JPH0853737A - High strength and high toughness hot-dip plated steel wire and its production - Google Patents

Abstract

PURPOSE:To develop a high strength and high toughness hot-dip plated steel wire excellent in corrosion resistance by subjecting the hot rolled material of high carbon steel to patenting treatment, thereafter subjecting it to cold wire drawing to form into a steel wire, subjecting only the surface to tempering treatment and subsequently applying plating of Zn or the like thereto. CONSTITUTION:A high carbon steel contg., by weight, 0.7 to 1.2% C, 0.5 to 2.0% Si, 0.2 to 1.0% Mn, 0.02 to 0.07% Al and 0.003 to 0.015% N, furthermore contg. specified small amounts of one or more kinds among Cu, Cr, Ni, Co and W and moreover contg. one or more kinds among V, Nb, Ti and B is subjected to hot rolling to form into a wire rod. After that, it is subjected to patenting treatment or is subjected to patenting treatment after reaustenitization to form into a steel wire rod having a main structure of fine pearlite, which is thereafter subjected to cold wire drawing to form into a steel wire having a required diameter. Next, only the surface of the steel wire is subjected to heating and tempering treatment by the induction hardening method, etc., and is thereafter applied with galvanizing or Zn-Al allay plating. HV/TS, i.e., the average Vickers thickness of the steel wire stock to 50mum toward the center of the steel wire from the boundary of the plating layer and the steel wire stock to the tensile strength TS (kgf/mm<2>) of the plated steel wire is regulated to <2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a high-strength, high-toughness hot-dip galvanized steel wire having excellent corrosion resistance, which is useful for PC steel wire, galvanized steel stranded wire, spring steel wire, suspension bridge cable and the like. Is.

[0002]

2. Description of the Related Art When manufacturing high-strength wires such as PC steel wires and cables for suspension bridges, which are required to have corrosion resistance, high carbon steel wires having a certain diameter are subjected to patenting treatment to a predetermined wire diameter. In general, wire drawing is performed, and then hot dip Zn plating for imparting corrosion resistance is performed. However, with this method, 400 ° C after wire drawing
Since the hot-dip galvanizing process is performed at the above-mentioned high temperature, there is a problem that the strength of the wire material improved by the wire drawing is reduced again. Further, the higher the degree of wire drawing and the higher the strength, the greater the decrease in strength due to the plating treatment. Therefore, it was difficult to increase the strength of the plated steel wire by this method.

Therefore, increasing the C content of the high carbon steel wire rod to improve the strength has been studied as an industrially desirable method because it is inexpensive and has a great effect. However, in the hyper-eutectoid region where the C content is 0.9% or more, brittle pro-eutectoid cementite forms along the austenite grain boundaries during patenting in the form of a network. Disconnection occurs,
A new problem has arisen that wire drawability deteriorates.

On the other hand, Si has the effect of increasing the strength of the steel wire after patenting and improving the strength of the steel wire after drawing, and the effect of improving the hardenability of the steel wire and suppressing the precipitation of pro-eutectoid cementite. It is an element that has. In addition to these effects, it also has the effect of suppressing the strength reduction due to plating treatment, and it is a very effective element for increasing the strength of hot dip plated steel wire, but excessive addition causes toughness of the steel wire. It is also known to reduce ductility.

Therefore, several proposals have been made to obtain a steel wire having high strength and high toughness by subjecting a high carbon steel wire material containing Si to hot-dip plating, and then applying working and heat. For example, Japanese Patent Application Laid-Open No. 4-246125 discloses a method of performing a straightening process and a bluing process after performing a hot dip Zn-Al plating. In addition, Japanese Patent Laid-Open Nos. 4-236756 and 4-236742 disclose that
A method of performing wire drawing and heat treatment after performing hot dip Zn-Al plating is disclosed. However, in the case of a type such as a plated bridge steel wire for suspension bridges in which the steel wire after plating cannot be processed, these conventional techniques cannot be applied.

[0006] On the other hand, it is known that by using the compressive stress as the residual stress on the surface of the steel wire, vertical cracking at the time of twisting can be suppressed. For example, Japanese Patent Publication No. 3-66386 discloses the compressive residual stress on the surface. A steel wire controlled within a specific range is disclosed. However, even if the residual stress is controlled in this way, in the case of a steel wire that passes through the hot dip plating process, the effect of residual stress is hardly obtained because the wire temperature rises.

[0007]

DISCLOSURE OF THE INVENTION In the present invention, a high strength and high toughness hot dip galvanized steel wire having good longitudinal cracking characteristics during twisting and rotary bending fatigue characteristics even after passing through a plating step and a method for producing the same are provided. The purpose is to provide.

[0008]

The high-strength and high-toughness hot-dip galvanized steel wire according to the present invention, which has solved the above-mentioned problems, is C: 0.7-1.2% Si: 0.5-2.0% Mn: 0. 2 to 1.0% Al: 0.02 to 0.07% N: 0.0030 to 0.0150%, balance Fe
And a high-carbon steel wire consisting of unavoidable impurities, which is hot-dipped galvanized steel wire having an average Vickers hardness Hv of the surface layer of the base material of up to 50 μm from the interface between the plating layer and the base material toward the center, and plating Steel wire tensile strength TS (kgf / mm ² )
Ratio: Hv / TS is 2 or less.

The high carbon steel wire further comprises Cu:
0.05-0.5%, Cr: 0.05-1.0%, N
i: 0.05 to 1.0%, Co: 0.05 to 1.0%,
W: 0.05 to 1.0% or more, V: 0.05 to
0.5%, Nb: 0.01 to 0.2%, Ti: 0.01
.About.0.2% and B: 0.0005 to 0.0050% may be contained.

In the coated steel wire of the present invention, the average Vickers hardness Hv of the surface layer of the base material up to 50 μm from the interface between the plated layer and the base material and the tensile strength TS (kgf / mm ^{2) of the} plated steel wire. Ratio: Hv / TS of 2 or less, the high carbon steel wire is directly subjected to patenting treatment after hot rolling, or patenting treatment after re-austenization to make fine pearlite a main structure. Cold drawing is performed after the steel wire has been formed, and only the surface of the steel wire after the cold drawing is subjected to tempering treatment, and then molten Zn or Z
A method of applying n-Al plating is recommended. At this time,
It is a preferred embodiment of the method of the present invention that the tempering means is a high frequency heating method or a laser heating method.

Further, the ratio of the average Vickers hardness Hv of the surface layer of the base material up to 50 μm from the interface between the plating layer and the base material and the tensile strength TS (kgf / mm ² ) of the plated steel wire: H
In order to reduce v / TS to 2 or less, it is also a preferred embodiment of the method of the present invention to employ a method of decarburizing the steel wire before cold drawing instead of tempering.

[0012]

First, the reason for limiting the optimum chemical composition of the plated steel wire of the present invention will be explained. C: 0.7 to 1.2% C is an element effective for increasing the strength of the steel wire and is economical. If the C content is less than 0.7%, it is insufficient to exert the effect of improving the strength of the steel wire. But,
If the C content exceeds 1.2%, the ductility of the steel wire will be significantly reduced.

Si: 0.5 to 2.0% Si acts as a deoxidizing agent and also has the effect of forming a solid solution with ferrite to remarkably increase the strength of the solid solution. Further, Si in the ferrite has an effect of reducing the strength reduction during hot dipping performed after wire drawing. These effects are recognized when the steel wire contains Si, but the more remarkable effect is when Si is 0.5% or more. But Si
However, since the ductility of the steel wire after wire drawing is deteriorated, the upper limit of the amount of Si was set to 2.0%.

Mn: 0.2 to 1.0% Mn has an effect as a deoxidizing agent and an effect of improving the hardenability of the steel wire and enhancing the uniformity of the structure in the cross section of the steel wire.
However, if Mn is excessively added, a supercooled structure such as martensite or bainite is generated in the segregated portion of Mn to deteriorate the wire drawing workability. Therefore, the upper limit of the content is set to 1.0%.

Al: 0.02 to 0.07% Al is effective as a deoxidizing agent, and is effective in preventing coarsening of the austenite grain size by adding N together. However, if the added amount is less than 0.02%, this effect is insufficiently expressed, and if added excessively, the amount of nitride increases excessively and the wire drawability deteriorates. I won't.

N: 0.0030 to 0.0150% N becomes a nitride of Al in the steel wire and is effective in preventing coarsening of the austenite grain size during heating. 0.00 0.00
If it is less than 30%, this effect is not sufficiently exhibited. Also, if added in excess of 0.0150%, not only does Al nitride increase too much, which adversely affects the wire drawability, but also solid solution N
May accelerate aging during wire drawing, so the upper limit is 0.0
It was set to 150%.

The galvanized steel wire of the present invention has the above-mentioned essential components and is composed of the balance Fe and unavoidable impurities. However, the following chemical components, that is, Cu, Cr and N.
one or more selected from the group consisting of i, Co and W,
Alternatively, the method of the present invention can be preferably used for steel grades to which one or more chemical components selected from the group consisting of V, Nb and Ti are positively added.

Cu: 0.05 to 0.5% Cu improves the strength of the steel wire by the precipitation hardening action, but if the addition amount is less than 0.05%, the effect is too small. However, if it is added excessively, not only the strength improving effect is saturated, but also grain boundary embrittlement is caused, and the ingot surface may be cracked during hot rolling, so the upper limit was made 0.5%.

Cr: 0.05 to 1.0% Cr improves the strength and drawability of the steel wire. This is because Cr reduces the lamellar spacing in pearlite. This effect is observed at 0.05
%, But when added in excess of 1.0%, the transformation end time becomes too long, which is not preferable from the viewpoint of productivity.

Ni: 0.05 to 1.0% Ni does not contribute much to the improvement of the strength of the steel wire, but has the effect of increasing the toughness of the drawn wire. This effect is recognized when the addition amount is 0.05% or more, but if the addition amount exceeds 1.0%, the transformation end time becomes too long,
It is not preferable in terms of productivity.

Co: 0.05 to 1.0% Addition of 0.05% or more of Co suppresses the precipitation of pro-eutectoid cementite. However, even if added over 1.0%, the effect is saturated and it is uneconomical, so the upper limit was made 1.0%.

W: 0.05 to 1.0% W is added in an amount of 0.05% or more and has the effect of improving the strength of the steel wire. However, even if added over 1.0%, the effect is saturated and conversely causes a decrease in ductility, so the upper limit was made 1.0%.

V: 0.05 to 0.5%, Nb: 0.01
-0.2%, Ti: 0.01-0.2%, B: 0.00
05 to 0.0050% These elements form fine carbonitrides in the steel wire, improve the strength of the steel wire by precipitation hardening, and serve to prevent coarsening of the austenite grain size during heating. This effect is not observed when the amount added is less than the above lower limit. On the other hand, if the amount exceeds the upper limit, the amount of carbonitrides increases too much and the particle size of the carbonitride itself becomes too large, resulting in poor ductility.

The galvanized steel wire of the present invention contains the above-mentioned chemical components, and the essential constituent requirement which is the most important point in the present invention is from the interface between the plating layer of the hot dip galvanized steel wire and the substrate toward the center. Average Vickers hardness Hv of the surface layer of the base material up to 50 μm and tensile strength TS (kg
Ratio of f / mm ² ): Hv / TS is 2 or less. When the present inventors examined the above-mentioned ratio Hv / TS of a general steel wire, it was 2.8 to 2.9. Therefore, it can be seen that Hv increases as the strength TS increases. However, as the strength of the steel wire increases, the ductility deteriorates, and the vertical cracking property during twisting also deteriorates. As a result of the present inventors' study on this point, it was found that by softening only the surface layer of the steel wire, it is possible to obtain a steel wire having high strength and free from vertical cracks during twisting.

In the present invention, the surface layer of the steel wire to be softened is 50 from the interface between the plating layer and the metal substrate toward the center.
The part up to μm. That is, in the steel wire before plating, it is a portion from the surface of the steel wire to a depth of 50 μm. Only this surface layer is softened by quenching or decarburization described later (the surface layer after softening may be referred to as surface softening layer)
As a result, vertical cracking during twisting can be suppressed as much as possible. FIG. 1 shows the depth of the surface softening layer (the depth of the layer measured from the interface between the plating layer and the metal substrate toward the center).
The fatigue limit (stress that does not break after 10 million cycles) was measured in the rotating bending fatigue test of the plated steel wire when the value was changed. As is clear from FIG. 1, the surface softening layer is 5
If it exceeds 0 μm, the fatigue limit will decrease, so in the present invention, the surface layer to be softened is defined as 50 μm from the steel wire surface.

The degree of softening the surface layer is defined by the average Vickers hardness of the surface layer. As the average Vickers hardness Hv of the surface layer, a value measured by the code method was adopted.
The code method is RHGassner, Metal Progress, March,
59 (1978). Specifically, as shown in FIG. 2, a steel wire is polished obliquely from the surface layer toward the center,
Vickers hardness is measured at the point Δ from the end of the polished surface. If the polished surface length is C and the radius of the steel wire is r, the depth d of the measurement point is
Is given by d = r− {r ² −Δ · (C−Δ)} ^1/2 . In the present invention, the Hv of the surface layer is set to a depth of 10, 20, 3 from the interface between the plating layer and the metal substrate toward the center of the steel wire.
It was defined as the average value of Hv measured for each part of 0, 40 and 50 μm. The code method can measure the hardness near the surface of the steel wire with a relatively large load, so the error is much smaller than in the conventional method.

FIG. 3 shows the relationship between the tensile strength TS of the plated steel wire obtained in the examples described later and the average Vickers hardness Hv of the surface softening layer. The normal fracture surface of the twist test is plotted as a white circle, and the abnormal fracture surface is plotted as a black circle. The dotted line is a straight line of Hv / TS = 2. As is clear from FIG. 3, even in the case of plated steel wire showing the same TS, Hv / T
All the plated steel wires with S exceeding 2 are abnormal fracture surfaces. It can be seen that Hv of the surface softening layer has a great influence on the fracture surface state during twisting. Therefore, in the present invention, it is an essential requirement that Hv / TS is 2 or less.

Next, a method for reducing Hv / TS to 2 or less will be described. The galvanized steel wire of the present invention is obtained by subjecting the high carbon steel wire having the above chemical composition to hot rolling → direct or after reaustenizing, patenting → cold drawing → molten Zn or Z.
High-strength and high-toughness hot-dip galvanized steel wire is obtained through a process called n-Al plating. In the present invention, since it is necessary to soften the surface layer of the steel wire as described above, during the above step, a method of tempering only the steel wire surface layer before or after cold drawing, or the steel wire before cold drawing It is recommended to adopt the method of decarburizing the surface layer. Preferred methods for tempering the surface layer of the steel wire include high frequency heating or laser heating.

Further, it is preferable from the viewpoint of production efficiency that the decarburizing treatment is carried out before cold drawing, especially at the same time as the patenting treatment. Decarburization is possible by setting a long heating time during patenting. The surface layer may be softened by performing both tempering and decarburization.

[0030]

The present invention will be described in more detail with reference to the following examples, but the following examples do not limit the present invention.
All modifications and implementations that do not depart from the spirit of the description below are included in the technical scope of the present invention.

In Table 1, the chemical composition of the steel used in the examples is shown in% by weight. The steels shown in Table 1 were first hot-rolled to 7.5 mm for a final wire diameter of 3 mm after hot dipping, 12 mm for a final wire diameter of 5 mm, and 14 mm for a final wire diameter of 7 mm. Lead patenting treatment (reheating: 950 ° C x 5 minutes, constant temperature transformation:
540 ° C. × 4 minutes). When decarburizing was performed during patenting (Table 4), the reheating time was 10 minutes.

After that, the wire rod is cooled at the exit of the die and 170
The wire was drawn to the target wire diameter while maintaining the temperature below ℃. After the subsequent linear processing, in the experiment shown in Table 2, the steel wire was passed through a high-frequency heating furnace with a constant output. At this time, the depth (thickness) and hardness of the surface softening layer are changed while changing the linear velocity. After tempering, hot dip Zn plating was performed. Table 3 shows the results for the steel wire which was subjected to the hot-dip Zn plating by performing the surface layer softening treatment while changing the linear velocity with a CO ₂ laser having a constant output. Table 4 shows the characteristic results of the hot-dip galvanized steel wire that was decarburized during patenting.

The methods for measuring the characteristics shown in Tables 2 to 4 are as follows. [Average Vickers hardness Hv of surface layer: abbreviated as average hardness Hv] A value measured by the code method is adopted, and 10 or 2 is measured from the interface between the plating layer and the metal substrate toward the center of the steel wire.
Average value of Vickers hardness Hv measured for each part of 0, 30, 40, and 50 μm. [Abnormal Fracture Surface Ratio During Twisting] Ten samples were subjected to a twisting test, and the ratio of occurrence of abnormal fracture surface was shown in percent. [Rotary Bending Fatigue Properties] The stress (fatigue limit) that does not break after the number of repetitions of 10 million times is 40 kgf / mm ² or more is defined as “good”. [Judgment] When the tensile strength of the plated steel wire was 200 kgf / mm ² or more, the abnormal fracture surface ratio was 0%, and the rotary bending fatigue property was good, it was evaluated as ◯, and when any one was not satisfied, it was evaluated as x.

[0034]

[Table 1]

[0035]

[Table 2]

[0036]

[Table 3]

[0037]

[Table 4]

From the above experimental example, the following was found. Experiment Nos. 1-28 are experimental examples in which the surface layer was softened by high frequency heating. Since No. 1 uses steel type A with less C, the tensile strength was low. Nos. 2, 3 and 7, 8 were examples of the present invention, and were excellent in all of strength, twisting characteristics, and rotational fatigue characteristics. No. 4 has a surface softening layer of 25 μm
And within the specified range of the present invention, the softening is insufficient and Hv / T
Since S exceeds 2, the vertical crack occurrence rate during twisting is 100%
And very inferior. Since No. 5 is not surface softened, it has a high abnormal fracture rate. No. 6, 10 are
Since the softened surface layer exceeded 50 μm, the rotary bending property was inferior. No. 7 and 8 use B, but the strength is low due to the low surface reduction rate in the wire drawing process after plating, and No. 9 is twisted because Hv / TS exceeds 2 because of insufficient softening. There are many abnormal fracture rates during the test.

Since C of steel type D exceeds the upper limit value, in No. 11 using this steel, a large amount of pro-eutectoid cementite was precipitated and the wire drawability was deteriorated, and wire breakage occurred during cold wire drawing. No. 12 uses the steel type E with too much Si, so the ductility decreases,
After all, there were many disconnections. Further, No. 13 was able to be drawn because it used the steel type F with a small amount of Mn, but the strength of the steel wire is insufficient. Since steel type G has a large amount of Mn, the wire drawability is poor due to the presence of a supercooled structure (No. 14), and steel type I has a large amount of Al and therefore a large amount of nitride is formed and wire drawing is impossible (No. 1)
6). In addition, No. 15 using the steel type H with less Al,
Since the crystal grain size became coarse, the wire drawability was inferior.

Nos. 17, 18, 21 to 27 all use the steel of the present invention and have a surface softening layer within the specified range of the present invention to satisfy Hv / TS. The plated steel wire has been obtained that is excellent in both time characteristics and rotary bending fatigue characteristics. In No. 19, Hv / TS exceeded 2 because the degree of softening of the surface layer was insufficient.
Since No. 18 uses the steel type L in which Cr exceeds the upper limit value, the transformation time becomes long, and under the patenting conditions of this time, the transformation did not end within the time, so there was a supercooled structure and there was a wire breakage. Is a frequent occurrence. No. 28
Since the steel type T in which N exceeds the upper limit value was used, the age hardening action during wire drawing was too strong and the wire was broken.

Experiment Nos. 31 to 36 shown in Table 3 are experimental examples in which the surface layer of the steel wire before plating was tempered by laser heating. In Table 3, as in the case of high frequency heating in Table 2, Hv / having a surface softening layer within the specified range of the present invention was used.
In the experimental example satisfying TS (inventive example), a plated steel wire having excellent tensile strength, twisting characteristics, and rotational bending fatigue characteristics was obtained. Further, Table 4 shows an experimental example in which decarburization was performed during patenting to soften the surface layer of the steel wire. Also in this example, the effect of the present invention is clear, and in Experiment No. 43 in which the surface softening layer is too large, the rotational bending fatigue property is poor, and the softening of the surface softening layer is insufficient, so that Hv
In Experiment Nos. 42, 45, and 47 in which / TS exceeds 2, the abnormal fracture surface rate at the time of twisting was high.

[0042]

According to the present invention, in order to suppress vertical cracking during twisting of a high carbon steel wire having an optimum chemical composition, it is effective to soften the surface layer 50 μm of the steel wire before plating by tempering or decarburizing. Therefore, it is possible to provide a hot-dip galvanized steel wire that has high strength and high toughness, does not cause vertical cracks during twisting, and has excellent rotary bending fatigue properties, and a manufacturing method thereof. did it. The method of the present invention is applicable to PC steel wire, galvanized steel wire, spring steel wire, suspension bridge cable, ACS.
It is also very useful for steel wire applications such as plated steel wire for R (strengthening wire of a transmission line cable) requiring high strength.

[Brief description of drawings]

FIG. 1 is a graph showing the influence of the depth of a surface softening layer on a rotary bending fatigue test.

FIG. 2 is a side view and a sectional view of a steel wire for explaining a Vickers hardness measurement method by a cord method.

FIG. 3 is a graph showing the relationship between the tensile strength TS of the plated steel wire and the average Vickers hardness Hv of the surface softening layer.

Claims (7)

[Claims] 1. C: 0.7 to 1.2% (weight%, the same applies hereinafter) Si: 0.5 to 2.0% Mn: 0.2 to 1.0% Al: 0.02 to 0. A high-carbon steel wire containing 07% N: 0.003 to 0.015%, the balance of which is Fe and unavoidable impurities, obtained by hot-dip plating. Ratio of the average Vickers hardness Hv of the surface layer of the base material up to 50 μm and the tensile strength TS (kgf / mm ² ) of the plated steel wire: Hv / TS is 2 or less, high strength and high toughness Hot dip steel wire. 2. C: 0.7 to 1.2% Si: 0.5 to 2.0% Mn: 0.2 to 1.0% Al: 0.02 to 0.07% N: 0.003 .About.0.015%, and further, Cu: 0.05-0.5% Cr: 0.05-1.0% Ni: 0.05-1.0% Co: 0.05-1.0 % W: Containing one or more of 0.05 to 1.0%, balance Fe
And a high-carbon steel wire consisting of unavoidable impurities, which is hot-dipped galvanized steel wire having an average Vickers hardness Hv of the surface layer of the base material of up to 50 μm from the interface between the plating layer and the base material toward the center, and plating Steel wire tensile strength TS (kgf / mm ² )
Ratio: Hv / TS is 2 or less, a high-strength, high-toughness hot-dip galvanized steel wire. 3. C: 0.7 to 1.2% Si: 0.5 to 2.0% Mn: 0.2 to 1.0% Al: 0.02 to 0.07% N: 0.0030 .About.0.0150%, and further, Cu: 0.05-0.5% Cr: 0.05-1.0% Ni: 0.05-1.0% Co: 0.05-1.0 % W: One or more of 0.05 to 1.0%, V: 0.05 to 0.5% Nb: 0.01 to 0.2% Ti: 0.01 to 0.2% B: 0 A high-carbon steel wire containing at least one of 0.0005 to 0.0050% and the balance being Fe and unavoidable impurities, and a hot-dip plated steel wire, which is directed from the interface between the plating layer and the base material to the center. Average Vickers hardness Hv of the substrate surface layer up to 50 μm and tensile strength T of the plated steel wire
Ratio of S (kgf / mm ² ): Hv / TS is 2 or less, high strength and high toughness hot-dip galvanized steel wire. 4. The high carbon steel wire according to any one of claims 1 to 3 is directly subjected to patenting treatment after hot rolling or is subjected to patenting treatment after re-austenization to form fine pearlite as a main structure. Cold drawing is performed after the steel wire to be formed is subjected to a tempering treatment only on the surface of the steel wire after the cold drawing, and then a hot dip Zn or Zn-Al plating is applied to the plated layer and the base material. The average Vickers hardness Hv of the steel wire surface layer portion of 50 μm or less from the metal interface toward the center and the tensile strength TS (kgf / mm ² ) of the plated steel wire
Ratio: Hv / TS is set to 2 or less, a method for producing a high-strength and high-toughness hot-dip galvanized steel wire. 5. The manufacturing method according to claim 4, wherein only the surface of the steel wire is tempered by a high frequency heating method. 6. The method according to claim 4, wherein only the surface of the steel wire is tempered by a laser heating method. 7. The high carbon steel wire according to any one of claims 1 to 3 is directly subjected to patenting treatment after hot rolling or is subjected to patenting treatment after re-austenization to make fine pearlite as a main structure. Steel wire to be used, decarburizing only the surface of this steel wire, then cold drawing,
Then, by performing hot dip Zn or Zn-Al plating, the average Vickers hardness Hv of the steel wire surface layer portion of 50 μm or less from the interface between the plated layer and the base metal toward the center.
And the tensile strength TS (kgf / mm ² ) of the plated steel wire: Hv /
A method for producing a high-strength, high-toughness hot-dip galvanized steel wire, characterized in that TS is 2 or less.