Aquadag for high-temperature drawing of superfine tungsten filament and preparation method of aquadag

Abstract

The invention relates to the technical field of metal wire deep processing, in particular to aquadag for superfine tungsten filament high-temperature drawing and a preparation method of the aquadag. The preparation method comprises the following steps: adding a dispersing agent, ammonia water and graphite powder into ultrapure water, pre-dispersing by using a dispersing disc, adding a stabilizer, a lubrication enhancer, a thickening agent and an adhesive, uniformly mixing, and sanding the mixed solution in a sand mill to obtain aquadag; according to the aquadag for high-temperature drawing of the superfine tungsten filament and the preparation method of the aquadag, the aquadag has good storage stability and excellent lubricating effect, in the high-temperature drawing process of the tungsten filament, the aquadag can uniformly cover the surface of the tungsten filament to form a compact graphite layer, and the superfine tungsten filament obtained after high-temperature drawing is small in wire diameter (smaller than or equal to 36 micrometers), large in ring diameter (larger than or equal to 30 mm) and low in wire drawing breakage rate (2.1%); the wire drawing qualification rate is high (92.6%), and the method is suitable for large-scale drawing production of superfine tungsten wires; the aquadag has few organic components, ash content generated after high-temperature drawing is low, the production method is simple, and the cost is low.

Description

Technical Field

[0001] This invention relates to the field of metal wire deep processing technology, specifically to a graphite emulsion for high-temperature drawing of ultrafine tungsten wire and its preparation method. Background Technology

[0002] With the surge in demand for ultrafine tungsten wires (diameter ≤36μm) from the photovoltaic industry and precision electronic devices, the drawing process places higher demands on the performance of lubricants. Traditional graphite emulsions commonly suffer from insufficient lubrication, poor dispersion stability, and weak high-temperature adhesion during the high-temperature drawing process of ultrafine tungsten wires, resulting in defects such as severe die wear, obvious scratches on the wire surface, and high wire breakage rate.

[0003] In the high-temperature drawing process of ultrafine tungsten wire, graphite emulsion, as a key lubricating medium, directly determines the die life and wire quality. Existing technology provides a graphite emulsion for lubrication in the drawing process of high-strength tungsten wire, and its preparation method, as disclosed in Chinese Patent Publication No. CN118028046A. This method improves graphite dispersibility through multiple sand milling and high-energy mixing processes, and adds silicone masterbatch as a lubricant, significantly reducing the coefficient of friction. However, the complex preparation process significantly increases costs, and the tungsten wire qualification rate is only 70-85%, still failing to meet the requirements for large-scale application. CN116921484A provides a graphite emulsion for drawing high-strength fine tungsten wire, using a simplified process with low-viscosity water-based graphite emulsion, but the graphite content is relatively low (3%-8%), making it difficult to meet the dual requirements of ultrafine tungsten wire for extreme lubrication and tensile strength (≥5.8GPa).

[0004] In summary, existing graphite emulsions still suffer from problems such as insufficient dispersion stability, poor adhesion, and reduced high-temperature lubrication performance in the high-temperature drawing of ultrafine tungsten wires. These problems not only reduce the service life of the mold and accelerate mold wear, but also reduce the lubrication effect of the graphite emulsion, while increasing the wire breakage rate and reducing the pass rate.

[0005] Therefore, there is an urgent need for a graphite emulsion for high-temperature drawing of ultrafine tungsten wires and its preparation method. Summary of the Invention

[0006] The purpose of this invention is to provide a novel graphite emulsion that combines high dispersibility, high temperature resistance, and excellent adhesion, so as to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, firstly, the present invention provides a graphite emulsion for high-temperature drawing of ultrafine tungsten wires, comprising the following raw materials: The composition comprises: graphite powder (5-25% by weight), dispersant (0.1-5% by weight), stabilizer (0.1-3% by weight), lubricant / enhancer (0.1-10% by weight), thickener (0.1-15% by weight), binder (0.5-15% by weight), ammonia (0.1-5% by weight), and ultrapure water as the balance. The graphite emulsion has a solids content of 10%-20%, a pH of 9-11, a particle size ≤0.7 μm, and a viscosity ≤300 mPa·s. The graphite powder is made from natural cryptocrystalline graphite with a D50 particle size ≤3 μm and a purity ≥99.99%. The dispersant is one or more of sodium carboxymethyl cellulose, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, phytic acid, and polyvinylpyrrolidone. The stabilizer is one or more of fumed silica, magnesium aluminosilicate, and organobentonite. The lubricating enhancer is one or more of the following: triethyl phosphate, nonylphenol polyoxyethylene ether phosphate, isooctanol phosphate, sodium polyphosphate, and potassium dihydrogen phosphate. The thickener is one or more of hydroxyethyl cellulose, methyl cellulose, sodium polyacrylate, and xanthan gum; The adhesive is one or more of polyvinyl alcohol, polyethylene glycol, and styrene-maleic anhydride copolymer emulsion.

[0008] Secondly, the present invention also provides a method for preparing graphite emulsion for high-temperature drawing of ultrafine tungsten wires, comprising the following steps: Dispersant, ammonia, and graphite powder are added to ultrapure water and pre-dispersed using a dispersion disc. Then, stabilizer, lubricant, thickener, and binder are added and mixed evenly to obtain a mixed solution. Next, the mixed solution is placed in a sand mill and ground to obtain a uniformly dispersed graphite emulsion.

[0009] Furthermore, the pre-dispersion time is 0.5-3 hours, the mixing time of the raw materials is 1-5 hours, the speed of the sand mill is 1000-2000 r / min, the sand milling medium is zirconia beads, the volume of the zirconia beads accounts for 50-80% of the total volume of the sand milling jar, and the sand milling time is 8-36 hours.

[0010] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. In the graphite emulsion for high-temperature drawing of ultrafine tungsten wire and its preparation method, the graphite emulsion has good storage stability and excellent lubrication effect. During the high-temperature drawing process of tungsten wire, it can uniformly cover the surface of tungsten wire to form a dense graphite layer. The ultrafine tungsten wire obtained after high-temperature drawing has a small wire diameter (≤36μm), a large coil diameter (≥30mm), a low wire breakage rate (2.1%), and a high wire qualification rate (92.6%), which is suitable for large-scale drawing production of ultrafine tungsten wire. The graphite emulsion has low organic content and produces less ash after high-temperature drawing. The production method is simple and low-cost.

[0011] 2. In the graphite emulsion for high-temperature drawing of ultrafine tungsten wire and its preparation method, when cryptocrystalline graphite is selected as the lubricating material, low shear slip is achieved through the weak van der Waals forces of the layered structure of cryptocrystalline graphite, reducing the coefficient of friction; the small particle size (≤3μm) can promote the uniform dispersion of cryptocrystalline graphite, which can be stably suspended in the graphite emulsion for a long time, while reducing scratches on the surface of the tungsten wire, resulting in high-quality ultrafine tungsten wire; the abundant structural defects and high specific surface area enhance the physical anchoring effect with the matrix, improve the coating uniformity and interface coverage efficiency of the graphite emulsion on the ultrafine tungsten wire, thereby effectively blocking direct contact between metals.

[0012] 3. In the graphite emulsion for high-temperature drawing of ultrafine tungsten wire and its preparation method, when organic phosphate molecules are selected as lubricating and reinforcing agents, the phosphate groups of the organic phosphate molecules are physically adsorbed onto the surface of the tungsten wire to form an ordered adsorption layer, and a tribochemical reaction occurs with the metal surface to generate a phosphorus-containing protective film. Alkaline elements ( As a charge compensator, it promotes the formation of a phosphorus protective film, reduces friction, and improves high-temperature lubrication performance. Attached Figure Description

[0013] Figure 1 This is Embodiment 1 of the present invention ( Figure 1 a) Example 2 ( Figure 2 a) Example 3 ( Figure 3 a) A photograph of the prepared graphite emulsion; Figure 2 This is Embodiment 1 of the present invention ( Figure 1 A) Example 2 ( Figure 2 A) Example 3 ( Figure 3 A) A photograph of the prepared graphite emulsion after standing for 30 days; Figure 3 This is a SEM image of the tungsten wire after high-temperature drawing of the graphite emulsion prepared in Example 1 of this invention. Figure 4 This is a SEM image of a tungsten wire after high-temperature drawing of an ultrafine tungsten wire using the THL-16 commercial graphite emulsion of this invention. Figure 5This is a SEM image of a tungsten wire after high-temperature drawing using the commercial graphite emulsion of copper chloride 4b of this invention. Detailed Implementation

[0014] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0015] Example 1 Particle size 2.5μm, purity 99.99%, cryptocrystalline graphite 20% (by weight); dispersant 4% (by weight), sodium dodecyl sulfate and polyvinylpyrrolidone; stabilizer 3% (by weight), fumed silica; lubricant 2% (by weight), triethyl phosphate and potassium dihydrogen phosphate; thickener 5% (by weight), sodium polyacrylate and xanthan gum; binder 12% (by weight), polyvinyl alcohol; ammonia 5% (by weight); ultrapure water balance.

[0016] Dispersant, ammonia, and cryptocrystalline graphite were added to ultrapure water and pre-dispersed in a dispersion pan for 2 hours. Then, stabilizer, lubricant, thickener, and binder were added and mixed for 1 hour to obtain a mixed solution. The solution was then placed in a sand mill and milled at 1500 r / min for 20 hours. The milling media was zirconia beads, and the volume of the zirconia beads accounted for 65% of the total volume of the milling jar, resulting in a uniformly dispersed graphite emulsion.

[0017] The obtained graphite emulsion had a specific gravity of 1.092, an ash content of 2%, a solid content of 22%, a viscosity of 172 mPa·s, and a D50 particle size of 0.648 μm.

[0018] Example 2 Particle size 3μm, purity 99.99%, cryptocrystalline graphite 18% (by weight); dispersant 6% (by weight), sodium carboxymethyl cellulose and polyvinylpyrrolidone; stabilizer 4% (by weight), magnesium aluminosilicate; lubricant 3% (by weight), nonylphenol polyoxyethylene ether phosphate and sodium polyphosphate; thickener 7% (by weight), hydroxyethyl cellulose and sodium polyacrylate; binder 15% (by weight), polyethylene glycol and styrene-maleic anhydride copolymer emulsion; ammonia 4% (by weight); ultrapure water balance.

[0019] Dispersant, ammonia, and cryptocrystalline graphite were added to ultrapure water and pre-dispersed in a dispersion pan for 3 hours. Then, stabilizer, lubricant, thickener, and binder were added and mixed for 1.5 hours to obtain a mixed solution. The solution was then placed in a sand mill and milled at 2100 r / min for 30 hours. The milling medium was zirconia beads, and the volume of the zirconia beads accounted for 80% of the total volume of the milling jar, resulting in a uniformly dispersed graphite emulsion.

[0020] The obtained graphite emulsion had a specific gravity of 1.018, an ash content of 2.3%, a solid content of 24%, a viscosity of 196 mPa·s, and a D50 particle size of 0.648 μm.

[0021] Example 3 Particle size 1.8μm, purity 99.99%, cryptocrystalline graphite 21% (by weight); dispersant 6% (by weight), using phytic acid and sodium dodecylbenzenesulfonate; stabilizer 3% (by weight), using organobentonite; lubricant enhancer, using isooctanol phosphoric acid and sodium polyphosphate 5% (by weight); thickener 5% (by weight), using methylcellulose and xanthan gum; binder 13% (by weight), using polyvinyl alcohol and styrene-maleic anhydride copolymer emulsion; ammonia 6% (by weight); ultrapure water balance.

[0022] Dispersant, ammonia, and cryptocrystalline graphite were added to ultrapure water and pre-dispersed in a dispersion pan for 4 hours. Then, stabilizer, lubricant, thickener, and binder were added and mixed for 3 hours to obtain a mixed solution. The solution was then placed in a sand mill and milled at 3000 r / min for 28 hours. The milling medium was zirconia beads, and the volume of the zirconia beads accounted for 70% of the total volume of the milling tank to obtain a uniformly dispersed graphite emulsion.

[0023] The obtained graphite emulsion had a specific gravity of 1.022, an ash content of 2.1%, a solid content of 21%, a viscosity of 163 mPa·s, and a D50 particle size of 0.652 μm.

[0024] according to Figure 1 and Figure 2 As shown, the graphite emulsion is a black emulsion that remains homogeneous and stable after standing for 30 days at room temperature and pressure, without any stratification or change in properties; this demonstrates that the graphite emulsion system has excellent physical stability.

[0025] To verify that the graphite emulsion prepared in the embodiments of the present invention has good uniformity, actual lubrication performance and drawing stability, the following experimental examples are used to illustrate the graphite emulsion provided in the embodiments of the present invention.

[0026] Test case The purpose of this experimental group is to investigate the effect of different component ratios on graphite emulsions, and to test the uniformity, actual lubrication performance and wire drawing stability of the graphite emulsion of this invention.

[0027] Experimental Objective: Experimental groups A, B, and C used the graphite emulsion composition ratios provided in Examples 1-3, respectively; the control group consisted of control groups A, B, C, D, and E, wherein: Control group A The raw material composition differs from that of Example 1 only in the type and particle size of graphite powder. Specifically, it consists of: 20% (by weight) crystalline graphite with a particle size of 8 μm and a purity of 99.99%; 4% (by weight) dispersant (made by mixing sodium dodecyl sulfate and polyvinylpyrrolidone in the proportion of Example 1); 3% (by weight) stabilizer (made by fumed silica); 2% (by weight) lubricant enhancer (made by mixing triethyl phosphate and potassium dihydrogen phosphate in the proportion of Example 1); 5% (by weight) thickener (made by mixing sodium polyacrylate and xanthan gum in the proportion of Example 1); 12% (by weight) binder (made by polyvinyl alcohol); 5% (by weight) ammonia; and ultrapure water to bring the total weight to 100%. The preparation method is as follows: The dispersant, ammonia, and crystalline graphite in the above proportions are added to ultrapure water and pre-dispersed in a dispersion disc for 2 hours. Then, the corresponding proportions of stabilizer, lubricant enhancer, thickener, and binder are added and mixed for 1 hour to obtain a mixed solution. The mixed solution is placed in a sand mill and milled at a speed of 1500 r / min for 20 hours. The milling medium is zirconia beads, and the volume of zirconia beads accounts for 65% of the total volume of the milling tank. Finally, a uniformly dispersed graphite emulsion is obtained. The graphite emulsion has a specific gravity of 1.089, an ash content of 2%, a solid content of 22%, a viscosity of 199 mPa·s, and a D50 particle size of 3.433 μm.

[0028] Control group B The raw material composition differs from that of Example 2 only in that it does not contain the lubricating enhancer (nonylphenol polyoxyethylene ether phosphate and sodium polyphosphate). Specifically, it consists of: 18% (by weight) cryptocrystalline graphite with a particle size of 3 μm and a purity of 99.99%; 6% (by weight) dispersant (made by mixing sodium carboxymethyl cellulose and polyvinylpyrrolidone in the proportion of Example 2); 4% (by weight) stabilizer (made by magnesium aluminosilicate); 7% (by weight) thickener (made by mixing hydroxyethyl cellulose and sodium polyacrylate in the proportion of Example 2); 15% (by weight) binder (made by mixing polyethylene glycol and polystyrene maleic anhydride copolymer emulsion in the proportion of Example 2); 4% (by weight) ammonia; and ultrapure water to make up to 100% by weight. The preparation method is as follows: The dispersant, ammonia, and cryptocrystalline graphite in the above proportions are added to ultrapure water and pre-dispersed in a dispersion pan for 3 hours. Then, the corresponding proportions of stabilizer, thickener, and binder are added and mixed for 1.5 hours to obtain a mixed solution. The mixed solution is placed in a sand mill and milled at a speed of 2100 r / min for 30 hours. The milling medium is zirconia beads, and the volume of zirconia beads accounts for 80% of the total volume of the milling tank. Finally, a uniformly dispersed graphite emulsion is obtained. The graphite emulsion has a specific gravity of 1.089, an ash content of 1.6%, a solid content of 22%, a viscosity of 159 mPa·s, and a D50 particle size of 0.633 μm.

[0029] Control group C The raw material composition differs from that of Example 3 only in that it does not contain a binder (polyvinyl alcohol and styrene-maleic anhydride copolymer emulsion). Specifically, it consists of: 21% (by weight) cryptocrystalline graphite with a particle size of 1.8 μm and a purity of 99.99%; 6% (by weight) dispersant (made by mixing phytic acid and sodium dodecylbenzenesulfonate in the proportions of Example 3); 3% (by weight) stabilizer (made by organic bentonite); 5% (by weight) lubricant enhancer (made by mixing isooctanol phosphoric acid and sodium polyphosphate in the proportions of Example 3); 5% (by weight) thickener (made by mixing methylcellulose and xanthan gum in the proportions of Example 3); 6% (by weight) ammonia; and ultrapure water to bring the total to 100% by weight. The preparation method is as follows: The dispersant, ammonia, and cryptocrystalline graphite in the above proportions are added to ultrapure water and pre-dispersed in a dispersion pan for 4 hours. Then, the corresponding proportions of stabilizer, lubricant enhancer, and thickener are added and mixed for 3 hours to obtain a mixed solution. The mixed solution is placed in a sand mill and milled at a speed of 3000 r / min for 28 hours. The milling medium is zirconia beads, and the volume of zirconia beads accounts for 70% of the total volume of the milling tank. Finally, a uniformly dispersed graphite emulsion is obtained. The graphite emulsion has a specific gravity of 1.083, an ash content of 1.3%, a solid content of 19%, a viscosity of 144 mPa·s, and a D50 particle size of 0.677 μm.

[0030] Control group D The commercially available mainstream graphite emulsion product THL-16 is used.

[0031] Control group E The commercially available graphite emulsion product, copper chloride ore 4b, was used.

[0032] according to Figures 3-5 As shown, scanning electron microscope images of the tungsten wire surface sampled on-site during the wire drawing process are presented. The actual coating effect of the graphite emulsion is evaluated through the microscopic morphology characterization of the graphite coating: according to Figure 3 As shown, the graphite emulsion prepared in Example 1 exhibits good coating effect, with uniform distribution of graphite particles on the tungsten wire surface. In contrast, Figure 4 The THL-16 shown is Figure 5 The coating effects of the copper chloride 4b shown are all significantly different: although graphite is visible on the surface, it exhibits an uneven distribution; this unevenness is directly related to the regular trembling phenomenon during the wire drawing process.

[0033] Test methods: Based on the uniformity, actual lubrication performance, and drawing stability of the graphite emulsion according to the present invention, tests were conducted respectively. The specific test methods are as follows: Uniformity: The experimental group AC and the control group AE were compared according to the particle size distribution test requirements in GB / T15064-2008 "Test Methods for Graphite Emulsions in CRTs". A laser particle size analyzer was used to detect the particle size of the graphite emulsion samples from both groups. The specific steps were as follows: First, the graphite emulsion samples were diluted with ultrapure water to a suitable concentration (ensuring the laser shielding rate was within the instrument's optimal detection range of 5%-15%). The samples were then ultrasonically dispersed for 10 minutes to eliminate particle agglomeration. The diluted samples were then injected into the detection cell of the laser particle size analyzer. After the instrument stabilized, the particle size distribution was tested. Each sample was tested in triplicate, and the average value was taken as the final result. The uniformity of the graphite emulsion was evaluated by calculating the particle size distribution span. The span calculation formula is as follows: Where: D10 is the particle size corresponding to 10% of the cumulative particle size distribution, D50 is the median particle size corresponding to 50% of the cumulative particle size distribution, and D90 is the particle size corresponding to 90% of the cumulative particle size distribution. The smaller the Span value, the more concentrated the particle size distribution in the graphite emulsion and the better the uniformity. Table 1. Uniformity Detection Indicators

[0034] As shown in Table 1, the experimental data show that the particle size distribution of the graphite emulsion in experimental group AC is comparable to that in control group E. Specifically, the average D50 particle size of the graphite emulsion in experimental group AC is 0.652 μm, which is 17.05% lower than that in control group E (0.786 μm). In particular, the average D90 particle size of the graphite emulsion in experimental group AC is only 1.995 μm, which is 14.45% and 81.05% lower than that in control groups E and D, respectively, indicating that its particle size distribution is more concentrated and its uniformity is better. Meanwhile, the D50 particle size of the graphite emulsion in control group A is 3.769 μm and the D90 particle size is 8.572 μm, while the D50 particle size of the graphite emulsions in control groups B and C is <0.7 μm and the D90 particle size is ≤2 μm, indicating that the graphite emulsion prepared using crystalline graphite has a wide particle size distribution and poor uniformity.

[0035] Actual lubrication performance: By analyzing the performance of graphite emulsion during the high-temperature drawing process of ultrafine tungsten wire, the focus was on examining the die force and tungsten wire vibration to evaluate its actual lubrication effect. The experiment used ultrafine tungsten wire drawing equipment adapted to each graphite emulsion sample, and set uniform drawing process conditions (drawing temperature was the conventional process temperature for high-temperature drawing of ultrafine tungsten wire, drawing speed was 3-5 m / min, and die specifications matched the target wire diameter ≤36 μm tungsten wire). The graphite emulsions of the experimental group AC and the control group AE were used for tungsten wire drawing tests respectively: the coarse tungsten wire was first dipped in the corresponding graphite emulsion, and then the graphite emulsion was dried by high-temperature baking. The graphite was uniformly attached to the surface of the tungsten wire using the binder in the system to form a lubricating protective layer, and then it entered the drawing die to complete the drawing. The ejection force was measured using a handheld tension meter with an accuracy of 0.01N. The ejection force values ​​were measured at three key nodes: the finished wire, the wire feed, and the third-to-last die. Each node was measured five times in parallel, and the average value was taken as the final result. The tungsten wire vibration phenomenon was judged by manual observation. The specific standards were as follows: smooth tungsten wire operation was defined as level 0, slight vibration was defined as level 1-2, general vibration was defined as level 3 (the common level of mainstream products in current mass production), and severe vibration was defined as level 4. Each sample was observed continuously for 30 minutes, and the average vibration level was recorded. Table 2 Actual Lubrication Performance Test Indicators

[0036] As shown in Table 2, under the same working conditions, the graphite emulsion in experimental group AC exhibited better lubrication performance, with the lowest demolding force, and its lubrication effect was significantly better than that of the control group. Among them, the graphite emulsion in control group E performed second best, while the graphite emulsion in control group D not only had a relatively higher demolding force, but also exhibited obvious tungsten wire vibration during the drawing process, which easily led to unevenness of the tungsten wire surface adhesion layer. Furthermore, the graphite emulsion in experimental group AC maintained a vibration level of 0-1 throughout the test, demonstrating good process stability. In contrast, the graphite emulsion in control group AC had a significantly higher demolding force than experimental group AC, and the severe tungsten wire vibration phenomenon damaged the integrity of the tungsten wire surface adhesion layer. This indicates that the use of crystalline graphite during the drawing process resulted in poor lubrication of the tungsten wire. The lack of added organophosphate molecules led to insufficient lubrication performance of the graphite emulsion, and the lack of added binder prevented the graphite emulsion from forming a complete adhesion layer on the tungsten wire surface, resulting in poor lubricity and uniformity of the graphite emulsion.

[0037] Wire drawing stability: Graphite emulsion samples from experimental group AC and control group AE were subjected to a uniform drawing test of ultrafine tungsten wires. The test conditions were as follows: Coarse tungsten wires of suitable diameter were used as raw materials. After impregnation with graphite emulsion, the graphite emulsion was dried by high-temperature baking. The binder in the system was used to firmly adhere the graphite to the surface of the tungsten wire, forming a lubricating protective layer. Subsequently, ultrafine tungsten wire (target wire diameter ≤ 36 μm) drawing operations were performed. The cumulative drawing time ensured that the cumulative output length of each group reached over 2000 km. The detection method was as follows: the cumulative output length of each group was recorded, and the wire lengths meeting the requirements for coil shape (coil diameter ≥ 30 mm) were selected through visual inspection and dimensional measurement. The coil shape qualification rate was calculated as follows: Formula for calculating the wire shape qualification rate; count the number of wire breaks during the drawing process, and calculate the wire breakage rate as follows: The breakage rate is calculated using a formula; the surface condition of the tungsten wire is observed using a scanning electron microscope, and wire lengths with no obvious scratches and a uniform graphite coating are selected. The surface qualification rate is calculated as follows: The formula calculates the surface pass rate; Table 3. Fiber Drawing Stability Test Indicators

[0038] As shown in Table 3, the graphite emulsion in experimental group AC exhibited excellent comprehensive performance: an average diameter qualification rate of 93.1%, a breakage rate of 2.0%, and a surface qualification rate of 97.9%. All three indicators were significantly better than those in control group D (corresponding values ​​of 75.4%, 22.5%, and 78.5%), and also showed advantages over control group E (corresponding values ​​of 89.5%, 6.5%, and 96.4%). Among these, experimental group A performed best, with a diameter qualification rate of 93.5% and a surface qualification rate as high as 97.9%. Experimental group B maintained the lowest breakage rate. The efficiency was 2.0%, demonstrating good process stability. However, the graphite emulsion of the control group AC had poorer overall performance compared to that of the experimental group AC. The pass rate of the coil diameter, the breakage rate, and the surface pass rate were all significantly lower than those of the experimental group AC. This indicates that the lubrication effect of crystalline graphite is worse than that of cryptocrystalline graphite. Without the addition of organophosphate molecules, the lubrication effect of cryptocrystalline graphite alone is insufficient, resulting in insufficient lubrication of the graphite emulsion. The lack of binder also prevents the graphite emulsion from forming a complete adhesion layer on the surface of the tungsten wire, leading to insufficient lubrication and frequent wire breakage when the wire passes through the die.

[0039] In summary, this invention, by selecting cryptocrystalline graphite as a lubricating material, using organophosphate molecules as lubricant enhancers, and rationally controlling the composition of the graphite emulsion, prepares a graphite emulsion with good storage stability and excellent lubrication effect. Furthermore, during the high-temperature drawing process of tungsten wire, the graphite emulsion can uniformly cover the surface of the tungsten wire and form a dense graphite layer, greatly improving the lubrication effect on the ultrafine tungsten wire, reducing the wire breakage rate during the drawing process, and thus improving the yield of ultrafine tungsten wires.

[0040] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A graphite emulsion for high-temperature drawing of ultrafine tungsten wire, characterized in that, Including the following raw materials: The weight percentages of graphite powder are 5-25%, dispersant is 0.1-5%, stabilizer is 0.1-3%, lubricant and reinforcing agent is 0.1-10%, thickener is 0.1-15%, binder is 0.5-15%, ammonia is 0.1-5%, and ultrapure water makes up the remainder.

2. The graphite emulsion for high-temperature drawing of ultrafine tungsten wire according to claim 1, characterized in that, The graphite emulsion has a solid content of 10%-20%, a pH of 9-11, a particle size of ≤0.7 μm, and a viscosity of ≤300 mPa.s.

3. The graphite emulsion for high-temperature drawing of ultrafine tungsten wire according to claim 1, characterized in that, The graphite powder is made of natural cryptocrystalline graphite with a D50 particle size ≤ 3 μm and a purity ≥ 99.99%.

4. The graphite emulsion for high-temperature drawing of ultrafine tungsten wire according to claim 1, characterized in that, The dispersant is one or more of sodium carboxymethyl cellulose, sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, phytic acid, and polyvinylpyrrolidone.

5. The graphite emulsion for high-temperature drawing of ultrafine tungsten wire according to claim 1, characterized in that, The stabilizer is one or more of fumed silica, magnesium aluminosilicate, and organobentonite.

6. The graphite emulsion for high-temperature drawing of ultrafine tungsten wire according to claim 1, characterized in that, The lubricating enhancer is one or more of the following: triethyl phosphate, nonylphenol polyoxyethylene ether phosphate, isooctanol phosphate, sodium polyphosphate, and potassium dihydrogen phosphate.

7. The graphite emulsion for high-temperature drawing of ultrafine tungsten wire according to claim 1, characterized in that, The thickener is one or more of hydroxyethyl cellulose, methyl cellulose, sodium polyacrylate, and xanthan gum.

8. The graphite emulsion for high-temperature drawing of ultrafine tungsten wire according to claim 1, characterized in that, The adhesive is one or more of polyvinyl alcohol, polyethylene glycol, and styrene-maleic anhydride copolymer emulsion.

9. A method for preparing graphite emulsion for high-temperature drawing of ultrafine tungsten wire according to any one of claims 1-8, characterized in that, Includes the following steps: Dispersant, ammonia, and graphite powder are added to ultrapure water and pre-dispersed using a dispersion disc. Then, stabilizer, lubricant, thickener, and binder are added and mixed evenly to obtain a mixed solution. Next, the mixed solution is placed in a sand mill and ground to obtain a uniformly dispersed graphite emulsion.

10. The method for preparing graphite emulsion for high-temperature drawing of ultrafine tungsten wire according to claim 9, characterized in that, The pre-dispersion time is 0.5-3 hours, the mixing time of the raw materials is 1-5 hours, the speed of the sand mill is 1000-2000 r / min, the sand milling medium is zirconia beads, the volume of the zirconia beads accounts for 50-80% of the total volume of the sand milling jar, and the sand milling time is 8-36 hours.

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