A method for manufacturing a high-strength molybdenum wire

Abstract

The application discloses a kind of high-strength molybdenum wire manufacturing method, it belongs to molybdenum wire manufacturing technical field, lanthanum oxide rare earth powder is mixed with molybdenum powder, powder is pressed into shape using cold isostatic pressing and carries out high-temperature sintering, subsequently using high-temperature rolling, high-temperature drawing two kinds of pressure processing methods are reduced in diameter to molybdenum wire, annealing treatment is carried out to molybdenum wire in high-temperature drawing process, finally using high-speed cold drawing process obtains commodity molybdenum wire;The application develops a kind of high-speed cold drawing process, so that cold drawing speed can reach 400-1000m / min, using the molybdenum wire prepared in the application has higher tensile strength, good elongation and higher production efficiency, tensile strength reaches 2900MPa or more, elongation is greater than 2%;Molybdenum wire produced by the preparation method of the application has higher uniformity of structure, relatively smaller wear to die, greatly improve the wire drawing yield and production efficiency, reduce production cost.

Description

Technical Field

[0001] This application belongs to the field of molybdenum wire manufacturing technology, and in particular relates to a method for manufacturing high-strength molybdenum wire. Background Technology

[0002] Wire electrical discharge machining (EDM) is widely used in the machining industry due to its simple electrode tools, small machining allowance, low cost, and easy operation. Molybdenum and its alloys have high melting points, good thermal and electrical conductivity, low coefficients of thermal expansion, and stable chemical properties, making molybdenum wire an ideal choice for wire EDM electrodes. As a key material in EDM, the performance of molybdenum wire directly affects machining efficiency and accuracy. However, traditional molybdenum wires still have certain limitations in terms of strength and elongation, making it difficult to meet the requirements of high-precision and high-efficiency processing. To improve the service life and cutting efficiency of molybdenum wires, researchers have conducted corresponding studies on the composition and processing methods of molybdenum wires. Patent 200610043762.5 discloses a special wire cutting electrode molybdenum wire and its manufacturing method, which adds lanthanum nitrate aqueous solution to molybdenum oxide and obtains molybdenum powder containing La2O3 through hydrogen reduction. The molybdenum wire processed from the La2O3-containing molybdenum powder has improved tensile strength and wear resistance. Patent 201610790276.3 discloses a method for producing wire cutting molybdenum wire, which improves the tensile strength of molybdenum wire by adding solid solution metal elements and rare earth oxides to molybdenum. The tensile strength of molybdenum wire produced by this method can generally reach 1900-2300 MPa. Patent 201511027765.5 discloses a composite molybdenum wire for wire cutting and its manufacturing method. By adding solid solution metal elements, the content of rare earth oxides is reduced, thereby improving the tensile strength and wear resistance of the molybdenum wire.

[0003] High-speed cold drawing, as a crucial process in molybdenum wire processing, can significantly improve production efficiency, reduce manufacturing costs, optimize the microstructure of molybdenum wire, and enhance its mechanical properties. However, existing molybdenum wire cold drawing processes typically involve low speeds (not exceeding 300 m / min) and suffer from poor diameter uniformity and insufficient microstructure. Patent 202210817779.0 discloses a high-speed cold drawing method for preparing wire-cut molybdenum wire, which improves the lubrication method during the cold drawing process. By adding a graphite emulsion lubricant coating and drying step, a drawing process with a speed of 260-400 m / min is achieved. Tensile strength is one of the important parameters affecting the performance of wire-cut molybdenum wire, directly related to cutting quality, efficiency, tool life, and cost control. Improving the tensile strength of wire-cut molybdenum wire not only helps to improve cutting accuracy, processing efficiency, tool life, and material utilization, but also meets the processing requirements of high-difficulty workpieces. However, the cold drawing process for preparing high-strength rare earth oxide reinforced molybdenum wire is prone to cracking, and the high die wear also results in low surface quality and uniformity of processing dimensions, making it difficult to achieve efficient production. Summary of the Invention

[0004] The purpose of this application is to provide a method for manufacturing high-strength molybdenum wire, so as to solve the technical problems of low cold drawing speed, low tensile strength, poor elongation and low production efficiency in the prior art.

[0005] To achieve the above objectives, the technical solution adopted in this application is: to provide a method for manufacturing high-strength molybdenum wire, specifically including the following steps:

[0006] (I) Pressing and molding: Molybdenum powder and lanthanum oxide rare earth powder are mixed to obtain mixed powder, and the mixed powder is pressed to obtain a blank.

[0007] (II) Sintering: The billet is sintered under gas protection to obtain sintered molybdenum rods;

[0008] (III) Rolling: The sintered molybdenum rods are rolled at high temperature to obtain molybdenum wire rods;

[0009] (iv) Drawing: The molybdenum wire rod is gradually drawn into molybdenum wire through multiple high-temperature drawing processes; annealing is carried out during the drawing process to ensure the uniformity of the internal structure of the molybdenum wire;

[0010] (V) High-speed cold drawing: The molybdenum wire is drawn in multiple passes at room temperature using a non-slip wire drawing machine. Anti-wear hydraulic oil is used as a lubricant and coolant during the drawing process to obtain the finished molybdenum wire. The cold drawing speed is 400-1000 m / min, and the deformation per pass is 10-18%. Preferably, the drawing speed is 500-700 m / min.

[0011] In one embodiment,

[0012] Step (1): The mass ratio of molybdenum powder to lanthanum oxide rare earth powder is 1:0.005-0.01; the average particle size of molybdenum powder is 2-5 μm, and the average particle size of lanthanum oxide rare earth powder is 0.2-1 μm.

[0013] In one embodiment,

[0014] Step (1) The pressing conditions are cold isostatic pressing, with a pressing force of 140-200MPa and a holding time of 1-3min.

[0015] In one embodiment,

[0016] Step (II) The sintering temperature is 2050-2150℃, and the sintering time is 8-12h; the gas is hydrogen; the diameter of the sintered molybdenum rod is 50-55mm.

[0017] In one embodiment,

[0018] Step (3) The temperature of high-temperature rolling is 1350-1450℃, the rolling speed is 5-10m / min, and the rolling passes are no less than 20, preferably 20-30; the diameter of the molybdenum wire rod is 5.5-6.5mm.

[0019] In one embodiment,

[0020] Step (iv) The temperature of high-temperature drawing gradually decreases as the diameter of the molybdenum wire decreases, and the drawing temperature is reduced from 1100℃ to 600℃. The deformation per pass is controlled between 17-34%. Graphite emulsion is used as a lubricant during the drawing process.

[0021] In one embodiment,

[0022] Step (iv) The annealing temperature is 800-1300℃, and the annealing speed is 1-12m / min; the diameter of the molybdenum wire is 0.5-1.2mm.

[0023] In one embodiment,

[0024] Step (5) The number of high-speed cold drawing passes shall not be less than 10, preferably 10-15; the processing deformation amount of the last two passes shall be 10-13%.

[0025] In one embodiment,

[0026] Step (5) High-speed cold drawing: During the drawing process, a tension force F is applied to the molybdenum wire. fThe tension force gradually decreases as the diameter of the drawn molybdenum wire decreases, and the tension force is 5-60N. The tension force is applied to the drawn molybdenum wire by a tensioning device composed of a servo torque motor. High-speed drawing is achieved by a servo motor driving a take-up device. The power of the servo motor is greater than that of formula (1).

[0027] P = F z V max Formula (1)

[0028] Where P is the power required for drawing, and F z For the total pull-out force, v max Maximum drawing speed;

[0029] The force required for pulling satisfies formula (2).

[0030]

[0031] Where S1 is the cross-sectional area of ​​the molybdenum wire after drawing, S0 is the cross-sectional area of ​​the molybdenum wire before drawing, and σ f The rheological stress of the molybdenum wire. The molybdenum wire is denoted by μ, which is the equivalent deformation degree after passing through the die; μ is the coefficient of friction; and α is the inclination angle of the die drawing hole.

[0032] In one embodiment,

[0033] Step (5): The diameter of the finished molybdenum wire is 0.18 mm.

[0034] This application provides a method for manufacturing high-strength molybdenum wire, further increasing the drawing speed of the molybdenum wire to 400-1000 m / min, enhancing the thermal activation effect during the drawing process, and thus improving the processing plasticity of the molybdenum wire during high-speed drawing. Furthermore, during high-speed cold drawing, a tension force is applied to the molybdenum wire, which causes a change in the entry profile. This change helps reduce radial pressure, decreases frictional shear stress during high-speed cold drawing, improves the lubrication effect of the lubricant, reduces die wear, and improves the uniformity of the molybdenum wire diameter and surface quality. Through optimization of the molybdenum wire processing technology, this application produces molybdenum wire with a tensile strength exceeding 2900 MPa and an elongation greater than 2%, far surpassing traditional molybdenum wire. Using a high-speed cold drawing process, the drawing speed can reach 400-1000 m / min, significantly improving production efficiency. Through reasonable process design, production costs are reduced, resulting in high market competitiveness. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the manufacturing process of molybdenum wire;

[0037] Figure 2 A schematic diagram showing the change in the profile of the die inlet after applying tension during the cold drawing process of molybdenum wire;

[0038] Figure 3 The image shows the cross-sectional metallographic structure of the molybdenum wire.

[0039] Figure 4 This is a cross-sectional scanning electron microscope image of a molybdenum wire;

[0040] Figure 5 This is a surface morphology diagram of a molybdenum wire. Detailed Implementation

[0041] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, this application will be further described in detail. It should be understood that the specific embodiments described herein are only for explaining this application and are not intended to limit this application.

[0042] Example 1

[0043] A method for manufacturing high-strength molybdenum wire, such as Figure 1 As shown, the specific steps include:

[0044] (I) Pressing and molding: Molybdenum powder with an average particle size of 3μm is mixed with lanthanum oxide rare earth powder with a particle size of 0.5μm. The mass ratio of molybdenum powder to lanthanum oxide rare earth powder is 1:0.007. After mixing for 10h, mixed powder is obtained. The mixed powder is then subjected to cold isostatic pressing with a pressing force of 160MPa and a holding pressure of 2min to obtain a billet.

[0045] (II) Sintering: The billet was sintered under hydrogen protection at 2100℃ for 8 hours to obtain a sintered molybdenum rod with a diameter of 55mm.

[0046] (III) Rolling: The sintered molybdenum rods are rolled at a rolling temperature of 1398℃ and a rolling speed of 8m / min to obtain molybdenum wire rods with a diameter of 6mm; the rolling passes are 24.

[0047] (iv) Drawing: The molybdenum wire rod is drawn through multiple high-temperature passes, with the deformation per pass controlled between 17-34%, gradually drawing it to a molybdenum wire with a diameter of 0.39 mm. The drawing temperature gradually decreases as the diameter of the molybdenum wire decreases, from 1100℃ to 600℃. During the drawing process, the 1 mm diameter molybdenum wire is annealed at a temperature of 950℃ and an annealing speed of 2 m / min. Graphite emulsion is used as a lubricant during the drawing process.

[0048] (V) High-speed cold drawing: Molybdenum wire with a diameter of 0.39 mm is drawn in multiple passes at room temperature through a non-slip wire drawing machine. Anti-wear hydraulic oil is used as lubricant and coolant during the drawing process. The drawing speed is 500 m / min and the number of drawing passes is 10. The drawing deformation of the last two passes is controlled at about 13%, and the drawing deformation of the other passes is between 15-18%. The applied tension gradually decreases from 60 N to 10 N as the number of drawing passes increases, and a finished molybdenum wire with a diameter of 0.18 mm is obtained.

[0049] Step (5) High-speed cold drawing During the drawing process, such as Figure 2 As shown, a tension force F is applied to the molybdenum wire. f The tension force gradually decreases as the diameter of the drawn molybdenum wire decreases, and the tension force is 10-60N. The tension force is applied to the drawn molybdenum wire by a tensioning device composed of a servo torque motor. High-speed drawing is achieved by a take-up device driven by a servo motor. This process does not depend on specific equipment. Existing equipment is relatively mature and will not be elaborated here. The power of the servo motor is greater than that of formula (1).

[0050] P = F z V max Formula (1)

[0051] Where P is the power required for drawing, and F z For the total pull-out force, v max Maximum drawing speed;

[0052] The force required for pulling satisfies formula (2).

[0053]

[0054] Where S1 is the cross-sectional area of ​​the molybdenum wire after drawing, S0 is the cross-sectional area of ​​the molybdenum wire before drawing, and σ f The rheological stress of the molybdenum wire. The molybdenum wire is denoted by μ, which is the equivalent deformation degree after passing through the die; μ is the coefficient of friction; and α is the inclination angle of the die drawing hole.

[0055] (vi) The tensile strength and elongation of the finished molybdenum wire were tested. Three parallel tests were conducted, and the results are shown in Table 1. Figure 3-5 .

[0056] Example 2

[0057] The difference between this embodiment and Embodiment 1 is step (5), which is as follows: a molybdenum wire with a diameter of 0.39 mm is drawn at room temperature through a non-slip wire drawing machine in multiple passes. During the drawing process, anti-wear hydraulic oil is used as a lubricant and coolant. The drawing speed is 600 m / min. The drawing deformation of the last two passes is controlled at about 12%, and the drawing deformation of other passes is between 14-17%. The applied tension force gradually decreases from 50 N to 10 N as the number of drawing passes increases. The rest of the operation is the same, and the finished molybdenum wire is obtained. The tensile strength and elongation of the finished molybdenum wire are tested, and the results are shown in Table 1.

[0058] Example 3

[0059] The difference between this embodiment and Embodiment 1 is step (5), which is as follows: a molybdenum wire with a diameter of 0.39 mm is drawn at room temperature through a non-slip wire drawing machine in multiple passes. During the drawing process, anti-wear hydraulic oil is used as a lubricant and coolant. The drawing speed is 700 m / min. The drawing deformation of the last two passes is controlled at about 11%, and the drawing deformation of other passes is between 14-17%. The applied tension force gradually decreases from 45 N to 5 N as the number of drawing passes increases. The rest of the operation is the same, and the finished molybdenum wire is obtained. The tensile strength and elongation of the finished molybdenum wire are tested, and the results are shown in Table 1.

[0060] Example 4

[0061] The difference between this embodiment and Embodiment 1 is step (five), which is as follows: a molybdenum wire with a diameter of 0.39 mm is drawn at room temperature through a non-slip wire drawing machine in multiple passes. During the drawing process, anti-wear hydraulic oil is used as a lubricant and coolant. The drawing speed is 400 m / min, and the number of drawing passes is 15. The drawing deformation of the last two passes is controlled at about 13%, and the drawing deformation of the other passes is between 15% and 18%. The applied tension gradually decreases from 60 N to 10 N as the number of drawing passes increases. The rest of the operation is the same, and the finished molybdenum wire is obtained.

[0062] Example 5

[0063] The difference between this embodiment and Embodiment 1 is step (5), which is as follows: a molybdenum wire with a diameter of 0.39 mm is drawn at room temperature through a non-slip wire drawing machine in multiple passes. During the drawing process, anti-wear hydraulic oil is used as a lubricant and coolant. The drawing speed is 1000 m / min. The deformation of the last two passes is controlled at about 10%, and the deformation of the other passes is between 10-14%. The applied tension gradually decreases from 45 N to 5 N as the number of drawing passes increases. The rest of the operation is the same, and the finished molybdenum wire is obtained.

[0064] Example 6

[0065] The difference between this embodiment and Example 1 is that the mass ratio of molybdenum powder to lanthanum oxide rare earth powder is 1:0.005; the average particle size of molybdenum powder is 2 μm, and the average particle size of lanthanum oxide rare earth powder is 0.2 μm; the rest of the operations are the same.

[0066] Example 7

[0067] The difference between this embodiment and Example 1 is that the mass ratio of molybdenum powder to lanthanum oxide rare earth powder is 1:0.01; the average particle size of molybdenum powder is 5 μm, and the average particle size of lanthanum oxide rare earth powder is 1 μm; the rest of the operations are the same.

[0068] Example 8

[0069] The difference between this embodiment and embodiment 1 is that in step (i), the pressing force of cold isostatic pressing is 140 MPa, the holding time is 3 min, and the rest of the operation is the same.

[0070] Example 9

[0071] The difference between this embodiment and embodiment 1 is that in step (i), the pressing force of the cold isostatic pressing is 200 MPa, the holding time is 1 min, and the rest of the operation is the same.

[0072] Example 10

[0073] The difference between this embodiment and embodiment 1 is that in step (ii), the sintering temperature is 2050℃, the sintering time is 12h, and the diameter of the sintered molybdenum rod is 50mm. The rest of the operations are the same.

[0074] Example 11

[0075] The difference between this embodiment and embodiment 1 is that in step (ii), the sintering temperature is 2150℃ and the sintering time is 10h, while the rest of the operations are the same.

[0076] Example 12

[0077] The difference between this embodiment and Embodiment 1 is that in step (iii), the high-temperature rolling temperature is 1350℃, the rolling speed is 5m / min, the rolling passes are 20, and the diameter of the molybdenum wire rod is 6.5mm. The rest of the operations are the same.

[0078] Example 13

[0079] The difference between this embodiment and embodiment 1 is that in step (iii), the high-temperature rolling temperature is 1450℃, the rolling speed is 10m / min, the rolling passes are 30, and the diameter of the molybdenum wire rod is 5.5mm. The rest of the operations are the same.

[0080] Example 14

[0081] The difference between this embodiment and Embodiment 1 is that in step (iv), the annealing temperature is 800℃, the annealing speed is 12m / min, the diameter of the molybdenum wire is 0.5mm, and the rest of the operations are the same.

[0082] Example 15

[0083] The difference between this embodiment and Embodiment 1 is that in step (iv), the annealing temperature is 1100℃, the annealing speed is 1m / min, the diameter of the molybdenum wire is 1.2mm, and the rest of the operations are the same.

[0084] Example 16

[0085] The difference between this embodiment and Embodiment 1 is that in step (iv), the annealing temperature is 1300℃, the annealing speed is 6m / min, the diameter of the molybdenum wire is 0.9mm, and the rest of the operations are the same.

[0086] Table 1. Tensile strength and elongation tests in Examples 1-3

[0087]

[0088] The tensile strength of the molybdenum wires in Examples 1-3 was tested using a tensile testing machine. Table 1 shows that the tensile strength of the molybdenum wires prepared in this application is all higher than 2900 MPa, and the elongation is all greater than 2%. Figure 3 As shown, no cracks were generated in the molybdenum wire; as Figure 4 As shown, the internal structure of the molybdenum wire is dense and uniform, and no obvious defects were found; Figure 5 As shown, the surface morphology of molybdenum wire at the 50,000-meter mark of single-hole drawing is relatively uniform, with no obvious deep grooves, indicating that the molybdenum wire has high uniformity. The optimized process causes relatively less wear on the mold, greatly improving the wire drawing yield and production efficiency, and reducing production costs.

[0089] This application provides a method for manufacturing high-strength molybdenum wire, including pressing, sintering, rolling, drawing, annealing, and high-speed cold drawing. Typically, as the drawing rate increases, dislocation movement is suppressed, leading to enhanced work hardening. Simultaneously, at high strain rates, deformation heat accumulates rapidly, and localized temperature rises cause material softening, partially offsetting the work hardening effect. Existing molybdenum wire cold drawing processes are generally relatively low-speed, typically not exceeding 300 m / min. This application further increases the drawing speed of molybdenum wire to 400-1000 m / min, enhancing the thermal activation effect during the drawing process and thus improving the processing plasticity of the molybdenum wire during high-speed drawing. Furthermore, at high speed... During the cold drawing process, a tension force is applied to the molybdenum wire, which causes a change in the inlet profile. This change helps reduce radial pressure, decrease frictional shear stress during high-speed cold drawing, improve the lubrication effect of the lubricant, reduce die wear, and improve the uniformity of the molybdenum wire diameter and surface quality. This application optimizes the processing technology of the molybdenum wire, producing a molybdenum wire with a tensile strength of over 2900 MPa and an elongation of over 2%, far exceeding that of traditional molybdenum wire. Using a high-speed cold drawing process, the drawing speed can reach 400-1000 m / min, significantly improving production efficiency. Through reasonable process design, production costs are reduced, giving it high market competitiveness.

[0090] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0091] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A method for manufacturing a high-strength molybdenum wire, characterized in that, Specifically, the following steps are included: (i) Pressing and molding: Molybdenum powder and lanthanum oxide rare earth powder are mixed to obtain mixed powder, and the mixed powder is pressed to obtain a blank strip; (ii) Sintering: The billet is sintered under gas protection to obtain sintered molybdenum rods; (III) Rolling: The sintered molybdenum rod is rolled at high temperature to obtain molybdenum wire rod; (iv) Drawing: The molybdenum wire rod is gradually drawn into molybdenum wire through multiple high-temperature drawing processes; annealing is carried out during the drawing process; (V) High-speed cold drawing: The molybdenum wire is drawn in multiple passes at room temperature using a non-slip wire drawing machine. Anti-wear hydraulic oil is used as a lubricant and coolant during the drawing process to obtain the finished molybdenum wire. The cold drawing speed is 400-1000 m / min, and the deformation per pass is 10-18%. In step (i), the mass ratio of molybdenum powder to lanthanum oxide rare earth powder is 1:0.005-0.01; the average particle size of the molybdenum powder is 2-5 μm, and the average particle size of the lanthanum oxide rare earth powder is 0.2-1 μm. The sintering temperature in step (ii) is 2050-2150 ℃, and the sintering time is 8-12 h; the gas is hydrogen; and the diameter of the sintered molybdenum rod is 50-55 mm. The high-temperature rolling temperature in step (iii) is 1350-1450 ℃, and the rolling speed is 5-10 m / min; The annealing temperature in step (iv) is 800-1300 ℃, and the annealing speed is 1-12 m / min; the diameter of the molybdenum wire is 0.35-0.5 mm; In step (5), during the high-speed cold drawing process, a tension force F is applied to the molybdenum wire. f The tension force gradually decreases as the diameter of the drawn molybdenum wire decreases, and the tension force is 5-60 N. The tension force is applied to the drawn molybdenum wire by a tensioning device composed of a servo torque motor. High-speed drawing is achieved by a servo motor driving a take-up device. The power of the servo motor is greater than that of formula (1). Official (1) Where P is the power required for drawing, and F z For the total pull-out force, v max Maximum drawing speed; The force required for pulling satisfies formula (2). Official (2) Where S1 is the cross-sectional area of ​​the molybdenum wire after drawing, S0 is the cross-sectional area of ​​the molybdenum wire before drawing, and σ f The rheological stress of the molybdenum wire. l α represents the equivalent deformation of the molybdenum wire after passing through the mold, μ is the coefficient of friction, and α is the inclination angle of the drawing hole in the mold.

2. The method for manufacturing a high-strength molybdenum wire according to claim 1, characterized in that, The pressing conditions described in step (1) are cold isostatic pressing, with a pressing force of 140-200 MPa and a holding time of 1-3 min.

3. The method for manufacturing a high-strength molybdenum wire according to claim 1, characterized in that, Step (3) involves 20-30 rolling passes; the diameter of the molybdenum wire rod is 5.5-6.5 mm.

4. The method for manufacturing a high-strength molybdenum wire according to claim 1, characterized in that, In step (iv), the high-temperature drawing temperature gradually decreases as the diameter of the molybdenum wire decreases, and the drawing temperature is reduced from 1100 ℃ to 600 ℃. The deformation per pass is controlled between 17-34%. Graphite emulsion is used as a lubricant during the drawing process.

5. The method for manufacturing a high-strength molybdenum wire according to claim 1, characterized in that, Step (5) involves 10-15 high-speed cold drawing passes, with the last two passes having a deformation amount of 10-13%.

6. The method for manufacturing a high-strength molybdenum wire according to claim 1, characterized in that, The diameter of the finished molybdenum wire in step (5) is 0.18 mm.

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