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
  • C21D7/00—Modifying the physical properties of iron or steel by deformation
  • C21D7/13—Modifying the physical properties of iron or steel by deformation by hot working
• • 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
  • 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
  • C21D9/0081—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for slabs; for billets
• • 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 by deformation combined with, or followed by, heat treatment
  • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
  • C21D8/0221—Modifying the physical properties 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
  • 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
  • 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
  • C21D9/0075—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for rods of limited length
• • 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
  • C21D9/22—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for drills; for milling cutters; for machine cutting tools
• • 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
  • C22C38/008—Ferrous alloys, e.g. steel alloys containing tin
• • 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
  • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
• • 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
  • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
• • C—CHEMISTRY; METALLURGY
  • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
  • C22C—ALLOYS
  • C22C38/00—Ferrous alloys, e.g. steel alloys
  • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
• • C—CHEMISTRY; METALLURGY
  • 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
  • C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
• • 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
  • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
  • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
  • C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
• • 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

Definitions

• the present invention relates to free-cutting steel, particularly a steel that is a substitute for free-cutting steel containing sulfur, which is a machinability-improving element, and a trace amount of lead, and is equal to or higher than low-carbon sulfur-lead composite free-cutting steel. It relates to a free-cutting steel having machinability and a method for producing the same.
• Low-carbon sulfur lead free-cutting steel represented by JIS standard SUM24L secures its excellent machinability by adding a large amount of lead (Pb) and sulfur (S) as free-cutting elements.
• lead In steel materials, lead is useful for reducing tool wear and improving chip control during cutting. Therefore, lead is heavily used as an element that greatly improves the machinability of materials, and is used in steel products manufactured by many cutting processes.
• lead is also mentioned as one of them, and its use is required to be restricted.
• Patent Document 1 discloses a Pb-free free-cutting non-tempered steel.
• Patent Document 2 also discloses a Pb-free free-cutting steel.
• Patent Document 3 discloses a free-cutting steel in which Mn-Cr-S-based inclusions are present and machinability is ensured by adding Cr, which is easier to form a compound with S than Mn. ..
• Patent Document 1 has a problem that it is hard because the target steel type is a non-microalloyed steel containing C: 0.2% or more, and the manufacturing cost is high because Nd, which is a special element, is used. There is. Further, the technique described in Patent Document 2 has low hot ductility because a large amount of S is added, and cracks occur during continuous casting or hot rolling, which is problematic from the viewpoint of surface properties. On the other hand, in the technique described in Patent Document 3, Cr and S are added by reducing the amount of Mn added, but the amount of Cr added is as high as 3.5% or more, which makes it difficult to reduce the cost and a large amount. Since CrS is generated, there is a manufacturing problem that it is difficult to melt the material in the steelmaking process.
• the present invention has been made to solve the above-mentioned problems, and despite the fact that Pb is not added, the present invention has machinability equal to or higher than that of low-carbon sulfur-lead composite free-cutting steel. It is an object of the present invention to provide free-cutting steel which does not require addition of Nd or a large amount of S or Cr as in Patent Documents 1 to 3 described above, together with a method for producing the same.
• the present invention has been made based on the above findings, and the gist thereof is as follows. 1.
• C By mass% C: less than 0.09%, Mn: 0.50 to 1.50%, S: 0.250 to 0.600%, O: More than 0.0100% and less than 0.0500% and Cr: 0.50 to 1.50% It is composed of the balance Fe and unavoidable impurities, and has a component composition in which the A value defined by the following formula (1) satisfies 6.0 to 18.0.
• Free-cutting steel having a steel structure in which 500 sulfides with a diameter equivalent to a circle of less than 1 ⁇ m are distributed at least 500 pieces / mm 2 and sulfides with a diameter equivalent to a circle of 1 to 5 ⁇ m are distributed at 2000 pieces / mm 2 or more.
• a value 2 ([Mn] + 2 [Cr]) / [S] ⁇ ⁇ ⁇ (1)
• [M] is the content (mass%) of the element in [].
• the component composition is Si: 0.50% or less in mass%, P: 0.10% or less,
• the component composition is Ca: 0.0010% or less in mass%, Se: 0.30% or less, Te: 0.15% or less, Bi: 0.20% or less, Sn: 0.020% or less, Sb: 0.025% or less, B: 0.010% or less, Cu: 0.50% or less, Ni: 0.50% or less, Ti: 0.100% or less, V: 0.20% or less,
• the component composition is Si: 0.50% or less in mass%, P: 0.10% or less,
• the component composition is Ca: 0.0010% or less in mass%, Se: 0.30% or less, Te: 0.15% or less, Bi: 0.20% or less, Sn: 0.020% or less, Sb: 0.025% or less, B: 0.010% or less, Cu: 0.50% or less, Ni: 0.50% or less, Ti: 0.100% or less, V: 0.20% or less,
• C Less than 0.09% C is an important element that has a great influence on the strength and machinability of steel. However, if the content is 0.09% or more, the hardness becomes too high and the machinability deteriorates. Therefore, the C content is set to less than 0.09%. Preferably, it is within the range of 0.07% or less. From the viewpoint of ensuring strength, the C content is preferably 0.01% or more. Further, it is more preferably 0.03% or more.
• Mn 0.50 to 1.50%
• Mn is a sulfide-forming element that is important for improving machinability.
• the Mn content is preferably 0.70% or more.
• the upper limit of the Mn content is set to 1.50%.
• the Mn content is preferably 1.20% or less.
• S 0.250 to 0.600%
• S is a sulfide-forming element effective for improving machinability.
• the content is less than 0.250%, the machinability is not improved because there are few fine sulfides.
• the content exceeds 0.600%, the sulfide becomes too coarse and the number of fine sulfides decreases, so that the machinability is lowered. It also reduces hot workability and ductility, which is an important mechanical property. Therefore, the S content is in the range of 0.250 to 0.600%. Preferably, it is 0.300% or more. Preferably, it is 0.450% or less.
• O More than 0.0100% and 0.0500% or less O is an element that forms oxides and becomes precipitation nuclei of sulfides, and is also an effective element for suppressing elongation of sulfides during hot working such as rolling. By this action, machinability can be improved. However, if the content is 0.0100% or less, the effect of suppressing the elongation of sulfide is not sufficient, and the elongated sulfide remains, and the original effect cannot be expected. Therefore, the content of O is set to more than 0.0100%.
• the upper limit is 0.0500%.
• Cr 0.50 to 1.50% Cr forms sulfide and has the effect of improving machinability by lubricating action during cutting. Further, since the elongation of sulfide during hot working such as rolling is suppressed, the machinability can be improved. However, if the content is less than 0.50%, the formation of sulfide is not sufficient and the elongated sulfide tends to remain, so that the original effect cannot be sufficiently expected. On the other hand, if it is added in excess of 1.50%, in addition to hardening, the sulfide becomes coarse and the effect of suppressing elongation is saturated, and the machinability is rather lowered. Also, adding an excessive amount of alloy cost is economically disadvantageous. Therefore, the Cr content is set to 0.50 to 1.50%. Preferably, it is 0.70% or more. Preferably, it is 1.30% or less.
• the balance contains Fe and unavoidable impurities, or further contains optional components described later.
• the above components, or further optional components described later are composed of the remaining Fe and unavoidable impurities.
• the A value defined by the following formula (1) is 6.0 to 18.0.
• a value 2 ([Mn] + 2 [Cr]) / [S] ⁇ ⁇ ⁇ (1)
• [M] is the content (mass%) of the element in []. That is, the A value is an important index that influences the miniaturization of Mn-Cr-S sulfide during hot working such as rolling, and by limiting this A value, machinability can be improved. can.
• the A value is set to 6.0 to 18.0.
• it is 6.5 or more.
• it is 17.0 or less.
• the optional contained components will be described.
• the following components can be contained, if necessary.
• Si 0.50% or less
• Si is a deoxidizing element, and the oxide of Si acts as a sulfide formation nucleus, promotes the formation of sulfide, refines the sulfide, and improves the life of the cutting tool. Therefore, if it is desired to further extend the tool life, it may be contained in steel. However, if it is added in excess of 0.50%, the oxide will become large and the number will decrease, so that it will not be effective as a nucleation nuclei of sulfide, and in addition, it will induce abrasive wear due to the hard oxide and the tool life will be shortened. It causes deterioration. Therefore, the Si content should be 0.50% or less. Preferably, it is 0.03% or less. In addition, in order to exhibit the above-mentioned action by Si, it is preferably contained in an amount of 0.001% or more.
• P 0.10% or less
• P is an element effective in reducing the roughness of the finished surface by suppressing the formation of landmarks during cutting. From this viewpoint, P is preferably contained in an amount of 0.01% or more. However, if the content exceeds 0.10%, the material becomes hard and the machinability is lowered, and the hot workability and ductility are remarkably lowered. Therefore, the P content is preferably 0.10% or less. More preferably, it is 0.08% or less.
• Al 0.010% or less
• Al is a deoxidizing element like Si and may be contained.
• Al produces Al 2 O 3 in steel, but since this oxide is hard, so-called abrasive wear deteriorates the life of the cutting tool, so it is necessary to avoid excessive Al content. ..
• the amount of Al added is 0.010% or less. More preferably, it is 0.005% or less. From the viewpoint of exhibiting the deoxidizing effect of Al, it is preferable that Al is contained in an amount of 0.001% or more.
• N 0.0150% or less N forms a nitride with Cr and the like, and the nitride decomposes due to the temperature rise during cutting to form an oxide film called bellague on the tool surface. Since the bellag has an effect of protecting the tool surface and thus improves the tool life, N may be contained. In order to effectively exhibit this effect, it is preferable that N is contained in an amount of 0.0050% or more. On the other hand, if it is added in excess of 0.0150%, the effect of Belag is saturated and the material is hardened, so that the tool life is shortened. Therefore, the N content is preferably 0.0150% or less. More preferably, it is 0.0060% or more. More preferably, it is 0.0120% or less.
• the following components can be further contained, if necessary.
• Ca, Se, Te, Bi, Sn, Sb, B, Cu, Ni, Ti, V, Zr, Mg are all covered. Since it has an action of improving machinability, it may be added when machinability is important.
• the amount of these elements added is Ca: less than 0.0001%, Se: less than 0.02%, Te: less than 0.10%, Bi: less than 0.02%, Sn: less than 0.003%, Sb: less than 0.003%, B: less than 0.003%, Cu: less than 0.05%, Ni: less than 0.50%, Ti: less than 0.003%, V: less than 0.005%, Zr: less than 0.005%, Mg: less than 0.0005% is sufficient Since no effect can be obtained, Ca: 0.0001% or more, Se: 0.02% or more, Te: 0.10% or more, Bi: 0.02% or more, Sn: 0.003% or more, Sb: 0.003% or more, B: 0.003% or more, respectively. , Cu: 0.05% or more, Ni: 0.05% or more, Ti: 0.003% or more, V: 0.005% or more, Zr: 0.005% or more, Mg: 0.0005% or more.
• the contents of these elements are Ca: 0.0010% or less, Se: 0.30% or less, Te: 0.15% or less, Bi: 0.20% or less, Sn: 0.020% or less, Sb: 0.025% or less, B: 0.010%, respectively.
• Step structure Distribution of 500 pieces / mm 2 or more of sulfides with a diameter equivalent to a circle of less than 1 ⁇ m, and 2000 pieces / mm 2 or more of sulfides with a diameter equivalent to a circle of 1 to 5 ⁇ m. It is advantageous to promote the lubricating action between the tool and the work material during cutting. In order to ensure the machinability of free-cutting steel by fine dispersion of sulfides, sulfides with a circle-equivalent diameter of less than 1 ⁇ m and a circle-equivalent diameter of 1 to 5 ⁇ m are dispersed in a certain amount or more in the steel structure. There is a need.
• Sulfide with a circular equivalent diameter of less than 1 ⁇ m is mainly effective for lubrication between the tool and the work material. Further, a sulfide having a circle-equivalent diameter of 1 to 5 ⁇ m is effective not only for the above-mentioned lubrication effect but also for chip fragmentation. Therefore, the number of sulfides with a circle-equivalent diameter of less than 1 ⁇ m is 500 pieces / mm 2 or more, and the number of sulfides with a circle-equivalent diameter of 1 to 5 ⁇ m is 2000 pieces / mm 2 or more.
• a rectangular slab having the above-mentioned composition and having a side length of 250 mm or more perpendicular to the longitudinal direction is rolled at a heating temperature of 1120 ° C. or higher and a surface reduction rate of 60% or higher to billet.
• the billet is hot-worked at a heating temperature of 1050 ° C. or higher and a surface reduction rate of 75% or higher.
• the length of one side in the cross section of the slab shall be 250 mm or more. More preferably, it is 300 mm or more.
• the upper limit of the length of one side in the cross section of the slab does not need to be particularly regulated, but from the viewpoint of feasibility of hot rolling following casting, the length is preferably 600 mm or less.
• Heating temperature of slabs 1120 ° C or higher
• the slabs are hot-rolled to form billets, but the heating temperature during this hot rolling must be 1120 ° C or higher. If the heating temperature is less than 1120 ° C., the coarse sulfide crystallized during cooling-solidification in the casting stage does not dissolve in solid solution, and the coarse sulfide remains even after the billet is formed. As a result, the sulfide remains coarse even after the subsequent hot working, and the desired fine sulfide distribution state cannot be obtained. Therefore, the heating temperature when hot rolling the slabs into billets is 1120 ° C or higher, preferably 1150 ° C or higher.
• the upper limit of the heating temperature of the slab does not need to be particularly regulated, but from the viewpoint of suppressing scale loss, the heating temperature is preferably 1300 ° C. or lower, more preferably 1250 ° C. or lower.
• the surface reduction ratio (%) of hot rolling is such that the cross-sectional area of the slab before hot rolling is S0 in the cross section perpendicular to the hot rolling direction, and the hot rolling direction of the billet manufactured by hot rolling.
• S1 be the cross-sectional area of the cross section perpendicular to, and the following formula 100 ⁇ (S0-S1) / S0 Can be obtained by.
• Heating temperature 1050 ° C or higher
• the heating temperature when hot-working billets into steel bars or wires is an important factor. If the heating temperature is less than 1050 ° C., the sulfide is not finely dispersed, so that the lubricating action during cutting is reduced. As a result, the tool wear is increased and the tool life is shortened. Therefore, the heating temperature of the billet is set to 1050 ° C. or higher. More preferably, it is 1080 ° C. or higher. Although it is not necessary to regulate the upper limit, it is preferable to set the temperature to 1250 ° C. or lower from the viewpoint of suppressing the decrease in yield due to scale loss.
• the surface reduction rate for hot working is also an important factor for the miniaturization of sulfides. If the surface reduction rate is less than 75%, the sulfide is not sufficiently refined, so the lower limit of the surface reduction rate is set to 75%. More preferably, it is 80% or more.
• the surface reduction rate of hot working is S1 for the cross-sectional area of the billet before hot rolling, which is perpendicular to the hot working direction, and the hot working direction (stretching) of the steel bar or wire rod manufactured by hot working.
• S2 be the cross-sectional area of the cross section perpendicular to the direction), and the following equation 100 ⁇ (S1-S2) / S1 Can be obtained by.
• the steel having the chemical composition shown in Table 1 was made into a rectangular slab having a cross section perpendicular to the longitudinal direction with the dimensions shown in Table 2-1 and Table 2-2 by a continuous casting machine.
• the obtained slabs were rolled into steel bars under the production conditions shown in Table 2-1 and Table 2-2.
• the steel of the present invention and the comparative steel were subjected to the following tests. That is, the slabs are hot-rolled at the heating temperature and surface reduction rate shown in Tables 2-1 and 2-2, and the long piece dimensions and short piece dimensions are as shown in Tables 2-1 and 2-2. It was a square billet.
• the obtained billets were heated at the heating temperatures shown in Tables 2-1 and 2-2 and hot-rolled to obtain steel bars having the diameters shown in Tables 2-1 and 2-2.
• the obtained steel bars (steel of the present invention and comparative steel) were subjected to the tests shown below.
• a test piece was collected from a cross section parallel to the rolling direction of the obtained steel bar, and the 1/4 position in the radial direction from the peripheral surface of the cross section was observed with a scanning electron microscope (SEM). , The circle-equivalent diameter and number density of sulfide in steel were investigated.
• the composition of the precipitate was analyzed by Energy Dispersive X-ray spectrum (EDX), and the obtained SEM image of the precipitate confirmed to be sulfide by EDX is imaged. The analysis was performed and binarization was performed to obtain the equivalent circle diameter and the number density.
• EDX Energy Dispersive X-ray spectrum
• the machinability was evaluated by an outer peripheral turning test.
• BNC-34C5 manufactured by Citizen Machinery was used as the cutting machine
• Carbide EX 35-bit TNGG160404R-N manufactured by Hitachi Tool was used as the turning tip
• DTGNR2020 manufactured by Kyocera was used as the holder.
• As the lubricant a 15-fold diluted emulsion of Yushiroken FGE1010 manufactured by Yushiro Chemical Industry Co., Ltd. was used.
• the cutting conditions were a cutting speed of 120 m / min, a feed rate of 0.05 mm / rev, a depth of cut of 2.0 mm, and a machining length of 10 m.
• the machinability was evaluated by the flank wear Vb of the tool after the cutting test for a length of 10 m was completed.
• the flank wear Vb after the completion of the cutting test was 200 ⁇ m or less, it was rated as “ ⁇ ”, and when the flank wear was more than 200 ⁇ m, it was rated as “x”.
• Table 2-1 and Table 2-2 show the test results of the invention steel and the comparative steel. As is clear from Table 2-1 and Table 2-2, the steel of the present invention has good machinability with respect to the comparative steel.

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• 2021
  • 2021-03-31 JP JP2021538730A patent/JP7024922B1/ja active Active
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  • 2021-03-31 CN CN202180025472.0A patent/CN115362278B/zh active Active
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