Platinum-iridium gold wire and method of forming

Abstract

The application relates to the technical field of precious metal processing, in particular to a platinum-iridium gold wire and a forming method, which comprises the following steps: S1. alloy smelting and ingot preparation; S2. homogenizing annealing; S3. blooming forging to obtain a forged blank; S4. hot rolling treatment to obtain a hot-rolled rod; S5. multi-pass cold drawing and on-line annealing until the wire reaches a target size; S6. finished product relaxation annealing; and S7. post-processing to obtain the platinum-iridium gold wire. The platinum-iridium gold wire is based on the basic components of platinum and iridium, lays a foundation for the intrinsic characteristics of high strength and high toughness of the material, further utilizes the micro-alloying design of ruthenium or yttrium, cooperates with the instantaneous high temperature and millisecond-level holding time generated by on-line electric annealing, effectively overcomes the inherent high work hardening characteristics of the platinum-iridium alloy, and can avoid sacrificing the intrinsic performance of the material or introducing serious processing defects.

Description

Technical Field

[0001] This invention relates to the field of precious metal processing technology, and more specifically, to a platinum-iridium wire and a forming method thereof. Background Technology

[0002] Platinum-iridium alloy, as a superior precious metal material, has secured an irreplaceable position in numerous cutting-edge technology fields due to its unique and excellent physicochemical properties, including extremely high melting point, outstanding mechanical strength, excellent electrical conductivity, superior corrosion resistance, and biocompatibility. Specifically, in the manufacture of high-end electronic components, such as precision sensors, micro-connectors, and high-reliability electrical contacts, its stability and conductivity are crucial. In medical devices, such as implantable electrodes, catheter guidewires, and surgical instruments, platinum-iridium alloy is the preferred material due to its bioinertness and durability. Furthermore, in the extreme conditions of the aerospace industry, its high-temperature strength and oxidation resistance make it a core component in nozzles, thermocouples, and other critical parts. However, despite its many advantages, platinum-iridium alloy still faces numerous severe technical challenges in practical applications, especially when processing it into wire. Due to its high strength and significant work hardening effect, the preparation and forming processes of traditional wires are complex and costly, directly restricting the full realization of its performance and the further expansion of its application range.

[0003] In existing technologies, various technical solutions have been explored to address the machinability and cost issues of platinum-iridium alloys. For example, patent CN114351003B discloses a copper-platinum-iridium alloy brush material and its preparation method. This technical solution aims to prepare a novel brush material with both high cost-effectiveness and excellent conductivity and wear resistance by alloying platinum-iridium alloy with copper. This material is suitable for high-end potentiometers and conductive slip rings that are cost-sensitive and have specific requirements for conductivity. The design concept is to improve the overall machinability of platinum-iridium alloys and reduce material costs by introducing copper, which has relatively low cost and good plasticity. Building on this, patent CN118003084B provides a method for preparing medical platinum-iridium rings. This method focuses on a series of precise process steps, including vacuum melting, homogenization heat treatment, piercing extrusion, and subsequent drawing forming, to obtain platinum-iridium alloy rings with uniform wall thickness and no damage or contamination on the inner and outer surfaces, in order to meet the stringent requirements of medical implant materials for precise geometry and surface integrity. The core of this method lies in the strategy of combining multiple cold deformation and annealing to gradually achieve the forming of complex shapes, while attempting to control the microstructure and surface quality of the material.

[0004] However, with the continuous development of related technologies and the increasingly stringent performance requirements for platinum-iridium wires in high-end applications, some inherent characteristics of the aforementioned existing technical solutions at the principle level have gradually revealed their limitations in addressing new challenges and exposed deep-seated technical contradictions. Specifically, regarding the copper-platinum-iridium alloy proposed in CN114351003B, although the introduction of copper has achieved cost control and improved processing performance to some extent, this alloying strategy essentially comes at the cost of sacrificing the overall strength, corrosion resistance, and long-term stability of the material. The reason for this is that there is a significant difference in the coefficient of thermal expansion between copper and the platinum-iridium alloy matrix. This can easily lead to interfacial stress concentration under high temperature or long-term service conditions, resulting in interfacial delamination or the initiation and propagation of microcracks, ultimately seriously affecting the long-term reliability and stability of the material. In addition, the introduction of copper may also reduce the inherent high corrosion resistance of the alloy in certain applications, making it difficult to meet the service requirements in extreme environments. More importantly, this approach, which involves extensive alloying of dissimilar elements, results in an extremely narrow range of composition ratios and processing techniques. This increases the complexity of production and the risks associated with quality control, making it difficult to apply on a large scale to the field of precision wires, where material purity and intrinsic properties are of paramount importance.

[0005] Meanwhile, the traditional multi-pass cold drawing and frequent intermediate annealing forming strategy, represented by CN118003084B, while enabling a certain degree of plastic deformation in platinum-iridium alloys, reveals increasingly prominent inherent defects when producing high-performance, high-precision, long-diameter platinum-iridium wires. This method requires multiple high-temperature intermediate annealing processes to eliminate work hardening effects and restore material plasticity for subsequent deformation. However, high temperatures and relatively long holding times, especially repeated processes, inevitably lead to significant grain coarsening, directly weakening the material's tensile strength, fatigue performance, and overall toughness—unacceptable for fine wires requiring high strength, high toughness, and long service life. Grain coarsening not only degrades the material's mechanical properties but also makes surface quality difficult to control, easily resulting in orange peel defects or surface inhomogeneity, which is fatal in high-precision and miniaturized applications. Furthermore, this frequent heat treatment significantly increases production cycle time and unit energy consumption, leading to low production efficiency and high costs. Furthermore, during the cold drawing process, the high strength and hardness of the platinum-iridium alloy lead to exceptionally severe wear on the die. This not only significantly shortens the die's lifespan but, more importantly, the inconsistency in die wear directly results in unstable control of the wire's dimensional accuracy, causing fluctuations in wire dimensions between batches and even within the same batch. This severely restricts its applicability in high-precision, high-consistency applications (such as precision sensor leads and miniature medical guidewires). These issues demonstrate that existing technologies present an irreconcilable contradiction between improving the overall performance of platinum-iridium wires, simplifying the forming process, ensuring dimensional accuracy, and reducing production costs.

[0006] Therefore, how to design an advanced platinum-iridium wire and its forming method that can effectively overcome the inherent high work hardening characteristics of platinum-iridium alloys, while avoiding the need to sacrifice the intrinsic properties of the material or introduce serious processing defects (such as grain coarsening and dimensional instability) to achieve the deformation purpose, and ultimately realize the preparation of high-performance, high-precision, low-cost, and high-efficiency wires, has become a key challenge and an urgent technical problem to be solved by those skilled in the art. Summary of the Invention

[0007] To achieve the above objectives, this invention provides a platinum-iridium wire and a forming method. The basic components of platinum and iridium establish the intrinsic properties of the material's high strength and high toughness. Furthermore, by utilizing the micro-alloying design of ruthenium or yttrium, combined with the instantaneous high temperature and millisecond-level holding time generated by online electric annealing, high-performance, high-precision, low-cost, and high-efficiency wire preparation can be achieved.

[0008] To achieve the above objectives, the technical solution of the present invention is: a method for forming platinum-iridium wire, comprising the following steps:

[0009] By weight,

[0010] S1. Alloy Smelting and Ingot Preparation: A vacuum induction melting process is used to melt platinum and iridium raw materials into a uniform platinum-iridium alloy ingot, wherein the mass fraction of platinum is 75-85 parts and the mass fraction of iridium is 15-25 parts; the smelting process is carried out under a vacuum degree better than 5×10⁻⁶. -2 The procedure is carried out under the protection of Pa or high-purity argon gas;

[0011] S2. Homogenization annealing: The ingot is placed in a vacuum or protective atmosphere heat treatment furnace and held at 1200-1500℃ for 5-20 hours to eliminate dendritic segregation inside the ingot.

[0012] S3. Forging: The homogenized ingot is heated to 1200-1400℃ and forged using a fast forging method. The initial forging temperature is ≥1200℃, the final forging temperature is ≥950℃, and the total forging ratio is not less than 3:1 to obtain the forging billet.

[0013] S4. Hot rolling treatment: The forging billet is reheated to 1250-1400℃ for hot rolling, the final rolling temperature is controlled at ≥1000℃, the total deformation is 40%-80%, and then sandblasting and pickling treatment are performed to completely remove the surface oxide scale and obtain hot-rolled bar stock.

[0014] S5. Multi-pass cold drawing and online annealing:

[0015] S5.1 The surface-treated bar is subjected to multi-pass cold drawing process using polycrystalline diamond wire drawing dies, and the deformation amount per pass is controlled at 8%-22%;

[0016] S5.2 During the cold drawing process, when the cumulative reduction of area reaches 55%-75% of the current cold drawing, the wire is subjected to online intermediate annealing treatment with electric current. The wire is continuously passed through a pair of conductive rollers and current is applied. The intermediate annealing temperature is monitored in real time by an infrared thermometer and controlled in a closed loop at 1000-1150℃. The wire speed is 5-20m / min, and the treatment atmosphere is high-purity argon or nitrogen with a dew point below -60℃.

[0017] After S5.3 annealing, the wire is immediately subjected to controlled cooling in a closed cooling chamber filled with protective gas, with the cooling rate controlled at 50-200℃ / s.

[0018] S5.4 Repeat steps S5.1 to S5.3 until the wire reaches the target size;

[0019] S6. Finished product relaxation annealing: The wire that has reached the target size is subjected to final relaxation annealing treatment at a temperature of 700-900℃ and a holding time of 10-60min. The treatment atmosphere is vacuum or high-purity argon.

[0020] S7. Post-processing: The finished wire is ultrasonically cleaned and dried to obtain platinum-iridium wire.

[0021] This scheme establishes a collaborative system from material composition design to process parameter setting. The composition setting of 75-85 parts platinum and 15-25 parts iridium determines the ultimate performance and machinability of the material. Excessive iridium content will drastically increase the strength and work hardening tendency of the alloy, making subsequent deformation difficult; while too low iridium content will fail to achieve the required high performance indicators.

[0022] Given the aforementioned composition, the logical progression of the process design is as follows: Homogenization annealing addresses the inherent dendritic segregation and compositional inhomogeneity issues in platinum-iridium alloy ingots, aiming to provide a uniform composition for subsequent plastic deformation and prevent machining cracks caused by variations in hardness. Subsequently, forging and hot rolling are performed above the recrystallization temperature. Utilizing the material's high plasticity at high temperatures, significant deformation thoroughly breaks down the coarse as-cast crystalline structure, transforming it into a fine, equiaxed machined structure, thus preparing a fine-grained, dense billet for subsequent cold working.

[0023] The key lies in the combination of cold drawing and in-line electro-annealing. Cold drawing aims to continuously reduce diameter and strengthen the material, but inevitably causes work hardening. Traditional techniques use batch furnace annealing to eliminate hardening, but its slow heating and cooling process allows sufficient time for atomic diffusion, resulting in ample opportunity for recrystallized grains to grow, thus weakening material properties. This solution utilizes in-line electro-annealing, which, while already used in conventional metal industries, is crucial because platinum-iridium wire, as a special precious metal, exhibits significantly different physical properties compared to conventional metals. In-line electro-annealing utilizes the Joule heat generated directly by the current through the wire itself for instantaneous heating, achieving an extremely rapid heating rate (on the order of 10³°C / s). This allows the material to reach its recrystallization temperature and soften in a very short time (in seconds), followed by rapid cooling through forced cooling. The core advantage of this lightning-fast heat treatment is that it significantly shortens the material's residence time at high temperatures, thereby inhibiting grain growth. While efficiently eliminating work hardening, it perfectly preserves the fine grain structure, achieving a balance between processability and performance. Relaxation annealing, as a final process, no longer aims to change the microstructure, but rather to eliminate residual stress inside the product at a lower temperature, thereby improving dimensional stability and reliability.

[0024] Preferably, in step S1, 0.5-2 parts by mass of ruthenium are added to the smelting raw materials, wherein the ruthenium is added in pure metallic form.

[0025] Preferably, the temperature control range of the online electro-annealing process in step S5.2 is 1050-1150℃, in order to promote the full solid solution of ruthenium and suppress the precipitation of brittle phase.

[0026] Ruthenium, as a platinum group element, possesses unique atomic radius and electronic structure that allows it to dissolve extensively into a platinum-iridium matrix, forming substitutional solid solutions and resulting in significant solid solution strengthening. However, ruthenium has a high diffusion activation energy, making it difficult to achieve sufficient homogenization at the relatively low temperatures or short durations of traditional annealing processes. This can easily lead to compositional fluctuations or even brittle intermetallic compound phases at grain boundaries, thereby impairing ductility. Increasing the annealing temperature to the higher range of 1050-1150℃ significantly increases the atomic diffusion coefficient. This provides ruthenium atoms with sufficient kinetic energy to overcome the energy barrier and enter the lattice sites, thereby achieving rapid and sufficient solid solution. However, this temperature range is strictly limited to below the significant grain growth initiation temperature of platinum-iridium alloys. By utilizing the millisecond to second-level ultra-short thermal cycling characteristics unique to online electric annealing, the material is rapidly cooled immediately after obtaining a single-phase solid solution, thereby kinetically suppressing the nucleation and growth trend of brittle phases such as ruthenium-rich phases, and ultimately achieving a synergistic improvement in strength and plasticity.

[0027] Preferably, in step S1, 0.1-0.5 parts by mass of yttrium are added to the smelting raw materials, wherein the yttrium is added in the form of a platinum-yttrium or iridium-yttrium master alloy.

[0028] Preferably, the temperature control range of the online power-on intermediate annealing process in step S5.2 is 1000-1100℃, which utilizes the ultra-short time heating and the grain boundary pinning effect of yttrium to synergistically suppress grain growth.

[0029] The addition of 0.1-0.5 parts of yttrium in the form of an intermediate alloy is based on the extremely high chemical activity of yttrium and its strong affinity for impurities such as oxygen and sulfur. Yttrium deeply purifies the alloy melt, generating fine, dispersed yttrium oxides or yttrium-platinum / iridium compounds with extremely high thermal stability that strongly pin grain boundaries. Precisely controlling the subsequent online intermediate annealing temperature within the 1000-1100℃ range is precisely to synergistically leverage yttrium's pinning advantage and the characteristics of the ultra-short-time process. This temperature is sufficient to drive dislocation rearrangement and recrystallization nucleation to eliminate work hardening, while remaining far below the critical temperature point for significant coarsening or dissolution of yttrium precipitates, thus ensuring the stability of the pinned particle size and distribution. The extremely short-time characteristic of online annealing, measured in milliseconds, allows recrystallized grains to be effectively anchored by yttrium pinned particles the instant they begin to nucleate and grow. The rapid cooling process further freezes this fine-grained metastable structure, theoretically achieving the simultaneous attainment of two seemingly contradictory goals: recrystallization softening and grain refinement.

[0030] Preferably, the power supply for the online intermediate annealing process in step S5.2 is a DC power supply with a working voltage of 1-10V and a working current of 200-2000A.

[0031] Choosing a DC power supply and setting the operating voltage to 1-10V and the operating current to 200-2000A is a necessary and optimized engineering decision based on Joule's law (P=I²R), Ohm's law (U=IR), and the resistivity characteristics of the material. The core theoretical basis for this parameter range is that the wire's resistance is extremely low, typically in the milliohm range. To achieve the Joule heat power sufficient to instantly raise it to its recrystallization temperature above 1000℃, a very large current must be applied according to P=I²R. However, according to U=IR, given the extremely low resistance R, the voltage required to generate such a large current is naturally only a few volts. This low-voltage, high-current mode is not only a necessary result of physical laws but also possesses significant technical advantages: low voltage ensures inherent operational safety, fundamentally eliminating the risk of electric shock; high current generates a highly uniform and instantaneous heating effect within the wire, avoiding the skin effect that may exist in induction heating or the surface-level temperature unevenness of laser heating, thus ensuring the synchronicity and consistency of the entire cross-sectional microstructure transformation. This parameter range covers all requirements from thick to thin wire diameters. For different wire specifications (corresponding to different R values), the closed-loop control system can make precise adjustments within this voltage and current range. This ensures that the core temperature remains stable within the preset recrystallization temperature range regardless of changes in wire diameter. This is a key technical guarantee for achieving a high degree of consistency in product performance.

[0032] Preferably, the packaging in step S7 is vacuum packaging or protection with high-purity inert gas.

[0033] This solution also proposes a platinum-iridium wire prepared by the above-described molding process.

[0034] Compared to existing technologies, the advantages of this solution are:

[0035] 1. This scheme establishes the intrinsic properties of high strength and high toughness of the material through the basic components of platinum and iridium. It further utilizes the microalloying design of ruthenium or yttrium to endow the material with higher strength limit and microstructure thermal stability through solid solution strengthening and grain boundary purification pinning mechanisms, respectively. It is deeply coupled with the subsequent online electric annealing process: the annealing temperature window of 1050-1150℃ ensures the rapid and complete solid solution of ruthenium, while the range of 1000-1100℃ perfectly matches the temperature environment in which the yttrium precipitate phase exerts the best pinning effect. This maximizes the function of trace additives and realizes the designability and customization of material properties.

[0036] 2. By utilizing the instantaneous high temperature and millisecond-level holding time generated by online power-on annealing, combined with high-speed cooling, an extremely short-time, high-energy-density thermal cycle process is formed. This process can provide enough activation energy to drive dislocation recombination and recrystallization, effectively eliminating work hardening. Furthermore, because its action time is much shorter than the diffusion time for significant grain boundary migration, it reduces the size of recrystallized grains. Detailed Implementation

[0037] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. 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 of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0038] General Implementation Examples

[0039] A method for forming a platinum-iridium wire includes the following steps:

[0040] S1. Alloy Smelting and Ingot Preparation: A vacuum induction melting process is used to melt platinum and iridium raw materials into uniform platinum-iridium alloy ingots, wherein the mass fraction of platinum is 75-85 parts and the mass fraction of iridium is 15-25 parts; the melting process is carried out under a vacuum degree better than 5×10⁻⁶. -2 The procedure is carried out under the protection of Pa or high-purity argon gas;

[0041] S2. Homogenization annealing: Place the ingot in a vacuum or protective atmosphere heat treatment furnace and hold it at 1200-1500℃ for 5-20 hours to eliminate dendritic segregation inside the ingot.

[0042] S3. Forging: The homogenized ingot is heated to 1200-1400℃ and forged using a fast forging method. The initial forging temperature is ≥1200℃, the final forging temperature is ≥950℃, and the total forging ratio is not less than 3:1 to obtain the forging billet.

[0043] S4. Hot rolling treatment: The forging billet is reheated to 1250-1400℃ for hot rolling. The final rolling temperature is controlled at ≥1000℃, and the total deformation is 40%-80%. Then, sandblasting and pickling are performed to completely remove the surface oxide scale and obtain hot-rolled bar stock.

[0044] S5. Multi-pass cold drawing and online annealing:

[0045] S5.1 The surface-treated bar is subjected to multi-pass cold drawing process using polycrystalline diamond wire drawing dies, and the deformation amount per pass is controlled at 8%-22%;

[0046] S5.2 During the cold drawing process, when the cumulative reduction of area reaches 55%-75% of the current cold drawing, the wire is subjected to online intermediate annealing with power supply. The wire is continuously passed through a pair of conductive rollers and a DC power supply is applied. The working voltage is 1-10V and the working current is 200-2000A. The intermediate annealing temperature is monitored in real time by an infrared thermometer and controlled in a closed loop at 1000-1150℃. The wire speed is 5-20m / min and the treatment atmosphere is high-purity argon or nitrogen with a dew point below -60℃.

[0047] After S5.3 annealing, the wire is immediately subjected to controlled cooling in a closed cooling chamber filled with protective gas, with the cooling rate controlled at 50-200℃ / s.

[0048] S5.4 Repeat steps S5.1 to S5.3 until the wire reaches the target size;

[0049] S6. Finished product relaxation annealing: The wire that has reached the target size is subjected to final relaxation annealing treatment at a temperature of 700-900℃ and a holding time of 10-60min. The treatment atmosphere is vacuum or high-purity argon.

[0050] S7. Post-processing: The finished wire is ultrasonically cleaned and dried to obtain platinum-iridium wire;

[0051] In step S1, 0.5-2 parts by mass of ruthenium are added to the smelting raw materials. The ruthenium is added in pure metal form, corresponding to the temperature control range of 1050-1150℃ for the online intermediate annealing treatment in step S5.2.

[0052] Alternatively, in step S1, 0.1-0.5 parts by mass of yttrium are added to the smelting raw materials. The yttrium is added in the form of a platinum-yttrium or iridium-yttrium master alloy, corresponding to a temperature control range of 1000-1100℃ for the online electric intermediate annealing treatment in step S5.2.

[0053] In this design, the target wire diameter is 0.5mm;

[0054] The specific process of ultrasonic cleaning in step S7 is as follows: the wire is immersed in an ultrasonic cleaning tank containing the cleaning medium and cleaned for 5 minutes at a frequency of 40 kHz and a temperature of 60 ℃; the cleaning medium is a 3% vol Citranox® water-based cleaning agent solution (i.e., 97 parts deionized water and 3 parts Citranox® stock solution mixed).

[0055] The specific drying process in step S7 is as follows: the cleaned wire is placed in a vacuum drying oven, and the drying process is carried out under a vacuum degree better than 5×10⁻⁶. -3 Keep warm for 60 min at a temperature of 80 ℃.

[0056] Example 1

[0057] A method for forming a platinum-iridium wire includes the following steps:

[0058] S1. Alloy Melting and Ingot Preparation: A vacuum induction melting process is used to melt platinum and iridium raw materials into a uniform platinum-iridium alloy ingot, wherein the mass fraction of platinum is 80 parts and the mass fraction of iridium is 20 parts; the melting process is carried out under a vacuum degree better than 5 × 10⁻⁶. -2 Performed under Pa;

[0059] S2. Homogenization annealing: The ingot is placed in a vacuum heat treatment furnace and held at 1350℃ for 12 hours to eliminate dendritic segregation inside the ingot.

[0060] S3. Forging: The homogenized ingot is heated to 1300℃ and forged using a fast forging method. The initial forging temperature is 1220℃, the final forging temperature is 1000℃, and the total forging ratio is 4:1 to obtain the forging billet.

[0061] S4. Hot rolling treatment: The forging billet is reheated to 1325℃ for hot rolling, and the final rolling temperature is controlled at 1025℃. The total deformation is 60%. Then, sandblasting and pickling are performed to completely remove the surface oxide scale and obtain hot-rolled bar stock.

[0062] S5. Multi-pass cold drawing and online annealing:

[0063] S5.1 The surface-treated bar is subjected to multi-pass cold drawing process using polycrystalline diamond wire drawing dies, and the deformation amount per pass is controlled at 15%.

[0064] S5.2 During the cold drawing process, when the cumulative reduction of area reaches 65% of the current cold drawing, the wire is subjected to online intermediate annealing with power supply. The wire is continuously passed through a pair of conductive rollers and a DC power supply is applied. The working voltage is 5V and the working current is 1100A. The intermediate annealing temperature is monitored in real time by an infrared thermometer and controlled in a closed loop at 1100℃. The wire speed is 12m / min and the treatment atmosphere is high-purity argon with a dew point below -60℃.

[0065] After S5.3 annealing, the wire is immediately subjected to controlled cooling in a closed cooling chamber filled with protective gas, with the cooling rate controlled at 125℃ / s.

[0066] S5.4 Repeat steps S5.1 to S5.3 until the wire reaches the target size;

[0067] S6. Finished product relaxation annealing: The wire that has reached the target size is subjected to final relaxation annealing treatment at a temperature of 800℃ and a holding time of 35min, in a vacuum.

[0068] S7. Post-processing: Ultrasonic cleaning, drying and vacuum packaging of finished wires;

[0069] In step S1, 1.2 parts by mass of ruthenium are added to the smelting raw materials. The ruthenium is added in pure metal form, corresponding to the temperature control of 1100°C for the online intermediate annealing treatment in step S5.2.

[0070] Example 2

[0071] A method for forming a platinum-iridium wire includes the following steps:

[0072] S1. Alloy smelting and ingot preparation: The platinum and iridium raw materials are smelted into a platinum-iridium alloy ingot with uniform composition using a vacuum induction melting process, wherein the mass fraction of platinum is 75 parts and the mass fraction of iridium is 25 parts; the smelting process is carried out under the protection of high-purity argon gas;

[0073] S2. Homogenization annealing: The ingot is placed in a protective atmosphere heat treatment furnace and held at 1200℃ for 20 hours to eliminate dendrite segregation inside the ingot.

[0074] S3. Forging: The homogenized ingot is heated to 1200℃ and forged using a fast forging method. The initial forging temperature is 1210℃, the final forging temperature is 950℃, and the total forging ratio is 3:1 to obtain the forging billet.

[0075] S4. Hot rolling treatment: The forging billet is reheated to 1250℃ for hot rolling, the final rolling temperature is controlled at 1000℃, the total deformation is 40%, and then sandblasting and pickling are performed to completely remove the surface oxide scale and obtain hot-rolled bar stock.

[0076] S5. Multi-pass cold drawing and online annealing:

[0077] S5.1 The surface-treated bar is subjected to multi-pass cold drawing process using polycrystalline diamond wire drawing dies, and the deformation amount per pass is controlled at 8%;

[0078] S5.2 During the cold drawing process, when the cumulative reduction of area reaches 55% of the current cold drawing, the wire is subjected to online intermediate annealing treatment with power supply. The wire is continuously passed through a pair of conductive rollers and a DC power supply is applied. The working voltage is 1V and the working current is 200A. The intermediate annealing temperature is monitored in real time by an infrared thermometer and controlled in a closed loop at 1000℃. The wire speed is 5m / min and the treatment atmosphere is high-purity nitrogen with a dew point below -60℃.

[0079] After S5.3 annealing, the wire is immediately subjected to controlled cooling in a closed cooling chamber filled with protective gas, with the cooling rate controlled at 50℃ / s.

[0080] S5.4 Repeat steps S5.1 to S5.3 until the wire reaches the target size;

[0081] S6. Finished product relaxation annealing: The wire that has reached the target size is subjected to final relaxation annealing treatment at a temperature of 700℃ and a holding time of 60min. The treatment atmosphere is high-purity argon.

[0082] S7. Post-processing: Ultrasonic cleaning, drying and vacuum packaging of finished wires;

[0083] In step S1, 0.1 parts by mass of yttrium are added to the smelting raw materials. The yttrium is added in the form of a platinum-yttrium master alloy, corresponding to the temperature control of 1000°C for the online electric intermediate annealing treatment in step S5.2.

[0084] Example 3

[0085] A method for forming a platinum-iridium wire includes the following steps:

[0086] S1. Alloy Melting and Ingot Preparation: A vacuum induction melting process was used to melt platinum and iridium raw materials into a homogeneous platinum-iridium alloy ingot, wherein the mass fraction of platinum was 85 parts and the mass fraction of iridium was 15 parts; the melting process was carried out under a vacuum degree better than 5 × 10⁻⁶. -2 Performed under Pa;

[0087] S2. Homogenization annealing: The ingot is placed in a vacuum heat treatment furnace and held at 1500℃ for 5 hours to eliminate dendritic segregation inside the ingot.

[0088] S3. Forging: The homogenized ingot is heated to 1400℃ and forged using a fast forging method. The initial forging temperature is 1250℃, the final forging temperature is 1000℃, and the total forging ratio is 5:1 to obtain the forging billet.

[0089] S4. Hot rolling treatment: The forging billet is reheated to 1400℃ for hot rolling, and the final rolling temperature is controlled at 1050℃. The total deformation is 80%. Then, sandblasting and pickling are performed to completely remove the surface oxide scale and obtain hot-rolled bar stock.

[0090] S5. Multi-pass cold drawing and online annealing:

[0091] S5.1 The surface-treated bar is subjected to multi-pass cold drawing process using polycrystalline diamond wire drawing dies, and the deformation amount per pass is controlled at 22%;

[0092] S5.2 During the cold drawing process, when the cumulative reduction of area reaches 75% of the current cold drawing, the wire is subjected to online intermediate annealing with power supply. The wire is continuously passed through a pair of conductive rollers and a DC power supply is applied. The working voltage is 10V and the working current is 2000A. The intermediate annealing temperature is monitored in real time by an infrared thermometer and controlled in a closed loop at 1150℃. The wire speed is 20m / min and the treatment atmosphere is high-purity argon with a dew point below -60℃.

[0093] After S5.3 annealing, the wire is immediately subjected to controlled cooling in a closed cooling chamber filled with protective gas, with the cooling rate controlled at 200℃ / s.

[0094] S5.4 Repeat steps S5.1 to S5.3 until the wire reaches the target size;

[0095] S6. Finished product relaxation annealing: The wire that has reached the target size is subjected to final relaxation annealing treatment at a temperature of 900℃ and a holding time of 10min, in a vacuum.

[0096] S7. Post-processing: Ultrasonic cleaning, drying and vacuum packaging of finished wires;

[0097] In step S1, 2 parts by mass of ruthenium are added to the smelting raw materials. The ruthenium is added in pure metal form, corresponding to the temperature control of 1150°C for the online intermediate annealing treatment in step S5.2.

[0098] Example 4

[0099] A method for forming a platinum-iridium wire includes the following steps:

[0100] S1. Alloy smelting and ingot preparation: The platinum and iridium raw materials are smelted into a platinum-iridium alloy ingot with uniform composition using a vacuum induction melting process, wherein the mass fraction of platinum is 78 parts and the mass fraction of iridium is 22 parts; the smelting process is carried out under the protection of high-purity argon gas;

[0101] S2. Homogenization annealing: The ingot is placed in a protective atmosphere heat treatment furnace and held at 1250℃ for 15 hours to eliminate dendrite segregation inside the ingot.

[0102] S3. Forging: The homogenized ingot is heated to 1250℃ and forged using a fast forging method. The initial forging temperature is 1200℃, the final forging temperature is 970℃, and the total forging ratio is 3.5:1 to obtain the forged billet.

[0103] S4. Hot rolling treatment: The forging billet is reheated to 1280℃ for hot rolling, and the final rolling temperature is controlled at 1010℃. The total deformation is 55%. Then, sandblasting and pickling are performed to completely remove the surface oxide scale and obtain hot-rolled bar stock.

[0104] S5. Multi-pass cold drawing and online annealing:

[0105] S5.1 The surface-treated bar is subjected to multi-pass cold drawing process using polycrystalline diamond wire drawing dies, and the deformation amount per pass is controlled at 12%;

[0106] S5.2 During the cold drawing process, when the cumulative reduction of area reaches 60% of the current cold drawing, the wire is subjected to online intermediate annealing with power supply. The wire is continuously passed through a pair of conductive rollers and a DC power supply is applied. The working voltage is 3V and the working current is 600A. The intermediate annealing temperature is monitored in real time by an infrared thermometer and controlled in a closed loop at 1050℃. The wire speed is 8m / min and the treatment atmosphere is high-purity argon with a dew point below -60℃.

[0107] After S5.3 annealing, the wire is immediately subjected to controlled cooling in a closed cooling chamber filled with protective gas, with the cooling rate controlled at 80℃ / s.

[0108] S5.4 Repeat steps S5.1 to S5.3 until the wire reaches the target size;

[0109] S6. Finished product relaxation annealing: The wire that has reached the target size is subjected to final relaxation annealing treatment at a temperature of 750℃ and a holding time of 45min. The treatment atmosphere is high-purity argon.

[0110] S7. Post-processing: Ultrasonic cleaning, drying and vacuum packaging of finished wires;

[0111] In step S1, 0.3 parts by mass of yttrium are added to the smelting raw materials. The yttrium is added in the form of an iridium-yttrium master alloy, corresponding to the temperature control of 1050°C for the online electric intermediate annealing treatment in step S5.2.

[0112] Example 5

[0113] A method for forming a platinum-iridium wire includes the following steps:

[0114] S1. Alloy Melting and Ingot Preparation: A vacuum induction melting process was used to melt platinum and iridium raw materials into a uniform platinum-iridium alloy ingot, with platinum comprising 82 parts by mass and iridium comprising 18 parts by mass. The melting process was carried out under a vacuum degree better than 5 × 10⁻⁶. -2 Performed under Pa;

[0115] S2. Homogenization annealing: The ingot is placed in a vacuum heat treatment furnace and held at 1450℃ for 8 hours to eliminate dendrite segregation inside the ingot.

[0116] S3. Forging: The homogenized ingot is heated to 1350℃ and forged using a fast forging method. The initial forging temperature is 1220℃, the final forging temperature is 980℃, and the total forging ratio is 4.5:1 to obtain the forged billet.

[0117] S4. Hot rolling treatment: The forging billet is reheated to 1380℃ for hot rolling, the final rolling temperature is controlled at 1050℃, the total deformation is 70%, and then sandblasting and pickling are performed to completely remove the surface oxide scale and obtain hot-rolled bar stock.

[0118] S5. Multi-pass cold drawing and online annealing:

[0119] S5.1 The surface-treated bar is subjected to multi-pass cold drawing process using polycrystalline diamond wire drawing dies, and the deformation amount per pass is controlled at 18%;

[0120] S5.2 During the cold drawing process, when the cumulative reduction of area reaches 70% of the current cold drawing, the wire is subjected to online intermediate annealing treatment with power supply. The wire is continuously passed through a pair of conductive rollers and a DC power supply is applied. The working voltage is 8V and the working current is 1700A. The intermediate annealing temperature is monitored in real time by an infrared thermometer and controlled in a closed loop at 1120℃. The wire speed is 18m / min and the treatment atmosphere is high-purity nitrogen with a dew point below -60℃.

[0121] After S5.3 annealing, the wire is immediately subjected to controlled cooling in a closed cooling chamber filled with protective gas, with the cooling rate controlled at 180℃ / s.

[0122] S5.4 Repeat steps S5.1 to S5.3 until the wire reaches the target size;

[0123] S6. Finished product relaxation annealing: The wire that has reached the target size is subjected to final relaxation annealing treatment at a temperature of 850℃ and a holding time of 20min, in a vacuum.

[0124] S7. Post-processing: Ultrasonic cleaning, drying and vacuum packaging of finished wires;

[0125] In step S1, 1.5 parts by mass of ruthenium are added to the smelting raw materials. The ruthenium is added in pure metal form, corresponding to the temperature control of 1120°C for the online intermediate annealing treatment in step S5.2.

[0126] Comparative Example 1

[0127] The difference from Example 1 is that ruthenium or yttrium was not added.

[0128] Comparative Example 2

[0129] The difference from Example 1 is that the amount of platinum added is 90 parts and the amount of iridium added is 10 parts.

[0130] Comparative Example 3

[0131] The difference from Example 1 is that the amount of platinum added is 70 parts and the amount of iridium added is 30 parts.

[0132] Comparative Example 4

[0133] The difference from Example 1 is that the amount of ruthenium added is 3 parts.

[0134] Comparative Example 5

[0135] The difference from Example 2 is that the amount of yttrium added is 0.6 parts.

[0136] Comparative Example 6

[0137] The difference from Example 1 is that when the cumulative section shrinkage rate reaches 55%-75% of the current cold drawing, the wire is subjected to intermediate annealing treatment. The annealing is carried out in a tube furnace under an argon atmosphere.

[0138] Comparative Example 7

[0139] The difference from Example 1 is that the wire speed is 22m / min.

[0140] Comparative Example 8

[0141] The difference from Example 1 is that the wire speed is 3m / min.

[0142] Comparative Example 9

[0143] The difference from Example 1 is that the temperature control of the online power-on intermediate annealing process in step S5.2 is 1000°C.

[0144] Comparative Example 10

[0145] The difference from Example 1 is that the temperature control of the online power-on intermediate annealing process in step S5.2 is 1200°C.

[0146] Performance testing:

[0147] 1. Wire diameter: Non-contact measurement using a laser diameter gauge;

[0148] 2. Tensile properties: Refer to the test methods for fine wires in ASTM E8 standard to test tensile strength (MPa) and elongation after fracture (%).

[0149] 3. Resistivity Measurement: DC four-probe method for measuring the resistivity of a thin wire;

[0150] 4. Fatigue resistance test: Rotational bending fatigue test.

[0151] The test results of the examples and comparative examples are shown in Table 1.

[0152] Table 1. Detection results of the examples and comparative examples.

[0153] Group Ingredient Design Wire diameter (mm) Tensile strength (MPa) Elongation after fracture (%) Resistivity (μΩ・cm) Fatigue resistance life (times) Example 1 Pt80Ir20+1.2%Ru 0.500±0.002 1280±20 18±1 28.5±0.5 <![CDATA[2.1×10 6 ]]> Example 2 Pt75Ir25+0.1%Y 0.500±0.003 1150±15 22±1.5 30.2±0.8 <![CDATA[1.8×10 6 ]]> Example 3 Pt85Ir15+2%Ru 0.500±0.001 1350±25 16±0.8 27.8±0.4 <![CDATA[1.9×10 6 ]]> Example 4 Pt78Ir22+0.3%Y 0.500±0.002 1220±18 20±1.2 29.5±0.6 <![CDATA[2.0×10 6 ]]> Example 5 Pt82Ir18+1.5%Ru 0.500±0.001 1320±22 17±0.9 28.1±0.5 <![CDATA[2.2×10 6 ]]> Comparative Example 1 Pt80Ir20 (No additives) 0.500±0.004 980±12 25±2 35.0±1.2 <![CDATA[8.5×10 5 ]]> Comparative Example 2 Pt90Ir10 0.500±0.005 850±10 28±2.5 38.2±1.5 <![CDATA[6.2×10 5 ]]> Comparative Example 3 Pt70Ir30 0.500±0.006 1450±30 12±0.5 25.0±0.3 <![CDATA[1.2×10 6 ]]> Comparative Example 4 Pt80Ir20+3%Ru 0.500±0.003 1420±28 14±0.6 26.5±0.4 <![CDATA[1.5×10 6 ]]> Comparative Example 5 Pt75Ir25+0.6%Y 0.500±0.004 1080±15 19±1.3 32.0±0.9 <![CDATA[1.4×10 6 ]]> Comparative Example 6 Traditional tube furnace annealing 0.500±0.007 820±12 27±2.2 36.5±1.1 <![CDATA[7.8×10 5 ]]> Comparative Example 7 The cable travels too fast 0.500±0.003 1180±18 17±1.1 29.8±0.7 <![CDATA[1.7×10 6 ]]> Comparative Example 8 The wire feed rate is too slow (over-annealing). 0.500±0.004 950±15 24±1.8 34.2±1.0 <![CDATA[9.2×10 5 ]]> Comparative Example 9 Annealing temperature too low 0.500±0.003 1120±15 19±1.2 31.0±0.8 <![CDATA[1.6×10 6 ]]> Comparative Example 10 Annealing temperature too high 0.500±0.005 1050±13 21±1.4 33.5±1.0 <![CDATA[1.3×10 6 ]]>

[0154] The performance advantages of the embodiment stem from the deep synergy between the platinum-iridium base ratio, the microalloying design of ruthenium or yttrium, and the online electric annealing process: the reasonable platinum-iridium ratio lays the foundation for the intrinsic characteristics of high strength and high toughness of the alloy, ruthenium strengthens the matrix through full solid solution to improve strength and conductivity, yttrium refines grains and optimizes toughness through grain boundary pinning effect, and online electric annealing eliminates work hardening rapidly with instantaneous high temperature, while ultra-short holding time and rapid cooling effectively suppress grain growth, ultimately achieving a balance between strength, plasticity and stability. Comparative Example 1, lacking the addition of ruthenium or yttrium, lacked solid solution strengthening and grain boundary pinning, leading to grain coarsening, resulting in low alloy strength, increased resistivity, and poor fatigue resistance. Comparative Example 2, with excessively high platinum and low iridium content, suffered from insufficient strengthening effect of iridium, resulting in decreased overall strength and fatigue resistance. Excessive platinum also increased electron scattering, causing increased resistivity. Comparative Example 3, with excessively low platinum and high iridium content, while the addition of iridium improved strength, the excessive work hardening effect significantly reduced the alloy's plasticity and toughness. Comparative Example 4, with excessive ruthenium addition exceeding the reasonable solid solution range of the platinum-iridium matrix, although higher solid solution Ru... While the content itself significantly increases matrix strength, it easily leads to the precipitation of brittle phases at grain boundaries, disrupting grain boundary integrity and resulting in decreased elongation and shortened fatigue life. In Comparative Example 5, excessive yttrium addition easily forms coarse oxide inclusions, failing to effectively perform grain boundary pinning and instead becoming stress concentration points, causing a decrease in alloy strength and an increase in resistivity. Comparative Example 6 uses traditional tube furnace annealing; the slow heating and long holding time allow for sufficient atomic diffusion, leading to severe grain coarsening and a significant decrease in strength. Furthermore, grain boundaries are prone to oxidation at high temperatures, further affecting conductivity and fatigue resistance. In Comparative Example 7, the wire speed is too fast, exceeding the reasonable rate range for online annealing, resulting in insufficient high-temperature dwell time, inadequate recrystallization, and incomplete elimination of work hardening, leading to… The alloy strength was slightly lower and the grain size was slightly larger. In Comparative Example 8, the wire speed was too slow, which led to an extended effective holding time for the substrate or workpiece within the annealing temperature range. This may have caused the annealing process, originally designed to eliminate internal stress and optimize microstructure, to be overdone, potentially resulting in abnormal grain growth and a decrease in mechanical properties. In Comparative Example 9, the annealing temperature was too low, failing to reach the temperature range where ruthenium was fully dissolved or yttrium exerted its pinning effect. The recrystallization process was incomplete, and the alloy's strength and conductivity decreased due to insufficient solid solution. In Comparative Example 10, the annealing temperature was too high, exceeding the temperature range where grains could exist stably. This accelerated grain boundary migration, leading to grain coarsening and a weakened fine-grain strengthening effect, ultimately resulting in a significant reduction in the alloy's strength and fatigue resistance.

Claims

1. A method for forming a platinum-iridium wire, characterized in that, The method includes the following steps: S1. Alloy smelting and ingot preparation: Platinum and iridium raw materials are smelted into a uniform platinum-iridium alloy ingot, wherein the mass fraction of platinum is 75-85 parts and the mass fraction of iridium is 15-25 parts; the smelting process is carried out under a vacuum degree better than 5×10 -2 The procedure is carried out under the protection of Pa or high-purity argon gas; S2. Homogenization annealing: The ingot is placed in a vacuum or protective atmosphere heat treatment furnace and held at 1200-1500℃ for 5-20 hours; S3. Forging: The homogenized ingot is heated to 1200-1400℃ and forged using a fast forging method. The initial forging temperature is ≥1200℃, the final forging temperature is ≥950℃, and the total forging ratio is ≥3:1 to obtain the forging billet. S4. Hot rolling treatment: The forging billet is reheated to 1250-1400℃ for hot rolling, the final rolling temperature is controlled at ≥1000℃, the total deformation is 40%-80%, and then sandblasting and pickling treatment are performed to completely remove the surface oxide scale and obtain hot-rolled bar stock. S5. Multi-pass cold drawing and online annealing: S5.1 The surface-treated bar is subjected to multi-pass cold drawing process using polycrystalline diamond wire drawing dies, and the deformation amount per pass is controlled at 8%-22%; S5.2 During the cold drawing process, when the cumulative reduction of area reaches 55%-75% of the current cold drawing, the wire is subjected to online intermediate annealing treatment with electric current. The wire is continuously passed through a pair of conductive rollers and current is applied. The intermediate annealing temperature is monitored in real time by an infrared thermometer and controlled in a closed loop at 1000-1150℃. The wire speed is 5-20m / min, and the treatment atmosphere is high-purity argon or nitrogen with a dew point below -60℃. After S5.3 annealing, the wire is immediately subjected to controlled cooling in a closed cooling chamber filled with protective gas, with the cooling rate controlled at 50-200℃ / s. S5.4 Repeat steps S5.1 to S5.3 until the wire reaches the target size; S6. Finished product relaxation annealing: The wire that has reached the target size is subjected to final relaxation annealing treatment at a temperature of 700-900℃ and a holding time of 10-60min. The treatment atmosphere is vacuum or high-purity argon. S7. Post-processing: The finished wire is ultrasonically cleaned and dried to obtain platinum-iridium wire.

2. The method for forming platinum-iridium wire as described in claim 1, characterized in that, In step S1, 0.5-2 parts by mass of ruthenium are added to the smelting raw materials, wherein the ruthenium is added in pure metallic form.

3. The method for forming platinum-iridium wire as described in claim 2, characterized in that, The temperature control range for the online power-on intermediate annealing process described in step S5.2 is 1050-1150℃.

4. The method for forming platinum-iridium wire as described in claim 1, characterized in that, In step S1, 0.1-0.5 parts by mass of yttrium are added to the smelting raw materials, wherein the yttrium is added in the form of a platinum-yttrium or iridium-yttrium master alloy.

5. The method for forming platinum-iridium wire as described in claim 4, characterized in that, The temperature control range for the online power-on intermediate annealing process described in step S5.2 is 1000-1100℃.

6. The method for forming platinum-iridium wire as described in claim 1, characterized in that, The power supply for the online intermediate annealing process described in step S5.2 is a DC power supply with a working voltage of 1-10V and a working current of 200-2000A.

7. The method for forming platinum-iridium wire as described in claim 1, characterized in that, The specific process of ultrasonic cleaning in step S7 is as follows: immerse the wire in an ultrasonic cleaning tank containing a cleaning medium and clean it for 3-10 minutes at a frequency of 25-40 kHz and a temperature of 50-60 ℃; the cleaning medium is a water-based cleaning agent solution or an organic solvent.

8. The method for forming platinum-iridium wire as described in claim 1, characterized in that, The specific drying process described in step S7 is as follows: the cleaned wire is placed in a vacuum drying oven, and the drying process is carried out under a vacuum degree better than 1×10⁻⁶. -2 Keep warm for 30-60 minutes at a temperature of 60-80 ℃.

9. A platinum-iridium wire obtained by the forming method of platinum-iridium wire as described in any one of claims 1-8.