A processing method of chromium-zirconium-copper microporous tube and chromium-zirconium-copper microporous tube

Abstract

The invention discloses a processing method for a chromium-zirconium-copper microporous tube and the chromium-zirconium-copper microporous tube, belonging to the technical field of chromium-zirconium-copper microporous tubes. The method is specifically as follows: S1, preparation of rod raw materials, S2, hollow continuous casting and grain refinement, S3, wire forging dynamic strengthening, S4, cold drawing precision shaping, S5, inner wall port secondary processing, wherein metallic chromium, metallic zirconium and electrolytic copper are mixed according to a mass percentage ratio of 0.6-1.2%, 0.1-0.25% and the balance being copper, and then vacuum induction melting is performed to obtain a molten liquid with uniform composition; the molten liquid obtained in the previous step is horizontally continuously cast through a hollow crystallizer to obtain a hollow round rod with an outer diameter of 30 mm and an inner diameter of 8 mm. The processing method for the chromium-zirconium-copper microporous tube and the chromium-zirconium-copper microporous tube of the invention can avoid the influence of drilling, grinding and hot drawing, avoid excessive cold drawing times, ensure the precise equal diameter of the micropore inner diameter and improve the overall service life.

Description

Technical Field

[0001] The invention specifically relates to a processing method of a chromium-zirconium-copper microporous tube and the chromium-zirconium-copper microporous tube, and belongs to the technical field of chromium-zirconium-copper microporous tubes. Background Art

[0002] In the prior art, the material for making chromium-zirconium-copper conductive nozzles is generally solid rods. The process is to first cut the solid rods into segments according to the required length, then drill holes in the cut solid rods, and finally machine them. The conductive nozzles made by this process have high production costs and poor inner hole surface smoothness. During welding, the friction rate between the welding wire and the inner hole of the conductive nozzle increases, making the conductive nozzle damage rate extremely high. To this end, Chinese Patent Publication No.: CN109201769A discloses a processing method and chromium-zirconium-copper microporous tube, wherein copper, chromium and zirconium are proportioned according to chemical composition requirements, and then melted and cast into solid round ingots. The solid round ingots are subjected to composition inspection, metal flaw detection and surface inspection. If all are qualified, they are sawed into segments; the sawed solid round ingots are hot extruded to obtain round tube billets; the round tube billets are stretched 10 times through a straight stretching machine. The microporous tube blank is formed in 10 steps; each stretching step has its own matching stretching outer die and stretching inner die; since the composition inspection and metal flaw detection are completed in the solid round ingot casting process, the solid round ingot undergoes a subsequent hot extrusion process, which is easy to affect the composition inspection and metal flaw detection results, that is, it is easy to change the metallographic structure, resulting in a decrease in tensile strength, and then undergo a subsequent cold stretching process, which is prone to internal defects and cannot guarantee the structural strength of the entire microporous tube; in addition, the above-mentioned processing and stretching process requires 10 processing steps, the stretching time is too long, and the energy consumption is too high. In addition, there is no radial stamping in the entire microporous tube stretching process, and the internal pores of the microporous tube cannot be eliminated. In addition, during the use of the existing chromium-zirconium-copper microporous tube, the welding wire swings in an undirected manner at the end of the microporous tube, and the wear rate of the end is often many times that of the inner wall, which causes the microporous tube to be damaged too quickly. Summary of the Invention

[0003] To solve the above problems, the present invention proposes a processing method for chromium-zirconium-copper microporous tubes and chromium-zirconium-copper microporous tubes, which can avoid the influence of drilling, grinding and hot drawing, and avoid excessive cold drawing times, and can ensure the precise equal diameter of the micropore inner diameter and improve the overall service life.

[0004] The processing method of the chromium-zirconium-copper microporous tube of the present invention is as follows:

[0005] S1. Preparation of rod raw materials: metallic chromium, metallic zirconium and electrolytic copper are mixed in a mass percentage ratio of 0.6-1.2%, 0.1-0.25% and the balance copper, followed by vacuum induction melting to obtain a molten liquid with uniform composition;

[0006] S2. Hollow continuous casting and grain refinement: The molten liquid obtained in the previous step is horizontally continuously cast through a hollow crystallizer to obtain a hollow round rod with an outer diameter of 30 mm and an inner diameter of 8 mm. The hollow round rod is cooled, and the cooling gradient is controlled to eliminate shrinkage cavities. After cooling, homogenization annealing and water quenching are performed to achieve a grain size of ≤4 μm and a grain distribution standard deviation of ≤2 μm. The hollow round rod is then cut into multiple standard rods of set lengths.

[0007] S3: Dynamic strengthening by wire forging: A 9.8mm diameter molybdenum bar is inserted into the standard rod, with both ends of the molybdenum bar protruding from the standard rod. The rod is then heated to 750-850°C and subjected to dynamic multi-directional forging with a forging ratio of ≥3:1. After forging, the rod is water-cooled to retain the fine grain structure. The molybdenum bar supports the hole wall to prevent forging deviation. Internal shrinkage defects in the standard rod are closed through repeated extrusion forging, and the rod is immediately water-cooled after forging.

[0008] S4. Precision cold drawing and shaping: The standard rod processed in the previous step is subjected to multiple drawing passes according to the inner diameter and wall thickness requirements of the microporous tube. The deformation of a single pass is ≤15%, the outer diameter tolerance after stretching is ±0.02mm, and the inner diameter roundness error is ≤0.003mm. Vacuum annealing is performed after each pass to restore the elongation to ≥15%;

[0009] S5. Secondary processing of the inner wall port: According to the application requirements, the standard rod processed in the previous step is cut into hole tube segments of the target length. Through Hawking high-frequency vibration, a 5-10μm nanocrystalline layer is generated at the outer and inner ends of the hole tube segment. The residual compressive stress reaches -300MPa, and the wear resistance is greatly improved.

[0010] Furthermore, before the secondary processing of the inner wall port, the inner wall end is firstly expanded by turning, and then high-frequency induction welding is used to inject silicon carbide powder into the expanded port to form a composite coating with a thickness of 2 μm.

[0011] Furthermore, before the silicon carbide powder is fusion-welded, the expanded port is pre-plated with a nickel layer having a thickness of 0.5 μm. The pre-plated nickel layer improves the bonding strength of the silicon carbide and improves the problem of insufficient adhesion of the silicon carbide.

[0012] Furthermore, before the nanocrystal strengthening, the inside of the microporous tube is electrolytically polished to remove slag and correct the hole shape.

[0013] Furthermore, the electrolytic polishing process is as follows: the microporous tube is placed in a phosphoric acid-ethylene glycol electrolyte for electrolysis, with a voltage of 12V and an electrolysis time of 2.5 minutes.

[0014] Furthermore, the cold drawing precision shaping process uses a combination of a carbide outer mold and a core mold with a mold angle of 12-15 degrees. After each drawing is completed, it enters the intermediate annealing process. The intermediate annealing process uses 450-500°C, a holding time of 30 minutes, and argon protection to restore the elongation to ≥15%.

[0015] Furthermore, after the intermediate annealing process is completed, nano-molybdenum disulfide lubricant is sprayed before entering the next drawing process.

[0016] Furthermore, the metal chromium, metal zirconium and electrolytic copper are mixed in a mass percentage ratio of 0.8%, 0.2% and the balance being copper.

[0017] Furthermore, during the dynamic multi-directional forging, each region is alternately forged 3-5 times.

[0018] A chromium-zirconium-copper microporous tube is processed using a chromium-zirconium-copper microporous tube processing method, comprising a bore tube section, wherein the outer end portions and the inner wall of both ends of the bore tube section are integrally formed with a 5-10 μm nanocrystalline layer; compared with existing chromium-zirconium-copper microporous tubes, the chromium-zirconium-copper microporous tube processed using the above method has an overall anti-fracture performance and structural strength that are improved by several times, and by secondary processing the ends of the chromium-zirconium-copper microporous tube, the problem of premature scrapping of the chromium-zirconium-copper microporous tube due to eccentric wear of the ends can be solved, thereby greatly extending the service life.

[0019] Compared with the prior art, the processing method of the chromium-zirconium-copper microporous tube and the chromium-zirconium-copper microporous tube of the present invention are achieved by hollow continuous casting of hollow round rods with small aperture and small outer diameter, and then further reducing the wall thickness of the hollow round rod through dynamic forging, and closing the internal pores and shrinkage of the entire hollow round rod through dynamic extrusion, with an internal aperture tolerance of ±0.01mm; the surface roughness Ra≤0.4μm; due to the small-diameter structure of the hollow round rod through continuous casting and the keyhole processing through dynamic forging, the number of cold drawing passes can be greatly reduced, and the precise shaping of the inner diameter and outer diameter can be achieved through precise cold drawing, the density of the inner wall of the hollow round rod is further enhanced, and the precise shaping of the hollow round rod is achieved at the same time, and finally a nanocrystalline layer is integrally formed at both ends of the micro-pipe to avoid eccentric wear at both ends of the micro-pipe, which leads to premature scrapping of the entire micro-pipe; the processing procedure is simpler, and the conductive performance of the entire micro-porous tube is more stable. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic flow chart of the processing method of the chromium-zirconium-copper microporous tube according to Example 1 of the present invention.

[0021] Figure 2 This is a schematic flow chart of the processing method of the chromium-zirconium-copper microporous tube according to Example 2 of the present invention. DETAILED DESCRIPTION

[0022] like Figure 1The processing method of the chromium-zirconium-copper microporous tube shown is as follows:

[0023] S1. Preparation of rod raw materials: metallic chromium, metallic zirconium and electrolytic copper are mixed in a mass percentage ratio of 0.6-1.2%, 0.1-0.25% and the balance copper, followed by vacuum induction melting to obtain a molten liquid with uniform composition;

[0024] S2, hollow continuous casting and grain refinement, the molten liquid obtained in the previous step is horizontally continuously cast through a hollow crystallizer to obtain a hollow round rod with an outer diameter of 30 mm and an inner diameter of 8 mm. After the hollow round rod is cooled, it is homogenized annealed and water quenched for solid solution; and the hollow round rod is cut into multiple standard rods of set lengths;

[0025] S3: Dynamic strengthening by wire forging: A 9.8mm diameter molybdenum bar is inserted into the standard rod, with both ends of the molybdenum bar protruding from the standard rod. The rod is then heated to 750-850°C and subjected to dynamic multi-directional forging with a forging ratio of ≥3:1. After forging, the rod is water-cooled to retain the fine grain structure.

[0026] S4, cold drawing precision shaping, according to the inner diameter and wall thickness requirements of the microporous tube, the standard rod processed in the previous step is drawn in multiple passes, the deformation of a single pass is ≤15%, the outer diameter tolerance after stretching is ±0.02mm, and the inner diameter roundness error is ≤0.003mm;

[0027] S5. Secondary processing of the inner wall port: according to the application requirements, the standard rod processed in the previous step is cut into the target length of the hole tube segment, and the 5~10μm nanocrystalline layer is generated on the outer and inner ends of the hole tube segment through Hawkes energy high-frequency vibration.

[0028] Furthermore, before the secondary processing of the inner wall port, the inner wall end is firstly expanded by turning, and then high-frequency induction welding is used to inject silicon carbide powder into the expanded port to form a composite coating with a thickness of 2 μm.

[0029] Furthermore, before the silicon carbide powder is fusion-welded, the expanded port is pre-plated with a nickel layer having a thickness of 0.5 μm. The pre-plated nickel layer improves the bonding strength of the silicon carbide and improves the problem of insufficient adhesion of the silicon carbide.

[0030] Furthermore, before the nanocrystal strengthening, the inside of the microporous tube is electrolytically polished to remove slag and correct the hole shape.

[0031] Furthermore, the electrolytic polishing process is as follows: the microporous tube is placed in a phosphoric acid-ethylene glycol electrolyte for electrolysis, with a voltage of 12V and an electrolysis time of 2.5 minutes.

[0032] Furthermore, the cold drawing precision shaping process uses a combination of a carbide outer mold and a core mold with a mold angle of 12-15 degrees. After each drawing is completed, it enters the intermediate annealing process. The intermediate annealing process uses 450-500°C, a holding time of 30 minutes, and argon protection to restore the elongation to ≥15%.

[0033] Furthermore, after the intermediate annealing process is completed, nano-molybdenum disulfide lubricant is sprayed before entering the next drawing process.

[0034] Furthermore, the metal chromium, metal zirconium and electrolytic copper are mixed in a mass percentage ratio of 0.8%, 0.2% and the balance being copper.

[0035] Furthermore, during the dynamic multi-directional forging, each region is alternately forged 3-5 times.

[0036] A chromium-zirconium-copper microporous tube is processed using a chromium-zirconium-copper microporous tube processing method, comprising a bore tube section, wherein the outer end portions and the inner wall of both ends of the bore tube section are integrally formed with a 5-10 μm nanocrystalline layer; compared with existing chromium-zirconium-copper microporous tubes, the chromium-zirconium-copper microporous tube processed using the above method has an overall anti-fracture performance and structural strength that are improved by several times, and by secondary processing the ends of the chromium-zirconium-copper microporous tube, the problem of premature scrapping of the chromium-zirconium-copper microporous tube due to eccentric wear of the ends can be solved, thereby greatly extending the service life.

[0037] Example 1:

[0038] like Figure 1 As shown, the processing method of the chromium-zirconium-copper microporous tube of the present invention is as follows:

[0039] Step 1: Casting hollow ingots. First, the materials are proportioned and vacuum melted. The raw material ratio is: 0.8wt% Cr, 0.2wt% Zr, and the balance is copper. The temperature is 1250±10℃ through vacuum induction melting, and argon protection is used to ensure the uniformity of the composition.

[0040] Step 2: Hollow continuous casting process: Using a horizontal continuous casting line and a hollow mold, directly cast into hollow round ingots with an outer diameter of 30 mm and an inner diameter of 8 mm. The continuous casting speed is 300-650 mm / min, and the cooling gradient is controlled to eliminate shrinkage cavities.

[0041] Step 3: Grain refinement: After casting, homogenization annealing is performed at 920±5℃ for 3 hours, followed by water quenching and solutionization. The grain size is ≤4μm, and the standard deviation of the grain distribution is ≤2μm.

[0042] Step 4: Wire forging dynamic strengthening: a molybdenum bar with a wire diameter of 7.8 mm is embedded into the hollow round ingot, with standard rods protruding from both ends of the molybdenum bar;

[0043] Step 5: Dynamic multi-directional forging shrinkage cavities: First, heat the hollow ingot to 800±5℃ and apply an isostatic pressure of 280±10MPa, with a forging ratio of 4:1. Repeat the extrusion 3-5 times to close the internal shrinkage defects and form a dense area on the inner wall.

[0044] Step 6: Cooling control: water-cool immediately after forging, with a quenching rate of 50±5℃ / s to retain fine grain structure;

[0045] Step 7: Cold-draw precision forming, using a multi-pass drawing process (adjustable based on the desired aperture), with a 12° die angle and single-pass deformations of 12%, 12%, 11%, and 10%. The outer diameter tolerance after drawing is ±0.02mm, and the inner diameter roundness error is ≤0.003mm. After each drawing pass, vacuum annealing at 450±10°C for 30 minutes under argon protection is performed to restore the elongation to ≥15%. Nano-molybdenum disulfide lubricant is then sprayed on, achieving a friction coefficient of less than 0.1 to reduce surface scratches.

[0046] Step 8: End processing. Cut the chromium zirconium copper microporous tube to the required length and perform end processing. First, perform electrolytic polishing (phosphoric acid-ethylene glycol system, voltage 12V, time 3 minutes). Then, use Hawking high-frequency vibration (20-30kHz, amplitude 30-50μm) to generate a 5-10μm nanocrystalline layer on the end and inner end surface of the chromium zirconium copper microporous tube. The residual compressive stress reaches -300MPa, and the wear resistance is improved by 3-5 times.

[0047] Example 2:

[0048] like Figure 2 As shown, the processing method of the chromium-zirconium-copper microporous tube of the present invention, steps 1 to 7 are consistent with those of Example 1, and the process of step 8 of this embodiment is as follows: before electrolytic polishing, before the secondary processing of the inner wall port of the chromium-zirconium-copper microporous tube, the inner wall end is first turned to expand the diameter, and the difference between the maximum and minimum apertures of the expanded diameter is 30 μm. Then, the expanded diameter is pre-plated with a 0.5 μm thick nickel layer, and then high-frequency induction welding is used to inject silicon carbide powder into the expanded diameter to form a composite coating with a thickness of 2 μm.

[0049] The present invention's processing method for chromium-zirconium-copper microporous tubes employs high-frequency induction welding (temperature 1000-1200°C) on the inner wall end (the area contacting the welding wire) and simultaneously injects silicon carbide (SiC) powder to form a composite coating with a thickness of 2 μm or less, reducing the friction coefficient to below 0.1. Furthermore, high-frequency Hawking vibration (20-30 kHz, amplitude 30-50 μm) is used to generate a 5-10 μm nanocrystalline layer, resulting in a residual compressive stress of -300 MPa and a 3-5-fold increase in wear resistance.

[0050] When the chromium-zirconium-copper microporous tubes prepared in Examples 1 and 2 were sampled and tested, the conductivity was not less than 85% IACS, and the tensile strength was not less than 480 Mp. The performance of the conductive tip prepared by the present invention and the conventional chromium-zirconium-copper conductive tip (Yangtong-M18) on the market were compared as follows:

[0051]

[0052] When the chromium-zirconium-copper microporous tubes prepared in Examples 1 and 2 were subjected to wear resistance tests, the chromium-zirconium-copper microporous tube prepared in Example 1 had an end aperture expansion of only 0.031 mm after 5 million meters of wire feeding, and an internal maximum aperture expansion of 0.029 mm, far exceeding the ISO5821:2019 standard of 0.15 mm); the chromium-zirconium-copper microporous tube prepared in Example 2 had an end aperture expansion (minimum tube diameter position of the expansion port) of only 0.029 mm after 5 million meters of wire feeding, and an internal maximum aperture expansion of 0.030 mm, far exceeding the ISO 5821:2019 standard of 0.15 mm; the wear resistance life was not less than 1500 hours, which was greatly reduced due to the 500-hour drilling and wire-threading process.

[0053] The processing method of the chromium-zirconium-copper microporous tube of the present invention uses horizontal continuous casting to directly cast hollow ingots instead of traditional hot extrusion, reducing the process by 40%. Molybdenum bars are used to support multi-directional dynamic extrusion, ensuring a tube diameter tolerance of ±0.01 mm. Cold drawing is used for precise shaping, and the ends of the microporous tubes are welded with wear-resistant hot melt welding to combine the silicon carbide composite coating and the nanocrystalline layer, increasing the end life by three times. For residual shrinkage cavities in the hollow ingot, a continuous casting cooling gradient (such as gradient water cooling) is used to reduce central shrinkage.

[0054] The above embodiments are only preferred implementations of the present invention. Therefore, any equivalent changes or modifications made according to the structures, features and principles described in the scope of application of the present invention are included in the scope of application of the present invention.

Claims

1. A method for processing a chromium-zirconium-copper microporous tube, characterized in that: The method is specifically as follows: S1. Preparation of rod raw materials: metallic chromium, metallic zirconium and electrolytic copper are mixed in a mass percentage ratio of 0.6-1.2%, 0.1-0.25% and the balance copper, followed by vacuum induction melting to obtain a molten liquid with uniform composition; S2, hollow continuous casting and grain refinement, the molten liquid obtained in the previous step is horizontally continuously cast through a hollow crystallizer to obtain a hollow round rod with an outer diameter of 30 mm and an inner diameter of 8 mm. After the hollow round rod is cooled, it is homogenized annealed and water quenched for solid solution; and the hollow round rod is cut into multiple standard rods of set lengths; S3: Dynamic strengthening by wire forging: A 9.8mm diameter molybdenum bar is inserted into the standard rod, with both ends of the molybdenum bar protruding from the standard rod. The rod is then heated to 750-850°C and subjected to dynamic multi-directional forging with a forging ratio of ≥3:

1. After forging, the rod is water-cooled to retain the fine grain structure. S4, cold drawing precision shaping, according to the inner diameter and wall thickness requirements of the microporous tube, the standard rod processed in the previous step is drawn in multiple passes, the deformation of a single pass is ≤15%, the outer diameter tolerance after stretching is ±0.02mm, and the inner diameter roundness error is ≤0.003mm; S5. Secondary processing of the inner wall port: according to the application requirements, the standard rod processed in the previous step is cut into the target length of the hole tube segment, and the 5~10μm nanocrystalline layer is generated on the outer and inner ends of the hole tube segment through Hawkes energy high-frequency vibration.

2. The method for processing a chromium-zirconium-copper microporous tube according to claim 1, characterized in that: Before the secondary processing of the inner wall port, the inner wall end is first expanded by turning, and then high-frequency induction welding is used to inject silicon carbide powder into the expanded port to form a composite coating with a thickness of 2μm.

3. The method for processing the chromium-zirconium-copper microporous tube according to claim 2, characterized in that: Before the silicon carbide powder is fused and welded, the expanded port is pre-plated with a nickel layer having a thickness of 0.5 μm.

4. The method for processing a chromium-zirconium-copper microporous tube according to claim 1, characterized in that: Before strengthening the nanocrystalline layer, the interior of the microporous tube is electrolytically polished.

5. The method for processing the chromium-zirconium-copper microporous tube according to claim 3, characterized in that: The electrolytic polishing process is as follows: the microporous tube is placed in a phosphoric acid-ethylene glycol electrolyte for electrolysis at a voltage of 12 V and an electrolysis time of 2.5 minutes.

6. The method for processing chromium-zirconium-copper microporous tube according to claim 1, characterized in that: The cold drawing precision shaping process uses a combination of a carbide outer die and a core die with a die angle of 12-15 degrees. After each drawing is completed, it enters an intermediate annealing process. The intermediate annealing process uses 450-500℃, a holding time of 30 minutes, and argon protection to restore the elongation to ≥15%.

7. The method for processing a chromium-zirconium-copper microporous tube according to claim 6, characterized in that: After completing the intermediate annealing process, nano-molybdenum disulfide lubricant is sprayed before entering the next drawing process.

8. The method for processing a chromium-zirconium-copper microporous tube according to claim 1, characterized in that: The metal chromium, metal zirconium and electrolytic copper are mixed in a mass percentage ratio of 0.8%, 0.2% and the balance being copper.

9. The method for processing a chromium-zirconium-copper microporous tube according to claim 1, characterized in that: During the dynamic multi-directional forging, each area is alternately forged 3-5 times.

10. A chromium-zirconium-copper microporous tube, processed by the processing method of any one of claims 1 to 9, characterized in that: The invention comprises a hole tube section, wherein the outer end portions and the inner wall of both ends of the hole tube section are integrally made into a 5-10 μm nanocrystalline layer.

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