WO2022145066A1 - Steel material - Google Patents

Steel material Download PDF

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Publication number
WO2022145066A1
WO2022145066A1 PCT/JP2021/014772 JP2021014772W WO2022145066A1 WO 2022145066 A1 WO2022145066 A1 WO 2022145066A1 JP 2021014772 W JP2021014772 W JP 2021014772W WO 2022145066 A1 WO2022145066 A1 WO 2022145066A1
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WIPO (PCT)
Prior art keywords
content
less
steel
amount
solid solution
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PCT/JP2021/014772
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French (fr)
Japanese (ja)
Inventor
恭平 石川
耕平 中田
謙 木村
美百合 梅原
真吾 山▲崎▼
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日本製鉄株式会社
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Publication of WO2022145066A1 publication Critical patent/WO2022145066A1/en

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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C19/00—Alloys based on nickel or cobalt
    • C22C19/03—Alloys based on nickel or cobalt based on nickel
    • C22C19/05—Alloys based on nickel or cobalt based on nickel with 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
    • 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 steel materials.
  • Phosphorus (P) dissolved in the steel (hereinafter, also referred to as “solid solution P”) is concentrated in a specific part in the steel, for example, between dendrite trees and grain boundaries, and the toughness and ductility of the steel material are increased. It is known that properties such as corrosion resistance and weldability may be deteriorated. In order to improve these characteristics of the steel material, it is important to reduce the amount of solid solution P in the steel, but in order to drastically reduce the P content, an increase in manufacturing cost is unavoidable. Therefore, a method for detoxifying P in steel has been proposed in the prior art (see, for example, Patent Documents 1 to 4).
  • Patent Document 1 describes a high-strength pearlite rail containing Zr, Nb, Ti, and Mo. Further, in Patent Document 1, P, which is an element that lowers toughness, is fixed as a phosphide of Zr, Nb, Ti, and Mo, and the solid solution P concentration is 0.018% or less to improve toughness. Is taught.
  • Patent Document 2 describes a tempered high-strength steel for large heat input welding containing a rare earth element (REM). Further, in Patent Document 2, by setting the B content to 0.0010% by weight and the REM content to 0.002% by weight or more, stress relief annealing is performed without drastically reducing P. It is taught that the deterioration of the toughness of the base metal can be made to the extent that there is no problem in practical use, and that the large heat input welding characteristics are also excellent.
  • REM rare earth element
  • Patent Document 3 describes a steel in which microsegregation of P is dispersed by containing Nd according to the P content. Patent Document 3 describes that P concentrated in dendrite trees and added Nd are combined to finely disperse P in steel to make it harmless.
  • Patent Document 4 describes high-strength bolts containing Ce according to the P content. Further, Patent Document 4 teaches that P and Ce are combined to form a phosphide to suppress grain boundary embrittlement, the amount of solid solution P is reduced, and the hydrogen embrittlement resistance of the bolt is improved. Has been done.
  • Japanese Unexamined Patent Publication No. 2001-40453 Japanese Unexamined Patent Publication No. 59-159966 Japanese Unexamined Patent Publication No. 2010-100923 Japanese Unexamined Patent Publication No. 2017-160525
  • Patent Document 1 teaches that the content of Zr, Nb, Ti and Mo is specified within a predetermined range to generate a phosphide thereof, thereby reducing the amount of solid-dissolved P. Other factors that may affect production have not always been thoroughly investigated.
  • Patent Document 2 no specific element that can be used as REM is taught or suggested, and sufficient studies have not been made from the viewpoint of reducing the amount of solid solution P in steel.
  • Patent Document 3 describes that among REMs, those that can be added to practical steel are limited to La, Ce and Nd, and Nd is selected as the most effective REM for detoxifying P.
  • Patent Document 3 elements other than La, Ce and Nd have not always been sufficiently studied, and therefore, in the invention described in Patent Document 3, the reduction of the amount of solid melt P in steel still remains. There was room for improvement. This point is the same as the invention described in Patent Document 4, in which elements other than Ce have not been sufficiently studied.
  • the present invention has been made in view of such circumstances, and an object thereof is that the amount of solid solution P in steel can be reduced or the amount of solid solution P in steel can be reduced by a novel configuration.
  • the purpose is to provide the steel products that have been made.
  • the present inventors have studied elements that can reduce the amount of solid solution P in steel in order to achieve the above object. As a result, the present inventors secure the amount of the specific element to a certain amount or more, and set the relationship between the amount of the specific element and the P content in the steel within a predetermined range to solidify the steel. We have found that the amount of dissolved P can be reduced, and completed the present invention.
  • the steel materials that have achieved the above objectives are as follows. (1) By mass%, C: 0.001 to 1.000%, Si: 0.01-3.00%, Mn: 0.10 to 4.50%, P: 0.300% or less, S: 0.0300% or less, Al: 0.001-5.000%, N: 0.2000% or less, O: 0.0100% or less, At least one Z element selected from the group consisting of Zr: 0 to 0.8000% and Hf: 0 to 0.8000%.
  • Nb 0-3.000%, Ti: 0 to 0.500%, Ta: 0 to 0.500%, V: 0 to 1.00%, Cu: 0 to 3.00%, Ni: 0-60.00%, Cr: 0 to 30.00%, Mo: 0 to 5.00%, W: 0 to 2.00%, B: 0-0.0200%, Co: 0 to 3.00%, Be: 0 to 0.050%, Ag: 0 to 0.500%, Ca: 0-0.0500%, Mg: 0-0.0500%, At least one of La, Ce, Nd, Y, Pm, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc: 0 to 0.5000% in total.
  • Equation 2 [Zr], [Hf], [O], [N], [S], and [P] are the content [mass%] of each element, and are 0 when the element is not contained. .. (2)
  • the chemical composition is mass%.
  • Nb 0.003 to 3.000%
  • the steel material according to the embodiment of the present invention is based on mass%.
  • Nb 0-3.000%, Ti: 0 to 0.500%, Ta: 0 to 0.500%, V: 0 to 1.00%, Cu: 0 to 3.00%, Ni: 0-60.00%, Cr: 0 to 30.00%, Mo: 0 to 5.00%, W: 0 to 2.00%, B: 0-0.0200%, Co: 0 to 3.00%, Be: 0 to 0.050%, Ag: 0 to 0.500%, Ca: 0-0.0500%, Mg: 0-0.0500%, At least one of La, Ce, Nd, Y, Pm, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc: 0 to 0.5000% in total.
  • tempering treatment is typically performed at a predetermined temperature after quenching in order to secure low temperature toughness. If the solid solution P in the steel is relatively large, the solid solution P segregates at the former austenite grain boundaries during such tempering treatment, causing so-called tempering embrittlement, and as a result, the toughness of the steel material is reduced. May reduce.
  • the present inventors have investigated an element that can react with the solid solution P in steel to reduce the amount thereof.
  • the present inventors have determined the amounts of the elements Zr and Hf (hereinafter, also referred to as “Z element”) as inclusions formed in the steel by those elements, more specifically, oxides of these elements.
  • Z element the elements Zr and Hf
  • the present inventors Secure a certain amount or more while considering the relationship with nitrides and sulfides (that is, the effective amount of the Z element corresponding to the left side of the formula 1 is 0.0003% or more), and further, the effective amount of the specific element.
  • the above-mentioned Z element has a property of easily forming inclusions composed of oxides, nitrides and sulfides in combination with O (oxygen), N (nitrogen) and S (sulfur) existing in steel.
  • O oxygen
  • N nitrogen
  • S sulfur
  • the amount of the Z element that can contribute to the reaction with the solid solution P decreases, and the amount of the solid solution P can be sufficiently reduced. It disappears.
  • the amount of the Z element in consideration of such inclusions is calculated as the effective amount of the Z element by the above formula 1 which will be described in detail later, and the effective amount is set to a certain amount or more, that is, 0.
  • the Z element can be reacted with the solid solution P to form a phosphide.
  • the phosphide By forming the phosphide, at least a part of the solid solution P can be fixed, and the segregation of the solid solution P to the grain boundaries and the like can be remarkably suppressed.
  • the above-mentioned equation 2 has a higher effect of reducing solid solution P. Was found to be achievable.
  • the present invention it is possible to obtain a steel material in which the solid solution P amount in the steel can be sufficiently reduced or the solid solution P amount in the steel is sufficiently reduced without excessively reducing the P content. Therefore, it is possible to remarkably improve the characteristics of the steel material related to the solid solution P, for example, the characteristics such as toughness, ductility, corrosion resistance, and weldability. More specifically, by reducing the amount of the solid solution P in the steel, it is possible to prevent the solid solution P from segregating at a specific place such as the old austenite grain boundary during, for example, tempering treatment. .. As a result, according to the present invention, it is possible to suppress the occurrence of tempering embrittlement and the like, and therefore it is possible to significantly improve the toughness and other properties of the steel material.
  • the Z element in the present invention easily combines with O, N and S to form inclusions as described above, and therefore it is generally difficult to secure a predetermined effective amount in steel. Due to such circumstances, the effect of reducing the solid solution P by the Z element has not been known so far. However, recent advances in refining technology have made it possible to reduce the content of elements such as O, N, and S, which are generally present in steel as impurities, to extremely low levels. It was possible to realize an effective amount of the Z element within a predetermined range. Therefore, the effect of reducing the solid solution P on the Z element has been clarified for the first time by the present inventors, and is extremely surprising and surprising.
  • Carbon (C) is an element necessary for stabilizing hardness and / or ensuring strength. In order to sufficiently obtain these effects, the C content is 0.001% or more. The C content may be 0.005% or more, 0.010% or more, or 0.020% or more. On the other hand, if C is excessively contained, toughness, bendability and / or weldability may decrease. Therefore, the C content is 1.000% or less. The C content may be 0.800% or less, 0.600% or less, or 0.500% or less.
  • Si is a deoxidizing element and is an element that also contributes to the improvement of strength. In order to sufficiently obtain these effects, the Si content is 0.01% or more. The Si content may be 0.05% or more, 0.10% or more, or 0.30% or more. On the other hand, if Si is excessively contained, the toughness may be lowered or surface quality defects called scale defects may occur. Therefore, the Si content is 3.00% or less. The Si content may be 2.00% or less, 1.00% or less, or 0.60% or less.
  • Manganese (Mn) is an element effective for improving hardenability and / or strength, and is also an effective austenite stabilizing element. In order to sufficiently obtain these effects, the Mn content is 0.10% or more. The Mn content may be 0.50% or more, 0.70% or more, or 1.00% or more. On the other hand, if Mn is excessively contained, MnS harmful to toughness may be generated or the oxidation resistance may be lowered. Therefore, the Mn content is 4.50% or less. The Mn content may be 4.00% or less, 3.50% or less, or 3.00% or less.
  • Phosphorus (P) is an element mixed in the manufacturing process. From the viewpoint of reducing the amount of solid solution P in the steel, the smaller the amount of P, the more preferable, and the P content may be 0%. However, in order to reduce the P content to less than 0.0001%, it takes time for refining, which leads to a decrease in productivity. Therefore, the P content may be 0.0001% or more, 0.0005% or more, 0.001% or more, 0.003% or more, or 0.005% or more. The P content may be 0.007% or more from the viewpoint of manufacturing cost.
  • the P content is 0.300% or less.
  • the P content may be 0.100% or less, 0.030% or less, or 0.010% or less.
  • S 0.0300% or less
  • Sulfur (S) is an element mixed in the manufacturing process, and is preferable from the viewpoint of reducing inclusions formed with the Z element according to the embodiment of the present invention, so that the S content is 0%. There may be. However, in order to reduce the S content to less than 0.0001%, it takes time for refining, which leads to a decrease in productivity. Therefore, the S content may be 0.0001% or more, 0.0005% or more, or 0.0010% or more. On the other hand, if S is excessively contained, the effective amount of the Z element may decrease and the toughness may decrease. Therefore, the S content is 0.0300% or less.
  • the S content is preferably 0.0100% or less, more preferably 0.0050% or less, and most preferably 0.0030% or less.
  • Aluminum (Al) is a deoxidizing element and is also an effective element for improving corrosion resistance and / or heat resistance.
  • the Al content is 0.001% or more.
  • the Al content may be 0.010% or more, 0.100% or more, or 0.200% or more.
  • the Al content may be 1.000% or more, 2.000% or more, or 3.000% or more.
  • the Al content is 5.000% or less.
  • the Al content may be 4.500% or less, 4000% or less, or 3.500% or less.
  • the Al content may be 1.500% or less, 1.000% or less, or 0.300% or less.
  • N Nitrogen (N) is an element mixed in the manufacturing process, and is preferable from the viewpoint of reducing inclusions formed with the Z element according to the embodiment of the present invention, so that the N content is 0%. There may be. However, in order to reduce the N content to less than 0.0001%, it takes time for refining, which leads to a decrease in productivity. Therefore, the N content may be 0.0001% or more, 0.0005% or more, or 0.0010% or more. On the other hand, N is also an element effective for stabilizing austenite, and may be intentionally contained if necessary. In this case, the N content is preferably 0.0100% or more, and may be 0.0200% or more and 0.0500% or more. However, if N is excessively contained, the effective amount of the Z element may decrease and the toughness may decrease. Therefore, the N content is 0.2000% or less. The N content may be 0.1500% or less, 0.1000% or less, or 0.0800% or less.
  • Oxygen (O) is an element mixed in the manufacturing process, and is preferable from the viewpoint of reducing inclusions formed with the Z element according to the embodiment of the present invention, so that the O content is 0%. There may be. However, in order to reduce the O content to less than 0.0001%, it takes time for refining, which leads to a decrease in productivity. Therefore, the O content may be 0.0001% or more, 0.0005% or more, or 0.0010% or more. On the other hand, if O is excessively contained, coarse inclusions may be formed, the effective amount of the Z element may be lowered, and the formability and / or toughness of the steel material may be lowered. Therefore, the O content is 0.0100% or less. The O content may be 0.0080% or less, 0.0060% or less, or 0.0040% or less.
  • the Z element according to the embodiment of the present invention is Zr: 0 to 0.8000% and Hf: 0 to 0.8000%, and zirconium (Zr) and hafnium (Hf) are solid-dissolved based on the formation of a phosphide.
  • the effect of reducing P can be exhibited.
  • By exhibiting the effect of reducing the solid solution P it is possible to remarkably improve the characteristics of the steel material related to the solid solution P, such as toughness, ductility, corrosion resistance, and weldability.
  • any one element may be used alone, or both may be used. Further, the Z element may be present in an amount satisfying the formulas 1 and 2 described in detail later, and the lower limit thereof is not particularly limited. However, for example, the content of each Z element or the total content may be 0.0010% or more, preferably 0.0050% or more, more preferably 0.0150% or more, and even more. It is preferably 0.0300% or more, and most preferably 0.0500% or more. On the other hand, even if the Z element is excessively contained, the effect is saturated, and therefore, if the Z element is contained in the steel material more than necessary, the manufacturing cost may increase.
  • the content of each Z element is 0.8000% or less, for example, 0.7000% or less, 0.6000% or less, 0.5000% or less, 0.4000% or less, or 0.3000% or less. May be good.
  • the total content of the Z element is 1.6000% or less, for example, 1.2000% or less, 1.000% or less, 0.8000% or less, 0.6000% or less, or 0.5000% or less. You may.
  • the steel material may contain one or more of the following optional elements, if necessary.
  • the steel material has Nb: 0 to 3.000%, Ti: 0 to 0.500%, Ta: 0 to 0.500%, V: 0 to 1.00%, Cu: 0 to 3.00%, Ni: 0 to 60.00%, Cr: 0 to 30.00%, Mo: 0 to 5.00%, W: 0 to 2.00%, B: 0 to 0.0200%, Co: 0 to 3 It may contain one or more of .00%, Be: 0 to 0.050%, and Ag: 0 to 0.500%.
  • the steel materials include Ca: 0 to 0.0500%, Mg: 0 to 0.0500%, and La, Ce, Nd, Y, Pm, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er. At least one of Tm, Yb, Lu, and Sc: one or more of 0 to 0.5000% in total may be contained. Further, the steel material may contain one or two of Sn: 0 to 0.300% and Sb: 0 to 0.300%. The steel materials are Te: 0 to 0.100%, Se: 0 to 0.100%, As: 0 to 0.050%, Bi: 0 to 0.500%, and Pb: 0 to 0.500%. One or more of them may be contained. Hereinafter, these optional elements will be described in detail.
  • Niobium (Nb) is an element that contributes to strengthening precipitation and suppressing recrystallization.
  • the Nb content may be 0%, but in order to obtain these effects, the Nb content is preferably 0.003% or more.
  • the Nb content may be 0.005% or more or 0.010% or more.
  • the Nb content may be 1.000% or more or 1.500% or more from the viewpoint of sufficiently strengthening precipitation.
  • the Nb content is 3.000% or less.
  • the Nb content may be 2.800% or less, 2.500% or less, or 2.000% or less.
  • the Nb content is preferably 0.100% or less, 0.080% or less, 0.050% or less, or 0.030. It may be less than or equal to%.
  • Titanium (Ti) is an element that contributes to improving the strength of steel materials by strengthening precipitation.
  • the Ti content may be 0%, but in order to obtain such an effect, the Ti content is preferably 0.005% or more.
  • the Ti content may be 0.010% or more, 0.050% or more, or 0.080% or more.
  • the Ti content is 0.500% or less.
  • the Ti content may be 0.300% or less, 0.200% or less, or 0.100% or less.
  • Tantalum (Ta) is an element effective in controlling the morphology of carbides and increasing their strength.
  • the Ta content may be 0%, but in order to obtain these effects, the Ta content is preferably 0.001% or more.
  • the Ta content may be 0.005% or more, 0.010% or more, or 0.050% or more.
  • the Ta content is 0.500% or less.
  • the Ta content may be 0.300% or less, 0.100% or less, or 0.080% or less.
  • Vanadium (V) is an element that contributes to improving the strength of steel materials by strengthening precipitation.
  • the V content may be 0%, but in order to obtain such an effect, the V content is preferably 0.001% or more.
  • the V content may be 0.01% or more, 0.02% or more, 0.05% or more, or 0.10% or more.
  • the V content is 1.00% or less.
  • the V content may be 0.80% or less, 0.60% or less, or 0.50% or less.
  • Copper (Cu) is an element that contributes to the improvement of strength and / or corrosion resistance.
  • the Cu content may be 0%, but in order to obtain these effects, the Cu content is preferably 0.001% or more.
  • the Cu content may be 0.01% or more, 0.10% or more, 0.15% or more, 0.20% or more, or 0.30% or more.
  • the Cu content is 3.00% or less.
  • the Cu content may be 2.00% or less, 1.50% or less, 1.00% or less, or 0.50% or less.
  • Nickel (Ni) is an element that contributes to the improvement of strength and / or heat resistance, and is also an effective austenite stabilizing element.
  • the Ni content may be 0%, but in order to obtain these effects, the Ni content is preferably 0.001% or more.
  • the Ni content may be 0.01% or more, 0.10% or more, 0.50% or more, 0.70% or more, 1.00% or more, or 3.00% or more.
  • the Ni content may be 30.00% or more, 35.00% or more, or 40.00% or more.
  • the deformation resistance during hot working increases in addition to the increase in alloy cost, which may increase the equipment load.
  • the Ni content is 60.00% or less.
  • the Ni content may be 55.00% or less or 50.00% or less.
  • the Ni content is 15.00% or less, 10.00% or less, 6.00% or less, or 4.00% or less. You may.
  • Chromium (Cr) is an element that contributes to the improvement of strength and / or corrosion resistance.
  • the Cr content may be 0%, but in order to obtain these effects, the Cr content is preferably 0.001% or more.
  • the Cr content may be 0.01% or more, 0.05% or more, 0.10% or more, or 0.50% or more.
  • the Cr content may be 10.00% or more, 12.00% or more, or 15.00% or more.
  • the Cr content is 30.00% or less.
  • the Cr content may be 28.00% or less, 25.00% or less, or 20.00% or less.
  • the Cr content may be 10.00% or less, 9.00% or less, or 7.50% or less.
  • Molybdenum is an element that enhances the hardenability of steel and contributes to the improvement of strength, and is also an element that contributes to the improvement of corrosion resistance.
  • the Mo content may be 0%, but in order to obtain these effects, the Mo content is preferably 0.001% or more.
  • the Mo content may be 0.01% or more, 0.02% or more, 0.50% or more, or 1.00% or more.
  • Mo content is 5.00% or less.
  • the Mo content may be 4.50% or less, 4.00% or less, 3.00 or less, or 1.50% or less.
  • Tungsten is an element that enhances the hardenability of steel and contributes to the improvement of strength.
  • the W content may be 0%, but in order to obtain such an effect, the W content is preferably 0.001% or more.
  • the W content may be 0.01% or more, 0.02% or more, 0.05% or more, 0.10% or more, or 0.50% or more.
  • the W content is 2.00% or less.
  • the W content may be 1.80% or less, 1.50% or less, or 1.00% or less.
  • B is an element that contributes to the improvement of strength.
  • the B content may be 0%, but in order to obtain such an effect, the B content is preferably 0.0001% or more.
  • the B content may be 0.0003% or more, 0.0005% or more, or 0.0007% or more.
  • the B content is 0.0200% or less.
  • the B content may be 0.0100% or less, 0.0050% or less, 0.0030% or less, or 0.0020% or less.
  • Co is an element that contributes to the improvement of hardenability and / or heat resistance.
  • the Co content may be 0%, but in order to obtain these effects, the Co content is preferably 0.001% or more.
  • the Co content may be 0.01% or more, 0.02% or more, 0.05% or more, 0.10% or more, or 0.50% or more.
  • the Co content is 3.00% or less.
  • the Co content may be 2.50% or less, 2.00% or less, 1.50% or less, or 0.80% or less.
  • Beryllium (Be) is an element effective for increasing the strength of the base metal and refining the structure.
  • the Be content may be 0%, but in order to obtain such an effect, the Be content is preferably 0.0003% or more.
  • the Be content may be 0.0005% or more, 0.001% or more, or 0.010% or more.
  • the Be content is 0.050% or less.
  • the Be content may be 0.040% or less, 0.030% or less, or 0.020% or less.
  • Silver (Ag) is an element effective for increasing the strength of the base material and refining the structure.
  • the Ag content may be 0%, but in order to obtain such an effect, the Ag content is preferably 0.001% or more.
  • the Ag content may be 0.010% or more, 0.020% or more, 0.030% or more, or 0.050% or more.
  • the Ag content is 0.500% or less.
  • the Ag content may be 0.400% or less, 0.300% or less, or 0.200% or less.
  • Ca 0-0.0500%
  • Ca is an element that can control the morphology of sulfides.
  • the Ca content may be 0%, but in order to obtain such an effect, the Ca content is preferably 0.0001% or more.
  • the Ca content is 0.0500% or less.
  • Magnesium (Mg) is an element that can control the morphology of sulfides.
  • the Mg content may be 0%, but in order to obtain such an effect, the Mg content is preferably 0.0001% or more.
  • the Mg content may be greater than 0.0015%, greater than 0.0016%, greater than or equal to 0.0018% or greater than or equal to 0.0020%.
  • the Mg content is 0.0500% or less.
  • the Mg content may be 0.0400% or less, 0.0300% or less, or 0.0200% or less.
  • the total content of at least one of La, Ce, Nd, Y, Pm, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc is 0%. However, in order to obtain such an effect, it is preferably 0.0001% or more.
  • the total content of at least one of La, Ce, Nd, Y, Pm, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc is 0.0002% or more. It may be 0.0003% or more or 0.0004% or more.
  • the total content of at least one of La, Ce, Nd, Y, Pm, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc is 0.5000%. It may be less than or equal to 0.4000%, 0.3000% or less, or 0.2000% or less.
  • Tin (Sn) is an element effective for improving corrosion resistance.
  • the Sn content may be 0%, but in order to obtain such an effect, the Sn content is preferably 0.001% or more.
  • the Sn content may be 0.010% or more, 0.020% or more, 0.030% or more, or 0.050% or more.
  • the Sn content is 0.300% or less.
  • the Sn content may be 0.250% or less, 0.200% or less, or 0.150% or less.
  • Antimony (Sb) is an element effective for improving corrosion resistance like Sn, and the effect can be increased by including it in combination with Sn.
  • the Sb content may be 0%, but in order to obtain the effect of improving the corrosion resistance, the Sb content is preferably 0.001% or more.
  • the Sb content may be 0.010% or more, 0.020% or more, 0.030% or more, or 0.050% or more.
  • excessive content of Sb may lead to a decrease in toughness, particularly low temperature toughness. Therefore, the Sb content is 0.300% or less.
  • the Sb content may be 0.250% or less, 0.200% or less, or 0.150% or less.
  • Tellurium is an element effective for improving the machinability of steel because it forms a low melting point compound with Mn, S and the like to enhance the lubricating effect.
  • the Te content may be 0%, but in order to obtain such an effect, the Te content is preferably 0.001% or more.
  • the Te content may be 0.010% or more, 0.020% or more, 0.030% or more, or 0.040% or more.
  • the Te content is 0.100% or less.
  • the Te content may be 0.090% or less, 0.080% or less, or 0.070% or less.
  • Selenium (Se) is an effective element for improving the machinability of steel because the selenium produced in the steel changes the shear-plastic deformation of the work material and the chips are easily crushed. ..
  • the Se content may be 0%, but in order to obtain such an effect, the Se content is preferably 0.001% or more.
  • the Se content may be 0.010% or more, 0.020% or more, 0.030% or more, or 0.040% or more.
  • the Se content is 0.100% or less.
  • the Se content may be 0.090% or less, 0.080% or less, or 0.070% or less.
  • Arsenic (As) is an element effective in improving the machinability of steel.
  • the As content may be 0%, but in order to obtain such an effect, the As content is preferably 0.001% or more.
  • the As content may be 0.005% or more or 0.010% or more.
  • the As content is 0.050% or less.
  • the As content may be 0.040% or less, 0.030% or less, or 0.020% or less.
  • Bismuth (Bi) is an element effective in improving the machinability of steel.
  • the Bi content may be 0%, but in order to obtain such an effect, the Bi content is preferably 0.001% or more.
  • the Bi content may be 0.010% or more, 0.020% or more, 0.030% or more, or 0.050% or more.
  • the Bi content is 0.500% or less.
  • the Bi content may be 0.400% or less, 0.300% or less, or 0.200% or less.
  • Pb 0 to 0.500%
  • Lead (Pb) is an element effective for improving the machinability of steel because it melts when the temperature rises due to cutting and promotes the growth of cracks.
  • the Pb content may be 0%, but in order to obtain such an effect, the Pb content is preferably 0.001% or more.
  • the Pb content may be 0.010% or more, 0.020% or more, 0.030% or more, or 0.050% or more.
  • the Pb content is 0.500% or less.
  • the Pb content may be 0.400% or less, 0.300% or less, or 0.200% or less.
  • the balance other than the above elements consists of Fe and impurities.
  • Impurities are components that are mixed in by various factors in the manufacturing process, including raw materials such as ore and scrap, when steel materials are industrially manufactured.
  • the effective amount of the Z element consisting of Zr and Hf is determined by the left side of the following formula 1, and the value thereof satisfies the following formula 1. 0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1.74 [S] ⁇ 0.0003 ⁇ ⁇ ⁇ Equation 1
  • [Zr], [Hf], [O], [N], and [S] are the content [mass%] of each element, and are 0 when the element is not contained.
  • the effective amount of the Z element By making the effective amount of the Z element satisfy the above formula 1, it is possible to react the Z element existing in the steel with the solid solution P in the steel to form a phosphide. With the formation of the phosphide, it becomes possible to reduce the amount of solid melt P in the steel. More specifically, these Z elements (hereinafter, also simply referred to as “Z”) are combined with O (oxygen), N (nitrogen) and S (sulfur) present in steel to form an oxide (ZO 2 ). , Tends to form inclusions consisting of nitrides (ZN) and sulfides (ZS). Once the inclusions are formed, at least the Z element in these inclusions cannot contribute to the reaction with the solid solution P. Therefore, in order to promote the reaction with the solid solution P and reduce the amount of the solid solution P in the steel, it is necessary to increase the amount of the Z element that can form a phosphide in the steel without forming inclusions. There is.
  • the amount of Z element that can form a phosphide is the amount of Z element contained in the steel minus the maximum amount that can be consumed to form inclusions (oxides, nitrides and sulfides). It is possible to estimate by. Therefore, in the embodiment of the present invention, the amount of Z element effective for reducing the amount of solid solution P in the steel estimated in this way (that is, "effective amount of Z element") is specifically determined. Is defined by the following formula A.
  • Effective amount of Z [atomic%] ⁇ (M [Fe] / M [Z] ) x [Z]-(M [Fe] / M [O] ) x [O] x 1 / 2- (M [Fe ] ] / M [N] ) x [N]-(M [Fe] / M [S] ) x [S] ... Equation A
  • Z represents each Z element of Zr and Hf
  • M [Z] is the atomic weight of the Z element
  • M [Fe] is the atomic weight of Fe
  • M [O] is the atomic weight of O
  • M [N] is N.
  • M [S] represents the atomic weight of S
  • [Z], [O], [N] and [S] are the corresponding element content [mass%], respectively, and when no element is contained. It is 0.
  • the steel material according to the embodiment of the present invention contains various alloying elements, the steel material as a whole is almost composed of Fe or is an optional element.
  • the steel material when a certain Ni and / or Cr is contained in a relatively large amount (the maximum contents are 60.00% and 30.00%, respectively), it is clear that it is almost composed of Ni and / or Cr in addition to Fe. Is.
  • the atomic weights of Ni and Cr are equivalent to the atomic weights of Fe. Therefore, even when the steel material contains a relatively large amount of Ni and / or Cr, the atomic% of each Z element of Zr and Hf is approximately Fe in the content [mass%] of each Z element.
  • the maximum amount (atomic%) that can be consumed to form oxides (ZO 2 ), nitrides (ZN) and sulfides (ZS) is solidified. It is possible to calculate the amount of Z element in steel that can effectively act to reduce the amount of molten P.
  • the maximum amount (atomic%) of Z element that can be consumed to form oxides (ZO 2 ), nitrides (ZN) and sulfides (ZS) is for the same reasons as described above.
  • Effective amount of Z [atomic%] ⁇ (M [Fe] / M [Z] ) x [Z]-(M [Fe] / M [O] ) x [O] x 1 / 2- (M [Fe ] ] / M [N] ) x [N]-(M [Fe] / M [S] ) x [S] ... Equation A
  • [Zr], [Hf], [O], [N], and [S] are the content [mass%] of each element, and are 0 when the element is not contained.
  • the effective amount of the Z element determined by the above formula B is 0.0003% or more, that is, at least satisfy the following formula 1. 0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1.74 [S] ⁇ 0.0003 ⁇ ⁇ ⁇ Equation 1
  • the effective amount of the Z element may be, for example, 0.0005% or more or 0.0007% or more, preferably 0.0010% or more, more preferably 0.0015% or more, still more preferably 0.0030%. The above is most preferably 0.0050% or more or 0.0100% or more.
  • the effective amount of the Z element is preferably 2.000% or less, for example, 1.8000% or less, 1.5000% or less, 1.2000% or less, 1.000% or less, or 0.8000% or less. You may.
  • the effective amount of the Z element and the P content in the steel satisfy the following formula 2. 1.80 x [P]-(0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1.74 [S]) ⁇ 0.010 ... Equation 2
  • [Zr], [Hf], [O], [N], [S], and [P] are the content [mass%] of each element, and are 0 when the element is not contained. ..
  • the effective amount of the Z element (atomic%) is subtracted from the P content (atomic%) in the steel.
  • the theoretical amount of solid solution P obtained from the chemical composition of the steel material can be calculated.
  • the value of the P content by atomic% is approximately the atomic weight of Fe and P in the steel and the P content by mass% for the same reason as described above in relation to the effective amount of the Z element. It can be calculated as (M [Fe] / M [P] ) ⁇ [P] using the amount (where M [Fe] represents the atomic weight of Fe and M [P] represents the atomic weight of P.
  • the atomic weights of Fe and P are Fe: 55.845 and P: 30.738, respectively. Therefore, by substituting the atomic weights of Fe and P and the formula B into the above formula C, the theoretical solid solution P amount in terms of atomic% can be approximately expressed by the following formula D.
  • Theoretical solid solution P amount [atomic%] 1.80 ⁇ [P]-(0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1. 74 [S]) ⁇ ⁇ ⁇ Expression D
  • [Zr], [Hf], [O], [N], [S], and [P] are the content [mass%] of each element, and are 0 when the element is not contained. ..
  • the amount of solid solution P actually measured is reduced, thereby improving the characteristics of the steel material related to the solid solution P, such as toughness, ductility, corrosion resistance, and weldability.
  • the theoretical solid solution P amount obtained by the above formula D is less than 0.010%, that is, the following formula 2 is satisfied. 1.80 ⁇ [P]-(0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1.74 [S) ⁇ 0.010 ...
  • the theoretical solid solution P amount (that is, the left side of the formula 2) is preferably 0.008% or less, more preferably 0.005% or less, still more preferably 0.003% or less, and most preferably 0% or less. be. Further, in order to reduce the theoretical solid solution P content and surely satisfy the above formula 2, it is naturally preferable to reduce the P content in the steel as much as possible.
  • the lower limit of the theoretical solid solution P amount is not particularly limited, but even if the theoretical solid solution P amount is excessively reduced, the effect is saturated and the manufacturing cost increases (the increase in the refining cost related to P and the increase in the refining cost related to P). / Or an increase in alloy cost due to an increase in the content of Z element), which is not always preferable. Therefore, the theoretical solid solution P amount is preferably -2.90% or more, for example, -1.80% or more, -1.50% or more, -1.30% or more, -1,000% or more or. It may be ⁇ 0.800% or more.
  • the steel material according to the embodiment of the present invention may be any steel material and is not particularly limited.
  • the steel material according to the embodiment of the present invention includes, for example, slabs, billets, blooms, and steel materials after hot rolling, which are steel materials before hot rolling.
  • the steel material after hot rolling is not particularly limited, but includes, for example, thick steel plates, thin steel plates, steel bars, wire rods, shaped steels, steel pipes, and the like.
  • the steel material according to the embodiment of the present invention can be manufactured by any suitable method known to those skilled in the art, depending on the form of the final product and the like.
  • the manufacturing method includes a step generally applied when manufacturing the thick steel plate, for example, a step of casting a slab having the chemical composition described above, and casting. It includes a step of hot rolling the slab and a step of cooling the obtained rolled material, and may further include heat treatment such as a quenching step and a tempering step, if necessary.
  • the steel material manufacturing process according to the embodiment of the present invention may be a thermal processing control process (TMCP) that combines controlled rolling and accelerated cooling.
  • TMCP thermal processing control process
  • the manufacturing method includes a step generally applied when manufacturing the thin steel plate, for example, a step of casting a slab having the chemical composition described above, and casting. It may further include a step of hot rolling the slab, a step of cooling and winding the obtained rolled material, a cold rolling step, a baking step and the like, if necessary.
  • a step generally applied when manufacturing steel bars and other steel materials is included, and for example, a steelmaking process for forming molten steel having the chemical composition described above is formed. It includes a step of casting slabs, billets, blooms, etc.
  • the amount of solid melt P in steel can be reduced by forming a phosphide (P fixing treatment) by holding it at a predetermined temperature in the range of 900 to 1100 ° C., preferably 950 to 1100 ° C. for 6000 seconds or longer.
  • the P fixing process may be a heat history in the hot rolling process or a heat treatment after the hot rolling process.
  • the holding temperature of the P fixing process may be a constant temperature within the range of 900 to 1100 ° C., or may vary within the range.
  • the holding time in the range of 900 to 1100 ° C. from the heating of steel materials such as slabs, billets and blooms to the completion of hot rolling. May be 6000 seconds or more.
  • the term “retention” includes a case where the temperature gradually decreases due to cooling, air cooling, or the like within the above temperature range.
  • the upper limit of the holding time is not particularly limited, but may be, for example, 15,000 seconds or less or 12,000 seconds or less.
  • the production of the steel material according to the embodiment of the present invention it is important to secure an effective amount of the Z element for fixing the solid solution P, and for that purpose, inclusions are formed in the Z element and the steel. It is extremely important that the contents of O, N and S obtained are sufficiently reduced in the refining step.
  • Example A In this example, first, slabs having various chemical compositions were cast, and then hot rolling was carried out at a rolling reduction of 50% or more and cooled. Next, the obtained rolled material is heated to a predetermined temperature in the range of 950 to 1100 ° C. and held for 6000 to 12000 seconds to form a phosphide (P fixing treatment), that is, at least P in steel. A steel material partially fixed as a phosphide was obtained. The chemical composition obtained by analyzing the samples collected from each of the obtained steel materials is as shown in Table 1 below. The amount of solid solution P in each of the obtained steel materials was measured by the following method.
  • the amount of solid solution P in the steel material was measured by the extraction residue method. More specifically, first, a sample containing a depth position of 0.5 mm from the surface of the steel material taken from the steel material is subjected to a constant current of 500 mmA in a 10% acetylacetone-1% tetramethylammonium chloride-methanol solution under the condition of 2 hours. 1 g or more of the steel material was electrolyzed by electrolysis, and then filtered using a membrane filter having a pore size of 0.2 ⁇ m to separate precipitates (phosphorus products).
  • the separated precipitate was decomposed with a solution in which nitric acid (HNO 3 ) and perchloric acid (HClO 4 ) were mixed at a ratio of 2: 1 and the obtained residue was then subjected to ICP-MS (inductively coupled plasma mass spectrometer). ) was used to determine the amount of P (% by mass) precipitated as a phosphate in the steel material.
  • the solid solution P amount (mass%) in each steel material was determined by subtracting this precipitated P amount (mass%) from the P content (mass%) in each steel material shown in Table 1. The results are shown in Table 1.
  • the effective amount of the Z element is 0.0003% or more, and further satisfies the formula 2 (that is, the left side of the formula 2 is less than 0.010%).
  • the amount of solid solution P in the steel material actually measured could be sufficiently reduced.
  • the P content in the steel material is relatively low, by satisfying the configuration of the present invention, a part thereof is precipitated as a phosphide in the steel material. It can be seen that the amount of solid solution P in the above can be reduced to an extremely low value.
  • Example B In order to ensure low temperature toughness, tempering may be performed at a predetermined temperature after quenching. If the solid solution P in the steel is relatively large, the solid solution P may segregate at the old austenite grain boundaries or the like during such tempering treatment, causing so-called tempering embrittlement. In such a case, the grain boundary fracture is likely to occur, and the toughness of the steel material is lowered. Therefore, in this example, the effect caused by the reduction of the solid solution P was verified for some of the steel materials of Example A.
  • Example 1 the steel materials of Examples 49, 63, 75 and 84 and Comparative Examples 90 and 93 after the P fixing treatment of Example A (details are shown in Table 2 below) are quenched, and then at 550 ° C. and 1200 ° C.
  • a quenching treatment was carried out under the condition of seconds, and a JIS No. 4 test piece (V notch test piece: 10 mm ⁇ 10 mm ⁇ 55 mm) was collected from a 1 / 4t portion of the obtained steel material.
  • the longitudinal direction of the test piece was the plate width direction, and the notch was provided so that the fracture propagated in the rolling direction. Based on this JIS No. 4 test piece, a Charpy impact test was performed at ⁇ 100 ° C.
  • the steel material according to the embodiment of the present invention is, for example, a steel material before hot rolling, such as slab, billet, bloom, or a steel material after hot rolling.
  • Steel materials after hot rolling include, for example, thick steel plates used for bridges, construction, shipbuilding, pressure vessels, etc., thin steel plates used for automobiles, home appliances, etc., as well as steel bars, wire rods, and shaped steel. , And steel pipes and the like.
  • the steel material according to the embodiment of the present invention is applied to these materials, the amount of solid solution P in the steel is sufficiently reduced, so that the characteristics of the steel material related to the solid solution P, for example, toughness. It is possible to significantly improve properties such as ductility, corrosion resistance, and weldability.

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Abstract

Provided is a steel material having a prescribed chemical composition which satisfies Z≥0.0003 and 1.80×[P]-Z<0.010 (In the formulas, Z=0.61[Zr]+0.31[Hf]-1.75[O]-3.99[N]-1.74[S], and [Zr], [Hf], [O], [N], [S] and [P] represent the content (mass%) of each element).

Description

鋼材Steel material
　本発明は、鋼材に関する。 The present invention relates to steel materials.
　鋼中に固溶したリン（Ｐ）（以下、「固溶Ｐ」ともいう）は、鋼中の特定の箇所、例えば、デンドライト樹間、結晶粒界に濃化して、鋼材の靭性、延性、耐食性及び溶接性などの特性を低下させる場合があることが知られている。鋼材のこれらの特性を向上させるためには、鋼中の固溶Ｐ量を低減することが重要であるが、Ｐ含有量を極端に低減させるには製造コストの上昇が避けられない。そのため、従来技術において鋼中のＰを無害化する方法が提案されている（例えば、特許文献１～特許文献４参照）。 Phosphorus (P) dissolved in the steel (hereinafter, also referred to as “solid solution P”) is concentrated in a specific part in the steel, for example, between dendrite trees and grain boundaries, and the toughness and ductility of the steel material are increased. It is known that properties such as corrosion resistance and weldability may be deteriorated. In order to improve these characteristics of the steel material, it is important to reduce the amount of solid solution P in the steel, but in order to drastically reduce the P content, an increase in manufacturing cost is unavoidable. Therefore, a method for detoxifying P in steel has been proposed in the prior art (see, for example, Patent Documents 1 to 4).
　特許文献１では、Ｚｒ、Ｎｂ、Ｔｉ、Ｍｏを含有する高強度パーライト系レールが記載されている。また、特許文献１では、靭性を低下させる元素であるＰを、Ｚｒ、Ｎｂ、Ｔｉ、Ｍｏのリン化物として固定し、固溶Ｐ濃度を０．０１８％以下とすることにより、靭性が向上することが教示されている。 Patent Document 1 describes a high-strength pearlite rail containing Zr, Nb, Ti, and Mo. Further, in Patent Document 1, P, which is an element that lowers toughness, is fixed as a phosphide of Zr, Nb, Ti, and Mo, and the solid solution P concentration is 0.018% or less to improve toughness. Is taught.
　特許文献２では、希土類元素（ＲＥＭ）を含有する大入熱溶接用調質高張力鋼が記載されている。また、特許文献２では、Ｂ含有量を０．００１０重量％までにして、ＲＥＭ含有量を０．００２重量％以上とすることにより、Ｐを極端に低下させなくても応力除去焼なましによる母材靭性の劣化を実用上問題のない程度にすることが可能であり、かつ大入熱溶接特性も優れることが教示されている。 Patent Document 2 describes a tempered high-strength steel for large heat input welding containing a rare earth element (REM). Further, in Patent Document 2, by setting the B content to 0.0010% by weight and the REM content to 0.002% by weight or more, stress relief annealing is performed without drastically reducing P. It is taught that the deterioration of the toughness of the base metal can be made to the extent that there is no problem in practical use, and that the large heat input welding characteristics are also excellent.
　特許文献３では、Ｐ含有量に応じてＮｄを含有することによって、Ｐのミクロ偏析が分散された鋼が記載されている。特許文献３では、デンドライト樹間において濃化するＰと添加したＮｄとを化合させ、Ｐを鋼中に微細に分散させて無害化することが記載されている。 Patent Document 3 describes a steel in which microsegregation of P is dispersed by containing Nd according to the P content. Patent Document 3 describes that P concentrated in dendrite trees and added Nd are combined to finely disperse P in steel to make it harmless.
　特許文献４では、Ｐ含有量に応じてＣｅを含有する高強度ボルトが記載されている。また、特許文献４では、ＰとＣｅを結合させてリン化物を生成させて粒界脆化を抑制し、固溶Ｐ量を低減させて、ボルトの耐水素脆化特性を向上させることが教示されている。 Patent Document 4 describes high-strength bolts containing Ce according to the P content. Further, Patent Document 4 teaches that P and Ce are combined to form a phosphide to suppress grain boundary embrittlement, the amount of solid solution P is reduced, and the hydrogen embrittlement resistance of the bolt is improved. Has been done.
特開２００１－４０４５３号公報Japanese Unexamined Patent Publication No. 2001-40453 特開昭５９－１５９９６６号公報Japanese Unexamined Patent Publication No. 59-159966 特開２０１０－１００９２３号公報Japanese Unexamined Patent Publication No. 2010-100923 特開２０１７－１６０５２５号公報Japanese Unexamined Patent Publication No. 2017-160525
　特許文献１では、Ｚｒ、Ｎｂ、Ｔｉ及びＭｏの含有量を所定範囲内に規定してそれらのリン化物を生成することで固溶Ｐ量を低減することが教示されているが、リン化物の生成に影響を及ぼし得る他の因子については必ずしも十分な検討はなされていない。特許文献２では、ＲＥＭとして使用し得る具体的な元素については何ら教示も示唆もされておらず、また鋼中の固溶Ｐ量を低減するという観点からも十分な検討はなされていない。特許文献３では、ＲＥＭのうち実用鋼に添加可能なものはＬａ、Ｃｅ及びＮｄに限られ、Ｐを無害化するために最も有効なＲＥＭとしてＮｄを選択した旨が記載されている。したがって、特許文献３では、Ｌａ、Ｃｅ及びＮｄ以外の元素については必ずしも十分な検討はなされておらず、それゆえ特許文献３に記載の発明においては、鋼中における固溶Ｐ量の低減に関して依然として改善の余地があった。この点はＣｅ以外の元素について十分な検討がされていない特許文献４に記載の発明も同様である。 Patent Document 1 teaches that the content of Zr, Nb, Ti and Mo is specified within a predetermined range to generate a phosphide thereof, thereby reducing the amount of solid-dissolved P. Other factors that may affect production have not always been thoroughly investigated. In Patent Document 2, no specific element that can be used as REM is taught or suggested, and sufficient studies have not been made from the viewpoint of reducing the amount of solid solution P in steel. Patent Document 3 describes that among REMs, those that can be added to practical steel are limited to La, Ce and Nd, and Nd is selected as the most effective REM for detoxifying P. Therefore, in Patent Document 3, elements other than La, Ce and Nd have not always been sufficiently studied, and therefore, in the invention described in Patent Document 3, the reduction of the amount of solid melt P in steel still remains. There was room for improvement. This point is the same as the invention described in Patent Document 4, in which elements other than Ce have not been sufficiently studied.
　本発明は、このような実情に鑑みてなされたものであり、その目的とするところは、新規な構成により、鋼中の固溶Ｐ量を低減可能な又は鋼中の固溶Ｐ量が低減された鋼材を提供することにある。 The present invention has been made in view of such circumstances, and an object thereof is that the amount of solid solution P in steel can be reduced or the amount of solid solution P in steel can be reduced by a novel configuration. The purpose is to provide the steel products that have been made.
　本発明者らは、上記目的を達成するために、鋼中の固溶Ｐ量を低減させることのできる元素について検討を行った。その結果、本発明者らは、特定元素の量を一定量以上確保するとともに、当該特定元素の量と鋼中のＰ含有量との関係を所定の範囲内とすることにより、鋼中の固溶Ｐ量を低減させることができることを見出し、本発明を完成させた。 The present inventors have studied elements that can reduce the amount of solid solution P in steel in order to achieve the above object. As a result, the present inventors secure the amount of the specific element to a certain amount or more, and set the relationship between the amount of the specific element and the P content in the steel within a predetermined range to solidify the steel. We have found that the amount of dissolved P can be reduced, and completed the present invention.
　上記目的を達成し得た鋼材は、以下のとおりである。
　（１）質量％で、
　Ｃ：０．００１～１．０００％、
　Ｓｉ：０．０１～３．００％、
　Ｍｎ：０．１０～４．５０％、
　Ｐ：０．３００％以下、
　Ｓ：０．０３００％以下、
　Ａｌ：０．００１～５．０００％、
　Ｎ：０．２０００％以下、
　Ｏ：０．０１００％以下、
　Ｚｒ：０～０．８０００％、及びＨｆ：０～０．８０００％からなる群より選択される少なくとも１種のＺ元素、
　Ｎｂ：０～３．０００％、
　Ｔｉ：０～０．５００％、
　Ｔａ：０～０．５００％、
　Ｖ：０～１．００％、
　Ｃｕ：０～３．００％、
　Ｎｉ：０～６０．００％、
　Ｃｒ：０～３０．００％、
　Ｍｏ：０～５．００％、
　Ｗ：０～２．００％、
　Ｂ：０～０．０２００％、
　Ｃｏ：０～３．００％、
　Ｂｅ：０～０．０５０％、
　Ａｇ：０～０．５００％、
　Ｃａ：０～０．０５００％、
　Ｍｇ：０～０．０５００％、
　Ｌａ、Ｃｅ、Ｎｄ、Ｙ、Ｐｍ、Ｐｒ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、及びＳｃの少なくとも１種：合計で０～０．５０００％、
　Ｓｎ：０～０．３００％、
　Ｓｂ：０～０．３００％、
　Ｔｅ：０～０．１００％、
　Ｓｅ：０～０．１００％、
　Ａｓ：０～０．０５０％、
　Ｂｉ：０～０．５００％、
　Ｐｂ：０～０．５００％、並びに
　残部：Ｆｅ及び不純物からなり、
　下記式１及び式２を満たす化学組成を有する、鋼材。
　０．６１［Ｚｒ］＋０．３１［Ｈｆ］－１．７５［Ｏ］－３．９９［Ｎ］－１．７４［Ｓ］　≧　０．０００３　　　・・・式１
　１．８０×［Ｐ］－（０．６１［Ｚｒ］＋０．３１［Ｈｆ］－１．７５［Ｏ］－３．９９［Ｎ］－１．７４［Ｓ］）　＜　０．０１０　　　・・・式２
　ここで、［Ｚｒ］、［Ｈｆ］、［Ｏ］、［Ｎ］、［Ｓ］、及び［Ｐ］は、各元素の含有量［質量％］であり、元素を含有しない場合は０である。
　（２）前記化学組成が、質量％で、
　Ｎｂ：０．００３～３．０００％、
　Ｔｉ：０．００５～０．５００％、
　Ｔａ：０．００１～０．５００％、
　Ｖ：０．００１～１．００％、
　Ｃｕ：０．００１～３．００％、
　Ｎｉ：０．００１～６０．００％、
　Ｃｒ：０．００１～３０．００％、
　Ｍｏ：０．００１～５．００％、
　Ｗ：０．００１～２．００％、
　Ｂ：０．０００１～０．０２００％、
　Ｃｏ：０．００１～３．００％、
　Ｂｅ：０．０００３～０．０５０％、
　Ａｇ：０．００１～０．５００％、
　Ｃａ：０．０００１～０．０５００％、
　Ｍｇ：０．０００１～０．０５００％、
　Ｌａ、Ｃｅ、Ｎｄ、Ｙ、Ｐｍ、Ｐｒ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、及びＳｃの少なくとも１種：合計で０．０００１～０．５０００％、
　Ｓｎ：０．００１～０．３００％、
　Ｓｂ：０．００１～０．３００％、
　Ｔｅ：０．００１～０．１００％、
　Ｓｅ：０．００１～０．１００％、
　Ａｓ：０．００１～０．０５０％、
　Ｂｉ：０．００１～０．５００％、並びに
　Ｐｂ：０．００１～０．５００％
のうち１種又は２種以上を含む、上記（１）に記載の鋼材。 The steel materials that have achieved the above objectives are as follows.
(1) By mass%,
C: 0.001 to 1.000%,
Si: 0.01-3.00%,
Mn: 0.10 to 4.50%,
P: 0.300% or less,
S: 0.0300% or less,
Al: 0.001-5.000%,
N: 0.2000% or less,
O: 0.0100% or less,
At least one Z element selected from the group consisting of Zr: 0 to 0.8000% and Hf: 0 to 0.8000%.
Nb: 0-3.000%,
Ti: 0 to 0.500%,
Ta: 0 to 0.500%,
V: 0 to 1.00%,
Cu: 0 to 3.00%,
Ni: 0-60.00%,
Cr: 0 to 30.00%,
Mo: 0 to 5.00%,
W: 0 to 2.00%,
B: 0-0.0200%,
Co: 0 to 3.00%,
Be: 0 to 0.050%,
Ag: 0 to 0.500%,
Ca: 0-0.0500%,
Mg: 0-0.0500%,
At least one of La, Ce, Nd, Y, Pm, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc: 0 to 0.5000% in total.
Sn: 0 to 0.300%,
Sb: 0 to 0.300%,
Te: 0 to 0.100%,
Se: 0 to 0.100%,
As: 0 to 0.050%,
Bi: 0 to 0.500%,
Pb: 0 to 0.500%, and the balance: Fe and impurities.
A steel material having a chemical composition satisfying the following formulas 1 and 2.
0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1.74 [S] ≧ 0.0003 ・ ・ ・ Equation 1
1.80 x [P]-(0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1.74 [S]) <0.010 ... Equation 2
Here, [Zr], [Hf], [O], [N], [S], and [P] are the content [mass%] of each element, and are 0 when the element is not contained. ..
(2) The chemical composition is mass%.
Nb: 0.003 to 3.000%,
Ti: 0.005 to 0.500%,
Ta: 0.001 to 0.500%,
V: 0.001 to 1.00%,
Cu: 0.001 to 3.00%,
Ni: 0.001 to 60.00%,
Cr: 0.001 to 30.00%,
Mo: 0.001 to 5.00%,
W: 0.001 to 2.00%,
B: 0.0001-0.0200%,
Co: 0.001 to 3.00%,
Be: 0.0003 to 0.050%,
Ag: 0.001 to 0.500%,
Ca: 0.0001-0.0500%,
Mg: 0.0001-0.0500%,
At least one of La, Ce, Nd, Y, Pm, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc: 0.0001 to 0.5000% in total.
Sn: 0.001 to 0.300%,
Sb: 0.001 to 0.300%,
Te: 0.001 to 0.100%,
Se: 0.001 to 0.100%,
As: 0.001 to 0.050%,
Bi: 0.001 to 0.500%, and Pb: 0.001 to 0.500%
The steel material according to (1) above, which comprises one or more of the above.
　本発明によれば、鋼中の固溶Ｐ量を低減可能な又は鋼中の固溶Ｐ量が低減された鋼材を提供することができる。 According to the present invention, it is possible to provide a steel material capable of reducing the amount of solid solution P in steel or having a reduced amount of solid solution P in steel.
＜鋼材＞
　本発明の実施形態に係る鋼材は、質量％で、
　Ｃ：０．００１～１．０００％、
　Ｓｉ：０．０１～３．００％、
　Ｍｎ：０．１０～４．５０％、
　Ｐ：０．３００％以下、
　Ｓ：０．０３００％以下、
　Ａｌ：０．００１～５．０００％、
　Ｎ：０．２０００％以下、
　Ｏ：０．０１００％以下、
　Ｚｒ：０～０．８０００％、及びＨｆ：０～０．８０００％からなる群より選択される少なくとも１種のＺ元素、
　Ｎｂ：０～３．０００％、
　Ｔｉ：０～０．５００％、
　Ｔａ：０～０．５００％、
　Ｖ：０～１．００％、
　Ｃｕ：０～３．００％、
　Ｎｉ：０～６０．００％、
　Ｃｒ：０～３０．００％、
　Ｍｏ：０～５．００％、
　Ｗ：０～２．００％、
　Ｂ：０～０．０２００％、
　Ｃｏ：０～３．００％、
　Ｂｅ：０～０．０５０％、
　Ａｇ：０～０．５００％、
　Ｃａ：０～０．０５００％、
　Ｍｇ：０～０．０５００％、
　Ｌａ、Ｃｅ、Ｎｄ、Ｙ、Ｐｍ、Ｐｒ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、及びＳｃの少なくとも１種：合計で０～０．５０００％、
　Ｓｎ：０～０．３００％、
　Ｓｂ：０～０．３００％、
　Ｔｅ：０～０．１００％、
　Ｓｅ：０～０．１００％、
　Ａｓ：０～０．０５０％、
　Ｂｉ：０～０．５００％、
　Ｐｂ：０～０．５００％、並びに
　残部：Ｆｅ及び不純物からなり、
　下記式１及び式２を満たす化学組成を有することを特徴としている。
　０．６１［Ｚｒ］＋０．３１［Ｈｆ］－１．７５［Ｏ］－３．９９［Ｎ］－１．７４［Ｓ］　≧　０．０００３　　　・・・式１
　１．８０×［Ｐ］－（０．６１［Ｚｒ］＋０．３１［Ｈｆ］－１．７５［Ｏ］－３．９９［Ｎ］－１．７４［Ｓ］）　＜　０．０１０　　　・・・式２
　ここで、［Ｚｒ］、［Ｈｆ］、［Ｏ］、［Ｎ］、［Ｓ］、及び［Ｐ］は、各元素の含有量［質量％］であり、元素を含有しない場合は０である。 <Steel material>
The steel material according to the embodiment of the present invention is based on mass%.
C: 0.001 to 1.000%,
Si: 0.01-3.00%,
Mn: 0.10 to 4.50%,
P: 0.300% or less,
S: 0.0300% or less,
Al: 0.001-5.000%,
N: 0.2000% or less,
O: 0.0100% or less,
At least one Z element selected from the group consisting of Zr: 0 to 0.8000% and Hf: 0 to 0.8000%.
Nb: 0-3.000%,
Ti: 0 to 0.500%,
Ta: 0 to 0.500%,
V: 0 to 1.00%,
Cu: 0 to 3.00%,
Ni: 0-60.00%,
Cr: 0 to 30.00%,
Mo: 0 to 5.00%,
W: 0 to 2.00%,
B: 0-0.0200%,
Co: 0 to 3.00%,
Be: 0 to 0.050%,
Ag: 0 to 0.500%,
Ca: 0-0.0500%,
Mg: 0-0.0500%,
At least one of La, Ce, Nd, Y, Pm, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc: 0 to 0.5000% in total.
Sn: 0 to 0.300%,
Sb: 0 to 0.300%,
Te: 0 to 0.100%,
Se: 0 to 0.100%,
As: 0 to 0.050%,
Bi: 0 to 0.500%,
Pb: 0 to 0.500%, and the balance: Fe and impurities.
It is characterized by having a chemical composition satisfying the following formulas 1 and 2.
0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1.74 [S] ≧ 0.0003 ・ ・ ・ Equation 1
1.80 x [P]-(0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1.74 [S]) <0.010 ... Equation 2
Here, [Zr], [Hf], [O], [N], [S], and [P] are the content [mass%] of each element, and are 0 when the element is not contained. ..
　鋼材の靭性、延性、耐食性及び溶接性などの特性を向上させるためには、先に述べたとおり、鋼中の固溶Ｐ量を低減することが一般に重要である。例えば、高強度化のためにマルテンサイト及びベイナイトなどの組織を利用した鋼材においては、低温靭性を確保するため、焼入れ後に所定の温度で焼き戻し処理が典型的に行われる。鋼中の固溶Ｐが比較的多いと、このような焼き戻し処理の際に当該固溶Ｐが旧オーステナイト粒界に偏析して、いわゆる焼き戻し脆化を引き起こし、その結果として鋼材の靭性を低下させることがある。これに関連して、鋼中のＰ自体の含有量を低減すれば、それに応じて固溶Ｐ量を低減することができるため、当該固溶Ｐに起因する焼き戻し脆化等の発生を抑制することが可能である。しかしながら、Ｐ含有量を過度に低減することは、精錬に時間を要し、生産性の低下や製造コストの大幅な上昇を招くという問題がある。 As mentioned above, it is generally important to reduce the amount of solid solution P in steel in order to improve the toughness, ductility, corrosion resistance and weldability of steel materials. For example, in a steel material using a structure such as martensite and bainite for high strength, tempering treatment is typically performed at a predetermined temperature after quenching in order to secure low temperature toughness. If the solid solution P in the steel is relatively large, the solid solution P segregates at the former austenite grain boundaries during such tempering treatment, causing so-called tempering embrittlement, and as a result, the toughness of the steel material is reduced. May reduce. In relation to this, if the content of P itself in the steel is reduced, the amount of solid solution P can be reduced accordingly, so that the occurrence of temper embrittlement and the like caused by the solid solution P is suppressed. It is possible to do. However, excessively reducing the P content has a problem that it takes time for refining, which leads to a decrease in productivity and a significant increase in production cost.
　そこで、本発明者らは、鋼中の固溶Ｐと反応してその量を低減させることのできる元素について検討を行った。その結果、本発明者らは、Ｚｒ及びＨｆの元素（以下、「Ｚ元素」ともいう）の量をそれらの元素が鋼中で形成する介在物、より具体的にはこれらの元素の酸化物、窒化物及び硫化物との関係を考慮しつつ一定量以上確保し（すなわち、式１の左辺に対応する当該Ｚ元素の有効量を０．０００３％以上とし）、さらに当該特定元素の有効量と鋼中のＰ含有量との関係を所定の範囲内とすることにより（すなわち、式２の左辺に対応する量を０．０１０％未満とすることにより）、Ｐの少なくとも一部をリン化物として固定することができ、このようなリン化物の生成に起因して鋼中の固溶Ｐ量を低減することができることを見出した。 Therefore, the present inventors have investigated an element that can react with the solid solution P in steel to reduce the amount thereof. As a result, the present inventors have determined the amounts of the elements Zr and Hf (hereinafter, also referred to as “Z element”) as inclusions formed in the steel by those elements, more specifically, oxides of these elements. , Secure a certain amount or more while considering the relationship with nitrides and sulfides (that is, the effective amount of the Z element corresponding to the left side of the formula 1 is 0.0003% or more), and further, the effective amount of the specific element. By keeping the relationship between and the P content in the steel within a predetermined range (that is, by setting the amount corresponding to the left side of Equation 2 to less than 0.010%), at least a part of P is phospholated. It was found that the amount of solid melt P in the steel can be reduced due to the formation of such a phosphonic acid.
　上記のＺ元素は、鋼中に存在するＯ（酸素）、Ｎ（窒素）及びＳ（硫黄）と結びついて、酸化物、窒化物及び硫化物からなる介在物を形成しやすいという性質を有する。Ｚ元素が鋼中でこのような介在物を形成してしまうと、固溶Ｐとの反応に寄与することができるＺ元素の量が少なくなり、固溶Ｐ量を十分に低減することができなくなる。本発明においては、このような介在物を考慮したＺ元素の量を、後で詳しく説明する上記式１によって当該Ｚ元素の有効量として算出し、そして当該有効量を一定量以上、すなわち０．０００３％以上確保することで、当該Ｚ元素を固溶Ｐと反応させてリン化物を形成することができる。リン化物を形成することで、固溶Ｐの少なくとも一部を固定することができ、固溶Ｐの粒界などへの偏析を顕著に抑制することが可能となる。本発明者らの検討の結果、Ｚ元素の有効量と鋼中のＰ含有量を同様に後で詳しく説明する上記式２の関係を満たすようにすることで、より高い固溶Ｐの低減効果を達成できることが見出された。したがって、本発明によれば、Ｐ含有量を過度に低減することなしに鋼中の固溶Ｐ量を十分に低減可能な又は鋼中の固溶Ｐ量が十分に低減された鋼材を得ることができるため、当該固溶Ｐに関連する鋼材の特性、例えば、靭性、延性、耐食性、溶接性などの特性を顕著に改善することが可能となる。より具体的には、鋼中の固溶Ｐ量を低減することで、例えば焼き戻し処理等の際に固溶Ｐが旧オーステナイト粒界などの特定の箇所に偏析することを抑制することができる。その結果として、本発明によれば、焼き戻し脆化等の発生を抑制することができ、それゆえ鋼材の靭性等の特性を顕著に向上させることが可能となる。 The above-mentioned Z element has a property of easily forming inclusions composed of oxides, nitrides and sulfides in combination with O (oxygen), N (nitrogen) and S (sulfur) existing in steel. When the Z element forms such inclusions in the steel, the amount of the Z element that can contribute to the reaction with the solid solution P decreases, and the amount of the solid solution P can be sufficiently reduced. It disappears. In the present invention, the amount of the Z element in consideration of such inclusions is calculated as the effective amount of the Z element by the above formula 1 which will be described in detail later, and the effective amount is set to a certain amount or more, that is, 0. By securing 0003% or more, the Z element can be reacted with the solid solution P to form a phosphide. By forming the phosphide, at least a part of the solid solution P can be fixed, and the segregation of the solid solution P to the grain boundaries and the like can be remarkably suppressed. As a result of the studies by the present inventors, by satisfying the relationship between the effective amount of the Z element and the P content in the steel, which will be described in detail later, the above-mentioned equation 2 has a higher effect of reducing solid solution P. Was found to be achievable. Therefore, according to the present invention, it is possible to obtain a steel material in which the solid solution P amount in the steel can be sufficiently reduced or the solid solution P amount in the steel is sufficiently reduced without excessively reducing the P content. Therefore, it is possible to remarkably improve the characteristics of the steel material related to the solid solution P, for example, the characteristics such as toughness, ductility, corrosion resistance, and weldability. More specifically, by reducing the amount of the solid solution P in the steel, it is possible to prevent the solid solution P from segregating at a specific place such as the old austenite grain boundary during, for example, tempering treatment. .. As a result, according to the present invention, it is possible to suppress the occurrence of tempering embrittlement and the like, and therefore it is possible to significantly improve the toughness and other properties of the steel material.
　本発明におけるＺ元素は、上記のとおりＯ、Ｎ及びＳと結びついて介在物を形成しやすく、それゆえ鋼中で所定の有効量を確保することは一般に困難である。このような事情から、上記Ｚ元素による固溶Ｐの低減効果は従来知られていなかった。しかしながら、近年の精錬技術の進歩により、一般に不純物として鋼中に存在するＯ、Ｎ及びＳなどの元素の含有量を非常に低いレベルにまで低減することが可能となったこともあり、今回、上記Ｚ元素の所定範囲内における有効量を実現することができた。したがって、上記Ｚ元素に関する固溶Ｐの低減効果は、今回、本発明者らによって初めて明らかにされたことであり、極めて意外であり、また驚くべきことである。 The Z element in the present invention easily combines with O, N and S to form inclusions as described above, and therefore it is generally difficult to secure a predetermined effective amount in steel. Due to such circumstances, the effect of reducing the solid solution P by the Z element has not been known so far. However, recent advances in refining technology have made it possible to reduce the content of elements such as O, N, and S, which are generally present in steel as impurities, to extremely low levels. It was possible to realize an effective amount of the Z element within a predetermined range. Therefore, the effect of reducing the solid solution P on the Z element has been clarified for the first time by the present inventors, and is extremely surprising and surprising.
　以下、本発明の実施形態に係る鋼材についてより詳しく説明する。以下の説明において、各元素の含有量の単位である「％」は、特に断りがない限り「質量％」を意味するものである。また、本明細書において、数値範囲を示す「～」とは、特に断りがない場合、その前後に記載される数値を下限値及び上限値として含む意味で使用される。 Hereinafter, the steel material according to the embodiment of the present invention will be described in more detail. In the following description, "%", which is a unit of the content of each element, means "mass%" unless otherwise specified. Further, in the present specification, "-" indicating a numerical range is used to mean that the numerical values described before and after the numerical range are included as the lower limit value and the upper limit value unless otherwise specified.
［Ｃ：０．００１～１．０００％］
　炭素（Ｃ）は、硬さの安定化及び／又は強度の確保に必要な元素である。これらの効果を十分に得るために、Ｃ含有量は０．００１％以上である。Ｃ含有量は０．００５％以上、０．０１０％以上又は０．０２０％以上であってもよい。一方で、Ｃを過度に含有すると、靭性、曲げ性及び／又は溶接性が低下する場合がある。したがって、Ｃ含有量は１．０００％以下である。Ｃ含有量は０．８００％以下、０．６００％以下又は０．５００％以下であってもよい。 [C: 0.001 to 1.000%]
Carbon (C) is an element necessary for stabilizing hardness and / or ensuring strength. In order to sufficiently obtain these effects, the C content is 0.001% or more. The C content may be 0.005% or more, 0.010% or more, or 0.020% or more. On the other hand, if C is excessively contained, toughness, bendability and / or weldability may decrease. Therefore, the C content is 1.000% or less. The C content may be 0.800% or less, 0.600% or less, or 0.500% or less.
［Ｓｉ：０．０１～３．００％］
　ケイ素（Ｓｉ）は脱酸元素であり、強度の向上にも寄与する元素である。これらの効果を十分に得るために、Ｓｉ含有量は０．０１％以上である。Ｓｉ含有量は０．０５％以上、０．１０％以上又は０．３０％以上であってもよい。一方で、Ｓｉを過度に含有すると、靭性が低下したり、スケール疵と呼ばれる表面品質不良を発生したりする場合がある。したがって、Ｓｉ含有量は３．００％以下である。Ｓｉ含有量は２．００％以下、１．００％以下又は０．６０％以下であってもよい。 [Si: 0.01 to 3.00%]
Silicon (Si) is a deoxidizing element and is an element that also contributes to the improvement of strength. In order to sufficiently obtain these effects, the Si content is 0.01% or more. The Si content may be 0.05% or more, 0.10% or more, or 0.30% or more. On the other hand, if Si is excessively contained, the toughness may be lowered or surface quality defects called scale defects may occur. Therefore, the Si content is 3.00% or less. The Si content may be 2.00% or less, 1.00% or less, or 0.60% or less.
［Ｍｎ：０．１０～４．５０％］
　マンガン（Ｍｎ）は、焼入れ性及び／又は強度の向上に有効な元素であり、有効なオーステナイト安定化元素でもある。これらの効果を十分に得るために、Ｍｎ含有量は０．１０％以上である。Ｍｎ含有量は０．５０％以上、０．７０％以上又は１．００％以上であってもよい。一方で、Ｍｎを過度に含有すると、靭性に有害なＭｎＳが生成したり、耐酸化性を低下させたりする場合がある。したがって、Ｍｎ含有量は４．５０％以下である。Ｍｎ含有量は４．００％以下、３．５０％以下又は３．００％以下であってもよい。 [Mn: 0.10 to 4.50%]
Manganese (Mn) is an element effective for improving hardenability and / or strength, and is also an effective austenite stabilizing element. In order to sufficiently obtain these effects, the Mn content is 0.10% or more. The Mn content may be 0.50% or more, 0.70% or more, or 1.00% or more. On the other hand, if Mn is excessively contained, MnS harmful to toughness may be generated or the oxidation resistance may be lowered. Therefore, the Mn content is 4.50% or less. The Mn content may be 4.00% or less, 3.50% or less, or 3.00% or less.
［Ｐ：０．３００％以下］
　リン（Ｐ）は製造工程で混入する元素である。鋼中の固溶Ｐ量を低減するという観点からはＰは少ないほど好ましく、よってＰ含有量は０％であってもよい。しかしながら、Ｐ含有量を０．０００１％未満に低減するためには精錬に時間を要し、生産性の低下を招く。したがって、Ｐ含有量は０．０００１％以上、０．０００５％以上、０．００１％以上、０．００３％以上、又は、０．００５％以上であってもよい。Ｐ含有量は、製造コストの観点から、０．００７％以上であってもよい。一方で、Ｐを過度に含有すると、鋼中の固溶Ｐ量が増加し、鋼材の種々の特性、例えば靭性、延性、耐食性及び／又は溶接性などの特性が低下する場合がある。したがって、Ｐ含有量は０．３００％以下である。Ｐ含有量は０．１００％以下、０．０３０％以下又は０．０１０％以下であってもよい。 [P: 0.300% or less]
Phosphorus (P) is an element mixed in the manufacturing process. From the viewpoint of reducing the amount of solid solution P in the steel, the smaller the amount of P, the more preferable, and the P content may be 0%. However, in order to reduce the P content to less than 0.0001%, it takes time for refining, which leads to a decrease in productivity. Therefore, the P content may be 0.0001% or more, 0.0005% or more, 0.001% or more, 0.003% or more, or 0.005% or more. The P content may be 0.007% or more from the viewpoint of manufacturing cost. On the other hand, if P is excessively contained, the amount of solid solution P in the steel may increase, and various properties of the steel material such as toughness, ductility, corrosion resistance and / or weldability may decrease. Therefore, the P content is 0.300% or less. The P content may be 0.100% or less, 0.030% or less, or 0.010% or less.
［Ｓ：０．０３００％以下］
　硫黄（Ｓ）は製造工程で混入する元素であり、本発明の実施形態に係るＺ元素との間で形成される介在物を低減する観点からは少ないほど好ましく、よってＳ含有量は０％であってもよい。しかしながら、Ｓ含有量を０．０００１％未満に低減するためには精錬に時間を要し、生産性の低下を招く。したがって、Ｓ含有量は０．０００１％以上、０．０００５％以上又は０．００１０％以上であってもよい。一方で、Ｓを過度に含有すると、Ｚ元素の有効量が低下するとともに、靭性が低下する場合がある。したがって、Ｓ含有量は０．０３００％以下である。Ｓ含有量は好ましくは０．０１００％以下、より好ましくは０．００５０％以下、最も好ましくは０．００３０％以下である。 [S: 0.0300% or less]
Sulfur (S) is an element mixed in the manufacturing process, and is preferable from the viewpoint of reducing inclusions formed with the Z element according to the embodiment of the present invention, so that the S content is 0%. There may be. However, in order to reduce the S content to less than 0.0001%, it takes time for refining, which leads to a decrease in productivity. Therefore, the S content may be 0.0001% or more, 0.0005% or more, or 0.0010% or more. On the other hand, if S is excessively contained, the effective amount of the Z element may decrease and the toughness may decrease. Therefore, the S content is 0.0300% or less. The S content is preferably 0.0100% or less, more preferably 0.0050% or less, and most preferably 0.0030% or less.
［Ａｌ：０．００１～５．０００％］
　アルミニウム（Ａｌ）は、脱酸元素であり、耐食性及び／又は耐熱性を向上させるのに有効な元素でもある。これらの効果を得るために、Ａｌ含有量は０．００１％以上である。Ａｌ含有量は０．０１０％以上、０．１００％以上又は０．２００％以上であってもよい。とりわけ、耐熱性を十分に向上させる観点からは、Ａｌ含有量は１．０００％以上、２．０００％以上又は３．０００％以上であってもよい。一方で、Ａｌを過度に含有すると、粗大な介在物が生成して靭性を低下させたり、製造過程で割れなどのトラブルが発生したり、及び／又は耐疲労特性を低下させたりする場合がある。したがって、Ａｌ含有量は５．０００％以下である。Ａｌ含有量は４．５００％以下、４．０００％以下又は３．５００％以下であってもよい。とりわけ、靭性の低下を抑制するという観点からは、Ａｌ含有量は１．５００％以下、１．０００％以下又は０．３００％以下であってもよい。 [Al: 0.001-5.000%]
Aluminum (Al) is a deoxidizing element and is also an effective element for improving corrosion resistance and / or heat resistance. In order to obtain these effects, the Al content is 0.001% or more. The Al content may be 0.010% or more, 0.100% or more, or 0.200% or more. In particular, from the viewpoint of sufficiently improving the heat resistance, the Al content may be 1.000% or more, 2.000% or more, or 3.000% or more. On the other hand, if Al is excessively contained, coarse inclusions may be generated to reduce toughness, troubles such as cracking may occur in the manufacturing process, and / or fatigue resistance may be deteriorated. .. Therefore, the Al content is 5.000% or less. The Al content may be 4.500% or less, 4000% or less, or 3.500% or less. In particular, from the viewpoint of suppressing the decrease in toughness, the Al content may be 1.500% or less, 1.000% or less, or 0.300% or less.
［Ｎ：０．２０００％以下］
　窒素（Ｎ）は製造工程で混入する元素であり、本発明の実施形態に係るＺ元素との間で形成される介在物を低減する観点からは少ないほど好ましく、よってＮ含有量は０％であってもよい。しかしながら、Ｎ含有量を０．０００１％未満に低減するためには精錬に時間を要し、生産性の低下を招く。したがって、Ｎ含有量は０．０００１％以上、０．０００５％以上又は０．００１０％以上であってもよい。一方で、Ｎはオーステナイトの安定化に有効な元素でもあり、必要に応じて意図的に含有させてもよい。この場合には、Ｎ含有量は０．０１００％以上であることが好ましく、０．０２００％以上、０．０５００％以上であってもよい。しかしながら、Ｎを過度に含有すると、Ｚ元素の有効量が低下するとともに、靭性が低下する場合がある。したがって、Ｎ含有量は０．２０００％以下である。Ｎ含有量は０．１５００％以下、０．１０００％以下又は０．０８００％以下であってもよい。 [N: 0.2000% or less]
Nitrogen (N) is an element mixed in the manufacturing process, and is preferable from the viewpoint of reducing inclusions formed with the Z element according to the embodiment of the present invention, so that the N content is 0%. There may be. However, in order to reduce the N content to less than 0.0001%, it takes time for refining, which leads to a decrease in productivity. Therefore, the N content may be 0.0001% or more, 0.0005% or more, or 0.0010% or more. On the other hand, N is also an element effective for stabilizing austenite, and may be intentionally contained if necessary. In this case, the N content is preferably 0.0100% or more, and may be 0.0200% or more and 0.0500% or more. However, if N is excessively contained, the effective amount of the Z element may decrease and the toughness may decrease. Therefore, the N content is 0.2000% or less. The N content may be 0.1500% or less, 0.1000% or less, or 0.0800% or less.
［Ｏ：０．０１００％以下］
　酸素（Ｏ）は製造工程で混入する元素であり、本発明の実施形態に係るＺ元素との間で形成される介在物を低減する観点からは少ないほど好ましく、よってＯ含有量は０％であってもよい。しかしながら、Ｏ含有量を０．０００１％未満に低減するためには精錬に時間を要し、生産性の低下を招く。したがって、Ｏ含有量は０．０００１％以上、０．０００５％以上又は０．００１０％以上であってもよい。一方で、Ｏを過度に含有すると、粗大な介在物が形成され、Ｚ元素の有効量が低下するとともに、鋼材の成形性及び／又は靭性が低下する場合がある。したがって、Ｏ含有量は０．０１００％以下である。Ｏ含有量は０．００８０％以下、０．００６０％以下又は０．００４０％以下であってもよい。 [O: 0.0100% or less]
Oxygen (O) is an element mixed in the manufacturing process, and is preferable from the viewpoint of reducing inclusions formed with the Z element according to the embodiment of the present invention, so that the O content is 0%. There may be. However, in order to reduce the O content to less than 0.0001%, it takes time for refining, which leads to a decrease in productivity. Therefore, the O content may be 0.0001% or more, 0.0005% or more, or 0.0010% or more. On the other hand, if O is excessively contained, coarse inclusions may be formed, the effective amount of the Z element may be lowered, and the formability and / or toughness of the steel material may be lowered. Therefore, the O content is 0.0100% or less. The O content may be 0.0080% or less, 0.0060% or less, or 0.0040% or less.
［Ｚｒ：０～０．８０００％、及びＨｆ：０～０．８０００％からなる群より選択される少なくとも１種のＺ元素］
　本発明の実施形態に係るＺ元素は、Ｚｒ：０～０．８０００％、及びＨｆ：０～０．８０００％であり、ジルコニウム（Ｚｒ）及びハフニウム（Ｈｆ）はリン化物の形成に基づく固溶Ｐの低減効果を発現することができる。当該固溶Ｐの低減効果を発現することで、当該固溶Ｐに関連する鋼材の特性、例えば、靭性、延性、耐食性、溶接性などの特性を顕著に改善することが可能となる。 [At least one Z element selected from the group consisting of Zr: 0 to 0.8000% and Hf: 0 to 0.8000%]
The Z element according to the embodiment of the present invention is Zr: 0 to 0.8000% and Hf: 0 to 0.8000%, and zirconium (Zr) and hafnium (Hf) are solid-dissolved based on the formation of a phosphide. The effect of reducing P can be exhibited. By exhibiting the effect of reducing the solid solution P, it is possible to remarkably improve the characteristics of the steel material related to the solid solution P, such as toughness, ductility, corrosion resistance, and weldability.
　上記Ｚ元素は、いずれか１つの元素を単独で使用してもよいし、又は両方を使用してもよい。また、当該Ｚ元素は、後で詳しく説明する式１及び２を満たす量において存在すればよく、その下限値は特に限定されない。しかしながら、例えば、各Ｚ元素の含有量又は合計の含有量は０．００１０％以上であってもよく、好ましくは０．００５０％以上であり、より好ましくは０．０１５０％以上であり、さらにより好ましくは０．０３００％以上であり、最も好ましくは０．０５００％以上である。一方で、Ｚ元素を過度に含有しても効果が飽和し、それゆえ当該Ｚ元素を必要以上に鋼材中に含有させることは製造コストの上昇を招く虞がある。したがって、各Ｚ元素の含有量は０．８０００％以下であり、例えば０．７０００％以下、０．６０００％以下、０．５０００％以下、０．４０００％以下又は０．３０００％以下であってもよい。また、Ｚ元素の含有量の合計は１．６０００％以下であり、例えば１．２０００％以下、１．００００％以下、０．８０００％以下、０．６０００％以下又は０．５０００％以下であってもよい。 As the Z element, any one element may be used alone, or both may be used. Further, the Z element may be present in an amount satisfying the formulas 1 and 2 described in detail later, and the lower limit thereof is not particularly limited. However, for example, the content of each Z element or the total content may be 0.0010% or more, preferably 0.0050% or more, more preferably 0.0150% or more, and even more. It is preferably 0.0300% or more, and most preferably 0.0500% or more. On the other hand, even if the Z element is excessively contained, the effect is saturated, and therefore, if the Z element is contained in the steel material more than necessary, the manufacturing cost may increase. Therefore, the content of each Z element is 0.8000% or less, for example, 0.7000% or less, 0.6000% or less, 0.5000% or less, 0.4000% or less, or 0.3000% or less. May be good. The total content of the Z element is 1.6000% or less, for example, 1.2000% or less, 1.000% or less, 0.8000% or less, 0.6000% or less, or 0.5000% or less. You may.
　本発明の実施形態に係る鋼材の基本化学組成は上記のとおりである。さらに、当該鋼材は、必要に応じて以下の任意選択元素のうち１種又は２種以上を含有してもよい。例えば、鋼材は、Ｎｂ：０～３．０００％、Ｔｉ：０～０．５００％、Ｔａ：０～０．５００％、Ｖ：０～１．００％、Ｃｕ：０～３．００％、Ｎｉ：０～６０．００％、Ｃｒ：０～３０．００％、Ｍｏ：０～５．００％、Ｗ：０～２．００％、Ｂ：０～０．０２００％、Ｃｏ：０～３．００％、Ｂｅ：０～０．０５０％、及びＡｇ：０～０．５００％のうち１種又は２種以上を含有してもよい。また、鋼材は、Ｃａ：０～０．０５００％、Ｍｇ：０～０．０５００％、並びにＬａ、Ｃｅ、Ｎｄ、Ｙ、Ｐｍ、Ｐｒ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、及びＳｃの少なくとも１種：合計で０～０．５０００％のうち１種又は２種以上を含有してもよい。また、鋼材は、Ｓｎ：０～０．３００％、及びＳｂ：０～０．３００％のうち１種又は２種を含有してもよい。また、鋼材は、Ｔｅ：０～０．１００％、Ｓｅ：０～０．１００％、Ａｓ：０～０．０５０％、Ｂｉ：０～０．５００％、及びＰｂ：０～０．５００％のうち１種又は２種以上を含有してもよい。以下、これらの任意選択元素について詳しく説明する。 The basic chemical composition of the steel material according to the embodiment of the present invention is as described above. Further, the steel material may contain one or more of the following optional elements, if necessary. For example, the steel material has Nb: 0 to 3.000%, Ti: 0 to 0.500%, Ta: 0 to 0.500%, V: 0 to 1.00%, Cu: 0 to 3.00%, Ni: 0 to 60.00%, Cr: 0 to 30.00%, Mo: 0 to 5.00%, W: 0 to 2.00%, B: 0 to 0.0200%, Co: 0 to 3 It may contain one or more of .00%, Be: 0 to 0.050%, and Ag: 0 to 0.500%. The steel materials include Ca: 0 to 0.0500%, Mg: 0 to 0.0500%, and La, Ce, Nd, Y, Pm, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er. At least one of Tm, Yb, Lu, and Sc: one or more of 0 to 0.5000% in total may be contained. Further, the steel material may contain one or two of Sn: 0 to 0.300% and Sb: 0 to 0.300%. The steel materials are Te: 0 to 0.100%, Se: 0 to 0.100%, As: 0 to 0.050%, Bi: 0 to 0.500%, and Pb: 0 to 0.500%. One or more of them may be contained. Hereinafter, these optional elements will be described in detail.
［Ｎｂ：０～３．０００％］
　ニオブ（Ｎｂ）は、析出強化及び再結晶の抑制等に寄与する元素である。Ｎｂ含有量は０％であってもよいが、これらの効果を得るためには、Ｎｂ含有量は０．００３％以上であることが好ましい。例えば、Ｎｂ含有量は０．００５％以上又は０．０１０％以上であってもよい。とりわけ、析出強化を十分に図る観点からは、Ｎｂ含有量は１．０００％以上又は１．５００％以上であってもよい。一方で、Ｎｂを過度に含有すると、効果が飽和し、加工性及び／又は靭性を低下させる場合がある。したがって、Ｎｂ含有量は３．０００％以下である。Ｎｂ含有量は２．８００％以下、２．５００％以下又は２．０００％以下であってもよい。とりわけ、溶接熱影響部（ＨＡＺ）の靭性低下を抑制するという観点からは、Ｎｂ含有量は０．１００％以下であることが好ましく、０．０８０％以下、０．０５０％以下又は０．０３０％以下であってもよい。 [Nb: 0-3.000%]
Niobium (Nb) is an element that contributes to strengthening precipitation and suppressing recrystallization. The Nb content may be 0%, but in order to obtain these effects, the Nb content is preferably 0.003% or more. For example, the Nb content may be 0.005% or more or 0.010% or more. In particular, the Nb content may be 1.000% or more or 1.500% or more from the viewpoint of sufficiently strengthening precipitation. On the other hand, if Nb is excessively contained, the effect may be saturated and the processability and / or toughness may be lowered. Therefore, the Nb content is 3.000% or less. The Nb content may be 2.800% or less, 2.500% or less, or 2.000% or less. In particular, from the viewpoint of suppressing the decrease in toughness of the weld heat affected zone (HAZ), the Nb content is preferably 0.100% or less, 0.080% or less, 0.050% or less, or 0.030. It may be less than or equal to%.
［Ｔｉ：０～０．５００％］
　チタン（Ｔｉ）は、析出強化等により鋼材の強度向上に寄与する元素である。Ｔｉ含有量は０％であってもよいが、このような効果を得るためには、Ｔｉ含有量は０．００５％以上であることが好ましい。Ｔｉ含有量は０．０１０％以上、０．０５０％以上又は０．０８０％以上であってもよい。一方で、Ｔｉを過度に含有すると、多量の析出物が生成して靭性を低下させる場合がある。したがって、Ｔｉ含有量は０．５００％以下である。Ｔｉ含有量は０．３００％以下、０．２００％以下又は０．１００％以下であってもよい。 [Ti: 0 to 0.500%]
Titanium (Ti) is an element that contributes to improving the strength of steel materials by strengthening precipitation. The Ti content may be 0%, but in order to obtain such an effect, the Ti content is preferably 0.005% or more. The Ti content may be 0.010% or more, 0.050% or more, or 0.080% or more. On the other hand, if Ti is excessively contained, a large amount of precipitates may be formed and the toughness may be lowered. Therefore, the Ti content is 0.500% or less. The Ti content may be 0.300% or less, 0.200% or less, or 0.100% or less.
［Ｔａ：０～０．５００％］
　タンタル（Ｔａ）は、炭化物の形態制御と強度の増加に有効な元素である。Ｔａ含有量は０％であってもよいが、これらの効果を得るためには、Ｔａ含有量は０．００１％以上であることが好ましい。Ｔａ含有量は０．００５％以上、０．０１０％以上又は０．０５０％以上であってもよい。一方で、Ｔａを過度に含有すると、微細なＴａ炭化物が多数析出し、鋼材の過度な強度上昇を招き、結果として延性の低下及び冷間加工性を低下させる場合がある。したがって、Ｔａ含有量は０．５００％以下である。Ｔａ含有量は、０．３００％以下、０．１００％以下又は０．０８０％以下であってもよい。 [Ta: 0 to 0.500%]
Tantalum (Ta) is an element effective in controlling the morphology of carbides and increasing their strength. The Ta content may be 0%, but in order to obtain these effects, the Ta content is preferably 0.001% or more. The Ta content may be 0.005% or more, 0.010% or more, or 0.050% or more. On the other hand, if Ta is excessively contained, a large amount of fine Ta carbides may be deposited, which may lead to an excessive increase in strength of the steel material, resulting in a decrease in ductility and a decrease in cold workability. Therefore, the Ta content is 0.500% or less. The Ta content may be 0.300% or less, 0.100% or less, or 0.080% or less.
［Ｖ：０～１．００％］
　バナジウム（Ｖ）は、析出強化等により鋼材の強度向上に寄与する元素である。Ｖ含有量は０％であってもよいが、このような効果を得るためには、Ｖ含有量は０．００１％以上であることが好ましい。Ｖ含有量は０．０１％以上、０．０２％以上、０．０５％以上又は０．１０％以上であってもよい。一方で、Ｖを過度に含有すると、多量の析出物が生成して靭性を低下させる場合がある。したがって、Ｖ含有量は１．００％以下である。Ｖ含有量は０．８０％以下、０．６０％以下又は０．５０％以下であってもよい。 [V: 0 to 1.00%]
Vanadium (V) is an element that contributes to improving the strength of steel materials by strengthening precipitation. The V content may be 0%, but in order to obtain such an effect, the V content is preferably 0.001% or more. The V content may be 0.01% or more, 0.02% or more, 0.05% or more, or 0.10% or more. On the other hand, if V is excessively contained, a large amount of precipitates may be formed and the toughness may be lowered. Therefore, the V content is 1.00% or less. The V content may be 0.80% or less, 0.60% or less, or 0.50% or less.
［Ｃｕ：０～３．００％］
　銅（Ｃｕ）は強度及び／又は耐食性の向上に寄与する元素である。Ｃｕ含有量は０％であってもよいが、これらの効果を得るためには、Ｃｕ含有量は０．００１％以上であることが好ましい。Ｃｕ含有量は０．０１％以上、０．１０％以上、０．１５％以上、０．２０％以上又は０．３０％以上であってもよい。一方で、Ｃｕを過度に含有すると、靭性や溶接性の劣化を招く場合がある。したがって、Ｃｕ含有量は３．００％以下である。Ｃｕ含有量は２．００％以下、１．５０％以下、１．００％以下又は０．５０％以下であってもよい。 [Cu: 0 to 3.00%]
Copper (Cu) is an element that contributes to the improvement of strength and / or corrosion resistance. The Cu content may be 0%, but in order to obtain these effects, the Cu content is preferably 0.001% or more. The Cu content may be 0.01% or more, 0.10% or more, 0.15% or more, 0.20% or more, or 0.30% or more. On the other hand, if Cu is excessively contained, the toughness and weldability may be deteriorated. Therefore, the Cu content is 3.00% or less. The Cu content may be 2.00% or less, 1.50% or less, 1.00% or less, or 0.50% or less.
［Ｎｉ：０～６０．００％］
　ニッケル（Ｎｉ）は強度及び／又は耐熱性の向上に寄与する元素であり、有効なオーステナイト安定化元素でもある。Ｎｉ含有量は０％であってもよいが、これらの効果を得るためには、Ｎｉ含有量は０．００１％以上であることが好ましい。Ｎｉ含有量は０．０１％以上、０．１０％以上、０．５０％以上、０．７０％以上、１．００％以上又は３．００％以上であってもよい。とりわけ、耐熱性を十分に向上させる観点からは、Ｎｉ含有量は３０．００％以上、３５．００％以上又は４０．００％以上であってもよい。一方で、Ｎｉを過度に含有すると、合金コストの増加に加えて熱間加工時の変形抵抗が増大し、設備負荷が大きくなる場合がある。したがって、Ｎｉ含有量は６０．００％以下である。Ｎｉ含有量は５５．００％以下又は５０．００％以下であってもよい。とりわけ、経済性の観点及び／又は溶接性の低下を抑制するという観点からは、Ｎｉ含有量は１５．００％以下、１０．００％以下、６．００％以下又は４．００％以下であってもよい。 [Ni: 0-60.00%]
Nickel (Ni) is an element that contributes to the improvement of strength and / or heat resistance, and is also an effective austenite stabilizing element. The Ni content may be 0%, but in order to obtain these effects, the Ni content is preferably 0.001% or more. The Ni content may be 0.01% or more, 0.10% or more, 0.50% or more, 0.70% or more, 1.00% or more, or 3.00% or more. In particular, from the viewpoint of sufficiently improving the heat resistance, the Ni content may be 30.00% or more, 35.00% or more, or 40.00% or more. On the other hand, if Ni is excessively contained, the deformation resistance during hot working increases in addition to the increase in alloy cost, which may increase the equipment load. Therefore, the Ni content is 60.00% or less. The Ni content may be 55.00% or less or 50.00% or less. In particular, from the viewpoint of economic efficiency and / or from the viewpoint of suppressing deterioration of weldability, the Ni content is 15.00% or less, 10.00% or less, 6.00% or less, or 4.00% or less. You may.
［Ｃｒ：０～３０．００％］
　クロム（Ｃｒ）は強度及び／又は耐食性の向上に寄与する元素である。Ｃｒ含有量は０％であってもよいが、これらの効果を得るためには、Ｃｒ含有量は０．００１％以上であることが好ましい。Ｃｒ含有量は０．０１％以上、０．０５％以上、０．１０％以上又は０．５０％以上であってもよい。とりわけ、耐食性を十分に向上させる観点からは、Ｃｒ含有量は１０．００％以上、１２．００％以上又は１５．００％以上であってもよい。一方で、Ｃｒを過度に含有すると、合金コストの増加に加えて靭性が低下する場合がある。したがって、Ｃｒ含有量は３０．００％以下である。Ｃｒ含有量は２８．００％以下、２５．００％以下又は２０．００％以下であってもよい。とりわけ、溶接性及び／又は加工性の低下を抑制するという観点からは、Ｃｒ含有量は１０．００％以下、９．００％以下又は７．５０％以下であってもよい。 [Cr: 0 to 30.00%]
Chromium (Cr) is an element that contributes to the improvement of strength and / or corrosion resistance. The Cr content may be 0%, but in order to obtain these effects, the Cr content is preferably 0.001% or more. The Cr content may be 0.01% or more, 0.05% or more, 0.10% or more, or 0.50% or more. In particular, from the viewpoint of sufficiently improving the corrosion resistance, the Cr content may be 10.00% or more, 12.00% or more, or 15.00% or more. On the other hand, if Cr is excessively contained, the toughness may decrease in addition to the increase in alloy cost. Therefore, the Cr content is 30.00% or less. The Cr content may be 28.00% or less, 25.00% or less, or 20.00% or less. In particular, from the viewpoint of suppressing deterioration of weldability and / or processability, the Cr content may be 10.00% or less, 9.00% or less, or 7.50% or less.
［Ｍｏ：０～５．００％］
　モリブデン（Ｍｏ）は鋼の焼入れ性を高め、強度の向上に寄与する元素であり、耐食性の向上にも寄与する元素である。Ｍｏ含有量は０％であってもよいが、これらの効果を得るためには、Ｍｏ含有量は０．００１％以上であることが好ましい。Ｍｏ含有量は０．０１％以上、０．０２％以上、０．５０％以上又は１．００％以上であってもよい。一方で、Ｍｏを過度に含有すると、熱間加工時の変形抵抗が増大し、設備負荷が大きくなる場合がある。したがって、Ｍｏ含有量は５．００％以下である。Ｍｏ含有量は４．５０％以下、４．００％以下、３．００以下又は１．５０％以下であってもよい。 [Mo: 0 to 5.00%]
Molybdenum (Mo) is an element that enhances the hardenability of steel and contributes to the improvement of strength, and is also an element that contributes to the improvement of corrosion resistance. The Mo content may be 0%, but in order to obtain these effects, the Mo content is preferably 0.001% or more. The Mo content may be 0.01% or more, 0.02% or more, 0.50% or more, or 1.00% or more. On the other hand, if Mo is excessively contained, the deformation resistance during hot working increases, and the equipment load may increase. Therefore, the Mo content is 5.00% or less. The Mo content may be 4.50% or less, 4.00% or less, 3.00 or less, or 1.50% or less.
［Ｗ：０～２．００％］
　タングステン（Ｗ）は鋼の焼入れ性を高め、強度の向上に寄与する元素である。Ｗ含有量は０％であってもよいが、このような効果を得るためには、Ｗ含有量は０．００１％以上であることが好ましい。Ｗ含有量は０．０１％以上、０．０２％以上、０．０５％以上、０．１０％以上又は０．５０％以上であってもよい。一方で、Ｗを過度に含有すると、延性や溶接性が低下する場合がある。したがって、Ｗ含有量は２．００％以下である。Ｗ含有量は１．８０％以下、１．５０％以下又は１．００％以下であってもよい。 [W: 0 to 2.00%]
Tungsten (W) is an element that enhances the hardenability of steel and contributes to the improvement of strength. The W content may be 0%, but in order to obtain such an effect, the W content is preferably 0.001% or more. The W content may be 0.01% or more, 0.02% or more, 0.05% or more, 0.10% or more, or 0.50% or more. On the other hand, if W is excessively contained, ductility and weldability may decrease. Therefore, the W content is 2.00% or less. The W content may be 1.80% or less, 1.50% or less, or 1.00% or less.
［Ｂ：０～０．０２００％］
　ホウ素（Ｂ）は強度の向上に寄与する元素である。Ｂ含有量は０％であってもよいが、このような効果を得るためには、Ｂ含有量は０．０００１％以上であることが好ましい。Ｂ含有量は０．０００３％以上、０．０００５％以上又は０．０００７％以上であってもよい。一方で、Ｂを過度に含有すると、靭性及び／又は溶接性が低下する場合がある。したがって、Ｂ含有量は０．０２００％以下である。Ｂ含有量は０．０１００％以下、０．００５０％以下、０．００３０％以下又は０．００２０％以下であってもよい。 [B: 0 to 0.0200%]
Boron (B) is an element that contributes to the improvement of strength. The B content may be 0%, but in order to obtain such an effect, the B content is preferably 0.0001% or more. The B content may be 0.0003% or more, 0.0005% or more, or 0.0007% or more. On the other hand, if B is excessively contained, toughness and / or weldability may decrease. Therefore, the B content is 0.0200% or less. The B content may be 0.0100% or less, 0.0050% or less, 0.0030% or less, or 0.0020% or less.
［Ｃｏ：０～３．００％］
　コバルト（Ｃｏ）は焼入れ性及び／又は耐熱性の向上に寄与する元素である。Ｃｏ含有量は０％であってもよいが、これらの効果を得るためには、Ｃｏ含有量は０．００１％以上であることが好ましい。Ｃｏ含有量は０．０１％以上、０．０２％以上、０．０５％以上、０．１０％以上又は０．５０％以上であってもよい。一方で、Ｃｏを過度に含有すると、熱間加工性が低下する場合があり、原料コストの増加にも繋がる。したがって、Ｃｏ含有量は３．００％以下である。Ｃｏ含有量は２．５０％以下、２．００％以下、１．５０％以下又は０．８０％以下であってもよい。 [Co: 0 to 3.00%]
Cobalt (Co) is an element that contributes to the improvement of hardenability and / or heat resistance. The Co content may be 0%, but in order to obtain these effects, the Co content is preferably 0.001% or more. The Co content may be 0.01% or more, 0.02% or more, 0.05% or more, 0.10% or more, or 0.50% or more. On the other hand, if Co is excessively contained, the hot workability may be lowered, which leads to an increase in raw material cost. Therefore, the Co content is 3.00% or less. The Co content may be 2.50% or less, 2.00% or less, 1.50% or less, or 0.80% or less.
［Ｂｅ：０～０．０５０％］
　ベリリウム（Ｂｅ）は、母材の強度の上昇及び組織の微細化に有効な元素である。Ｂｅ含有量は０％であってもよいが、このような効果を得るためには、Ｂｅ含有量は０．０００３％以上であることが好ましい。Ｂｅ含有量は０．０００５％以上、０．００１％以上又は０．０１０％以上であってもよい。一方で、Ｂｅを過度に含有すると、成形性が低下する場合がある。したがって、Ｂｅ含有量は０．０５０％以下である。Ｂｅ含有量は０．０４０％以下、０．０３０％以下又は０．０２０％以下であってもよい。 [Be: 0 to 0.050%]
Beryllium (Be) is an element effective for increasing the strength of the base metal and refining the structure. The Be content may be 0%, but in order to obtain such an effect, the Be content is preferably 0.0003% or more. The Be content may be 0.0005% or more, 0.001% or more, or 0.010% or more. On the other hand, if Be is excessively contained, the moldability may be deteriorated. Therefore, the Be content is 0.050% or less. The Be content may be 0.040% or less, 0.030% or less, or 0.020% or less.
［Ａｇ：０～０．５００％］
　銀（Ａｇ）は、母材の強度の上昇及び組織の微細化に有効な元素である。Ａｇ含有量は０％であってもよいが、このような効果を得るためには、Ａｇ含有量は０．００１％以上であることが好ましい。Ａｇ含有量は０．０１０％以上、０．０２０％以上、０．０３０％以上又は０．０５０％以上であってもよい。一方で、Ａｇを過度に含有すると、成形性が低下する場合がある。したがって、Ａｇ含有量は０．５００％以下である。Ａｇ含有量は０．４００％以下、０．３００％以下又は０．２００％以下であってもよい。 [Ag: 0 to 0.500%]
Silver (Ag) is an element effective for increasing the strength of the base material and refining the structure. The Ag content may be 0%, but in order to obtain such an effect, the Ag content is preferably 0.001% or more. The Ag content may be 0.010% or more, 0.020% or more, 0.030% or more, or 0.050% or more. On the other hand, if Ag is excessively contained, the moldability may be deteriorated. Therefore, the Ag content is 0.500% or less. The Ag content may be 0.400% or less, 0.300% or less, or 0.200% or less.
［Ｃａ：０～０．０５００％］
　カルシウム（Ｃａ）は、硫化物の形態を制御できる元素である。Ｃａ含有量は０％であってもよいが、このような効果を得るためには、Ｃａ含有量は０．０００１％以上であることが好ましい。一方で、Ｃａを過度に含有しても効果が飽和し、それゆえＣａを必要以上に鋼材中に含有させることは製造コストの上昇を招く虞がある。したがって、Ｃａ含有量は０．０５００％以下である。 [Ca: 0-0.0500%]
Calcium (Ca) is an element that can control the morphology of sulfides. The Ca content may be 0%, but in order to obtain such an effect, the Ca content is preferably 0.0001% or more. On the other hand, even if Ca is excessively contained, the effect is saturated, and therefore, if Ca is contained in the steel material more than necessary, the manufacturing cost may increase. Therefore, the Ca content is 0.0500% or less.
［Ｍｇ：０～０．０５００％］
　マグネシウム（Ｍｇ）は、硫化物の形態を制御できる元素である。Ｍｇ含有量は０％であってもよいが、このような効果を得るためには、Ｍｇ含有量は０．０００１％以上であることが好ましい。Ｍｇ含有量は０．００１５％超、０．００１６％以上、０．００１８％以上又は０．００２０％以上であってもよい。一方で、Ｍｇを過度に含有しても効果が飽和し、粗大な介在物の形成に起因して冷間成形性及び／又は靭性が低下する場合がある。したがって、Ｍｇ含有量は０．０５００％以下である。Ｍｇ含有量は０．０４００％以下、０．０３００％以下又は０．０２００％以下であってもよい。 [Mg: 0 to 0.0500%]
Magnesium (Mg) is an element that can control the morphology of sulfides. The Mg content may be 0%, but in order to obtain such an effect, the Mg content is preferably 0.0001% or more. The Mg content may be greater than 0.0015%, greater than 0.0016%, greater than or equal to 0.0018% or greater than or equal to 0.0020%. On the other hand, even if Mg is excessively contained, the effect is saturated, and cold formability and / or toughness may decrease due to the formation of coarse inclusions. Therefore, the Mg content is 0.0500% or less. The Mg content may be 0.0400% or less, 0.0300% or less, or 0.0200% or less.
［Ｌａ、Ｃｅ、Ｎｄ、Ｙ、Ｐｍ、Ｐｒ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、及びＳｃの少なくとも１種：合計で０～０．５０００％］
　ランタン（Ｌａ）、セリウム（Ｃｅ）、ネオジム（Ｎｄ）、イットリウム（Ｙ）、プロメチウム（Ｐｍ）、プラセオジム（Ｐｒ）、サマリウム（Ｓｍ）、ユウロピウム（Ｅｕ）、ガドリニウム（Ｇｄ）、テルビウム（Ｔｂ）、ジスプロシウム（Ｄｙ）、ホルミウム（Ｈｏ）、エルビウム（Ｅｒ）、ツリウム（Ｔｍ）、イッテルビウム（Ｙｂ）、ルテチウム（Ｌｕ）、及びスカンジウム（Ｓｃ）は、Ｃａ及びＭｇと同様に硫化物の形態を制御できる元素である。Ｌａ、Ｃｅ、Ｎｄ、Ｙ、Ｐｍ、Ｐｒ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、及びＳｃの少なくとも１種の含有量の合計は０％であってもよいが、このような効果を得るためには０．０００１％以上であることが好ましい。Ｌａ、Ｃｅ、Ｎｄ、Ｙ、Ｐｍ、Ｐｒ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、及びＳｃの少なくとも１種の含有量の合計は０．０００２％以上、０．０００３％以上又は０．０００４％以上であってもよい。一方で、これらの元素を過度に含有しても効果が飽和し、それゆえこれらの元素を必要以上に鋼材中に含有させることは製造コストの上昇を招く虞がある。したがって、Ｌａ、Ｃｅ、Ｎｄ、Ｙ、Ｐｍ、Ｐｒ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、及びＳｃの少なくとも１種の含有量の合計は０．５０００％以下であり、０．４０００％以下、０．３０００％以下又は０．２０００％以下であってもよい。 [At least one of La, Ce, Nd, Y, Pm, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc: 0 to 0.5000% in total]
Lantern (La), Cerium (Ce), Neogym (Nd), Yttrium (Y), Promethium (Pm), Placeozim (Pr), Samarium (Sm), Europium (Eu), Gadrinium (Gd), Terbium (Tb), Dysprosium (Dy), formium (Ho), elbium (Er), yttrium (Tm), yttrium (Yb), lutetium (Lu), and scandium (Sc) can control the morphology of sulfides as well as Ca and Mg. It is an element. Even if the total content of at least one of La, Ce, Nd, Y, Pm, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc is 0%. However, in order to obtain such an effect, it is preferably 0.0001% or more. The total content of at least one of La, Ce, Nd, Y, Pm, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc is 0.0002% or more. It may be 0.0003% or more or 0.0004% or more. On the other hand, even if these elements are excessively contained, the effect is saturated, and therefore, including these elements in the steel material more than necessary may lead to an increase in manufacturing cost. Therefore, the total content of at least one of La, Ce, Nd, Y, Pm, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc is 0.5000%. It may be less than or equal to 0.4000%, 0.3000% or less, or 0.2000% or less.
［Ｓｎ：０～０．３００％］
　錫（Ｓｎ）は耐食性の向上に有効な元素である。Ｓｎ含有量は０％であってもよいが、このような効果を得るためには、Ｓｎ含有量は０．００１％以上であることが好ましい。Ｓｎ含有量は０．０１０％以上、０．０２０％以上、０．０３０％以上又は０．０５０％以上であってもよい。一方で、Ｓｎを過度に含有すると、靭性、特には低温靭性の低下を招く場合がある。したがって、Ｓｎ含有量は０．３００％以下である。Ｓｎ含有量は０．２５０％以下、０．２００％以下又は０．１５０％以下であってもよい。 [Sn: 0 to 0.300%]
Tin (Sn) is an element effective for improving corrosion resistance. The Sn content may be 0%, but in order to obtain such an effect, the Sn content is preferably 0.001% or more. The Sn content may be 0.010% or more, 0.020% or more, 0.030% or more, or 0.050% or more. On the other hand, excessive inclusion of Sn may lead to a decrease in toughness, particularly low temperature toughness. Therefore, the Sn content is 0.300% or less. The Sn content may be 0.250% or less, 0.200% or less, or 0.150% or less.
［Ｓｂ：０～０．３００％］
　アンチモン（Ｓｂ）は、Ｓｎと同様に耐食性の向上に有効な元素であり、特にＳｎと複合して含有させることにより効果を増大させることができる。Ｓｂ含有量は０％であってもよいが、耐食性向上の効果を得るためには、Ｓｂ含有量は０．００１％以上であることが好ましい。Ｓｂ含有量は０．０１０％以上、０．０２０％以上、０．０３０％以上又は０．０５０％以上であってもよい。一方で、Ｓｂを過度に含有すると、靭性、特には低温靭性の低下を招く場合がある。したがって、Ｓｂ含有量は０．３００％以下である。Ｓｂ含有量は０．２５０％以下、０．２００％以下又は０．１５０％以下であってもよい。 [Sb: 0 to 0.300%]
Antimony (Sb) is an element effective for improving corrosion resistance like Sn, and the effect can be increased by including it in combination with Sn. The Sb content may be 0%, but in order to obtain the effect of improving the corrosion resistance, the Sb content is preferably 0.001% or more. The Sb content may be 0.010% or more, 0.020% or more, 0.030% or more, or 0.050% or more. On the other hand, excessive content of Sb may lead to a decrease in toughness, particularly low temperature toughness. Therefore, the Sb content is 0.300% or less. The Sb content may be 0.250% or less, 0.200% or less, or 0.150% or less.
［Ｔｅ：０～０．１００％］
　テルル（Ｔｅ）は、ＭｎやＳなどと低融点化合物を形成して潤滑効果を高めるため、鋼の被削性を改善するのに有効な元素である。Ｔｅ含有量は０％であってもよいが、このような効果を得るためには、Ｔｅ含有量は０．００１％以上であることが好ましい。Ｔｅ含有量は０．０１０％以上、０．０２０％以上、０．０３０％以上又は０．０４０％以上であってもよい。一方で、Ｔｅを過度に含有しても効果が飽和し、合金コストの増加を招く。したがって、Ｔｅ含有量は０．１００％以下である。Ｔｅ含有量は０．０９０％以下、０．０８０％以下又は０．０７０％以下であってもよい。 [Te: 0 to 0.100%]
Tellurium (Te) is an element effective for improving the machinability of steel because it forms a low melting point compound with Mn, S and the like to enhance the lubricating effect. The Te content may be 0%, but in order to obtain such an effect, the Te content is preferably 0.001% or more. The Te content may be 0.010% or more, 0.020% or more, 0.030% or more, or 0.040% or more. On the other hand, even if Te is excessively contained, the effect is saturated and the alloy cost increases. Therefore, the Te content is 0.100% or less. The Te content may be 0.090% or less, 0.080% or less, or 0.070% or less.
［Ｓｅ：０～０．１００％］
　セレン（Ｓｅ）は、鋼中に生成するセレン化物が被削材のせん断塑性変形に変化を与え、切りくずが破砕されやすくなるため、鋼の被削性を改善するのに有効な元素である。Ｓｅ含有量は０％であってもよいが、このような効果を得るためには、Ｓｅ含有量は０．００１％以上であることが好ましい。Ｓｅ含有量は０．０１０％以上、０．０２０％以上、０．０３０％以上又は０．０４０％以上であってもよい。一方で、Ｓｅを過度に含有しても効果が飽和し、合金コストの増加を招く。したがって、Ｓｅ含有量は０．１００％以下である。Ｓｅ含有量は０．０９０％以下、０．０８０％以下又は０．０７０％以下であってもよい。 [Se: 0 to 0.100%]
Selenium (Se) is an effective element for improving the machinability of steel because the selenium produced in the steel changes the shear-plastic deformation of the work material and the chips are easily crushed. .. The Se content may be 0%, but in order to obtain such an effect, the Se content is preferably 0.001% or more. The Se content may be 0.010% or more, 0.020% or more, 0.030% or more, or 0.040% or more. On the other hand, even if Se is excessively contained, the effect is saturated and the alloy cost increases. Therefore, the Se content is 0.100% or less. The Se content may be 0.090% or less, 0.080% or less, or 0.070% or less.
［Ａｓ：０～０．０５０％］
　ヒ素（Ａｓ）は、鋼の被削性を改善するのに有効な元素である。Ａｓ含有量は０％であってもよいが、このような効果を得るためには、Ａｓ含有量は０．００１％以上であることが好ましい。Ａｓ含有量は０．００５％以上又は０．０１０％以上であってもよい。一方で、Ａｓを過度に含有すると、熱間加工性が低下する場合がある。したがって、Ａｓ含有量は０．０５０％以下である。Ａｓ含有量は０．０４０％以下、０．０３０％以下又は０．０２０％以下であってもよい。 [As: 0 to 0.050%]
Arsenic (As) is an element effective in improving the machinability of steel. The As content may be 0%, but in order to obtain such an effect, the As content is preferably 0.001% or more. The As content may be 0.005% or more or 0.010% or more. On the other hand, if As is excessively contained, the hot workability may be deteriorated. Therefore, the As content is 0.050% or less. The As content may be 0.040% or less, 0.030% or less, or 0.020% or less.
［Ｂｉ：０～０．５００％］
　ビスマス（Ｂｉ）は、鋼の被削性を改善するのに有効な元素である。Ｂｉ含有量は０％であってもよいが、このような効果を得るためには、Ｂｉ含有量は０．００１％以上であることが好ましい。Ｂｉ含有量は０．０１０％以上、０．０２０％以上、０．０３０％以上又は０．０５０％以上であってもよい。一方で、Ｂｉを過度に含有しても効果が飽和し、合金コストの増加を招く。したがって、Ｂｉ含有量は０．５００％以下である。Ｂｉ含有量は０．４００％以下、０．３００％以下又は０．２００％以下であってもよい。 [Bi: 0 to 0.500%]
Bismuth (Bi) is an element effective in improving the machinability of steel. The Bi content may be 0%, but in order to obtain such an effect, the Bi content is preferably 0.001% or more. The Bi content may be 0.010% or more, 0.020% or more, 0.030% or more, or 0.050% or more. On the other hand, even if Bi is excessively contained, the effect is saturated and the alloy cost increases. Therefore, the Bi content is 0.500% or less. The Bi content may be 0.400% or less, 0.300% or less, or 0.200% or less.
［Ｐｂ：０～０．５００％］
　鉛（Ｐｂ）は、切削による温度上昇で溶融してクラックの進展を促進するため、鋼の被削性を改善するのに有効な元素である。Ｐｂ含有量は０％であってもよいが、このような効果を得るためには、Ｐｂ含有量は０．００１％以上であることが好ましい。Ｐｂ含有量は０．０１０％以上、０．０２０％以上、０．０３０％以上又は０．０５０％以上であってもよい。一方で、Ｐｂを過度に含有すると、熱間加工性が低下する場合がある。したがって、Ｐｂ含有量は０．５００％以下である。Ｐｂ含有量は０．４００％以下、０．３００％以下又は０．２００％以下であってもよい。 [Pb: 0 to 0.500%]
Lead (Pb) is an element effective for improving the machinability of steel because it melts when the temperature rises due to cutting and promotes the growth of cracks. The Pb content may be 0%, but in order to obtain such an effect, the Pb content is preferably 0.001% or more. The Pb content may be 0.010% or more, 0.020% or more, 0.030% or more, or 0.050% or more. On the other hand, if Pb is excessively contained, the hot workability may be deteriorated. Therefore, the Pb content is 0.500% or less. The Pb content may be 0.400% or less, 0.300% or less, or 0.200% or less.
　本発明の実施形態に係る鋼材において、上記の元素以外の残部は、Ｆｅ及び不純物からなる。不純物とは、鋼材を工業的に製造する際に、鉱石やスクラップ等のような原料を始めとして、製造工程の種々の要因によって混入する成分等である。 In the steel material according to the embodiment of the present invention, the balance other than the above elements consists of Fe and impurities. Impurities are components that are mixed in by various factors in the manufacturing process, including raw materials such as ore and scrap, when steel materials are industrially manufactured.
［Ｚ元素の有効量］
　本発明の実施形態によれば、Ｚｒ及びＨｆからなるＺ元素の有効量は、下記式１の左辺によって求められ、そしてその値は下記式１を満たすようにする。
　０．６１［Ｚｒ］＋０．３１［Ｈｆ］－１．７５［Ｏ］－３．９９［Ｎ］－１．７４［Ｓ］　≧　０．０００３　　　・・・式１
　ここで、［Ｚｒ］、［Ｈｆ］、［Ｏ］、［Ｎ］、及び［Ｓ］は、各元素の含有量［質量％］であり、元素を含有しない場合は０である。 [Effective amount of Z element]
According to the embodiment of the present invention, the effective amount of the Z element consisting of Zr and Hf is determined by the left side of the following formula 1, and the value thereof satisfies the following formula 1.
0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1.74 [S] ≧ 0.0003 ・ ・ ・ Equation 1
Here, [Zr], [Hf], [O], [N], and [S] are the content [mass%] of each element, and are 0 when the element is not contained.
　上記Ｚ元素の有効量を上記式１を満たすようにすることで、鋼中に存在しているＺ元素と鋼中の固溶Ｐを反応させてリン化物を形成することができ、このようなリン化物の形成に伴い、鋼中の固溶Ｐ量を低減することが可能となる。より詳しく説明すると、これらのＺ元素（以下、単に「Ｚ」ともいう）は、鋼中に存在するＯ（酸素）、Ｎ（窒素）及びＳ（硫黄）と結びついて、酸化物（ＺＯ2）、窒化物（ＺＮ）及び硫化物（ＺＳ）からなる介在物を形成する傾向がある。当該介在物を形成してしまうと、少なくともこれらの介在物中のＺ元素は固溶Ｐとの反応に寄与することはできない。したがって、固溶Ｐとの反応を促進して鋼中の固溶Ｐ量を低減するためには、介在物を形成せずに鋼中でリン化物を形成し得るＺ元素の量を増加させる必要がある。 By making the effective amount of the Z element satisfy the above formula 1, it is possible to react the Z element existing in the steel with the solid solution P in the steel to form a phosphide. With the formation of the phosphide, it becomes possible to reduce the amount of solid melt P in the steel. More specifically, these Z elements (hereinafter, also simply referred to as “Z”) are combined with O (oxygen), N (nitrogen) and S (sulfur) present in steel to form an oxide (ZO 2 ). , Tends to form inclusions consisting of nitrides (ZN) and sulfides (ZS). Once the inclusions are formed, at least the Z element in these inclusions cannot contribute to the reaction with the solid solution P. Therefore, in order to promote the reaction with the solid solution P and reduce the amount of the solid solution P in the steel, it is necessary to increase the amount of the Z element that can form a phosphide in the steel without forming inclusions. There is.
　ここで、リン化物を形成し得るＺ元素の量は、鋼中に含まれるＺ元素の量から介在物（酸化物、窒化物及び硫化物）を形成するのに消費され得る最大量を差し引くことによって概算することが可能である。そこで、本発明の実施形態においては、このようにして概算される鋼中の固溶Ｐ量を低減するのに有効なＺ元素の量（すなわち「Ｚ元素の有効量」）は、具体的には下記式Ａによって定義される。
　Ｚの有効量［原子％］＝Σ（Ｍ[Fe]／Ｍ[Z]）×［Ｚ］－（Ｍ[Fe]／Ｍ[O]）×［Ｏ］×１／２－（Ｍ[Fe]／Ｍ[N]）×［Ｎ］－（Ｍ[Fe]／Ｍ[S]）×［Ｓ］　　　・・・式Ａ
　ここで、ＺはＺｒ及びＨｆの各Ｚ元素を表し、Ｍ[Z]はＺ元素の原子量、Ｍ[Fe]はＦｅの原子量、Ｍ[O]はＯの原子量、Ｍ[N]はＮの原子量、Ｍ[S]はＳの原子量を表し、［Ｚ］、［Ｏ］、［Ｎ］及び［Ｓ］は、それぞれ対応する元素の含有量［質量％］であり、元素を含有しない場合は０である。 Here, the amount of Z element that can form a phosphide is the amount of Z element contained in the steel minus the maximum amount that can be consumed to form inclusions (oxides, nitrides and sulfides). It is possible to estimate by. Therefore, in the embodiment of the present invention, the amount of Z element effective for reducing the amount of solid solution P in the steel estimated in this way (that is, "effective amount of Z element") is specifically determined. Is defined by the following formula A.
Effective amount of Z [atomic%] = Σ (M [Fe] / M [Z] ) x [Z]-(M [Fe] / M [O] ) x [O] x 1 / 2- (M [Fe ] ] / M [N] ) x [N]-(M [Fe] / M [S] ) x [S] ... Equation A
Here, Z represents each Z element of Zr and Hf, M [Z] is the atomic weight of the Z element, M [Fe] is the atomic weight of Fe, M [O] is the atomic weight of O, and M [N] is N. Atomic weight, M [S] represents the atomic weight of S, and [Z], [O], [N] and [S] are the corresponding element content [mass%], respectively, and when no element is contained. It is 0.
　上記式Ａについて以下に詳しく説明すると、まず、本発明の実施形態に係る鋼材には種々の合金元素が含有されているものの、鋼材全体としてはほぼＦｅによって構成されているか、あるいは任意選択元素であるＮｉ及び／又はＣｒを比較的多く含む場合（それぞれの最大含有量は６０．００％及び３０．００％）には、Ｆｅに加えてＮｉ及び／又はＣｒによってほぼ構成されていることが明らかである。一方で、Ｎｉ及びＣｒの原子量はＦｅの原子量と同等であることが周知である。このため、たとえ鋼材がＮｉ及び／又はＣｒを比較的多く含む場合であっても、Ｚｒ及びＨｆの各Ｚ元素の原子％は、近似的には各Ｚ元素の含有量［質量％］にＦｅの原子量と当該各Ｚ元素の原子量の比を掛け算すること、すなわち（Ｍ[Fe]／Ｍ[Z]）×［Ｚ］によって算出することができる。したがって、（Ｍ[Fe]／Ｍ[Z]）×［Ｚ］によって算出される各Ｚ元素の量を合計することで（すなわちΣ（Ｍ[Fe]／Ｍ[Z]）×［Ｚ］を計算することで）、Ｚ元素全体の原子％を算出することができる。 The above formula A will be described in detail below. First, although the steel material according to the embodiment of the present invention contains various alloying elements, the steel material as a whole is almost composed of Fe or is an optional element. When a certain Ni and / or Cr is contained in a relatively large amount (the maximum contents are 60.00% and 30.00%, respectively), it is clear that it is almost composed of Ni and / or Cr in addition to Fe. Is. On the other hand, it is well known that the atomic weights of Ni and Cr are equivalent to the atomic weights of Fe. Therefore, even when the steel material contains a relatively large amount of Ni and / or Cr, the atomic% of each Z element of Zr and Hf is approximately Fe in the content [mass%] of each Z element. It can be calculated by multiplying the atomic weight of each Z element by the ratio of the atomic weight of each Z element, that is, (M [Fe] / M [Z] ) × [Z]. Therefore, by summing up the amounts of each Z element calculated by (M [ Fe ] / M [Z ] ) × [Z] (that is, Σ (M [Fe] / M [Z] ) × [Z]. By calculation), the atomic% of the entire Z element can be calculated.
　次に、Ｚ元素全体の原子％のうち、酸化物（ＺＯ2）、窒化物（ＺＮ）及び硫化物（ＺＳ）を形成するのに消費され得る最大量（原子％）を差し引くことで、固溶Ｐ量を低減するのに有効に作用し得る鋼中のＺ元素の量を算出することができる。ここで、酸化物（ＺＯ2）、窒化物（ＺＮ）及び硫化物（ＺＳ）を形成するのに消費され得るＺ元素の最大量（原子％）は、上で説明したのと同様の理由から近似的には鋼中のＦｅ、Ｏ、Ｎ及びＳの原子量並びにＯ、Ｎ及びＳの含有量を用いて、それぞれ（Ｍ[Fe]／Ｍ[O]）×［Ｏ］×１／２、（Ｍ[Fe]／Ｍ[N]）×［Ｎ］、及び（Ｍ[Fe]／Ｍ[S]）×［Ｓ］として算出することが可能である。したがって、固溶Ｐ量を低減するためのＺ元素の有効量は、下記式Ａによって定義することができる。
　Ｚの有効量［原子％］＝Σ（Ｍ[Fe]／Ｍ[Z]）×［Ｚ］－（Ｍ[Fe]／Ｍ[O]）×［Ｏ］×１／２－（Ｍ[Fe]／Ｍ[N]）×［Ｎ］－（Ｍ[Fe]／Ｍ[S]）×［Ｓ］　　　・・・式Ａ Next, by subtracting the maximum amount (atomic%) that can be consumed to form oxides (ZO 2 ), nitrides (ZN) and sulfides (ZS) from the atomic% of the total Z element, it is solidified. It is possible to calculate the amount of Z element in steel that can effectively act to reduce the amount of molten P. Here, the maximum amount (atomic%) of Z element that can be consumed to form oxides (ZO 2 ), nitrides (ZN) and sulfides (ZS) is for the same reasons as described above. Approximately, using the atomic weights of Fe, O, N and S and the contents of O, N and S in the steel, (M [Fe] / M [O] ) × [O] × 1/2, respectively. It can be calculated as (M [Fe] / M [N] ) × [N] and (M [Fe] / M [S] ) × [S]. Therefore, the effective amount of the Z element for reducing the amount of solid solution P can be defined by the following formula A.
Effective amount of Z [atomic%] = Σ (M [Fe] / M [Z] ) x [Z]-(M [Fe] / M [O] ) x [O] x 1 / 2- (M [Fe ] ] / M [N] ) x [N]-(M [Fe] / M [S] ) x [S] ... Equation A
　ここで、Ｆｅ、Ｏ、Ｎ及びＳ並びに各Ｚ元素の原子量は、それぞれＦｅ：５５．８４５、Ｏ：１５．９９９４、Ｎ：１４．００６９、Ｓ：３２．０６８、Ｚｒ：９１．２２４、Ｈｆ：１７８．４９である。したがって、上記式Ａに各元素の原子量を代入して整理すると、Ｚ元素の原子％による有効量は近似的には下記式Ｂによって表すことが可能となる。
　有効量＝０．６１［Ｚｒ］＋０．３１［Ｈｆ］－１．７５［Ｏ］－３．９９［Ｎ］－１．７４［Ｓ］　　　・・・式Ｂ
　ここで、［Ｚｒ］、［Ｈｆ］、［Ｏ］、［Ｎ］、及び［Ｓ］は、各元素の含有量［質量％］であり、元素を含有しない場合は０である。 Here, the atomic weights of Fe, O, N and S and each Z element are Fe: 55.845, O: 15.9994, N: 14.0069, S: 32.068, Zr: 91.224, Hf, respectively. It is 178.49. Therefore, by substituting the atomic weight of each element into the above formula A and rearranging it, the effective amount of the Z element in terms of atomic% can be approximately expressed by the following formula B.
Effective amount = 0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1.74 [S] ... Expression B
Here, [Zr], [Hf], [O], [N], and [S] are the content [mass%] of each element, and are 0 when the element is not contained.
　本発明の実施形態においては、固溶Ｐ量を低減するためには、上記式Ｂによって求められるＺ元素の有効量は０．０００３％以上、すなわち下記式１を満たすことが少なくとも必要である。
　０．６１［Ｚｒ］＋０．３１［Ｈｆ］－１．７５［Ｏ］－３．９９［Ｎ］－１．７４［Ｓ］　≧　０．０００３　　　・・・式１
　Ｚ元素の有効量は、例えば０．０００５％以上又は０．０００７％以上であってもよく、好ましくは０．００１０％以上、より好ましくは０．００１５％以上、さらにより好ましくは０．００３０％以上、最も好ましくは０．００５０％以上又は０．０１００％以上である。また、上記式１からも明らかなように、当該有効量を安定的に確保するためには、鋼中のＯ、Ｎ及びＳの含有量を極力低減することが好ましい。ここで、Ｚ元素の有効量の上限は特に限定されないが、当該Ｚ元素の有効量を過度に増加させても効果が飽和するとともに、製造コストの上昇（Ｚ元素の含有量増加に伴う合金コストの上昇及び／又はＯ、Ｎ及びＳに関する精錬コストの上昇）を招くことになり必ずしも好ましくない。したがって、Ｚ元素の有効量は好ましくは２．００００％以下であり、例えば１．８０００％以下、１．５０００％以下、１．２０００％以下、１．００００％以下又は０．８０００％以下であってもよい。 In the embodiment of the present invention, in order to reduce the amount of solid solution P, it is necessary that the effective amount of the Z element determined by the above formula B is 0.0003% or more, that is, at least satisfy the following formula 1.
0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1.74 [S] ≧ 0.0003 ・ ・ ・ Equation 1
The effective amount of the Z element may be, for example, 0.0005% or more or 0.0007% or more, preferably 0.0010% or more, more preferably 0.0015% or more, still more preferably 0.0030%. The above is most preferably 0.0050% or more or 0.0100% or more. Further, as is clear from the above formula 1, in order to stably secure the effective amount, it is preferable to reduce the contents of O, N and S in the steel as much as possible. Here, the upper limit of the effective amount of the Z element is not particularly limited, but even if the effective amount of the Z element is excessively increased, the effect is saturated and the manufacturing cost increases (alloy cost due to the increase in the content of the Z element). And / or an increase in refining cost for O, N and S), which is not always preferable. Therefore, the effective amount of the Z element is preferably 2.000% or less, for example, 1.8000% or less, 1.5000% or less, 1.2000% or less, 1.000% or less, or 0.8000% or less. You may.
［Ｚ元素の有効量と鋼中のＰ含有量との関係］
　本発明の実施形態によれば、上記のＺ元素の有効量と鋼中のＰ含有量は、下記式２を満たす。
　１．８０×［Ｐ］－（０．６１［Ｚｒ］＋０．３１［Ｈｆ］－１．７５［Ｏ］－３．９９［Ｎ］－１．７４［Ｓ］）　＜　０．０１０　　　・・・式２
　ここで、［Ｚｒ］、［Ｈｆ］、［Ｏ］、［Ｎ］、［Ｓ］、及び［Ｐ］は、各元素の含有量［質量％］であり、元素を含有しない場合は０である。 [Relationship between effective amount of Z element and P content in steel]
According to the embodiment of the present invention, the effective amount of the Z element and the P content in the steel satisfy the following formula 2.
1.80 x [P]-(0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1.74 [S]) <0.010 ... Equation 2
Here, [Zr], [Hf], [O], [N], [S], and [P] are the content [mass%] of each element, and are 0 when the element is not contained. ..
　Ｚ元素とＰは１：１の割合で結合してリン化物（ＺＰ）を形成することから、鋼中のＰ含有量（原子％）からＺ元素の有効量（原子％）を差し引くことで、鋼材の化学組成から求められる理論上の固溶Ｐ量を算出することができる。ここで、原子％によるＰ含有量の値は、Ｚ元素の有効量に関連して上で説明したのと同様の理由から近似的には鋼中のＦｅ及びＰの原子量並びに質量％によるＰ含有量を用いて（Ｍ[Fe]／Ｍ[P]）×［Ｐ］として算出することが可能である（ここで、Ｍ[Fe]はＦｅの原子量、Ｍ[P]はＰの原子量を表し、［Ｐ］はＰ含有量［質量％］であり、Ｐを含有しない場合は０である）。したがって、理論上の固溶Ｐ量は近似的には下記式Ｃによって表すことが可能となる。
　理論上の固溶Ｐ量［原子％］
　　　　　　　＝（Ｍ[Fe]／Ｍ[P]）×［Ｐ］－Ｚの有効量［原子％］　　　・・・式Ｃ Since the Z element and P are combined at a ratio of 1: 1 to form a phosphite (ZP), the effective amount of the Z element (atomic%) is subtracted from the P content (atomic%) in the steel. The theoretical amount of solid solution P obtained from the chemical composition of the steel material can be calculated. Here, the value of the P content by atomic% is approximately the atomic weight of Fe and P in the steel and the P content by mass% for the same reason as described above in relation to the effective amount of the Z element. It can be calculated as (M [Fe] / M [P] ) × [P] using the amount (where M [Fe] represents the atomic weight of Fe and M [P] represents the atomic weight of P. , [P] is the P content [mass%], and is 0 when P is not contained). Therefore, the theoretical amount of solid solution P can be approximately expressed by the following formula C.
Theoretical solid solution P amount [atomic%]
= (M [Fe] / M [P] ) × [P] -Z effective amount [atomic%] ... Equation C
　ここで、Ｆｅ及びＰの原子量は、それぞれＦｅ：５５．８４５及びＰ：３０．９７３８である。したがって、上記式ＣにＦｅ及びＰの原子量並びに式Ｂを代入して整理すると、原子％による理論上の固溶Ｐ量は近似的には下記式Ｄによって表すことが可能となる。
　理論上の固溶Ｐ量［原子％］＝１．８０×［Ｐ］－（０．６１［Ｚｒ］＋０．３１［Ｈｆ］－１．７５［Ｏ］－３．９９［Ｎ］－１．７４［Ｓ］）　　　・・・式Ｄ
　ここで、［Ｚｒ］、［Ｈｆ］、［Ｏ］、［Ｎ］、［Ｓ］、及び［Ｐ］は、各元素の含有量［質量％］であり、元素を含有しない場合は０である。 Here, the atomic weights of Fe and P are Fe: 55.845 and P: 30.738, respectively. Therefore, by substituting the atomic weights of Fe and P and the formula B into the above formula C, the theoretical solid solution P amount in terms of atomic% can be approximately expressed by the following formula D.
Theoretical solid solution P amount [atomic%] = 1.80 × [P]-(0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1. 74 [S]) ・ ・ ・ Expression D
Here, [Zr], [Hf], [O], [N], [S], and [P] are the content [mass%] of each element, and are 0 when the element is not contained. ..
　本発明の実施形態においては、実際に測定される固溶Ｐ量を低減し、それによって当該固溶Ｐに関連する鋼材の特性、例えば、靭性、延性、耐食性、溶接性などの特性を改善するためには、上記式１を満たすことに加えて、上記式Ｄによって求められる理論上の固溶Ｐ量が０．０１０％未満であること、すなわち下記式２を満たすことが必要である。
　１．８０×［Ｐ］－（０．６１［Ｚｒ］＋０．３１［Ｈｆ］－１．７５［Ｏ］－３．９９［Ｎ］－１．７４［Ｓ）　＜　０．０１０　　　・・・式２
　理論上の固溶Ｐ量（すなわち式２の左辺）は、好ましくは０．００８％以下、より好ましくは０．００５％以下、さらにより好ましくは０．００３％以下、最も好ましくは０％以下である。また、理論上の固溶Ｐ量を低減して上記式２を確実に満足させるためには、当然ながら鋼中のＰ含有量を極力低減することが好ましい。ここで、理論上の固溶Ｐ量の下限は特に限定されないが、理論上の固溶Ｐ量を過度に低減しても効果が飽和するとともに、製造コストの上昇（Ｐに関する精錬コストの上昇及び／又はＺ元素の含有量増加に伴う合金コストの上昇）を招くことになり必ずしも好ましくない。したがって、理論上の固溶Ｐ量は好ましくは－２．０００％以上であり、例えば－１．８００％以上、－１．５００％以上、－１．３００％以上、－１．０００％以上又は－０．８００％以上であってもよい。 In the embodiment of the present invention, the amount of solid solution P actually measured is reduced, thereby improving the characteristics of the steel material related to the solid solution P, such as toughness, ductility, corrosion resistance, and weldability. For this purpose, in addition to satisfying the above formula 1, it is necessary that the theoretical solid solution P amount obtained by the above formula D is less than 0.010%, that is, the following formula 2 is satisfied.
1.80 × [P]-(0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1.74 [S) <0.010 ... 2
The theoretical solid solution P amount (that is, the left side of the formula 2) is preferably 0.008% or less, more preferably 0.005% or less, still more preferably 0.003% or less, and most preferably 0% or less. be. Further, in order to reduce the theoretical solid solution P content and surely satisfy the above formula 2, it is naturally preferable to reduce the P content in the steel as much as possible. Here, the lower limit of the theoretical solid solution P amount is not particularly limited, but even if the theoretical solid solution P amount is excessively reduced, the effect is saturated and the manufacturing cost increases (the increase in the refining cost related to P and the increase in the refining cost related to P). / Or an increase in alloy cost due to an increase in the content of Z element), which is not always preferable. Therefore, the theoretical solid solution P amount is preferably -2.90% or more, for example, -1.80% or more, -1.50% or more, -1.30% or more, -1,000% or more or. It may be −0.800% or more.
　本発明の実施形態に係る鋼材は、任意の鋼材であってよく、特に限定されない。本発明の実施形態に係る鋼材は、例えば、熱間圧延前の鋼材であるスラブ、ビレット、ブルームや熱間圧延後の鋼材を包含するものである。熱間圧延後の鋼材としては、特に限定されないが、例えば、厚鋼板、薄鋼板、さらには棒鋼、線材、形鋼、及び鋼管等をも包含するものである。 The steel material according to the embodiment of the present invention may be any steel material and is not particularly limited. The steel material according to the embodiment of the present invention includes, for example, slabs, billets, blooms, and steel materials after hot rolling, which are steel materials before hot rolling. The steel material after hot rolling is not particularly limited, but includes, for example, thick steel plates, thin steel plates, steel bars, wire rods, shaped steels, steel pipes, and the like.
　本発明の実施形態に係る鋼材は、最終的な製品の形態等に応じて、当業者に公知の任意の適切な方法によって製造することが可能である。例えば、鋼材が厚鋼板の場合には、その製造方法は、一般に厚鋼板を製造する際に適用される工程を含み、例えば、上で説明した化学組成を有するスラブを鋳造する工程、鋳造されたスラブを熱間圧延する工程、及び得られた圧延材を冷却する工程を含み、必要に応じて焼入れ工程及び焼戻し工程等の熱処理をさらに含んでいてもよい。本発明の実施形態に係る鋼材の製造工程は、制御圧延と加速冷却を組み合わせた熱加工制御プロセス（ＴＭＣＰ）であってもよい。 The steel material according to the embodiment of the present invention can be manufactured by any suitable method known to those skilled in the art, depending on the form of the final product and the like. For example, when the steel material is a thick steel plate, the manufacturing method includes a step generally applied when manufacturing the thick steel plate, for example, a step of casting a slab having the chemical composition described above, and casting. It includes a step of hot rolling the slab and a step of cooling the obtained rolled material, and may further include heat treatment such as a quenching step and a tempering step, if necessary. The steel material manufacturing process according to the embodiment of the present invention may be a thermal processing control process (TMCP) that combines controlled rolling and accelerated cooling.
　また、鋼材が薄鋼板の場合には、その製造方法は、一般に薄鋼板を製造する際に適用される工程を含み、例えば、上で説明した化学組成を有するスラブを鋳造する工程、鋳造されたスラブを熱間圧延する工程、及び得られた圧延材を冷却して巻き取る工程、必要に応じて冷間圧延工程、焼鈍工程等をさらに含んでいてもよい。棒鋼や他の鋼材の製造方法においても同様に、一般に棒鋼や他の鋼材を製造する際に適用される工程を含み、例えば、上で説明した化学組成を有する溶鋼を形成する製鋼工程、形成された溶鋼からスラブ、ビレット、ブルーム等を鋳造する工程、鋳造されたスラブ、ビレット、ブルーム等を熱間圧延する工程、及び得られた圧延材を冷却する工程を含み、他の工程は、それらの鋼材を製造するのに当業者に公知の適切な工程を適宜選択し、実施することができる。 Further, when the steel material is a thin steel plate, the manufacturing method includes a step generally applied when manufacturing the thin steel plate, for example, a step of casting a slab having the chemical composition described above, and casting. It may further include a step of hot rolling the slab, a step of cooling and winding the obtained rolled material, a cold rolling step, a baking step and the like, if necessary. Similarly, in the method for producing steel bars and other steel materials, a step generally applied when manufacturing steel bars and other steel materials is included, and for example, a steelmaking process for forming molten steel having the chemical composition described above is formed. It includes a step of casting slabs, billets, blooms, etc. from molten steel, a step of hot rolling the cast slabs, billets, blooms, etc., and a step of cooling the obtained rolled material, and other steps include those steps. Appropriate steps known to those skilled in the art for producing steel materials can be appropriately selected and carried out.
　鋼中の固溶Ｐ量は、９００～１１００℃、好ましくは９５０～１１００℃の範囲内の所定の温度で６０００秒以上保持することによりリン化物を形成し（Ｐ固定処理）、低減することができる。Ｐ固定処理は、熱間圧延工程での熱履歴であってもよく、熱間圧延工程後の熱処理であってもよい。Ｐ固定処理の保持温度は、９００～１１００℃の範囲内の一定の温度であってもよく、当該範囲内で変動してもよい。Ｐ固定処理が熱間圧延工程での熱履歴である場合は、スラブ、ビレット、ブルームなどの鋼素材の加熱から熱間圧延の完了までの間に、９００～１１００℃の範囲内での保持時間が６０００秒以上であればよい。「保持」とは、上記の温度範囲内で放冷又は空冷等により徐々に温度が低下する場合を包含するものである。保持時間の上限は、特に限定されないが、例えば１５０００秒以下又は１２０００秒以下であってよい。熱間圧延工程の熱履歴又は熱間圧延工程後の熱処理にＰ固定処理を含めることで、鋼中の固溶Ｐをリン化物として十分に固定することができるため、その後の焼き戻し処理によってもＰが粒界等へ偏析することを抑制することができる。その結果として、焼き戻し脆化等の発生を抑制することができ、それゆえ鋼材の靭性等の特性を顕著に向上させることが可能となる。また、本発明の実施形態に係る鋼材の製造では、固溶Ｐを固定するためのＺ元素の有効量を確保することが重要であり、そのためにはＺ元素と鋼中で介在物を形成し得るＯ、Ｎ及びＳの含有量を精錬工程において十分に低減しておくことが極めて重要である。 The amount of solid melt P in steel can be reduced by forming a phosphide (P fixing treatment) by holding it at a predetermined temperature in the range of 900 to 1100 ° C., preferably 950 to 1100 ° C. for 6000 seconds or longer. can. The P fixing process may be a heat history in the hot rolling process or a heat treatment after the hot rolling process. The holding temperature of the P fixing process may be a constant temperature within the range of 900 to 1100 ° C., or may vary within the range. When the P fixing process is the heat history in the hot rolling process, the holding time in the range of 900 to 1100 ° C. from the heating of steel materials such as slabs, billets and blooms to the completion of hot rolling. May be 6000 seconds or more. The term "retention" includes a case where the temperature gradually decreases due to cooling, air cooling, or the like within the above temperature range. The upper limit of the holding time is not particularly limited, but may be, for example, 15,000 seconds or less or 12,000 seconds or less. By including the P fixing process in the heat history of the hot rolling process or the heat treatment after the hot rolling process, the solid-melt P in the steel can be sufficiently fixed as a phosphite, so that it can be sufficiently fixed by the subsequent tempering process. It is possible to suppress the segregation of P into the grain boundaries and the like. As a result, it is possible to suppress the occurrence of tempering embrittlement and the like, and therefore it is possible to significantly improve the toughness and other properties of the steel material. Further, in the production of the steel material according to the embodiment of the present invention, it is important to secure an effective amount of the Z element for fixing the solid solution P, and for that purpose, inclusions are formed in the Z element and the steel. It is extremely important that the contents of O, N and S obtained are sufficiently reduced in the refining step.
　以下、実施例によって本発明をより詳細に説明するが、本発明はこれらの実施例に何ら限定されるものではない。 Hereinafter, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.
［例Ａ］
　本例では、まず、種々の化学組成を有するスラブを鋳造し、次いで熱間圧延を圧下率５０％以上で実施し、冷却した。次に、得られた圧延材を９５０～１１００℃の範囲内の所定の温度に加熱し、６０００～１２０００秒保持することによりリン化物を形成し（Ｐ固定処理）、すなわち鋼中のＰの少なくとも一部がリン化物として固定された鋼材を得た。得られた各鋼材から採取した試料を分析した化学組成は、下表１に示すとおりである。また、得られた各鋼材中の固溶Ｐ量は以下の方法によって測定した。 [Example A]
In this example, first, slabs having various chemical compositions were cast, and then hot rolling was carried out at a rolling reduction of 50% or more and cooled. Next, the obtained rolled material is heated to a predetermined temperature in the range of 950 to 1100 ° C. and held for 6000 to 12000 seconds to form a phosphide (P fixing treatment), that is, at least P in steel. A steel material partially fixed as a phosphide was obtained. The chemical composition obtained by analyzing the samples collected from each of the obtained steel materials is as shown in Table 1 below. The amount of solid solution P in each of the obtained steel materials was measured by the following method.
［鋼材中の固溶Ｐ量の測定］
　鋼材中の固溶Ｐ量は抽出残渣法によって測定した。より具体的には、まず、鋼材から採取した鋼材表面から０．５ｍｍ深さ位置を含む試料を１０％アセチルアセトン－１％テトラメチルアンモニウムクロライド－メタノール溶液中５００ｍｍＡ及び２時間の条件下での定電流電解によって鋼材１ｇ以上を電解し、次いで孔径０．２μｍのメンブレンフィルタを用いて濾過し、析出物（リン化物）を分離した。次に、分離した析出物を硝酸（ＨＮＯ3）と過塩素酸（ＨＣｌＯ4）を２：１で混合した溶液にて分解し、次いで得られた残渣をＩＣＰ－ＭＳ（誘導結合プラズマ質量分析計）で測定することにより鋼材中でリン化物として析出したＰ量（質量％）を決定した。この析出Ｐ量（質量％）を、表１に示される各鋼材中のＰ含有量（質量％）から差し引くことにより各鋼材中の固溶Ｐ量（質量％）を決定した。その結果を表１に示す。 [Measurement of solid solution P amount in steel material]
The amount of solid solution P in the steel material was measured by the extraction residue method. More specifically, first, a sample containing a depth position of 0.5 mm from the surface of the steel material taken from the steel material is subjected to a constant current of 500 mmA in a 10% acetylacetone-1% tetramethylammonium chloride-methanol solution under the condition of 2 hours. 1 g or more of the steel material was electrolyzed by electrolysis, and then filtered using a membrane filter having a pore size of 0.2 μm to separate precipitates (phosphorus products). Next, the separated precipitate was decomposed with a solution in which nitric acid (HNO 3 ) and perchloric acid (HClO 4 ) were mixed at a ratio of 2: 1 and the obtained residue was then subjected to ICP-MS (inductively coupled plasma mass spectrometer). ) Was used to determine the amount of P (% by mass) precipitated as a phosphate in the steel material. The solid solution P amount (mass%) in each steel material was determined by subtracting this precipitated P amount (mass%) from the P content (mass%) in each steel material shown in Table 1. The results are shown in Table 1.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000004
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000005
Figure JPOXMLDOC01-appb-T000006
Figure JPOXMLDOC01-appb-T000006
　本例では、リン化物が析出しかつ固溶Ｐ量が０．０１０原子％に相当する０．００６質量％よりも低減されている場合を固溶Ｐ量が低減された鋼材として評価した。表１を参照すると、比較例８５～９２では、Ｚｒ及びＨｆからなるＺ元素の有効量が低かったために、鋼材中の固溶Ｐをリン化物として析出させることができないか又は十分に析出させることができず、結果として鋼材中の固溶Ｐ量を低減することができなかった。一方、比較例９３では、Ｚ元素の有効量は０．０００３％よりも高く、それゆえ式１を満足するものであったが、鋼材中のＰ含有量が比較的高かったために式２を満足せず、結果として固溶Ｐ量を十分に低減することができなかった。これとは対照的に、本発明に係る全ての実施例において、Ｚ元素の有効量を０．０００３％以上とし、さらには式２を満足する（すなわち式２の左辺を０．０１０％未満にする）ことで、実際に測定される鋼材中の固溶Ｐ量を十分に低減することができた。例えば、実施例９、２５、４９及び６２では、鋼材中のＰ含有量が比較的低いにもかかわらず、本発明の構成を満足することで、その一部をリン化物として析出させて鋼材中の固溶Ｐ量を極めて低い値まで低減できていることがわかる。 In this example, the case where the phosphide was precipitated and the amount of solid-dissolved P was reduced from 0.006% by mass, which corresponds to 0.010 atomic%, was evaluated as a steel material having a reduced amount of solid-dissolved P. Referring to Table 1, in Comparative Examples 85 to 92, since the effective amount of the Z element composed of Zr and Hf was low, the solid-dissolved P in the steel material could not be precipitated as a phosphor or sufficiently precipitated. As a result, the amount of solid-dissolved P in the steel material could not be reduced. On the other hand, in Comparative Example 93, the effective amount of the Z element was higher than 0.0003%, and therefore satisfied the formula 1, but the P content in the steel material was relatively high, so that the formula 2 was satisfied. As a result, the amount of solid solution P could not be sufficiently reduced. In contrast, in all the embodiments according to the present invention, the effective amount of the Z element is 0.0003% or more, and further satisfies the formula 2 (that is, the left side of the formula 2 is less than 0.010%). By doing so, the amount of solid solution P in the steel material actually measured could be sufficiently reduced. For example, in Examples 9, 25, 49 and 62, although the P content in the steel material is relatively low, by satisfying the configuration of the present invention, a part thereof is precipitated as a phosphide in the steel material. It can be seen that the amount of solid solution P in the above can be reduced to an extremely low value.
［例Ｂ］
　低温靭性を確保するため、焼入れ後に所定の温度で焼き戻し処理が行われることがある。鋼中の固溶Ｐが比較的多いと、このような焼き戻し処理の際に当該固溶Ｐが旧オーステナイト粒界等に偏析して、いわゆる焼き戻し脆化を引き起こす場合がある。このような場合には、粒界破壊が起こりやすくなるため、鋼材の靭性が低下する。そこで、本例では、例Ａの幾つかの鋼材について、固溶Ｐの低減に起因する効果を検証した。具体的には、まず、例ＡのＰ固定処理（詳細は下表２に示す）後の実施例４９、６３、７５及び８４並びに比較例９０及び９３の鋼材を焼入れし、次いで５５０℃及び１２００秒の条件下で焼き戻し処理を実施し、得られた鋼材の板厚１／４ｔ部分からＪＩＳ４号試験片（Ｖノッチ試験片：１０ｍｍ×１０ｍｍ×５５ｍｍ）を採取した。試験片の長手方向は板幅方向であり、ノッチは圧延方向に破壊が伝播するように設けられた。このＪＩＳ４号試験片に基づいてＪＩＳ　Ｚ２２４２：２００５の規定に準拠して－１００℃でシャルピー衝撃試験を行った。次いで、シャルピー衝撃試験後の試験片の破面をＳＥＭ（走査型電子顕微鏡）で観察した。より具体的にはＳＥＭにより、破面のノッチ底の中央部付近の３００μｍ×３００μｍの範囲を試験片の長軸方向（圧延材の板幅方向）から撮影し、得られた画像から全破面の面積に対する粒界破面の面積の割合（粒界破面率）を算出した。その結果を表２に示す。 [Example B]
In order to ensure low temperature toughness, tempering may be performed at a predetermined temperature after quenching. If the solid solution P in the steel is relatively large, the solid solution P may segregate at the old austenite grain boundaries or the like during such tempering treatment, causing so-called tempering embrittlement. In such a case, the grain boundary fracture is likely to occur, and the toughness of the steel material is lowered. Therefore, in this example, the effect caused by the reduction of the solid solution P was verified for some of the steel materials of Example A. Specifically, first, the steel materials of Examples 49, 63, 75 and 84 and Comparative Examples 90 and 93 after the P fixing treatment of Example A (details are shown in Table 2 below) are quenched, and then at 550 ° C. and 1200 ° C. A quenching treatment was carried out under the condition of seconds, and a JIS No. 4 test piece (V notch test piece: 10 mm × 10 mm × 55 mm) was collected from a 1 / 4t portion of the obtained steel material. The longitudinal direction of the test piece was the plate width direction, and the notch was provided so that the fracture propagated in the rolling direction. Based on this JIS No. 4 test piece, a Charpy impact test was performed at −100 ° C. in accordance with the regulations of JIS Z2242: 2005. Next, the fracture surface of the test piece after the Charpy impact test was observed with an SEM (scanning electron microscope). More specifically, the area of 300 μm × 300 μm near the center of the notch bottom of the fracture surface was photographed by SEM from the long axis direction of the test piece (plate width direction of the rolled material), and the total fracture surface was taken from the obtained image. The ratio of the area of the grain boundary fracture surface to the area of the grain boundary fracture surface (grain boundary fracture surface ratio) was calculated. The results are shown in Table 2.
Figure JPOXMLDOC01-appb-T000007
Figure JPOXMLDOC01-appb-T000007
　固溶Ｐ量が小さいほど、当該固溶Ｐの粒界への偏析が抑制されるため、焼き戻し脆化による粒界破壊が起こりにくくなり、結果として粒界破面率が小さくなる。表２を参照すると、固溶Ｐ量が比較的高い比較例９０及び９３では、粒界破面率が１００％であり、固溶Ｐに起因する焼き戻し脆化が認められた。これとは対照的に、実施例４９、６３、７５及び８４では、Ｚ元素の有効量が高く、それゆえ固溶Ｐ量が十分に低減されているために、粒界破面率が１０％以下であり、鋼材の靭性、特に低温靭性が顕著に向上していることを確認した。 The smaller the amount of solid solution P, the more the segregation of the solid solution P into the grain boundaries is suppressed, so that the grain boundary fracture due to temper embrittlement is less likely to occur, and as a result, the grain boundary fracture surface ratio becomes smaller. Referring to Table 2, in Comparative Examples 90 and 93 in which the amount of solid solution P was relatively high, the grain boundary fracture surface ratio was 100%, and temper embrittlement due to solid solution P was observed. In contrast, in Examples 49, 63, 75 and 84, the effective amount of element Z is high and therefore the amount of solid solution P is sufficiently reduced, so that the grain boundary fracture surface ratio is 10%. It was confirmed that the toughness of the steel material, especially the low temperature toughness, was remarkably improved.
　本発明の実施形態に係る鋼材は、例えば、熱間圧延前の鋼材であるスラブ、ビレット、ブルームや熱間圧延後の鋼材である。熱間圧延後の鋼材としては、例えば、橋梁、建築、造船及び圧力容器等の用途に使用される厚鋼板、自動車及び家電等の用途に使用される薄鋼板、さらには棒鋼、線材、形鋼、及び鋼管等をも包含するものである。これらの材料において本発明の実施形態に係る鋼材を適用した場合には、鋼中の固溶Ｐ量が十分に低減されているため、当該固溶Ｐに関連する鋼材の特性、例えば、靭性、延性、耐食性、溶接性などの特性を顕著に改善することが可能である。 The steel material according to the embodiment of the present invention is, for example, a steel material before hot rolling, such as slab, billet, bloom, or a steel material after hot rolling. Steel materials after hot rolling include, for example, thick steel plates used for bridges, construction, shipbuilding, pressure vessels, etc., thin steel plates used for automobiles, home appliances, etc., as well as steel bars, wire rods, and shaped steel. , And steel pipes and the like. When the steel material according to the embodiment of the present invention is applied to these materials, the amount of solid solution P in the steel is sufficiently reduced, so that the characteristics of the steel material related to the solid solution P, for example, toughness. It is possible to significantly improve properties such as ductility, corrosion resistance, and weldability.

Claims (5)

  1. 　質量％で、
    　Ｃ：０．００１～１．０００％、
    　Ｓｉ：０．０１～３．００％、
    　Ｍｎ：０．１０～４．５０％、
    　Ｐ：０．３００％以下、
    　Ｓ：０．０３００％以下、
    　Ａｌ：０．００１～５．０００％、
    　Ｎ：０．２０００％以下、
    　Ｏ：０．０１００％以下、
    　Ｚｒ：０～０．８０００％、及びＨｆ：０～０．８０００％からなる群より選択される少なくとも１種のＺ元素、
    　Ｎｂ：０～３．０００％、
    　Ｔｉ：０～０．５００％、
    　Ｔａ：０～０．５００％、
    　Ｖ：０～１．００％、
    　Ｃｕ：０～３．００％、
    　Ｎｉ：０～６０．００％、
    　Ｃｒ：０～３０．００％、
    　Ｍｏ：０～５．００％、
    　Ｗ：０～２．００％、
    　Ｂ：０～０．０２００％、
    　Ｃｏ：０～３．００％、
    　Ｂｅ：０～０．０５０％、
    　Ａｇ：０～０．５００％、
    　Ｃａ：０～０．０５００％、
    　Ｍｇ：０～０．０５００％、
    　Ｌａ、Ｃｅ、Ｎｄ、Ｙ、Ｐｍ、Ｐｒ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、及びＳｃの少なくとも１種：合計で０～０．５０００％、
    　Ｓｎ：０～０．３００％、
    　Ｓｂ：０～０．３００％、
    　Ｔｅ：０～０．１００％、
    　Ｓｅ：０～０．１００％、
    　Ａｓ：０～０．０５０％、
    　Ｂｉ：０～０．５００％、
    　Ｐｂ：０～０．５００％、並びに
    　残部：Ｆｅ及び不純物からなり、
    　下記式１及び式２を満たす化学組成を有する、鋼材。
    　０．６１［Ｚｒ］＋０．３１［Ｈｆ］－１．７５［Ｏ］－３．９９［Ｎ］－１．７４［Ｓ］　≧　０．０００３　　　・・・式１
    　１．８０×［Ｐ］－（０．６１［Ｚｒ］＋０．３１［Ｈｆ］－１．７５［Ｏ］－３．９９［Ｎ］－１．７４［Ｓ］）　＜　０．０１０　　　・・・式２
    　ここで、［Ｚｒ］、［Ｈｆ］、［Ｏ］、［Ｎ］、［Ｓ］、及び［Ｐ］は、各元素の含有量［質量％］であり、元素を含有しない場合は０である。     By mass%,
    C: 0.001 to 1.000%,
    Si: 0.01-3.00%,
    Mn: 0.10 to 4.50%,
    P: 0.300% or less,
    S: 0.0300% or less,
    Al: 0.001-5.000%,
    N: 0.2000% or less,
    O: 0.0100% or less,
    At least one Z element selected from the group consisting of Zr: 0 to 0.8000% and Hf: 0 to 0.8000%.
    Nb: 0-3.000%,
    Ti: 0 to 0.500%,
    Ta: 0 to 0.500%,
    V: 0 to 1.00%,
    Cu: 0 to 3.00%,
    Ni: 0-60.00%,
    Cr: 0 to 30.00%,
    Mo: 0 to 5.00%,
    W: 0 to 2.00%,
    B: 0-0.0200%,
    Co: 0 to 3.00%,
    Be: 0 to 0.050%,
    Ag: 0 to 0.500%,
    Ca: 0-0.0500%,
    Mg: 0-0.0500%,
    At least one of La, Ce, Nd, Y, Pm, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc: 0 to 0.5000% in total.
    Sn: 0 to 0.300%,
    Sb: 0 to 0.300%,
    Te: 0 to 0.100%,
    Se: 0 to 0.100%,
    As: 0 to 0.050%,
    Bi: 0 to 0.500%,
    Pb: 0 to 0.500%, and the balance: Fe and impurities.
    A steel material having a chemical composition satisfying the following formulas 1 and 2.
    0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1.74 [S] ≧ 0.0003 ・ ・ ・ Equation 1
    1.80 x [P]-(0.61 [Zr] +0.31 [Hf] -1.75 [O] -3.99 [N] -1.74 [S]) <0.010 ... Equation 2
    Here, [Zr], [Hf], [O], [N], [S], and [P] are the content [mass%] of each element, and are 0 when the element is not contained. ..
  2. 　前記化学組成が、質量％で、
    　Ｎｂ：０．００３～３．０００％、
    　Ｔｉ：０．００５～０．５００％、
    　Ｔａ：０．００１～０．５００％、
    　Ｖ：０．００１～１．００％、
    　Ｃｕ：０．００１～３．００％、
    　Ｎｉ：０．００１～６０．００％、
    　Ｃｒ：０．００１～３０．００％、
    　Ｍｏ：０．００１～５．００％、
    　Ｗ：０．００１～２．００％、
    　Ｂ：０．０００１～０．０２００％、
    　Ｃｏ：０．００１～３．００％、
    　Ｂｅ：０．０００３～０．０５０％、及び
    　Ａｇ：０．００１～０．５００％
    のうち１種又は２種以上を含む、請求項１に記載の鋼材。     The chemical composition is by mass%.
    Nb: 0.003 to 3.000%,
    Ti: 0.005 to 0.500%,
    Ta: 0.001 to 0.500%,
    V: 0.001 to 1.00%,
    Cu: 0.001 to 3.00%,
    Ni: 0.001 to 60.00%,
    Cr: 0.001 to 30.00%,
    Mo: 0.001 to 5.00%,
    W: 0.001 to 2.00%,
    B: 0.0001-0.0200%,
    Co: 0.001 to 3.00%,
    Be: 0.0003 to 0.050%, and Ag: 0.001 to 0.500%
    The steel material according to claim 1, which comprises one or more of the above.
  3. 　前記化学組成が、質量％で、
    　Ｃａ：０．０００１～０．０５００％、
    　Ｍｇ：０．０００１～０．０５００％、並びに
    　Ｌａ、Ｃｅ、Ｎｄ、Ｙ、Ｐｍ、Ｐｒ、Ｓｍ、Ｅｕ、Ｇｄ、Ｔｂ、Ｄｙ、Ｈｏ、Ｅｒ、Ｔｍ、Ｙｂ、Ｌｕ、及びＳｃの少なくとも１種：合計で０．０００１～０．５０００％
    のうち１種又は２種以上を含む、請求項１又は２に記載の鋼材。     The chemical composition is by mass%.
    Ca: 0.0001-0.0500%,
    Mg: 0.0001 to 0.0500%, and at least one of La, Ce, Nd, Y, Pm, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and Sc. : 0.0001 to 0.5000% in total
    The steel material according to claim 1 or 2, which comprises one or more of the above.
  4. 　前記化学組成が、質量％で、
    　Ｓｎ：０．００１～０．３００％、及び
    　Ｓｂ：０．００１～０．３００％
    のうち１種又は２種を含む、請求項１～３のいずれか１項に記載の鋼材。     The chemical composition is by mass%.
    Sn: 0.001 to 0.300%, and Sb: 0.001 to 0.300%
    The steel material according to any one of claims 1 to 3, which comprises one or two of the above.
  5. 　前記化学組成が、質量％で、
    　Ｔｅ：０．００１～０．１００％、
    　Ｓｅ：０．００１～０．１００％、
    　Ａｓ：０．００１～０．０５０％、
    　Ｂｉ：０．００１～０．５００％、及び
    　Ｐｂ：０．００１～０．５００％
    のうち１種又は２種以上を含む、請求項１～４のいずれか１項に記載の鋼材。     The chemical composition is by mass%.
    Te: 0.001 to 0.100%,
    Se: 0.001 to 0.100%,
    As: 0.001 to 0.050%,
    Bi: 0.001 to 0.500%, and Pb: 0.001 to 0.500%
    The steel material according to any one of claims 1 to 4, which comprises one or more of the two or more.
PCT/JP2021/014772 2020-12-28 2021-04-07 Steel material WO2022145066A1 (en)

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JPS61136662A (en) * 1984-12-06 1986-06-24 Kawasaki Steel Corp Austenitic stainless steel having superior resistance to stress corrosion cracking
JPH01149917A (en) * 1987-12-04 1989-06-13 Kawasaki Steel Corp Manufacture of steel ingot with very slight segregation of phosphorus
JP2007327122A (en) * 2006-06-09 2007-12-20 Sumitomo Metal Ind Ltd TREATMENT METHOD FOR MOLTEN IRON BY Nd AND Ca ADDITION
JP2010100923A (en) * 2008-10-27 2010-05-06 Sumitomo Metal Ind Ltd Steel sheet in which microsegregation of phosphorous is dispersed and continuously cast slab
JP2015190058A (en) * 2014-03-31 2015-11-02 新日鐵住金株式会社 Carbon steel casting piece and production method thereof
WO2019188094A1 (en) * 2018-03-30 2019-10-03 日鉄ステンレス株式会社 Ferritic stainless steel sheet and method for producing same
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JPS61136662A (en) * 1984-12-06 1986-06-24 Kawasaki Steel Corp Austenitic stainless steel having superior resistance to stress corrosion cracking
JPH01149917A (en) * 1987-12-04 1989-06-13 Kawasaki Steel Corp Manufacture of steel ingot with very slight segregation of phosphorus
JP2007327122A (en) * 2006-06-09 2007-12-20 Sumitomo Metal Ind Ltd TREATMENT METHOD FOR MOLTEN IRON BY Nd AND Ca ADDITION
JP2010100923A (en) * 2008-10-27 2010-05-06 Sumitomo Metal Ind Ltd Steel sheet in which microsegregation of phosphorous is dispersed and continuously cast slab
JP2015190058A (en) * 2014-03-31 2015-11-02 新日鐵住金株式会社 Carbon steel casting piece and production method thereof
WO2019188094A1 (en) * 2018-03-30 2019-10-03 日鉄ステンレス株式会社 Ferritic stainless steel sheet and method for producing same
JP2019183208A (en) * 2018-04-05 2019-10-24 日鉄ステンレス株式会社 Complete austenitic stainless steel

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2023053829A1 (en) * 2021-09-28 2023-04-06 日本製鉄株式会社 Steel plate

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