WO2022176707A1 - ブレーキディスクローター用マルテンサイト系ステンレス鋼板、ブレーキディスクローターおよびブレーキディスクローター用マルテンサイト系ステンレス鋼板の製造方法 - Google Patents
ブレーキディスクローター用マルテンサイト系ステンレス鋼板、ブレーキディスクローターおよびブレーキディスクローター用マルテンサイト系ステンレス鋼板の製造方法 Download PDFInfo
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- WO2022176707A1 WO2022176707A1 PCT/JP2022/004892 JP2022004892W WO2022176707A1 WO 2022176707 A1 WO2022176707 A1 WO 2022176707A1 JP 2022004892 W JP2022004892 W JP 2022004892W WO 2022176707 A1 WO2022176707 A1 WO 2022176707A1
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- WIPO (PCT)
- Prior art keywords
- stainless steel
- martensitic stainless
- brake disc
- steel sheet
- precipitates
- Prior art date
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- 229910001105 martensitic stainless steel Inorganic materials 0.000 title claims abstract description 38
- 238000004519 manufacturing process Methods 0.000 title claims description 13
- 238000000034 method Methods 0.000 title claims description 8
- 239000002244 precipitate Substances 0.000 claims abstract description 65
- 238000005098 hot rolling Methods 0.000 claims abstract description 29
- 238000010791 quenching Methods 0.000 claims abstract description 20
- 230000000171 quenching effect Effects 0.000 claims abstract description 20
- 238000005496 tempering Methods 0.000 claims abstract description 8
- 238000010438 heat treatment Methods 0.000 claims description 44
- 239000000463 material Substances 0.000 claims description 20
- 229910052799 carbon Inorganic materials 0.000 claims description 14
- 229910052757 nitrogen Inorganic materials 0.000 claims description 14
- 229910052750 molybdenum Inorganic materials 0.000 claims description 13
- 229910052758 niobium Inorganic materials 0.000 claims description 13
- 230000007423 decrease Effects 0.000 claims description 11
- 239000011159 matrix material Substances 0.000 claims description 8
- 238000004804 winding Methods 0.000 claims description 8
- 229910052802 copper Inorganic materials 0.000 claims description 7
- 229910052720 vanadium Inorganic materials 0.000 claims description 7
- 239000012535 impurity Substances 0.000 claims description 5
- 229910052742 iron Inorganic materials 0.000 claims description 4
- 229910052710 silicon Inorganic materials 0.000 claims description 4
- 238000000137 annealing Methods 0.000 abstract description 16
- 238000005336 cracking Methods 0.000 abstract description 5
- 239000002245 particle Substances 0.000 abstract description 4
- 229910000831 Steel Inorganic materials 0.000 description 34
- 229910001220 stainless steel Inorganic materials 0.000 description 34
- 239000010959 steel Substances 0.000 description 34
- 239000010935 stainless steel Substances 0.000 description 31
- 238000007792 addition Methods 0.000 description 23
- 230000007797 corrosion Effects 0.000 description 23
- 238000005260 corrosion Methods 0.000 description 23
- 230000003647 oxidation Effects 0.000 description 16
- 238000007254 oxidation reaction Methods 0.000 description 16
- 238000001556 precipitation Methods 0.000 description 14
- 230000000052 comparative effect Effects 0.000 description 12
- 238000007670 refining Methods 0.000 description 12
- 238000005728 strengthening Methods 0.000 description 12
- 239000006104 solid solution Substances 0.000 description 11
- 230000000694 effects Effects 0.000 description 10
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 9
- 229910001018 Cast iron Inorganic materials 0.000 description 8
- 238000001816 cooling Methods 0.000 description 8
- 229910000734 martensite Inorganic materials 0.000 description 7
- 239000000203 mixture Substances 0.000 description 7
- 239000000047 product Substances 0.000 description 7
- 238000005554 pickling Methods 0.000 description 6
- 229910052719 titanium Inorganic materials 0.000 description 6
- 229910052721 tungsten Inorganic materials 0.000 description 6
- 230000006866 deterioration Effects 0.000 description 5
- 238000012545 processing Methods 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 238000011084 recovery Methods 0.000 description 5
- 238000005266 casting Methods 0.000 description 4
- 229910052735 hafnium Inorganic materials 0.000 description 4
- 229910001068 laves phase Inorganic materials 0.000 description 4
- 238000000465 moulding Methods 0.000 description 4
- 229910052761 rare earth metal Inorganic materials 0.000 description 4
- 229910052715 tantalum Inorganic materials 0.000 description 4
- 238000009864 tensile test Methods 0.000 description 4
- 230000002159 abnormal effect Effects 0.000 description 3
- 229910001566 austenite Inorganic materials 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 3
- 230000006698 induction Effects 0.000 description 3
- 238000009628 steelmaking Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- 229910052726 zirconium Inorganic materials 0.000 description 3
- 230000015572 biosynthetic process Effects 0.000 description 2
- 239000003795 chemical substances by application Substances 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 239000000446 fuel Substances 0.000 description 2
- 229910000765 intermetallic Inorganic materials 0.000 description 2
- 238000011835 investigation Methods 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 229910052748 manganese Inorganic materials 0.000 description 2
- 150000001247 metal acetylides Chemical class 0.000 description 2
- 230000006911 nucleation Effects 0.000 description 2
- 238000010899 nucleation Methods 0.000 description 2
- 230000001376 precipitating effect Effects 0.000 description 2
- 230000000717 retained effect Effects 0.000 description 2
- 238000005096 rolling process Methods 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- 230000001629 suppression Effects 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 150000003568 thioethers Chemical class 0.000 description 2
- 239000013585 weight reducing agent Substances 0.000 description 2
- 229910000859 α-Fe Inorganic materials 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 241000704611 Fig cryptic virus Species 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910052765 Lutetium Inorganic materials 0.000 description 1
- 241000282342 Martes americana Species 0.000 description 1
- 238000003723 Smelting Methods 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229910052785 arsenic Inorganic materials 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 238000004040 coloring Methods 0.000 description 1
- 238000009749 continuous casting Methods 0.000 description 1
- 230000000593 degrading effect Effects 0.000 description 1
- 238000006477 desulfuration reaction Methods 0.000 description 1
- 230000023556 desulfurization Effects 0.000 description 1
- 230000002542 deteriorative effect Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000011156 evaluation Methods 0.000 description 1
- 238000003944 fast scan cyclic voltammetry Methods 0.000 description 1
- -1 further by mass% Substances 0.000 description 1
- 229910002804 graphite Inorganic materials 0.000 description 1
- 239000010439 graphite Substances 0.000 description 1
- 150000004678 hydrides Chemical class 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 229910052747 lanthanoid Inorganic materials 0.000 description 1
- 150000002602 lanthanoids Chemical class 0.000 description 1
- 229910052746 lanthanum Inorganic materials 0.000 description 1
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 description 1
- 229910052745 lead Inorganic materials 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- OHSVLFRHMCKCQY-UHFFFAOYSA-N lutetium atom Chemical compound [Lu] OHSVLFRHMCKCQY-UHFFFAOYSA-N 0.000 description 1
- 150000004767 nitrides Chemical class 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000001172 regenerating effect Effects 0.000 description 1
- 229910052706 scandium Inorganic materials 0.000 description 1
- SIXSYDAISGFNSX-UHFFFAOYSA-N scandium atom Chemical compound [Sc] SIXSYDAISGFNSX-UHFFFAOYSA-N 0.000 description 1
- 238000007493 shaping process Methods 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000000992 sputter etching Methods 0.000 description 1
- 229910052717 sulfur Inorganic materials 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 1
Classifications
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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
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/18—Hardening; Quenching with or without subsequent tempering
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0205—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips of ferrous alloys
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0221—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the working steps
- C21D8/0226—Hot rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—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
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
- C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
- C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
- C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
-
- 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
- C22C38/001—Ferrous alloys, e.g. steel alloys containing N
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/004—Very low carbon steels, i.e. having a carbon content of less than 0,01%
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—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
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/46—Ferrous alloys, e.g. steel alloys containing chromium with nickel with vanadium
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
-
- 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
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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
- C21D2211/008—Martensite
Definitions
- the present invention relates to a martensitic stainless steel sheet for brake disc rotors, which is excellent in hardenability, formability, temper softening resistance, and high-temperature strength, a brake disc rotor, and a method for producing a martensitic stainless steel sheet for brake disc rotors.
- the present invention relates to a stainless steel plate suitable for use in disc rotors that require thinness and weight reduction, which has excellent productivity, reduces pad wear, has stable hardness, and the like.
- a disc brake is widely used as one of the braking systems.
- a disc brake has a disk-shaped structure called a disc rotor that is connected to a tire. By pressing the disc rotor between the brake pads, the kinetic energy is converted into heat energy by friction, which reduces the speed of automobiles and motorcycles.
- a disk rotor for a disk brake is hereinafter also referred to as a "brake disk rotor".
- cast iron flake graphite cast iron
- cast iron flake graphite cast iron
- the wheel material has been changed to aluminum, and the spokes of the wheel have become thinner, making the disc rotor more conspicuous. improvement is desired.
- cast iron has low strength and is manufactured by casting, so there is a limit to how thin it can be made.
- the maximum temperature reached when the brakes of an automobile are applied reaches around 700°C. In some cases, the temperature reaches 300° C. under driving conditions such as mountain roads where brakes are frequently used.
- Cast iron has low high-temperature strength, and when it is thinned, it cannot secure the strength necessary for a disc rotor at high temperatures, so there was a problem that it was not possible to reduce the thickness and weight.
- cast iron since cast iron is formed by casting, if the disk rotor is made thin, it may not be possible to form it due to poor fluidity.
- Stainless steel is a material with excellent corrosion resistance, and SUS410, a martensitic stainless steel, is widely used for motorcycles and other motorcycles. This is because the disc rotor of a two-wheeled vehicle is exposed and easily visible, and corrosion resistance is emphasized. On the other hand, stainless steel has a problem that its thermal conductivity is inferior to that of cast iron. In motorcycles, the brake system is exposed, and because of its excellent cooling performance, stainless steel is used without problems in normal use. However, even in a two-wheeled vehicle, there is a problem that the disc rotor is excessively heated and the amount of wear of the brake pad increases under severe braking conditions such as racing.
- a disk rotor for a motorcycle is a ring-shaped disk, stamped from a sheet of stainless steel, and then manufactured by induction hardening.
- the disk rotors of current automobiles have a shape called a hat shape, which looks like a disk whose center is squeezed, and are manufactured by casting. Deep drawing is required to form such a shape by processing a stainless steel plate as a raw material.
- the stainless steel that has been used for motorcycles is martensitic stainless steel, which is extremely hard and difficult to deep draw.
- hot stamping which is press molding at high temperatures, has been widely used in recent years.
- the brake system including the tires, is housed in the tire house, so the disc rotor is difficult to cool and has low thermal conductivity.
- the disc rotor is excessively heated under severe braking conditions such as racing.
- martensitic stainless steel holding at a high temperature causes precipitation of C and N and recovery of dislocations, resulting in temper softening.
- temper softening occurs, there is a problem that the amount of pad wear increases excessively.
- abnormal wear of the disc rotors and brake pads leads to unstable braking effectiveness and shortened service life. That is, in order to apply martensitic stainless steel to the disc rotor of automobiles, it is necessary to meet the demand for reducing the amount of brake pad wear.
- Patent Documents 1 and 2 regarding stainless steel disk rotors. These documents describe steels in which the grain size of the prior austenite and the precipitated Nb are specified to improve the temper softening resistance. The document relates to an invention with improved temper softening resistance at 600°C. Further, Patent Documents 3 and 4 describe steel in which the grain size of prior austenite and precipitated Nb and Cu are defined to improve temper softening resistance. The document relates to an invention with improved temper softening resistance at 650°C. In addition, both inventions are used as components and utilize precipitates that precipitate when exposed to high temperatures due to braking. If the exposure time to high temperature is short, the time required for precipitation may not be reached.
- the present invention relates to a stainless steel plate for brake disc rotors that is excellent in hardenability, formability, temper softening resistance, and high-temperature strength.
- a component to be solved by the present invention is a braking system component, particularly a disc rotor.
- the processing of stainless steel plates into disc rotors is done by induction hardening, since motorcycles do not require large-scale processing, and for automobiles, it is done by hot stamping, which presses at high temperatures.
- Stainless steel sheets for hot stamping are manufactured by hot rolling and hot-rolled sheet annealing.
- the high temperature treatment of hot stamping also serves as quenching treatment. From the viewpoint of productivity, the quenching heat treatment is preferably performed at a low temperature for a short period of time.
- coarse Cr carbonitrides precipitate during hot-rolled sheet annealing when manufacturing stainless steel sheets. In order to obtain sufficient hardness as a disk rotor, it is necessary to ensure solid solution C and N.
- the steel plate must have formability. Specifically, press moldability at high temperatures during hot stamping for shaping into a hat shape is required.
- the present invention provides marten for brake disc rotors, which has excellent hardenability and formability when a steel plate is processed into brake disc rotors, and which has excellent temper softening resistance and high-temperature strength when used as brake disc rotors.
- a site-based stainless steel sheet, a brake disk rotor using the same, and a method for producing a martensite-based stainless steel sheet for a brake disk rotor are provided.
- the steel sheet used for brake disc rotors which is the object of the present invention, is manufactured through hot rolling and hot-rolled sheet annealing. Precipitates are deposited in the steel sheet during the hot rolling stage and the hot rolled sheet annealing stage. Precipitates include Cr carbonitrides and others. Of these precipitates, Cr carbonitride precipitates can be melted at a low temperature in a short period of time during heating for molding by appropriately controlling their size and dispersion state to improve hardenability and productivity. Improve.
- precipitates other than Cr carbonitrides do not dissolve during heating for molding, and because they are present in minute amounts in the product, the precipitates hinder the recovery of dislocations when used as parts, reducing temper softening resistance. Improve.
- the Cr carbonitride precipitates are coarse, dissolution requires a high temperature and a long period of time, resulting in a decrease in productivity.
- precipitates other than Cr carbonitrides are coarse, cracks are likely to occur during hot stamping and use, and the resistance to temper softening may not be improved, resulting in a decrease in high-temperature strength.
- the steel composition is appropriately controlled, the heating temperature before hot rolling is 1000 to 1200°C, the hot rolling finishing temperature is 800°C or lower, the cooling rate is 10°C/sec or higher, and the coiling temperature is 550°C or lower.
- Refinement of precipitates during hot rolling and hot-rolled sheet annealing firstly improves hardenability due to refinement of Cr carbonitride precipitates. It is possible to ensure sufficient quenching hardness as a disc rotor.
- the refinement of precipitates other than Cr carbonitrides improves temper softening resistance during use as a component, suppresses cracking during hot stamping, and further suppresses a decrease in high-temperature strength.
- Precipitates exist before use as a product sheet, that is, as a part, so high strength is exhibited even in a temperature range where temper softening does not occur.
- Precipitates during hot rolling and hot-rolled sheet annealing are mainly carbonitrides such as Fe, Ti, Nb, V, Cu, Mo, W, Zr, Ta, Hf, intermetallic compounds, and metallic Cu. .
- the gist of the present invention for solving the above problems is as follows. (1) in % by mass, C: 0.001 to 0.500%, N: 0.001 to 0.500%, Si: 0.01 to 5.00%, Mn: 0.010 to 12.000%, P: 0.001 to 0.100%, S: 0.0001 to 1.0000%, Cr: 10.0 to 35.0%, Ni: 0.010 to 5.000%, Cu: 0.0010 to 3.0000%, Mo: 0.0010 to 3.0000%, Nb: 0.0010 to 1.0000%, V: contains 0.0010 to 1.0000%,
- the balance is Fe and impurities, the average grain size of precipitates present in the matrix phase is 2 ⁇ m or less, the precipitates exist at a density of 0.01 to 20 pieces/ ⁇ m 2 , and the quenching represented by the following formula
- a martensitic stainless steel sheet for a brake disc rotor characterized by having a hardness index A of 200-800.
- A 2566 [% C] + 1282 [% N] - 12 [% Si] + 4 [% Cu] -6 [% Mo] -184 [% Nb] -125 [% V] +239
- Martensitic stainless steel for brake disc rotors according to any one of (1) to (5), characterized in that the finishing temperature during hot rolling is 800° C. or less and the winding temperature is 550° C. or less.
- a method of manufacturing a steel plate characterized in that the finishing temperature during hot rolling is 800° C. or less and the winding temperature is 550° C. or less.
- the hardenability and formability of the stainless steel plate are improved, and the temper softening resistance and high-temperature strength of the stainless steel plate after pseudo heat treatment are improved, providing a material suitable for disc rotors of automobiles and motorcycles, It is highly effective in improving appearance and safe braking in various environments.
- the martensitic stainless steel sheet means a stainless steel sheet having a martensitic phase of 80 area % or more when the steel sheet is quenched.
- the hot-rolled sheet (stainless steel sheet before hot-rolled and annealed) has the martensite phase
- the hot-rolled and annealed sheet (stainless steel sheet of the present invention) has the ferrite phase.
- the brake disc rotor of the present invention has a structure of martensite phase or martensite phase + ferrite phase. In some cases, a small amount of austenite phase remains.
- a preferred chemical composition (% by mass) of the stainless steel sheet of the present invention is described below.
- C is an element that dissolves in the matrix and has a great effect on hardness.
- the content of (A) is set because, depending on the heat treatment, carbides are formed, which deteriorates the formability and corrosion resistance, and lowers the high-temperature strength. Also, excessive reduction leads to an increase in refining costs, so the content of (B) is desirable. More preferably, the content of (C) is used.
- (A) 0.001 to 0.500%
- (B) 0.010 to 0.300%
- (C) 0.030-0.070%.
- N like C, is an element that forms a solid solution in the matrix and greatly affects hardness.
- the content of (A) was set because Ni forms nitrides depending on the heat treatment, deteriorating formability and corrosion resistance, and lowering high-temperature strength. Also, excessive reduction leads to an increase in refining costs, so the content of (B) is desirable. More preferably, the content of (C) is used.
- (A) 0.001 to 0.500%
- (B) 0.010 to 0.100%
- (C) 0.020-0.050%.
- Si is an element that is useful as a deoxidizing agent and also an element that improves oxidation resistance and high-temperature salt damage resistance.
- the content of (A) was set.
- the content of (B) is desirable.
- the content of (C) is desirable.
- Mn is an element added as a deoxidizing agent and contributes to an increase in high-temperature strength in a medium temperature range.
- excessive addition causes the formation of Mn-based oxides on the surface layer at high temperatures, which tends to cause poor scale adhesion and abnormal oxidation.
- Mo and W are added in combination, abnormal oxidation tends to occur more easily than the amount of Mn, so the content of (A) was set.
- the content of (B) is desirable in consideration of the pickling property and room temperature ductility in steel plate production. More preferably, the content of (C) is used.
- (A) 0.010 to 12.000%
- (B) 0.400 to 2.000%
- (C) 1.000-1.500%.
- P is an impurity mainly mixed from raw materials during steelmaking refining, and when the content increases, toughness and weldability decrease. For this reason, it is desirable to reduce the P content as much as possible.
- the use of a low-P raw material causes an increase in cost.
- the content exceeds 0.100%, the hardness is significantly increased, and the corrosion resistance, toughness, and pickling property are deteriorated.
- it is preferably 0.008 to 0.080%, more preferably 0.010 to 0.050%.
- S is an element that deteriorates corrosion resistance and oxidation resistance, but it not only improves workability by combining with Ti and C, but also forms sulfides by combining with Cr, Mn, etc., and exhibits lubricity. It is an element that Since the effect appears from 0.0001%, the lower limit was made 0.0001%. On the other hand, excessive addition combines with Ti and C to reduce the amount of solid-solution Ti and cause coarsening of precipitates, resulting in a decrease in high-temperature strength, so the upper limit was made 1.0000%. Further, 0.0005 to 0.0500% is desirable in consideration of refining cost and high-temperature oxidation characteristics. More preferably, it is 0.0010 to 0.0100%.
- Mo is an element effective for solid-solution strengthening at high temperatures, and is added to improve temper softening resistance, corrosion resistance, and high-temperature salt damage resistance.
- Nb is an element effective for improving temper softening resistance and high-temperature strength by solid-solution strengthening and precipitation strengthening of fine precipitates. It also has the role of fixing C and N as carbonitrides and contributing to the development of a recrystallized texture that affects the corrosion resistance and r-value of the product sheet (hot-rolled and annealed sheet).
- the steel sheet of the present invention is further characterized by having a quenching hardness index A of 200 to 800, which is represented by the following formula based on the component contents.
- [% element symbol] means the content (% by mass) of the element.
- the balance is Fe and impurities. Further, if necessary, the following components may be contained in place of part of the Fe.
- Ti is an element that combines with C, N, and S to improve corrosion resistance, intergranular corrosion resistance, normal temperature ductility, and deep drawability.
- adding an appropriate amount increases the solid solution amount of Nb and Mo during hot rolling annealing, improves high-temperature strength, and improves temper softening resistance and thermal fatigue properties. Since the effect is exhibited from 0.001% or more, the lower limit was made 0.001%.
- the addition exceeds 1.00%, the amount of solid solution Ti increases and the room temperature ductility decreases, and in addition, coarse Ti-based precipitates are formed, which become the starting points of cracks during hole expansion, resulting in press formability. deteriorate.
- the amount of Ti added is set to 1.00% or less. Further, 0.001 to 0.20% is desirable considering the occurrence of surface flaws and toughness.
- B is an element that improves the secondary workability, high-temperature strength, and thermal fatigue properties during press molding of the product.
- B brings about fine precipitations such as Laves phases, develops long-term stability of these precipitation strengthening, and contributes to suppression of strength reduction and improvement of thermal fatigue life. This effect is expressed at 0.0001% or more.
- excessive addition causes hardening, degrades intergranular corrosion resistance and oxidation resistance, and causes weld cracking.
- 0.0001 to 0.0050% is desirable. More preferably, it is 0.0001 to 0.0020%.
- Al is an element that improves oxidation resistance.
- it is useful as a solid-solution strengthening element for improving high-temperature strength and temper softening resistance. Its action is stably expressed from 0.001%.
- excessive addition causes hardening and significantly lowers uniform elongation and toughness, so the upper limit was made 4.0%.
- 0.003 to 2.0% is desirable.
- W is an element effective for solid-solution strengthening at high temperatures, and produces a Laves phase (Fe 2 W) to bring about precipitation strengthening.
- the Laves phase of Fe 2 (Nb, Mo, W) precipitates, but when W is added, the coarsening of the Laves phase is suppressed, the precipitation strengthening ability is improved, and the sintering The reversion softening resistance is also improved. It works with additions above 0.001%. On the other hand, addition of more than 3.0% increases the cost and lowers room-temperature ductility, so the upper limit was made 3.0%.
- the W addition amount is preferably 0.001 to 1.5%.
- Sn is an element that improves corrosion resistance, and is added as necessary to improve high temperature strength in the medium temperature range. These effects are expressed at 0.001% or more. On the other hand, if the addition exceeds 1.00%, the manufacturability and toughness are significantly lowered, so the content was made 1.00% or less. Furthermore, considering the oxidation resistance and manufacturing cost, 0.01 to 0.10% is desirable.
- Mg is sometimes added as a deoxidizing element, and is an element that refines the structure of the slab and contributes to the improvement of formability. Moreover, Mg oxide serves as precipitation sites for carbonitrides such as Ti(C,N) and Nb(C,N), and has the effect of finely dispersing and precipitating them. This action appears at 0.0001% or more and contributes to the improvement of toughness. However, excessive addition leads to deterioration of weldability, corrosion resistance and surface quality, so the upper limit was made 0.0100%. Considering refining cost, 0.0003 to 0.0010% is desirable.
- Sb contributes to the improvement of corrosion resistance and high-temperature strength, so 0.001% or more is added as necessary. Addition of more than 0.50% may excessively cause slab cracking and ductility deterioration during steel sheet production, so the upper limit is made 0.50%. Furthermore, considering refining cost and manufacturability, 0.01 to 0.30% is desirable.
- Zr is a carbonitride-forming element like Ti and Nb, and is an element that improves corrosion resistance and deep drawability, and is added as necessary. These effects are expressed at 0.001% or more. On the other hand, addition of more than 1.000% significantly deteriorates the manufacturability, so the content was made 1.000% or less. Furthermore, considering cost and surface quality, 0.001 to 0.200% is desirable.
- Ta and Hf combine with C and N and contribute to the improvement of toughness, so 0.001% or more is added as necessary.
- addition of more than 1.00% increases the cost and significantly deteriorates manufacturability, so the upper limit is made 1.00%.
- 0.01 to 0.08% is desirable.
- Co contributes to the improvement of high-temperature strength, so 0.001% or more is added as necessary. Addition of more than 1.00% leads to deterioration of toughness, so the upper limit is made 1.00%. Furthermore, considering the refining cost and manufacturability, 0.01 to 0.10% is desirable. More preferably, it is 0.01 to 0.03%.
- Ca may be added for desulfurization, and this effect is expressed at 0.0001% or more.
- addition of more than 0.0200% generates coarse CaS, degrading toughness and corrosion resistance, so the upper limit was made 0.0200%.
- 0.0003 to 0.0020% is desirable.
- REM may be added as necessary from the viewpoint of improving toughness and oxidation resistance by refining various precipitates, and this effect is manifested at 0.001% or more.
- 0.001 to 0.05% is desirable.
- REM rare earth element
- Sc scandium
- Y yttrium
- Lu Lu
- Ga may be added at 0.5000% or less in order to improve corrosion resistance and suppress hydrogen embrittlement.
- the lower limit is preferably 0.0001%.
- 0.0020% or less is preferable from the viewpoints of manufacturability and cost as well as ductility and toughness.
- Bi or the like may be added in an amount of 0.001 to 0.1% as needed.
- general harmful elements such as As and Pb and impurity elements as much as possible.
- the product sheet (hot rolled and annealed sheet) should contain fine precipitates. is important.
- the composition of each element should be appropriately controlled, dislocations should be made difficult to recover during hot rolling, and dislocations should be used as nucleation sites.
- the hot rolling finish temperature is set to 800° C. or lower
- the cooling rate is set to 10° C./sec or higher
- the winding temperature is set to 550° C. or lower.
- the product sheet (hot-rolled and annealed sheet) must have precipitates with a specific size and density.
- the precipitates are classified into Cr carbonitride precipitates and other precipitates.
- Other precipitates are mainly carbonitrides such as Fe, Ti, Nb, V, Cu, Mo, W, Zr, Ta and Hf, intermetallic compounds and metallic Cu.
- the average grain size of precipitates present in the mother phase is 2 ⁇ m or less, and the number of precipitates is 0.01 to 20/ ⁇ m 2 . It is defined as existing in density. Some precipitates dissolve at the temperature of the quenching heat treatment, while others do not. Cr carbonitride dissolves, and other precipitates hardly dissolve.
- Processing into disk rotors is performed by hot stamping or induction hardening, and the heating time for hardening heat treatment is generally very short for productivity.
- the Cr carbonitrides precipitated during hot rolling or hot-rolled sheet annealing must be dissolved even by heating for a short period of time, and solid solution C and N must be ensured. Since the Cr carbonitrides are present in fine amounts, they are easily dissolved and contribute to ensuring solid solution C and N, thereby improving the hardenability.
- the average grain size of precipitates present in the matrix phase is 2 ⁇ m or less, and the precipitates are finely present at a density of 0.01 to 20/ ⁇ m 2 , so that Cr carbonitrides can be formed in a short time during quenching heat treatment. Dissolves even when heated. If the average grain size exceeds 2 ⁇ m, the Cr carbonitride cannot be completely dissolved by heating for a short period of time during the quenching heat treatment, and sufficient dissolved C and N cannot be secured, resulting in insufficient quenching hardness. If the heating time is lengthened, productivity will be hindered.
- Precipitates other than Cr carbonitrides are hardly dissolved by heating for quenching heat treatment, and are finely present in the product that has been formed and quenched to prevent the movement of dislocations. Contributes to suppression of deterioration in high-temperature strength.
- the precipitates are made finer, they are less likely to become starting points for cracks during working, and formability can be improved. That is, the average grain size of the precipitates present in the matrix phase is 2 ⁇ m or less, and the precipitates are present finely at a density of 0.01 to 20/ ⁇ m 2 , so that the precipitates effectively move dislocations. and contributes to improved temper softening resistance and high temperature strength.
- the average grain size of the precipitates exceeds 2 ⁇ m, they are less likely to act as resistance during movement of dislocations, and contribute less to the improvement of temper softening resistance and high-temperature strength. In addition, it tends to become a starting point of cracks during hot stamping or use, which impairs formability. If the density of the precipitates is less than 0.01/ ⁇ m 2 , the distance between dislocation pinning is widened, so that it is difficult to resist the movement of dislocations. If the density of precipitates exceeds 20/ ⁇ m 2 , the strength will be excessively increased and cracks will easily occur. From the above, the precipitates are defined as having an average grain size of 2 ⁇ m or less in the matrix phase after hot-rolled sheet annealing, and having a density of 0.01 to 20/ ⁇ m 2 . do.
- the average grain size of precipitates is preferably 5 nm or more and 1.5 ⁇ m or less. More desirably, the thickness is 5 nm or more and 1.0 ⁇ m or less.
- the density of precipitates is desirably 0.1/ ⁇ m 2 or more and 20/ ⁇ m 2 or less. More desirably, it is 1/ ⁇ m 2 or more and 20/ ⁇ m 2 or less.
- a transmission electron microscope for example, a 200 kV field emission transmission electron microscope JEM2100F manufactured by JEOL Ltd.
- an attached EDS device for example, a 200 kV field emission type transmission electron microscope manufactured by JEOL Ltd.
- JEM2100F a transmission electron microscope
- the sample was collected by ion milling so that t/4 depth (t is the thickness of the steel sheet) in the thickness direction of the steel sheet could be observed, and 10 arbitrary points were observed and analyzed at a magnification of 50,000. At this magnification, it is possible to observe the state of precipitates almost uniformly.
- the composition of Fe, Cr, Si, Mn, Ti, Nb, V, Cu, Mo, W, Zr, Ta, and Hf was quantified by mass% with an EDS device, and the addition of steel sheet components If a value greater than the amount was detected, it was regarded as a precipitate.
- the grain size and density of the precipitates are calculated by observing the sample in the same manner, and after observing these places, coloring only the precipitates and performing image processing, using image analysis software "ImageJ" manufactured by NIH.
- the particle size of each particle was calculated by equivalent circle diameter, and the average particle size and average density of 5 fields of view were calculated.
- the martensitic stainless steel sheet for brake disc rotors of the present invention is characterized by having an elongation at break of 50% or more at 1050°C. This makes it possible to achieve excellent formability as a steel sheet.
- the martensitic stainless steel sheet for a brake disc rotor of the present invention is heated to 1050 ° C., retained for 5 seconds or more, and then subjected to hot stamping simulated heat treatment (pseudo heat treatment) for water cooling. It is characterized in that the decrease in hardness after further tempering at 700° C. for 10 minutes is Hv 150 or less. This makes it possible to achieve excellent temper softening resistance as a brake disc rotor.
- the martensitic stainless steel plate for brake disc rotors of the present invention is characterized in that the 0.2% yield strength of the material at 700°C is 50 MPa or more when subjected to the above-described pseudo heat treatment. As a result, it is possible to achieve excellent high-temperature strength as a brake disc rotor.
- the brake disc rotor of the present invention uses the martensitic stainless steel plate for brake disc rotors of the present invention.
- the martensitic stainless steel sheet for a brake disc rotor of the present invention is subjected to hot stamping to form the shape of a brake disc rotor, and is quenched by heat treatment during hot stamping. It has excellent temper softening resistance and excellent high temperature strength.
- the method for producing a stainless steel sheet for a brake disc rotor according to the present invention comprises the steps of steelmaking, hot rolling, annealing, and pickling.
- steelmaking a method of smelting steel containing the above-mentioned essential components and optionally added components in a converter and then secondary refining is suitable.
- the melted molten steel is made into a slab according to a known casting method (continuous casting).
- the slab is heated to a specified temperature and hot-rolled continuously to a specified thickness.
- Hot rolling is performed by a hot rolling mill consisting of multiple stands and then coiled.
- the carbonitrides can be solid-dissolved in the matrix even with short-time heating during hot stamping.
- dislocations should be made difficult to recover during hot rolling, and dislocations should be used as nucleation sites.
- the hot rolling finishing temperature is set to 800° C. or lower, and the coiling temperature is set to 550° C. or lower. Desirably, from the viewpoint of productivity, the finishing temperature is 750° C.
- the winding temperature is 500° C. or lower. More preferably, the finishing temperature is 700°C or lower, the winding temperature is 450°C or lower, and the finishing temperature is more preferably lower than 700°C.
- the cooling rate between finishing and winding is preferably 10° C./sec or more and less than 25° C./sec.
- the wound hot-rolled coil is annealed at a predetermined temperature using an annealing furnace and then pickled.
- Annealing temperature is 820° C. or higher and 900° C. or lower for 3 hours or longer and 5 hours or lower.
- an existing pickling method may be applied.
- a martensitic stainless steel plate for a brake disc rotor manufactured in this manner can be used with a plate thickness of 2.0 mm or more and 15.0 mm or less.
- the length is preferably 3.0 mm or more and 13.0 mm or less, more preferably 4.1 mm or more and 9.0 mm or less.
- the hot-rolled and annealed sheet was subjected to hot stamping simulative heat treatment (hereinafter simply referred to as "pseudo heat treatment") in which the steel was heated to 1050°C, retained for 5 seconds or longer, and then water-cooled. After the simulated heat treatment, the steel plate was pickled. Hardenability of the steel sheet, temper softening resistance after hot stamping, and high-temperature strength were evaluated by evaluating the steel sheet after the simulated heat treatment.
- the difference in hardness between the 900°C quenched and heat treated material and the 1100°C quenched and heat treated material is 50 or less in Hv, it can be applied to a general disc rotor, so the 900°C quenched and heat treated material and 1100° C. quenching heat-treated materials with a difference in hardness of Hv of 50 or less was judged to pass (“A” mark in “Hardenability” in Tables 3 and 4).
- tempered and softened material a test piece obtained by subjecting the simulated heat-treated material to tempering treatment at 700 ° C. for 10 minutes
- the hardenability, press formability, temper softening resistance after simulated heat treatment, and 0.2% yield strength at 700°C of the steel sheets are superior to the comparative examples. ing. Any one of the difference between the 900°C quenching hardness and the 1100°C quenching hardness, the difference in hardness before and after tempering, the breaking elongation at 1050°C, and the 0.2% proof stress at 700°C fails. In that case, it was determined that the application as a disc rotor is inappropriate. From this, it can be seen that the steel specified in the present invention is excellent in hardenability, temper softening resistance, formability and high temperature strength.
- Comparative Examples B1 and B2 the concentrations of C and N deviated from the upper limits, respectively, and a large amount of coarse carbonitrides were precipitated, so the Cr carbides were not sufficiently solidified by the simulated heat treatment, and the temper softening resistance was poor. In addition, coarse carbonitrides do not contribute to precipitation strengthening and become starting points for cracks, so the 0.2% proof stress at 700° C. and press formability were poor.
- Comparative Example B3 the Si concentration exceeded the upper limit. Since Si increases the activity of C, coarse carbide precipitates, resulting in insufficient temper softening resistance, 0.2% yield strength at 700° C., and press formability.
- Comparative Example B4 the Mn concentration was below the lower limit, and the 0.2% yield strength at 700°C was insufficient.
- the P concentration exceeded the upper limit and a large amount of coarse phosphide precipitated, so the 0.2% proof stress at 700°C was insufficient.
- press formability was insufficient due to hardening.
- the S concentration exceeded the upper limit, the Ti-based precipitates were coarsened, and the 0.2% yield strength at 700°C was insufficient.
- Comparative Example B7 the Cr concentration exceeded the upper limit, and a large amount of coarse Cr carbonitrides precipitated, so that the hardenability, temper softening resistance, and 0.2% yield strength at 700°C were insufficient.
- the press moldability was poor due to hardening.
- the Cu concentration was below the lower limit, Cu precipitation did not occur sufficiently, precipitation strengthening was insufficient, and temper softening resistance and 0.2% yield strength at 700°C were insufficient.
- Comparative Examples B9, 10, and 11 the concentrations of Mo, Nb, and V deviated from the lower limits, and the precipitates containing each element were not sufficiently precipitated, and the precipitation strengthening was insufficient, resulting in a temper softening resistance of 0.2% at 700 ° C. lacked endurance.
- Comparative Example B12 the hot-rolling finishing temperature and the hot-rolling coiling temperature deviated from the upper limits, Cr carbonitrides and precipitates were excessively coarsened, and temper softening resistance, 0.2% yield strength at 700 ° C., and press formability were poor. was bad.
- Comparative Example B13 the Ni concentration was below the lower limit, and the 0.2% yield strength at 700°C was insufficient.
Abstract
Description
こうした背景のなか、自動車における近年の美観や成形性、薄肉軽量化の要請に対応するためには、ディスクローターのステンレス鋼化が必要となる。
(1)質量%にて、
C:0.001~0.500%、
N:0.001~0.500%、
Si:0.01~5.00%、
Mn:0.010~12.000%、
P:0.001~0.100%、
S:0.0001~1.0000%、
Cr:10.0~35.0%、
Ni:0.010~5.000%、
Cu:0.0010~3.0000%、
Mo:0.0010~3.0000%、
Nb:0.0010~1.0000%、
V:0.0010~1.0000%を含有し、
残部がFeおよび不純物であり、母相に存在する析出物の平均粒径が2μm以下であり、析出物が0.01~20個/μm2の密度で存在し、下記式で表される焼入れ硬さ指標Aが200~800であることを特徴とするブレーキディスクローター用マルテンサイト系ステンレス鋼板。
A=2566[%C]+1282[%N]-12[%Si]+4[%Cu]
-6[%Mo]-184[%Nb]-125[%V]+239
(2)前記Feの一部に替え、質量%にてさらに、
Ti:0.001~1.00%、
B:0.0001~0.0100%、
Al:0.001~4.0%、
W:0.001~3.0%、
Sn:0.001~1.00%、
Mg:0.0001~0.0100%、
Sb:0.001~0.50%、
Zr:0.001~1.000%、
Ta:0.001~1.00%、
Hf:0.001~1.000%、
Co:0.001~1.00%、
Ca:0.0001~0.0200%、
REM:0.001~0.50%、
Ga:0.0001~0.5000%
の1種以上を含有することを特徴とする(1)に記載のブレーキディスクローター用マルテンサイト系ステンレス鋼板。
(4)(1)~(3)のいずれか1つに記載のブレーキディスクローター用マルテンサイト系ステンレス鋼板であって、1050℃に加熱後に5秒以上滞留させ、その後水冷するホットスタンプ模擬熱処理(以下単に「疑似熱処理」という。)を施したときの硬さに対して、前記疑似熱処理後にさらに700℃で10分焼き戻し後の硬さの低下代がHvで150以下であることを特徴とするブレーキディスクローター用マルテンサイト系ステンレス鋼板。
(5)(1)~(4)のいずれか1つに記載のブレーキディスクローター用マルテンサイト系ステンレス鋼板であって、1050℃に加熱後に5秒以上滞留させ、その後水冷するホットスタンプ模擬熱処理(以下単に「疑似熱処理」という。)を施したときに、材料の700℃における0.2%耐力が50MPa以上となることを特徴とするブレーキディスクローター用マルテンサイト系ステンレス鋼板。
Cは、母相に固溶し硬さに大きな影響を与える元素である。熱処理によっては炭化物を生成し、成形性や耐食性を劣化させ、高温強度の低下をもたらすため(A)の含有量とした。また過度の低減は精錬コストの増加に繋がるため(B)の含有量が望ましい。さらに望ましくは(C)の含有量とする。
(A)=0.001~0.500%、
(B)=0.010~0.300%、
(C)=0.030~0.070%。
(A)=0.001~0.500%、
(B)=0.010~0.100%、
(C)=0.020~0.050%。
(A)=0.01~5.00%、
(B)=0.10~1.00%、
(C)=0.20~0.40%。
(A)=0.010~12.000%、
(B)=0.400~2.000%、
(C)=1.000~1.500%。
(A)=10.0~35.0%、
(B)=10.5~15.0%、
(C)=11.0~13.0%。
(A)=0.010~5.000%、
(B)=0.030~0.600%、
(C)=0.050~0.080%。
(A)=0.0010~3.0000%、
(B)=0.0100~2.0000%、
(C)=0.2000~1.6000%。
(A)=0.0010~3.0000%、
(B)=0.0100~1.0000%、
(C)=0.0300~0.5000%。
(A)=0.0010~1.0000%、
(B)=0.0100~0.7000%、
(C)=0.1000~0.5000%。
(A)=0.0010~1.0000%、
(B)=0.0030~0.5000%、
(C)=0.1000~0.4000%。
A=2566[%C]+1282[%N]-12[%Si]+4[%Cu]
-6[%Mo]-184[%Nb]-125[%V]+239
即ち、母相に存在する析出物の平均粒径が2μm以下であり、析出物が0.01~20個/μm2の密度で微細に存在することとで、析出物が転位の移動を効果的に妨げ、焼き戻し軟化抵抗および高温強度の向上に寄与する。
これによりディスクローターに適用可能なステンレス鋼板を提供することに成功した。
本発明のブレーキディスクローター用ステンレス鋼板の製造方法は、製鋼-熱間圧延-焼鈍-酸洗の各工程よりなる。製鋼においては、前記必須成分および必要に応じて添加される成分を含有する鋼を、転炉溶製し続いて2次精錬を行う方法が好適である。溶製した溶鋼は、公知の鋳造方法(連続鋳造)に従ってスラブとする。
比較例B3はSi濃度が上限を外れた。SiはCの活量を上げるため粗大な炭化物が析出し、焼き戻し軟化抵抗、700℃における0.2%耐力、プレス成形性が不足した。
比較例B4はMn濃度が下限を外れ、700℃における0.2%耐力が不足した。
比較例B5はP濃度が上限を外れ、粗大なリン化物が多量に析出したため、700℃における0.2%耐力が不足した。また硬質化によってプレス成形性が不足した。
比較例B6はS濃度が上限を外れ、Ti系の析出物を粗大化させ、700℃における0.2%耐力が不足した。
比較例B7はCr濃度が上限を外れ、粗大なCr炭窒化物が多量に析出したため、焼き入れ性、焼き戻し軟化抵抗、700℃における0.2%耐力が不足した。また硬質化によってプレス成形性が不良であった。
比較例B8はCu濃度が下限を外れ、Cu析出が十分生じず、析出強化が不十分となり焼き戻し軟化抵抗および700℃における0.2%耐力が不足した。
比較例B9、10、11はそれぞれMo、Nb、V濃度が下限を外れ、各元素を含む析出物が十分析出せず、析出強化が不十分となり焼き戻し軟化抵抗および700℃における0.2%耐力が不足した。
比較例B13はNi濃度が下限を外れ、700℃における0.2%耐力が不足した。
Claims (7)
- 質量%にて、
C:0.001~0.500%、
N:0.001~0.500%、
Si:0.01~5.00%、
Mn:0.010~12.000%、
P:0.001~0.100%、
S:0.0001~1.0000%、
Cr:10.0~35.0%、
Ni:0.010~5.000%、
Cu:0.0010~3.0000%、
Mo:0.0010~3.0000%、
Nb:0.0010~1.0000%、
V:0.0010~1.0000%を含有し、
残部がFeおよび不純物であり、母相に存在する析出物の平均粒径が2μm以下であり、析出物が0.01~20個/μm2の密度で存在し、下記式で表される焼入れ硬さ指標Aが200~800であることを特徴とするブレーキディスクローター用マルテンサイト系ステンレス鋼板。
A=2566[%C]+1282[%N]-12[%Si]+4[%Cu]
-6[%Mo]-184[%Nb]-125[%V]+239 - 前記Feの一部に替え、質量%にてさらに、
Ti:0.001~1.00%、
B:0.0001~0.0100%、
Al:0.001~4.0%、
W:0.001~3.0%、
Sn:0.001~1.00%、
Mg:0.0001~0.0100%、
Sb:0.001~0.50%、
Zr:0.001~1.000%、
Ta:0.001~1.00%、
Hf:0.001~1.000%、
Co:0.001~1.00%、
Ca:0.0001~0.0200%、
REM:0.001~0.50%、
Ga:0.0001~0.5000%
の1種以上を含有することを特徴とする請求項1に記載のブレーキディスクローター用マルテンサイト系ステンレス鋼板。 - 1050℃における破断伸びが50%以上となることを特徴とする請求項1又は請求項2に記載のブレーキディスクローター用マルテンサイト系ステンレス鋼板。
- 請求項1~請求項3のいずれか1項に記載のブレーキディスクローター用マルテンサイト系ステンレス鋼板であって、1050℃に加熱後に5秒以上滞留させ、その後水冷するホットスタンプ模擬熱処理(以下単に「疑似熱処理」という。)を施したときの硬さに対して、前記疑似熱処理後にさらに700℃で10分焼き戻し後の硬さの低下代がHvで150以下であることを特徴とするブレーキディスクローター用マルテンサイト系ステンレス鋼板。
- 請求項1~請求項4のいずれか1項に記載のブレーキディスクローター用マルテンサイト系ステンレス鋼板であって、1050℃に加熱後に5秒以上滞留させ、その後水冷するホットスタンプ模擬熱処理(以下単に「疑似熱処理」という。)を施したときに、材料の700℃における0.2%耐力が50MPa以上となることを特徴とするブレーキディスクローター用マルテンサイト系ステンレス鋼板。
- 請求項1~請求項5のいずれか1項に記載のブレーキディスクローター用マルテンサイト系ステンレス鋼板を用いてなるブレーキディスクローター。
- 熱延時の仕上げ温度を800℃以下、巻き取り温度を550℃以下にすることを特徴とする請求項1~請求項5のいずれか1項に記載のブレーキディスクローター用マルテンサイト系ステンレス鋼板の製造方法。
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