Method for modifying an entire metal workpiece, gas guide assembly and equipment for modification

Abstract

The present invention relates to the technical field of medical devices, and more particularly to a method for modifying an entire metal workpiece, a gas guide assembly, and an apparatus for the modification. The method includes the steps of modifying the metal workpiece by placing it in a gas flow and cooling the modified metal workpiece, where the gas flow is preheated to a temperature close to the modification temperature before flowing onto the surface of the metal workpiece. The gas guide assembly includes a gas guide tube, and the relationship between the length L and the inner radius R of the gas guide tube is expressed as E=LR. 2 +A, 0≦A≦5cm 3 , 0.3cm 3 ≦E≦400cm 3 According to the above relationship, the length and inner radius of the gas guide tube can be set, and the non-metallic gas can be preheated to the reaction temperature through the gas guide tube before being discharged. The discharged gas can maintain a stable temperature, decomposition rate, and appropriate flow rate, thereby improving the uniformity of the non-metallic infiltration treatment of the metal workpiece. The equipment of the present invention allows for the modification processing of a large number of metal workpieces in preforms, and the modification treatment effect of the metal workpieces is relatively good.

Description

[Technical Field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This invention claims priority to a Chinese patent application filed with the State Intellectual Property Office on August 1, 2022, bearing application number 202210916370.4 and entitled "Method for modifying the entire metal workpiece," and a Chinese patent application filed with the State Intellectual Property Office on September 7, 2022, bearing application number 202211091239.5 and entitled "Gas guide assembly for non-metallic infiltration, non-metallic infiltration equipment, and non-metallic infiltration method," the entire contents of which are incorporated herein by reference.

[0002] The present invention belongs to the technical field of medical devices, and in particular to a method for modifying an entire metal workpiece, a gas guide assembly and an apparatus for the modification. [Background technology]

[0003] Because metals and metal alloys often have certain deficiencies or shortcomings in their performance, new nonmetallic elements are often introduced into their surfaces to improve their specific performance. For example, the introduction of nitrogen into the surface of a metal or nonmetal improves its hardness, wear resistance, and corrosion resistance. Nitriding increases the surface hardness of the workpiece, placing the surface under compressive stress, significantly improving the workpiece's wear resistance and fatigue strength, as well as its scratch resistance and corrosion resistance. After sulfurizing a steel surface, a chemical conversion coating containing FeS or FeS + FeS2 can be formed on the steel workpiece surface, effectively reducing the friction coefficient during machining and improving its scratch resistance and seizure resistance. Oxidizing the surface of titanium and titanium alloys improves the wear resistance of the workpiece.

[0004] However, currently disclosed methods for introducing non-metallic elements into workpieces require relatively long processing times and are only suitable for processing workpieces with flat surfaces and simple structures. For workpieces with complex structures or deep holes, it is difficult to ensure uniformity of the introduced elements. For example, a vascular stent is a long, tubular device with a relatively complex structure that is transported through a blood vessel to a lesion, expands to a diameter equivalent to the diameter of the blood vessel at the lesion, and resists the inward contraction force of the blood vessel inner wall. Therefore, the vascular stent itself must have excellent plasticity and backward expansion ability, and must be free from fractures or other abnormalities during expansion. At the same time, it must also have strong radial support, otherwise the blood vessel will not be able to expand and the desired therapeutic effect will not be achieved. This leads to very strict requirements for various process parameters for the processing of preforms or semi-finished products in various manufacturing processes for vascular stents, especially for the modification process of the substrate. Not only must the processing efficiency be high, but the performance of the processed product must also meet requirements, minimizing subsequent medical risks as much as possible.

[0005] In commonly used metal workpiece modification processes, nonmetallic elements such as N, S, and C are introduced into the workpiece to improve its overall performance. However, some existing or traditional methods tend to result in significant differences in the content of nonmetallic elements between the inner and outer walls, ends, and center of the workpiece. For example, traditional nonmetallic introduction methods result in uneven gas flow temperatures. During nitriding of metal workpieces, heated hot air and relatively cool cold air coexist in the generator. When these two gas flows coexist in the generator, the cold air has a higher density than the hot air, causing it to sink to the bottom. The hot air contains more decomposed atomic elements than the cold air. This results in a higher atomic element content in the upper half of the gas flow and a lower atomic element content in the lower half. This results in a higher content of nonmetallic elements infiltrating the upper half of the device and a lower content in the lower half. Ultimately, the nonmetallic element content infiltrating the top and bottom of the metal workpiece is significantly uneven. On the other hand, some metal workpieces have precise and complex structures, especially for metal workpieces with tubular or complex internal structures. Conventional nitriding methods result in a relatively small amount of gas penetrating the inner wall of the metal workpiece, preventing the gas from flowing for replenishment. This results in a low content of nonmetallic elements in the inner wall of the metal workpiece and a high content of nonmetallic elements in the outer wall. The uneven content of nonmetallic elements between the inner and outer walls, and between the top and bottom of the metal workpiece, can easily lead to uneven performance in the various parts of the final modified metal workpiece, potentially causing quality problems for the final metal workpiece during use. For example, if the finished metal workpiece is a medical device, it is likely to cause medical accidents after implantation, resulting in secondary injuries to the patient.

[0006] For metal workpieces with complex structures or deep cavities, existing nonmetallic infiltration equipment has difficulty achieving uniform longitudinal infiltration of the nonmetal, resulting in a much higher nonmetallic content at one end of the preform than at the other end. Furthermore, because the inner lumens of these metal workpieces are relatively narrow, typically with inner diameters of 0.5 to 10 mm, existing nonmetallic infiltration equipment has difficulty achieving a uniform nonmetallic infiltration effect on both the inner and outer walls, resulting in a much higher nonmetallic content at the outer wall of the prefabricated pipe than at the inner wall. Furthermore, existing nonmetallic infiltration equipment is not suitable for large-scale nonmetallic infiltration of metal workpieces. Summary of the Invention [Problem to be solved by the invention]

[0007] In consideration of the above technical problems, the technical solution of the present invention provides a method for modifying an entire metal workpiece, and a gas guide assembly and equipment for the modification. This method for modifying an entire metal workpiece is simple to operate, easy to industrialize, and suitable for processing workpieces requiring highly uniform mechanical properties across each part, i.e., workpieces requiring highly uniform content of infiltrated nonmetallic elements. The method of the present invention has the advantages of simple operation, high element infiltration efficiency, a safe and environmentally friendly preparation process (no toxic by-products are produced, and no toxic or highly polluting substances are used), and low cost. The modified product has the advantages of the newly introduced elements being uniformly distributed throughout the workpiece, having small particle size, and good mechanical properties. The gas guide assembly of the present invention is applicable to the modification of metal workpieces, especially nonmetallic infiltration modification of metal workpieces, and allows the nonmetallic gas to be preheated to the reaction temperature before being discharged through the gas guide pipe. The gas can maintain a stable temperature, stable decomposition rate, and appropriate flow rate, thereby improving the uniformity of the distribution of nonmetallic elements after infiltrating the metal workpiece with the nonmetallic material. The apparatus of the present invention can be used for large-scale non-metallic infiltration treatment of metal workpieces, and also has a relatively good non-metallic infiltration treatment effect. [Means for solving the problem]

[0008] A first aspect of the present invention is a method for modifying an entire metal workpiece, comprising the steps of modifying the metal workpiece by placing it in a gas flow and cooling the modified metal workpiece, The present invention proposes a method for modifying the entire metal workpiece, characterized in that in the modification step, the gas flow is preheated to a temperature close to the modification temperature before flowing onto the surface of the metal workpiece.

[0009] In the present invention, by controlling the temperature of the gas stream after preheating, the temperature difference between the temperature of the gas stream and the temperature of the metal workpiece is minimized, and the concentration difference between the preheated gas stream and the atomic non-metallic elements produced by the decomposition of the existing gas stream near the metal workpiece is further reduced. As a result, by making the content or concentration of the atomic non-metallic elements in the preheated gas stream and the temperature of the gas stream as similar as possible to the gas stream near the metal workpiece, the rate at which the non-metallic elements are introduced to each part of the metal workpiece and the final content introduced are ensured to be as uniform as possible.

[0010] A second aspect of the present invention is a gas guide assembly for modifying a metal workpiece, comprising: The relationship between length and inner radius is E=LR 2 +A gas guide tube, L is the length of the gas guide tube, R is the inner radius of the gas guide tube, E and A are both constants, 0≦A≦5cm 3 , 0.3cm 3 ≦E≦400cm 3 and The gas guide assembly for modifying metal workpieces is proposed, in which the gas flow is preheated to a temperature close to the modification temperature before being passed over the surface of the metal workpiece.

[0011] The gas guide assembly of the present invention has a length L and an inner radius R in the relationship E=LR. 2 + A gas guide tube, where 0≦A≦5 cm 3 , 0.3cm 3 ≦E≦400cm 3According to the above relationship, by setting the length and inner radius of the gas guide tube, the preheating time of the gas within the gas guide tube can be controlled, and the gas can be sufficiently preheated by the gas guide tube to a temperature close to the transformation temperature before being discharged from the gas guide tube, thereby ensuring a stable temperature and decomposition rate of the gas and relatively uniform non-metallic infiltration along the length of the metal workpiece. Furthermore, the above relationship can be used to control the flow rate of the gas after it leaves the gas guide tube. By controlling the gas flow rate within a reasonable range, the gas can be fully in contact with the metal workpiece, avoiding the inefficiency and material waste caused by a flow rate that is too fast and results in insufficient contact, and also avoiding the premature completion of decomposition caused by a flow rate that is too slow and results in non-uniform non-metallic infiltration along the length of the metal workpiece.

[0012] A third aspect of the present invention is a reaction tooling including a heating unit and a reaction unit, the heating unit being provided outside the reaction unit, the reaction unit having a reaction chamber, and an inlet opening in the reaction unit that communicates with the reaction chamber; a cover for closing the intake port through which an air intake hole is provided; We propose an instrument including the above-mentioned gas guide assembly, in which an end of a gas guide tube close to the cover is connected to an air intake hole in the cover, or a gas guide assembly further including the above-mentioned gas diversion member, in which an end of the gas guide assembly remote from the gas diversion member is connected to an air intake hole in the cover.

[0013] The equipment proposed by the present invention includes a reaction tooling, a cover, and a gas guide tube. The reaction tooling includes a heating section and a reaction section. The heating section is located outside the reaction section, and the reaction section has a reaction chamber, which has an inlet opening communicating with the reaction chamber. The cover is used to cover the inlet opening and has an air inlet opening passing through it. The end of the gas guide tube close to the cover is connected to the wall of the air inlet opening. Therefore, the heating section can heat and keep the reaction section warm, providing conditions for the non-metallic infiltration reaction to occur. The metal workpiece enters the reaction chamber through the inlet opening of the reaction section, and the reaction chamber is where the non-metallic infiltration reaction occurs. The cover covers the inlet opening, and the non-metallic gas can enter the reaction chamber through the air inlet opening passing through the cover. The gas guide pipe is connected to the wall of the air inlet opening. The non-metallic gas is preheated to the reaction temperature by the gas guide pipe before being discharged from the gas guide pipe and contacting the metal workpiece to be infiltrated with the non-metallic. In this case, the non-metallic gas preheated and discharged by the gas guide tube has a relatively stable temperature, decomposition rate, and appropriate flow rate, which can improve the uniformity of the surface compound layer on the metal workpiece after non-metallic infiltration treatment in the longitudinal direction.If the non-metallic infiltration equipment includes a gas diverting element, the non-metallic gas flowing out of the gas guide tube can flow into the trunk of the gas diverting element and then out through the branch connected to the trunk.The branch can diverge the non-metallic gas flowing out of the gas guide tube, thereby improving the effect of non-metallic gas diffusion in various directions, allowing more non-metallic gas to enter the lumen of the metal workpiece (tube), improving the non-metallic infiltration effect on the inner wall of the preform (tube), and thereby improving the uniformity of non-metallic infiltration on the inner and outer walls of the metal workpiece (tube). [Brief explanation of the drawings]

[0014] Various other advantages and benefits will become apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments. The drawings are only for the purpose of illustrating the preferred embodiments and are not to be construed as limiting the invention. Like parts throughout the drawings are designated by like reference numerals. [Figure 1]1 is a perspective view of one embodiment of a non-metal infiltration gas guide assembly of the present invention; FIG. [Figure 2a] FIG. 2 is a cross-sectional view of the non-metal infiltration gas guide assembly shown in FIG. 1. [Figure 2b] FIG. 2 is a cross-sectional view of another embodiment of the non-metallic infiltration gas guide assembly of the present invention. [Figure 3a-3c] 1 is a schematic diagram of several embodiments of the non-metallic infiltration equipment of the present invention; [Figure 4a] 1 is a cross-sectional view of a partial structure of one embodiment of a non-metallic infiltration device of the present invention. [Figure 4b] 4b is an enlarged view of part A of the non-metallic infiltration equipment shown in FIG. 4a. [Figure 5a] 10 is a cross-sectional view of a partial structure of another embodiment of the non-metallic infiltration equipment of the present invention. [Figure 5b] 5b is an enlarged view of part B of the non-metallic infiltration equipment shown in FIG. 5a. [Figure 6] 6A and 6B are diagrams showing the metal structure of the iron pipe of Example 3 after nitriding and annealing in a homemade nitriding furnace. Fig. 6A is a photograph showing the metal structure of the tip of the iron pipe of Example 3, Fig. 6B is a photograph showing the metal structure of the center of the iron pipe of Example 3, and Fig. 6C is a photograph showing the metal structure of the end of the iron pipe of Example 3. [Figure 7] 7A and 7B are diagrams showing the metal structure of the iron pipe of Comparative Example 1 after nitriding in a well-type nitriding furnace. Fig. 7A is a photograph showing the metal structure of the tip of the iron pipe of Comparative Example 1, Fig. 7B is a photograph showing the metal structure of the middle of the iron pipe of Comparative Example 1, and Fig. 7C is a photograph showing the metal structure of the end of the iron pipe of Comparative Example 1. DETAILED DESCRIPTION OF THE INVENTION

[0015] Exemplary embodiments of the present invention will now be described in more detail with reference to the drawings. While exemplary embodiments of the present invention are illustrated in the drawings, it should be understood that the present invention can be embodied in various forms and should not be limited to the embodiments described herein. Rather, these embodiments are provided to provide a complete understanding of the present invention and fully convey the scope of the present invention to those skilled in the art. For example, although the examples use the nitridation of vascular stents as an illustrative example, this does not mean that the technical solutions of the present invention are only applicable to vascular stents, nor that the technical solutions of the present invention are only suitable for nitriding, but can also be used for nitriding other types of non-metallic elements. Those skilled in the art will recognize that any modifications and improvements made based on the concept of the present invention are within the scope of protection of the present invention. Unless manufacturers are specified, commercially available conventional reagents and instruments are used.

[0016] The technical solution of the present invention provides a method for modifying an entire metal workpiece, which belongs to the method for infiltrating non-metallic elements, and includes the steps of modifying the metal workpiece by placing it in a gas flow and cooling the modified metal workpiece. In the modification step, the gas flow is preheated to a temperature close to the modification temperature before flowing onto the surface of the metal workpiece to be modified. That is, in the technical solution of the present invention, the gas flow is sufficiently preheated when it flows onto the surface of the metal workpiece to be modified. The closer the preheated temperature is to the modification temperature of the entire metal workpiece, the more uniformly the newly introduced elements will be distributed within the metal.

[0017] The method and location of preheating the gas stream in the present invention are not limited, and the gas stream may be preheated outside the modification generator before flowing into the modification generator, or may be preheated after flowing into the modification generator. Regardless of the method used, the gas stream is preheated and completely decomposed before reaching the surface of the metal workpiece to be modified.

[0018] When the gas stream according to the above technical solution of the present invention is completely decomposed, the decomposition rate of the gas can reach 15%-65%.

[0019] In the present invention, by controlling the temperature of the gas stream after preheating, the temperature difference between the temperature of the gas stream and the temperature of the metal workpiece to be modified is minimized, and the concentration difference between the preheated gas stream and the atomic non-metallic elements produced by the decomposition of the existing gas stream near the metal workpiece to be modified is further reduced.As a result, by making the content or concentration of the atomic non-metallic elements in the preheated gas stream and the temperature of the gas stream as similar as possible to the gas stream near the metal workpiece to be modified, the rate at which the non-metallic elements are introduced to each part of the metal workpiece to be modified and the final content introduced are ensured to be as uniform as possible.

[0020] In the above technical solution of the present invention, the preheating time of the gas flow before flowing onto the surface of the metal workpiece to be modified is 5 to 120 seconds, and even 10 to 100 seconds, and even 12 to 90 seconds. If the preheating time is too short, the gas temperature will be too low, and the relatively cold gas will impinge on the surface of the metal workpiece, affecting the workpiece surface temperature and the content of atomic nonmetallic elements near the workpiece, thereby adversely affecting the uniformity and final performance of the metal workpiece. The gas continues to heat up after flowing onto the metal surface, and because the metal workpiece itself has a certain size, the temperature of the gas flow when it reaches the workpiece will vary from location to location, resulting in different atomic nonmetallic element contents near the workpiece. The content of atomic nonmetallic elements will be lower in low-temperature areas and higher in high-temperature areas. Furthermore, the higher the temperature, the faster the workpiece's transformation speed and the higher the content of infiltrated atoms. As a result, the portion of the metal workpiece where the gas flow first enters will have a low content of nonmetallic elements after transformation, while the portion of the metal workpiece where the gas flow enters later will have a relatively high content of nonmetallic elements after transformation, resulting in uneven content of nonmetallic elements introduced into various portions of the metal workpiece. On the other hand, if the preheating time is too long, the gas decomposition basically reaches equilibrium, and new intermediate products, i.e., atomic nonmetallic elements, are not continuously produced. Consequently, there are no or only small amounts of atomic nonmetallic elements near the workpiece to be transformed, which does not contribute to the transformation of the metal workpiece. This reduces the overall transformation efficiency of the metal workpiece, which in turn increases gas consumption and production costs.

[0021] In the above technical solutions according to the present invention, the difference between the temperature of the gas flow after preheating and the temperature of any part of the workpiece is within 10°C. In the present invention, the temperature of the gas flow after preheating is as close as possible to the temperature of any part of the workpiece, and the temperature difference is as small as possible. In some embodiments, the difference between the temperature of the gas flow after preheating and the temperature of any part of the workpiece is within 8°C. In another embodiment, the temperature difference between the temperature of the gas flow after preheating and the temperature of any part of the workpiece is within 5°C.

[0022] The present invention controls the preheating time and preheating temperature of the gas flow containing non-metallic elements, thereby comprehensively controlling the temperature of the gas flow that reaches the vicinity of the metal workpiece to be modified, as well as the content and concentration of atomic non-metallic elements, so that the gas flow that continuously flows onto the surface of the metal workpiece to be modified is as consistent as possible with the surface temperature and concentration of atomic non-metallic elements of the original metal workpiece to be modified, and the temperature and concentration of decomposed non-metallic atoms in each part of the workpiece to be modified are as consistent as possible, that is, ensuring the uniformity or consistency of the reaction temperature in each part of the workpiece, and also ensuring the uniformity of the concentration of reaction raw materials in each part of the workpiece, thereby ensuring the uniformity of the distribution of atomic elements after decomposition, and further ensuring the uniformity of the amount of non-metallic elements introduced into each part of the workpiece.

[0023] In the above technical solution of the present invention, the temperature difference ΔT of the gas flow at each part of the workpiece to be modified is 10°C or less, further, the temperature difference ΔT of the gas flow at each part of the workpiece to be modified is 8°C or less, and further, the temperature difference ΔT of the gas flow at each part of the workpiece to be modified is 6°C or less. The temperature difference at each part of the workpiece to be modified is related to the temperature of the gas itself, the uniformity of heating at various parts in the modification device, and the size of the workpiece. Only by fully controlling the first two influencing factors and combining them with the third factor, the size of the workpiece to be modified, can the temperature of the workpiece surface be effectively controlled.

[0024] In the present invention, "the temperature difference ΔT of the gas flow at each part of the work to be modified is 10°C or less" means that the difference between the maximum temperature and the minimum temperature at each part of the work to be modified is within 10°C.

[0025] In the above technical solution of the present invention, the flow velocity of the gas flow is 0.5 to 28.0 cm / s, and further, the flow velocity of the gas flow is 0.8 to 27.0 cm / s, 1.0 to 25 cm / s, 0.5 to 20 cm / s, 0.8 to 20 cm / s, 0.8 to 18 cm / s, 0.8 to 15 cm / s, 0.8 to 12 cm / s, 0.8 to 10 cm / s, 0.8 to 8 cm / s, 0.5 to 18 cm / s, 1.0 to 6.5 cm / s, 1.0 to 7.5 cm / s, and further, the flow velocity of the gas flow is 1.2 to 6 cm / s. In the present invention, the content of atomic non-metallic elements in the workpiece to be modified is controlled by controlling the gas flow velocity, but if the flow velocity is too fast, it will affect the adsorption and infiltration of atoms onto the surface of the metal to be modified after decomposition, reducing the efficiency of introducing the non-metallic elements into the workpiece to be modified. If the flow rate is too slow, the decomposition rate of the gas into atomic elements is basically fixed under certain conditions. Therefore, if the gas flow rate is too slow, the gas flow within the modification generator cannot be ensured sufficiently, and the content of atomic non-metallic elements on the surface of the workpiece to be modified cannot always be stable and balanced, resulting in uneven element content introduced into each part of the final modified workpiece. Furthermore, if the flow rate is too slow, the decomposition of the gas flow on the surface of each part of the workpiece will reach an equilibrium state, and no or very little new atomic non-metallic elements will be generated, resulting in a slow modification rate and low introduction efficiency of non-metallic elements. Therefore, the gas flow rate in the present invention is controlled within a relatively optimal range. The flow rate here refers to the flow rate of the gas flow in the ventilation pipe or the flow rate of the gas flow inside the workpiece during the modification process.

[0026] In the present invention, gas flows through all surfaces of the workpiece to be modified, and particularly in non-planar workpieces, the gas flow also flows through the interior. For example, if the workpiece is a vascular stent preform or other tubular structure, there is always a gas flow passing through the workpiece's internal pipeline. Here, the gas flow velocity is 0.5 to 28.0 cm / s, and further, the gas flow velocity may be 0.8 to 27.0 cm / s, 1.0 to 25 cm / s, 0.5 to 20 cm / s, 0.8 to 20 cm / s, 0.8 to 18 cm / s, 0.8 to 15 cm / s, 0.8 to 12 cm / s, 0.8 to 10 cm / s, 0.8 to 8 cm / s, 0.5 to 18 cm / s, 1.0 to 6.5 cm / s, 1.0 to 7.5 cm / s, or even 1.2 to 6 cm / s. This ensures that the atomic non-metallic element contents or concentrations on each surface of the workpiece to be modified are as close or equivalent as possible, or vary only within a relatively narrow range, for example, the difference in atomic non-metallic element contents or concentrations is only 20%, 15%, or 10%. That is, in the present invention, the difference in atomic non-metallic element contents or concentrations on each surface of the workpiece during the entire modification process is maintained within 20%, further maintained within 15%, further maintained within 10%, and even maintained within 5%.

[0027] In the above technical solution according to the present invention, the gas flow introduction amount is 1.5-6 L / h.

[0028] The nonmetallic element described in the present invention includes at least one of N, C, and S. In the present invention, the nonmetallic element may be one of N, C, and S, or two or more of N, C, and S. For example, in some embodiments, C and N are co-infiltrated. In other embodiments, N is infiltrated.

[0029] The non-metallic element described in the present invention is at least one of C and N, and further, the non-metallic element described in the present invention is N. In this case, the method for modifying the entire workpiece refers to a method for modifying the entire workpiece through gas nitriding.

[0030] In the above technical solution of the present invention, the temperature for modifying the entire metal workpiece is 410-950°C, and the processing time is 10 min-5 h. In the present invention, the temperature range for introducing nonmetallic elements also varies slightly depending on the type of nonmetallic element introduced into the workpiece to be modified. For example, if the introduced nonmetallic element is N, the nitriding temperature is 410-570°C, or alternatively, 450-570°C, or alternatively, 490-570°C. If the introduced nonmetallic element is C, the carburizing temperature is relatively high at 800-950°C, or alternatively, 850-950°C, or alternatively, 850-930°C. If the introduced nonmetallic element is S, the sulfurizing temperature is 450-580°C, or alternatively, 480-580°C, or alternatively, 500-560°C. In the present invention, the time for modifying the entire metal workpiece is 10 min to 5 h, further 10 min to 4.5 h, 10 min to 4 h, 10 min to 3.5 h, 10 min to 3 h, and further 10 min to 2.5 h, or 10 min to 2 h.

[0031] The above technical solution of the present invention can further include an annealing step after the introduction of the nonmetallic element. In the present invention, high-temperature annealing is performed after the introduction of the nonmetallic element into the workpiece. This high-temperature annealing process can more uniformly disperse the introduced nonmetallic element in the workpiece to be modified. In the present invention, the annealing temperature is 800-1200°C. When the nonmetallic element is N, the annealing temperature is 800-1000°C and the annealing time is 5 min-5 h. When the nonmetallic element is C, the annealing temperature is 600-1200°C and the annealing time is 20 min-10 h. Furthermore, when the nonmetallic element is N, the annealing temperature is 850-1000°C and the annealing time is 5 min-4.5 h, or when the annealing temperature is 870-1000°C and the annealing time is 5 min-4 h. Furthermore, when the nonmetallic element is N, the annealing temperature is 901-1000°C and the annealing time is 5 min-3 h.

[0032] In the present invention, "cooling" in the "step of placing the metal workpiece in a gas flow to modify it and cooling the modified metal workpiece" refers to removing the modified workpiece and placing it at room temperature to cool it. In the present invention, cooling in air refines the crystal morphology inside the workpiece (the smaller the crystal grain, the larger the crystal grain size), further improving the mechanical properties of the workpiece, increasing the strength of the modified workpiece, and improving its plasticity. In the present invention, "cooling" refers to a cooling temperature near room temperature, in the range of 5 to 40°C. The cooling medium is not particularly limited, and cooling can be performed in air, water, oil, or other media.

[0033] In the above technical solutions according to the present invention, the gas stream comprises at least one of N2, NH3, CO2, CH4, and H2S. In some embodiments of the present invention, the gas stream is one of the above gases. For example, when the element to be introduced is N, the gas stream is NH3. In another embodiment of the present invention, the gas stream is at least two of the above gas streams. For example, when C and N elements are introduced simultaneously, the gas streams are NH3 and CH4.

[0034] The above technical solution of the present invention further includes a step of pre-oxidizing the workpiece to be modified in air at high temperature before introducing the non-metallic element, which in this invention can significantly improve the efficiency of the subsequent introduction of the non-metallic element and significantly shorten the subsequent modification time of the workpiece.

[0035] In the above technical solution of the present invention, the pre-oxidation is performed at 410 to 950°C for 2 to 60 minutes. In the technical solution of the present invention, the specific temperature of the pre-oxidation can be appropriately adjusted within the above range depending on the specific non-metallic element introduced. For example, in some embodiments of the present invention, when the introduced non-metallic element is N, the pre-oxidation time is 410 to 570°C. In another embodiment of the present invention, when the introduced non-metallic element is C, the pre-oxidation time is 450 to 950°C.

[0036] In the above technical solution of the present invention, the metal workpiece includes any of a vascular stent, a non-intravascular stent, an occluder, an orthopedic implant, a spacer, an artificial blood vessel, a dental implant device, a vascular clamp, a dental implant, a respiratory implant, a gynecological implant, a male medical implant, a suture, a valve, a wire preform, and a semi-finished product, and the orthopedic implant includes at least one of a bone nail, a bone plate, a joint, an intramedullary needle, an anchor, a bolt, and an intervertebral fusion cage. For example, in some embodiments of the present invention, the workpiece to be modified is one of a vascular stent semi-finished product, a valve semi-finished product, a bone nail semi-finished product, a bone plate semi-finished product, a joint semi-finished product, an intramedullary needle semi-finished product, an anchor semi-finished product, an intervertebral fusion cage semi-finished product, and a metal wire semi-finished product. In another embodiment of the present invention, the workpiece to be modified is one of a vascular stent preform, a valve preform, a bone nail preform, a bone plate preform, a joint preform, an intramedullary needle preform, an anchor preform, an intervertebral fusion cage preform, and a metal preform.

[0037] The term "preform" used in this specification refers to the upstream raw material of a workpiece. The preform may be a thin, prefabricated strip or rod, with a length of 10 to 1,000 cm. Furthermore, the preform may have an elongated internal cavity, i.e., a prefabricated tube, with an inner diameter of 0.5 to 10 mm. Of course, the preform may also be a workpiece with a simple structure, such as a prefabricated block or piece. For example, a vascular stent preform refers to the upstream raw material of the vascular stent. If the vascular stent is an iron-based vascular stent, the vascular stent preform would be the upstream raw material iron pipe. Semi-finished products refer to the semi-finished products in each processing step. For example, in the case of a vascular stent, semi-finished products of the vascular stent refer to the polished parts after polishing and the galvanized parts after galvanizing, etc.

[0038] The metal workpiece of the present invention is not limited to the metal workpiece of a stent, which is a medical device, but the non-metallic infiltration process using the non-metallic infiltration gas guide assembly of the present invention can also be applied to workpieces of other types of medical devices, and even to metal workpieces in other technical fields (e.g., electronic information technology, computers and automation, instrumentation, materials and mechanical devices).

[0039] The method according to the invention is suitable for the modification of all workpieces with relatively high requirements for the incorporation of elements, and is also suitable for the modification of iron-containing workpieces, and is further suitable for the modification of iron-based medical devices and iron-based vascular stents.

[0040] It should be noted that the metal in the present invention may be a pure metal or an alloy. For example, in some embodiments of the present invention, the metal is pure iron, and in other embodiments, the metal is an iron alloy.

[0041] In this application, the term "specific alloy" refers to an alloy containing a specific element. For example, an iron alloy refers to an alloy containing iron. Furthermore, the term "specific alloy" may refer to an alloy in which the mass or volume content of the "specific element" in the alloy is 0.25% or more, with the remaining 99.75% being composed of any other metallic and / or non-metallic elements. For example, an ferroalloy refers to an alloy in which the mass / volume content of iron in the alloy is 0.25% or more, and similarly applies to others. Furthermore, the term "iron alloy" as used herein includes, but is not limited to, iron-manganese alloy, iron-zinc alloy, iron-magnesium alloy, iron-calcium alloy, iron-zirconium alloy, iron-manganese-carbon alloy, iron-molybdenum alloy, iron-manganese-copper alloy, iron-manganese-silicon-carbon alloy, iron-silicon-manganese alloy, iron-copper alloy, iron-copper-manganese-carbon alloy, iron-gold alloy, iron-silver alloy, iron-manganese-silver alloy, iron-magnesium alloy, iron-hydrogen alloy, iron-phosphorus alloy, iron-sulfur alloy, iron-manganese-carbon alloy, iron-boron alloy, iron-titanium alloy, and iron-titanium-carbon alloy.

[0042] In this application, "pure metal" means that the total content of other impurities in the metal is 0.5 wt.% or less. For example, "pure iron" means that the total amount of other metals and / or non-metals other than iron is 0.5 wt.% or less.

[0043] In the above technical solution of the present invention, the material of the metal workpiece is pure iron or iron alloy, and the material of the workpiece to be modified is pure iron or iron-based alloy with a carbon content of 2.11 wt% or less.

[0044] In the method for modifying an entire workpiece according to the above technical solution of the present invention, the workpiece may be an iron-containing pipe having an inner diameter of 0.3 mm to 12.0 mm. Furthermore, the workpiece may be an iron-containing pipe having an inner diameter of 0.5 mm to 12.0 mm. Furthermore, the workpiece may be an iron-containing pipe having an inner diameter of 0.5 mm to 10.0 mm. In some embodiments of the present invention, the workpiece has a tubular structure with a very small inner diameter, which makes it difficult for gas flow to enter the pipe. This makes it easy for uneven modification of the inner wall of the pipe to occur, resulting in uneven modification of the workpiece and uneven mechanical properties of the workpiece. In some embodiments of the present invention, the inner diameter of the workpiece is 0.5 mm, 1 mm, 1.5 mm, 2 mm, 2.5 mm, 3 mm, 3.5 mm, 4 mm, 4.5 mm, 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, 8.5 mm, 9 mm, 9.5 mm, or 10 mm. In another embodiment of the present invention, the inner diameter of the workpiece is 0.8 mm, 1.3 mm, 1.8 mm, 2.3 mm, 2.8 mm, 3.3 mm, 3.8 mm, 4.3 mm, 4.8 mm, 5.3 mm, 5.8 mm, 6.3 mm, 6.8 mm, 7.3 mm, 7.8 mm, 9.3 mm, or 9.8 mm.

[0045] In the method for modifying the entire workpiece according to the above technical solution of the present invention, the thickness of the workpiece is 0.05 to 8.0 mm, further, the thickness of the workpiece is 0.1 to 7 mm, and further, the thickness of the workpiece is 0.1 to 6.5 mm.

[0046] In the above technical solution of the present invention, the higher the content of the introduced non-metallic elements, the better. If the content of the introduced non-metallic elements is too low, the workpiece will not be sufficiently modified, and various mechanical properties of the workpiece will not meet the specifications. If the content of the introduced non-metallic elements is too high, the workpiece will become both harder and more brittle, making it more prone to fracture and not meeting the requirements. Therefore, the present invention comprehensively combines various parameters to control the final content of the introduced non-metallic elements within a relatively appropriate range.

[0047] In the method for modifying a workpiece according to the above technical solution of the present invention, the content of non-metallic elements introduced into the workpiece by modifying the entire workpiece is 300 to 4000 ppm, and further, the content of non-metallic elements introduced into the workpiece by modifying the entire workpiece in the present invention is 300 to 3500 ppm, and further, the content of non-metallic elements introduced into the workpiece by modifying the entire workpiece in the present invention is 300 to 1500 ppm. For example, if the non-metallic element introduced in the present invention is N, the nitrogen content of the workpiece after nitriding is 300 to 2500 ppm, and further, the nitrogen content of the workpiece after nitriding is 300 to 2000 ppm, and further, the nitrogen content of the workpiece after nitriding is 300 to 1500 ppm.

[0048] The present invention provides a method for modifying a workpiece, particularly an entire iron-containing workpiece, by introducing other non-metallic elements into the workpiece, primarily through gas nitriding or infiltration of other non-metallic elements, to completely improve various mechanical properties of the workpiece.

[0049] The present invention improves the process to sufficiently improve the temperature uniformity of the gas near the modified workpiece, ensuring the consistency of the concentration of decomposed atomic elements and the reaction temperature near each part of the workpiece as much as possible, ultimately improving the stability of the elements introduced at each position of the workpiece, ensuring uniformity of mechanical properties, and reducing medical accidents. The various parts of the workpiece referred to in this invention include the inner and outer walls of the workpiece, as well as the tip, the end corresponding to the tip, and the central part located between the tip and the end. In other words, to fully ensure the uniformity of mechanical properties in each part of the final workpiece, it is necessary to ensure the uniformity of the atomic element concentration along the length of the workpiece and the width corresponding to the length, as well as the uniformity of the atomic element concentration inside and outside the workpiece.

[0050] In the present invention, by introducing a high-temperature annealing process after modifying the workpiece, the non-metallic elements introduced into the workpiece are rearranged at high temperature, further reducing the difference in the content of the newly introduced elements in each part, making the elements introduced in each part more uniform, and also adjusting the size of the crystal shape inside the metal workpiece to make the crystal grains smaller, thereby improving the mechanical properties of the workpiece.

[0051] In the present invention, by introducing a pre-oxidation step before the workpiece modification step, the effect of the subsequent modification can be significantly improved, the modification time and production cost can be significantly reduced, and the modification uniformity of the product can be improved.

[0052] In the present invention, by comprehensively controlling the temperature and time of pre-oxidation and nitriding, the content of non-metallic elements introduced into the workpiece can be controlled within an appropriate range, so that the workpiece has excellent comprehensive properties within this range.

[0053] In the present invention, by improving the cooling conditions after the modification and annealing steps, the crystal structure inside the workpiece can be reduced and the mechanical properties of the workpiece can be improved. For example, if the workpiece is a vascular stent preform, the completed vascular stent will have better plasticity and stronger mechanical properties, which means that the vascular stent's backward expansion ability will be stronger and the vascular stent will be almost impossible to break during backward expansion. In addition, the radial support force for the blood vessel will be stronger, which can effectively support the blood vessel.

[0054] In the present invention, the uniformity of the nitrogen content is measured by the Vickers hardness measurement index, where the higher the nitrogen content, the greater the hardness, and conversely, the lower the nitrogen content, the less the hardness. The uniformity of nitriding throughout the cross section of the iron pipe can be expressed by the nitrogen content.

[0055] In this invention, the "tip" of the workpiece to be modified refers to the part of the workpiece to be modified that is close to the vent, the "end" refers to the part of the workpiece to be modified that is far from the vent, and the "center" of the workpiece to be modified is located between the tip and end of the workpiece to be modified.

[0056] The present invention also provides a gas guide assembly that can be used to modify a metal workpiece, and in particular to perform non-metallic infiltration modification by placing the metal workpiece in a gas stream.

[0057] The gas guide assembly of the present invention will be described by way of example with a metal workpiece modified by non-metallic infiltration.

[0058] The nonmetallic infiltration gas guide assembly can guide a nonmetallic gas. The nonmetallic gas may be a gas nitriding agent, such as ammonia gas, a mixture of ammonia gas / nitrogen gas, or hydrogen gas / nitrogen gas, or a gas carburizing agent, a mixture of a gas carburizing agent / nitriding agent, or a gas sulfurizing agent. There are many types of metal workpieces suitable for nonmetallic infiltration treatment using the nonmetallic infiltration gas guide assembly of the present invention, including the metal workpieces mentioned above, but these will not be repeated here.

[0059] 1 to 4a and 5a, a gas guide assembly 100 for non-metallic infiltration according to the present invention may include a gas guide tube 11. The gas guide tube 11 may be a round tube, a triangular tube, a square tube, a polygonal tube, etc. The gas guide tube 11 may be made of an alloy or quartz material that is resistant to high temperatures and has good thermal conductivity.

[0060] The gas guide tube 11 may have an inner radius. The inner radius of the gas guide tube 11 can be defined as follows: If the gas guide tube 11 is a round tube, the inner radius of the gas guide tube 11 is the radius of the inner wall of the gas guide tube 11; if the gas guide tube 11 is a rectangular tube or other tube other than a round tube, the inner radius of the gas guide tube 11 may be the radius of the circumscribed circle of the inner wall of the gas guide tube 11. Referring to FIGS. 4A and 5A, when the gas guide assembly 100 is attached to the non-metallic infiltration apparatus 200, at least a portion of the gas guide tube 11 is located within the reaction chamber 221 of the non-metallic infiltration apparatus 200. Referring to FIG. 4A, the length L of the gas guide tube 11 can be defined as the length of the portion of the gas guide tube 11 located below the second seal member 26b of the non-metallic infiltration apparatus 200.

[0061] The relation between the length and the inner radius of the gas guide tube 11 is E=LR 2 +A, where L is the length of the gas guide tube 11 and R is the inner radius of the gas guide tube 11. A may be a constant, and 0≦A≦5 cm 3 E can also be a constant, e.g., 0.3 cm 3 ≦E≦400cm 3 Furthermore, 0.5cm 3 ≦A≦4.5cm 3 Furthermore, 1cm 3 ≦A≦4cm 3 A is 0.0.3cm 3 , 0.5cm 3 , 0.7cm 3 , 1cm 3, 1.5cm 3 , 2cm 3 , 3cm 3 , 3.5cm 3 , 4cm 3 , 4.5cm 3 , or 5 cm 3 Furthermore, 0.5 cm 3 ≦E≦350cm 3 Furthermore, 1cm 3 ≦E≦300cm 3 E is 0.3cm 3 , 0.5cm 3 , 1cm 3 , 5cm 3 , 10cm 3 , 50cm 3 , 60cm 3 , 70cm 3 , 80cm 3 , 90cm 3 , 100cm 3 , 120cm 3 , 150cm 3 , 180cm 3 , 200cm 3 , 220cm 3 , 250cm 3 , 280cm 3 , 300cm 3 , 320cm 3 , 350cm 3 , 370cm 3 , 390cm 3 , or 400cm 3 may include, but is not limited to:

[0062] By setting the length and inner radius of the gas guide tube 11 using the above formula, the preheating time of the gas within the gas guide tube 11 can be controlled, allowing the gas to be fully preheated to the reaction temperature by the gas guide tube 11 before being discharged from the gas guide tube 11. As a result, the gas contacting the metal workpiece 3 has a stable temperature and decomposition rate, resulting in relatively uniform non-metallic infiltration (modification) along the length of the metal workpiece 3. The above formula can also be used to control the flow rate of the gas after it leaves the gas guide tube 11. By controlling the gas flow rate within a reasonable range, the gas can be fully contacted with the metal workpiece 3, avoiding the inefficiency and material waste caused by a flow rate that is too fast and results in insufficient contact with the metal workpiece 3, and also avoiding the non-uniform non-metallic infiltration along the length of the metal workpiece 3 caused by a flow rate that is too slow and results in premature completion of decomposition.

[0063] The length of the gas guide tube 11 may be 10 cm or more and 1000 cm or less. Therefore, the gas guide tube 11 has an appropriate length and can be adjusted to fit the size of the metal workpiece 3 to be subjected to the non-metallic infiltration treatment. Furthermore, the length L of the gas guide tube 11 satisfies 15 cm≦L≦700 cm, or even 18 cm≦L≦500 cm. Specifically, the length of the gas guide tube 11 may be 10 cm, 15 cm, 18 cm, 60 cm, 100 cm, 300 cm, 500 cm, 700 cm, 900 cm, or 1000 cm.

[0064] The value of R in the above formula may be the average value of the inner radius of the gas guide tube 11, or the value of the inner radius at any radial cross section of the gas guide tube 11. The inner radius of the gas guide tube 11 may gradually increase along the flow direction of the nonmetallic gas. This allows the gas guide tube 11 to accommodate nonmetallic gases whose volume gradually increases with heating, thereby extending the life of the gas guide tube 11. The inner radius of the gas guide tube 11 may be kept constant, gradually decreased, or alternately increased and decreased.

[0065] The wall thickness of the gas guide tube 11 may be 0.25 mm or more and 25 mm or less. Therefore, the gas guide tube 11 has relatively good pressure resistance and heat transfer capabilities for non-metallic gases. Similarly, the above values may be the average value of the wall thickness of the gas guide tube 11 or the wall thickness value at any radial cross section of the gas guide tube 11. The wall thickness of the gas guide tube 11 may gradually increase along the flow direction of the non-metallic gas. This improves the pressure resistance of the gas guide tube 11 for non-metallic gases whose volume gradually increases due to heat, thereby extending the life of the gas guide tube 11. Furthermore, the wall thickness of the gas guide tube 11 may be 0.5 mm or more and 22 mm or less. Furthermore, the wall thickness of the gas guide tube 11 may be 1 mm or more and 18 mm or less. The wall thickness of the gas guide tube 11 may be kept constant, gradually decreased, or alternately increased and decreased. Specifically, the wall thickness of the gas guide tube 11 may be 0.25 mm, 0.5 mm, 1 mm, 1.5 mm, 2 mm, 3 mm, 5 mm, 8 mm, 10 mm, 15 mm, 18 mm, 20 mm, 22 mm, 24 mm, or 25 mm.

[0066] 3a to 4a, the gas guide tube 11 may have a linear shape, i.e., the gas guide tube 11 may be a straight pipe. Referring to Fig. 5a, the gas guide tube 11 may be a curved pipe, or may be wavy, zigzag, spiral, etc. Therefore, the shape of the gas guide tube 11 is set according to the length of the metal workpiece 3 and the shape of the reaction chamber 221.

[0067] 1-2c and 4a-5b, in some embodiments, the gas guide assembly 100 for non-metallic infiltration of the present invention may further include a gas diverting member 12. The gas diverting member 12 includes a trunk 121 and a branch 122 that communicate with each other. The branch 122 extends radially outward from the trunk 121, and one end of the trunk 121 may communicate with one end of the gas guide tube 11. Therefore, the non-metallic gas flowing through the gas guide tube 11 can flow into the trunk 121 and then out through the branch 122 that communicates with the trunk 121. The branch 122 can diverge the non-metallic gas flowing out of the gas guide tube 11, thereby improving the diffusion effect of the non-metallic gas in each direction. When the metal workpiece 3 has an elongated internal cavity, the gas diverting member 12 can increase the amount of non-metallic gas entering the internal cavity of the metal workpiece (tube) 3, thereby improving the uniformity of non-metallic infiltration into and within the metal workpiece (tube) 3.

[0068] In some embodiments, the gas diverting member 12 and the gas guide tube 11 may be integrally formed, i.e., the trunk 121 may be one end of the gas guide tube 11, and the branches 122 may be spaced apart circumferentially from the end. Alternatively, the gas diverting member 12 and the gas guide tube 11 may be separate. The trunk 121 and the gas guide tube 11 may be nested, welded, glued, fastened, or screwed together.

[0069] The trunk 121 and the branch 122 may be integrally formed. The trunk 121 and the branch 122 may be detachably connected (by welding, adhesive, fastening, screwing, etc.). The shape of the branch 122 may be an arc, for example, approximately a quarter circle, a quarter ellipse, or a quarter egg. Therefore, the smooth curvature can reduce the obstruction of the inner wall of the branch 122 to the flow of the non-metallic gas, thereby further improving the flow effect of the non-metallic gas. The shape of the branch 122 may be straight or may be a folded line (for example, an L-shape).

[0070] The definition of the inner radii of the trunk 121 and the branch 122 can be referred to the gas guide tube 11 described above, and therefore will not be described again. JPEG2025525804000002.jpg31170

[0071] Furthermore, 0.5≦B≦2.5. Furthermore, 0.7≦B≦2. B may be 0.3, 0.35, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, 1.1, 1.2, 1.3, 1.5, 1.8, 2.0, 2.2, 2.5, 2.8, or 3. Furthermore, 0.5mm≦C≦4.5mm. Furthermore, 1mm≦C≦4mm. C may be 0, 0.5mm, 1mm, 1.5mm, 2mm, 2.5mm, 3mm, 3.5mm, 4mm, 4.5mm, or 5mm.

[0072] The above formula allows the flow rate of the gas after it leaves the branch 122 to be controlled within an appropriate range, ensuring sufficient contact of the gas with the metal workpiece 3 and improving the uniformity of non-metallic infiltration of the inner and outer walls of the metal workpiece 3. Specifically, if the radial cross-sectional area of the cavity at the exhaust end 122a (the single area when there is one branch 122, or the total area when there are multiple branches 122) is significantly smaller than the radial cross-sectional area of the cavity in the trunk 121, the flow rate of the gas after it leaves the exhaust end 122a will be significantly greater than the flow rate of the gas within the trunk 121. If the gas flow rate is too fast, the gas will not sufficiently contact the metal workpiece 3 and will move away from the metal workpiece 3, resulting in low reaction efficiency and wasted material. Furthermore, if the gas flow rate is too fast, the impact of the branch 122 on the inner wall will be significant, shortening the life of the branch 122. If the radial cross-sectional area (as defined above) of the cavity at the exhaust end 122a is much larger than the radial cross-sectional area of the cavity at the trunk portion 121, the flow rate of the gas flowing out of the exhaust end 122a will be relatively small, and the gas will be completely decomposed by the time it reaches the other end of the metal workpiece 3, resulting in uneven non-metallic infiltration along the length of the metal workpiece 3.

[0073] The inner radius of the branch 122 may be 0.5 mm or more and 20 mm or less. Furthermore, the inner radius of the branch 122 may be 1 mm or more and 18 mm or less. Furthermore, the inner radius of the branch 122 may be 2 mm or more and 15 mm or less. Specifically, the inner diameter of the branch 122 may be 0.5 mm, 0.8 mm, 1 mm, 1.5 mm, 2 mm, 4 mm, 5 mm, 8 mm, 10 mm, 12 mm, 14 mm, 15 mm, 18 mm, 19 mm, or 20 mm.

[0074] The inner radius of the branch 122 can be constant, gradually increasing, gradually decreasing, or alternately increasing and decreasing. The value of the inner radius of the branch 122 can be the value of the inner radius at the outlet end of the branch 122, or the average value of the inner radii of all the branches 122. Since there can be multiple branches 122, the inner radius of the branch 122 can be the inner radius of a single branch 122 or the average value of the inner radii of all the branches 122. Similarly, in the above formula, the inner radius of the trunk 121 can be the inner radius of the end of the trunk 121 connected to the gas guide tube 11, or the average value of the inner radii of all the branches 121.

[0075] The exhaust end 122a of the branch 122 may be positioned close to one end of the metal workpiece 3. The exhaust end 122a may face one end of the preform 3, i.e., the end face of the exhaust end 122a may face one end face of the metal workpiece 3. This increases the amount of nonmetallic gas flowing into the inner cavity of the metal workpiece (tube) 3, further improving the effectiveness of the nonmetallic infiltration process on the inner wall of the metal workpiece (tube) 3. The end face of the exhaust end 122a may face the end face of the preform 3. The end face of the exhaust end 122a may be parallel to the end face of the preform 3, with the overlapping area of the two end faces equal to the area of the smaller of the two end faces. The exhaust end 122a does not have to face the end face of the metal workpiece 3. The end face of the exhaust end 122a may be parallel to the end face of the metal workpiece 3, or the two may be at least partially offset from each other. The end face of the exhaust end 122a may be angled relative to the end face of the metal workpiece 3. The range of the angle may be greater than 0° and less than 90°. Furthermore, the range of the angle may be greater than 0° and not greater than 60°, or greater than 0° and not greater than 45°. Specifically, the range of the angle may be 10°, 15°, 20°, 30°, 45°, 50°, 60°, 65°, 70°, 80°, or 89°.

[0076] Furthermore, if the area of the end face of the exhaust end 122a is larger than the area of the end face of the metal workpiece 3 (for example, larger than 30%), even if the angle between the two end faces is 90° or even 100° (i.e., the exhaust end 122a does not face the preform 3), the non-metallic gas discharged from the exhaust end 122a can enter the internal cavity of the metal workpiece (tube) 3 in a sufficient amount to achieve a uniform non-metallic infiltration effect.

[0077] 4a and 4b, in some embodiments, the exhaust end 122a of the branch 122 may not extend into the end of the metal workpiece 3 closest to the branch 122. The distance between the exhaust end 122a of the branch 122 and the end of the metal workpiece 3 closest to the branch (shown as H1 in FIG. 4b) may be between 0 and 20 mm. In this configuration, a sufficient amount of gas flowing out from the exhaust end 122a can enter the internal cavity of the metal workpiece (tube) 3, thereby achieving excellent non-metallic infiltration treatment effects on both the inner and outer walls of the metal workpiece (tube) 3. If the distance between the exhaust end 122a of the branch 122 and the end of the metal workpiece 3 closest to the branch 122 exceeds 20 mm, the non-metallic infiltration treatment effect on the inner wall of the metal workpiece (tube) 3 will be insufficient. The distance between the exhaust end 122a of the branch 122 and the end of the metal workpiece 3 remote from the cover 23 may be 0, 2 mm, 5 mm, 10 mm, 15 mm, 18 mm, or 20 mm.

[0078] As another example, referring to FIGS. 5a and 5b, in another embodiment, the exhaust end 122a of the branch 122 may extend into the end of the metal workpiece (tube) 3 closest to the branch 122, and the distance between the exhaust end 122a of the branch 122 and the end of the metal workpiece (tube) 3 closest to the branch 122 (shown as H2 in FIG. 5b) may be greater than 0 and less than or equal to 10 mm. This provides an excellent non-metallic infiltration effect. If the extension distance exceeds 10 mm, the non-metallic infiltration effect at the overlapping portion between the metal workpiece (tube) 3 and the branch 122 may be insufficient. The distance between the exhaust end 122a of the branch 122 and the end of the metal workpiece (tube) 3 far from the cover 23 may be 0.1 mm, 0.3 mm, 0.5 mm, 0.7 mm, 1 mm, 3 mm, 5 mm, 8 mm, 9 mm, or 10 mm.

[0079] Referring to FIGS. 1 to 2b, an opening 121a may be formed at the end of the trunk 121 away from the gas guide tube 11. This allows the nonmetallic gas in the gas guide tube 11 to flow out through the opening 121a, increasing the amount of nonmetallic gas that comes into contact with the outer wall of the metal workpiece (tube) 3. A uniform nonmetallic infiltration effect can be achieved on both the inner and outer walls of the metal workpiece (tube) 3. The definition of the radius of the opening 121a can also refer to the gas guide tube 11 described above. The radius of the opening 121a may be identical to the inner radius of the branch 122. In this case, the end of the trunk 121 away from the gas guide tube 11 may correspond to one branch 122. The gas flowing out from the opening 121a has a relatively appropriate flow rate, further improving the uniformity of nonmetallic infiltration of the inner and outer walls of the metal workpiece (tube) 3. The radius of the opening 121a may be identical to the inner radius of any of the branch 122 or the average of the inner radii of the branch 122. Furthermore, the radius of the opening 121a may be larger or smaller than the inner radius of the branch portion 122. Of course, the end of the trunk portion 121 remote from the gas guide tube 11 may be sealed, and part of the gas flowing out from the exhaust end 122a may overflow onto the outer wall of the metal workpiece (tube) 3.

[0080] 3a to 4a and 5a, the present invention proposes a metal workpiece modification apparatus 200 that can be used to modify metal workpieces, particularly for non-metallic infiltration modification of metal workpieces. Taking non-metallic infiltration modification as an example, the non-metallic infiltration apparatus 200 may include a reaction tooling 20, a cover 23, and a non-metallic infiltration gas guide assembly 100. The reaction tooling 20 may include a heating section 21 and a reaction section 22, and the heating section 21 may be located outside the reaction section 22. The reaction section 22 may have a reaction chamber 221, and the reaction section 22 may have an inlet 222 communicating with the reaction chamber 221. The cover 23 may be used to close the inlet 222, and an air intake hole 231 may be provided therethrough. The non-metallic infiltration apparatus 200 may also include the gas guide tube 11 of the non-metallic infiltration gas guide assembly 100. The end of the gas guide tube 11 closest to the cover 23 may be connected to the wall of the intake hole 231. In this non-metallic infiltration equipment 200, the heating unit 21 may heat and maintain the temperature of the reaction unit 22, providing conditions for the non-metallic infiltration reaction to occur. The metal workpiece 3 enters the reaction chamber 221 through the intake port 222 of the reaction unit 22, and the reaction chamber 221 is where the non-metallic infiltration reaction occurs. The cover 23 closes the intake port 222, and the non-metallic gas can enter the reaction chamber 221 through the intake hole 231 that penetrates the cover 23. The end of the gas guide tube 11 closest to the cover 23 is connected to the wall of the intake hole 231. As described above, the nonmetallic gas is preheated to a reaction temperature by the gas guide tube 11 before being discharged from the gas guide tube 11 and contacting the metal workpiece 3 to be infiltrated. In this case, the nonmetallic gas preheated and discharged by the gas guide tube 11 has a stable temperature and decomposition rate and an appropriate flow rate, thereby improving the uniformity of the surface compound layer along the length of the metal workpiece 3 after nonmetallic infiltration. Therefore, the nonmetallic infiltration equipment 200 can achieve a relatively good nonmetallic infiltration effect on the elongated metal workpiece 3. In addition, because the gas guide tube 11 is connected to the cover 23, the gas guide tube 11 and the cover 23 can move simultaneously, improving work efficiency and convenience.

[0081] The non-metallic infiltration equipment 200 may further include a gas diverting member 12 of the non-metallic infiltration gas guide assembly 100. The end of the gas guide tube 11 remote from the cover 23 may be connected to the trunk 121 of the gas diverting member 12. The branch 122 of the gas diverting member 12 can diverge the non-metallic gas flowing out of the gas guide tube 11, thereby improving the gas diffusion effect in all directions, increasing the amount of gas entering the internal cavity of the metal workpiece (tube) 3, and improving the uniformity of the surface compound layer on the inner and outer walls of the metal workpiece (tube) 3. Therefore, the non-metallic infiltration equipment 200 can achieve a relatively good non-metallic infiltration effect for a metal workpiece (tube) 3 with an elongated internal cavity.

[0082] In the non-metallic infiltration equipment 200, the heating unit 21 and the reaction unit 22 may be integrally formed or detachably connected. The heating unit 21 may be provided on the outer periphery of the reaction unit 22, i.e., at least a portion of the reaction unit 22 may be located within the heating unit 21, thereby allowing the heating chamber 211 to heat the reaction unit 22 uniformly and achieving a better heating effect. The heating unit 21 may be provided on one surface of the reaction unit 22, such as the upper surface, lower surface, or peripheral surface.

[0083] 3a to 4a and 5a, the heating unit 21 may be a heating furnace. The heating unit 21 may have a heating chamber 211, and the reaction unit 22 may be located within the heating chamber 211 for heating. Thus, the heating unit 21 can provide a relatively good heating effect to the reaction unit 22. The shape of the heating chamber 211 may be set to match the shape of the reaction unit 22. The shape of the heating chamber 211 may be an elongated cylinder, and the cross section of the heating chamber 211 may be triangular, circular, square, or polygonal. The heating unit 21 may include a heat-generating member 213. The heat-generating member 213 may be provided between the furnace wall of the heating unit 21 and the heating chamber 211. The heating member 213 may be provided spirally around the heating chamber 211, thereby improving the heating effect. The heating member 213 may be provided on one side of the heating chamber 211, such as the top, bottom, or peripheral surface. The heating element 213 may be a heating coil or a flame gun.

[0084] 3a to 3c, the heating unit 21 may have an opening 212 communicating with the heating chamber 211, and the reaction unit 22 can enter and exit the heating chamber 211 through the opening 212. The opening 212 may be provided on the top, side, or bottom surface of the heating unit 21. The shape of the opening 212 may be circular, polygonal, square, irregular, or the like.

[0085] 3a to 4a and 5a, the reaction section 22 may be in the shape of an elongated cylinder, and the cross section of the reaction section 22 may be in the shape of a triangle, a circle, a square, or a polygon. The reaction section 22 may be made of a high-temperature resistant alloy or a quartz material. The reaction section 22 may be made of a transparent or translucent material, which allows for easy observation of each component located within the reaction section 22 and better control of the non-metallic infiltration process.

[0086] 4a and 5a, the reaction section 22 may have a reaction chamber 221. The shape of the reaction chamber 221 may be set to match the shape of the preform 3, and the reaction chamber 221 may be in the shape of an elongated cylinder, and the cross section of the reaction chamber 221 may be in the shape of a triangle, a circle, a square, or a polygon. In this way, the reaction section 22 has a relatively good non-metallic infiltration effect on the preform 3.

[0087] 3a to 4a and 5a, the reaction unit 22 may have an inlet 222 communicating with the reaction chamber 221. The inlet 222 may be provided on the top, side, or bottom surface of the heating unit 21. The shape of the inlet 222 may be circular, polygonal, square, irregular, or the like.

[0088] 3a to 4a and 5a, cover 23 may be used to close intake port 222. Cover 23 may be plate-shaped, and the shape of cover 23 may be set to match the shape of intake port 222, and may be, for example, a circular plate, a square plate, a polygonal plate, or an irregular-shaped plate. Cover 23 may be made of an alloy or quartz material.

[0089] 4A and 5A, an air intake hole 231 may be formed through the cover 23. The shape of the air intake hole 231 may be circular, square, polygonal, or irregular. The end of the gas guide tube 11 closest to the cover 23 may communicate with the air intake hole 231 of the cover 23. When one end of the gas guide tube 11 is connected to the gas diverting member 12, the end of the gas guide tube 11 remote from the gas diverting member 12 may communicate with the air intake hole 231. Specifically, the one end of the gas guide tube 11 may communicate with the wall of the air intake hole 231. The air intake hole 231 may be a through-hole, and the wall of the air intake hole 231 may extend outside the cover 23. The wall of the air intake hole 231 may extend away from and / or close to the reaction region 22. This improves the connection between the wall of the air intake hole 231 and the gas guide tube 11. The air intake hole 231 does not have to extend outside the cover 23. The end of the gas guide tube 11 connected to the cover 23 can extend outside the air intake hole 231 or can be located inside the air intake hole 231. The gas guide tube 11 and the air intake hole 231 can be welded together, which improves the sealing of the connection between the gas guide tube 11 and the air intake hole 231. The gas guide tube 11 and the air intake hole 231 can also be nested, glued, fastened, or screwed together.

[0090] 4a and 5a, in some embodiments, the cover 23 may be provided with a blow-out hole 232 penetrating therethrough. The shape of the blow-out hole 232 may be circular, square, polygonal, irregular, or the like. The blow-out hole 232 may be a through-hole, and the hole wall of the blow-out hole 232 may extend away from the reaction section 22. Therefore, a transfer pipe for transferring the exhaust gas can be easily connected to the hole wall of the blow-out hole 232. The hole wall of the blow-out hole 232 does not need to extend outside the cover 23, or may extend in a direction approaching the reaction section 22. In another embodiment, the blow-out hole 232 may open to the reaction section 22 and communicate with the reaction chamber 221.

[0091] The detachable connection of the heating section 21, the reaction section 22, and the cover 23 can improve the efficiency and effectiveness of the nonmetallic infiltration process. Specifically, referring to FIGS. 3a-4a and 5a, while the heating section 21 is being heated to the reaction temperature, the reaction section 22, the cover 23, the gas guide tube 11, and the metal workpieces 3 can be assembled outside the reaction chamber 221 for pre-treatment preparation. The assembly of the cover 23 and the reaction section 22 can be achieved by moving the cover 23 toward the inlet 222, by moving the reaction section 22 to bring the inlet 222 closer to the cover 23, or by moving the cover 23 and the reaction section 22 toward each other. After the reaction is complete, the reaction section 22, the cover 23, the gas guide tube 11, and the metal workpieces 3 are removed from the heating chamber 211 and cooled, while the heating section 21 is used to perform the nonmetallic infiltration reaction of the next batch of metal workpieces 3. Therefore, multiple processes can be performed simultaneously and independently. This non-metallic infiltration equipment 200 can be used for large-scale non-metallic infiltration treatment of metal workpieces 3. When the heating section 21 reaches the reaction temperature, the assembled reaction section 22, cover 23, gas guide tube 11, and metal workpiece 3 are placed in the heating chamber 211, and the reaction chamber 221 rapidly heats up, and the non-metallic gas discharged from the gas guide tube 11 has been preheated to the reaction temperature by the gas guide tube 11. The gas has a stable temperature and decomposition rate, and an appropriate flow rate, thereby achieving a relatively good non-metallic infiltration treatment effect.

[0092] 4a and 5a, as described above, the non-metallic infiltration equipment 200 of the present invention may include a fixing member 24, which may be connected to the gas guide tube 11 and used to fix the metal workpiece 3. Thus, the cover 23, the gas guide tube 11, the fixing member 24, and the metal workpiece 3 can move together, thereby improving the efficiency and convenience of operation. The fixing member 24 may be connected to one end of the gas guide tube 11 (or the metal workpiece 3) or to the center of the gas guide tube 11 (or the metal workpiece 3).

[0093] The fixing member 24 may be made of a high-temperature resistant alloy material or a quartz material. The fixing member 24 may include a sub-fixing member (described in detail below). The number of the sub-fixing members may be one or at least two, and the at least two sub-fixing members may be spaced apart along the axial direction of the gas guide tube 11. The at least two sub-fixing members may be fixing plates, fixing rods, fixing grooves, or fixing frames, respectively. The at least two fixing members may have the same or different structures.

[0094] 4a and 5a, when the non-metallic infiltration equipment 200 includes the gas diverting member 12, the fixing member 24 may direct the end of the preform (tube) 3 away from the cover 23 toward the exhaust end 122a of the branch 122. This allows the gas flowing out from the exhaust end 122a to directly flow into the internal cavity of the metal workpiece (tube) 3, thereby increasing the amount of gas flowing into the internal cavity of the metal workpiece (tube) 3, improving the non-metallic infiltration effect on the inner wall of the metal workpiece (tube) 3, and improving the uniformity of the non-metallic infiltration on the inner and outer walls of the metal workpiece (tube) 3.

[0095] 4A and 5A, in some embodiments, as described above, the fixing member 24 may include a first sub-fixing member 241. The first sub-fixing member 241 may be connected to an end of the gas guide tube 11 remote from the cover 23, or may be connected to a central portion of the gas guide tube 11. The first sub-fixing member 241 is a fixing plate having a fixing hole 241a formed therethrough, and the outer wall of the gas guide tube 11 may be connected to the hole wall of the fixing hole 241a. The fixing hole 241a may be a fixing through-hole, which can improve the connection strength between the gas guide tube 11 and the first sub-fixing member 241. The hole wall of the fixing hole 241a may extend toward the cover 23 or away from the cover 23. One end of the gas guide tube 11 may or may not extend outside the fixing hole 241a. The gas guide tube 11 and the hole wall of the fixing hole 241a may be welded, nested, engaged, glued, or screwed together.

[0096] 4a to 5b, the first sub-fixing member 241 may be provided with a fixing groove 241b, which can fix the end of the preform 3 remote from the cover 23. The fixing groove 241b may be formed such that the surface of the first sub-fixing member 241 closest to the cover 23 is recessed in a direction away from the cover 23, i.e., the notch of the fixing groove 241b faces the cover 23. This prevents the fixing groove 241b from occupying extra space or interfering with the flow of non-metallic gas, improving the effectiveness of the non-metallic infiltration process. The shape of the fixing groove 241b may be set to match the preform 3. The fixing groove 241b and the preform 3 may be in contact with each other or engaged with each other. A vent hole 241c may be formed through the bottom of the fixing groove 241b, and gas may enter the preform 3 through this vent hole 241c. The radius of the vent hole 241c may be larger, the same as, or smaller than the inner radius of the exhaust end 122a of the branch portion 122. The shape of the vent hole 241c may be circular, rectangular, triangular, waist-shaped, polygonal, or irregular. The number of vent holes 241c may be one or more. The fixing groove 241b may be formed so that the surface of the first sub-fixing member 241 closest to the cover 23 extends toward the cover 23. That is, the fixing groove 241b protrudes from the surface of the first sub-fixing member 241 closest to the cover 23. The fixing groove 241b and the first sub-fixing member 241 may be detachably connected by, for example, adhesive, welding, or fastening. The first sub-fixing member 241 may fix the center of the preform 3, and the fixing groove 241b may be an attachment through-groove, and the preform 3 may be inserted through the fixing groove 241b.

[0097] Referring to FIG. 4a, in some embodiments, the fixing member 24 may further include a second sub-fixing member 242. The method for connecting the second sub-fixing member 242 to the gas guide tube 11 can refer to the first sub-fixing member 241 described above, and the second sub-fixing member 242 may also be a fixing plate. While the first sub-fixing member 241 fixes the end of the metal workpiece 3 far from the cover 23, the second sub-fixing member 242 can fix the end of the metal workpiece 3 closer to the cover 23. Therefore, post-processing only requires cutting both ends of the metal workpiece 3, reducing the complexity of post-processing the metal workpiece 3. The second sub-fixing member 242 may also be connected to the center of the metal workpiece 3. The second sub-fixing member 242 may abut against the metal workpiece 3, or the second sub-fixing member 242 may have a through-hole formed therethrough, and the metal workpiece 3 may pass through the through-hole and partially abut against the wall of the through-hole. The diameter of the through-hole may be significantly larger than the outer diameter of the metal workpiece 3, allowing the non-metallic gas to flow into the gap between the through-hole and the metal workpiece 3, thereby achieving a better non-metallic infiltration effect. The diameter of the through-hole may be slightly larger than the outer diameter of the metal workpiece 3. The provision of the second auxiliary fixing member 242 can improve the stability of the elongated metal workpiece 3 when it is placed in the reaction chamber 221.

[0098] 5a, in another embodiment, the fixing member 24 may include a first sub-fixing member 241 and a third sub-fixing member 243. The third sub-fixing member 243 may be a fixing frame with both ends open, or a fixing cylinder with a plurality of holes in its peripheral wall. The end of the third sub-fixing member 243 close to the first sub-fixing member 241 may be connected to the first sub-fixing member 241, and the end face of the third sub-fixing member 243 may face the notch of the fixing groove 241b. In addition, the provision of the third sub-fixing member 243 can improve the stability when the metal workpiece 3 is placed in the reaction chamber 221.

[0099] As described above, the cover 23 can move toward the reaction unit 22, and the reaction unit 22 can move toward the cover 23 and the heating unit 21. There are various methods for driving the movement of the cover 23 and the reaction unit 22, for example, they can be driven manually. As another example, they can be driven by a cylinder. Specifically, there may be two cylinders, and the drive shafts of the two cylinders may be connected to the cover 23 and the reaction unit 22, respectively. As another example, they can be driven by a motor. In some embodiments, the motor may be connected to a robot arm, and there may be two robot arms, each connected to the cover 23 and the reaction unit 22. The robot arm may include multiple sub-arms connected to each other via mechanical joints. At least one sub-arm can swing in different planes (such as a horizontal plane and a vertical plane) around the mechanical joint and may include a clamping unit for clamping / releasing the cover 23 and the reaction unit 22. In another embodiment, the motor may be connected to a slider, and the number of sliders may be two, each connected to the cover 23 and the reaction section 22, and the sliders can drive the movement of the cover 23 and the reaction section 22 by sliding along guide rails.

[0100] 3a to 3c, the non-metallic infiltration equipment 200 of the present invention may further include a driving device 25. The driving device 25 may include a first driving unit 251. A side (end) of the first driving unit 251 close to the cover 23 may be connected to the cover 23. The first driving unit 251 and the cover 23 may be joined by welding, screwing, fastening, adhesive, or the like. The driving device 25 may further include a second driving unit 252 connected to the reaction unit 22. The second driving unit 252 and the reaction unit 22 may also be joined by welding, screwing, fastening, adhesive, or the like. As described above, the driving device 25 may include a cylinder, and the first driving unit 251 and the second driving unit 252 may be drive shafts connected to the cylinder. The driving device 25 may include a motor, and the first driving unit 251 and the second driving unit 252 may be mechanical arms or sliders connected to the motor. The first driving unit 251 can drive the cover 23 to move in and out of the reaction chamber 221 through the inlet 222. The second driving unit 252 can drive and move the reaction unit 22 to move the inlet 222 closer to or farther away from the cover 23, or move the reaction unit 22 in and out of the heating chamber 211 through the opening 212.

[0101] Referring to FIGS. 3a to 3c, in some embodiments, the drive device 25 may further include a guide rail 253. The guide rail 253 may include a first sub-portion 253a extending along a first direction and a second sub-portion 253b extending along a second direction, and the angle between the first direction and the second direction may be greater than 0° and less than or equal to 90°. Referring to FIG. 3c, in some embodiments, the first direction is parallel to the horizontal direction, the second direction is perpendicular to the horizontal direction, the number of second sub-portions 253b may be multiple, and the second sub-portions 253b may be spaced apart along the first direction. The guide rail 253 may include slide grooves 253c, and the slide grooves 253c may extend along a predetermined direction. The predetermined direction may be the extension direction of the guide rail 253, i.e., the predetermined direction may include the first direction and the second direction. The first driving portion 251 and the second driving portion 252 may be sliders, and are slidably connected to the slide grooves 253c, respectively.

[0102] The non-metallic infiltration apparatus 200 of the present invention may include a sealing structure. Referring to FIGS. 4a and 5a, the non-metallic infiltration apparatus 200 of the present invention may include a first sealing member 26a. When the cover 23 closes the inlet 222, the first sealing member 26a can seal the gap between the cover 23 and the inlet 222, thereby preventing outside air from entering the reaction chamber 211 of the reaction unit 22 and achieving a better non-metallic infiltration effect. The first sealing member 26a may be provided on the cover 23, for example, on the side of the cover 23 close to the inlet 222 or on the outer periphery of the cover 23. The first sealing member 26a may also be provided on the inlet 222 of the reaction unit 22. Two first sealing members 26a may be provided, one on the cover 23 and one on the reaction unit 22, or they may be provided on the same component. Two or more first sealing members 26a may be provided. The first seal member 26a can be made of at least one of high temperature resistant rubber, fire resistant wool, asbestos, quartz fiber, and aerogel.

[0103] 4a and 5a, the non-metallic infiltration equipment 200 of the present invention may include a second seal member 26b. When the cover 23 closes the inlet 222, the second seal member 26b can be positioned within the reaction chamber 221 to seal the reaction chamber 221. This allows the reaction chamber 221 to have a relatively good thermal insulation effect, thereby achieving a relatively good non-metallic infiltration effect. The second seal member 26b may be connected to the gas guide tube 11 and may be located near the cover 23. When the cover 23 drives the gas guide tube 11 to enter the reaction chamber 221, the gas guide tube 11 can drive the second seal member 26b, the fixing member 24, and the metal workpiece 3 fixed to the fixing member 24 together into the reaction chamber 221, thereby preventing the second seal member 26b from blocking the metal workpiece 3 from entering the reaction chamber 221. The shape of the second seal member 26b may be set to match the shape of the reaction chamber 221, and for example, the second seal member 26b may be a circular block, a square block, or a polygonal block.

[0104] The second seal member 26b may be a refractory brick. The thickness of the second seal member 26b may be 20 mm or more and 150 mm or less. Furthermore, the thickness of the second seal member 26b may be 30 mm or more and 140 mm or less. Furthermore, the thickness of the second seal member 26b may be 40 mm or more and 130 mm or less. The thickness of the second seal member 26b may be 20 mm, 30 mm, 32 mm, 40 mm, 45 mm, 55 mm, 65 mm, 75 mm, 90 mm, 110 mm, 120 mm, 130 mm, 135 mm, 140 mm, or 150 mm. The second seal member 26b may be made of at least one of silicon, carbon, zirconium, aluminum, aluminum silicate, magnesium, magnesium-calcium, magnesium-chromium, magnesia-aluminum, or magnesium-silicon refractory materials.

[0105] 4a and 5a, the non-metallic infiltration equipment 200 of the present invention may further include a third seal member 26c. When the reaction section 22 is located within the heating chamber 211, the third seal member 26c can be positioned at the opening 222 to seal the heating chamber 211. Referring to FIGS. 5 and 7, the third seal member 26c may be provided in a portion of the heating chamber 211 near the opening 222 and fill the gap between the heating chamber 211 and the reaction section 22 to seal the heating chamber 211. In another embodiment, the third seal member 26c may be provided outside the heating chamber 211. A boss (not shown) extending circumferentially of the reaction section 22 may be provided on the outer wall of the reaction section 22 near the inlet 222, and the third seal member 26c may be positioned between the heating section 22 and the boss to seal the heating chamber 211. A single third seal member 26c may be provided in either the reaction section 22 or the heating section 21. There may be two third seal members 26c, and they may be provided in the reaction unit 22 and the heating unit 21, respectively, or they may be provided in the same component. The number of third seal members 26c may be two or more. The second seal member 26b may also be made of at least one material selected from the group consisting of high-temperature resistant rubber, fire-resistant wool, asbestos, quartz fiber, and aerogel.

[0106] In the technical solution according to the present invention, the non-metallic infiltration method carried out by the above non-metallic infiltration equipment 200 may include the following steps: S0: Set the heating unit 21 to heat up to the nonmetallic infiltration reaction temperature. S1: Place the gas guide tube 11, the fixing member 24 (if present), and the metal workpiece 3 in the reaction chamber 221 of the reaction unit 22, close the reaction chamber 221 with the cover 23, and move the assembled cover 23, reaction unit 22, gas guide tube 11, fixing member 24 (if present), and metal workpiece 3 into the heating chamber to carry out the nonmetallic infiltration reaction. S2: After the nonmetallic infiltration reaction is completed, evacuate the reaction chamber 221 or fill it with an inert gas (e.g., argon gas, helium gas, or nitrogen gas), change the temperature of the heating chamber 211 to the annealing temperature, and carry out the annealing reaction. S3: After the annealing reaction is completed, remove the assembled reaction unit 22, cover 23, gas guide tube 11, fixing member 24 (if present), and metal workpiece 3 from the heating chamber and allow them to cool. After cooling is complete, remove the metal workpiece 3 with the nonmetallic infiltration reaction completed from the reaction chamber 221.

[0107] In this specification, the terms "within," "greater than," "less than," and "outside" include the numerical values themselves unless otherwise specified. For example, "the difference between the decomposition rate of the gas flow after preheating and the decomposition rate of the gas flow existing on the surface of the workpiece to be modified is within 10%" means that the difference between the decomposition rate of the gas flow after preheating and the decomposition rate of the gas flow existing on the surface of the workpiece to be modified is 10% or less than 10%. In other words, the value of 10% is also included.

[0108] It is to be understood that the terminology used herein is for the purpose of describing particular exemplary embodiments only and is not intended to be limiting. As used herein, the singular forms "a," "an," and "said" are intended to include the plural forms unless the context clearly dictates otherwise. The terms "comprise," "include," "contain," and "have" are inclusive and thus indicate the presence of stated features, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, steps, operations, elements, components, and / or combinations thereof. Method steps, processes, and operations described herein should not be construed as requiring performance in the particular order described or illustrated, unless an order of performance is explicitly indicated. It is also to be understood that additional or alternative steps may be employed.

[0109] Test Method The test methods for each parameter in the present invention are as follows. 1. Vickers hardness test The samples were mounted in resin and polished, and then tested according to the standard “GB / T 4340.1-2012 Vickers hardness test for metallic materials.”

[0110] 2. Nitrogen content test Tests were conducted in accordance with the standard "GB / T 20124-2006 Determination of Nitrogen Content in Steel - Inert Gas Fusion Thermal Conductivity Method."

[0111] 3. Crystal grain size test The samples were mounted in resin, polished, and etched in a 4% nitric acid alcohol solution for 10 seconds. They were then photographed and observed under a metallurgical microscope, and the photographs were tested in accordance with the standard "GB / T 6394-2017 Method for Determining Average Crystal Grain Size."

[0112] 4. Testing various sizes of iron pipes The diameter parameters of the iron pipes were measured with a laser caliper, the wall thickness was measured with a three-dimensional microscope, and the length was measured with a metric ruler or calipers.

[0113] Example 1 3a, 3b, 4a and 5b, when nitriding the same batch of preforms 3, the method of use of the non-metallic infiltration apparatus 200 may be as follows. S0: Heat the heating chamber 211 to the non-metallic infiltration reaction temperature and keep it at that temperature. S1: The preform 3 is placed between the second sub-fixing member 242 and the first sub-fixing member 241. S2: The cover 23 is driven by the first driving unit 251 to move from the first position to the second position. S3: Ammonia gas is introduced into the reaction chamber 221 through the gas guide tube 11, and air within the reaction chamber 221 is discharged from the blowout holes 232. S4: The cover 23 is driven by the first driving unit 251, and the reaction unit 22 is driven by the second driving unit 252, and both are moved from the second position to the third position. S5: Preheated ammonia gas is discharged into the reaction chamber 221 via the gas guide tube 11, and is decomposed at high temperature to obtain active nitrogen ions, which are used to nitride the outer and inner tube walls of the preform 3. S6: After the nitriding reaction is completed, the reaction section 22 is evacuated. S7: The temperature of the heating chamber 211 is changed to the annealing temperature and kept at that temperature, and annealing for the nitriding reaction is carried out. S8: When the annealing is completed, the cover 23 is driven by the first driving unit 251, and the reaction unit 22 is driven by the second driving unit 252, and both are returned from the third position to the second position, and cooled. S9: Once cooling is complete, stop the vacuum suction and break the vacuum. S10: The cover 23 is driven by the first drive unit 251 to return from the second position to the first position. S11: The preform 3 after the nitriding treatment is taken out.

[0114] <Example 2> 3c, 4a and 5a, when nitriding multiple batches of preforms 3, the method of use of the non-metallic infiltration apparatus 200 may be as follows. S1: The first batch of preforms 3 is nitrided in the same manner as in the processes S0 to S5 of Example 1. S2: The first batch of preforms 3 is nitrided, and at the same time, a second batch of preforms 3 is prepared in the same manner as in the processes S0 to S3 of Example 1. S3: After the nitriding reaction is completed, the first batch of preforms 3 is annealed and cooled in the same manner as in the processes of S6 to S8 in Example 1. S4: The second batch of preforms 3 is nitrided in the same manner as in the processes of S4 and S5 in Example 1. S5: While the second batch of preforms 3 is being nitrided, a third batch of preforms 3 is prepared while monitoring whether the first batch of preforms 3 has been completely cooled. S6: When the cooling of the first batch of preforms 3 is complete, similar to S9 to S11 in Example 1, the vacuum suction is stopped, the vacuum is broken, the preforms 3 are removed, and preforms 3 for which the nitriding treatment has been completed are obtained. S7: Repeat the process of the first batch of preforms 3 for the second batch of preforms 3 and subsequent batches of preforms 3.

[0115] Example 3 In this example, the entire metal workpiece was modified using the non-metallic infiltration equipment 200. Taking the same batch as an example, an iron pipe was used as the metal workpiece. The iron pipe was a cold-drawn pipe with an outer diameter of 6 mm, a wall thickness of 0.5 mm, and an inner diameter of 5 mm. The longitudinal metal structure showed deformation. Ammonia gas was used as the nitrogen flow for nitriding. 1. The iron pipe was cleaned to remove oil, rinsed with alcohol to remove any remaining moisture on the surface, dried with an air gun, and then placed vertically in the nitriding equipment 200 and fixed in place. 2. The equipment was started and pre-oxidation treatment was carried out at 570°C for 30 minutes, and after the oxidation was completed, it was cooled in air. 3. The nitriding parameters were set as follows: ammonia gas flow rate 6 L / h, flow velocity 8 cm / s, preheating time 5 s, ammonia decomposition rate 20%, nitriding time 2 h, nitriding temperature 570 °C, and temperature difference between the tip and end of the iron pipe 10 °C. After nitriding was completed, the iron pipe was taken out and cooled in air to obtain a nitrided iron pipe sample. 4. After nitriding, the iron pipe was annealed in a high-temperature annealing furnace at 800°C for 10 minutes, and after annealing was completed, it was cooled in air, completing the nitriding annealing of the iron pipe. Using a grinding stone cutter, approximately 500g of iron pipe samples were cut from the tip, center, and end to serve as nitrogen content test samples, 1cm samples were cut from the tip, center, and end to serve as hardness test samples, and 1cm samples were cut from the tip, center, and end to prepare metal structure samples. The nitrogen content data was measured using an ONH analyzer, and the hardness data of three hardness samples was tested using a Vickers hardness tester. Three metallographic samples were polished using an automatic polishing machine and etched using a 4% nitric acid alcohol solution for 10 seconds to obtain metallographic samples. The metallographic structures were observed using a metallographic microscope, and the metallographic photographs and grain size data are shown below. JPEG2025525804000003.jpg49170

[0116] Example 4 The iron pipe used in this example was drawn from a pipe material. The iron pipe was in a cold drawn state, with an outer diameter of φ6 mm, a wall thickness of 0.5 mm, and an inner diameter of 5 mm. Deformed structures were observed in the longitudinal metal structure, and ammonia gas was used as the nitrogen flow for nitriding. 1. The iron pipe was cleaned to remove oil, rinsed with alcohol to remove any remaining moisture on the surface, dried with an air gun, and placed vertically in the nitriding equipment 200. 2. The equipment was started and pre-oxidation treatment was carried out at a pre-oxidation temperature of 470°C for 2 minutes. After oxidation was completed, the equipment was cooled in air. 3. The nitriding parameters were set as follows: ammonia gas flow rate 1.5 L / h, ammonia gas flow rate 0.5 cm / s, preheating time 120 s, ammonia decomposition rate 65%, nitriding time 10 min, nitriding temperature 470°C, and temperature difference between the tip and end of the iron pipe 0.8°C. After nitriding was completed, the iron pipe was taken out and cooled in air to obtain a nitrided iron pipe sample. 4. After nitriding, the iron pipe was annealed in a high-temperature annealing furnace at an annealing temperature of 1200°C for 2 hours, and after annealing was completed, it was cooled in air, completing the nitriding annealing of the iron pipe. Using a grinding stone cutter, approximately 500g of iron pipe samples were cut from the tip, center, and end to serve as nitrogen content test samples, 1cm samples were cut from the tip, center, and end to serve as hardness test samples, and 1cm samples were cut from the tip, center, and end to prepare metal structure samples. The nitrogen content data was measured using an ONH analyzer, and the hardness data of three hardness samples was tested using a Vickers hardness tester. Three metallographic samples were polished using an automatic polishing machine and etched using a 4% nitric acid alcohol solution for 10 seconds to obtain metallographic samples. The metallographic structures were observed using a metallographic microscope, and the metallographic photographs and grain size data are shown below. JPEG2025525804000004.jpg50170

[0117] <Example 5> The iron pipe used in this example was drawn from a pipe material. The iron pipe was in a cold drawn state, with an outer diameter of φ6 mm, a wall thickness of 0.5 mm, and an inner diameter of 5 mm. Deformed structures were observed in the longitudinal metal structure, and ammonia gas was used as the nitrogen flow for nitriding. 1. The iron pipe was cleaned to remove oil, rinsed with alcohol to remove any remaining moisture on the surface, dried with an air gun, and placed vertically in the nitriding equipment 200. 2. The equipment was started and pre-oxidation treatment was carried out at a temperature of 540°C for 5 minutes. After oxidation was completed, the equipment was cooled in air. 3. The nitriding parameters were set as follows: ammonia gas flow rate 4.7 L / h, ammonia gas flow velocity 4 cm / s, preheating time 40 s, ammonia decomposition rate 42%, nitriding time 30 min, nitriding temperature 540°C, and temperature difference between the tip and end of the iron pipe 3.9°C. After nitriding was completed, the iron pipe was taken out and cooled in air to obtain a nitrided iron pipe sample. 4. After nitriding, the iron pipe was annealed in a high-temperature annealing furnace at an annealing temperature of 950°C for 30 minutes, and after annealing was completed, it was cooled in air, completing the nitriding annealing of the iron pipe. Using a grinding stone cutter, approximately 500g of iron pipe samples were cut from the tip, center, and end to serve as nitrogen content test samples, 1cm samples were cut from the tip, center, and end to serve as hardness test samples, and 1cm samples were cut from the tip, center, and end to prepare metal structure samples. The nitrogen content data was measured using an ONH analyzer, and the hardness data of three hardness samples was tested using a Vickers hardness tester. Three metallographic samples were polished using an automatic polishing machine and etched using a 4% nitric acid alcohol solution for 10 seconds to obtain metallographic samples. The metallographic structures were observed using a metallographic microscope, and the metallographic photographs and grain size data are shown below. JPEG2025525804000005.jpg50170

[0118] Example 6 The iron pipe used in this example was drawn from a pipe material. The iron pipe was in a cold drawn state, with an outer diameter of φ6 mm, a wall thickness of 0.5 mm, and an inner diameter of 5 mm. Deformed structures were observed in the longitudinal metal structure, and ammonia gas was used as the nitrogen source for nitriding. 1. The iron pipe was cleaned to remove oil, rinsed with alcohol to remove any remaining moisture on the surface, dried with an air gun, and then placed vertically in the nitriding equipment 200 and fixed in place. 2. The equipment was started and pre-oxidation treatment was carried out at a pre-oxidation temperature of 560°C for 25 minutes, and after oxidation was completed, it was cooled in air. 3. The nitriding parameters were set as follows: ammonia gas flow rate 5.5 L / h, ammonia gas flow velocity 7.5 cm / s, preheating time 15 s, ammonia decomposition rate 26%, nitriding time 90 min, nitriding temperature 560°C, and temperature difference between the tip and end of the iron pipe 7.2°C. After nitriding was completed, the iron pipe was taken out and cooled in air to obtain a nitrided iron pipe sample. 4. After nitriding, the iron pipe was annealed in a high-temperature annealing furnace at an annealing temperature of 850°C for 20 minutes, and after annealing was completed, it was cooled in air, completing the nitriding annealing of the iron pipe. Using a grinding stone cutter, approximately 500g of iron pipe samples were cut from the tip, center, and end to serve as nitrogen content test samples, 1cm samples were cut from the tip, center, and end to serve as hardness test samples, and 1cm samples were cut from the tip, center, and end to prepare metal structure samples. The nitrogen content data was measured using an ONH analyzer, and the hardness data of three hardness samples was tested using a Vickers hardness tester. Three metallographic samples were polished using an automatic polishing machine and etched using a 4% nitric acid alcohol solution for 10 seconds to obtain metallographic samples. The metallographic structures were observed using a metallographic microscope, and the metallographic photographs and grain size data are shown below. JPEG2025525804000006.jpg48170

[0119] Example 7 The iron pipe used in this example was drawn from a pipe material. The iron pipe was in a cold drawn state, with an outer diameter of φ6 mm, a wall thickness of 0.5 mm, and an inner diameter of 5 mm. Deformed structures were observed in the longitudinal metal structure, and ammonia gas was used as the nitrogen source for nitriding. 1. The iron pipe was cleaned to remove oil, rinsed with alcohol to remove any remaining moisture on the surface, dried with an air gun, and then placed vertically in the nitriding equipment 200 and fixed in place. 2. The equipment was started and pre-oxidation treatment was carried out at a pre-oxidation temperature of 550°C for 20 minutes, and after oxidation was completed, it was cooled in air. 3. The nitriding parameters were ammonia gas flow rate 4.5 L / h, ammonia gas flow velocity 6 cm / s, preheating time 30 s, ammonia decomposition rate 39%, nitriding time 60 min, nitriding temperature 550°C, and temperature difference between the tip and end of the iron pipe 4.7°C. After nitriding was completed, the iron pipe was removed and cooled in air to obtain a nitrided iron pipe sample. 4. After nitriding, the iron pipe was annealed in a high-temperature annealing furnace at an annealing temperature of 901°C for 30 minutes, and after annealing was completed, it was cooled in air, completing the nitriding annealing of the iron pipe. Using a grinding stone cutter, approximately 500g of iron pipe samples were cut from the tip, center, and end to serve as nitrogen content test samples, 1cm samples were cut from the tip, center, and end to serve as hardness test samples, and 1cm samples were cut from the tip, center, and end to prepare metal structure samples. The nitrogen content data was measured using an ONH analyzer, and the hardness data of three hardness samples was tested using a Vickers hardness tester. Three metallographic samples were polished using an automatic polishing machine and etched using a 4% nitric acid alcohol solution for 10 seconds to obtain metallographic samples. The metallographic structures were observed using a metallographic microscope, and the metallographic photographs and grain size data are shown below. JPEG2025525804000007.jpg48170

[0120] Example 8 The iron pipe used in this example was drawn from a pipe material. The iron pipe was in a cold drawn state, with an outer diameter of 6 mm, a wall thickness of 0.3 mm, and an inner diameter of 5.4 mm. Deformed structures were observed in the longitudinal metal structure, and ammonia gas was used as the nitrogen source for nitriding. 1. The iron pipe was cleaned to remove oil, rinsed with alcohol to remove any remaining moisture on the surface, dried with an air gun, and then placed vertically in the nitriding equipment 200 and fixed in place. 2. The equipment was started and pre-oxidation treatment was carried out at a pre-oxidation temperature of 530°C for 10 minutes. After oxidation was completed, the equipment was cooled in air. 3. The nitriding parameters were ammonia gas flow rate 4 L / h, ammonia gas flow velocity 4 cm / s, preheating time 40 s, ammonia decomposition rate 44%, nitriding time 45 min, nitriding temperature 530°C, and temperature difference between the tip and end of the iron pipe 2.1°C. After nitriding was completed, the iron pipe was removed and cooled in air to obtain a nitrided iron pipe sample. 4. After nitriding, the iron pipe was annealed in a high-temperature annealing furnace at an annealing temperature of 940°C for 40 minutes, and after annealing was completed, it was cooled in air, completing the nitriding annealing of the iron pipe. Using a grinding stone cutter, approximately 500g of iron pipe samples were cut from the tip, center, and end to serve as nitrogen content test samples, 1cm samples were cut from the tip, center, and end to serve as hardness test samples, and 1cm samples were cut from the tip, center, and end to prepare metal structure samples. The nitrogen content data was measured using an ONH analyzer, and the hardness data of three hardness samples was tested using a Vickers hardness tester. Three metallographic samples were polished using an automatic polishing machine and etched using a 4% nitric acid alcohol solution for 10 seconds to obtain metallographic samples. The metallographic structures were observed using a metallographic microscope, and the metallographic photographs and grain size data are shown below. JPEG2025525804000008.jpg48170

[0121] Example 9 The iron pipe used in this example was drawn from a pipe material. The iron pipe was in a cold drawn state, with an outer diameter of φ6 mm, a wall thickness of 0.5 mm, and an inner diameter of 5 mm. Deformed structures were observed in the longitudinal metal structure, and ammonia gas was used as the nitrogen source for nitriding. 1. The iron pipe was cleaned to remove oil, rinsed with alcohol to remove any remaining moisture on the surface, dried with an air gun, and then placed vertically in the nitriding equipment 200 and fixed in place. 2. The equipment was started and pre-oxidation treatment was carried out at a pre-oxidation temperature of 520°C for 4 minutes, and after oxidation was completed, it was cooled in air. 3. The nitriding parameters were set as follows: ammonia gas flow rate 3.5 L / h, ammonia gas flow velocity 3 cm / s, preheating time 50 s, ammonia decomposition rate 48%, nitriding time 30 min, nitriding temperature 520°C, and temperature difference between the tip and end of the iron pipe 1.4°C. After nitriding was completed, the iron pipe was taken out and cooled in air to obtain a nitrided iron pipe sample. 4. After nitriding, the iron pipe was annealed in a high-temperature annealing furnace at an annealing temperature of 960°C for 50 minutes, and after annealing was completed, it was cooled in air, completing the nitriding annealing of the iron pipe. Using a grinding stone cutter, approximately 500g of iron pipe samples were cut from the tip, center, and end to serve as nitrogen content test samples, 1cm samples were cut from the tip, center, and end to serve as hardness test samples, and 1cm samples were cut from the tip, center, and end to prepare metal structure samples. The nitrogen content data was measured using an ONH analyzer, and the hardness data of three hardness samples was tested using a Vickers hardness tester. Three metallographic samples were polished using an automatic polishing machine and etched using a 4% nitric acid alcohol solution for 10 seconds to obtain metallographic samples. The metallographic structures were observed using a metallographic microscope, and the metallographic photographs and grain size data are shown below. JPEG2025525804000009.jpg47170

[0122] Example 10 The iron pipe used in this example was drawn from a pipe material. The iron pipe was in a cold drawn state, with an outer diameter of φ6 mm, a wall thickness of 0.5 mm, and an inner diameter of 5 mm. Deformed structures were observed in the longitudinal metal structure, and ammonia gas was used as the nitrogen source for nitriding. 1. The iron pipe was cleaned to remove oil, rinsed with alcohol to remove any remaining moisture on the surface, dried with an air gun, and then placed vertically in the nitriding equipment 200 and fixed in place. 2. The equipment was started and pre-oxidation treatment was carried out at a pre-oxidation temperature of 500°C for 2 minutes, and after oxidation was completed, it was cooled in air. 3. The nitriding parameters were set as follows: ammonia gas flow rate 3 L / h, ammonia gas flow velocity 1 cm / s, preheating time 80 s, ammonia decomposition rate 53%, nitriding time 25 min, nitriding temperature 500 °C, and temperature difference between the tip and end of the iron pipe 1.2 °C. After nitriding was completed, the iron pipe was taken out and cooled in air to obtain a nitrided iron pipe sample. 4. After nitriding, the iron pipe was annealed in a high-temperature annealing furnace at an annealing temperature of 1000°C for 60 minutes, and after annealing was completed, it was cooled in air, completing the nitriding annealing of the iron pipe. Using a grinding stone cutter, approximately 500g of iron pipe samples were cut from the tip, center, and end to serve as nitrogen content test samples, 1cm samples were cut from the tip, center, and end to serve as hardness test samples, and 1cm samples were cut from the tip, center, and end to prepare metal structure samples. The nitrogen content data was measured using an ONH analyzer, and the hardness data of three hardness samples was tested using a Vickers hardness tester. Three metallographic samples were polished using an automatic polishing machine and etched using a 4% nitric acid alcohol solution for 10 seconds to obtain metallographic samples. The metallographic structures were observed using a metallographic microscope, and the metallographic photographs and grain size data are shown below. JPEG2025525804000010.jpg47170

[0123] Example 11 The iron pipe used in this example was a cold-drawn pipe with an outer diameter of 6 mm, a wall thickness of 0.5 mm, and an inner diameter of 5 mm. Deformed structures were observed in the longitudinal metal structure, and methane was used as the carbon source for carburization. 1. The iron pipe was cleaned to remove oil, rinsed with alcohol to remove any remaining moisture on the surface, dried with an air gun, and then placed vertically in the carburizing equipment 200 and fixed in place. 2. The carburizing parameters were set as follows: methane flow rate 3 L / h, methane flow velocity 3 cm / s, preheating time 60 s, methane decomposition rate 20%, carburizing time 1 h, carburizing temperature 950 °C, and temperature difference between the tip and end of the iron pipe 1 °C. After carburizing was completed, the iron pipe was removed and cooled in air to obtain a carburized iron pipe sample. 3. After nitriding, the iron pipe was annealed in a high-temperature annealing furnace at 1000°C for 60 minutes, and after annealing was completed, it was cooled in air, completing the carburizing annealing of the iron pipe. Using a grinding stone cutter, approximately 500g of iron pipe samples were cut from the tip, center, and end to serve as nitrogen content test samples, 1cm samples were cut from the tip, center, and end to serve as hardness test samples, and 1cm samples were cut from the tip, center, and end to prepare metal structure samples. The carbon content data was measured using a CS analyzer, and the hardness data of three hardness samples was tested using a Vickers hardness tester. Three metallographic samples were polished with an automatic polishing machine and etched for 10 seconds using a 4% nitric acid alcohol solution to obtain metallographic samples. The metallographic structures were observed using a metallographic microscope, and the metallographic photographs and grain size data are shown below. JPEG2025525804000011.jpg49170

[0124] Example 12 The iron pipe used in this example was drawn from a pipe material. The iron pipe was in a cold drawn state, with an outer diameter of φ6 mm, a wall thickness of 0.5 mm, and an inner diameter of 5 mm. Deformed structures were observed in the longitudinal metal structure, and ammonia gas was used as the nitrogen source for nitriding. 1. The iron pipe was cleaned to remove oil, rinsed with alcohol to remove any remaining moisture on the surface, dried with an air gun, and then placed vertically in a homemade nitriding furnace. 2. The equipment was started and pre-oxidation treatment was carried out at a pre-oxidation temperature of 570°C for 50 minutes. After oxidation was completed, the equipment was cooled in air. 3. The nitriding parameters were set as follows: ammonia gas flow rate 20 L / h, ammonia gas flow velocity 28 cm / s, preheating time 30 s, ammonia decomposition rate 41%, nitriding time 5 h, nitriding temperature 570°C, and temperature difference between the tip and end of the iron pipe 0.8°C. After nitriding was completed, the iron pipe was taken out and cooled in air to obtain a nitrided iron pipe sample. 4. After nitriding, the iron pipe was annealed in a high-temperature annealing furnace at an annealing temperature of 800°C for 10 hours, and after annealing was completed, it was cooled in air, completing the nitriding annealing of the iron pipe. Using a grinding stone cutter, approximately 500g of iron pipe samples were cut from the tip, center, and end to serve as nitrogen content test samples, 1cm samples were cut from the tip, center, and end to serve as hardness test samples, and 1cm samples were cut from the tip, center, and end to prepare metal structure samples. The nitrogen content data was measured using an ONH analyzer, and the hardness data of three hardness samples was tested using a Vickers hardness tester. Three metallographic samples were polished using an automatic polishing machine and etched using a 4% nitric acid alcohol solution for 10 seconds to obtain metallographic samples. The metallographic structures were observed using a metallographic microscope, and the metallographic photographs and grain size data are shown below. JPEG2025525804000012.jpg50170

[0125] Example 13 The iron pipe used in this example was obtained by drawing the pipe material. The iron pipe was in a cold drawn state, with an outer diameter of φ1.4 mm, a wall thickness of 0.08 mm, and an inner diameter of 1.24 mm. Deformed structures were observed in the metal structure in the longitudinal direction, and ammonia gas was used as the nitrogen source for nitriding. 1. The iron pipe was cleaned to remove oil, rinsed with alcohol to remove any remaining moisture on the surface, dried with an air gun, and then placed vertically in the nitriding equipment 200 and fixed in place. 2. The equipment was started and pre-oxidation treatment was carried out at a pre-oxidation temperature of 570°C for 50 minutes. After oxidation was completed, the equipment was cooled in air. 3. The nitriding parameters were set as follows: ammonia gas flow rate 20 L / h, ammonia gas flow velocity 28 cm / s, preheating time 30 s, ammonia decomposition rate 41%, nitriding time 1 h, nitriding temperature 570°C, and temperature difference between the tip and end of the iron pipe 0.8°C. After nitriding was completed, the iron pipe was taken out and cooled in air to obtain a nitrided iron pipe sample. 4. After nitriding, the iron pipe was annealed in a high-temperature annealing furnace at 800°C for 10 minutes, and after annealing was completed, it was cooled in air, completing the nitriding annealing of the iron pipe. Using a grinding stone cutter, approximately 500g of iron pipe samples were cut from the tip, center, and end to serve as nitrogen content test samples, 1cm samples were cut from the tip, center, and end to serve as hardness test samples, and 1cm samples were cut from the tip, center, and end to prepare metal structure samples. The nitrogen content data was measured using an ONH analyzer, and the hardness data of three hardness samples was tested using a Vickers hardness tester. Three metallographic samples were polished using an automatic polishing machine and etched using a 4% nitric acid alcohol solution for 10 seconds to obtain metallographic samples. The metallographic structures were observed using a metallographic microscope, and the metallographic photographs and grain size data are shown below. JPEG2025525804000013.jpg52170

[0126] <Comparative Example 1> The iron pipe used in this example was drawn from a pipe material. The iron pipe was in a cold drawn state, with an outer diameter of φ6 mm, a wall thickness of 0.5 mm, and an inner diameter of 5 mm. Deformed structures were observed in the longitudinal metal structure, and ammonia gas was used as the nitrogen flow for nitriding. 1. The iron pipe was cleaned to remove oil, rinsed with alcohol to remove any remaining moisture on the surface, dried with an air gun, and then placed in an automatic nitriding furnace. 2. The nitriding temperature was set to 540°C, the nitrogen gas flow rate was set to 8cm / s, the iron pipe was placed horizontally, the temperature difference between the tip and end of the iron pipe was set to 1.1°C, and the nitriding time was set to 12 hours, and after nitriding was completed, it was cooled in air. Using a grinding stone cutter, approximately 500g of iron pipe samples were cut from the tip, center, and end to serve as nitrogen content test samples, 1cm samples were cut from the tip, center, and end to serve as hardness test samples, and 1cm samples were cut from the tip, center, and end to prepare metal structure samples. The nitrogen content data was measured using an ONH analyzer, and the hardness data of three hardness samples was tested using a Vickers hardness tester. Three metallographic samples were polished using an automatic polishing machine and etched using a 4% nitric acid alcohol solution for 10 seconds to obtain metallographic samples. The metallographic structures were observed using a metallographic microscope, and the metallographic photographs and grain size data are shown below. JPEG2025525804000014.jpg49170

[0127] <Comparative Example 2> The iron pipe used in this example was drawn from a pipe material. The iron pipe was in a cold drawn state, with an outer diameter of φ6 mm, a wall thickness of 0.5 mm, and an inner diameter of 5 mm. Deformed structures were observed in the longitudinal metal structure, and ammonia gas was used as the nitrogen flow for nitriding. 1. The iron pipe was cleaned to remove oil, rinsed with alcohol to remove any remaining moisture on the surface, dried with an air gun, and then placed vertically in a homemade nitriding furnace. 2. The equipment was started and pre-oxidation treatment was carried out at a pre-oxidation temperature of 540°C for 5 minutes. After oxidation was completed, the equipment was cooled in air. 3. The nitriding parameters were set as follows: ammonia gas flow rate 4.7 L / h, ammonia gas flow velocity 4 cm / s, no preheating, ammonia decomposition rate 10%, nitriding time 30 min, nitriding temperature 540°C, and temperature difference between the tip and end of the iron pipe 12.9°C. After nitriding was completed, the iron pipe was taken out and cooled in air to obtain a nitrided iron pipe sample. 4. After nitriding, the iron pipe was annealed in a high-temperature annealing furnace at an annealing temperature of 950°C for 30 minutes, and after annealing was completed, it was cooled in air, completing the nitriding annealing of the iron pipe. The nitrogen content data was measured using an ONH analyzer, and the hardness data of three hardness samples was tested using a Vickers hardness tester. Three metallographic samples were polished using an automatic polishing machine and etched using a 4% nitric acid alcohol solution for 10 seconds to obtain metallographic samples. The metallographic structures were observed using a metallographic microscope, and the metallographic photographs and grain size data are shown below. JPEG2025525804000015.jpg52170

[0128] <Comparative Example 3> The iron pipe used in this example was drawn from a pipe material. The iron pipe was in a cold drawn state, with an outer diameter of φ6 mm, a wall thickness of 0.5 mm, and an inner diameter of 5 mm. Deformed structures were observed in the longitudinal metal structure, and ammonia gas was used as the nitrogen flow for nitriding. 1. The iron pipe was cleaned to remove oil, rinsed with alcohol to remove any remaining moisture on the surface, dried with an air gun, and placed vertically in a homemade nitriding furnace. 2. The equipment was started and the following nitriding parameters were set: ammonia gas flow rate 4.5 L / h, ammonia gas flow velocity 6 cm / s, preheating time 30 s, ammonia decomposition rate 39%, nitriding time 60 min, nitriding temperature 550°C, and temperature difference between the tip and end of the iron pipe 2.5°C. After nitriding was completed, the iron pipe was taken out and cooled in air to obtain a nitrided iron pipe sample. 3. After nitriding, the iron pipe was annealed in a high-temperature annealing furnace at an annealing temperature of 900°C for 30 minutes, and after annealing was completed, it was cooled in air, completing the nitriding annealing of the iron pipe. The nitrogen content data was measured using an ONH analyzer, and the hardness data of three hardness samples was tested using a Vickers hardness tester. Three metallographic samples were polished using an automatic polishing machine and etched using a 4% nitric acid alcohol solution for 10 seconds to obtain metallographic samples. The metallographic structures were observed using a metallographic microscope, and the metallographic photographs and grain size data are shown below. JPEG2025525804000016.jpg49170

[0129] From the above, comparing Comparative Example 1 and Example 3, both have similar nitrogen content, but Example 3 has larger grain size and smaller grain size. This is because the annealing step, which involves annealing the iron tube preform of the vascular stent after nitriding, causes the internal nitrogen atoms to diffuse uniformly in the preform and refines the grain size. As a result, the radial strength of the vascular stent is improved and good support is obtained.

[0130] Compared with Comparative Example 1 and Example 4, in Comparative Example 1, the lack of gas flow in the center of the vascular stent preform resulted in a low nitrogen content in the inner wall of the preform and a high nitrogen content in the outer wall. This resulted in uneven hardness across the entire cross section of the preform. When processed into a vascular stent, the inner wall had low hardness and the outer wall had high hardness. This high hardness easily led to cracks in the outer wall during expansion, ultimately resulting in stent fracture. In Example 4, the flow of ammonia gas passed through the interior, allowing the inner and outer walls to be nitrided simultaneously. This resulted in uniform hardness of the inner and outer walls and effectively improved the overexpansion performance of the vascular stent.

[0131] Comparing Comparative Example 2 with Example 5, the hardness of the distal end of Comparative Example 2 was generally lower than that of the distal end. This was because, in Comparative Example 2, gas was passed directly over the inner surface of the workpiece without preheating, resulting in uneven temperatures at the distal and distal ends of the workpiece, resulting in the largest temperature difference between the distal and distal ends. The distal end was cooled by low-temperature gas, resulting in a low surface temperature, low nitriding, and low hardness. The distal end, however, had a low cooling effect due to the high nitrogen content and high hardness. After cutting the vascular stent, the strength of the vascular stent manufactured at the distal end was low, while the strength of the vascular stent manufactured at the distal end was high. This meant that the stability of the product's performance could not be guaranteed.

[0132] Comparing Comparative Example 3 and Example 7, it was found that Comparative Example 3 did not have a pre-oxidation step under the same nitriding conditions, resulting in a significant decrease in nitriding efficiency. The nitrogen content of Comparative Example 3 is much lower than that of Example 7. Due to the lack of a pre-oxidation step, the nitriding time must be extended to achieve the required nitrogen content during production, resulting in a significant decrease in production efficiency.

[0133] In Examples 3 to 10, the nitriding temperature, nitriding time, gas flow rate, preheating time, annealing temperature, and annealing time were all different. This is reflected in the difference in nitrogen content in the preform, and as the nitrogen content decreases, the hardness of the preform also decreases. In all Examples, the cross-section of the preform was found to have good uniformity. This is due to the good nitriding effect on both the inner and outer walls of the vascular stent preform.

[0134] The above are only preferred specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto, and any modifications or replacements that can be easily thought of by those skilled in the art within the scope of the technology disclosed in the present invention should be included in the protection scope of the present invention.

Claims

1. 1. A method for modifying an entire metal workpiece, comprising the steps of: placing the metal workpiece in a gas stream to modify it; and cooling the modified metal workpiece, A method for modifying the entire metal workpiece, characterized in that in the modification step, the gas flow is preheated to a temperature close to the modification temperature before flowing onto the surface of the metal workpiece.

2. The method for modifying an entire metal workpiece as described in claim 1, characterized in that the preheating time when flowing the gas flow onto the surface of the modified metal workpiece is 5 seconds to 120 seconds, the difference between the temperature of the gas flow after preheating and the temperature of any part of the workpiece is within 10°C, and the temperature difference ΔT of each part of the workpiece to be modified is 10°C or less.

3. The method for modifying the entire metal workpiece as described in claim 1, characterized in that the flow rate of the gas flow is 0.5 to 28.0 cm / s, the modification temperature of the entire metal workpiece is 410 to 950°C, the modification treatment time is 10 minutes to 5 hours, the cooling is performed by removing the modified workpiece and placing it at room temperature to cool, and the non-metallic elements include N, C, and S.

4. The method for transforming the entire metal workpiece as described in claim 1, characterized in that the method further includes an annealing step, the annealing temperature is 800 to 1200°C, and the annealing time is 10 minutes to 10 hours.

5. The method for modifying the entire metal workpiece as described in claim 1, further comprising a step of performing high-temperature pre-oxidation in an air medium before the modification of the workpiece to be modified, wherein the high-temperature pre-oxidation is performed at 410 to 950°C for 2 to 60 minutes.

6. 2. The method of claim 1, wherein the workpiece to be modified comprises any of a vascular stent, a non-intravascular stent, an occluder, an orthopedic implant, a spacer, an artificial blood vessel, a dental implant device, a vascular clamp, a dental implant, a respiratory implant, a gynecological implant, a male medical implant, a suture, a valve, a wire preform, or a semi-finished product, and the orthopedic implant comprises at least one of a bone nail, a bone plate, a joint, an intramedullary needle, an anchor, a bolt, and an intervertebral disc fusion cage.

7. 2. The method for modifying an entire metal workpiece according to claim 1, wherein the material of the workpiece to be modified is pure iron or an iron alloy, and the workpiece is an iron-containing pipe having an inner diameter of 0.3 mm to 12.0 mm.

8. 1. A gas guide assembly for modifying a metal workpiece, comprising: The relationship between length and inner radius is E = LR ２ +A gas guide tube, L is the length of the gas guide tube, R is the inner radius of the gas guide tube, E and A are both constants, 0≦A≦5 cm ３ , 0.3 cm ３ ≦E≦400cm ３ and A gas guide assembly for modifying a metal workpiece, characterized in that the gas guide assembly preheats the gas flow to a temperature close to the modification temperature before flowing it onto the surface of the metal workpiece.

9. 9. The gas guide assembly according to claim 8, wherein the length of the gas guide tube is 10 cm or more and 1000 cm or less, and the wall thickness of the gas guide tube is 0.25 mm or more and 25 mm or less.

10. 9. The gas guide assembly according to claim 8, comprising a trunk and a branch portion that communicate with each other, one end of the trunk communicating with one end of the gas guide tube, and the branch portion further comprising a gas flow dividing member extending outward along a radial direction of the trunk.

11.

12. 12. The gas guide assembly according to claim 11, wherein the inner radius of the branch is between 0.5 mm and 20 mm.

13. an exhaust end of the branch portion faces one end of the preform, and a distance between the exhaust end of the branch portion and an end of the preform close to the branch portion is 0 to 20 mm, Alternatively, the exhaust end of the branch extends into the end of the preform closer to the branch, and a distance between the exhaust end of the branch and the end of the preform closer to the branch is greater than 0 and not greater than 10 mm.

14. 11. The gas guide assembly of claim 10, wherein the end of the stem remote from the gas guide tube is open.

15. 1. An apparatus for modifying metal workpieces, comprising: a reaction tooling including a heating unit and a reaction unit, the heating unit being provided outside the reaction unit, the reaction unit having a reaction chamber, and an inlet opening in the reaction unit that communicates with the reaction chamber; a cover for closing the intake port through which an air intake hole is provided; 15. An apparatus for modifying a metal workpiece, comprising: a gas guide assembly according to claim 8 or 9, wherein an end of a gas guide tube close to the cover communicates with an air inlet of the cover; or a gas guide assembly according to any one of claims 10 to 14, wherein an end of the gas guide assembly remote from the gas diverting member communicates with an air inlet of the cover.

16. 16. The apparatus of claim 15, further comprising a fixing member connected to the gas guide tube for fixing the metal workpiece.

17. The device of claim 16, wherein the fixing member includes a first sub-fixing member and a second sub-fixing member, and the first sub-fixing member and the second sub-fixing member are respectively used to fix both ends of the metal workpiece.

18. a first seal member positioned between the cover and the inlet when the cover closes the inlet, and sealingly connecting the cover and the inlet; 16. The apparatus of claim 15, further comprising a second seal member positioned within the reaction chamber to seal the reaction chamber when the cover closes the inlet.

19. 20. The apparatus of claim 18, wherein the second seal member has a thickness of at least 20 mm and at most 150 mm, and wherein the second seal member is fabricated from at least one of silicon, carbon, zirconium, aluminum, aluminum silicate, magnesia, magnesium calcium, magnesium chromium, magnesium aluminum, or magnesium silicon refractory material.

20. The device according to claim 15, wherein the heating section has a heating chamber, the heating section has an opening communicating with the heating chamber, and the reaction section can enter and exit the heating chamber through the opening.

21. The device of claim 20, further comprising a first drive unit and a second drive unit, wherein the first drive unit is connected to the cover and drives the cover to move toward / away from the intake port, and the second drive unit is connected to the reaction unit and drives the reaction unit to move toward / away from the cover and / or the opening.

22. 22. The device of claim 21, wherein the driving device includes a guide rail, the guide rail includes a slide groove, the slide groove extends in a predetermined direction, and the first driving unit and the second driving unit are respectively slidably connected to the guide groove.

23. 21. The device of claim 20, further comprising a third sealing member positioned at the opening to seal the heating chamber when the reaction unit is positioned within the heating chamber.

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