Hot forging free machining process of medical palladium platinum alloy rod and medical palladium platinum alloy rod

Abstract

The application relates to a hot forging non-cutting forming process of a medical palladium-platinum alloy rod and the medical palladium-platinum alloy rod, the forming process comprises the following steps: raw materials are subjected to high-frequency smelting and casting to obtain a palladium-platinum cast rod, the palladium-platinum cast rod is sequentially subjected to multi-stage reducing hot forging and cold forming, and the medical palladium-platinum alloy rod without turning is obtained; wherein the multi-stage reducing hot forging is carried out by using a multi-stage forging die in cooperation with an air hammer, the total deformation is more than 50%, and the method comprises the following steps: (1) the palladium-platinum cast rod is preheated to more than 1000 DEG C and is kept for not less than 90 min; (2) the multi-stage reducing hot forging is continuously or intermittently carried out at not less than 900 DEG C, a hot-forged rod material is obtained, and the reducing ratio between the forging dies is 5-25%; (3) the hot-forged rod material is heated to more than 1000 DEG C in a vacuum environment with a pressure of less than 10 Pa, is kept for not less than 20 min, is cooled to 600-800 DEG C and is kept for 40-60 min, and is then naturally cooled. ‑1 The hot-forged rod material is heated to more than 1000 DEG C in a vacuum environment with a pressure of less than 10 Pa, is kept for not less than 20 min, is cooled to 600-800 DEG C and is kept for 40-60 min, and is then naturally cooled.

Description

Technical Field

[0001] This invention relates to the field of palladium-platinum alloy forming technology, specifically to a hot forging process for medical palladium-platinum alloy rods without machining, and the medical palladium-platinum alloy rods themselves. Background Technology

[0002] Palladium-platinum alloys are used to manufacture ablation head parts for medical physiological therapy due to their excellent chemical stability, high temperature resistance and corrosion resistance, as well as good biocompatibility with human tissue. These parts play a key role in the precise tissue ablation treatment in minimally invasive interventional surgery, and the requirements for the surface precision and performance stability of the material are extremely high.

[0003] As a precious metal alloy, palladium-platinum is expensive to produce and has a high melting point. Currently, regardless of whether casting or sprue casting is used to produce palladium-platinum alloy bars, defects and pits are unavoidable on the surface of the cast billet. If these surface defects are not effectively eliminated, even if conventional cold working processes are followed by heat treatment to process the billet to a final size of less than 3.0 mm in diameter, a large number of defects and pits will still remain on the surface of the alloy bar. This results in the bar failing to meet the processing requirements of high-precision medical parts, leading to an extremely low yield and severely restricting the large-scale production and cost control of medical parts.

[0004] In existing technologies, the preparation of metal or alloy products generally adopts a full-process technology of melting and casting - homogenization heat treatment - lathe peeling - rolling - stress-relief annealing - cold drawing - straightening. Among them, the lathe peeling step for castings is a key step to improve the surface quality of the finished product. Patent CN116351894B discloses a method for preparing ultra-thin palladium-silver alloy capillary tubes, including the following steps: a. preparing palladium-silver alloy ingots; homogenizing heat treatment at 950℃ for 2.5 hours under high-purity nitrogen protection, followed by water quenching after removal from the furnace; lathe turning of the ingot surface to remove surface defects; b. hot forging of palladium-silver alloy: hot forging at 900-950℃ to the diameter required for subsequent processing; followed by machining such as drilling, cold rolling, and drawing. For example, patent application CN120861718A discloses a forging process for a high-temperature alloy, including cutting the smelted alloy ingot into alloy billets; removing oxide scale, inclusions, and other defects from the ingot surface using a turning machine; slowly heating to 400~600℃, then accelerating to 600~900℃, then heating to 1000℃ and holding for 2 hours, and then raising to 1150℃ and holding for 1 hour; followed by two stages of forging, solution treatment, nitriding, and annealing. Furthermore, patent CN111676407B discloses a method for preparing a high-strength, low-elasticity modulus medical implant zirconium alloy, including preparing raw materials in a specified proportion, melting the prepared raw materials to obtain a uniformly composed ingot, hot forging the ingot into a bar and solution treating it, then quenching and cooling it in water, then turning to remove the oxide scale from the bar surface, followed by cold deformation processing and aging heat treatment to obtain a high-strength, low-elasticity modulus medical implant zirconium alloy with a β matrix and a small amount of submicron α precipitates. It is evident that machining the ingot before or after forging is a necessary step in obtaining alloy intermediates with acceptable surface quality. However, machining results in scrap loss and recycling problems, reducing raw material utilization. This is especially true when using precious metal raw materials, where material loss and waste lead to high costs. Furthermore, the machining process consumes a large amount of consumables such as cutting tools, is time-consuming and energy-intensive, resulting in low overall production efficiency and difficulty in reducing costs.

[0005] Therefore, there is an urgent need in this field to provide a preparation process that does not require machining to remove the outer layer and is optimized through key processing steps such as hot forging. This process can reduce overall production costs, improve production efficiency, and produce alloy bars with no surface defects and excellent comprehensive properties such as mechanical properties and precision. The aim is to meet the stringent requirements of the medical field for the precision of parts processing and the safety of use, promote the upgrading of the preparation process of precious metal bars for medical use, and ultimately improve the yield and application benefits. Summary of the Invention

[0006] To address the shortcomings of existing technologies that require surface treatment processes such as machining and peeling of castings or forgings to produce medical palladium-platinum alloy rods, which waste precious metal raw materials and increase production costs, this invention provides a hot forging process for medical palladium-platinum alloy rods without machining, as well as the medical palladium-platinum alloy rods themselves. From high-frequency melting and casting of raw materials to multi-stage diameter-reducing hot forging, subsequent cold forming, and various heat treatment stages, this process balances surface forming and internal structure control, ensuring that the rods always have a smooth surface, which is maintained and optimized during subsequent plastic processing, ultimately directly yielding high-quality medical palladium-platinum alloy rod products with excellent internal and external properties.

[0007] In a first aspect of the present invention, a hot forging process for forming a medical palladium-platinum alloy rod without cutting is provided, wherein the raw material of the palladium-platinum alloy rod comprises, by weight percentage: 20 ± 1.5 wt% platinum, with the balance being palladium and unavoidable impurities.

[0008] The forming process includes obtaining palladium-platinum casting rods by high-frequency melting and casting of raw materials, and sequentially performing multi-stage diameter reduction hot forging and cold forming on the palladium-platinum casting rods to obtain medical palladium-platinum alloy rods that do not require machining.

[0009] Multi-stage diameter reduction hot forging is carried out using a multi-stage forging die in conjunction with an air hammer, with a total deformation of over 50%, and includes the following steps:

[0010] (1) Preheat the palladium-platinum casting rod to above 1000℃ and keep it at that temperature for no less than 90 minutes; by preheating and keeping it at above 1000℃ for a long time, ensure that the casting rod reaches the best plastic state as a whole.

[0011] (2) At least three stages of shrinkage hot forging are carried out continuously or intermittently at a temperature of not less than 900℃ to obtain hot forged bar stock, with the shrinkage ratio between each stage of forging die being 5-25%;

[0012] (3) In 10 -1 In a vacuum environment below Pa, the hot forged bar stock is heated to above 1000℃ and held for at least 20 minutes, then cooled to 600~800℃ and held for 40~60 minutes, and then allowed to cool naturally.

[0013] This invention utilizes at least three stages of diameter reduction hot forging to fully break down coarse grains in the as-cast state and weld together microscopic defects such as porosity and looseness within the bar, thereby improving the density and microstructure uniformity of the bar. Furthermore, at 10... -1In a vacuum environment below Pa, hot-forged bars are heated to above 1000℃ and held at this temperature. Under these conditions, the oxide layer on the surface of the palladium-platinum alloy readily undergoes thermal decomposition. Simultaneously, impurity atoms dissolved within the palladium-platinum alloy gain sufficient diffusion kinetic energy to migrate from the interior to the surface, thus achieving purification of both the interior and exterior of the palladium-platinum alloy. This provides a clean and high-quality billet surface for subsequent processing. In particular, vacuum annealing in the mid-temperature range of 600~800℃ is beneficial for further removing the oxide layer. This temperature range also promotes the recrystallization process of the alloy, resulting in a uniform and stable fine-grained structure, eliminating processing stress accumulated during hot forging, and significantly improving the internal quality of the bar. Natural cooling, with a smooth transition to room temperature, facilitates the full diffusion of atoms within the alloy, resulting in a more uniform element distribution at grain boundaries and a fully stabilized grain structure. It also effectively avoids new thermal stresses caused by excessively rapid cooling, thus providing billets with good plasticity and low internal stress for subsequent cold forming. This ensures uniform deformation during subsequent cold working and avoids surface wrinkles caused by localized stress concentration or insufficient plasticity.

[0014] Preferably, the process involves intermittent 3-6 stages of diameter reduction hot forging, with the palladium-platinum casting rod heated to above 1000°C and held for 20-40 minutes between each stage of diameter reduction hot forging.

[0015] After each stage of necking hot forging, the bar stock, having undergone plastic deformation, is reheated to above 1000℃ and held at that temperature, triggering the recrystallization process. This process promptly eliminates the work hardening and internal stress accumulated from the previous hot forging, rearranging the high-density dislocations generated during deformation to form new, stress-free, fine equiaxed grains, thus fully restoring the material's plasticity before entering the next stage of forging. This ensures that even with a large total deformation, the material maintains excellent plastic deformation capacity, avoiding internal cracks or surface wrinkles. Furthermore, each stage of necking hot forging deformation and recrystallization is equivalent to forging and repairing the microscopic defects within the material. Intermittently performing 3-6 cycles fully breaks down and reorganizes the anisotropic coarse dendrites in the as-cast structure, transforming them into a uniform, fine equiaxed grain structure, significantly improving the material's density. This not only provides a foundation for excellent mechanical properties of the product, but also, through step-by-step deformation and repair, can gradually eliminate surface defects existing in the early casting process and suppress the generation of new defects. Thus, without turning, high-quality bars with smooth surfaces and uniform internal structure can be obtained directly, laying the foundation for the final realization of high-quality medical rods that do not require turning.

[0016] Preferably, each forging die has an elliptical cavity, and the diameter reduction ratio between each forging die decreases sequentially, taking the minor axis of the elliptical cavity as the reference.

[0017] In the initial stage of hot forging, the material is in its optimal high-temperature plasticity state. At this stage, a larger reduction ratio allows for greater deformation, effectively breaking down coarse cast dendrites and welding together any voids or porosity within the cast bar, significantly improving the material's density. As the number of forging stages increases and the bar diameter decreases, work hardening intensifies, and plasticity relatively decreases. At this point, gradually reducing the reduction ratio, i.e., decreasing the deformation per pass, avoids surface wrinkles or internal microcracks caused by excessive deformation in a single pass. Simultaneously, it facilitates further grain refinement and improves the uniformity of the microstructure.

[0018] Preferably, five-stage reduction hot forging is used, with each stage having a reduction ratio of 16-25%, 15-20%, 11-15%, 8-12%, and 5-10%.

[0019] Preferably, each stage of diameter reduction hot forging includes heavy forging and light forging finishing, with the forging force ratio of heavy forging to light forging finishing being (25~40):(5~15).

[0020] The reforging process employs greater forging force to apply sufficient plastic deformation to the material, thereby breaking up the as-cast structure, welding together internal porosity and other defects, and refining the grain size. The subsequent light forging finishing process uses less force to address the microscopic inhomogeneities that arise after reforging. Specifically, the less force can smooth out the tiny wrinkles formed on the bar surface during reforging, eliminate stress concentration points, and improve the surface finish of the bar.

[0021] As the diameter reduction ratio between each forging die decreases sequentially, the forging force of heavy forging and light forging not only meets the aforementioned ratio, but also preferably decreases sequentially with the diameter reduction ratio. This ensures that in each stage of diameter reduction hot forging, heavy forging has sufficient energy to apply plastic deformation to the material, while the light forging force is sufficiently gentle to avoid causing new impact damage to the already formed surface. Furthermore, each stage of hot forging simultaneously takes into account both plastic deformation and surface finishing. Through the accumulation of multiple stages of diameter reduction hot forging, high-quality bar stock with uniform and dense internal structure and smooth and flat surface can be obtained directly without turning, providing an ideal billet for subsequent cold working.

[0022] Preferably, heavy forging and light forging finishing include feed hammer forging and draw hammer forging, respectively;

[0023] In the reforging process, after the feed hammer forging, the palladium-platinum casting rod is rotated at a certain angle and then pulled hammer forging is performed.

[0024] During light forging and finishing, the palladium-platinum casting rod is continuously rotated during both the feeding hammer and the pulling hammer processes.

[0025] In the reforging process, feeding hammer forging, rotation, and pulling hammer forging are employed, with several reforging cycles. The rotation angle in each cycle is approximately 90°. This aims to ensure that the material undergoes significant plastic deformation in two directions sequentially, effectively breaking down the anisotropic cast coarse dendritic structure, promoting equiaxed grains, and welding internal defects at multiple angles, thereby significantly improving the density and microstructure uniformity of the bar stock macroscopically. Between each reforging cycle, the bar stock is preferably rotated to approximately 360° / n between two feeding hammer forging cycles, where n is the number of reforging cycles, 2≤n, preferably 3≤n≤6.

[0026] In the light forging finishing process, the bar is continuously rotated during both the feeding and drawing processes, and this process is repeated several times. This can more effectively eliminate the circumferential wrinkles or surface micro-cracks remaining after reforging, thereby obtaining a higher surface finish and roundness.

[0027] Preferably, in step (1), the preheating of the palladium-platinum casting rod involves at least two heating steps, including:

[0028] One-step heating: Heat to 400-600℃ at a rate of 25-35℃ / min, and hold for 20-40 minutes;

[0029] Two-step heating: Heat to above 1000℃ at a rate of 15~30℃ / min, and hold for more than 90 minutes.

[0030] During preheating of the cast ingot, the temperature is first increased to 400-600℃ at a rate of 25-35℃ / min and held at this temperature. This allows the palladium and platinum atoms within the ingot to gain sufficient diffusion kinetic energy, eliminating residual internal stress formed during casting. This avoids the risk of cracking caused by the superposition of thermal and residual stresses during rapid heating. Simultaneously, this medium-temperature holding process promotes material recovery, partially eliminates lattice defects, initially improves material plasticity, and promotes microstructure homogenization. Subsequently, a second-step heating process is performed at a slower rate of 15-30℃ / min. This aims to control the temperature difference between the core and surface of the ingot, ensuring that the entire cross-section of the ingot reaches the optimal hot forging temperature above 1000℃ uniformly and stably. This ensures that the entire ingot is in a highly plastic austenitic state during hot forging. Material in this state has good fluidity and can more effectively fill the forging mold cavity, thus significantly reducing the probability of surface wrinkles and internal cracks caused by uneven plasticity or thermal stress.

[0031] Preferably, the preheating process of the palladium-platinum casting rod is carried out within 10 hours. -1 The experiment was conducted in a vacuum environment below Pa.

[0032] Preferably, the high-frequency melting and casting process includes the following steps:

[0033] High-frequency melting: First, evacuate the high-frequency melting furnace to 10°C.-1 Below Pa, argon gas is introduced until the furnace pressure is above 0.03 MPa, the melting power is 5~8 kW, the melting temperature is not lower than 1700℃, and the holding time of the alloy melt is not less than 3 min;

[0034] Preheating and casting: Boron nitride molds with an inner diameter of 20-40 mm and a height of 100 mm or more are used. The boron nitride molds are preheated to above 500℃ and held for 20-40 minutes before the alloy melt is poured in. The melt is slowly solidified to obtain palladium-platinum casting rods. The total time from loading the melting power to completing the pouring is 10-15 minutes.

[0035] The high-frequency melting method of this invention ensures that the high-melting-point palladium-platinum alloy can be fully melted, its composition homogenized, and that gases and light impurities can float and escape, thereby obtaining a pure and homogeneous alloy melt. During the preheating and casting stage, boron nitride material itself possesses excellent high-temperature resistance, lubricity, and non-adhesion properties to the palladium-platinum alloy. Preheating it to above 500°C reduces the significant temperature difference between the melt and the mold at the moment of injection, alleviating the sudden drop in melt fluidity and uneven solidification shrinkage caused by rapid cooling. This prevents casting defects such as cold shuts, wrinkles, or depressions on the surface of the cast rod. Furthermore, the high-temperature preheated boron nitride mold helps to reduce the solidification rate of the alloy melt, and the slow cooling further improves the surface quality of the cast rod.

[0036] This invention uses a densely sintered zirconia crucible, and fills the space between the crucible and the induction coil with a mixture of zirconia powder and refractory adhesive. The casting is controlled by a rocker arm, and the alloy melt is cast into a high-temperature preheated mold without the need to add any reinforcing agents.

[0037] Preferably, cold forming includes multiple cold rolling and cold drawing processes, and the total deformation of cold forming is over 80%.

[0038] Each cold rolling process includes multiple rolling passes, with each pass deformation being less than 10%. Intermediate annealing is performed between multiple cold rolling processes, including heating to 400-800°C at a rate of 15-30°C / min in a vacuum environment, holding at that temperature for 30-60 minutes, and then slowly cooling to room temperature.

[0039] Setting the total cold forming deformation to over 80% aims to apply sufficiently large plastic deformation to the material. Through the generation of high-density dislocations and significant grain elongation and fragmentation, the strength and hardness of the material can be significantly improved. However, such large cold deformation accumulates enormous internal stress and work hardening, making the material brittle. Therefore, the deformation per cold rolling pass and intermediate annealing treatment must be controlled in the process. Controlling the deformation per single pass to below 10%, preferably below 6%, can avoid microcracks caused by excessive single-pass deformation, ensuring the stability of the bar surface quality during cold rolling. Intermediate annealing between multiple cold rolling passes can periodically repair the bar, effectively eliminating the processing stress accumulated from previous cold rolling passes, restoring the material's plasticity, and promoting recovery and partial recrystallization to form a fine and uniform grain structure. This allows the material to achieve high strength and hardness while maintaining good plasticity and toughness. Through this cold working process, a final product with excellent comprehensive mechanical properties and a smooth surface can be obtained directly without turning.

[0040] Preferably, after cold drawing, the bar is heated to 400-600°C at a rate of 10-20°C / min, held at that temperature for 30-60 minutes, and then slowly cooled to room temperature. The heat treatment step after cold drawing can eliminate the residual internal stress generated by cold drawing without causing recrystallization or grain growth of the material, thus preserving the high strength and high hardness obtained by cold working.

[0041] In a second aspect of the present invention, a medical palladium-platinum alloy rod is also provided, which is prepared by the aforementioned hot forging and non-machining forming process for medical palladium-platinum alloy rods. The medical palladium-platinum alloy rod has a diameter of 0.8 to 3.0 mm, a hardness of 130 HV or higher, a tensile strength of 430 MPa or higher, and an elongation of 9% or higher.

[0042] Compared with the prior art, the present invention has at least the following beneficial effects:

[0043] (1) The present invention strictly controls the surface quality of the bar throughout the entire process from high-frequency melting, preheating casting, and diameter reduction hot forging to cold working. In particular, the controlled multi-stage diameter reduction hot forging method avoids the turning treatment of ingots and forging bars in the traditional alloy bar forming process. While ensuring the excellent comprehensive performance of the bar, it reduces raw material loss and lowers production costs.

[0044] (2) The present invention adopts a high-frequency melting combined with a precise control of the preheating and casting process, preheating the boron nitride mold to a high temperature and holding it at that temperature, and obtaining a casting rod with excellent surface quality through slow solidification. This reduces casting defects such as defects and pits on the surface of the palladium-platinum casting rod from the source, laying the foundation for subsequent multi-stage diameter reduction hot forging to avoid machining.

[0045] (3) The present invention further optimizes the surface finish by combining cold forming and heat treatment after hot forging, and finally obtains finished bar stock with smooth surface and no hardened layer directly without additional surface treatment process. This overcomes the defects of traditional preparation process, such as turning and peeling, which waste precious metal raw materials and increase production costs. Attached Figure Description

[0046] The present invention will now be described with reference to the accompanying drawings:

[0047] Figure 1 This is a schematic diagram of the multi-stage diameter reduction hot forging process of the present invention;

[0048] Figure 2 This is a flowchart of the hot forging and non-machining forming process for the medical palladium-platinum alloy rod of the present invention;

[0049] Figure 3 This is a photograph of the appearance of the medical palladium-platinum alloy rod sample of Embodiment 3 of the present invention;

[0050] Figure 4 A photograph of the appearance of the alloy rod sample in Comparative Example 1;

[0051] Figure 5 This is a photograph of the appearance of the alloy rod sample of Comparative Example 3. Detailed Implementation

[0052] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0053] As described in the background section, there is an urgent need in the field to provide a preparation process that eliminates the need for machining and peeling, optimizes the coordination of each step, reduces overall production costs, improves production efficiency, and produces alloy rods with no surface defects and excellent comprehensive properties such as strength, hardness, and toughness. This ensures that the rods meet the stringent requirements of the medical field for the precision of parts processing and the safety of use, promotes the upgrading of the preparation process of precious metal rods for medical use, and ultimately improves the yield and application benefits.

[0054] To solve the above problems, refer to Figure 1-2 In a first aspect of the present invention, a hot forging process for forming a medical palladium-platinum alloy rod without machining is provided, comprising the following steps:

[0055] Step 1: High-frequency melting

[0056] The high-frequency melting furnace was evacuated to 10°C. -1Below Pa, maintain for 2-3 minutes, then introduce argon gas with a purity ≥99.99% until the furnace pressure reaches above 0.03 MPa, for example, around 0.05 MPa. Melt the palladium-platinum alloy raw material (platinum content 20±1.5wt%, balance being palladium and unavoidable impurities, raw material purity higher than 99.95%) under argon protection. Control the melting power at 5-8 kW, the melting temperature at no less than 1700℃, and hold the material at that temperature for at least 3 minutes after complete melting. The total time from power application to casting completion should be controlled at 10-15 minutes to obtain a pure and homogeneous alloy melt. Maintain positive argon pressure protection throughout the melting process, and ensure a sealed connection between the casting runner and the mold.

[0057] Step 2: Preheating and Casting

[0058] A boron nitride mold with an inner diameter of 20-40 mm, preferably 30-38 mm, and more preferably 32-36 mm, and a height of over 100 mm, is used. The mold is preheated to over 500°C and held at that temperature for 20-60 minutes. Molten alloy rods are poured into the preheated mold under argon protection. After casting, the mixture is kept at 10... -1 Slow solidification in a vacuum environment below Pa promotes compositional homogenization and reduces surface defects.

[0059] Step 3: Diffusive hot forging

[0060] 3.1 Preheat the casting rod in stages under a protective atmosphere:

[0061] Heating to 400-600℃ at a rate of 25-35℃ / min and holding for 20-40 minutes helps to eliminate casting stress.

[0062] Then, raise the temperature to above 1000℃ at a rate of 15~30℃ / min and hold for at least 90 minutes to promote homogenization of the tissue structure.

[0063] 3.2 At least three stages of diameter reduction hot forging, preferably using 3-6 stage elliptical cavity forging dies (major-to-minor axis ratio 12:10-18:10), performed continuously or intermittently at a temperature not lower than 900℃, with each stage of diameter reduction accounting for 5-25%, and the total deformation exceeding 50%. Each stage of hot forging includes:

[0064] Re-forging (force 25~40kg): After feeding and hammer forging, rotate the casting bar about 90° and then pull and hammer forging to fully break the as-cast structure. Perform several re-forging cycles, such as 2 times or 3-6 times. Rotate the bar at a certain angle between adjacent feeding and hammer forging.

[0065] Light forging finishing (force 5~15kg): The bar is continuously rotated to perform feeding hammering and pulling hammering, to finish the surface wrinkles, and to perform several light forging cycles.

[0066] Stress-relief annealing is performed between each stage of hot forging: holding at above 1000℃ for 20-40 minutes to restore the material's plasticity; and the bar stock is reversed at both ends during the next stage of hot forging.

[0067] Preferably, the hot forging process involves five stages of diameter reduction, with each stage having a diameter reduction ratio of 16-25%, 15-20%, 11-15%, 8-12%, and 5-10%. The diameter reduction ratio decreases sequentially with each stage, as does the forging intensity. Optionally, the forging intensity decreases sequentially with each stage.

[0068] After the final stage of hot forging, at 10 -1 Under vacuum, the temperature is maintained at 1000℃ or above for no less than 20 minutes, then cooled to 600~800℃ and maintained for 40~60 minutes before being slowly cooled to room temperature. The heat preservation process at different temperatures can effectively remove the oxide layer, improve the surface quality, and eliminate stress.

[0069] Step 4: Cold forming, with a total deformation of over 80% during cold forming.

[0070] The hot forged bar stock is subjected to multiple cold rolling processes, each of which includes multiple rolling passes. The deformation per pass is ≤10%, preferably ≤6%, and the total deformation during cold rolling is less than 80%. Intermediate annealing is carried out between rolling passes, with the stock held at 400~800℃ for 30~60 minutes and then slowly cooled.

[0071] After cold rolling, the material is cold-drawn with a total deformation of over 50%. Finally, it undergoes stress-relief annealing, holding at 400-600℃ for 30-60 minutes followed by slow cooling to ensure dimensional stability. The resulting medical palladium-platinum alloy rods have a diameter of 0.8-3.0 mm, a hardness of over 130 HV, a strength of over 430 MPa, and an elongation of over 9%.

[0072] Example 1

[0073] The medical palladium-platinum alloy rod of Example 1 was prepared by the following hot forging and non-machining forming process:

[0074] Step 1: High-frequency melting

[0075] The high-frequency melting furnace was evacuated to a vacuum level of 5×10. -2 After maintaining the pressure at 0.05 MPa for 2.5 minutes, argon gas with a purity ≥99.99% is introduced to bring the furnace pressure to 0.05 MPa. The palladium-platinum alloy raw material (platinum content 20.0 wt%, balance being palladium and unavoidable impurities, raw material purity higher than 99.95%) is melted under argon protection. The melting power is controlled at 7 kW, the melting temperature at 1750 ± 10℃, and the material is held at this temperature for 6 minutes after complete melting. The total time from power application to casting completion is controlled at 12 minutes, resulting in a homogeneous alloy melt. Argon gas is maintained under positive pressure throughout the melting process, and the casting runner and mold are sealed together.

[0076] Step 2: Preheating and Casting

[0077] A boron nitride mold with an inner diameter of 36 mm and a height of 110 mm (inner wall roughness Ra≤0.8μm) was used. The mold was preheated to 550℃ and held for 40 min. Molten alloy was poured into the preheated mold under argon protection. After casting, the mixture was heated to 5×10⁻⁶ mm. -2 The palladium-platinum casting rod with a smooth surface and a diameter of about 36 mm was obtained by slow solidification in a vacuum environment.

[0078] Step 3: Diffusive hot forging

[0079] The casting rod is heated in stages under argon protection:

[0080] Heat to 500℃ at a rate of 30℃ / min and hold for 25 min;

[0081] Then raise the temperature to 1100℃ at a rate of 20℃ / min and hold for 100min.

[0082] Five-stage elliptical cavity forging dies (each die with a major-to-minor axis ratio of approximately 15:10) were used for intermittent hot forging at 1100℃. Specific parameters were as follows:

[0083] First stage: diameter reduction ratio of approximately 19% (36mm→29.0mm), heavy forging force of 35kg, light forging force of 13kg;

[0084] Second stage: diameter reduction ratio of approximately 15% (29.0mm→24.5mm), heavy forging force of 32kg, light forging force of 12kg;

[0085] Level 3: The diameter reduction ratio is about 12% (24.5mm → 21.5mm), the heavy forging force is 30kg, and the light forging force is 10kg;

[0086] Level 4: The diameter reduction ratio is approximately 9% (21.5mm → 19.5mm), the heavy forging force is 28kg, and the light forging force is 8kg;

[0087] Grade 5: The diameter reduction ratio is about 7.7% (19.5mm→18.0mm), the heavy forging force is 26kg, and the light forging force is 6kg.

[0088] Each stage of hot forging involves: first, three cycles of heavy forging (feed hammer forging - 90° rotation - pull hammer forging), followed by two cycles of light forging finishing (continuous rotation finishing).

[0089] Stress-relief annealing was performed between each hot forging stage: holding at 1150℃ for 30 minutes.

[0090] After the final stage of hot forging, at 10 -1The sample was held at 1150℃ for 20 minutes under vacuum, then cooled to 700℃ at a rate of 15℃ / min and held for 50 minutes. Finally, it was slowly cooled to room temperature at a rate not exceeding 100℃ / h.

[0091] Step 4: Cold forming, with a total deformation of approximately 91%.

[0092] The hot-forged bar stock was subjected to three cold rolling passes, each consisting of 10 passes with a deformation of approximately 5% per pass and a total deformation of approximately 78%, resulting in a cold-rolled bar with a diameter of approximately 3.6 mm. Intermediate annealing was performed in a vacuum environment between cold rolling passes: after the first cold rolling (with a deformation of approximately 40%), the bar was held at 650℃ for 40 min; after the second cold rolling (with a cumulative deformation of approximately 65%), the bar was held at 500℃ for 30 min. After annealing, the bar was slowly cooled to room temperature at a rate of ≤50℃ / h.

[0093] The cold-rolled bar was drawn 16 times, with each drawing deformation amounting to about 5%, and the total deformation amounting to about 55%, ultimately yielding a palladium-platinum alloy bar with a diameter of 1.6 mm.

[0094] Example 2

[0095] The medical palladium-platinum alloy rod of Example 2 was prepared by the following hot forging and non-machining forming process:

[0096] Step 1: High-frequency melting

[0097] The high-frequency melting furnace was evacuated to a vacuum level of 5×10. -2 After maintaining the pressure at 0.05 MPa for 2.5 minutes, argon gas with a purity ≥99.99% is introduced to bring the furnace pressure to 0.05 MPa. The palladium-platinum alloy raw material (platinum content 20.0 wt%, balance being palladium and unavoidable impurities, raw material purity higher than 99.95%) is melted under argon protection. The melting power is controlled at 7 kW, the melting temperature at 1750 ± 10℃, and the material is held at this temperature for 6 minutes after complete melting. The total time from power application to casting completion is controlled at 12 minutes, resulting in a homogeneous alloy melt. Argon gas is maintained under positive pressure throughout the melting process, and the casting runner and mold are sealed together.

[0098] Step 2: Preheating and Casting

[0099] A boron nitride mold with an inner diameter of 32 mm and a height of 110 mm (inner wall roughness Ra≤0.8μm) was used. The mold was preheated to 550℃ and held for 40 min. Molten alloy was poured into the preheated mold under argon protection. After casting, the mixture was heated to 5×10⁻⁶ mm. -2 Palladium-platinum casting rods with a smooth surface and a diameter of approximately 32 mm were obtained by slow solidification in a vacuum environment.

[0100] Step 3: Diffusive hot forging

[0101] The casting rod is heated in stages under argon protection:

[0102] Heat to 500℃ at a rate of 30℃ / min and hold for 25 min;

[0103] Then raise the temperature to 1100℃ at a rate of 20℃ / min and hold for 100min.

[0104] Five-stage elliptical cavity forging dies (each die with a major-to-minor axis ratio of approximately 15:10) were used for intermittent hot forging at 1100℃. Specific parameters were as follows:

[0105] First stage: diameter reduction ratio of approximately 17% (32mm→26.5mm), heavy forging force of 35kg, light forging force of 12kg;

[0106] Second stage: diameter reduction ratio of approximately 15% (26.5mm → 22.5mm), heavy forging force of 32kg, light forging force of 11kg;

[0107] Level 3: The diameter reduction ratio is about 13% (22.5mm → 19.5mm), the heavy forging force is 30kg, and the light forging force is 10kg;

[0108] Level 4: The diameter reduction ratio is about 10% (19.5mm → 17.5mm), the heavy forging force is 28kg, and the light forging force is 8kg;

[0109] Grade 5: The diameter reduction ratio is about 8% (17.5mm→16.0mm), the heavy forging force is 25kg, and the light forging force is 5kg.

[0110] Each stage of hot forging involves: first, three cycles of heavy forging (feed hammer forging - 90° rotation - pull hammer forging), followed by two cycles of light forging finishing (continuous rotation finishing).

[0111] Stress-relief annealing was performed between each stage of hot forging: holding at 1150℃ for 30 minutes.

[0112] After the final stage of hot forging, at 10 -1 The sample was held at 1150℃ for 20 minutes under vacuum, then cooled to 700℃ at a rate of 15℃ / min and held for 50 minutes. Finally, it was slowly cooled to room temperature at a rate not exceeding 100℃ / h.

[0113] Step 4: Cold forming, with a total deformation of approximately 93%.

[0114] The hot-forged bar stock was subjected to three cold rolling passes, each consisting of 10 passes with a deformation of approximately 5% per pass and a total deformation of approximately 78%, resulting in a cold-rolled bar with a diameter of approximately 3.5 mm. Intermediate annealing was performed in a vacuum environment between cold rolling passes: after the first cold rolling (with a deformation of approximately 40%), the bar was held at 500℃ for 40 min; after the second cold rolling (with a cumulative deformation of approximately 65%), the bar was held at 650℃ for 45 min. After annealing, the bar was slowly cooled to room temperature at a rate of ≤50℃ / h.

[0115] The cold-rolled bar was drawn 20 times, with each drawing yielding a deformation of approximately 6%, resulting in a total deformation of approximately 71%, ultimately yielding a palladium-platinum alloy bar with a diameter of 1.0 mm. Finally, under argon protection, the bar was heated to 400 °C at a rate of 15 °C / min and held for 45 min, followed by slow cooling to room temperature at a rate of approximately 50 °C / h to complete the stress relief treatment.

[0116] Example 3

[0117] The medical palladium-platinum alloy rod of Example 3 was prepared by the following hot forging and non-machining forming process:

[0118] Step 1: High-frequency melting

[0119] The high-frequency melting furnace was evacuated to a vacuum level of 5×10. -2 After maintaining the pressure at 0.05 MPa for 2.5 minutes, argon gas with a purity ≥99.99% is introduced to bring the furnace pressure to 0.05 MPa. The palladium-platinum alloy raw material (platinum content 20.0 wt%, balance being palladium and unavoidable impurities, raw material purity higher than 99.95%) is melted under argon protection. The melting power is controlled at 7 kW, the melting temperature at 1750 ± 10℃, and the material is held at this temperature for 6 minutes after complete melting. The total time from power application to casting completion is controlled at 12 minutes, resulting in a homogeneous alloy melt. Argon gas is maintained under positive pressure throughout the melting process, and the casting runner and mold are sealed together.

[0120] Step 2: Preheating and Casting

[0121] A boron nitride mold with an inner diameter of 36 mm and a height of 110 mm (inner wall roughness Ra≤0.8μm) was used. The mold was preheated to 550℃ and held for 40 min. Molten alloy was poured into the preheated mold under argon protection. After casting, the mixture was heated to 5×10⁻⁶ mm. -2 Slow solidification was carried out in a vacuum environment: the temperature was reduced from the casting temperature (about 1750°C) to 1150°C at a rate of 25°C / h and held for 1.0h; then it was slowly cooled to 600°C at a rate of about 50°C / h, and finally cooled to room temperature with the furnace to obtain a palladium-platinum casting rod with a smooth surface and a diameter of about 36mm.

[0122] Step 3: Diffusive hot forging

[0123] The casting rod is heated in stages under argon protection:

[0124] Heat to 500℃ at a rate of 30℃ / min and hold for 25 min;

[0125] Then raise the temperature to 1100℃ at a rate of 20℃ / min and hold for 100min.

[0126] Five-stage elliptical cavity forging dies (each die with a major-to-minor axis ratio of approximately 15:10) were used for intermittent hot forging at 1100℃. Specific parameters were as follows:

[0127] First stage: diameter reduction ratio of approximately 18% (36mm→29.5mm), heavy forging force of 36kg, light forging force of 14kg;

[0128] Second stage: diameter reduction ratio of approximately 15% (29.5mm → 25.0mm), heavy forging force of 34kg, light forging force of 12kg;

[0129] Level 3: The diameter reduction ratio is about 12% (25.0mm→22.0mm), the heavy forging force is 32kg, and the light forging force is 10kg;

[0130] Level 4: The diameter reduction ratio is approximately 9% (22.0mm → 20.0mm), the heavy forging force is 30kg, and the light forging force is 8kg;

[0131] Grade 5: The diameter reduction ratio is about 7.5% (20.0mm→18.5mm), the heavy forging force is 27kg, and the light forging force is 6kg.

[0132] Each stage of hot forging involves: first, three cycles of heavy forging (feed hammer forging - 90° rotation - pull hammer forging), followed by two cycles of light forging finishing (continuous rotation finishing).

[0133] Stress-relief annealing was performed between each hot forging stage: holding at 1150℃ for 30 minutes.

[0134] After the final stage of hot forging, at 10 -1 The sample was held at 1150℃ for 70 min under vacuum, then cooled to 700℃ at a rate of 15℃ / min and held for 50 min. Finally, it was slowly cooled to room temperature at a rate not exceeding 100℃ / h.

[0135] Step 4: Cold forming. The total deformation during cold forming is approximately 86%.

[0136] The hot-forged bar stock was subjected to three cold rolling passes, each consisting of eight passes with a deformation of approximately 5% per pass and a total deformation of approximately 70%, resulting in a cold-rolled bar with a diameter of approximately 5.6 mm. Intermediate annealing was performed in a vacuum environment between cold rolling passes: after the first cold rolling (with a deformation of approximately 35%), the bar was held at 500℃ for 40 min; after the second cold rolling (with a cumulative deformation of approximately 56%), the bar was held at 650℃ for 45 min. After annealing, the bar was slowly cooled to room temperature at a rate of ≤50℃ / h.

[0137] The cold-rolled bar was drawn 13 times, with each drawing causing a deformation of approximately 6%, resulting in a total deformation of approximately 54%, ultimately yielding a palladium-platinum alloy bar with a diameter of 2.6 mm. Finally, under argon protection, the bar was heated to 400 °C at a rate of 15 °C / min and held for 45 min, followed by slow cooling to room temperature at a rate of approximately 50 °C / h to complete the stress relief treatment.

[0138] Example 4

[0139] The difference between Example 4 and Example 3 lies in the diameter reduction hot forging process. Example 4 uses a 5-stage diameter reduction hot forging process, but the diameter reduction ratio is different. The specific parameters are as follows:

[0140] First stage: diameter reduction ratio of about 17% (36mm→30mm), heavy forging force of 36kg, light forging force of 14kg;

[0141] Second stage: diameter reduction ratio of approximately 8% (30mm→27.5mm), heavy forging force of 34kg, light forging force of 12kg;

[0142] Level 3: The diameter reduction ratio is about 11% (27.5mm → 24.5mm), the heavy forging force is 32kg, and the light forging force is 10kg;

[0143] Level 4: The diameter reduction ratio is approximately 14% (24.5mm → 21.0mm), the heavy forging force is 30kg, and the light forging force is 8kg;

[0144] Grade 5: The diameter reduction ratio is about 12% (21.0mm→18.5mm), the heavy forging force is 27kg, and the light forging force is 6kg.

[0145] Example 5

[0146] The difference between Example 5 and Example 3 lies in the diameter reduction hot forging process. Example 5 uses a three-stage diameter reduction hot forging process with different diameter reduction ratios. The specific parameters are as follows:

[0147] First stage: diameter reduction ratio of about 22% (36mm→28mm), heavy forging force of 36kg, light forging force of 14kg;

[0148] Second stage: diameter reduction ratio of about 21% (28mm→22mm), heavy forging force of 34kg, light forging force of 12kg;

[0149] Level 3: The diameter reduction ratio is about 16% (22mm→18.5mm), the heavy forging force is 32kg, and the light forging force is 10kg.

[0150] Example 6

[0151] The difference between Example 6 and Example 3 is that the preheating method before hot forging is different. The palladium-platinum casting rod is preheated to 1000°C at a rate of 30°C / min and held for 90 minutes, and then multi-stage diameter reduction hot forging is performed.

[0152] Example 7

[0153] The difference between Example 7 and Example 3 is that, during the high-frequency melting and casting process, the preheating temperature of the boron nitride mold is 400°C for 15 minutes, and then the alloy solution is injected and allowed to cool naturally.

[0154] Comparative Example 1

[0155] The difference between Comparative Example 1 and Example 3 is that only two-stage diameter reduction hot forging was performed, with the specific parameters as follows:

[0156] First stage: diameter reduction ratio of approximately 29% (36mm→25.5mm), heavy forging force of 35kg, light forging force of 15kg;

[0157] Second stage: diameter reduction ratio of approximately 27% (25.5mm → 18.5mm), heavy forging force of 32kg, light forging force of 10kg.

[0158] Comparative Example 2

[0159] The difference between Comparative Example 2 and Example 3 lies in the use of three-stage diameter reduction hot forging with different diameter reduction ratios. The specific parameters are as follows:

[0160] First stage: diameter reduction ratio of approximately 26% (36mm → 26.5mm), heavy forging force of 36kg, light forging force of 14kg;

[0161] Second stage: diameter reduction ratio of approximately 24.5% (26.5mm→20.0mm), heavy forging force of 34kg, light forging force of 12kg;

[0162] Level 3: The diameter reduction ratio is about 7.5% (27.5mm→18.5mm), the heavy forging force is 30kg, and the light forging force is 10kg.

[0163] Comparative Example 3

[0164] The difference between Comparative Example 3 and Example 3 is that, after the final stage of hot forging, at 10... -1 It was kept at 1150℃ for 70 minutes under vacuum and then naturally cooled to room temperature.

[0165] Comparative Example 4

[0166] Traditional commercially available products.

[0167] Tests and Results

[0168] The following tests were performed on the bar samples obtained in Examples 1-7, Comparative Examples 1-3, and the commercially available bar (φ2.6mm × 100mm length) in Comparative Example 4:

[0169] Mechanical property testing:

[0170] Yield strength, tensile strength, and elongation were determined according to the national standard GB / T228.1~2021 "Metallic materials, tensile testing—Part 1: Test at room temperature". A universal testing machine was used to take samples along the length of the final obtained bar, process them into standard tensile specimens, and conduct tensile tests at room temperature until the specimens fractured. The software automatically recorded and calculated the various mechanical property parameters.

[0171] 1. The mechanical property test results are shown in Table 1:

[0172] Table 1:

[0173]

[0174] The mechanical property test results show that the samples in Examples 1-7 all simultaneously meet the requirements for medical palladium-platinum alloy rods: hardness above 130 HV, strength ≥ 430 MPa, and elongation above 9%. The samples in Examples 1-4 further demonstrate improved hardness to above 135 HV and strength to above 435 MPa. Using the preparation process of this invention without turning, not only can the surface quality of the rods meet medical requirements be obtained, but also... (See...) Figure 3 (Example 3) can also impart good mechanical properties to the alloy rod. However, due to variations in the diameter reduction hot forging or heat treatment steps in the hot forging process of Comparative Examples 1-3, it is difficult to simultaneously meet the requirements for comprehensive properties such as surface quality and mechanical properties of medical alloy rods. Figure 4 The sample surface showed defects (Comparative Example 1). Figure 5 Numerous cracks appeared on the surface of the sample (Comparative Example 3). Commercially available products achieved better surface quality through processes such as turning, but their overall mechanical properties failed to meet the requirements.

[0175] 2. Dimensional error detection

[0176] The diameter of the bar samples from Examples 1-7 and Comparative Examples 1-4 was tested. Three samples were selected for each group, and the average of the three diameters measured at the front end, midpoint, and rear end of each sample along its length was taken as the sample diameter. The maximum error value was calculated based on the diameter of each sample. The results are shown in Table 2.

[0177] Table 2:

[0178]

[0179] The dimensional error detection results show that the maximum error of samples 1-7 can be controlled within 0.015. Without machining or other mechanical treatments, the stable macroscopic dimensions are closely related to the uniform and dense internal structure. This indicates that the preparation process of this invention improves the microscopic quality of the rods while eliminating surface defects. Correspondingly, the alloy rods of Comparative Examples 1-3, with numerous surface defects, also exhibit larger overall dimensional errors. (See [reference]). Figure 4 and Figure 5 Commercially available products achieve good surface quality and high bar precision through processes such as turning, but this results in significant material loss and higher costs.

[0180] Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including both the preferred embodiments and all changes and modifications falling within the scope of the invention. Clearly, those skilled in the art can make various alterations and modifications to the invention without departing from its spirit and scope. Thus, if these modifications and modifications of the invention fall within the scope of the claims and their equivalents, the invention is also intended to include these modifications and modifications.

Claims

1. A hot forging process for medical palladium-platinum alloy rods without machining, characterized in that, The raw materials for the palladium-platinum alloy rod, by weight percentage, consist of: 20 ± 1.5 wt% platinum, with the balance being palladium and unavoidable impurities; The forming process includes obtaining palladium-platinum casting rods by high-frequency melting and casting of the raw materials, and sequentially performing multi-stage diameter reduction hot forging and cold forming on the palladium-platinum casting rods to obtain medical palladium-platinum alloy rods that do not require machining. The multi-stage diameter reduction hot forging is carried out using a multi-stage forging die in conjunction with an air hammer, with a total deformation of over 50%, and includes the following steps: (1) Preheat the palladium-platinum casting rod to above 1000℃ and keep it at that temperature for no less than 90 minutes; (2) At least three stages of shrinkage hot forging are carried out continuously or intermittently at a temperature of not less than 900℃ to obtain hot forged bar stock, with the shrinkage ratio between each stage of forging die being 5-25%; (3) In 10 -1 In a vacuum environment below Pa, the hot forged bar stock is heated to above 1000℃ and held for at least 20 minutes, then cooled to 600~800℃ and held for 40~60 minutes, and then allowed to cool naturally.

2. The hot forging and non-machining forming process as described in claim 1, characterized in that, Intermittently perform 3-6 stages of diameter reduction hot forging. Between each stage of diameter reduction hot forging, heat the palladium-platinum casting rod to above 1000℃ and hold for 20-40 minutes.

3. The hot forging non-machining forming process as described in claim 1 or 2, characterized in that, Each forging die has an elliptical cavity, and the reduction ratio between each forging die decreases sequentially, taking into account the minor axis of the elliptical cavity.

4. The hot forging non-machining forming process as described in claim 3, characterized in that, Five-stage reduction hot forging is adopted, with reduction ratios of 16~25%, 15~20%, 11~15%, 8~12%, and 5~10% for each stage.

5. The hot forging non-machining forming process as described in claim 3, characterized in that, Each stage of diameter reduction hot forging includes heavy forging and light forging finishing, with the forging force ratio of heavy forging to light forging finishing being (25-40):(5-15).

6. The hot forging and non-machining forming process as described in claim 5, characterized in that, Heavy forging and light forging finishing include feed hammer forging and draw hammer forging, respectively. In the reforging process, after the feed hammer forging, the palladium-platinum casting rod is rotated at a certain angle and then pulled hammer forging is performed. During light forging and finishing, the palladium-platinum casting rod is continuously rotated during both the feeding hammer and the pulling hammer processes.

7. The hot forging non-machining forming process as described in claim 1 or 2, characterized in that, In step (1), the preheating of the palladium-platinum casting rod involves at least two heating steps, including: One-step heating: Heat to 400-600℃ at a rate of 25-35℃ / min, and hold for 20-40 minutes; Two-step heating: Heat to above 1000℃ at a rate of 15~30℃ / min, and hold for more than 90 minutes.

8. The hot forging non-machining forming process as described in claim 1 or 2, characterized in that, The high-frequency melting and casting process includes the following steps: High-frequency melting: First, evacuate the high-frequency melting furnace to 10°C. -1 Below Pa, argon gas is introduced until the furnace pressure is above 0.03 MPa, the melting power is 5~8 kW, the melting temperature is not lower than 1700℃, and the holding time of the alloy melt is not lower than 3 min; Preheating and casting: Boron nitride molds with an inner diameter of 20-40 mm and a height of 100 mm or more are used. The boron nitride molds are preheated to above 500℃ and held for 20-40 minutes before the alloy melt is poured in. The melt is slowly solidified to obtain palladium-platinum casting rods. The total time from loading the melting power to completing the pouring is 10-15 minutes.

9. The hot forging non-machining forming process as described in claim 8, characterized in that, Cold forming includes multiple cold rolling and cold drawing processes, with a total deformation rate of over 80%. Each cold rolling process includes multiple rolling passes, with each pass deformation being less than 10%. Intermediate annealing is performed between multiple cold rolling processes, including heating to 400-800°C at a rate of 15-30°C / min in a vacuum environment, holding at that temperature for 30-60 minutes, and then slowly cooling to room temperature.

10. A medical palladium-platinum alloy rod, characterized in that, The medical palladium-platinum alloy rod is prepared by the hot forging and non-machining forming process according to any one of claims 1 to 9. The medical palladium-platinum alloy rod has a diameter of 0.8 to 3.0 mm, a hardness of 130 HV or higher, a tensile strength of 430 MPa or higher, and an elongation of 9% or higher.

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