Laves phase precipitation strengthened tungsten wire and its preparation and application

Abstract

The present invention belongs to the technical field of tungsten filaments, and specifically relates to a laves-phase precipitation-strengthened tungsten filament comprising a tungsten matrix, oxides dispersed therein, and an in-situ formed laves-strengthening phase. The laves-strengthening phase comprises NiW2, WFe2, and WZr2; the oxides are ZrO2 and CeO2. In the laves-phase precipitation-strengthened tungsten filament, the Ni content is 0.2-0.6 wt%, the Fe content is 0.2-0.6 wt%, the Zr content is 0.3-0.8 wt%, the Ce content is 0.1-1.2 wt%, and the balance is tungsten. The present invention also relates to an in-situ synthesis method for the tungsten filament. The process described in the present invention can improve the performance of the tungsten filament.

Description

Technical Field

[0001] The present invention belongs to the technical field of tungsten wire materials, and in particular, provides an ultrafine high-strength tungsten wire strengthened by laves phase precipitation and a preparation method thereof. Background Art

[0002] Diamond wire has replaced traditional mortar cutting for semiconductor silicon panels, driving rapid growth in the photovoltaic industry. Diamond wire cutting, with its high efficiency and gentle processing environment, is poised to become the mainstream development direction for future photovoltaic consumables processing. However, compared to mortar cutting, the excessive material loss caused by large cutting marks during diamond wire cutting warrants further optimization. Reducing the size of the diamond wire core to reduce silicon loss is a proven technical solution. However, this continuous reduction in core size inevitably leads to lower breaking force values. Consequently, continuously improving the core's tensile strength is crucial to further refine diamond wire. Currently, mainstream diamond wire uses steel as its core. While cold drawing, work hardening, grain refinement, and composition optimization can further enhance the tensile strength of the steel wire, the resulting overall performance improvement is insufficient to meet the industry's demand for ultra-fine core wire. At the same time, there is still a long way to go to solve the technical bottlenecks that need to be solved to improve the performance of ultra-fine and ultra-high-strength steel wires. Although my country's steel production is far ahead of other countries in the world, there is still a large gap in the field of ultra-high-strength steel and related products. In order to occupy a place in the field of ultra-fine diamond wires, it is urgent to develop high-performance core wire materials with greater prospects to achieve overtaking.

[0003] Research indicates that, given the inherent properties of the material and my country's resource reserves, high-strength tungsten wire has the potential to replace steel wire and achieve further thinning of diamond wire. Tungsten wire boasts a higher elastic modulus, theoretical tensile strength, and superior conductivity than steel wire, making it an ideal choice for the next generation of ultrafine diamond wire cores. Currently, mainstream tungsten cores are often doped with rare earth elements such as lanthanum, cerium, and rhenium. These elements achieve impressive tensile strength through work hardening and grain refinement through multiple drawing passes. However, grain boundary strengthening and work hardening achieved solely through deformation-induced grain refinement are insufficient to fully achieve the desired mechanical properties. While rare earth element doping enhances both performance and machinability, the secondary phase strengthening provided by a small amount of dispersed rare earth oxides is insufficient to achieve the desired material strengthening effect. While excessive rare earth element additions can significantly enhance material properties through significant secondary phase strengthening, the hard and brittle rare earth oxides significantly narrow the processing window for tungsten wire. The lower processing yield and excessive addition of precious rare earth elements significantly increase material preparation costs. Insufficient material strengthening and performance improvement have become the main obstacles limiting the further refinement of tungsten wire diameter. In addition, the oxide dispersion strengthening during the drawing process is insufficient to provide sufficient work hardening capacity, which easily causes necking and wire breakage during the tungsten wire drawing process, greatly limiting the yield rate of tungsten wire. Summary of the Invention

[0004] In order to solve the performance deficiencies of high-strength steel core wire in the process of pursuing wire diameter refinement of diamond wire, and to further strengthen the tungsten wire and solve the problem of wire breakage during drawing, the purpose of this invention is to provide a laves phase precipitation strengthened tungsten wire, aiming to provide a tungsten wire with excellent performance.

[0005] The second object of the present invention is to provide an ultrafine high-strength tungsten wire strengthened by precipitation of a second phase (Laves phase) and a preparation method thereof, in order to obtain an ultra-high-strength tungsten core wire with a finer wire diameter.

[0006] The third object of the present invention is to provide an application of the laves phase precipitation strengthened tungsten wire in cutting semiconductor silicon plates and an apparatus thereof.

[0007] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is as follows:

[0008] Laves phase precipitation strengthened tungsten wire, including tungsten matrix, oxides dispersed therein and in-situ generated laves strengthening phase;

[0009] The laves strengthening phase includes NiW2, WFe2 and WZr2;

[0010] The oxides are ZrO2 and CeO2;

[0011] In the laves phase precipitation strengthened tungsten wire, the content of Ni is 0.2-0.6 wt%, the content of Fe is 0.2-0.6 wt%, the content of Zr is 0.3-0.8 wt%, the content of Ce is 0.1-1.2 wt%, and the balance is tungsten.

[0012] The present invention provides a tungsten wire with an in-situ composite laves strengthening phase of NiW2, WFe2 and WZr2, which can achieve synergy based on the combined control of the strengthening phase components and proportions, and can synergistically improve the performance of the tungsten wire.

[0013] In the present invention, the combined control of the composition of the laves strengthening phase and the in-situ dispersion strengthening structure and content is the key to synergistically improving the performance of the tungsten wire.

[0014] Preferably, in the laves phase precipitation strengthened tungsten wire, the Ni content is 0.2-0.5wt%, the Fe content is 0.2-0.4wt%, the Zr content is 0.3-0.7wt%, the Ce content is 0.2-1.0wt%, and the balance is W;

[0015] Preferably, the Ni content is 0.2-0.45 wt%, the Fe content is 0.2-0.35 wt%, the Zr content is 0.4-0.7 wt%, the Ce content is 0.4-1.0 wt%, and the balance is W;

[0016] More preferably, the Ni content is 0.3-0.4 wt%, the Fe content is 0.25-0.3 wt%, the Zr content is 0.6-0.7 wt%, the Ce content is 0.7-0.9 wt%, and the balance is W;

[0017] Preferably, the size of the laves reinforcement phase is less than 300 nm;

[0018] Preferably, the diameter of the laves phase precipitation strengthened tungsten wire is 30-40 μm.

[0019] The present invention also provides a method for preparing the laves phase precipitation-strengthened tungsten wire, comprising the following steps:

[0020] Step (1): preparing the ingredients according to the element content of the laves phase precipitation strengthened tungsten wire, spraying a solution containing the required amount of nickel source, iron source and cerium source on the surface of the tungsten source powder, and then performing a reduction treatment to obtain Ni-Fe-Ce coated W composite particles, wherein the temperature of the reduction stage is 800-900°C;

[0021] Step (2): compounding Ni-Fe-Ce coated W composite particles and a required amount of zirconium hydride and forming a composite blank;

[0022] Step (3): pre-sintering the composite blank at 1200-1400° C., and then finally sintering at 2000-2400° C. to obtain a sintered blank;

[0023] Step (4): The sintered material is subjected to rotary forging, annealing, stringing and drawing to obtain the laves phase precipitation strengthened tungsten wire.

[0024] The key and challenge in successfully preparing the tungsten filaments described herein is how to disperse the laves phase in situ within the tungsten filament matrix. To address this manufacturing challenge, the present invention has innovatively employed a nickel source, an iron source, a cerium source, and zirconium hydride in the aforementioned ratios as raw materials. Furthermore, the nickel, iron, and cerium sources are pre-wet-loaded and reduction-coated on the surface of the tungsten source powder before being composited, formed, and sintered with the zirconium hydride. Furthermore, the combined reduction and sintering processes achieve synergistic results, unexpectedly allowing the in-situ dispersion of a laves-reinforced phase comprising NiW2, WFe2, and WZr2 within the tungsten matrix, thereby improving the overall performance of the prepared material.

[0025] In the present invention, the joint control of the type, type, ratio of the raw materials, the reduction pre-coating after liquid phase spraying, and the subsequent sintering process is the key to synergistically inducing the formation of the synergistic laves strengthening phase and uniform dispersion distribution.

[0026] In the present invention, in step 1, the required content of nickel source, iron source, and cerium source are dissolved in advance to form a homogeneous solution, and then uniformly compounded on the surface of the tungsten source powder based on known means such as spraying and stirring, and then reduced to reduce the required amount of nickel and iron in situ and coat the surface of the tungsten source powder. This can be combined with subsequent processes to facilitate the induction of the formation of laves strengthening phase.

[0027] In the present invention, the nickel source can be any soluble nickel raw material, such as nickel nitrate.

[0028] In the present invention, the iron source can be any soluble iron raw material, such as ferric nitrate;

[0029] In the present invention, the cerium source can be any soluble cerium raw material, such as ferric nitrate.

[0030] Preferably, the solvent in the solution is at least one of alcohol and water, preferably an alcohol-water mixed solvent, more preferably an alcohol-water solvent with an alcohol volume content of 30 to 80% by volume;

[0031] Preferably, in the solution, the total concentration of solute is 0.2-0.4 g / ml;

[0032] Preferably, the tungsten source powder is metallic tungsten powder and / or blue tungsten powder, preferably blue tungsten powder. Studies have shown that the use of blue tungsten powder can further enhance the overall performance of the prepared material by synergizing with the process of the present invention.

[0033] In the present invention, the particle size of the tungsten source powder is less than 2 μm;

[0034] Preferably, the solution is sprayed onto the surface of the tungsten source powder while being stirred and evenly mixed, and then subjected to subsequent reduction treatment after drying.

[0035] In the present invention, the atmosphere in the reduction stage is a hydrogen-containing atmosphere; it can be pure hydrogen, hydrogen-nitrogen composite gas, or hydrogen-argon composite gas.

[0036] In the present invention, the temperature in the reduction stage is 840-860° C.; under the preferred conditions, better tungsten filament performance can be obtained.

[0037] Preferably, the treatment time of the reduction stage is 2-4 hours, and further can be 2 to 3 hours.

[0038] In the present invention, in step (2), zirconium hydride is used as a zirconium source, and it is coated with Ni-Fe-Ce W composite particles, which facilitates the preparation of the laves phase precipitation-strengthened tungsten wire. By designing the addition of zirconium hydride powder, the Laves phase-forming components are successfully added. Simultaneously, the oxidation of trace amounts of zirconium introduces thermally stable zirconium oxide into the tungsten wire, effectively suppressing grain coarsening during processing while achieving a certain dispersion strengthening effect. The overall preparation technology route is simple and highly repeatable.

[0039] In the present invention, the zirconium hydride and Ni-Fe-Ce coated W composite particles can be combined and formed in a conventional manner. For example, the Ni-Fe-Ce coated W composite particles and zirconium hydride are combined in a protective atmosphere. The forming method is one of steel die pressing and isostatic pressing; the pressing pressure is 200-300 MPa, and the holding time is 3-5 minutes.

[0040] Preferably, the green density of the composite blank obtained by molding is 9.0 to 14.0 g / cm 3 .

[0041] In the present invention, the formed composite blank is sintered. The combination of sintering processes is beneficial to the synergy with the preceding processes and parameters, and is more conducive to the in-situ formation and uniform dispersion strengthening of the laves phase.

[0042] In the present invention, the formed composite blank can be heated to a pre-sintering temperature, kept at this temperature for deoxidation and impurity removal, and then heated again to the sintering temperature for densification sintering. During the pre-sintering process, four heat preservation platforms are set at 350-450°C, 550-650°C, 750-850°C, and 1200-1400°C, and the heat preservation time of each heat preservation platform is 10-30 minutes.

[0043] Preferably, the pre-sintering time is 45 to 80 minutes;

[0044] Preferably, the final densification sintering time is 200 to 300 minutes.

[0045] In the present invention, after the sintering treatment, the sintered material can be subjected to rotary forging, annealing, stringing, and drawing based on known principles and means to obtain the laves phase precipitation-strengthened tungsten wire.

[0046] Before rotary forging, preheat the blank in a hydrogen atmosphere protection furnace for 20 to 40 minutes at a preheating temperature of 1400 to 1600°C. The deformation of the rotary forging process is 1 to 1.5 mm. After each process, return to the furnace and keep warm for 3 to 5 minutes before the next rotary forging process.

[0047] The thin tungsten rod with a diameter of 3.5-3.9 mm is obtained by rotary forging.

[0048] The atmosphere during the annealing stage is a hydrogen-containing atmosphere;

[0049] The annealing temperature is 1600-1900°C;

[0050] The drawing steps are chain drawing and turntable drawing, wherein the diameter of the tungsten wire in chain drawing is 2.4-2.8 mm;

[0051] The tungsten wire after chain drawing is then turned on a rotary table. The diameter of the tungsten wire after turntable drawing is 30 to 40 μm.

[0052] The present invention also provides an application of the laves phase precipitation-strengthened tungsten wire, which is used in a cutting tool for semiconductor silicon wafers.

[0053] The present invention also provides a semiconductor silicon plate cutting tool, which comprises the laves phase precipitation-strengthened tungsten wire prepared by the preparation method of the present invention.

[0054] The beneficial effects of the present invention are:

[0055] 1. The present invention provides a laves phase precipitation strengthened tungsten wire having excellent tensile strength and high elastic modulus.

[0056] 2. The present invention innovatively adopts the nickel source, iron source, cerium source and zirconium hydride in the proportions described above as raw materials, and innovatively wet-loads and reduction-coates the nickel source, iron source and cerium source on the surface of the tungsten source powder in advance, and then composites, shapes and sinters them with zirconium hydride. Further, the combination of the reduction process and the sintering process can achieve synergy, and can unexpectedly disperse in situ in the tungsten matrix to form a laves strengthening phase synergistically containing NiW2, WFe2 and WZr2, which helps to improve the comprehensive performance of the prepared material.

[0057] 3. The present invention prepares low-cost, high-performance ultrafine tungsten wire through the combined effects of fine grain strengthening, Laves phase precipitation strengthening and oxide dispersion strengthening, avoiding the large amount of expensive rare earth elements added in the preparation of traditional high-strength ultrafine tungsten wire, and greatly reducing the preparation cost. DETAILED DESCRIPTION

[0058] The present invention will be further described below in combination with specific examples based on the technical solution of the present invention, but the protection scope of the present invention is not limited to the following embodiments.

[0059] The present invention relates to an ultrafine high-strength tungsten wire strengthened by precipitation of a second phase, wherein the final wire diameter of the tungsten wire can be adjusted according to the usage scenario. For example, when the tungsten wire is used for cutting semiconductor silicon wafer plates, considering the compatibility of the tungsten wire and the semiconductor silicon plate cutting process, the final wire diameter can be 0.03 to 0.04 mm.

[0060] The high-strength tungsten alloy wire of the present invention comprises a tungsten matrix and oxides dispersed therein and an in-situ generated Laves phase, wherein the oxides are ZrO2 and rare earth oxide CeO2 generated by reaction, and the Laves phase mainly comprises NiW2, WFe2 and WZr2.

[0061] Preferably, the rare earth oxides and Laves phases are both generated in situ, and after the tungsten wire undergoes multiple drawing and crushing passes, the rare earth oxides and Laves phases in the finished tungsten wire have reached nanometer level (<300 nm).

[0062] Preferably, the tungsten wire is prepared by powder metallurgy process + multi-pass drawing, and the raw material powder is commercial high-purity (>99.9%) ultrafine (<2μm) powder.

[0063] In the laves phase precipitation strengthened tungsten wire, the content of Ni is 0.2-0.6 wt%, the content of Fe is 0.2-0.6 wt%, the content of Zr is 0.3-0.8 wt%, the content of Ce is 0.1-1.2 wt%, and the balance is tungsten.

[0064] The laves phase precipitation strengthened tungsten wire has a Ni content of 0.2-0.5wt%, a Fe content of 0.2-0.4wt%, a Zr content of 0.3-0.7wt%, a Ce content of 0.2-1.0wt%, and the balance being W.

[0065] Preferably, the Ni content is 0.2-0.45 wt%, the Fe content is 0.2-0.35 wt%, the Zr content is 0.4-0.7 wt%, the Ce content is 0.4-1.0 wt%, and the balance is W;

[0066] More preferably, the Ni content is 0.3-0.4 wt%, the Fe content is 0.25-0.3 wt%, the Zr content is 0.6-0.7 wt%, the Ce content is 0.7-0.9 wt%, and the balance is W.

[0067] In a preferred embodiment, the ultrafine tungsten wire has a diameter of 30 to 40 μm, a tensile strength of ≥6300 MPa, an elongation at break of 1.4 to 2.8%, and an elastic modulus of 350 to 430 GPa.

[0068] In a further preferred embodiment, the ultrafine tungsten wire has a diameter of 30 to 40 μm, a tensile strength of ≥6800 MPa, an elongation at break of 1.5 to 2.2%, and an elastic modulus of 380 to 430 GPa.

[0069] The present invention provides a typical intermetallic compound reinforced ultrafine high-strength tungsten wire and a preparation method thereof, comprising the following steps:

[0070] Step 1: Weigh nickel nitrate, ferric nitrate nine hydrate and cerium nitrate in proportion and fully dissolve them, and then evenly spray them onto the tungsten source powder under stirring.

[0071] Step 2: The uniformly doped powder obtained in step 1 is subjected to a hydrogen reduction in a hydrogen reduction furnace at 800-900° C. to obtain alloy tungsten powder.

[0072] Step 3: Evenly mix the reduced tungsten alloy powder obtained in step 2 with a small amount of added zirconium hydride powder under a protective atmosphere.

[0073] Step 4: Compact the tungsten alloy powder obtained in step 3 to obtain a tungsten rod with a green density of 9.0 to 14.0 g / cm 3 .

[0074] Step 5: Pre-sinter the tungsten rod blank obtained in step 4 at 1200-1400°C in a hydrogen furnace for 45-80 minutes. After pre-sintering, re-sinter the rod in a medium frequency induction furnace at a sintering temperature of 2000-2400°C and a maximum temperature sintering time of 200-300 minutes.

[0075] Step 6: The sintered tungsten alloy rod obtained in step 5 is subjected to rotary forging to form a blank, and then annealed in a medium frequency induction heating furnace in a hydrogen atmosphere at an annealing temperature of 1600-1900°C.

[0076] Step 7: The annealed tungsten rod obtained in step 6 is subjected to rotary forging to obtain a thin tungsten rod with a diameter of 3.5 to 3.9 mm.

[0077] Step 8: Evenly coat the thin tungsten rod obtained in step 7 with graphite emulsion and then chain-draw it through a carbide die. After four passes of die drawing, the diameter of the tungsten wire is 2.4 to 2.8 mm.

[0078] Step 9: The tungsten wire obtained in step 8 is further drawn on a turntable through a diamond die, and is drawn through multiple passes until the tungsten wire has a diameter of 30 to 40 microns.

[0079] Preferably, the tungsten raw material powder in step 1 is preferably ultrafine (<2 μm) blue tungsten (WO 2.9 ) powder. Blue tungsten powder has better fluidity than ultrafine tungsten powder, making it easier to fully mix with other metal components. Solid-liquid doping with oxide powder and nickel nitrate, iron, and cerium alcohol solutions facilitates uniform doping. Furthermore, tungsten, nickel, and iron oxides are easily reduced in a hydrogen atmosphere, making the addition process feasible.

[0080] Zirconium and tungsten are uniformly mixed through powder, while Ni, Fe and Ce are added in the form of nickel nitrate, iron nitrate nonahydrate and cerium nitrate respectively. The nitric acid compounds of nickel, iron and cerium are fully dissolved in anhydrous ethanol, and then the alcohol solution is mixed with tungsten powder for solid-liquid doping under stirring.

[0081] Ultrafine ZrH2 powder (<2μm) is used instead of Zr powder to avoid complete oxidation of Zr before sintering.

[0082] The sum of the mass percentages of Ni and Fe in the tungsten wire is 0.4-0.8%, and the mass percentage of Zr added is 0.3-0.7%. In the present invention, Ni, Fe, and Zr are added as Laves phase-forming elements to react with the matrix tungsten element to precipitate a second phase. Excessive Laves phase is not conducive to drawing processing.

[0083] The mass percentage of cerium in tungsten filaments is 0.2-1.0%. During the manufacturing process, the rare earth element cerium is converted into cerium oxide, which is dispersed in the matrix. Simultaneously, zirconium dioxide, produced by trace oxidation of zirconium during the process, also contributes to suppressing grain coarsening and dispersion strengthening during sintering and hot working. Too little cerium addition will not achieve the desired effect of suppressing grain coarsening and dispersion strengthening, while the combined effect of zirconium can reduce the need for excessive cerium addition, thereby reducing costs.

[0084] The added elements are as follows by mass percentage: Ni: 0.2-0.5%, Fe: 0.2-0.4%, Zr: 0.3-0.7%, Ce: 0.2-1.0%, impurity content is less than 0.01%, and the balance is W.

[0085] The added elements are as follows by mass percentage: Ni: 0.2-0.45%, Fe: 0.2-0.35%, Zr: 0.4-0.7%, Ce: 0.4-1.0%, impurity content is less than 0.01%, and the balance is W.

[0086] The added elements are as follows by mass percentage: Ni: 0.3-0.4wt%, Fe: 0.25-0.3wt%, Zr: 0.6-0.7wt%, Ce: 0.7-0.9wt%, and the balance is W.

[0087] Preferably, the hydrogen concentration in the hydrogen reduction in step 2 is not less than 99%, and the high-temperature insulation time of the hydrogen furnace reduction is not less than 2 hours.

[0088] Preferably, the reduced tungsten alloy powder and the ultrafine zirconium hydride powder (<2 μm) in step 3 are mixed for more than 12 hours using a V-type mixer, and then pre-vacuumed and filled with argon atmosphere for protection.

[0089] Preferably, the pressing described in step 4 can be one of steel die pressing and isostatic pressing. Isostatic pressing is preferably used to ensure uniformity of density of the green compact, with a pressing pressure of 200-300 MPa and a holding time of 3-5 min.

[0090] Preferably, the pre-sintering of the pressed tungsten rod in step 5 is performed at three insulation platforms of 400° C., 600° C. and 800° C., each for 20 minutes, to ensure that the zirconium hydride powder is gently and completely dehydrogenated into zirconium powder during the low-temperature insulation stage.

[0091] Preferably, the sintered tungsten rod in step 6 is preheated in a hydrogen atmosphere protection furnace for 30 minutes before rotary forging, the preheating temperature is 1400-1600°C, the rotary forging process deformation is 1-1.5mm, and after each process is completed, the next rotary forging is performed after returning to the furnace and keeping warm for 3-5 minutes.

[0092] Preferably, the preheating temperature of the rotary forging tungsten rods in step 7 is 1350-1550°C, and an insulation furnace is added between the two passes of the stringing equipment to heat and keep the tungsten rods passing through, and the temperature of the insulation furnace is 1300-1500°C.

[0093] Preferably, the lubricant graphite emulsion in step 8 is D 50 Nanographite powder ≤ 0.2μm and thickener are continuously stirred and mixed evenly. Before drawing, the tungsten rod is evenly passed through and immersed in the pumped graphite emulsion slurry to ensure that the tungsten wire surface is fully coated with graphite emulsion. Using finer graphite powder can enhance the lubrication effect of the wire drawing process, further reducing the occurrence of surface defects in the wire and reducing the loss of the drawing die.

[0094] Preferably, the tungsten wire in step 8 is preheated to 1100-1200°C before chain drawing, and the drawing die is heated to 800-900°C before drawing. The drawing die is preferably a carbide die, which is more resistant to high-temperature oxidation than a diamond die. The carbide die is preferably used for chain drawing to extend the service life of the die.

[0095] Preferably, the preheating temperature for the turntable filament drawing process described in step 9 is 500-1100°C, and the drawing die is heated to 400-800°C. The filament is drawn through multiple passes until it reaches a diameter of 30-40 μm. The drawing die preferably uses a carbide die with a small angle of 7-8° to reduce localized large deformation during the wire drawing process and avoid necking and wire breakage. The amount of deformation per pass gradually decreases as the wire diameter decreases, and the preheating temperature and die temperature of the wire also gradually decrease as the wire diameter decreases.

[0096] More preferably, the small diameter tungsten wire of 30-40 μm in step 9 can be obtained by drawing with a diamond die 40 times.

[0097] In the technical solution of the present invention, controlling the relative contents of transition metal elements and tungsten is fundamental to achieving the precipitation of the Laves phase. However, this requires coordinated coordination of the manufacturing process technologies to achieve the desired microstructure and distribution, and to ensure the feasibility of the process from tungsten powder to the final ultrafine micron-scale tungsten wire. Highly fluid blue tungsten powder is uniformly mixed with nickel nitrate, iron, and cerium solutions to achieve uniform mixing of transition elements. The addition of zirconium hydride powder ensures the successful alloying of easily oxidizable elements into the matrix. During the process, rare earth cerium forms a dispersed oxide, while the small amount of oxidized zirconium also acts as a grain coarsening inhibitor and a dispersion-strengthened secondary phase in the matrix. Multiple drawing passes achieve sufficient work hardening and grain refinement. The combined action of these multiple strengthening mechanisms ensures the production of high-performance ultrafine tungsten wire.

[0098] Example 1

[0099] An ultrafine high-strength tungsten wire strengthened by laves phase precipitation is prepared. Raw material powder is weighed according to the designed formula. The mass percentage composition of the tungsten wire is: Ni: 0.4%, Fe: 0.3%, Zr: 0.7%, Ce: 0.8%, the impurity content is less than 0.01%, and the balance is W. The preparation method is as follows:

[0100] (1) Weigh nickel nitrate, ferric nitrate nonahydrate, and cerium nitrate according to the composition ratio, stir thoroughly and dissolve in sufficient alcohol. Spray the nitrate alcohol solution evenly on the surface of the blue tungsten powder in a mixer, and stir the solid-liquid mixture until the alcohol evaporates and the powder no longer agglomerates.

[0101] (2) The uniformly doped mixed powder was reduced in a hydrogen reduction furnace at 850°C for 3 hours to obtain alloy tungsten powder. After sufficient cooling, the alloy tungsten powder was uniformly mixed with zirconium hydride powder added according to the composition ratio in a V-type mixer under argon protection for 24 hours. The mixed alloy tungsten powder was isostatically pressed into a tungsten rod at a pressure of 200 MPa, and the pressing and holding time was 5 minutes.

[0102] (3) The pressed tungsten rod was pre-sintered at 1300°C in a hydrogen furnace for 50 min. Three insulation platforms of 400°C, 600°C and 800°C were set before the highest temperature for 20 min each. Then, the pre-sintered tungsten rod was re-sintered at 2100°C in a medium frequency induction furnace (densification sintering, temperature marked as T1) for 240 min to obtain a sintered tungsten rod.

[0103] (4) The sintered tungsten rod is preheated in a hydrogen atmosphere protective furnace for 30 minutes and then rotary forged. The preheating temperature is 1550℃. The deformation of the rotary forging process is 1-1.5mm. After each process, it is returned to the furnace and kept warm for 4 minutes before the next rotary forging process. The rotary forging process produces a tungsten rod with a diameter of 9mm. It is then annealed at 1800℃ for 1 minute by medium frequency induction. The annealed tungsten rod is preheated at 1450℃ for 15 minutes and then rotary forged to obtain a thin tungsten rod with a diameter of 3.6mm.

[0104] (5) The thin tungsten rod obtained by rotary forging is uniformly passed through the flowing graphite slurry and then preheated in a furnace at 1150℃. It is then chain-drawn through a carbide die. The carbide die is heated at 900℃. After four die drawing passes, the tungsten wire has a diameter of 2.8mm. The tungsten wire obtained by chain drawing is then turned on a rotary table. The tungsten wire drawing process goes through the thick wire to the thin wire stage. As the wire diameter decreases, the preheating temperature and die temperature gradually decrease. The preheating temperature is 500-1100℃, and the drawing die heating temperature is 400-800℃. After 40 passes, it is drawn to a thin black tungsten wire with a diameter of 34μm.

[0105] The black tungsten wire with a diameter of 34 μm prepared above has a tensile strength of 7124 MPa, an elongation at break of 1.5%, and an elastic modulus of 408 GPa.

[0106] Example 2

[0107] Compared to Example 1, Example 2 differs only in that the Ni, Fe, Zr, and Ce contents in the raw materials are controlled. The mass percentage composition of the tungsten wire is: Ni: 0.2%, Fe: 0.2%, Zr: 0.4%, Ce: 0.4%, and impurity content is less than 0.01%, with the remainder being W. The preparation process of Example 2 is the same as that of Example 1, except that the tungsten blank is densified and sintered at a temperature of 2200°C (T1). The tungsten blank undergoes the same 40-pass diamond die drawing process to obtain a fine black tungsten wire with a diameter of 34 μm. Testing shows that the 34 μm diameter black tungsten wire prepared above has a tensile strength of 6336 MPa, an elongation at break of 2.7%, and an elastic modulus of 427 GPa.

[0108] Example 3

[0109] Compared to Example 1, Example 3 employed the same tungsten filament composition by mass percentage, directly using tungsten powder as the raw material. Following the same preparation process, fine black tungsten filament with a diameter of 34 μm was produced. Testing revealed that the resulting 34 μm black tungsten filament had a tensile strength of 6814 MPa, an elongation at break of 1.8%, and an elastic modulus of 412 GPa. Using tungsten powder, which has poor fluidity, as the raw material for the mixture, the uniformity of the mixture when nickel, iron, and cerium sources were introduced was inferior to that of tungsten oxide, a raw material with excellent fluidity. Consequently, the tensile strength of the tungsten filament produced with the same composition was inferior to that of tungsten filament produced with a more uniform mixture.

[0110] Example 4

[0111] Compared to Example 1, Example 4 uses exactly the same tungsten wire mass percentage composition, and the final densification sintering is carried out at 2300°C (T1) for 240 minutes. Subsequently, the same preparation process is used to obtain a fine black tungsten wire with a diameter of 34μm. After testing, the 34μm diameter black tungsten wire prepared above has a tensile strength of 6774MPa, an elongation at break of 1.9%, and an elastic modulus of 415GPa. In Example 4, increasing the densification temperature of the tungsten blank causes the grains of the sintered tungsten blank to be coarser. Subsequently, the same process is used to prepare tungsten wire. The coarser grain size in the primary blank causes the final wire tensile strength to be slightly lower than that of Example 1.

[0112] Example 5

[0113] Compared with Example 2, the only difference is that in step 2, the reduction temperature is 900° C. and the reduction time is 4 hours. Other operations and parameters are the same as in Example 2.

[0114] Testing showed that the 34μm diameter black tungsten wire prepared above had a tensile strength of 6156MPa, an elongation at break of 2.8%, and an elastic modulus of 423GPa. The W-coated Ni-Fe-Ce composite metal powder obtained using a higher reduction temperature and longer reduction time has a coarser powder particle size. When the same sintering and processing techniques are subsequently used, the coarse powder has poorer sintering activity than the fine powder, resulting in a slightly lower density and coarser grain size in the sintered blank. The tensile strength of the wire after subsequent drawing is slightly lower than that of tungsten wire prepared from the raw powder using a shorter, faster reduction time.

[0115] Comparative Example 1

[0116] Compared with Example 1, the only difference is that the designed mass percentage composition of the raw materials in the tungsten wire is: Ni: 0.1%, Fe: 0.1%, Zr: 0.2%, Ce: 0.1%, the impurity content is less than 0.01%, and the balance is W. Other operations and parameters are the same as in Example 1.

[0117] The resulting 34μm-diameter black tungsten wire exhibited a tensile strength of 5673MPa, an elongation at break of 2.8%, and an elastic modulus of 429GPa. Comparative Example 1 demonstrates that when relatively low amounts of intermetallic and rare earth oxide-forming elements are added, it is difficult to significantly increase the tensile strength of the tungsten wire solely through work hardening, grain refinement, and weak intermetallic precipitation and oxide dispersion strengthening during the drawing process. Therefore, the Laves phase-forming and rare earth element content must be maintained.

[0118] Comparative Example 2

[0119] Compared with Example 1, the only difference is that in step 1, Ni, Fe and Zr are not added, that is, the designed mass percentage composition of the raw materials in the tungsten wire is: Ni: 0%, Fe: 0%, Zr: 0%, Ce: 0.5%, the impurity content is less than 0.01%, and the balance is W.

[0120] The preparation process of Comparative Example 2 is the same as that of Example 1, except that the densification sintering temperature of the tungsten blank is 2300° C. and the fine black tungsten wire with a diameter of 34 μm is obtained through the same 40 diamond die drawing passes.

[0121] Testing revealed that the 34μm diameter black tungsten wire produced above had a tensile strength of 5215MPa, an elongation at break of 3.1%, and an elastic modulus of 433GPa. The high performance of ultrafine tungsten wire is not solely due to dispersion strengthening of a small amount of rare earth oxides, grain refinement through drawing, and work hardening.

[0122] Comparative Example 3

[0123] Compared with Example 1, the only difference is that in step 1, Fe, Zr and Ce are not added, that is, the mass percentage composition of the raw materials of the tungsten wire is designed to be: Ni: 0.4%, Fe: 0%, Zr: 0%, Ce: 0%, the impurity content is less than 0.01%, and the balance is W.

[0124] Testing revealed that the 34μm-diameter black tungsten wire produced above exhibited a tensile strength of 5732MPa, an elongation at break of 2.2%, and an elastic modulus of 418GPa. The production of ultra-high-strength, ultrafine tungsten wire requires the coordinated addition of intermetallic compound-forming elements and rare earth elements to achieve in-situ Laves phase and rare earth oxide composite reinforcement.

[0125] Comparative Example 4

[0126] Compared with Example 1, the only difference is that in step 1, raw material powder is weighed according to the designed formula, wherein the mass percentage composition of the tungsten wire is: Ni: 0.9%, Fe: 0.8%, Zr: 0.9%, Ce: 1.2%, the impurity content is less than 0.01%, and the balance is W. The preparation method is as follows:

[0127] (1) Weigh nickel nitrate, ferric nitrate nonahydrate, and cerium nitrate according to the composition ratio, stir thoroughly and dissolve in sufficient alcohol. Spray the nitrate alcohol solution evenly on the surface of the blue tungsten powder in a mixer, and stir the solid-liquid mixture until the alcohol evaporates and the powder no longer agglomerates.

[0128] (2) The uniformly doped mixed powder was reduced in a hydrogen reduction furnace at 850°C for 3 hours to obtain alloy tungsten powder. After sufficient cooling, the alloy tungsten powder was uniformly mixed with zirconium hydride powder added according to the composition ratio in a V-type mixer under argon protection for 24 hours. The mixed alloy tungsten powder was isostatically pressed into a tungsten rod at a pressure of 200 MPa, and the pressing and holding time was 5 minutes.

[0129] (3) The pressed tungsten rod was pre-sintered at 1300°C in a hydrogen furnace for 50 min. Three insulation platforms of 400°C, 600°C and 800°C were set before the highest temperature for 20 min each. Then the pre-sintered tungsten rod was re-fired at 2100°C in a medium frequency induction furnace for 240 min to obtain a sintered tungsten rod.

[0130] (4) The sintered tungsten rod was preheated in a hydrogen atmosphere protective furnace for 30 minutes before being forged into a blank. The preheating temperature was 1500°C, and the deformation of the forging process was 1-1.5 mm. After the forging process was completed, forging cracks occurred during the subsequent stringing process. Excessive addition of transition metal-forming elements caused the formation of an excessive amount of brittle Laves phase, which deteriorated the thermoplasticity of the tungsten rod and made it impossible to produce ultrafine tungsten wire through subsequent stringing and drawing.

[0131] Comparative Example 5

[0132] Compared with Example 1, the only difference is that in step 1, the same tungsten wire mass percentage group as in Example 1 is used, blue tungsten powder is used as the mixed raw material powder, Ni and Fe are directly added using micron-sized metal powder, the cerium source is added in the mixing process in the form of nano-oxide, and the Zr source is still added in the form of ZrH2 powder.

[0133] Using the same preparation process as Example 1, the sintered rod exhibited severe forging cracking during the rotary forging process, making subsequent stringing and drawing processing impossible. Intermetallic compound-forming elements were added in powder form and in situ composited with the tungsten matrix to form a coarse-sized brittle Laves phase, resulting in a composition formula that could not be used throughout the entire process of ultrafine tungsten wire production.

[0134] Table 1 Comparison of mechanical properties of high-speed steel prepared in Example and Comparative Example

[0135]

[0136] Through the performance comparison of the examples and comparative examples, it can be seen that the ultrafine tungsten wire prepared by the present invention has the characteristics of high fracture strength and high elastic modulus. The elemental metal elements nickel, iron and zirconium are formed by composite intermetallic compounds through powder metallurgy technology. The in-situ precipitation of Laves phase during the sintering preparation process can bring significant precipitation strengthening effect to the tungsten wire. At the same time, it is supplemented by the drawing grain refinement strengthening and the cerium dioxide and zirconium dioxide to inhibit grain coarsening and dispersion strengthening effects. Under the joint action of multiple strengthening mechanisms, the ultrafine tungsten wire with excellent performance is obtained. Compared with the preparation of ultrafine tungsten wire by rare earth addition, the tungsten wire prepared by the present invention has excellent performance. At the same time, it does not require the addition of large amounts of expensive rare earth elements. The process is simple and the cost is low, which can better meet the application requirements of diamond wire core wire.

Claims

1. Laves phase precipitation strengthened tungsten wire, characterized in that: It includes tungsten matrix, oxides dispersed therein and laves strengthening phase formed in situ; The laves strengthening phase includes NiW2, WFe2 and WZr2; the oxides are ZrO2 and CeO2; In the laves phase precipitation strengthened tungsten wire, the content of Ni is 0.2-0.6wt%, the content of Fe is 0.2-0.6wt%, the content of Zr is 0.3-0.8wt%, the content of Ce is 0.1-1.2wt%, and the balance is tungsten; The steps for preparing the laves phase precipitation strengthened tungsten wire include: Step (1): preparing the ingredients according to the element content of the laves phase precipitation strengthened tungsten wire, spraying a solution containing the required amount of nickel source, iron source and cerium source on the surface of the tungsten source powder, and then performing a reduction treatment to obtain Ni-Fe-Ce coated W composite particles, wherein the temperature of the reduction stage is 800-900°C; Step (2): compounding Ni-Fe-Ce coated W composite particles and a required amount of zirconium hydride and forming a composite blank; Step (3): pre-sintering the composite blank at 1200-1400° C., and then sintering at 2000-2400° C. to obtain a sintered blank; Step (4): The sintered material is subjected to rotary forging, annealing, stringing, and drawing to obtain the laves phase precipitation-strengthened tungsten wire.

2. The laves phase precipitation strengthened tungsten wire according to claim 1, characterized in that: In the laves phase precipitation strengthened tungsten wire, the Ni content is 0.2-0.5wt%, the Fe content is 0.2-0.4wt%, the Zr content is 0.3-0.7wt%, the Ce content is 0.2-1.0wt%, and the balance is W.

3. The laves phase precipitation strengthened tungsten wire according to claim 1, characterized in that: The Ni content is 0.2~0.45wt%, the Fe content is 0.2~0.35wt%, the Zr content is 0.4~0.7wt%, the Ce content is 0.4~1.0wt%, and the balance is W.

4. The laves phase precipitation strengthened tungsten wire according to claim 1, characterized in that: The Ni content is 0.3~0.4wt%, the Fe content is 0.25~0.3wt%, the Zr content is 0.6~0.7wt%, the Ce content is 0.7~0.9wt%, and the balance is W.

5. The laves phase precipitation strengthened tungsten wire according to claim 1, characterized in that: The size of the laves reinforcement phase is <300nm.

6. The laves phase precipitation strengthened tungsten wire according to claim 1, characterized in that: The diameter of the laves phase precipitation strengthened tungsten wire is 30-40 μm.

7. A method for preparing a laves phase precipitation-strengthened tungsten wire according to any one of claims 1 to 6, characterized in that the steps include: Step (1): preparing the ingredients according to the element content of the laves phase precipitation strengthened tungsten wire, spraying a solution containing the required amount of nickel source, iron source and cerium source on the surface of the tungsten source powder, and then performing a reduction treatment to obtain Ni-Fe-Ce coated W composite particles, wherein the temperature of the reduction stage is 800-900°C; Step (2): compounding Ni-Fe-Ce coated W composite particles and a required amount of zirconium hydride and forming a composite blank; Step (3): pre-sintering the composite blank at 1200-1400° C., and then sintering at 2000-2400° C. to obtain a sintered blank; Step (4): The sintered material is subjected to rotary forging, annealing, stringing, and drawing to obtain the laves phase precipitation-strengthened tungsten wire.

8. The method for preparing laves phase precipitation strengthened tungsten wire according to claim 7, characterized in that: The nickel source is nickel nitrate; The iron source is ferric nitrate; The cerium source is cerium nitrate.

9. The method for preparing laves phase precipitation strengthened tungsten wire according to claim 7, characterized in that: The solvent in the solution is at least one of alcohol and water.

10. The method for preparing laves phase precipitation strengthened tungsten wire according to claim 8, characterized in that: The solvent in the solution is an alcohol-water solvent with an alcohol volume content of 30-80 vol%.

11. The method for preparing laves phase precipitation strengthened tungsten wire according to claim 8, characterized in that: In the solution, the total concentration of solute is 0.2-0.4 g / ml.

12. The method for preparing laves phase precipitation strengthened tungsten wire according to claim 7, characterized in that: The tungsten source powder is metal tungsten powder and / or blue tungsten powder.

13. The method for preparing laves phase precipitation strengthened tungsten wire according to claim 7, characterized in that: The solution is sprayed on the surface of the tungsten source powder while being stirred and evenly mixed, and then subjected to subsequent reduction treatment after drying treatment.

14. The method for preparing laves phase precipitation strengthened tungsten wire according to claim 7, characterized in that: The atmosphere in the reduction stage is a hydrogen-containing atmosphere; The temperature in the reduction stage is 840~860℃; The treatment time of the reduction stage is 2~4h.

15. The method for preparing laves phase precipitation strengthened tungsten wire according to claim 7, characterized in that: In step (2), Ni-Fe-Ce coated W composite particles and zirconium hydride are compounded in a protective atmosphere; The molding method is steel die pressing or isostatic pressing; the pressing pressure is 200~300MPa, and the holding time is 3~5min; The green density of the composite blank obtained by molding is 9.0~14.0g / cm 3 .

16. The method for preparing laves phase precipitation strengthened tungsten wire according to claim 7, characterized in that: During the process of heating to pre-sintering, four insulation platforms are set at 350~450℃, 550~650℃, 750~850℃ and 1200~1400℃, and the insulation time of each insulation platform is 10~30min.

17. The method for preparing laves phase precipitation strengthened tungsten wire according to claim 16, wherein: The pre-sintering time is 45 to 80 minutes.

18. The method for preparing laves phase precipitation strengthened tungsten wire according to claim 16, wherein: The final densification sintering time is 200~300min.

19. The method for preparing laves phase precipitation strengthened tungsten wire according to claim 7, characterized in that: Before rotary forging, preheat the blank in a hydrogen atmosphere protection furnace for 20-40 minutes at a preheating temperature of 1400-1600°C. The deformation of the rotary forging process is 1-1.5mm. After each process, return to the furnace and keep warm for 3-5 minutes before the next rotary forging process. The thin tungsten rod with a diameter of 3.5~3.9mm can be obtained by rotary forging. The atmosphere during the annealing stage is a hydrogen-containing atmosphere; The annealing temperature is 1600~1900℃; The drawing steps are chain drawing and turntable drawing, wherein the diameter of the tungsten wire in chain drawing is 2.4~2.8mm; The diameter of the rotary table drawing is 30~40μm.

20. Use of the laves phase precipitation strengthened tungsten wire according to any one of claims 1 to 6 or the laves phase precipitation strengthened tungsten wire prepared by the preparation method according to any one of claims 7 to 19, characterized in that: A cutting tool for semiconductor silicon wafers.

21. A semiconductor silicon plate cutting tool, characterized in that: The invention comprises the laves phase precipitation-strengthened tungsten wire according to any one of claims 1 to 6 or the laves phase precipitation-strengthened tungsten wire prepared by the preparation method according to any one of claims 7 to 19.

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