in step 1) is used as a consumable electrode and smelted in a vacuum consumable arc furnace to obtain a primary ingot with a diameter of 500mm. During the smelting stage, the smelting current is 15.0~18.0KA, the smelting voltage is 28.0~35.0V, and the arc stabilizing current is DC 10.0~20.0A.

[0081] 3) Secondary smelting

[0082] The primary ingot obtained in step 2) is used as a consumable electrode and then remelted in a vacuum consumable arc furnace to obtain a secondary ingot with a diameter of 560mm. When loading the furnace, the electrode should be inverted, i.e., head down. During the remelting stage, the remelting current is 18.0~24.0KA, the remelting voltage is 29.0~36.0V, the arc stabilizing current is AC 10.0~20.0A, and the stirring cycle is 15~60s.

[0083] 4) Three-stage smelting

[0084] The secondary ingot obtained in step 3) was used as a consumable electrode and smelted three times in a vacuum consumable arc furnace to obtain a 630mm tertiary ingot. The arc-starting current was set to 4.0KA, the smelting current was 24.0KA, the smelting voltage was 30.0~40.0V, the arc-stabilizing current was AC 15.0~25.0A, and the stirring cycle was 15~60s. The arc-stabilizing current in the arc-starting stage was DC. The smelting current regime (KA / min) from arc-starting to smelting stage was: 4.0 / 1~8→16.0 / 2~2→24.5 / 3→24.0. When the current rose to 24.5KA, the arc-stabilizing current was changed from DC to AC.

[0085] 5) Finally, the bottom of the triple-layer ingot obtained in step 4) is machined by turning, with a machining allowance of approximately 7-8 mm, to completely remove metallurgical defects such as cold shuts and porosity. Simultaneously, samples are taken from the bottom, including chip samples from the core, 1 / 3R, 2 / 3R, and edges, for transverse chemical composition analysis. See the attached diagram for sampling locations. Figure 1 The results of the cross-sectional chemical composition test are shown in Table 3 below.

[0086] Table 3. Horizontal Chemical Composition of Casting Ingots

[0087]

[0088] Example 4

[0089] Preparation of 720mm TC4 titanium alloy (nominal composition Ti-6Al-4V) ingots

[0090] 1) Electrode preparation

[0091] Titanium sponge, aluminum-vanadium master alloy, aluminum granules, and titanium dioxide are weighed according to the mass percentage, mixed evenly, and then the electrode blocks are pressed. The pressed electrode assemblies are then welded into electrodes.

[0092] 2) One-time smelting

[0093] The electrode obtained in step 1) is used as a consumable electrode and smelted in a vacuum consumable arc furnace to obtain a primary ingot with a diameter of 540mm. During the smelting stage, the smelting current is 16.0~20.0KA, the smelting voltage is 28.0~37.0V, and the arc stabilizing current is DC 10.0~20.0A.

[0094] 3) Secondary smelting

[0095] The primary ingot obtained in step 2) is used as a consumable electrode and then remelted in a vacuum consumable arc furnace to obtain a secondary ingot with a diameter of 630mm. When loading the furnace, the electrode should be inverted, i.e., head down. During the remelting stage, the remelting current is 20.0~25.0KA, the remelting voltage is 30.0~38.0V, the arc stabilizing current is AC 10.0~20.0A, and the stirring cycle is 15~60s.

[0096] 4) Three-stage smelting

[0097] The secondary ingot obtained in step 3) was used as a consumable electrode and smelted three times in a vacuum consumable arc furnace to obtain a 720mm tertiary ingot. The arc-starting current was set to 4.0KA, the smelting current in the smelting stage was 25.5KA, the smelting voltage was 30.0~40.0V, the arc-stabilizing current was AC 15.0~25.0A, and the stirring cycle was 15~60s. Among them, the arc-stabilizing current in the arc-starting stage was DC, and the smelting current regime (KA / min) from arc-starting to smelting stage was: 4.0 / 1~9→17.0 / 2~3→26.5 / 3→25.5. When the current rose to 26.5KA, the arc-stabilizing current was changed from DC to AC.

[0098] 5) Finally, the bottom of the triple-layer ingot obtained in step 4) is machined by turning, with a machining allowance of approximately 7-8 mm, to completely remove metallurgical defects such as cold shuts and porosity. Simultaneously, samples are taken from the bottom, including chip samples from the core, 1 / 3R, 2 / 3R, and edges, for transverse chemical composition analysis. See the attached diagram for sampling locations. Figure 1 The results of the cross-sectional chemical composition test are shown in Table 4 below.

[0099] Table 4. Horizontal chemical composition at the bottom of the ingot

[0100]

[0101]

[0102] Example 5

[0103] Preparation of 720mm TA15 titanium alloy (nominal composition Ti-6.5Al-1Mo-1V-2Zr) ingots

[0104] 1) Electrode preparation

[0105] Titanium sponge, aluminum-vanadium master alloy, aluminum-molybdenum master alloy, aluminum granules, sponge zirconium, and titanium dioxide are weighed according to the mass percentage, mixed evenly, and then the electrode blocks are pressed. The pressed electrode assemblies are then welded into electrodes.

[0106] 2) One-time smelting

[0107] The electrode obtained in step 1) is used as a consumable electrode and smelted in a vacuum consumable arc furnace to obtain a primary ingot with a diameter of 540mm. During the smelting stage, the smelting current is 16.0~20.0KA, the smelting voltage is 28.0~37.0V, and the arc stabilizing current is DC 10.0~20.0A.

[0108] 3) Secondary smelting

[0109] The primary ingot obtained in step 2) is used as a consumable electrode and then remelted in a vacuum consumable arc furnace to obtain a secondary ingot with a diameter of 630mm. When loading the furnace, the electrode should be inverted, i.e., head down. During the remelting stage, the remelting current is 20.0~25.0KA, the remelting voltage is 30.0~38.0V, the arc stabilizing current is AC 10.0~20.0A, and the stirring cycle is 15~60s.

[0110] 4) Three-stage smelting

[0111] The secondary ingot obtained in step 3) was used as a consumable electrode and smelted three times in a vacuum consumable arc furnace to obtain a 720mm tertiary ingot. The arc-starting current was set to 4.0KA, the smelting current in the smelting stage was 28.5KA, the smelting voltage was 30.0~40.0V, the arc-stabilizing current was AC 15.0~25.0A, and the stirring cycle was 15~60s. Among them, the arc-stabilizing current in the arc-starting stage was DC, and the smelting current regime (KA / min) from arc-starting to smelting stage was: 4.0 / 1~10→19.0 / 2~2→29.0 / 4→28.5. When the current rose to 29.0KA, the arc-stabilizing current was changed from DC to AC.

[0112] 5) Finally, the bottom of the triple-layer ingot obtained in step 4) is machined by approximately 8-10 mm to completely remove metallurgical defects such as cold shuts and porosity. Simultaneously, samples are taken from the bottom, including chip samples from the core, 1 / 3R, 2 / 3R, and edges, for transverse chemical composition analysis. See the attached diagram for sampling locations. Figure 1 The results of the cross-sectional chemical composition test are shown in Table 5 below.

[0113] Table 5. Horizontal chemical composition at the bottom of the ingot.

[0114]

[0115] In summary, based on Examples 1-5 and the corresponding data from Tables 1-5 showing the test results of the bottom composition of the ingots obtained using the smelting method of this invention, the bottom machining allowance of various titanium alloy ingots of different specifications prepared using this invention is all within 10 mm. Compared with the prior art, this significantly reduces bottom defects, decreases machining workload, and improves the yield of the ingots. At the same time, the transverse composition of the bottom of the ingots meets the requirements of GB / T3620.1 "Titanium and Titanium Alloy Grades and Chemical Compositions" and has good compositional uniformity. That is, through this smelting method, especially by adjusting the current regime during the third smelting process, the quality of the bottom of the titanium alloy ingots is significantly improved.

[0116] The above description is merely a specific embodiment of the present invention, enabling those skilled in the art to understand or implement the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention.

[0117] It should be understood that the present invention is not limited to the content already described above, and various modifications and changes can be made without departing from its scope. The scope of the present invention is limited only by the appended claims.

Claims

1. A smelting method for improving the bottom quality of titanium alloy ingots, characterized in that, The smelting method includes the following steps: Step 1: Electrode Preparation Weigh the raw materials of the target titanium alloy ingot and mix them evenly. First, press the electrode blocks, and then weld the pressed electrode assembly into an electrode. Step 2: First Melting The electrode obtained in step one is used as a consumable electrode and smelted in a vacuum consumable arc furnace to obtain a primary ingot. Step 3: Secondary smelting The primary ingot obtained in step two is used as a consumable electrode in a vacuum consumable arc furnace for secondary melting to obtain a secondary ingot. The primary ingot must be inverted when loading it into the furnace. Step 4: Three-stage smelting The secondary ingot obtained in step three is used as a consumable electrode and is smelted three times in a vacuum consumable arc furnace. In the later stage of smelting, the ingot is fed back to obtain a tertiary ingot. Step 5: Casting the finished ingot The three-stage ingots obtained in step four are subjected to peeling, sampling, flaw detection, and sawing of risers to obtain the target titanium alloy ingot. During the three melting processes in step four, the arc stabilization current is DC during the arc initiation stage and AC during the arc stabilization current during the melting stage. In step four, during the three melting processes, the arc-starting current is set to 4.0 kA, the melting current is set to 19.5–28.5 kA, the melting voltage is set to 30.0–40.0 V, the arc-stabilizing current is set to 15.0–25.0 A, and the stirring cycle is 15–60 s. In step four, during the three melting processes, the current regime during the specific melting process is as follows: 4 / 1~A→(2B / 3) / 2~(2~3)→[B+(0.5~1)KA] / (3~5)→B; Where A is the time it takes for the arc-starting current of 4KA to rise to 2 / 3 of the melting current in the melting stage, with the time unit being min and the current-rise rate being 1.5KA / min; B represents the melting current in the melting stage, with the current unit being KA. The smelting method is used to prepare titanium alloy ingots with dimensions of Φ630~Φ720mm.

2. The smelting method for improving the bottom quality of titanium alloy ingots according to claim 1, characterized in that, In step two, during the first melting stage, the melting current is set to 15.0–20.0 kA, the melting voltage is set to 28.0–37.0 V, and the arc stabilizing current is DC 10.0–20.0 A.

3. The smelting method for improving the bottom quality of titanium alloy ingots according to claim 1, characterized in that, During the secondary melting in step three, the melting current is set to 18.0–25.0 kA, the melting voltage is set to 29.0–38.0 V, the arc stabilization current is AC 10.0–20.0 A, and the stirring cycle is 15–60 s.

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