JP3298686B2 - Method for producing high-strength galvanized steel wire for ACSR with excellent corrosion resistance - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission line cable A
(1) The present invention relates to a method for manufacturing a strand of steel stranded wire (ACSR steel wire) used to mechanically reinforce a conductive wire, and more particularly, to an ACSR having a tensile strength of 240 kgf / mm ² or more used in a corrosive environment. The present invention relates to a method for producing a high-strength Zn-plated steel wire.

[0002]

2. Description of the Related Art Zn-plated steel wires for ACSR are usually J-plated.
It is manufactured by applying a patent to a hard steel wire specified in IS G3506, drawing the wire, and then applying hot-dip Zn plating. However, in recent years, as the length of the power transmission cable has become longer, the capacity has been increased, the size has been reduced, and the use environment has become more severe, the ACSR steel wire is required to have improved corrosion resistance and heat resistance in addition to high strength. It became so.

To cope with this, Japanese Patent Laid-Open Publication No. 63-186
No. 852 discloses a technique relating to a 2 mm ACSR steel wire having good heat resistance, that is, C, Si, M.
By adding REM, Ca, Mg, Ba, and Sr in addition to n and Cr, a high-tensile steel wire having a tensile strength of 200 kgf / mm ² or more can be obtained. However, with respect to corrosion resistance, it is merely described that ordinary hot-dip Zn plating is performed after wire drawing.

On the other hand, in order to improve the corrosion resistance of steel wires,
Various Zn-Al alloy platings have been developed in place of conventional Zn plating. For example, Japanese Patent Publication No. 55-26702 discloses Zn-Al, Japanese Patent Publication No. 54-33223 discloses Zn-Al-Mg, Japanese Patent Publication No. 57-500475 discloses Zn-Al-mish metal, 56-112
No. 452 discloses Zn-Al-Na and the like. Each of these methods is a method of immersing a steel wire in an alloy plating bath in a molten state (about 450 ° C.) as in the conventional hot-dip Zn plating method.

[0005] As described in JP-A-63-186852, ordinary ACSR steel wires are made of molten Zn after drawing.
Since the plating step (about 450 ° C.) is involved, there is a problem that much of the work hardening accompanying drawing is reduced. Since this is a major obstacle in increasing the strength, conventionally, it has been considered to add a wire drawing process after Zn plating (so-called afterdraw). In this case, in order to secure the elongation of the product, it is necessary to perform bluing at 300 ° C. or more after afterdrawing. However, exposing a Zn-plated steel wire to a high temperature of 200 ° C. or more develops a brittle Zn—Fe alloy layer, and as a result, plating adhesion and corrosion resistance are significantly deteriorated. Therefore, this method is actually employed. Absent.

[0006]

As described above, in the prior art, high strength Zn for ACSR having excellent corrosion resistance is used.
It was not possible to produce plated steel wire. An object of the present invention is to provide a method for producing a Zn-plated steel wire for ACSR having higher strength and higher corrosion resistance than the conventional method by solving the above problems of the conventional method.

[0007]

According to the present invention, C:
0.75 to 1.0%, Si: 0.15 to 1.3%, M
n: 0.3 to 1.0%, if necessary, Cr: 0.1 to
1.0%, V: 0.02 to 0.30% 1 to 2
A steel wire containing one or two kinds of Al and Ti, each containing 0.1% or less, and a balance of Fe and unavoidable impurities, Al: 2 to 12% by weight, Si:
Corrosion resistance characterized in that after hot-dip plating using an alloy bath containing 0.01 to 0.12%, wire drawing is performed at a total area reduction rate of 20 to 80%, and then blueing is performed at 300 to 370 ° C. This is a method for producing a high-strength galvanized steel wire for ACSR with excellent performance.

Hereinafter, the present invention will be described in detail. First, the reasons for limiting the components of the present invention will be described. C is an effective and economical element for increasing the strength, and is one of the most important elements of the present invention. As the C content is increased, the strength after patenting and the amount of work hardening during drawing are increased. Therefore, in order to obtain a high-strength steel wire by wire drawing, a higher C content is advantageous, and in the present invention, it is set to 0.75% or more. On the other hand, the C content is 1.0%
If the ratio exceeds 1, special consideration is required to prevent the generation of proeutectoid cementite, so the upper limit of the C content is set to 1.0%.

[0009] Si is added as a deoxidizing agent in an amount of 0.15% or more. On the other hand, Si forms a solid solution in ferrite as an alloy element and exhibits a remarkable solid solution strengthening action. Further, Si in ferrite is an essential element for producing a high-strength steel wire because it has an effect of reducing a reduction in strength of the steel wire in a hot-dip galvanizing or bluing step after drawing. However, 1.
If it exceeds 3%, the ductility of the steel wire decreases in the wire drawing step (afterdrawing) after plating, so the upper limit is 1.3%.

Mn is also added as a deoxidizing agent in an amount of 0.3% or more. Further, since Mn has a large effect of improving hardenability, when the wire diameter is large, it is possible to increase the Mn content to improve the uniformity in the cross section, and to improve the ductility of the steel wire after drawing. It is effective for improvement. However, when the content exceeds 1.0%, martensite is generated in the center segregation portion, and the wire drawing workability is deteriorated. Therefore, the upper limit is 1.0%.

[0011] Cr is added in an amount of 0.1% or more as necessary in order to reduce the lamella spacing of pearlite and to improve the strength and drawability of the wire. If it is less than 0.1%, the effect is not sufficient. On the other hand, if it exceeds 1.0%, the time required for the transformation becomes longer, and the equipment becomes larger or the production efficiency decreases. Upper limit.

V, like Mn, improves the hardenability and is effective for strengthening when the wire diameter is large. Also,
Form carbonitrides and strengthen pearlite by precipitation hardening. For this purpose, 0.02% or more is added as necessary. However, the addition of V delays the pearlite transformation,
Since martensite and bainite are easily generated,
Further, the precipitation hardening effect of V carbonitride is saturated, so
The upper limit is 3%.

In the case where the wire rod is cooled immediately after high-speed and high-area-reduction wire rolling in the austenitic region, the austenite crystal grains tend to be finer than in the case of reheating patenting. However, if it is desired to further improve the drawing value of the wire rod and the ductility of the steel wire, Al,
One or more kinds of Ti are added in an amount of 0.1% or less. All of these elements tend to form carbides and nitrides,
Therefore, the effect of reducing the austenite grains and improving the ductility of the wire is strong. However, even if added in excess of 0.1%, the effect is not only saturated, but also nonmetallic inclusions increase, so the upper limit is 0.1%.

Next, the reasons for limiting the composition of the hot-dip Zn plating bath will be described. The corrosion resistance of a Zn-Al alloy depends on the Al concentration, and the higher the Al concentration, the better the corrosion resistance. Therefore, in order to obtain a sufficient effect of improving the corrosion resistance, it is necessary to contain 2% or more. On the other hand, if it exceeds 12%, the effect of addition becomes saturated, and the plating temperature increases due to an increase in the melting point, resulting in a decrease in the strength of the steel wire. Thus, the lower limit of the Al concentration of the Zn—Al alloy is set to 2%, and the upper limit is set to 12%.

The purpose of adding Si to the Zn-Al alloy bath is to suppress the elution of Fe from a steel plating tank, a steel sinker roll, and various steel jigs, thereby reducing dross generation. Is to prevent it. Accordingly, plating defects such as non-plating are reduced by the addition of Si, and the red rust resistance of the plated steel wire is remarkably improved. When the Si content is 0.01%, the above-mentioned effects are not recognized. On the other hand, even if it exceeds 0.12%, it does not dissolve in the alloy bath. Therefore, the added amount of Si is set to 0.01 to 0.12%.

The steel wire after plating is subjected to wire drawing. The purpose of wire drawing is to recover the steel wire strength reduced by hot-dip plating by work hardening and to achieve even higher strength. When the total area reduction rate is 20% or less, the effect is insufficient.
The ductility of the steel wire deteriorates. Therefore, the lower limit of the total area reduction rate of the wire drawing is 20%, and the upper limit is 80%.

The drawn steel wire is subjected to bluing. The purpose of bluing is to restore the ductility (elongation and torsion value) that has been reduced by drawing. The bluing temperature is
If the temperature is lower than 300 ° C., the recovery of ductility is insufficient.
The above is preferred. On the other hand, when the temperature exceeds 370 ° C., the plating layer softens, and when the temperature exceeds 382 ° C., a part of the plating layer melts.
Therefore, the lower limit of the bluing temperature is 300 ° C. and the upper limit is 3
70 ° C. In the method of the present invention, Zn-
When hot-dip plating is performed using an Al alloy, unlike the case of normal hot-dip Zn plating, the development of the Zn—Fe alloy layer is not observed, and the plating surface gloss hardly changes. The reason why the steel wire produced by the method of the present invention exhibits better corrosion resistance than the hot-dip galvanized steel wire is, in addition to the plating composition having excellent corrosion resistance, as described above,
This is due to the high thermal stability of the plating layer.

[0018]

THE PREFERRED EMBODIMENTS Hereinafter, as an example, shows a diameter 2.3 mm, producing a result of the tensile strength of 240 kgf / mm ² primary and 260kgf / mm ² class high tensile ACSR steel wire. A wire having a diameter of 5.5 to 9.5 mm manufactured from steel having the chemical composition shown in Table 1 was patented and drawn to obtain a steel wire having a diameter of 2.5 to 5.5 mm.
This was pickled, hot-dip Zn-plated, and then drawn again, and then blued using a fluidized bed furnace. The plating weight is 250 to 270 g / m ² .

The corrosion resistance was evaluated by a salt spray test specified in JIS Z2371 and the time of occurrence of red rust was compared with that of a hot-dip galvanized steel wire. The results were quantified as the corrosion resistance magnification defined by the following equation (1).

(Equation 1)

The target intensity level is Cr or V
(A, B, F, G groups) without the addition of
kgf / mm class ² , added (C, D, E, H groups)
Is 260 kgf / mm ² class. The target ductility is 20 times or more in torsion value (100d), and the corrosion resistance is 3 or more in corrosion resistance magnification.

[0021]

[Table 1]

[0022]

[Table 2]

[0023]

[Table 3]

In Table 1, Group A shows the effect of C content, Group B shows the effect of Si content, Group C shows the effect of Cr content, and Group D shows the effect of V content. E-1 has both Cr and V elements added. A-1 has not reached the target strength due to the shortage of carbon. On the other hand, in A-4, since proeutectoid cementite was generated, the twist value of the steel wire was significantly reduced. Similarly, in group B,
B-4 containing 1.43% of Si has a low twist value of the steel wire. In C-4 having a Cr content of more than 1%, a small amount of martensite was generated in the central segregation portion of the patenting material, and the torsion value of the steel wire was significantly deteriorated. 0.3 in group D
For the same reason, the twist value of D-4 containing 8% is low.

Group F shows the effect of the Al concentration in the Zn plating bath. F-1 is normal Zn plating. Since F-2 has an Al concentration of less than 2%, the corrosion resistance magnification has not reached 3. With an increase in the Al concentration, the corrosion resistance is initially improved, but tends to saturate soon. However, F-5 has the highest Al concentration and a plating temperature of 5%.
Since the temperature reached 00 ° C., the steel wire strength was lower than the target value, and the twisting characteristics were further deteriorated. D-5 was obtained by plating D-1 in a plating bath containing no Si, and the corrosion resistance magnification did not reach three times that of hot-dip Zn plating. Each of the samples in Groups A to H, which was plated in the Al and Si concentration ranges according to the method of the present invention, exhibited excellent corrosion resistance of at least three times that of hot-dip Zn plating.

Group G shows the effect of wire drawing reduction. The strength of G-1 having a wire drawing reduction ratio of less than 20% does not reach the target. On the other hand, G-5 in which the wire drawing reduction rate exceeds 80%
The torsion value and elongation were much lower than the target values. Group H shows the effect of bluing temperature. H-
1 is a bluing at a temperature lower than 300 ° C., a torsion value,
Both growth is well below target.

[0027]

As apparent from the foregoing description, according to the present invention, conventional melt Zn 240 kgf / mm ² grade which has a 3-fold or more the corrosion resistance of the plating and 260kgf / mm ² class high strength ACSR steel wire Can be manufactured.

Continuation of the front page (51) Int.Cl. ⁷ identification code FI C23C 2/38 C23C 2/38 (58) Investigated field (Int.Cl. ⁷ , DB name) C21D 8/00-8/10 C21D 9 / 52 C22C 38/00-38/60 C23C 2/06 C23C 2/38

Claims (2)

(57) [Claims] 1. A weight ratio of C: 0.75 to 1.0%, Si: 0.15 to 1.3%, Mn: 0.3 to 1.0%, the balance being Fe and unavoidable impurities After hot-dip coating a steel wire using an alloy bath composed of Al: 2 to 12%, Si: 0.01 to 0.12%, and the balance of Zn and unavoidable impurities, the total area reduction rate is 20 to A method for producing a high-strength Zn-plated steel wire for ACSR having excellent corrosion resistance, wherein the wire is drawn at 80% and then blued at 300 to 370 ° C. 2. C: 0.75 to 1.0%, Si: 0.15 to 1.3%, Mn: 0.3 to 1.0%, and Cr: 0.1 to 1 by weight ratio. 1.0%, V: 0.02 to 0.30%, one or two types, and one or two types of Al and Ti each containing 0.1% or less, and the balance Fe and unavoidable A steel wire made of impurities is hot-dip by using an alloy bath consisting of Al: 2 to 12%, Si: 0.01 to 0.12%, the balance being Zn and unavoidable impurities, and then reducing the total area. A method for producing a high-strength Zn-plated steel wire for ACSR having excellent corrosion resistance, wherein the wire is drawn at a rate of 20 to 80% and then bluened at 300 to 370 ° C.