Passivation process method of medical elbow scissors body
By employing a segmented temperature-controlled, multi-physical-field synergistic passivation process, the problem of insufficient passivation uniformity in medical curved scissors was solved, achieving a dense, uniform, and corrosion-resistant passivation film, thus improving the performance of the scissors and making it suitable for passivation treatment of medical curved scissors.
Patent Information
- Application Number
- CN202511815369.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-04
- Publication Date
- 2026-02-24
AI Technical Summary
The existing passivation process for medical curved scissors has problems such as insufficient passivation uniformity, the blade edge being prone to having a passivation film that is too thin or too thick, resulting in impaired sharpness, and the difficulty in solving the passivation dead angles in the joint gaps.
The passivation process employs segmented temperature control and multi-physics field synergy, including steps such as degreasing, rinsing, vacuum drying, and silane sealing. By dynamically adapting concentration, temperature, and ultrasonic power, and combining ultrasonic, electric field, nitrogen, and vacuum technologies, the uniformity and integrity of the passivation film are ensured.
This achieves a dense and uniform passivation film, improves the corrosion resistance and biocompatibility of the shear body, extends its service life, ensures the sharpness of the cutting edge and the complete coverage of the passivation film within the crevices, and meets the needs of minimally invasive surgery.
Smart Images
Figure CN121556017A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of medical device manufacturing technology, and in particular to a passivation process for the shear body of a medical curved scissor. Background Technology
[0002] As a key instrument in surgical procedures, medical curved scissors are made of 420B stainless steel, requiring excellent corrosion resistance, sharp cutting edges, and biocompatibility. Passivation treatment is the core process for improving the corrosion resistance of 420B stainless steel. It forms a dense oxide film on the surface of the scissor body to prevent the substrate from contacting corrosive media. Currently, the passivation process for medical curved scissors generally suffers from insufficient uniformity, especially in the critical areas of the blade edge and joint gaps. Specifically, this manifests in two ways: First, the blade edge of medical curved scissors is a thin-bladed structure (typically ≤0.2mm thick). In existing passivation processes, the residence time and reaction rate of the passivation fluid on the blade surface are difficult to control precisely, easily resulting in a passivation film that is too thin (insufficient corrosion resistance) or too thick (decreased blade hardness and damaged sharpness). Second, the joint gaps of the scissors are narrow spaces. In existing processes, the passivation fluid has poor flowability, and air or contaminants easily remain in the gaps, leading to incomplete passivation film coverage. Although some processes attempt to improve uniformity by extending the passivation time or increasing the stirring rate, extending the time will further aggravate the edge corrosion, while increasing the stirring rate will easily lead to the splashing of passivation liquid and cannot effectively solve the problem of passivation dead corners in the joint gaps.
[0003] Therefore, it is urgent for technical personnel to solve the above problems. Summary of the Invention
[0004] The purpose of this invention is to provide a passivation process for the shear body of a medical curved scissor, aiming to solve the problems of insufficient passivation uniformity in existing designs, the tendency for the passivation film on the cutting edge to be too thin or too thick, resulting in poor corrosion resistance and damaged sharpness, and the existence of passivation dead angles in the joint gaps.
[0005] This invention relates to a passivation process for the cutter body of medical curved scissors, comprising the following steps: S1. Degreasing treatment: Use a 5% sodium hydroxide solution as a degreasing agent. Place the medical curved scissors in the degreasing agent and soak them at 55℃ for 12 minutes. S2, First rinse: Rinse the shears after the degreasing treatment in S1 with pure water for 3-5 minutes, and then soak the shears in deionized water with a conductivity of ≤10μS / cm for 5 minutes to complete the first rinse. S3, Citric Acid Passivation: Prepare a 5% (w / w) citric acid passivation solution, and add 0.1%–0.2% sodium silicate as a film conditioning agent to the passivation solution; place the shear body after the initial rinse in S2 into the passivation solution, and adopt a segmented temperature control mode: the first stage controls the temperature at 40℃ and maintains it for 15 minutes, while stirring the passivation solution unidirectionally at a speed of 30–50 r / min; the second stage raises the temperature to 45℃ and maintains it for 20 minutes, adjusts the stirring direction to bidirectional alternation, and gently shakes the shear body once every 10 minutes in the second stage; S4. Second rinsing: Immerse the shear body after S3 passivation in deionized water for 10 minutes, then take it out and immerse it in fresh deionized water for 10 minutes to complete the second rinsing. S5. Vacuum drying: Place the shear body after the second rinse in S4 into a vacuum drying equipment, set the temperature to 50℃ and the vacuum degree to 0.08MPa, and dry for 40 minutes. S6, Silane sealing: Prepare a 2.5% silane sealing agent, place the shear body after vacuum drying in S5 into the silane sealing agent, and soak it at room temperature for 5 minutes; S7. Secondary vacuum drying: The shear body sealed with silane in S6 is placed back into the vacuum drying equipment. The temperature is set to 50℃ and the vacuum degree is 0.08MPa. The drying time is 40 minutes to complete the passivation treatment of the shear body.
[0006] As a further improvement to the technical solution disclosed in this invention, a pre-activation treatment step is added between S1 degreasing and S3 passivation: the shear body after initial rinsing in S2 is placed in a 0.5-0.8% dilute nitric acid solution and soaked at room temperature for 2-3 minutes, and then immediately rinsed with deionized water for 1 minute.
[0007] As a further improvement to the technical solution disclosed in this invention, during bidirectional alternating stirring in S3, nitrogen gas with a purity of ≥99.99% is simultaneously introduced into the passivation liquid at a rate of 0.5 to 1 L / min. As a further improvement to the technical solution disclosed in this invention, the S4 secondary rinsing adopts ultrasonic-assisted rinsing: the shear body is placed in deionized water, an ultrasonic generator with a power of 100-150W is turned on, the frequency is set to 40kHz, and the ultrasonic action lasts for 5 minutes during each rinsing process.
[0008] As a further improvement to the technical solution disclosed in this invention, during vacuum drying in S5, a zoned temperature control module is set in the drying equipment: the temperature of the shear blade area is controlled at 45°C, and the temperature of the shear body area is controlled at 50°C. As a further improvement to the technical solution disclosed in this invention, in addition to nano-silica particles, 0.1-0.15% of polyethylene glycol is added to the S6 silane sealing agent. As a further improvement to the technical solution disclosed in this invention, during the S1 degreasing process, pulsed ultrasonic degreasing is adopted: the shear body is placed in a sodium hydroxide solution, and an ultrasonic wave with a power of 200W and a frequency of 28kHz is turned on every 3 minutes, each lasting for 30 seconds.
[0009] As a further improvement to the technical solution disclosed in this invention, after the secondary vacuum drying of S7 is completed, a low-temperature plasma treatment step is added: the shear body is placed in a plasma device, argon gas is introduced, the power is set to 80-100W, and the treatment time is 3-5 minutes.
[0010] In practical applications, the passivation process method for the cutter body of the medical curved scissors disclosed in this invention can achieve at least the following beneficial technical effects, specifically: 1) Entering the S3 passivation stage, at a low temperature (40℃), unidirectional stirring allows citric acid to slowly penetrate to the surface of the shear body, reacting with chromium in the stainless steel. At this time, sodium silicate adheres to thin areas such as the cutting edge through adsorption, inhibiting the local reaction rate from being too fast and preventing the passivation film at the cutting edge from growing too thick. After the temperature is raised to 45℃, the chemical reaction activity is enhanced. Bidirectional alternating stirring breaks the concentration gradient and bubble retention in the joint gap through fluid dynamics, promoting the continuous contact of fresh passivation liquid with the inner wall of the gap, ensuring that chromium is uniformly oxidized on the inner wall of the gap. Moreover, sodium silicate undergoes hydrolysis after the temperature rises, and the resulting silicate ions combine with hydroxyl groups in the passivation film, further regulating the film growth direction, so that the passivation film in both the cutting edge and the main body area forms a dense Cr2O3 structure, thereby effectively solving the problems of difficult-to-control reaction rate at thin cutting edges and insufficient reaction in narrow gaps. 2) In the S4 secondary rinsing stage, a continuous concentration gradient is established by replacing the deionized water twice. This allows residual citric acid (unreacted portion) and sodium silicate (unbonded portion) on the surface and in the gaps of the shear body to diffuse into the water, preventing these substances from crystallizing during subsequent drying (crystallization would damage the integrity of the passivation film). The S5 vacuum drying utilizes a negative pressure environment to lower the boiling point of water, achieving rapid dehydration at a lower temperature. The vacuum state also inhibits the oxidation reaction on the stainless steel surface during the drying process, preventing the formation of a new oxide layer that would affect the film bonding, ensuring that the passivation film enters the sealing stage in a clean and intact state. The synergistic mechanism of S6 silane sealing and S7 secondary drying is reflected at the molecular bonding level: the siloxane groups in the silane sealant can undergo a condensation reaction with the hydroxyl groups on the surface of the passivation film to form a chemically bonded, tightly sealed layer. This sealing layer can physically block the contact between external corrosive media and the passivation film. The secondary vacuum drying further removes solvent molecules from the sealant, promoting tighter cross-linking of silane molecules to form a three-dimensional network structure, thereby significantly improving the bonding strength between the sealing layer and the passivation film. Attached Figure Description
[0011] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0012] Figure 1 This is a physical image of the medical curved scissors body disclosed in this invention. Detailed Implementation
[0013] The technical solution disclosed in this invention will be further described in detail below with reference to specific embodiments. The passivation process, as a key finishing step in the processing of medical curved scissors, is applied to scissors that have passed all-dimensional final inspections. Through steps such as degreasing, rinsing, passivation, secondary rinsing, vacuum drying, silane sealing, and secondary vacuum drying, the corrosion resistance and biocompatibility of the scissors are synergistically improved to form a complete passivation treatment system.
[0014] As a prerequisite for passivation, the degreasing process (corresponding to step S1 in the process method) directly affects the quality of the subsequent passivation film formation. Based on the material stress state of different areas of the shear body (stress concentration in the cutting edge area after heat treatment, and relatively gentler stress in the main body area), a dynamic adaptation strategy of concentration, temperature, and ultrasonic power is adopted: a 5% sodium hydroxide solution is used as the base degreasing agent. Processors completely immerse the final-inspection-qualified shear body in the degreasing agent. For the cutting edge area, the surface temperature is monitored in real time using an infrared temperature measurement module. When the temperature reaches 55℃, the system automatically triggers the ultrasonic power adjustment module, reducing the power from 200W to 180W to avoid damage to the microstructure of the cutting edge from high-power ultrasound. For the main body area, the ultrasonic power is maintained at 200W to ensure efficient decomposition of oil contaminants. The overall immersion time is controlled at 12 minutes, and the rotation speed is dynamically adjusted via a rotatable hanger: initially set at 5 r / min, after 5 minutes, the surface oil contaminant is detected by a surface oil contaminant detector. If the oil contaminant residue exceeds the standard, the rotation speed is automatically increased to 8 r / min until the detection standard is met. In this way, on the one hand, the synergistic effect of a 5% sodium hydroxide concentration and a temperature of 55°C allows for the efficient decomposition of residual cutting oil in the cutting edge and joint gaps through saponification; on the other hand, the dynamic adaptation of ultrasonic power and hanger rotation speed prevents microscopic cracks from forming in the high-stress cutting edge area due to excessive degreasing, thus laying a good foundation for subsequent rinsing and passivation processes. Furthermore, microscopic observation shows that the surface roughness of the treated shear body remains at a low level. After degreasing, the process proceeds to the initial rinsing stage (corresponding to step S2 in the process method), which is closely linked to this stage. Its core function is to remove residual degreasing agent and oil decomposition products from the surface of the shear body to prevent them from interfering with the subsequent passivation reaction. The initial rinsing process employs a gradient water quality and time-adaptive rinsing system: Processors first rinse the degreased shears with purified water for 3-5 minutes. The rinsing time is dynamically adjusted based on the residual alkali on the shears' surface after degreasing. A pH sensor monitors the surface pH in real time; if the pH is too high, the rinsing time is extended to 5 minutes; if the pH is within acceptable limits, it is shortened to 3 minutes. This initially removes free sodium hydroxide and oil debris from the surface. The shears are then transferred to graded deionized water and soaked for 5 minutes. The deionized water is supplied in three stages, with each stage equipped with a conductivity meter for real-time monitoring. Specifically: the first stage uses a spray system to clean the main body area; the second stage uses fine-diameter nozzles to clean joint gaps; and the third stage uses micro-diameter nozzles to precisely clean the cutting edge area. The spray pressure is adjusted according to the characteristics of each area, maintaining normal pressure in the main body area and appropriately reducing pressure in the cutting edge area to avoid excessive pressure damaging the cutting edge. The value of this gradient rinsing system lies in the fact that, based on the different sensitivities of different regions of the shear body to impurity ions (the passivation film in the cutting edge region is thinner and more sensitive to residual ions, which can easily lead to localized failure of the film), a combination of graded water quality and precise spraying is used to ensure that the content of impurity ions on the surface of the shear body is controlled differently in different regions. The cutting edge region and the main body region are maintained at different low residual levels, avoiding side reactions between these ions and citric acid in the subsequent passivation stage, and creating a pure reaction environment for the subsequent passivation process. After the initial rinsing, the shear body enters the citric acid passivation stage (corresponding to step S3 in the process). Based on segmented temperature control, a multi-physics synergistic mechanism involving temperature, stirring, electric field, and nitrogen is introduced for the first time: when preparing a 5% citric acid passivation solution, the chromium content of the shear body is first detected using a material analyzer, and then the amount of sodium silicate added is dynamically adjusted according to the detection results. The amount added is adjusted accordingly for different chromium contents, and trisodium citrate is added as an auxiliary regulator. The two are compounded in proportion, and the passivation film growth rate is synergistically controlled through the complexation effect, avoiding the film roughness problem caused by a single regulator. The shear body, after its initial rinse, is then placed in a passivation solution. A segmented approach combining low-temperature electric field assistance and high-temperature nitrogen stirring is employed: In the first stage, a micro-electric field is applied to the passivation solution via electrode plates. A shielding electrode is specifically set up for the cutting edge area to reduce the electric field strength and prevent excessively thick film due to rapid local reactions. Simultaneously, unidirectional stirring is used, with the stirring blades made of a special material to avoid metal contamination. The micro-electric field promotes the directional migration of citrate ions to the shear body surface, accelerating the oxidation reaction of chromium. At the same time, sodium silicate preferentially adheres to thin areas such as the cutting edge through adsorption, suppressing excessively rapid local reaction rates. To ensure the passivation film thickness on the cutting edge remains stable within a reasonable range that balances corrosion resistance and sharpness, the micro-electric field output is stopped in the second stage, and the stirring system automatically switches to a bidirectional alternating stirring mode to increase the rotation speed. At the same time, a local stirring paddle is added near the joint gap area to further increase the rotation speed and enhance the flow of liquid in the gap. High-purity nitrogen is simultaneously introduced into the passivation liquid, and the gas flow rate is dynamically adjusted according to the width of the shear gap. After being dispersed by the microbubble generator, the nitrogen enters the joint gap evenly with the stirring, breaking the concentration gradient and bubble retention in the gap, and promoting the continuous contact of fresh passivation liquid with the inner wall of the gap.
[0015] Furthermore, it should be noted that in the pre-activation treatment step added between degreasing and passivation, a specific ratio of activation solution is used. After soaking at room temperature for 2-3 minutes, it is immediately rinsed with tertiary deionized water for 1 minute. In actual operation, the activation solution not only slightly activates the oxide layer on the shear surface, enhances the reactivity of citric acid and chromium, and improves the passivation film formation efficiency, but also avoids excessive corrosion of the cutting edge caused by a single acid agent through complexation, improving the adhesion between the film and the substrate. This results in a significant increase in the passivation film coverage at the joint gaps, while maintaining a high level of Cr2O3 purity in the passivation film. The secondary rinsing step (corresponding to step S4 in the process) adds a combined ultrasonic and negative pressure cleaning mechanism to the two deionized water soakings: during each soaking, ultrasonic waves are introduced into the deionized water, equipped with a power adjustment module and a separate ultrasonic attenuator for the cutting edge area to reduce power; simultaneously, a micro-negative pressure is applied to the joint gaps of the shear body through a micro-negative pressure suction cup. This maintains the residual chloride ion content on the shear body surface at an extremely low level, and significantly improves the removal rate of residues in the gaps, effectively preventing passivation film failure caused by residual ions. After the second rinsing, the film enters the vacuum drying stage (corresponding to step S5 in the process method). Based on the zoned temperature control module, a humidity and vacuum degree linkage control system is introduced: In the initial drying stage, when the humidity sensor inside the vacuum drying equipment detects high humidity, the system automatically maintains a lower vacuum degree to accelerate surface moisture evaporation; in the middle stage, when the humidity drops to a reasonable range, the vacuum degree is increased to deeply remove moisture from the crevices; in the later stage, a high vacuum degree is maintained until the humidity drops to an extremely low level. By adopting the above technical solution, it is ensured that the passivation film dries uniformly, without any moisture residue dead zones, and to avoid film oxidation caused by moisture.
[0016] After drying, the shear body enters the silane sealing stage (corresponding to step S6 in the process) as a reinforcement step for the passivation film. An appropriate amount of γ-glycidoxypropyltrimethoxysilane is added to the silane sealant to form a complex system with γ-aminopropyltriethoxysilane. The complex sealant forms a dual-site binding with the hydroxyl groups on the passivation film surface; simultaneously, nano-silica particles are added to specifically fill the voids in the sealing layer in the cutting edge area. Testing shows that the sealing layer's barrier ability against corrosive media is significantly improved, and its flexibility is significantly enhanced, showing no cracking even after multiple bends. In the secondary vacuum drying stage (corresponding to step S7 in the process method), a mixed plasma of argon and oxygen is used in the low-temperature plasma treatment step, with the treatment power and time precisely controlled according to requirements. The mixed plasma not only activates the activity of the sealing layer molecules and enhances the bonding force, but also forms an extremely thin oxide layer on the surface of the sealing layer, further improving corrosion resistance; moreover, it significantly increases the contact angle of the shear body surface, reducing the adhesion of contaminants such as blood and tissue fluid during subsequent use. From the perspective of the synergistic effect of the entire passivation process, each step forms significant technical advantages through innovative design: dynamic degreasing and gradient rinsing in the degreasing and initial rinsing stages provide a regionally differentiated clean foundation for the core passivation stage, ensuring that the passivation reaction is free from impurity interference; the synergistic effect of multi-physics fields in the passivation stage achieves a precise balance between edge protection and gap passivation, solving the core technical bottleneck; the synergistic enhancement of secondary rinsing, vacuum drying, silane sealing, and secondary vacuum drying further improves the performance stability of the passivation film and sealing layer, extending their service life. Ultimately, this process creates a multi-layered protective structure on the surface of the scissors, with the passivation film thickness within a reasonable range. The thickness of different areas is adapted to their functional requirements, significantly extending the salt spray resistance test duration. Furthermore, it can withstand multiple high-temperature and high-pressure sterilizations at 134℃ without rust or deformation. Simultaneously, the targeted protective design at each stage ensures the sharpness of the scissor blade and keeps shearing force fluctuations within a low range. Ultimately, this achieves a simultaneous leap in the corrosion resistance, biocompatibility, and performance of the scissors, meeting the stringent requirements of minimally invasive surgery and providing an effective solution for the multi-performance synergistic optimization of the passivation process for medical curved scissors.
[0017] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A passivation process for the cutter body of medical curved scissors, characterized in that, Includes the following steps: S1. Degreasing treatment: Use a 5% sodium hydroxide solution as a degreasing agent. Place the medical curved scissors in the degreasing agent and soak them at 55℃ for 12 minutes. S2, First rinse: Rinse the shears after the degreasing treatment in S1 with pure water for 3-5 minutes, and then soak the shears in deionized water with a conductivity of ≤10μS / cm for 5 minutes to complete the first rinse. S3, Citric Acid Passivation: Prepare a 5% (w / w) citric acid passivation solution, and add 0.1%–0.2% sodium silicate as a film conditioning agent to the passivation solution; place the shear body after the initial rinse in S2 into the passivation solution, and adopt a segmented temperature control mode: the first stage controls the temperature at 40℃ and maintains it for 15 minutes, while stirring the passivation solution unidirectionally at a speed of 30–50 r / min; the second stage raises the temperature to 45℃ and maintains it for 20 minutes, adjusts the stirring direction to bidirectional alternation, and gently shakes the shear body once every 10 minutes in the second stage; S4. Second rinsing: Immerse the shear body after S3 passivation in deionized water for 10 minutes, then take it out and immerse it in fresh deionized water for 10 minutes to complete the second rinsing. S5. Vacuum drying: Place the shear body after the second rinse in S4 into a vacuum drying equipment, set the temperature to 50℃ and the vacuum degree to 0.08MPa, and dry for 40 minutes. S6, Silane sealing: Prepare a 2.5% silane sealing agent, place the shear body after vacuum drying in S5 into the silane sealing agent, and soak it at room temperature for 5 minutes; S7. Secondary vacuum drying: The shear body sealed with silane in S6 is placed back into the vacuum drying equipment. The temperature is set to 50℃ and the vacuum degree is 0.08MPa. The drying time is 40 minutes to complete the passivation treatment of the shear body.
2. The passivation process method for the cutter body of the medical curved scissors according to claim 1, characterized in that, A pre-activation treatment step is added between S1 degreasing and S3 passivation: the shear body after the initial rinsing in S2 is placed in a 0.5-0.8% dilute nitric acid solution and soaked at room temperature for 2-3 minutes, and then immediately rinsed with deionized water for 1 minute.
3. The passivation process method for the cutter body of the medical curved scissors according to claim 1, characterized in that, During bidirectional alternating stirring in S3, nitrogen gas with a purity ≥99.99% is simultaneously introduced into the passivation solution at a rate of 0.5–1 L / min.
4. The passivation process of the medical curved scissors body according to claim 1, characterized in that, The S4 secondary rinse uses ultrasonic-assisted rinsing: the shear body is placed in deionized water, and an ultrasonic generator with a power of 100-150W is turned on, with the frequency set to 40kHz. The ultrasonic action lasts for 5 minutes during each rinse.
5. The passivation process method for the cutter body of the medical curved scissors according to claim 1, characterized in that, During S5 vacuum drying, a zoned temperature control module is set up inside the drying equipment: the temperature of the shear blade area is controlled at 45℃, and the temperature of the shear body area is controlled at 50℃.
6. The passivation process method for the cutter body of the medical curved scissors according to claim 1, characterized in that, In addition to nano-silica particles, S6 silane sealant contains 0.1-0.15% polyethylene glycol.
7. The passivation process method for the cutter body of the medical curved scissors according to claim 1, characterized in that, During the S1 degreasing process, pulsed ultrasonic degreasing is used: the shear body is placed in a sodium hydroxide solution, and an ultrasonic wave with a power of 200W and a frequency of 28kHz is turned on every 3 minutes, each lasting 30 seconds.
8. The passivation process method for the cutter body of the medical curved scissors according to claim 1, characterized in that, After the secondary vacuum drying of S7 is completed, a low-temperature plasma treatment step is added: place the shear body in the plasma device, introduce argon gas, set the power to 80-100W, and the treatment time to 3-5 minutes.