A high-conductivity, free-cutting copper alloy material suitable for welding and cutting applications and its preparation method

Abstract

This invention provides a high-conductivity, free-cutting copper alloy material and its preparation method suitable for the welding and cutting field, belonging to the field of alloy smelting technology. The preparation method of the high-conductivity, free-cutting copper alloy material suitable for the welding and cutting field provided by this invention includes the following steps: (1) Optimizing the chemical composition of the alloy: using tellurium, rare earth deoxidizer, and high-purity copper as the main components; (2) Using a closed-loop melting and casting process with full coverage of high-purity flake graphite and full protection of high-purity argon gas; (3) Combining a complete set of preparation processes including precise temperature-controlled melting, static casting, hot extrusion molding, acid pickling to remove oxidation, and multi-pass cold drawing molding. The copper alloy material prepared by this invention has a conductivity ≥95% IACS, and with HPB63-3 leaded brass as the reference standard, a relative cutting performance ≥85%, and fine grains; the material also has excellent cold working adaptability, and can meet various processing methods such as cold extrusion, cold heading, and precision turning, and is specially adapted to the production of core welding and cutting components such as welding and cutting nozzles, welding and cutting conductive ends, and flame diverters.

Description

Technical Field

[0001] This invention belongs to the field of alloy smelting technology, specifically relating to a high-conductivity, easily machinable copper alloy material suitable for welding and cutting, and its preparation method. It is applicable to copper alloy material preparation, metal smelting, and plastic processing technologies. Background Technology

[0002] In industrial welding and cutting operations such as flame welding, gas shielded welding, and plasma cutting, nozzles, distributors, conductive nozzles, and conductive tips are the core vulnerable components of welding and cutting torches. Their comprehensive performance directly determines the stability of the welding and cutting flame, the concentration of the arc, the accuracy of operation, and the service life of the equipment. Currently, most welding and cutting accessories on the market are made of pure copper, ordinary oxygen-free copper, or simple free-machining brass: Pure copper and oxygen-free copper have excellent electrical conductivity, but poor machinability, making precision hole machining difficult, resulting in high tool wear, and low pass rates in cold heading and cold extrusion forming, making them difficult to adapt to automated precision machining; Ordinary brass and leaded brass have good machinability, but poor electrical and thermal conductivity, resulting in insufficient heat dissipation efficiency under high-temperature conditions, and long-term welding and cutting operations are prone to problems such as nozzle erosion, deformation, and clogging. At the same time, leaded brass contains the heavy metal lead, which does not meet green manufacturing standards and limits its application.

[0003] Industry research indicates that tellurium copper alloys (typical grades C14500, QTe0.3), as lead-free, free-machining high-end copper alloys, can simultaneously compensate for the performance deficiencies of pure copper and leaded brass. They possess multiple advantages, including high electrical and thermal conductivity, easy machinability, and resistance to high temperatures and arc erosion, making them an ideal replacement material for precision welding and cutting torch components. The International Copper Association's 2023 technical report verifies that tellurium copper has an electrical conductivity of 85-94% IACS, machinability exceeding 85% of leaded brass, is lead-free and environmentally friendly, and exhibits significantly superior high-temperature resistance to welding and plasma erosion compared to conventional brass, making it suitable for automated precision machining and long-term continuous welding and cutting operations.

[0004] Tellurium copper alloy, as a lead-free, free-machining high-end copper alloy, has become the preferred material for welding and cutting parts due to its advantages such as high electrical and thermal conductivity, easy machinability, and high-temperature resistance and ablation resistance. However, existing conventional tellurium copper alloy preparation processes have significant defects: First, the smelting process lacks closed-loop protection measures, making the molten copper highly susceptible to oxygen absorption and oxidation, resulting in the formation of brittle copper oxide inclusions, which reduces the material's electrical conductivity and high-temperature stability. Second, the deoxidation process is rudimentary, relying solely on ordinary phosphorus copper for deoxidation, which is incomplete, leading to the enrichment of impurity elements at grain boundaries, easily causing coarse grains and uneven microstructure. Third, the composition ratio is unreasonable, with severe tellurium segregation, making it impossible to consistently meet the free-machining performance standards. These problems make it difficult for conventional tellurium copper alloys to simultaneously meet the multiple requirements of the welding and cutting industry, such as high electrical conductivity and heat dissipation, high-precision cutting, low-temperature cold forming, and high-temperature ablation resistance, thus restricting the large-scale domestic production of high-end welding and cutting parts.

[0005] The multiple defects of the aforementioned traditional materials and preparation processes make it difficult for conventional tellurium copper alloys to simultaneously meet the four stringent requirements of the welding and cutting industry: ultra-high conductivity and heat dissipation, high-precision cutting, low-temperature cold plastic forming, and high-temperature resistance to electric arc erosion. High-end robotic welding and cutting equipment still relies heavily on imported special tellurium copper profiles for conductive nozzles and plasma nozzles, which restricts the localization and low-cost large-scale production of core vulnerable components in welding and cutting.

[0006] Therefore, optimizing the alloy composition ratio and improving the processing technology to develop a tellurium copper alloy material that is suitable for welding and cutting applications, and that combines ultra-high conductivity with excellent machinability and cold working performance, in order to solve the above-mentioned defects, has become an urgent technical problem to be solved. Summary of the Invention

[0007] The present invention aims to solve the aforementioned technical problems by providing a high-conductivity, easily machinable copper alloy material and its preparation method suitable for the welding and cutting field. The technical objective of this invention is to overcome the technical difficulties of traditional welding and cutting copper alloys, such as the inability to simultaneously achieve conductivity and machinability, easy oxidation of the melt, uneven grain structure, and difficulty in cold forming. The invention aims to produce a high-performance lead-free tellurium copper alloy suitable for precision components such as welding and cutting nozzles, which can be mass-produced industrially.

[0008] To achieve the above-mentioned technical objectives, the technical solution adopted by the present invention is as follows: This invention first provides a high-conductivity, free-cutting copper alloy material suitable for welding and cutting applications. The copper alloy material is composed of the following components by mass percentage: tellurium (Te): 0.2%~0.4%; rare earth deoxidizer: 0.002%~0.006%; the balance being high-purity cathode copper and trace impurities unavoidable during the production process.

[0009] Specifically, the rare earth deoxidizing agent is selected from any single element of lanthanum (La) or cerium (Ce).

[0010] The working principle of each component in the above alloy material is explained below: Tellurium (Te): Tellurium has extremely low solid solubility in copper matrix. After melting and forming, it is mainly distributed as fine Cu2Te particles in the grain boundaries and grain interiors. It can effectively break the continuity of copper matrix, reduce chip adhesion during cutting, reduce tool wear, and significantly improve the machinability of the alloy. Controlling the content in the range of 0.2% to 0.4% can ensure excellent machinability and avoid the problem of reduced alloy plasticity and conductivity caused by excessive precipitation of tellurium.

[0011] Rare earth elements lanthanum (La) / cerium (Ce): Trace amounts of rare earth elements have a triple effect of deep deoxidation, impurity removal, and grain refinement. They can combine with harmful impurities such as oxygen and sulfur in molten copper to form high-melting-point composite compounds, which then float to the surface and are discharged, reducing the oxygen content of the alloy and eliminating brittle oxide inclusions. At the same time, rare earth compounds can act as heterogeneous nucleation sites, refining as-cast grains, purifying grain boundaries, and improving the alloy's plasticity and hot and cold working properties, making it suitable for cold heading and cold extrusion forming processes. The addition amount is limited to 0.002%~0.006% to avoid excessive accumulation of rare earth elements that could lead to compositional segregation and affect electrical conductivity.

[0012] High-purity copper matrix: 99.99% high-purity cathode copper is selected as the matrix to reduce the initial impurity content from the source, ensuring that the alloy has ultra-high electrical and thermal conductivity, meeting the core requirement of high-temperature and rapid heat dissipation of welding and cutting nozzles.

[0013] This invention also provides a method for preparing a high-conductivity, free-cutting copper alloy material suitable for welding and cutting applications, comprising the following steps: (1) Raw material pretreatment: Select 99.99% high-purity cathode copper, high-purity tellurium blocks, and rare earth lanthanum / cerium elemental raw materials, remove oxide scale, oil stains and impurities from the surface of the raw materials, and weigh them accurately according to the ratio for later use; (2) Closed melting: The pretreated high-purity cathode copper is put into the graphite melting crucible and heated to 1150~1200℃ until the copper material is completely melted into liquid copper. Throughout the melting process, high-purity argon gas (purity ≥99.999%) is continuously introduced into the furnace cavity as a protective atmosphere. At the same time, high-purity flake graphite is fully covered on the surface of the copper liquid to isolate it from the air and prevent secondary oxidation of the copper liquid. (3) Deoxidation and alloying: After the copper liquid is completely melted, a predetermined mass of rare earth lanthanum or cerium is added to the copper liquid in batches and stirred at a constant temperature for 3-5 minutes to complete deep deoxidation and impurity removal; then, high-purity tellurium blocks are added by pressing in a high-purity graphite bell jar and kept at a constant temperature for 8-12 minutes, and electromagnetic stirring is used to promote uniform diffusion of tellurium elements and avoid component segregation. (4) Static casting: After alloying, adjust the melting temperature to 1160~1190℃ and let it stand for 10~15 minutes to allow impurities and slag inside the melt to float to the surface and be removed; then cast in an argon-protected environment to obtain a dense cylindrical alloy ingot without pores or inclusions. (5) Hot extrusion molding: The alloy ingot is fed into the heating furnace and preheated to 720~760℃ and held for 20~30min; hot extrusion molding is carried out using a horizontal extruder, and the extrusion ratio is controlled at 12~18:1 to prepare a dense alloy extrusion billet; hot extrusion can break up coarse cast grains, eliminate casting internal stress, and optimize the uniformity of the structure. (6) Pickling to remove oxidation: Immerse the extruded billet in a dilute sulfuric acid solution (concentration of 15%~20wt%) for 10~15 minutes to thoroughly remove the high-temperature oxide layer on the inner and outer surfaces of the billet; after pickling, rinse with deionized water under high pressure and hot air to avoid acid residue corroding the substrate. (7) Multi-pass cold drawing: According to the requirements of finished product specifications, the extruded billet after pickling and drying is subjected to multi-pass progressive cold drawing. The deformation amount of a single pass is controlled at 10%~18%, and the total deformation amount is controlled at 20%~40% (the deformation amount is determined according to the state); finally, high-conductivity free-cutting tellurium copper alloy finished products of different specifications such as bars and wires are obtained.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: (1) This invention provides a high-conductivity, easily machinable copper alloy material and its preparation method suitable for the welding and cutting field. By optimizing the alloy composition ratio, introducing trace rare earth elements for deep deoxidation and grain refinement, and combining oxygen-free closed melting and casting with full-process plastic processing technology, a tellurium copper alloy material suitable for welding and cutting field, which takes into account ultra-high conductivity, excellent machinability, and cold working performance has been developed. This invention effectively solves the technical problems of traditional copper alloys for welding and cutting that cannot take into account both conductivity and machinability, easy oxidation of melt, uneven grain structure, and difficulty in cold forming. A high-performance lead-free tellurium copper alloy suitable for precision parts such as welding and cutting nozzles and capable of mass industrial production has been prepared.

[0015] (2) The finished copper alloy for welding and cutting prepared by this invention has the following performance indicators: room temperature conductivity ≥95% IACS; relative cutting performance ≥85% based on HPB63-3 leaded brass; fine and uniform grain size, free from defects such as pores and oxide inclusions; excellent cold working adaptability, allowing direct secondary processing such as cold extrusion, cold heading, precision turning, and drilling without additional heat treatment. The finished material is specifically used to prepare core components such as various gas welding / cutting nozzles, gas shielded welding conductive nozzles, plasma welding and cutting distributors, and welding and cutting torch conductive connectors, and is compatible with various industrial welding and cutting equipment. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described in detail below with reference to embodiments. It should be noted that the following embodiments are for explanation and illustration only and are not intended to limit the invention. Non-essential improvements and adjustments made by those skilled in the art based on the above description are still within the scope of protection of this invention.

[0017] Example 1

[0018] A high-conductivity, free-machining copper alloy material suitable for welding and cutting applications has the following chemical composition by mass: Te: 0.25%, rare earth lanthanum La: 0.003%, with the balance being high-purity copper and trace impurities; its preparation process is as follows: (1) Raw material pretreatment: 99.99% high-purity cathode copper, 99.99% high-purity tellurium blocks and metallic lanthanum were selected, and the surface impurities were cleaned and weighed accurately. (2) Melting: Cathode copper is melted at 1180℃, with high-purity argon gas introduced throughout the process for protection, and the surface of the copper liquid is covered with high-purity flake graphite. (3) Alloying: Add lanthanum metal and stir to deoxidize, then press in tellurium blocks, keep warm for 10 minutes and stir electromagnetically; (4) Casting: Let stand at 1160℃ for 12 minutes, then cast into an ingot under argon protection; (5) Hot extrusion: Preheat at 730℃ for 25 min, extrusion ratio 15:1, to prepare extruded billets; (6) Pickling: Use 16% dilute sulfuric acid for pickling for 12 minutes, then rinse with clean water; (7) Cold drawing: multiple drawing passes, with a total deformation of 20%, to obtain Φ14mm alloy bars.

[0019] The high-conductivity, free-machining copper alloy material prepared by the above method was subjected to performance testing, and the testing methods were carried out in accordance with existing standards and conventional methods. The test results showed that the alloy in this embodiment had a conductivity of 96.2% IACS, a relative machinability of 87.3% (HPB63-3), and an average grain size of 22 μm, making it suitable for direct cold heading of weld-cut nozzle blanks.

[0020] Example 2

[0021] A high-conductivity, free-machining copper alloy material suitable for welding and cutting applications has the following chemical composition by mass: Te: 0.22%, rare earth lanthanum La: 0.004%, with the balance being high-purity copper and trace impurities; its preparation process is as follows: (1) Raw material pretreatment: 99.99% high-purity cathode copper, 99.99% high-purity tellurium blocks and metallic lanthanum were selected, and the surface impurities were cleaned and weighed accurately. (2) Melting: The cathode copper is melted at 1180℃, with high-purity argon gas introduced throughout the process for protection, and the surface of the copper liquid is covered with high-purity flake graphite. (3) Alloying: Add lanthanum metal and stir to deoxidize, then press in tellurium blocks, keep warm for 10 minutes and stir electromagnetically; (4) Casting: Let stand at 1180℃ for 12 minutes, then cast into an ingot under argon protection; (5) Hot extrusion: Preheat at 740℃ for 25 min, extrusion ratio 15:1, to prepare extruded billets; (6) Pickling: Use 16% dilute sulfuric acid for pickling for 12 minutes, then rinse with clean water; (7) Cold drawing: multiple drawing passes, with a total deformation of 30%, to obtain Φ16mm alloy bars.

[0022] The high-conductivity, free-machining copper alloy material prepared by the above method was subjected to performance testing, and the testing methods were carried out in accordance with existing standards and conventional methods. The test results showed that the alloy in this embodiment had a conductivity of 95.8% IACS, a relative machinability of 88.5% (HPB63-3), and an average grain size of 18 μm, making it suitable for direct cold heading of weld-cut nozzle blanks.

[0023] The copper alloy material prepared by this invention has a conductivity of ≥95% IACS, with HPB63-3 leaded brass as the reference standard, a relative machinability of ≥85%, and fine grain size. The material also has excellent cold working adaptability and can meet various processing methods such as cold extrusion, cold heading, and precision turning. It is specifically adapted to the production of core welding and cutting components such as welding and cutting nozzles, welding and cutting conductive terminals, and flame diverters.

[0024] The above embodiments are only some implementations of the present invention. Various improvements and modifications can be made without departing from the principle of the present invention, and all such improvements and modifications fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-conductivity, free-cutting copper alloy material suitable for welding and cutting applications, characterized in that, Includes the following steps: (1) Raw material pretreatment: Select high-purity cathode copper, high-purity tellurium blocks, rare earth lanthanum or cerium as raw materials, remove surface oxide scale and oil stains, and weigh them according to the ratio for later use; (2) Closed smelting: High-purity cathode copper is put into the smelting furnace and heated to 1150~1200℃ to melt; high-purity argon gas is introduced throughout the smelting process for protection, and the surface of the copper liquid is fully covered with high-purity flake graphite to isolate it from air and prevent oxidation. (3) Deoxidation alloying: After the copper liquid is melted, rare earth lanthanum or cerium is added and stirred for 3-5 min to complete deep deoxidation; then tellurium blocks are pressed in through a high-purity graphite bell jar, kept at a temperature for 8-12 min and electromagnetically stirred to achieve uniform distribution of elements; (4) Static casting: Adjust the melt temperature to 1160~1190℃, let it stand for 10~15 min, remove the floating slag, and cast the alloy ingot with a specification of φ120mm under argon protection. (5) Hot extrusion molding: The ingot is preheated to 720~760℃ and held for 20~30 min. It is then hot extruded using a horizontal extruder with an extrusion ratio of 12~18:1 to obtain the extruded billet. (6) Pickling to remove oxidation: Place the extruded billet in a dilute sulfuric acid solution for pickling for 10-15 min to remove the surface oxide layer, and rinse with plenty of deionized water; (7) Cold drawing forming: The billet is subjected to multiple cold drawing processes, with a single-pass deformation of 10%~18% and a total deformation of 20%~40%, to obtain alloy finished products of different specifications.

2. The method according to claim 1, characterized in that, The copper content in the high-purity cathode copper mentioned in step (1) is Cu%≥99.99% by weight percentage.

3. The method according to claim 1, characterized in that, The tellurium content in the high-purity tellurium block mentioned in step (1) is Te%≥99.99% by weight percentage.

4. The method according to claim 1, characterized in that, The rare earth element mentioned in step (1) is either lanthanum or cerium, with a purity of La%≥99.99% and Ce%≥99.99%.

5. The method according to claim 1, characterized in that, The purity of the high-purity argon gas mentioned in step (2) is ≥99.999%, and the purity of the high-purity flake graphite is ≥99.95%.

6. The method according to claim 1, characterized in that, The amount of high-purity flake graphite used in step (2) is 15kg~20kg / furnace.

7. The method according to claim 1, characterized in that, The smelting furnace mentioned in step (2) is a 500 kg industrial frequency smelting furnace.

8. The method according to claim 1, characterized in that, The concentration of the dilute sulfuric acid mentioned in step (6) is 15~20wt%.

9. A high-conductivity, free-machining copper alloy material prepared by the method according to any one of claims 1-8, characterized in that, The copper alloy material consists of the following components by weight percentage. Composition: Tellurium: 0.2%~0.4%; Rare earth deoxidizing agent: 0.002%~0.006%; Balance is 99.99% high-purity cathode copper and unavoidable trace elements; The rare earth deoxidizing agent is any one of lanthanum or cerium.

10. The high-conductivity, free-machining copper alloy material according to claim 9, characterized in that, The conductivity of the copper alloy material is ≥95% IACS, with HPB63-3 leaded brass as the reference standard, and the relative machinability of the material is ≥85%.