KR100544743B1 - Method for manufacturing high Si added medium carbon wire rod by forming decarburinized ferritic layer - Google Patents

Abstract

The present invention relates to a method for manufacturing a wire rod that is processed by bolts and the like, and its purpose is to heat-treat the surface decarburization layer generated by the addition of silicon in a steel that can be graphitized for the purpose of improving cold formability. It is to provide a method for producing a wire rod that can be reduced by forming a ferrite decarburization layer with low carbon utilization.

The present invention for achieving the above object, by weight% contains carbon 0.40-0.60%, silicon 2.0-4.0%, manganese 0.1-0.8%, phosphorus and sulfur 0.01% or less, nitrogen 0.002-0.01%, oxygen 0.002% or less Nickel 0.3-2.0%, boron 0.001-0.003%, vanadium: 0.01-0.5%, niobium: 0.01-0.5%, molybdenum 0.01-0.5%, titanium 0.01-0.2%, tungsten 0.01-0.5%, copper 0.01 Billet composed of one or two or more selected from the group consisting of -0.2%, the remaining Fe and other impurities is heated at a heating rate of 20 ± 5 ℃ / min to Ac1 transformation point, Ac3 transformation point at the abnormal range of Ac1 transformation point High silicon with low surface decarburization including heating at 9 ± 4 ℃ / min heating rate, heating at 15 ± 5 ℃ / min up to 1050 ± 100 ℃, and maintaining the wire for 30 minutes The technical subject matter is a method for producing an added heavy carbon wire rod.

Medium carbon steel, high strength, bolt, cold forming, wire rod, surface decarburization

Description

 Method for manufacturing high silicon added medium carbon wire rod with low surface decarburization {method for manufacturing high Si added medium carbon wire rod by forming decarburinized ferritic layer}

The present invention relates to a method for manufacturing wire rods that are processed by bolts and the like, and more particularly, heating the surface decarburization layer generated by increasing the amount of silicon in the steel that can be graphitized for the purpose of improving cold forming properties. The present invention relates to a method for producing a wire rod which can reduce and reduce the ferrite decarburization layer having low carbon employment.

Wire rod is processed to a certain shape and used for various mechanical parts, for example, bolts, nuts, springs and the like. In order to reduce the weight and performance of such mechanical parts, demand for high strength of wire rods continues to increase. High-strength materials can cause delayed fracture, in which cracks are propagated by hydrogen under constant load.

For example, the bolt is a problem that the delayed fracture resistance is deteriorated, it is currently impossible to use the tensile strength of 130 kg / mm ² or more, the situation is limited in its use and range. The followings are expected advantages when developing bolt steel with high delay fracture resistance and high strength. In other words, in terms of steel structures, bolt fastening does not require more skilled techniques than welding joints, and considering the advantages of replacing weak welds, firstly, the stability of steel structures can be increased by strengthening bolt fastening force, and second, the number of bolt fastenings is reduced. It is possible to reduce the amount of steel used. In addition, in terms of automotive parts, third, it contributes to the lightening of parts. Fourth, there is an advantage in that the design diversification and compactness of the automobile assembly apparatus according to the lighter parts are possible. Therefore, if the high strength can be achieved without lowering the delay fracture resistance of the material, the ripple is expected to be considerably large considering the advantages in use and the effect on the industry.

The delayed fracture resistance of high-strength materials is known to be degraded because precipitates distributed at grain boundaries act as trapped sites of hydrogen and degrade the strength of grain boundaries. It is most important to suppress the distribution of Fe-based precipitates to the maximum.

In addition, the shape of the various bolts are usually manufactured by cold forming, high-strength material is required to soften the material heat treatment before the cold molding high strength, it is desirable to secure the tensile strength of less than 60kg / mm ² before cold forming. This is to suppress the increase of the die wear rate during cold forming to the maximum. Domestic steel structure fastening bolts are currently capable of cold forming bolts under tensile strength of 60kg / mm ² or less. Therefore, in order to use high-strength bolt material, it is necessary to secure not only excellent delayed fracture resistance but also cold forming required for bolt manufacturing.

In cold forming high strength bolts, the present inventors can obtain excellent cold formability in terms of material tensile strength or surface hardness, regardless of the presence of alloying elements, and delayed fracture resistance when using graphitized structures. In order to develop a steel made of high-silicon-added medium carbon having a fine composite structure with no possibility of precipitation of Fe-based precipitates in grains. However, when manufacturing high-silicon-added heavy carbon steel as a wire rod, silicon has a great influence on reducing the carbon diffusion coefficient while increasing the activity of carbon in the material during reheating in the wire rod rolling process. As a result, carbon activity increases during reheating in the wire rod rolling process, and the decarburization rate increases on the surface. On the contrary, the carbon supply is not smooth to the surface due to the reduction of diffusion coefficient from the center to the surface, thereby enhancing the concentration of carbon at the surface. Done. As the depth of the decarburized layer deepens on the surface, the tightening force of the bolt decreases and the fatigue characteristics of the spring deteriorate. As such, it is well known that the surface decarburization of the high silicon-added steel is because the surface decarburization rate is very fast compared to the low silicon-added steel. Therefore, when manufacturing a high silicon-added steel wire, many problems in use may occur when the decarburization control of the material is not appropriate.

Representative examples of decarburization control methods known so far include Korean Patent Nos. 92-24974, 92-24163, 92-24161, Japanese Patent Publications (Pyeong) 2-301514, (Pyeong) 1-31960, (Small) 63 And -216591. Most of these methods control decarburization by lowering the silicon content or adding alloying elements such as lead and tin. However, it is not possible to lower the silicon content in steel grades in which high silicon addition is inevitable for high strength, and when alloying elements such as lead and tin are added, mechanical properties such as impact toughness become poor.

The present invention was devised in the research process to prevent the decarburization layer on the surface in the wire heating process of high-silicon-added medium-carbon steel that can be graphitized for the purpose of improving the cold formability, the carbon on the surface of the billet in the wire heating process It is an object of the present invention to provide a method for producing a wire rod which can reduce the thickness of the surface decarburization layer by forming a ferrite decarburization layer having a low solubility and significantly reducing the decarburization speed on the surface of the billet.

Wire rod manufacturing method of the present invention for achieving the above object, by weight% carbon 0.40-0.60%, silicon 2.0-4.0%, manganese 0.1-0.8%, phosphorus and sulfur 0.01% or less, nitrogen 0.002-0.01%, oxygen 0.002 % Or less, nickel 0.3-2.0%, boron 0.001-0.003%, vanadium: 0.01-0.5%, niobium: 0.01-0.5%, molybdenum 0.01-0.5%, titanium 0.01-0.2%, tungsten 0.01-0.5 %, Copper 0.01-0.2% selected from the group consisting of one or more selected from the group consisting of the remaining Fe and other impurities, heated to a Ac1 transformation point at a heating rate of 20 ± 5 ℃ / min, Ac1 in the ideal range The transformation point from the transformation point to the Ac3 transformation point is heated to a heating rate of 9 ± 4 ℃ / min, and then heated to a heating rate of 15 ± 5 ℃ / min to 1050 ± 100 ℃ to hold for 30 minutes or more, the wire rod.

Hereinafter, the present invention will be described in detail.

The present inventors have studied in various angles to reduce the decarburization of high-silicon-added medium-carbon steel wires.As a result, the temperature between the Ac1 transformation point and the Ac3 transformation point, the ferrite and austenite at the time of heating the billet for the wire rod (heating with the wire heating) By controlling the heating rate of heating through the mixed phase), it was found that the ferrite layer having a very low carbon solubility on the billet surface can be uniformly induced to a thickness of 0.05-0.5 mm. In addition, since the surface ferrite layer has a very low carbon solubility, the diffusion of carbon atoms through this region immediately after precipitation of the ferrite phase becomes very slow, thereby significantly reducing the rate of decarburization and the degree of oxidation of the surface ferrite layer. According to the present invention, the thickness can be adjusted according to the present invention, thereby obtaining a result of remarkably improving the billet surface decarburized layer during extraction by wire heating, thereby completing the present invention. The high silicon-added medium-carbon steel, which is the subject of the present invention, will be described first, and then a method of manufacturing the steel as a wire will be described.

[Composition of High Silicon-added Medium Carbon Steel]

Carbon (C): 0.40-0.6%

If the carbon content is less than 0.40%, it is difficult to obtain an adequate amount of retained austenite, shape and size in the composite structure after heat treatment for the production of fine composite steel which is effective for delayed fracture resistance. This is because it is difficult to secure sufficient tensile strength and yield strength. In addition, when the content of carbon is more than 0.60%, characteristics such as cross-sectional reduction rate, elongation and impact toughness after heat treatment are lowered, segregation and surface flaws occur during wire rod manufacturing, and surface decarburization is intensified when charging furnace, Permanent deformation and static fatigue characteristics deteriorate at the same time, the proper shape and size of microcomposite tissues, the time required for transformation to secure the composite tissues, and adversely affect the carbon concentration and interfacial concentration of residual austenite. Because.

Silicon (Si): 2.0-4.0%

If the silicon is less than 2.0%, the graphitization heat treatment time for improving the cold forming property is long, and the mechanical and thermal stability of the retained austenite is degraded after the ferrite transformation, resulting in the ferrite + residual austenite composite structure and the amount of retained austenite. In addition, it is difficult to secure the strength of the ferrite, and it is difficult to secure the strength due to the insufficient effect of strengthening the ferrite, and also affects the delayed fracture resistance, surface corrosion characteristics, impact toughness, permanent deformation during bolting, and also for controlling wire decarburization. This is because it is difficult to secure uniformity and proper thickness of the surface ferrite decarburization layer in the wire heating furnace, so that decarburization is intensified, and it is difficult to control the surface scale characteristics by increasing the hardenability during wire rod cooling. If the silicon exceeds 4.0%, the above-mentioned effect is saturated and adversely affects the hardenability, the composition of the composite tissue steel, the impact toughness, the fatigue characteristics, and the production of bloom or billet for wire rod manufacturing. This is because the quality characteristics in the final product are deteriorated due to the inhomogeneity of the microstructure due to the segregation of silicon at the same time, and it is difficult to control the homogeneous surface decarburization because the thickness of the surface ferrite layer increases during heat treatment. More preferred silicon component range in the present invention is 2.8-3.3%, isothermal heat treatment time and residual austenite fraction and size, shape, ferrite + residual austenite composite structure for producing bainite structure (ferrite + residual austenite) Strength, high toughness, delayed fracture resistance (diffuse hydrogen content, precipitation control of grain boundary precipitates), surface decarburization, stress relaxation or permanent deformation resistance after bolting, and dynamic and static fatigue characteristics This can be effectively improved.

Manganese (Mn): 0.1% to 0.8%

Manganese (Mn) is an element that forms a solid solution to form a solid to form a solid solution, and is very soluble in high-strength bolt characteristics. Therefore, its content is detrimental to the strength of the base metal, hardenability during heat treatment, stress relaxation, and segregation. It is preferable to set it as 0.1-0.8% in consideration of these. If the content of manganese exceeds 0.8%, the local annealing property due to the simple manganese stone is increased rather than the effect of strengthening the solid solution. Because it is crazy.

Phosphorus (P) and sulfur (S): 0.01% or less each

Phosphorus segregates at grain boundaries and degrades toughness, limiting its upper limit to 0.01%. Sulfur is a low melting point element, and segregates grains to reduce toughness and form an emulsion, which has a detrimental effect on delayed fracture resistance and stress relaxation characteristics. The upper limit is limited to 0.01%.

Nitrogen (N): 0.002-0.01%

This is because when the nitrogen content is less than 0.002%, it is difficult to form vanadium and niobium-based nitrides that act as non-diffusion hydrogen trap sites, and when the content exceeds 0.01%, the effect is saturated.

Oxygen (O): 0.0020% or less

This is because when the content of oxygen exceeds 0.0020%, coarse oxide-based nonmetallic inclusions are easily formed and fatigue life is reduced.

In the above composition, nickel 0.3-2.0%, boron 0.001-0.003%, vanadium: 0.01-0.5%, niobium: 0.01-0.5%, molybdenum 0.01-0.5%, titanium 0.01-0.2%, tungsten 0.01-0.5%, One or more selected from the group of 0.01-0.2% copper is added.

Vanadium (V) or niobium (Nb): 0.01 to 0.5% each

Vanadium (V) or niobium (Nb) is an element that improves delayed fracture resistance and stress relaxation. If the content is less than 0.01%, the distribution of vanadium or niobium-based precipitates in the base material decreases, and thus the role of the non-diffusible hydrogen trap site is insufficient. Therefore, it is difficult to expect the effect of improving the delayed fracture resistance and the precipitation strengthening is expected. This is because it is difficult to improve the stress relaxation resistance is not sufficient, and it is difficult to expect attenuation of austenite grains, which affects the microstructure of the ferrite + residual austenite composite. In addition, if it exceeds 0.5%, the graphitization heat treatment time is long, and the improvement effect on delayed fracture resistance and stress relaxation resistance by V or Nb-based precipitates is saturated and coarse that is not dissolved in the base material during austenite heat treatment. This is because the amount of alloy carbide increases and acts like a non-metallic inclusion, leading to a decrease in fatigue properties.

Nickel (Ni): 0.3 to 2.0%

Nickel (Ni) is a graphitization-promoting element and forms a nickel thickening layer on the surface during heat treatment to suppress permeation of external hydrogen to improve delayed fracture resistance. The content is 0.3-2.0%. desirable. If the nickel content is less than 0.3%, the surface thickening layer formation is incomplete, so it is difficult to expect the effect of improving the delayed fracture resistance, and the heat treatment time is increased during the spheroidization or graphitization treatment to improve the decarburization control, toughness and cold forming. This is because there is no improvement effect of cold forming during bolt forming. If it exceeds 2.0%, the effect is saturated and negatively affects the appropriate amount, size and shape of the amount of retained austenite.

Boron (B, B): 0.001% to 0.003%

Boron (boron, B) is a graphitization promoting element in the present invention, and is a grain boundary strengthening element for improving quenchability and delayed fracture resistance. If the content of boron is less than 0.0010%, the effect of improving grain boundary strength due to grain boundary strengthening of boron atoms due to grain boundary segregation during heat treatment is insufficient, and the graphitization promoting effect is insufficient during graphitization treatment to improve cold forming. If the content of boron exceeds 0.003%, the effect is saturated, rather, the precipitation of boron nitride at the grain boundary leads to a decrease in grain boundary strength.

Molybdenum (Mo), Tungsten (W): 0.01-0.5% each

If the content is less than 0.01%, the grain boundary strengthening effect of the ferrite and the retained austenite is insufficient, and the hardenability during the heat treatment, the solid solution strengthening of the ferrite, and the Mo and W system precipitation strengthening effects are insufficient. If it exceeds 0.5%, the effect is saturated, and as the hardenability is increased, it is easy to form low-temperature structure (martensite + bainite) during wire rod manufacturing, and the heat treatment time during spheroidization or graphitization treatment to improve cold formability This is because it has a long disadvantage.

Copper (Cu): 0.01-0.2%

If the copper content is less than 0.01%, the effect of promoting graphitization and improvement of corrosion resistance is insufficient. If the copper content is more than 0.2%, the improvement effect is saturated, and the melting point is lowered during the grain boundary segregation. This is because surface flaw is more likely to occur due to grain embrittlement during charging, and impact toughness of the final product is lowered.

Titanium: 0.01-0.2%

If the content of titanium is less than 0.01%, the effect of promoting graphitization and miniaturizing austenite grains is insufficient, and the precipitation distribution of titanium-based carbon and nitride in the grain boundary effective for delayed fracture resistance is insufficient, so that improvement effect is difficult to expect. This is because when it exceeds 0.2%, the additive effect is saturated, and coarse titanium-based carbon and nitride are formed to affect the mechanical properties.

[Manufacturing method of wire rod]

In the steel formed as described above, a decarburized layer is generated on the surface in the heating process for manufacturing the wire rod. In order to prevent this, the ferrite decarburized layer is formed on the surface of the billet by appropriately adjusting the heating conditions in the heating process for rolling the billet. It is important to form.

First, according to the present invention, the billet is heated to a heating rate of 20 ± 5 ° C./minute to the Ac1 transformation point. The heating rate is set for convenience in manufacturing process rather than decarburization improvement effect. This is because the charging time becomes too long at the heating rate of 15 ° C. or lower, and at 25 ° C. or higher, a temperature difference between the surface of the billet and the inside occurs, which causes the Ac1 transformation time to be different.

Then, from the Ac1 transformation point in the ideal range to the Ac3 transformation point, the heating rate is 9 ± 4 ° C./min. At this time, if the heating rate is less than 5 ℃ / min, the thickness of the abnormal region ferrite layer on the billet surface of the wire heating furnace is increased more than necessary (≥0.5mm), so it is difficult to obtain the decarburization improvement effect. Charge time) is long. In addition, it is because it is difficult to form the appropriate surface ferrite layer (0.05-0.5mm) of the billet necessary for suppressing a decarburization reaction when temperature rising rate exceeds 13 degreeC / min.

Subsequently, heating is carried out at a heating rate of 15 ± 5 ° C./minute to 1050 ± 100 ° C. for 30 minutes or more, and then the wire is rolled. After the abnormal zone end temperature, the microstructure of the base material is transformed from the abnormal structure (ferrite + austenite) to the austenite single phase structure. At this time, when the temperature increase rate up to the heating maintenance temperature is less than 10 ℃ / min, This is because when the temperature exceeds 20 ° C / min, the billet warpage is likely to occur due to the deep temperature deviation inside and outside the billet, and it is difficult to control the inside and outside temperature of the billet suitable for hot rolling. In addition, when the heating temperature of the wire heating furnace is less than 950 ℃, there is a problem in controlling the proper thickness of the billet surface ferrite layer for decarburization control, and it is not easy to re-use the vanadium-based or niobium-based precipitates coarse precipitated during the manufacture of the billet. This is because the workability becomes poor due to the overload during rolling due to the increase in the resistance to hot deformation, and when it exceeds 1150 ° C., a uniform ferrite layer for decarburization control cannot be deposited on the surface. In other words, in order to precipitate the surface ferrite layer having a very low carbon solubility, the surface ferrite layer must remain at the heating and maintaining temperature, but when the heating temperature is higher than 1150 ℃, the surface ferrite layer is transformed into austenite. This is because the decarburization rate increases sharply, which causes deep surface decarburization. If the heating holding time is less than 30 minutes, it is difficult to secure a uniform temperature distribution inside the billet for wire rod rolling.

As described above, the billet is heated to roll the wire. At this time, the decarburization area of the billet extracted from the heating furnace is the same as the decarburization area of the wire after the wire rolling. Therefore, in the present invention, in consideration of this point, it is preferable to roll the wire to a diameter of 30 mm or less.

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

EXAMPLE

The high-silicon-added medium-carbon steel billet having the component system as shown in Table 1 below was heated according to the present invention and then rolled into a wire to make the invention example (1-14), while heating to a condition outside the conditions of the present invention and then rolling the wire. It was set as the comparative example (1-5).

Inventive Example (1-14) was heated to Ac1 transformation point at 25 ± 5 ° C./min and heated at a heating rate in the range of 9 ± 4 ° C./min from Ac1 to Ac3, which was an abnormal range, and then to a range of 1050 ± 100 ° C. After heating at a heating rate of 15 ± 5 ° C./min for 30 minutes or more, the wire was rolled to a diameter of 16 mm. In Comparative Example (1-5), the billet was heated to Ac1 at a heating rate of 20 ° C / min, and was heated at a heating rate in the range of 3-17 ° C / min from Ac1 to Ac3, which was an ideal range, and then a heating rate of 5-25 ° C to 1050 ° C. Heated at ℃ / min and maintained for 30-60 minutes, the wire was rolled to a diameter of 16mm.

After rolling at high speed as described above, the rolled diameter 13 mm wire rod product was rapidly cooled by winding at 950 ° C. by water spraying, and then slowly cooled to 1.0 ° C./sec up to 600 ° C. and air cooled. The surface decarburized layer depth of the wire rod manufactured as described above was measured by the KS standard (KD D 0216). According to this standard, an optical microscope observation method and a microhardness measuring method are proposed, but the microhardness measuring method was used in the present Example. The decarburized layer depth measured as described above is shown in Table 2 below. The measurement position was measured at 8 equal sections of wire rod section, and the measured value was based on the average value.

Chemical composition C Si Mn Cr V Ni Mo Ti W B Cu P S N2 O2 Invention steel One 0.44 3.03 0.63 - 0.05 - - - - - 0.03 0.008 0.009 0.005 0.0013 2 0.43 3.24 0.62 - 0.06 - - 0.02 - 0.001 0.04 0.008 0.008 0.005 0.0014 3 0.56 3.23 0.68 - 0.07 0.70 - - 0.04 - 0.15 0.009 0.009 0.005 0.0015 4 0.42 2.35 0.68 - Nb: 0.01 - 0.25 0.04 0.12 - 0.05 0.007 0.009 0.005 0.0016 5 0.45 3.99 0.75 - 0.04 - - - 0.0020 0.04 0.008 0.009 0.005 0.0017 6 0.58 3.12 0.74 - - - 0.06 0.03 0.06 0.0020 0.03 0.009 0.008 0.004 0.0017 7 0.57 2.37 0.82 - - 1.10 0.23 0.09 - - 0.20 0.009 0.008 0.004 0.0018

Steel grade used Heating rate up to Ac1 (C / min) Ideal temperature rise rate (C / min) Heating rate up to heating holding temperature after Ac3 Heating holding temperature (C) Heating holding time (min) Wire stripping depth of 16mm in diameter (mm) Invention 1 Inventive Steel 1 20 5 15 1000 40 0.03 Invention 2 Inventive Steel 1 20 9 15 1050 30 0.04 Invention 3 Inventive Steel 1 20 13 15 1050 30 0.03 Invention 4 Inventive Steel 1 20 9 10 1050 30 0.02 Invention 5 Inventive Steel 1 20 9 15 1050 30 0.04 Invention 6 Inventive Steel 1 20 9 20 1050 30 0.05 Invention 7 Inventive Steel 1 20 9 15 950 40 0.03 Invention Material 8 Inventive Steel 1 20 9 15 1100 30 0.02 Invention 9 Inventive Steel 2 20 9 15 1050 30 0.04 Invention 10 Invention Steel 3 20 9 15 1050 30 0.02 Invention 11 Inventive Steel 4 20 9 15 1050 30 0.03 Invention Material12 Inventive Steel 5 20 9 15 1050 30 0.04 Invention Material 13 Inventive Steel 6 20 9 15 1050 30 0.03 Invention 14 Inventive Steel 7 20 9 15 1050 30 0.05 Comparative Material 1 Inventive Steel 1 20 3 15 1050 30 0.13 Comparative Material 2 Inventive Steel 1 20 17 15 1050 30 0.12 Comparative Material 3 Inventive Steel 1 20 17 5 1050 30 0.16 Comparative Material 4 Inventive Steel 1 20 17 25 1050 30 0.19 Comparative Material 5 Inventive Steel 1 20 17 25 1200 30 0.20

As shown in Table 2, the surface decarburization depth of the wire rod of the invention example (1-14) shows a range of 0.03-0.05mm, whereas the wire rod surface decarburization of the comparative example (1-5) is 0.12-0.20mm range It can be seen that it is very effective in improving decarburization.

As described above, the present invention is a high-silicon-added heavy carbon bolt steel wire rod with an effect of suppressing the decarburization reaction upon heating by depositing a uniform and thin ferrite layer on the surface of the billet by reducing the temperature rise rate of the abnormal pass through heating the wire rod. It can provide.

Claims (4)

By weight% carbon 0.40-0.60%, silicon 2.0-4.0%, manganese 0.1-0.8%, phosphorus and sulfur 0.01% or less, nitrogen 0.002-0.01%, oxygen 0.002% or less, including nickel 0.3-2.0%, Boron 0.001-0.003%, Vanadium: 0.01-0.5%, Niobium: 0.01-0.5%, Molybdenum 0.01-0.5%, Titanium 0.01-0.2%, Tungsten 0.01-0.5%, Copper 0.01-0.2% Or heating a billet composed of two or more kinds, the remaining Fe and other impurities, at a heating rate of 20 ± 5 ° C./min to Ac1 transformation point, and a heating rate of 9 ± 4 ° C./min from Ac1 transformation point to Ac3 transformation point in the ideal range. A method for producing a high-silicon-added medium-carbon wire rod with low surface decarburization comprising heating the furnace at 1050 ± 100 ° C. and heating it at a heating rate of 15 ± 5 ° C./minute for at least 30 minutes. The method for producing a high-silicon-added heavy carbon wire having low surface decarburization according to claim 1, wherein the heating rate from the Ac1 transformation point to the Ac3 transformation point is in a range of 9 ± 2 ° C / min. The method of claim 1, wherein the heating rate from the Ac 3 transformation point to 1050 ± 50 ℃ has a range of 10 ± 5 ℃ / min method for producing a high-silicon high carbon-added medium carbon wire. The method for producing a high-silicon-added medium-carbon wire rod having low surface decarburization according to any one of claims 1 to 3, wherein a ferrite decarburization layer having a thickness of 0.05 to 0.5 mm is formed on the surface of the heated billet as described above.