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WO-2026095364-A1 - WIRE ROD AND METHOD FOR MANUFACTURING SAME

WO2026095364A1WO 2026095364 A1WO2026095364 A1WO 2026095364A1WO-2026095364-A1

Abstract

The present invention relates to a wire rod and a method for manufacturing same and, more specifically, to a wire rod and a method for manufacturing same, the wire rod containing, in wt%, 0.600-1.000% of carbon (C), 1.500-1.990% of silicon (Si), 0.100-0.600% of manganese (Mn), 0.010-0.150% of sulfur (S), 0.005-0.020% of titanium (Ti), 0.003-0.015% of nitrogen (N), 0.005-0.050% of chromium (Cr), 0.005-0.050% of molybdenum (Mo), 0.005-0.150% of nickel (Ni), 0.005-0.150% of copper (Cu), 0.005-0.100% of aluminum (Al), and 0.005-0.050% of phosphorus (P), with the remainder comprising Fe and other impurities, and having a microstructure including graphite grains and ferrite.

Inventors

  • CHOI, SANGWOO

Assignees

  • 주식회사 포스코

Dates

Publication Date
20260507
Application Date
20250924
Priority Date
20241104

Claims (12)

  1. In wt%, Carbon (C): 0.600%–1.000%, Silicon (Si): 1.500%–1.990%, Manganese (Mn): 0.100%–0.600%, Sulfur (S): 0.010%–0.150%, Titanium (Ti): 0.005%–0.020%, Nitrogen (N): 0.003%–0.015%, Chromium (Cr): 0.005%–0.050%, Molybdenum (Mo): 0.005%–0.050%, Nickel (Ni): 0.005%–0.150%, Copper (Cu): 0.005%–0.150%, Aluminum (Al): 0.005%–0.100%, Phosphorus (P): 0.005%–0.050%, the remainder being Fe and others. A wire containing impurities and a microstructure containing graphite grains and ferrite.
  2. In claim 1, A wire rod having an area fraction of the graphite grains of 1.0% to 4.0% and an average diameter of the graphite grains of 0.5μm to 5.0μm.
  3. In claim 1, A wire rod having an area fraction of the graphite grains of 1.0% to 3.0% and an average diameter of the graphite grains of 1.8 μm to 4.5 μm.
  4. In claim 1, A wire rod having an area fraction of the graphite grains of 3.0% to 4.0% and an average diameter of the graphite grains of 1.1 μm to 4.0 μm.
  5. In claim 1, The above wire has an HRB hardness of 95 or less.
  6. In claim 1, A wire with a graphite content of 95% or more according to the following formula (1). Formula (1): (1 - Carbon content in undissolved pearlite / Carbon content in steel) x 100
  7. In wt%, Carbon (C): 0.600%–1.000%, Silicon (Si): 1.500%–1.990%, Manganese (Mn): 0.100%–0.600%, Sulfur (S): 0.010%–0.150%, Titanium (Ti): 0.005%–0.020%, Nitrogen (N): 0.003%–0.015%, Chromium (Cr): 0.005%–0.050%, Molybdenum (Mo): 0.005%–0.050%, Nickel (Ni): 0.005%–0.150%, Copper (Cu): 0.005%–0.150%, Aluminum (Al): 0.005%–0.100%, Phosphorus (P): 0.005%–0.050%, the remainder being Fe and others. Step of manufacturing a billet containing impurities; A step of heating the above billet at 950 to 1150℃ for at least 60 minutes; A step of hot rolling the heated billet at 900 to 1150℃; A step of cooling the hot-rolled billet to 500℃ at a cooling rate of 0.1 to 10℃/s in a temperature range of 750 to 900℃; A step of naturally air-cooling the above-mentioned cooled billet; and A method for manufacturing a wire rod comprising: a step of graphitizing heat treatment for at least 3 hours in a temperature range of A1-100℃ to A1 after the above natural air cooling step.
  8. In claim 7, A method for manufacturing a wire rod in which the microstructure of the wire rod that has undergone the above graphitization heat treatment step includes graphite grains and ferrite.
  9. In claim 8, A method for manufacturing a wire rod in which the area fraction of the graphite grains is 1.0% to 4.0% and the average diameter of the graphite grains is 0.5μm to 5.0μm.
  10. In claim 8, A method for manufacturing a wire rod in which the area fraction of the graphite grains is 1.0% to 3.0% and the average diameter of the graphite grains is 1.8 μm to 4.5 μm.
  11. In claim 8, A method for manufacturing a wire rod in which the area fraction of the graphite grains is 3.0% to 4.0% and the average diameter of the graphite grains is 1.1 μm to 4.0 μm.
  12. In claim 7, A method for manufacturing a wire rod having a graphitization fraction of 95% or more according to the following formula (1) of the wire rod that has undergone the above graphitization heat treatment step. Formula (1): (1 - Carbon content in undissolved pearlite / Carbon content in steel) x 100

Description

Wire rod and method of manufacturing the same The present invention relates to a wire and a method for manufacturing the same. Free-cutting steels with large amounts of machinability-enhancing elements such as Pb, Bi, and S are used as materials for machine parts that require machinability. By adding low-melting-point machinability-enhancing elements such as Pb, Bi, and S to the steel, liquid metal embrittlement is utilized, or a large amount of MnS is formed within the steel. Such free-cutting steels exhibit excellent machinability, including surface roughness, chip handling, and tool life, during machining. Graphite free-cutting steel is a steel containing fine graphite particles within a ferrite matrix or a ferrite and pearlite matrix, and the fine graphite particles within it act as a crack source during cutting, thereby improving machinability by acting as a chip breaker. Despite these advantages of graphite free-cutting steel, the bit wear characteristics are severe compared to lead free-cutting steel, resulting in a short bit replacement cycle. In addition, there was a problem that it was uneconomical because graphitization heat treatment had to be performed for a long time. Figure 1 is a photograph of the microstructure measured with an optical microscope after graphitization heat treatment according to one embodiment. Figure 2 is a scanning electron microscope (SEM) image of the graphite grain distribution after graphitization heat treatment according to one embodiment. Figure 3 is a photograph of the chip length distribution after a cutting evaluation according to one embodiment. Figure 4 is a photograph of the chip length distribution after cutting evaluation according to one comparative example. Preferred embodiments of the present invention are described below. However, embodiments of the present invention may be modified in various other forms, and the technical concept of the present invention is not limited to the embodiments described below. Furthermore, the embodiments of the present invention are provided to more completely explain the present invention to those with average knowledge in the relevant technical field. The terms used in this application are used merely to describe specific examples. For this reason, singular expressions include plural expressions unless the context clearly requires them to be singular. Additionally, it should be noted that terms such as “comprising” or “comprising” used in this application are used to clearly indicate the presence of features, steps, functions, components, or combinations thereof described in the specification, and are not used to preliminarily exclude the existence of other features, steps, functions, components, or combinations thereof. Meanwhile, unless otherwise defined, all terms used in this specification shall be understood to have the same meaning as generally understood by those skilled in the art to which the present invention pertains. Accordingly, unless explicitly defined in this specification, specific terms should not be interpreted in an overly ideal or formal sense. Additionally, terms such as "about," "substantially," etc., in this specification are used to mean at or near the stated value when inherent manufacturing and material tolerances are presented in the said sense, and are used to prevent unscrupulous infringers from unfairly exploiting the disclosed content in which precise or absolute values are mentioned to aid in understanding the invention. Unless otherwise specifically stated in this specification, the % indicating the content of each element is based on weight. A wire rod according to one embodiment of the present invention comprises, in weight%, carbon (C): 0.600%~1.000%, silicon (Si): 1.500%~1.990%, manganese (Mn): 0.100%~0.600%, sulfur (S): 0.010%~0.150%, titanium (Ti): 0.005%~0.020%, nitrogen (N): 0.003%~0.015%, chromium (Cr): 0.005%~0.050%, molybdenum (Mo): 0.005%~0.050%, nickel (Ni): 0.005%~0.150%, copper (Cu): 0.005%~0.150%, aluminum (Al): 0.005%~0.100%, phosphorus (P): It contains 0.005% to 0.050%, and the remainder is Fe and other impurities. Hereinafter, the reason for the numerical limitation of the alloy component content in the embodiments of the present invention will be explained. The carbon (C) content may be 0.600% to 1.000%. Carbon is an essential element for forming graphite grains. If the carbon content is less than 0.600%, the effect of improving machinability is insufficient, and even when graphitization is complete, the distribution of graphite grains is uneven and cementite formation is difficult. On the other hand, if the carbon content is excessive at 1.000% or more, coarse graphite grains are formed, and there is a risk that surface roughness will decrease due to an increase in intergranular precipitated graphite grains. Considering this, it is desirable to control the C content to 0.600% to 1.000%. The silicon (Si) content may be 1.500% to 1.990%. Silicon is a necessary component