Pure copper directional solidification method

Abstract

The invention relates to a directional solidification method for pure copper, which comprises the following steps of: preserving heat of an ingot mould at the temperature of 300-400 DEG C for 12-18 hours, and preheating the ingot mould; the electrolytic copper is melted into molten copper in the vacuum atmosphere; a first cooling water circulating pump is started, so that cooling water flows through a circulating flow channel in the cooling base, and the ingot mold on the cooling base is cooled; molten copper is poured into the ingot mold, heating coils are started, and the heating coils are arranged in multiple circles in the height direction of the ingot mold; and pouring is completed, specifically, the molten copper is subjected to standing in the ingot mold for 120-180 min, and a directionally-solidified copper ingot is obtained. One-way heat dissipation of the bottom of the ingot mold is forcibly achieved through a circulating runner on the cooling base, a stable temperature gradient is formed, and columnar crystal growth is promoted so as to optimize the mechanical property. A plurality of circles of heating coils and a plurality of circles of cooling water pipes are arranged on the ingot mold, the temperature of the ingot mold is dynamically adjusted, gradient distribution of the temperature of the ingot mold is achieved, and therefore directional sequential solidification is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of metallurgy, and in particular to a pure copper directional solidification method. Background Art

[0002] Directional solidification is an advanced materials processing technology that precisely controls the solidification process of molten metals or alloys, causing crystals to grow in a specific direction. This technique can produce materials with oriented columnar or single-crystal structures, significantly improving their mechanical properties, thermal fatigue resistance, and creep resistance. Directional solidification technology is widely used in high-temperature alloys, semiconductor materials, and in-situ composite materials, and plays a particularly crucial role in the manufacture of aerospace engine blades.

[0003] During directional solidification, the material undergoes forced solidification in a directional solidification device. Existing devices use a heat shield to separate the upper heating zone from the lower cooling zone, creating a one-dimensional temperature gradient along the material's axis. After the metal is gradually melted in the upper heating zone, it is transferred to the lower cooling zone via a pull-out system for forced cooling, resulting in a unidirectionally aligned solidified structure. Currently, the directional solidification process technology used in industry faces the following challenges: 1) Insufficient temperature gradient: The solidification interface is unstable and defects such as stray crystals and equiaxed crystals are easily generated; 2) Inaccurate cooling rate control: Uneven cooling rate leads to local overcooling or overheating, causing asynchronous phase transformation, resulting in differences in grain size, morphology or phase distribution, and resulting in uneven structure; 3) Low cooling efficiency: As the solid phase grows, the accumulation of latent heat of the crystal leads to a decrease in the efficiency of the cooling medium, and then the cooling rate and the temperature gradient at the solid-liquid interface decrease, affecting the solidification rate. Summary of the Invention

[0004] The present invention aims to solve the existing technical problems and provides a pure copper directional solidification method.

[0005] The present invention solves the above technical problems with the following technical solutions: A method for directional solidification of pure copper comprises the following steps: S10, initial preparation: preheating the ingot mold at a temperature of 300°C-400°C for 12h-18h; S20, smelting: melting the electrolytic copper into molten copper in a vacuum; S30, pouring: S31: starting a first cooling water circulation pump to allow cooling water to flow through a circulation channel in the cooling base to cool the ingot mold on the cooling base; S32: pouring molten copper into the ingot mold and starting a heating coil, wherein the heating coil is provided with multiple turns along the height direction of the ingot mold; S40, pouring completed: the molten copper is allowed to stand in the ingot mold for 120-180 minutes to obtain a directionally solidified copper ingot.

[0006] On the basis of the above technical solution, the present invention can also make the following improvements: Preferably, step S20 includes S21, placing the electrolytic copper in a graphite crucible, heating it to 1100° C.-1300° C., and melting all the electrolytic copper into molten copper.

[0007] Preferably, after step S21, the method includes step S22, adding calcium boride to the graphite crucible, raising the temperature of the graphite crucible to 1350-1500° C. and keeping the temperature for 15 min-20 min, and performing deoxidation and dehydrogenation treatment on the molten copper.

[0008] Preferably, step S32 further includes starting a second cooling water circulation pump, and cooling water cools the ingot mold through a cooling water pipe, and the cooling water pipe is provided with multiple loops in parallel along the height direction of the ingot mold.

[0009] Preferably, the flow rate of the cooling water pumped by the first cooling water circulation pump is 15m / s-23m / s.

[0010] Preferably, the first cooling water circulation pump and the second cooling water circulation pump draw cooling water from a cooling pool, and the temperature of the cooling water in the cooling pool is 5°C-10°C.

[0011] Preferably, the circulation channel is spiral-shaped, a water inlet is provided on the side wall of the circulation channel, and a water outlet is provided at the center of the circulation channel.

[0012] Preferably, the heating coil is provided with multiple turns in series or in parallel along the height direction of the ingot mold.

[0013] The beneficial effects of the present invention are: 1) Multi-zone dynamic temperature control: By setting up multiple heating coils for independent heating and cooperating with cooling water pipes, the temperature of the ingot mold can be dynamically adjusted. This achieves a gradient temperature distribution of the ingot mold and suppresses the rapid cooling of the copper liquid at the side wall of the ingot mold, thereby ensuring the quality of directional solidification of the ingot.

[0014] 2) Unidirectional heat flow directional solidification: The first cooling water circulation pump drives the cooling water to circulate in the cooling base, and the cooling base is made of pure copper with good heat dissipation effect, which realizes forced unidirectional heat dissipation of the bottom of the ingot mold, forms a stable temperature gradient, promotes the growth of columnar crystals to optimize mechanical properties.

[0015] 3) High-efficiency latent heat dissipation design: Low-temperature cooling water is used in the cooling pool, and combined with the high-flow flow channel of the cooling base, this avoids latent heat accumulation in the cooling base and significantly improves the solidification rate of the copper liquid.

[0016] 4) Low-resistance and uniform heat dissipation structure: The unobstructed circulation flow channel layout eliminates turbulence and dead zones, ensuring uniform heat dissipation and reducing thermal stress.

[0017] 5) Spiral anti-deformation cooling base: The spiral structure of the cooling base can disperse the load and thermal stress, prevent local deformation of the cooling base, and adapt to the needs of heavy ingots. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 A schematic diagram of a directional solidification device used in the present invention; Figure 2 A schematic cross-sectional view of a directional solidification apparatus used in the present invention; Figure 3 A schematic diagram of the directional solidification equipment used in the present invention with the support sleeve removed; Figure 4 This is a schematic diagram of the circulation channel in the directional solidification equipment used in the present invention.

[0019] The accompanying drawings are marked as follows: 1. Cooling pool; 11. Support plate; 12. Opening; 2. Cooling base; 21. Water inlet; 22. Water outlet; 23. Circulating channel; 3. First cooling water circulation pump; 31. Suction pipe; 32. Drain pipe; 4. Hopper; 41. Casting mouth; 5. Support sleeve; 6. Ingot mold; 7. Heating coil; 8. Cooling water pipe; 81. Water inlet pipe; 82. Water outlet pipe; 9. Second cooling water circulation pump. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand the solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts should fall within the scope of protection of the present invention.

[0021] like Figures 1 to 4As shown, the present invention discloses a pure copper directional solidification method, which adopts pure copper directional solidification equipment, wherein the pure copper directional solidification equipment includes a cooling pool 1, a cooling base 2, a first cooling water circulation pump 3, a hopper 4, a support sleeve 5, an ingot mold 6 and a second cooling water circulation pump 9. The cooling base 2, the first cooling water circulation pump 3 and the second cooling water circulation pump 9 are installed on the support plate 11 of the cooling pool 1, so that the overall structure is more compact and the occupied space is reduced. The ingot mold 6 is installed on the cooling base 2, and the ingot mold 6 is provided with a hopper 4, which is installed on the support sleeve 5. The hopper 4 is provided with a casting port 41, and the casting port 41 is located above the opening of the ingot mold 6, which is convenient for pouring copper liquid into the ingot mold 6. One end of the first cooling water circulation pump 3 is connected to the cooling pool 1 through a water pump 31, and the other end of the first cooling water circulation pump 3 is connected to the water inlet 21 of the cooling base 2 through a drain pipe 32. The cooling base 2 is connected to the cooling pool 1 through a water outlet 22 to realize the circulation of cooling water.

[0022] The cooling base 2 is provided with a spiral circulation channel 23. The water inlet 21 is located on the outer wall of the circulation channel 23, and the water outlet 22 is located at the center of the circulation channel 23. The cooling water returns to the cooling pool 1 through the water outlet 22. The spiral structure allows the cooling water to flow unimpeded within the circulation channel 23, avoiding turbulence or dead zones, ensuring uniform heat dissipation, reducing local thermal stress, and extending the service life of the cooling base 2. The spiral structure also disperses loads and thermal stresses, preventing local deformation of the cooling base 2. It can also adapt to the needs of heavy ingots, expanding its scope of application.

[0023] A plurality of groups of parallel heating coils 7 are provided on the outside of the ingot mold 6, and each group of heating coils 7 is provided with a control switch. The plurality of groups of heating coils 7 are arranged at intervals along the height direction of the ingot mold 6, so as to facilitate the separate control of the heating temperature of each group of heating coils 7, thereby adjusting the temperature at different heights outside the ingot mold 6 to ensure that the copper liquid solidifies directionally from bottom to top.

[0024] In this embodiment, three groups of heating coils 7 are provided. The heating coils 7 are arranged in the heating tube and wrapped around the outside of the ingot mold 6. The temperature of the ingot mold 6 is dynamically adjusted by multiple groups of heating coils 7 to ensure that the temperature on the outside of the ingot mold 6 is distributed in a gradient, further promoting the growth of columnar crystals and optimizing the mechanical properties. At the same time, it can inhibit the casting liquid from cooling and solidifying too quickly at the side wall of the ingot mold 6, ensuring uniform cooling of the casting liquid inside and outside.

[0025] Furthermore, multiple groups of parallel cooling water pipes 8 are provided on the outside of the ingot mold 6. The multiple groups of cooling water pipes 8 are spaced apart along the height direction of the ingot mold 6. A vertical water inlet pipe 81 and a water outlet pipe 82 are provided on one side of the ingot mold 6. The multiple groups of cooling water pipes 8 are connected to the water inlet pipe 81 and the water outlet pipe 82 respectively. The second cooling water circulation pump 9 draws water from the cooling pool 1 to the water inlet pipe 81. The cooling water enters the multiple groups of cooling water pipes 8 through the water inlet pipe 81 to cool the ingot mold 6. The cooling water then returns to the cooling pool 1 through the water outlet pipe 82 to achieve the circulation of cooling water and ensure the precise control of the temperature on the outside of the ingot mold 6. By arranging corresponding valves on different cooling water pipes 8, the temperature at different heights of the ingot mold 6 can be individually controlled, thereby improving the accuracy of temperature control.

[0026] In this embodiment, three groups of cooling water pipes 8 are provided, and the number and position of the cooling water pipes 8 correspond to the number and position of the heating coils 7. The cooperation between the cooling water pipes 8 and the heating coils 7 allows for more precise control of the temperature outside the ingot mold 6, achieving a gradient temperature distribution outside the ingot mold 6 and optimizing the mechanical properties of the casting.

[0027] In other optional embodiments, multiple turns of the heating coil 7 are provided in series, and multiple groups of cooling water pipes 8 are provided in parallel. The ingot mold 6 is heated by the heating coil 7. By controlling the flow rate and flow rate of water in the cooling water pipe 8 at different heights, the temperature outside the ingot mold 6 is distributed in a gradient, which can also achieve the effect of directional solidification of the copper liquid and reduce the complexity of control.

[0028] The cooling base 2 is made of pure copper. Pure copper has high thermal conductivity, further accelerating the heat dissipation of the ingot mold 6. The copper cooling base 2, in conjunction with the cooling water from the first cooling water circulating pump 3, creates a stable temperature gradient across the ingot mold 6, promoting columnar crystal growth and optimizing the mechanical properties of the casting.

[0029] Openings 12 are provided on both sides of the upper support plate 11 of the cooling pool 1. The cooling water in the cooling pool 1 dissipates heat through the openings 12, lowering the cooling water temperature and improving the directional solidification effect. The openings 12 also facilitate monitoring the amount of cooling water, allowing for timely addition of cooling water to ensure sufficient cooling water is available to cool the ingot mold 6. Furthermore, ice cubes can be added to the cooling pool 1 through the openings 12 to maintain the temperature of the coolant in the cooling pool 1 within a specified temperature range, ensuring effective cooling of the ingot mold 6. This is simple to operate and low in cost.

[0030] The pure copper directional solidification method of the present invention comprises the following steps: S10. Initial preparation: Use Fangyuan A-grade electrolytic copper, clean the copper beans and copper rust on the surface, use high-purity graphite crucible, and remove the residue inside the crucible; clean the dust and inclusions in the vacuum furnace, and there must be no oil stains and accumulated water.

[0031] The ingot mold 6 is coated with a coating such as an alcohol-based coating and zircon powder and held at 300-400°C for 12-18 hours to preheat the mold, remove moisture and volatiles, and prevent gases and impurities from entering the molten copper, ensuring ingot quality. An ingot is a block of metal of a defined shape and size formed by pouring molten metal or alloy into a mold of a specific shape and allowing it to cool and solidify.

[0032] During operation, the graphite crucible and the ingot mold 6 are both located in the vacuum furnace, so that they are always in a vacuum atmosphere, which is conducive to removing gases such as hydrogen and oxygen dissolved in the molten copper, thereby reducing or avoiding the formation of defects such as pores inside the casting and improving the quality of the ingot.

[0033] S20, smelting: melting the electrolytic copper into molten copper in a vacuum atmosphere, wherein the vacuum degree is -0.1 MPa; S21. Cover the bottom of the vacuum furnace with sufficient calcined charcoal, place the electrolytic copper in a graphite crucible, raise the temperature to 1100°C-1300°C, and melt all the electrolytic copper into molten copper; S22, add calcium boride to the graphite crucible, raise the temperature of the graphite crucible to 1350-1500 ℃ and keep it warm for 15min-20min, and deoxidize and dehydrogenate the molten copper. Calcium boride can effectively remove oxygen from the copper liquid. At high temperatures, boron and oxygen have a strong affinity and can combine the oxygen dissolved in the copper liquid to form boron oxide, thereby reducing the oxygen content in the copper liquid and improving the quality of the copper. Under a vacuum environment, the gas dissolved in the molten metal escapes more easily, thereby reducing defects such as pores that may occur in the casting and improving the quality of the ingot.

[0034] Among them, 100g-150g of calcium boride is added to melt 3t of copper liquid to ensure the deoxidation effect.

[0035] S30, pouring: S31: Start the first cooling water circulation pump 3 to flow cooling water through the circulation channel 23 within the cooling base 2, cooling the ingot mold 6 on the cooling base 2. The cooling water drawn by the first cooling water circulation pump 3 has a flow rate of 15m / s-23m / s, cooling the cooling base 2 and the bottom of the ingot mold 6. The circulation channel 23 on the cooling base 2 achieves forced unidirectional heat dissipation from the bottom of the ingot mold 6, forming a stable temperature gradient, promoting columnar crystal growth, and optimizing mechanical properties.

[0036] S32: Pour molten copper into the ingot mold 6 and start the heating coil 7, which is provided with multiple coils in parallel along the height direction of the ingot mold 6; the temperature of the ingot mold 6 is dynamically adjusted by multiple sets of heating coils 7 to ensure that the temperature outside the ingot mold 6 is distributed in a gradient, further promoting the growth of columnar crystals and optimizing mechanical properties. At the same time, it can inhibit the casting liquid from cooling and solidifying too quickly at the side wall of the ingot mold 6, ensuring uniform cooling inside and outside the casting liquid. By providing multiple coils of heating coils 7 on the ingot mold 6, the temperature of the ingot mold 6 is dynamically adjusted to achieve a gradient temperature distribution of the ingot mold 6, achieving directional sequential solidification, and thus obtaining better mechanical properties, strength, and toughness.

[0037] Further, the second cooling water circulation pump 9 is started, and the cooling water cools the ingot mold 6 through the cooling water pipe 8. The cooling water pipe 8 is provided with multiple turns in parallel along the height direction of the ingot mold 6. The first cooling water circulation pump 3 and the second cooling water circulation pump 9 extract cooling water from the cooling pool 1. The temperature of the cooling water in the cooling pool 1 is 5°C-10°C. Through the cooperation of the cooling water pipe 8 and the heating coil 7, the temperature outside the ingot mold 6 can be controlled more accurately, and the temperature outside the ingot mold 6 is distributed in a gradient, thereby optimizing the mechanical properties of the casting. By arranging the cooling water pipe 8 in parallel on the ingot mold 6, the temperature of the ingot mold 6 is assisted to be regulated, and the temperature at a certain height of the ingot mold 6 is adjusted separately, ensuring that the temperature of the ingot mold 6 is distributed in a gradient, and ensuring the effect of directional solidification of the copper liquid. At the same time, by arranging multiple turns of heating coil 7 and multiple turns of cooling water pipe 8 on the outside of the ingot mold 6, the situation of excessive cooling of the side of the ingot mold 6 can be suppressed, the quality of the ingot surface can be improved, the surface roughness or other surface defects caused by the difference in cooling rate can be reduced, and the quality of the ingot can be further improved.

[0038] S40, pouring completed: let the molten copper stand in the ingot mold 6 for 120-180 minutes to obtain a directionally solidified copper ingot. The molten copper slowly solidifies from the bottom upwards, which is conducive to forming a columnar crystal structure and reducing the equiaxed crystal area, thereby improving the mechanical properties and electrical conductivity of the material. The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for directional solidification of pure copper, characterized in that: The following steps are involved: S10, initial preparation: preheating the ingot mold at a temperature of 300°C-400°C for 12h-18h; S20, smelting: melting the electrolytic copper into molten copper in a vacuum atmosphere; S30, pouring: S31: starting a first cooling water circulation pump to allow cooling water to flow through a circulation channel in the cooling base to cool the ingot mold on the cooling base; S32: pouring molten copper into the ingot mold and starting a heating coil, wherein the heating coil is provided with multiple turns along the height direction of the ingot mold; S40, pouring completed: the molten copper is allowed to stand in the ingot mold for 120-180 minutes to obtain a directionally solidified copper ingot.

2. The pure copper directional solidification method according to claim 1, characterized in that: Step S20 includes S21 , placing electrolytic copper into a graphite crucible, heating the crucible to 1100° C.-1300° C., and melting all the electrolytic copper into molten copper.

3. The pure copper directional solidification method according to claim 2, characterized in that: After step S21, the method includes step S22, adding calcium boride into the graphite crucible, raising the temperature of the graphite crucible to 1350-1500° C. and keeping the temperature for 15-20 minutes, and performing deoxidation and dehydrogenation treatment on the molten copper.

4. The pure copper directional solidification method according to claim 1, characterized in that: Step S32 also includes starting a second cooling water circulation pump, and cooling water cools the ingot mold through a cooling water pipe, and the cooling water pipe is provided with multiple circles in parallel along the height direction of the ingot mold.

5. The pure copper directional solidification method according to claim 1, characterized in that: The flow rate of the cooling water pumped by the first cooling water circulation pump is 15m / s-23m / s.

6. The pure copper directional solidification method according to claim 4, characterized in that: The first cooling water circulation pump and the second cooling water circulation pump draw cooling water from a cooling pool, and the temperature of the cooling water in the cooling pool is 5°C-10°C.

7. The pure copper directional solidification method according to claim 1, characterized in that: The circulation channel is spiral-shaped, a water inlet is provided on the side wall of the circulation channel, and a water outlet is provided at the center of the circulation channel.

8. The pure copper directional solidification method according to claim 1, characterized in that: The heating coil is provided with a plurality of turns in series or in parallel along the height direction of the ingot mold.

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