JP2003201540A - Steel wire and steel wire - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steel wire having a small variation in strength, which is suitable for a steel cord used as a reinforcing material for a radial tire of an automobile, and a steel wire made of the steel wire under high productivity. To provide good yields at low cost. SOLUTION: C: 0.7 to 1.1%, Si: 0.1 to 1%, M
n: 0.1 to 1%, Mo: 0.01 to 0.2%, with the balance being Fe and impurities, Al: 0.002% or less, Ti: 0.002% or less, P: 0.012% or less, S: 0.010
% Or less, N: 0.005% or less and O: 0.002% or less, and satisfy the following expressions (1) and (2). 6 <6 × Si (%) + 7 × Mn (%) + 9 × Cr (%) + 60 × Mo (%)-200 × Nb (%)-1.5 × Co (%) <11・ ・ (1) N (%)-(14/48) × Ti (%)-(14/11) × B (%) ≧ 0 ・ ・ ・ ・ ・ ・ ・ (2)

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a steel wire rod and a steel wire. More specifically, the present invention relates to a steel wire material and a steel wire suitable for applications such as a radial tire of an automobile, various industrial belts, a steel cord used as a reinforcing material for various hoses, and a sewing wire.

[0002]

2. Description of the Related Art FIG. 1 is an explanatory view showing an example of a manufacturing process of a steel cord used as a reinforcing material for radial tires of automobiles, various industrial belts, and various hoses. As shown in the figure, the steel wire for steel cord is generally a steel wire rod having a wire diameter (diameter) of 5 to 6 mm obtained by hot-rolling a round bar, which is a raw material, and then adjusting and cooling it. Primary wire drawing is performed to make the diameter 3-4 mm, then patenting treatment is performed, and then secondary wire drawing is performed to
The diameter is 2 mm. After this, a final patenting treatment is carried out, then brass plating is carried out, and further final wet drawing is carried out to obtain a diameter of 0.15 to 0.4 mm. Further, a steel cord is manufactured by performing a twisting process in which a plurality of the ultrafine steel wires thus obtained are twisted to form a twisted steel wire.

As a steel wire rod which is a raw material of such a steel wire, as disclosed in JP-A-2000-309849, C:
0.75 to 0.92% (hereinafter, "%" in the present specification means "mass%" unless otherwise specified)
, Si: 0.1 to 1.0%, Mn: 0.1 to 1.0%, Cr: 1.0%
Below, 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: 0.03% or less, Ca: 0.003%
Below, containing Mg: 0.003% or less, B: 0.005% or less,
As impurities, Al: 0.0020% or less, Ti: 0.0020% or less,
N: 0.005% or less, P: 0.012% or less, S: 0.01% or less, O: 0.0020%, Ti × N ≦ 6 × 10 ⁻⁶ %, N−
Steel wire rods with 1.3 B-0.3 Ti ≤ 0.0035% are known.

By the way, in order to increase the strength of the product,
It is effective to increase the strength after the final patenting treatment. Therefore, the structure after the final patenting treatment is generally a pearlite structure with a small lamella spacing.

In order to obtain such a structure, it is necessary to heat it to the austenite region, then rapidly cool it to a temperature range of 550 to 600 ° C., and transform it in that temperature range. For this reason, the patenting process using a lead bath was widely used before, but in recent years, to improve the working environment, the bottom part has been put into a tank containing powder such as aluminum oxide, zirconium oxide and carbon powder. A fluidized bed furnace that uses a fluidized bed formed by suspending the powder by blowing air from below a ventilation plate provided in the plant is often used.

[0006]

However, since this fluidized bed has a lower heat transfer coefficient than that of the lead bath, there are problems (1) to (4) listed below. (1) Since the cooling rate of the processed product becomes low, transformation may start during cooling and the strength may decrease. (2) In order to increase the cooling rate, the fluidized bed is divided into two zones, and the temperature of one zone is often set lower than the temperature of the other zone. Since there is variation in control, the bainite structure may be mixed in the pearlite structure due to overcooling, and the strength is not stable. (3) When the pearlite transformation progresses rapidly, transformation heat is generated.Therefore, heat removal in the fluidized bed is small, and the temperature of the steel wire rises during the patenting treatment in the fluidized bed, which raises the pearlite transformation temperature. Is reduced. (4) The variation in strength after the final heat treatment is further increased by the final wet wire drawing, which causes variation in the strength of the product. Further, when the bainite structure is mixed, the work hardening amount due to wire drawing becomes small, and the strength of the final product decreases.

As described above, even with the conventional technique, it was not possible to reduce the variation in strength after the final heat treatment and prevent the mixture of bainite structures. The present invention is
It has been made in view of such problems of the conventional technology, and is suitable for use in, for example, radial tires of automobiles, various industrial belts, steel cords used as reinforcements for various hoses, and further sewing wires. It is another object of the present invention to provide a steel wire rod having a small variation in strength and a steel wire made of the steel wire rod at a low cost with high productivity under high productivity.

[0008]

The present invention provides C: 0.7-1.
1%, Si: 0.1-1%, Mn: 0.1-1%, Mo: 0.01-0.
It contains 2% and the balance is Fe and impurities. Al: 0.002% or less, Ti: 0.002% or less, P: 0.
012% or less, S: 0.01% or less, N: 0.005% or less, and O: 0.002% or less, and the following formula (1) and
The steel wire rod is characterized by satisfying the equation (2). 6 <6 × Si (%) + 7 × Mn (%) + 9 × Cr (%) + 60 × Mo (%)-200 × Nb (%)-1.5 × Co (%) <11・ ・ (1) N (%)-(14/48) × Ti (%)-(14/11) × B (%) ≧ 0 ・ ・ ・ ・ ・ ・ ・ (2) Steel wire according to the present invention In addition, Nb: 0.
003 to 0.016% and / or B: 0.0003 to 0.0035
% Is preferable in order to secure sufficient wire drawability.

Further, in these steel wire rods according to the present invention, Cr: 0.1 to 1% and / or C
It is preferable that the content of o: 0.2 to 2% is contained in order to enhance the strength.

Further, in order to improve hot workability, the steel wire rod according to the present invention further contains Ca: 0.0001 to 0.003% and / or Mg: 0.0001 to 0.003%. desirable.

From another point of view, the present invention has the above-mentioned steel composition and the following with respect to the tensile strength after the final wet drawing.
The steel wire is characterized by having a standard deviation of 30 MPa or less, which is obtained by the equation (3).

[0012]

[Equation 2]

However, in the equation (3), TSm is 20 of the steel wire.
Shows the average value of the tensile strength at 20 points measured at m intervals.
i indicates the measured value of the tensile strength at the i-th measurement point of 20 points.

In the present invention, the "steel wire material" means a material as hot-rolled. The "steel wire" means a wire rod that has been cold rolled or drawn. As described above, the present invention is, in brief, the variation in the strength of the steel wire (standard deviation) according to the formula (1), which is an invention specifying matter not found in the invention disclosed in JP 2000-309849 A mentioned above. ) Is remarkably reduced to such an extent that there is no problem.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a steel wire rod and a steel wire according to the present invention will be described in detail below. We have
As a result of investigating and studying the influence of the composition of the wire on the variation in the tensile strength of the steel wire after the final heat treatment,
The findings (a) to (g) listed below were obtained.

(A) Currently, most of wire rods used for applications such as steel cords and sawing wires contain Si and Mn, which are elements that greatly affect hardenability, and their contents are Si: 0.1 to 0.3. %, Mn: 0.3 to 0.5%. However, since the hardenability is low, the patenting treatment using the fluidized bed causes large variations in strength.

(B) In the steel wire of the conventional composition, the pearlite transformation is rapidly progressing in the fluidized bed, which causes transformation heat generation, which raises the temperature during transformation and makes the strength unstable. (c) Mo can reliably delay the progress of pearlite transformation even with a small amount of content.Therefore, if Mo is included, variations in strength are remarkable even when performing patenting treatment using a fluidized bed. Suppressed to. However, when the Mo content is too large, the time until the pearlite transformation ends is too long, the pearlite transformation does not end in the fluidized bed, and a martensite structure is formed in the subsequent cooling process, resulting in wire drawability. It gets extremely bad.

(D) Cr, which may be contained in order to increase the strength, has a smaller effect than Mo, but has an effect of delaying the pearlite transformation. (e) Co, which may be contained for the purpose of increasing the strength, and Nb, which may be contained for the purpose of improving the wire drawability, both have the effect of accelerating the pearlite transformation.

(F) By optimizing the composition of the steel wire rod by combining the findings of the above items (a) to (d), the variation in strength after the final heat treatment is small, and the productivity is not reduced. The transformation can be terminated in the fluidized bed.

(G) B is likely to combine with N to form BN, which has the effect of reducing the free N in the steel and increasing the wire drawability, but if B alone exists in the steel, it has hardenability. It is not preferable because it becomes too large and a martensite structure is generated. However, since it is difficult to control the amount of B alone, it is effective to use B as a compound in the steel in order to reduce the variation in strength. Therefore, by controlling the contents of B, Ti, and N, including Ti, which is more likely to combine with N than B, the amount of B existing alone in steel can be almost eliminated, and the effect on hardenability is eliminated. be able to.

The present invention has been made on the basis of these findings (a) to (g), and by optimizing the composition of the steel wire rod, it is possible to perform patenting treatment using a fluidized bed. Since it suppresses the variation in strength after the final heat treatment, the optimum composition of the steel wire will be described below.

C: 0.7 to 1.1% C is an element effective for increasing the strength of the wire. However, when the C content is less than 0.7%, it becomes difficult to stably give a high strength such as 3000 MPa in tensile strength to the final product. On the other hand, if the C content exceeds 1.1%, the steel material becomes hard and the drawability deteriorates. In particular, when the C content exceeds 1.1%, it becomes difficult to prevent the formation of pro-eutectoid cementite, that is, cementite along the austenite grain boundaries, and wire breakage frequently occurs during wire drawing. Therefore, in the present invention, the C content is limited to 0.7% or more and 1.1% or less. From the same viewpoint, it is desirable that the lower limit be 0.8%.

Si: 0.1 to 1% Si is an element that is effective for increasing the strength and also improves the hardenability. Further, it is an element necessary as a deoxidizing agent. However, if the Si content is less than 0.1%, such an effect is not observed, while if the Si content exceeds 1%, the limit workability in wire drawing is lowered. Therefore,
In the present invention, the Si content is limited to 0.1% or more and 1% or less. From the same viewpoint, the upper limit of the Si content is preferably 0.5%, and the lower limit is preferably 0.2%.

Mn: 0.1 to 1% Mn is an element effective for increasing the strength and also improving the hardenability. In addition, S in steel is Mn
It also fixes as S, and also has an effect of preventing hot brittleness. However, if the Mn content is less than 0.1%, it is difficult to obtain this effect.
On the other hand, Mn is an element that easily segregates, and when it exceeds 1%, it is segregated particularly in the center of the wire, and a martensite structure or bainite structure is easily generated in the center of the wire after hot rolling.
The frequency of wire breakage during primary wire drawing increases. Therefore, in the present invention, the Mn content is limited to 0.1% or more and 1% or less. From the same viewpoint, the upper limit of the Mn content is preferably 0.5%, and the lower limit is preferably 0.2%.

Mo: 0.01 to 0.2% Mo has the effect of greatly improving the hardenability, and thereby has the effect of reducing the variation in strength. In order to reliably obtain such effects, Mo is preferably contained in an amount of 0.01% or more. On the other hand, if the Mo content exceeds 0.2%, the hardenability becomes too high, and a martensite structure is easily generated in the structure after the patenting treatment using the fluidized bed, which deteriorates the wire drawability. Therefore, in the present invention, the Mo content is 0.01%
The limit is not less than 0.2%. From the same viewpoint, the upper limit of the Mn content is preferably 0.1% and the lower limit is preferably 0.02%.

In the present embodiment, the balance other than the above is Fe
And impurities. Here, Al: 0.
002% or less, Ti: 0.002% or less, P: 0.012% or less,
S: 0.01% or less, N: 0.005% or less and O: 0.002%
The following is exemplified. Therefore, the impurity elements Al, Ti,
The reasons for limiting the contents of P, S, N and O will be described.

Al: 0.002% or less Al forms oxide-based inclusions containing Al ₂ O ₃ as a main component and reduces wire drawability. Especially the Al content is 0.002%
If it exceeds, the oxide-based inclusions are coarsened, wire breaks frequently occur during wire drawing, and the wire drawing workability is significantly deteriorated. Therefore, in the present invention, the Al content is limited to 0.002% or less.

Ti: 0.002% or less Ti combines with N to form TiN. This TiN becomes a starting point of disconnection during wire drawing, so that wire drawability is deteriorated. In particular, when the content exceeds 0.002%, TiN is coarsened and wire breakage frequently occurs during wire drawing, resulting in a remarkable decrease in wire drawing workability. Therefore, in the present invention, the Ti content is 0.002
% Or less.

[0029] P: 0.012% or less P segregates at the grain boundaries and reduces wire drawability. In particular,
If the P content exceeds 0.012%, the wire drawing workability is significantly deteriorated. Therefore, in the present invention, the P content is limited to 0.012% or less.

S: 0.01% or less S reduces wire drawing workability. Especially, S content is 0.01%
If it exceeds, the wire drawing workability is significantly deteriorated. Therefore, in the present invention, the S content is limited to 0.01% or less.

N: 0.005% or less N sticks to dislocations during cold wire drawing to increase the strength of the steel wire, but reduces wire drawability. In particular, N
If the content exceeds 0.005%, the wire drawing workability deteriorates significantly. Therefore, in the present invention, the N content is limited to 0.005% or less.

O: 0.002% or less O forms oxide inclusions and deteriorates wire drawability. In particular, when the O content exceeds 0.002%, the oxide-based inclusions are coarsened, so that the wire drawing workability is remarkably deteriorated, resulting in frequent disconnection during wire drawing. Therefore, in the present invention, the O content is limited to 0.002% or less.

Further, the steel wire rod of the present embodiment contains Nb: 0.003 to 0.016% and / or B: 0.0003 to 0.0035% in order to secure sufficient wire drawability.
Cr: 0.1 to 1% to increase strength, and / or
It is desirable to contain Co: 0.2 to 2%, and further to contain Ca: 0.0001 to 0.003% and / or Mg: 0.0001 to 0.003% in order to enhance hot workability. Therefore, these optional additional elements will be described below.

Nb: 0.003 to 0.016% Nb has a function of refining austenite crystal grains and enhancing wire drawing workability. Further, it is an element that reduces hardenability. However, when the Nb content exceeds 0.016%, coarse NbC is generated and becomes a starting point of wire breakage during wire drawing, so that wire drawability is deteriorated. Therefore, when adding Nb, it is desirable to limit its content to 0.016% or less. However, since Nb is an element that easily causes solidification and segregation, coarse NbC
In order to reliably prevent the formation of Nb, it is more desirable that the Nb content is less than 0.010%. On the other hand, the Nb content is 0.003
If it is less than%, it is difficult to obtain the above-mentioned effect, so Nb
The lower limit of the content of 0.003% was 0.003%.

B: 0.0003 to 0.0035% B has an effect of combining with N dissolved in steel to form BN, reducing the dissolved N, and improving drawability. In order to reliably obtain such effects, N and Ti as impurity elements are
It is desirable to contain 0.0003% or more although it depends on the content of. However, if B is contained in an amount of more than 0.0035%, the formula (2) described later is not satisfied in many cases, the hardenability is improved, and the martensite structure is mixed in the steel wire after the final patenting treatment. As a result, variations in strength increase and the frequency of wire breakage during wire drawing increases. Therefore, when B is added, its content is preferably limited to 0.0035% or less.

Cr: 0.1 to 1% Cr has the effect of reducing the lamellar spacing of pearlite and increasing the strength after rolling and after patenting. Further, it has a function of increasing the work hardening rate during cold working such as wire drawing. Furthermore, it is an element that improves hardenability. To ensure this effect, the Cr content should be 0.1%.
The above content is preferable. However, Cr content is 1%
When it exceeds, a martensite structure and a bainite structure are generated in the central part of the wire rod after hot rolling, so that the frequency of wire breakage during primary wire drawing increases. Therefore, when Cr is added, its content is preferably limited to 0.1% or more and 1% or less.

Co: 0.2 to 2% Co has the effect of preventing the precipitation of pro-eutectoid cementite, and further refining the lamellar spacing of the pearlite structure to increase the strength. To ensure this effect, the Co content should be 0.2.
It is better to set it to% or more. However, when the Co content exceeds 2%, such an effect is saturated and the cost is increased. Therefore, when Co is added, its content is 2%.
It is desirable to limit to the following.

Ca: 0.0001 to 0.003% Ca has an effect of enhancing hot workability. In order to reliably obtain this effect, the Ca content is preferably 0.0001% or more. However, even if Ca is contained in an amount of more than 0.003%, the effect is saturated and the cost is increased. So Ca
If added, the content should be 0.0001% or more and 0.003% or more.
It is desirable to limit it to less than or equal to%.

Mg: 0.0001 to 0.003% Mg has the effect of enhancing hot workability. In order to surely obtain such an effect, it is preferable that the content of Mg be 0.0001% or more. However, even if the content of Mg exceeds 0.003%, the effect is saturated and the cost is increased. So Mg
If added, the content should be 0.0001% or more and 0.003% or more.
It is desirable to limit it to less than or equal to%.

Further, the steel wire rod according to the present embodiment is (1)
Formula: 6 <6 × Si (%) + 7 × Mn (%) + 9 × Cr (%) + 60 × Mo (%)-20
0 × Nb (%)-1.5 × Co (%) <11, and (2) Formula: N (%)-
(14/48) × Ti (%)-(14/11) × B (%) ≧ 0 are both satisfied. Therefore, these will also be described below.

(1) Formulas Steels A to Y having the compositions shown in Table 1 have a diameter of 3.2 mm.
A specimen for measuring thermal expansion having a diameter of 3 mm and a length of 10 mm was taken from the cold drawn wire of No. 3, heated to 985 ° C at an average heating rate of 50 ° C / sec, and then held at 985 ° C for 10 seconds, and then averaged. Cooling rate 70
After cooling to 575 ° C at ℃ / sec, hold at that temperature,
The thermal expansion curve was measured.

[0042]

[Table 1]

The transformation end time was determined from the thermal expansion curve thus measured, and the results are shown in Table 2.

[0044]

[Table 2]

Assuming that the effects of Si, Mn, Cr, Mo, Nb and Co on the transformation end time are independent of each other, from the results shown in Tables 1 and 2, the formula for obtaining the pearlite transformation end time is 6 × Si (%) + 7 × Mn (%) + 9 × Cr (%) + 60 ×
Mo (%)-200 x Nb (%)-1.5 x Co (%) ".

Further, steels A to Y having the compositions shown in Table 1
A cold drawn wire having a diameter of 1.5 mm was made to undergo patenting treatment using a fluidized bed using the apparatus schematically shown in FIG.

At this time, the linear velocity was set to 10 m / min, and the heating furnace was set so that the temperature of the steel wire rod was kept at 980 to 1000 ° C. for 10 to 20 seconds. In addition, the connection part is set in a nitrogen atmosphere and set at 580 ° C. One zone of the fluidized bed is 540 ° C, and two zones are 580 ° C.
Set to.

Each of the steels A to Y was subjected to a patenting treatment with a length of 500 m, and a tensile test piece was taken every 20 m.
Tensile tests were conducted with 20 surveys for each steel. Table 2 shows the standard deviation of tensile strength obtained from the results.

From the experience based on the studies so far, it was evaluated that the variation was small if the standard deviation of the tensile strength was 10 MPa or less. Standard deviation of tensile strength is 10 MPa
What became the following was "6 x Si (%) + 7 x Mn (%) +
The value of “9 × Cr (%) + 60 × Mo (%)-200 × Nb (%)-1.5 × Co (%)” was greater than 6 and less than 11.

Therefore, in the present invention, “6 <6 × Si
(%) + 7 × Mn (%) + 9 × Cr (%) + 60 × Mo (%)-200 × Nb (%)-1.5
× Co (%) <11 ”was defined. (2) Since both formulas Ti and B are extremely likely to bond with N, if N exceeds (Ti + B) in molar content, so-called free B existing in the steel can be made substantially zero. it can.
Since Ti and N form TiN, B and N form BN, and the atomic weight of each is Ti: 48, B: 11, and N: 14, "N (%)-(14/48) Ti (%)-(14/11) B (%)
≧ 0 ”.

In the present embodiment, the steel wire rod having such a composition is subjected to hot rolling, controlled cooling, primary wire drawing, patenting and secondary wire drawing, followed by final heat treatment, plating treatment and wet wire drawing. Was carried out to manufacture a steel wire. And
With respect to the steel wire thus obtained, the standard deviation of the tensile strength after the final patenting treatment was determined.

That is, for the steels A to Y shown in Table 1, with a pass schedule in which the area reduction rate of each die is 15% on average for a length of 100 m not used in the tensile test,
Wet wire drawing was performed from a diameter of 1.5 mm to a diameter of 0.20 mm.
About this 0.20mm diameter steel wire, 20 times each for every 20m in length,
A tensile test was conducted.

As a result, the standard deviation of the tensile strength before drawing was
If it is 10MPa, the standard deviation of tensile strength after wire drawing is 30MPa.
It was confirmed that the variation was sufficiently small as a steel cord product.

Therefore, in the present invention, the standard deviation of the tensile strength of the steel wire after the final heat treatment is defined as 30 MPa or less. As described above, in the present embodiment, the ultrafine steel wire for the steel cord and the sawing wire is subjected to the ordinary cold working on the steel wire rod having the chemical composition described above, and then subjected to the final heat treatment by the ordinary method. (Patenting treatment), and further plating treatment such as brass plating, Cu plating or Ni plating for the purpose of reducing pull-out resistance in the next wet drawing process and improving adhesion with rubber, Further, by performing wet drawing, an ultrafine steel wire is manufactured.

The ultrafine steel wire thus obtained is then processed into a predetermined final product. For example, a steel cord is manufactured by further twisting a plurality of extra fine steel wires by a twisting process to form a twisted steel wire.

Since the steel wire rod and the steel wire of the present embodiment obtained in this way have small variations in strength and are provided at a low cost with high productivity and high productivity, they can be used, for example, in radial tires of automobiles and various types. It is suitable for industrial belts, steel cords used as reinforcing materials for various hoses, and sewing wire.

[0057]

The present invention will be described in detail below with reference to examples. Steels A to Y having the chemical compositions shown in Table 1 above are
It was melted using a 180 kg vacuum furnace. Steel C in Table 1
H, K, L, N, O, Q and S are examples of the invention within the scope of the invention. On the other hand, steels A and B in Table 1
I, J, M, P, R and T to Y are comparative examples outside the scope of the present invention.

Then, these steels were hot forged by a usual method to form a round bar having a diameter of 80 mm, and then this steel having a diameter of 80 mm was used.
The rod was heated to 1180 ° C, then hot-rolled to a diameter of 5.5 mm at a rolling finishing temperature of 880 ° C, and cooled by a usual method.

The steel wire rod thus obtained was successively subjected to primary wire drawing, primary patenting treatment and secondary wire drawing to obtain a steel wire with a diameter of 1.5 mm. Furthermore, this diameter 1.
A 5 mm steel wire was subjected to patenting treatment using a fluidized bed using the apparatus shown in FIG. Zirconium oxide was used as the heat medium of the fluidized bed. The linear velocity in the patenting process using this fluidized bed was set to 10 m / min, and the heating furnace was set so that the temperature of the steel wire was maintained at 980 to 1000 ° C for 10 to 20 seconds. The connection part was set to 580 ° C. in a nitrogen atmosphere, and one zone of the fluidized bed was set to 540 ° C. and two zones were set to 580 ° C.

Each steel was subjected to a patenting treatment with a length of 500 m, tensile test pieces were taken every 20 m, and each steel was subjected to a tensile test with a test number of 20 to determine the average tensile strength and the tensile strength, respectively. The standard deviation of was calculated.

Further, for the steels A to Y shown in Table 1,
Wet-drawing was carried out to a diameter of 0.20 mm by a pass schedule in which the surface reduction rate of each die was 15% on average for the patented material using a fluidized bed of 100 m in length that was not used in the tensile test. . This 0.20 mm diameter steel wire was subjected to a tensile test 20 times for each 20 m length. Also for this, the average tensile strength and the standard deviation of each tensile strength were determined.

Table 2 shows the results of these tests.
In addition, it was judged that the wire drawability was poor if the wire was drawn once even when drawn from the diameter of 1.5 mm to 0.20 mm shown in Table 2. From Table 2, in Test Nos. 1, 2, and 13 in which the value of the formula (1) in the present invention is less than 6, the standard deviation of the tensile strength of the drawn wire with a diameter of 0.20 mm exceeds the target value of 30 MPa. Cage,
Moreover, the standard deviation of the tensile strength of the patenting material using a fluidized bed with a diameter of 1.5 mm exceeded 10 MPa. Of these, Test No. 13 had a Nb content of more than 0.016%, and thus had poor wire drawability.

Further, in the test numbers 9 and 18 in which the value of the formula (1) exceeds 11, the standard deviation of the tensile strength of the drawn wire having a diameter of 0.20 mm exceeds the target value of 30 MPa, and the diameter of 1.5 mm Standard deviation of tensile strength of patenting material using fluidized bed is 10MP
It exceeded a, and wire drawing workability also deteriorated.

Further, the test number in which the value of the expression (1) exceeds 11
In Nos. 10 and 20, wire drawing workability of 0.20 mm was not obtained because wire drawing workability was extremely poor, and the standard deviation of the tensile strength of the patenting material using a fluidized bed of 1.5 mm in diameter exceeded 10 MPa. It was

On the other hand, in the test number 16 in which the value of the formula (2) is less than 0.0000, the standard deviation of the tensile strength of the drawn wire with a diameter of 0.20 mm exceeds the target value of 30 MPa, and the fluidized bed with a diameter of 1.5 mm is used. The standard deviation of the tensile strength of the patenting material using
The wire drawing workability was also deteriorated.

Test number 21 in which the Al content as an impurity exceeds 0.002%, test number 22 in which the N content exceeds 0.0050%, test number 23 in which the Ti content exceeds 0.002%, and the P content is 0.012% , Test No. 24 with S content exceeding 0.01%,
Test No. 25 in which the O content exceeds 0.002% is
The drawability was poor.

In contrast to the above comparative example, in the case of the test number using the steel of the present invention example, that is, test numbers 3 to 8, 11, 12, 1
In the case of 4, 15, 17 and 19, the standard deviation of the tensile strength of the drawn wire with a diameter of 0.20 mm is below the target value of 30 MPa, and the tensile strength of the patenting material using a fluidized bed with a diameter of 1.5 mm. Has a standard deviation of less than 10 MPa and is excellent in wire drawing workability.

[0068]

As described above in detail, according to the present invention, for example, radial tires for automobiles, various industrial belts, steel cords used as reinforcing materials for various hoses, and further applications such as sawing wires. It was possible to provide a suitable steel wire material having a small variation in strength and a steel wire made of this steel wire material with high productivity at low cost and with high productivity.

That is, since the wire rod according to the present invention has little variation in tensile strength and is excellent in wire drawing workability, a steel cord, a sewing wire or the like can be produced from this wire rod as a material with high productivity. Can be well served.

[Brief description of drawings]

[Fig. 1] Radial tires for automobiles and belts for various industries,
Furthermore, it is an explanatory view showing an example of a manufacturing process of a steel cord used as a reinforcing material for various hoses.

FIG. 2 is an explanatory view schematically showing an apparatus for performing patenting processing using a fluidized bed.

Claims (5)

[Claims] 1. In mass%, C: 0.7-1.1%, Si: 0.1
~ 1%, Mn: 0.1-1%, Mo: 0.01-0.2%,
The balance is Fe and impurities, and Al in the impurities: 0.00
2% or less, Ti: 0.002% or less, P: 0.012% or less, S:
A steel wire rod which is 0.01% or less, N: 0.005% or less, and O: 0.002% or less and satisfies the following formulas (1) and (2). 6 <6 × Si (%) + 7 × Mn (%) + 9 × Cr (%) + 60 × Mo (%)-200 × Nb (%)-1.5 × Co (%) <11・ ・ (1) N (%)-(14/48) × Ti (%)-(14/11) × B (%) ≧ 0 ・ ・ ・ ・ ・ ・ ・ (2) 2. Nb: 0.003 to 0.016 in mass%
% And / or B: 0.0003 to 0.0035%, the steel wire rod according to claim 1. 3. The steel wire rod according to claim 1, further comprising Cr: 0.1 to 1% and / or Co: 0.2 to 2% by mass. 4. Further, in mass%, Ca: 0.0001 to 0.003
% And / or Mg: 0.0001 to 0.003%, The steel wire rod according to any one of claims 1 to 3. 5. Any one of claims 1 to 4
With the steel composition described in paragraph (3), the standard deviation of the tensile strength after final wet drawing is calculated by the following equation (3).
A steel wire characterized by having a pressure of 30 MPa or less. [Equation 1] However, in Eq. (3), TSm represents the average value of the tensile strength at 20 points measured at 20m intervals of the steel wire, and TSi is the measured value of the tensile strength at the i-th measurement point of 20 points. Show.