JP3388012B2 - Method of manufacturing steel wire for steel cord with reduced delamination - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-strength, high-ductility ultrafine steel wire such as a steel cord used for reinforcing rubber and organic materials such as tires and belt cords. These steel wires are used for long rubber belts, steel tire cords, and the like.

[0002]

2. Description of the Related Art In general, drawn high carbon steel ultrafine wire such as steel cord is usually hot-rolled as necessary, and then adjusted and cooled, and a wire having a diameter of 4.0 to 5.5 mm is subjected to primary wire drawing. A final patenting treatment is performed, and then a brass plating treatment is performed, followed by final wet drawing.
Most of such ultra-fine steel wires are used as steel cords after being twisted, such as by twisting two strands and five strands. 1) Higher strength, 2) High-speed wire drawability Are excellent, 3) are excellent in fatigue properties, 4) are excellent in high-speed twistability, and the like.

Therefore, high-quality steel materials have been developed in response to demands. For example, JP-A-60-2048
No. 65 discloses that the Mn content is regulated to less than 0.3% to suppress the generation of a supercooled structure after lead patenting, and
By controlling the amounts of elements such as i and Mn, there has been disclosed an ultrafine wire with high strength and high toughness and ductility, and a high carbon steel wire material for steel cords, which has less breakage when twisted, and JP-A-63- No. 24046 discloses that the Si content is 1.00.
A high toughness and high ductility wire rod for ultrafine wires in which the tensile strength of the lead patenting material is increased and the wire drawing work ratio is reduced by setting the content to be at least 10% is disclosed.

On the other hand, a hard oxide type non-metallic inclusion is one of those which adversely affect these characteristics. Generally, among oxide-based inclusions, Al ₂ O ₃ , S
Inclusions having a single composition such as iO ₂ , CaO, TiO ₂ , and MgO have high hardness and are non-ductile. Therefore, it is a known fact that in order to produce a high carbon steel wire rod having excellent wire drawability, it is necessary to enhance the cleanliness of molten steel and to lower the melting point and soften the oxide inclusions.

As a method for improving the cleanliness of steel and softening the non-ductile inclusions as described above, Japanese Patent Publication No. 57-22969.
Japanese Unexamined Patent Publication (Kokai) No. JP-A-2004-115242 discloses a method for producing a steel for high-carbon steel wire rod having good wire drawability, and Japanese Unexamined Patent Publication (Kokai) No. 55-24961 discloses an ultra-fine wire manufacturing method. Was limited to the composition control of the ternary oxide-based nonmetallic inclusions of Al ₂ O ₃ —SiO ₂ —MnO.

On the other hand, in Japanese Unexamined Patent Publication (Kokai) No. 50-71507, the wire drawability of a product is improved by making a non-metallic inclusion a spacer tight region in the ternary phase diagram of Al ₂ O ₃ , SiO ₂ and MnO. Japanese Patent Application Laid-Open No. 50-81907 discloses a method of restricting the amount of Al added to molten steel to reduce harmful inclusions and improve drawability.

Further, in Japanese Patent Publication No. 57-35243, regarding the production of steel cords having a non-ductile inclusion index of 20 or less, a CaO-containing flux together with a carrier gas (inert gas) in a ladle molten steel under Al complete control. After injecting and pre-deoxidizing, one or two of Ca, Mg and REM
It proposes a method of softening inclusions by blowing an alloy containing at least one kind.

However, as the required quality becomes stricter, a material having higher strength and ductility has been required, and a good steel wire manufacturing method has been required.

[0009]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for producing a steel wire having high strength and ductility which cannot be achieved by the conventional steel wire.

[0010]

In order to achieve the above object, the present invention comprises: (1) C: 0.7 to 1.10% by weight, Si: 0.4
% Or less, Mn: 0.5% or less, P: 0.020% or less,
S: 0.020% or less, a balance of iron and unavoidable impurities, and an inevitable Al content of 0.003% or less of a hot-rolled wire made of steel made of steel 1) 1.1 by wire drawing To 2.7 mmφ wire, and 2) the tensile strength is {(589 + 922 × Cwt%) by patenting treatment.
−39} to {(589 + 922 × Cwt%) + 42} MP
Adjusted to a, 3) by selecting any of brass plating, Cu plating, and Ni plating on the surface by plating treatment, and 4) in wet drawing, the area reduction rate per sheet other than the final die is 10%. 25% or less of continuous drawing is performed, and 5) in final finish drawing, the area reduction rate is 2% due to the die having an approach angle of 5 ° or more and 10 ° or less.
The above processing was performed at 6% or less, and the total wire drawing area reduction rate after the final patenting treatment in 6) 4) and 5) was true strain.
The equivalent circle diameter is set to 4 or more and 4.5 or less.
(2800-1200 Log D) MP with 15-0.4mmφ
A method of manufacturing a steel wire for a steel cord, which is a high-strength steel wire having a tensile strength of a or more. However, {D: wire diameter (mm)} (2) wt% C: 0.7 to 1.10%, Si: 0.4
% Or less, Mn: 0.5% or less, P: 0.020% or less,
S: In addition to more than 0.020%, less Cr: 0.3% or less, Ni: 1.0% or less, Cu: 0.8% or less of one or more kinds
Including the above, the hot-rolled wire rod of steel consisting of balance iron and unavoidable impurities is 1) 1.1 to 2.7 mmφ wire by wire drawing and intermediate patenting, and 2) tensile strength by patenting. {(589 + 922 × Cwt%)
−39} to {(589 + 922 × Cwt%) + 42} MP
Adjusted to a, 3) brass plating, Cu plating, or Ni plating is performed on the surface by plating treatment, and 4) the area reduction rate per sheet other than the final die is 10% or more and 25% in the wet wire drawing process. The following continuous wire drawing is performed: 5) In the final finish wire drawing, a die with an approach angle of 5 ° or more and 10 ° or less is used to perform a reduction in area of 2% or more and 6% or less, 6) 4) , 5) the total wire drawing area reduction after the final patenting treatment is 3.4 or more and 4.5 in true strain.
The equivalent circle diameter is set to be 0.15 to 0.4
It is a method of manufacturing a steel wire for steel cord, which is a high-strength steel wire having a tensile strength of (2800-1200 Log D) MPa or more in mmφ.

[0011]

The present invention will be described in detail below. The reasons for limiting the steel composition of the present invention are as follows. In addition,% shown below is weight%. Although C is an economical and effective strengthening element, it is also an effective element for reducing the precipitation amount of this first-order ferrite. Therefore, the required final wire strength (2800-
In order to obtain 1200 Log D or more and D: wire diameter), C must be 0.70% or more, but if it is too high, ductility decreases and wire drawability deteriorates, so the upper limit is 1.10. %.

[0012] Si is an element necessary for deoxidizing steel, so when its content is too low, the deoxidizing effect becomes insufficient. Further, Si dissolves in the ferrite phase in the pearlite formed after heat treatment to increase the strength after patenting, but on the other hand, it reduces the ductility of ferrite and reduces the ductility of the ultrafine wire after drawing, so 0.4% Below.
As for Mn, it is desirable to add a small amount of Mn in order to secure the hardenability of steel. However, addition of a large amount of Mn causes unevenness and causes a supercooled structure such as bainite and martensite during patenting, which impairs the subsequent wire drawability, so the content is made 0.5% or less.

In the case of the high carbon steel according to the present invention, a cementite network is likely to occur in the microstructure after patenting, and a cementite having a thickness is likely to precipitate. In order to realize high strength and high ductility in this steel, it is necessary to make pearlite fine and to eliminate the cementite network and thick cementite as described above. Cr has the effect of suppressing the appearance of such abnormal portions of cementite and further refining pearlite. However, addition of a large amount increases the dislocation density in the ferrite after heat treatment, and therefore significantly impairs the ductility of the ultrafine wire after drawing. Therefore, in order to obtain a wire of higher strength, the amount of Cr added is preferably 0.
1% or more and 0.30% or less, which does not impair ductility by increasing the transition density in ferrite.

Since Ni also has the same effect as Cr, 0.1% or more is desirably added so as to exert the effect. If Ni is added too much, the ductility of the ferrite phase deteriorates, so the upper limit is made 1.0%. Since Cu is an element that improves the corrosion fatigue characteristics of the wire rod, it is desirable to add 0.1% or more which exhibits its effect, if necessary. Cu
However, if the amount of addition is too large, the ductility of the ferrite phase decreases, so the upper limit is made 0.8%. Similar to the conventional ultra-fine steel wire, the content of S is 0.020% or less to secure the ductility, and P also impairs the ductility of the wire material like S, so the content thereof is 0.020% or less. Is desirable.

Al as a cause of reducing the ductility of the ultrafine wire
There are non-ductile inclusions containing Al ₂ O ₃ as a main component, such as ₂ O ₃ and Al ₂ O ₃ —MgO. Therefore, in the present invention, it is desirable that the Al content in the steel is 0.003% or less in order to avoid a decrease in ductility due to non-ductile inclusions.

The reasons for limiting the manufacturing method will be described below.
Hot-rolled wire rod with the above steel composition (generally 4.0 to 16 mm
φ) wire rod may be used, and the conditioned cooling after the wire rod rolling may be adjusted to a pearlite structure or a bainite structure. 1) The wire diameter of these hot rolled wire rods is 1.
If the wire diameter is from 1 to 2.7 mmφ and the wire diameter is less than 1.0 mmφ without intermediate patenting, cracks will occur in the wire drawing wire and adversely affect subsequent processing, so the wire diameter is set to 1.0 mmφ or more. Further, the wire diameter before final patenting treatment and less 2.7mmφ it is not possible to obtain good results when less 0.4 the final product wire diameter When 2.7mmφ than wire. At this time, the drawing process may be either a drawing process or a roller die.
In the method of the present invention, the intermediate patenting is not used, but the intermediate patenting may be interposed if necessary.

2) For the patenting treatment, any of a lead bath furnace, a fluidized bed furnace, a molten salt furnace, a resistance furnace and the like may be used. However, the tensile strength is {(589 + 922 × Cwt%)-3
9} to {(589 + 922 × Cwt%) + 42} MPa. This strength is {(589 + 922 × Cwt%)
If it is less than −39}, a wire having higher strength than that of the conventional method cannot be obtained, and {(589 + 922 × Cwt%) + 42} M
If it exceeds Pa, sufficient ductility cannot be secured in the subsequent wire drawing.

3) After that, brass plating, Cu plating, N
Perform either i plating. These platings are selected according to how the final wire will be used.

4) In the subsequent final wet drawing process, continuous wire drawing with a surface reduction rate of 10% or more and 25% or less per sheet except for the final die is performed. If it is less than 10%, defects are likely to occur inside during wire drawing, and if it exceeds 25%, it becomes difficult to pull it out.

5) In the final finish drawing, it is necessary to adjust the residual stress in order to suppress delamination in the final wire. Therefore, skin pass wire drawing is performed,
In the case of skin pass wire drawing, there is a drawback that die wear becomes extremely fast. In order to suppress this defect, a die having an approach angle (see FIG. 1) of 5 ° or more and 10 ° or less is used. If the approach angle is less than 5 °, the frictional force becomes large and the wire drawing process is adversely affected. Also, if it exceeds 10 °, the wear becomes faster. Moreover, in order to suppress delamination, it is necessary to reduce the area by 6% or less.
If it is less than%, the wear of the die will be accelerated, so the surface reduction rate is 2%
Above 6% or less.

6) Further, in order to obtain a wire having a higher strength than that of the conventional method, the total wire drawing area reduction rate after the final patenting treatment needs to be 3.4 or more in true strain, and the true strain of the total area reduction rate is required. When the value exceeds 4.5, delamination occurs even if skin pass is performed.

A wire having a circle-equivalent diameter of 0.15 to 0.4 mmφ manufactured according to the above process is (2800-120).
0Log D) The wire has a strength of MPa or more and does not cause delamination.

[0023]

EXAMPLES Examples of the present invention will be described below. Table 1 shows the chemical composition of the steel used in the trial production. Further, Table 2 shows the manufacturing process of the steel cord. As shown in Table 2, after the hot-rolled wire rod is drawn to a predetermined wire diameter, patenting treatment (LP, FBP, SB) is performed to adjust the strength, and then the area reduction ratio shown in the table. The final wet wire drawing process is performed. However, LP, FBP, and SB indicate that the patenting treatment was performed using a lead bath furnace, a fluidized bed furnace, and a salt bath furnace, respectively.

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

The methods 1 to 14 of the present invention are the cases where the method is manufactured according to the method of the present invention. Comparative method 15 is a case where the steel composition is the same and the area reduction rate of the wire before finishing in the final wire drawing is as low as 9%. Comparative method 16 is the case where the steel composition is the same and the surface reduction ratio of the finishing die in final wire drawing is 10%, which is larger than the method of the present invention. Comparative method 17 is a case where the steel composition is the same and the approach angle of the finishing die in the final wire drawing is as low as 4%. Comparative method 18 is the case where the steel composition is the same and the total area reduction ratio in the final wire drawing is larger than the method of the present invention by 4.37 in true strain. Comparative method 19 is a case where the steel composition is different and the manufacturing process is the same. Table 3 shows the tensile strength and drawing value of the obtained wire, and the presence or absence of delamination in the twist test. Any 1 to 14 of the wire made in accordance with the present invention method (2800 - 1200Log D) above MPa tensile strength and good aperture, and delamination with no good wire is obtained. On the other hand, comparison method 15,1
6, delamination occurred, and the comparison method 17,
In 18, the target steel wire could not be obtained, and in Comparative method 19, the tensile strength was ( 2800-1200 Lo).
g D) It has not reached over MPa.

[0028]

[Table 4]

[0029]

EFFECTS OF THE INVENTION Steel that does not cause delamination when an ultrafine steel wire having a diameter of 0.4 mm or less is produced using the high strength and high ductility steel wire and the slab and wire rod for producing the high strength and high ductility ultrafine wire of the present invention. A steel wire for cord can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a die.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁷ identification code FI C23C 30/00 C23C 30/00 A (58) Fields investigated (Int.Cl. ⁷ , DB name) B21C 1/00-19 / 00 C21D 7/00-8/10 C23C 30/00 C22C 38/00-38/04

Claims (2)

(57) [Claims] 1. By weight%, C: 0.7 to 1.10%, Si: 0.4% or less, Mn: 0.5% or less, P: 0.020% or less, S: 0.020% Below, a hot-rolled wire rod consisting of the balance iron and unavoidable impurities, and an inevitable Al content of 0.003% or less made of steel 1) Wire of 1.1 to 2.7 mmφ by wire drawing 2) The tensile strength is increased by the patenting process.
{(589 + 922 × Cwt%)-39} to {(589+
922 × Cwt%) + 42} MPa, 3) Select either brass plating, Cu plating or Ni plating on the surface by plating treatment, and 4) In wet drawing, except for the final die Reduction rate of 10% or more 2
5) Continuous wire drawing of 5% or less is performed. 5) In final finishing wire drawing, a die with an approach angle of 5 ° or more and 10 ° or less is used to perform a surface reduction ratio of 2% or more and 6% or less,
6) The total wire drawing area reduction ratio after the final patenting treatment in 4) and 5) is set to be 3.4 or more and 4.5 or less in true strain, and the circle equivalent diameter is 0.15 to 0.4 mmφ. (280
0-1200 Log D) A method for producing a steel wire for steel cord, which is a high-strength steel wire having a tensile strength of MPa or more. However, {D: wire diameter (mm)} 2. By weight%, C: 0.7 to 1.10%, Si: 0.4% or less, Mn: 0.5% or less, P: 0.020% or less, S: 0.020% In addition to the following, one or more of the following are included: Cr: 0.3% or less, Ni: 1.0% or less, Cu: 0.8% or less, 1 part of the hot-rolled wire rod of steel consisting of balance iron and unavoidable impurities. ) Wire drawing and intermediate patenting to make a wire of 1.1 to 2.7 mmφ, and 2) Patenting treatment to obtain tensile strength of {(589 + 922 × Cwt%)-39} ~
{(589 + 922 × Cwt%) + 42} MPa, 3) brass plating, Cu plating, or Ni plating is performed on the surface by plating treatment, and 4) per wet die drawing except for the final die. Area reduction rate is 10%
5) In the final finish drawing, the die with an approach angle of 5 ° or more and 10 ° or less is used to perform a reduction in area of 2% or more and 6% or less. ) 4), 5), the total wire drawing area reduction ratio after the final patenting treatment is 3.4 or more and 4.5 or less in true strain, and the equivalent circle diameter is 0.15 to 0.4 mmφ ( Two
800-1200 Log D) A method for producing a steel wire for steel cord, which is a high-strength steel wire having a tensile strength of at least MPa.