A tungsten alloy wire, its preparation method and application

Abstract

The present invention relates to the technical field of tungsten alloy materials, and particularly relates to a tungsten alloy wire and a preparation method and application thereof. In terms of mass fraction, the components of the tungsten alloy include: 0.3-0.75 wt% of element L, 0.001-0.18% of oxygen element, and the balance is tungsten element and inevitable impurities; wherein, L is one or more of lanthanum, cerium, praseodymium, neodymium, gadolinium, and erbium; the wire diameter of the wire is 0.3-0.6 mm; and in the wire, the average radial width of the tungsten fibers is ≤0.4 μm; the number of cracks per 100 meters of flaw detection on the surface of the wire is ≤5. The tungsten alloy wire provided by the present invention has finer internal tungsten fibers, the tungsten fibers are effectively strengthened and the density is improved, and the flaw detection number on the surface of the tungsten alloy wire is small; the effective strengthening of the internal tungsten fibers and the improvement of the density enable the medium-temperature breaking force, medium-temperature creep resistance and winding performance of the wire to be improved; therefore, when it is used as a tungsten wire rope for pulling single crystal silicon, both the reliability and the service life are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of tungsten alloy materials, and particularly relates to a tungsten alloy wire and its preparation method and application. Background Art

[0002] With the rapid development of the semiconductor industry and the photovoltaic industry, the demand for high-purity monocrystalline silicon is also increasing day by day. At the same time, the material requirements for the raw material monocrystalline silicon are getting higher and higher. Currently known ropes used for pulling monocrystalline silicon in a monocrystalline silicon growth furnace include steel wires, pure tungsten wires, potassium-doped tungsten wires, etc. There are also a small number of customers using tungsten rhenium wires as raw materials for tungsten ropes.

[0003] During the use of the rope for pulling monocrystalline silicon, the highest temperature in the monocrystalline silicon furnace reaches 1500 °C or even higher. However, the rope is located near the upper end inside the furnace and is affected by the radiant heat inside the furnace. The temperature of the rope fluctuates between 900 and 1300 °C. At the same time, since the rope is in a continuous repeated lifting process, therefore, it is required that the rope for pulling monocrystalline silicon has good breaking retention force in the range of 900 to 1300 °C, and at the same time, it is required to have a low creep displacement at this temperature to avoid large elongation of the tungsten rope and resulting in wire breakage.

[0004] In the prior art, steel ropes are often used for pulling monocrystalline silicon. The steel ropes themselves contain Fe and C contents, resulting in excessive crystal impurity elements and seriously affecting their purity. In addition, due to the high temperature of 1500 °C inside the monocrystalline silicon furnace and the continuous increase in the self-weight of the monocrystalline silicon, the tensile force of the traditional steel rope will rapidly decrease at high temperatures. Its medium-temperature creep resistance and breaking force are insufficient (that is, the load-bearing capacity of the rope at high temperatures is poor). Limited by this, the traditional steel rope is difficult to effectively pull the monocrystalline silicon. Therefore, it is necessary to design a tungsten rope to meet the above requirements.

[0005] Currently, the tungsten ropes used in known crystal growth high-temperature furnaces use potassium-doped tungsten wires or pure tungsten wires. With the continuous increase in the weight of the silicon ingot, the high-temperature creep resistance and high-temperature load-bearing weight required for the tungsten rope are insufficient, resulting in phenomena such as loose wires, broken wires, and broken strands of the tungsten wire, and even major quality problems such as dropping of the ingot. Specifically, the breaking retention force of pure tungsten wire and potassium-doped tungsten wire is insufficient in a medium-temperature environment (the tensile strength of potassium-doped tungsten wire at medium temperature is only about 42% of that at room temperature), resulting in insufficient load-bearing capacity of the rope and limited application as the weight of the silicon ingot increases.

[0006] In addition, as the size of the crystal growth furnace continues to increase, the diameter requirement for the tungsten wire rope also further increases. However, the winding performance of potassium-doped tungsten wire and tungsten-rhenium wire at room temperature is insufficient (the number of wire breaks during the winding of 100,000 meters of potassium-doped tungsten wire and tungsten-rhenium wire is greater than or equal to 4 times), and the tungsten wire fibers with a diameter of φ0.3 - 0.6 mm and above are not well-developed, resulting in brittle cracking or splitting during the winding process and a relatively high wire breakage rate during the rope braiding process, thus affecting the winding stability of the tungsten wire rope. Moreover, the defect sources generated during the winding process will further expand in a heating environment, leading to insufficient service life of the tungsten wire rope or even wire breakage problems during use.

[0007] Therefore, based on the application requirements of the ropes for single-crystal silicon pulling, how to develop a wire with fewer surface crack points, good intermediate-temperature creep resistance, good high-temperature tensile fracture resistance, and easy to braid without wire breakage is exactly the technical problem that those skilled in the art are committed to solving. Summary of the Invention

[0008] To solve the deficiencies of the prior art mentioned in the background art, the present invention provides a tungsten alloy wire, and its technical solution is as follows:

[0009] By mass fraction, the components of the tungsten alloy include: 0.3 - 0.75 wt% of element L, 0.001 - 0.18% of oxygen element, and the balance is tungsten element and unavoidable impurities;

[0010] Among them, L is one or more of lanthanum, cerium, praseodymium, neodymium, gadolinium, and erbium;

[0011] The wire diameter of the wire is 0.3 - 0.6 mm; and in the wire, the average radial width of the tungsten fibers is ≤0.4 μm; the number of surface flaw points per 100 meters of the wire is ≤5.

[0012] In some embodiments, the number of wire breaks during the winding of 100,000 meters of the wire is ≤3 times.

[0013] In some embodiments, the ratio of the wire breaking force of the wire at a heating temperature of 1000 °C to the wire breaking force at room temperature is ≥50%; and the creep rate of the wire is ≤0.6 mm / min.

[0014] The present invention also provides a method for preparing the tungsten alloy wire as described above, which successively includes the following preparation steps: reducing to prepare blue tungsten powder, doping, reducing to prepare alloy powder, mixing powders, powder pressing and pre-sintering, high-temperature sintering, cogging, hot working, and drawing to form a wire of the required specification; wherein, the process of reducing to prepare blue tungsten powder is: feeding ammonium paratungstate into a reduction furnace, and continuously reducing it under the protection of hydrogen and nitrogen at 400-600°C to obtain blue tungsten powder; wherein, the thickness of the ammonium paratungstate powder layer is ≤10 mm, the hydrogen flow rate in the reduction furnace is 20-40 L / min, the nitrogen flow rate is 80-160 L / min, the oxygen index of the blue tungsten powder is 2.85±0.03, and the content of the ammonium tungsten bronze phase is >60%.

[0015] In some embodiments, the powder pressing and pre-sintering process is: by isostatic pressing, pressing the mixed powder into a green compact, and performing low-temperature pre-sintering on the green compact at 1000-1400°C for 15-30 minutes in a hydrogen atmosphere to obtain a pre-sintered billet; the process of high-temperature sintering is: subjecting the pre-sintered billet to electric sintering, and the sintering is carried out in two stages. After the first sintering at a current intensity of 58-62% of the tungsten bar fusing current for 30-45 minutes, the temperature is lowered. The second sintering is carried out at a current intensity of 90%-92% of the tungsten bar fusing current for 40-80 minutes to obtain a sintered billet with a density of 18.4-18.8 g / cm 3 The tungsten bar fusing current is the maximum current that the pre-sintered billet can pass through when it fuses.

[0016] In some embodiments, the conditions of the isostatic pressing process are: by isostatic pressing, pressing the mixed powder into a green compact with a single weight of 1.5-5.0 kg under a pressure of 140-240 MPa; the second sintering is carried out in a hydrogen atmosphere, and the purity of the hydrogen is ≥99%.

[0017] In some embodiments, the process of the cogging step is: using a multi-roll rolling mill to cog the sintered billet obtained by high-temperature sintering into an alloy rod with a diameter of 8.0-12.0 mm; the hot working process is: annealing the alloy rod with a diameter of 8.0-12.0 mm by recrystallization annealing, and then forging it through a multi-pass continuous swaging device to obtain an alloy rod with a diameter of 2.5-4.0 mm; the drawing process is: the alloy rod with a diameter of 2.5-4.0 mm is drawn through different specifications of wire drawing dies, and the drawing reduction ratio of multiple drawing passes is 35%-60%. Among them, the drawing force of the last pass needs to reach 60%-70% of the room-temperature breaking force of the finally obtained tungsten alloy wire to obtain tungsten alloy wires with different diameter specifications.

[0018] In some embodiments, the doping process is as follows: soaking blue tungsten powder in a nitrate solution formed by element L, stirring evenly, and then evaporating to dryness to obtain doped blue tungsten powder; the process of reducing to prepare alloy powder is: reducing the doped blue tungsten powder in a hydrogen reduction furnace at 600-1000°C to form alloy powder with a particle size of 1.5-5μm; the process of powder mixing is: mixing the alloy powder to form a mixed powder; the process of blooming is: continuously rolling with a multi-roll mill at a heating temperature of 1600-1700°C to bloom a sintered billet with a diameter of 15-25mm into an alloy rod with a diameter of 8.0-12.0mm; the process of pressure processing is: heating the alloy rod with a diameter of 8.0-12.0mm to 2000-2600°C for recrystallization annealing, and then forging with a pass-through continuous rotary forging device to obtain an alloy rod with a diameter of 2.5-4.0mm.

[0019] The present invention also provides an application of the tungsten alloy wire as described above in a single crystal silicon pulling rope.

[0020] The present invention also provides an application of the tungsten alloy wire as described above in the fields of cutting, cut-resistant protection, cables, screen printing, ropes or textiles.

[0021] Compared with the prior art, the tungsten alloy wire provided by the present invention has the following advantages:

[0022] For the tungsten alloy wire provided by the present invention, the internal tungsten fibers are finer, the tungsten fibers are effectively strengthened and the density is improved, and the number of flaw detections on the surface of the tungsten alloy wire is small; the internal tungsten fibers are effectively strengthened and the density is improved, so that the medium-temperature breaking force, medium-temperature creep resistance and winding performance of the wire are improved; its high medium-temperature breaking force, good medium-temperature creep resistance and good winding performance make its reliability and service life both improved when used as a tungsten wire rope for single crystal silicon pulling. Description of the Drawings

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0024] Figure 1 It is a schematic diagram of the measurement method of the radial average width of the tungsten fibers provided by the present invention;

[0025] Figure 2 It is a graph showing the morphology display of tungsten grains and the statistical data of the width of tungsten grains in Example 1 provided by the present invention;

[0026] Figure 3 Schematic diagram of the wire winding structure of the present invention.

[0027] Reference signs in the drawings: 1 Tungsten alloy wire, 10 Tungsten fibers. Detailed implementation manners

[0028] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0029] The present invention provides a tungsten alloy wire, and the solution is as follows:

[0030] By mass fraction, the tungsten alloy components include: 0.3 - 0.75 wt% of element L, 0.001 - 0.18% of oxygen element, and the balance is tungsten element and inevitable impurities;

[0031] Wherein, L is one or more of lanthanum, cerium, praseodymium, neodymium, gadolinium, erbium; for example, L is lanthanum, or cerium, or praseodymium, or neodymium, or gadolinium, or erbium; or lanthanum and cerium, lanthanum and neodymium, lanthanum and praseodymium, lanthanum and gadolinium, cerium and neodymium, cerium and praseodymium, cerium and gadolinium, cerium and neodymium, neodymium and praseodymium, etc.;

[0032] The wire diameter of the wire is 0.3 - 0.6 mm; for example, the wire diameter of the wire is 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm, 0.5 mm, 0.55 mm, etc., and for another example, 0.3 - 0.35 mm, 0.35 - 0.4 mm, 0.4 - 0.45 mm, 0.45 - 0.5 mm, 0.5 - 0.55 mm, 0.55 - 0.6 mm, etc.; the tungsten alloy wire can be uniform, or can be incompletely uniform, and can also contain, for example, a difference of several percentages such as 2% according to different parts;

[0033] In the wire, the radial average width of the tungsten fibers is ≤ 0.4 μm; for example, the radial average width of the tungsten fibers is 0.1 μm, 0.2 μm, 0.3 μm, 0.35 μm, 0.4 μm, etc.;

[0034] The number of cracks per 100 meters on the surface of the wire for flaw detection is ≤ 5; for example, the number of cracks per 100 meters for flaw detection is 0.5, 1, 1.5, etc., and for another example, ≤ 3, ≤ 2, ≤ 1, ≤ 0.5, etc.

[0035] The number of wire breaks when the wire is wound for 100,000 meters is ≤ 3 times. For example, the number of wire breaks when the wire is wound for 100,000 meters is 2 times, 1 time, 0.5 times, etc., and for another example, ≤ 2 times, ≤ 1 time, ≤ 0.5 times, etc.

[0036] The ratio of the wire breaking force of the wire at a heating temperature of 1000°C to the wire breaking force at room temperature is ≥ 50%; for example, the ratio is 55%, 60%, 65%, etc., and for another example, ≥ 55%, ≥ 60%, ≥ 65%, etc. The creep rate of the wire is ≤ 0.6 mm / min; for example, the creep rate is 0.55 mm / min, 0.5 mm / min, 0.4 mm / min, 0.3 mm / min, etc., and for another example, ≤ 0.55 mm / min, ≤ 0.5 mm / min, ≤ 0.4 mm / min, ≤ 0.3 mm / min, etc.

[0037] It should be noted that:

[0038] The inevitable impurities described in this article are: other elements inevitably introduced during the preparation process;

[0039] The "radial width" described in this article refers to the size of the tungsten fiber in the wire along the radial direction of the wire. Among them, the axial direction refers to the axis direction extending along the length direction of the wire, and the radial direction is perpendicular to the axial direction; for the detection and measurement methods of the average radial width of the tungsten fiber, please refer to the test method content in the embodiments of this article;

[0040] The meaning of "number of fracture points per 100 meters for flaw detection" in this article is: the number of fracture points detected in every 100 meters of tungsten alloy wire; for the detection and measurement methods of the number of fracture points per 100 meters for flaw detection, please refer to the test method content in the embodiments of this article;

[0041] The detection and measurement methods of "number of wire breaks after winding 100,000 meters", "ratio of the wire breaking force of the wire at a heating temperature of 1000°C to the wire breaking force at room temperature", and "creep rate" in this article are detailed in the test method content of the embodiments of this article.

[0042] The present invention provides a method for preparing a tungsten alloy wire, and the scheme is as follows:

[0043] This preparation method successively includes the following preparation steps: reducing to prepare blue tungsten powder, doping, reducing to prepare alloy powder, mixing powder, powder pressing and pre-sintering, high-temperature sintering, cogging, hot working, and wire drawing to form a wire of the required specification.

[0044] Step 1. The process of reducing to prepare blue tungsten powder is as follows:

[0045] Feeding ammonium paratungstate into a reduction furnace, and performing continuous reduction under the protection of hydrogen and nitrogen at 400 - 600°C to obtain blue tungsten powder; wherein, the thickness of the ammonium paratungstate powder layer is ≤ 10 mm, the hydrogen flow rate in the reduction furnace is 20 - 40 L / min, the nitrogen flow rate is 80 - 160 L / min, the oxygen index of the blue tungsten powder is 2.85 ± 0.03, and the content of the ammonium tungsten bronze phase is > 60%.

[0046] Step 2: The doping process is as follows:

[0047] Immerse the blue tungsten powder in the nitrate solution formed by element L, stir well, and then evaporate to dryness to obtain doped blue tungsten powder;

[0048] Step 3: The process of reducing and preparing alloy powder is as follows:

[0049] Reduce the doped blue tungsten powder in a hydrogen reduction furnace at 600 - 1000 °C to obtain alloy powder with a particle size of 1.5 - 5 μm in one step.

[0050] Step 4: The powder mixing process is as follows:

[0051] Mix the alloy powders to form a mixed powder. Through the powder mixing process, it avoids the local doping unevenness during the reduction process of coarse - grained powders in different batches, and effectively inhibits the agglomeration and enrichment of fine - grained powders after reduction, preventing the generation of defects in the subsequent pressure processing due to the microscopic non - uniformity of alloy powder doping and reducing the risk of wire breakage.

[0052] Optionally, place the alloy powders prepared in different batches in a V - type powder mixer and mix them at a rotation speed of 6 - 10 revolutions per minute for 60 - 90 minutes to obtain the mixed powder.

[0053] Step 5: The powder pressing and pre - sintering process is as follows:

[0054] By isostatic pressing, press the mixed powder into a green compact, and perform low - temperature pre - sintering on the green compact in a hydrogen atmosphere at 1000 - 1400 °C for 15 - 30 minutes to increase the strength of the green compact and obtain a pre - sintered blank bar;

[0055] Optionally, by isostatic pressing, press the mixed powder into a green compact with a single weight of 1.5 - 5.0 kg under a pressure of 140 - 240 MPa.

[0056] Step 6: The high - temperature sintering process is as follows:

[0057] Perform electric sintering on the pre - sintered blank bar. The sintering is carried out in two stages. After the first sintering at a current intensity of 58 - 62% of the tungsten bar fusing current for 30 - 45 minutes, cool down. The second sintering is carried out at a current intensity of 90% - 92% of the tungsten bar fusing current for 40 - 80 minutes to obtain a sintered blank bar with a density of 18.4 - 18.8 g / cm 3 ³.

[0058] Among them, the "tungsten bar" in the "tungsten bar fusing current" specifically refers to the pre - sintered blank bar obtained in Step 5, and the "tungsten bar fusing current" is the maximum current that the pre - sintered blank bar can pass when it fuses.

[0059] Preferably, hydrogen gas purging is adopted before the second sintering to enable the second sintering to be carried out in an atmosphere, and the purity of hydrogen is ≥99%. Optionally, the hydrogen gas is used to purge the vertical melting hood to enable the second sintering to be carried out in a hydrogen atmosphere.

[0060] Step 7, the process of the blanking step is as follows:

[0061] The sintered blank bar obtained by the high-temperature sintering is blanked into an alloy rod with a diameter of 8.0 - 12.0 mm by a multi-roll rolling mill;

[0062] Optionally, a multi-roll rolling mill is used for continuous rolling at a heating temperature of 1600 - 1700 °C to blank the sintered blank bar with a diameter of 15 - 25 mm into an alloy rod with a diameter of 8.0 - 12.0 mm.

[0063] Step 8, the process of the pressure processing is as follows:

[0064] The alloy rod with a diameter of 8.0 - 12.0 mm is subjected to recrystallization annealing, and then forged by a multi-pass continuous swaging device to obtain an alloy rod with a diameter of 2.5 - 4.0 mm;

[0065] Optionally, the alloy rod with a diameter of 8.0 - 12.0 mm is heated to 2000 - 2600 °C for recrystallization annealing, and then forged by a multi-pass continuous swaging device to obtain an alloy rod with a diameter of 2.5 - 4.0 mm. Optionally, the alloy rod is heated to 2000 - 2600 °C by a medium / high-frequency induction coil.

[0066] Step 9, the process of the drawing processing is as follows:

[0067] The alloy rod with a diameter of 2.5 - 4.0 mm is subjected to drawing processing through wire drawing dies of different specifications, and the drawing pass reduction ratio of 35% - 60% is repeated. Among them, the drawing force in the last pass needs to reach 60% - 70% of the room-temperature breaking force of the finally obtained tungsten alloy wire, and tungsten alloy wires with different diameter specifications are obtained. The multi-pass drawing processing process of the wire in the present invention may not require annealing treatment.

[0068] It should be noted that:

[0069] The formula definition of the reduction ratio described in this article is: reduction ratio = (1 - D1) * D1 / D2 2 ; where D1 represents the diameter of the wire after drawing, and D2 represents the diameter of the wire before drawing.

[0070] The tungsten alloy wire provided by the present invention has the following characteristics and advantages compared with conventional tungsten alloy wires (pure tungsten wire and potassium-doped tungsten wire):

[0071] The differences and performance disparities between the tungsten alloy solution of the present application and traditional pure tungsten wires and potassium-doped tungsten wire ropes lie in:

[0072] For pure tungsten wires and potassium-doped tungsten wires, their breaking retention force is insufficient in a medium-temperature environment, resulting in an insufficient load-carrying capacity of the rope and limited application as the weight of the silicon ingot increases. Additionally, since potassium-doped tungsten wires are used in lamps in the lighting industry and their operating temperature is higher, with a normal heating temperature above 2500 °C, the potassium bubbles in potassium-doped tungsten wires have a good pinning effect above 2500 °C, which can maintain the high-temperature resistance of the tungsten wire. Different from potassium-doped tungsten wires, currently, the operating temperature of tungsten wire ropes for pulling single-crystalline silicon is 900 - 1300 °C, which is inconsistent with the operating environment of lighting fixtures. The effect of potassium bubbles in potassium-doped tungsten wires is not obvious. At the same time, due to the problem of sintering volatilization in potassium-doped tungsten wires, the difference in tissue uniformity is large, resulting in underdeveloped tungsten wire fibers in thick specifications. Its winding performance at room temperature is poor, leading to the generation of defects in the tungsten wire rope and causing problems of failure during the use of the rope.

[0073] In the present invention, by adding rare earth elements with a mass fraction of 0.3 - 0.75% into the tungsten matrix, the medium-temperature breaking force of tungsten-based alloy wire rods is increased, thereby improving the breaking force of tungsten alloy wire rods in the medium-temperature range, and enhancing the reliability and service life of tungsten alloy wire rods. Moreover, through the design of a specific reduction process for preparing blue tungsten powder, the oxygen index of blue tungsten and the composition of ammonium tungsten bronze phase are controlled, improving the doping effectiveness of rare earth elements in tungsten alloy wire rods and enhancing the medium-temperature creep resistance rate of tungsten alloy wire rods. By means of segmented electric heating high-temperature sintering, a high-density tungsten billet is obtained, and through a specific rapid large compression ratio processing technology (i.e., drawing processing technology) for thick tungsten wires, the strengthening and densification of tungsten fibers are achieved (so that the radial width of tungsten fibers is controlled within the required data range), thereby improving the winding performance of tungsten alloy wire rods.

[0074] In summary, the present application uses doping of rare earth elements with a specific mass fraction, combined with the processes of reducing and preparing blue tungsten powder, high-temperature sintering, and drawing processing, to obtain a tungsten alloy wire rod. The internal tungsten fibers are effectively strengthened and the densification is improved (i.e., the tungsten fibers are refined and their width is controlled within the required range), with high medium-temperature breaking force, good medium-temperature creep resistance, few surface cracks, and good winding performance. When used as a tungsten wire rope for pulling single-crystalline silicon, its reliability and service life are both improved.

[0075] Among them, the specific mechanism of action of the above processing technology of the present invention lies in:

[0076] First, in the preparation process of blue tungsten in the present invention, a hydrogen-nitrogen mixed gas is used as a reduction protection medium. The properties of the discharged blue tungsten powder are controlled by the thickness of the material layer, the size and flow direction of hydrogen. Specifically, the oxygen index of the blue tungsten is controlled at 2.85 ± 0.03, the proportion of the ammonium tungsten bronze phase exceeds 60%, and solid-liquid doping is carried out on the blue tungsten. Since the blue tungsten particles are coarse and have many surface cracks, it is beneficial for the rare earth solution to enter in the subsequent doping step, improving the doping effectiveness and enhancing the intermediate-temperature creep resistance of the tungsten wire.

[0077] Second, the present invention adopts two-stage segmented electric heating high-temperature sintering, which is different from the traditional single-stage electric heating high-temperature sintering or the combined sintering mode of electric heating sintering and intermediate-frequency indirect sintering; through the first-stage electric heating sintering, the impurity elements in the tungsten billet are fully volatilized and the surface voids of the tungsten billet are closed. In the second-stage electric heating high-temperature sintering, the purity of hydrogen is increased to improve the densification of the billet, obtaining a uniform billet with a density of more than 96% (obtaining a sintered tungsten billet with a density of 18.4 - 18.8 g / cm 3 indicating its high densification), thereby improving the tissue uniformity of the billet, improving the subsequent tungsten wire fiber uniformity, and improving the winding performance of the tungsten wire. While the density of the conventional single-stage electric heating sintered billet or the combined sintering billet of vertical melting and intermediate frequency can only reach 17.2 - 18.2 g / cm 3 , basically below 92% of the theoretical density, and the large difference in the tissue uniformity between the edge and the center results in poor consistency of the tungsten wire fiber size, leading to fracture during the subsequent winding of the tungsten wire and a large number of wire breaks during the winding of 100,000 meters.

[0078] Third, the present invention controls the wire drawing compression ratio to reach 35% - 60%. By increasing the wire drawing speed, the drawing force is increased to ensure that the drawing force reaches 60 - 70% of the wire breaking force of the wire material, which is different from the conventional compression ratio of tungsten wire under this wire diameter being 10 - 30%. Using a large compression ratio for tungsten wire processing, the obtained tungsten wire fibers are more developed and uniform, which is beneficial for the subsequent winding of the tungsten wire.

[0079] The present invention also provides the following examples and comparative examples to verify the effectiveness of the present invention's solution:

[0080] The formulation compositions of the examples and comparative examples are as shown in Table 1 below (unit: mass fraction %):

[0081] Table 1

[0082]

[0083]

[0084] The preparation processes of the examples and comparative examples are specifically as follows:

[0085] Example 1.1

[0086] This group of embodiments is about preparing a high-temperature creep-resistant tungsten alloy wire according to the present invention. The elemental composition of the material is as follows: cerium has a mass fraction of 0.5%, oxygen has a mass fraction of 0.114%, and the balance is tungsten and inevitable impurities. The preparation steps are as follows:

[0087] Step 1, Reduction: Ammonium paratungstate is successively reduced by hydrogen in a reverse hydrogen continuous reduction furnace at 400 °C, 450 °C, 500 °C, and 560 °C (with four temperature zones, and the wire passes through each temperature zone for 10 minutes). The thickness of the powder layer is 8 mm, the hydrogen flow rate is 30 L / min, and the nitrogen flow rate is 140 L / min to obtain blue tungsten powder. The oxygen index of the blue tungsten powder is 2.87, and the composition of the ammonium tungsten bronze phase is 82%;

[0088] Step 2, Doping: The blue tungsten powder obtained in step (1) is soaked in a rare earth nitrate solution and stirred evenly, and then dried at 120 °C to obtain doped blue tungsten powder;

[0089] Step 3, Reduction: The doped blue tungsten powder obtained in step (2) is successively reduced in a four-temperature-zone hydrogen reduction furnace at 680 °C, 750 °C, 860 °C, and 950 °C to form tungsten alloy powder with a particle size of 3 μm in one step;

[0090] Step 4, Powder Mixing: The materials obtained in different batches in step (3) are placed in a V-type powder mixer and mixed at a rotation speed of 6 revolutions per minute for 90 minutes;

[0091] Step 5, Powder Compression: The powder with different particle sizes is pressed into a green compact with a single weight of 4.0 kg under an isostatic pressure of 200 MPa, and the green compact is pre-sintered at a low temperature of 1400 °C for 20 minutes in a hydrogen atmosphere to increase the strength of the green compact;

[0092] Step 6, High-temperature Sintering: The pre-sintered billet obtained in step (4) is directly sintered by passing an electric current. The sintering needs to be carried out in two stages. First, it is heated to 60% of the tungsten bar fusing current at a high temperature for 35 minutes and then cooled down. The vertical melting hood is purged with hydrogen and dried. In a hydrogen atmosphere with a purity ≥ 99%, it is sintered at a high temperature for 60 minutes using 90% of the fusing current for the second time to obtain a sintered tungsten billet with a density of 18.65 g / cm 3 ;

[0093] Step 7, Billet Opening: A multi-roll mill is used to continuously roll the sintered billet with a diameter of 20 mm into an alloy rod with a diameter of 8.0 mm at a heating temperature of 1630 °C;

[0094] Step 8, Pressure Processing: The tungsten rod obtained in step 7 is heated to 2200 °C by a medium / high-frequency induction coil for recrystallization annealing, and then forged into a tungsten rod with a diameter of φ3.0 mm through a multi-pass continuous swaging device;

[0095] Step 9: Drawing Then, perform drawing processing through wire drawing dies of different specifications. Repeat the drawing process multiple times with a drawing reduction ratio of 35% - 60% in each pass. The drawing force in the final pass is 60 - 70% of the wire breaking force, and tungsten wires with specifications of φ0.3, 0.4, and 0.6 mm are obtained respectively.

[0096] Among them, a total of 10 drawing passes are experienced when drawing to the φ0.3 specification. The drawing reduction ratios in each pass are 39%, 37%, 40%, 42%, 45%, 41%, 39%, 37%, 37%, and 38% respectively.

[0097] A total of 9 drawing passes are experienced when drawing to the φ0.4 specification. The drawing reduction ratios in each pass are 39%, 37%, 40%, 42%, 45%, 41%, 36%, 35%, and 35% respectively.

[0098] A total of 7 drawing passes are experienced when drawing to the φ0.6 specification. The drawing reduction ratios in each pass are 39%, 37%, 40%, 42%, 45%, 41%, and 39% respectively.

[0099] Example 1.2

[0100] The elemental composition of its tungsten alloy material is: the mass fraction of cerium is 0.32%, the mass fraction of oxygen is 0.073%, and the balance is tungsten and inevitable impurities. The processing steps are the same as those in Example 1.1.

[0101] Example 1.3

[0102] The elemental composition of its tungsten alloy material is: the mass fraction of neodymium is 0.73%, the mass fraction of oxygen is 0.122%, and the balance is tungsten and inevitable impurities. The processing steps are the same as those in Example 1.1.

[0103] Example 1.4

[0104] The elemental composition of its tungsten alloy material is: the mass fraction of lanthanum is 0.25%, the mass fraction of cerium is 0.45%, the mass fraction of oxygen is 0.135%, and the balance is tungsten and inevitable impurities. The processing steps are the same as those in Example 1.1.

[0105] Example 1.5

[0106] The elemental composition of its tungsten alloy material is: the mass fraction of lanthanum is 0.25%, the mass fraction of cerium is 0.25%, the mass fraction of oxygen is 0.1%, and the balance is tungsten and inevitable impurities. The processing steps are the same as those in Example 1.1.

[0107] Example 1.6

[0108] The elemental composition of its tungsten alloy material is: the mass fraction of gadolinium is 0.25%, the mass fraction of praseodymium is 0.25%, the mass fraction of oxygen is 0.149%, and the balance is tungsten and inevitable impurities. The processing steps are the same as those in Example 1.1.

[0109] Comparative Example 2.1

[0110] The elemental composition of its tungsten alloy material is: cerium mass fraction 0.28%, oxygen mass fraction 0.064%, and the balance is tungsten and inevitable impurities. The processing steps are the same as those in Example 1.1.

[0111] Comparative Example 2.2

[0112] The elemental composition of its tungsten alloy material is: cerium mass fraction 0.78%, oxygen mass fraction 0.178%, and the balance is tungsten and inevitable impurities. The processing steps are the same as those in Example 1.1.

[0113] Comparative Example 2.3

[0114] The elemental composition of its tungsten alloy material is: potassium content 80 ppm, W is 99.992% wt, and other processing steps are the same as those in Example 1.1.

[0115] Comparative Example 2.4

[0116] The elemental composition of its tungsten alloy material is: rhenium content 1%, W is 99% wt, and the processing steps are the same as those in Example 1.1.

[0117] Comparative Example 2.5

[0118] The elemental composition of its tungsten alloy material is: cerium mass fraction 0.5%, oxygen mass fraction 0.114%, and the balance is tungsten and inevitable impurities. In processing step 1, ammonium paratungstate is sequentially passed through a hydrogen reduction furnace at 440, 480, 540, and 600 °C for hydrogen reduction (there are four temperature zones, and the wire passes through each temperature zone for 10 min), the hydrogen flow rate is 60 L / min, and the obtained blue tungsten powder has an oxygen index of 2.80 and an ammonium tungsten bronze phase ratio of 58%. Other processing steps are the same as those in Example 1.1.

[0119] Comparative Example 2.6

[0120] The elemental composition of its tungsten alloy material is: cerium mass fraction 0.5%, oxygen mass fraction 0.114%, and the balance is tungsten and inevitable impurities. Processing step 6 uses a secondary sintering process changed to: high-temperature sintering in an intermediate-frequency sintering furnace, the highest sintering temperature is 2100 °C, sintering for 36 h, and the density of the obtained tungsten alloy billet is 18.13 g / cm 3 Other processing steps are the same as those in Example 1.1.

[0121] Comparative Example 2.7

[0122] The elemental composition of its tungsten alloy material is as follows: the mass fraction of cerium is 0.5%, the mass fraction of oxygen is 0.114%, and the balance is tungsten and inevitable impurities. The reduction ratio of the drawing passes in processing step 9 is changed to 15-25%, and wire rods with diameters of φ0.3, φ0.4, and φ0.6 mm are obtained. Other processing steps are the same as those in Example 1.1.

[0123] Among them, a total of 23 drawing passes are experienced when drawing to the φ0.3 specification, and the reduction ratios of each drawing pass are 25%, 21%, 20%, 19%, 24%, 19%, 21%, 18%, 20%, 22%, 20%, 18%, 20%, 18%, 18%, 20%, 19%, 17%, 23%, 17%, 19%, 16%, 17% respectively.

[0124] A total of 20 drawing passes are experienced when drawing to the φ0.4 specification, and the reduction ratios of each drawing pass are 25%, 21%, 20%, 19%, 24%, 19%, 21%, 18%, 20%, 22%, 20%, 18%, 20%, 18%, 18%, 20%, 19%, 17%, 23%, 17% respectively.

[0125] A total of 16 drawing passes are experienced when drawing to the φ0.6 specification, and the reduction ratios of each drawing pass are 25%, 21%, 20%, 19%, 24%, 19%, 21%, 18%, 20%, 22%, 20%, 18%, 20%, 18%, 18%, 20% respectively.

[0126] Perform performance tests on the wire rods prepared in the examples and comparative examples.

[0127] 1. The test method is as follows:

[0128] (1) The breaking force and creep rate V of the wire rod

[0129] Test method for the breaking force of the wire rod:

[0130] Use a high-temperature tensile testing machine to measure the maximum breaking force F of the wire rod at room temperature and the maximum breaking force F1 of the wire rod at 1000°C respectively. Among them, the calculation formula for the ratio λ of the breaking force of the wire rod at 1000°C heating temperature to the breaking force of the wire rod at room temperature is:

[0131] λ = F1 / F;

[0132] The specific process is as follows: The high-temperature tensile testing machine can provide constant temperature and constant stress conditions (the model of the high-temperature tensile testing machine used is Shimadzu tensile testing machine AGS-H), and use the high-temperature tensile testing machine to measure the maximum breaking force F1 of the required sample at 1000°C and the maximum breaking force F at room temperature.

[0133] Test method for the creep rate V:

[0134] Using a high-temperature tensile testing machine, at room temperature, stretch the wire material until the tensile force reaches 50% of the specified force value F. Observe whether there is slippage in the sample at room temperature to avoid slippage at the chuck (which can be determined by observing whether the indicated value of the tensile testing machine changes). The clamped length of the wire material is 450 mm, and the effective heating length is 110 mm. Reset the displacement value to zero and heat up to the test temperature (the test temperature is 1000 °C). At this time, the force value of the tensile testing machine will show a downward trend. By increasing the stretching length, keep the force value of the tensile testing machine at 50% of the specified force value F. During the test time, in order to maintain a constant force of 50% F, the displacement within 1 minute of the high-temperature tensile testing machine is the creep rate V.

[0135] Among them, the breaking tensile force and creep rate V results data of different specifications of wire materials in the specific examples and comparative examples are shown in Table 2-4.

[0136] (2) Radial average width of tungsten fiber

[0137] The measurement method of the width of tungsten grain fiber is as follows: Use a focused ion beam cutting device to cut out thin slices along the radial direction of the wire material, place the thin slices in a scanning electron microscope equipped with an electron backscatter diffraction (EBSD) instrument, collect the morphology of the tungsten grains of the sample to be measured, and use conventional measurement software to measure the width of the upper and lower grain boundaries, that is, obtain the width of the tungsten grain fiber; the specific process is as follows:

[0138] As Figure 1 shown in the left figure 1 (schematic diagram of tungsten alloy wire 1), use a focused ion beam cutting device to cut out thin slices along the direction perpendicular to the axial x-axis of tungsten alloy wire 1 (obtain a transverse cross-section), place the thin slices in a scanning electron microscope equipped with an electron backscatter diffraction (EBSD) instrument, after confirming tungsten fiber 10 at the cross-section of the thin slice, measure the radial width of tungsten fiber through the scale of the measurement software;

[0139] Specifically, as Figure 1 shown in the right figure 1 (local enlarged structural schematic diagram of the cross-section of tungsten alloy wire) and Figure 2 shown, along the radial y-axis, measure the radial widths D1 of multiple tungsten fibers 10 respectively and then calculate the average value, which is the radial average width of tungsten fiber 10.

[0140] It can be understood that for the convenience of description, Figure 1 the right figure 1 and Figure 2 only show the local cross-section of the thin slice of tungsten alloy wire 1, not the whole picture of the thin slice. What the scale indicates is only the radial width of a single tungsten fiber 10, for example only.

[0141] Among them, the morphology display diagram of tungsten grains and the tungsten grain width statistical data diagram in specific example 1 are shown in Figure 2 , and the statistical data of the radial average width of tungsten fibers measured in the examples and comparative examples are shown in Table 2.

[0142] (3) Number of cracks per 100 meters detected by flaw detection, number of wire breaks during winding of 100,000 meters of wire

[0143] The calculation formula for the number of cracks per 100 meters detected by flaw detection is: Number of cracks per 100 meters detected by flaw detection = Number of cracks (pieces) / Wire length (m) * 100; it is defined as the number of cracks in every 100 m of wire.

[0144] Among them, the measurement method for the number of cracks is: Pass the obtained tungsten alloy wire through an eddy current flaw detector for surface defect detection, and define a flaw signal depth exceeding 15% of the wire diameter as a defect (i.e., a crack). Using this eddy current flaw detector for detection is a full inspection of the wire.

[0145] Number of wire breaks during winding of 100,000 meters of wire: It is defined as the number of times the wire breaks during winding of 100,000 meters of wire. The winding method includes an inner layer, a middle layer, and an outer layer. The total number of windings in the three layers is 19 strands, with 1 strand in the inner layer, 6 strands in the middle layer, and 12 strands in the outer layer. Each strand is wound by seven white tungsten wires. For the specific wire structure during winding, see Figure 3 。

[0146] 2. See Table 2 for specific test results:

[0147] Table 2

[0148]

[0149]

[0150] Analysis of the test data of the examples and comparative examples shows that:

[0151] (1) From the comparison between the examples and Comparative Examples 2.1 - 2.2 in Table 2, it can be seen that:

[0152] As the content of rare earth elements increases, the high-temperature tensile strength shows a positive increase. This is because rare earth elements or rare earth compounds play a role of dispersion pinning in tungsten fibers, hindering the slip of grain boundaries at high temperatures and thus improving the mid-temperature creep resistance.

[0153] It can be seen from Comparative Example 2.1 that as the content of rare earth elements decreases, the high-temperature tensile strength and mid-temperature creep resistance decrease. However, it can be seen from Comparative Example 2.2 that after the content of rare earth elements increases to above the limit range defined in this application, the number of cracks per 100 meters of the wire and the number of wire breaks during winding of 100,000 meters increase significantly, and the wire performance deteriorates.

[0154] (2) From the comparison results between Comparative Examples 2.3 - 2.4 and the examples in Table 2, it can be seen that:

[0155] Compared with the potassium-doped tungsten wire in Comparative Example 2.3 and the tungsten rhenium wire in Comparative Example 2.4, the tungsten grain fiber width of the wire of the present invention is more refined at a specific wire diameter specification, and its corresponding high-temperature tensile strength is higher and the high-temperature creep value is lower;

[0156] This is because for potassium-doped tungsten wires and tungsten-rhenium wires, their tungsten fibers are relatively thick and their winding performance at room temperature is insufficient. For tungsten wires with a diameter of φ0.3 mm and above, the tungsten fibers are not well-developed (in Comparative Example 2.3, the width of the tungsten fibers exceeds the range defined in this application), resulting in brittle cracking or splitting during the winding process, thus affecting the winding stability of the tungsten rope. Moreover, the defect sources generated during the winding process will further expand in a heating environment, leading to insufficient lifespan of the tungsten wire rope or even wire breakage during use.

[0157] (3) It can be seen from the comparison results between Comparative Examples 2.3 - 2.4 and the Examples in Table 2-3:

[0158] It can be seen from the comparison results between Comparative Example 2.5 and the Examples that because the blue tungsten powder of the present invention has a higher ammonium tungsten bronze phase, the doping effect is better during the doping process. Therefore, the rare earth second-phase particles have a more obvious effect on refining tungsten grains. At the same time, the good doping effect can effectively prevent the mutual slip of tungsten grains at high temperatures, thereby improving the intermediate-temperature creep resistance.

[0159] It can be seen from the comparison results between Comparative Example 2.6 and the Examples that by using the high-temperature two-stage sintering method of the present invention, billets with higher density can be obtained. After processing into tungsten wires, the tungsten grain fibers are more developed and the tungsten fibers are more refined, thus effectively avoiding the generation of surface cracks and ensuring good winding performance of the tungsten wires at room temperature.

[0160] It can be seen from the comparison results between Comparative Example 2.7 and the Examples that by using the processing technology with a fast large compression ratio of the present invention, the strengthening of tungsten fibers can be achieved, and the obtained tungsten wire fibers are more developed and uniform, thereby improving the winding performance and surface cracks of tungsten alloy wire rods.

[0161] It should be noted that:

[0162] The tungsten alloy wire rod provided by the present invention has the advantages of high intermediate-temperature breaking force, good intermediate-temperature creep resistance, and good winding performance. Therefore, it is suitable for use as a tungsten wire rope for pulling single-crystalline silicon in a high-temperature environment. Similarly, based on the above characteristics, it can be applied to other application fields that require wire rods with excellent properties such as high intermediate-temperature breaking force, good intermediate-temperature creep resistance, and good winding performance, including but not limited to tungsten wire ropes for pulling single-crystalline silicon, cutting, cut-resistant protection, cables, screen printing, ropes, or textiles, etc.

[0163] In this article, "~" is used to represent a numerical range, and this expression method includes the two endpoint values within the represented range;

[0164] In summary, the specific parameters, some common reagents or raw materials in the above embodiments are specific embodiments or preferred embodiments under the concept of the present invention, rather than limitations thereto; those skilled in the art can make adaptive adjustments within the concept and protection scope of the present invention. In addition, unless otherwise specified, the raw materials used may also be conventional commercially available products in the art or prepared by conventional methods in the art.

[0165] In addition, those skilled in the art should understand that although there are many problems in the prior art, each embodiment or technical solution of the present invention can be improved in only one or several aspects, and it is not necessary to solve all the technical problems listed in the prior art or the background art at the same time. Those skilled in the art should understand that the content not mentioned in a claim should not be regarded as a limitation to that claim.

[0166] Although terms such as starting recrystallization temperature and average oxide size are used more frequently herein, the possibility of using other terms is not excluded. These terms are used only to more conveniently describe and explain the essence of the present invention; interpreting them as any additional limitation is contrary to the spirit of the present invention.

Claims

1. A tungsten alloy wire, characterized in that: In terms of mass fraction, the tungsten alloy components include: 0.3 - 0.75 wt% of element L, 0.001 - 0.18% of oxygen element, and the balance is tungsten element and inevitable impurities; wherein, L is one or more of lanthanum, cerium, praseodymium, neodymium, gadolinium, and erbium; the wire diameter of the wire is 0.3 - 0.6 mm; and in the wire, the average radial width of tungsten fibers is ≤ 0.4 μm; the number of hundred-meter crack points detected on the surface of the wire is ≤ 5.

2. The tungsten alloy wire according to claim 1, wherein: the number of wire breaks when the wire is wound for 100,000 meters is ≤ 3 times.

3. The tungsten alloy wire according to claim 1, wherein: the ratio of the wire breaking force of the wire at a heating temperature of 1000 °C to the wire breaking force at room temperature is ≥ 50%; and the creep rate of the wire is ≤ 0.6 mm / min.

4. A method for preparing a tungsten alloy wire according to any one of claims 1-3, characterized in that, It successively includes the following preparation steps: reduction to prepare blue tungsten powder, doping, reduction to prepare alloy powder, powder mixing, powder pressing and pre-sintering, high-temperature sintering, ingot opening, hot working, and drawing to form a wire of the required specification; wherein, the process of reduction to prepare blue tungsten powder is: feeding ammonium paratungstate into a reduction furnace, and performing continuous reduction under the protection of hydrogen and nitrogen at 400 - 600 °C to obtain blue tungsten powder; wherein, the thickness of the ammonium paratungstate powder layer is ≤ 10 mm, the hydrogen flow rate in the reduction furnace is 20 - 40 L / min, the nitrogen flow rate is 80 - 160 L / min, the oxygen index of the blue tungsten powder is 2.85 ± 0.03, and the content of the ammonium tungsten bronze phase is > 60%; the process of high-temperature sintering is: performing electric sintering on the pre-sintered billet, and the sintering is carried out in two stages. After the first sintering at a current intensity of 58 - 62% of the tungsten bar fusing current for 30 - 45 min and then cooling down, the second sintering is carried out at a current intensity of 90% - 92% of the tungsten bar fusing current for 40 - 80 min to obtain a sintered billet with a density of 18.4 - 18.8 g / cm3; the tungsten bar fusing current is the maximum current that the pre-sintered billet can pass through when it fuses; the drawing process is: an alloy rod with a diameter of 2.5 - 4.0 mm is drawn through drawing dies of different specifications, and the compression ratio of multiple drawing passes is 35% - 60%. Among them, the drawing force in the last pass needs to reach 60% - 70% of the room-temperature wire breaking force of the finally obtained tungsten alloy wire to obtain tungsten alloy wires of different diameter specifications.

5. The preparation method of the tungsten alloy wire according to claim 4, wherein: the powder pressing and pre-sintering process is: by isostatic pressing, pressing the mixed powder into a green compact, and performing low-temperature pre-sintering on the green compact at 1000 - 1400 °C for 15 - 30 minutes in a hydrogen atmosphere to obtain a pre-sintered billet.

6. The method for preparing a tungsten alloy wire according to claim 5, wherein: The conditions of the isostatic pressing method are: by isostatic pressing, pressing the mixed powder into a green compact with a single weight of 1.5 - 5.0 kg under a pressure of 140 - 240 MPa; the second sintering is carried out in a hydrogen atmosphere, and the purity of the hydrogen is ≥ 99%.

7. The preparation method of the tungsten alloy wire according to claim 4, characterized in that: The process of the cogging step is as follows: using a multi-roll rolling mill to cog the sintered blank bar obtained by high-temperature sintering into an alloy rod with a diameter of 8.0 - 12.0 mm; The process of the pressure processing is as follows: subjecting the alloy rod with a diameter of 8.0 - 12.0 mm to recrystallization annealing, and then forging it through a pass continuous swaging device to obtain an alloy rod with a diameter of 2.5 - 4.0 mm.

8. The method for preparing tungsten alloy wire according to claim 4, wherein: The process of the doping is as follows: soaking blue tungsten powder in a nitrate solution formed by element L, stirring evenly, and then evaporating to dryness to obtain doped blue tungsten powder; The process of the reduction to prepare alloy powder is as follows: subjecting the doped blue tungsten powder to primary reduction in a hydrogen reduction furnace at 600 - 1000 °C to obtain alloy powder with a particle size of 1.5 - 5 μm; The process of the powder mixing is as follows: mixing the alloy powder to form a mixed powder; The process of the cogging step is as follows: continuously rolling using a multi-roll rolling mill at a heating temperature of 1600 - 1700 °C to cog a sintered blank bar with a diameter of 15 - 25 mm into an alloy rod with a diameter of 8.0 - 12.0 mm; The process of the pressure processing is as follows: heating the alloy rod with a diameter of 8.0 - 12.0 mm to 2000 - 2600 °C for recrystallization annealing, and then forging it through a pass continuous swaging device to obtain an alloy rod with a diameter of 2.5 - 4.0 mm.

9. The application of the tungsten alloy wire according to claim 1 or 2 in a single crystal silicon pulling rope.

10. The application of the tungsten alloy wire according to claim 1 or 2 in the fields of cutting, cutting-resistant protection, cables, screen printing, ropes or textiles.

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