Titanium alloy electric arc additive interlayer cooling system and control method thereof

Abstract

The invention relates to a titanium alloy electric arc additive interlayer cooling system and a control method thereof. The cooling system comprises a low-temperature argon preparation system, a cold air spraying system, an infrared thermometer and a control system. The control system is respectively connected with the low-temperature argon preparation system, the cold air spraying system and the infrared thermometer through data lines; according to the method, by controlling the reasonable cooling speed, the situation that a large number of alpha'phase and beta columnar crystals are generated due to too high and too low cooling speed is avoided; the interlayer temperature is controlled, so that the thermal cycle transferred from a newly deposited layer to a previous layer is lower than the process from alpha to beta of titanium alloy, the growth of columnar crystals between cladding layers is blocked, the formation of coarse columnar crystal beta grains is controlled, and the structure property of a formed part is improved. Meanwhile, the retention time between the deposition layers is shortened, and the manufacturing efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of arc additive manufacturing, and relates to a titanium alloy arc additive interlayer cooling system and a control method thereof, and in particular to a titanium alloy arc additive interlayer cooling system and a control method thereof in a fully enclosed argon-rich environment. Background Art

[0002] The organization and performance of arc additive manufacturing materials are closely related to the interlayer temperature and cooling rate. In addition, the complex thermal cycle between the deposited layers leads to a high heat accumulation during the forming process. Titanium alloys are very sensitive to thermal history. As the forming height increases, the heat dissipation effect of the matrix weakens, and the heat dissipation conditions also change. The thermal experience of each weld layer is different. The different forming temperatures and cooling rates at different positions of the formed parts make the formed parts anisotropic in terms of macro / microstructure and mechanical properties. Since the welds of titanium alloys are very easy to absorb hydrogen and oxygen during the arc additive process, titanium alloy arc additive needs to be operated in a fully enclosed and argon-rich environment to ensure the forming quality of each weld during the additive process, and interlayer cooling relies only on natural heat dissipation.

[0003] Arc additive manufacturing of titanium alloys requires operation in a fully enclosed and argon-rich environment, and interlayer cooling relies solely on natural heat dissipation. In a fully enclosed argon-rich environment, gas convection is weak, and the heat generated by the arc additive process cannot be dissipated in time. In addition, the thermal conductivity of titanium alloys is low, and too slow cooling efficiency leads to excessive coarse columnar β grains, which seriously affects the strength and hardness of the formed parts. In addition, arc additive manufacturing of titanium alloys requires reasonable interlayer temperature control to avoid welding overheating and reduce the anisotropy of material properties. Excessive interlayer temperature will cause the heat cycle from the newly deposited layer to the previous layer to be higher than the titanium alloy α→β process, resulting in the continued growth of columnar crystals between the deposited layers and reduced performance of the formed parts. The lack of an effective interlayer cooling control method seriously restricts the quality, efficiency and engineering application of titanium alloy arc additive manufacturing. Summary of the invention

[0004] The present invention provides a titanium alloy arc additive interlayer cooling system and a control method thereof, and the technical problem to be solved is: by cooling the cladding layer by low-temperature argon gas and combining with a temperature sensing system, the problem that the current titanium alloy arc additive is fully enclosed and has no effective cooling method in an argon-rich environment is solved.

[0005] In order to solve the above technical problems, the present invention provides a titanium alloy arc additive interlayer cooling system, which is characterized by: comprising a low-temperature argon preparation system 1, a cold gas ejection system 2, and an infrared thermometer 3; the low-temperature argon preparation system 1 comprises a low-temperature gas preparation machine 101, a liquid argon dewar tank 102 and a high-pressure connecting pipe 103; the low-temperature gas preparation machine 101 is connected to the liquid argon dewar tank 102 through the high-pressure connecting pipe 103 to refrigerate the argon; the cold gas ejection system 2 comprises a low-temperature argon main connecting pipe 201, a low-temperature argon auxiliary connecting pipe 203, and a multi-head array gas outlet device 204; The argon main connecting pipe 201 is connected to the multi-head array gas outlet device 204 through multiple low-temperature argon auxiliary connecting pipes 203; the low-temperature argon main connecting pipe 201 is connected to the output end of the low-temperature gas preparation machine 101 of the low-temperature argon preparation system 1; the cold air ejection system 2, the infrared thermometer 3, the welding gun 6, the molded part 7, the titanium alloy substrate 8, and the platform 9 are all arranged in a fully enclosed argon-rich environment 5; the molded part 7, the titanium alloy substrate 8, and the platform 9 are arranged in sequence from top to bottom, the welding gun 6 is used for the manufacture of the molded part 7, the infrared thermometer 3 is used to measure the interlayer temperature, and the cold air ejection system 2 is used to cool the workpiece.

[0006] Furthermore, the control system 4 is connected to the low-temperature argon preparation system 1, the cold air ejection system 2, and the infrared thermometer 3 respectively through data cables.

[0007] Furthermore, the argon gas in the liquid argon dewar 102 is cooled by a low-temperature gas preparation machine 101 to obtain low-temperature argon gas at 0°C to -30°C, and the output gas pressure is 2-4 Bar.

[0008] Furthermore, the cryogenic gas preparation machine 101 is refrigerated by mechanical compression and binary enrichment.

[0009] Furthermore, the multi-head array type air outlet device 204 is composed of a rectangular air collecting plate 205 and a plurality of air outlet holes 206 .

[0010] Furthermore, the plurality of gas outlet holes 206 are separated by partitions in pairs, with two in each row forming a group, and are connected to the corresponding low-temperature argon gas auxiliary connecting pipes 203 .

[0011] Furthermore, each cryogenic argon gas secondary connecting pipe 203 is provided with a solenoid valve 202 for controlling the opening and closing of the cryogenic argon gas secondary connecting pipe 203 .

[0012] Furthermore, the cold air ejection system 2 is arranged at the end of the dedicated robot or the end of the extended shaft of the gantry structure.

[0013] A titanium alloy arc additive interlayer cooling control method, characterized in that the specific steps are as follows:

[0014] S1. Before the titanium alloy arc additive operation, start the titanium alloy arc additive interlayer cooling system;

[0015] S2. For molded parts with different characteristics, the number of cooling system intervention layers is different:

[0016] (1) For solid parts or parts with a wall thickness exceeding 30 mm, the number of cooling system intervention layers is 3;

[0017] (2) For hollow or thin-walled molded parts, the number of cooling system intervention layers is 6;

[0018] S3. When the number of additive layers reaches the cooling system intervention standard, the cooling operation begins;

[0019] S4, cooling speed needs to be controlled at 20℃ / s-40℃ / s;

[0020] S5. Considering the quality and efficiency of additive manufacturing, the interlayer temperature is controlled between 150℃ and 180℃. After the regional temperature collected by the infrared thermometer meets the requirements, it enters the next regional cooling; if the overall cooling area temperature of the multi-head array gas outlet device does not meet the requirements, but the cooling area corresponding to the single cooling head reaches the required interlayer temperature, the low-temperature argon gas output is closed by controlling the corresponding solenoid valve.

[0021] Furthermore, in S4, parameters are adjusted according to the different printing areas in the height direction of the molded part, specifically:

[0022] (1) Additive bottom area: output cooling argon gas temperature: 0℃~-10℃, output gas pressure 2Bar;

[0023] (2) Additive middle area: output cooling argon gas temperature: -10℃~-30℃, output gas pressure 3-4Bar;

[0024] (3) Additive top area: output cooling argon gas temperature: 0℃~-10℃, output gas pressure 2Bar.

[0025] Beneficial effects: The present invention controls a reasonable cooling rate to avoid the massive generation of α′ phase and β columnar crystals due to excessively fast or slow cooling rate; the control of interlayer temperature can make the heat cycle from a newly deposited layer to the previous layer lower than the α→β process of titanium alloy, block the growth of columnar crystals between the cladding layers, control the formation of coarse columnar crystal β grains, and improve the microstructure and performance of the molded parts. At the same time, the residence time between deposition layers is shortened to improve manufacturing efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of interlayer cooling system for titanium alloy arc additive

[0027] Figure 2 Schematic diagram of cold air ejection system

[0028] Figure 3 Schematic diagram of the eight-head array air outlet device. DETAILED DESCRIPTION

[0029] In order to make the purpose, content and advantages of the present invention more clear, the specific implementation methods of the present invention are further described in detail below.

[0030] The present invention proposes a titanium alloy arc additive interlayer cooling system, comprising a low-temperature argon gas preparation system 1, a cold gas ejection system 2, an infrared thermometer 3, and a control system 4;

[0031] The control system 4 is connected to the low-temperature argon preparation system 1, the cold gas ejection system 2, and the infrared thermometer 3 through data cables;

[0032] The cryogenic argon preparation system 1 includes a cryogenic gas preparation machine 101, a liquid argon dewar 102 and a high-pressure connecting pipe 103; it is connected to the control system through a data line, see Figure 1 The cryogenic gas preparation machine 101 is connected to the liquid argon dewar tank 102 through a high-pressure connecting pipe 103. The argon gas in the liquid argon dewar tank 102 is mechanically compressed and refrigerated by a binary enrichment layer by the cryogenic gas preparation machine 101 to obtain 0°C to -30°C low-temperature argon gas, with an output pressure of 2-4 Bar.

[0033] The cold air ejection system 2 is composed of a cryogenic argon main connecting pipe 201, a cryogenic argon auxiliary connecting pipe 203, a solenoid valve 202, and an eight-head array type air outlet device 204. Figure 2 The eight-head array gas outlet device 204 is composed of a rectangular gas collecting plate 205 and eight gas outlet holes 206. The eight gas outlet holes 206 are separated by partitions in pairs, and each row of two gas outlet holes is connected to the corresponding low-temperature argon gas auxiliary connecting pipe 203.

[0034] A solenoid valve 202 is provided on each cryogenic argon gas secondary connecting pipe 203, which is used to control the opening and closing of the cryogenic argon gas secondary connecting pipe 203; the cryogenic argon gas main connecting pipe 201 is connected to the output end of the cryogenic gas preparation machine 101 of the cryogenic argon gas preparation system 1, and each cryogenic argon gas secondary connecting pipe 203 is connected to two gas outlets 205, and the gas switch of the two gas outlets 205 in the same column of the eight-head array gas outlet device 204 is controlled by the solenoid valve 202.

[0035] Considering the accessibility of the cold air ejection system, the eight-head array type air outlet device should not be too large. The reference design is 60mm in length and 30mm in width, with a 10mm interval between each adjacent air outlet. The cold air ejection system 2 can be arranged at the end of a dedicated robot or at the end of the extended shaft of a gantry structure according to the size of the molded part and the working environment.

[0036] The cold air ejection system 2, the infrared thermometer 3, the welding gun 6, the molded part 7, the titanium alloy substrate 8, and the platform 9 are all arranged in a fully enclosed argon-rich environment 5; the molded part 7, the titanium alloy substrate 8, and the platform 9 are arranged in sequence from top to bottom, the welding gun 6 is used for manufacturing the molded part 7, the infrared thermometer 3 is used to measure the interlayer temperature, and the cold air ejection system 2 is used to cool the workpiece.

[0037] Titanium alloy arc additive interlayer cooling and temperature control method, the specific steps are as follows:

[0038] S1. Before the titanium alloy arc additive operation, start the titanium alloy arc additive interlayer cooling system;

[0039] S2. For molded parts with different characteristics, the number of cooling system intervention layers is different:

[0040] (1) For solid parts or parts with a wall thickness exceeding 30 mm, the number of cooling system intervention layers is 3;

[0041] (2) For hollow or thin-walled molded parts, the cooling system intervention layer is the 6th layer.

[0042] S3. When the number of additive layers reaches the cooling system intervention standard, the cooling operation begins.

[0043] S4. According to the CCT curve of TC4 titanium alloy, the cooling rate is 10℃ / s-80℃ / s to obtain α+β phase. In order to obtain fine α phase and control the formation of α′ phase and β columnar crystal, the cooling rate needs to be controlled at 20℃ / s-40℃ / s. In view of the different printing areas in the height direction of the molded parts, the bottom area can dissipate heat toward the substrate, the top area has a small thermal cycle, and the middle area has a large thermal cycle and difficult heat dissipation. Therefore, the cooling system has different cooling temperatures and output air pressures. The control system is used to adjust the parameters, specifically:

[0044] (1) Additive bottom area: output cooling argon gas temperature: 0℃~-10℃, output gas pressure 2Bar;

[0045] (2) Additive middle area: output cooling argon gas temperature: -10℃~-30℃, output gas pressure 3-4Bar;

[0046] (3) Additive top area: output cooling argon gas temperature: 0℃~-10℃, output gas pressure 2Bar.

[0047] S5. Comprehensively consider the quality and efficiency of additive manufacturing, and control the interlayer temperature between 150℃ and 180℃. After the regional temperature collected by the infrared thermometer meets the requirements, enter the next regional cooling. If the overall cooling area temperature of the eight-head array outlet device does not meet the requirements, but the cooling area corresponding to the single cooling head reaches the required interlayer temperature, the low-temperature argon gas output is closed by controlling the corresponding solenoid valve.

[0048] Key Points:

[0049] 1. Titanium alloy arc additive manufacturing uses low-temperature argon gas to cool the cladding layer in a fully enclosed and argon-rich environment, and combines a temperature sensing system to control the cooling rate and interlayer temperature.

[0050] 2. For molded parts with different characteristics, the number of cooling system intervention layers is different.

[0051] 3. Control of cooling rate and interlayer temperature.

[0052] 4. Due to the different printing areas in the height direction of the molded parts, the heat dissipation difficulty and the number of thermal cycles in the bottom area, middle area and top area are different, and the cooling temperature and output air pressure of the cooling system are different.

[0053] The present invention solves the problem that titanium alloy arc additive is fully enclosed and there is no effective cooling method for the cladding layer in an argon-rich environment. The cooling rate and interlayer temperature of the titanium alloy arc additive cladding layer are controllable, and the microstructure and cladding efficiency of the additively formed part are guaranteed.

[0054] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A titanium alloy arc additive interlayer cooling system, characterized by: The invention comprises a low-temperature argon preparation system 1, a cold gas ejection system 2, and an infrared thermometer 3; the low-temperature argon preparation system 1 comprises a low-temperature gas preparation machine 101, a liquid argon dewar tank 102, and a high-pressure connecting pipe 103; the low-temperature gas preparation machine 101 is connected to the liquid argon dewar tank 102 through the high-pressure connecting pipe 103 to refrigerate the argon gas; the cold gas ejection system 2 comprises a low-temperature argon main connecting pipe 201, a low-temperature argon auxiliary connecting pipe 203, and a multi-head array gas outlet device 204; the low-temperature argon main connecting pipe 201 is connected to the liquid argon dewar tank 102 through a plurality of low-temperature argon auxiliary connecting pipes 203, and a multi-head array gas outlet device 204; The tube 203 is connected to the multi-head array gas outlet device 204; the low-temperature argon main connecting tube 201 is connected to the output end of the low-temperature gas preparation machine 101 of the low-temperature argon preparation system 1; the cold air ejection system 2, the infrared thermometer 3, the welding gun 6, the molded part 7, the titanium alloy substrate 8, and the platform 9 are all arranged in a fully enclosed argon-rich environment 5; the molded part 7, the titanium alloy substrate 8, and the platform 9 are arranged in sequence from top to bottom, the welding gun 6 is used for the manufacture of the molded part 7, the infrared thermometer 3 is used to measure the interlayer temperature, and the cold air ejection system 2 is used to cool the workpiece.

2. A titanium alloy arc additive interlayer cooling system according to claim 1, characterized in that: The control system 4 is connected to the low-temperature argon preparation system 1, the cold air ejection system 2, and the infrared thermometer 3 through data cables.

3. The titanium alloy arc additive interlayer cooling system according to claim 1, characterized in that: The argon gas in the liquid argon dewar 102 is cooled by a low-temperature gas preparation machine 101 to obtain low-temperature argon gas at 0°C to -30°C, and the output gas pressure is 2-4 Bar.

4. The titanium alloy arc additive interlayer cooling system according to claim 1, characterized in that: The cryogenic gas preparation machine 101 uses mechanical compression and binary enrichment refrigeration.

5. The titanium alloy arc additive interlayer cooling system according to claim 1, characterized in that: The multi-head array type air outlet device 204 is composed of a rectangular air collecting plate 205 and a plurality of air outlet holes 206 .

6. A titanium alloy arc additive interlayer cooling system according to claim 5, characterized in that: The plurality of gas outlet holes 206 are separated by partitions in pairs, with two in each row forming a group, and are connected to the corresponding low-temperature argon gas auxiliary connecting pipes 203 .

7. The titanium alloy arc additive interlayer cooling system according to claim 5, characterized in that: A solenoid valve 202 is provided on each cryogenic argon gas secondary connecting pipe 203 to control the opening and closing of the cryogenic argon gas secondary connecting pipe 203 .

8. The titanium alloy arc additive interlayer cooling system according to claim 1, characterized in that: The cold air ejection system 2 is arranged at the end of the dedicated robot or the end of the extended shaft of the gantry structure.

9. A titanium alloy arc additive interlayer cooling control method, characterized in that: The specific steps are as follows: S1. Before the titanium alloy arc additive operation, start the titanium alloy arc additive interlayer cooling system; S2. For molded parts with different characteristics, the number of cooling system intervention layers is different: (1) For solid parts or parts with a wall thickness exceeding 30 mm, the number of cooling system intervention layers is 3; (2) For hollow or thin-walled molded parts, the number of cooling system intervention layers is 6; S3. When the number of additive layers reaches the cooling system intervention standard, the cooling operation begins; S4, cooling speed needs to be controlled at 20℃ / s-40℃ / s; S5. Considering the quality and efficiency of additive manufacturing, the interlayer temperature is controlled between 150℃ and 180℃. After the regional temperature collected by the infrared thermometer meets the requirements, it enters the next regional cooling. If the overall cooling area temperature of the multi-head array gas outlet device does not meet the requirements, but the cooling area corresponding to the single cooling head reaches the required interlayer temperature, the low-temperature argon gas output is closed by controlling the corresponding solenoid valve.

10. A titanium alloy arc additive interlayer cooling control method according to claim 9, characterized in that: In S4, parameters are adjusted according to the different printing areas in the height direction of the molded parts, specifically: (1) Additive bottom area: output cooling argon gas temperature: 0℃~-10℃, output gas pressure 2Bar; (2) Additive middle area: output cooling argon gas temperature: -10℃~-30℃, output gas pressure 3-4Bar; (3) Additive top area: output cooling argon gas temperature: 0℃~-10℃, output gas pressure 2Bar.

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