JPH11229088A - High tensile strength wire rod for steel wire excellent in twisting value and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a wire rod capable of obtaining a high tensile strength steel wire strengthened by wire working, in which delamination is hard to be generated and excellent in twisting value by specifying the compsn. composed of C, Si, Mn, P, S and Fe, specifying the content of Al as inevitable impurities and moerover specifying the content of O. SOLUTION: As for a wire rod having a compsn. contg., by weight, 0.9 to 1.2% C, 0.2 to 1.5% Si, 0.2 to 1.0% Mn, <=0.02% P and <=0.02% S, furthermore contg., at need, one or more kinds among 0.1 to 0.5% Cr, 0.1 to 0.5% Ni and 0.1 to 0.5% Cu, and the balance Fe with inevitable impurities, in which the content of Al as inevitable impurities is regulated to <=0.002%, and moreover, the content of O is regulated to <=30 ppm, its wire diameter is regulated to 5.0 to 7.0 mm by hot working. This wire rod is subjected to patenting treatment at 550 to 650 deg.C and wire drawing to obtain a high tensile strength steel wire having 1.5 to 2.5 mm, 2200 to 2600 MPa tensile strength and excellent in twisting value. Moreover, this steel wire can be formed into a hot dip galvanized high tensile strength steel wire having 2,100 to 2,400 MPa.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength steel wire, a galvanized steel wire used for reinforcing ACSR wire such as an Al transmission line, an elevator cable, a rope wire, and the like, and a wire used for manufacturing the same.

[0002]

2. Description of the Related Art Generally, high-carbon steel of 0.8% or more is subjected to a patenting treatment to change its steel structure to pearlite.
Furthermore, it is reinforced by using wire drawing. A part of such a steel wire is subjected to a hot-dip galvanizing process to provide corrosion resistance.

For example, ACSR (alumum conductor std.)
A high-strength galvanized steel wire used for eel reinforced wire or the like is usually hot-rolled and then adjusted and cooled to a diameter of 5.
The strength of the wire rod of 5 to 8.0 mm or the cooled wire rod after hot rolling is adjusted again by a patenting process, the wire is drawn to 1.8 to 2.5 mmφ by wire drawing, and hot-dip galvanized. Furthermore, it is used by twisting.

[0004] Such a high-strength galvanized steel wire is used for reinforcement or for holding heavy objects, so that a higher-strength material is required to improve economic efficiency. For this reason, high-quality steel materials have been conventionally developed in response to requests.

For example, Japanese Patent Publication No. 3-73625 discloses that C: 0.7 to 1.0%, Si: 2.0% or less, Mn:
2.0% or less, Cr: 0.5 to 1.5% or less, Al:
0.1% or less, Mo: 0.3% or less, B: 0.003%
The following discloses a galvanized steel wire excellent in twisting characteristics and a manufacturing method in which the total area reduction rate in wire drawing is 2 or more as a true strain.

[0006] However, in the case of increasing the strength by the method of adding Mo, there is a problem of the plating processability such that the processing time of the hot-dip galvanizing needs to be 80 s or more. Therefore, development of a high-strength galvanized steel wire having higher strength and excellent ductility has been desired.

[0007]

DISCLOSURE OF THE INVENTION The present invention relates to a wire capable of obtaining a steel wire having an excellent torsion value which is less likely to cause delamination in a high tensile steel wire reinforced by wire drawing after a patenting process. provide.

[0008]

First, the reasons for limiting the steel composition will be described. All components are by weight. In general,
Increasing the strength of the steel wire decreases the ductility of the steel wire. In particular, in the case of a wire, an index of ductility is a twist value. When using high-carbon steel by wire drawing to increase the strength, in the case of wires used with a wire diameter of 1 mm or more, the torsion value of the steel wire improves as the amount of Al decreases and the amount of oxygen decreases (FIG. 1).

Further, the improvement of the twisting characteristics is maintained in the same manner even when hot-dip galvanizing is performed. Therefore, in the present invention, Al, which is an unavoidable impurity, is adjusted to 0.002% or less. Also, the lower the oxygen content, the higher the torsion value.
Therefore, the oxygen content is adjusted to 30 ppm or less.

C is an element effective for strengthening, and it is necessary that C is 0.9% or more in order to obtain a high-strength steel wire. However, if it is too high, ductility is reduced and drawability is deteriorated. The upper limit is 1.2%.

[0011] Si is an element necessary for deoxidation of steel. Therefore, when its content is too small, the deoxidizing effect becomes insufficient. In addition, Si
Is dissolved in the ferrite phase in the pearlite formed after heat treatment to increase the strength after patenting, but on the other hand, it impairs the heat treatment property, so that the content is 1.5% or less.

Mn is desirably added at 0.2% or more of Mn in order to secure the hardenability of the steel. However, when a large amount of Mn is added, segregation is caused, and a supercooled structure such as bainite and martensite is generated at the time of patenting, which impairs the subsequent drawability.

In the case of the hypereutectoid steel as in the present invention, a cementite network is easily generated in the structure after the patenting, and a cementite having a large thickness is easily precipitated. In order to achieve high strength and high ductility in this steel, it is necessary to make pearlite fine and eliminate the cementite network and thick cementite as described above.

Cr has the effect of suppressing the appearance of such an abnormal portion of cementite and further reducing the pearlite. However, the addition of a large amount increases the transition density in the ferrite after the heat treatment, and thus significantly impairs the ductility of the ultrafine wire after the drawing. Therefore, the addition amount of Cr is set to 0.1% or more where the effect can be expected, and 0.5% or less which does not increase the transition density in ferrite and does not impair ductility.

Since Ni also has the same effect as Cr, if necessary, 0.1% or more is added to exhibit the effect. If the addition amount of Ni is too large, the ductility of the ferrite phase is reduced, so the upper limit is made 0.5%.

[0016] Since Cu is an element for improving the corrosion fatigue properties of the wire, it is necessary to use 0.1% of the element to exhibit its effect if necessary.
It is desirable to add above. If the addition amount of Cu is too large, the ductility of the ferrite phase is reduced, so the upper limit is made 0.5%.

As in the case of the conventional ultrafine steel wire, the content of S is set to 0.02% or less in order to secure the ductility, and P also impairs the ductility of the wire in the same manner as S, so the content is set to 0.02% or less. It is desirable that

Next, the features of the steel wire will be described. Less than,
The reason for limiting the manufacturing method will be described. The wire diameter of the wire rod manufactured by hot rolling must be at least 5 mmφ or more in order to secure a certain area reduction ratio or more in the wire drawing process. However, if the diameter exceeds 7 mm, the area reduction rate becomes too large, and delamination occurs.
φ or less.

At a temperature lower than 550 ° C. in a subsequent patenting treatment after hot rolling, a bainite structure appears and ductility cannot be ensured. Further, if patenting is performed at a temperature higher than 600 ° C., a steel wire having a strength of 2200 MPa or more cannot be obtained.

If the wire diameter of the wire is smaller than 1.5 mm, the amount of processing is too large and the wire becomes brittle. When the wire diameter exceeds 2.5 mm, the strength of the wire cannot be sufficiently increased, so that the wire diameter is set to 2.5 mm or less. The influence of the Al amount and the O amount is when the tensile strength at which the strength increases is 2200 MPa or more.

Further, even if such a method is used, 2600
If it is not more than MPa, sufficient ductility cannot be obtained. Therefore, the tensile strength of the drawn steel wire is 2200 MPa or more and 260
0 MPa or less.

The manufactured wire is subjected to hot-dip galvanizing in a temperature range of 400 ° C. or more and 500 ° C. or less. At this time, since the decrease in tensile strength is generally about 50 MPa to 200 MPa, the strength of the hot-dip galvanized wire is set to 2100 MPa or more and 2400 MPa or less.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The effects of the present invention will be described below based on embodiments. First, a method for manufacturing these wires will be described as an example. As a test steel, a 122 mm square billet having a steel composition of Nos. 1 to 17 shown in Table 1 was rolled to 5 to 7 mmφ by hot rolling. Adjustment cooling by immersion in a bath was performed to obtain a pearlite-structured wire.

On the other hand, in the methods 11 to 15 of the present invention, stermore cooling was performed as conditioning cooling, followed by lead patenting treatment to obtain a pearlite-structured wire. Table 2 shows the adjusted cooling temperature or lead patenting temperature and the mechanical properties of the wire in each case.

Using these wires, wire drawing is performed.
The wire had a diameter of 1.5 to 2.5 mmφ. Table 3 shows the mechanical properties of the obtained steel wire. Further, Table 4 shows changes in mechanical properties when hot dip galvanizing is performed on these drawn wires. The test was performed with a twist value of 100 times the wire diameter shown in Tables 3 and 4, and the results were shown. The tensile test values shown in Table 4 were obtained by conducting tests on as-plated wires, and the values were recorded.

[0026]

[Table 1]

[0027]

[Table 2]

[0028]

[Table 3]

[0029]

[Table 4]

In the methods 1 to 15 of the present invention, since the drawn wire and the galvanized steel wire are manufactured according to the present invention, the as-drawn steel wire and the steel wire after hot-dip galvanizing have high tensile strength and are excellent. The torsion value is shown.

In Comparative Method 16, the O content is within the range of the present invention, but the Al content is as large as 0.02%. For this reason,
A steel wire having a tensile strength within the range of the present invention has a low twist value in a steel wire as drawn and a steel wire after galvanizing.

In Comparative Method 17, the Al content is within the range of the present invention, but the oxygen content is as high as 32 ppm. For this reason, a steel wire having a tensile strength in the range of the present invention has a low twist value in a steel wire as drawn and a steel wire after galvanizing.

[0033]

According to the present invention, a high-strength galvanized steel wire can easily obtain a high-strength and excellent ductile wire free from delamination.

[Brief description of the drawings]

FIG. 1 shows the change of the twist value when the tensile strength is almost constant.

Claims (6)

[Claims] 1. In weight% C: 0.9% or more and 1.2% or less Si: 0.2% or more and 1.5% or less Mn: 0.2% or more and 1.0% or less P: 0.02% S: 0.02% or less A wire composed of the balance iron and inevitable impurities, in particular, the amount of Al which is an inevitable impurity is 0.002% or less and the O content is 30 ppm or less. 2.% by weight: C: 0.9% to 1.2% Si: 0.2% to 1.5% Mn: 0.2% to 1.0% P: 0.02% The following S: 0.02% or less The balance consists of iron and unavoidable impurities. In particular, Al which is an unavoidable impurity is 0.002% or less and an O content is 30 ppm or less. Wire diameter 1.5 to 2.5 mm and tensile strength of 2200 MPa or more 2
Steel wire of 600 MPa or less. 3. The wire rod according to claim 1, wherein the steel component further comprises: Cr: 0.1% or more and 0.5% or less Ni: 0.1% or more and 0.5% or less Cu: 0.1% or more and 0.5% or less % Or less. 4. The steel wire according to claim 2, further comprising: Cr: 0.1% or more and 0.5% or less Ni: 0.1% or more and 0.5% or less Cu: 0.1% or more and 0.5% or less. A steel wire having a wire diameter of 1.5 to 2.5 mm and a tensile strength of 2200 MPa or more and 2600 MPa or less, obtained by drawing a wire rod comprising at least one of 5% or less. 5. A high-strength steel wire according to claim 2 or 4, which is hot-dip galvanized and has a tensile strength of 2100 MPa.
A high-strength steel wire having an excellent torsion value, which is not less than 2400 MPa. 6. A wire having a diameter of 5.0 to 7.0 mm produced by hot rolling the steel component according to claim 1 or 3
It is characterized by applying a patenting process at a temperature of ~ 600 ° C and conducting wire drawing, and performing wire drawing to a wire diameter of 1.5mm or more and 2.5mm or less to obtain a steel wire having a tensile strength of 2200MPa or more and 2600MPa or less. A method for producing a high-tensile steel wire having an excellent torsion value, further comprising hot-dip galvanizing to obtain a steel wire having a tensile strength of 2100 MPa or more and 2400 MPa or less.