A smelting process for producing titanium-aluminum base alloy ingot

Abstract

This invention belongs to the field of titanium alloy smelting, specifically a smelting process for producing titanium-aluminum based alloy ingots. It solves the technical problem that the production of large-sized titanium-aluminum based alloy ingots is difficult due to easy compositional segregation and a high tendency to crack. This invention uses a vacuum consumable electrode solidification furnace equipped with a dedicated electromagnetic cold crystallizer for smelting. The crystallizer uses a graphite crucible, and a sleeve with the same inner cavity size as the graphite crucible is welded from a 2mm thick pure titanium plate and placed inside the graphite crucible. Before smelting, the graphite crucible and sleeve are baked to remove moisture. After the alloy liquid is poured into the sleeve of the crystallizer crucible, the cooling rate of the alloy ingot is controlled by adjusting the crystallizer current parameters. The solidification furnace smelting process parameters are: arc voltage: 30V, arc current: 10KA. This invention solves the problems of initial ingot spalling and compositional segregation in titanium-aluminum based alloys by controlling the smelting process parameters.

Description

Technical Field

[0001] This invention belongs to the field of titanium alloy smelting, specifically a smelting process for producing titanium-aluminum based alloy ingots. Background Technology

[0002] Titanium-aluminum based alloys possess excellent properties such as low density, high specific strength, strong corrosion resistance, resistance to high and low temperatures, good sound transmission, non-magnetic properties, cold / hot formability, and good weldability. They exhibit particularly excellent corrosion resistance in seawater and acidic media, making them one of the most promising metallic materials. However, titanium-aluminum based alloys are lightweight and difficult-to-deform structural materials. The bottleneck restricting their widespread engineering applications lies in overcoming their inherent brittleness, high deformation resistance, and the lack of effective processing and forming technologies.

[0003] Casting large-sized, crack-free titanium-aluminum alloy ingots is fundamental to the application of titanium-aluminum alloys. Currently, domestic titanium-aluminum alloy ingot production is limited to ingots with a diameter ≤ φ200 and a weight ≤ 100 kg. When producing large-sized titanium-aluminum alloy ingots with a diameter φ300 and a weight 300 kg, the initial ingot material crumbles during the smelting process, making it impossible to control the solidification rate. This results in ingots with coarse dendritic grains, significant porosity and compositional segregation, and the inability to eliminate crack defects. Summary of the Invention

[0004] The technical problem to be solved by this invention is as follows:

[0005] The problem of being unable to control the solidification rate when producing titanium-aluminum based alloy ingots;

[0006] Solve the technical problems of coarse grains, compositional segregation, and crack defects in titanium-aluminum based alloy ingots;

[0007] Solve the problem of lumps falling off titanium-aluminum based alloy ingots during the smelting process;

[0008] Solve the reaction problem between titanium-aluminum based alloy ingots and graphite crucibles.

[0009] The present invention is achieved by the following technical solution: a smelting process for producing titanium-aluminum based alloy ingots, which uses a vacuum consumable electrode solidification furnace equipped with a special electromagnetic cold crucible crystallizer for smelting. The electromagnetic cold crucible crystallizer is located inside the vacuum consumable electrode solidification furnace and includes a graphite crucible, a water-cooling pipe set on the outer wall of the graphite crucible, a spiral induction coil set on the outside of the water-cooling pipe, and a sleeve made of pure titanium plate welded inside the graphite crucible with the same size as the inner cavity of the graphite crucible. A copper crucible that can be automatically flipped is set above the graphite crucible. The special equipment also includes an electrode rod set above the copper crucible and raised and lowered by pneumatic control. The copper crucible and the electrode rod are equipped with a smelting power supply, and the electromagnetic cold crucible crystallizer is equipped with a heat preservation power supply. The method includes the following steps: (1) using pure titanium welding wire, the titanium-aluminum based alloy ingot is welded to the lower end of the auxiliary electrode by multi-layer multi-pass manual argon arc welding; the titanium-aluminum based alloy ingot is connected to the electrode rod through the auxiliary electrode.

[0010] (2) Before melting, the graphite crucible and sleeve of the electromagnetic cold crystallizer are baked. The baking process is as follows: On the first day, the power is 20, 40 and 60KW respectively, and the baking time is 2 hours for each day; on the second day, the baking power is 40, 60 and 80KW respectively, and the baking time is 2 hours for each day; on the third day, the baking power is 60, 80 and 100KW respectively, and the baking time is 2 hours for each day.

[0011] (3) Pre-melting inspection and confirmation: The vacuum degree of the special equipment is within 1×10 -1 When the above conditions are met, smelting can proceed;

[0012] (4) Smelting process

[0013] In the initial stage, adjust the arc-stabilizing voltage of the melting power supply to 2.0V, then control the electrode rod to move downwards so that the titanium-aluminum based alloy ingot contacts the copper crucible. Slowly adjust the arc voltage of the melting power supply to 70±5V and the arc current to 3.2KA, waiting for an arc ignition reaction in the copper crucible. After arc ignition, adjust the current back to zero until the electrode rod is stationary. After a molten pool forms in the copper crucible, start adjusting the melting rate. At this time, increase the melting current. After reaching the normal melting state, the current reaches 10±0.2KA. Monitor the change in melting voltage and control it at 30±3V. At the same time, adjust the downward speed of the electrode rod to maintain a stable melting voltage. When the amount of titanium liquid required by the process is reached, the melting is ended.

[0014] (5) Cut off the smelting power supply, control the electrode rod to lift it quickly pneumatically, and then control the copper crucible to flip over and pour the titanium liquid into the graphite crucible with a sleeve below.

[0015] (6) After the vacuum is continuously pumped and the casting is completed, the electromagnetic cold crucible crystallizer is immediately powered on. The heat preservation process is as follows: the heat preservation power is 120, 100, 80, 60 and 40KW respectively, and the heat preservation time is 2 hours for each power. After that, take out the large-size titanium-aluminum based alloy ingot with a diameter greater than or equal to 300mm and a weight of not less than 300kg.

[0016] In step (2), the graphite crucible and the outer casing are baked in a solidification furnace before melting to effectively remove moisture. In step (4), the titanium-aluminum based alloy ingots that have been melted in the first melting are melted under vacuum. During the process, the alloy ingot itself acts as the upper electrode (negative electrode). Under the action of the current power supply, it generates an electric arc with the lower electrode (positive electrode) placed in the crucible. The high temperature of the electric arc melts the upper electrode itself and forms liquid metal in the crucible.

[0017] In step (6), after the alloy liquid is poured into the graphite crucible with a sleeve in the crystallizer, the cooling rate of the alloy ingot is controlled by adjusting the current parameters of the crystallizer.

[0018] This invention solves the problems of shavings and compositional segregation in titanium-aluminum based alloy ingots by controlling the smelting process parameters, and at the same time obtains titanium-aluminum based alloy ingots with a diameter of not less than 300 mm.

[0019] The beneficial effects of this invention are as follows: This invention uses a vacuum consumable electrode solidification furnace equipped with an electromagnetic cold crystallizer to melt titanium-aluminum based alloy ingots. By adopting a reasonable melting process, it ensures that the titanium-aluminum based alloy ingots do not fall off during the melting process. This solves the primary technical problem of the difficulty in controlling the cooling rate during the solidification process of large-sized titanium-aluminum based alloy ingots. The produced titanium-aluminum based alloy ingots are free of cracks and have uniform composition.

[0020] The biggest problem in producing large-size, crack-free titanium-aluminum-based alloy ingots is the presence of cracks and significant compositional segregation. This invention solves this problem by utilizing specially designed and manufactured casting equipment and employing a rational smelting process. The successful trial of large-size, crack-free titanium-aluminum-based alloy ingots lays the foundation for the development of titanium-aluminum-based alloys. Attached Figure Description

[0021] Figure 1 A schematic diagram of the special smelting and solidification equipment described in this invention.

[0022] 1-Vacuum consumable electrode solidification furnace, 2-Electromagnetic cold crucible crystallizer, 3-Graphite crucible and sleeve, 4-Copper crucible, 5-Electrode rod, 6-Titanium alloy ingot. Detailed Implementation

[0023] The production of large-sized titanium-aluminum alloy ingots is technically challenging due to the tendency for compositional segregation and cracking.

[0024] The titanium-aluminum based alloy ingot preparation process of the present invention involves melting and casting in a special equipment (the main structure of which is described in Chinese Patent 201620948655.6) with an electromagnetic cold crucible crystallizer installed on a vacuum consumable solidification furnace. By controlling the casting process and cooling rate of the ingot, high-quality titanium-aluminum based alloy ingots with less segregation, no cracks and fine grains are obtained.

[0025] Specific embodiments of the present invention:

[0026] 1. The specialized smelting and solidification equipment consists of two parts: a vacuum consumable electrode solidification furnace and an electromagnetic cold crucible crystallizer (see attached). Figure 1 The power system on the left side of the diagram serves as the heat preservation power source for the induction coil of the electromagnetic cold crucible crystallizer, while the water cooling system acts as the circulation system for the water cooling pipes of the electromagnetic cold crucible crystallizer. The vacuum system on the right side of the diagram is used to evacuate the furnace body, the pneumatic system controls the raising and lowering of the electrode rods, the water cooling system controls the operation of the circulation system, and the power system controls the main switch of the furnace body and serves as the smelting power source for the copper crucible and electrodes.

[0027] 2. Using pure titanium welding wire, the auxiliary electrode is welded to the titanium-aluminum alloy ingot using multi-layer, multi-pass manual argon arc welding, with the lower end of the electrode rod clamping the auxiliary electrode.

[0028] 3. Before melting, the graphite crucible and sleeve of the electromagnetic cold crystallizer are baked. The baking process is shown in Table 1:

[0029]

[0030] 4. Pre-melting checks and confirmations: Air source (compressed air pressure): ≥0.8MPa. Water source inlet pressure: 0.3~0.4MPa.

[0031] The return water flow rate for the graphite crucible needs to reach 25–28 m³ / h. 3 / h.

[0032] The vacuum level of the specialized equipment is 1×10 -1 When the above conditions are met, smelting can proceed.

[0033] 5. Smelting process

[0034] a. Turn on the power distribution cabinet, switch the green button on the screen to remote control and turn on the power, turn on the pure water filter, and click on the "Process Monitoring" interface in the software to start smelting.

[0035] b. Confirm that the "current adjustment" and "melting rate adjustment" potentiometers are at zero.

[0036] c. Press the "Close" and "Unblock" buttons, then press the "Servo Switch" button. Adjust the "Arc Stabilizing Voltage" to 2.0.

[0037] d. Slowly rotate the "Arc Voltage" clockwise to approximately 70V, and the "Arc Current" to 3.2KA. Wait for an arc ignition reaction to occur in the crucible. After arc ignition, the "Manual Adjustment" potentiometer should be returned to zero to the stationary position of the electrode rod. Only after a molten pool has formed can the melting rate be adjusted. Adjust the "Current Adjustment" potentiometer to increase the melting current until normal melting conditions are achieved (10KA). Monitor the melting voltage (maintaining it around 30V), and use the "Melting Rate Adjustment" potentiometer and manual adjustment to regulate the electrode rod's descent speed to maintain a stable melting voltage. When the required amount of molten titanium is reached, end the melting process.

[0038] 6. Pouring

[0039] a. Press the "Hydraulic Motor" button, then press the "Automatic Casting" button. This will cut off the smelting power supply and simultaneously initiate the automatic casting process. At this moment, the electrode rod will be rapidly pneumatically lifted. After reaching the desired position, the copper crucible will flip and remain in that position for 5 seconds before resetting. Once back in position, the electrode rod will automatically pneumatically descend, restoring the crucible to its original state. The automatic casting process is now complete.

[0040] b. Turn off the "Automatic Pouring" button, turn off the "Hydraulic Motor" button, and manually operate all actuators. Open the circuit breaker, release the circuit breaker, and turn off the power to the downstream machine room.

[0041] 7. Ingot insulation

[0042] The vacuum process continues until casting is complete, at which point power is immediately supplied to the crystallizer. The insulation process is shown in Table 2.

[0043]

[0044] After the ingot insulation operation is completed, the power is cut off and the vacuuming is stopped.

[0045] Eight hours later, the vent valve was opened, and the furnace was filled with atmospheric air.

[0046] 8. Take the ingot.

[0047] The innovative aspects of this invention:

[0048] (1) A melting process for the ingot was designed to ensure that the titanium-aluminum alloy ingot does not fall off during the melting process and that the titanium ingot has a uniform composition after refining (see the test report in the table below).

[0049] (2) The heat preservation process parameters of the ingot solidification process were designed, and the technical problem of ingot cracking during the solidification process of large-size (300mm diameter) aluminum-based alloy ingots was solved.

[0050] (3) A pure titanium protective sleeve was designed to solve the reaction problem between titanium-aluminum based alloy and graphite crucible.

[0051] 。

Claims

1. A smelting process for producing titanium-aluminum based alloy ingots, characterized in that, The melting process employs a vacuum consumable electrode solidification furnace equipped with a specialized electromagnetic cold crucible crystallizer. The electromagnetic cold crucible crystallizer, located within the vacuum consumable electrode solidification furnace, includes a graphite crucible, a water-cooling pipe mounted on the outer wall of the graphite crucible, a spiral induction coil mounted outside the water-cooling pipe, and a sleeve made of pure titanium plate welded to the inside of the graphite crucible, with dimensions matching the inner cavity of the graphite crucible. Above the graphite crucible is a copper crucible capable of automatic rotation. The specialized equipment also includes a pneumatically controlled electrode rod positioned above the copper crucible. The copper crucible and electrode rod are equipped with a melting power source, and the electromagnetic cold crucible crystallizer is equipped with a heat-preservation power source. The method includes the following steps: (1) Using pure titanium welding wire, the titanium-aluminum based alloy ingot is welded to the lower end of the auxiliary electrode by multi-layer and multi-pass manual argon arc welding; the titanium-aluminum based alloy ingot is connected to the electrode rod through the auxiliary electrode. (2) Before melting, the graphite crucible and sleeve of the electromagnetic cold crystallizer are baked. The baking process is as follows: On the first day, the power is 20, 40 and 60KW respectively, and the baking time is 2 hours for each day; on the second day, the baking power is 40, 60 and 80KW respectively, and the baking time is 2 hours for each day; on the third day, the baking power is 60, 80 and 100KW respectively, and the baking time is 2 hours for each day. (3) Pre-melting inspection and confirmation: The vacuum degree of the special equipment is within 1×10 -1 When the above conditions are met, smelting can proceed; (4) Smelting process In the initial stage, adjust the arc-stabilizing voltage of the melting power supply to 2.0V, then control the electrode rod to move downwards so that the titanium-aluminum based alloy ingot contacts the copper crucible. Slowly adjust the arc voltage of the melting power supply to 70±5V and the arc current to 3.2KA, waiting for an arc ignition reaction in the copper crucible. After arc ignition, adjust the current back to zero until the electrode rod is stationary. After a molten pool forms in the copper crucible, start adjusting the melting rate. At this time, increase the melting current. After reaching the normal melting state, the current reaches 10±0.2KA. Monitor the change in melting voltage and control it at 30±3V. At the same time, adjust the downward speed of the electrode rod to maintain a stable melting voltage. When the amount of titanium liquid required by the process is reached, the melting is ended. (5) Cut off the smelting power supply, control the electrode rod to lift it quickly pneumatically, and then control the copper crucible to flip over and pour the titanium liquid into the graphite crucible with a sleeve below. (6) After the vacuum is continuously pumped and the casting is completed, the electromagnetic cold crucible crystallizer is immediately powered on. The heat preservation process is as follows: the heat preservation power is 120, 100, 80, 60 and 40KW respectively, and the heat preservation time is 2 hours for each power. After that, take out the large-size titanium-aluminum based alloy ingot with a diameter greater than or equal to 300mm and a weight of not less than 300kg.

2. The smelting process for producing titanium-aluminum based alloy ingots as described in claim 1, characterized in that, In step (3), the gas source pressure is ≥0.8 MPa, the water source inlet pressure is 0.3–0.4 MPa, and the return water flow rate of the graphite crucible needs to reach 25–28 m³ / h. 3 / h.

3. The smelting process for producing titanium-aluminum based alloy ingots as described in claim 1 or 2, characterized in that, Copper crucible dimensions: φ450mm×600 mm, crucible turning speed: 100° / 3s; graphite crucible capacity: ≥φ300mm×800 mm.

4. A smelting process for producing titanium-aluminum based alloy ingots as described in claim 1 or 2, characterized in that, The sleeve is made of 2mm thick pure titanium plate.

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