JP2007330288A - Core material or guide wire composed of core material and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a core material or a guide wire composed of the core material not to be broken, for which the core material of a base part has relatively high rigidity, and a catheter. <P>SOLUTION: In the core 20 of the guide wire, a carbide is dispersed in a base comprising austenitic stainless steel at least in the surface layer of the sectional structure of a core base part 21 or the surface layer of the catheter. In the catheter or the guide wire, tensile strength in a tension test is ≥1,000 MPa at the time of 2% strain and breaking elongation is ≥5% in at least a part of the core base part. Further, for the guide wire, a carbide layer in the sectional structure is made less than the carbide amount of the surface layer part of the base part or is eliminated in at least a part of a core distal end part 22 and flexibility is provided compared with the core base part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention comprises a stainless steel core material or a core material used for medical technology under fluoroscopy represented by percutaneous angioplasty (PTCA) in the medical field such as radiology and cardiovascular medicine. It relates to a guide wire.

  A guide wire is used as a leading catheter in catheter treatment techniques such as percutaneous angioplasty, and is inserted from the femoral or wrist artery puncture opening and sent to a target site while selecting a blood vessel. Is. Although the required physical properties related to the material are described in detail in Patent Document 1, torque transmission (direction control of the G / W tip portion by hand twisting in the branch vessel), kink resistance (after the branch vessel enters the zigzag) Shape restoration), extrudability (rigidity that easily conveys the proximal protrusion to the tip), tip flexibility (softness that does not damage the blood vessel at the time of introduction), X-ray contrast (when branching vessel is selected, X-ray wire tip Can be observed).

  Patent Document 1 describes a catheter guide wire in which a main body part and a part of a tip part are formed of amorphous metal. Thereby, the main body portion provides a guide wire made of a core material or a core material that is not buckled or twisted and deformed by insertion and crown searcher operation.

On the other hand, in Patent Document 3 filed by the present applicant, using the continuous vacuum carburizing apparatus of Patent Document 4, continuous carburization from the surface of the ultrafine wire of austenitic stainless steel having a diameter of 10 to 50 μm is performed, Disclosed is a carbide fine wire having a particle size of 2 μm or less dispersed in the base, and gradually reducing the density of the carbide from the outside toward the core, and a stainless fine wire having a tensile strength of 1400 MPa to 2600 MPa and an elongation of 10% is disclosed. The application of is disclosed.
Japanese Patent Publication No. 3-015914 JP 2004-290466 A JP 2006-89836 A International Publication WO2005 / 003400

  However, the thing of the patent document 1 had the problem that it was easy to break since the base part with comparatively high rigidity was insufficient with less than 5% of elongation of tensile strength. In addition, the material of Patent Document 2 is rigid due to the surface layer of stainless steel at the base portion of the core material, and the tip portion is flexible because the surface layer of the core material is removed by processing to become the Ni—Ti alloy of the center layer. There is. However, since a composite material process is employed in order to have such a gradient composition, there is a problem that the manufacturing cost is greatly increased. Moreover, it is not disclosed about how rigid the base is.

  Moreover, in the thing of patent document 3, although the tensile strength as a stainless fine wire with a wire mesh diameter of 10-50 micrometers is high and has obtained a large elongation, strength and flexibility like a guide wire are required. Moreover, the application of the guide wire having a thin wire diameter of about 0.1 to 1 mm has not been studied.

  In view of the above-described problems, an object of the present invention is to provide a catheter core material or a guide wire made of a core material that has relatively high rigidity and does not break.

  In order to solve the above-mentioned problems, the present applicants filed a guide wire of Japanese Patent Application No. 2004-378622 (not disclosed at the time of filing). The structure is such that carbide is dispersed in a matrix made of austenitic stainless steel in the surface layer of the cross-sectional structure of the core base 21 shown in FIG. 1, and at least a part of the core base has a tensile strength in a tensile test of 1000 MPa at 2% strain. As described above, the elongation at break is 4% or more, and at least a part of the core tip 22 has no carbide in the cross-sectional structure, and is more flexible than the core base. Thereby, both elongation and rigidity at the time of the tensile test were achieved.

  However, if the guide wire having the same characteristics as the guide wire having a wire diameter of 0.1 mm in Japanese Patent Application No. 2004-378622 is to be implemented with a guide wire having a wire diameter of 0.2 mm to 0.8 mm, carbides are dispersed in the surface layer in the base. Therefore, the time required for carburizing and diffusion treatment operation is drastically increased, which is disadvantageous in terms of cost. In particular, since the time required for the diffusion treatment after carburizing is proportional to the square of the distance, the influence of the difference in wire diameter is extremely large. On the other hand, when trying to process forcibly in a short time, the carburized layer is more limited to the surface layer and it becomes difficult to obtain rigidity, or if the rigidity of the carburized part is increased locally, it will cause the elongation to decrease. In the former case, the operability as a guide wire is deteriorated, and in the latter case, the flexibility is impaired.

  Therefore, in the present invention, a core material comprising a tapered core tip and a core base having a diameter of 0.2 mm or more and 0.5 mm or less following the tip, and at least in the surface layer of the cross-sectional structure of the core base. A core material or core in which carbide is dispersed in a base made of a stainless steel, the core base has a 0.2% proof stress in a tensile test of 900 MPa or more, 1100 MPa or more at 2% strain, and a breaking elongation of 5% or more The above-mentioned problems have been solved by providing a guide wire made of a material.

  That is, since the carbide is distributed in the base made of austenitic stainless steel in the surface layer portion of the cross-sectional structure of the base portion, by distributing the carbide phase having high rigidity in the surface layer portion, depending on the volume ratio, the entire material The rigidity of becomes higher. The 0.2% proof stress in the tensile test was set to 900 MPa or more, and the problem of low rigidity before plastic deformation was solved. The 0.2% proof stress is a numerical value representing an elastic limit at the initial stage of application of a load. If this value is low, plastic deformation easily occurs due to the load at the time of blood vessel insertion, and operability is poor. The 0.2% proof stress is desirably 900 MPa or more, and more preferably 1000 MPa or more.

  Furthermore, the stress at 2% strain was also increased from 1000 MPa to 1100 MPa to further improve the operability. The tensile strength at 2% strain is a mechanical characteristic corresponding to the waist strength of the guide wire as well as the proof stress, and particularly represents the strength when subjected to deformation. The reason why the tensile strength at 2% strain is 1100 MPa or more is that if it is less than 1100 MPa, sufficient rigidity cannot be obtained at the hand portion. More preferably, it is 1200 MPa or more.

  Furthermore, the elongation at break is less than 4% as disclosed in Patent Document 1 even for a highly rigid material of 3.6%. In this case, it is easy to break. In the present invention, as will be described later, there are those in which elongation at break of 10% or more is obtained.

  Further, the distal end portion of the guide wire is usually made thinner than the base portion so as not to damage the blood vessel, and further flexibility is required. Accordingly, in the invention according to claim 2, the core in which the carbide is dispersed in the base in the core base portion in which the cross-sectional structure of the core tip portion has less or no carbide compared to the core base portion. A guide wire made of a material or a core material was used.

  Since the inner side has less carbide than the outer side, it becomes flexible, and even if it undergoes unreasonable deformation, it is difficult to break. Furthermore, it is more preferable if the amount of carbide dispersion in the cross-sectional structure is gradually decreased from the surface layer portion toward the inside.

Such a core material or a guide wire made of the core material is obtained as follows. That is, in the invention according to claim 3, after the carbide is dispersed in a thin wire base having a finished diameter of 0.2 mm or more and 0.5 mm or less after a skin pass made of austenitic stainless steel, surface reduction is performed. Provided is a core material for performing skin pass drawing at a rate of 2.9% or more and 10% or less, or a method for manufacturing a guide wire made of a core material.

  That is, after dispersing carbide in a base made of austenitic stainless steel, skin pass wire drawing with a surface area reduction rate of 10% or less is performed, so that 0.2% proof stress can be improved. If the area reduction rate exceeds 10%, the elongation at break is significantly reduced, and a break elongation of 4% or more cannot be obtained. On the other hand, if the area reduction rate is less than 2.9%, the yield strength cannot be obtained. The rate was 2.9% to 10%. As a result, even when carburizing under the condition that 0.2% proof stress is insufficient at the time of carburizing, the base portion without carbides is work-hardened after skin pass drawing, and the proof stress is drastically improved and the proof stress is greatly increased. Improved. If the finished dimension after skin pass is less than 0.2 mm and more than 0.5 mm, the other method is preferable, and the effect of the skin pass cannot be expected.

  Furthermore, in the invention described in claim 4, after the skin pass wire drawing (manufacturing according to claim 3), the surface portion of the carbide layer is removed from the base portion by taper-shaped the tip portion than in the base portion. Provided is a method for manufacturing a core material or a guide wire made of a core material that forms a core tip with little or no core.

  That is, it is obtained by finishing a carburized material from the surface of a long material having a diameter corresponding to the core of the base portion in advance to a shape dimension as a core material or a guide wire made of the core material. In this case, the closer to the tip, that is, the smaller the outer diameter, the more the carbide dispersion region after carburization is removed, so the flexibility is increased, and the rigidity at hand and the flexibility of the tip are more effectively balanced. Core material or guide wire made of core material can be obtained at low cost without manufacturing composite wire

  In the present invention, in the base made of austenitic stainless steel in the surface layer of the cross-sectional structure of the core base portion of the core material composed of the core base portion having a diameter of 0.2 mm or more and 0.5 mm or less following the tip portion of the tapered core A core material having a 0.2% proof stress in a tensile test of the core base of 900 MPa or more, a strain of 1100 MPa or more at 2% strain, and a elongation at break of 5% or more is distributed on the surface layer. By increasing the rigidity of the whole material according to the volume ratio, and making the interior relatively flexible compared to the surface layer and increasing the flexibility, it will not break even if it is deformed by any chance. . Further, the core material of the base portion has a relatively high rigidity and has an effect that it does not break.

  Further, in the invention according to claim 2, the cross-sectional structure of the core tip portion has less or no carbide compared to the core base portion, and in the core base portion, the carbide is dispersed in the base, and at hand Since the guide wire is made of a core material or a core material that achieves both rigidity and flexibility at the tip, the guide wire is made of a core material or a core material that is easier to use.

  When manufacturing such a core material or a guide wire made of a core material, the yield strength of the base core material is dramatically increased by applying a skin pass treatment after distributing a rigid carbide phase on the surface layer of the core material, further operability. There is an effect of improving. Further, in the invention of claim 4, by removing the surface of the tip portion, the carbide phase is reduced, and the rigidity at the base portion and the property of being hard to break are achieved, and the rigidity of the hand and the flexibility of the tip portion are more effectively made compatible. Since the core wire or the guide wire made of the core material is used, the guide wire made of the core material or the core material is easier to use.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a core material of a guide wire showing an embodiment of the present invention. As shown in FIG. 1, the metal core 20 of the guide wire of the present invention has a base portion 21 having a relatively high rigidity and a tip portion 22 that is relatively flexible. Further, the base 21 is an alloy in which the surface layer portion is carburized and then subjected to a skin pass treatment, and the surface portion has a higher carbon content than the inside, and the mechanical properties are proof stress in the elastic deformation region and work hardening during plastic deformation. And also has a predetermined elongation at break. In the cross section of the front end portion 22, both the surface layer and the inside thereof are less flexible than the base portion 21 because the carbon content is less than that of the base portion.

  Next, a method for obtaining the core material of the present invention or a guide wire made of the core material will be described. Such a core material or a guide wire made of the core material can be obtained by drawing an austenitic stainless steel wire to a predetermined wire diameter, carburizing, and further performing skin pass drawing as necessary. However, the carburizing process is preferably performed by vacuum carburizing from the viewpoints of impurity contamination, surface texture stability, uniformity, and the like. Furthermore, in order to make the quality of the wire obtained constant, carburizing unevenness may occur in the batch processing in which the coil is processed, and it is preferable to perform carburizing by continuous vacuum carburizing. Then, it implements using the method and apparatus as described in the continuous vacuum carburizing method of the metal wire of the patent document 4 which this applicant applied for internationally, a metal strip, or a metal pipe, and its manufacturing method. This manufacturing apparatus is shown in FIG. This is an example of what is described in Patent Document 4.

  FIG. 5 is a cross-sectional explanatory view of a continuous vacuum carburizing apparatus or furnace for carburizing austenitic stainless steel wire rod (hereinafter referred to as “steel wire”) 7 drawn to a predetermined wire diameter before the skin pass of this embodiment. It is. This continuous vacuum carburizing furnace 1 includes an elongated vacuum vessel 9, three core tubes 11, 21, 31 and a steel wire 7 arranged in the vessel along the longitudinal direction thereof in a core portion composed of these core tubes. It has a pay-out take-up mechanism.

  Each core tube 11, 21, 31 has an elongated shape with openings at both ends, two introduction tubes 12, 13, 22, 23, 32, 33 and a pair of exhaust tubes 14, 14 ′, 24, 24 ′, 34, 34 '. Further, each furnace core tube is provided with an electric heater 10 along its longitudinal direction. The two introduction pipes are composed of central introduction pipes 13, 23, 33 located substantially in the center of the core tube, and inlet side introduction pipes 12, 22, 32 located almost at the center of the central introduction pipe and the reactor core inlet side. A pair of exhaust pipes 14, 14 ′, 24, 24 ′, 34, 34 ′ are arranged on both sides of the inlet side introduction pipe at a certain distance. Further, the introduction pipe and the exhaust pipe are connected to the reactor core tube through the vacuum vessel 9, and various gases are introduced from the outside of the vacuum vessel to the reactor core tube and discharged to the outside of the vacuum vessel.

  The exhaust pipes 14, 14 ', 24, 24', 34, 34 'are arranged on both sides of the inlet side introduction pipes 12, 22, 32 in the longitudinal direction of the core tube, respectively, and supply the carburizing source gas to the inlet side core tube. By introducing, the inside of the core tube between these exhaust pipes forms a carburized portion 5 occupied by the carburizing gas. The central introduction pipes 13, 23, and 33 are arranged on the downstream side of the respective inlet side introduction pipes and the exhaust pipes on both sides with respect to the moving direction of the steel wire 7. The inside of the furnace tube on the side is a diffusion portion 6 filled with a carrier gas.

  Further, the vacuum container 9 has an exhaust pipe 8 provided with a vacuum exhaust valve (not shown), and the inside of the container can be exhausted. The pay-out take-up mechanism includes a pay-out side bobbin 3 and a take-up side bobbin 4 arranged on both sides of the core tube 11, 21, 31 in the vacuum vessel. These bobbins 3 and 4 are rotationally driven to feed out the steel wire 7 wound around the bobbin 3 and wind it around the bobbin 14 through the core tubes 11, 21 and 31.

  In such a continuous vacuum carburizing furnace, for example, in the example of Patent Document 4, the following operation is performed. First, the steel wire 7 is passed through the core tube 11, 21, 31 from the feeding side bobbin 3 and connected to the winding side bobbin 4. Next, the entire vacuum vessel 9 is sufficiently exhausted from the exhaust pipe 8. When the inside of the vacuum vessel reaches a predetermined vacuum level of 10 Pa or less, a current is supplied to the heater 10 to heat the core tubes 11, 21, 31 to a predetermined temperature of 850 ° C to 1050 ° C.

  Thereafter, a carburizing source gas such as ethylene is introduced from the inlet side introduction pipes 12, 22 and 32, and a carrier gas such as nitrogen or argon is introduced from the central introduction pipes 13, 23 and 33, and at the same time, the exhaust pipe 8 is evacuated. By adjusting the valve to control the vacuum inside the vacuum vessel 9, the pressure inside the core tube 11, 21, 31 is restored to 5 kPa or less, preferably 1 to 3 kPa. After such an atmosphere adjustment, the take-up winding mechanism is operated, and the steel wire 7 is wound around the bobbin 4 through the core tubes 11, 21, 31. When the required amount of steel wire is obtained, the furnace is cooled, the vacuum vessel is vacuum broken, the bobbin and the steel wire 7 are taken out of the furnace, and a carburized steel wire is obtained.

  The carburizing source gas is continuously introduced into each core tube heated to 850 ° C. to 1050 ° C. from the inlet side introduction pipes 12, 22, 32 and the exhaust pipes 14, 14 ′, 24, 24 ′, 34, 34 ′. By being exhausted, it functions as a constant carburizing atmosphere of pressure and composition gas that can be vacuum carburized. This atmosphere causes the steel wire 7 passing therethrough to be carburized. The carburized steel wire 7 then passes through the heated diffusion section 6 of each core tube. There is no gas which becomes a carburizing source in this diffusion part, and carbon carburized from the oil supply surface of the steel wire 7 diffuses inside the alloy cross section. Thus, while slowly moving the steel wire, carburizing / diffusion can be performed with one core tube 11 and carburizing / diffusion can be repeatedly performed with the core tubes 21 and 31, By adjusting the concentration of the carburizing source gas and the like, and further adjusting the carburizing depth and the amount of carburizing, various carburizing / diffusion conditions can be obtained.

  In the present embodiment, from the viewpoint of easy adjustment of the carburizing time and the diffusion time, the inlet side introduction pipe 12 of the core tube 11 is closed, and the carburizing gas is introduced from the central introduction pipe 13 to each of the core pipes 21 and 31. The inlet side introduction pipes 22 and 32 are closed, and the carrier gas is introduced into the central introduction pipes 23 and 33. Further, the inlet side exhaust pipe 14 of the core tube 11 and the inlet side exhaust pipe 24 of the core tube 21 are used, and other exhaust pipes are not used. Thus, the core tube 11 was used as a carburizing portion, and the core tubes 21 and 31 were used as diffusion portions.

  Next, the performance of the core material of the present invention or the guide wire made of the core material will be described. FIG. 2 shows that SUS304 and SUS316L, which are austenitic stainless steel wires, are drawn to a predetermined wire diameter and then carburized using the above-described continuous vacuum carburizing furnace 1 to reduce the area reduction rate to 2.9% or more. The core material of the products 1 and 2 of the present invention obtained by drawing the skin pass at 10% or less or a guide wire made of the core material (1-2, 1-3, 1-4, 2-2, 2-3, 2 -4) and comparative steel wires 1, 2 (1-0, 1-1, 1-5, 2-0, 2) with skin pass drawing at a surface reduction rate of less than 2.9% or more than 10% -1, 2-5) As a comparative example, the SUS304 and SUS316L wires of various wire diameters (Comparative Examples 1 to 7), the wire type, the wire diameter, the finished state, and the elongation until the wire diameter is obtained. It shows the cumulative area reduction by wire processing, carburizing / diffusion conditions, skin pass conditions and tensile test results.

  The provision wire is a wire in a state before the carburizing treatment, and the finished product of the present invention, the comparative steel wire, and Comparative Examples 1 to 4 are so-called soft wires. The provision strands of Comparative Examples 5 to 7 are so-called hard wires that are formed into a certain size and then drawn into wire diameters corresponding to the respective area reduction ratios. Carburization was performed in the vacuum carburizing furnace described above, but the time when the steel wire passed through the carburizing source gas atmosphere was defined as the carburizing time for convenience, and the time when it passed through the atmosphere without the carburizing source gas was defined as the diffusion time. In the product of the present invention and the comparative steel wire, skin pass wire drawing was performed after carburizing at a reduction in area as shown in the figure. In addition, the comparative example 1 is a result of the diameter of 0.1 mm in the Example of Japanese Patent Application No. 2004-376822. All results except for Comparative Example 1 have a diameter of 0.2 mm or more. Comparative Examples 1 to 3 show the results of aiming for high rigidity without performing skin pass drawing after carburizing, and Comparative Examples 4 to 7 show a guide wire made of a core material or a core material without performing carburization and skin pass after carburizing. The result of making is shown.

  As shown in FIG. 2, in the inventive product 1 and the comparative steel wire 1, an austenitic stainless steel wire having a diameter of 0.36 mm corresponding to SUS304 (JIS G 4308) was carburized at 980 ° C. at a carburizing temperature of 5 minutes + diffusion time. Carburizing was performed for 10 minutes. This processing time is about 2/3 with respect to Comparative Example 1 having a diameter of 0.1 mm that is vacuum carburized by the same apparatus. A micrograph of the cross-sectional corrosion structure of the product 1 of the present invention and the comparative steel wire 1 before skin pass treatment is shown in FIG. As shown in FIG. 3A, in the austenite structure of the substrate, a region where fine carbides are dispersed in the outer peripheral portion is distinguished from the inside. Black dots are carbides. Carbide is much on the outer periphery and decreasing on the core side, and the density of carbide gradually decreases from the outer periphery toward the core. The size of the carbide is 0.5 μm or less. As for the size of the carbide, it is preferable that the particle diameter represented by an equivalent circular diameter is 2 μm or less.

  Furthermore, the comparative steel wire 1 and the product 1 of the present invention were drawn under the skin pass drawing conditions of 2.0, 2.9, 4.4, 9.8, and 13.4% without any reduction in area. As shown in FIG. 2, in Comparative Example 1 having a thin wire diameter of 0.1 mm, 0.2% proof stress, 2% strain stress is 1000 or more, and elongation is 7.7 even without a skin pass after carburizing. In contrast, Comparative Example 2 and Comparative Steel Wire 1-0, in which the wire diameter of carburized only is thick, are 5.7 to 18.1, whereas the yield strength and stress are low. Further, increasing the carburizing amount increases the yield strength and stress, but tends to decrease the elongation.

  On the other hand, according to 1-1 to 1-5 in which skin pass was performed after carburizing, the 0.2% proof stress and 2% strain stress increased and the elongation decreased as the skin pass area reduction rate increased. After the skin pass treatment, the 0.2% proof stress and 2% strain stress increased by about 2 times and 1.5 times, respectively, and the elongation decreased by about half compared to before the skin pass. In 3 and 1-4, the 0.2% proof stress is 1000 MPa or more, the 2% strain stress is 1100 MPa or more, the elongation is 5% or more, and the rigidity and elongation characteristics comparable to those of Comparative Example 1 having a diameter of 0.1 mm. A wire having a diameter of 0.36 mm was obtained under conditions close to the carburizing conditions of Comparative Example 1. In particular, the inventive product 1-3 was able to obtain a breaking elongation as high as 12% at the same time while the yield strength was 1043 MPa and the 2% strain stress was a high level of 1163 MPa. Incidentally, in the comparative steel wire 1-5 exceeding the area reduction rate of 10%, the decrease in elongation is remarkable.

  Next, a case where a wire having a diameter of 0.36 mm corresponding to SUS316L (JIS G 4308) of austenitic stainless steel is used will be described. As shown in FIG. 2, carburization was performed at a carburizing temperature of 980 ° C. under conditions of carburizing time 10 minutes + diffusion time 20 minutes. This processing time is about 1.3 times that of Comparative Example 1 having a diameter of 0.1 mm that was vacuum carburized with the same apparatus. A micrograph of the cross-sectional corrosion structure of the present invention product 2 and the comparative steel wire 2 before the skin pass is shown in FIG. As in the case of the product 1 of the present invention and the comparative steel wire 1 described above, a carburized region in the outer periphery is observed.

  As described above, the comparative steel wire 2 and the product 2 of the present invention were drawn under the skin pass drawing conditions of 2.0, 2.9, 4.0, 6.7, and 11.3% with no area reduction. . As shown in FIG. 2, the comparative example 3 and the comparative steel wire 2-0 having a thick wire diameter of only carburized have an elongation of 3.2 to 20.0, whereas the proof stress and the stress are low. Further, increasing the carburizing amount increases the yield strength and stress, but tends to decrease the elongation.

  According to 2-1 to 2-5 in which the skin pass was performed after carburizing, the 0.2% proof stress and the 2% strain stress increase as the skin pass area reduction rate increases, and the elongation decreases on the contrary. After skin pass treatment, the 0.2% proof stress and 2% strain stress increased to about 2 times and 1.5 times, respectively, and the elongation decreased to about half or less, and as a result, the product of the present invention 2 In -3 and 2-4, the 0.2% proof stress is 900 MPa or more, the 2% strain stress is 1100 MPa or more, and an elongation of 5% or more can be secured, and the rigidity and elongation comparable to those of Comparative Example 1 having a diameter of 0.1 mm. A line having a characteristic diameter of 0.36 mm was obtained under conditions close to the carburizing conditions of Comparative Example 1. In particular, in the product 2-3 of the present invention, an elongation of 10.9% at break elongation was obtained while obtaining a yield strength of 996 MPa and a 2% strain stress of 1132 MPa. In the present product 2-4, the 0.2% proof stress and the 2% strain stress were further increased, and the elongation at break was reduced, but a high elongation of 9% was still obtained. In addition, like the above-mentioned, in the comparative steel wire 2-5 which exceeds 10% of area reduction rate, the tendency for elongation to fall significantly was seen.

  In applying these results as a core material or a guide wire made of a core material, between comparative steel wire 1-2 (area reduction rate 2.9%) and comparative configuration 1-5 (area reduction rate 13.4%) Moreover, it is preferable as a guide wire which consists of a core material or a core material to make between comparative steel wire 2-2 (area reduction rate 2.9%) and comparative structure 2-5 (area reduction rate 11.3%). Therefore, in the present invention, in the skin pass processing after the continuous vacuum carburization, the area reduction rate of 2.9% or more and 10% or less is the most preferable range.

  The comparative example will be described in detail. As described above, when the wire diameter is 0.2 mm or more, the skin treatment is not performed and the high rigidity comparable to that of the comparative example 1 having the wire diameter of 0.1 mm is the same processing time. If it is going to be obtained by this, it is necessary to make the thinner surface carburized portion more rigid, and the diffusion time must be reduced. Comparative examples 2 and 3 are examples in which the ratio of the diffusion time is reduced. In Comparative Example 2, a SUS304 wire having a wire diameter of 0.36 mm was carburized under the conditions of a carburizing temperature of 980 ° C., a carburizing time of 20 minutes + a diffusion time of 10 minutes, that is, with the diffusion time being half of the carburizing time. This processing time is about 1.3 times that of Comparative Example 1 having a diameter of 0.1 mm. The 2% strain stress is 1087 MPa and the elongation is 5.7%, but the 0.2% proof stress is as low as 703 MPa. In Comparative Example 3, SUS316L wire having a wire diameter of 0.5 mm was carburized under the conditions of a carburizing temperature of 980 ° C., a carburizing time of 10 minutes + a diffusion time of 0 minutes, that is, with no diffusion time. This processing time is about half that of Comparative Example 1 having a diameter of 0.1 mm. Although the 2% strain stress reached 1048 MPa, the elongation was as low as 3.2%, and the 0.2% proof stress was only 863 MPa as in Comparative Example 2.

  Comparative Examples 4 to 7 are examples of lines that are not carburized. Comparative Example 4 is a solution-finished line of SUS304 having a diameter of 0.36 mm. Elongation is high but there is no rigidity. Comparative Example 5 is the same hard finish line of SUS304 as Comparative Example 4, but it is an example where a very rigid line can be obtained by increasing the area reduction rate of wire drawing, but the elongation is 2.4%. Low. Although it is generally known that these rigidity and elongation can be adjusted by an intermediate area reduction rate, those examples in SUS316L are shown in Comparative Examples 6 and 7, but 0.2% proof stress is 1000 MPa. As described above, there is no one that can secure a 2% strain of 1100 MPa or more and an elongation of 5% or more.

  FIG. 4 shows a summary of the results described above with respect to 0.2% proof stress and elongation at break. The product 1 of the present invention and the comparative steel wire 1 are plotted with white triangles, from the upper left to before the skin pass, that is, only carburizing, and from the 1-0 to the 1- Connected up to 5 with a thick solid line. 2-0 to 2-5 of the product 2 of the present invention and the comparative steel wire 2 are similarly plotted with white squares and similarly connected with thick solid lines. Comparative Example 1 having a wire diameter of 0.1 mm is a large black circle plotted near the center of the figure.

  On the other hand, Comparative Examples 2 and 3 correspond to the lower right two points among the four points plotted with small black circles, and are connected with a thin solid line in the case of carburizing alone in combination with the ones of Examples 1 and 2 before the skin pass. ing. If an attempt is made to increase the 0.2% yield strength only by adjusting the carburizing conditions without performing the skin pass drawing after carburizing, the elongation at break decreases to 4% or less before reaching 1000 MPa, so that no effect is obtained. Comparative Examples 4 to 7 are plotted with white circles and connected with an alternate long and short dash line. The point with the highest elongation in the upper left is Comparative Example 4 in the form of a solution. Hereinafter, 0.2% proof stress increases and elongation at break decreases as the wire drawing area reduction ratio increases, so Comparative Examples 7 and 6 Plotted in the order of 5 to the lower right. As in the case of carburizing alone described above, since the elongation at break begins to interrupt 4% when the 0.2% proof stress reaches 1000 MPa, it is extremely difficult to obtain the effect.

  When the product of the present invention and the comparative steel wire are compared with Comparative Examples 2 and 3, when the wire diameter is large, it can be obtained in approximately the same processing time within twice the (carburizing + diffusion) time of 0.1 mm in Comparative Example 1. There is a difference that an area that cannot be obtained, that is, an elongation of 4% or more, more preferably 5% or more and a 0.2% proof stress of 1000 MPa or more is obtained. On the other hand, it was the same in comparison with Comparative Examples 4 to 7 in which rigidity was obtained only by overlapping the wire drawing without carburizing the solution wire. Therefore, in this example, it can be seen that the combination of the carbide distributed in the surface layer in the austenite structure and the skin pass drawing works effectively.

  Further, there has been no core material or a guide wire made of the core material in the conventional manufacturing method, but according to the present invention, the 0.2% proof stress in the core base tensile test is 900 MPa or more when the diameter is 0.2 mm or more and 0.5 mm or less. A guide wire made of a core material or a core material having a strain at 2% strain of 1100 MPa or more and a breaking elongation of 5% or more was realized.

  In the present embodiment, it has been described that the carbide is dispersed on the surface of a wire based on SUS304 and SUS316L, which are typical austenitic stainless steels, and the skin pass wire drawing is performed. Any other steel grade can be used, and furthermore, carbide can be dispersed in the surface layer portion, so that it can be applied to other metal wires as long as a predetermined tensile strength and elongation can be secured. Needless to say. For example, the present invention may be applied to an Fe—Mn—Si alloy.

It is a schematic diagram of the core material of the guide wire which shows embodiment of this invention. It is a figure which shows the strand of this invention product, a comparative steel wire, and a comparative example, carburizing conditions, skin pass conditions, and a tensile test result. (A) is a micrograph of a cross-sectional corrosion structure before skin pass treatment in the product 1 of the present invention and the comparative steel wire 1, and (b) in the product 2 of the present invention and the comparative steel wire 2. It is a graph which shows the result of 0.2% yield strength and breaking elongation among the test results of the product of the present invention, the comparative steel wire, and the comparative example. It is sectional explanatory drawing of the continuous vacuum carburizing apparatus (furnace) for manufacturing the stainless steel wire for guide wires which consists of a core material described in embodiment of this invention product or a core material.

Explanation of symbols

20 Core (material)
21 (core) base 22 (core) tip

Claims (5)

  A core material comprising a tapered core tip and a core base having a diameter of 0.2 mm or more and 0.5 mm or less following the tip, and at least in the base layer made of austenitic stainless steel in the surface layer of the cross-sectional structure of the core base The core material or core material is characterized in that the carbide is dispersed in the core base, the 0.2% proof stress in the tensile test of the core base is 900 MPa or more, 1100 MPa or more at 2% strain, and the elongation at break is 5% or more. Guide wire.   2. The core material according to claim 1, wherein the cross-sectional structure of the core tip portion has less or no carbide in comparison with the core base portion, and the core base portion has carbide dispersed in the matrix. Or a guide wire made of a core material.   After dispersing carbide in a thin wire base with a finished diameter of 0.2 mm to 0.5 mm after skin pass made of austenitic stainless steel, a skin pass elongation of 2.9% to 10% in area reduction A method of manufacturing a guide wire comprising a core material or a core material, wherein the wire is formed.   After the manufacture according to claim 3, the tip of the core is subjected to surface removal processing into a taper shape, thereby forming a core tip having less or no surface carbide phase than in the base. A core material or a guide wire manufacturing method comprising the core material. A guide wire comprising the core material or the core material according to claim 1 or 2, wherein the guide wire is manufactured by the manufacturing method according to claim 3 or / and 4.