CN111118421A - Method for eliminating transverse grain boundary of high-conductivity pure copper wire - Google Patents
Method for eliminating transverse grain boundary of high-conductivity pure copper wire Download PDFInfo
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- CN111118421A CN111118421A CN202010047003.6A CN202010047003A CN111118421A CN 111118421 A CN111118421 A CN 111118421A CN 202010047003 A CN202010047003 A CN 202010047003A CN 111118421 A CN111118421 A CN 111118421A
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22F—CHANGING THE PHYSICAL STRUCTURE OF NON-FERROUS METALS AND NON-FERROUS ALLOYS
- C22F1/00—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working
- C22F1/08—Changing the physical structure of non-ferrous metals or alloys by heat treatment or by hot or cold working of copper or alloys based thereon
Abstract
The invention discloses a method for eliminating transverse grain boundary of a high-conductivity pure copper wire, which comprises the following steps: drawing a pure copper wire blank for electricians to 3mm, then carrying out intermediate annealing at 550-650 ℃, then drawing to below 1mm, carrying out stress relief annealing at 260-300 ℃, carrying out directional heat treatment on the obtained sample, setting the temperature of a hot zone to be 550-850 ℃, the drawing rate to be 3-100 mu m/s, and the temperature gradient at the front end of the hot zone to be more than or equal to 30 ℃/mm. The method adopts a directional heat treatment method to ensure that fine isometric crystals in the initial pure copper wire selectively grow along the heat flow direction to obtain a columnar crystal structure, eliminate transverse crystal boundaries, reduce the resistivity, weaken the capacitance-inductance effect and improve the conductivity, and meanwhile, the method has the advantages of simple process, good controllability, low consumption, high efficiency, energy conservation, environmental protection, suitability for large-scale production and the like.
Description
Technical Field
The invention relates to a metal material processing method, in particular to a method for eliminating transverse grain boundary of a high-conductivity pure copper wire.
Background
The pure copper wire has excellent conductivity and is widely applied to the fields of electricity, electronics and the like. With the progress of high and new technologies, electronic devices such as transformers, generators and the like, printed circuit boards, integrated circuits and the like, have been developed towards miniaturization and precision, and higher requirements are put forward on the conductivity of the wires. The method for improving the purity of the conducting wire is adopted to improve the conducting performance of the conducting wire before the 80 th of the 20 th century, but the purity of the conducting wire quickly reaches the limit, so that the improvement of the internal structure becomes a new way for improving the conducting performance of the pure copper conducting wire. Researches show that the resistivity is greatly increased by a transverse grain boundary in a pure copper wire, a capacitance inductance effect is formed, and high-frequency signal transmission is distorted. The pure copper wire with the columnar crystal structure is mainly produced by a hot continuous casting method at present, but the diameter of the cast pure copper wire is usually 4-8 mm, and the pure copper wire needs to be subjected to drawing deformation before practical application, so that the columnar crystal structure can be damaged, and the conductivity is reduced.
Disclosure of Invention
The invention aims to provide a method for eliminating transverse grain boundaries of a high-conductivity pure copper wire, which is used for carrying out directional heat treatment on a fine-diameter polycrystalline pure copper wire subjected to drawing deformation, so that the grain can grow directionally to obtain a columnar crystal structure, the transverse grain boundaries are eliminated, and the conductivity is improved.
The purpose of the invention is realized by the following technical scheme: a method for eliminating transverse grain boundary of high-conductivity pure copper wire is characterized in that an electrician pure copper wire blank is subjected to intermediate annealing at 550-650 ℃ after being greatly drawn to 3mm, then is subjected to intermediate drawing to below 1mm, is subjected to stress relief annealing at 260-300 ℃, is subjected to directional heat treatment, and has a hot zone temperature of 550-850 ℃, a drawing rate of 3-100 mu m/s and a temperature gradient at the front end of the hot zone of more than or equal to 30 ℃/mm.
Preferably, electrician pure copper wire blanks are low-oxygen copper rods with the diameter of 8mm and the mark T1M 20.
Preferably, before the directional heat treatment, the sample is ultrasonically cleaned with acetone twice, each time for 10-15 min, and then ultrasonically cleaned with absolute ethyl alcohol for 20 min.
Preferably, the specific process of the directional heat treatment is as follows:
1) putting the cleaned sample into a ceramic crucible and fixing the ceramic crucible at the upper end of a drawing rod, wherein the drawing rod is connected with a servo motor, and the temperature gradient is controlled by adjusting the distance between a graphite heating element and the Ga-In-Sn alloy cooling liquid level to ensure that the temperature gradient at the front end of a hot zone is more than or equal to 30 ℃/mm;
2) the furnace door is closed and the vacuum pump is started, so that the vacuum degree in the furnace is reduced to 10-3Pa below;
3) starting a heating power supply, keeping the temperature for 3-8 min after the temperature of a hot zone reaches 550-850 ℃, and then starting a servo motor to enable a sample to move from bottom to top at a drawing speed of 3-100 mu m/s;
4) after the primary directional heat treatment is finished, the directional heat treatment process can be repeated as needed.
Compared with the prior art, the invention has the following beneficial effects:
(1) according to the invention, the pure copper wire with the diameter smaller than 1mm after the drawing deformation is subjected to the directional heat treatment, so that the oriented growth of crystal grains is realized, the transverse crystal boundary is eliminated, the conductivity is improved, and the subsequent drawing deformation is avoided.
(2) Compared with the hot continuous casting method, the directional heat treatment carries out zone heating below the melting point of the sample, thereby greatly reducing energy consumption and production cost.
(3) The method has good controllability and simple operation, and is suitable for industrial mass production. Can be directly applied to the continuous drawing and continuous annealing process, and improves the production efficiency.
Drawings
FIG. 1 is a microstructure diagram of a stress relief annealing after being drawn to 1mm and 0.85mm in a low-oxygen copper rod of 8mmT1M20 type diameter according to the present invention, and equiaxed crystals are fine.
FIG. 2 is a microstructure of the pure copper wire of example 1 after directional heat treatment at a hot zone temperature of 850 deg.C, a temperature gradient of 30 deg.C/mm, and a drawing rate of 55 μm/s, and the aspect ratio of the columnar crystal is 6.
FIG. 3 is a microstructure of a pure copper wire of example 2 after an oriented heat treatment at a hot zone temperature of 850 deg.C, a temperature gradient of 30 deg.C/mm, and a drawing rate of 45 μm/s, and a columnar aspect ratio of 5.
FIG. 4 is a microstructure of the pure copper wire of example 3 after directional heat treatment at a hot zone temperature of 550 deg.C, a temperature gradient of 30 deg.C/mm, and a drawing rate of 35 μm/s, and the aspect ratio of the columnar crystals is 3.5.
FIG. 5 is a microstructure of the pure copper wire of example 4 after the directional heat treatment at a hot zone temperature of 550 deg.C, a temperature gradient of 30 deg.C/mm, and a drawing rate of 25 μm/s, and the aspect ratio of the columnar crystals is 3.
FIG. 6 is a microstructure of the pure copper wire of comparative example 1 after the directional heat treatment at a hot zone temperature of 550 deg.C, a temperature gradient of 30 deg.C/mm, and a drawing rate of 5 μm/s, and the equiaxed grains are coarse.
FIG. 7 is a microstructure of the pure copper wire of comparative example 2 after the directional heat treatment at a hot zone temperature of 550 deg.C, a temperature gradient of 30 deg.C/mm, and a drawing rate of 55 μm/s, and the equiaxed crystal is small.
FIG. 8 is a microstructure of the pure copper wire of comparative example 3 after the directional heat treatment at a hot zone temperature of 850 deg.C, a temperature gradient of 30 deg.C/mm, and a drawing rate of 45 μm/s, showing a large equiaxial crystal.
FIG. 9 is a microstructure of the pure copper wire of comparative example 4 after the directional heat treatment at a hot zone temperature of 550 deg.C, a temperature gradient of 30 deg.C/mm, and a drawing rate of 25 μm/s, showing small equiaxial crystals.
Fig. 10 is a graph showing the change in resistivity of the pure copper wires of examples 1 to 4, comparative example 1 and comparative example 2 after stress relief annealing of the pure copper wires having a diameter of 0.85 mm.
Detailed Description
The present invention is further illustrated by the following examples.
The diameter of the 8 mm-brand T1M20 low-oxygen copper rod is greatly drawn to 3mm, then the middle annealing is carried out at 550-650 ℃, then the middle drawing is carried out to 0.6-1 mm, and then the stress relief annealing is carried out at 260-300 ℃, wherein figure 1 is a microstructure diagram of the T1M20 low-oxygen copper rod which is drawn to the diameter of 0.85mm and the stress relief annealing is carried out at 1 mm. Cutting the sample into 150mm length, ultrasonically cleaning the sample twice with acetone for 10-15 min each time, and then ultrasonically cleaning the sample with absolute ethyl alcohol for 20 min.
Example 1:
the specific method for eliminating the transverse grain boundary of the high-conductivity pure copper wire comprises the following steps:
1) a sample with the diameter of 0.85mm is put into a ceramic crucible and then fixedly connected to the upper end of a pulling rod. Adjusting the liquid level height of the Ga-In-Sn alloy to ensure that the temperature gradient of the front end of the hot zone is 30 ℃/mm when the temperature of the hot zone is 850 ℃;
2) closing the furnace door and starting the vacuum pump to make the vacuum degree in the furnace lower than 10-3Pa；
3) And starting a heating power supply to raise the temperature, raising the temperature of the hot zone to 850 ℃, keeping the temperature for 5min, starting a servo motor, and moving the sample from bottom to top along with the drawing rod at the speed of 55 mu m/s.
Fig. 2 is a microstructure of a pure copper wire after directional heat treatment. It can be seen that a columnar grain boundary structure with an aspect ratio of 6 appears in the pure copper wire after the directional heat treatment.
Example 2:
the specific method for eliminating the transverse grain boundary of the high-conductivity pure copper wire comprises the following steps:
1) a sample with the diameter of 0.85mm is put into a ceramic crucible and then fixedly connected to the upper end of a pulling rod. Adjusting the liquid level height of the Ga-In-Sn alloy to ensure that the temperature gradient of the front end of the hot zone is 30 ℃/mm when the temperature of the hot zone is 850 ℃;
2) closing the furnace door and starting the vacuum pump to make the vacuum degree in the furnace lower than 10-3Pa；
3) And starting a heating power supply to raise the temperature, raising the temperature of the hot zone to 850 ℃, keeping the temperature for 5min, starting a servo motor, and moving the sample from bottom to top along with the drawing rod at the speed of 45 mu m/s.
Fig. 3 is a microstructure of a pure copper wire after directional heat treatment. It can be seen that a columnar grain boundary structure with an aspect ratio of 5 appears in the pure copper wire after the directional heat treatment.
Example 3:
the specific method for eliminating the transverse grain boundary of the high-conductivity pure copper wire comprises the following steps:
1) a sample with the diameter of 0.85mm is put into a ceramic crucible and then fixedly connected to the upper end of a pulling rod. Adjusting the liquid level height of the Ga-In-Sn alloy to ensure that the temperature gradient of the front end of the hot zone is 30 ℃/mm when the temperature of the hot zone is 550 ℃;
2) closing the furnace door and starting the vacuum pump to make the vacuum degree in the furnace lower than 10-3Pa；
3) And starting a heating power supply to raise the temperature, raising the temperature of the hot zone to 550 ℃, keeping the temperature for 5min, starting a servo motor, and moving the sample along with the drawing rod from bottom to top at the speed of 35 mu m/s.
Fig. 4 is a microstructure of a pure copper wire after directional heat treatment. It can be seen that a columnar grain boundary structure with an aspect ratio of 3.5 appears in the pure copper wire after the directional heat treatment.
Example 4:
the specific method for eliminating the transverse grain boundary of the high-conductivity pure copper wire comprises the following steps:
1) a sample with the diameter of 0.85mm is put into a ceramic crucible and then fixedly connected to the upper end of a pulling rod. Adjusting the liquid level height of the Ga-In-Sn alloy to ensure that the temperature gradient of the front end of the hot zone is 30 ℃/mm when the temperature of the hot zone is 550 ℃;
2) closing the furnace door and starting the vacuum pump to make the vacuum degree in the furnace lower than 10-3Pa；
3) And starting a heating power supply to raise the temperature, raising the temperature of the hot zone to 550 ℃, keeping the temperature for 5min, starting a servo motor, and moving the sample along with the drawing rod from bottom to top at the speed of 25 mu m/s.
Fig. 5 is a microstructure view of a pure copper wire after directional heat treatment. It can be seen that a columnar grain boundary structure with an aspect ratio of 3 appears in the pure copper wire after the directional heat treatment.
Comparative example 1:
the same as the step of the example 3, only the pulling rate is changed to 5 μm/s, the pulling rate is slower, the directional growth capability of the crystal grains is weakened, and the pure copper wire obtains larger equiaxed crystals after directional heat treatment, as shown in figure 6.
Comparative example 2:
as with the step of example 3, only the pulling rate is changed to 55 μm/s, the pulling rate is faster, the heating time of the crystal grain is short and the crystal grain is not too large, and the pure copper wire obtains smaller equiaxed crystal after the oriented heat treatment, as shown in FIG. 7.
Comparative example 3:
as in the case of example 2, only the diameter of the pure copper wire was changed to 1mm, and a large equiaxed crystal was obtained after the directional heat treatment, as shown in FIG. 8.
Comparative example 4:
as in the case of example 4, only the diameter of the pure copper wire was changed to 1mm, and a small equiaxed crystal was obtained after the orientation heat treatment, as shown in FIG. 9.
FIG. 10 is a graph showing the resistivity of pure copper wires of examples 1 to 4, comparative example 1 and comparative example 2, which decreases as the aspect ratio of columnar crystals increases, after stress relief annealing of the pure copper wires having a diameter of 0.85 mm.
Claims (4)
1. A method for eliminating transverse grain boundaries of a high-conductivity pure copper wire is characterized in that a pure copper wire blank for electricians is subjected to intermediate annealing at 550-650 ℃ after being drawn to 3mm, then is drawn to below 1mm, is subjected to stress relief annealing at 260-300 ℃, and is subjected to directional heat treatment, the temperature of a hot zone is set to be 550-850 ℃, the drawing rate is 3-100 mu m/s, and the temperature gradient of the front end of the hot zone is larger than or equal to 30 ℃/mm.
2. The method of claim 1, wherein electrician pure copper wire billets are formed from low-oxygen copper rods having a diameter of 8mm and a designation T1M 20.
3. The method of claim 1, wherein the sample is ultrasonically cleaned with acetone twice each for 10-15 min and then with absolute ethanol for 20min before the directional heat treatment.
4. The method of claim 1, wherein the directional heat treatment is carried out by:
1) putting the cleaned sample into a ceramic crucible and fixing the ceramic crucible at the upper end of a drawing rod, wherein the drawing rod is connected with a servo motor, and the temperature gradient is controlled by adjusting the distance between a graphite heating element and the Ga-In-Sn alloy cooling liquid level to ensure that the temperature gradient at the front end of a hot zone is more than or equal to 30 ℃/mm;
2) the furnace door is closed and the vacuum pump is started, so that the vacuum degree in the furnace is reduced to 10-3Pa below;
starting a heating power supply, keeping the temperature for 3-8 min after the temperature of a hot zone reaches 550-850 ℃, and then starting a servo motor to enable a sample to move from bottom to top at a drawing speed of 3-100 mu m/s;
3) after the primary directional heat treatment is finished, the directional heat treatment process is repeated as required.
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Citations (7)
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| US4372789A (en) * | 1980-08-07 | 1983-02-08 | General Electric Company | Directionally strengthened copper alloy parts for a gas turbine |
| JPS6369953A (en) * | 1986-09-11 | 1988-03-30 | Kobe Steel Ltd | Manufacture of aluminum alloy excellent in directionality |
| CN1562514A (en) * | 2004-03-18 | 2005-01-12 | 上海交通大学 | Method for preparing superfine filament from metal and alloy material |
| CN100999793A (en) * | 2007-01-12 | 2007-07-18 | 焦作市森格高新材料有限责任公司 | High strength, high electroconductive copper alloy material and preparation tech. thereof |
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2020
- 2020-01-16 CN CN202010047003.6A patent/CN111118421A/en active Pending
Patent Citations (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US4372789A (en) * | 1980-08-07 | 1983-02-08 | General Electric Company | Directionally strengthened copper alloy parts for a gas turbine |
| JPS6369953A (en) * | 1986-09-11 | 1988-03-30 | Kobe Steel Ltd | Manufacture of aluminum alloy excellent in directionality |
| CN1562514A (en) * | 2004-03-18 | 2005-01-12 | 上海交通大学 | Method for preparing superfine filament from metal and alloy material |
| CN100999793A (en) * | 2007-01-12 | 2007-07-18 | 焦作市森格高新材料有限责任公司 | High strength, high electroconductive copper alloy material and preparation tech. thereof |
| CN101524721A (en) * | 2008-03-19 | 2009-09-09 | 兰州理工大学 | Method for preparing single-crystal copper bonding wire |
| CN108486512A (en) * | 2018-03-01 | 2018-09-04 | 南京理工大学 | A kind of tissue orientation method without transverse grain boundaries copper conductor |
| CN109112349A (en) * | 2018-10-25 | 2019-01-01 | 哈尔滨工程大学 | A kind of CuAlMn marmem and preparation method thereof |
Non-Patent Citations (3)
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| 王鑫等: "定向凝固纯铜组织性能研究", 《西安工业大学学报》 * |
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