WO2012111536A1 - 二相ステンレス鋼およびその製造方法 - Google Patents
二相ステンレス鋼およびその製造方法 Download PDFInfo
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- WO2012111536A1 WO2012111536A1 PCT/JP2012/053036 JP2012053036W WO2012111536A1 WO 2012111536 A1 WO2012111536 A1 WO 2012111536A1 JP 2012053036 W JP2012053036 W JP 2012053036W WO 2012111536 A1 WO2012111536 A1 WO 2012111536A1
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/005—Heat treatment of ferrous alloys containing Mn
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D6/00—Heat treatment of ferrous alloys
- C21D6/008—Heat treatment of ferrous alloys containing Si
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/02—Making non-ferrous alloys by melting
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
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- 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
- C22C38/005—Ferrous alloys, e.g. steel alloys containing rare earths, i.e. Sc, Y, Lanthanides
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
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- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/005—Ferrite
Definitions
- the present invention relates to a duplex stainless steel and a manufacturing method thereof, and more particularly to a duplex stainless steel suitable as a steel material for a line pipe and a manufacturing method thereof.
- Oil and natural gas produced from oil and gas fields contain associated gas.
- the accompanying gas contains a corrosive gas such as carbon dioxide (CO 2 ) and hydrogen sulfide (H 2 S).
- a line pipe conveys the above-mentioned accompanying gas while conveying oil and natural gas. Therefore, in a line pipe, stress corrosion cracking (SCC), sulfide stress corrosion cracking (SSC), and overall corrosion cracking that causes a reduction in wall thickness are problems. Therefore, excellent corrosion resistance is required for stainless steel for line pipes.
- Duplex stainless steel has excellent corrosion resistance. Therefore, duplex stainless steel is used for line pipes.
- the duplex stainless steel for line pipes is required to have excellent yield strength and toughness.
- Techniques aimed at improving the strength and toughness of the duplex stainless steel are disclosed in JP-A-10-60598, JP-A-10-60526, JP-A-7-268552, and JP-A-6-184699. No. 6-145903, Japanese Patent No. 2726591 and Japanese Patent No. 3155431.
- the duplex stainless steel disclosed in JP-A-10-60598 and JP-A-10-60526 contains 2 to 6% Mo and 4 to 10% W, and further contains 1 to 4% Cu. Containing.
- the duplex stainless steel is described as having excellent strength by aging heat treatment at 480 ° C. for 4 hours.
- duplex stainless steel cast disclosed in Japanese Patent Laid-Open No. 7-268552 contains 0.1 to 2% C and 2% or less Cu. It is described that duplex stainless steel has high strength by performing precipitation hardening heat treatment at 600 to 700 ° C.
- the duplex stainless steel disclosed in JP-A-6-184699 is made of a cast material.
- the duplex stainless steel contains 0.5-4% Cu and 0.5-3% W.
- fine Nb carbonitride and V carbonitride are dispersed by performing precipitation hardening heat treatment at 600 to 700 ° C. This describes that high strength can be obtained.
- the duplex stainless steel disclosed in JP-A-6-145903 is made of a cast material.
- the duplex stainless steel contains 0.5-4% Cu, 0.5-3% W, and 0.1-0.5% Ta.
- Cu and W are solid-solved in ferrite and strengthen the ferrite.
- Ta forms carbides and finely disperses in ferrite, increasing the strength. Thereby, it is described that the duplex stainless steel has an excellent corrosion display strength.
- duplex stainless steel disclosed in Japanese Patent No. 2726591 contains 1 to 4% Cu and 2% or less W.
- the duplex stainless steel is precipitation strengthened by precipitating Cu by a precipitation strengthening treatment at 600 to 700 ° C. Thereby, duplex stainless steel is described as having excellent strength.
- the duplex stainless steel cast member disclosed in Japanese Patent No. 3155431 contains 2.6 to 3.5% Cu and is aged at 480 ° C. for 4 hours.
- Japanese Patent No. 3155431 describes that the strength of steel is improved by precipitation strengthening of Cu.
- the duplex stainless steel described in the above patent document may not be able to achieve both excellent strength and excellent toughness.
- excellent strength may not be obtained.
- excellent toughness may not be obtained due to excessive precipitation of carbides.
- JP-A-7-268552, JP-A-6-184699, and JP-A-2726591 excellent strength and toughness may not be obtained.
- JP-A-6-145903 coarse carbides are formed by Ta, and excellent toughness may not be obtained.
- Japanese Patent No. 3155431 an excellent strength may not be obtained.
- An object of the present invention is to provide a duplex stainless steel having high strength and high toughness.
- the stainless steel according to the present invention is, in mass%, C: 0.030% or less, Si: 0.20 to 1.00%, Mn: 8.00% or less, P: 0.040% or less, S: 0.00. 0100% or less, Cu: more than 2.00% and 4.00% or less, Ni: 4.00 to 8.00%, Cr: 20.0 to 30.0%, Mo: 0.50% to 2.00 %, N: 0.100 to 0.350% and sol. Al: 0.040% or less is contained, and the balance has a chemical composition composed of Fe and impurities, and a structure in which the ferrite ratio is 30 to 70% and the hardness of the ferrite is 300 Hv 10 gf or more.
- the duplex stainless steel according to the present invention has high strength and high toughness.
- the chemical composition of the above-mentioned duplex stainless steel contains one or more elements selected from at least one of the following first to third groups instead of a part of Fe. Also good.
- Group 1 V: 1.50% or less
- Group 2 Ca: 0.0200% or less, Mg: 0.02% or less, and B: 0.0200% or less
- Group 3 Rare earth elements (REM): 0. 2000% or less
- the duplex stainless steel according to the present invention is solution-treated at 980 to 1200 ° C. and further subjected to aging heat treatment at 460 to 630 ° C.
- the production method of the duplex stainless steel material according to the present invention is, in mass%, C: 0.030% or less, Si: 0.20 to 1.00%, Mn: 8.00% or less, P: 0.040% or less.
- Al a step of producing a duplex stainless steel material containing 0.040% or less, the balance being Fe and impurities, and a solution treatment of the produced duplex stainless steel material at 980 to 1200 ° C. And a aging heat treatment at 460 to 630 ° C. for the solution-treated duplex stainless steel material.
- FIG. 1A is a diagram showing the relationship between the aging heat treatment temperature and the yield strength of the duplex stainless steel.
- FIG. 1B is a diagram showing the relationship between the aging heat treatment temperature and the toughness of the duplex stainless steel.
- FIG. 2 is a diagram showing the relationship between the aging heat treatment temperature and the ferrite hardness and austenite hardness in the duplex stainless steel.
- % of the element content means mass%.
- the present inventors have conducted various experiments and detailed studies, and obtained the following knowledge.
- FIG. 1A is a diagram showing the relationship between the aging heat treatment temperature (° C.) and the yield strength (MPa) of the duplex stainless steel.
- FIG. 1A was obtained by the following method.
- a duplex stainless steel having the same chemical composition as steel A in Table 1 described later was melted.
- An ingot was produced by casting the melted duplex stainless steel. Each manufactured ingot was heated to 1250 ° C. The heated ingot was hot forged to produce a plate material. The manufactured plate was again heated to 1250 ° C. The heated plate was hot rolled to produce a plurality of steel plates. The surface temperature of the steel material during rolling was 1050 ° C.
- the solution treatment was performed at 1070 ° C. on the manufactured plurality of steel plates. At this time, the soaking time was 5 minutes. After the solution treatment, aging heat treatment was performed on the plurality of steel plates at various aging heat treatment temperatures. The soaking time of the aging heat treatment was 30 minutes. The yield strength (MPa) of the heat-treated steel sheet was measured. At this time, 0.2% offset proof stress based on ASTM A370 was defined as yield strength (MPa). Based on the yield strength obtained, FIG. 1A was created.
- the yield strength graph G YS of the duplex stainless steel shows an upwardly convex shape having a peak near the aging heat treatment temperature of 550 ° C. More specifically, the yield strength increases as the aging heat treatment temperature increases until the aging heat treatment temperature reaches 550 ° C. On the other hand, when the aging heat treatment temperature exceeds 550 ° C., the yield strength decreases as the aging heat treatment temperature increases. As shown in FIG. 1A, when the aging heat treatment temperature is 460 to 630 ° C., the yield strength of the duplex stainless steel is 550 MPa or more. Further, when the aging heat treatment temperature is 480 to 600 ° C., the yield strength of the duplex stainless steel becomes 580 MPa or more.
- FIG. 1B is a diagram showing the relationship between the aging heat treatment temperature and the absorbed energy (vE0) of the duplex stainless steel obtained by the Charpy impact test at 0 ° C.
- FIG. 1B was obtained by the following method.
- a full-size V-notch specimen (width 10 mm, thickness 10 mm, length 55 mm, notch depth 2 mm) was collected from each steel plate produced when creating FIG. 1A.
- the Charpy impact test was implemented at 0 degreeC using the extract
- the absorbed energy vE0 of the duplex stainless steel gradually decreases with the aging heat treatment temperature when the aging heat treatment temperature is 630 ° C. or lower.
- the toughness of the duplex stainless steel rapidly decreases as the aging heat treatment temperature increases. That is, the absorbed energy vE0 has an inflection point when the aging heat treatment temperature is around 630 ° C.
- the absorbed energy vE0 is as high as 100 J or higher.
- the absorbed energy vE0 of the duplex stainless steel is 150 J or more.
- FIG. 2 is a diagram showing the relationship between the aging heat treatment temperature and the Vickers hardness (Hv 10 gf ) of the ferrite phase and austenite phase in the duplex stainless steel.
- FIG. 2 was obtained by the following method.
- Samples for observing the structure were collected from each steel plate produced when creating FIG. 1A. After the collected sample was mechanically polished, the polished sample was electrolytically etched in a 30% KOH solution. The etched sample surface was observed using an optical microscope, and a ferrite phase and an austenite phase were confirmed. Arbitrary 10 points were selected from the confirmed ferrite phase. Vickers hardness according to JISZ2244 was measured at 10 selected points. The test force at the time of measurement was 98.07 N (the hardness symbol is “Hv 10 gf ”). The average of 8 points obtained by removing the maximum value and the minimum value from the measured Vickers hardness was defined as the hardness of the ferrite. Similarly, arbitrary 10 points were selected from the confirmed austenite phase. Vickers hardness was measured at the 10 selected points in the same manner as the ferrite phase. The average of 8 points obtained by removing the maximum value and the minimum value from the measured Vickers hardness was defined as the hardness of austenite.
- the ferrite phase hardness graph GFH has the same shape as the yield strength of the duplex stainless steel shown in FIG. 1A. Specifically, the curve GFH shows an upwardly convex shape having a peak near the aging heat treatment temperature of 550 ° C.
- the hardness of the ferrite phase is 300 Hv 10 gf or more when the aging heat treatment temperature is 460 to 630 ° C. Furthermore, when the aging heat treatment temperature is 480 to 600 ° C., the hardness of the ferrite phase is 315 Hv 10 gf or more.
- the graph GAH indicating the hardness of the austenite phase is substantially constant at 245 to 250 MPa even when the aging heat treatment temperature is increased.
- the yield strength of the duplex stainless steel decreases (see FIG. 1A). Furthermore, if the aging heat treatment temperature is too high, ⁇ phase, Mo carbide and Cr carbide are generated in the steel, and the toughness of the duplex stainless steel is reduced (see FIG. 1B).
- the aging heat treatment temperature is 460 to 630 ° C.
- the ferrite ratio in the steel is 30 to 70%, and a sufficient amount of fine Cu is precipitated in the ferrite. Therefore, as shown in FIG. 2, the ferrite hardness is 300 Hv 10 gf or more.
- the strength of the duplex stainless steel becomes 550 MPa or more. Furthermore, if it is the above-mentioned temperature range, since the production
- the duplex stainless steel according to the present invention has the following chemical composition.
- C 0.030% or less Carbon (C) stabilizes austenite.
- C Carbon
- Mo carbides in particular reduce the toughness of the steel. Therefore, the C content is 0.030% or less.
- a preferable upper limit of the C content is further 0.020%, and a more preferable C content is less than 0.020%.
- Si 0.20 to 1.00%
- Silicon (Si) suppresses the decrease in fluidity of the molten metal during welding and suppresses the generation of weld defects.
- the Si content is 0.20 to 1.00%.
- the upper limit with preferable Si content is further 0.80%, More preferably, it is 0.65%.
- the minimum with preferable Si content is 0.30% further, More preferably, it is 0.35%.
- Mn 8.00% or less
- Manganese (Mn) desulfurizes and deoxidizes steel and improves the hot workability of steel. Mn further increases the solubility of nitrogen (N). On the other hand, if Mn is contained excessively, the corrosion resistance decreases. Therefore, the Mn content is 8.00% or less.
- the upper limit with preferable Mn content is further 7.50%, More preferably, it is 5.00%.
- the minimum with preferable Mn content is 0.03%, More preferably, it is 0.05%.
- Phosphorus (P) is an impurity. P decreases the corrosion resistance and toughness of the steel. Therefore, it is preferable that the P content is small.
- the P content is 0.040% or less.
- P content is preferably 0.030% or less, more preferably 0.020% or less.
- S 0.0100% or less Sulfur (S) is an impurity. S decreases the hot workability of steel. S further forms sulfides. Since sulfide is a starting point of pitting corrosion, it reduces the pitting corrosion resistance of steel. Therefore, it is preferable that the S content is small.
- the S content is 0.0100% or less.
- the preferable S content is 0.0050% or less, more preferably 0.0010% or less.
- Cu more than 2.00% and 4.00% or less Copper (Cu) reinforces the passive film and enhances corrosion resistance including SCC resistance. Further, Cu precipitates finely in ferrite by aging heat treatment. The deposited Cu increases the hardness of the ferrite and increases the strength of the steel. Further, Cu precipitates extremely finely in the base metal even during high heat input welding, and suppresses the precipitation of the ⁇ phase at the ferrite / austenite phase boundary. On the other hand, if Cu is contained excessively, the hot workability of the steel is lowered. Therefore, the Cu content is more than 2.00% and 4.00% or less. The minimum with preferable Cu content is further 2.20%, More preferably, it is 2.40%.
- Ni 4.00 to 8.00%
- Nickel (Ni) stabilizes austenite. Ni further increases the toughness of the steel and the corrosion resistance including the SCC resistance of the steel.
- Ni is excessively contained, an intermetallic compound represented by the ⁇ phase is likely to be generated. Therefore, the Ni content is 4.00 to 8.00%.
- the minimum with preferable Ni content is 4.20%, More preferably, it is 4.50%.
- the upper limit with preferable Ni content is 7.50%, More preferably, it is 7.00%.
- Chromium (Cr) increases the corrosion resistance of steel.
- Cr increases the SCC resistance of steel.
- an intermetallic compound represented by the ⁇ phase is generated.
- Cr carbide is generated.
- the sigma phase and Cr carbide reduce the toughness of the steel and the hot workability. Therefore, the Cr content is 20.0 to 30.0%.
- the minimum with preferable Cr content is 22.0%, More preferably, it is 24.0%.
- the upper limit with preferable Cr content is further 28.0%, More preferably, it is 27.0%.
- Mo Molybdenum
- Mo improves the SCC resistance of steel.
- Mo an intermetallic compound typified by a ⁇ phase is generated.
- the ⁇ phase reduces the toughness, weldability and hot workability of steel.
- Mo carbide is further generated.
- Mo carbide reduces the toughness of steel. Therefore, the Mo content is 0.50% or more and less than 2.00%.
- the minimum of preferable Mo content is 0.80%, More preferably, it is 1.00%.
- N 0.100 to 0.350%
- Nitrogen (N) is a strong austenite forming element and enhances the thermal stability and corrosion resistance of steel.
- the duplex stainless steel according to the present invention contains Cr and Mo which are ferrite forming elements. Considering the balance between the ferrite content and the austenite content in the duplex stainless steel, the N content is 0.100% or more.
- the N content is 0.100 to 0.350%.
- the minimum with preferable N content is 0.120%, More preferably, it is 0.150%.
- Al aluminum (Al) deoxidizes steel. On the other hand, if Al is contained excessively, aluminum nitride (AlN) is formed, and the toughness and corrosion resistance of the steel are lowered. Therefore, the Al content is 0.040% or less.
- the Al content referred to in the present specification means the content of acid-soluble Al (sol. Al). In the present invention, Al is an essential element.
- the preferable lower limit of the Al content is 0.003%, and more preferably 0.005%.
- the upper limit with preferable Al content is 0.035%, More preferably, it is 0.030%.
- the balance of the duplex stainless steel according to the present invention consists of Fe and impurities.
- the impurities here mean ores and scraps used as raw materials for steel, or elements mixed in due to various factors in the manufacturing process.
- W is an impurity.
- W promotes the formation of the ⁇ phase.
- W further forms carbides.
- the sigma phase and the W carbide reduce the toughness of the steel. Therefore, in the present invention, W is an impurity, and the W content is 0.1% or less.
- the chemical composition of the duplex stainless steel according to the present invention may contain one or more elements selected from at least one of the following first to third groups, instead of Fe: . That is, the elements of the first group to the third group are selective elements that can be contained as necessary.
- Group 1 V: 1.50% or less
- Group 2 Ca: 0.0200% or less, Mg: 0.02% or less
- B 0.0200% or less
- Group 3 Rare earth elements (REM): 0. 2000% or less
- V Vanadium
- V is a selective element.
- V enhances the corrosion resistance of the duplex stainless steel, and particularly enhances the corrosion resistance in an acidic environment. More specifically, if V is contained together with Mo and Cu, the crevice corrosion resistance of the steel is increased. On the other hand, if V is contained excessively, the amount of ferrite in the steel excessively increases and the corrosion resistance of the steel decreases. Therefore, the V content is 1.50% or less, preferably less than 1.50%. If V content is 0.05% or more, the said effect will be acquired notably. However, even if the V content is less than 0.05%, the above effect can be obtained to some extent.
- the upper limit with preferable V content is further 0.50%, More preferably, it is 0.10%.
- the S content of the duplex stainless steel according to the present invention is low. Therefore, even if Ca, Mg and B are not contained, the hot workability of steel is high. However, for example, when producing a seamless steel pipe by a tilt rolling method, higher hot workability may be required. When one or more selected from the group consisting of Ca, Mg and B are contained, higher hot workability can be obtained.
- non-metallic inclusions such as oxides and sulfides of Ca, Mg and B
- the Ca content is 0.0200% or less
- the Mg content is 0.02% or less
- the B content is 0.0200% or less.
- the content of at least one of Ca, Mg and B or the total content of two or more is S (mass%) + 1/2 ⁇ O (mass%) or more. Is preferred. However, the above effect can be obtained to some extent if at least one or more of Ca, Mg and B are contained.
- the total content of these elements is 0.04% or less.
- the total content of these elements is 0.06% or less.
- Rare earth element (REM) 0.2000% or less
- Rare earth element (REM) is a selective element. REM, like Ca, Mg, and B, fixes S and O (oxygen) in steel and improves hot workability of steel.
- the REM content is 0.2000% or less.
- the REM content is preferably S (mass%) + 1/2 ⁇ O (mass%) or more. However, if REM is contained even a little, the above effect can be obtained to some extent.
- REM is a generic name including 15 lanthanoid elements, Y and Sc. One or more of these elements are contained. The content of REM means the total content of one or more elements described above.
- the structure of the duplex stainless steel according to the present invention is composed of ferrite and austenite, and the balance is precipitates and inclusions.
- the ferrite ratio is 30 to 70%.
- the ferrite ratio is a ferrite area ratio and is measured by the following method. A sample is taken from any point of the duplex stainless steel. After the collected sample is mechanically polished, the polished sample is electrolytically etched in a 30% KOH solution. The etched sample surface is observed using an optical microscope. At this time, the ferrite rate is measured by a point count method according to ASTM E562.
- the hardness of the ferrite is 300 Hv 10 gf or more.
- the hardness of the ferrite is determined by the following method. Of the samples used for the above-described structure observation, 10 points in arbitrary ferrite are selected. At the selected 10 points, the Vickers hardness according to JISZ2244 is measured. The test force at the time of measurement is 98.07 N (the hardness symbol is “Hv 10 gf ”). The average of 8 points excluding the maximum value and the minimum value of the measured Vickers hardness is defined as the hardness of the ferrite.
- the ferrite ratio When the ferrite ratio is less than 30%, the duplex stainless steel cannot obtain a sufficient yield strength. Specifically, the yield strength of the duplex stainless steel is less than 550 MPa. On the other hand, when the ferrite ratio exceeds 70%, the toughness of the duplex stainless steel becomes too low. Therefore, the upper limit of the ferrite rate is 70%.
- the duplex stainless steel cannot obtain a sufficient yield strength unless Cu is sufficiently precipitated in the ferrite. Specifically, even if the ferrite ratio is 30 to 70%, if the ferrite hardness is less than 300 Hv 10 gf , the yield strength of the duplex stainless steel is less than 550 MPa.
- duplex stainless steel has excellent strength. Furthermore, if the ferrite ratio is 30 to 70%, the duplex stainless steel has excellent toughness. When the ferrite ratio is 30 to 70% and the ferrite hardness is 300 Hv 10 gf or more, the yield strength of the duplex stainless steel is 550 MPa or more, and the absorbed energy vE0 is 100 J or more.
- the ferrite hardness is 315 Hv 10 gf or more.
- the yield strength of the duplex stainless steel is 580 MPa or more.
- a duplex stainless steel having the above chemical composition is melted.
- the duplex stainless steel may be melted by an electric furnace or by an Ar—O 2 mixed gas bottom blowing decarburization furnace (AOD furnace).
- the duplex stainless steel may also be melted by a vacuum decarburization furnace (VOD furnace).
- the melted duplex stainless steel may be manufactured into an ingot by an ingot forming method, or may be manufactured into a slab (slab, bloom or billet) by a continuous casting method.
- duplex stainless steel material is, for example, a duplex stainless steel plate or a duplex stainless steel pipe.
- the duplex stainless steel sheet is manufactured, for example, by the following method.
- the manufactured ingot or slab is hot-worked to manufacture a duplex stainless steel sheet.
- Hot working is, for example, hot forging or hot rolling.
- the duplex stainless steel pipe is manufactured, for example, by the following method.
- a billet is manufactured by hot-working the manufactured ingot, slab or bloom.
- the manufactured billet is hot-worked to produce a duplex stainless steel pipe.
- Hot working is, for example, piercing and rolling by the Mannesmann method. Hot extrusion may be performed as hot working, or hot forging may be performed.
- the manufactured duplex stainless steel pipe may be a seamless pipe or a welded steel pipe.
- duplex stainless steel pipe is a welded steel pipe
- the above duplex stainless steel pipe is bent into an open pipe. Both end surfaces in the longitudinal direction of the open pipe are welded by a known welding method such as a submerged arc welding method to produce a welded steel pipe.
- Solution treatment is performed on the manufactured duplex stainless steel. Specifically, the duplex stainless steel material is charged into a heat treatment furnace and soaked at a solution treatment temperature of 980 to 1200 ° C. After soaking, the duplex stainless steel is quenched by water cooling or the like. A preferable soaking time in the solution treatment is 2 to 60 minutes.
- aging heat treatment is performed on the duplex stainless steel material. Specifically, a duplex stainless steel material is charged into a heat treatment furnace. Then, soaking is performed at an aging heat treatment temperature of 460 to 630 ° C. After soaking, the duplex stainless steel is air-cooled. A preferable soaking time in the aging heat treatment is 2 to 60 minutes.
- the ferrite ratio of the duplex stainless steel is adjusted to 30 to 70%. Further, the ferrite hardness is 300 Hv 10 gf or more. As a result, the duplex stainless steel obtains excellent yield strength and toughness.
- a preferred solution treatment temperature is 1050 to 1150 ° C.
- a preferred aging heat treatment temperature is 480 to 600 ° C.
- the ferrite ratio is 35 to 55%
- the ferrite hardness is 315 Hv 10 gf or more.
- the yield strength of the duplex stainless steel becomes 580 MPa or more.
- a more preferable aging heat treatment temperature is higher than 480 ° C. and not higher than 600 ° C., more preferably 500 to 600 ° C.
- Duplex stainless steels having various chemical compositions were melted using a 150 kg capacity vacuum melting furnace.
- a plurality of duplex stainless steel sheets were produced under various production conditions using the melted duplex stainless steel.
- the yield strength and toughness of the manufactured steel sheet were investigated.
- the chemical composition of Steel A to Steel F was within the range of the chemical composition of the present invention.
- the chemical composition of Steel X to Steel Z was outside the range of the chemical composition of the present invention.
- the Cr content of Steel X was less than the lower limit of the Cr content of the present invention.
- the Cu content of steel Y was less than the lower limit of the Cu content of the present invention.
- the Cu content of steel Z was less than the lower limit of the Cu content of the present invention.
- Mo content of steel Z exceeded the upper limit of Mo content of the present invention.
- Ingots were produced by casting molten duplex stainless steel.
- the manufactured ingot was heated to 1250 ° C.
- the heated ingot was hot forged to produce a plate material.
- the manufactured plate was again heated to 1250 ° C.
- the heated plate material was hot-rolled to produce a plurality of steel plates having a thickness of 15 mm.
- the surface temperature of the steel material during rolling was 1050 ° C.
- a plurality of manufactured steel sheets were subjected to solution treatment and aging heat treatment, and steel sheets with test numbers 1 to 15 in Table 2 were manufactured.
- the solution treatment was carried out on the steel plates of each test number.
- the solution treatment temperature (° C.) was as shown in Table 2, and the soaking time was 5 minutes for all test numbers. More specifically, each steel plate was charged into a heat treatment furnace and then held at a solution treatment temperature (° C.) shown in Table 2 for 5 minutes. Then, each steel plate was taken out from the heat treatment and cooled with water until the surface temperature of the steel plate reached ordinary temperature (25 ° C.).
- aging heat treatment was performed on the steel sheet.
- the aging heat treatment temperature (° C.) was as shown in Table 2, and the soaking time was 30 minutes for all test numbers. More specifically, each steel plate was charged into a heat treatment furnace and then held at the aging heat treatment temperature (° C.) shown in Table 2 for 30 minutes. Then, each steel plate was taken out from the heat treatment furnace and air-cooled until the surface temperature of the steel plate reached normal temperature (25 ° C.).
- the ferrite rate of the steel sheet of each test number was determined by the following method. A specimen for structure observation was taken from each steel plate. The collected specimen was mechanically polished, and the polished specimen was electrolytically etched in a 30% KOH solution. The surface of the sample after etching was observed using an optical microscope (400 times). At this time, the area of the observed region was about 2000 ⁇ m 2 . The ferrite percentage (%) was determined within the observed region. The ferrite ratio was determined by a point count method based on ASTM E562.
- the ferrite hardness of each test number steel sheet was determined by the following method. Ten points in arbitrary ferrite were selected from the observation region of the above-described specimen for tissue observation. At each selected point, the Vickers hardness according to JISZ2244 was measured. The test force at the time of measurement was 98.07N. The average of 8 points excluding the maximum and minimum values of the measured Vickers hardness was defined as the ferrite hardness (Hv 10 gf ).
- yield strength and tensile strength test A round bar tensile test piece was taken from each test number steel plate. The outer diameter of the round bar tensile test piece was 6.35 mm, and the parallel part length was 25.4 mm. The parallel part extended in the rolling direction of the steel sheet. A tensile test was performed at room temperature on the collected round bar test pieces, and yield strength YS (MPa) and tensile strength TS (MPa) were obtained. The 0.2% offset proof stress based on ASTM A370 was defined as the yield strength YS (MPa).
- the chemical compositions of the steel plates with test numbers 1 to 8 were within the scope of the present invention. Further, the solution treatment temperature and the aging heat treatment temperature of the steel plates of Test Nos. 1 to 8 were within the scope of the present invention. Therefore, the ferrite ratios of the steel sheets with test numbers 1 to 8 were in the range of 30 to 70%, and the ferrite hardness was 300 Hv 10 gf or more. As a result, the yield strength YS of the steel plates with test numbers 1 to 8 was 550 MPa or more, and more specifically, 580 MPa or more. Further, the absorbed energy vE0 at 0 ° C. of the steel plates of test numbers 1 to 8 was 100 J or more.
- the chemical composition of the steel plate of test number 9 was within the scope of the present invention, but the aging heat treatment temperature was 450 ° C., which was lower than the lower limit of the aging heat treatment temperature of the present invention. Therefore, the yield strength YS of the steel plate of test number 9 was less than 550 MPa. It is presumed that the amount of Cu sufficient to increase the strength of the entire ferrite did not precipitate because the aging heat treatment temperature was too low.
- the chemical composition of the steel plate of test number 10 was within the range of the present invention, the aging heat treatment temperature was 700 ° C., which exceeded the upper limit of the present invention. Therefore, the ferrite hardness of the steel sheet of test number 10 was less than 300 Hv 10 gf , and the yield strength YS was 550 MPa or less. It is presumed that because the aging heat treatment temperature was too high, Cu was dissolved in ferrite and the amount of Cu precipitation was low.
- the absorbed energy vE0 of the steel plate of test number 10 was less than 100J. It is presumed that because the aging heat treatment temperature was too high, a large amount of ⁇ phase, Mo carbide, and Cr carbide precipitated.
- the Cr content of the steel plate of test number 11 was less than the lower limit of the Cr content of the present invention. Therefore, the ferrite rate was less than 30%, and the yield strength YS was less than 550 MPa. It is estimated that the yield strength YS was low because the ferrite rate was too small.
- the Cu content of the steel plate of test number 12 was less than the lower limit of the Cu content of the present invention. Therefore, the ferrite hardness was less than 300 Hv 10 gf , and the yield strength YS was less than 550 MPa. It is presumed that the amount of Cu deposited in the ferrite was small because the Cu content was too small.
- the Cu content of the steel plate of test number 13 was less than the lower limit of the Cu content of the present invention. Furthermore, the Mo content of the steel plate of test number 13 exceeded the upper limit of the Mo content of the present invention. Therefore, the yield strength YS was less than 550 MPa, and the absorbed energy vE0 was less than 100J. Since the Cu content was too small, the amount of Cu precipitation was small, and it was estimated that the yield strength YS was low. Furthermore, since there was too much Mo content, it is estimated that the (sigma) phase and Mo carbide precipitated abundantly and toughness was low.
- the chemical composition of the steel plate of test number 14 was within the scope of the present invention, and the solution treatment temperature was also within the scope of the present invention.
- the steel sheet of test number 14 was not subjected to aging heat treatment. Therefore, the ferrite hardness was less than 300 Hv 10 gf , and the yield strength was less than 550 MPa.
- the chemical composition of the steel plate of test number 15 was within the range of the present invention, the aging heat treatment temperature was 700 ° C., which exceeded the upper limit of the present invention. Therefore, the ferrite rate of the steel sheet of test number 15 was less than 30%, the ferrite hardness was less than 300 Hv 10 gf , and the yield strength was less than 550 MPa. It is presumed that the target performance was not satisfied because the aging heat treatment temperature was too high and the ferrite rate was too low.
- duplex stainless steel according to the present invention is widely applicable in fields where high strength and high toughness are required.
- the duplex stainless steel according to the present invention is applicable as a steel material for line pipes.
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Abstract
Description
第1群:V:1.50%以下
第2群:Ca:0.0200%以下、Mg:0.02%以下及びB:0.0200%以下
第3群:希土類元素(REM):0.2000%以下
本発明による二相ステンレス鋼は、以下の化学組成を有する。
炭素(C)は、オーステナイトを安定化する。一方、Cが過剰に含有されれば、炭化物が生成されやすくなる。Mo炭化物は特に、鋼の靭性を低下する。したがって、C含有量は、0.030%以下である。C含有量の好ましい上限はさらに、0.020%であり、さらに好ましいC含有量は、0.020%未満である。
珪素(Si)は、溶接時の溶融金属の流動性の低下を抑制し、溶接欠陥の生成を抑制する。一方、Siが過剰に含有されれば、σ相に代表される金属間化合物が生成されやすくなる。したがって、Si含有量は、0.20~1.00%である。Si含有量の好ましい上限はさらに、0.80%であり、さらに好ましくは、0.65%である。Si含有量の好ましい下限はさらに、0.30%であり、さらに好ましくは、0.35%である。
マンガン(Mn)は、鋼を脱硫及び脱酸し、鋼の熱間加工性を高める。Mnはさらに、窒素(N)の溶解度を高める。一方、Mnが過剰に含有されれば、耐食性が低下する。したがって、Mn含有量は、8.00%以下である。Mn含有量の好ましい上限はさらに、7.50%であり、さらに好ましくは、5.00%である。Mn含有量の好ましい下限は、0.03%であり、さらに好ましくは、0.05%である。
燐(P)は不純物である。Pは、鋼の耐食性及び靭性を低下する。したがって、P含有量は少ない方が好ましい。P含有量は、0.040%以下である。好ましいP含有量は、0.030%以下であり、さらに好ましくは0.020%以下である。
硫黄(S)は不純物である。Sは、鋼の熱間加工性を低下する。Sはさらに、硫化物を形成する。硫化物は、孔食の発生起点となるため、鋼の耐孔食性を低下する。したがって、S含有量は少ない方が好ましい。S含有量は、0.0100%以下である。好ましいS含有量は、0.0050%以下であり、さらに好ましくは0.0010%以下である。
銅(Cu)は、不動態皮膜を強化し、耐SCC性を含む耐食性を高める。Cuはさらに、時効熱処理により、フェライト中に微細に析出する。析出されたCuは、フェライトの硬度を高め、鋼の強度を高める。Cuはさらに、大入熱溶接時にも母材中に極微細に析出し、フェライト/オーステナイト相境界でのσ相の析出を抑制する。一方、Cuが過剰に含有されれば、鋼の熱間加工性が低下する。したがって、Cu含有量は、2.00%を超え4.00%以下である。Cu含有量の好ましい下限はさらに、2.20%であり、さらに好ましくは、2.40%である。
ニッケル(Ni)はオーステナイトを安定化する。Niはさらに、鋼の靭性を高め、鋼の耐SCC性を含む耐食性を高める。一方、Niが過剰に含有されれば、σ相に代表される金属間化合物が生成されやすくなる。したがって、Ni含有量は、4.00~8.00%である。Ni含有量の好ましい下限は、4.20%であり、さらに好ましくは、4.50%である。Ni含有量の好ましい上限は、7.50%であり、さらに好ましくは7.00%である。
クロム(Cr)は、鋼の耐食性を高める。Crは特に、鋼の耐SCC性を高める。一方、Crが過剰に含有されれば、σ相に代表される金属間化合物が生成される。さらに、Cr炭化物が生成される。σ相及びCr炭化物は、鋼の靭性を低下し、熱間加工性も低下する。したがって、Cr含有量は、20.0~30.0%である。Cr含有量の好ましい下限は、22.0%であり、さらに好ましくは、24.0%である。Cr含有量の好ましい上限はさらに、28.0%であり、さらに好ましくは27.0%である。
モリブデン(Mo)は、鋼の耐SCC性を高める。一方、Moが過剰に含有されれば、σ相に代表される金属間化合物が生成される。σ相は、鋼の靭性、溶接性及び熱間加工性を低下する。Moが過剰に含有されればさらに、Mo炭化物が生成される。Mo炭化物は、鋼の靭性を低下する。したがって、Mo含有量は、0.50%以上2.00%未満である。好ましいMo含有量の下限は、0.80%であり、さらに好ましくは、1.00%である。
窒素(N)は、強力なオーステナイト形成元素であり、鋼の熱的安定性及び耐食性を高める。本発明による二相ステンレス鋼は、フェライト形成元素であるCrとMoとを含有する。二相ステンレス鋼内のフェライト量とオーステナイト量のバランスを考慮すれば、N含有量は0.100%以上である。一方、Nが過剰に含有されれば、溶接欠陥であるブローホールが発生する。Nが過剰に含有されればさらに、溶接時に窒化物が生成されやすくなり、鋼の靭性及び耐食性が低下する。したがって、N含有量は、0.100~0.350%である。N含有量の好ましい下限は、0.120%であり、さらに好ましくは、0.150%である。
アルミニウム(Al)は、鋼を脱酸する。一方、Alが過剰に含有されれば、窒化アルミニウム(AlN)を形成し、鋼の靭性及び耐食性を低下する。したがって、Al含有量は、0.040%以下である。本明細書でいうAl含有量は、酸可溶Al(sol.Al)の含有量を意味する。本発明において、Alは必須元素である。
本発明による二相ステンレス鋼の化学組成は、Feに代えて、以下の第1群~第3群のうちの少なくとも1群から選択される1種又は2種以上の元素を含有してもよい。つまり、第1群~第3群の元素は、必要に応じて含有可能な選択元素である。
第1群:V:1.50%以下
第2群:Ca:0.0200%以下、Mg:0.02%以下及びB:0.0200%以下
第3群:希土類元素(REM):0.2000%以下
以下、これらの選択元素について詳述する。
V:1.50%以下
バナジウム(V)は、選択元素である。Vは、二相ステンレス鋼の耐食性を高め、特に、酸性環境下での耐食性を高める。より具体的には、VがMo及びCuと共に含有されれば、鋼の耐隙間腐食性が高まる。一方、Vが過剰に含有されれば、鋼中のフェライト量が過剰に増加し、鋼の耐食性が低下する。したがって、V含有量は1.50%以下であり、好ましくは、1.50%未満である。V含有量が0.05%以上であれば、上記効果が顕著に得られる。しかしながら、V含有量が0.05%未満であっても、上記効果はある程度得られる。V含有量の好ましい上限はさらに、0.50%であり、さらに好ましくは、0.10%である。
Ca:0.0200%以下
Mg:0.02%以下
B:0.0200%以下
カルシウム(Ca)、マグネシウム(Mg)及びボロン(B)は、いずれも選択元素である。Ca、Mg及びBはいずれも、鋼中のS及びO(酸素)を固定して、鋼の熱間加工性を高める。本発明による二相ステンレス鋼のS含有量は少ない。したがって、Ca、Mg及びBが含有されていなくても、鋼の熱間加工性は高い。しかしながら、たとえば、傾斜圧延法により継目無鋼管を製造する場合、さらに高い熱間加工性が求められる場合がある。Ca、Mg及びBからなる群から選択される1種又は2種以上を含有すれば、さらに高い熱間加工性が得られる。
希土類元素(REM):0.2000%以下
希土類元素(REM)は、選択元素である。REMは、Ca、Mg及びBと同様に、鋼中のS及びO(酸素)を固定して、鋼の熱間加工性を高める。一方、REMが過剰に含有されれば、非金属介在物(希土類元素の酸化物及び硫化物等)が増加し、鋼の耐食性が低下する。したがって、REM含有量は、0.2000%以下である。上記効果を顕著に得るためには、REM含有量がS(質量%)+1/2×O(質量%)以上であるのが好ましい。しかしながら、REMが少しでも含有されれば、上記効果はある程度得られる。
本発明による二相ステンレス鋼の組織は、フェライトとオーステナイトとからなり、残部は、析出物及び介在物である。
上述の化学組成を有する二相ステンレス鋼を溶製する。二相ステンレス鋼は、電気炉により溶製されてもよいし、Ar-O2混合ガス底吹き脱炭炉(AOD炉)により溶製されてもよい。二相ステンレス鋼はまた、真空脱炭炉(VOD炉)により溶製されてもよい。溶製された二相ステンレス鋼は、造塊法によりインゴットに製造されてもよいし、連続鋳造法により鋳片(スラブ、ブルーム又はビレット)に製造されてもよい。
各試験番号の鋼板のフェライト率を以下の方法で求めた。各鋼板から組織観察用の試験片を採取した。採取された試験片を機械研磨し、研磨された試験片を30%KOH溶液中で電解エッチングした。光学顕微鏡(400倍)を用いてエッチング後の試料表面を観察した。このとき、観察される領域の面積は約2000μm2であった。観察された領域内でフェライト率(%)を求めた。フェライト率はASTM E562に準拠したポイントカウント法により求めた。
各試験番号の鋼板のフェライト硬度を以下の方法で決定した。上述の組織観察用の試験片の観察領域のうち、任意のフェライト内の10点を選択した。選択された各点において、JISZ2244に準拠したビッカース硬度を測定した。測定時の試験力は、98.07Nであった。測定したビッカース硬度の最大値と最小値とを除いた8点の平均を、フェライト硬度(Hv10gf)と定義した。
各試験番号の鋼板から、丸棒引張試験片を採取した。丸棒引張試験片の外径は、6.35mmであり、平行部長さは25.4mmであった。平行部は、鋼板の圧延方向に延在した。採取された丸棒試験片に対して、常温で引張試験を実施し、降伏強度YS(MPa)及び引張強度TS(MPa)を求めた。ASTM A370に基づく0.2%オフセット耐力を降伏強度YS(MPa)と定義した。
靭性試験として、シャルピー衝撃試験を実施した。シャルピー衝撃試験用に、各鋼板からフルサイズのVノッチ試験片(幅10mm、厚さ10mm、長さ55mm、ノッチ深さ2mm)を採取した。採取されたVノッチ試験片を用いて、JIS Z2242に基づいて、0℃にてシャルピー衝撃試験を実施し、吸収エネルギ(vE0)を求めた。
試験結果を表2に示す。表2中の「フェライト率」欄には、各試験番号のフェライト率(%)が記載される。「フェライト硬度」欄には、各試験番号のフェライト硬度(Hv10gf)が記載される。「YS」欄には、各試験番号の降伏強度(MPa)が記載される。「TS」欄には、各試験番号の引張強度(MPa)が記載される。「vE0」欄には、各試験番号の0℃における吸収エネルギ(J)が記載される。
Claims (6)
- 質量%で、C:0.030%以下、Si:0.20~1.00%、Mn:8.00%以下、P:0.040%以下、S:0.0100%以下、Cu:2.00%を超え4.00%以下、Ni:4.00~8.00%、Cr:20.0~30.0%、Mo:0.50%以上2.00%未満、N:0.100~0.350%及びsol.Al:0.040%以下を含有し、残部はFe及び不純物からなる化学組成と、
フェライト率が30~70%であり、前記フェライトの硬度が300Hv10gf以上である組織とを有する、二相ステンレス鋼。 - 請求項1に記載の二相ステンレス鋼であって、
前記化学組成は、前記Feの一部に代えて、V:1.50%以下を含有する、二相ステンレス鋼。 - 請求項1又は請求項2に記載の二相ステンレス鋼であって、
前記化学組成は、前記Feの一部に代えて、Ca:0.0200%以下、Mg:0.02%以下及びB:0.0200%以下からなる群から選択される1種又は2種以上を含有する、二相ステンレス鋼。 - 請求項1~請求項3のいずれか1項に記載に二相ステンレス鋼であって、
前記化学組成は、前記Feの一部に代えて、希土類元素:0.2000%以下を含有する、二相ステンレス鋼。 - 請求項1~請求項4のいずれか1項に記載の二相ステンレス鋼であって、
980~1200℃で溶体化処理され、さらに、460~630℃で時効熱処理される、二相ステンレス鋼。 - 質量%で、C:0.030%以下、Si:0.20~1.00%、Mn:8.00%以下、P:0.040%以下、S:0.0100%以下、Cu:2.00%を超え4.00%以下、Ni:4.00~8.00%、Cr:20.0~28.0%、Mo:0.50%以上2.00%未満、N:0.100~0.350%及びsol.Al:0.040%以下を含有し、残部はFe及び不純物からなる化学組成を有する二相ステンレス鋼材を製造する工程と、
製造された前記二相ステンレス鋼材を、980~1200℃で溶体化処理する工程と、
溶体化処理された前記二相ステンレス鋼材を、460~630℃で時効熱処理する工程とを備える、二相ステンレス鋼材の製造方法。
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CN201280008783.7A CN103370436B (zh) | 2011-02-14 | 2012-02-10 | 双相不锈钢及其制造方法 |
US13/984,314 US9771628B2 (en) | 2011-02-14 | 2012-02-10 | Duplex stainless steel and production method therefor |
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EP3040434A4 (en) * | 2013-08-28 | 2017-05-03 | Hitachi, Ltd. | Duplex stainless steel, and duplex stainless steel structure, marine structure, petroleum/gas environment structure, pump impeller, pump casing, and flow adjustment valve body using same |
EP3040434A1 (en) * | 2013-08-28 | 2016-07-06 | Hitachi, Ltd. | Duplex stainless steel, and duplex stainless steel structure, marine structure, petroleum/gas environment structure, pump impeller, pump casing, and flow adjustment valve body using same |
JP2018059157A (ja) * | 2016-10-06 | 2018-04-12 | 新日鐵住金株式会社 | 二相ステンレス鋼 |
JP2018193591A (ja) * | 2017-05-18 | 2018-12-06 | 新日鐵住金株式会社 | 二相ステンレス鋼材及びその製造方法 |
JPWO2020218426A1 (ja) * | 2019-04-24 | 2021-12-02 | 日本製鉄株式会社 | 二相ステンレス継目無鋼管、及び、二相ステンレス継目無鋼管の製造方法 |
WO2020218426A1 (ja) | 2019-04-24 | 2020-10-29 | 日本製鉄株式会社 | 二相ステンレス継目無鋼管、及び、二相ステンレス継目無鋼管の製造方法 |
JP7188570B2 (ja) | 2019-04-24 | 2022-12-13 | 日本製鉄株式会社 | 二相ステンレス継目無鋼管、及び、二相ステンレス継目無鋼管の製造方法 |
JP2020186442A (ja) * | 2019-05-14 | 2020-11-19 | 日本製鉄株式会社 | 2相ステンレス鋼及び2相ステンレス鋼の製造方法 |
JP7277731B2 (ja) | 2019-05-14 | 2023-05-19 | 日本製鉄株式会社 | 2相ステンレス鋼及び2相ステンレス鋼の製造方法 |
WO2020241084A1 (ja) * | 2019-05-29 | 2020-12-03 | Jfeスチール株式会社 | 二相ステンレス鋼およびその製造方法、並びに二相ステンレス鋼管 |
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JP7173359B2 (ja) | 2019-08-19 | 2022-11-16 | 日本製鉄株式会社 | 二相ステンレス鋼材 |
JPWO2021033672A1 (ja) * | 2019-08-19 | 2021-02-25 | ||
WO2021033672A1 (ja) * | 2019-08-19 | 2021-02-25 | 日本製鉄株式会社 | 二相ステンレス鋼材 |
JP7364955B1 (ja) | 2022-07-04 | 2023-10-19 | 日本製鉄株式会社 | 二相ステンレス鋼材 |
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MX355892B (es) | 2018-05-04 |
ES2795753T3 (es) | 2020-11-24 |
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AU2012218660B2 (en) | 2015-05-21 |
EP2677054A1 (en) | 2013-12-25 |
BR112013020445B1 (pt) | 2019-08-13 |
US20130312880A1 (en) | 2013-11-28 |
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MX2013009235A (es) | 2013-08-29 |
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