JPH0670268B2 - Method for producing high-strength Zn-plated 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 cable for power transmission line A.
The present invention relates to a method of manufacturing a strand of steel stranded wire (ACSR steel wire) used for mechanically reinforcing a conductive wire, more specifically, a tensile strength of 240 kgf / mm used in a corrosive environment.
^It relates to a method for producing ^two or more high-strength Zn-plated steel wires for ACSR.

[0002]

2. Description of the Related Art Zn-plated steel wire for ACSR is usually manufactured by J
It is manufactured by a method in which a hard steel wire material specified in IS G3506 is patented, drawn, and then hot-dip Zn plated.

However, in recent years, along with the long-span, large-capacity, compact size of power transmission cables, and the severer usage environment, the ACSR steel wire is required to have higher strength as well as improved corrosion resistance and heat resistance. Came to be.

In order to deal with this, it has hitherto been disclosed in Japanese Unexamined Patent Publication No. 63-
Japanese Patent No. 186852 is disclosed. This relates to a 2 mm ACSR steel wire with good heat resistance,
In addition to C, Si, Mn, Cr, REM, Ca, Mg, B
It is said that a and Sr are added to obtain a high-strength steel wire having a tensile strength of 200 kgf / mm ² or more. However, regarding the 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 the steel wire,
Various Zn-Al alloy platings have been developed in place of conventional Zn plating. For example, Japanese Patent Publication No. 55-26702, Zn-Al, Japanese Patent Publication No. 54-33223, Zn-Al-Mg, Japanese Patent Publication No. 1-24211, Zn-Al-Misch metal, JP-A-56, -11245
No. 2 discloses Zn-Al-Na and the like.
These are all methods of plating by dipping a steel wire in a molten alloy plating bath (about 450 ° C.) as in the conventional hot-dip Zn plating method.

Starting from the above-mentioned Japanese Patent Laid-Open No. 63-186852, ordinary ACSR steel wire is melted Zn after drawing.
Since the plating (about 450 ° C.) process is included, there is a problem that most of work hardening due to wire drawing is reduced. Since this is a great obstacle to achieving high strength, it has been conventionally considered to add wire drawing 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 higher after afterdrawing. However, exposing the Zn-plated steel wire to a high temperature of 200 ° C. or higher develops a brittle Zn—Fe alloy layer, and as a result, the plating adhesion and corrosion resistance are significantly deteriorated, so this method is actually adopted. Absent.

[0007]

As described above, according to the prior art, high strength Zn for ACSR having excellent corrosion resistance is obtained.
It was not possible to produce galvanized 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 corrosion resistance than ever before by solving the problems of the above conventional method.

[0008]

According to the present invention, the weight ratio of C: 0.75 to 1.0%, Si: 0.15 to 1.
3%, Mn: 0.3 to 1.0%, and if necessary, Cr:
0.1% to 1.0%, V: 0.02 to 0.30%, one or two kinds, further, Al and Ti, one or two kinds, and 0.1% or less, respectively, with the balance being Fe. And a steel wire consisting of inevitable impurities, Z containing 2 to 12% of Al in a weight ratio.
After hot-dip plating using n bath, total surface reduction rate is 20-80
%, And then blueing at 300 to 370 ° C. is a method for producing a high-strength galvanized steel wire for ACSR having excellent corrosion resistance.

The present invention will be described in detail below. First, the reasons for limiting the components of the present invention will be described.

C is an effective and economical element for increasing strength, and is one of the most important elements of the present invention. C
As the content increases, the strength after patenting and the amount of work hardening during wire drawing increase. Therefore, in order to obtain a high strength steel wire by wire drawing, it is advantageous that the C content is high, and in the present invention, it is 0.75% or more.
On the other hand, when the C content exceeds 1.0%, special consideration is required to prevent the occurrence of pro-eutectoid cementite, so the upper limit of the C content is 1.0%.

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

Mn is also added as a deoxidizing agent in an amount of 0.3% or more. Further, since Mn has a great effect of improving the hardenability, it is possible to improve the uniformity in the cross section by increasing the Mn content ratio when the wire diameter is large, and the ductility of the steel wire after drawing is increased. It is effective for improvement. However, if it exceeds 1.0%, martensite is generated in the central knitting portion and the wire drawability deteriorates, so 1.0% is made the upper limit.

In order to reduce the lamellar spacing of pearlite and improve the strength and wire drawability of the wire, Cr is added in an amount of 0.1% or more, if necessary. 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 transformation becomes long, the equipment becomes large, or the production efficiency is lowered. The upper limit.

V, like Mn, improves the hardenability and is therefore effective for strengthening when the wire diameter is large. It also forms carbonitrides and strengthens pearlite by precipitation hardening. For this purpose, 0.02% or more is added if necessary. However, the addition of V delays the pearlite transformation, facilitates the formation of martensite and bainite, and saturates the precipitation hardening action of V carbonitride.
The upper limit is 0.3%. When the wire rod is rolled at a high speed and with a high area reduction rate in the austenite region and then immediately cooled, the austenite crystal grains tend to be finer than in the case of reheating patenting. However, when it is desired to further improve the aperture value of the wire rod and the ductility of the steel wire, Al, T
0.1% or less of one or more of i is added. All of these elements easily generate carbides and nitrides, and therefore have the effect of making austenite grains finer and improving the ductility of the wire. However, even if added over 0.1%, the effect is not only saturated, but also nonmetallic inclusions increase, so 0.1% is made the upper limit.

Next, the reasons for limiting the composition of the hot-dip Zn plating bath will be described. The corrosion resistance of the 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 is saturated, and the melting point rises, the plating temperature rises and the strength of the steel wire decreases. From this, Zn-A
The lower limit of the Al concentration of the 1-alloy is 2% and the upper limit is 12%.
In addition to the Zn-Al binary alloy, it is also possible to use various alloys based on Zn-Al as shown in the prior art.

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

The steel wire after drawing is subjected to bluing. The purpose of bluing is to recover the ductility (elongation and twist values) that has been reduced by wire drawing. The brewing temperature is
If the temperature is less than 300 ° C, the recovery of ductility is insufficient,
The above is preferable. On the other hand, when the temperature exceeds 370 ° C, the plating layer softens, and when the temperature is 382 ° C or higher, part of the plating layer melts.
Therefore, the lower limit of the bluing temperature is 300 ° C. and the upper limit is 370 ° C. Incidentally, Z in the Al concentration range of the method of the present invention
When hot-dip plating is performed using an n-Al alloy, unlike the case of normal hot-dip Zn plating, the Zn-Fe alloy layer does not develop and the plating surface gloss hardly changes. The steel wire produced by the method of the present invention has a molten Z
The reason why the corrosion resistance is better than that of the n-plated steel wire is that the plating composition has excellent corrosion resistance and, as described above, the thermal stability of the plating layer is high.

[0018]

EXAMPLES As examples below, the diameter is 2.3 mm, the tensile strength is 240 kgf / mm ² grade and 260 kgf / m.
The production effect of m ² grade high tensile ACSR steel wire is shown.

A wire having a diameter of 5.5 to 9.5 mm manufactured from steel having the chemical composition shown in Table 1 was drawn after patenting to obtain a steel wire having a diameter of 2.5 to 5.5 mm. This was pickled, hot-dipped Zn was plated under the conditions shown in Table 2, wire-drawn again, and then bluing was performed using a fluidized bed furnace. The amount of plating adhered is 250 to 270 g / mm ² .
Table 2 shows the tensile strength, the number of twists, the elongation, and the corrosion resistance of each steel wire.

The corrosion resistance was evaluated by a salt spray test specified in JIS Z2371, and the rust generation time was compared with that of the hot dip galvanized steel wire. The result was quantified as the corrosion resistance magnification defined by the following formula 1.

[0021]

[Equation 1] The target strength level is 240 kg for those without addition of Cr or V (Groups A, B, F, G).
f / mm ² grade, added (C, D, E, H
Group) is a 260 kgf / mm ² class. The target ductility is 20 times or more in the twist value (100d), and the corrosion resistance is 3 or more in the corrosion resistance magnification.

In Table 1, the effects of C content in the A group, Si content in the B group, Cr content in the C group, and V content in the D group are shown. E-1 is added with both Cr and V elements. A-1 does not reach the target strength because the amount of C is insufficient. On the other hand, in the case of A-4, proeutectoid cementite was generated, so that the twist value of the steel wire was low. C with a Cr content exceeding 1%
In No. 4, since a small amount of martensite was generated in the center segregated portion of the patenting material, the twist value of the steel wire was significantly deteriorated. The twist value of D-4 containing 0.38% V in group D is low for the same reason.

Group F shows the effect of Al concentration in the Zn plating bath. F-1 is normal Zn plating. Since the Al concentration of F-2 is less than 2%, the corrosion resistance magnification does not reach 3. Although the corrosion resistance is improved initially as the Al concentration increases, it tends to saturate. However, F-5 has the highest AL concentration and the plating temperature is 5
Since the temperature reached 00 ° C, the strength of the steel wire fell below the target value, and the twisting characteristics were further deteriorated.

Each of the samples of groups A to H plated in the Al concentration range of the method of the present invention exhibits excellent corrosion resistance which is three times or more that of hot-dip Zn plating.

Group G shows the influence of the wire drawing area reduction rate. The strength of G-1 having a drawing area reduction rate of less than 20% does not reach the target. On the other hand, G-5 with a wire drawing reduction rate exceeding 80%
The values of twist and elongation were significantly lower than the target values.

Group H shows the influence of the brewing temperature. H-1 was bluing below 300 ° C, and both the twist value and the elongation were far below the target values.

[0027]

[Table 1]

[0028]

[Table 2]

[0029]

As is apparent from the above description, according to the present invention, 240 kgf / mm ² grade and 260 kgf / m having a corrosion resistance three times or more that of the conventional hot-dip Zn plating are used.
It is possible to manufacture m ² grade high strength ACSR steel wire.

Claims (4)

[Claims] 1. C: 0.75-1.0%, Si: 0.1
Steel wire consisting of 5 to 1.3%, Mn: 0.3 to 1.0%, balance Fe and unavoidable impurities, and Al in a weight ratio of 2 to 2
ACS having excellent corrosion resistance, which is characterized in that after hot dipping using a Zn bath containing 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.
A method for producing a high-strength Zn-plated steel wire for R. 2. C: 0.75-1.0%, Si: 0.1
5 to 1.3%, Mn: 0.3 to 1.0%, and Cr: 0.
Zn containing 1 to 1.0%, V: 0.02 to 0.30% of 1 type or 2 types, and a steel wire composed of the balance Fe and unavoidable impurities, containing 2 to 12% of Al by weight ratio. Manufacture of high-strength Zn-plated steel wire for ACSR having excellent corrosion resistance, which comprises hot-dip plating in a bath, wire drawing with a total area reduction rate of 20 to 80%, and then blueing at 300 to 370 ° C. Method. 3. C: 0.75-1.0%, Si: 0.1
5 to 1.3%, Mn: 0.3 to 1.0% Al, Ti
Steel wire containing 0.1% or less of 1 type or 2 types of the above and the balance Fe and unavoidable impurities, 2 to 12% Al by weight ratio
After hot dip plating using the contained Zn bath, 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, which comprises drawing at 80% and then bluing at 300 to 370 ° C. 4. C: 0.75 to 1.0%, Si: 0.1
5 to 1.3%, Mn: 0.3 to 1.0%, and Cr: 0.
1 to 1.0%, V: 0.02 to 0.30%, one or two, and Al and Ti, one or two, 0.1% or less, and the balance Fe and inevitable impurities. A steel wire is hot-dipped with a Zn bath containing 2 to 12% Al by weight and then drawn at a total area reduction of 20 to 80%, and then 300
A method for producing a high-strength Zn-plated steel wire for ACSR, which is excellent in corrosion resistance, characterized by being blued at 370 ° C.