CN101797639A - Device for directionally solidifying by locally and forcibly heating with resistance at high gradient - Google Patents

Abstract

A high-gradient directional solidification device with locally strengthened resistance heating includes an upper furnace body and a lower furnace body. In the upper furnace body, from the center of the upper furnace body to the outside, there are crucible, resistance ring, tungsten cylinder and shielding layer in sequence, and the crucible, resistance ring and tungsten cylinder are all located in the shielding layer. On the upper surface of the tungsten cylinder and the resistance ring, there are power lines connected respectively; the power line of the tungsten cylinder and the power line of the resistance ring are respectively connected to the power supply independently, and the sample in the crucible is heated through the tungsten cylinder as a whole. The resistance ring located at the lower part of the crucible locally strengthens the heating of the sample in the crucible. Two thermocouples are respectively located on the upper part of the tungsten cylinder and the lower part of the resistance ring, and are used to measure the temperature of the tungsten cylinder and the resistance ring respectively. The invention combines overall heating and local enhanced heating, so that the sample can be fully melted while obtaining a high temperature gradient at the front of the solid/liquid interface, reducing the burning loss of low melting point elements, expanding the type of applicable materials and the size of the sample, and The forced convection of the melt caused by traditional induction heating is eliminated.

Description

A high-gradient directional solidification device with locally enhanced resistance heating

technical field

The invention relates to the field of directional solidification material preparation, in particular to a locally enhanced resistance heating high-gradient directional solidification device.

Background technique

Directional solidification technology can arrange the solidified structure of the material in a specific direction, obtain directional and single crystal structure, and improve material performance. In the directional solidification process of materials, high temperature gradient is the guarantee to obtain ultra-fine structure, reduce composition segregation, control microscopic defects and phase distribution. In addition, high temperature gradients can increase the draw rate while ensuring an optimized solidification structure, thereby increasing production efficiency. Therefore, high temperature gradient is the goal pursued by directional solidification equipment. The development history of directional solidification technology is the history of continuously increasing the temperature gradient of directional solidification equipment. The large temperature gradient can be obtained by strengthening the heating and cooling conditions. Therefore, scholars and engineers from various countries have invented a series of methods to increase the temperature gradient at the front of the solid/liquid interface along these two lines of thought.

At present, the directional solidification methods widely used in industrial production mainly include rapid solidification (HRS) and liquid metal cooling (LMC). The HRS method is to heat and melt the sample as a whole by induction or resistance heating, and then remove the casting from the furnace at a certain pulling rate to complete directional solidification, with a temperature gradient of 60-100°C/cm. The main difference between the LMC method and the HRS method is that the cooling medium is forced to cool with a low melting point liquid metal, and the temperature gradient can reach 100-300°C/cm. However, because the HRS method and the LMC method are all melting the sample, if the temperature gradient is increased by intensive heating, it will cause the burning loss of the low melting point elements in the alloy. Although the high-energy beam zone fusion directional solidification method can obtain a high temperature gradient, it is only suitable for the directional solidification of small-sized samples. For example, Zhang Jun, Cui Chunjuan and others from the State Key Laboratory of Solidification Technology of Northwestern Polytechnical University prepared Si/TaSi ₂ eutectic self-generated composite field emission materials by melting and directional solidification in the electron beam suspension zone, with a temperature gradient of 350-500 °C/cm.

The State Key Laboratory of Solidification Technology of Northwestern Polytechnical University has developed a new type of directional solidification technology based on the LMC method—Zone Melting Liquid Metal Cooling Method ((ZMLMC)). The local heating technology enables the front of the solid/liquid interface to be fully heated, so that a temperature gradient as high as 1300 °C/cm can be obtained. However, in the case of a high drawing rate, the zone induction heating method adopted by the ZMLMC method lags behind the drawing rate for the melting ability of the sample, resulting in the incomplete melting of the real sample, which limits the further improvement of the cooling rate.

Aiming at the shortcomings of the LMC method and the ZMLMC method, the invention proposes a locally enhanced resistance heating high gradient directional solidification device. The device combines the LMC method with the zone melting technology, not only can obtain a temperature gradient as high as 600°C/cm, but also ensure the complete melting of the sample and reduce the burning loss of low melting point elements. In addition, due to the use of resistance heating, the scope of application is extended to non-conductive materials, and resistance heating will not cause forced convection like induction heating, and stable crystal growth can be obtained, thus facilitating the study of solidification theory.

Contents of the invention

In order to overcome the defects in the prior art that the temperature gradient is low due to the overall heating and melting of the sample; or the insufficient melting of the sample due to regional induction heating, the present invention proposes a local enhanced resistance heating high gradient directional solidification device .

The present invention includes a power cord, a thermocouple, a heat shield, a crystallizer, a furnace body, liquid metal, a drawing system, a crucible, a tungsten cylinder and a shielding layer. The furnace body includes an upper furnace body and a lower furnace body. In the lower furnace body, the The center of the lower furnace body faces outwards, and there are a drawing system and a crystallizer in sequence, and liquid metal is installed in the crystallizer; the drawing system passes through the furnace bottom of the lower furnace body and is connected with a servo motor; at the bottom of the crystallizer, there are two Cooling water inlet; in the upper furnace body, from the center of the upper furnace body to the outside, there are crucible, tungsten cylinder and shielding layer in sequence. One end of the crucible passes through the center hole at the bottom of the upper furnace body and connects with the drawing system located in the center of the lower furnace body. connected; and the temperature of the tungsten cylinder is measured by a thermocouple; it is characterized in that the local enhanced resistance heating high-gradient directional solidification device also includes a resistance ring and a tantalum electrode; On the outer circumference of the tantalum electrode; one end of the tantalum electrode is connected to the water-cooled power line fixed on the upper furnace wall, and the other end has a groove on the end surface, and the unclosed end of the resistance ring is embedded in the groove to form a closed loop; There are thermocouples.

The resistance ring is a sleeve with openings on its circumference. There is no interference between the resistance ring and the tungsten cylinder and the crucible; there is a gap between the resistance ring and the heat shield; the axis of the resistance ring coincides with the center line of the furnace body.

The power line of the tungsten cylinder and the power line of the resistance ring are independently connected to the power supply.

The beneficial effects of the present invention are: the present invention combines the advantages of the ZMLMC method and the HRS method, heats the sample as a whole through a tungsten cylinder, and locally strengthens the front edge of the solid-liquid interface of the sample through a resistance ring and cools it with liquid metal. The overall heating ensures that the sample is fully melted, so that no undissolved particles will appear in the sample even when it is pulled at a high speed; the local enhanced heating at the front of the solid-liquid interface enables the equipment to provide a high temperature gradient. Therefore, the present invention is guaranteed A high temperature gradient can be obtained while the sample is completely melted. The specific effects are shown in Table 1. At the same time, the material, height, thickness and inner diameter of the resistance ring can be adjusted according to the size of the sample and the required temperature gradient.

Due to the resistance heating, the device is suitable not only for conductive materials, but also for non-conductive materials such as ceramics, semiconductors, and ceramic matrix composites. In addition, the tungsten cylinder and the resistance ring are powered by two DC power supplies respectively, and the power of the two can be adjusted separately, so that it is convenient to realize the overall heating and local enhanced heating of the sample. The DC power supply also ensures that no electromagnetic disturbance will be formed during the heating process, which reduces the flow of the melt during the directional solidification process and facilitates the theoretical research of directional solidification.

Table 1 Comparison of melting effect and orientation of samples prepared by different directional solidification devices

Description of drawings

Figure 1 is a schematic diagram of a device incorporated in the present invention.

Fig. 2 is a schematic structural view of the resistance ring heating body of the present invention.

Fig. 3 is a top view of the resistance ring heating body of the present invention. in:

1. Power cord 2. Thermocouple 3. Heat shield 4. Crystallizer 5. Liquid metal 6. Pulling system

7. Lower furnace body 8. Cooling water inlet 9. Crucible 10. Tungsten cylinder 11. Shielding layer 12. Sample

13. Resistance ring 14. Upper furnace body 15. Tantalum electrode

Detailed ways

Embodiment one

This embodiment is a local enhanced resistance heating high-gradient directional solidification device, including a power line 1, a thermocouple 2, a heat shield 3, a crystallizer 4, a furnace body, a liquid metal 5, a drawing system 6, a crucible 9, tungsten Barrel 10, shielding layer 11, resistance ring 13 and tantalum electrode 15. The alloy heated in this example is DZ125 directionally solidified nickel-based superalloy, the local strengthening temperature is 2000°C, the overall heating temperature is 1500°C, and a temperature gradient of 600°C/cm is obtained on the basis of ensuring the complete melting of the sample.

The furnace body includes an upper furnace body 14 and a lower furnace body 7. In the lower furnace body 7, from the center of the lower furnace body to the outside, there are successively a drawing system 6 and a crystallizer 4. Liquid metal 5 is housed in the crystallizer 4; The pulling system 6 passes through the furnace bottom of the lower furnace body 7 and is connected with the servo motor; there are two cooling water inlets 8 at the bottom of the crystallizer 4 .

In the upper furnace body 14, from the center of the upper furnace body to the outside, there are crucible 9, resistance ring 13, tungsten cylinder 10 and shielding layer 11 in sequence, and the crucible 9, resistance ring 13 and tungsten cylinder 10 are all located in the shielding layer 11 . On the upper surface of the tungsten cylinder 10 and the resistance ring 13, there are power lines 1 respectively; The sample 12 is heated as a whole, and the sample 12 in the crucible is locally heated through the resistance ring 13 located at the bottom of the crucible 9 . One end of the crucible 9 passes through the central hole at the bottom of the upper furnace body 14 and is connected with the drawing system 6 located in the center of the lower furnace body 7 . Two thermocouples 2 are located on the upper part of the tungsten cylinder 10 and the lower part of the resistance ring 13 respectively, and are used to measure the temperature of the tungsten cylinder 10 and the resistance ring 13 respectively.

A heat insulating board 3 is arranged between the upper furnace body 14 and the lower furnace body 7 .

The resistor ring 13 made of tantalum is a sleeve with openings on the circumference. The outer diameter of the resistance ring 13 is smaller than the inner diameter of the tungsten cylinder 10 , and the inner diameter is larger than the outer diameter of the crucible 9 . The resistance ring 13 is located in the tungsten cylinder 10 above the heat shield, and is set on the outer circumference of the crucible 9, and the resistance ring 13 does not interfere with the tungsten cylinder 10 and the crucible 9; there is a gap between the resistance ring and the heat shield; The axis of the resistance ring coincides with the centerline of the furnace body. The height and thickness of the resistance ring 13 are determined according to the heated temperature and the temperature gradient at the front of the solid/liquid interface, and the determination principle is that the resistance ring 13 does not soften under the required temperature gradient. In this embodiment, the height of the resistance ring 13 is 10 mm; the thickness of the resistance ring 13 is 0.5 mm.

The tantalum electrode 15 is rod-shaped, and is used for fixing the resistance ring 13 and connecting the power line. One end of the tantalum electrode 15 is connected to the water-cooled power line fixed on the upper furnace wall; the other end of the tantalum electrode 15 has a groove on the end surface, and the unclosed end of the resistance ring 13 is embedded in the groove to form a closed circuit.

When in use, first clamp the crucible 9 on the drawing system 6, then place the heat shield 3 with a through hole in the center, then put the alloy sample 12 into the crucible 9, lower the upper furnace body 14 and ensure that the upper furnace body It is concentric with the lower furnace body, so as to ensure that the crucible and the heating device are concentric. After the upper and lower furnace bodies are closed, connect the four power lines 1 of the heating device to two DC power supplies, and then turn on the DC power supply, and pass the tungsten cylinder 10 to the sample 12 Carry out overall heating. When the sample reaches the required temperature, adjust the input power of the resistance ring 13 to obtain the required temperature gradient. Then, the drawing system 6 passes the sample 12 and the crucible 9 through the drawing system 6 at a set speed. Directional solidification is achieved by moving down into the liquid metal coolant 5 .

According to the requirements of the experimental design, multiple alloy samples with the same composition were directional solidified at different rates to obtain tissue patterns at different growth rates, and further analyzed the structure evolution law. According to the final experimental results, the temperature gradient of this device is as high as 600K/cm, and it is not found that the finally obtained sample has no unmelted particles when the pulling rate reaches 1mm/s.

Embodiment two

This embodiment is a local enhanced resistance heating high-gradient directional solidification device, including a power line 1, a thermocouple 2, a heat shield 3, a crystallizer 4, a furnace body, a liquid metal 5, a drawing system 6, a crucible 9, tungsten Barrel 10, shielding layer 11, resistance ring 13 and tantalum electrode 15. The alloy heated in this example is AM3 single crystal superalloy alloy, the local strengthening temperature is 1650°C, the overall heating temperature is 1500°C, and a temperature gradient of 290°C/cm is obtained on the basis of ensuring the complete melting of the sample.

The furnace body includes an upper furnace body 14 and a lower furnace body 7. In the lower furnace body 7, from the center of the lower furnace body to the outside, there are successively a drawing system 6 and a crystallizer 4. Liquid metal 5 is housed in the crystallizer 4; The pulling system 6 passes through the furnace bottom of the lower furnace body 7 and is connected with the servo motor; there are two cooling water inlets 8 at the bottom of the crystallizer 4 .

In the upper furnace body 14, from the center of the upper furnace body to the outside, there are crucible 9, resistance ring 13, tungsten cylinder 10 and shielding layer 11 in sequence, and the crucible 9, resistance ring 13 and tungsten cylinder 10 are all located in the shielding layer 11 . On the upper surface of the tungsten cylinder 10 and the resistance ring 13, there are power lines 1 respectively; The sample 12 is heated as a whole, and the sample 12 in the crucible is locally heated through the resistance ring 13 located at the bottom of the crucible 9 . One end of the crucible 9 passes through the central hole at the bottom of the upper furnace body 14 and is connected with the drawing system 6 located in the center of the lower furnace body 7 . Two thermocouples 2 are located on the upper part of the tungsten cylinder 10 and the lower part of the resistance ring 13 respectively, and are used to measure the temperature of the tungsten cylinder 10 and the resistance ring 13 respectively.

A heat insulating board 3 is arranged between the upper furnace body 14 and the lower furnace body 7 .

The resistance ring 13 made of molybdenum is a sleeve with openings on the circumference. The outer diameter of the resistance ring 13 is smaller than the inner diameter of the tungsten cylinder 10 , and the inner diameter is larger than the outer diameter of the crucible 9 . The resistance ring 13 is located in the tungsten cylinder 10 above the heat shield, and is set on the outer circumference of the crucible 9, and the resistance ring 13 does not interfere with the tungsten cylinder 10 and the crucible 9; there is a gap between the resistance ring and the heat shield; The axis of the resistance ring coincides with the centerline of the furnace body. The height and thickness of the resistance ring 13 are determined according to the heated temperature and the temperature gradient at the front of the liquid-solid interface, and the determination principle is that the resistance ring 13 does not soften under the required temperature gradient. In this embodiment, the height of the resistance ring 13 is 5 mm; the thickness of the resistance ring 13 is 1 mm.

The tantalum electrode 15 is rod-shaped, and is used for fixing the resistance ring 13 and connecting the power line. One end of the tantalum electrode 15 is connected to the water-cooled power line fixed on the upper furnace wall; the other end of the tantalum electrode 15 has a groove on the end surface, and the resistance ring 13 is not closed and embedded in the groove to form a closed circuit.

When in use, first clamp the crucible 9 on the drawing system 6, then place the heat shield 3 with a through hole in the center, then put the alloy sample into the crucible 9, lower the upper furnace body 14 and ensure that the upper furnace body and the lower furnace body The furnace body is concentric, so as to ensure that the crucible and the heating device are concentric. After the upper and lower furnace bodies are closed, the four power lines 1 of the heating device are connected to two DC power supplies, and then the DC power supply is turned on, and the sample 12 is integrated through the tungsten cylinder 10. Heating, when the sample reaches the required temperature, adjust the input power of the resistance ring 13 to obtain the required temperature gradient, and then, the drawing system 6 moves the sample 12 and the crucible 9 downward through the drawing system 6 at a set speed Move into liquid metal coolant 5 to achieve directional solidification.

According to the requirements of the experimental design, multiple alloy samples with the same composition were directional solidified at different rates to obtain tissue patterns at different growth rates, and further analyzed the structure evolution law. According to the final experimental results, the temperature gradient of this device is 290K/cm, and when the pulling rate reaches 0.9mm/s, it is not found that there are no unmelted particles in the finally obtained sample.

Embodiment three

This embodiment is a local enhanced resistance heating high-gradient directional solidification device, including a power line 1, a thermocouple 2, a heat shield 3, a crystallizer 4, a furnace body, a liquid metal 5, a drawing system 6, a crucible 9, tungsten Barrel 10, shielding layer 11, resistance ring 13 and tantalum electrode 15. The alloy heated in this example is DZ125 directionally solidified nickel-based superalloy, the local strengthening temperature is 2000°C, the overall heating temperature is 1500°C, and a temperature gradient of 600°C/cm is obtained on the basis of ensuring the complete melting of the sample.

The furnace body includes an upper furnace body 14 and a lower furnace body 7. In the lower furnace body 7, from the center of the lower furnace body to the outside, there are successively a drawing system 6 and a crystallizer 4. Liquid metal 5 is housed in the crystallizer 4; The pulling system 6 passes through the furnace bottom of the lower furnace body 7 and is connected with the servo motor; there are two cooling water inlets 8 at the bottom of the crystallizer 4 .

In the upper furnace body 14, from the center of the upper furnace body to the outside, there are crucible 9, resistance ring 13, tungsten cylinder 10 and shielding layer 11 in sequence, and the crucible 9, resistance ring 13 and tungsten cylinder 10 are all located in the shielding layer 11 . On the upper surface of the tungsten cylinder 10 and the resistance ring 13, there are power lines 1 respectively; The sample 12 is heated as a whole, and the sample 12 in the crucible is locally heated through the resistance ring 13 located at the bottom of the crucible 9 . One end of the crucible 9 passes through the central hole at the bottom of the upper furnace body 14 and is connected with the drawing system 6 located in the center of the lower furnace body 7 . Two thermocouples 2 are located on the upper part of the tungsten cylinder 10 and the lower part of the resistance ring 13 respectively, and are used to measure the temperature of the tungsten cylinder 10 and the resistance ring 13 respectively.

A heat insulating board 3 is arranged between the upper furnace body 14 and the lower furnace body 7 .

The resistance ring 13 made of tungsten is a sleeve with openings on the circumference. The outer diameter of the resistance ring 13 is smaller than the inner diameter of the tungsten cylinder 10 , and the inner diameter is larger than the outer diameter of the crucible 9 . The resistance ring 13 is located in the tungsten cylinder 10 above the heat shield, and is set on the outer circumference of the crucible 9, and the resistance ring 13 does not interfere with the tungsten cylinder 10 and the crucible 9; there is a gap between the resistance ring and the heat shield; The axis of the resistance ring coincides with the centerline of the furnace body. The height and thickness of the resistance ring 13 are determined according to the heated temperature and the temperature gradient at the front of the solid/liquid interface, and the determination principle is that the resistance ring 13 does not soften under the required temperature gradient. In this embodiment, the height of the resistance ring 13 is 10 mm; the thickness of the resistance ring 13 is 0.5 mm.

The tantalum electrode 15 is rod-shaped, and is used for fixing the resistance ring 13 and connecting the power line. One end of the tantalum electrode 15 is connected to the water-cooled power line fixed on the upper furnace wall; the other end of the tantalum electrode 15 has a groove on the end surface, and the unclosed end of the resistance ring 13 is embedded in the groove to form a closed circuit.

When in use, first clamp the crucible 9 on the drawing system 6, then place the heat shield 3 with a through hole in the center, then put the alloy sample 12 into the crucible 9, lower the upper furnace body 14 and ensure that the upper furnace body Concentric with the lower furnace body so as to ensure the concentricity of the crucible and the heating device, after the upper and lower furnace body is closed, connect the four power lines 1 of the heating device to two DC power sources, then turn on the DC power source, and conduct the test on the sample 12 through the tungsten cylinder 10 Overall heating, when the sample reaches the required temperature, adjust the input power of the resistance ring 13 to obtain the required temperature gradient, and then, the drawing system 6 passes the sample 12 and the crucible 9 through the drawing system 6 at a set speed. Move down into the liquid metal coolant 5 to realize directional solidification.

According to the requirements of the experimental design, multiple alloy samples with the same composition were directional solidified at different rates to obtain tissue patterns at different growth rates, and further analyzed the structure evolution law. According to the final experimental results, the temperature gradient of this device is as high as 600K/cm, and it is not found that the finally obtained sample has no unmelted particles when the pulling rate reaches 1mm/s.

Embodiment four

This embodiment is a local enhanced resistance heating high-gradient directional solidification device, including a power line 1, a thermocouple 2, a heat shield 3, a crystallizer 4, a furnace body, a liquid metal 5, a drawing system 6, a crucible 9, tungsten Barrel 10, shielding layer 11, resistance ring 13 and tantalum electrode 15. The alloy heated in this example is DZ125 directionally solidified nickel-based superalloy, the local strengthening temperature is 1500°C, the overall heating temperature is 1500°C, and a temperature gradient of 120°C/cm is obtained on the basis of ensuring that the sample is completely melted.

The furnace body includes an upper furnace body 14 and a lower furnace body 7. In the lower furnace body 7, from the center of the lower furnace body to the outside, there are successively a drawing system 6 and a crystallizer 4. Liquid metal 5 is housed in the crystallizer 4; The pulling system 6 passes through the furnace bottom of the lower furnace body 7 and is connected with the servo motor; there are two cooling water inlets 8 at the bottom of the crystallizer 4 .

In the upper furnace body 14, from the center of the upper furnace body to the outside, there are crucible 9, resistance ring 13, tungsten cylinder 10 and shielding layer 11 in sequence, and the crucible 9, resistance ring 13 and tungsten cylinder 10 are all located in the shielding layer 11 . On the upper surface of the tungsten cylinder 10 and the resistance ring 13, there are power lines 1 respectively; The sample 12 is heated as a whole, and the sample 12 in the crucible is locally heated through the resistance ring 13 located at the bottom of the crucible 9 . One end of the crucible 9 passes through the central hole at the bottom of the upper furnace body 14 and is connected with the drawing system 6 located in the center of the lower furnace body 7 . Two thermocouples 2 are located on the upper part of the tungsten cylinder 10 and the lower part of the resistance ring 13 respectively, and are used to measure the temperature of the tungsten cylinder 10 and the resistance ring 13 respectively.

A heat insulating board 3 is arranged between the upper furnace body 14 and the lower furnace body 7 .

The resistor ring 13 made of graphite is a sleeve with openings on the circumference. The outer diameter of the resistance ring 13 is smaller than the inner diameter of the tungsten cylinder 10 , and the inner diameter is larger than the outer diameter of the crucible 9 . The resistance ring 13 is located in the tungsten cylinder 10 above the heat shield, and is set on the outer circumference of the crucible 9, and the resistance ring 13 does not interfere with the tungsten cylinder 10 and the crucible 9; there is a gap between the resistance ring and the heat shield; The axis of the resistance ring coincides with the centerline of the furnace body. The height and thickness of the resistance ring 13 are determined according to the heated temperature and the temperature gradient at the front of the liquid-solid interface, and the determination principle is that the resistance ring 13 does not soften under the required temperature gradient. In this embodiment, the height of the resistance ring 13 is 5 mm; the thickness of the resistance ring 13 is 0.5 mm.

The tantalum electrode 15 is rod-shaped, and is used for fixing the resistance ring 13 and connecting the power line. One end of the tantalum electrode 15 is connected to the water-cooled power line fixed on the upper furnace wall; the other end of the tantalum electrode 15 has a groove on the end surface, and the resistance ring 13 is not closed and embedded in the groove to form a closed circuit.

When in use, first clamp the crucible 9 on the drawing system 6, then place the heat shield 3 with a through hole in the center, then put the alloy sample into the crucible 9, lower the upper furnace body 14 and ensure that the upper furnace body and the lower furnace body The furnace body is concentric, so as to ensure that the crucible and the heating device are concentric. After the upper and lower furnace bodies are closed, the four power lines 1 of the heating device are connected to two DC power supplies, and then the DC power supply is turned on to heat the sample as a whole through the tungsten cylinder 10. , when the sample reaches the required temperature, adjust the input power of the resistance ring 13 to obtain the required temperature gradient, and then, the drawing system 6 moves the sample 12 and the crucible 9 downwards through the drawing system 6 at a set speed. Liquid metal coolant 5 to achieve directional solidification.

According to the requirements of the experimental design, multiple alloy samples with the same composition were directional solidified at different rates to obtain tissue patterns at different growth rates, and further analyzed the structure evolution law. According to the final experimental results, the temperature gradient of this device can reach up to 120°C/cm, and when the pulling rate reaches 0.8mm/s, it is not found that the finally obtained sample has no unmelted particles.

Embodiment five

This embodiment is a local enhanced resistance heating high-gradient directional solidification device, including a power line 1, a thermocouple 2, a heat shield 3, a crystallizer 4, a furnace body, a liquid metal 5, a drawing system 6, a crucible 9, tungsten Barrel 10, shielding layer 11, resistance ring 13 and tantalum electrode 15. The alloy heated in this example is DZ125 directionally solidified nickel-based superalloy, the local strengthening temperature is 1500°C, the overall heating temperature is 1500°C, and a temperature gradient of 120°C/cm is obtained on the basis of ensuring that the sample is completely melted.

The furnace body includes an upper furnace body 14 and a lower furnace body 7. In the lower furnace body 7, from the center of the lower furnace body to the outside, there are successively a drawing system 6 and a crystallizer 4. Liquid metal 5 is housed in the crystallizer 4; The pulling system 6 passes through the furnace bottom of the lower furnace body 7 and is connected with the servo motor; there are two cooling water inlets 8 at the bottom of the crystallizer 4 .

In the upper furnace body 14, from the center of the upper furnace body to the outside, there are crucible 9, resistance ring 13, tungsten cylinder 10 and shielding layer 11 in sequence, and the crucible 9, resistance ring 13 and tungsten cylinder 10 are all located in the shielding layer 11 . On the upper surface of the tungsten cylinder 10 and the resistance ring 13, there are power lines 1 respectively; The sample 12 is heated as a whole, and the sample 12 in the crucible is locally heated through the resistance ring 13 located at the bottom of the crucible 9 . One end of the crucible 9 passes through the central hole at the bottom of the upper furnace body 14 and is connected with the drawing system 6 located in the center of the lower furnace body 7 . Two thermocouples 2 are located on the upper part of the tungsten cylinder 10 and the lower part of the resistance ring 13 respectively, and are used to measure the temperature of the tungsten cylinder 10 and the resistance ring 13 respectively.

A heat insulating board 3 is arranged between the upper furnace body 14 and the lower furnace body 7 .

The resistance ring 13 made of silicon-molybdenum compound is a sleeve with openings on the circumference. The outer diameter of the resistance ring 13 is smaller than the inner diameter of the tungsten cylinder 10 , and the inner diameter is larger than the outer diameter of the crucible 9 . The resistance ring 13 is located in the tungsten cylinder 10 above the heat shield, and is set on the outer circumference of the crucible 9, and the resistance ring 13 does not interfere with the tungsten cylinder 10 and the crucible 9; there is a gap between the resistance ring and the heat shield; The axis of the resistance ring coincides with the centerline of the furnace body. The height and thickness of the resistance ring 13 are determined according to the heated temperature and the temperature gradient at the front of the liquid-solid interface, and the determination principle is that the resistance ring 13 does not soften under the required temperature gradient. In this embodiment, the height of the resistance ring 13 is 5 mm; the thickness of the resistance ring 13 is 0.5 mm.

The tantalum electrode 15 is rod-shaped, and is used for fixing the resistance ring 13 and connecting the power line. One end of the tantalum electrode 15 is connected to the water-cooled power line fixed on the upper furnace wall; the other end of the tantalum electrode 15 has a groove on the end surface, and the resistance ring 13 is not closed and embedded in the groove to form a closed circuit.

When in use, first clamp the crucible 9 on the drawing system 6, then place the heat shield 3 with a through hole in the center, then put the alloy sample into the crucible 9, lower the upper furnace body 14 and ensure that the upper furnace body and the lower furnace body The furnace body is concentric so as to ensure that the crucible and the heating device are concentric. After the upper and lower furnace bodies are closed, the four power lines 1 of the heating device are connected to two DC power supplies, and then the DC power supply is turned on to heat the sample as a whole through the tungsten cylinder 10. When the sample reaches the required temperature, adjust the input power of the resistance ring 13 to obtain the required temperature gradient, and then the drawing system 6 moves the sample 12 and the crucible 9 down into the liquid state through the drawing system 6 at a set speed. Metal cooling liquid 5 to achieve directional solidification.

According to the requirements of the experimental design, multiple alloy samples with the same composition were directional solidified at different rates to obtain tissue patterns at different growth rates, and further analyzed the structure evolution law. According to the final experimental results, the temperature gradient of this device can reach up to 120°C/cm, and when the pulling rate reaches 0.8mm/s, it is not found that the finally obtained sample has no unmelted particles.

Embodiment six

This embodiment is a local enhanced resistance heating high-gradient directional solidification device, including a power line 1, a thermocouple 2, a heat shield 3, a crystallizer 4, a furnace body, a liquid metal 5, a drawing system 6, a crucible 9, tungsten Barrel 10, shielding layer 11, resistance ring 13 and tantalum electrode 15. The alloy heated in this example is DZ125 directionally solidified nickel-based superalloy, the local strengthening temperature is 1200°C, the overall heating temperature is 1200°C, and a temperature gradient of 90°C/cm is obtained on the basis of ensuring that the sample is completely melted.

The furnace body includes an upper furnace body 14 and a lower furnace body 7. In the lower furnace body 7, from the center of the lower furnace body to the outside, there are successively a drawing system 6 and a crystallizer 4. Liquid metal 5 is housed in the crystallizer 4; The pulling system 6 passes through the furnace bottom of the lower furnace body 7 and is connected with the servo motor; there are two cooling water inlets 8 at the bottom of the crystallizer 4 .

In the upper furnace body 14, from the center of the upper furnace body to the outside, there are crucible 9, resistance ring 13, tungsten cylinder 10 and shielding layer 11 in sequence, and the crucible 9, resistance ring 13 and tungsten cylinder 10 are all located in the shielding layer 11 . On the upper surface of the tungsten cylinder 10 and the resistance ring 13, there are power lines 1 respectively; The sample 12 is heated as a whole, and the sample 12 in the crucible is locally heated through the resistance ring 13 located at the bottom of the crucible 9 . One end of the crucible 9 passes through the central hole at the bottom of the upper furnace body 14 and is connected with the drawing system 6 located in the center of the lower furnace body 7 . Two thermocouples 2 are located on the upper part of the tungsten cylinder 10 and the lower part of the resistance ring 13 respectively, and are used to measure the temperature of the tungsten cylinder 10 and the resistance ring 13 respectively.

A heat insulating board 3 is arranged between the upper furnace body 14 and the lower furnace body 7 .

The resistance ring 13 made of nickel-chromium alloy is a sleeve with openings on the circumference. The outer diameter of the resistance ring 13 is smaller than the inner diameter of the tungsten cylinder 10 , and the inner diameter is larger than the outer diameter of the crucible 9 . The resistance ring 13 is located in the tungsten cylinder 10 above the heat shield, and is set on the outer circumference of the crucible 9, and the resistance ring 13 does not interfere with the tungsten cylinder 10 and the crucible 9; there is a gap between the resistance ring and the heat shield; The axis of the resistance ring coincides with the centerline of the furnace body. The height and thickness of the resistance ring 13 are determined according to the heated temperature and the temperature gradient at the front of the liquid-solid interface, and the determination principle is that the resistance ring 13 does not soften under the required temperature gradient. In this embodiment, the height of the resistance ring 13 is 5 mm; the thickness of the resistance ring 13 is 0.5 mm.

The tantalum electrode 15 is rod-shaped, and is used for fixing the resistance ring 13 and connecting the power line. One end of the tantalum electrode 15 is connected to the water-cooled power line fixed on the upper furnace wall; the other end of the tantalum electrode 15 has a groove on the end surface, and the resistance ring 13 is not closed and embedded in the groove to form a closed circuit.

When in use, first clamp the crucible 9 on the drawing system 6, then place the heat shield 3 with a through hole in the center, then put the alloy sample into the crucible 9, lower the upper furnace body 14 and ensure that the upper furnace body and the lower furnace body The furnace body is concentric so as to ensure that the crucible and the heating device are concentric. After the upper and lower furnace bodies are closed, the four power lines 1 of the heating device are connected to two DC power supplies, and then the DC power supply is turned on to heat the sample as a whole through the tungsten cylinder 10. When the sample reaches the required temperature, adjust the input power of the resistance ring 13 to obtain the required temperature gradient, and then the drawing system 6 moves the sample 12 and the crucible 9 down into the liquid state through the drawing system 6 at a set speed. Metal cooling liquid 5 to achieve directional solidification.

According to the requirements of the experimental design, multiple alloy samples with the same composition were directional solidified at different rates to obtain tissue patterns at different growth rates, and further analyzed the structure evolution law. According to the final experimental results, the temperature gradient of this device can reach up to 90°C/cm, and it is not found that the finally obtained sample has no unmelted particles when the pulling rate reaches 0.8mm/s.

Claims (4)

1. A high-gradient directional solidification device with local enhanced resistance heating, including a power line (1), a thermocouple (2), a heat shield (3), a crystallizer (4), a furnace body, a liquid metal (5), a pump Pulling system (6), crucible (9), tungsten cylinder (10) and shielding layer (11), the furnace body includes upper furnace body (14) and lower furnace body (7), in the lower furnace body (7), from the lower The center of the furnace body faces outwards, and there are drawing system (6) and crystallizer (4) in sequence, liquid metal (5) is installed in the crystallizer (4); the drawing system (6) passes through the lower furnace body (7) The bottom of the furnace is connected with the servo motor; there are two cooling water inlets 8 at the bottom of the crystallizer (4); in the upper furnace body (14), from the center of the upper furnace body to the outside, there are crucibles (9), The tungsten cylinder (10) and shielding layer (11), one end of the crucible (9) passes through the central hole at the bottom of the upper furnace body (14), and is connected to the drawing system (6) located in the inner center of the lower furnace body (7); and Measure the temperature of the tungsten cylinder (10) by a thermocouple (2); it is characterized in that, the described local enhanced resistance heating high gradient directional solidification device also includes a resistance ring (13) and a tantalum electrode (15); the resistance ring (13) Located in the tungsten cylinder (10) above the heat shield (3), set on the outer circumference of the crucible (9); one end of the tantalum electrode (15) is connected to the power line; the other end of the tantalum electrode (15) has a concave groove, and the unclosed end of the resistance ring (13) is embedded in the groove to form a closed loop; the resistance ring (13) is connected with a thermocouple (2). 2. A local enhanced resistance heating high gradient directional solidification device according to claim 1, characterized in that the resistance ring (13) is a sleeve with openings on its circumference. 3. a kind of local strengthening resistance heating high-gradient directional solidification device as claimed in claim 1, is characterized in that, resistance ring (13) does not interfere with tungsten cylinder (10) and crucible (9); Resistance ring (13) There is a gap between the heat shield; the axis of the resistance ring (13) coincides with the centerline of the body of heater. 4. A local enhanced resistance heating high-gradient directional solidification device as claimed in claim 1, characterized in that the power line of the tungsten cylinder (10) and the power line of the resistance ring (13) are independently connected to the power supply.

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