JPS62124002A - Production of extra fine metallic wire - Google Patents

Abstract

PURPOSE:To make mass production of extra fine wires with a short stage by further combining the bundle of hot rolled composite wires each consisting of a stainless steel bar and low carbon steel sheath with a low carbon steel sheath material to produce a hot rolled wire then eluting the low carbon steel with an acid. CONSTITUTION:The composite billet formed by inserting a single bar-shaped internal insertion material consisting of a stainless steel into the low carbon sheath material is hot rolled to form the composite wire of which the sheath part consists of the low carbon steel and the inside consists of the stainless steel. The composite material formed by inserting the parallel bundle of the above-mentioned composite wires into the low carbon steel sheath material is made into a wire by hot rolling. Such stage is repeated at least once or more. Solid members are fixed into the front end and rear end of the above- mentioned composite material according to need and further a packing material is packed into the gap between the composite materials, then the composite material is rolled. The resulted wire is dipped in the acid to elute away the low carbon steel. The mass production of the extra fine wires consisting of the stainless steel is thus made possible with the short stage.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for manufacturing ultrafine metal wires such as ultrafine wires made of stainless steel.

[Conventional technology] Fine metal wire with a thickness on the order of microns (stainless steel ultra-fine wire)
:J) In the first method of manufacturing, FIG. 2(A)
As shown in (Special Publication No. 55-1843) 5.
A wire rod 11 with a diameter of about 5 am is made to have a diameter of 0.0 mm by intermediate annealing 2 and wire drawing 1 using a die. A thin wire 12 of about l+im is made, plated 31 is applied to this thin wire 12, and a large number of wires are bundled in parallel and inserted into an exterior material made of different metals such as a steel pipe to create an east wire material 3, which is then subjected to intermediate annealing 5 and a multi-stage die. After repeating the wire drawing step 4, the sheathing material is dissolved and removed (6), and the plating layer applied to the wire is also removed (6). According to this method, for example, if 7,000 wires of O, Immφ are bundled together, inserted into a steel pipe with an outer diameter of 12.6 mmφ and a thickness of 2.3 mm, and drawn to 1.65 mmφ, the wire will weigh approximately 12 g. The thin line of φ is 7
You can get 000 pieces.

[Problems to be Solved by the Invention] However, in the first method, 5.5 mm
By repeating intermediate annealing 2 and wire drawing 1 with a die for a wire rod 11 of about φ, a strand of about 0.1+s■φ is manufactured, and because it goes through many processes, it requires a lot of energy, labor, and This requires time and increases manufacturing costs. In particular, fine austenitic stainless steel wire (e.g. 5
US304), by cold working (wire drawing),
Martensite is generated and work hardening is significant, so intermediate annealing is required to achieve a large reduction in area.

In another method for manufacturing thin metal wires, as illustrated in FIG. 2(B) (Japanese Patent Publication No. 59-28381),
■φ, inner diameter 170■φ low carbon steel pipe (exterior material) 20 insert 170ma+φ stainless steel rod W410,
A hot extrusion material 31-1 is produced and hot extruded 32) to form a wire rod rolling billet 33 with a diameter of 80 mm. This was heated 8 and rolled 9 to form a wire rod 11-1 of 8■φ.
get. This is roughly cold wire drawn 1 (with annealing if necessary) to obtain a wire 11-2 having a diameter of 2.5 mm. Cut this to an appropriate length and use the exterior material 20 (outer diameter 200mm) again.
Insert approximately 3280 pieces into IIlφ, inner diameter 170■φ),
A hot extrusion material 31-2 is made. Repeat this for 80m+s
After extruding into Robilet 33-2, +3■φ wire rod 11
-3 bundle rolling (9), at this time the inner wire is about 1
It is 40p, mmφ. This is cold wire drawing 1 (
If necessary, the wire is annealed) to form a thin wire of 1.13 mmφ. This is immersed in an acid such as nitric acid, and the carbon steel of the exterior material is dissolved and removed to obtain an ultrafine stainless steel wire of 12 gmmφ. In some cases, instead of cold drawing the wire rod 11-3 for wire bundle drawing, the process of hot pressing → wire rod bundle rolling may be repeated, and then the sheathing material is dissolved away with acid.

Even in the case of this second method, hot pressing → wire rod rolling → wire drawing → hot pressing → wire rod bundle rolling → bundle drawing (or hot pressing → wire rod bundle rolling) → acid dissolution and a large amount of The process requires a lot of energy, labor and time, and the manufacturing cost is also high.

In addition, as in the second method described in Section 2, if a material in which wire rods are densely inserted into a tubular sheathing material is rolled as it is, voids will always be created between the inserted materials, so that The exterior material protrudes to a large extent, making it impossible to continue rolling. This phenomenon is particularly noticeable at the leading and trailing ends of the material, and if it occurs at the leading end, it will not enter the entrance guide for the next stage of rolling, making it impossible for the material to advance. Figure 2 (
In example B), before rolling the composite material 13-1.13-2, the void between the inserted materials is eliminated by hot extrusion, and the unsteady deformed parts at the leading and trailing ends are cut off to form a normal composite billet. Therefore, the above problems are expected to be alleviated. However, at the billet end, the insert material remains exposed, and when there is a hard material that does not easily deform, such as stainless steel, on the inside, the easily deformable low carbon steel material on the outside will bite in the oval direction, especially at the leading and trailing ends. It is easy to take out and easily becomes an obstacle to rolling.

An object of the present invention is to efficiently manufacture a large amount of thin wire through a short process.

[Means for Solving the Problems] The method for manufacturing ultrafine metal wire according to the first aspect of the present invention is a composite billet in which an insert made of a single bar of stainless steel is inserted into a low carbon steel exterior material. After hot rolling to obtain a composite wire rod in which the exterior part is made of the low carbon steel and the inside is stainless steel, an insert material in which the above composite wire rod is made into a parallel bundle is placed inside the low carbon steel exterior material. After repeating the step of hot rolling the inserted composite material to obtain a wire rod at least once, the wire rod is immersed in acid to dissolve the low carbon steel.

The second method of manufacturing ultra-fine metal wire of the present invention is to hot-roll a composite billet in which an insert made of a single bar of stainless steel is inserted into a low-carbon steel exterior material, so that the exterior part is Next to the step of obtaining a composite wire rod made of low carbon steel and having a stainless steel interior, hot rolling a composite material in which an insert material in which the composite wire rod is in the form of a parallel bundle is inserted into the inside of a low carbon steel exterior material. A method for producing ultrafine metal wires, which comprises repeating the step of obtaining a wire rod at least once or more, and then immersing the wire rod in acid to dissolve away the low carbon steel. A solid member is fixed to the part and hot rolled.

The third method of manufacturing ultra-fine metal wire of the present invention is to hot-roll a composite billet in which an insert made of a single bar of stainless steel is inserted inside a low-carbon steel exterior material, so that the exterior part is Next to the step of obtaining a composite wire rod made of low carbon steel and having a stainless steel interior, the composite material is hot-rolled by forming a parallel bundle of the composite wire material and inserting an interpolation material inside the low carbon steel exterior material. A method for producing ultrafine metal wires, in which the process of obtaining wire rods is repeated at least once, and then the wire rods are immersed in acid to dissolve away the low carbon steel, the method comprising filling voids formed inside the composite material. It is filled with material and hot rolled.

[Function] According to the method for producing ultra-fine metal wire according to the first aspect of the present invention, the ultra-fine wire is produced only by hot rolling, and it becomes possible to efficiently produce a large amount of thin wire through a short process. .

According to the method for manufacturing ultra-fine metal wire according to the second aspect of the present invention, the ultra-fine wire is manufactured only by hot rolling while avoiding biting of the leading and trailing ends during rolling of the composite billet or composite material. The short process makes it possible to efficiently produce a large amount of thin wire.

According to the method for manufacturing ultra-fine metal wire according to the third aspect of the present invention, by removing the voids that occur inside the composite material, it is possible to heat Ultra-fine wires are produced only by inter-rolling, making it possible to efficiently produce a large amount of thin wires through a short process.

[Example] The present invention will be explained in more detail below.

In hot rolling of wire rods, the maximum diameter that can be efficiently manufactured is approximately 5 m + * φ, and wire rods smaller than this are normally produced by wire drawing. As with rolling, it is almost impossible to directly roll each piece of wood with rolls in terms of maintaining temperature, adjusting the roll hole shape, controlling tension, etc., and requires some ingenuity.

As a method for efficiently hot rolling fB wire, it is preferable to perform unrolling using the same concept as bundle drawing in wire drawing. In hot rolling equipment for wire rods, a large reduction in area can be obtained through multiple passes in one heating process. For example, 150+e1
5.5111+1φ wire from the mouth billet +oo
It can be rolled at a high speed of m/sec. In this case, the area reduction rate is (3,14/4) x (5,52/+502) 1/950, and the rolling efficiency is about 87 tan/hour. Therefore, if ultra-fine wire could be manufactured only by hot rolling.

Becomes very economical. The specific method is: 1. Insert a large number of wire rods into the tube and repeat unrolling.

■Take measures against crimping between wires.

■Avoid unsteady deformation of composite material edges.

It consists of things.

Hot bundle rolling involves heating a tubular material such as a circular tube, a square tube, or a square material with round holes in which wire rods are inserted in parallel as closely as possible (so that there are fewer voids). Rolled using a multi-stand wire rod rolling mill. If necessary, this wire rod is inserted into the tubular material again and the unrolling process is repeated. This is shown in Figure 2 (
As explained above, method B) is also a conventional technique.

When rolling a composite material in which many wire rods are inserted into a tubular material, the third
As shown in Figure (A), the insert material 1
1 is exposed, a large protrusion 101 (protrusion amount b = b + + b 2
) occurs, and it hits the entrance guide of the next stand and stops progressing, making subsequent rolling impossible. This is because if there is a gap between the inserts, they will not stretch in the rolling direction but will be crushed by rolling, so they will spread in the width (oval) direction and protrude from the caliber. Additionally, if the voids were removed, this tendency would be reduced, but since the leading and trailing ends are free ends, there is less restraint on spreading in the width direction, making it easy for low-carbon steel pipes to bulge out in the width direction. When the inner material is a material that is less stretchable than the outer material, such as when stainless steel is inserted, the easily deformed outer material tends to deform in the width direction, where there is less resistance, and the above tendency is exacerbated. .

In order to prevent the leading and trailing edges from sticking out and to enable stable rolling, solid members 102 of appropriate lengths may be welded to both ends of the material, as shown in FIG. 3(B). , this solid material can suppress its own protrusion to a small level similar to the rolling of a single solid material, and by welding the solid material to the end of the composite material, Chewing and free end deformation can be restrained, and bite deformation near the welded portion corresponding to the end of the composite material can also be suppressed to a small level. In addition, in order to suppress large bite deformation at the edge of the composite material, it is not effective just to cover it with a plate lid, and the length of the solid material must be appropriate for the outer diameter of the material. There must be.

In addition, when rolling with multiple stands, the unsteady part at the tip is cut off when the elongation length is at least three times as large, so that subsequent rolling can proceed smoothly, so the length of the cut off part should also be considered. I have to keep it. Assuming that the first tip is cut at a length L C1 = 80 mm at an elongation ratio input C1 = 3.0, this is converted to the length of the material before rolling as LOCI = L (:1/ input C1 = [10
/3.0 = 201 layers The second time, after increasing the number by three times, that is, if we cut down 80 layer votes at input C2 = 3X3 = 9.0, L, OC2 = LC2 / input C2 = 80 / 9 .0 = 8.9mm Therefore, in total, L OG = (LC1/Input C1) ÷ (LC2/λC
2) = 28.9mm is sufficient.

On the other hand, as determined from the experimental results shown in Fig. 4, the length LOS of the solid part necessary to suppress the protrusion is to suppress the protrusion amount to approximately 7% of the diameter (the guide width is approximately 7% of the diameter). ) and LOS/DO must be 0.09 or more. Therefore, the required length L C2S of the solid part after the second cutting is, where the diameter is DC2, L C2S / DC2 = 0.09DC2 = DO /
8] Shore iJ L C2S = 0.09 (DO77m)
When converted to material length, L 0C2S= L C2S /λC2= 0.09D
O(input C2)-372, and the length LO' of the solid material required is LO°=L OG+L 0G2S
=(LCI/C1/Input C1+ (LC2/8C2)+
(Q, 09DO) (, 1tC2) = /2Do =
In the case of 189m layer φ, L O' = 28.9+
0.58=28.5 intestinal liters. In addition, this LO is also the 4th
From the figure, it is necessary to satisfy LO/DO≧0.08, so in the end, the larger of LO° and 0.0900 should be the LO.The rear end is not cut off, so if the length is 0.090 or more, All you need to do is weld a piece of real wood with a gas vent in the center.

In addition, as shown in FIG. 5, the insert material 1 for the exterior material 20
Filling in step 1 is performed to minimize voids as much as possible, but voids always remain. As shown in FIGS. 6 and 7, this void is filled with a soft W4 wire 34 that is thinner than the interpolation wire, or a powder 35 such as iron powder, steel powder, scale powder, or metal oxide powder.
May be filled with

Next, as a measure to prevent the inserted wire rods from sticking together, since it is fine as long as the stainless steel wires are not crimped together, we use wire rods in which stainless steel wires are coated with low carbon steel, as shown in the example in Figure 2 (B). Even if the low carbon steel of the exterior is crimped together during hot rolling, or even if the stainless steel wire and the low carbon steel are crimped together, it will not be a problem because the low carbon steel will eventually be dissolved away by the acid. Stainless steel wire coated with low carbon steel is manufactured by hot rolling. That is, low carbon steel pipe material (outer diameter 189
mmφ inner diameter 118■φ), stainless steel rod (outer diameter 11 mmφ)
After inserting the 8IfiIlφ) and welding the solid material to both ends, the length of the solid part at both ends, which is hot rolled into a wire with multiple stands, can be determined in the same manner as the method for determining Lθ described above. Further, it is advantageous for the thickness of the wire to be as thin as possible; for example, the minimum diameter for normal wire rod rolling is 5.5 m+sΦ. This is used as a wire for bundle rolling.

In addition, as another method for preventing crimping between stainless steel wires, stainless steel wire rods (for example, 5.5 mm diameter) are hot-rolled using a normal method, and the wire rods with scale still attached to the surface are rolled for the first time. used as wire for bundle rolling, in this case,
To prevent the stainless steel wires from contacting each other by increasing the voids slightly, as shown in Figs. Fill the void with powder 35. These filling materials work together with scale on the stainless steel surface to prevent crimping. The scale of the stainless steel wire rod is attached to the wire rod with a diameter of 5.5 mm and has a thickness of about 5 B. At rolling temperatures of 850°C or higher, the scale deforms plastically along with the stainless steel, so the scale deforms plastically along with the powder filling the voids. Effective in preventing crimping between stainless steel wires. In the second width rolling, since the exterior of the stainless steel wire is made of ordinary steel, there is no problem even if the strands come into contact with each other.

From this point onwards, it becomes possible to produce ultra-fine stainless steel wire using only hot rolling.

An example is shown in FIG.

Outer diameter 189+sm $, inner diameter 119mmφ (7) Low carbon steel pipe 2°, outer diameter 118+sm stainless steel rod
316t) Insert l O to make a composite billet) 31-1. After aligning both ends of the inner and outer members, solid members (common steel) 29-1 and 29-2 are welded, as shown in FIG. The length of this end solid material for use as a rolling tip is determined as described above in consideration of truncation and suppression of chewing during the rolling process. In other words, truncated length 28.9 mm, bite suppression length 0.09XDO (input C2) - "" = 0.08X 1
81]X (9) = 0.58wmte, so
LO' = 28.9 + 0.58 = 28.5ms +, while from the bite limit in the first pass, LO = 0.09
X D O = 0.09X 189 = 15.2 + m,
Therefore, the length of the solid material at the rolling tip is 29.5
Just use the larger one of m+* and 15.2mm (,3
As long as it is 0mm or more, it is fine.Here, we took a little margin and set it at 50mm.
+am. Further, the rear end may be approximately the above LO, and is set to 30 wm with some margin. In addition, the solid material 29 for the rear end
-2 is provided with a through hole 30 approximately 5 mm in diameter, which serves as an air vent between the stainless steel rod and the exterior material.

The material thus prepared is hot-rolled using a conventional wire rod rolling mill as shown in FIG. That is, continuous heating furnace 2
1 to about 1150"c, a rough rolling mill group 22 (for example, 6 stands), an intermediate rolling mill group 23 (for example, 12 stands) and a finishing mill group 24 (for example, 1O stand).
After rolling to 5.5 φ at 100 Il/sec, it is cooled in a water-cooling zone 25, formed into a ring shape by a laying head 26, dropped onto a comparer, air-cooled by a Stelmore device 27, and then formed into a coil 28. Note that the tip is cut off between the outlet side of the rough rolling mill 22 and the intermediate rolling mill 23. The wire rod 11-1 thus obtained has an outer diameter of 5.5 m+sφ, an internal stainless steel having a substantially circular cross section, and a diameter of 3.8 φ.

This wire rod 11-1 is made straight and has a certain length, for example, 10 m.
) and insert it into the ordinary steel pipe 2o so as to form a parallel bundle. The tube has an outer diameter of 189mmφ and an inner diameter of 119mmφ.
Approximately 400 wire rods with a diameter of 5.5 mm can be inserted. Both ends of this composite material 31-2 are made in the same manner as described above,
Ordinary steel solid material (length 50mm for the tip, length 3 for the rear end)
Weld a 5mmφ through hole in the center with a length of 0m5. This was hot rolled using the same wire rod rolling mill as above, and 5.5
The wire is m+sφ. At this time, the interpolation element line is 0.17
9 m + sφ After one east rolling, the diameter becomes 5.5/189 = 1/30.7.

This wire rod coil is again cut into a certain length (for example, 10 m), and approximately 400 pieces are inserted into a Dantsu steel pipe with an outer diameter of 169 mm and an inner diameter of 119 mm, and a solid material is welded to both ends. Roll. If the finished outer diameter of the wire at this time is dO, and the desired stainless steel wire diameter is ds, then ds = 0.12
4X (do/169), so if ds=12gm, do=18.4mφ, if ds=84m, dQ=8.2mφ, and if ds=4gts, dO=5.5mφ. In the above example, the diameter of the stainless steel wire was 3.8 mφ, and the wire material J: diameter of the first die rolling was 5°5 mmφ, but when performing bundle rolling twice, each finishing The outer diameter is d01. d
02, the stainless steel wire diameter is dsB, and the desired stainless steel wire diameter ds is: ds = dsBX (d01/189) X (
d02/189) and determine dol and d02 so as to increase the rolling efficiency.

As mentioned above, the wire rod obtained by bundle rolling twice (in the example, 5
．． 51Φ) is immersed in an acid such as a nitric acid bath to dissolve away the low carbon steel on the exterior, an ultrafine stainless steel wire can be obtained. In this example, the ultra-fine wire of 4 irises φ is approximately 400X 400=
In addition, in the composite material 31-2 or 31-3 in which wire rods were inserted for die rolling,
There are always gaps between the Ti materials. If the number of wires close to the densest packing is inserted, there will be no problems such as sticking out, but if the number of wires packed is small and the gap is large due to bending of the wire, etc., as described above, the soft steel wire 34 with a diameter of about 115 Alternatively, a powder 35 such as iron powder or scale powder may be filled.

As described above, according to the present invention, it is possible to efficiently mass-produce micron-order stainless steel ultrafine wires by repeating only hot bundle rolling.

As a result, compared to the conventional method shown in Figure 2 CB), two hot extrusions and two cold wire drawings are omitted, and the die rolling is performed twice (increased by one), resulting in a thinner wire of approximately 4 gmφ. It becomes possible to freely manufacture ultrafine wires up to (approximately 12 gmφ). In addition,
The process of welding a solid material to the edge of a composite material is a negligible process compared to hot extrusion or wire drawing, and is said to take about 90 days using conventional methods. In the present invention, as a result of omitting hot extrusion and wire drawing twice, approximately 1
/2 shortened to about 40 days. Moreover, a large amount of thinner lines can be obtained than in the conventional method (compared with Fig. 2 (B), the thickness is 1
2gm is 4゜4 tiles ■, wood a 3280 pieces are If (000
0 tree).

[Effects of the Invention] As described in 2 below, the method for producing ultrafine metal wire according to the first aspect of the present invention includes inserting an insert material made of a width-bar material of stainless steel into the interior of a low carbon steel exterior material. Following the step of hot rolling the composite billet to obtain a composite wire rod whose exterior part is made of the above-mentioned low carbon steel and whose interior is made of stainless steel, the above-mentioned composite wire rod is formed into a parallel bundle inside the low carbon steel exterior material and then inserted. After repeating the process of hot rolling the composite material into which the wire rod is inserted at least once, the wire rod is immersed in acid to dissolve away the low i-Km. be. Therefore, the ultra-fine wire is manufactured only by hot rolling, and it becomes possible to efficiently manufacture the fixed fine wire through a short process.

Further, the second method of manufacturing ultrafine metal wire of the present invention includes hot rolling a composite billet in which an insert made of a single bar of stainless steel is inserted inside a low carbon steel exterior material. ,
Next to the step of obtaining a composite wire whose exterior part is made of the low carbon steel and whose interior is made of stainless steel, the composite wire is made into a parallel bundle inside the low carbon steel exterior material and the composite wire is inserted with a sintered insert, which is heated. A method for producing ultrafine metal wires, in which the process of obtaining a wire rod by rolling is repeated at least once, and then the L wiring material is immersed in acid to dissolve away the low carbon steel, the method comprising: A solid member is fixed to the front end and rear end and hot rolled. Therefore, in order to avoid biting of the leading and trailing edges during rolling of composite billets and composite materials.

Ultra-fine wires are produced only by hot rolling, making it possible to efficiently produce a large amount of thin wires through a short process.

In addition, in the method for producing ultra-fine metal wire according to the third aspect of the present invention, a composite billet in which an insert made of a single wire of stainless steel is inserted inside a low carbon steel exterior material is hot-rolled, and the exterior part is Next to the step of obtaining a composite wire rod made of low carbon steel and stainless steel inside, the composite wire rod is formed into a parallel bundle inside a low carbon steel exterior material, and a composite material is hot-rolled with an insert insert inserted. A method for producing ultrafine metal wires, in which the process of obtaining a wire rod is repeated at least once or more, and then the wire rod is immersed in acid to dissolve away the low carbon steel, the method comprising filling voids formed inside the composite material with filling material. The material is filled with and hot-rolled. Therefore, by removing the voids that occur inside the composite material, ultra-fine wires can be manufactured only by hot rolling, with a shape pfH') that avoids biting of the leading and trailing edges during rolling of the composite material, resulting in a short manufacturing process. This makes it possible to produce a large amount of thin wire at a high rate of 1@.

[Brief explanation of drawings]

FIG. 1 is a manufacturing process diagram schematically showing an embodiment of the present invention;
Figure 2 (A) is a manufacturing process diagram showing the conventional method, Figure 2 (B)
) is a manufacturing process diagram showing another conventional method, FIG. 3(A) is a schematic diagram showing a bundle rolling state by the conventional method, FIG. 3(B) is a schematic diagram showing an east rolling state by the present invention, and FIG. The figure is a diagram showing the relationship between the solid length and the amount of protrusion used in the present invention, FIG. 5 is an end view showing a composite material, FIG. 6 is an end view showing another example of the composite material, and FIG. 7 8 is an end view showing another example of a composite material, FIG. 8 is a side view showing a state in which solid parts are provided at both ends of the composite material, and FIG. 9 is a schematic diagram showing an example of a rolling apparatus. 10...Stainless steel round bar, 11...Stainless steel wire rod, 20...Exterior material, 29-1.29-2...Solid material, 31-1.31-2...For hot extrusion Material, 34...
- Mild steel wire for void filling, 35... powder for void filling. Agent Patent Attorney Osamu Shiokawa Figure 2 (△) 3rd session (A) (B) 4th session Figure 5 Figure 6 Figure 7

Claims (3)

[Claims] (1) A composite billet in which an insert made of a single bar of stainless steel is inserted inside a low-carbon steel exterior material is hot-rolled, and the composite wire is made of the low-carbon steel in the exterior part and stainless steel in the interior. Next, the step of obtaining a wire rod by hot rolling a composite material in which an insert material made of parallel bundles of the above composite wire rods was inserted into the inside of a low carbon steel exterior material was repeated at least once. A method for producing ultrafine metal wires, in which the wire rod is then immersed in acid to dissolve away the low carbon steel. (2) A composite billet in which an insert made of a single bar of stainless steel is inserted inside a low-carbon steel exterior material is hot-rolled, and the composite wire is made of the low-carbon steel in the exterior part and stainless steel in the interior. Next, the step of obtaining a wire rod by hot rolling a composite material in which an insert material made of parallel bundles of the above composite wire rods was inserted into the inside of a low carbon steel exterior material was repeated at least once. A method for producing ultrafine metal wires in which the wire rod is then immersed in acid to dissolve the low carbon steel, and solid members are fixed to the leading and trailing ends of the composite billet and the composite material and then hot rolled. A method for manufacturing ultrafine metal wire. (3) A composite billet in which an insert made of a single bar of stainless steel is inserted inside a low-carbon steel exterior material is hot-rolled, and the composite wire is made of the low-carbon steel in the exterior part and stainless steel in the interior. Next, the step of obtaining a wire rod by hot rolling a composite material in which an insert material made of parallel bundles of the above composite wire rods was inserted into the inside of a low carbon steel exterior material was repeated at least once. After that, the above-mentioned wire rod is immersed in acid to dissolve away the low carbon steel, and the method for manufacturing ultra-fine metal wire comprises filling the voids formed inside the composite material with a filler material and hot rolling it. Method.