JP3461604B2 - Method for producing steel wire with low power loss - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a steel wire used for reinforcing a transmission line and having a low power loss.

[0002]

2. Description of the Related Art Currently used as a transmission line is a composite stranded wire in which a steel wire (hereinafter referred to as "reinforcing steel wire") is combined as a core material for strength reinforcement inside the stranded wire of an aluminum wire. (Hereinafter “ACSR”). Among such ACSRs, a single-strand aluminum stranded wire (hereinafter referred to as “single-layer ACSR”) causes a large power loss in the reinforcing steel wire in the central portion, which lowers power transmission efficiency.

[0003]

The power loss in the single-layer ACSR is caused by the portion caused by the hysteresis loss in the AC magnetic field of the transmitted power and the portion caused by the heat generated by the induced current. As a material having less hysteresis loss, a soft magnetic electromagnetic material is well known. As a steel material, an electromagnetic steel sheet called silicon steel containing Si around several% corresponds to this, but silicon steel is generally a low strength steel material,
In addition, the workability is inferior, so new technical problems to improve the workability and strength must be solved before it can be used as a reinforcing steel.

On the other hand, in order to suppress the heat generation due to the induced current, it is sufficient to increase the DC electric resistance of the reinforcing steel wire to suppress the generation of the induced current, and also to secure the strength as the steel wire for ACSR. Therefore, it is convenient for the development of the steel wire for ACSR because it is consistent with the solution of the technical problem for In view of the problem that the present invention provides a steel wire having a required strength as a reinforcing steel wire with less hysteresis loss and heat loss as described above, as a reinforcing steel wire that is a soft magnetic steel material. It is an object of the present invention to provide a method for manufacturing a steel wire that can secure the strength of the steel wire and that can suppress the generation of an induced current and have a small power loss.

[0005]

The subject matter of the present invention is as follows. (1) Si: 1.0 to 3.5 wt% Al: 0.05 to 0.5 wt% Mn: 0.2 to 3.0 wt% as a basic component, and Nb: 0.1 wt% or less V: 0. 1 wt% or less Cr: A steel billet containing one or two or more of 1.5 wt% or less and the balance iron and unavoidable impurities is formed into a wire rod having an intermediate wire diameter by hot rolling. A method for manufacturing a steel wire with a low power loss, which is characterized in that a wire having a final wire diameter is obtained by the above cold drawing.

(2) The steel billet further contains one or two of Cu: 1.5 wt% or less and Ni: 3.0 wt% or less. Manufacturing method.

(3) The wire rod having the final wire diameter is formed by cold drawing and then decarburized and annealed to make C: 0.1 wt% or less, and at the same time, a primary recrystallization structure is formed. A method for producing a steel wire having a low power loss as described. The constituent features of the present invention will be described below. Generally, in order to reduce the hysteresis loss of steel materials, increasing the Si concentration, decreasing the S concentration, reducing the C concentration as much as possible, and recrystallizing so as to develop a specific crystal orientation by AlN, etc. Is known to be effective. For example, in JP-A-6-49607, C: 0.01% or less, acid-soluble Al: 0.003 to 0.015% and N: together with appropriate amounts of Si, Mn, and S:
Disclosed is a manufacturing method for providing a grain-oriented electrical steel sheet having a small hysteresis loss by combining a steel slab containing 0.010% or less by hot rolling, annealing, and then a combination of steps such as cold rolling and continuous annealing. . Alternatively, JP-A-6-
Japanese Patent Publication No. 49534 discloses a method for producing a grain-oriented electrical steel sheet having a low hysteresis loss as well, but the composition is Si: 2.0 to 4.8%, acid-soluble Al: 0.00.
After annealing a hot-rolled steel strip of silicon steel consisting of 8 to 0.05% and N: 0.010% or less, cold rolling was performed once or many times including intermediate annealing, and also served as an insulating coating treatment. It consists of performing primary recrystallization annealing at a high temperature. Of course, although these known techniques aim to provide a thin steel sheet for electromagnetic use, they also provide useful knowledge to the method of manufacturing a steel wire, which is the object of the present invention. However, these technical measures alone can reduce the hysteresis loss, but cannot secure the strength required for the reinforcing steel wire.

On the other hand, in order to obtain a steel wire having a tensile strength of 120 kgf / mm ² or more, which is generally required as a reinforcing steel wire, it is necessary to cold-draw a wire having a C concentration of about eutectoid steel. Although strength is generally secured, such a steel wire cannot sufficiently reduce hysteresis loss and heat generation loss due to induced current. The present inventors have conducted various studies to complete the present invention in order to realize a reinforcing ACSR steel wire with less hysteresis loss, which can be said to have fallen into such a bottleneck of the conventional technique. That is,
With the aim of suppressing the hysteresis loss, a method that does not rely on high C as in the past was examined in order to secure the strength as a reinforcing steel wire. In the case of the conventional reinforcing steel wire, a pearlite structure was cold-drawn to secure the necessary strength. However, securing the strength is a structure having a low C concentration, that is, composed of a ferrite phase. Even if it is possible, it is possible to strengthen the ferrite phase by appropriate alloying, cold drawing, and utilizing fine precipitates.
It has been found that a steel having such a ferrite phase can be made into a steel material having a small hysteresis loss by appropriate annealing.

That is, the strengthening of the ferrite phase mainly uses solid solution strengthening by Si. It is well known that Si is an element that has a large effect of solid solution strengthening on the ferrite phase, but if it is less than 1.0 wt%, strengthening of the ferrite phase as a reinforcing steel wire is not sufficient. The amount of Si added is preferably 1.0 wt% or more for strengthening the ferrite phase and for reducing hysteresis loss, but if it exceeds 3.5 wt%, it is melted in a normal steel wire manufacturing process. The difficulty in the process and hot rolling process increases significantly. Therefore, the amount of Si added is 1.0 to 3.5 wt.
%.

Since Al increases the electrical resistance of the steel wire when added in combination with Si, it suppresses the generation of induced current. As a result, heat generation due to eddy current is suppressed, and heat loss when used as a reinforcing wire for ACSR can be suppressed to a low level. The increase in electrical resistance by adding Al is 1.0 for Si.
In the case of the steel according to the present invention added by ~ 3.5 wt%,
The effect comes to be recognized at 0.05% or more. This effect becomes more remarkable as the amount of Al added increases, but 0.5 wt%
If it exceeds, hot rolling and cold drawing become difficult. For the above reasons, the amount of Al added is 0.05 to 0.
It was set to 5%.

The C content is preferably as low as possible in order to reduce the hysteresis loss, but on the other hand, it is necessary to add an appropriate amount in order to secure the strength of the steel wire. As described above, the strength of the steel wire according to the present invention uses 0.1 wt% as an upper limit because it utilizes strength securing by precipitation hardening by fine carbonitrides such as Nb, V, Cr in addition to solid solution strengthening of ferrite by Si. As a value, C is an essential element. However, even if the C concentration in the steel billet before hot rolling exceeds this value, it may be 0.1 wt% or less after decarburization annealing.

The amount of Mn added was 0.2 to 3.0 wt% for the purpose of stabilizing the strength of the steel wire.

Nb, V, and Cr are added in order to secure strength by precipitating as fine and stable carbides in the decarburization annealing step after cold drawing as described below. Therefore, Nb is added in the range of 0.1 wt% or less, V is added in the range of 0.1 wt% or less, and Cr is added in the range of 1.5 wt% or less. With an appropriate addition amount within such a range, even if any of the elements of Nb, V and Cr is added alone or in combination, a uniform effect can be exhibited. The selection of single addition or multiple addition may be made optimally according to the combination of the intermediate wire diameter or the final wire diameter according to the specifications of the manufacturing mill.

Cu is added to the F matrix in the Fe matrix during annealing.
It utilizes age hardening by depositing as extremely fine intermetallic compound particles with e. This gives N
It is possible to obtain a steel wire having a higher strength than in the case of adding b, V and Cr. 1.5w for Cu for this purpose
Add in the range of t% or less. The addition of Cu simultaneously increases the corrosion resistance of the steel wire. When Cu is added, hot cracking during steel billet casting is likely to occur, so Ni is added for the purpose of preventing this. Similar to Cu, the addition of Ni is effective for improving the corrosion resistance, and for both purposes, 3.0 wt% is added as the upper limit.

In the cold wire drawing before decarburization annealing, the cold work structure is utilized to increase the diffusion rate of C to facilitate decarburization, and at the same time, fine precipitation of Nb, V or Cr in the annealing step. This is an essential step for making the most of the refinement and precipitation strengthening of the recrystallized grains by utilizing it, and for this purpose, wire drawing is performed at a cross-section reduction rate of 50% or more.

[0016]

When the steel wire obtained by the present invention is used for the ACSR reinforcing wire, the hysteresis loss is small, and at the same time, the heat generated by the induced current is also small, so that the loss of the transmission power is small.
Is obtained. Above all, in single-layer ACSR, it is difficult to suppress the generation of the magnetic field by the aluminum conductor, so this effect is great, and the single-layer AC used as a transmission line of 6.6 kV or less inside and in the suburbs of the city.
If applied as a reinforcing steel wire for SR, high power transmission efficiency can be obtained.

[0017]

EXAMPLES Various steel wires having the components shown in Table 1 were made into steel wires having the wire diameters shown in the table by the manufacturing process according to the present invention. Table 2 shows the results of strength, drawing value and iron loss of each steel wire. Steel wire a was added with Nb and had a relatively high C concentration after decarburization. Steel wires b, c, d and e were sufficiently decarburized. Compensation for strength by lowering the C concentration was compensated by adding Cr in steel wire b, adding Mn and V in steel c, and adding Nb, Cr and Cu in steel d. In addition, in the same e, it was supplemented by addition of Nb, V, Cr and Cu. In the steel wire f, the C concentration was increased similarly to the case a, and in addition, Nb and V were added to secure the strength. The steel wires d, e,
In f, it is intended to enhance the corrosion resistance of the steel wire by adding Cu and Ni alone or in combination. These steel wires obtained according to the present invention exhibit strength and ductility required for a reinforcing steel wire for ACSR, and at the same time, have extremely low iron loss.

On the other hand, the steel wire g is 0.8% C-
The final product of 2.8 mmφ was finished by the manufacturing process of the present invention using the material of 1.2% Si.
The reduction of the C concentration after decarburization annealing is also insufficient, and the mechanical properties and iron loss are not satisfactory for the intended use.

[0019]

[Table 1]

[0020]

[Table 2]

[0021]

According to the present invention, AC of high strength and low iron loss
A reinforcing steel wire for SR is provided. If the steel wire obtained by the present invention is used for a single-layer ACSR, heat generation due to the induced current and hysteresis loss and the induced current generated in the reinforcing steel wire can be suppressed, and thus the ACSR having high power transmission efficiency can be obtained.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI C21D 9/56 102 C21D 9/56 102 C22C 38/48 C22C 38/48 H01B 13/00 501 H01B 13/00 501L (58) Survey Areas (Int.Cl. ⁷ , DB name) C22C 38/00 B21B 3/00 B21C 1/00 C21D 1/00-11/00 H01B 13/00

Claims (3)

(57) [Claims] 1. Si: 1.0 to 3.5 wt% Al: 0.05 to 0.5 wt% Mn: 0.2 to 3.0 wt% as a basic component, and Nb: 0.1 wt% or less V: 0.1 wt% or less Cr: A steel billet containing one or two or more of 1.5 wt% or less and the balance iron and unavoidable impurities is formed into a wire rod having an intermediate wire diameter by hot rolling. A method for producing a steel wire with low power loss, which comprises forming a wire material having a final wire diameter by cold drawing of 50% or more. 2. The steel billet further contains one or two of Cu: 1.5 wt% or less and Ni: 3.0 wt% or less.
A method for producing a steel wire having a low power loss as described. 3. A wire rod having a final wire diameter by cold drawing, which is then annealed for decarburization to have a C: 0.1 wt% or less and at the same time a primary recrystallization structure. A method for producing a steel wire having a low power loss as described.