JP2000309849A - Steel wire rod, steel wire, and their manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wire rod excellent in wire drawability and to inexpensively manufacture a steel wire using the wire rod as a stock in high yield with high productivity. SOLUTION: A steel is used which has a composition ansisting of 0.75-0.92% C, 0.1-1.0% Si, 0.1-1.0% Mn, <=1.0% Cr, <=0.5% Cu, <=1.0% Ni, <=2.0% Co, <=0.5% Mo, <=0.5% W, <=0.2% V, <=0.1% Nb, <=0.03% REN, <=0.003% Ca, <=0.003% Mg, <=0.005% B, ad the balance Fe with impurities, in which the contents of Al, insol. Al, Ti, N, P, S, and O among the impurities are regulated to <=0.0020%, <=0.0012%, <=0.0020%, <=0.005%, <=0.012%, <=0.01%, and <=0.0020%, respectively, and also in which Ti(%)×N(%)<=6×10-6 and N(%)-1.3B(%)-0.3Ti(%)<=0.0035% are satisfied. It is preferable to regulate the contents of Sn, As, and Sb among the impurities to <=0.005%, <=0.003%, and <=0.003%, respectively.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a steel wire, a steel wire and a method for manufacturing the same. More specifically, for example, a radial tire of an automobile, a steel cord used as a reinforcing material for various industrial belts and hoses, and further, a steel wire material suitable for applications such as sewing wires and the above-described steel wire material. The present invention relates to a steel wire and a method for manufacturing the same.

[0002]

2. Description of the Related Art Steel wires for steel cords used as reinforcing materials for automobile radial tires, various belts and hoses, or steel wires for sawing wires are generally prepared by hot rolling and adjusting and cooling the wire diameter ( 5-6mm in diameter)
Steel wire rod (hereinafter referred to simply as "wire rod")
Is first drawn to a diameter of 3 to 4 mm,
A patenting process is performed, and a secondary wire drawing is performed.
Make a diameter of 2 mm. Thereafter, a final patenting process is performed, then, a brass plating is performed, and a final wet drawing process is performed to a diameter of 0.15 to 0.40 mm. A steel cord is manufactured by twisting a plurality of the extra-fine steel wires obtained in this manner by twisting to obtain a twisted steel wire.

[0003] In general, when a wire breaks when a wire is formed into a steel wire or when a steel wire is twisted, productivity and yield are greatly reduced. Therefore, it is strongly required that wires and steel wires belonging to the above technical field do not break during wire drawing or twisting.

Further, in the case of manufacturing a steel cord, many intermediate processing steps are required to convert a hot-rolled wire having a diameter of 5 to 6 mm into a steel wire having a diameter of 1 to 2 mm, which leads to an increase in manufacturing cost. Have been. Therefore, there is an increasing demand from the industry to simplify the manufacturing process without deteriorating the performance of the final product. For this reason, in a relatively low-strength carbon steel wire rod having a C content of less than 0.7%,
Omitting the intermediate processing, for example, from 5.5 mm to 1.7 mm in diameter
A technology for drawing directly down to mm has been developed. In addition,
The true strain amount in the wire drawing is 2.35. Here, the true strain (ε) is represented by the following equation (i) using the diameter (d ₀ ) of the wire and the diameter (d) of the drawn steel wire.

Ε = 2log _e (d ₀ / d) (i) On the other hand, in recent years, there has been an increasing movement to reduce the weight of steel cords and the like for various purposes. For this reason, high strength is required for the various products described above, and the above C
With a carbon steel wire having a content of less than 0.7%, a desired high strength cannot be obtained. For this reason, there is an extremely large demand for a wire rod which has a high C content and can secure a high strength to a steel wire, and which has excellent drawability such that the intermediate treatment can be omitted.

[0006] In response to the above-mentioned demands from the industry in recent years, there has been proposed a technique for controlling segregation and microstructure to enhance the drawability of a wire.

[0007] For example, Japanese Patent Publication No. 7-11060 discloses a "high-strength steel wire excellent in wire drawing workability" for controlling segregation of Mn in a wire. However, the technology proposed in this publication is to increase the pressure reduction ratio by increasing the slab size in order to reduce the Mn segregation peak width in the wire, and to improve the center segregation in order to improve center segregation. Special treatments such as lowering the temperature, performing electromagnetic stirring in the mold, applying pressure to the slab at the end of solidification, and heating the slab in a soaking furnace to diffuse segregated elements are required. For this reason, when the manufacturing process or manufacturing equipment of a wire is different, it cannot always be applied, and even if it can be applied, the manufacturing cost increases. Furthermore,
Controlling the segregation of Mn also contributes to the improvement of the drawing of the hot-rolled wire rod, but is insufficient to omit the patenting as the intermediate treatment described above.

Japanese Patent Application Laid-Open No. Hei 6-145895 discloses a "high-strength high-toughness steel" comprising a steel material having a specific chemical composition and defining the average area ratio of proeutectoid cementite and the composition of nonmetallic inclusions. Wires, ultrafine steel wires using the steel wires, methods for producing the same, and twisted steel wires ”are disclosed. However, in the production of steel, particularly in the production of steel on an industrial scale, it is difficult to avoid a large change in the composition of nonmetallic inclusions due to a change in steelmaking raw materials. For this reason, it is not easy to control the composition of the nonmetallic inclusion within a certain range. In addition,
Even if the control of the composition of the nonmetallic inclusions can be performed, the cost increases, and further, the above-mentioned intermediate treatment step cannot always be omitted.

According to the technology proposed in Japanese Patent Publication No. Hei 7-11060 and Japanese Patent Laid-Open Publication No. H6-145895,
First of all, it is possible to obtain a wire excellent in wire drawing workability. However, as described above, there are problems that the equipment cost and the manufacturing cost increase, and that the above-described intermediate processing step cannot always be omitted.

[0010]

SUMMARY OF THE INVENTION The present invention has been made in view of the above situation, and has as its object to provide excellent cold workability such as wire drawing workability suitable for uses such as steel cords and sawing wires. An object of the present invention is to provide a wire rod and to provide a steel wire using the above-described wire rod as a material at a high yield with a high productivity at a low cost. In addition, as the above-mentioned steel wire, in particular, a steel wire that is subjected to cold working with a true strain of 2.3 or more is targeted.

[0011]

The gist of the present invention resides in a method of manufacturing a wire rod shown in the following (1) to (3), a steel wire shown in (4) and a steel wire shown in (5).

(1) By weight%, C: 0.75 to 0.92
%, Si: 0.1 to 1.0%, Mn: 0.1 to 1.0
%, Cr: 1.0% or less, Cu: 0.5% or less, Ni:
1.0% or less, Co: 2.0% or less, Mo: 0.5% or less, W: 0.5% or less, V: 0.2% or less, Nb: 0.
1% or less, REM (rare earth element): 0.03% or less,
Ca: 0.003% or less, Mg: 0.003% or less,
B: 0.005% or less, the balance consists of Fe and unavoidable impurities, Al in the impurities is 0.0020% or less, and insol. Al is 0.0012% or less, Ti is 0.0020% or less, N is 0.005% or less, and P is 0.2% or less.
012% or less, S is 0.01% or less, and O (oxygen) is 0.1% or less.
0020% or less, and the value of fn1 represented by the following equation is 6 × 10 ⁻⁶ or less, and fn2 represented by the following equation:
That satisfies the value of 0.0035% or less.

Fn1 = Ti (%) × N (%)... Fn2 = N (%)-1.3B (%)-0.3Ti (%) (2) By weight% And Sn as an impurity further 0.005.
%, As is 0.003% or less, Sb is 0.003%
The following wire according to the above (1).

(3) It has the chemical composition described in (1) or (2) above, has a diameter of 4 to 6 mm, and has a tensile strength of 1120.
{C (%) / 0.9} ^{1/2 to} 1300 ° C (%) / 0.
9｝ ^1/2 MPa wire.

(4) A steel wire obtained by cold working the wire described in (1) to (3) with a true strain of 2.35 or more.

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

Here, "insol. Al" is a so-called "acid-insoluble Al" and refers to Al as Al ₂ O ₃ in the present invention.

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

"Cold processing" for processing a wire into a steel wire
Used not only wire drawing using a normal hole die, but also wire drawing using a roller die, so-called “2 roll rolling mill”, “3 roll rolling mill” or “4 roll rolling mill”. Including cold rolling.

The true strain (ε) is expressed by the following equation (i) using the diameter (d ₀ ) of the wire or steel wire before working and the diameter (d) of the steel wire after working.

Ε = 2log _e (d ₀ / d) (i) “final heat treatment” refers to the final patenting process. In addition, the “plating treatment” is to reduce the drawing resistance in the next wet drawing process, such as brass plating, Cu plating, and Ni plating, and to increase the adhesion to rubber as in the case of steel cord applications. Refers to things given for the purpose.

Hereinafter, the inventions described in the above (1) to (5) are referred to as inventions (1) to (5), respectively.

The present inventors have proposed that the chemical composition and mechanical properties of the wire are reduced to cold workability such as drawability and cold rollability (hereinafter simply referred to as “drawability” for simplicity). Through repeated investigations and studies on the effects, the following findings were obtained.

(A) In order to increase the tensile strength (hereinafter referred to as TS), the content of alloying elements such as C, Si, Mn and Cr may be increased, but the content of these alloying elements is not increased. This leads to a reduction in wire drawing workability, that is, a reduction in the limit workability during wire drawing.

(B) In order to increase the critical working degree at the time of wire drawing, the contents of Al, Ti, N, S and O (oxygen) as impurity elements may be strictly limited.

(C) Concerning the contents of Ti and N in the impurity elements, when fn1 represented by the above formula is not more than a specific value, the temperature at which TiN precipitates becomes low and TiN becomes finer. The wire drawing workability does not decrease.

(D) In addition to fixing N as an impurity element with Ti as the same impurity element and fixing it as fine TiN, if B is added to form BN and N is fixed, Since the amount of solute N (so-called "free N") in steel is greatly reduced, the wire drawing workability is greatly improved.

(E) In addition to reducing the content of O (oxygen) to reduce the total amount of oxide-based inclusions, the amount of hard oxide-based inclusions Al ₂ O ₃ produced, in other words Baso
l. If the amount of Al is reduced, the drawability is greatly improved.

(F) If the contents of Sn, As and Sb as impurity elements are strictly restricted, the wire drawing workability becomes extremely high.

(G) By setting the TS of the wire in a specific range according to the C content, extremely good drawability can be obtained.

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

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Each requirement of the present invention will be described in detail below. In addition, "%" of the content of each element means "% by weight".

(A) Chemical composition C: 0.75 to 0.92% C is an element effective for increasing the strength of a wire. However, when the content is less than 0.75%, for example, T
It is difficult to stably impart a high strength of 3200 MPa in S to a final product. On the other hand, if the content of C is too large, the steel material is hardened, which causes a decrease in drawability.
In particular, if the C content exceeds 0.92%, it is necessary to increase the cooling rate after hot rolling in order to prevent the formation of proeutectoid cementite (that is, cementite along the prior austenite grain boundaries). Since the strength of the hot-rolled wire is greatly increased by increasing the cooling rate, the drawability is greatly reduced, and even if the impurity element described below is reduced to a specified content, the true strain is reduced. When wire drawing is performed at a working ratio of 2.0 or more, disconnection frequently occurs. Therefore, C
Was 0.75 to 0.92%.

Si: 0.1 to 1.0% Si is an effective element for increasing the strength. Further, it is an element necessary as a deoxidizing agent. However, if the content is less than 0.1%, the effect of addition is poor, while if it exceeds 1.0%, the limit workability in wire drawing decreases. Therefore, the content of Si is set to 0.1 to 1.0%.

Mn: 0.1-1.0% In addition to the effect of increasing the strength, Mn also reduces S in steel to MnS
And has the effect of preventing hot brittleness. However, if the content is less than 0.1%, it is difficult to obtain the above effects. On the other hand, Mn is an element that is easily segregated. If it exceeds 1.0%, Mn is segregated particularly at the center of the wire, and martensite and bainite are generated at the segregated portion, so that the wire drawing workability is reduced. . Therefore, the content of Mn is 0.1
To 1.0%.

Cr: 1.0% or less Cr need not be added. If added, it has the effect of reducing the lamella spacing of pearlite and increasing the strength after rolling and after patenting. Further, it has the function of increasing the work hardening rate during cold working such as wire drawing. In order to surely obtain such an effect, the content of Cr is preferably set to 0.1% or more. However, when the content exceeds 1.0%, the time until the pearlite transformation ends is increased, and martensite and bainite are formed at the center of the wire after hot rolling. The disconnection frequency increases. Therefore, the content of Cr is set to 1.0% or less.

Cu: 0.5% or less Cu need not be added. If added, it has the effect of increasing corrosion resistance. To ensure this effect, Cu must be 0.0
Preferably, the content is 5% or more. However, if the content exceeds 0.5%, segregation occurs at the crystal grain boundaries, and cracks and flaws become noticeable during hot working such as bulk rolling of steel ingots and hot rolling of wire rods. Therefore, the content of Cu is set to 0.5% or less.

Ni: 1.0% or less Ni may not be added. When added, it has the effect of forming a solid solution in the ferrite and improving the toughness of the ferrite. To ensure this effect, the content of Ni is preferably set to 0.1% or more. However, if the content exceeds 1.0%, the hardenability becomes too high, so that martensite is easily formed and the wire drawing workability deteriorates. Therefore, the content of Ni is set to 1.0% or less.

Co: 2.0% or less Co may not be added. When added, it has the effect of preventing precipitation of proeutectoid cementite and further increasing the strength by refining pearlite. To ensure this effect, C
It is preferable that the content of o is 0.2% or more. However, even if the content exceeds 2.0%, the above effect is saturated and the cost is increased. Therefore, the content of Co is set to 2.0% or less.

Mo: 0.5% or less Mo may not be added. If added, it has the effect of forming a solid solution in cementite and ferrite and increasing the strength.
To ensure this effect, it is preferable that the content of Mo be 0.05% or more. On the other hand, if it exceeds 0.5%, the hardenability becomes too high, so that martensite is easily generated and the wire drawing workability is deteriorated. Therefore, the content of Mo is set to 0.5% or less.

W: 0.5% or less W may not be added. If added, cementite,
It dissolves in ferrite and has the effect of increasing strength. To ensure this effect, the content of W is preferably set to 0.05% or more. On the other hand, if it exceeds 0.5%, the hardenability becomes too high, so that martensite is easily generated and the wire drawing workability is deteriorated. Therefore, the content of W is set to 0.1.
5% or less.

V: 0.2% or less V may not be added. If added, it has the effect of refining austenite crystal grains and increasing ductility and toughness. In order to ensure this effect, it is preferable that the content of V is 0.05% or more. However, even if the content exceeds 0.2%, the above effect is saturated and the cost is increased. Therefore, the content of V is set to 0.2% or less.

Nb: 0.1% or less Nb may not be added. If added, it has the effect of refining austenite crystal grains and increasing ductility and toughness. In order to surely obtain this effect, the content of Nb is preferably set to 0.01% or more. However, even if the content exceeds 0.1%, the above effect is saturated and the cost is increased. Therefore, the content of Nb is set to 0.1% or less.

REM (rare earth element): 0.03% or less REM may not be added. If added, it has the effect of increasing hot workability. To ensure this effect, R
It is preferable that the content of EM is 0.001% or more. However, even if REM is contained in an amount exceeding 0.03%, the above effect is saturated and the cost is increased. Therefore, the content of REM is set to 0.03% or less. The “REM content” in the present invention refers to “total REM content”.

Ca: 0.003% or less Ca may not be added. If added, it has the effect of increasing hot workability. To ensure this effect, Ca
Is preferably 0.0001% or more.
However, even if Ca is contained in an amount exceeding 0.003%, the above effects are saturated, and the cost is only increased. Therefore, the content of Ca is set to 0.003% or less.

Mg: 0.003% or less Mg need not be added. If added, it has the effect of increasing hot workability. To ensure this effect, use Mg
Is preferably 0.0001% or more.
However, even if Mg is contained in an amount exceeding 0.003%, the above effect is saturated, and the cost is only increased. Therefore, the content of Mg is set to 0.003% or less.

B: 0.005% or less B may not be added. If added, it combines with N dissolved in steel to form BN, reduces solid solution N, improves wire drawing workability, and generates longitudinal cracks in the twist test after final drawing. Has the effect of suppressing In order to surely obtain this effect, the content is preferably 0.0003% or more, although it depends on the content of N and Ti as impurity elements as described later. However, when B is contained in excess of 0.005%, coarse BN is generated, and wire drawing workability is reduced. Therefore, the content of B is set to 0.005% or less.

Further, in the invention of (1), the contents of the impurity elements Al, Ti, N, P, S and O are limited as follows.

Al: not more than 0.0020% Al forms oxide-based inclusions containing Al ₂ O ₃ as a main component, thereby deteriorating drawability. In particular, when the content exceeds 0.0020%, the oxide-based inclusions are coarsened, the wire is frequently broken during wire drawing, and the wire drawing workability is significantly reduced. Therefore, the content of Al is set to 0.002.
0% or less.

Insol. Al: 0.0012% or less As already described, “insol. Al” is a so-called “acid-insoluble Al”, and in the present invention, Al as Al ₂ O ₃
Point to. 0.0020% of the total Al content
After limiting to the following, insol. Al content 0.001
If it is limited to 2% or less, the frequency of disconnection decreases and sufficient productivity can be secured on an industrial scale. Therefore, insol. The Al content was set to 0.0012% or less.

Ti: 0.0020% or less Ti combines with N to form TiN. If this TiN is coarse, it becomes a starting point of wire breakage during wire drawing, so that wire drawing workability deteriorates. However, as described later, fn1 represented by the above formula for the content of Ti and N is 6 × If it is 10 ^-6 or less, the temperature at which TiN precipitates becomes low and TiN becomes finer, so that the wire drawing workability does not decrease. However, if the content of N is reduced below about 0.003% in order to make the value of fn1 6 × 10 ⁻⁶ or less, the steelmaking cost increases and the economy is lacking. Therefore, the content of Ti is preferably limited to a low value.
0020% or less.

N: 0.005% or less N adheres to dislocations during cold drawing and increases the strength of the steel wire, but decreases the drawability. In particular, when the content exceeds 0.005%, the wire drawing workability is significantly reduced. Therefore, the content of N is 0.00
5% or less.

P: 0.012% or less P segregates at the grain boundaries and lowers the drawability. In particular, when the content exceeds 0.012%, the wire drawing workability is significantly reduced. Therefore, the content of P is 0.01
2% or less.

S: 0.01% or less S lowers the 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.

O (oxygen): 0.0020% or less O forms oxide-based inclusions and lowers the drawability. In particular, when the content of O exceeds 0.0020%, the oxide-based inclusions are coarsened, so that the drawability is significantly reduced, and the wire is frequently broken during the wire drawing. Therefore, the content of O is set to 0.0020% or less.

Fn1: 6 × 10 ⁻⁶ or less Ti combines with N to form TiN. When the TiN is coarse, it becomes a starting point of the wire break during the wire drawing, so that the wire drawing workability is deteriorated. The size of the TiN has a close relationship with the precipitation temperature in steel, and becomes larger as the precipitation proceeds at higher temperatures. The deposition temperature of TiN is fn1 represented by the above equation.
When this value exceeds 6 × 10 ⁻⁶ , the temperature at which TiN precipitates increases, the TiN coarsens, and the wire drawing workability decreases. Therefore, the value of fn1 is set to 6 × 10 ⁻⁶ or less.

Fn2: 0.0035% or less N dissolved in a steel matrix is fixed to dislocations during cold drawing and increases the strength of the steel wire. Workability is reduced. N is Ti,
Because it has a strong tendency to form TiN and BN by combining with B,
The above-mentioned amount of solute N can be estimated by fn2 represented by the above formula, and when this value exceeds 0.0035%, the wire drawing workability is greatly reduced. Therefore, the value of fn2 is set to 0.0035% or less.

If the contents of Sn, As and Sb as impurity elements are restricted, the wire drawing workability can be further improved. For this reason, when extremely excellent drawability is required, Sn, As, and S in addition to the various elements described above.
The content of b should be strictly limited. Therefore,
In the invention of (2), the impurity elements Sn, As
And the contents of Sb are limited as follows.

Sn: 0.005% or less Sn is mixed in as an impurity element especially when scrap is used as a steelmaking raw material. When the content is limited to 0.005% or less, extremely good drawing workability can be obtained. Can be Therefore, the content of Sn is set to 0.005% or less.

As: 0.003% or less As is mixed as an impurity element particularly when scrap is used as a steelmaking raw material, but if the content is limited to 0.003% or less, extremely good drawability can be obtained. Can be Therefore, the amount of As is set to 0.003% or less.

Sb: 0.003% or less Sb is also mixed as an impurity element, particularly when scrap is used as a steelmaking raw material, but if the content is limited to 0.003% or less, extremely good drawability can be obtained. Can be Therefore, the content of Sb is set to 0.003% or less.

(B) Diameter and TS of Wire Rod In addition to the chemical composition of the above item (A), the diameter and TS of the wire rod of the invention of (3) are also specified.

When manufacturing a steel wire for a steel cord or a steel wire for a sawing wire, in order to reduce the cost by omitting an intermediate treatment step, the diameter of the wire to be subjected to cold working should be as small as possible. It is particularly preferable that the thickness be 6 mm or less. On the other hand, if the diameter of the wire is reduced, the productivity is lowered, and the wire is frequently broken or flawed during hot rolling. Therefore, the lower limit of the diameter is preferably 4 mm.

By setting the TS of the wire to a specific range according to the C content, that is, by using the results shown in Tables 3 and 4 in Examples described later, the steel satisfying the chemical composition of the invention of (2) can be obtained. As can be seen from FIG. 1, where TS (MPa) is plotted on the vertical axis and C content is plotted on the horizontal axis, TS is 1120 ° C. (%).
^{/0.9} 1/2 ~1300 {C (%} ) / 0.9} 1/2 MP
With a, extremely good drawability can be obtained.

Therefore, in the invention of (3), the diameter of the wire having the chemical composition of the above item (A) is 4 to 6 m.
m, TS is 1120 ° C (%) / 0.9% ^{1/2 to} 130
0 ° C (%) / 0.9% ^1/2 MPa. As shown in the examples, the value of the drawing in the tensile test is also related to the drawability, and when the drawing is 35% or more, the drawability is improved. Plus 3
It is more preferable that the diaphragm has an aperture of 5% or more.

A hole die was used for the wire having the chemical composition described in the above item (A) or the wire having the chemical composition described in the above item (A) and the diameter and TS described in the above item (B). Normal cold working such as wire drawing, wire drawing using a roller die, so-called "2 roll rolling mill", "3 roll rolling mill" or cold rolling using "4 roll rolling mill" A steel wire is machined. Assuming that the amount of processing in the cold state is 2.35 in true strain, the diameter of 5.35 which is currently commonly used as a material for steel wires for steel cords and steel wires for sawing wires.
Since a 5 mm wire can be processed into a 1.7 mm steel wire, the intermediate processing step already described can be omitted in many cases. Therefore, in the invention of (4), the lower limit of the cold working amount of the steel wire is set to 2.35 in true strain. Further, when the cold working amount is 3.0 in true strain, a commonly used diameter of 5.
Since a 5 mm wire can be directly processed into a 1.2 mm steel wire, the true strain is preferably 3.0 or more.

An ultrafine steel wire for a steel cord or a sawing wire is produced by the method of the invention (5). That is, normal cold working is performed on a wire having the chemical composition described in the above item (A) or a wire having the chemical composition described in the above item (A) and the diameter and TS described in the item (B). After applying, final heat treatment (patenting treatment) in the usual way
And, such as brass plating, Cu plating, Ni plating, etc., subjected to plating treatment for the purpose of reducing the drawing resistance in the process of the next wet drawing and improving the adhesion with rubber,
Further, ultrafine steel wire is manufactured by performing wet drawing.

The thus obtained ultrafine steel wire 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.

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

[0070]

EXAMPLES Steels A to Z having the chemical compositions shown in Tables 1 and 2
The steels A1 to F1 were melted using a 150 kg vacuum melting furnace. Steels BD in Table 1 and Steels FO and Steels A1 to F1 in Table 2 are examples of the present invention in which the chemical composition is within the range defined by the present invention. On the other hand, steel A and steel E in Table 1 and steels P to Z in Table 2 are comparative examples in which any of the components is out of the range of the content specified in the present invention.

[0071]

[Table 1]

[0072]

[Table 2]

Next, these steels were hot-forged into a round bar having a diameter of 80 mm by a usual method, heated to 1150 ° C., and then hot-rolled into a rod having a diameter of 5.5 mm at a finishing temperature of 880 ° C. Then, it was cooled under four conditions. That is, after the completion of the hot rolling, cooling was performed under four conditions of standing cooling, weak cooling, medium cooling, and strong cooling. 80 in each of the above cooling conditions
The average cooling rate of 0 to 600 ° C. is 5 ° C./sec and 12 ° C.
/ Sec, 18 ° C / sec, and 25 ° C / sec.

The tensile properties and structure of each wire cooled to room temperature were examined. The structure observed with a scanning electron microscope was mainly pearlite for all the wires.

Next, the wire obtained as described above is pickled by an ordinary method, descaled, and subjected to a zinc phosphate coating treatment as a lubrication treatment. Dry drawing was performed to a diameter of 1.0 mm with a pass schedule of 20%. At this time, when the wire was not broken even when the wire was drawn to a diameter of 1.7 mm or less, it was evaluated that the wire drawing workability was good. Incidentally, the true strain when drawing from 5.5 mm in diameter to 1.7 mm in diameter is 2.35.

Tables 3 and 4 summarize the cooling conditions of the wire rod hot-rolled to 5.5 mm in diameter and the results of the above-mentioned investigations. In Tables 3 and 4, the cooling conditions for the wire rods are as follows: conditions a to d, in order of cooling, weak air cooling, medium air cooling, and strong air cooling. FIG. 1 shows the effects on the wire drawing workability of the steel satisfying the chemical composition of the invention (2), with TS (MPa) on the vertical axis and C content on the horizontal axis.

[0077]

[Table 3]

[0078]

[Table 4]

As is clear from Tables 3 and 4, and FIG.
In the case of the test numbers using the steels A, E and P to Z of the comparative example, that is, the C content was as low as 0.73% but Al and in
sol. The content of Al is 0.0020% and the content of 0.
Test number 1 exceeding 0012%, C content 0.92%
No. 14-17, B content 0.005%
Test No. 37 having a P content of more than 0.012%, Test No. 38 having a P content of more than 0.0020%, Test No. 39 having a P content of more than 0.0020%, insol. The content of Al is 0.001
Test No. 40 exceeding 2%, Test No. 41 having an N content exceeding 0.005%, Test Nos. 42 to 44 having a value of fn1 represented by the above formula exceeding 6.0 × 10 ⁻⁶ , Test numbers 45 and 46 in which the value of fn2 represented exceeds 0.0035%, and test number 47 in which the O content exceeds 0.0020% have poor drawability, and are broken at a wire diameter larger than 1.7 mm in diameter. did.

In comparison with the above comparative examples, test numbers using the steel of the present invention, that is, test numbers 2 to 13, 18 to 36
And in the case of 48 to 53, the wire drawing workability is good,
No wire breakage occurred when the wire was drawn from 5.5 mm to 1.7 mm in diameter.

Among the test numbers using the steels of the examples of the present invention, the contents of Sn, As, and Sb as the impurity elements in the steel are low, and are 0.005% or less, 0.003% or less, and 0. 003% or less, or the TS of the wire
Is 1120 ｛C (%) / 0.9｝ ^{1/2 to} 1300 ｛C (%)
/0.9} If a ^1/2 MPa (Test No. 2,6,1
0, 21, 24, 25, 49, 51 and 53), even when drawn from 5.5 mm to 1.5 mm in diameter, did not break, and the wire drawing processability was further improved. Furthermore, the contents of Sn, As, and Sb as impurity elements in steel are each 0.0%.
05% or less, 0.003% or less, 0.003% or less,
Moreover, the TS of the wire is 1120 ° C (%) / 0.9 °.
^{In the case of 1/2 to} 1300 ° C (%) / 0.9｝ ^1/2 MPa (test numbers 3 to 5, 7 to 9, 11 to 13, 18 to 2)
0, 22, 23, 30 to 36, 48, 50, and 52), the wire was not broken even when drawn from 5.5 mm to 1.2 mm in diameter, and the wire drawing workability was extremely excellent.

[0082]

Since the wire of the present invention is excellent in wire drawing workability, it is possible to provide a steel cord, a sawing wire and the like using the wire as a material at a high yield with a high productivity.

[Brief description of the drawings]

FIG. 1 is a graph showing TS on a vertical axis for a part of steel used in Examples.
(MPa), and the C content is plotted on the horizontal axis, and the effect on wire drawing workability is arranged.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Shoji Nishimura, Inventor F-term, 4K032 AA01 AA02 AA06 AA08 AA09 AA10 AA11 AA14 AA16 AA19 AA21 AA22 AA23 AA26 AA27 AA29 AA31 AA35 AA36 AA37 AA40 BA02 CM01

Claims (5)

[Claims] (1) C: 0.75 to 0.92% by weight, S
i: 0.1 to 1.0%, Mn: 0.1 to 1.0%, C
r: 1.0% or less, Cu: 0.5% or less, Ni: 1.0
% Or less, Co: 2.0% or less, Mo: 0.5% or less,
W: 0.5% or less, V: 0.2% or less, Nb: 0.1%
REM (rare earth element): 0.03% or less, C
a: 0.003% or less, Mg: 0.003% or less, B:
0.005% or less, the balance is composed of Fe and unavoidable impurities, Al in the impurities is 0.0020% or less, i
nsol. Al is 0.0012% or less, Ti is 0.00
20% or less, N is 0.005% or less, P is 0.012%
Hereinafter, S is 0.01% or less, and O (oxygen) is 0.0020.
% Or less, and the value of fn1 represented by the following formula is 6 ×
A steel wire rod having a value of 10 ⁻⁶ or less and a value of fn2 represented by the following formula of 0.0035% or less. fn1 = Ti (%) x N (%) ... fn2 = N (%)-1.3B (%)-0.3 Ti (%) ... 2. The composition according to claim 2, wherein Sn is added as an impurity in an amount of 0.1% by weight.
005% or less, As is 0.003% or less, and Sb is 0.0
The steel wire according to claim 1, which is not more than 03%. 3. It has the chemical composition according to claim 1 or 2,
The diameter is 4-6mm and the tensile strength is 1120 ° C (%) /
0.9｝ ^{1/2 to} 1300 ｛C (%) / 0.9｝ ^1/2 MPa
Is a steel wire rod. 4. A steel wire obtained by cold working the steel wire according to claim 1 with a true strain of 2.35 or more. 5. A method for producing a steel wire, comprising subjecting the steel wire according to claim 1 to cold working, followed by final heat treatment, plating, and wet drawing.