Classifications

• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/06—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
• • 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
  • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21B—ROLLING OF METAL
  • B21B1/00—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations
  • B21B1/16—Metal-rolling methods or mills for making semi-finished products of solid or profiled cross-section; Sequence of operations in milling trains; Layout of rolling-mill plant, e.g. grouping of stands; Succession of passes or of sectional pass alternations for rolling wire rods, bars, merchant bars, rounds wire or material of like small cross-section
• • 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
  • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
  • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
• • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
  • C21D8/0226—Hot rolling
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
  • C21D9/525—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length for wire, for rods
• • 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
  • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
  • C21D9/52—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for wires; for strips ; for rods of unlimited length
  • C21D9/54—Furnaces for treating strips or wire
  • C21D9/56—Continuous furnaces for strip or wire
  • C21D9/573—Continuous furnaces for strip or wire with cooling
• • 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
  • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
• • 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
  • 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
• • 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
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
  • B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES, PROFILES OR LIKE SEMI-MANUFACTURED PRODUCTS OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
  • B21C47/00—Winding-up, coiling or winding-off metal wire, metal band or other flexible metal material characterised by features relevant to metal processing only
  • B21C47/02—Winding-up or coiling
• • 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
  • C21D2211/004—Dispersions; Precipitations
• • 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

Definitions

• the present disclosure relates to a non-quenched and tempered steel rod wire with excellent machinability and impact toughness and a method for manufacturing the same, and more particularly, to a non-quenched and tempered steel rod wire suitable for use as a material for automobiles or mechanical parts and a method for manufacturing the same.
• non-quenched and tempered steels are not only economically advantageous by reducing heat treatment costs, simplifying processes to shorten delivery time, and improving productivity, but also eco-friendly by reducing CO 2 that is generated by operating a furnace during heat treatment.
• non-quenched and tempered steels were applied only to parts that do not require high toughness due to relatively inferior toughness thereof to that of quenched and tempered steels.
• the present disclosure provides a non-quenched and tempered steel rod wire having impact toughness and providing cutting tools with abrasion resistance by adjusting a microstructure, for example, refining a structure via AlN grain boundary peening and low-temperature rolling or by obtaining a sufficient fraction of ferrite, which is a soft phase, in order to improve impact toughness inferior to that of conventional quenched and tempered steels, and a method for manufacturing the same.
• a non-quenched and tempered steel rod wire with improved machinability and impact toughness includes, in percent by weight (wt%), 0.3% to 0.5% of C, 0.4% to 0.9% of Si, 0.5% to 1.2% of Mn, 0.02% or less of P, 0.01% to 0.05% of S, 0.015% to 0.05% of sol.Al, 0.1% to 0.3% of Cr, 0.007% to 0.020% of N, and the balance being Fe and inevitable impurities, wherein a microstructure includes ferrite and pearlite, and Relational Expression 1 below is satisfied.
• N ⁇ A1 / 1.93 ⁇ 0.009
• a method for manufacturing a non-quenched and tempered steel rod wire with improved machinability and impact toughness includes: reheating a steel piece including, in percent by weight (wt%), 0.3% to 0.5% of C, 0.4% to 0.9% of Si, 0.5% to 1.2% of Mn, 0.02% or less of P, 0.01% to 0.05% of S, 0.015% to 0.05% of sol.Al, 0.1% to 0.3% of Cr, 0.007% to 0.020% of N, and the balance being Fe and inevitable impurities at a temperature of 950°C to 1100°C; finish rolling the reheated steel piece into a steel rod wire at a temperature of 750°C to 850°C; and winding and cooling the steel rod wire, wherein the cooling performed after the winding includes a process of cooling the steel rod wire to 400°C at an average cooling rate more than 0.1°C/s but not more than 5.0°C/s, and the steel rod wire satisfies the Relational Expression 1.
• Al combines with N to form an AlN nitride, which inhibits the growth of grain boundaries during heating and refines grains, thereby improving impact toughness.
• impact toughness is further improved by adjusting an area fraction of ferrite to 20% to 40% in a region from the center to a quarter or more of the diameter of the steel rod wire from the surface. Deterioration of impact toughness may be minimized and machinability, particularly, abrasion resistance of cutting tools, may be obtained by decreasing the size of MnS, which improves machinability but may deteriorate impact toughness. Therefore, the steel rod wire may be applied to materials for automobiles or mechanical parts that require machinability and impact toughness even after omitting heat treatment.
• a non-quenched and tempered steel rod wire with improved machinability and impact toughness includes, in percent by weight (wt%), 0.3% to 0.5% of C, 0.4% to 0.9% of Si, 0.5% to 1.2% of Mn, 0.02% or less of P, 0.01% to 0.05% of S, 0.015% to 0.05% of sol.Al, 0.1% to 0.3% of Cr, 0.007% to 0.02% of N, and the balance being Fe and inevitable impurities, wherein a microstructure includes ferrite and pearlite, and Relational Expression 1 below is satisfied.
• N ⁇ A1 / 1.93 ⁇ 0.009 .
• the present inventors have examined a method for providing a steel rod wire with machinability and impact toughness from various angles and have found that machinability and toughness may be obtained by appropriately controlling a composition of alloying elements and a microstructure of the steel rod wire without heat treatment, thereby completing the present disclosure.
• a non-quenched and tempered steel rod wire with improved machinability and impact toughness includes, in percent by weight (wt%), 0.3% to 0.5% of C, 0.4% to 0.9% of Si, 0.5% to 1.2% of Mn, 0.02% or less of P, 0.01% to 0.05% of S, 0.015% to 0.05% of sol.Al, 0.1% to 0.3% of Cr, 0.007% to 0.02% of N, and the balance being Fe and inevitable impurities, wherein a microstructure includes ferrite and pearlite, and Relational Expression 1 below is satisfied.
• N ⁇ A1 / 1.93 ⁇ 0.009
• the content of C is 0.3% to 0.5%.
• Carbon (C) is an element serving to improve strength of a steel rod wire. To obtain the above-described effect, it is preferable to include C in an amount of 0.3% or more. However, an excessive C content may deteriorate toughness and machinability, and thus the upper limit of the C content may be controlled to 0.5%.
• the content of Si is 0.4% to 0.9%.
• Silicon (Si) an element effective as a deoxidizer, serves to improve strength. With a Si content less than 0.4%, the above-described effect cannot be obtained. With a Si content exceeding 0.9%, deformation resistance of a steel rapidly increases due to solid solution strengthening resulting in deterioration of cold workability, and therefore, the upper limit of the Si content may be controlled to 0.9%.
• the content of Mn is 0.5% to 1.2%.
• Manganese (Mn) is an element effective as a deoxidizer and a desulfurizer. With a Mn content less than 0.5%, the above-described effect cannot be obtained. With a Mn content exceeding 1.2%, strength of the steel excessively increases to rapidly increase deformation resistance of the steel, resulting in deterioration of cold workability, and therefore, the upper limit of the Mn content may be controlled to 1.2%.
• the content of P is 0.02% or less.
• Phosphorus (P) is a major causative element of segregation into grain boundaries resulting in deterioration of toughness and reduction in delayed fracture resistance. Therefore, it is preferable to control the P content as low as possible. Theoretically, it is preferable to control the P content to 0% but P is inevitably included therein during a manufacturing process. Therefore, it is important to control the upper limit, and the upper limit of the P content may be controlled to 0.02% in the present disclosure.
• the content of S is 0.01% to 0.05%.
• S Sulfur
• MnS MnS
• the S content is controlled within a range of 0.01% to 0.05% in the present disclosure in consideration of an S content effective for improvement of machinability without significantly impairing toughness of the steel.
• the content of sol.Al is 0.015% to 0.05%.
• the sol.Al is an element effective as a deoxidizer.
• the sol.Al may be contained in an amount of 0.015% to obtain the above-describe effect.
• the upper limit of the Al content may be controlled to 0.05% in the present disclosure.
• the content of Cr is 0.1% to 0.3%.
• Chromium (Cr) is an element serving to promote transformation of ferrite and pearlite during hot rolling.
• Cr does not increase the strength of the steel more than necessary, reduces an amount of a solid solution of C by precipitating carbides, and contributes to reduction in dynamic deformation aging caused by the solid solution of carbon.
• the upper limit of the Cr content may be controlled to 0.3%.
• the content of N is 0.007% to 0.02%.
• N is an essential element for implementing an effect on improving impact toughness by decreasing grain sizes via formation of a nitride with Al.
• a N content less than 0.007%, it is difficult to obtain a sufficient amount of the nitride, resulting in a decrease in production of AlN precipitates, failing to obtain toughness desired in the present disclosure.
• a N content exceeding 0.02% a solid solution of N, not present as a nitride, increases to deteriorate toughness and ductility of the steel rod wire. Therefore, the upper limit of the N content may be controlled to 0.02% in the present disclosure.
• the remaining component of the non-quenched and tempered steel rod wire of the present disclosure is iron (Fe).
• the non-quenched and tempered steel rod wire may include other impurities incorporated during common industrial manufacturing processes of steels.
• the impurities are not specifically mentioned in the present disclosure, as they are known to any person skilled in the art of manufacturing.
• the non-quenched and tempered steel rod wire according to an embodiment of the present disclosure may satisfy Relational Expressions 1 and 2.
• Relational Expressions 1 and 2 [Al], [N], [C], [S], [Mn], and [Si] respectively represent contents (wt%) of the elements. N ⁇ A1 / 1.93 ⁇ 0.009
• Relational Expression 1 is an expression related to toughness.
• AlN is formed by adding high contents of N and Al. Because fine AlN precipitates in a steel inhibit the growth of crystal grains, particles are refined to improve impact toughness of the non-quenched and tempered steel rod wire according to the present disclosure.
• Relational Expression 2 is an expression related to tool wear among machinability.
• addition of S causes formation of MnS that serves as a stress concentrator during a cutting process to deteriorate cutting resistance and performs lubrication to improve lifespan of tools.
• MnS serves as a stress concentrator during a cutting process to deteriorate cutting resistance and performs lubrication to improve lifespan of tools.
• Relational Expression 2 reflects these effects, complexly, and at a value of 0 or more, tool wear is not serious.
• the non-quenched and tempered steel rod wire according to an embodiment of the present disclosure includes ferrite and pearlite as microstructures, wherein an area fraction of ferrite, measured in a region from the center to a quarter or more of the diameter of the steel rod wire from the surface, satisfies a range of 20 to 40%.
• an area fraction of the formed AlN may be 0.03% or more.
• a size of the formed AlN may be 150 nm or less.
• the number of carbonitrides having an average equivalent circular diameter of 100 nm or less per unit area may be 2 ea./ ⁇ m 2 or more.
• non-quenched and tempered steel material according to the present disclosure may have a tensile strength of 700 MPa or more.
• non-quenched and tempered steel material according to the present disclosure may have a yield strength of 350 to 450 MPa.
• non-quenched and tempered steel material according to the present disclosure may have a yield ratio of 0.45 to 0.65.
• non-quenched and tempered steel material according to the present disclosure may have an impact toughness of 60 J/cm 2 or more.
• non-quenched and tempered steel material according to the present disclosure may have a product of tensile strength and impact toughness of 30000 to 60000.
• the non-quenched and tempered steel rod wire with improved machinability and impact toughness according to the present disclosure may be manufactured in various methods, and the manufacturing method therefor is not particularly limited.
• the steel rod wire may be manufactured according to the following method.
• a method for manufacturing a non-quenched and tempered steel rod wire with improved machinability and impact toughness includes: reheating a steel piece including, in percent by weight (wt%), 0.3% to 0.5% of C, 0.4% to 0.9% of Si, 0.5% to 1.2% of Mn, 0.02% or less of P, 0.01% to 0.05% of S, 0.015% to 0.05% of sol.Al, 0.1% to 0.3% of Cr, 0.007% to 0.020% of N, and the balance being Fe and inevitable impurities; hot rolling the reheated steel piece into a steel rod wire; and winding and cooling the steel rod wire,
• cooling performed after the winding includes a process of cooling the steel rod wire to 400°C at an average cooling rate more than 0.1 °C/s but not more than 5.0°C/s, and the steel rod wire satisfies Relational Expression 1 below.
• a bloom satisfying the above-described composition of alloying elements is heated and rolled into a billet.
• the reheating process is a process for lowering a rolling load while rolling the steel rod wire.
• the reheating may be performed at a temperature of 950°C to 1100°C.
• the rolling load may increase causing difficulties in the manufacturing method.
• AlN formed in the pieces of the steel may form a solid solution again during heating, so that the area fraction of AlN changed to be less than 0.03%, thereby significantly decreasing the grain refinement effect.
• the reheated steel pieces are hot-rolled into a steel rod wire.
• a finish rolling temperature of the hot rolling may be 750°C to 850°C.
• a rolling load may increase, and at a finish rolling temperature above 850°C, crystal grains may coarsen so that it may be difficult to obtain a high toughness desired in the present disclosure.
• a process of winding the steel rod wire manufactured as described above into a coil shape may be performed.
• a winding temperature may be 750°C to 850°C. Because a temperature of the steel rod wire obtained by finish rolling may increase by transformation heating, a temperature of the steel rod wire immediately before winding may be higher than a final rolling temperature. In this case, the steel rod wire may be wound after being cooled to the winding temperature or may be wound without the separate cooling process depending on the temperature increased by the heating.
• a winding temperature below 750°C martensite generated in a surface layer during cooling cannot be restored due to double rows, and tempered martensite may be formed causing a problem of increasing a potential to induce surface defects during a drawing process.
• thick scales may be formed on the surface of the steel rod wire so that surface defects may easily occur during descaling and productivity may deteriorate due to an increase in cooling time in a subsequent cooling process.
• the wound steel rod wire may be cooled, and in this case, the cooling process may be performed to 400°C at an average cooling rate more than 0.1°C/s but not more than 5.0°C/s by air cooling or control cooling after hot forging.
• the cooling process may be performed to 400°C at an average cooling rate more than 0.1°C/s but not more than 5.0°C/s by air cooling or control cooling after hot forging.
• an average cooling rate lower than 0.1°C/s while cooling to 400°C after winding a desired strength cannot be obtained due to excessive formation of proeutectoid ferrite.
• low-temperature structures such as martensite may be formed and thus toughness and machinability may deteriorate.
• a bloom having a composition of alloying elements shown in Table 1 was heated at 1,200°C for 4 hours, and rolled into a billet at a finish rolling temperature of 1,100°C. Then, the billet was heated at 1090°C for 90 minutes, finish-rolled at 800°C, wound at 780°C, and cooled into a steel rod wire having a diameter of 26 mm.
• Steel rod wires including components of Inventive Steels 1 to 7 and Comparative Steels 1 to 7 were manufactured (Table 1) and tensile strength, impact toughness, wear depth of cutting tool, and area fractions of ferrite and AlN of the specimens of the steel rod wires were measured and shown in Table 2 below.
• room-temperature tensile strength was measured at the center of the specimens of the non-quenched and tempered steels at 25°C
• room-temperature impact toughness was measured at the specimens having a U-notch (based on a standard sample, 10x10x55 mm) at 25°C using a Charpy impact energy value obtained by the Charpy impact test.
• the steel rod wire having a diameter of 26 mm was processed with a reduction rate of 14.8% into cold drawn bars (CD-Bars) with a diameter of 24 mm.
• the degree of tool wear was evaluated by using a CNC lathe. After the CD-Bar with a diameter of 24 mm was subject to a turning operation to a diameter of 15 mm and a length of 20 mm, the degree of tool wear was evaluated. In this case, cutting was performed under the conditions of a cutting rate of 100 mm/min, a feedrate of 0.1 mm/rev, and a cutting depth of 1.0 mm by using a cutting oil, and a Cermet tool with a chip breaker was used as the cutting tool.
• a tool wear depth was evaluated by measuring a depth of flank wear, and a depth more than 0.2 mm was evaluated as poor and a depth not more than 0.2 mm was evaluated as good.
• transmission electron microscope specimens were prepared and observed at a magnification of 100,000x using the replica method, and then an arithmetic mean of the AlN area fraction was obtained from 50 images using image analysis software.
• the steel rod wires of Examples 1 to 7 satisfying all of the chemical composition, the relational expressions, and the manufacturing conditions provided in the present disclosure had an impact toughness of 60 J/cm 2 or more desired in the present disclosure, a tensile strength of 700 MPa or more, and good cutting tool wear properties.
• the steel rod wires of Comparative Examples 1 to 10 not satisfying all of the conditions suggested by the present disclosure had one or more poor properties among tensile strength, impact toughness, and cutting tool wear depth.
• Comparative Steel 1 of Comparative Example 1 having a low C content could not satisfy the suggested tensile strength of 700 MPa or more, and Comparative Examples 2 and 3 having an excess of Si and an excess of Mn, respectively, had insufficient impact toughness.
• Comparative Examples 4 and 5 having Al and N contents lower than those suggested by the present disclosure could not satisfy the suggested AlN area fraction of 0.03% or more, and thus low impact toughness values were obtained.
• Comparative Examples 6 and 7 satisfied the chemical composition suggested by the present disclosure, the Relational Expressions 1 and 2 were not satisfied, thereby obtaining low impart toughness and poor cutting tool wear.
• Comparative Examples 8 to 10 also satisfied the chemical composition suggested by the present disclosure, the heating temperature of the steel piece was higher and the average cooling rate range to 400°C during cooling after rolling was not satisfied, so that impact toughness and tensile strength were out of the target values or cutting tool wear was poor.
• a non-quenched and tempered steel rod wire having improved impact toughness and machinability may be provided while solving environmental problems and reducing costs, and therefore the present disclosure has industrial applicability.

Landscapes

• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Materials Engineering (AREA)
• Metallurgy (AREA)
• Organic Chemistry (AREA)
• Physics & Mathematics (AREA)
• Thermal Sciences (AREA)
• Crystallography & Structural Chemistry (AREA)
• Manufacturing & Machinery (AREA)
• Heat Treatment Of Steel (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=88919803

Family Applications (1)

Country Status (6)

Family Cites Families (16)

• 2022
  • 2022-05-27 KR KR1020220065638A patent/KR20230165627A/ko active Pending
• 2023
  • 2023-05-26 EP EP23812206.3A patent/EP4509632A4/de active Pending
  • 2023-05-26 JP JP2024570366A patent/JP2025517816A/ja active Pending
  • 2023-05-26 CN CN202380040387.0A patent/CN119213160A/zh active Pending
  • 2023-05-26 WO PCT/KR2023/007297 patent/WO2023229432A1/ko not_active Ceased
  • 2023-05-26 US US18/867,954 patent/US20250333811A1/en active Pending

Also Published As

Similar Documents

Legal Events