KR101795863B1 - Wire rod having excellent hot workability and machinability and method for manafacturing the same - Google Patents

Wire rod having excellent hot workability and machinability and method for manafacturing the same Download PDF

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KR101795863B1
KR101795863B1 KR1020150153179A KR20150153179A KR101795863B1 KR 101795863 B1 KR101795863 B1 KR 101795863B1 KR 1020150153179 A KR1020150153179 A KR 1020150153179A KR 20150153179 A KR20150153179 A KR 20150153179A KR 101795863 B1 KR101795863 B1 KR 101795863B1
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hot
calcium
steel
content
machinability
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KR1020150153179A
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KR20170051829A (en
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이형직
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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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
    • 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
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur
    • 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
    • C21D2211/005—Ferrite
    • 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

The present invention relates to a wire rod excellent in hot rolling property and machinability and a manufacturing method thereof.

Description

TECHNICAL FIELD [0001] The present invention relates to a wire rod having excellent hot-rolling property and cutting property, and a method of manufacturing the wire rod.

The present invention relates to a wire rod excellent in hot rolling property and machinability and a manufacturing method thereof.

Recently, efforts to reduce the emission of carbon dioxide (CO 2 ), which is considered to be the main cause of environmental pollution, have become a global issue.

As a part of this, there has been an active regulation to regulate the exhaust gas of automobiles, and measures for improving the fuel efficiency of automobiles have been continuously studied as countermeasures thereto.

As described above, in order to improve the fuel efficiency of automobiles, it is required to increase the weight of automobiles as well as high performance, and accordingly, the necessity of high strength of automobile materials or parts is increasing. In addition, as the stability against external impact increases, impact toughness is recognized as an important physical property of the material or parts. In addition, if the required shape can not be achieved by hot or cold forging only as the shape of the parts becomes complicated, machining of the material is also considered to be an important property in this respect, since mechanical machining is inevitable.

Among steels used for materials such as automobiles, wire rods having a medium carbon range, which is mainly used in wire rods, are composed of ferrite and pearlite. Normally, sulfur (S) is added in several hundreds of thousands of ppm for the purpose of improving machinability.

Sulfur (S) is combined with manganese (Mn) from molten steel and crystallized into MnS, and it continues to grow to a certain size even during solidification. Since MnS is harder than ferrite base, stress is concentrated on the interface And cracks are easily induced. Cracks induced in this manner are connected to each other to facilitate chip formation, resulting in improvement in machinability (for example, Patent Document 1).

However, if sulfur (S) useful for improving machinability is increased as described above, a large amount of MnS is formed and the remaining sulfur S bonds with iron (Fe) to form FeS having a low melting point, There is a problem of causing surface defects of the material during rolling.

That is, due to the formation of FeS, the hot rolled property is inferior, resulting in a low product yield and low productivity.

Accordingly, it is required to develop a technique capable of ensuring hot rolling property even if a large amount of sulfur (S) is contained in order to improve machinability.

Korean Patent Registration No. 10-1281376

An aspect of the present invention is to provide a wire having excellent hot-rolling resistance and cutting performance even when the content of sulfur (S) in steel is high, and a method of manufacturing the wire.

One aspect of the present invention provides a method of manufacturing a semiconductor device, comprising: 0.2 to 0.6% carbon (C), 0.5% or less (excluding 0%) silicon (Mn) 0.05 to 0.5% nickel, 0.05 to 0.5% vanadium, 0.03 to 0.2% phosphorus, 0.01 to 0.05% sulfur, 0.01 to 0.1% nitrogen, Wherein the ratio of the average sulfur concentration [S] to the average calcium concentration [Ca] satisfies the following relational expression 1: 0.01 to 0.01%, Ca: 0.0005 to 0.003%, balance Fe and unavoidable impurities, Thereby providing an excellent wire rod.

[Relation 1]

0.5? [S] 2 / [Ca]? 2.0

(In the above-mentioned relational expression 1, S and Ca mean the content by weight of each corresponding element.)

According to another aspect of the present invention, there is provided a method of manufacturing a steel plate, comprising the steps of: preparing a steel material satisfying the above- Reheating the steel material to a temperature range of Ae3 + 150 DEG C to Ae3 + 250 DEG C; Finishing hot-rolling the reheated steel material in a temperature range of Ar3 to Ar3 + 100 占 폚; And cooling the hot-rolled steel material at a cooling rate of 0.5 DEG C / s or less. The present invention also provides a method of manufacturing a wire material excellent in hot-rolling property and machinability.

According to the present invention, it is possible to provide a wire rod in which surface defects are greatly suppressed during hot rolling because of high temperature ductility, while facilitating machining from the formation of a sulfide having a high resistance to hot deformation.

In addition, the wire of the present invention can provide a wire having excellent machinability and hot rolling property, which is required in an industrial machine, an automobile material or a part, even if it contains sulfur (S) in a high content.

When a relatively large amount of sulfur (S) is included in order to improve the machinability of the steel, surface defects occur during hot rolling because MnS is formed in a larger amount than the ferrite matrix structure and stress is concentrated at the interface, Sulfur (S) which is not bonded to manganese (Mn) has a problem of forming very low FeS at the melting point by binding with iron (Fe) and causing very brittleness during hot rolling.

The inventors of the present invention have conducted intensive studies to solve the problem of surface defects in the presence of a certain amount of sulfur (S) or less and the problem of lowering the hot rolling resistance due to the formation of low melting point inclusions. As a result, ) Was added so as to modify the oxidation inclusions in the steel and to form a sulfide having a greater resistance to hot deformation than that of the conventional MnS, whereby the machinability and the hot rolling property can be improved at the same time, and the present invention has been accomplished .

Hereinafter, the present invention will be described in detail.

(C): 0.2 to 0.6%, silicon (Si): not more than 0.5% (exclusive of 0%), manganese (Mn), and the like are contained in weight% in accordance with one aspect of the present invention. (S): 0.8 to 2.0%, Cr: 0.05 to 0.5%, Ni: 0.05 to 0.5%, vanadium (V): 0.03 to 0.2% : 0.01 to 0.1%, nitrogen (N): 0.01% or less, and calcium (Ca): 0.0005 to 0.003%.

Hereinafter, the reasons for limiting the alloy composition of the wire material provided in the present invention as described above will be described in detail. Here, the content of each component means weight% unless otherwise specified.

C: 0.2 to 0.6%

Carbon (C) is an essential element for ensuring the strength of steel, and is either dissolved in steel or in the form of carbide or cementite. The easiest way to improve the strength is to increase the content of C in the steel to form a carbide or cementite, but in such a case, there is a problem that the ductility and the impact toughness are lowered. Therefore, the addition amount of C needs to be limited within a certain range .

In the case of the present invention, it is preferable to control the content of C to 0.2 to 0.6%. If the content of C is less than 0.2%, it is difficult to secure the desired strength. On the other hand, when the content of C exceeds 0.6%, impact toughness and machinability It is undesirable because there is a problem that it rapidly decreases.

Si: 0.5% or less (excluding 0%)

Silicon (Si) is solidified in ferrite and is known to be a very effective element for enhancing strength through solidification of steel. The addition of such Si greatly increases the strength, while the ductility and the impact toughness decrease sharply. Therefore, the addition of Si is generally limited to the cold forging parts requiring sufficient ductility.

In the case of the present invention, it is preferable to limit the content of Si to 0.5% or less. If the content of Si exceeds 0.5%, it is not preferable because it has difficulty in securing the desired impact toughness and excellent cutting performance .

Mn: 0.8 to 2.0%

Manganese (Mn) is an element that is added to the matrix to increase the strength of the steel, as well as to improve the strength of the steel by making the lamellar spacing of the pearlite fine.

When the content of Mn is less than 0.8%, the effect of improving the strength is not sufficient. On the other hand, when the content of Mn exceeds 2.0%, segregation is promoted. In such a segregation zone, the hardening ability is increased and low temperature tissue such as bainite or martensite It is not preferable because there is a possibility of causing unevenness of the structure such as being generated.

Cr: 0.05 to 0.5%

Chromium (Cr) is an element that affects corrosion resistance and incombustibility. If the content of Cr is less than 0.05%, the effect of improving the corrosion resistance of the steel hardly appears. On the other hand, if the content of Cr exceeds 0.5%, the incombustibility of the steel increases excessively, So that the toughness of the steel is lowered, which is not preferable.

Ni: 0.05 to 0.5%

Nickel (Ni) has an effect of improving impact toughness by lowering the brittle-ductile transition temperature (DBTT) and improving the incombustibility.

If the content of Ni is less than 0.05%, the effect of improving the impact toughness is hardly exhibited. On the other hand, if the content exceeds 0.5%, the incombustibility of the steel is excessively increased, so that the bainite or martensite And the toughness of the steel is lowered, which is not preferable.

V: 0.03 to 0.2%

Vanadium (V) is an element that plays a role in forming minute carbon and nitride in the steel to make fine grains and improve impact properties.

If the content of V is less than 0.03%, the precipitation amount of vanadium tantalum nitride is decreased, and the grain boundary can not be sufficiently fixed, so that the effect of improving the toughness of the steel becomes insignificant. On the other hand, when the content exceeds 0.2%, coarse vanadium carbon and nitride are formed and adversely affect the toughness, which is not preferable.

P: 0.01 to 0.05%

Phosphorus (P) is segregated in grain boundaries to lower toughness and reduce delayed fracture resistance, but is an effective element for improving cutting performance. If the content of P is less than 0.01%, the effect of improving machinability is insignificant. On the other hand, if the content exceeds 0.05%, impact toughness and delayed fracture resistance are drastically reduced.

Therefore, the content of P in the present invention is preferably limited to 0.01 to 0.05%.

S: 0.01 to 0.1%

Sulfur (S) is segregated in grain boundaries to reduce toughness and form a low melting point emulsion to inhibit hot rolling property. Therefore, it is preferable to positively limit the content thereof. However, in order to secure machinability, S It is preferable to induce precipitation.

Therefore, it is preferable to limit the content of S to 0.01 to 0.1% in consideration of this. If it is less than 0.01%, it becomes difficult to secure machinability. On the other hand, when the content exceeds 0.1%, the impact toughness sharply decreases, And thus it is undesirable to cause a lot of material defects.

N: 0.01% or less (excluding 0%)

Nitrogen (N), together with elements such as vanadium (V), is an effective element for forming fine niobium in the steel to fine grain and improving impact properties. However, when the content is excessive, the strength is increased, There is a problem of dipping. Therefore, it is preferable to limit the upper limit of N to 0.01%.

Ca: 0.0005 to 0.003%

Calcium (Ca) is an element having stronger oxidizing power than Mn and Si, and serves to modify oxides by reducing Mn and Si and forming complex oxides with alumina. In addition, Ca has good reactivity with Mn to form calcium-manganese sulfide, thereby improving mechanical properties and improving machinability. In order to sufficiently obtain the above-mentioned effect, Ca is preferably contained in an amount of 0.0005% or more. If the content exceeds 0.003%, a large amount of calcium oxide is produced, which is not effective in reforming the oxide, And adversely affect mechanical properties such as ductility and impact toughness.

Therefore, it is preferable to limit the content of Ca to 0.0005 to 0.003% in consideration of this, more advantageously to limit it to 0.001 to 0.003%.

The remainder of the present invention is iron (Fe). However, in the ordinary steel manufacturing process, impurities which are not intended from the raw material or the surrounding environment may be inevitably incorporated, so that it can not be excluded. These impurities are not specifically mentioned in this specification, as they are known to any person skilled in the art of steel making.

In the wire material of the present invention having the above-mentioned composition, it is preferable that the ratio of the average sulfur concentration [S] and the average calcium concentration [Ca] present in the wire material satisfies the following relational expression 1:

[Relation 1]

0.5? [S] 2 / [Ca]? 2.0

(In the above-mentioned relational expression 1, S and Ca mean the content by weight of each corresponding element.)

In the present invention, sulfur (S) is very effective for improving machinability. However, there is a fear that low temperature ductility of the steel is lowered to thereby deteriorate hot rolling property. However, by adding calcium (Ca) in an appropriate amount, sulfur content Cutting property and hot rolling property can be simultaneously improved. However, it is preferable to limit the concentration of sulfur (S) and calcium (Ca) in the wire so as to satisfy the relational expression (1).

The wire of the present invention is a microstructure including a ferrite and a composite of pearlite, wherein the ferrite has an area fraction of 15 to 28% and preferably contains pearlite as the remainder.

If the ferrite fraction is less than 15%, the strength of the steel increases but the impact toughness may be deteriorated rapidly. On the other hand, if the ferrite fraction exceeds 28%, impact toughness can be sufficiently secured, but the target strength can not be secured have.

In addition, the average crystal grain size of the ferrite is preferably 20 탆 or less. If the average ferrite grain size exceeds 20 탆, there is a problem that impact toughness deteriorates.

In addition, the wire rod of the present invention includes calcium-manganese sulfide, and the calcium-manganese sulfide has a greater resistance to hot deformation than MnS, and is advantageous for improving machinability and hot rolling resistance.

Hereinafter, a method for manufacturing a wire rod excellent in hot rolling property and machinability according to one aspect of the present invention will be described in detail.

The wire according to the present invention can be manufactured by preparing a steel material satisfying the alloy composition and composition relationship proposed in the present invention and then subjecting it to a reheating-hot rolling-cooling step. Hereinafter, Will be described in detail.

Reheating process

In the present invention, it is preferable to carry out a step of reheating the prepared steel material before performing the hot rolling.

At this time, reheating is preferably performed in a temperature range of Ae3 + 150 deg. C to Ae3 + 250 deg. If the reheating temperature is lower than Ae3 + 150 deg. C, there is a possibility that the surface temperature of the steel becomes too low during the subsequent hot rolling process. When the temperature exceeds Ae3 + 250 deg. C, austenite grains grow to a great extent, And the like.

More preferably, the reheating temperature range is from 950 to 1050 ° C, more advantageously from 950 to 1030 ° C, even more advantageously from 950 to 1000 ° C.

According to the present invention, by setting the temperature range to a low value in the reheating step, austenite grains of the heat-treated steel material can be finely formed, and the effects thereof are reflected in the subsequent rolling and cooling steps as they are, Can be advantageously obtained, and the impact toughness of the steel can be further secured.

Hot rolling process

Preferably, the reheated steel is hot-rolled to form a wire, and the hot-rolled steel is preferably subjected to finish hot rolling in a temperature range of Ar 3 to Ar 3 + 100 ° C.

If the finish hot rolling temperature is lower than Ar3, there is a problem that surface defects are likely to be caused in the steel material. On the other hand, when the final hot rolling temperature is higher than Ar3 + 100 deg. C, crystal grains do not become finer and the desired physical properties can not be secured .

More preferably, the finish hot rolling temperature range is preferably 750 to 850 ° C.

Cooling process

It is preferable to cool the hot-rolled steel material, and it is preferable to perform the cooling to a normal temperature at a cooling rate of 0.5 ° C / s or less (excluding 0 ° C / s).

When the cooling rate exceeds 0.5 占 폚 / s during cooling, bainite or martensite, which is a low-temperature structure, is formed and impact toughness is inferior.

Hereinafter, the present invention will be described more specifically by way of examples. It should be noted, however, that the following examples are intended to illustrate the invention in more detail and not to limit the scope of the invention. The scope of the present invention is determined by the matters set forth in the claims and the matters reasonably inferred therefrom.

( Example )

Molten steel having an alloy component as shown in Table 1 was cast into an ingot, and then homogenized at 1250 占 폚 for 12 hours. Thereafter, the homogenized steel material was reheated under the conditions shown in Table 2, hot rolled to a final thickness of 15 mm, and then cooled.

The ferrite fraction and the average grain size were measured for the cooled steel products. The machinability and high temperature ductility were also tested and measured, and the results are shown in Table 2 below.

The ferrite fraction and the average grain size were measured using an image analyzer.

In order to measure the machinability and high temperature ductility, the turning test and the high temperature tensile test were carried out at 850 ° C. At this time, the cutting performance was evaluated by a turning test using a CNC lathe without using cutting oil for a 25 mm diameter bar, the feed rate was set to 0.06 mm / rev, the cutting depth was set to 0.5 mm, and the cutting speed was set to 100 m / min .

On the other hand, in order to confirm the degree of tool wear, the flank wear depth (Vc) of the tool and the surface roughness of the workpiece after the turning test at the same time were measured and compared.

Steel grade Alloy component (% by weight) Relationship 1 C Si Mn Cr Ni V P S N Ca One 0.43 0.1 1.5 0.23 0.10 0.11 0.02 0.05 0.0042 0.0015 1.67 2 0.42 0.3 1.0 0.26 0.15 0.14 0.01 0.03 0.0057 0.0017 0.53 3 0.47 0.4 1.8 0.20 0.12 0.10 0.03 0.04 0.0047 0.0011 1.45 4 0.38 0.1 1.3 0.17 0.18 0.15 0.05 0.07 0.0053 0.0028 1.75 5 0.49 0.2 1.2 0.18 0.23 0.08 0.02 0.06 0.0065 0.0025 1.44 6 0.40 0.2 1.4 0.19 0.22 0.12 0.04 0.20 0.0043 0.0019 21.05 7 0.43 0.4 1.2 0.24 0.17 0.10 0.03 0.04 0.0054 0.0062 0.26 8 0.39 0.3 1.1 0.20 0.15 0.09 0.01 0.07 0.0045 0.0002 24.50 9 0.41 0.1 1.6 0.22 0.11 0.11 0.03 0.05 0.0043 0.0012 2.08 10 0.39 0.3 1.3 0.18 0.21 0.16 0.01 0.03 0.0056 0.0018 0.50 11 0.42 0.5 1.4 0.23 0.23 0.12 0.04 0.06 0.0044 0.0014 2.57

Steel grade Manufacturing conditions Microstructure Mechanical properties division Reheating
Temperature (℃) Wrap-up
Hot rolling
Temperature (℃) Cooling rate
(° C / s) F fraction
(%) F average
Crystal grain size
(탆) High temperature ductility
(%) Tool wear
(탆) Surface roughness
(탆) One 1000 800 0.4 24 11 87 67 1.7 Inventory 1 2 980 810 0.1 26 20 93 70 0.9 Inventory 2 3 950 840 0.3 22 16 91 71 1.2 Inventory 3 4 1020 780 0.2 25 16 84 73 1.5 Honorable 4 5 970 770 0.5 28 10 85 69 1.3 Inventory 5 6 1030 810 0.4 18 15 73 47 0.6 Comparative Example 1 7 1050 800 0.5 17 18 77 75 1.8 Comparative Example 2 8 980 790 0.4 26 13 79 99 1.6 Comparative Example 3 9 1010 960 0.3 11 41 89 68 2.2 Comparative Example 4 10 1160 830 0.1 13 37 92 66 2.0 Comparative Example 5 11 1030 840 2.0 9 16 86 105 1.4 Comparative Example 6

(In Table 2, 'F' means ferrite. In the inventive examples 1 to 5, the remainder excluding the F fraction is a pearlite (P) phase.)

As shown in Tables 1 and 2, in Inventive Examples 1 to 5, which satisfy both the alloy composition, the component relationship (relational expression 1), and the manufacturing conditions, fine ferrite having an average grain size of 20 μm or less was formed, And excellent cutting performance.

On the other hand, in the case of Comparative Example 1 in which the content of sulfur (S) is excessively large, it can be confirmed that a high amount of sulfide is formed in the steel, and the high temperature ductility is heated.

In the case of Comparative Example 2 in which the content of Ca was excessive, a high-temperature ductility was weakened due to generation of a hard oxide in the steel, and in Comparative Example 3 in which the Ca content was insignificant, oxide modification and calcium- It can be confirmed that a large amount of abrasion of the cutting tool has occurred.

In Comparative Examples 4 to 6, the alloy composition and the compositional relationship (Relational Expression 1) satisfy the present invention, but when the finish hot rolling temperature range, the reheating temperature range and the cooling rate do not satisfy the present invention, 5, it can be confirmed that the austenite is not sufficiently refined so that the average grain size of the ferrite as the final structure becomes large, and the surface of the workpiece becomes rough after the cutting, and the surface roughness becomes weak.

Further, in the case of Comparative Example 6, it is confirmed that the low temperature structure is formed and the wear of the cutting tool is increased.

Claims (8)

(Si): not more than 0.5% (excluding 0%), manganese (Mn): 0.8 to 2.0%, chromium (Cr): 0.05 to 0.5%, nickel (P): 0.01 to 0.05%, sulfur (S): 0.01 to 0.1%, nitrogen (N): 0.01% or less, calcium (Ca) ): 0.0005 to 0.003%, the balance Fe and inevitable impurities,
The ratio of the average sulfur concentration [S] to the average calcium concentration [Ca] satisfies the following relational expression 1,
Wherein the microstructure has a composite structure of ferrite and residual pearlite having an area fraction of 15 to 28% and an average grain size of the ferrite of 20 m or less.

[Relation 1]
0.5? [S] 2 / [Ca]? 2.0
(In the above-mentioned relational expression 1, S and Ca mean the content by weight of each corresponding element.)
The method according to claim 1,
Wherein the wire comprises 0.001 to 0.003% calcium (Ca), and is excellent in hot rolling property and cutting ability.
delete delete (Si): not more than 0.5% (excluding 0%), manganese (Mn): 0.8 to 2.0%, chromium (Cr): 0.05 to 0.5%, nickel (P): 0.01 to 0.05%, sulfur (S): 0.01 to 0.1%, nitrogen (N): 0.01% or less, calcium (Ca) ): 0.0005 to 0.003%, the balance Fe and inevitable impurities, and the ratio of the average sulfur concentration [S] to the average calcium concentration [Ca] satisfies the following relational expression 1:
Reheating the steel material to a temperature range of Ae3 + 150 DEG C to Ae3 + 250 DEG C;
Finishing hot-rolling the reheated steel material in a temperature range of 750 to 850 캜; And
Cooling the hot-rolled steel at a cooling rate of 0.5 DEG C / s or less
Wherein the hot-rolled steel sheet has excellent hot-rolling property and machinability.

[Relation 1]
0.5? [S] 2 / [Ca]? 2.0
(In the above-mentioned relational expression 1, S and Ca mean the content by weight of each corresponding element.)
6. The method of claim 5,
Wherein the steel material contains 0.001 to 0.003% calcium (Ca), and the hot-rolling property and the cutting property are excellent.
6. The method of claim 5,
Wherein the reheating temperature range is 950 to 1050 占 폚.
delete
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Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000119808A (en) 1998-10-13 2000-04-25 Kobe Steel Ltd Steel wire capable of papid spheroidizing and excellent in cold forgeability, and its manufacture
JP2010229512A (en) 2009-03-27 2010-10-14 Jfe Steel Corp Method for producing ferrite-pearlite type rolled non-heat treated steel material
JP2012041601A (en) * 2010-08-19 2012-03-01 Kobe Steel Ltd Steel material for machine structural use suitable for friction pressure welding, and friction pressure welding part superior in impact property and bending fatigue property

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2000119808A (en) 1998-10-13 2000-04-25 Kobe Steel Ltd Steel wire capable of papid spheroidizing and excellent in cold forgeability, and its manufacture
JP2010229512A (en) 2009-03-27 2010-10-14 Jfe Steel Corp Method for producing ferrite-pearlite type rolled non-heat treated steel material
JP2012041601A (en) * 2010-08-19 2012-03-01 Kobe Steel Ltd Steel material for machine structural use suitable for friction pressure welding, and friction pressure welding part superior in impact property and bending fatigue property

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