JP2000219938A - Wire rod for high tensile strength steel wire and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire rod for producing a wire having high strength and high ductility. SOLUTION: This wire rod for superhigh tensile strength steel is the one having a compsn. contg., by weight, 0.7 to 1.2% C, 0.1 to 1.5% Si, 0.1 to 1.2% Mn, <=0.003% Al, <=30 ppm O and 25 to 200 ppm solid solution N, contg., at need, 0.1 to 1.0% Cr, and the balance iron with inevitable impurities. As to the method for producing the wire rod, an ingot having the above steel components is hot-rolled to 5 to 16 mm and is subjected to controlled cooling into a wire rod having a pearlitic structure free from the presence of pro- eutectoid cementite. Furthermore, a high tensile strength steel wire is obtd. by subjecting the above wire rod to wire drawing, in which diameter is <=0.4 mm, and tensile strength is >=3 GPa.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ACSR wire (aluminum conductor) for reinforcing steel cords, aluminum transmission lines and the like.
or Steel Reinforced Wire), high-strength steel wire used for elevator cables, rope wires, etc., galvanized steel wire, and wires used in the production thereof.

[0002]

2. Description of the Related Art In general, ultra-fine high-carbon steel wires drawn such as steel cords are hot-rolled as needed, and then cooled and adjusted to a diameter of 4.0 to 6.0 mm.
It is manufactured by final patenting, followed by brass plating and final wet drawing. Many of such ultra-fine steel wires are used as steel cords after being subjected to stranded wire processing such as double twisting or five twisting. These steel cords are required to have 1) higher strength, 2) excellent high-speed drawability, 3) excellent fatigue characteristics, 4) excellent high-speed stranded wire, and the like. And must have these characteristics.

[0003] For this reason, high-quality steel materials have been conventionally developed in response to requests. For example, JP-A-60-2048
No. 65 discloses that the Mn content is regulated to less than 0.3% to suppress the generation of a supercooled structure after lead patenting,
It is disclosed that by controlling the amounts of elements such as i and Mn, a very fine wire having high strength and high toughness and a high carbon steel wire for a steel cord can be obtained with less breakage at the time of stranded wire. Japanese Patent Application Laid-Open No. 63-24046 discloses a high toughness and high ductility in which the Si content is set to 1.00% or more to increase the tensile strength of a lead patenting material and reduce the wire drawing rate. An ultrafine wire is disclosed. However, at present, there is a demand for the development of a higher-strength high-strength steel wire due to the need for further weight reduction.

[0004]

The present invention provides a high-strength steel wire of 0.1 to 0.4 mm used for steel cords, hose wires, etc. in order to meet the above-mentioned demands. The purpose is to:

[0005]

In order to achieve the above object, the present invention has the following constitution. That is, in the present invention, C: 0.7 to 1.2%, Si: 0.1 to 1.5%, Mn: 0.1 to 1.2%, Al: 0.003% or less by weight%, A high-strength steel wire comprising O: 30 ppm or less, solute N: 25 to 200 ppm, and the balance of iron and unavoidable impurities. The wire may further contain Cr: 0.1 to 1.0%. Further, in the above-mentioned wire rod, P is set to 0.02% or less, and S is set to 0.1%.
It is preferable to regulate the content to not more than 02%. Further, in the wire having the above steel component, it is preferable that the steel structure be a pearlite structure substantially free of a cementite structure.

Further, the billet having the above-described steel component is hot-rolled into a wire having a diameter of 5 to 16 mm, and adjusted and cooled.
Provided is a method for producing a wire for a high-strength steel wire, which is a wire having a pearlite structure substantially free of proeutectoid cementite.

Further, the present invention provides a high-strength steel wire characterized in that a diameter obtained by drawing the above-mentioned wire is 0.4 mm or less and a tensile strength is 3 GPa or more. And a hot-rolled wire having a diameter of 5.0 to 6.0 mm made of the above steel component and having a diameter of 5.0 to 6.0 mm by wire drawing and intermediate heat treatment.
The steel wire of 8 to 2.3 mm is drawn, then the tensile strength is adjusted to 1.2 to 1.6 GPa by a patenting process, then brass plating is performed, and the diameter is reduced to 0 by wet drawing. A method for producing a high-tensile steel wire, characterized in that the wire has a diameter of 0.1 to 0.4 mm.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
First, the reason for defining the steel composition of the present invention will be described. All component amounts are% by weight. C is an element effective for strengthening, and in order to obtain a high-strength steel wire, the amount of C needs to be 0.7% or more. However, if it is too high, proeutectoid cementite tends to precipitate, and ductility decreases. In addition, the drawability is deteriorated, and the upper limit is set to 1.2%.

[0010] Si is an element necessary for deoxidizing steel, and if its content is too small, the deoxidizing effect becomes insufficient. Further, Si forms a solid solution in the ferrite phase in the pearlite formed after the heat treatment and increases the strength after patenting, but on the other hand, impairs the heat treatment property, so that the content is 1.5% or less.

Mn must be added in an amount of 0.1% or more in order to secure the hardenability of steel. However, a large amount of Mn
Addition also delays the recovery of ductility during hot-dip galvanizing, so it is set to 1.2% or less.

Al is an impurity element, and if unavoidably enters, it is likely to combine with N to form a nitride, which hinders the effect of increasing the amount of solute N, so that it is made 0.003% or less.

When O exceeds 30 ppm, oxide-based inclusions increase, which adversely affects ductility. Therefore, the content of O is set to 30 ppm or less, at which the influence is reduced.

Solid solution N increases the work hardening as an age hardening element and makes it easy to obtain high strength. Desirably, 50 ppm or more is added. When added in excess of 200 ppm,
200 pp
m or less. Here, the amount of solute nitrogen is a value obtained by subtracting the nitrogen present as AlN, TiN, BN, etc., which obviously becomes nitride, from the amount of nitrogen in the steel.

In the case of hypereutectoid steel, a cementite network is easily generated in the structure after patenting, and a thick cementite is likely to precipitate. Cr has the effect of suppressing the appearance of such an abnormal portion of cementite, and further has the effect of making pearlite finer, and is added as necessary to achieve such an effect. However, large additions slow the recovery of ductility during hot dip galvanizing. Therefore, the addition amount of Cr is expected to be 0.
1% or more, and 1.0% or less, which does not delay the recovery of ductility during plating.

[0015] As in the case of the conventional ultrafine steel wire, the content of S is set to 0.02% or less in order to ensure ductility, and P also impairs the ductility of the wire similarly to S. It is desirable to do the following.

The steel adjusted to the above-mentioned steel composition is continuously cast into a bloom or a billet after being melted. The bloomed steel is hot rolled into billets by slab rolling. These billets have a diameter of 5.0 to 16 by hot rolling.
The wire rod is processed to a pearlite structure with no proeutectoid cementite by controlled cooling. Here, blast cooling, molten salt cooling, mist cooling, or the like can be applied to the adjustment cooling. At this time, when pro-eutectoid cementite precipitates,
Since the primary workability of the wire is significantly impaired, the structure adjustment at this time is adjusted so that proeutectoid cementite does not precipitate.

Next, these wires are processed into wires having a diameter of 0.8 to 2.3 mm by using wire drawing and intermediate heat treatment. The wire drawing at this time may be any of drawing using a hole die, roller dies, and rolling. The intermediate heat treatment may be any heat treatment that reduces strength and recovers ductility, such as patenting and annealing.

This wire is subjected to a final patenting treatment and adjusted to a fine pearlite structure. For the final patenting treatment, lead patenting, fluidized bed treatment or the like can be used. By this patenting, the tensile strength is set to 1.2 to 1.6 GPa. The final product has a diameter of 0.1 to 0.4 mm and a tensile strength of 3.0 to 5.0 GPa. For that purpose, a diameter of 0.8 to 2.3 mm is required.
It is necessary to set the tensile strength at the time point to 1.2 to 1.6 GPa. That is, if it is less than 1.2 GPa, 3.0 GPa or more cannot be secured as a final product after wire drawing, and 1.6 GPa or more.
This is because if it is excessive, subsequent wire drawing becomes difficult.

After the wire whose texture has been adjusted is subjected to a treatment such as brass plating, the diameter of the wire is adjusted to 0.4 mm by wet continuous drawing.
mm or less, an ultrafine steel wire of 0.1 to 0.4 mm that is industrially easy to manufacture. At this time, the wire strength becomes a tensile strength of about 3 GPa or more. In particular, the work hardening increases due to the addition of nitrogen, and a more ductile wire can be obtained as compared with conventional materials. FIG. 1 shows the relationship between C and the tensile strength of the 0.3 mm wire when compared at the same processing amount (true strain 3.6). The circles in this figure indicate the amounts of dissolved nitrogen 70 to 9
0 ppm and ● marks are 20 to 30 ppm, and a high strength wire can be obtained even at the same area reduction rate.

[0020]

Embodiments of the present invention will be described below. Table 1 shows the chemical components of the test steel used for the trial production. Invention Steels 1 to 15
According to the present invention, the chemical composition and microstructure of the steel are adjusted. On the other hand, Comparative Steels 16, 17, 18, and 20 are cases where the amount of nitrogen is low. Comparative steel 19 has a large amount of nitrogen. These steels were formed into a wire having a diameter of 5.0 mm or 5.5 mm by hot rolling to have a structure free of proeutectoid cementite by controlled cooling. Adjustment cooling method and mechanical properties after rolling,
Table 2 shows the presence or absence of proeutectoid cementite.

Next, each wire has a diameter of 0.1 to 0.1 mm.
A 0.4 mm wire was manufactured. Table 3 shows the processing conditions at this time.
Shown in Table 4 shows the mechanical properties of the obtained wire. First, as shown in Table 3, a wire of 1.0 to 2.0 mm was formed by wire drawing and intermediate heat treatment. These wires were adjusted to a pearlite structure by a final patenting treatment, subjected to brass plating as a lubricating aid, and then wet-drawn to obtain wires of 0.1 to 0.4 mm.

The steels 1 to 15 of the present invention are adjusted to the component ranges of the present invention, and the production method is in accordance with the method of the present invention. Comparing steel components other than nitrogen with almost the same composition,
As shown in FIG. 1, steel having a higher nitrogen content has higher strength.

Comparative steels 16 to 18 have a lower amount of solute nitrogen than the steel of the present invention. For this reason, the comparative steels 16 to 18 have lower strength than the steels 1 to 3 of the present invention having a high N content.
This is as shown in FIG. Comparative steel 19
Is the case where the amount of nitrogen exceeds 200 ppm. Delamination occurred in the final wire because the nitrogen content was too high. Since the comparative steel 20 had a low nitrogen content, the area reduction rate was increased to increase the strength, but the ductility was insufficient and delamination occurred in the final wire.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

[0027]

[Table 4]

[0028]

As described above, by using the steel of the present invention, it is possible to easily obtain a wire having high strength and excellent ductility without delamination.

[Brief description of the drawings]

FIG. 1 is a view showing the relationship between the amount of carbon and the tensile strength that affect the amount of N.

Claims (7)

[Claims] 1. C: 0.7 to 1.2%, Si: 0.1 to 1.5%, Mn: 0.1 to 1.2%, Al: 0.003% or less, O by weight% : High-strength steel wire comprising 30 ppm or less, solute N: 25 to 200 ppm, and the balance consisting of iron and unavoidable impurities. 2. The high-strength steel wire according to claim 1, further comprising a steel component to which Cr: 0.1 to 1.0% by weight is added. 3. The wire rod for a high-tensile steel wire according to claim 1, wherein the steel component is a steel component which is regulated to P: 0.02% or less and S: 0.02% or less by weight%. . 4. A high tensile strength wire comprising the steel component according to claim 1 and a steel structure having a pearlite structure substantially free of a cementite structure. Wire for steel wire. 5. A billet having a steel structure having a steel component according to claim 1 having a diameter of 5 to 5 by hot rolling.
A method for producing a high-strength steel wire, characterized in that a wire having a diameter of 16 mm, a controlled cooling, and a pearlite wire substantially free of proeutectoid cementite are used. 6. A wire obtained by drawing a wire according to claim 1 having a diameter of 0.4.
A high-strength steel wire characterized by having a tensile strength of 3 GPa or less and a tensile strength of 3 GPa or less. 7. A hot-rolled wire made of the steel component according to any one of claims 1 to 4 and having a diameter of 5.0 to 6.0 mm is subjected to 0.1% by wire drawing and intermediate heat treatment. 8 ~
Wire drawing is performed on a 2.3 mm steel wire, and then the tensile strength is adjusted to 1.2 to 1.6 GPa by a patenting process.
Thereafter, brass plating is performed, and a wire having a diameter of 0.1 to 0.4 mm is formed by wet wire drawing.