JPH10128402A - Manufacture of steel wire and manufacturing device therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To spheroidize a wire as hot-rolled in a short time and also to make shape and size adjustable. SOLUTION: While transporting hot-rolled wires in the state of a strand in the axial direction and as heating the part of the wire between a power feeding electrode which is brought into contact with the wire and finishing rolls to a temp. T1 at the heating rate of >=100 deg.C/sec by directly energizing, rolling is executed so that the total reduction of area with an intermediate roll group and finishing rolls becomes >=10%, after cooling the wire to the temp. T2 at the cooling rate of C1 deg.C/sec immediately after completing rolling, the wire is charged into a furnace whose temp. is T3 and held for 3-30min. Where, point Ae1 +40 deg.C<=T1<=poit Ae1 +160 deg.C, point Ae1 -60 deg.C<=T2<=point Ae1 +20 deg.C, point Ae1 -100 deg.C<=T3<=point Ae1 -10 deg.C, (T1-point Ae1 )/30<=C1<=(T 1-point Ae1 )/1.5.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a steel wire for secondary working of a wire and a manufacturing apparatus therefor, and more particularly to a method of manufacturing a hot-rolled wire used as a material for a bearing element part. The present invention relates to a method of manufacturing a steel wire capable of performing spheroidizing annealing in a short time and performing dimensional adjustment, and a manufacturing apparatus for the same. Note that the wire rod to which the present invention is applied includes a so-called “bar-in coil”. Further, the “steel wire” in the present invention refers to a wire made of “steel” as a base material processed (rolled) and wound into a coil shape.

[0002]

2. Description of the Related Art Conventionally, wires (for example, wires made of JIS SUJ2 as a base steel) used as materials for balls, rollers, needles, shafts and the like constituting a bearing include cutting, cold forging and cutting. In order to facilitate cold forming, spheroidizing annealing has been performed for 10 to 25 hours after hot rolling.

[0003] The above-mentioned spheroidized and annealed wire is worked into a cold or warm steel wire for the purpose of adjusting it to a desired size or improving dimensional accuracy (for example, wire drawing of 10 to 50%).
In many cases, softening annealing is further performed thereafter.

[0004] As described above, wires and steel wires used as materials for bearing element parts are subjected to a large amount of processing over a long period of time, resulting in an increase in cost.

[0005] Therefore, from the viewpoint of reducing the manufacturing cost, there is a great demand to shorten the spheroidizing annealing time applied to the as-heated wire rod and to further reduce the steps of steel wire manufacturing.

[0006] In response to such a request, for example,
The -15930 discloses "a steel bar wire rod heated at the strand state Ac ₁ point + 30～Ac ₁ point + 150 to the heating temperature of ° C. The average heating rate 50 ° C. / min or more, after maintaining within 5 minutes, Ar ₁ transformation Cool to the point within 10 minutes, then
r Cooling the temperature range from _one point to -40 ° C at an average cooling rate of 0.5 to 5 ° C / min. ”discloses a method for spheroidizing a steel rod.

However, the technique described in the above-mentioned publication is to heat-treat a hot-rolled wire. Therefore, in the case of wires made of hypereutectoid steel as the base steel, mesh-like cementite often remains at the former austenite grain boundaries, which causes cracks during cold working as a post-step of annealing. In some cases, the yield was reduced. Furthermore, in many cases, the shape and dimensional accuracy of the wire are not sufficient when hot rolling is performed. For this reason, after spheroidizing annealing, it is often necessary to perform cold working such as cold drawing for the purpose of adjusting the shape and increasing the dimensional accuracy.

Japanese Patent Application Laid-Open No. Hei 2-221324 discloses "C
After the content was added between over-eutectoid steel to 30% or more of cold working of greater than 0.8 wt%, it is heated to a temperature range of Acm transformation point at A ₁ transformation point + 50 ℃ least 30 to 600 seconds A method of spheroidizing a hypereutectoid steel which "holds" is disclosed.

However, unlike the case where the steel material is softened by spheroidizing annealing, a steel material having a hard pearlite structure as hot-rolled is subjected to a powerful working machine in order to perform cold working of 30% or more. In particular, when the C content of the steel material is high, it is extremely hard, and it is often difficult to perform cold working of 30% or more. Further, in the case of cold drawing, which is a general method of cold working of a wire, unlike the case of cold rolling on a steel sheet, work is concentrated particularly on the surface layer of the steel. For this reason, it is difficult to uniformly cut and refine pearlite (layered carbide) for the purpose of cold working in the above-mentioned publication, and in addition, cracks from carbide and work hardening in ferrite are superimposed, and the steel material is hardened. The problem of "cracking" in the surface layer was inevitable.

The use of the techniques described in JP-B-61-15930 and JP-A-2-221324 makes it possible to shorten the spheroidizing annealing time. But,
These techniques still have problems in terms of manufacturing cost, productivity and the like.

[0011]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has been developed in a short time to spheroidize cementite to a hot-rolled wire used as a material for bearing element parts. It is an object of the present invention to provide a method for manufacturing a steel wire and a manufacturing facility capable of adjusting a shape and a dimension at the same time as being capable of being softened with a rate of 85% or more.

Here, the above-mentioned "spheroidization rate" means that when observed with a microscope, "a ratio of (minor axis) / (major axis) to cementite in the field of view is 0.5 or more. Percentage (%) ".

[0013] The target wire of the present invention is JIS G
No. 2033 refers to "a steel material which is hot-rolled into a bar shape and is wound in a coil shape", and includes "bar-in coil" as described above.

[0014]

The gist of the present invention resides in the following methods (1) to (3) for producing a steel wire and (4) and (5) for producing steel wire.

(1) A method for producing a steel wire using a feeder electrode, a facility including a rolling mill having n intermediate rolling roll groups, and a finishing rolling roll constituting the electrode, wherein the weight% , C: 0.7-1.5%, Mn + Cr:
A wire rod hot-rolled from steel containing 0.8 to 3.0% is conveyed in the axial direction in a strand state, and the wire portion between the power supply electrode in contact with the wire and the finish rolling roll is directly energized. Temperature T1 at a heating rate of 100 ° C / sec or more
While increasing the temperature, the rolling is performed as it is or the intermediate rolling rolls have a reduction in area of more than 0%, and the finish reduction rolls have a reduction in area of more than 0%. Rolling is performed so that the total area reduction by the roll is 10% or more. Immediately after finishing the rolling by the finish rolling roll, the roll is cooled to a temperature T2 at a cooling rate of C1 ° C./sec, and then mounted in a furnace at a temperature T3. A method for producing a steel wire, wherein the steel wire is inserted and held for 3 to 30 minutes.

However, Ae ₁ point + 40 ° C. ≦ T1 ≦ Ae ₁ point + 1
60 ° C, Ae ₁ point -60 ° C ≤ T2 ≤ Ae ₁ point + 20 ° C, Ae ₁
Point -100 ° C ≤ T3 ≤ Ae ₁ point -10 ° C, (T1-Ae ₁ point)
/ 30 ≦ C1 ≦ (T1-Ae ₁ point) /1.5, and n is a positive integer.

(2) A facility including a rolling mill having one or both of a power supply electrode and at least one of m intermediate rolling rolls constituting an electrode, and a finish rolling roll constituting an electrode. A method of producing a steel wire using C: 0.7 to 1.5% by weight, M:
n + Cr: While hot-rolled wire from steel containing 0.8 to 3.0% is conveyed in the axial direction in a strand state,
The wire portion between the power supply electrode and the finish rolling roll in contact with the wire or the wire portion between the intermediate rolling roll and the finish rolling roll constituting the electrode is directly energized by 100.
While the temperature is raised to the temperature T1 at a heating rate of not less than 0 ° C./sec, the rolling is performed as it is or the intermediate rolling roll group has a reduction of area exceeding 0%, and the reduction rate of the finishing roll exceeds 0%, and Rolling the intermediate rolling roll group and the finish rolling roll so that the total area reduction rate is 10% or more;
Immediately after finishing the rolling by the finish rolling roll, the temperature T
2 at a cooling rate of C1 ° C./sec.
A method for producing a steel wire, comprising charging the same in a furnace for 3 to 30 minutes.

However, T1, T2, T3 and C1 are the above (1)
And m is a positive integer.

(3) A steel wire characterized in that it is placed in a furnace at a temperature T3 according to any one of the above (1) and (2) and held for 3 to 30 minutes and then quenched. Production method.

(4) By weight%, C: 0.7-1.5%,
Mn + Cr: a manufacturing facility for manufacturing a steel wire using a wire rod hot-rolled from steel containing 0.8 to 3.0% as a raw material, including an uncoiler, a straightening machine, a feeding electrode, an intermediate rolling roll group, and an electrode. A finishing roll, a control cooling device, a furnace, a quenching device, and a winding device.

(5) By weight%, C: 0.7-1.5%,
Mn + Cr: a production facility for producing a steel wire from a wire rod hot-rolled from steel containing 0.8 to 3.0%, wherein an uncoiler, a straightening machine, a feeding electrode and / or at least one roll are provided. Intermediate rolling rolls constituting electrodes, finishing rolling rolls constituting electrodes, control cooling device,
A steel wire manufacturing facility, characterized in that a furnace, a quenching device, and a winding device are arranged so that a material to be processed passes in this order.

Here, the above "feeding electrode" refers to an electrode excluding "an intermediate rolling roll constituting an electrode" and a "finish rolling roll constituting an electrode". Further, "rolling is performed with a reduction ratio of more than 0% as it is or with an intermediate rolling roll group and rolling with a finish rolling roll" means "not rolling with an intermediate rolling roll group (that is, the intermediate rolling roll group is a so-called" Rolling with finish rolling rolls, or rolling with intermediate rolling rolls and then rolling with finish rolling rolls. "

In the following, the above (1) to (1)
(5) is referred to as the inventions of (1) to (5), respectively.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION The inventors of the present invention conducted experiments to adjust the shape and dimensions of a wire as hot-rolled as soon as the spheroidization ratio of cementite was increased to 85% or more in a short time.・ Repeated research. As a result, the following findings were obtained.

In order to form cementite into a spheroid, the target wire is _first heated to a temperature T1 in a temperature range higher than _one point Ae, and is controlled from the temperature T1 to a temperature T2 at an appropriate cooling rate to form a layer in the pearlite. If a part of cementite (and a part of network cementite on the former austenite grain boundary also exist) is dissolved in the matrix (solid solution) and the remaining cementite, that is, undissolved cementite, is grown as a nucleus. good.

The base steel of the above-mentioned wire rod contains Cr and / or M
If n is contained in an appropriate amount, the dissolution rate (solid solution rate) of cementite in a temperature range higher than _one point Ae becomes slow, so that only part of the layered cementite in pearlite dissolves in the matrix (solid solution). ), And when network-like cementite is present, only part of the cementite can be dissolved in the matrix.

In order to sufficiently grow undissolved cementite, the above-mentioned wire may be held in a furnace at a temperature T3 in a specific temperature range lower than _one point Ae.

In order to maintain an appropriate amount of cementite at the time of holding in the furnace at the temperature T3, the temperature T
After heating to 1, it is sufficient to cool to a temperature T2 in a specific temperature range at a cooling rate C1 according to the heating temperature.

When network cementite is formed at the former austenite grain boundary of the as-rolled wire structure, it is extremely important to cut and refine the network cementite in spheroidizing treatment.

If the wire is processed with an appropriate processing amount during heating, the layered cementite and the network cementite on the prior austenite grain boundary can be easily cut and refined.
Spheroidizing treatment of cementite becomes easy. Further, even if network-like cementite remains at the former austenite grain boundary after spheroidizing annealing, the amount thereof is extremely small, so that the cold workability is greatly improved.

As a heating method, a heating method in which a current is directly applied between electrodes in contact with a material to be heated (hereinafter referred to as an energization heating method) is employed. If a rolling roll is used as an electrode, heating and processing (rolling) can be performed simultaneously. Can be.

By performing the quenching treatment after holding in the furnace, the productivity of the steel wire can be extremely increased.

The present invention has been completed based on the above findings.

Hereinafter, each requirement of the present invention will be described in detail. In addition, “%” of the component content means “% by weight”.

(A) Chemical Composition The wire rod targeted by the present invention is processed into a predetermined shape and then subjected to a heat treatment such as quenching and tempering in the final step.
Given characteristics (hardness, wear resistance, etc.) are provided. From the viewpoint of imparting characteristics to the final product and obtaining a spheroidized annealed structure in which the spheroidization ratio of cementite is 85% or more in a short time, the chemical composition of the hot-rolled wire is C
Only the amount and the amount of Mn + Cr are limited to the following ranges.

C: 0.7-1.5% C is an element effective for increasing hardness and ensuring wear resistance. However, if the content is less than 0.7%, sufficient hardness and wear resistance cannot be obtained. On the other hand, if it exceeds 1.5%, hot workability and machinability are deteriorated, and productivity is reduced. Therefore, the C content is set to 0.7 to 1.5%.

Mn + Cr: 0.8-3.0% Both Mn and Cr are concentrated in cementite to stabilize cementite, reduce the rate of dissolution of cementite during heating, and have the effect of retaining an appropriate amount of cementite. Have. Furthermore, Mn and Cr have the effect of increasing the hardenability and improving the strength and toughness. The action described above is based on Mn.
And Cr are exhibited irrespective of whether they are contained alone or in combination. That is, one of Mn and Cr may be 0 (zero). However, if the sum of the contents of Mn and Cr is less than 0.8%, the desired effect cannot be obtained.
On the other hand, when the total content of Mn and Cr exceeds 3.0%, the growth of spherical cementite is significantly slowed down.
In other words, cementite cannot be spheroidized in a short time.
Therefore, the content of Mn + Cr is set to 0.8 to 3.0%.

The composition of the chemical components other than C and Mn + Cr of the hot-rolled wire as the target material of the present invention does not need to be particularly limited. It suffices if the component range is such that the characteristics required in the final product can be imparted and the spheroidizing annealing is completed in a short time.

Specifically, for example, as elements other than C and Mn + Cr, Si: 0 to 2.0%, Cu: 0 to 2.0%
%, Ni: 0 to 4.0%, Mo: 0 to 0.5%, V: 0
0.4%, Nb: 0-0.05%, Ti: 0-0.1
0%, Al: 0 to 0.10%, N: 0 to 0.03%,
B: 0 to 0.005%, S: 0 to 0.10%, Pb: 0
0.30%, rare earth element: 0 to 0.10%, Ca: 0
To 0.01% and Mg: 0 to 0.01%, the balance being Fe and unavoidable impurities, and P as an impurity being 0.1 to 0.1%.
What is necessary is just 05% or less.

When the above elements other than C and Mn + Cr are additionally contained for the purpose of improving the properties of steel materials, steel wires and final products, Si: 0.05 to 2.0
%, Cu: 0.05 to 2.0%, Ni: 0.3 to 4.0
%, Mo: 0.05-0.5%, V: 0.05-0.4
%, Nb: 0.002 to 0.05%, Ti: 0.005
0.10%, Al: 0.001 to 0.10%, N:
0.001 to 0.03%, B: 0.0003 to 0.00
5%, S: 0.005 to 0.10%, Pb: 0.02
0.30%, rare earth element: 0.002 to 0.10%, C
a: 0.0005 to 0.01%, Mg: 0.0005 to
Preferably, the content is 0.01%. Further, P as an impurity is preferably set to 0.04% or less.

(B) Heating In order to make the cementite spheroidized, the wire rod is firstly Ae ₁
Is heated to a temperature T1 in a temperature range higher than the temperature, and controlled cooling is performed at an appropriate cooling rate from this temperature T1 to form a portion of the layered cementite in the pearlite (if network cementite is present on the former austenite grain boundary, (Some of them) must be dissolved in the matrix, and the remaining cementite, that is, undissolved cementite, must be grown as a nucleus.

By the way, when the wire is once heated to a temperature T1 in a temperature range higher than the Ae ₁ point, if the heating rate is low, the wire is held in the temperature range higher than the Ae ₁ point for a long time during heating. Therefore, the amount of undissolved cementite becomes small, and a desired spheroidized structure cannot be obtained. Furthermore, in the present invention, since the wire is heated while traveling in a strand state, if the heating rate is low, the productivity is not improved, and the production cost increases. Therefore, it is necessary to raise the temperature by a rapid heating process.

As a rapid heating method, a high-frequency heating method, a current heating method and the like are known. However, when the wire is rapidly heated while traveling in a strand state by the high-frequency heating method, a large variation may occur in the temperature in the cross section with respect to the traveling direction.

On the other hand, in the case of the electric heating method, even if the wire is rapidly heated while traveling in a strand state, the temperature variation in the cross section in the traveling direction described above hardly occurs. Further, in the case of conducting heating by heating, a rolling roll can be used as an electrode. In this case, since heating and processing (rolling) of the wire can be performed simultaneously, not only can the process be omitted, but also the layered cementite and the network-like cementite on the old austenite grain boundary can be easily cut and formed.
Because it can be miniaturized, the spheroidization rate can be increased,
Since cracking at the time of cold working caused by the network cementite can be prevented, there is also an advantage that the cold workability is greatly improved. Therefore, the rapid heating method was limited to the electric heating method.

In the present invention, the heating rate when the temperature is raised to the temperature T1 by rapid heating by the electric heating method is 100.
It is specified as ° C / sec or more. When the heating rate is 100 ° C./sec or higher, little dissolution of the lamellar cementite occurs during the heating, so that part of the lamellar cementite in the pearlite (old If a network cementite is present on the austenite grain boundary, a part thereof can be dissolved in the matrix. Then, after cooling, if it is charged into a furnace at the temperature T3 and maintained for an appropriate time, the remaining cementite, that is, undissolved cementite, can be sufficiently grown and spheroidized. Furthermore,
A high heating rate also has the effect of increasing productivity. Therefore, the lower limit of the heating rate was set to 100 ° C./sec. By the way, the above "heating rate" is "the average heating rate of the surface of the wire to be heated from room temperature (room temperature) to temperature T1".
Refers to. The upper limit of the heating rate does not need to be specified. The upper limit heating rate may be set in terms of equipment, and may be, for example, an ultra-rapid heating rate of 10,000 ° C./sec.

[0046] In rapid heating by direct conduction method described above, it must be Atsushi Nobori Ae ₁ point from + 40 ℃ to a temperature T1 which is between Ae ₁ point + 160 ° C.. This is because the heating temperature T1 is Ae ₁ point + 40 ° C.
If it is less than 10, when cooling to the temperature T2 after heating, even if the cooling rate is controlled, the dissolution of the layered cementite (or the networked cementite when the networked cementite exists on the former austenite grain boundary) hardly occurs. Therefore, after the spheroidizing annealing, the desired spheroidizing rate of cementite is 85%.
% Or more cannot be obtained. On the other hand, Ae ₁ point + 1
If heated to a temperature exceeding 60 ° C., almost all of cementite (both layered cementite and network cementite on the prior austenite grain boundary) is dissolved, so that
Again, the spheroidization rate is low. Therefore, the heating temperature T1
Is a temperature between Ae ₁ point + 40 ° C. and Ae ₁ point + 160 ° C. Ae ₁ point (° C.) is as follows.

Ae ₁ point = 723-10.7 × Mn (%) + 29.1 ×
Si (%) + 16.9 × Cr (%).

By the way, the heated portion of the wire by the electric heating method, in other words, the energized portion is a portion between the power supply electrode in contact with the wire and the finish rolling roll constituting the electrode ((1),
(Invention of (2)), or a portion between the intermediate rolling roll constituting the electrode in contact with the wire and the finish rolling roll constituting the electrode (the invention of (2)).

In the invention of (2), the method for energizing the "portion between the power supply electrode in contact with the wire and the finish rolling roll forming the electrode" depends on the configuration of the rolling device as described below. different.

(A) In a case where the rolling apparatus has a power supply electrode and a finish rolling roll constituting the electrode, but does not have “an intermediate roll group in which at least one roll constitutes the electrode”, literally “the power supply electrode and The wire portion between the finish rolling rolls constituting the electrode is energized.

(B) When the rolling device has “an intermediate rolling roll group in which at least one roll forms an electrode”, (b-1) a case in which one intermediate rolling roll forms an electrode; -2) The number of intermediate rolling rolls constituting the electrode is 2
There are two or more cases. First, (b-1) in the case where the number of intermediate rolling rolls constituting the electrode is one, the "wire portion between the feeding electrode and the intermediate rolling roll constituting the electrode" is energized, and the "intermediate rolling roll constituting the electrode" is energized. The wire portion between the rolling roll and the finishing roll is also energized, and the wire portion between the power supply electrode and the finishing roll forming the electrode is energized as a whole. Next, (b-2) when the number of intermediate rolling rolls constituting the electrode is two or more, while energizing the “wire portion between the feeding electrode and the first middle rolling roll from the top constituting the electrode”, Energizing the “wire portion between the first middle rolling roll forming the electrode and the second middle rolling roll forming the electrode” and the final intermediate rolling forming the electrode in the same manner To the roll, and then also energize the "wire portion between the intermediate rolling roll and the finishing roll forming the final electrode", and as a whole "the wire portion between the feeding electrode and the finishing rolling roll forming the electrode" Is turned on.

When there are two or more intermediate rolling rolls constituting the electrode described in the above (b-2), only one intermediate rolling roll actually acting as an electrode may be used. In this way, "when there are two or more intermediate rolling rolls constituting an electrode, but the number of intermediate rolling rolls actually acting as an electrode is smaller than the number of intermediate rolling rolls constituting an electrode," Only the intermediate rolling roll to be operated is subjected to the above-described energization treatment, and as a whole, “the wire portion between the power supply electrode and the finish rolling roll constituting the electrode”
Will be energized.

In the case of the present invention, it is an object to adjust not only the spheroidizing process but also the shape and dimensions, that is, to add processing. For this reason, the finish roll has two roles of an electrode and a normal finish roll. When a specific portion of the wire rod running in the strand state is picked up, the temperature rises to T1 when this specific portion comes into contact with the finish rolling roll (role as an electrode), and at the same time, finish rolling is performed (finish rolling). Role as a role).

The "intermediate rolling roll constituting the electrode"
In addition, it is preferable to use a roller-type electrode as the “feeding electrode” as an electrode excluding the “finish rolling roll constituting the electrode”.

(C) Rolling When network cementite is formed on the former austenite grain boundaries of the as-rolled wire rod structure, it is extremely important to cut and refine the cementite in the spheroidizing treatment. If the wire rod is processed (rolled) with an appropriate processing amount during heating, the network cementite and the layered cementite on the old austenite grain boundary can be easily cut and refined, so that the cementite can be easily spheroidized. become.

In the above-mentioned rolling performed during the heating, when the amount of processing is 10% or more in terms of the total reduction in area, the above-mentioned network cementite and layered cementite on the former austenite grain boundary can be easily cut and divided. Fineness can be achieved, and the spheroidization rate and cold workability of cementite can be increased. Therefore, the rolling reduction in the inventions of (1) and (2) is 1
0% or more. The upper limit of the total area reduction rate is not particularly limited, and the total upper limit of the facilities is considered in consideration of the dimensions of the as-rolled wire rod and the desired dimensions of the steel wire after finish rolling. The area reduction rate may be used.

By the way, even if a wire rod which is high in strength as it is hot rolled and requires a strong working machine (rolling machine) for cold working (rolling), when the wire is heated, the wire rod becomes Decreases with increasing temperature, and particularly when the wire temperature is 400 ° C. or higher, the strength is greatly reduced. Therefore, the rolling of the wire rod which has been heated by the above-described electric heating method can be easily performed by a rolling facility having a normal output.

In the invention of (1), the above-mentioned total area reduction rate of 10% is used for n intermediate rolling roll groups and finishing rolling rolls.
The above rolling is performed. Note that the intermediate rolling roll group does not need to be rolled (it may be empty).

In the case of the invention (1), all the intermediate rolling rolls constituting the intermediate rolling roll group have no role as electrodes. For this reason, when rolling is performed by the above-mentioned n intermediate rolling roll groups, the wire temperature decreases due to heat removal by the rolls. Therefore, when rolling by the intermediate rolling roll group in the invention of (1), the wire temperature is 400 ° C.
It is preferable to adjust the pass schedule so that the upper limit of the area reduction by the group of intermediate rolling rolls is about 70%. In the case of rolling by the intermediate rolling roll group, the area reduction rate by the intermediate rolling roll group is naturally 0%.
Therefore, this provision was established.

As described above, in the invention of (1),
Since the finish roll has the role of an electrode, the temperature drop when rolling by the finish roll can be suppressed, and in addition, the wire temperature at the time of contact with the finish roll is as high as T1 ° C. It is also easy to perform rolling with a surface reduction rate of 10% or more using only the finish rolling roll.
In the present invention, not only the spheroidization treatment but also the adjustment of the shape and dimensions are performed, that is, the purpose is to add processing, and this processing is performed by a finish rolling roll. Therefore,
Since it is necessary to always perform rolling with a finish rolling roll, the area reduction rate by the finish rolling roll is specified to exceed 0%. It is preferable that the lowering ratio of the finish rolling roll is about 3% as a lower limit. Then, the total area reduction rate by the intermediate rolling roll group and the finishing rolling roll may be 10% or more as described above.

Hereinafter, with respect to the invention of (2), (a) a case where the rolling device has a feeder electrode and a finish rolling roll constituting an electrode but does not have an intermediate rolling roll group;
The description will be made separately for a case where the rolling device also has “m intermediate rolling roll groups in which at least one roll forms an electrode”.

First, in the case of (a), the above-mentioned rolling with a total area reduction rate of 10% or more is performed only by the finish rolling rolls. Since the finish roll has the role of an electrode, the temperature drop when rolling by the finish roll can be suppressed, and in addition, the wire temperature at the time of contact with the finish roll is as high as T1 ° C. It is easy to perform rolling with a surface reduction rate of 10% or more using only a finish rolling roll. In this case, the upper limit of the area reduction rate is not particularly specified similarly to the upper limit of the total area reduction rate already described, and takes into consideration the dimensions of the as-rolled wire rod and the desired dimensions of the steel wire after finish rolling. Then, the upper limit of the reduction in area that is possible in terms of equipment may be used.

Next, in the case of (b), the above-mentioned total area reduction rate of 10% was obtained with m intermediate rolling rolls and finishing rolling rolls.
The above rolling is performed. Incidentally, even in the case of the above (b), as in the case of the invention of the above (1), the intermediate rolling roll group does not need to be rolled (may be empty).

In the case of the above (b), at least one of the intermediate rolling rolls constituting the intermediate rolling roll group has a role as an electrode. For this reason, even when rolling is performed by the above-mentioned m intermediate rolling roll groups, a decrease in the wire rod temperature due to heat removal to the rolls can be suppressed to be smaller than in the case of the above-described invention (1). Therefore, in order to secure the preferable wire temperature of 400 ° C. or more, the rolling by the intermediate roll group may increase the upper limit of the area reduction rate to about 90%. In the case of rolling by the intermediate rolling roll group, the area reduction rate by the intermediate rolling roll group naturally exceeds 0%, so this provision is provided.

Also in the case of (b), since the finish rolling roll has the role of an electrode, the temperature drop when rolling by the finish rolling roll can be suppressed, and in addition, the contact with the finish rolling roll can be prevented. The wire temperature at the time of
Since the temperature is as high as 1 ° C., it is easy to perform rolling with a reduction in area of 10% or more using only a finish rolling roll. In the present invention, not only the spheroidization process but also the adjustment of the shape and dimensions are performed.
In other words, the purpose is to add processing, and this processing is performed by a finish rolling roll. Therefore, since it is necessary to always perform rolling with a finish rolling roll, the area reduction rate by the finish rolling roll is specified to exceed 0%. It is preferable that the lowering ratio of the finish rolling roll is about 3% as a lower limit. Then, the total area reduction rate by the intermediate rolling roll group and the finishing rolling roll may be 10% or more as described above.

(D) Cooling The hot-rolled wire rod is, as already described in the section (B),
It is heated to a temperature T1 at a very fast heating rate. Therefore, dissolution of the layered cementite hardly occurs during heating. However, since the rolling described in the above item (C) is performed during heating, a network cementite on the prior austenite grain boundary,
And the layered cementite is divided and refined.

In order to make the above-mentioned divided and finely divided network-like cementite or layered cementite into a spheroid, it is rolled under the conditions described in the above item (C) and immediately after the rolling by the finish rolling roll is completed, Ae It is cooled to a temperature T2, which is a temperature between ₁ point -60 ° C and Ae ₁ point + 20 ° C. During the cooling, an appropriate amount of the cementite is dissolved, and the remaining cementite (undissolved cementite) changes into a spherical shape. Need to be done. The cooling rate in this case is the following cooling rate C according to the above-mentioned heating temperature T1.
1 (° C / sec).

(T1-Ae ₁ point) / 30≤C1≤ (T1-Ae
₁ point) /1.5.

As will be shown in the embodiments described later, the cooling temperature T
When 2 exceeds Ae ₁ point + 20 ° C., almost all of the cementite is dissolved, so that a desired spheroidization ratio cannot be obtained. On the other hand, if the cooling temperature T2 is lower than Ae ₁ point -60 DEG C., pearlite is likely to be formed, so that a desired spheroidization ratio cannot be obtained. Therefore, the cooling temperature T2 is A
The temperature was between e ₁ point -60 ° C and Ae ₁ point + 20 ° C.

FIG. 1 shows the results in Examples 1 and 2 which will be described later in detail, and shows the spheroidization of cementite with the vertical axis representing the cooling rate C1 (° C./sec) and the horizontal axis representing T1−Ae ₁ point (° C.). FIG. In the figure, “○” indicates that the spheroidization rate of cementite is 85% or more, and “×” indicates the heating temperature T.
1. Due to the cooling rate C1, the spheroidization rate of cementite is 85
%.

[0071] From FIG. 1, the cooling rate C1 is {(T1-Ae ₁
Point) / 30 ° C / sec to {(T1-Ae ₁ point) /1.5}
℃ / sec, the spheroidization rate of cementite is 85%
It can be seen that the above desired spheroidized structure can be obtained.

When the cooling rate C1 is {(T1-Ae _one point) / 30}
When the heating temperature T1 is lower than Ae ₁ point + 40 ° C. to Ae ₁ point + 160 ° C.
Almost all of the cementite is dissolved, and the spheroidization ratio is reduced. On the other hand, the cooling rate C1 is {(T1-Ae ₁₎
/1.5｝°C/sec, the heating temperature T
Even if 1 is a temperature between Ae ₁ point + 40 ° C. and Ae ₁ point + 160 ° C., cementite does not sufficiently dissolve, so that the spheroidization ratio becomes low.

The above "cooling rate" refers to "the average cooling rate from the temperature T1 to the temperature T2 of the surface portion of the steel wire to be cooled".

(E) Loading into Furnace In order to spheroidize the hot-rolled wire, it is cooled to the above temperature T2 at a cooling rate C1, and the remaining cementite (undissolved cementite) is nucleated. In order to sufficiently grow the spherical cementite, it is necessary to load it into a furnace at the following temperature T3 and hold it for 3 to 30 minutes.

Ae ₁ point−100 ° C. ≦ T3 ≦ Ae ₁ point−10
° C.

If the temperature T3 satisfies the above condition, T2 <T3 or T2 ≧ T3 may be satisfied.

If the temperature T3 exceeds Ae ₁ point -10 ° C., it is necessary to keep the cementite in the furnace for a long time until the precipitation of cementite is completed, which increases the cost. On the other hand, when the temperature T3 is lower than Ae ₁ point -100 ° C, pearlite is easily formed, and the spheroidization rate of cementite is reduced. Therefore, the temperature T3 of the furnace to be charged after cooling at the cooling rate C1 to the temperature T2 is increased by _one point Ae.
The temperature was between 100 ° C. and Ae ₁ point −10 ° C.

If the holding time after charging into the furnace at the above-mentioned temperature is less than 3 minutes, the spheroidal cementite is rapidly cooled outside the furnace before it grows sufficiently. Conversion rate decreases. On the other hand, the retention time is 3
If the time exceeds 0 minutes, the annealing time becomes longer, so that the processing cost increases. Therefore, the holding time in the furnace at the above temperature is 3
３０30 minutes.

By the way, it is assumed that "the furnace charged at the temperature T3 is 3
"Hold for ~ 30 minutes" means "put in a furnace maintained at an arbitrary constant temperature T3 between Ae ₁ point -100 ° C and Ae ₁ point -10 ° C and hold for 3 to 30 minutes". It is also possible to charge the furnace at a temperature T3 and then continuously or stepwise raise the temperature T3 from Ae ₁ point-100 ° C to Ae ₁ point-
It means that the time maintained in the furnace while changing between 10 ° C. may be 3 to 30 minutes in total ”.

The wire as hot-rolled from the steel having the chemical composition of (A) is heated, rolled, cooled, and charged and held in a furnace under the conditions shown in (B) to (E). As a result, a steel wire having a desired structure in which the spheroidization ratio of cementite is 85% or more can be obtained. For this reason, the cooling rate of the steel wire after holding at the temperature T3 shown in the item (E) does not need to be particularly limited.

However, if the steel wire after holding at the temperature T3 is rapidly cooled, not only the productivity is improved by shortening the spheroidizing annealing time, but also a steel wire having good surface properties can be obtained. Therefore, in the invention of (3), the temperature T3
Quenching of the steel wire after the holding in step was an essential requirement. The cooling rate for rapid cooling may be 5 ° C./sec or more, more preferably 10 ° C./sec or more. by the way,
The "cooling rate" for the rapid cooling refers to "the average cooling rate from the temperature T3 of the surface portion of the steel wire to be cooled to the room temperature (room temperature)". The upper limit of the cooling rate does not need to be specified. The upper limit cooling rate may be set in terms of facilities such as air cooling or water cooling.

Hereinafter, the present invention will be described with reference to the drawings.

FIG. 2 is a diagram showing an example of a production facility for carrying out the method for producing a steel wire according to the present invention. Uncoiler 1, straightening machine 2, feeding electrode 3, intermediate rolling rolls
4, Finish rolling rolls that make up the electrode 5, Control cooling device
6, furnace 7, quenching device 8, and winding device 9 are arranged in series (the invention of (4)).

After being rewound by the uncoiler 1,
The material to be processed (wire as hot-rolled) 10 that has been straightened into a strand by the straightening machine 2 is
While the portion between the power supply electrode 3 and the finishing roll 5 constituting the electrode is heated and heated to a predetermined temperature at a predetermined heating rate by direct energization, the intermediate rolling roll group 4 and the finishing roll 5 constituting the electrode are heated. It is rolled so as to have a predetermined total area reduction rate. In this case, the intermediate rolling roll group 4 may be aired and not involved in rolling (0% area reduction) in some cases. After the above-mentioned rolling is completed, the material to be treated 10 is cooled to a predetermined temperature at a predetermined cooling rate by the control cooling device 6. Next, the material to be treated 10 is charged into the furnace 7 adjusted to a predetermined temperature and held for a predetermined time. By the above processing,
A steel wire having a desired structure in which the spheroidization ratio of cementite is 85% or more is obtained (the invention of (1)). This steel wire is wound by a winding device 9. When the material to be treated 10 is charged into the furnace 7 and held for a predetermined time and then quenched by the quenching device 8, a steel wire having a good surface property can be obtained (the invention of (3)). ).

FIG. 3 is a diagram showing another example of a manufacturing facility for carrying out the method for manufacturing a steel wire according to the present invention. Uncoiler 1, straightening machine 2, feeding electrode 3, intermediate rolling roll group 4 'in which at least one roll constitutes an electrode, finishing rolling roll 5, constituting an electrode, control cooling device 6, furnace 7,
A quenching device 8 and a winding device 9 are arranged in series (the invention of (5)).

After being rewound by the uncoiler 1,
The material to be processed (wire as hot-rolled) 10 that has been straightened into a strand by the straightening machine 2 is
A portion between the feeding electrode 3 and the finishing roll 5 constituting the electrode, or a portion between the intermediate rolling roll 4 "constituting the electrode in the intermediate rolling roll group 4 'and the finishing roll 5 constituting the electrode Is heated by a direct heating to a predetermined temperature at a predetermined heating rate to a predetermined temperature, and at least one roll has a predetermined total area reduction rate by an intermediate rolling roll group 4 ′ forming an electrode and a finishing rolling roll 5 forming an electrode. In this case, the intermediate rolling roll group 4 'may be air-tight and may not be involved in the rolling (0% area reduction rate), provided that the direct current is applied to the intermediate roll constituting the electrode. Roll Roll 4 "
In the case where the reduction is performed in a portion between the finishing rolling rolls 5 constituting the electrode and the intermediate rolling rolls 4 ', the area reduction rate is 0%.
Even in this case, it is necessary that at least the intermediate rolling roll 4 "is always in contact with the material to be treated 10 in order to heat and raise the temperature.

After the above-mentioned rolling is completed, the workpiece 10 is cooled by the control cooling device 6 at a predetermined cooling rate to a predetermined temperature. Next, the material to be treated 10 is charged into the furnace 7 adjusted to a predetermined temperature and held for a predetermined time. By the above treatment, a steel wire having a desired structure in which the spheroidization ratio of cementite is 85% or more is obtained (the invention of (2)).
This steel wire is wound by a winding device 9. When the material to be treated 10 is charged into the furnace 7 and held for a predetermined time and then quenched by the quenching device 8, a steel wire having good surface properties can be obtained (the invention of (3)). ).

[0088]

EXAMPLES Steel having the chemical composition shown in Table 1 was melted by a conventional method using a 150 kg vacuum furnace. Steels BF and IL in Table 1 are target steels of the method of the present invention.
Steels A, G, H and M are comparative steels in which any of the components do not fall within the range of the content specified in the present invention and are not the object of the present invention.

[0089]

[Table 1]

Next, these steels were hot-rolled into a wire having a diameter of 10 mm by a usual method, wound up in a coil shape and cooled to room temperature (room temperature).

Example 1 A part of the hot-rolled wire having a diameter of 10 mm obtained as described above was used as a test material, and FIG.
The steel wire having a diameter of 3.0 to 9.8 mm was manufactured by using the equipment shown in Table 2 under various conditions shown in Tables 2 and 3.

That is, the coiled wire is rolled while being heated to the temperature T1 by the heating method while the coil-shaped wire is straightened and run in a strand state, and immediately after the rolling is completed, the cooling rate C1 is continuously applied to the temperature T2. After cooling, the holding time was adjusted by changing the speed of the conveyor provided in the furnace at the temperature T3, and after holding for the described time, it was cooled to room temperature (room temperature) by allowing it to cool or water-cooled by a cooling device. .

The electrodes for directly energizing are:
Three sets of electrodes as shown in FIG. 4 were used. That is, a roller-type electrode was used as the first set of electrodes serving as the “feeding electrodes”. Rolling roll type electrodes were used for the second and third sets of electrodes, and not only the finish rolling rolls but also the intermediate rolling rolls constituted the electrodes. The wire was rolled to a diameter of 3.0 to 9.8 mm simultaneously with the heating. In addition,
The rolling temperature of the material to be treated (wire) by the intermediate rolling rolls, which is the second set of electrodes, was adjusted to 400 to 700 ° C.

The steel wire obtained as described above is
The spheroidization rate of cementite was measured by the usual method, and the scale adhesion was investigated as the surface properties of the steel wire.

Tables 2 and 3 also show the spheroidization ratio of cementite. In addition, when it was cooled to room temperature (room temperature) by water cooling with a cooling device after being charged into the furnace, adhesion of scale was extremely small and surface properties were good.

[0096]

[Table 2]

[0097]

[Table 3]

From Tables 2 and 3, it is clear that according to the method for producing a steel wire of the present invention, a steel wire having a spheroidizing ratio of cementite of 85% or more can be obtained in an extremely short time.

On the other hand, in the case of the comparative example in which either the chemical composition of the base steel of the test wire or the treatment conditions deviated from the conditions specified in the present invention, the spheroidization rate of cementite was inferior. .

That is, in Test No. 9, the heating temperature T1 is higher than Ae ₁ point + 160 ° C. In Test No. 10, the cooling rate C1 is lower than {(T1-Ae ₁ point) / 30} ° C./sec. Is dissolved in a large amount, and the spheroidization rate of cementite is low.

In Test No. 8, the heating temperature T1 was Ae ₁ point + 4
Since the cooling rate is lower than 0 ° C. and in Test No. 12, the cooling rate C1 exceeds {(T1-Ae ₁ point) /1.5} ° C./sec, cementite hardly dissolves, and the desired cementite spheroidization rate is obtained. A value of 85% or more is not obtained.

In Test No. 15, the cooling end temperature T2 was Ae ₁
Since the temperature is below −60 ° C., the furnace temperature T
Since 3 is below Ae ₁ point -100 ° C, pearlite is formed, and the spheroidization ratio is low.

In Test No. 13, the cooling end temperature T2 is Ae ₁
Since the temperature exceeds the point + 20 ° C., a large amount of cementite is dissolved, and the spheroidization rate after the heat treatment is low.

In Test No. 17, since the holding time in the furnace at the temperature T3 was less than 3 minutes, in Test No. 24, the temperature T3 of the furnace exceeded Ae ₁ point-10 ° C. In each case, pearlite was formed, and the desired spheroidization ratio was not obtained.

In Test No. 19, since the content of Cr + Mn in the base metal was less than 0.8%, a large amount of cementite was dissolved and the spheroidization ratio was low.

In Test No. 23, since the content of Cr + Mn in the base steel exceeded 3.0%, cementite hardly dissolved and the spheroidization ratio was low.

In Test No. 28, the total reduction in rolling was 10%.
Therefore, the reticulated cementite remains, and a desired cementite spheroidization ratio of 85% or more is not obtained.

In Test No. 1, although the spheroidizing ratio of cementite exceeded the desired value of 85%, the properties of the spheroidized annealed material when quenched and tempered were inferior. That is, in Test No. 1, since the content of C in the base steel was less than 0.7%, the wear resistance was significantly reduced.

In Test No. 7, the spheroidization ratio of cementite exceeded the desired value of 85%, but the C content of the base steel exceeded 1.5%. Low. For this reason, cracks occurred in a part of the hot-rolled wire having a diameter of 10 mm.

(Example 2) A part of the hot-rolled wire having a diameter of 10 mm obtained as described above was used as a test material, as shown in FIG.
The steel wire having a diameter of 5.0 to 9.8 mm was manufactured by using the equipment shown in Table 4 under various conditions shown in Table 4.

That is, as in the case of the first embodiment, the coil-shaped wire rod is straightened and rolled while being heated to the temperature T1 by the electric heating method while running in a strand state. Immediately and continuously cooling to the temperature T2 at the cooling rate C1, then adjusting the holding time by changing the speed of the conveyor provided in the furnace at the temperature T3,
After holding for the indicated time, the mixture was allowed to cool or water-cooled with a cooling device to cool to room temperature (room temperature).

The electrodes for directly energizing are:
Two sets of electrodes as shown in FIG. 5 were used. That is, a roller-type electrode was used for the first set of electrodes, which were the “feeding electrodes,” and a roll-type electrode was used only for the finish-rolling roll to form a second set of electrodes. That is, the intermediate rolling roll group according to the present embodiment shown in FIG.
Then, the wire was rolled to a diameter of 9.8 to 5.0 mm simultaneously with the heating. In addition, also in the case of this embodiment, the rolling temperature of the material to be processed (wire) by the intermediate rolling roll is 400 to 700.
The temperature was adjusted to be ° C.

With respect to the steel wire obtained as described above,
The spheroidization rate of cementite was measured by the usual method, and the scale adhesion was investigated as the surface properties of the steel wire.

Table 4 also shows the spheroidization rate of cementite. In addition, when it was cooled to room temperature (room temperature) by water cooling with a cooling device after being charged into the furnace, adhesion of scale was extremely small and surface properties were good.

[0115]

[Table 4]

From Table 4, it is clear that according to the steel wire manufacturing method of the present invention, a steel wire having a spheroidizing ratio of cementite of 85% or more can be obtained in a very short time.

On the other hand, in the case of the comparative example in which the processing conditions were out of the conditions specified in the present invention, the spheroidizing ratio of cementite was inferior.

That is, in test number 40, the heating temperature T1
Is higher than Ae ₁ point + 160 ° C., the cooling rate C1 is lower than {(T1-Ae ₁ point) / 30} ° C./sec in Test No. 41, and in Test No. 34, the temperature T2 is higher than Ae ₁ point + 20 ° C. Therefore, a large amount of cementite is dissolved, and the spheroidization rate of cementite is low.

In test No. 37, the heating temperature T1 was Ae ₁ point +
Since the cooling rate C1 exceeds {(T1-Ae ₁ point) /1.5} [deg.] C./sec in Test No. 44 since the temperature is lower than 40 [deg.] C., cementite hardly dissolves in each case, and the desired cementite spheroidization ratio is obtained. A value of 85% or more is not obtained.

In Test No. 36, the cooling end temperature T2 is Ae ₁
Since the temperature is below the temperature of −60 ° C., the furnace temperature T
Since 3 is below Ae ₁ point -100 ° C, pearlite is generated, and the spheroidization rate after the heat treatment is low.

In Test No. 45, the holding time in the furnace at the temperature T3 was less than 3 minutes, and in Test No. 50, the temperature T3 of the furnace exceeded ₁ Ae-10 ° C. In each case, pearlite was formed, and the desired spheroidization ratio was not obtained.

In Test No. 51, the total reduction in rolling was 10%.
Therefore, the reticulated cementite remains, and a desired cementite spheroidization ratio of 85% or more is not obtained.

[0123]

According to the method for producing a steel wire of the present invention, a hot-rolled wire, particularly a hot-rolled wire used as a material for bearing element parts,
In a short time, the spheroidization ratio of cementite can be set to 85% or more to soften, and at the same time, the shape and dimensions can be adjusted. This method of manufacturing a steel wire can be implemented relatively easily using the manufacturing equipment of the present invention.

[Brief description of the drawings]

FIG. 1 is a graph showing a result in an example, in which a vertical axis represents a cooling rate C1.
(° C./second) and T1-Ae _one point (° C.) on the abscissa, which is a diagram in which the spheroidization of cementite is arranged. "O" indicates that the spheroidization rate of cementite is 85% or more, and "X" indicates that the spheroidization rate is less than 85% due to the heating temperature T1 and the cooling rate C1.

FIG. 2 is a diagram illustrating an example of a manufacturing facility for performing the method of manufacturing a steel wire according to the present invention.

FIG. 3 is a diagram showing another example of a manufacturing facility for carrying out the method for manufacturing a steel wire according to the present invention.

FIG. 4 is a diagram showing the manufacturing equipment used in Example 1.

FIG. 5 is a diagram showing a manufacturing facility used in Example 2.

[Explanation of symbols]

1: Uncoiler 2: Straightening machine 3: Feeding electrode 4: Intermediate rolling roll group 4 ': Intermediate rolling roll group in which at least one roll constitutes an electrode 4 ": Intermediate rolling roll constituting an electrode 5: Forming an electrode Finishing roll 6: Control cooling device 7: Furnace 8: Rapid cooling device 9: Winding device 10: Material to be treated (wire as hot rolled)

────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code FI C21D 9/62 102 C21D 9/62 102 C22C 38/00 301 C22C 38/00 301Y 38/18 38/18 (72) Inventor Hamada Koichi 4-5-33 Kitahama, Chuo-ku, Osaka City, Osaka Prefecture Sumitomo Metal Industries, Ltd.

Claims (5)

[Claims] 1. A method for producing a steel wire using a feeder electrode, a facility including a rolling mill having n intermediate rolling roll groups, and a finishing rolling roll constituting the electrode, comprising: C: 0.7 to 1.5%, Mn + Cr:
A wire rod hot-rolled from steel containing 0.8 to 3.0% is conveyed in the axial direction in a strand state, and the wire portion between the power supply electrode in contact with the wire and the finish rolling roll is directly energized. Temperature T1 at a heating rate of 100 ° C / sec or more
While increasing the temperature, the rolling is performed as it is or the intermediate rolling rolls have a reduction in area of more than 0%, and the finish reduction rolls have a reduction in area of more than 0%. Rolling is performed so that the total area reduction by the roll is 10% or more. Immediately after finishing the rolling by the finish rolling roll, the roll is cooled to a temperature T2 at a cooling rate of C1 ° C./sec, and then mounted in a furnace at a temperature T3. A method for producing a steel wire, wherein the steel wire is inserted and held for 3 to 30 minutes. However, Ae ₁ point +
40 ° C ≦ T1 ≦ Ae ₁ point + 160 ° C, Ae ₁ point −60 ° C ≦ T2
≤ Ae ₁ point + 20 ° C, Ae ₁ point -100 ° C ≤ T3 ≤ Ae ₁ point-
10 ° C., (T1-Ae ₁ point) / 30 ≦ C1 ≦ (T1-Ae
₍₁ point) /1.5, and n is a positive integer. 2. A facility comprising a rolling device having one or both of a power supply electrode and at least one intermediate rolling roll group comprising m electrodes, and a finish rolling roll constituting an electrode. A steel wire by weight, C: 0.7-1.5%, Mn + C
r: a wire rod hot-rolled from steel containing 0.8 to 3.0% is conveyed in the axial direction in a strand state, and the wire portion or the electrode between the power supply electrode and the finish rolling roll that comes into contact with the wire rod. While the wire portion between the intermediate rolling roll and the finishing rolling roll is heated to a temperature T1 at a heating rate of 100 ° C./sec or more by direct energization, the area reduction rate is reduced to 0% as it is or in a group of intermediate rolling rolls. Rolling over, and the reduction of area exceeds 0% with the finish rolling roll,
In addition, rolling is performed so that the total area reduction rate by the intermediate rolling roll group and the finishing rolling roll is 10% or more, and immediately after finishing the rolling by the finishing rolling roll, cooling is performed at a cooling rate of C1 ° C./sec to a temperature T2. And then holding the furnace in a furnace at a temperature T3 for 3 to 30 minutes. However, Ae ₁ point + 40 ° C ≦ T1 ≦ Ae ₁ point + 1
60 ° C, Ae ₁ point -60 ° C ≤ T2 ≤ Ae ₁ point + 20 ° C, Ae ₁
Point -100 ° C ≤ T3 ≤ Ae ₁ point -10 ° C, (T1-Ae ₁ point)
/ 30 ≦ C1 ≦ (T1-Ae ₁ point) /1.5, and m is a positive integer. 3. The temperature T3 according to claim 1, wherein:
A method for producing a steel wire, comprising: performing a quenching process after a process of placing the device in a furnace and holding the device for 3 to 30 minutes. 4. C .: 0.7 to 1.5% by weight, Mn +
Cr: a production facility for producing a steel wire using a wire rod hot-rolled from steel containing 0.8 to 3.0% as a raw material,
Uncoiler, straightening machine, feeding electrode, intermediate rolling roll group, finishing rolling rolls constituting electrodes, control cooling device,
A steel wire manufacturing facility, characterized in that a furnace, a quenching device, and a winding device are arranged so that a material to be processed passes in this order. 5. C: 0.7 to 1.5% by weight, Mn +
Cr: a production facility for producing a steel wire using a wire rod hot-rolled from steel containing 0.8 to 3.0% as a raw material,
An uncoiler, a straightening machine, a feeding electrode and / or an intermediate rolling roll group in which at least one roll constitutes an electrode, a finishing rolling roll constituting an electrode, a control cooling device, a furnace, a quenching device, and a winding device are arranged in this order. A steel wire manufacturing facility, which is arranged to pass through.