KR101736618B1 - High strength steel wire rod and steel wire having excellent formability, and method for manufacturing thereof - Google Patents

High strength steel wire rod and steel wire having excellent formability, and method for manufacturing thereof Download PDF

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Publication number
KR101736618B1
KR101736618B1 KR1020150178610A KR20150178610A KR101736618B1 KR 101736618 B1 KR101736618 B1 KR 101736618B1 KR 1020150178610 A KR1020150178610 A KR 1020150178610A KR 20150178610 A KR20150178610 A KR 20150178610A KR 101736618 B1 KR101736618 B1 KR 101736618B1
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South Korea
Prior art keywords
steel wire
less
wire
bluing
workability
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KR1020150178610A
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Korean (ko)
Inventor
양요셉
박준학
김한휘
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주식회사 포스코
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire, a steel wire, and a method of manufacturing the same, which are used in automobile tires and the like.

Description

TECHNICAL FIELD [0001] The present invention relates to a high strength wire having excellent workability and a steel wire, and a manufacturing method thereof. BACKGROUND OF THE INVENTION 1. Field of the Invention [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wire, a steel wire, and a method of manufacturing the same, which are used in automobile tires and the like.

Bead wire is used for fixing tires and rims. It improves stability and driving ability. For the steel wire used for such a bead wire, general carbon steel having a carbon content of 0.6 to 0.8%, which is generally known in ASTM or JIS standard, is used.

The general purpose carbon steel wire is manufactured by subjecting a wire manufactured by hot rolling to a diameter of about 5.5 mm to a fresh wire by a fresh wire, an intermediate heat treatment, a fresh wire, and a blue wire. However, in recent years, many attempts have been made to eliminate intermediate heat treatment in order to reduce cost and prevent environmental pollution. The intermediate heat treatment furnace may include lead patenting, air patenting, and the like.

However, in the case of a steel wire having a small diameter (for example, 1.3 mm or less), heat treatment is indispensable. This is because, if the intermediate heat treatment is omitted, the amount of processing becomes too large to increase the strength, but the elongation is greatly reduced.

Therefore, it is very important to produce a steel wire which does not lower the elongation even when the amount of work is increased.

The present invention is to provide a wire rod and a steel wire having excellent processability, and a manufacturing method thereof.

In particular, the present invention is to provide a steel wire capable of omitting the intermediate heat treatment and capable of securing an excellent elongation rate even though a high processing amount is applied, and a wire rod capable of manufacturing the same. The present invention also provides a method of manufacturing the wire rod and the steel wire.

The problems to be solved by the present invention are not limited to the above-mentioned problems, and other matters not mentioned can be clearly understood by those skilled in the art from the following description.

An aspect of the present invention is a steel sheet comprising, by weight%, 0.62 to 0.82% of C, 0.1 to 0.5% of Si, 0.07 to 0.2% of Mn, 0.006% or less of N, 0.003 to 0.02% P: not more than 0.03%, and S: not more than 0.03%, the content of Ti and N satisfying Ti / N ≥ 3 in terms of weight ratio and the balance of Fe and unavoidable impurities .

In another aspect of the present invention, there is provided a ferritic stainless steel comprising: 0.62 to 0.82% of C, 0.1 to 0.5% of Si, 0.07 to 0.2% of Mn, 0.006% or less of N, 0.003 to 0.02% 0.03% or less of P and 0.03% or less of S, the content of Ti and N satisfying Ti / N ≥ 3 in terms of weight ratio and the balance of Fe and unavoidable impurities, The high potential wire of 2500 ~ 3500 pieces / 탆 2 is excellent in workability.

In another aspect of the present invention, there is provided a ferritic stainless steel comprising: 0.62 to 0.82% of C, 0.1 to 0.5% of Si, 0.07 to 0.2% of Mn, 0.006% or less of N, 0.003 to 0.02% Heating a steel material containing P: not more than 0.03% and S: not more than 0.03%, wherein the content of Ti and N satisfies Ti / N ≥ 3 in terms of weight ratio and the balance includes Fe and unavoidable impurities;

Hot-rolling the heated steel material;

Cooling the rolled steel material to a coiling temperature at a cooling rate of 100 to 150 DEG C / s;

Winding the cooled steel material; And

Cooling at 20 to 25 캜 / s in a temperature range of up to 700 캜 after completion of the winding, and then cooling at a temperature of 1 to 5 캜 / s in a temperature range of 700 to 200 캜. ≪ / RTI >

According to another aspect of the present invention,

Preparing a steel wire by drawing the wire material to a total machining amount of 94.0 to 95.0%; And

And a step of bluing the manufactured steel wire at 400 to 500 ° C for 1 to 3 seconds.

According to the present invention, in manufacturing a tire reinforcing product such as a bead wire in the past, a heat treatment step in the middle of the drawing process can be omitted and a steel wire excellent in strength and elongation can be provided even when a high processing amount is applied .

Particularly, the intermediate heat treatment can be omitted during the drawing process, and the bluing treatment temperature and time for increasing the elongation after drawing can be omitted. Accordingly, it is possible to reduce the energy consumption and the manufacturing cost, and to enhance the price competitiveness of the final product.

In the production of the steel wire, if the intermediate heat treatment is omitted and the amount of processing (which is the same concept as the freshness amount and the drawing amount in the present invention) is increased, the reason for the lowering of the elongation rate is as follows.

As the throughput increases, the dislocation density is greatly increased at the ferrite and cementite interfaces. In particular, when the throughput is 94.0% or more, the dislocation density increases to about 10 15 to 16 / mm 2. On the other hand, it is known that the Fe-C bonding force is similar to the bonding force between C and the dislocation. However, during the drawing process, the solid N from the ferrite and the solid N existing in the ferrite exits and is easily fixed to the dislocation line. The elongation of the steel wire is deteriorated due to C or N thus fixed.

Until now, the above problem can not be solved unless the temperature of the blueing heat treatment performed after the drawing is increased or the time is not changed for a long time.

Therefore, the inventors of the present invention have made a study of a method of securing the elongation of a steel wire without raising the temperature of the bluing heat treatment or setting the time for a long time, and as a result, the present invention has been derived.

Hereinafter, the present invention will be described in detail.

First, the alloy composition range of the present invention will be described in detail (hereinafter, wt%).

Carbon (C): 0.62 to 0.82%

C is the element that can most effectively increase the strength of the material, and it is known that when C is increased by 0.1%, tensile strength after drawing is improved to about 100 MPa. If the content of C is less than 0.62%, the percentage of pro-eutectoid ferrite is formed to exceed 17% (area fraction), and it is preferable that C contains 0.62% or more because C is likely to crack during drawing. On the other hand, when C is more than 0.82%, it is preferable to set the cementite cementite to 0.82% or less because the cementite is formed as a defective spot after disconnection and blooming treatment.

Silicon (Si): 0.1 to 0.5%

Si serves to strengthen the ferrite solid solution and refine the pearlite structure to increase the strength, and when Si is added at 0.1%, the strength improvement effect at the tensile strength level of 14-16 MPa can be obtained. Since Si is present in the ferrite or the ferrite / cementite interface, it is an element that can interfere with the elongation recovery in bluing after the final processing. If the content of Si is less than 0.1%, the effect as a deoxidizing agent is insufficient. Therefore, it is preferable that the Si content is 0.1% or more. If the Si content is more than 0.5% .

Manganese (Mn): 0.07 to 0.20%

Mn is added as a strong deoxidizing agent in addition to Si, added for the purpose of ensuring the ingotability which delays the transformation nose sufficiently when heat treated by the customer, rather than the role of increasing the strength. Mn is an element existing in cementite in place of Fe. Since Mn-C bond strength is weaker than that of Fe-C bond, when Mn is present in cementite, it plays a role of accelerating decomposition of cementite in drawing processing. Therefore, it is necessary to lower the content of Mn, but it is difficult to completely remove Mn, so it is necessary to maintain the content at an appropriate level.

Mn is present in the Fe site in the cementite, and the cementite decomposition is accelerated under severe conditions or a total reduction of 90% or more. Accordingly, the carbon generated by the decomposition of cementite is accelerated diffused out of the carbon, and the carbon exists in a state of being fixed to the potential present in the ferrite (cottrel atmosphere). The carbon adhered to the dislocations can not easily escape from the dislocation during the blueing heat treatment, and the dislocation is also suppressed, thereby reducing the elongation as a soft index.

Accordingly, when the Mn content exceeds 0.2%, the cementite decomposition inhibiting effect is insufficient and the effect of improving the elongation is small. When the content of Mn is less than 0.07%, the desulfurization process is not performed, leading to generation of FeS. .

Nitrogen (N): 0.006% or less (preferably 0.001 to 0.006%)

N is an interstitial element such as C, and when 0.1% is added, it is an element capable of increasing the strength by 80 to 100 MPa. However, as the strength increases, ductility such as elongation decreases, because it is easily adhered to the dislocations formed by machining and greatly reduces deformation resistance. If N is more than 0.006%, the amount of Ti added exceeds 0.02%. In this case, there is a possibility of disconnection during processing due to the formation of coarse TiN nitride. However, when N is controlled to be less than 0.001%, the cost of the denitration treatment is greatly increased.

Titanium (Ti): 0.003 to 0.02%

Ti is a ferrite stabilizing element and plays a role of improving the material strength due to precipitation strengthening effect when fine precipitates such as TiC are formed in the ferrite base upon cooling the wire after the austenizing treatment. In addition to the effect of increasing the strength, when N exists in the steel and is present as TiN, the solid solution N in the ferrite is significantly lowered, so that it plays a role of preventing the ferrite from being fixed to the strongly formed interface during the drawing process. aging effect does not occur, it not only inhibits the improvement of the strength of the material but also enhances the elongation and torsional characteristics. In the present invention, when the content of Ti is less than 0.003%, TiN can not be effectively formed. When the content of Ti exceeds 0.02%, coarse TiN is formed.

For this, Ti and N are preferably in a ratio of weight%, and preferably satisfy Ti / N? 3. In order to suppress N in ferrite as much as possible, it is necessary to control the nitrogen control at the time of refining to an extreme limit. In this case, since it leads to an increase in manufacturing cost, it is necessary to reduce N that can be dissolved in ferrite by adding Ti. For this purpose, the contents of Ti and N should be controlled. In the present invention, when the Ti / N is less than 3, since the solute N exists in excess of 0.0005%, it is preferable to control the ratio to be lower than 0.0005%.

Aluminum (Al): not more than 0.005%

Since Al forms a coarse hard inclusions such as Al 2 O 3 and Al 2 O 3 -CaO-SiO 2 in the presence of a large amount of Al, it is preferable to set the upper limit to 0.005% due to the presence of the inclusion.

Phosphorus (P) and sulfur (S): 0.03% or less

P and S are impurities, and their content is not particularly specified, but it is preferably 0.03% or less from the viewpoint of securing ductility.

In addition to the above composition, the balance includes Fe and unavoidable impurities. The present invention does not exclude the addition of alloys other than the alloy composition mentioned above.

Hereinafter, the microstructure of the wire rod of the present invention will be described in detail. The wire of the present invention preferably contains 83% or more of pearlite in an area fraction and the remainder is pro-eutectoid ferrite. In order to secure the excellent strength and processability of the present invention, it is desirable to secure a pearlite of 83% or more. Even if pro-eutectoid ferrite is formed, if the pro-eutectoid ferrite does not exceed 17% Can be suppressed.

On the other hand, the average pore size of the pearlite is preferably 120 to 180 nm. In the present invention, it is possible to obtain an excellent tensile strength by securing the pearlite average layer-to-layer spacing, thereby securing the target strength of the steel wire after bluing to 2000 MPa.

The wire material of the present invention preferably has a tensile strength of 950 MPa or more.

Meanwhile, the steel wire of the present invention includes a dislocation line formed strongly on the ferrite interface, and preferably has a supersaturated carbon content of 0.44 wt.% Or less, N) is preferably 0.005 wt.% Or less. The content of supersaturated carbon and the content of solid nitrogen coagulated in the above hypothetical line is the content of the steel wire after final drawing, and is preferably a state before bluing treatment. When the steel wire having the supersaturated carbon and the solid nitrogen is subjected to the bluing treatment, the elongation of the steel wire is improved.

When the supersaturated carbon content exceeds 0.44 wt.%, The amount of fixing on the hypocotyl is increased, and the bluing heat treatment temperature and time must be prolonged to solve this problem. Therefore, in order to increase the elongation rate using the bluing treatment condition of the present invention, it is preferable that the content of supersaturated carbon and the content of solubilized nitrogen coagulated at the above-mentioned potential line do not exceed the above range.

It is preferable that the dislocation line included in the steel wire is 2500 to 3500 per unit area (탆 2 ). The number of dislocations which can be formed on the ferrite and cementite interfaces when applied at a processing amount of 94% or more corresponds to 2500 to 3500 per unit area (탆 2 ), and the number thereof is 3500 There is a problem that the supersaturated carbon content and the solute nitrogen content must be controlled to an extreme limit. If the number of wires is less than 2500, the diameter of the wire rod must be made smaller, ), There is a problem that the fishy property is significantly lowered.

The steel wire of the present invention has a tensile strength of 2100 to 2300 MPa before bluing treatment. In particular, even when a drawing amount of 94.0% or more is applied, the present invention is particularly preferable even when the bluing treatment temperature is 1950 to 2100 MPa and the elongation is 7.8% .

Hereinafter, the production method of the present invention will be described. First, a manufacturing method of the wire rod of the present invention will be described in detail. A method of manufacturing a wire rod according to the present invention includes heating a steel material; Hot rolling; Quenching; A winding step and a cooling step.

The steel usually refers to a billet. The heating of the steel material is preferably carried out by heating for 90 to 120 minutes in a heating furnace at 1000 to 1100 캜. Through the heating, the steel forms a uniform austenite. Heating at this temperature is maintained in the austenite phase, which is a condition in which the austenite grains are not coarsened. When the temperature is less than 1000 ° C, the time required for formation of uniform austenite grains is required to exceed 120 minutes. When the temperature exceeds 1100 ° C, it is desirable to maintain the temperature at 1100 ° C or lower because of rapid growth of austenite grains and loss increase , And even if it is maintained for more than 120 minutes, rapid formation of austenite grains and formation of a high-temperature scale may be a problem, so that it is preferable that the time is 120 minutes or less

The heated steel material is hot-rolled. The hot rolling means machining in the form of a wire, and the hot rolling in the present invention is not particularly limited, but is performed in a conventional manner in the technical field of the present invention.

It is preferable to carry out the hot rolling at the hot rolling inlet temperature of 800 to 900 占 폚. If the temperature is lower than 800 ° C., the roll wear is severe due to the low temperature, and the production cost increases due to the increase of the replacement cycle. When the temperature exceeds 900 ° C., the pearlite uniformity decreases and coarse pearlite is formed There is a concern.

After the hot rolling, the steel sheet is quenched to a coiling temperature. The quenching is preferably carried out at a cooling rate of 100 to 150 ° C / s up to the coiling temperature. After hot rolling the hot rolled steel sheet at a hot rolling temperature of 800 to 900 DEG C in the hot rolling, cooling is carried out at a cooling rate of 100 to 150 DEG C / s from the cooling zone to the winding target temperature, thereby suppressing a temperature rise due to double heating.

The winding is preferably carried out in a temperature range of 800 to 850 캜. The coiling temperature is higher than the Ac3 temperature by 70 to 100 占 폚. The temperature is 800 占 폚 is the cooling limit in the environment where the manufacturing process is performed. If the coiling temperature is higher than 850 占 폚, coarse pearlite is formed, It is preferable to do it below.

After the winding, the steel is cooled at a cooling rate of 20 to 25 DEG C / s in a temperature range of up to 700 DEG C, and when the cooling rate is less than 20 DEG C / s, a fraction of pro- Cooling is the limit of the process, so it is desirable to keep it below that.

Thereafter, it is preferable to cool the cast steel to 700 ° C to 200 ° C at a cooling rate of 1 to 5 ° C / s, which does not affect the shape of the coil, since it does not affect the pearlite growth and the shape of the pro-eutectoid ferrite phase.

Next, a method for manufacturing the steel wire of the present invention will be described in detail.

The method for manufacturing the steel wire of the present invention includes a step of drawing the preceding wire and a step of bluing heat treatment.

The drawing step is carried out in order to secure size reduction and strength, and the steel wire is manufactured by drawing at a total drawing amount of 94.0 to 95.0%. At this time, the drawing speed is preferably 3.3 m / s or more when passing through the final dies.

On the other hand, in the case where a scale is formed on the surface of the wire before the drawing, a step of removing the scale through a process such as mechanical peeling or pickling can be preceded. If the scale is present, there is a risk of breakage due to scale intrusion during drawing processing.

The freshly prepared steel wire is subjected to bluing treatment. The bluing treatment is preferably carried out by heat treatment at a temperature of 400 to 500 ° C for 1 to 3 seconds to recover the elongation. According to the present invention, it is possible to provide a steel wire having an excellent elongation without increasing the bluing temperature and time, even if the wire is processed at a machining amount of 94% or more as described above.

Hereinafter, embodiments of the present invention will be described in detail. The following examples are for the purpose of understanding the present invention and are not intended to limit the present invention.

(Example)

This example is a wire rod having the composition shown in Table 1 (the remainder being Fe and unavoidable impurities) and diameter. Particularly, in the conventional example, JIS-SWRH72A, which is currently commercially available, was used.

The wire rod was produced by casting a 100 kg ingot to prepare a 160 X 160 (mm) billet, heating the billet, and then rolling the wire. The heating was carried out by heating at a temperature of 1050 DEG C for 95 minutes, and hot rolling was performed under ordinary conditions to produce a wire rod.

The hot rolling inlet temperature was maintained at 900 ° C and the cooling rate was 140 ° C / s in the cooling zone before winding. The steel was rolled at 820 ° C and cooled to 23 ° C / s up to 700 ° C, Followed by cooling to produce a wire rod.

The properties of the wire thus prepared are summarized in Table 2 below

The wire rod was transferred to a processing machine to produce a 1.2 mm steel wire with a total processing amount of 94.2% at a machining speed of 4.0 m / s. Thereafter, bluing treatment was performed at 430 캜 for 3 seconds to complete the final product, and the properties thereof are shown in Table 3.

division C Si Mn Ti N Ti / N Al S P diameter Conventional example 0.72 0.20 0.50 2 40 0.05 11 100 110 5.5 Inventory 1 0.72 0.20 0.20 130 40 3.25 10 90 100 5.0 Inventory 2 0.72 0.10 0.20 130 40 3.25 12 85 100 5.0 Inventory 3 0.72 0.50 0.20 130 40 3.25 9 90 100 5.0 Honorable 4 0.72 0.20 0.07 130 40 3.25 10 85 100 5.0 Comparative Example 1 0.72 0.20 0.30 130 40 3.25 10 90 100 5.0 Comparative Example 2 0.52 0.20 0.20 130 40 3.25 10 85 100 5.0 Inventory 5 0.62 0.20 0.20 130 40 3.25 10 85 100 5.0 Inventory 6 0.82 0.20 0.20 130 40 3.25 10 85 100 5.0 Comparative Example 3 0.92 0.20 0.20 130 40 3.25 10 85 100 5.0 Honorable 7 0.72 0.10 0.20 70 20 3.50 9 95 110 5.0 Honors 8 0.72 0.10 0.20 35 10 3.50 10 98 100 5.0 Proposition 9 0.72 0.10 0.20 190 60 3.17 11 95 100 5.0 Comparative Example 4 0.72 0.10 0.20 220 70 3.14 10 98 100 5.0 Comparative Example 5 0.72 0.10 0.20 110 40 2.75 10 90 120 5.0

(The content of the composition in Table 1 is% by weight and the content of Ti, N, Al, S and P is expressed in ppm, while the diameter of the wire is mm)

division Wire rod Lead patterning processing Tensile Strength (MPa) Perlite fraction
(area%) Corundum ferrite fraction (area%) Crude stone cementitious fraction (area%) Tensile Strength (MPa) Conventional example 1012 97.2 2.8 0 1112 Inventory 1 1024 95.9 4.1 0 skip Inventory 2 1009 95.3 4.7 0 skip Inventory 3 1069 97.1 2.9 0 skip Honorable 4 987 95.7 4.3 0 skip Comparative Example 1 1052 96.9 3.1 0 skip Comparative Example 2 1124 69.5 30.5 0 skip Inventory 5 924 83.4 16.6 0 skip Inventory 6 1124 100 0.0 0 skip Comparative Example 3 1224 97.0 0.0 3 skip Honorable 7 1008 95.3 4.6 0 skip Honors 8 1006 95.7 4.3 0 skip Proposition 9 1009 95.1 4.9 0 skip Comparative Example 4 1010 95.6 4.4 0 skip Comparative Example 5 1008 95.7 4.3 0 skip

division 1.2mm steel wire After bluing treatment Tensile Strength (MPa) Potential number (/ 탆 2 ) Concentration of carbon concentration in the hypothalamus (%) Nitrogen Concentration Concentration (%) Tensile Strength (MPa) Total elongation (%) Conventional example 2110 520 1.12 38 1950 7.6 Inventory 1 2200 3100 0.44 4 2050 8.7 Inventory 2 2189 3000 0.44 3 2039 9.0 Inventory 3 2249 3050 0.44 5 2099 8.0 Honorable 4 2167 3000 0.17 4 2017 9.2 Comparative Example 1 2232 3100 0.51 4 2082 7.6 Comparative Example 2 2304 3050 0.43 5 2154 3.5 Inventory 5 2104 3000 0.43 3 1954 8.0 Inventory 6 2304 3050 0.47 5 2154 8.2 Comparative Example 3 2404 3090 0.52 4 2254 2.8 Honorable 7 2190 3080 0.43 4 2049 9.1 Honors 8 2188 3040 0.42 4 2042 9 Proposition 9 2189 3060 0.43 3 2044 9.2 Comparative Example 4 monorail monorail monorail monorail monorail monorail Comparative Example 5 2190 3065 0.41 4 2043 7.1

As shown in Tables 1 to 3, when the conditions of the present invention are satisfied, excellent strength and elongation can be ensured without intermediate heat treatment and without increasing the bluing treatment temperature or time.

On the other hand, in the conventional example, as described above, JIS-SWRH72A has a high Mn content, while the Ti content has a low component composition. In the conventional example, the steel wire is manufactured by performing an intermediate heat treatment (lead patterning). It can be seen that the elongation percentage of the conventional example does not achieve the object of the present invention. The reason for this is that when the amount of drawn wire is increased to 94% or more, the number of dislocations increases and the amount of interstitial elements such as C or N is increased, resulting in low elongation. In the conventional example, the number of dislocations is small by carrying out the intermediate heat treatment, but the amount of C or N fixed is high, and the temperature and time of the bluing treatment are required to be increased.

However, in order to secure an excellent elongation rate of the steel wire even if a high wire drawing amount is applied without intermediate heat treatment, the amount of C and N adhering to the wire line should be reduced and the potential generation itself reduced.

In Comparative Examples 2 and 3, the content of Mn and C exceeded the range of the present invention, and the content of carbon fixed to the hypothalamus was large, and sufficient elongation was not ensured. Comparative Example 1 is a case where the content of C does not fall within the range of the present invention, and it was confirmed that excessive pro-eutectoid ferrite was formed in the produced wire rod. It can be confirmed that a sufficient elongation ratio can not be secured.

In Comparative Example 4, it was confirmed that a large amount of Ti and N was added in the alloy composition of the present invention, and coarse TiN-based precipitates were formed in the ferrite and acted as a point of occurrence of cracking during machining, thereby causing breakage. In Comparative Example 5, the alloy composition of the present invention was satisfied but the value of Ti / N was less than 3, which satisfied the values required in the present invention. However, it was confirmed that the elongation was not within the range of the present invention, As a result, it was confirmed that the ratio of Ti / N is a factor affecting elongation.

Claims (13)

delete delete delete 0.006% or less; N: 0.003% or less; Ti: 0.003% to 0.02%; Al: 0.005% or less; P: 0.03% or less; S: not more than 0.03%, the content of Ti and N satisfies Ti / N ≥ 3 by weight, the remainder contains Fe and unavoidable impurities, and the pre-line of the steel wire before bluing is 2500 to 3500 / ㎛ 2 high strength steel wire with excellent workability.
The method of claim 4,
A high strength steel wire excellent in workability having a supersaturated carbon content of 0.44% or less aggregated in a dislocation line among the internal microstructures of the steel wire before the bluing treatment.
The method of claim 4,
A high strength steel wire excellent in workability having a nitrogen content of 0.005% or less solidified in the dislocation line among the internal microstructures of the steel wire before the bluing treatment.
The method of claim 4,
The high strength steel wire excellent in workability having an elongation after bluing of the steel wire of 7.8% or more.
0.006% or less; N: 0.003% or less; Ti: 0.003% to 0.02%; Al: 0.005% or less; P: 0.03% or less; S: 0.03% or less, the contents of Ti and N being in a weight ratio of Ti / N? 3, and the balance being Fe and unavoidable impurities;
Hot-rolling the heated steel material;
Cooling the rolled steel material to a coiling temperature at a cooling rate of 100 to 150 DEG C / s;
Winding the cooled steel material; And
After the completion of the winding, cooling is performed at a temperature of from 20 to 25 ° C / s in a temperature range of up to 700 ° C and then cooling to 1 to 5 ° C / s in a temperature range of 700 to 200 ° C
And a high-strength wire having a high workability.
The method of claim 8,
Wherein the heating is carried out in a heating furnace at 1000 to 1100 占 폚 for 90 to 120 minutes and is excellent in workability.
The method of claim 8,
Wherein the hot rolling is performed at a hot rolling inlet temperature of 800 to 900 占 폚.
The method of claim 8,
Wherein the winding is performed in a temperature range of 800 to 850 占 폚.
A method of manufacturing a wire rod according to any one of claims 8 to 11, And
The step of preparing the steel wire by drawing the wire rod to a total machining amount of 94.0 to 95.0%
Wherein the steel wire has an excellent workability.
The method of claim 12,
Further comprising a step of bluing at 400 to 500 ° C for 1 to 3 seconds after the drawing.


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Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001294981A (en) * 2000-04-07 2001-10-26 Kobe Steel Ltd High strength wire rod excellent in delayed fracture resistance and forgeability and/or under head toughness and its producing method

Patent Citations (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2001294981A (en) * 2000-04-07 2001-10-26 Kobe Steel Ltd High strength wire rod excellent in delayed fracture resistance and forgeability and/or under head toughness and its producing method

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