JP2007023373A - Method for producing stainless steel high strength extrafine flat wire - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for efficiently producing a high strength extrafine flat wire having high strength and excellent dimensional stability. <P>SOLUTION: The method for producing a high strength extrafine flat wire of stainless steel is characterized in that, when a stainless steel extrafine flat wire with a thickness of ≤0.1 mm having high strength properties satisfying a tensile strength of ≥2,000 N/mm<SP>2</SP>by cold rolling, it comprises: a stage 1 where a stainless steel soft wire having a fine austenitic structure with a crystal grain size of No. ≥8 based on JISG-0551 is obtained; a stage 2 where the soft wire is subjected to cold wire drawing at a working ratio of ≥60%, so as to obtain a hard fine wire with a wire diameter of ≤0.5 mm having a strain-induced martensitic structure in which crystals fibrously elongate along the longitudinal direction of the wire; and a stage 3 where the hard fine wire is cold-rolled at a draft of ≥40% while applying back tension thereto without performing heat treatment. The high strength extrafine flat wire is obtained by the method. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention has high strength and excellent dimensional stability. For example, a stainless steel that can be suitably used for a braided body inserted as a reinforcing member in various pressure-resistant ultrathin tubes such as medical catheters and endoscopes, or a deformed wire spring. The present invention relates to a method for producing a stainless steel high-strength ultrathin flat wire.

  A catheter inserted into a blood vessel is a thin tube that is used as a guide member for inserting a stent for expanding a blood vessel in a necessary affected area, or as a chemical liquid tube for injecting a chemical liquid such as an angiographic contrast medium. In order to smoothly insert the branching blood vessel to the target site, it is required to have excellent characteristics such as flexibility and torque transmission property that transmits torque at the root to the tip, and excellent operability. In addition, the catheter has a small outer diameter so that it can be inserted into a thin blood vessel, but also has an internal space that does not interfere with the passage of the inserted stent and drug solution, and withstands the contrast agent injection pressure. Is also requested.

  For such a request, for example, as illustrated in FIG. 9, a reinforcing member b in which a spiral wound body of metal thin wires a or a plurality thereof is braided (braided) is embedded in the peripheral wall of the catheter. A catheter that enhances performance has been proposed (for example, Patent Document 1). This is intended to make the peripheral wall of the catheter thin by using the metal thin wire a having a large tensile strength, to impart flexibility while increasing rigidity, and to prevent kinking.

  Further, as the metal thin wire used for the reinforcing member, there is provided a reinforcing member formed by alternately braiding one thin wire and the other thin wire in a spiral shape so as to form a tube shape. For example, Patent Document 2 proposes a catheter using a 0.12 mm stainless steel wire and an ultrathin flat wire formed by rolling a flat strip having a width of 0.26 mm and a thickness of 0.06 mm. Further, as a reinforcing member, for example, Patent Document 3 proposes that a high-strength ultrathin flat wire is obtained by performing a solution heat treatment and then tempering without tempering.

Japanese Patent Laid-Open No. 7-194707 JP-A-8-317986 JP 2002-282366 A

  As described above, Patent Document 1 uses a reinforcing member made of a fine metal wire with increased tensile strength, thereby reducing the wall thickness of the catheter and increasing the inner diameter while providing sufficient flexibility and rigidity. Patent Document 2 proposes to use a rolled ultrathin flat wire as a thin metal wire, and Patent Document 3 proposes to use a high-strength metal thin wire without tempering. However, since the catheter is bent and twisted along the complicated and branched blood vessels as described above, deformation stress is applied to the fine metal wires constituting the reinforcing member according to these deformations. In particular, in an ultrathin flat wire, the stress on both side surfaces at both ends in the width direction is larger than that in other portions.

  Therefore, when there are fluctuations in the width of the ultra-thin flat line, such as waviness, in the part where the curvature of the horizontal bending in the width direction plane is forced to be the same, the width of the side of both ends in the width direction is large. On the other hand, a large stress is generated, and on the other hand, the in-plane bending rigidity is increased in the portion where the width dimension is large, and the curvature becomes smaller compared to the other portions. Will impair durability.

  However, although each of the above-mentioned patent documents describes forming into an ultrathin flat wire by rolling a fine metal wire and drawing a strong wire, it does not take into account variations in width.

  In addition, it has been found that if waviness or unevenness is present on the surface of the fine metal wire, particularly on both sides in the width direction, it becomes the starting point of stress concentration, particularly in the recess, and there is a risk of causing disconnection due to the notch effect. .

  It is an object of the present invention to provide a method for producing a stainless steel high-strength ultrathin flat wire that can efficiently produce a stainless steel high-strength ultrathin flat wire having high strength, excellent dimensional stability, and excellent width dimension stability. It is said.

The invention according to claim 1 of the present application is a stainless steel high-strength ultrathin flat plate manufactured by cold rolling of a stainless steel ultrathin wire having a thickness of 0.1 mm or less and a tensile strength of 2000 N / mm ² or more. A method of manufacturing a wire,
a) obtaining a stainless steel soft wire having a fine austenite structure having a crystal grain size of # 8 or more based on JISG-0551 by solution heat treatment;
b) subjecting the soft wire to cold drawing at a processing rate of 60% or more to obtain a hard fine wire having a wire diameter of 0.5 mm or less of a work-induced martensite structure in which crystals extend in a fiber shape along the longitudinal direction; C) performing a cold rolling at a rolling reduction of 40% or more while applying a reverse tension without applying heat treatment to the hard thin wire to obtain a stainless steel high-strength ultra-thin flat wire,
The stainless steel high-strength ultrathin flat wire has a width variation (S) of 20 μm or less.

  According to a second aspect of the present invention, the stainless steel is, in mass%, C: 0.05 to 0.15%, Si ≦ 1.0%, Mn ≦ 2.0%, Ni: 7.0 to 11. N-added stainless steel comprising 0% (claim 1), Cr: 17.0 to 21.0%, N: 0.10 to 0.30%, and remaining Fe and inevitable impurities It is characterized by.

  According to a third aspect of the present invention, in the stainless steel high-strength ultrathin flat wire, the surface roughness in the longitudinal direction of the side surface in the width direction is 0.5 μm or less in terms of 10-point average roughness (Rz), In the invention according to Item 4, the stainless steel soft wire is subjected to a solution heat treatment at a temperature of about 950 to 1050 ° C. for 1 to 20 seconds after performing cold wire drawing with a strength of 75% or more. In the invention according to claim 5, the cold wire drawing in the stage of obtaining the hard fine wire adopts a wet wire drawing using a diamond die, and the surface of the hard fine wire has 10 points. A smooth finish surface having a roughness (Rz) of 1.0 μm or less, and the invention according to claim 6 is characterized in that the cold drawing is performed at a processing rate of 65 to 98% and the surface of the hard fine wire is 10 points. The roughness (Rz) is 0.2 μm or less, and claims In the invention according to the present invention, the cold rolling makes the hard fine wire a flat wire having a ratio (W / t) of 2.5 times or more in the ratio of width (W) to thickness (t), respectively. It is a feature. Furthermore, in the invention of claim 8, after the cold rolling process, a low temperature strain relief heat treatment at 350 to 550 ° C. is further applied.

  As a result of having such a configuration, the invention according to claim 1 is a fibrous work-induced martensite in which the cold rolling is preliminarily stretched along the longitudinal axis by the wire drawing performed in the preceding stage. Since it is a hard thin wire made into a structure, each crystal of the fiber structure extending in the longitudinal direction immediately below the rolling roll is rolled while spreading in a fan shape, and a stainless steel high-strength ultrathin flat of a wider strip. A wire can be formed.

Moreover, since the fiber structure is the same for the side surfaces at both ends in the width direction as well as the upper and lower surfaces, the surface property of the side surface part is excellent, and the direction along the longitudinal direction is already in the state of the strands, that is, in the state of the hard fine wires Because it has a fiber structure, and rolling is performed while applying reverse tension, it can prevent the occurrence of undulations and irregularities on the side surface in the length direction, reduce fluctuations in the width dimension, and surface condition As a result, the variation in the width dimension of the side surface portion can be 20 μm or less. Therefore, it is possible to reduce the bending stiffness variation due to the width dimension variation, smooth the bending, and reduce the occurrence of stress concentration, notch effect and the like. The stainless steel high-strength ultrathin flat wire has a thickness of 0.1 mm or less and a tensile strength of 2000 N / mm ² or more, so it is excellent in elasticity and improves usability. sell.

  Moreover, the structure of Claims 2-8 can improve the said characteristic of the said stainless steel high intensity | strength extra fine flat wire by adoption of each structure.

A method for producing a stainless steel high-strength ultrathin flat wire of the present invention (hereinafter sometimes simply referred to as a production method) will be described with reference to the drawings. As shown in the block diagram of FIG. 1, the manufacturing method according to the present invention obtains a hard thin wire 3 by subjecting a soft wire to cold drawing and a stainless steel soft wire having a fine austenite structure as a primary wire. A cold-drawing stage B and a cold-rolling stage C that cold-rolls the hard fine wire 3 to obtain a tentress steel high-strength ultrafine flat wire 4 (sometimes referred to as an ultrafine flat wire 4). By performing such cold rolling with reverse tension applied, a stainless steel high-strength ultrathin flat with a thickness of 0.1 mm or less, a tensile strength of 2000 N / mm ² or more, and a variation of the width dimension w of 20 μm or less. A line can be obtained.

  In this specification, the width dimension variation s is obtained by measuring the width dimension w of the ultrathin flat line along the length direction by any number of points (for example, several to several tens, preferably about 10 to 30). It means the time variation, that is, the standard deviation, and can be obtained by the following equation (1). For example, an enlargement projector or a laser size measuring instrument is used for the measurement. Preferably, it is based on measuring 20 points at intervals of 10 mm.

s = √ [1 / (n−1)] × [Σ (wi−wm) 2] (1)
* Wm is the width dimension at each point, wi is the average value, and n is the number of measurement points.

Stage A is a process for obtaining a stainless steel soft wire as a raw wire. The stainless steel soft wire has a fine austenite structure with a crystal grain size of 8 or more and can be obtained by solution heat treatment. Wherein the crystal grain size, JISG-0551 based on the "austenite grain size testing method of steel", and the grain size number # 8, the size of one crystal 0.00049Mm ^2, namely 2048 by the cross-sectional area 1 mm ² per It has a crystal number. In order to further enhance the effect of the present invention, it is preferable to use a finer crystal grain size of No. 9 or more, but the upper limit is defined only by the grain size of No. 10 in the JIS standard. A thing, for example, about 0.00001 mm can also be used.

  In order to obtain a stainless steel soft wire having such a fine austenite structure, for example, after performing cold wire drawing with a strength of 75 to 99.5% or more, preferably 95% or more, the temperature is about 1000 ° C. It can be obtained by performing a solution heat treatment at a temperature of about 10 seconds. Further, for example, by performing the treatment at 900 ° C. or lower, which is lower than the above temperature, the crystal grains can be further refined. Similarly, the heat treatment time can be obtained, for example, by obtaining a refined structure in the same manner as described above by performing the shorter time treatment. be able to. Under this condition, recrystallization is performed while suppressing crystal growth by suppressing heat absorption during heat treatment. Although it can be carried out as appropriate depending on the setting of conditions such as temperature, time, atmosphere, etc., the solution heat treatment is usually performed at about 850 to 1050 ° C. for about 2 to 20 seconds.

For example, austenitic stainless steel such as SUS302, SUS304, and SUS316 can be used as a material for the original wire that can be used, and a high-strength ultrathin flat wire having a tensile strength of 2000 N / mm ² or more can be obtained. Preferably, by mass, C: 0.05 to 0.15%, Si ≦ 1.0%, Mn ≦ 2.0%, Ni: 7.0 to 10, 0%, Cr: 17.0 to 20 0.0%, N: 0.10 to 0.30% is included, and N-added stainless steel composed of the balance Fe and inevitable impurities is used. In the stainless steel of this kind of composition, since N is an interstitial element, the crystal grains can be further refined, and the work hardening rate accompanying processing is large, for example, 2800 N / mm ² or more, more preferably A high-strength ultrathin flat wire of 3000 N / mm ² or more can be obtained. The upper limit is about 3200 N / mm ² to prevent an excessive increase in rigidity.

  Since the N-containing stainless steel has a high work-hardening rate, a predetermined strength can be obtained with a relatively small amount of processing. Therefore, it is preferable as a stainless steel high-strength ultra-thin wire with excellent corrosion resistance and excellent corrosion resistance. It becomes a steel grade. Moreover, what formed the lubricating film, such as Ni plating, on the surface of the stainless steel soft wire of an original wire can also be used as needed. As the coating technique, for example, the technique of a spring stainless steel wire disclosed in Japanese Patent Application Laid-Open No. 2005-15826 can be used. The reason why the content of each element is set in the N-added stainless steel wire will be described below.

  C is an austenite-generating element that contributes to increasing the strength by increasing the amount of martensite induced by cold working, and at least 0.05% is effective, but it exceeds 0.15%. If it is contained in a large amount, the brittleness will increase, and this will cause a decrease in productivity such as cracks and breaks during rolling, and it is preferable to increase the strength to 0.09 to 0.13%.

  Si is necessary from the property of increasing the tensile strength and elasticity limit of the wire, but the toughness is reduced accordingly, and the adverse effect due to the occurrence of δ ferrite phase is also seen, so the upper limit is 1.0%, More preferably, it is less than 0.4 to 1.0%.

  Mn is added as a desulfurization and deoxidizing agent or for stabilization of the austenite phase, but a large amount of addition decreases the workability, so the upper limit is made 2.0%, more preferably 0.8. 8% or less, and the lower limit is 0.3% or more.

  Ni is a basic element of austenitic stainless steel, and its inclusion can stabilize the austenite structure and increase the corrosion resistance. However, if added in a large amount, it becomes difficult to obtain high strength properties, so 7.0- 11.0%, preferably 8.0 to 10.5%.

  Cr is also a basic element of stainless steel like Ni, and its inclusion promotes passivation and improves corrosion resistance. However, since a large amount of addition affects productivity, 17 to 21%, Preferably it is 18.0 to 20.5%.

  N is an austenite-generating element, and it is possible to improve the mechanical properties by refining the crystal grains. Addition of 0.10% or more is preferable from the viewpoint of obtaining a fine fiber structure. However, when the content exceeds 0.30%, the hot workability is lowered, which increases the cost.

  As another form, together with each of the above elements, for example, further including any one or more of 0.4 to 1.2% Mo, 0.5% or less Cu, 0.30% or less Nb, and the balance Fe and Stainless steel containing inevitable impurities can also be used.

  In addition, about the wire diameter and rolling process performed after that, the wire diameter of this soft wire is set to about 0.08 to 1.5 mm, for example. In addition, in order to improve the surface texture and roughness of the final ultrafine flat wire, the original wire is a bright precision finished surface processed by wet drawing with a diamond die, for example. The solution heat treatment is performed.

  Next, the cold drawing process for obtaining the hard wire 3 of the stage B is performed by using a hard die such as a diamond die at a processing rate of 60% or more on the stainless steel soft wire obtained in the stage A. By performing wire processing, the wire is formed into a hard thin wire having a fibrous stress-induced martensite structure that extends finely, for example, a wire diameter of about 0.02 to 0.8 mm. Preferably, the processing rate is about 75 to 90%. Here, the processing rate refers to a percentage of [(initial cross-sectional area−post-processing cross-sectional area) / initial cross-sectional area].

  An example of the crystal structure of the hard thin wire 3 is shown in FIG. In FIG. 2, the cross section in the length direction is enlarged 400 times. In the cross-sectional view, crystals are distributed in a state where fine fiber structures are continuously and densely arranged along the longitudinal direction. The fiber thickness d of the crystal can be confirmed to be 25 μm or less, for example, about 10 μm or less. The fiber thickness varies depending on the size of the crystal grain size in the soft wire and the processing amount in the cold wire drawing, and preferably, as shown in FIG. 3 where one fibrous crystal is taken out. The ratio of the crystal width (d) to the crystal length (L), that is, the average aspect ratio (L / d) is 20 to 1500 times, preferably about 100 to 1000 times.

  As for the cold wire drawing, as in the case of the soft wire, it is preferable to improve the surface properties by wet wire drawing with a diamond die, for example, with a processing rate of 60% or more. The 10-point surface roughness (Rz) of the line can be made to be an ultra-smooth finished surface of 1.0 μm or less, preferably 0.5 μm or less. Further, in the case of a processed material having a processing rate of 65% or more, the surface property is increased to 0.2 μm or less. If the processing rate is so high that it exceeds 98% (matching with claim 6), the subsequent rolling process becomes difficult. Therefore, in consideration of productivity, it is more preferably 65 to 90%, and further 70 to 90%. To do. The hard thin wire 3 can be formed in a circular cross section shown in FIG. 4, an elliptical shape, or an oval shape.

  Further, cold rolling is performed on the hard thin wire 3 to obtain a stainless steel high-strength ultrathin flat wire 4 as a cold rolling stage C. The drawn hard thin wire 3 is subjected to cold rolling without heat treatment. Done. An ultrathin flat wire 4 illustrated in cross section in FIG. 5 having a rectangular cross section having a reduction ratio of 40% or more and a predetermined width (w) and thickness (t) is formed. The ultrathin flat wire of the present invention has a thickness (t) of 0.1 mm or less, and its width (w) dimension is 1.5 to 15 times the thickness (t), preferably 2.5 to 5 times. The target is about double, for example, 0.5 mm or less. Here, the average value wi in the formula (1) is used for the width (w) dimension.

  Cold rolling is always performed while applying reverse tension. This makes it possible to perform rolling up to the final dimension using one set of rolling rolls, can be continuously rolled into an ultrafine flat wire 4 having a thickness of 0.1 mm or less, and avoid multi-stage continuous rolling. Can do. Reverse tension is the tension in the direction opposite to the direction of winding by winding, and the addition of this reverse tension stabilizes the width dimension of the flat wire, enhances linearity, and reduces the amount of remaining deflection. Keep it low.

  FIG. 6 shows an example of the cold rolling apparatus 10 used for this rolling process. A supply block 10A for supplying the hard thin wire 3, a rolling block 10B that is rolled to form a very thin flat wire of a predetermined size, and a winding block 10C that winds the drawn ultra thin flat wire are arranged in series. ing.

  The supply block 10A includes a supply reel 10a containing a hard thin wire, guide rollers 10b, 10b on both sides arranged side by side, and a dancer roller 10c located between and below the tension device 10d, and a tension measuring device 10e. With The reverse tension device 10d improves the linearity by causing the dancer roller 10c to bend in a direction opposite to the winding direction of the hard thin wire 3 in the supply reel 10a, thereby applying reverse tension and reducing the winding. The rolling accuracy in the rolling block 10B is increased.

  The rolling block 10B includes four backup rolls 10f, upper and lower work rolls 10g and 10g supported by upper and lower pairs of backup rolls 10f and 10f, and a liquid draining device 10i. Have. As described above, the work rolls 10g and 10g perform cold rolling with a rolling reduction of 40% or more. Note that, by rolling, an ultrathin flat wire having a rectangular cross-section illustrated in FIG. 5 and having a width (w) / thickness (t) = 1.5 to 15 which is a ratio of the width (w) to the thickness (t). Form.

  The take-up block 10C includes a reverse tension device 10m, a tension measuring device 10n, a dimension measuring device 10o, and a take-up reel 10p, which are composed of guide rollers 10j, 10j on both sides juxtaposed and a dancer roller 10k located between and below them. With. The reverse tension device 10m can improve the linearity at the time of rewinding from the take-up reel 10p by applying a reverse stress to the take-up stress prior to the take-up by the take-up reel 10p.

  Further, the supply reel 10a, the rolling roll 10h, and the take-up reel 10p are rotated by controlling the respective linear speeds to optimum speeds that take into account rolling by a driving source (motor) (not shown). The tension measuring devices 10e and 10n are controlled so that the tension measurement results are fed back by electronic control so that the operation of the entire device can be performed smoothly and with high precision.

  The cold rolling apparatus 10 enables a high-quality ultra-thin flat wire while suppressing dimensional variation by a predetermined reverse tension load in the rolling process, and the surface state is also good. In the rolling apparatus 10 shown in FIG. 6, the reverse tension moves so that the dancer rolls 10c and 10k provided in the winding block 10C and the supply block 10A slide up and down due to their own weight and tension. Although it is performed by the method of detecting the degree of the amount, for example, both dancer rolls 10c and 10k can be added by providing a rotational speed difference with the respective drive types. The reverse tension is most excellent when it is in the range of 2 to 15% (more preferably 5 to 10%) of the breaking load of the hard thin wire, and the reverse tension load is only one pass. Even in the rolling process, it becomes possible to bring about a good straightness without bending deformation.

  The ultra-thin flat wire thus obtained has high strength and excellent dimensional stability, but has a large processing strain due to cold drawing or rolling, so that it can be improved, for example, at a temperature of 350 to 350 It is preferable to perform low-temperature heat treatment at 550 ° C. This treatment improves toughness, improves the fatigue characteristics against bending, and enhances the life characteristics. This heat treatment is called tempering and is achieved by maintaining the temperature for a predetermined time (for example, about 0.5 to 20 s).

  Such a stainless steel high-strength ultrathin flat wire 4 is braided, for example, as shown in FIG. In addition, it may be braided on the outer peripheral surface of the inner tube 6, and at this time, the outer tube 7 can be formed by a method such as extrapolation or casting to produce a catheter. Various methods can be employed for forming the catheter, such as embedding the ultrafine flat wire 4 in the inner peripheral surface of the outer tube 7.

  As a raw wire, a SUS304 stainless steel hard wire having a wire diameter of 0.3 mm was subjected to a solution heat treatment at a temperature of 950 ° C. to obtain a soft wire as a raw wire. Therefore, in order to measure the crystal grain size of this soft wire, a part thereof was cut out and buffed with # 1200 polishing paper and subjected to electrolytic etching with an oxalic acid solution to obtain a measurement sample. As a result of measuring the crystal structure of the original line with a microscope enlarged 200 times, the average crystal grain size was a fine one corresponding to JIS: 9.

  Next, Ni plating having a thickness of 0.2 μm is applied to the surface of the original wire by an electrolytic plating method, and this is set in a continuous wire drawing machine using this as a lubricant. %, Wire drawing speed 150 m / min. To obtain a hard fine wire having a wire diameter of 70 μm. The hard fine wire has a smooth surface and excellent gloss, and the inside of the wire has a stress-induced martensite phase in which the fine fiber structure extends along the longitudinal direction. The thickness of the fiber structure is The fine surface roughness of 2 μm or less and the 10-point average surface roughness of the side surface of the line were Rz = 0.18 μm.

Then, this hard fine wire is processed at a reduction rate of 70% while applying a reverse tension of 100 MPa by a cold rolling mill (manufactured by Asahi Seiki) shown in FIG. , Thickness: 0.02 mm extra fine flat wire was obtained. This ultra-thin flat wire has a high strength of 2600 N / mm ² in tensile strength and smooth surface, and has a very high accuracy with a surface roughness Rz of about 0.3 μm with little unevenness on the side surface of the flat wire. It was. The variation (S) in the width dimension of the ultrafine flat wire was 3.3 μm, which was very good. An appearance photograph of this flat line is shown in FIG.

Four types of N-containing stainless steel soft wires having the composition shown in Table 1 are used as original wires, respectively, and cold drawing at a processing rate of 97% and hard fine wires by the drawing are as described in Example 1. Set in the same rolling machine, cold rolling was performed at a reduction rate of 50%. The obtained ultrafine flat wire has a high strength of thickness 0.025 mm, width 0.08 mm, tensile strength 2800 to 32200 N / mm ² , and the surface roughness at the side portion of the flat wire is Rz: 0.02 A high-quality ultrathin flat wire excellent in straightness of ˜0.035 μm was obtained.

In this example, the size of the crystal grain in the original wire is about 0.00009 mm ² and has a fine austenite structure of No. 10 or more, and in cold rolling, The reverse tension is performed while applying a stress corresponding to 5% of the tensile strength of the hard thin wire. The variation of the width dimension w according to this example was 2.1 to 6.3 μm, which was very preferable.

Next, this ultra-thin flat wire (sample C) was set in a tubular strand heat treatment furnace set at a temperature of 420 ° C., and tempered by running at a speed adjusted so as to satisfy the condition of time 1.3 seconds. Heat treatment than those in an inert atmosphere with argon gas, the tensile strength of 2920N / mm ² This treatment was strength of about 70N / mm ² up tension than 1.2% elongation and the rolling state and Strength Ratio The (yield strength / tensile strength) was also improved by about 8% from 88% to 96%.

Comparative example

As a comparative example for this example, the SUS304 stainless soft steel used in Example 1 was used as the original wire, and the soft wire was directly cold-rolled to obtain an ultrathin flat wire having the same dimensions as in Example 1. Although the tensile strength of the flat wire was almost the same as 2450 N / mm ² , the width variation was as large as 25 μm, and the average roughness at the side surface was Rz: 1.3 μm. A photograph of the appearance of a flat wire according to this comparative example is shown in FIG. 8B, and it can be seen that there are large irregularities in the longitudinal direction.

  Therefore, in order to further confirm the effect of the invention, a 180 ° repeated bending test using the ultrathin flat wire according to Example 1 and the comparative example was performed, and the number of times of bending until breakage was measured. The test was carried out by gripping an ultra-thin flat wire with a pliers and bending the vicinity of the grip portion by hand. The test was conducted with one side bent as one time. The ultra-thin flat wire of Example 1 withstands 153 times of bending. I was able to. On the other hand, in the comparative example, the surface roughness of the side surface portion was large, and the fracture occurred at the number of bending times of 102.

  Furthermore, for both of these samples, a braided tube product having an outer diameter of 2.5 mm and a pitch of 70 / inch was braided. Moreover, since the fatigue characteristics were excellent, it was possible to perform good processing.

  As shown in FIG. 7, the ultra-thin flat wire of the present invention is formed inside the tubular body composed of an outer tube 7 made of high-density polyethylene extruded into a hollow and an inner tube 6 made of low-density polyethylene. It is an example of the cross section of the catheter which embedded the reinforcement member 5 which consists of the braided body by the wire 4, A pressure resistance and torque transmission property are improved from the ultrathin flat wire being high strength and excellent in fatigue characteristics, and resistance to bending is large. In addition to being suitable as a reinforcing member for ultra-thin tube products that enhance durability, this braided body can also be used as, for example, a flexible shaft or rope product. It can be used as a wire spring and can be used in a wide range of applications.

It is a block diagram which shows the manufacturing process of the manufacturing method of this invention. It is an example of the magnification microscope which shows the fiber structure in a hard fine wire. It is the schematic which illustrates the state which took out the metal structure of a hard fine wire. It is sectional drawing which illustrates a hard fine wire. It is sectional drawing which illustrates an ultra-thin flat line. It is a block diagram which illustrates a cold rolling apparatus. It is the front view which removed a part which illustrates a catheter. (A) is an appearance photograph illustrating an ultrathin flat wire according to the present invention, and (B) is an appearance photograph illustrating a comparative example product. It is sectional drawing which shows the conventional catheter schematically.

Explanation of symbols

3 Hard fine wire 4 Extra fine flat wire 10d Reverse tension device

Claims (8)

Thickness 0.1mm or less, and the ultrafine flat wire of stainless steel having a tensile strength of 2000N / mm ² or more high strength characteristics to a method for producing a stainless steel high-strength ultra-fine flat wire produced by cold rolling,
a) obtaining a stainless steel soft wire having a fine austenite structure having a crystal grain size of # 8 or more based on JISG-0551 by solution heat treatment;
b) subjecting the soft wire to cold drawing at a processing rate of 60% or more to obtain a hard fine wire having a wire diameter of 0.5 mm or less of a work-induced martensite structure in which crystals extend in a fiber shape along the longitudinal direction; C) performing a cold rolling at a rolling reduction of 40% or more while applying a reverse tension without applying heat treatment to the hard thin wire to obtain a stainless steel high-strength ultra-thin flat wire,
The method for producing a stainless steel high-strength ultrathin flat wire, characterized in that the variation (S) in the width dimension of the stainless steel high-strength ultrathin flat wire is 20 μm or less.   The stainless steel is, by mass%, C: 0.05 to 0.15%, Si ≦ 1.0%, Mn ≦ 2.0%, Ni: 7.0 to 11.0%, Cr: 17.0 The stainless steel according to claim 1, wherein the stainless steel is N-added stainless steel including ˜21.0%, N: 0.10 to 0.30%, and the balance being Fe and inevitable impurities. Manufacturing method of high-strength ultrafine flat wire.   3. The stainless steel high-strength ultrathin flat wire has a 10-point average roughness (Rz) of 0.5 μm or less in terms of the surface roughness in the longitudinal direction of the side surface in the width direction. Stainless steel high-strength ultrafine flat wire manufacturing method.   The stainless steel soft wire is formed by performing a solution heat treatment at a temperature of about 950 to 1050 ° C. for 1 to 20 seconds after performing cold wire drawing with a strength of 75% or more. The method for producing a stainless steel high-strength ultrafine flat wire according to any one of claims 1 to 3.   The cold wire drawing process at the stage of obtaining the hard fine wire adopts a wet wire drawing method using a diamond die and has a 10-point surface roughness (Rz) of the hard fine wire to a smooth finish surface of 1.0 μm or less. A method for producing a stainless steel high-strength ultrathin flat wire according to any one of claims 1 to 4.   6. The stainless steel according to claim 4, wherein the cold wire drawing is performed at a processing rate of 65 to 98% and a 10-point surface roughness (Rz) of the hard fine wire of 0.2 μm or less. Manufacturing method of steel high-strength ultrafine flat wire.   The cold rolling is characterized in that the hard thin wire is a flat wire having a ratio (W / t) of width (W) to thickness (t) of 2.5 times or more. The manufacturing method of the stainless steel high intensity | strength extra fine flat wire in any one of -6.   The method for producing a stainless steel high-strength ultrathin flat wire according to any one of claims 1 to 7, wherein a low-temperature strain relief heat treatment at a temperature of 350 to 550 ° C is further applied after the cold rolling.