Method for improving surface quality and yield of titanium alloy cast ingot

Abstract

The invention discloses a method for improving the surface quality and yield of a titanium alloy cast ingot. The method comprises the following steps: 1, preparing, mixing, distributing and pressing according to the ratio and weight of a target product to obtain an electrode block; 2, welding the electrode block to obtain a consumable electrode; 3, welding a consumable electrode and an auxiliary electrode in a furnace, and performing primary smelting to obtain a primary ingot; fourthly, the primary ingot and an auxiliary electrode are welded in a furnace and then subjected to secondary smelting, and a secondary ingot is obtained; 5, welding the secondary ingot and an auxiliary electrode in a furnace, and then smelting for the third time to obtain a third ingot; and 6, machining the surface of the secondary ingot or the tertiary ingot to obtain the finished titanium alloy cast ingot. The liquid molten pool is quickly established by controlling the current change in the smelting arc starting period, the fluidity of the molten pool is guaranteed, the problems of pores and the like at the bottom of the titanium alloy cast ingot are solved, surface quality defects such as surface scabbing, cold shut, interlayers and pores are reduced, the scaling amount is reduced, the surface quality and the yield of the titanium alloy cast ingot are improved, and the production cost is reduced. The method is suitable for the technical field of titanium alloy ingots.

Description

Technical Field

[0001] The invention belongs to the technical field of titanium alloy ingot preparation, and in particular relates to a method for improving the surface quality and yield rate of titanium alloy ingots. Background Art

[0002] Vacuum consumable arc melting (VAR) is one of the main melting methods for titanium alloy ingots. For titanium alloy ingots, the losses in the melting process mainly include the following aspects: (1) cleaning of the weld and surrounding oxidation, volatiles, and weld nodules after electrode block assembly welding; (2) loss of flakes and deburring of semi-finished ingots during the melting process; (3) loss caused by ingot peeling. For ingots that need to be peeled, the amount of ingot peeling fluctuates in the range of 50kg to 350kg due to different ingot diameters, lengths, and surface defect depths. The positioning before peeling (determining the center of the ingot bottom or riser) also has a certain influence on the amount of peeling. Therefore, improving the surface quality of the ingot is an effective way to reduce the amount of peeling and increase the yield rate of the ingot.

[0003] In order to improve the surface quality of titanium and titanium alloy ingots, there are currently two most commonly used technologies. One is to increase the melting current or melting rate of the finished product so that the molten pool can reach the edge better; the other is to extend the duration of the arc initiation period, preheat the ingot, and bake the inner wall of the crucible, so that the molten pool can reach the edge better. The main disadvantages of these two methods are as follows: the increase in melting current or melting rate may lead to aggravated segregation of ingot components; extending the duration of the arc initiation period can improve the surface quality of the ingot to a certain extent, but because the cooling water of the VAR furnace is automatically controlled, after the ingot and crucible are preheated, the cooling water flow increases, and the molten pool established in the initial stage still cools quickly, and the effect of improving the fluidity of the molten pool is not obvious. Therefore, there are still many surface defects such as pores near the bottom of the ingot. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a method for improving the surface quality and yield rate of titanium alloy ingots in view of the deficiencies of the above-mentioned prior art. The method controls the current change during the arc starting period during the smelting process to quickly establish a liquid molten pool, thereby ensuring the fluidity of the molten pool, so that the smelting edge reaches the crucible wall, improving the problems of pores at the bottom of the titanium alloy ingot, reducing surface quality defects such as scarring, cold shut, interlayer and pores on the surface of the titanium alloy ingot, reducing the amount of peeling, greatly improving the surface quality and yield rate of the titanium alloy ingot, and solving the problem of low yield rate caused by poor surface quality of the titanium alloy ingot.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is: a method for improving the surface quality and yield rate of titanium alloy ingots, characterized in that the method comprises the following steps:

[0006] Step 1: Preparation of electrode blocks: batching, mixing, laying and pressing according to the ratio and weight of the target product titanium alloy ingot to obtain an electrode block;

[0007] Step 2: welding the electrode blocks: placing the electrode blocks obtained in step 1 in a vacuum plasma welding box for welding to obtain consumable electrodes;

[0008] Step 3, primary smelting: welding the consumable electrode and the auxiliary electrode obtained in step 2 in a furnace, and then performing a vacuum consumable arc smelting, taking out the ingot after the furnace is cooled and flattening the ingot to obtain a primary ingot;

[0009] Step 4, secondary smelting: the primary ingot obtained in step 3 is welded with the auxiliary electrode in a furnace, and then subjected to secondary vacuum consumable arc melting, and after furnace cooling, taken out and air-cooled to obtain a secondary ingot;

[0010] Step 5, tertiary smelting: the secondary ingot obtained in step 4 is welded with the auxiliary electrode in a furnace, and then subjected to three vacuum consumable arc melting, and after furnace cooling, taken out and air-cooled to obtain a tertiary ingot;

[0011] Step 6: Surface machining: The secondary ingot obtained in step 4 or the tertiary ingot obtained in step 5 is used as a finished ingot for surface machining to obtain a finished titanium alloy ingot.

[0012] Generally, with each additional melting, the impurity removal effect is improved, and the obtained titanium alloy ingot is purer, but at the same time, the ingot shape of the titanium alloy ingot will also change, resulting in poor composition uniformity. Therefore, the present invention follows the advantages and disadvantages of both, and generally adopts two or three vacuum consumable arc melting: civil titanium alloys are usually melted twice, and titanium alloys for important uses such as aerospace are usually melted three times.

[0013] The above-mentioned method for improving the surface quality and yield rate of titanium alloy ingots is characterized in that the equipment used for mixing in step one is an automatic weighing mixer, the equipment used for pressing is an electrode press, and the pressing pressure is 20MPa~120MPa, and the holding time is 5s~25s.

[0014] The above-mentioned method for improving the surface quality and yield rate of titanium alloy ingots is characterized in that the pre-welding vacuum degree of the welding in step 2 does not exceed 5Pa, the leakage rate does not exceed 1Pa / min, and the welding current is 200A to 600A.

[0015] The above-mentioned method for improving the surface quality and yield rate of titanium alloy ingots is characterized in that the processes of the primary smelting, the secondary smelting and the tertiary smelting all include: in the arc starting period, first use an arc starting current of 2kA to 8kA and maintain it for 2min to 10min, then gradually increase the arc starting current, and after the molten pool is sound, quickly increase the arc starting current to 1.2 to 1.5 times the melting current in the stable melting period and maintain it for 10min to 40min, and then reduce the current to enter the stable melting period and the shrinkage / arc closing period in turn.

[0016] The above-mentioned method for improving the surface quality and yield rate of titanium alloy ingots is characterized in that the pre-melting vacuum degree of the first smelting, the second smelting and the third smelting does not exceed 5Pa, the gas leakage rate does not exceed 0.9Pa / min, the smelting current during the stable smelting period is 10kA to 32kA, and the furnace cooling time after each smelting is completed is 200min to 600min. Different smelting currents and furnace cooling times are selected according to the diameter of the ingots of each smelting product.

[0017] The above-mentioned method for improving the surface quality and yield rate of titanium alloy ingots is characterized in that the diameters of the primary ingot, the secondary ingot and the tertiary ingot are 480 mm to 1020 mm.

[0018] The above method for improving the surface quality and yield rate of titanium alloy ingots is characterized in that the surface machining in step 6 is a peeling treatment of the ingots. The peeling treatment is usually performed using a lathe.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] 1. The vacuum consumable arc melting (VAR) process of titanium alloy ingots is divided into an arc starting period, a stable melting period and a feeding / arc closing period. Different from the conventional melting process in which the current is slowly increased and the molten pool is slowly established after arc starting, the present invention controls the current change in the arc starting period during the melting process to quickly establish a molten pool, so that the temperature inside the crucible rises rapidly, and the initial molten pool maintains a large depth, thereby ensuring the fluidity of the molten pool, so that the melting edge reaches the crucible wall, improving the problem of pores at the bottom of the titanium alloy ingot, and reducing surface quality defects such as scarring, cold shut, interlayer and pores on the surface of the titanium alloy ingot, thereby greatly improving the surface quality of the titanium alloy ingot and improving the yield rate of the titanium alloy ingot.

[0021] 2. The smelting process of the present invention ensures uniform composition of the titanium alloy ingot by precisely controlling the maximum arcing current and holding time during the arcing period to achieve rapid establishment of a liquid molten pool, thereby improving the surface quality of the titanium alloy ingot, reducing the amount of peeling, and achieving the purpose of increasing the yield rate and saving costs.

[0022] 3. The method of the present invention increases the yield rate of titanium alloy ingots by 1.0% to 1.5%, which is significantly more effective than the existing process and has significant practical value.

[0023] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of current changes in the smelting process in Example 1 of the present invention and Comparative Example 1.

[0025] Figure 2 Surface comparison diagram of titanium alloy ingots prepared in Example 1 of the present invention and Comparative Example 1.

[0026] Figure 3 It is a comparison diagram of the simulated composition distribution of the titanium alloy ingots prepared in Example 1 of the present invention and Comparative Example 1. DETAILED DESCRIPTION

[0027] Example 1

[0028] This embodiment includes the following steps:

[0029] Step 1, electrode block preparation: according to the ratio of the target product TC4 titanium alloy ingot Ti-6.0Al-4.0V, titanium sponge, aluminum vanadium alloy, and aluminum beans are selected for batching, mixing, laying and pressing to obtain electrode blocks; the equipment used for the mixing is an automatic weighing mixer, the equipment used for the pressing is an electrode press, and the pressing pressure is 26MPa, and the holding time is 10s;

[0030] Step 2, electrode block assembly welding: placing the electrode block obtained in step 1 in a vacuum plasma welding box for welding, the vacuum degree before welding does not exceed 5Pa, the gas leakage rate does not exceed 1Pa / min, the welding current is 200A-600A, and a consumable electrode is obtained;

[0031] Step 3, primary melting: The consumable electrode and the auxiliary electrode obtained in step 2 are welded in a furnace, the vacuum degree before welding does not exceed 5Pa, the welding current is 2kA-15kA, the arc stabilization current is 0-15A, and after welding in the furnace, they are placed in a crucible with a diameter of Φ640mm for primary melting. When the vacuum degree does not exceed 5Pa and the gas leakage rate does not exceed 0.9Pa / min, the arc is started. Figure 1 As shown, in the arc starting period, the arc starting current is firstly 2kA and maintained for 2min, then the arc starting current is gradually increased, and after the molten pool is sound, the arc starting current is quickly increased to 25kA and maintained for 20min, and then the current is reduced to enter the stable melting period and the feeding / arc closing period in sequence. The melting current in the stable melting period is 19kA. After the furnace is cooled for 270min, it is taken out and flattened to obtain a primary ingot with a diameter of Φ640mm.

[0032] Step 4, secondary smelting: The primary ingot obtained in step 3 is welded with the auxiliary electrode in a furnace, the vacuum degree before welding does not exceed 5Pa, the welding current is 2kA-15kA, the arc stabilization current is 0-15A, and after welding in the furnace, it is placed in a crucible with a diameter of Φ720mm for secondary smelting. When the vacuum degree does not exceed 5Pa and the leakage rate does not exceed 0.9Pa / min, the arc is started. Figure 1 As shown, in the arc starting period, the arc starting current of 2kA is first used and maintained for 2 minutes, and then the arc starting current is gradually increased. After the molten pool is sound, the arc starting current is quickly increased to 28kA and maintained for 20 minutes, and then the current is reduced to enter the stable melting period and the feeding / arc closing period in sequence. The melting current in the stable melting period is 23kA. After the furnace is cooled for 360 minutes, it is taken out and flattened to obtain a secondary ingot with a diameter of Φ720mm.

[0033] Step 5, tertiary smelting: The secondary ingot obtained in step 4 is furnace welded with the auxiliary electrode, the vacuum degree before welding does not exceed 5Pa, the welding current is 2kA-15kA, the arc stabilization current is 0-15A, and after furnace welding, it is placed in a crucible with a diameter of Φ820mm for tertiary smelting. When the vacuum degree does not exceed 5Pa and the gas leakage rate does not exceed 0.9Pa / min, the arc is started. Figure 1 As shown, in the arc starting period, the arc starting current is firstly 2kA and maintained for 2min, then the arc starting current is gradually increased, and after the molten pool is sound, the arc starting current is quickly increased to 35kA and maintained for 20min, and then the current is reduced to enter the stable melting period and the feeding / arc closing period in sequence. The melting current in the stable melting period is 27kA, and the furnace is cooled for 410min before being taken out for air cooling to obtain a tertiary ingot with a diameter of Φ820mm;

[0034] Step 6: Surface machining: The tertiary ingot obtained in step 5 is subjected to surface machining, i.e., ingot peeling, to obtain a finished TC4 titanium alloy ingot.

[0035] Comparative Example 1

[0036] The difference between this comparative example and Example 1 is that during the arc starting period of the first smelting in step 3, the second smelting in step 4, and the third smelting in step 5, an arc starting current of 2kA is first used and maintained for 2 minutes, and then gradually increased to enter a stable smelting period. Figure 1 shown.

[0037] Figure 2 The surface comparison diagram of the titanium alloy ingot prepared in Example 1 of the present invention and Comparative Example 1 is shown in FIG. Figure 2It can be seen that the surface of the titanium alloy ingot prepared in Comparative Example 1 has serious surface quality defects such as scarring, cold shut, interlayer and pores, while the surface quality defects of the titanium alloy ingot prepared in Example 1 are relatively few, indicating that the present invention greatly improves the surface quality of the titanium alloy ingot by controlling the current change in the arc starting period during the smelting process, thereby improving the yield rate of the titanium alloy ingot.

[0038] Figure 3 The simulated composition distribution comparison diagram of the titanium alloy ingots prepared in Example 1 of the present invention and Comparative Example 1 is shown in FIG. Figure 3 It can be seen that compared with Comparative Example 1, the molten pool depth in this embodiment is significantly shallower, the uniformity of the Al element at the core of the prepared titanium alloy ingot is better, and the distribution of Al and V near the riser is more uniform.

[0039] Example 2

[0040] This embodiment includes the following steps:

[0041] Step 1, electrode block preparation: according to the ratio of Ti-0.135Pd of the target product TA9 titanium alloy ingot, titanium sponge and palladium powder are selected for batching, mixing, laying and pressing to obtain electrode blocks; the equipment used for mixing is an automatic weighing mixer, the equipment used for pressing is an electrode press, and the pressing pressure is 26MPa, and the holding time is 10s;

[0042] Step 2, electrode block assembly welding: placing the electrode block obtained in step 1 in a vacuum plasma welding box for welding, the vacuum degree before welding does not exceed 5Pa, the gas leakage rate does not exceed 1Pa / min, the welding current is 200A-600A, and a consumable electrode is obtained;

[0043] Step 3, primary smelting: the consumable electrode obtained in step 2 is welded with the auxiliary electrode in a furnace, the vacuum degree before welding does not exceed 5Pa, the welding current is 2kA-15kA, the arc stabilization current is 0-15A, and after the furnace welding, it is placed in a crucible with a diameter of Φ560mm for primary smelting. In the arc starting period at the beginning of smelting, an arc starting current of 2kA is first used and maintained for 2min, and then the arc starting current is gradually increased. After the molten pool is sound, the arc starting current is quickly increased to 25kA and maintained for 20min, and then the current is reduced to enter the stable smelting period and the feeding / arc closing period in turn. The smelting current in the stable smelting period is 19kA. After the furnace is cooled for 240min, it is taken out and flattened to obtain a primary ingot with a diameter of Φ560mm;

[0044] Step 4, secondary smelting: the primary ingot obtained in step 3 is welded with the auxiliary electrode in a furnace, the vacuum degree before welding does not exceed 5Pa, the welding current is 2kA-15kA, the arc stabilization current is 0-15A, and after the furnace welding, it is placed in a crucible with a diameter of Φ640mm for secondary smelting. In the arc starting period at the beginning of smelting, an arc starting current of 2kA is first used and maintained for 2min, and then the arc starting current is gradually increased. After the molten pool is sound, the arc starting current is quickly increased to 33kA and maintained for 14min, and then the current is reduced to enter the stable melting period and the shrinkage / arc closing period in turn. The melting current in the stable melting period is 24kA. After the furnace is cooled for 320min, it is taken out and air-cooled to obtain a secondary ingot with a diameter of Φ640mm;

[0045] Step 5: Surface machining: Surface machining of the secondary ingot obtained in step 4, i.e., ingot peeling, is performed to obtain a finished TA9 titanium alloy ingot.

[0046] Example 3

[0047] This embodiment includes the following steps:

[0048] Step 1, electrode block preparation: according to the ratio of the target product TA10 titanium alloy ingot Ti-3.0Mo-0.7Ni, titanium sponge and nickel-molybdenum alloy are selected for batching, mixing, laying and pressing to obtain electrode blocks; the equipment used for the mixing is an automatic weighing mixer, the equipment used for the pressing is an electrode press, and the pressing pressure is 26MPa, and the holding time is 10s;

[0049] Step 2, electrode block assembly welding: placing the electrode block obtained in step 1 in a vacuum plasma welding box for welding, the vacuum degree before welding does not exceed 5Pa, the gas leakage rate does not exceed 1Pa / min, the welding current is 200A-600A, and a consumable electrode is obtained;

[0050] Step 3, primary smelting: the consumable electrode obtained in step 2 is welded with the auxiliary electrode in a furnace, the vacuum degree before welding does not exceed 5Pa, the welding current is 2kA-15kA, the arc stabilization current is 0-15A, and after the furnace welding, it is placed in a crucible with a diameter of Φ640mm for primary smelting. In the arc starting period at the beginning of smelting, an arc starting current of 2kA is first used and maintained for 2min, and then the arc starting current is gradually increased. After the molten pool is sound, the arc starting current is quickly increased to 25kA and maintained for 20min, and then the current is reduced to enter the stable smelting period and the shrinkage / arc closing period in turn. The smelting current in the stable smelting period is 19kA. After the furnace is cooled for 270min, it is taken out and flattened to obtain a primary ingot with a diameter of Φ640mm;

[0051] Step 4, secondary smelting: the primary ingot obtained in step 3 is furnace-welded with the auxiliary electrode, the vacuum degree before welding does not exceed 5Pa, the welding current is 2kA-15kA, the arc stabilization current is 0-15A, and after furnace welding, it is placed in a crucible with a diameter of Φ720mm for secondary smelting. In the arc starting period at the beginning of smelting, an arc starting current of 2kA is first used and maintained for 2min, and then the arc starting current is gradually increased. After the molten pool is sound, the arc starting current is quickly increased to 34kA and maintained for 24min, and then the current is reduced to enter the stable melting period and the shrinkage / arc closing period in turn. The melting current in the stable melting period is 26kA. After furnace cooling for 360min, it is taken out and air-cooled to obtain a secondary ingot with a diameter of Φ720mm;

[0052] Step 5: Surface machining: Surface machining of the secondary ingot obtained in step 4, i.e., ingot peeling, is performed to obtain a finished TA10 titanium alloy ingot.

[0053] Example 4

[0054] This embodiment includes the following steps:

[0055] Step 1, electrode block preparation: according to the ratio of the target product TC4 titanium alloy ingot Ti-6.0Al-4.0V, titanium sponge, aluminum vanadium alloy, and aluminum beans are selected for batching, mixing, laying and pressing to obtain electrode blocks; the equipment used for the mixing is an automatic weighing mixer, the equipment used for the pressing is an electrode press, and the pressing pressure is 26MPa, and the holding time is 10s;

[0056] Step 2, electrode block assembly welding: placing the electrode block obtained in step 1 in a vacuum plasma welding box for welding, the vacuum degree before welding does not exceed 5Pa, the gas leakage rate does not exceed 1Pa / min, the welding current is 200A-600A, and a consumable electrode is obtained;

[0057] Step 3, primary smelting: the consumable electrode obtained in step 2 is welded with the auxiliary electrode in a furnace, the vacuum degree before welding does not exceed 5Pa, the welding current is 2kA-15kA, the arc stabilization current is 0-15A, and after the furnace welding, it is placed in a crucible with a diameter of Φ720mm for primary smelting. In the arc starting period at the beginning of smelting, an arc starting current of 4kA is first used and maintained for 4min, and then the arc starting current is gradually increased. After the molten pool is sound, the arc starting current is quickly increased to 29kA and maintained for 20min, and then the current is reduced to enter the stable smelting period and the shrinkage / arc closing period in turn. The smelting current in the stable smelting period is 21kA. After the furnace is cooled for 400min, it is taken out and flattened to obtain a primary ingot with a diameter of Φ720mm;

[0058] Step 4, secondary smelting: the primary ingot obtained in step 3 is furnace-welded with the auxiliary electrode, the vacuum degree before welding does not exceed 5Pa, the welding current is 2kA-15kA, the arc stabilization current is 0-15A, and after furnace welding, it is placed in a crucible with a diameter of Φ820mm for secondary smelting. In the arc starting period at the beginning of smelting, an arc starting current of 4kA is first used and maintained for 4min, and then the arc starting current is gradually increased. After the molten pool is sound, the arc starting current is quickly increased to 32kA and maintained for 25min, and then the current is reduced to enter the stable melting period and the shrinkage / arc closing period in turn. The melting current in the stable melting period is 26kA. After the furnace is cooled for 410min, it is taken out and flattened to obtain a secondary ingot with a diameter of Φ820mm;

[0059] Step 5, tertiary smelting: the secondary ingot obtained in step 4 is furnace-welded with the auxiliary electrode, the vacuum degree before welding does not exceed 5Pa, the welding current is 2kA-15kA, the arc stabilization current is 0-15A, and after furnace welding, it is placed in a crucible with a diameter of Φ920mm for tertiary smelting. In the arc starting period, an arc starting current of 4kA is first used and maintained for 4min, and then the arc starting current is gradually increased. After the molten pool is sound, the arc starting current is quickly increased to 35kA and maintained for 25min, and then the current is reduced to enter the stable melting period and the shrinkage / arc closing period in turn. The melting current in the stable melting period is 29kA. After furnace cooling for 460min, it is taken out and air-cooled to obtain a tertiary ingot with a diameter of Φ920mm;

[0060] Step 6: Surface machining: The tertiary ingot obtained in step 5 is subjected to surface machining, i.e., ingot peeling, to obtain a finished TC4 titanium alloy ingot.

[0061] Example 5

[0062] This embodiment includes the following steps:

[0063] Step 1, electrode block preparation: according to the ratio of Ti-0.22Pd of the target product TA9 titanium alloy ingot, titanium sponge and palladium powder are selected for batching, mixing, laying and pressing to obtain electrode blocks; the equipment used for mixing is an automatic weighing mixer, the equipment used for pressing is an electrode press, and the pressing pressure is 20MPa, and the holding time is 25s;

[0064] Step 2, electrode block assembly welding: placing the electrode block obtained in step 1 in a vacuum plasma welding box for welding, the vacuum degree before welding does not exceed 5Pa, the gas leakage rate does not exceed 1Pa / min, the welding current is 200A-600A, and a consumable electrode is obtained;

[0065] Step 3, primary smelting: the consumable electrode obtained in step 2 is welded with the auxiliary electrode in a furnace, the vacuum degree before welding does not exceed 5Pa, the welding current is 2kA-15kA, the arc stabilization current is 0-15A, and after the furnace welding, it is placed in a crucible with a diameter of Φ480mm for primary smelting. In the arc starting period at the beginning of smelting, an arc starting current of 4kA is first used and maintained for 10min, and then the arc starting current is gradually increased. After the molten pool is sound, the arc starting current is quickly increased to 15kA and maintained for 20min, and then the current is reduced to enter the stable smelting period and the shrinkage / arc closing period in turn. The smelting current in the stable smelting period is 10kA. After the furnace is cooled for 200min, it is taken out and flattened to obtain a primary ingot with a diameter of Φ480mm;

[0066] Step 4, secondary smelting: the primary ingot obtained in step 3 is furnace-welded with the auxiliary electrode, the vacuum degree before welding does not exceed 5Pa, the welding current is 2kA-15kA, the arc stabilization current is 0-15A, and after furnace welding, it is placed in a crucible with a diameter of Φ560mm for secondary smelting. In the arc starting period at the beginning of smelting, an arc starting current of 4kA is first used and maintained for 10min, and then the arc starting current is gradually increased. After the molten pool is sound, the arc starting current is quickly increased to 30kA and maintained for 40min, and then the current is reduced to enter the stable melting period and the shrinkage / arc closing period in turn. The melting current in the stable melting period is 20kA. After furnace cooling for 300min, it is taken out and air-cooled to obtain a secondary ingot with a diameter of Φ560mm;

[0067] Step 5: Surface machining: Surface machining of the secondary ingot obtained in step 4, i.e., ingot peeling, is performed to obtain a finished TA9 titanium alloy ingot.

[0068] Example 6

[0069] This embodiment includes the following steps:

[0070] Step 1, electrode block preparation: according to the ratio of the target product TC4 titanium alloy ingot Ti-6.0Al-4.0V, titanium sponge, aluminum vanadium alloy, and aluminum beans are selected for batching, mixing, laying, and pressing to obtain an electrode block; the equipment used for the mixing is an automatic weighing mixer, the equipment used for the pressing is an electrode press, and the pressing pressure is 120MPa, and the holding time is 5s;

[0071] Step 2, electrode block assembly welding: placing the electrode block obtained in step 1 in a vacuum plasma welding box for welding, the vacuum degree before welding does not exceed 5Pa, the gas leakage rate does not exceed 1Pa / min, the welding current is 200A-600A, and a consumable electrode is obtained;

[0072] Step 3, primary smelting: the consumable electrode obtained in step 2 is welded with the auxiliary electrode in a furnace, the vacuum degree before welding does not exceed 5Pa, the welding current is 2kA-15kA, the arc stabilization current is 0-15A, and after the furnace welding, it is placed in a crucible with a diameter of Φ820mm for primary smelting. In the arc starting period at the beginning of smelting, an arc starting current of 8kA is first used and maintained for 2min, and then the arc starting current is gradually increased. After the molten pool is sound, the arc starting current is quickly increased to 32.5kA and maintained for 30min, and then the current is reduced to enter the stable smelting period and the shrinkage / arc closing period in turn. The smelting current in the stable smelting period is 27kA. After the furnace is cooled for 400min, it is taken out and flattened to obtain a primary ingot with a diameter of Φ820mm;

[0073] Step 4, secondary smelting: the primary ingot obtained in step 3 is furnace-welded with the auxiliary electrode, the vacuum degree before welding does not exceed 5Pa, the welding current is 2kA-15kA, the arc stabilization current is 0-15A, and after furnace welding, it is placed in a crucible with a diameter of Φ920mm for secondary smelting. In the arc starting period at the beginning of smelting, an arc starting current of 8kA is first used and maintained for 2min, and then the arc starting current is gradually increased. After the molten pool is sound, the arc starting current is quickly increased to 35kA and maintained for 30min, and then the current is reduced to enter the stable melting period and the shrinkage / arc closing period in turn. The melting current in the stable melting period is 29kA. After the furnace is cooled for 600min, it is taken out and flattened to obtain a secondary ingot with a diameter of Φ920mm;

[0074] Step 5, tertiary smelting: the secondary ingot obtained in step 4 is furnace-welded with the auxiliary electrode, the vacuum degree before welding does not exceed 5Pa, the welding current is 2kA-15kA, the arc stabilization current is 0-15A, and after furnace welding, it is placed in a crucible with a diameter of Φ1020mm for tertiary smelting. In the arc starting period, an arc starting current of 8kA is first used and maintained for 2min, and then the arc starting current is gradually increased. After the molten pool is sound, the arc starting current is quickly increased to 38kA and maintained for 25min, and then the current is reduced to enter the stable melting period and the feeding / arc closing period in turn. The melting current in the stable melting period is 31kA. After furnace cooling for 600min, it is taken out and air-cooled to obtain a tertiary ingot with a diameter of Φ1020mm;

[0075] Step 6: Surface machining: The tertiary ingot obtained in step 5 is subjected to surface machining, i.e., ingot peeling, to obtain a finished TC4 titanium alloy ingot.

[0076] The surface machining peeling amount of the titanium alloy ingots prepared in Examples 1 to 6 of the present invention and Comparative Example 1 was statistically compared, and the results are shown in Table 1 below.

[0077] Table 1

[0078]

[0079] It can be seen from Table 1 that compared with the titanium alloy ingot prepared by conventional smelting process in Comparative Example 1, the surface machining peeling amount of the titanium alloy ingot prepared in Examples 1 to 6 of the present invention is significantly reduced, indicating that the present invention controls the current change in the arc starting period during the smelting process to quickly establish a molten pool, so that the temperature inside the crucible rises rapidly, and the initial molten pool maintains a large depth, which ensures the fluidity of the molten pool, so that the smelting edge reaches the crucible wall, improves the problem of porosity at the bottom of the titanium alloy ingot, reduces surface quality defects such as scarring, cold shut, interlayer and porosity on the surface of the titanium alloy ingot, thereby greatly improving the surface quality of the titanium alloy ingot and improving the yield rate of the titanium alloy ingot.

[0080] The above is only a preferred embodiment of the present invention and does not limit the present invention in any way. Any simple modification, change and equivalent change made to the above embodiment according to the technical essence of the invention still falls within the protection scope of the technical solution of the present invention.

Claims

1. A method for improving the surface quality and yield rate of titanium alloy ingots, characterized in that: The method comprises the following steps: Step 1: Preparation of electrode blocks: batching, mixing, laying and pressing according to the ratio and weight of the target product titanium alloy ingot to obtain an electrode block; Step 2: welding the electrode blocks: placing the electrode blocks obtained in step 1 in a vacuum plasma welding box for welding to obtain consumable electrodes; Step 3, primary smelting: welding the consumable electrode and the auxiliary electrode obtained in step 2 in a furnace, and then performing a vacuum consumable arc smelting, taking out the ingot after the furnace is cooled and flattening the ingot to obtain a primary ingot; Step 4, secondary smelting: the primary ingot obtained in step 3 is welded with the auxiliary electrode in a furnace, and then subjected to secondary vacuum consumable arc melting, and after furnace cooling, taken out and air-cooled to obtain a secondary ingot; Step 5, tertiary smelting: the secondary ingot obtained in step 4 is welded with the auxiliary electrode in a furnace, and then subjected to three vacuum consumable arc melting, and after furnace cooling, taken out and air-cooled to obtain a tertiary ingot; Step 6: Surface machining: The secondary ingot obtained in step 4 or the tertiary ingot obtained in step 5 is used as a finished ingot for surface machining to obtain a finished titanium alloy ingot.

2. The method for improving the surface quality and yield rate of titanium alloy ingots according to claim 1, characterized in that: The equipment used for mixing in step 1 is an automatic weighing mixer, and the equipment used for pressing is an electrode press, and the pressing pressure is 20MPa to 120MPa, and the holding time is 5s to 25s.

3. The method for improving the surface quality and yield rate of titanium alloy ingots according to claim 1, characterized in that: The pre-welding vacuum degree of the welding in step 2 does not exceed 5Pa, the gas leakage rate does not exceed 1Pa / min, and the welding current is 200A to 600A.

4. The method for improving the surface quality and yield rate of titanium alloy ingots according to claim 1, characterized in that: The processes of the primary smelting, the secondary smelting and the tertiary smelting all include: in the arc starting period, first using an arc starting current of 2kA to 8kA and maintaining it for 2min to 10min, then gradually increasing the arc starting current, and after the molten pool is sound, rapidly increasing the arc starting current to 1.2 to 1.5 times the melting current in the stable melting period and maintaining it for 10min to 40min, and then reducing the current to enter the stable melting period and the supplementary / arc closing period in turn.

5. The method for improving the surface quality and yield rate of titanium alloy ingots according to claim 1, characterized in that: The vacuum degree before melting of the primary melting, the secondary melting and the tertiary melting does not exceed 5Pa, the gas leakage rate does not exceed 0.9Pa / min, the melting current during the stable melting period is 10kA-32kA, and the furnace cooling time after each melting is completed is 200min-600min.

6. The method for improving the surface quality and yield rate of titanium alloy ingots according to claim 1, characterized in that: The diameters of the primary ingot, the secondary ingot and the tertiary ingot are 480 mm to 1020 mm.

7. The method for improving the surface quality and yield rate of titanium alloy ingots according to claim 1, characterized in that: The surface machining described in step six is ​​the ingot peeling process.

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