JPH06158224A - High strength steel wire and production - Google Patents

Abstract

PURPOSE:To suppress the generation of cracks in the longitudinal direction in the process of a twisting test by subjecting a drawn steel wire having a specified compsn. to skin pass rolling and bending. CONSTITUTION:A steel wire having a compsn. contg., by weight, 0.70 to 1.10% C, 0.20 to 2.0% Si and 0.3 to 1.5% Mn and contg., as strengthening elements, one or two kinds of <=1.0% Cr, <=0.2% Mo, <=0.3% V and <=1.0% Ni, and the balance Fe with inevitable impurities is subjected to heat treatment for at least one or more times and wire drawing into a drawn steel wire having >=1900MPa strength. Next, it is passed through a skin pass die to reduce the tensile residual stress in the vicinity of the surface and to control it to the range of + or -150MPa by the residual stress of the outersurface layer. Otherwise, the drawn steel wire is passed through a skin pass die with 1 to 10% reduction rate of area for one to four times, and furthermore, it is passed through plural rolls at a bending angle of about 10 to 30 degrees.

Description

Detailed Description of the Invention

[0001]

The present invention relates to bridges, steel cords for automobile tires, fishing net ropes, reinforcing power lines,
Alternatively, it relates to a high-strength steel wire used as a wire for reinforcing a submarine optical fiber cable.

[0002]

2. Description of the Related Art In the case of wires for bridges, there is a demand for expanding the center span of the bridge, for wires for steel cords for automobiles because of the need for weight reduction of tires, and for wires for fishing net ropes, ships. With the downsizing of fishing boats and the increasing size of fishing nets, the need for higher tensile strength of steel wire has been increasing more and more recently.

As a result of vigorous research being conducted in order to meet such demands, the biggest problem in achieving high tensile strength of a steel wire is the ductility of the steel wire, especially during a torsion test. It has been found that a technique for suppressing the occurrence of cracks occurring in the longitudinal direction of the steel wire should be established. On the other hand, WIRE
JOURNAL INTERNATIONAL VOLUME 16 1983
Page 50 of NO4 describes that cracks in the longitudinal direction of galvanized steel wire can be suppressed by controlling the cementite lamella spacing of the pearlite structure constituting the steel wire to an appropriate size.

In Japanese Patent Publication No. 60-26805 and Japanese Patent Publication No. 60-26806, a blueing treatment (200.degree. C. to 400.degree. C.) for removing strain after processing such as twisting wire processing or spring winding processing. However, cracking in the longitudinal direction in the twisting test poses a problem because the toughness of the steel wire decreases, but it is necessary to perform straightening under certain conditions after or during wire drawing. It is described that the cracking in the longitudinal direction can be suppressed by this.

[0005]

However, according to the research conducted by the present inventors, even with these techniques, an ultra-high tensile steel wire, for example, a wire diameter of 5 mm and a tensile strength of 1900 MPa or more, 3 mm of 2100 MPa or more, 2 mm When trying to manufacture a steel wire of 2500 MPa or more and 0.5 mm or more and 3400 MPa or more, it is not possible to suppress the occurrence of longitudinal cracking in the twist test.

The present invention is directed to ductility of a high-strength steel wire used for a bridge, an automobile tire steel cord, a fishing net, a reinforcing wire for a power transmission line, a wire for reinforcing a submarine optical fiber cable, etc. The purpose was to establish a technique for suppressing the occurrence of cracks in the direction.

[0007]

In order to solve such a problem, the present invention releases the residual tensile stress in the vicinity of the surface layer of the wire drawing material by skin pass and straightening to improve the ductility of the high tensile steel wire,
Particularly, it suppresses the occurrence of cracks in the longitudinal direction during the twisting test. That is, the gist of the present invention is as a high-strength steel wire: (1) As a chemical component, 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: 1.0% or less, 1 or 2 or more, and the balance of Fe and unavoidable impurities is a steel wire at least 1900MP after at least one heat treatment and wire drawing step.
After the drawn steel wire having a strength of a or more is used, the tensile residual stress in the vicinity of the surface is reduced by the skin pass process, and the residual stress value of the outermost layer is controlled to within ± 150 MPa. (2) As a chemical component, 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: 1.0% or less, 1 or 2 or more, and the balance of Fe and unavoidable impurities is a steel wire at least 1900MP after at least one heat treatment and wire drawing step.
It is characterized by reducing the residual tensile stress in the vicinity of the surface by a skin pass process and a bending process after making a drawn steel wire having a strength of a or more, and controlling the residual stress value of the outermost surface layer within a range of ± 150 MPa. . As its manufacturing method, (3) as a chemical component, in% by weight, 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: 1.0% or less, 1 or 2 or more, and the balance of Fe and unavoidable impurities is a steel wire at least 1900MP after at least one heat treatment and wire drawing step.
After the drawn steel wire having a strength of a or more is used, the area reduction rate 1 to
The feature is that a skin pass is made by passing a 10% skin pass die once to four times. (4) As a chemical component, 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: 1.0% or less, 1 or 2 or more, and the balance of Fe and unavoidable impurities is a steel wire at least 1900MP after at least one heat treatment and wire drawing step.
After the drawn steel wire having a strength of a or more is used, the area reduction rate 1 to
It is characterized in that a 10% skin pass die is passed once or more and four times or less to perform a skin pass, and then a plurality of rolls are passed at a bending angle of 10 to 30 degrees to perform bending work. (5) As a chemical component, 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: 1.0% or less, a steel wire containing one or more kinds is made into a drawn steel wire having a strength of 1900 MPa or more by at least one heat treatment and a drawing process, It is characterized in that it is bent at a bending angle of 10 to 30 degrees between the rolls to be bent, and then a skin pass die having a surface reduction rate of 1 to 10% is passed once to four times to make a skin pass.

[0008]

The present invention is directed to a steel wire which is subjected to wire drawing after it is subjected to patenting heat treatment or the like to impart good wire drawing workability. The inventors investigated the effect of the skin pass processing after wire drawing on the occurrence of vertical cracks during the twisting test of the steel wire.

FIG. 1 shows a wire diameter of 5.02 to 7.30φ after wire drawing.
1 of the steel wire with a surface reduction rate of 0.5-14%
1900MPa, 20 which was applied 5 to 5 times to adjust the wire diameter to 5φ
A twisting test was conducted on a steel wire having a strength of 00 MPa and 2100 MPa to examine the effect of skin pass processing on the twisting property. In Fig. 1, ○ ● indicates 1900MPa.
, △ ▲ is the result of 2000MPa, □ ■ is the result of 2100MPa steel wire, white mark is 10% or less of crack occurrence, black mark is 10%.
Indicates that it is more than%. That is, it can be seen that the occurrence of cracks is suppressed only when the number of times is 1 to 4 times in the range of the surface reduction rate of the skin pass treatment of 1 to 10%.

This is because the tensile residual stress in the vicinity of the surface layer of the wire drawing material is released by the skin pass processing. That is,
Immediately after drawing, the residual stress is +200 to + 400MP on the tensile side.
Although there is about a, it is possible to suppress the range to ± 150 MPa by adding the skin pass treatment within the range of the present invention. According to many years of research conducted by the inventors, in order to suppress twisting cracks of a steel wire of 1900 MPa or more, the residual stress is 150 MPa.
I have found that the following controls are needed.

If the skin pass processing amount is less than 1%, the processing is insufficient and the residual stress cannot be controlled to 150 MPa or less even if the number of treatments within the range of the present invention is carried out. If the amount of skin pass processing exceeds 10%, abnormal strain is introduced, and the residual stress value deteriorates.
It cannot be controlled below 0MPa. The present inventors have studied a method of suppressing cracking of a steel wire having higher strength.

FIG. 2 shows a wire diameter of 2.01 to 2.92φ after wire drawing.
1 of the steel wire with a surface reduction rate of 0.5-14%
2500MPa, 27 adjusted to wire diameter 2φ by applying 5 times to 5 times
The results obtained by further bending a steel wire having a strength of 00 MPa and 2900 MPa with an apparatus as shown in FIG. 3 are shown. What is important is the bending work having an angle of θ which is applied to the wire rod by the second and third stage straightening rolls shown in FIG. 3 in order to release the tensile residual stress near the surface layer of the drawn wire product by straightening. The subsequent rolls straighten the wire. Fig. 2 shows the effect of the skin pass treatment and the straightening processing conditions on the twisting characteristics after performing a twisting test on this steel wire after processing the bending angle θ = 5 to 40 degrees with this straightening machine. Is. In Figure 2, ○ ●
The mark is 2500MPa, △ ▲ is 2700MPa, □ ■ is 2
In the result of the steel wire of 900 MPa, the white mark indicates that the crack occurrence rate is 10% or less, and the black mark indicates that the crack occurrence rate is over 10%. In other words, the number of times is 1
It can be seen that the occurrence of cracks is suppressed in the steel wire having higher strength only when the bending angle is 4 times and the bending angle is 10 to 30 degrees.

FIG. 4 shows a wire diameter of 2.01 to 2.92φ after wire drawing.
Straightening the steel wire at a bending angle of 5 to 40 degrees
2500MPa, 2700MPa adjusted to wire diameter 2φ by applying skin pass processing 1 to 5 times with surface reduction rate 0.5 to 14%
, A steel wire having a strength of 2900 MPa was subjected to a twisting test to examine the effect of skin pass treatment and straightening processing conditions on the twisting characteristics. In FIG. 4, 25 is the ○ mark.
00MPa, △ ▲ is 2700MPa, □ ■ is 2900MPa
In the result of the steel wire of a, the white mark indicates that the crack occurrence rate is 10% or less, and the black mark indicates that the crack occurrence rate exceeds 10%. In other words, the bending angle is 10
It can be seen that the cracking of the steel wire with higher strength is suppressed only when the surface reduction rate of the skin pass treatment is 1 to 10% and the number of times is 1 to 4 at 30 degrees.

This is because the residual stress of the wire drawing material is released by skin pass and straightening to suppress the ductility of the high-strength steel wire, especially the occurrence of cracks in the longitudinal direction during the twisting test. That is, the residual stress immediately after drawing is +2 on the tensile side.
Although it is about 00 to +400 MPa, it is possible to control to a range of ± 150 MPa by adding a skin pass treatment within the range of the present invention. Furthermore, by combining with bending, it becomes possible to control the residual stress within the range of ± 130 MPa.

When the steel wire twist crack cannot be suppressed even by the above-mentioned skin pass treatment, the residual stress is further increased to 130 MPa.
The following controls are effective. Next, the reasons for limiting the components will be described. <C> When C is less than 0.70%, it is difficult to stably secure a homogeneous pearlite structure regardless of selection of alloy composition and heat treatment conditions, and it is difficult to secure good twisting characteristics. Is. On the other hand, if it exceeds 1.1%, regardless of the selection of alloy composition and heat treatment conditions, the precipitation of pro-eutectoid cementite at grain boundaries cannot be suppressed and the torsion cracking resistance is deteriorated. % To 1.1%. << Si >> Si is an element necessary for deoxidizing steel, and 0.2
If it is less than%, the effect is insufficient, and it is 1900 MPa.
Since it becomes difficult to secure the above strength, it was set to 0.2% or more. Si also forms a solid solution in the ferrite phase in the pearlite obtained after heat treatment and increases the strength after heat treatment, but on the other hand reduces the ductility of the ferrite and deteriorates the cold drawability, and it becomes impossible to secure a high surface reduction rate. Since it segregates in the boundary and deteriorates the torsion cracking resistance, it is set to 2.0% or less. << Mn >> Mn is an element necessary for deoxidizing, desulfurizing and forming MnS and fixing S, and also for improving the hardenability of steel materials and for obtaining a uniform fine pearlite structure by the supercooling effect during heat treatment. Need to be added to. If it is less than 0.3%, its effect is insufficient. Therefore, it is set to 0.3% or more.
If it exceeds 1.5%, the transformation time becomes remarkably long, which is not practical, and an abnormal structure such as martensite is generated, making it impossible to perform die wire drawing. << Cr >> Cr is an element effective for making the pearlite structure fine and improving the strength of the steel material after heat treatment, but 1.0
If it exceeds 0.1%, the transformation time becomes remarkably long, which is not practical, and an abnormal structure such as martensite is generated, making it impossible to perform die wire drawing. << Mo >> Mo is an element that is effective in improving the strength of steel after heat treatment because it precipitates as carbonitrides in ferrite having a pearlite structure. However, if it exceeds 0.2%, the transformation time becomes remarkably long, which is not practical, and an abnormal structure such as martensite is generated, and die wire drawing becomes impossible. << V >> V is an element that is effective in improving the strength of steel after heat treatment because it precipitates as carbonitride in ferrite having a pearlite structure. However, if it exceeds 0.3%, the transformation time becomes extremely long and it is practical. However, an abnormal structure such as martensite is generated, and it becomes impossible to perform die wire drawing. << Ni >> Ni is an element effective for making the pearlite structure fine and improving the strength of the steel material after heat treatment.
If it exceeds 0.1%, the transformation time becomes remarkably long, which is not practical, and an abnormal structure such as martensite is generated, making it impossible to perform die wire drawing.

Although the impurity elements P and S are not specified, it is preferably 0.020% or less from the viewpoint of ensuring ductility as in the conventional steel wire. The effects of the present invention will be described in more detail below with reference to examples.

[0017]

EXAMPLES Based on the present invention, Table 1-1, Table 1-2, Table 1
-3, Table 2-1, Table 2-2, and Table 2-3 were used to prepare 5.0φ mm steel wire from 13φ rolled steel wire. No. 1 to 26 are examples of the present invention, and 27 to 49 are comparative examples.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

[0021]

[Table 4]

[0022]

[Table 5]

[0023]

[Table 6]

In Comparative Example 27, since C is lower than the specified amount, it is not possible to obtain a uniform pearlite structure, and the twist cracking resistance is poor. Comparative Example 28 is an example in which the pro-eutectoid cementite is precipitated at the grain boundaries because C is more than the specified amount, and the torsional cracking property is poor. Comparative Example 29 is an example in which high strength of 1900 MPa or more could not be obtained because Si was lower than the specified amount.

In Comparative Example 30, since the amount of Si was more than the specified amount, the ferrite constituting the pearlite became too hard,
This is an example of poor torsional cracking resistance. In Comparative Example 31, Mn is less than the specified amount, so a sufficient supercooling effect cannot be obtained, a homogeneous fine pearlite structure is not formed, and the torsion cracking resistance is poor. In Comparative Example 32, since Mn is more than the specified amount,
This is an example in which the pearlite transformation time becomes too long and martensite occurs due to incomplete transformation and wire drawing cannot be performed.

Comparative Example 33 is an example in which the pearlite transformation time was too long because the amount of Cr was more than the prescribed amount, and martensite was generated due to incomplete transformation and wire drawing could not be performed. Comparative Example 34 is an example in which the pearlite transformation time was too long because the amount of Mo was more than the specified amount, and martensite was not formed and the wire drawing could not be completed. Comparative Example 35 is an example in which the pearlite transformation time was too long and the martensite was not completed and wire drawing could not be performed because the V content was more than the specified amount.

Comparative Example 36 is an example in which the pearlite transformation time was too long because the amount of Ni was more than the specified amount, and martensite was not formed due to incomplete transformation, and wire drawing could not be performed. Comparative Examples 37, 40, and 42 are examples in which the amount of skin pass processing is more than the specified amount, and therefore the twist cracking resistance is poor. Comparative Examples 38, 41, and 43 are examples in which the amount of skin pass processing is too smaller than the specified amount, and therefore the twist cracking resistance is poor.

Comparative Examples 39, 46 and 47 are examples in which the twisting cracking resistance is poor because the number of times of skin pass processing is more than the specified amount. Comparative Example 44 is an example in which the twisting cracking resistance is poor because the bending amount is more than the specified amount. Comparative Example 45 is an example in which the twist cracking resistance is poor because the bending amount is too smaller than the specified amount.

Comparative Examples 48 and 49 are examples in which skin pass was not carried out, and were examples in which torsion cracking resistance was poor.

[0030]

As described above in detail, as a result of research on a technique for preventing the occurrence of cracks in the longitudinal direction during the twisting test of a steel wire, a skin pass treatment is performed on the steel wire after drawing. It has been found that carrying out, or skin pass treatment and straightening work are extremely effective for suppressing the occurrence of cracks.

With this technique, it is possible to manufacture a steel wire having a higher tensile strength, and its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a diagram showing the influence of skin pass conditions after wire drawing on the occurrence of vertical cracks during a twist test of a steel wire.

FIG. 2 is a diagram showing the influence of bending processing conditions after skin pass treatment on the occurrence of vertical cracks during the twisting test of a steel wire.

FIG. 3 is a diagram of a jig for bending a steel wire.

FIG. 4 is a diagram showing the effect of skin pass treatment after bending on the occurrence of vertical cracks during the twisting test of a steel wire.

[Explanation of symbols]

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

Claims (5)

[Claims] 1. A chemical component, in% by weight, C: 0.7.
0 to 1.10%, Si: 0.20 to 2.0%, Mn:
0.3 to 1.5%, and C as other strengthening element
r: 1.0% or less, Mo: 0.2% or less, V: 0.3%
Hereinafter, a steel wire containing one or two or more of Ni: 1.0% or less and the balance of Fe and unavoidable impurities is subjected to at least one heat treatment and wire drawing step to obtain a strength of 1900 MPa or more. After having a drawn steel wire having
High tensile strength steel with excellent torsional cracking resistance and high wire strength, characterized by reducing tensile residual stress in the vicinity of the surface by the skin pass process and controlling the residual stress value of the outermost layer to be within ± 150 MPa. line. 2. The chemical component, in% by weight, C: 0.7.
0 to 1.10%, Si: 0.20 to 2.0%, Mn:
0.3 to 1.5%, and C as other strengthening element
r: 1.0% or less, Mo: 0.2% or less, V: 0.3%
Hereinafter, a steel wire containing one or two or more of Ni: 1.0% or less and the balance of Fe and unavoidable impurities is subjected to at least one heat treatment and wire drawing step to obtain a strength of 1900 MPa or more. After having a drawn steel wire having
The tensile residual stress near the surface is reduced by the skin pass process and bending process, and the residual stress value of the outermost layer is ± 13.
A high-strength steel wire with excellent torsional cracking resistance, which is characterized by controlling in the range of 0 MPa. 3. The chemical component, in% by weight, C: 0.7.
0 to 1.10%, Si: 0.20 to 2.0%, Mn:
0.3 to 1.5%, and C as other strengthening element
r: 1.0% or less, Mo: 0.2% or less, V: 0.3%
Hereinafter, a steel wire containing one or two or more of Ni: 1.0% or less and the balance of Fe and unavoidable impurities is subjected to at least one heat treatment and wire drawing step to obtain a strength of 1900 MPa or more. After having a drawn steel wire having
A method for producing a high-strength steel wire having excellent resistance to twist cracking, which comprises passing through a skin pass die having a surface reduction rate of 1 to 10% once or more and four times or less. 4. The chemical component, in% by weight, C: 0.7.
0 to 1.10%, Si: 0.20 to 2.0%, Mn:
0.3 to 1.5%, and C as other strengthening element
r: 1.0% or less, Mo: 0.2% or less, V: 0.3%
Hereinafter, a steel wire containing one or two or more of Ni: 1.0% or less and the balance of Fe and unavoidable impurities is subjected to at least one heat treatment and wire drawing step to obtain a strength of 1900 MPa or more. After having a drawn steel wire having
A twist resistance, which is characterized in that a skin pass die having a surface reduction rate of 1 to 10% is passed once or more and four times or less to perform a skin pass, and then a plurality of rolls are passed at a bending angle of 10 to 30 degrees for bending. A method for manufacturing high-strength steel wire with excellent breaking properties. 5. The chemical component, in% by weight, C: 0.7.
0 to 1.10%, Si: 0.20 to 2.0%, Mn:
0.3 to 1.5%, and C as other strengthening element
r: 1.0% or less, Mo: 0.2% or less, V: 0.3%
Hereinafter, a steel wire containing one or two or more of Ni: 1.0% or less and the balance of Fe and unavoidable impurities is subjected to at least one heat treatment and wire drawing step to obtain a strength of 1900 MPa or more. After having a drawn steel wire having
Bending resistance by passing between a plurality of rolls at a bending angle of 10 to 30 degrees, and then performing a skin pass by passing a skin pass die with a surface reduction rate of 1 to 10% once to four times. A method for manufacturing high-strength steel wire with excellent breaking properties.