EP4112754A1 - Präzipitationsshärtender martensitischer edelstahl - Google Patents
Präzipitationsshärtender martensitischer edelstahl Download PDFInfo
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- EP4112754A1 EP4112754A1 EP20920783.6A EP20920783A EP4112754A1 EP 4112754 A1 EP4112754 A1 EP 4112754A1 EP 20920783 A EP20920783 A EP 20920783A EP 4112754 A1 EP4112754 A1 EP 4112754A1
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- precipitation hardening
- stainless steel
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- 238000004881 precipitation hardening Methods 0.000 title claims abstract description 44
- 229910001105 martensitic stainless steel Inorganic materials 0.000 title description 2
- 229910000734 martensite Inorganic materials 0.000 claims abstract description 21
- 229910052758 niobium Inorganic materials 0.000 claims abstract description 21
- 229910001220 stainless steel Inorganic materials 0.000 claims abstract description 21
- 239000010935 stainless steel Substances 0.000 claims abstract description 18
- 229910000765 intermetallic Inorganic materials 0.000 claims abstract description 13
- 229910052748 manganese Inorganic materials 0.000 claims abstract description 4
- 229910052760 oxygen Inorganic materials 0.000 claims abstract description 4
- 229910052804 chromium Inorganic materials 0.000 claims abstract description 3
- 229910052802 copper Inorganic materials 0.000 claims abstract description 3
- 239000012535 impurity Substances 0.000 claims abstract description 3
- 229910052750 molybdenum Inorganic materials 0.000 claims abstract description 3
- 229910052759 nickel Inorganic materials 0.000 claims abstract description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 3
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 3
- 229910052717 sulfur Inorganic materials 0.000 claims abstract description 3
- 239000013078 crystal Substances 0.000 claims description 12
- 239000002245 particle Substances 0.000 claims description 7
- 238000009826 distribution Methods 0.000 claims description 6
- 230000005540 biological transmission Effects 0.000 claims description 4
- 238000010884 ion-beam technique Methods 0.000 claims description 3
- 238000013507 mapping Methods 0.000 claims description 3
- 238000010191 image analysis Methods 0.000 claims 1
- 238000010438 heat treatment Methods 0.000 abstract description 41
- 230000032683 aging Effects 0.000 abstract description 25
- 238000001556 precipitation Methods 0.000 description 29
- 238000011156 evaluation Methods 0.000 description 21
- 235000019589 hardness Nutrition 0.000 description 19
- 230000003247 decreasing effect Effects 0.000 description 15
- 229910000831 Steel Inorganic materials 0.000 description 12
- 239000000243 solution Substances 0.000 description 12
- 239000010959 steel Substances 0.000 description 12
- 239000000463 material Substances 0.000 description 10
- 229910000859 α-Fe Inorganic materials 0.000 description 9
- 229910001566 austenite Inorganic materials 0.000 description 8
- 230000000052 comparative effect Effects 0.000 description 8
- 230000000694 effects Effects 0.000 description 7
- 239000000470 constituent Substances 0.000 description 5
- 238000002149 energy-dispersive X-ray emission spectroscopy Methods 0.000 description 5
- 230000007797 corrosion Effects 0.000 description 4
- 238000005260 corrosion Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000007545 Vickers hardness test Methods 0.000 description 3
- 229910045601 alloy Inorganic materials 0.000 description 3
- 239000000956 alloy Substances 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 3
- 230000008707 rearrangement Effects 0.000 description 3
- 238000009864 tensile test Methods 0.000 description 3
- 229910000963 austenitic stainless steel Inorganic materials 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 2
- 229910052742 iron Inorganic materials 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229910001018 Cast iron Inorganic materials 0.000 description 1
- 229910000943 NiAl Inorganic materials 0.000 description 1
- NPXOKRUENSOPAO-UHFFFAOYSA-N Raney nickel Chemical compound [Al].[Ni] NPXOKRUENSOPAO-UHFFFAOYSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 230000003749 cleanliness Effects 0.000 description 1
- 238000005097 cold rolling Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000001747 exhibiting effect Effects 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 150000001247 metal acetylides Chemical class 0.000 description 1
- 238000000034 method Methods 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 230000001376 precipitating effect Effects 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 239000006104 solid solution Substances 0.000 description 1
- 238000007711 solidification Methods 0.000 description 1
- 230000008023 solidification Effects 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 239000010409 thin film Substances 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
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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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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
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- 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
- C21D6/02—Hardening by precipitation
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/021—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips involving a particular fabrication or treatment of ingot or slab
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
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- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0236—Cold rolling
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
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- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
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- 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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- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
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- C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
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- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/34—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of silicon
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- 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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- 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
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D2211/00—Microstructure comprising significant phases
- C21D2211/004—Dispersions; Precipitations
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- 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
- C21D2211/008—Martensite
Definitions
- the present invention relates to a precipitation hardening martensite stainless steel exhibiting high strength and ductility after aging heat treatment.
- a precipitation hardening type stainless steel is used for a steel belt, press plate, or the like, because strength thereof can be increased by performing aging heat treatment.
- SUS630, SUS631, or the like may be mentioned.
- the above SUS631 is a semi-austenitic stainless steel, and it is a metastable austenitic stainless steel under a solid solution condition.
- NiAl is precipitated by aging heat treatment so as to strengthen it; however, there is a problem in that productivity is not satisfactory. Furthermore, there is also a problem in that a ⁇ ferrite phase is easily precipitated under high temperatures because Al is contained, and hot processing workability is not satisfactory.
- the above SUS630 is a martensitic stainless steel, and has a martensite structure after solution heat treatment. It is strengthened by precipitation of ⁇ -Cu phase by aging heat treatment; however, achievable strength is about 1500 MPa (Vickers hardness about 400).
- Precipitation hardening martensite stainless steels stronger than those disclosed in the techniques of the above Patent documents, are widely used. However, as purposes of use for the precipitation hardening martensite stainless steels increased, demands associated with the purpose of use increased, and there may be a case in which properties are not sufficient, depending on conditions for use.
- an object of the present invention is to provide a precipitation hardening martensite stainless steel in which even greater strength and toughness can be maintained by performing aging heat treatment.
- An aspect of the present invention is a precipitation hardening martensite stainless steel including: in mass%, indicated by "%", C: 0.01 to 0.05%, Si: 1.0 to 2.0%, Mn: 0.70 to 1.50%, P: not more than 0.04%, S: not more than 0.01%, Ni: 6.0 to 8.0%, Cr: 12.0 to 15.0%, Mo: 0.50 to 1.50%, Cu: 0.40 to 1.20%, Ti: 0.20 to 0.50%, Nb: 0.05 to 0.40%, N: 0.001 to 0.005%, Al: 0.001 to 0.2%, O: 0.0001 to 0.01%, with the remainder being inevitable impurities and Fe, in which Cu phase and Ni 16 (Ti, Nb) 6 Si 7 type intermetallic compounds phase are distributed, and Nb in the intermetallic compounds phase is 0.2 to 3.0 (at%).
- another aspect of the precipitation hardening martensite stainless steel of the present invention is that not less than 50 number% of the Cu phase and the Ni 16 (Ti, Nb) 6 Si 7 type intermetallic compounds phase is distributed in crystal grains, when a thin layer sample is prepared using a focused ion beam, an element mapping image is obtained by EDS by using an energy dispersive X-ray analyzer installed in a scanning transmission electron microscope (STEM), and the image is image-analyzed by observing and evaluating precipitation hardening phase at the nanoscale so as to obtain the distribution.
- STEM scanning transmission electron microscope
- Another aspect of the precipitation hardening martensite stainless steel of the present invention is that average diameter of the Cu phase and the Ni 16 (Ti, Nb) 6 Si 7 type intermetallic compounds phase is 1 to 20 nm.
- elongation is 2 to 15% and hardness is 400 to 600 Hv as a mechanical property.
- Fig. 1 is a conceptual diagram showing precipitation conditions of a Cu phase and a G phase in the stainless steel of the present invention, and showing neighbors at the grain boundary of three crystal grains.
- C is austenite forming element, and reduces generation of ⁇ ferrite phase at high temperatures. Furthermore, it solid-solves in a martensite phase so as to increase strength; however, a residual austenite phase may easily be increased after solution heat treatment, and sufficient strength may not be obtained after aging heat treatment. Furthermore, in a case in which C amount is large, Ti and Nb, which are constituent components of the G phase contributing to precipitation hardening, may be easily consumed by formation of TiC and NbC. Therefore, in order to reduce precipitation hardening ability by aging heat treatment, the content of C is set to be 0.01 to 0.10%. Furthermore, it is desirably set to be 0.03 to 0.05%.
- Si is set to be not less than 1.0%.
- content amount of Si is set to be not more than 2.0% since Si is a ferrite generating element, ⁇ ferrite phase may be easily generated by a large content amount of Si, and hot workability and strength around a welded portion may be decreased. Furthermore, it is desirably set to be 1.30 to 1.90%.
- Mn is an austenite forming element, generation of ⁇ ferrite phase at high temperatures is restrained. Furthermore, residual austenite phase may be easily increased after solution heat treatment, and toughness may be increased; but on the other hand, strength may be decreased after aging heat treatment. Furthermore, MnO and MnS are formed so that corrosion resistance is decreased. Therefore, the range of Mn is set to be 0.50 to 1.50%. Furthermore, it is desirably set to be 0.70 to 1.20%.
- P is segregated at a crystal grain boundary so that solidification crack susceptibility is increased and hot workability is decreased. Therefore, content amount of P is desirably as small as possible, and it is set to be not more than 0.04%.
- S is a harmful component since MnS is formed so that corrosion resistance is decreased and since S segregates at a grain boundary so that hot workability is decreased. Therefore, content amount of S is desirably as small as possible, and it is set to be not more than 0.01%.
- Ni is set to be not less than 6.0% since it is an austenite forming element, a constituent element of the G phase, and an important element for precipitation hardening. However, it is set to be not more than 8.0% since a residual austenite phase after solution heat treatment may be easily increased, and strength may be decreased if content amount of Ni is too high.
- Content amount of Cr is set to be not less than 12.0% in order to maintain corrosion resistance of the stainless steel. However, it is set to be not more than 15.0% since it is a ferrite forming element, ⁇ ferrite phase may be easily generated at high temperatures, and hot workability may be decreased.
- Mo is an element effective for increasing corrosion resistance; however, it may promote generation of ⁇ ferrite phase. Therefore, content amount of Mo is set to be 0.50 to 1.50%. Furthermore, it is desirably set to be 0.50 to 1.00%.
- Cu is an element effective for precipitation hardening since a Cu phase is generated by aging heat treatment. However, excess addition may cause deterioration of strength by increasing residual austenite phase and cause generation of cracks by decrease of hot workability. Therefore, content amount of Cu is set to be 0.40 to 1.20%. Furthermore, it is desirably set to be 0.50 to 1.00%.
- Ti is a necessary element for formation of a G phase and is an element effective for increasing strength by precipitation hardening. However, since it may easily form oxides and nitrides and may cause defects, the range of Ti content is set to be 0.20 to 0.50%.
- Nb is a constituent element for a G phase, and it is a very important element.
- Nb is an effective element since it has actions for controlling the G phase to be Ni 16 (Ti, Nb) 6 Si 7 type and for promoting generation of nucleus. Furthermore, it also has an effect of dispersing Cu phase finely, and ability for precipitation hardening by a Cu phase and a G phase is extremely improved.
- the content amount of Nb is set to be not less than 0.05%. However, it is set to be not more than 0.40% since excessive addition of Nb causes formation of excess NbC, decreasing solid-solved C amount, and decreasing elongation. Furthermore, it is desirably set to be 0.10 to 0.30%.
- N is an austenite generating element similar to C, and it solid-solves in a martensite phase so as to increase strength.
- Ti and Nb which are constituent elements of a G phase, contributing to precipitation hardening, may be easily consumed by forming TiN and NbN, and precipitation hardening ability by aging heat treatment is decreased. Therefore, the range of N is set to be 0.001 to 0.02%.
- Al is an effective deoxidizing agent element for decreasing amount of O. Furthermore, since Nb is an element which is relatively easily oxidized, by decreasing oxygen concentration by deoxidizing by Al, Nb can be reliably controlled in a range of the present invention. However, in a case in which an excessive amount is contained, generation of ⁇ ferrite phase is promoted and hot workability and toughness are decreased. Therefore, the range of Al is set to be 0.001 to 0.2%.
- O forms non-metallic inclusions by combining with Si and Ti, which are constituent elements of a G phase, contributing to precipitation hardening, strength after aging heat treatment is decreased. Furthermore, the oxide type inclusions may decrease cleanliness level of steel and cause defects. However, since excess deoxidizing may increase cost, the range of O is set to be from 0.0001 to 0.01%.
- the steel of the present invention is a precipitation hardening type martensite stainless steel having superior strength, which is realized by precipitating simultaneously a Cu phase and G phase Ni 16 X 6 Si 7 . Distribution conditions of these precipitation hardening phases and size of the precipitation hardening phase itself have a large effect on mechanical properties such as hardness and elongation.
- precipitations are uniformly dispersed by solution heat treatment and aging heat treatment under appropriate conditions.
- the appropriate heating treatment conditions here means, although not limited thereto in particular, performing solution heat treatment at 1000 to 1150 °C for 1 to 5 minutes, and then performing aging heat treatment at 400 to 600 °C for 30 minutes to 10 hours.
- ratio of Nb atom (at%) in the G phase can be described as x/(16+6+7).
- hardness, and elongation can be controlled within the present invention by setting Nb (at%) in the G phase 0.2 to 3.0.
- content amount of Nb is set to be 0.05 to 0.40%.
- Nb in the steel of the present invention, by adding Nb, generation of nucleus of the precipitation phase can be promoted, and precipitations can be dispersed uniformly. Therefore, by setting Nb within the range of the present invention, it is possible that not less than 50% of Cu phase and Ni 16 (Ti, Nb) 6 Si 7 type intermetallic compound phase are distributed inside crystal grains.
- This action of precipitations as a blockade varies depending on size of precipitation phase, and there is an optimal size of the precipitation phase.
- precipitation phase of a size of 1 nm to 20 nm has maximal action of precipitation phase as a blockade against rearrangement, it is necessary to optimize the size of the precipitation phase. Therefore, by performing solution heat treatment and aging heat treatment under appropriate conditions, and by setting Nb within the range of the present invention, it is possible for the average particle diameter of a Cu phase and Ni 16 (Ti, Nb) 6 Si 7 type intermetallic compound phase to be 1 to 20 nm.
- Table 1 shows chemical compositions, existence of precipitation hardening phase, Nb amount in G phase, ratio of precipitations inside of a grain, Vickers hardness, and elongation of each of sample materials. A bracketed value of a chemical composition is outside the range of the present invention.
- Examples 2 and 5 are Reference Examples. Table 1 Section Steel No.
- each of the steels raw materials were melted in a high-frequency induction furnace, and the melt was casted in a cast-iron mold so as to prepare an ingot of about 20 kg.
- the ingot was hot-forged at 1000 to 1200 °C so as to obtain a forged plate having a thickness of 12 mm.
- the forged plate was cold-rolled to obtain cold rolled material having a thickness of 2 mm, and solution heat treatment and aging heat treatment were performed with respect to this.
- the solution heat treatment was performed to solid-solve precipitations existing in a steel, and martensite transformation may occur by rapid cooling after the heat treatment. With respect to the cold-rolled material above, solution heat treatment was performed at 1050 °C for 2 minutes.
- the aging heat treatment is a treatment in which precipitation hardening phase, that is a Cu phase and a G phase in the steel of the present invention, is finely dispersed and precipitated after the solution heat treatment.
- aging heat treatment was performed at 480 °C for 1 hour.
- Nb (at%) in the G phase Ni 16 (Ti, Nb) 6 Si 7 can be described as x/(16+6+7), in a case of Ni 16 (Ti( 1-x ), Nb x ) 6 Si 7 .
- This Nb amount in a G phase during aging heat treatment was calculated by using a thermodynamic calculating software (trade name: Thermo-Calc). Furthermore, Nb amount in a G phase obtained by this thermodynamic calculation matches well with the result of STEM-EDS analysis. In view of mechanical properties such as hardness and elongation, Nb (at%) in G phase being 0.2 to 3.0 was evaluated as "Superior".
- Ratio of precipitations inside of grains being not less than 50% was evaluated as "Superior”.
- Average particle diameter of a precipitation phase being 1 to 20 nm was evaluated as "Superior”.
- Comparative Example 7 is out of the range of the present invention and hardness was low since Ti amount was low and no G phase existed.
- Comparative Example 10 residual ⁇ amount was extremely high, similar to the case of Comparative Example 6, since the Mn amount was high. Furthermore, Nb in the G phase was low since Nb amount was low, and hardness was low and elongation was high since ratio of precipitations inside of grains was low.
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JP2020031787A JP6776467B1 (ja) | 2020-02-27 | 2020-02-27 | 析出硬化型マルテンサイト系ステンレス鋼 |
PCT/JP2020/040211 WO2021171698A1 (ja) | 2020-02-27 | 2020-10-27 | 析出硬化型マルテンサイト系ステンレス鋼 |
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JPS63171857A (ja) * | 1987-01-10 | 1988-07-15 | Nippon Yakin Kogyo Co Ltd | 疲労特性に優れたステンレス鋼板帯 |
JP3384887B2 (ja) * | 1994-09-08 | 2003-03-10 | 日新製鋼株式会社 | 強度及び捩り特性に優れたバネ用析出硬化型ステンレス鋼 |
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JP2005232575A (ja) * | 2004-02-23 | 2005-09-02 | Mitsubishi Heavy Ind Ltd | 析出硬化型マルテンサイト鋼及びそれを用いたタービン翼 |
JP2005298840A (ja) * | 2004-04-06 | 2005-10-27 | Hitachi Metals Ltd | 靭性に優れた高強度析出硬化型マルテンサイト系ステンレス鋼 |
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