Apparatus and method for alloy vacuum consumable arc melting with magnetic pulse grain refinement

Abstract

The application discloses an alloy vacuum self-consumption electric arc smelting magnetic pulse grain refining device, which comprises a vacuum self-consumption electric arc furnace body and a copper crucible, a metal molten pool is arranged in the copper crucible, a plurality of non-contact magnetic pulse coils are wound on the outer wall of the copper crucibble, and a water-cooling interlayer is arranged between the vacuum self-consumption electric arc furnace body and the copper crucible; a screw rod is arranged between the vacuum self-consumption electric arc furnace body and the copper crucible, and the screw rod is connected with a motor. The application further discloses a method for alloy vacuum self-consumption electric arc smelting magnetic pulse grain refining, cooling water is introduced into the water-cooling interlayer, a power supply of the vacuum self-consumption electric arc furnace is turned on for smelting, a pulse power supply is turned on when the height of the metal molten pool formed at the bottom of the copper crucible reaches 50 mm, and the plurality of non-contact magnetic pulse coils are uniformly moved upwards until the process is finished. The metal molten pool is directionally treated by electromagnetic pulse in a moving mode, the columnar crystal-equiaxed crystal transition is realized in the alloy ingot preparation process, the grain is refined, and segregation is reduced, so that the overall organization of the large-size long ingot is refined.

Description

Technical Field

[0001] This invention belongs to the technical field of alloy melting equipment, specifically relating to a device for refining magnetic pulse grains in alloy vacuum self-consuming arc melting, and also relating to a method for refining magnetic pulse grains in alloy vacuum self-consuming arc melting. Background Technology

[0002] Controlling the solidification process and solidification structure of metals has been a long-term goal pursued and strived for by metallurgists and materials scientists. Refining the solidification structure can reduce material defects and improve the mechanical properties of materials. In the process of melting titanium alloys, high-temperature alloys, and special steels in a vacuum arc furnace, in order to obtain high-quality ingots, scholars have studied various methods to improve the structure and refine the grains. At present, the methods for refining the grains of metal solidification can be divided into the following categories: (1) casting process and heat transfer condition control methods; (2) chemical treatment methods; (3) micro-area composition disturbance nucleation treatment methods; (4) mechanical and physical field treatment methods. Among them, the physical external field method can improve the kinetics and thermodynamics of the new phase in the solidification and crystallization process, increase the nucleation rate, and thus achieve fine grains.

[0003] Physical field methods include electromagnetic stirring, ultrasonic stirring, pulsed current stirring, and pulsed magnetic field stirring. Ultrasonic fields have a significant effect on grain refinement during solidification, but their drawback is severe attenuation within the melt, preventing effective and uniform refinement of the solidified structure. Furthermore, the amplitude transformer directly contacts the melt, potentially contaminating the metal. Electromagnetic stirring can reduce columnar crystal regions and increase equiaxed crystal regions, thus refining the grain size, but its effect is not very pronounced. Similar to electromagnetic stirring, pulsed current and pulsed magnetic fields can generate electromagnetic forces within the molten metal, causing stirring and vibration. The stronger electromagnetic oscillations generated by pulsed current and pulsed magnetic fields can break down dendrites, creating free heterogeneous nuclei, thereby refining the solidified structure.

[0004] To date, pulsed magnetic fields have attracted increasing attention in the field of metal solidification. Significant progress has been made in their application to grain refinement, degassing, increasing the uniformity of casting structure, and reducing shrinkage porosity. However, no research has been found at home or abroad on the introduction of pulsed magnetic field technology to refine grains during vacuum arc furnace melting. Summary of the Invention

[0005] The purpose of this invention is to provide a device for refining the grains of alloys by magnetic pulse in vacuum consumable arc melting. The device uses a moving method to directionally apply electromagnetic pulses to the molten metal pool, thereby achieving grain refinement of large-size ingots.

[0006] Another object of the present invention is to provide a method for refining the magnetic pulse grains in vacuum consumable arc melting of alloys.

[0007] The technical solution adopted in this invention is an alloy vacuum consumable arc melting magnetic pulse grain refinement device, comprising a vacuum consumable arc furnace body, a copper crucible disposed inside the furnace body, a molten metal pool disposed inside the copper crucible, and an ingot disposed inside the molten metal pool; multiple layers of non-contact magnetic pulse coils are wound around the outer wall of the copper crucible, and the multiple layers of non-contact magnetic pulse coils are located between the vacuum consumable arc furnace body and the copper crucible; the multiple layers of non-contact magnetic pulse coils are connected to a pulse power supply; a water-cooled jacket is also disposed between the vacuum consumable arc furnace body and the copper crucible; several screws are also disposed between the vacuum consumable arc furnace body and the copper crucible, the multiple layers of non-contact magnetic pulse coils are fixed on the screws, and the screws are driven by a gear to a motor; the motor is electrically connected to a PLC controller.

[0008] The invention is further characterized in that,

[0009] It also includes a consumable electrode and a vacuum consumable arc melting auxiliary electrode, which are connected by in-furnace butt welding; the vacuum consumable arc melting auxiliary electrode and the vacuum consumable arc furnace body are also connected to the vacuum consumable arc furnace power supply.

[0010] The vacuum self-consuming electric arc furnace has a water inlet at the bottom and a water outlet on the side of the furnace body; cooling water is introduced into the water-cooled jacket through the water inlet and discharged through the water outlet.

[0011] The number of turns in a multilayer non-contact magnetic pulse coil ranges from 1 to 500, and the number of layers ranges from 1 to 15.

[0012] Another technical solution adopted in this invention is a method for refining the grain size of alloy vacuum consumable arc melting magnetic pulse, which is implemented according to the following steps:

[0013] Step 1: Circulate cooling water at 15℃-40℃ into the water-cooled jacket, then turn on the power supply of the vacuum arc furnace to perform vacuum arc welding and melting.

[0014] Step 2: After the arc is started during melting, once the height of the molten metal pool at the bottom of the copper crucible reaches 50mm, the pulse power supply is turned on to start melting. The motor is controlled by the PLC controller to move the multi-layer non-contact magnetic pulse coils evenly upward until the melting is finished. During the melting and feeding stage, the intensity of the pulse magnetic field is increased and maintained until the melting is finished.

[0015] The beneficial effects of this invention are:

[0016] 1. By using a moving method to directionally apply electromagnetic pulse treatment to the molten metal pool, the transformation of columnar crystals to equiaxed crystals and the refinement of grains and reduction of segregation during the alloy ingot preparation process can be achieved, which is beneficial to the overall microstructure refinement of large-sized long ingots;

[0017] 2. A stepped electromagnetic pulse treatment is adopted for the normal melting and feeding periods of vacuum self-consumable melting of titanium alloys, high-temperature alloys, and special steels. Furthermore, due to the use of moving directional area following treatment, it can achieve grain refinement at the head of large-size ingots, improve compositional uniformity, remove porosity and inclusions, thereby improving ingot quality and enhancing the quality of the final alloy bars and forgings.

[0018] 3. The device of this invention is inexpensive, simple and safe to operate, easy to assemble and disassemble, and can be adapted to different ingot specifications. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the structure of the device for refining the magnetic pulse grains of alloy vacuum self-consuming arc melting according to the present invention;

[0020] Figure 2 This is a schematic diagram of a solenoid pulse coil.

[0021] Figure 3 This is a low-magnification longitudinal section microstructure of a TC17 alloy ingot without magnetic pulse application;

[0022] Figure 4 This is a low-magnification longitudinal section microstructure of a TC17 alloy ingot subjected to magnetic pulse.

[0023] In the figure: 1. Vacuum consumable arc furnace auxiliary electrode; 2. Consumable electrode; 3. Vacuum consumable arc furnace body; 4. Copper crucible; 5. Pulse power supply; 6. Vacuum consumable arc furnace power supply; 7. Molten metal pool; 8. Multilayer non-contact magnetic pulse coil; 9. Screw; 10. Ingot; 11. Water-cooled jacket; 12. Motor; 13. PLC controller. Detailed Implementation

[0024] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0025] Example 1

[0026] The present invention relates to a device for refining the grain size of alloys through vacuum consumable arc melting and magnetic pulse, such as... Figure 1 As shown, the furnace includes a vacuum self-consuming electric arc furnace body 3, inside which is a copper crucible 4, within which is a molten metal pool 7, and within the molten metal pool 7 is an ingot 10; the outer wall of the copper crucible 4 is wound with multiple layers of non-contact magnetic pulse coils 8, such as... Figure 2As shown, the multi-layer non-contact magnetic pulse coil 8 is located between the vacuum self-consuming arc furnace body 3 and the copper crucible 4; the multi-layer non-contact magnetic pulse coil 8 is connected to the pulse power supply 5 through a flexible wire; it also includes a self-consuming electrode 2 and a vacuum self-consuming arc melting auxiliary electrode 1, which are connected by in-furnace butt welding; the vacuum self-consuming arc melting auxiliary electrode 1 and the vacuum self-consuming arc furnace body 3 are also connected to the vacuum self-consuming arc furnace power supply 6;

[0027] A water-cooled jacket 11 is provided between the vacuum self-consuming electric arc furnace body 3 and the copper crucible 4; a water inlet is provided at the bottom of the vacuum self-consuming electric arc furnace body 3 and a water outlet is provided on the side of the vacuum self-consuming electric arc furnace body 3; cooling water is introduced into the water-cooled jacket 11 through the water inlet and discharged through the water outlet.

[0028] Several screws 9 are also provided between the vacuum self-consuming electric arc furnace body 3 and the copper crucible 4. Multi-layer non-contact magnetic pulse coils 8 are fixed on the screws 9. The screws 9 and the motor 12 are driven by gears. The motor 12 is electrically connected to the PLC controller 13.

[0029] The speed and position of the multi-layer non-contact magnetic pulse coil 8 are controlled by the combined signal of the weight of the self-consuming electrode and the melting weight and the moving speed of the self-consuming electrode during the self-consuming arc melting process, so as to ensure that the pulse magnetic field always acts on the metal pool area; the entire multi-layer non-contact magnetic pulse coil 8 is placed in the cooling water jacket to ensure the cooling effect when the instantaneous strong pulse magnetic field occurs.

[0030] The number of turns of the multilayer non-contact magnetic pulse coil 8 is 1 to 500, and the number of layers is 1 to 15; the diameter of the copper crucible 4 ranges from Φ180mm to Φ1050mm, and the length is 50 to 4000mm; the current waveform of the input frustum-shaped coil of the pulse power supply 5 is pulsed AC current, pulsed square wave, and pulsed triangular wave, with an output current I = 0.4kA to 25kA, a pulse width of 0.01 to 600ms, and an actual operating frequency f = 0.5 to 6000Hz.

[0031] When using magnetic pulses for grain refinement: The innovation of the device for treating molten metal with instantaneous strong pulse magnetic field is that it introduces a larger electromagnetic force oscillation generated by the pulse magnetic field into the vacuum self-consuming electric arc furnace. The introduction method is that the pulse magnetic coil moves upward as the liquid level of the ingot metal pool 7 rises, that is, it is directionally introduced on the side of the crucible of the vacuum self-consuming electric arc furnace.

[0032] The device for refining grains in vacuum consumable arc melting of alloys using magnetic pulses, as described in this invention, operates on the following principle: During the vacuum consumable arc melting process of alloys such as titanium alloys, high-temperature alloys, and special steels, a momentary strong pulsed magnetic field is applied to the outside of a copper crucible corresponding to the high-temperature molten metal pool region. A multi-layer non-contact magnetic pulse coil moves upwards as the molten metal pool level rises. The upward movement speed of the pulse coil is comprehensively controlled by the combined melting weight of the consumable electrode and its moving speed during the consumable arc melting process. The speed and position of the multi-layer non-contact magnetic pulse coil are controlled by the combined signal of the melting weight of the consumable electrode and its moving speed during the consumable arc melting process, ensuring that the pulsed magnetic field always acts on the molten metal pool region. The entire multi-layer non-contact magnetic pulse coil is placed in a cooling water jacket to ensure effective cooling when the momentary strong pulsed magnetic field occurs.

[0033] Example 2

[0034] The method for refining magnetic pulse grains in vacuum consumable arc melting of alloys according to the present invention is implemented according to the following steps:

[0035] Step 1: Circulate cooling water into the water-cooled jacket 11, then turn on the vacuum arc furnace power supply 6 to perform vacuum arc welding and melting; before melting begins, circulate cooling water at a temperature of 15℃-40℃ is introduced until melting ends; during vacuum arc melting, the pre-vacuum is controlled below 5.5Pa, the current is controlled between 5-40KA, and the voltage is controlled between 15-45V.

[0036] Step 2: After the arc is ignited during melting, once the molten pool at the bottom of the copper crucible reaches a height of 50mm, turn on the pulse power supply 5. Different pulse parameters are used for melting according to different alloy types and properties. The output current of the pulse power supply 5 is 0.4kA to 25kA, the pulse width is 0.01 to 600ms, and the actual operating frequency is f = 0.5 to 6000Hz. The operation of the motor 12 is controlled by the PLC controller, which controls the multilayer non-contact magnetic pulse coil 8 to move upwards uniformly until the melting is completed. During the melting and feeding stage, the intensity of the pulse magnetic field is appropriately increased and maintained until the melting is completed.

[0037] The instantaneous high-energy electromagnetic force of the magnetic pulse generates electromagnetic oscillations and electromagnetic convection effects at the solid-liquid interface front in the molten pool 7 of the alloy remelting ingot. This intensely scours the columnar crystals, causing weak dendrites at the roots of secondary or tertiary dendrite arms to break and fragment. These fragmented dendrites are freed under electromagnetic convection, thereby increasing the nucleation rate. Simultaneously, the electromagnetic convection and Joule heating effect caused by the magnetic pulse reduce the temperature gradient of the melt within the liquid cavity, allowing these freed dendrite fragments to survive and become new crystal nuclei, increasing the number of grains and refining the solidification structure of the ingot.

[0038] Example 3

[0039] The method for refining magnetic pulse grains in vacuum consumable arc melting of alloys according to the present invention is implemented according to the following steps:

[0040] Step 1: Hoist the crucible with a diameter of Φ440mm and a length of 2200mm into the crucible water jacket, and circulate cooling water into the water-cooled jacket 11. Then turn on the vacuum consumable arc furnace power supply 6 to perform TC17 titanium alloy vacuum consumable electrode welding and melting. Before melting begins, circulate cooling water at a temperature of 25℃ is introduced until melting is completed. During the TC17 titanium alloy vacuum consumable arc melting process, the pre-vacuum is controlled below 5.5Pa, the current is controlled at 15-20KA, and the voltage is controlled at 28±0.5V. The multilayer non-contact magnetic pulse coil 8 has 200 turns and 3 layers.

[0041] Step 2: After arc initiation during melting, once the height of the TC17 alloy molten pool at the bottom of the copper crucible reaches 50mm, the pulse power supply 5 is turned on. During the arc initiation phase, the output current of the pulse power supply 5 is 10kA, the pulse width is 100ms, and the actual operating frequency is f=1000Hz. During the stable melting phase, the output current of the pulse power supply 5 is 15kA, the pulse width is 150ms, and the actual operating frequency is f=1200Hz. During the ingot melting and feeding phase, the output current of the pulse power supply 5 is 17kA, the pulse width is 180ms, and the actual operating frequency is f=1500Hz. The operation of the motor 12 is controlled by the PLC controller 13, which controls the multi-layer non-contact magnetic pulse coil 8 to move uniformly upward until the melting is completed. During the melting and feeding phase, the intensity of the pulse magnetic field is appropriately increased and maintained until the melting is completed. Finally, the ingot is longitudinally sectioned and its microstructure is observed at low magnification.

[0042] Under the same vacuum arc remelting process parameters, TC17 alloy, such as Figure 3 As shown, the low-magnification microstructure of a longitudinally sectioned ingot without magnetic pulse application shows an equiaxed crystal region area of ​​10%; Figure 4 As shown, the low-magnification microstructure of the ingot after longitudinal sectioning by applying magnetic pulses shows that the area of ​​the equiaxed crystal region is 29.5%.

[0043] This invention uses a moving method to directionally apply electromagnetic pulses to the molten metal pool, thereby achieving the transformation of columnar crystals to equiaxed crystals and refining grains, reducing segregation, and removing porosity and inclusions during the alloy ingot preparation process. This improves the quality of the ingot and enhances the quality of the final alloy bars and forgings.

Claims

1. A device for refining grains in alloy vacuum consumable arc melting using magnetic pulses, characterized in that, The system includes a vacuum self-consuming electric arc furnace body (3), inside which is a copper crucible (4), inside which is a molten metal pool (7), and inside which is an ingot (10); the outer wall of the copper crucible (4) is wound with multi-layer non-contact magnetic pulse coils (8), which are located between the vacuum self-consuming electric arc furnace body (3) and the copper crucible (4); the multi-layer non-contact magnetic pulse coils (8) are connected to a pulse power supply (5); a water-cooled jacket (11) is also provided between the vacuum self-consuming electric arc furnace body (3) and the copper crucible (4); several screws (9) are also provided between the vacuum self-consuming electric arc furnace body (3) and the copper crucible (4), the multi-layer non-contact magnetic pulse coils (8) are fixed on the screws (9), and the screws (9) are gear-driven to a motor (12); the motor (12) is electrically connected to a PLC controller (13). It also includes a consumable electrode (2) and a vacuum consumable arc melting auxiliary electrode (1), wherein the consumable electrode (2) and the vacuum consumable arc melting auxiliary electrode (1) are connected by in-furnace butt welding; the vacuum consumable arc melting auxiliary electrode (1) and the vacuum consumable arc furnace body (3) are also connected to the vacuum consumable arc furnace power supply (6). The number of turns of the multilayer non-contact magnetic pulse coil (8) is 1 to 500, and the number of layers is 1 to 15.

2. The apparatus for alloy vacuum consumable arc melting and magnetic pulse grain refinement as described in claim 1, characterized in that, The vacuum self-consuming electric arc furnace body (3) is provided with a water inlet at the bottom and a water outlet on the side of the vacuum self-consuming electric arc furnace body (3); cooling water is introduced into the water-cooled jacket (11) through the water inlet and discharged through the water outlet.

3. A method for refining grains in alloy vacuum self-consuming arc melting using magnetic pulses, comprising the apparatus for refining grains in alloy vacuum self-consuming arc melting using magnetic pulses as described in claim 1, characterized in that... The specific steps are as follows: Step 1: Circulating cooling water at 15℃-40℃ is introduced into the water-cooled jacket (11), and then the vacuum self-consuming arc furnace power supply (6) is turned on to carry out vacuum self-consuming arc welding and melting. During the vacuum self-consuming arc melting process, the pre-vacuum is controlled below 5.5 Pa, the current is controlled between 5-40 kA, and the voltage is controlled between 15-45 V. Step 2: After the arc is started during melting, once the height of the metal pool (7) formed at the bottom of the copper crucible (4) reaches 50mm, turn on the pulse power supply (5) to melt. Control the operation of the motor (12) through the PLC controller (13) to control the multi-layer non-contact magnetic pulse coil (8) to move upward evenly until the melting is finished. After increasing the intensity of the pulse magnetic field during the melting and feeding stage, maintain it until the melting is finished. The output current of the pulse power supply (5) is 0.4kA to 25kA, the pulse width is 0.01 to 600ms, and the actual operating frequency f is 0.5 to 6000Hz.

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