JP2000087186A - High carbon steel wire, ultrafine steel wire excellent in wire drawability, and method for producing the same - Google Patents

Abstract

(57) [Summary] [Problem] To obtain a wire excellent in wire drawing workability, and to produce a very fine steel wire suitable for use in a steel cord or a sawing wire using the wire as a material with high yield and good yield. To provide. SOLUTION: In weight%, C: 0.70 ~ 0.95%, Si: 0.1 ~ 0.
5%, Mn: 0.1-0.6%, P ≦ 0.01%, S ≦ 0.01%, N ≦ 0.004
%, Cu: 0.01-0.08%, Ni: 0.01-0.08%
%, Cr: 0.01 to 0.10%, and Mo: at least one of 0.01 to 0.05%, and the balance is Fe and impurities, and the symbol of the element in the formula is expressed as the content by weight% of the element (Cu / 3) + (N
A high carbon steel wire having a value of (i / 6) + (Cr / 3) + (Mo / 2) of 0.02 to 0.05%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel wire, an ultrafine steel wire, and a method for manufacturing the same. More specifically, for example, radial tires of automobiles, steel cords used as reinforcing materials for various industrial belts and hoses, and further, a steel wire excellent in wire drawing workability suitable for applications such as sewing wires, And a method of manufacturing the same.

[0002]

2. Description of the Related Art Ultra-fine steel wires for steel cords used as reinforcing materials for automobile radial tires, various belts and hoses, or ultra-fine steel wires for sawing wires are:
In general, a steel wire having a diameter of about 5.5 mm obtained by hot rolling (hereinafter referred to simply as "wire") is (i)
Primary wire drawing, patenting, secondary wire drawing, final patenting, then brass plating, and final wet wire drawing, or (ii) primary wire drawing, patenting It is manufactured by performing a plating process, then performing a brass plating, and further performing a final wet drawing process.

At present, among the above-mentioned manufacturing processes, one
The step (ii) of obtaining a thin steel wire of 1.5 to 2.0 mm by the secondary drawing and omitting the secondary drawing is becoming mainstream.

[0004] Generally, when a wire is broken into a steel wire when it is broken, productivity and yield are greatly reduced. Therefore, it is strongly required that wires belonging to the above technical field do not break during wire drawing.

On the other hand, in recent years, the above-mentioned various products for various purposes, particularly, radial tires of automobiles and various belts,
There has been an increasing movement to reduce the weight of hoses. Increasing the strength of the product can reduce its weight. Furthermore, if the strength of the ultrafine steel wire is increased, for example, the number of steel cords can be reduced, and the restriction on the design of the internal structure is reduced. For this reason, there is a demand for a steel component design that can increase the strength of a wire rod as a material.

[0006] In general, ultrafine steel wires for the various products described above,
In particular, for ultrafine steel wires with a diameter of 0.35 mm or less, steels with a basic chemical composition of highly purified carbon steel with a low content of various impurity elements are used for the purpose of improving drawability. Have been. That is, on an industrial production scale, steel having a basic chemical composition of carbon steel obtained by converting blast furnace pig steel into a converter is used. In order to increase the strength of a wire rod as a material,
However, when the C content of steel is increased, C is concentrated in the center of the steel ingot, and the absolute value of the C content is necessarily increased. That is, a C segregation region occurs in the central part of the steel ingot. For this reason, when such an ingot is rolled into a slab and rolled into a wire, a network-like pro-eutectoid cementite or martensitic phase is formed in the center of the wire during the cooling process after rolling, resulting in reduced wire drawing workability. I will.

[0007] Therefore, in order to suppress the formation of proeutectoid cementite and martensite phase, a cooling rate after rolling is adjusted, or a treatment for directly isothermal transformation after rolling (so-called "direct patenting treatment") is performed. Has been done. However, when the value of the C content of the central segregation part largely enters the hypereutectoid side, even if the cooling rate is adjusted, the generation of proeutectoid cementite cannot be completely suppressed. Further, C itself induces strain aging at the time of wire drawing, so that wire drawing workability is reduced.

Therefore, without increasing the content of C too much, elements such as Si, Mn, Cu, Cr and Mo are positively added to improve the hardenability to adjust the structure.
Attempts have been made to increase the strength of the wire as a raw material by solid solution strengthening.

However, when the content of the above-mentioned elements is large, processing conditions (patenting processing conditions) for dissolving the above-mentioned elements in the base material during the patenting processing performed in the intermediate stage of steel wire processing. Need to be changed. Furthermore, the pearlite transformation behavior changes under the influence of the above-mentioned elements, and in many cases, the temperature of the pearlite transformation nose rises to raise the optimum transformation temperature, and the pearlite transformation end time is delayed. Therefore, it becomes necessary to change the conditions of the patenting process, which is a daily work, and the problem that the operation is hindered becomes apparent.

[0010] Further, it is not preferable from the viewpoint of economy to include a large amount of the above elements.

[0011]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and has as its object to improve the purity of steel, such as blast furnace pig, by suppressing the content of various impurity elements to a low level. Using highly purified steel to obtain a wire with excellent drawability suitable for use in steel cords and sawing wires, and producing ultra-fine steel wires using the above-mentioned wire as a material under high productivity The goal is to provide a good yield at a low price. In addition, especially as for the said ultrafine steel wire, a diameter is 0.1.
A high-strength ultrafine steel wire having a tensile strength of 3000 MPa or more and a drawing of 30% or more, which is 35 mm or less, is targeted.

[0012]

SUMMARY OF THE INVENTION The gist of the present invention is to provide a wire rod having excellent drawability as shown in the following (1), a method for manufacturing an ultrafine steel wire as shown in (2) and a method for manufacturing an ultrafine steel wire as shown in (3). It is in.

(1) By weight%, C: 0.70 to 0.95
%, Si: 0.1 to 0.5%, Mn: 0.1 to 0.6
%, P: 0.01% or less, S: 0.01% or less, N:
0.004% or less, and Cu: 0.01 to
0.08%, Ni: 0.01 to 0.08%, Cr: 0.
01 to 0.10% and Mo: 0.01 to 0.05%, the balance being Fe and unavoidable impurities, and the value of fn1 represented by the following formula being 0.02
A high-carbon steel wire rod having excellent drawability, characterized in that the content is about 0.05%.

Fn1 = (Cu / 3) + (Ni / 6) + (Cr / 3) + (Mo / 2)... The symbol of the element in the formula represents the content by weight% of the element. .

(2) It has the chemical composition described in (1) above, has a diameter of 0.35 mm or less, and has a tensile strength of 3000M.
An ultrafine steel wire having a Pa of at least 30% and a drawing of at least 30%.

(3) A method for producing an ultrafine steel wire, comprising subjecting the steel wire described in (1) to cold working, followed by final heat treatment, plating, and wet drawing.

The term "wire" refers to steel that has been hot-rolled into a bar and is wound in a coil shape, and includes a so-called "bar-in coil".

The "cold working" for processing a wire into ultrafine steel wire includes not only wire drawing using a normal hole die but also wire drawing using a roller die, a so-called "two-roll rolling mill". ”,“ 3 roll rolling mill ”or“ 4 roll rolling mill ”.

"Final heat treatment" refers to a final patenting process. Also, “plating treatment” refers to brass plating,
Such as Cu plating, Ni plating, etc. are applied for the purpose of reducing the drawing resistance in the next wet drawing process or increasing the adhesion to rubber as in the case of steel cord applications. .

The present inventors have investigated and studied a high carbon steel wire rod having excellent drawability, which can suppress the content of C and can achieve high strength under ordinary patenting conditions. Was piled up.

First, as shown in Table 1, high-purity steels I to D, which are made of high-purity electrolytic iron and alloy raw materials by suppressing the contents of various impurity elements, are melted in a vacuum melting furnace. did. Next, these high carbon steels are hot forged by a usual method to obtain billets, and then rolled into a wire having a diameter of 5.5 mm by a usual method, and the cooling rate after the rolling is adjusted to directly apply a patenting treatment. did.

[0022]

[Table 1]

The thus obtained wire having a diameter of 5.5 mm was pickled and lubricated by a conventional method, and then drawn at room temperature to form a steel wire having a diameter of 1.5 mm. Next, these steel wires were austenitized at 950 ° C., passed through a lead bath maintained at 580 ° C., and subjected to a patenting treatment.
The strength (tensile strength) was measured.

As a result, it was found that the strength of the steel wire after patenting was improved by about 9 MPa per 0.01% by weight of the C content. This relationship is shown in FIG.

Next, steels A to C in Table 1 were used as basic chemical compositions, and Cu, Ni, and Cr were used as impurity elements.
And steel with various contents of Mo were melted in a vacuum melting furnace. Next, these high-carbon steels are rolled into a wire having a diameter of 5.5 mm and directly subjected to a patenting treatment, and then subjected to pickling / lubrication treatment and wire drawing to obtain a wire having a diameter of 1 mm, as in the case of the above-mentioned steels (1) to (2). 0.5 mm steel wire, and further subjected to a patenting treatment under the same conditions as in the case of the high-purity high-carbon steel of steels A to D. That is, after austenitizing at 950 ° C.,
The wire was passed through a lead bath maintained at 80 ° C. to perform a patenting treatment, and the strength (tensile strength) was measured.

The steel wire having a diameter of 1.5 mm after patenting was brass-plated by a usual method, and then wet-drawn to a diameter of 0.200 mm. As a result, the following items were found.

(A) The steel D with the C content increased to 1.03% by weight, despite being a highly purified steel with a low content of various impurity elements, was broken during wet drawing. As a result, it could not be processed to 0.200 mm. This is considered to be due to a decrease in drawability due to induction of center segregation of C and strain aging.

(B) The content of C is 0.71% by weight,
In a high-carbon steel having a basic chemical composition of 80% by weight and 0.92% by weight of steel A, steel B and steel C, if the content of Cu, Ni, Cr and Mo added as impurity elements is very small. For example, it is possible to achieve both high strength after the patenting treatment and good drawability. In addition, the patenting treatment conditions may be the same as those for high-purity high-carbon steel (steel a to c) in which the contents of various impurity elements are kept low.

(C) A high-carbon steel having a basic chemical composition of the steels (a) to (c) of the above (b) is added with a trace amount of Cu, Ni, Cr and 0.01% in terms of fn1 represented by the above formula. When Mo is contained, a strength increasing effect of about 9 MPa equivalent to increasing the C content by 0.01% is obtained. This situation is shown in Fig. 1 with □ (when steel A has the basic chemical composition), △ (when steel B has the basic chemical composition), and ◇ (when steel C has the basic chemical composition). ).

(D) From the above (a) to (c), if the content of C is suppressed, the center segregation is reduced, so that good drawing workability can be secured, and appropriate amounts of Cu, Ni, Cr and By including a small amount of Mo, it is possible to achieve high strength under ordinary patenting treatment conditions.

The present invention has been completed based on the above findings.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The requirements of the present invention will be described in detail below. In addition, “%” of the content of the chemical component means “% by weight”.

C: C is an element essential for increasing the strength of the steel wire. With an increase in the C content, the proportion of the pearlite phase in the structure of the steel wire after the patenting treatment increases. Accordingly, the strength of the steel wire increases. However, when the content of C is less than 0.70%, high-area reduction processing is required in order to wire-draw to a diameter of 0.35 mm and secure a desired tensile strength of 3000 MPa or more. The wire is sometimes broken, and the ductility of the steel wire is greatly reduced, which is not suitable for practical use. On the other hand, when the content exceeds 0.95%, center segregation cannot be ignored, such as generation of pro-eutectoid cementite and low-temperature transformation structure such as martensite. In addition, strain aging is induced. For this reason, the drawability is greatly reduced.
Therefore, the C content was set to 0.70 to 0.95%.

Si: Si has the effect of strengthening the ferrite phase in the pearlite phase and deoxidizing oxygen in the refined molten steel. However, if the content is less than 0.1%, the effect of addition is poor, and in particular, deoxidation becomes insufficient and causes internal defects. On the other hand, if the content of Si exceeds 0.5%, the amount of SiO ₂ -based inclusions increases and the wire drawing workability decreases. Therefore, the Si content is set to 0.1 to 0.5%.

Mn: Mn has the effect of enhancing the quenchability, promoting the pearlite transformation, increasing the proportion of the pearlite phase in the structure, and reducing the pearlite lamellar spacing to increase the strength. However, the content is 0.1
%, It is difficult to obtain the above effect. On the other hand, if the Mn content exceeds 0.6%, in a high-carbon steel wire rod, a low-temperature transformation structure such as martensite is generated in a cooling process or a patenting process after the wire rod rolling, so that the drawability is reduced. . In addition, the transformation end time during patenting becomes long. Further, Mn has a strong deoxidizing effect, and when contained in excess, increases hard oxide-based inclusions and decreases wire drawing workability. In particular, when the content exceeds 0.6%, hard Oxide inclusions increase remarkably. Therefore, the Mn content is set to 0.1 to 0.6%.

P: P lowers the ductility and toughness of the steel material and lowers the drawability. In particular, the content is 0.1.
If it exceeds 01%, the wire drawing workability is significantly reduced, and a high-strength ultrafine steel wire having a diameter of 0.35 mm or less, a tensile strength of 3000 MPa or more, and a drawing of 30% or more cannot be obtained. . Therefore, the content of P is 0.01%
It was as follows.

S: S reduces the ductility and toughness of the steel material,
Furthermore, it combines with Mn in steel and exists as MnS-based non-metallic inclusions, which hinders drawability. In particular, when the content exceeds 0.01%, the wire drawing workability is significantly reduced. Therefore, the content of S is set to 0.01% or less.

N: N forms a supersaturated solid solution in a steel material, induces strain aging during wire drawing, adversely affects ductility and toughness, and lowers wire drawability. In particular, when the content exceeds 0.004%, the wire drawing workability is significantly reduced. Therefore, the content of N is 0.004%
It was as follows. Note that the content of N is preferably set to 0.0035% or less.

Cu, Ni, Cr, Mo: The high-carbon steel wire and the ultrafine steel wire which are the object of the present invention have the above-mentioned amounts of C, S
"Purified steel" containing i, Mn, P, S, and N is used as the basic chemical composition to reduce the center segregation of C to ensure good drawability, and to use ordinary patenting conditions. Under high pressure to achieve high strength. For this purpose, 0.01-0.08% Cu, 0.01
At least one of -0.08% Ni, 0.01-0.10% Cr, and 0.02-0.05% Mo is contained. The above-mentioned Cu, Ni, Cr and Mo all enhance hardenability to promote pearlite transformation and suppress generation of pro-eutectoid cementite and pro-eutectoid ferrite phase, contributing to increase in strength and improvement in wire drawing workability. I do. However, if the content of Cu, Ni, Cr and Mo is less than 0.01%, the above effects cannot be obtained.
On the other hand, the contents of Cu, Ni, Cr, and Mo are each 0.1.
If it exceeds 08%, 0.08%, 0.10%, or 0.05%, it may be necessary to change the conditions of the patenting process and the operation may be hindered. Therefore, Cu, Ni,
The contents of Cr and Mo are respectively 0.01 to 0.08%,
0.01 to 0.08%, 0.01 to 0.10%, 0.0
2 to 0.05%. Note that the above-mentioned trace amounts of Cu and N
When i, Cr, and Mo are contained, scraps and scales of low alloy steel generated in a steelmaking plant can be used as a part of the iron source. Therefore, it is not necessary to add expensive ferromagnetic iron, and the material cost can be kept low.

Fn1: “Purified high-carbon steel” has the best wire drawing workability when the structure is a pearlite single phase, and the proportion of proeutectoid cementite or proeutectoid ferrite phase in the structure is high. The higher the value, the lower the drawability.

When the “highly purified high carbon steel” contains the above-mentioned trace amounts of Cu, Ni, Cr and Mo, if the value of fn1 represented by the formula is 0.02% or more, pearlite The transformation is promoted, and the ratio of the pearlite phase in the structure is increased, so that the drawability is improved. Further, the tensile strength per 0.01% of the value of fn1 is about 9MP.
a rise. However, when the value of fn1 exceeds 0.05%, it is necessary to change the conditions of the patenting process, which hinders the operation. Therefore, the value of fn1 is set to 0.02 to .0.
05%.

A wire having the above chemical composition is subjected to wire drawing using a hole die, wire drawing using a roller die, so-called “two-roll rolling mill”, “three-roll rolling mill” or “four-roll rolling mill”. After performing normal cold working such as cold rolling using "", the final heat treatment (patenting treatment) and the next wet drawing process such as brass plating, Cu plating, Ni plating, etc. The ultrafine steel wire according to the present invention is manufactured by performing a plating treatment for the purpose of reducing the pull-out resistance and improving the adhesion to rubber in the above, and further performing wet drawing.

The ultrafine steel wire thus obtained is thereafter processed into a predetermined end product. For example, a steel cord is formed by twisting a plurality of ultrafine steel wires by twisting to form a twisted steel wire.

In order to meet the demands of the industry to increase the strength of the steel wire and reduce the weight of the final product, the ultrafine steel wire according to the present invention has a diameter of 0.35 mm or less and a tensile strength of 3000 MPa or more. . If the diameter exceeds 0.35 mm, the product weight increases. On the other hand, if the tensile strength is less than 3000 MPa, if the diameter is 0.35 mm or less, the desired strength may not be imparted to the final product. When the drawing of the ultrafine steel wire is less than 30%, for example, if a plurality of the steel wires are twisted and twisted to form a twisted steel wire, the wire breakage occurs.

Therefore, the ultrafine steel wire of the present invention has a diameter of 0.35 mm or less, a tensile strength of 3000 MPa or more, and a reduction of 30% or more.

The lower limit of the diameter of the ultrafine steel wire and the upper limit of the tensile strength are not particularly defined. In order to reduce the weight of the final product, the smaller the diameter of the ultrafine steel wire, the better, while the higher the tensile strength, the better.

Further, in order to facilitate the processing into the final product, it is better that the drawing value of the ultrafine steel wire is larger.

Hereinafter, the present invention will be described in detail with reference to examples.

[0049]

EXAMPLES (Example 1) Steels 1 to 33 having the chemical compositions shown in Table 2 were melted using a vacuum furnace. The steels 1 to 20 in Table 2 are examples of the present invention in which the chemical composition is within the range of the content specified in the present invention. On the other hand, steels 21 to 33 are comparative examples in which any of the components is out of the range of the content specified in the present invention.

[0050]

[Table 2]

These steels were hot forged by a usual method to obtain billets, then hot-rolled into a wire having a diameter of 5.5 mm by a usual method, and the cooling rate after the rolling was adjusted to directly apply patenting. Processed. Next, it was pickled and descaled by a usual method, zinc phosphate coating was performed as a lubrication treatment, and wire drawing was performed to a diameter of 1.5 mm by a continuous wire drawing machine at room temperature.

The thus obtained steel wire having a diameter of 1.5 mm was austenitized at 950 ° C., passed through a lead bath maintained at 580 ° C., subjected to a patenting treatment, and examined for mechanical properties.

The above-patented steel wire was brass-plated by a usual method, and then drawn to a diameter of 0.200 mm using a wet wire drawing machine having 23 dies. investigated.

Table 3 shows the patented diameters of 1.
It shows the mechanical properties of a 5 mm steel wire and a steel wire that has been wet drawn to a diameter of 0.200 mm. In addition, any of those using steels 21 to 33 as base materials cause disconnection during wet wire drawing.
The size could not be reduced to 0.200 mm in diameter. For this reason, the mechanical properties of the wire diameter immediately before the wire diameter (diameter) at which the disconnection occurred were shown.

The point of view of the evaluation in this embodiment is that, first, wet wire drawing can be performed up to a diameter of 0.200 mm,
The target was to have a tensile strength of 000 MPa or more and a drawing value of 30% or more. If the steel wire has a drawing value of 30% or more, even if a plurality of steel wires are twisted and twisted in order to form a twisted steel wire, usually no breakage occurs.

[0056]

[Table 3]

From Table 3, it can be seen that all of the steels 1 to 20 of the present invention can be drawn to a diameter of 0.200 mm, have a high tensile strength of 3000 MPa or more, and have a drawing value of 30%.
The above is obtained, and it is clear that the material has properties that can withstand twisting.

Steel 1 has a chemical composition close to the lower limit of the content specified in the present invention, but it can be drawn to a diameter of 0.200 mm and has a high tensile strength of 3400 MPa.

Steels 17 to 20 are steels containing the upper limit of the amount of C specified in the present invention, but have higher drawability than steel 22 and a high strength and high ductility diameter. 0.2
A fine steel wire of 00 mm is obtained.

In particular, the diameter of steel 19 and steel 20 is 0.200 m
The drawn value of the steel wire finished to m is high, and the wire can be further drawn, suggesting that an ultra-high strength steel wire having a tensile strength of 4000 MPa or more can be obtained.

On the other hand, in the case of the steel of the comparative example, the drawability was low, and the aperture value did not reach the target of 30%.
Further, there is a case where the tensile strength does not reach the target of 3000 MPa.

[0062] Of the steels of the comparative examples, steels 21 to 29 are fn1
Is below the value specified in the present invention, and one of the components is out of the range of the content specified in the present invention.

Since the steel 21 has a C content lower than the value specified in the present invention, it has low drawability and a diameter of 0.200 mm.
Could not be drawn. 0.272 in diameter
The tensile strength of the steel wire of mm does not reach 3000 MPa, and the drawing value is as low as 27%.

In steel 22, since proeutectoid cementite is formed in a steel wire subjected to a patenting treatment when the C content exceeds the value specified in the present invention, the wire is frequently broken during the drawing process and has a diameter of 0.200 mm. Could not be drawn. In the case of this steel, the wire was broken before reaching a diameter of 0.35 mm.

In the steel 23, since the Mn content exceeds the value specified in the present invention, a slight martensite phase is formed in the central segregation portion of the patented steel wire, and therefore, the wire breaks during the wire drawing. Occurred frequently, and wire drawing could not be performed to a diameter of 0.200 mm. In the case of this steel as well, the wire was broken before reaching a diameter of 0.35 mm.

In the steel 24, since the Mn content is less than the value specified in the present invention, there are many pro-eutectoid ferrite phases in the structure, so that the wire drawability is low and the steel 24 cannot be processed to a diameter of 0.200 mm. Was. The diameter of this steel is 0.3
Disconnection occurred before reaching 5 mm.

The steel 25 had a low P drawability because the P content exceeded the value specified in the present invention, and could not be drawn to a diameter of 0.200 mm. 0.208m in diameter
The aperture value of the steel wire of m is as low as 23%.

Steel 26 has a low wire drawing property because the S content exceeds the value specified in the present invention, and could not be drawn to a diameter of 0.200 mm. 0.208m in diameter
The aperture value of steel wire m is as low as 21%.

Since the steel 27 had a Si content exceeding the value specified in the present invention, the wire was frequently broken with a 0.200 mm die and could not be drawn to a diameter of 0.200 mm. Observation of the broken surface of the broken steel wire revealed that SiO 2
_Two types of nonmetallic inclusions were frequently observed. Diameter 0.
The drawing value of a 228 mm steel wire is as low as 28%.

Since the steel 28 had a Si content below the value specified in the present invention, wire breakage occurred frequently during wire drawing, and the wire could not be drawn to a diameter of 0.200 mm.
As a result of observing the microstructure, many MnO and FeO-based nonmetallic inclusions were recognized, and deoxidation was insufficient. Diameter 0.2
The tensile strength of a 98 mm steel wire does not reach 3000 MPa, and its drawing value is as low as 25%.

Steel 29 has a low wire drawing property because the N content exceeds the value specified in the present invention, and could not be drawn to a diameter of 0.200 mm. 0.208m in diameter
The aperture value of the steel wire of m is as low as 25%.

The steels 30 to 33 among the steels of the comparative examples were fn1
Is a value satisfying the value specified in the present invention, but one of the components is out of the range of the content specified in the present invention.

Since the C content of the steel 30 was lower than the value specified in the present invention, the drawability was low as in the case of the steel 21, and the wire could not be drawn to a diameter of 0.200 mm.
The tensile strength of a steel wire with a diameter of 0.272 mm is 3000 MPa
, And the aperture value is as low as 26%.

In steel 31, since the C content exceeded the value specified in the present invention, martensite was formed and wire drawing workability was low, and wire drawing could not be performed to a diameter of 0.200 mm. In the case of this steel, the wire was broken before reaching a diameter of 0.35 mm.

Since the Mn content of the steel 32 is lower than the value specified in the present invention, the wire drawability is low similarly to the steel 24, and the wire cannot be drawn to a diameter of 0.200 mm.
The tensile strength of a steel wire with a diameter of 0.272 mm is 3000 MPa
And its aperture value is as low as 25%.

Since the Mn content of the steel 33 exceeds the value specified in the present invention, martensite was generated and the wire drawing workability was low, so that wire drawing could not be performed to a diameter of 0.200 mm. In the case of this steel as well, the wire was broken before reaching a diameter of 0.35 mm.

Example 2 Steels A and B having the chemical compositions shown in Table 4 were melted using a vacuum furnace. Steel A in Table 4 is an example of the present invention in which the chemical composition is within the range of the content specified in the present invention. On the other hand, Steel B is a comparative example in which the value of fn1 is lower than the value specified in the present invention.

[0078]

[Table 4]

These steels were hot forged by a usual method to obtain slabs, then hot rolled into a wire having a diameter of 5.5 mm by a usual method, and the cooling rate after rolling was adjusted to directly apply patenting. Processed. Next, it was pickled and descaled by a usual method, zinc phosphate coating was performed as a lubrication treatment, and wire drawing was performed to a diameter of 1.5 mm by a continuous wire drawing machine at room temperature.

The thus obtained steel wire having a diameter of 1.5 mm was austenitized at 950 ° C., passed through a lead bath maintained at 580 ° C. and subjected to a patenting treatment, and the mechanical properties were examined.

Further, after the patented steel wire is brass-plated by an ordinary method, a wet wire drawing machine having 16 holes dies is used, that is, the number of passes in the wet wire drawing is reduced. Then, the surface reduction rate per pass was increased to draw a wire to a diameter of 0.200 mm under severe processing conditions, and the mechanical properties were investigated.

Table 5 shows that the patented diameters of 1.
It shows the mechanical properties of a 5 mm steel wire and a steel wire that has been wet drawn to a diameter of 0.200 mm. FIG. 2 shows how the mechanical properties change when wet drawing is performed from a diameter of 1.5 mm to a diameter of 0.200 mm. The true strain (ε) in FIG. 2 is represented by the following equation using the diameter (d ₀ ) of the wire and the diameter (d) of the drawn steel wire.

Ε = 2log _e (d ₀ / d)

[0084]

[Table 5]

From Table 4, it can be seen that the strength of the 1.5 mm diameter patented steel wire is higher by an increase in the value of fn1 expressed by the formula in steel A than in steel B.

Steel A is a steel wire having a diameter of 0.200 mm
It has a tensile strength of 540 MPa and a high aperture value of 33%.

On the other hand, in the case of steel B, as is apparent from FIG. 2, the final position of 0.200 mm in diameter (FIG.
At a true strain of 4.0) is lower than the tensile strength when wire-drawing was performed with the previous die, and the drawing value was 20.
%.

(Example 3) Steels C to O having the chemical compositions shown in Table 6 were melted for 70 tons by converting blast furnace pig iron into steel. The steels C to G in Table 6 are examples of the present invention in which the chemical composition is within the range of the content specified in the present invention. On the other hand, steel H ~
O is a comparative example in which one of the components is out of the range of the content specified in the present invention.

[0089]

[Table 6]

These steels were slab-rolled by a conventional method into billets, then hot-rolled into a wire having a diameter of 5.5 mm by a conventional method, and the cooling rate after rolling was adjusted to directly apply patenting. Processed. Next, it was pickled and descaled by a usual method, zinc phosphate coating was performed as a lubrication treatment, and wire drawing was performed to a diameter of 1.5 mm by a continuous wire drawing machine at room temperature.

The thus obtained steel wire having a diameter of 1.5 mm was austenitized at 950 ° C., passed through a lead bath maintained at 580 ° C. and subjected to a patenting treatment, and the mechanical properties were examined.

After the patented steel wire is brass-plated by an ordinary method, a wet wire drawing machine having 16 holes dies is used, that is, the number of passes during wet wire drawing is reduced. Then, the surface reduction rate per pass was increased to draw a wire to a diameter of 0.200 mm under severe processing conditions, and the mechanical properties were investigated.

Table 7 shows that the patented diameters of 1.
It shows the mechanical properties of a 5 mm steel wire and a steel wire that has been wet drawn to a diameter of 0.200 mm. In the case of steel H to O as a base material, breakage occurs during wet wire drawing and the diameter is 0.20 mm.
The size could not be reduced to 0 mm. For this reason, the mechanical properties of the wire diameter immediately before the wire diameter (diameter) at which the disconnection occurred were shown.

As in the case of the first embodiment, the viewpoint of evaluation in this embodiment is that wet drawing can be performed up to a diameter of 0.200 mm.
The target was to have a tensile strength of 3000 MPa or more and a drawing value of 30% or more at a size of m.

[0095]

[Table 7]

From Table 7, all of the steels C to G of the present invention were
The wire can be drawn up to a diameter of 0.200 mm, and has a high tensile strength of 3000 MPa or more and a drawing value of 30% or more. It is clear that it has properties that can withstand twisting. is there.

On the other hand, in the case of the steel of the comparative example, the drawability was low, and at least one of the tensile strength and the reduction value did not reach the target.

[0098]

Since the wire of the present invention is excellent in wire drawing workability, it is possible to provide a high-strength steel cord, a sawing wire or the like using the wire as a material at a high yield with a high productivity. The base material steel of the wire rod and the steel wire of the present invention contains trace amounts of Cu, Ni, Cr, and Mo, but the range of the content is low alloy steel debris and scale generated in a steelmaking plant. It can be used as part of an iron source. For this reason, resources can be saved, and the environment is friendly to the global environment in terms of resource recycling.

[Brief description of the drawings]

FIG. 1 is a diagram showing the relationship between tensile strength and (C + fn1) when various high-carbon steels produced by a vacuum melting furnace are subjected to wire rod rolling, pickling / lubrication treatment, and patenting treatment.

FIG. 2 is a diagram showing how mechanical properties change when a patented steel wire having a diameter of 1.5 mm is wet drawn to a diameter of 0.200 mm in Example 2.

Claims (3)

[Claims] C. 0.70 to 0.95% by weight, S
i: 0.1 to 0.5%, Mn: 0.1 to 0.6%, P:
0.01% or less, S: 0.01% or less, N: 0.004
% Or less, and Cu: 0.01 to 0.08%,
Ni: 0.01 to 0.08%, Cr: 0.01 to 0.1
0% and Mo: at least one of 0.01 to 0.05%, the balance being Fe and unavoidable impurities,
The value of fn1 represented by the following equation is 0.02 to 0.05%
A high-carbon steel wire excellent in wire drawability, characterized in that: fn1 = (Cu / 3) + (Ni / 6) + (Cr / 3) + (Mo / 2)... The symbol of the element in the formula represents the content by weight% of the element. 2. The composition according to claim 1, which has a diameter of 0.35 mm or less, a tensile strength of 3000 MPa or more,
Extra fine steel wire with a drawing of 30% or more. 3. After cold working the steel wire according to claim 1,
A method for producing an ultrafine steel wire, comprising a final heat treatment, a plating treatment, and wet drawing.