JP3169454B2 - High strength steel wire and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a bridge, a steel cord of an automobile tire, a fishing net rope, a reinforcement of a transmission line,
Alternatively, the present invention relates to a high-tensile steel wire used as a wire for reinforcing a submarine optical fiber cable.

[0002]

2. Description of the Related Art In the case of bridge wires, there is a need to increase the central span of the bridge, in the case of steel cords for automobiles, in order to reduce the weight of tires, and in the case of wires for fishing net ropes. , With the downsizing of ships and the enlargement of fishing nets,
The need for higher tensile strength of steel wire has been increasing recently.

[0003] As a result of intensive development of a number of studies to meet such demands, the biggest problem in increasing the tensile strength of steel wires is that the ductility of steel wires, especially during torsional tests, is high. It has been found that it is to establish a technique for suppressing the occurrence of cracks that occur in the longitudinal direction of a steel wire. In contrast, WIRE
JOURNAL INTERNATIONAL VOLUME 16 1983 NO 4 Page 50 states that by controlling the cementite lamella spacing of the pearlite structure constituting the steel wire to an appropriate size, it is possible to suppress the longitudinal cracking of the galvanized steel wire. Have been.

Japanese Patent Publication Nos. 60-26805 and 60-26806 disclose a bluing process (200 ° C. to 400 ° C.) for removing distortion after forming such as twisting or spring winding. (Process at ℃ for minutes), the toughness of the steel wire decreases, causing a problem of cracking in the longitudinal direction in the torsion test. However, straightening under specific conditions after or during wire drawing must be performed. Describes that this longitudinal cracking can be suppressed.

[0005]

However, according to the study of the present inventors, even with the above-mentioned technique, an ultra-high tensile steel wire, for example, a tensile strength of 1900 MPa or more at a wire diameter of 5 mm, 2100 MPa or more at 3 mm, or 2 mm or more. When producing a steel wire of 2500 MPa or more at 0.5 mm and 3400 MPa or more at 0.5 mm, the occurrence of longitudinal cracks in the twist test cannot be suppressed.

The present invention relates to the ductility of high-tensile steel wires used for bridges, automobile tire steel cords, fishing nets, reinforcement of power transmission lines, or wires for reinforcing submarine optical fiber cables, and particularly, the ductility of high-strength steel wires during a torsion test. The purpose of the present invention is to establish a technique for suppressing the generation of cracks in the direction.

[0007]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention relieves tensile residual stress in the vicinity of the surface layer of a drawn material by skin pass, straightening, and high-temperature bluing to reduce the strength of a high-strength steel wire. It suppresses the ductility, particularly the occurrence of cracks that occur in the longitudinal direction during the torsion test. That is, it is an aspect of the present invention, as a high-strength steel wire, as (1) chemical composition, in mass%, C: 0.70 to 1.
10%, Si: 0.20 to 2.0%, Mn: 0.3 to
1.5%, and Cr: 1.
0% or less, Mo: 0.2% or less, V: 0.3% or less, N
i: A steel wire containing 1.0% or less of one or more kinds and the balance consisting of Fe and unavoidable impurities is subjected to at least one heat treatment and wire drawing step to 1900MPa.
a) After forming a drawn steel wire having a strength of not less than a skin pass step, and thereafter, at a temperature of 460 ° C. or more, T (20 + log ₁₀ t)> 13000 (T: a bluing temperature expressed in absolute temperature [K ],
t: the bluing time [hr]) expressed in time
The tensile residual stress in the vicinity of the surface is reduced by the bluing process that satisfies the above conditions, and the residual stress value of the outermost layer is ± 1.
It is characterized in that it is controlled within the range of 50 MPa. (2) as chemical components, in mass%, C: 0.70~1.
10%, Si: 0.20 to 2.0%, Mn: 0.3 to
1.5%, and Cr: 1.
0% or less, Mo: 0.2% or less, V: 0.3% or less, N
i: A steel wire containing 1.0% or less of one or more kinds and the balance consisting of Fe and unavoidable impurities is subjected to at least one heat treatment and wire drawing step to 1900MPa.
a After drawing into a drawn steel wire having a strength of not less than a skin pass step and bending, and then a temperature of 460 ° C. or more
_{In, T (20 + log 10 t} )> 13000 (T: brewing temperature displayed by the absolute temperature [K],
t: the bluing time [hr]) expressed in time
The tensile residual stress in the vicinity of the surface is reduced by the bluing process that satisfies the above conditions, and the residual stress value of the outermost layer is ± 1.
It is characterized in that it is controlled within the range of 00 MPa. As a manufacturing method, as (3) chemical components, in mass%, C: 0.70~1.
10%, Si: 0.20 to 2.0%, Mn: 0.3 to
1.5%, and Cr: 1.
0% or less, Mo: 0.2% or less, V: 0.3% or less, N
i: A steel wire containing 1.0% or less of one or more kinds and the balance consisting of Fe and unavoidable impurities is subjected to at least one heat treatment and wire drawing step to 1900MPa.
a After reducing to a drawn steel wire having a strength of
A skin pass is performed by passing through a 10% skin pass dice, and then, at a temperature of 460 ° C. or more, T (20 + log ₁₀ t)> 13000 (T: bluing temperature [K] expressed in absolute temperature,
t: a bluing process is performed so as to satisfy a relationship of bluing time [hr] displayed in time. (4) as chemical components, in mass%, C: 0.70~1.
10%, Si: 0.20 to 2.0%, Mn: 0.3 to
1.5%, and Cr: 1.
0% or less, Mo: 0.2% or less, V: 0.3% or less, N
i: A steel wire containing 1.0% or less of one or more kinds and the balance consisting of Fe and unavoidable impurities is subjected to at least one heat treatment and wire drawing step to 1900MPa.
a After reducing to a drawn steel wire having a strength of
A skin pass is performed by passing through a 10% skin pass die, and then a plurality of rolls are passed at a bending angle of 10 to 30 degrees to perform a bending process. Then, at a temperature of 460 ° C. or more, T (20 + log ₁₀ t)> 13000 (T: bluing temperature [K] expressed in absolute temperature,
t: a bluing process is performed so as to satisfy a relationship of bluing time [hr] displayed in time. (5) as chemical components, in mass%, C: 0.70~1.
10%, Si: 0.20 to 2.0%, Mn: 0.3 to
1.5%, and Cr: 1.
0% or less, Mo: 0.2% or less, V: 0.3% or less, N
i: A steel wire containing 1.0% or less of one or more kinds and the balance consisting of Fe and unavoidable impurities is subjected to at least one heat treatment and wire drawing step to 1900MPa.
a After forming a drawn steel wire having the above strength, a plurality of rolls are passed at a bending angle of 10 to 30 degrees to perform bending, and then passed through a skin pass die having a surface reduction rate of 1 to 10% to form a skin pass. After that, at a temperature of 460 ° C. or more, T (20 + log ₁₀ t)> 13000 (T: bluing temperature [K] expressed in absolute temperature,
t: a bluing process is performed so as to satisfy a relationship of bluing time [hr] displayed in time.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is directed to a steel wire which is subjected to a patenting heat treatment or the like so as to impart good drawability and then to a wire drawing. The present inventors examined the effects of the conditions on the skin pass processing and the bluing treatment after drawing on the occurrence of longitudinal cracks during the twist test of the steel wire.

FIG. 1 shows 2000 MPa and 2400 MP after wire drawing.
a, wire diameter 5.01 to 5.4 having a strength of 2800 MPa
% Steel wire was subjected to skin pass processing at a reduction rate of 0.5 to 14%, and further subjected to a blueing treatment at 410 ° C. and 510 ° C. for 10 seconds to examine the effect of the skin pass processing on the torsion characteristics. It is. In FIG.
MPa, △ ▲ are the results of 2400MPa, □ ■ are the results of 2800MPa steel wire.
Indicates that it is more than 0%. Reduction rate of skin pass treatment 1-1
It can be seen that the generation of cracks is suppressed only when the bluing treatment is performed at 510 ° C. in the range of 0%.

Next, the present inventors examined the effect of the conditions on the twisting characteristics of the steel wire regarding the bluing treatment performed after the skin pass processing. FIG. 2 shows 2000 MPa, 2
Wire diameter 5.01 having strength of 400 MPa and 2800 MPa
And, after the steel wire of 5.2φ is skin-passed and adjusted to a wire diameter of 5φ, the temperature is changed from 450 ° C to 550 ° C for 2 seconds to 10 minutes, and the bluing process is performed. It is the result of having investigated the effect which it has. ○ ● mark is 2000MPa, △ ▲ is 2400MPa, □ ■ is 280
In the result of the steel wire of 0MPa, the white mark shows the crack occurrence rate of 10% or less,
A black mark indicates that it is more than 10%.

As a result, at a temperature of 460 ° C. or more, T (20 + log ₁₀ t)> 13000 (1) (T: bluing temperature [K] expressed in absolute temperature,
t: bluing time [hr] expressed in time) is subjected to bluing treatment so as to satisfy the relationship, and only when the skin pass processing amount is 7.5%, generation of cracks in the longitudinal direction during the torsion test. It can be seen that it can be suppressed significantly.

That is, according to the above experimental results, after drawing a steel wire with a die and passing it through a skin pass die with a processing amount of 1 to 10% in area reduction rate, at a temperature of 460 ° C. or higher, (1)
It has been found that by performing the bluing treatment under the conditions satisfying the formula, cracks generated in the longitudinal direction during the torsion test can be suppressed. This is because the tensile residual stress near the surface layer of the drawn wire was released by the skin pass and the high-temperature bluing treatment. That is, the residual stress immediately after the drawing is about +200 to +400 MPa on the tensile side, but it can be controlled within the range of ± 200 MPa by applying a skin pass treatment within the range of the present invention. Further, by applying a bluing treatment within the scope of the present invention, the residual stress value can be reduced by ± 15.
It is possible to control within the range of 0 MPa. The inventors' long-term research has revealed that it is necessary to control the residual stress to 150 MPa or less in order to suppress the steel wire twist cracks of 1900 MPa class or more.

If the skin pass processing amount is less than 1%, the processing is insufficient. Even if the bluing treatment is performed within the scope of the present invention, the residual stress cannot be controlled to 150 MPa or less. Further, if the skin pass processing amount exceeds 10%, abnormal strain is introduced, and the residual stress value is rather deteriorated.
It cannot be controlled below 50MPa.

The bluing condition is out of the range of the present invention, that is, 460 ° C. or less, or T (20 + log ₁₀ t) ≦
In the case of 13000, the heat treatment is insufficient, and even if the skin pass is performed within the range of the present invention, the residual stress cannot be controlled to 150 MPa or less. The present inventors have studied a method of suppressing cracking of a steel wire having higher strength. Figure 3 shows 3000MPa after wire drawing
A steel wire having a wire diameter of 2.01 to 2.16φ having a strength of 3,300 MPa, 3500 MPa is skin-passed at a reduction ratio of 0.5 to 14% to adjust the wire diameter to 2φ, and further, as shown in FIG. The result of performing bending by the apparatus is shown. What is important is a bending process having an angle of θ which is applied to the wire by the second and third straightening rolls shown in FIG. 4 in order to release the residual stress of the tensile force near the surface layer of the drawn wire. Is for straightening a wire rod.

FIG. 3 shows a bending angle θ =
After processing at 5 to 40 degrees, 1 degree at 410 and 510 degrees
The effect of skin pass processing and bending processing on the torsional characteristics after baking treatment for 0 seconds was examined.
In FIG. 3, the mark ● ● is 3000 MPa, △ ▲ is 33
00MPa and □ ■ are the results of a 3500MPa steel wire. The white mark indicates that the crack occurrence rate is 10% or less, and the black mark indicates that the crack rate is more than 10%. The skin reduction rate is in the range of 1 to 10%,
In addition, it can be seen that the bending angle is in the range of 10 to 30 degrees, and that the occurrence of cracks is suppressed only when the bluing treatment is performed at 510 ° C thereafter.

FIG. 5 shows a drawing of 3000 MPa, 330 mm after drawing.
Wire diameter 2.01 with strength of 0MPa, 3500MPa
2. Bending angle θ = 5 for 24φ steel wire by straightening machine
After processing at 40 °, skin pass processing is performed at a reduction rate of 0.5 to 14% to adjust the wire diameter to 2φ.
The purpose of this study is to examine the effects of bending and skin pass on the torsion characteristics by performing a bluing treatment at 10 ° C. for 10 seconds.

In FIG. 5, the mark ●● is 3000 MPa,
Indicates results of a steel wire of 3300 MPa, and ■ indicates results of a steel wire of 3500 MPa. A white mark indicates that the crack occurrence rate is 10% or less, and a black mark indicates that it exceeds 10%. The angle of the bending process is in the range of 10 to 30 degrees, and the area reduction rate of the subsequent skin pass treatment is 1 to 10
%, And it can be seen that the generation of cracks is suppressed only when blueing treatment is performed at 510 ° C. thereafter.

Next, the present inventors examined the effect of the conditions on the twisting characteristics of the steel wire with respect to the bluing treatment performed after the skin pass processing and the bending processing. 6 and 7
Is a steel wire having a strength of 3000MPa, 3300MPa, 3500MPa and a wire diameter of 2.01 or 2.07φ, skin-passed, adjusted to a diameter of 2φ, and straightened at bending angles of 15 ° and 45 °. Later, at temperatures between 400 ° C. and 55
This is a result of examining the effect of bluing conditions on torsion characteristics by performing bluing treatment at 0 ° C. for a time ranging from 10 seconds to 10 minutes. ○ ● mark is 3000MPa, △ ▲ is 3
300 MPa, □ ■ are the results of a steel wire of 3500 MPa. The white marks indicate that the crack occurrence rate is 10% or less, and the black marks indicate that it exceeds 10%.

8 and 9 show 3000 MPa and 3300 MP, respectively.
a, wire diameters 2.01 and 2, having a strength of 3500 MPa.
After performing straightening at a bending angle of 15 degrees and 45 degrees on a 04φ steel wire, adjusting the wire diameter to 2φ by skin pass processing, and then changing the temperature to a range of 400 ° C to 550 ° C for 10 seconds to 10 minutes, blue 5 shows the results of examining the effect of bluing conditions on the torsion characteristics after baking. ○ ● mark is 3
000MPa, △ ▲ is 3300MPa, □ ■ is 3500
In the result of the steel wire of MPa, a white mark indicates that the crack occurrence rate is 10% or less, and a black mark indicates that the crack generation rate is more than 10%.

As a result, at a temperature of 460 ° C. or more, T (20 + log ₁₀ t)> 13000 (1) (T: bluing temperature [K] expressed in absolute temperature,
t: the bluing time [hr]) expressed in time, the bluing treatment was performed so as to satisfy the relationship, and the skin pass processing amount was 6.6% and the bending angle was 15 degrees. It can be seen that the generation of cracks in the longitudinal direction can be significantly suppressed.

That is, according to the above experimental results, after the steel wire is drawn by the die, the steel wire is passed through the skin pass die with the processing amount of the area reduction rate of 1 to 10%, and then the straightening process is performed at the bending angle of 10 to 30 degrees. After performing the straightening at a bending angle of 10 to 30 degrees, the sheet is passed through a skin pass die with a processing amount of a surface reduction rate of 1 to 10%. It has been found that by subjecting a steel wire to a bluing treatment under the conditions satisfying the expression (1), cracks occurring in the longitudinal direction during the twisting test can be suppressed.

[0022] This is because the residual stress of the drawn wire is released by skin pass, straightening and high-temperature bluing, and the ductility of the high-strength steel wire, particularly the generation of cracks that occur in the longitudinal direction during the twist test, is suppressed. It is. That is, the residual stress immediately after the drawing is about +200 to +400 MPa on the tensile side, but it can be controlled within the range of ± 200 MPa by applying a skin pass treatment within the range of the present invention. Furthermore, by combining with bending, the residual stress can be reduced to ± 150.
It becomes possible to control in the range of MPa. Further, by applying a bluing treatment within the range of the present invention, it becomes possible to control the residual stress value within a range of ± 100 MPa. When twisting cracks in the steel wire cannot be suppressed even by the skin pass and the bluing treatment described above, it is effective to further control the residual stress to 100 MPa or less.

If the skin pass processing amount is less than 1%, the processing is insufficient, and even if the bending processing and the bluing processing are performed within the scope of the present invention, the residual stress cannot be controlled to 100 MPa or less. If the skin pass processing amount exceeds 10%, an abnormal strain is introduced, and the residual stress value is rather deteriorated. Therefore, even if the bending processing and the bluing processing are performed within the scope of the present invention, the residual stress is 100 MPa. It cannot be controlled below.

If the bending amount is less than 10 degrees, the processing is insufficient. Even if the skin pass and the bluing treatment are performed within the scope of the present invention, the residual stress cannot be controlled to 100 MPa or less. If the bending amount exceeds 10%, an abnormal strain is introduced, and the residual stress value is rather deteriorated. Therefore, even if the skin pass and the bluing treatment are performed within the scope of the present invention, the residual stress is 100 MPa or less. Cannot be controlled.

The bluing condition is out of the range of the present invention, that is, 460 ° C. or less, or T (20 + log ₁₀ t) ≦
In the case of 13000, the heat treatment was insufficient, and even if skin pass and bending were performed within the scope of the present invention, the residual stress was 100%.
It cannot be controlled below MPa. Next, the reasons for limiting the components will be described. If ≪C≫C is less than 0.70%, it is difficult to stably maintain a homogeneous pearlite structure regardless of the selection of the alloy composition and heat treatment conditions, and it is difficult to ensure good torsion characteristics. It is. On the other hand, when the content exceeds 1.1%, regardless of the selection of the alloy composition and the heat treatment conditions, precipitation of pro-eutectoid cementite at the grain boundary cannot be suppressed, and the torsional cracking resistance deteriorates. % Or more and 1.1% or less. ≪Si≫Si is an element necessary for deoxidation of steel.
If it is less than 2%, the effect becomes insufficient, and 1900MP
Since it is difficult to secure a strength of a or more, the content is set to 0.2% or more. Also, Si forms a solid solution in the ferrite phase in the pearlite obtained after the heat treatment and increases the strength after the heat treatment, but on the other hand, reduces the ductility of the ferrite and deteriorates the cold drawing property,
A high area reduction rate cannot be ensured, and segregation at grain boundaries degrades torsional cracking resistance. {Mn} Mn is an element necessary for deoxidation, desulfurization and forming MnS to fix S. It also increases the hardenability of steel and obtains a homogeneous and fine pearlite structure due to the supercooling effect during heat treatment. Must be added to If the content is less than 0.3%, the effect is insufficient, so the content is set to 0.3% or more. Also, M
If n exceeds 1.5%, the transformation time becomes extremely long, which is not practical, and an abnormal structure such as martensite is formed, and it becomes impossible to draw a die. {Cr} Cr is an element effective for refining the pearlite structure and improving the strength of the steel material after heat treatment.
%, The transformation time becomes extremely long, which is not practical. An abnormal structure such as martensite is generated, and it becomes impossible to draw a die. ≪Mo≫Mo precipitates as carbonitrides in ferrite with a pearlite structure and is an effective element for improving the strength of steel after heat treatment. Instead, an abnormal structure such as martensite is generated, and it becomes impossible to draw a die. ≪V≫V precipitates as carbonitride in ferrite with a pearlite structure and is an effective element for improving the strength of a steel material after heat treatment. However, an abnormal structure such as martensite is generated, and it becomes impossible to draw a die. ≪Ni≫Ni is an element effective for refining the pearlite structure and improving the strength of the steel material after heat treatment.
%, The transformation time becomes extremely long, which is not practical. An abnormal structure such as martensite is generated, and it becomes impossible to draw a die.

Although P and S, which are impurity elements, are not particularly limited, they are desirably 0.020% or less from the viewpoint of ensuring ductility similarly to conventional steel wires. Hereinafter, the effects of the present invention will be described in more detail with reference to examples.

[0027]

EXAMPLES Based on the present invention, Table 1-1, Table 1-2, Table 1
A steel wire having a diameter of 5.0 mm was produced from a rolled steel wire having a diameter of 13 mm by using steels having the compositions shown in Table 3 and Tables 2-1 to 2-2. Nos. 1 to 23 are examples of the present invention, and 24 to 51 are comparative examples.

[0028]

[Table 1]

[0029]

[Table 2]

[0030]

[Table 3]

[0031]

[Table 4]

[0032]

[Table 5]

[0033]

[Table 6]

In Comparative Example 24, since C was lower than the specified amount, a uniform pearlite structure could not be obtained, and the resistance to twist cracking was poor. Comparative Example 25 is an example in which proeutectoid cementite was precipitated at the grain boundary because C was too large in the specified amount, and the twist crack resistance was poor. Comparative Example 26 is an example in which high strength of 1900 MPa or more was not obtained because Si was lower than the specified amount.

In Comparative Example 27, since the amount of Si was too large, the ferrite constituting pearlite became too hard.
This is an example of poor torsion cracking resistance. In Comparative Example 28, since Mn was less than the specified amount, a sufficient supercooling effect was not obtained, a uniform fine pearlite structure was not obtained, and the twist crack resistance was poor. In Comparative Example 29, Mn was too large than the specified amount,
This is an example in which the pearlite transformation time was too long, the transformation was not completed, martensite was formed, and the wire could not be drawn.

Comparative Example 30 is an example in which the pearlite transformation time was too long because the amount of Cr was larger than the specified amount, and the transformation was not completed, martensite was formed and wire drawing could not be performed. Comparative Example 31 is an example in which the pearlite transformation time was too long because the Mo amount was too large than the specified amount, martensite was generated due to incomplete transformation, and drawing could not be performed. Comparative Example 32 is an example in which the pearlite transformation time was too long because the V amount was larger than the specified amount, and the transformation was not completed, martensite was generated and wire drawing could not be performed.

Comparative Example 33 is an example in which the amount of Ni was too large than the specified amount, so that the pearlite transformation time was too long, and the transformation was not completed, martensite was formed, and the wire could not be drawn. Comparative Examples 34, 38, and 44 are examples in which the twisting crack resistance is poor because the skin pass processing amount is too small than the specified amount. Comparative Examples 35, 39, and 45 are examples in which the twisting crack resistance is poor because the skin pass processing amount is too large than the specified amount.

Comparative Examples 40 and 46 are examples in which the torsional cracking resistance is poor because the bending amount is too small. In Comparative Examples 41 and 47, the bending amount was too large than the specified amount.
Torsion cracking and twisting is an example of failure. Comparative Examples 36 and 42,
Sample No. 48 is an example of poor torsion cracking resistance because the bluing temperature is lower than 460 ° C.

Comparative Examples 37, 43, and 49 are examples in which the torsion cracking resistance is poor because the bluing condition is T (20 + log ₁₀ t) <13000.

[0040]

As described in detail above, as a result of research on the technology for preventing the occurrence of longitudinal cracks generated during the torsion test of a steel wire, the steel wire was subjected to a skin pass treatment after drawing. It has been found that performing a bluing treatment or performing a bluing treatment after applying a skin pass treatment and a straightening process is extremely effective for suppressing the occurrence of cracks. With this technology, it is possible to produce steel wires with even higher tensile strength, which is of great industrial value.

[Brief description of the drawings]

FIG. 1 is a view showing the effect of skin pass conditions after drawing on the occurrence of longitudinal cracks during a twist test of a steel wire.

FIG. 2 is a diagram showing the effect of bluing conditions after skin pass treatment on the occurrence of longitudinal cracks during a twist test of a steel wire.

FIG. 3 is a diagram showing the effects of skin pass treatment and bending conditions after wire drawing on the occurrence of vertical cracks during a twist test of a steel wire.

FIG. 4 is a view of a jig for bending a steel wire.

FIG. 5 is a diagram showing the effect of skin pass treatment and bending conditions after wire drawing on the occurrence of longitudinal cracks during a twist test of a steel wire.

FIG. 6 is a diagram showing the influence of skin pass treatment and bluing conditions after bending on the occurrence of vertical cracks during a twist test of a steel wire.

FIG. 7 is a diagram showing the effect of skin pass treatment and bluing conditions after bending on the occurrence of longitudinal cracks during a twist test of a steel wire.

FIG. 8 is a diagram showing the effect of bluing conditions after bending and skin pass treatment on the occurrence of vertical cracks during a twist test of a steel wire.

FIG. 9 is a diagram showing the influence of bluing conditions after bending and skin pass treatment on the occurrence of vertical cracks during a twist test of a steel wire.

[Explanation of symbols]

 1: Straightening roll 2: Wire rod 3: Bending angle

Continuation of the front page (56) References JP-A-62-77442 (JP, A) JP-A-50-161411 (JP, A) JP-A-63-179017 (JP, A) JP-B-60-26806 (JP) , B2) JP 60-26805 (JP, B2) (58) Fields investigated (Int. Cl. ⁷ , DB name) C22C 38/00 301 B21C 1/00 B21C 9/00 B21F 1/02 C21D 8 / 06

Claims (5)

(57) [Claims] As claimed in claim 1] chemical components, in mass%, C: 0.7
0 to 1.10%, Si: 0.20 to 2.0%, Mn:
0.3-1.5%, and C as another strengthening element
r: 1.0% or less, Mo: 0.2% or less, V: 0.3%
Hereinafter, a steel wire containing one or more of Ni: 1.0% or less, and the balance consisting of Fe and unavoidable impurities, is subjected to at least one heat treatment and at least one wire drawing step to have a strength of 1900 MPa or more. After having a drawn wire having
Skin pass process, and then temperature above 460 ° C
_{In, T (20 + log 10 t} )> 13000 (T: brewing temperature displayed by the absolute temperature [K],
t: the bluing time [hr]) expressed in time
The tensile residual stress in the vicinity of the surface is reduced by the bluing process that satisfies the above conditions, and the residual stress value of the outermost layer is ± 1.
High-strength steel wire with excellent twist cracking resistance characterized by being controlled within the range of 50 MPa. As wherein chemical components, in mass%, C: 0.7
0 to 1.10%, Si: 0.20 to 2.0%, Mn:
0.3-1.5%, and C as another strengthening element
r: 1.0% or less, Mo: 0.2% or less, V: 0.3%
Hereinafter, a steel wire containing one or more of Ni: 1.0% or less, and the balance consisting of Fe and unavoidable impurities, is subjected to at least one heat treatment and at least one wire drawing step to have a strength of 1900 MPa or more. After having a drawn wire having
Skin pass process and bending, and then 460 ° C or lower
At the above temperature, T (20 + log ₁₀ t)> 13000 T: bluing temperature [K] expressed in absolute temperature,
t: the bluing time [hr]) expressed in time
The tensile residual stress in the vicinity of the surface is reduced by the bluing process that satisfies the above conditions, and the residual stress value of the outermost layer is ± 1.
A high-strength steel wire with excellent twist crack resistance, characterized by being controlled within the range of 00 MPa. As wherein chemical components, in mass%, C: 0.7
0 to 1.10%, Si: 0.20 to 2.0%, Mn:
0.3-1.5%, and C as another strengthening element
r: 1.0% or less, Mo: 0.2% or less, V: 0.3%
Hereinafter, a steel wire containing one or more of Ni: 1.0% or less, and the balance consisting of Fe and unavoidable impurities, is subjected to at least one heat treatment and at least one wire drawing step to have a strength of 1900 MPa or more. After having a drawn wire having
A skin pass is performed by passing through a skin pass die having a surface reduction rate of 1 to 10%, and then, at a temperature of 460 ° C. or more, T (20 + log ₁₀ t)> 13000 (T: bluing temperature [K] expressed in absolute temperature,
t: A method for producing a high-strength steel wire excellent in twist crack resistance, characterized by performing a bluing treatment so as to satisfy a relationship of bluing time [hr] expressed in time. As wherein chemical components, in mass%, C: 0.7
0 to 1.10%, Si: 0.20 to 2.0%, Mn:
0.3-1.5%, and C as another strengthening element
r: 1.0% or less, Mo: 0.2% or less, V: 0.3%
Hereinafter, a steel wire containing one or more of Ni: 1.0% or less, and the balance consisting of Fe and unavoidable impurities, is subjected to at least one heat treatment and at least one wire drawing step to have a strength of 1900 MPa or more. After having a drawn wire having
A skin pass is performed by passing through a skin pass die having a surface reduction rate of 1 to 10%, and thereafter, a bending angle of 10 to 10 between a plurality of rolls is set.
After passing at 30 degrees and bending, 460
T (20 + log ₁₀ t)> 13000 (T: bluing temperature [K] expressed in absolute temperature)
t: A method for producing a high-strength steel wire excellent in twist crack resistance, characterized by performing a bluing treatment so as to satisfy a relationship of bluing time [hr] expressed in time. As wherein chemical components, in mass%, C: 0.7
0 to 1.10%, Si: 0.20 to 2.0%, Mn:
0.3-1.5%, and C as another strengthening element
r: 1.0% or less, Mo: 0.2% or less, V: 0.3%
Hereinafter, a steel wire containing one or more of Ni: 1.0% or less, and the balance consisting of Fe and unavoidable impurities, is subjected to at least one heat treatment and at least one wire drawing step to have a strength of 1900 MPa or more. After having a drawn wire having
A plurality of rolls are passed at a bending angle of 10 to 30 degrees to perform a bending process, and then pass through a skin pass die having a surface reduction rate of 1 to 10% to perform a skin pass.
T (20 + log ₁₀ t)> 13000 (T: bluing temperature [K] expressed in absolute temperature)
t: A method for producing a high-strength steel wire excellent in twist crack resistance, characterized by performing a bluing treatment so as to satisfy a relationship of bluing time [hr] expressed in time.