WO2021149601A1 - Martensitic stainless steel sheet and martensitic stainless steel member - Google Patents
Martensitic stainless steel sheet and martensitic stainless steel member Download PDFInfo
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- WO2021149601A1 WO2021149601A1 PCT/JP2021/001195 JP2021001195W WO2021149601A1 WO 2021149601 A1 WO2021149601 A1 WO 2021149601A1 JP 2021001195 W JP2021001195 W JP 2021001195W WO 2021149601 A1 WO2021149601 A1 WO 2021149601A1
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- 229910001105 martensitic stainless steel Inorganic materials 0.000 title claims abstract description 36
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 87
- 239000010959 steel Substances 0.000 claims abstract description 87
- 229910000859 α-Fe Inorganic materials 0.000 claims abstract description 12
- 239000000203 mixture Substances 0.000 claims description 12
- 239000012535 impurity Substances 0.000 claims description 4
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 230000000171 quenching effect Effects 0.000 description 53
- 238000010791 quenching Methods 0.000 description 52
- 230000007797 corrosion Effects 0.000 description 47
- 238000005260 corrosion Methods 0.000 description 47
- 238000001816 cooling Methods 0.000 description 21
- 238000010438 heat treatment Methods 0.000 description 13
- 230000000694 effects Effects 0.000 description 12
- 238000005496 tempering Methods 0.000 description 12
- 230000007423 decrease Effects 0.000 description 10
- 238000011156 evaluation Methods 0.000 description 10
- 238000004519 manufacturing process Methods 0.000 description 10
- 239000011651 chromium Substances 0.000 description 9
- 229910000734 martensite Inorganic materials 0.000 description 9
- 229910001566 austenite Inorganic materials 0.000 description 8
- 150000001247 metal acetylides Chemical class 0.000 description 8
- 238000000034 method Methods 0.000 description 7
- 238000001556 precipitation Methods 0.000 description 7
- 238000005498 polishing Methods 0.000 description 6
- 230000015572 biosynthetic process Effects 0.000 description 5
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 5
- 206010070834 Sensitisation Diseases 0.000 description 4
- 239000003153 chemical reaction reagent Substances 0.000 description 4
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- 239000000463 material Substances 0.000 description 3
- 150000003839 salts Chemical class 0.000 description 3
- 239000007921 spray Substances 0.000 description 3
- 229910001220 stainless steel Inorganic materials 0.000 description 3
- 239000010935 stainless steel Substances 0.000 description 3
- 238000009628 steelmaking Methods 0.000 description 3
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 2
- 229910000604 Ferrochrome Inorganic materials 0.000 description 2
- 229910045601 alloy Inorganic materials 0.000 description 2
- 239000000956 alloy Substances 0.000 description 2
- 229910052804 chromium Inorganic materials 0.000 description 2
- 230000000052 comparative effect Effects 0.000 description 2
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- 229910052748 manganese Inorganic materials 0.000 description 2
- 238000005259 measurement Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 229910052759 nickel Inorganic materials 0.000 description 2
- 229910000744 A-2 tool steel Inorganic materials 0.000 description 1
- 208000009205 Tinnitus Diseases 0.000 description 1
- 238000009825 accumulation Methods 0.000 description 1
- QZPSXPBJTPJTSZ-UHFFFAOYSA-N aqua regia Chemical compound Cl.O[N+]([O-])=O QZPSXPBJTPJTSZ-UHFFFAOYSA-N 0.000 description 1
- 229910052797 bismuth Inorganic materials 0.000 description 1
- 238000005422 blasting Methods 0.000 description 1
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- 238000009749 continuous casting Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
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- 238000010191 image analysis Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 238000000465 moulding Methods 0.000 description 1
- 229910052758 niobium Inorganic materials 0.000 description 1
- 238000005457 optimization Methods 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000010422 painting Methods 0.000 description 1
- 238000007747 plating Methods 0.000 description 1
- 230000003449 preventive effect Effects 0.000 description 1
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- 239000002994 raw material Substances 0.000 description 1
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- 238000010998 test method Methods 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000009941 weaving Methods 0.000 description 1
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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
- 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
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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
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
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- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/56—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering characterised by the quenching agents
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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
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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
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- C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
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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
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- C21D9/18—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for knives, scythes, scissors, or like hand cutting tools
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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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- C22C38/04—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
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- C22C38/48—Ferrous alloys, e.g. steel alloys containing chromium with nickel with niobium or tantalum
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- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
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- C22C38/50—Ferrous alloys, e.g. steel alloys containing chromium with nickel with titanium or zirconium
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- C21D2211/00—Microstructure comprising significant phases
- C21D2211/008—Martensite
Definitions
- the present invention relates to a martensitic stainless steel sheet and a martensitic stainless steel member having excellent corrosion resistance after quenching. More specifically, the present invention relates to martensitic stainless steel having excellent corrosion resistance even when air-cooled and hardened, which is used for manufacturing Western tableware knives, looms, tools, disc brakes and the like.
- Martensitic stainless steel sheets such as SUS420J1 and SUS420J2 steel are generally used for tools such as Western tableware knives (table knives), scissors, weaving machines, and calipers. In such applications, it is difficult to use plating, painting, and rust preventive oil, and the material itself is required to have rust resistance. It is also important that it does not wear easily, and high hardness is required.
- the manufacturing process of Western tableware knives, etc. is usually made by die-cutting from a steel plate, heating, quenching, and then polishing to make a knife.
- the quenching process is often performed by air cooling, which also depends on the characteristics of the martensitic stainless steel sheet, which has excellent quenching properties.
- Patent Document 1 discloses a martensitic stainless steel that is air-cooled and has excellent corrosion resistance during quenching.
- N is added up to about 0.06% as an element for improving corrosion resistance.
- Patent Document 2 discloses steel to which N is further added. Further, Patent Document 3 discloses a steel in which N is further increased by using special equipment.
- the present inventors first investigated the rusting situation of the table knife in detail. As a result, it was clarified that the rusting site starts from the end face of the steel sheet, more specifically, the central part of the thickness of the steel sheet. Furthermore, the formation of a ⁇ ferrite phase ( ⁇ Fe phase) due to macrosegregation was confirmed in the central part of the thickness of the steel plate, and the grain boundaries of this ⁇ Fe became the accumulation sites of carbides, and the carbides were melted by heating during quenching. It was found that the mechanism of carbide formation is that intergranular precipitation occurs during subsequent cooling, resulting in sensitization and intergranular corrosion.
- ⁇ Fe phase ⁇ ferrite phase
- the rusting depends on the cooling rate at the time of quenching.
- the cooling rate varies greatly depending on the quenching equipment, but when evaluated by the average cooling rate from the quenching temperature to 600 ° C, which is the temperature at which the precipitation of carbides is almost completed, the cooling rate exceeds 100 ° C / s in water quenching.
- the cooling rate is only about 5 ° C./s, and the precipitation of carbides cannot be suppressed and the quenching occurs. It turns out that is likely to occur.
- a martensitic stainless steel sheet having a ⁇ p of 120 or more represented by the following formula (1) When the martensitic stainless steel sheet is held at 1050 ° C. for 30 minutes, then air-cooled and quenched, and tempered at 150 ° C. for 30 minutes, the area of ⁇ ferrite ( ⁇ Fe) present in the center of the plate thickness in the plate thickness cross section.
- ⁇ p 420C + 470N + 30Ni + 7Mn + 9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-52Al + 189 ... Equation (1)
- the element symbol in the formula (1) means the content (mass%) of the element.
- the steel composition is further replaced with a part of the Fe in mass%.
- Mo 0.01-1.0%
- Ti 0.005 to 0.050%
- the steel composition is further replaced with a part of the Fe in mass%. Sn: 0.01 to 0.10%, Bi: 0.01 to 0.20%
- the martensitic stainless steel sheet according to (1) or (2) which contains one or two of the above.
- the ⁇ p represented by the above formula (1) is 120 or more, and Further, a martensitic stainless steel member having an area ratio of ⁇ ferrite ( ⁇ Fe) existing in the central portion of the plate thickness in a plate thickness cross section of less than 0.1%.
- the martensitic stainless steel sheet of the present invention has excellent corrosion resistance, especially end face corrosion resistance, while maintaining sufficient hardness to withstand use for martensitic stainless steel applications such as table knives and other Western tableware. Therefore, when it is used as a martensitic stainless steel member such as a Western tableware knife, it can be expected to have an effect of improving corrosion resistance and prolonging the product life.
- C is an element that determines the quenching hardness together with N, and is required to be 0.100% or more in order to obtain the hardness required for a Western tableware knife. It is preferably 0.110% or more, and 0.120% or more.
- the quenching hardness becomes larger than necessary, the load during polishing increases, and the toughness also decreases.
- Cr carbides are likely to precipitate during air-cooling quenching and the corrosion resistance is likely to be impaired, so the content is set to 0.170% or less. It is preferably 0.155% or less.
- Si 0.25 to 0.60% Since Si is necessary for deoxidation in steelmaking and is also effective in suppressing the formation of oxide scale after quenching heat treatment, it is contained in an amount of 0.25% or more. If it is less than 0.25%, an oxidation scale is excessively generated, which increases the final polishing load. However, excessive addition suppresses austenite production and impairs hardenability, so the content is set to 0.60% or less.
- Mn 0.10 to 0.60%
- Mn is an austenite-stabilizing element and is necessary for ensuring hardness and the amount of martensite during quenching. Therefore, it is contained in an amount of 0.10% or more. However, in order to promote the formation of oxide scale during quenching and increase the subsequent polishing load, the content is set to 0.60% or less. Further, if it is added excessively, a large amount of MnS is generated and the corrosion resistance is also lowered.
- P 0.035% or less
- P is an element contained as an impurity in alloys such as hot metal and ferrochrome, which are raw materials. Since it is an element harmful to the toughness of the steel sheet after hot rolling annealing and quenching, its content shall be 0.035% or less. Excessive addition reduces hot workability and corrosion resistance.
- S 0.015% or less S has a small solid solubility in the austenite phase and segregates at the grain boundaries to promote a decrease in hot workability. Further, if it is contained in an excessive amount, a large amount of MnS is generated and the corrosion resistance is also lowered. Therefore, the S content is set to 0.015% or less.
- Cr 11.0 to 15.0% Cr is required at least 11.0% or more in order to maintain corrosion resistance as a Western tableware knife. On the other hand, since it also has the effect of narrowing the stable temperature of austenite, it should be 15.0% or less. Preferably, it is 12.0 or more. The upper limit is preferably 14.0% or less. The range is preferably 12.0 to 14.0%.
- Ni 0.05-0.60% Like Mn, Ni is an austenite-stable element and is necessary for securing hardness and the amount of martensite during quenching. It also has the effect of improving corrosion resistance. Therefore, it is contained in an amount of 0.05% or more. However, excessive addition may increase the stability of the ⁇ phase and decrease the amount of martensite, and Ni is more expensive than other elements, so the upper limit is set to 0.60%.
- Cu 0.006 to 0.50%
- Cu is an austenite-stable element like Mn and Ni, and is an element that improves corrosion resistance. Although it is an element that cannot be avoided from scrap during steelmaking, it is contained in an amount of 0.006% or more in order to improve corrosion resistance. It is preferably contained in an amount of 0.02% or more. More preferably, the content is 0.05% or more. On the other hand, excessive content reduces hot workability and the like, so the content should be 0.50% or less. Although it is cheaper than Ni, it is relatively expensive, so its addition is an element that we want to keep as low as possible.
- V 0.010 to 0.10%
- V is an element that is often inevitably mixed with ferrochrome or the like, which is an alloy element. Since it is difficult to reduce the load and the steelmaking process is overloaded, 0.010% or more is contained. However, since excessive content narrows the austenite formation temperature range, it was set to 0.10% or less. Further, if it is added in an excessive amount, VN is formed and N is immobilized, which causes a decrease in hardness and a decrease in corrosion resistance, which is not preferable.
- Al 0.05% or less Al is an effective element for deoxidation, but its content is 0.05 because excessive content produces CaS, which is a soluble inclusion, during hot rolling and reduces corrosion resistance. % Or less.
- the Al content is preferably 0.001% or more. Al may not be contained.
- N 0.040% or more and less than 0.060%
- N is an element that determines quenching hardness together with C and is an important element in the present invention that improves corrosion resistance. Therefore, in the present invention, it is contained in an amount of 0.040% or more. 0.045% or more is preferable.
- N is excessively contained, bubble defects are likely to occur in the slab, and conversely, the corrosion resistance is lowered, and the manufacturing cost is increased in the secondary refining by VOD or the like.
- VOD secondary refining by VOD or the like.
- N should be low, and the content thereof should be less than 0.060%. Preferably, it is 0.057% or less.
- C + 1 / 2N 0.130 to 0.190%
- the elements that determine the hardness of the martensite phase in steel are C and N, the sum of which contributes to the hardness. According to the study of the present inventor, the contribution of N to hardness is half that of C, and it is necessary that C + 1 / 2N is 0.130% or more in order to obtain the hardness required for a Western tableware knife. .. It is preferably 0.150% or more. On the other hand, if C + 1 / 2N is excessive, the quenching hardness is excessively increased, and the toughness of the intermediate material (slab or the like) in the product or manufacturing process is impaired. It is preferably 0.180% or less, and may be 0.175% or less.
- ⁇ p may be adjusted to 130 or more, or 140 or more. In the present invention, it may be 170 or less, and may be 150 or less.
- the steel composition of the present invention contains the above components, and the balance consists of Fe and impurities.
- the steel composition in order to improve the rust resistance and corrosion resistance in place of a part of the Fe in addition to the elements described above, the steel composition is Mo, Nb, Ti and Sn, Bi. Elements can be added.
- Mo 0.01-1.0% Mo is an element that improves corrosion resistance, and its effect is exhibited by adding 0.01% or more. However, Mo is also an expensive element, and even if it is added excessively, the effect is not clear, and the upper limit is 1.0%.
- Ti 0.005 to 0.050%
- Ti is an element that suppresses sensitization and deterioration of corrosion resistance due to precipitation of chromium carbonitride in stainless steel by forming carbonitride. The effect is expressed at 0.005%. However, excessive addition destabilizes the martensite phase and reduces the hardness, so the upper limit is 0.050%.
- Nb 0.005 to 0.050%
- Nb is an element that suppresses sensitization and deterioration of corrosion resistance due to precipitation of chromium carbonitride in stainless steel by forming carbonitride. The effect is expressed at 0.005%. However, excessive addition destabilizes the martensite phase and reduces the hardness, so the upper limit is 0.050%.
- Sn 0.01 to 0.10%
- Sn is an element effective for improving corrosion resistance after quenching, preferably 0.01% or more, and preferably 0.05% or more if necessary. However, excessive addition is preferably 0.10% or less because it promotes ear cracking during hot spreading.
- Bi 0.01% to 0.20% Bi is an element that improves corrosion resistance. Although the mechanism has not been clarified, it is considered that the addition of Bi has the effect of miniaturizing MnS, which tends to be the starting point of rusting, and thus reduces the probability of becoming the starting point of rusting. It is effective when added at 0.01% or more. Even if more than 0.20% is added, the effect is only saturated, so the upper limit is set to 0.20%.
- ⁇ ferrite phase ratio of steel plate and steel member The present inventors have found that ⁇ ferrite ( ⁇ Fe) existing in the central portion of the thickness of the steel sheet has a great influence on the end face corrosion resistance of the steel sheet.
- ⁇ ferrite ( ⁇ Fe) existing in the central portion of the thickness of the steel sheet has a great influence on the end face corrosion resistance of the steel sheet.
- the grain boundary between ⁇ Fe and the matrix phase ( ⁇ phase) becomes a precipitation site for Cr carbides during cooling, causing sensitization in the vicinity of the precipitated Cr carbides and end face corrosion resistance. I think it will reduce.
- N improves the end face corrosion resistance is that it also has an effect of suppressing the precipitation of Cr carbides. Therefore, in the present invention, it is effective to suppress ⁇ Fe existing in the central portion of the plate thickness in the steel together with N content.
- the steel sheet of the present invention is a steel sheet before quenching. It would be good if ⁇ Fe existing in the steel sheet before quenching could be measured, but it is difficult to measure because all the periphery is a ferrite phase. Instead, ⁇ Fe present in the steel sheet after quenching / tempering is relatively easy to measure because the periphery is a martensite phase. Therefore, the steel sheet of the present invention (before quenching) is subjected to quenching / tempering treatment. After that, the amount of ⁇ Fe is evaluated.
- the quenching conditions for evaluation are heating to 1050 ° C., holding for 30 minutes, and then air cooling, and the tempering conditions are 150 ° C. and 30 minutes.
- the quenching method is air cooling.
- the steel sheet is hardened and tempered under the above evaluation conditions, and then evaluated by the abundance area ratio ( ⁇ Fe amount) of the ⁇ Fe layer in the sheet thickness cross section.
- the steel plate and steel member of the present invention do not have a sufficiently high N content as described above. Therefore, it is necessary to further reduce ⁇ Fe as compared with the case where the N content is higher. With the N amount of the present invention, good end face corrosion resistance can be obtained when the ⁇ Fe amount is less than 0.1%. Corrosion resistance improves as the amount of ⁇ Fe is reduced, but it is set to 0.05% or more because a longer heat treatment is required as described later. The range is preferably 0.05% or more and less than 0.1%.
- ⁇ Manufacturing method of steel sheet> As the method for producing the steel sheet of the present invention, a conventional method is used. A slab with adjusted components is obtained by melting and casting, which is hot-rolled, then box-annealed, shot, and pickled to obtain a product. However, in order to control the amount of ⁇ Fe to less than 0.1%, the slab is preheated. As a result, the amount of ⁇ Fe produced can be reduced more than before, and good end face corrosion resistance can be obtained.
- the heating conditions at this time are preferably 1100 to 1150 ° C. and the soaking time is more than 50 hours and 100 hours or less.
- the heating temperature exceeds 1150 ° C.
- the two phases ( ⁇ + ⁇ ) become stable and the amount of ⁇ Fe rapidly increases, which is not preferable.
- the rapidly increased ⁇ Fe remains in a large amount even in the subsequent process, which causes a decrease in hardness.
- ⁇ Fe does not decrease even if it is heated for a long time, which is not preferable. Since the amount of ⁇ Fe is smaller than that in the case of exceeding 1150 ° C., the hardness may be maintained depending on the post-process.
- This preheating may be performed as slab heating before hot rolling, and hot rolling may be performed as it is.
- the obtained steel sheet is punched, hardened, tempered, and polished to produce a steel member.
- forging may be performed to shape the shape.
- the following are preferable conditions for quenching and tempering.
- the quenching temperature is preferably 1000 to 1150 ° C. If the quenching temperature is less than 1000 ° C., the austenite phase is small at the high temperature, and the hardness after quenching becomes low, which is not preferable. On the other hand, if the quenching temperature exceeds 1150 ° C., the ⁇ phase and the stable austenite phase increase, and in this case as well, the hardness decreases, which is not preferable.
- the holding time during quenching is preferably 1 minute to 1 hour. If the holding time is less than 1 minute, the austenite phase is small at high temperature and the hardness after quenching is low, which is not preferable. On the other hand, if the holding time is more than 1 hour, the stable austenite phase increases, and in this case as well, the hardness decreases, which is not preferable.
- the cooling rate at the time of quenching is an average cooling rate from the quenching temperature to 600 ° C., preferably 1 ° C./sec or more. If it is less than this, the hardness is lowered, which is not preferable. By air-cooling the quenching, the preferable cooling rate can be realized.
- the tempering temperature is preferably 100 ° C to 250 ° C. If the tempering temperature is less than 100 ° C., the tempering effect is poor, and if the tempering temperature exceeds 250 ° C., the hardness decrease becomes too large, which is not preferable.
- the steel sheet of the present invention is hot-rolled, box-annealed, shot, and pickled to obtain a product. Further, the obtained steel sheet is punched, hardened, tempered, and polished to prepare the steel member of the present invention. That is, the steel sheet of the present invention is before quenching, and the steel structure of the steel sheet has a crystal structure mainly composed of ferrite or the like. On the other hand, the steel member of the present invention, which has been hardened and tempered after processing the steel sheet, has a structure in which the steel structure is mainly martensite.
- the steels having the composition shown in Tables 1 and 2 were melted and cast into a slab having a thickness of 250 mm.
- these slabs were preheated and heat-treated at 1150 ° C. for 60 hours to set the amount of ⁇ Fe within a certain range.
- the A2 steel was preheated at 1175 ° C. for 60 hours and at 950 ° C. for 60 hours to obtain A2'steel and A2'steel, respectively.
- the hot-rolled steel sheet was annealed by box annealing.
- the maximum heating temperature was set to a temperature range of 800 ° C. or higher and 900 ° C. or lower.
- the scale on the surface of the steel sheet after annealing was removed by shot blasting and pickled.
- Example 1 In order to evaluate the obtained steel sheet, a sample for evaluation is cut out from the steel sheet, and the sample is heated to 1050 ° C. for 30 minutes as a quenching / tempering process, held for 30 minutes, and then air-cooled at 150 ° C. for 30 minutes. It was tempered to make a steel member. After that, each evaluation of ⁇ Fe amount measurement, hardness measurement, and end face corrosion resistance was performed. The results obtained are shown in Table 3.
- ⁇ Fe The amount of ⁇ Fe was measured by mirror-polishing and etching the end face of the sample to reveal the structure.
- ⁇ Fe can be expressed in aqua regia or the like as the etching solution, it is preferable to use a reagent called the improved Murakami reagent described in Non-Patent Document 1 because ⁇ Fe is deeply etched in brown, and evaluation is performed using this. did.
- a typical example is shown in FIG.
- the tissue revealed by the improved Murakami reagent is examined under a microscope, a photograph of ⁇ Fe is taken from the total thickness of a certain width (2 mm in this example), the ⁇ Fe area is obtained from the image analysis, and then the area ratio ( ⁇ Fe area ( ⁇ Fe area ( ⁇ Fe area)). mm 2 ) / 2 mm ⁇ total thickness (mm) ⁇ 100 (%)) was calculated and used as the amount of ⁇ Fe.
- its value needs to be less than 0.1%. Further, it is preferably 0.05% or more and less than 0.1%.
- ⁇ Fe area ratio ( ⁇ Fe amount) Less than 0.1% was regarded as pass (A), and more than 0.1% was regarded as fail (X).
- the surface hardness is evaluated by the Rockwell hardness tester C scale in accordance with JIS Z2245, and 50 or more is passed (A), and the others are rejected (Failure). X).
- the end face corrosion resistance After polishing the sample surface and end face with # 600, the end face is used as the evaluation surface and the salt spray test is performed for 24 hours (JIS Z 2371 "salt spray test method") to determine the rusting point. I counted. A score of 2 or less was regarded as a pass (A), and a score exceeding that score was a failure (X). In particular, those with zero rusting points were regarded as passing (S). Even if the salt spray test was carried out for 24 hours or more, rust did not develop further, so the end face corrosion resistance was judged based on the results for 24 hours.
- the samples obtained by quenching and tempering the steel sheet of the present invention are not only excellent in end face corrosion resistance but also excellent in other characteristics, and Western tableware knives.
- Preferable as a steel plate for use Preferable as a steel plate for use.
- the comparative steel has inferior end face corrosion resistance or inferior other characteristics, and it is clear that it is not preferable as a steel plate for Western tableware knives.
- Example 2 Using the member cut out from the obtained steel sheet, quenching and tempering were performed under the conditions shown in Table 4 to obtain a steel member. Quenching was performed by heating at 1050 to 1150 ° C., and then cooling was performed by controlling the cooling rate from the quenching temperature to 600 ° C. to the cooling rate shown in Table 4. Further, a tempering treatment for 1 to 2 hours was carried out at 150 to 250 ° C. to obtain a steel member. Further, A2'steel and A2'steel were also treated in the same manner.
- Table 4 shows the ⁇ Fe amount measurement, hardness measurement, and end face corrosion resistance evaluation of the obtained steel member together with the heat treatment conditions.
- the evaluation method and evaluation criteria were the same as in Example 1.
- All of the steel members of the present invention are excellent not only in end face corrosion resistance but also in other characteristics, and are preferable as steel members for Western tableware knives.
- the comparative steel has inferior end face corrosion resistance or inferior other characteristics, and it is clear that it is not preferable as a steel member for Western tableware knives.
- the present invention it is possible to produce a martensitic stainless steel member having excellent end face corrosion resistance after air-cooling quenching and a martensitic stainless steel sheet as a material thereof with high productivity, and a Western food produced using the martensitic stainless steel sheet.
- the corrosion resistance of the vessel knife is improved, which is very useful industrially.
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Abstract
Description
すなわち、
(1)質量%で、
C:0.100~0.170%、
Si:0.25~0.60%、
Mn:0.10~0.60%、
P:0.035%以下、
S:0.015%以下、
Cr:11.0~15.0%、
Ni:0.05~0.60%、
Cu:0.006~0.50%、
V:0.010~0.10%、
Al:0.05%以下
N:0.040%以上0.060%未満、
C+1/2N:0.130~0.190%であり、残部がFeおよび不純物からなる鋼組成を有し、
下記式(1)で示されるγpが120以上であるマルテンサイト系ステンレス鋼板において、
前記マルテンサイト系ステンレス鋼板を1050℃で30分保持後空冷焼き入れし、150℃、30分の焼き戻しを行ったとき、板厚中央部に存在するδフェライト(δFe)の板厚断面における面積率が0.1%未満となることを特徴とするマルテンサイト系ステンレス鋼板。
γp=420C+470N+30Ni+7Mn+9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-52Al+189 ・・・ 式(1)
式(1)中の元素記号は、当該元素の含有量(質量%)を意味する。
(2)前記鋼組成が、さらに前記Feの一部に替えて、質量%で、
Mo:0.01~1.0%、
Ti:0.005~0.050%、
Nb:0.005~0.050%の1種または2種以上を含有することを特徴とする(1)に記載のマルテンサイト系ステンレス鋼板。
(3)前記鋼組成が、さらに前記Feの一部に替えて、質量%で、
Sn:0.01~0.10%、
Bi:0.01~0.20%
の1種または2種を含有することを特徴とする(1)または(2)に記載のマルテンサイト系ステンレス鋼板。
(4)(1)~(3)の何れか1つに記載の鋼組成を有するマルテンサイト系ステンレス鋼部材において、
前記式(1)で示されるγpが120以上であり、
さらに、板厚中央部に存在するδフェライト(δFe)の板厚断面における面積率が0.1%未満であることを特徴とするマルテンサイト系ステンレス鋼部材。 After that, a more detailed study was conducted, and the invention was completed.
That is,
(1) By mass%
C: 0.100 to 0.170%,
Si: 0.25 to 0.60%,
Mn: 0.10 to 0.60%,
P: 0.035% or less,
S: 0.015% or less,
Cr: 11.0 to 15.0%,
Ni: 0.05-0.60%,
Cu: 0.006 to 0.50%,
V: 0.010 to 0.10%,
Al: 0.05% or less N: 0.040% or more and less than 0.060%,
C + 1 / 2N: 0.130 to 0.190%, with a steel composition with the balance consisting of Fe and impurities.
In a martensitic stainless steel sheet having a γp of 120 or more represented by the following formula (1),
When the martensitic stainless steel sheet is held at 1050 ° C. for 30 minutes, then air-cooled and quenched, and tempered at 150 ° C. for 30 minutes, the area of δ ferrite (δFe) present in the center of the plate thickness in the plate thickness cross section. A martensitic stainless steel sheet having a rate of less than 0.1%.
γp = 420C + 470N + 30Ni + 7Mn + 9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-52Al + 189 ... Equation (1)
The element symbol in the formula (1) means the content (mass%) of the element.
(2) The steel composition is further replaced with a part of the Fe in mass%.
Mo: 0.01-1.0%,
Ti: 0.005 to 0.050%,
The martensitic stainless steel sheet according to (1), wherein Nb: contains one or more of 0.005 to 0.050%.
(3) The steel composition is further replaced with a part of the Fe in mass%.
Sn: 0.01 to 0.10%,
Bi: 0.01 to 0.20%
The martensitic stainless steel sheet according to (1) or (2), which contains one or two of the above.
(4) In the martensitic stainless steel member having the steel composition according to any one of (1) to (3).
The γp represented by the above formula (1) is 120 or more, and
Further, a martensitic stainless steel member having an area ratio of δ ferrite (δFe) existing in the central portion of the plate thickness in a plate thickness cross section of less than 0.1%.
<鋼板および鋼部材の化学成分>(%は質量%を意味する。)
C:0.100~0.170%
CはNとともに焼き入れ硬さを決める元素であり、洋食器ナイフに必要な硬さを得るためには0.100%以上必要である。好ましくは0.110%以上であり、0.120%以上である。一方、過度に添加すると焼き入れ硬さが必要以上に大きくなり、研磨時の負荷が増えるほか、靱性も低下させる。また、本発明をもってしても空冷焼き入れ時にCr炭化物が析出し耐食性を損なうことも起こりやすくなるため、0.170%以下とする。好ましくは0.155%以下である。 Further, it will be described in detail.
<Chemical composition of steel sheet and steel member> (% means mass%)
C: 0.100 to 0.170%
C is an element that determines the quenching hardness together with N, and is required to be 0.100% or more in order to obtain the hardness required for a Western tableware knife. It is preferably 0.110% or more, and 0.120% or more. On the other hand, if it is added excessively, the quenching hardness becomes larger than necessary, the load during polishing increases, and the toughness also decreases. Further, even with the present invention, Cr carbides are likely to precipitate during air-cooling quenching and the corrosion resistance is likely to be impaired, so the content is set to 0.170% or less. It is preferably 0.155% or less.
Siは製鋼での脱酸のために必要であるほか、焼き入れ熱処理後の酸化スケールの生成を抑制するにも有効であるため、0.25%以上含有させる。0.25%未満であると酸化スケールが過度に生成し、最終の研磨負荷を増大させる。しかし、過剰の添加はオーステナイト生成を抑制し、焼き入れ性を損ねるために、0.60%以下とする。 Si: 0.25 to 0.60%
Since Si is necessary for deoxidation in steelmaking and is also effective in suppressing the formation of oxide scale after quenching heat treatment, it is contained in an amount of 0.25% or more. If it is less than 0.25%, an oxidation scale is excessively generated, which increases the final polishing load. However, excessive addition suppresses austenite production and impairs hardenability, so the content is set to 0.60% or less.
Mnはオーステナイト安定元素であり、焼き入れ時の硬さとマルテンサイト量確保のために必要である。そのため、0.10%以上含有させる。しかし、焼き入れ時の酸化スケール生成を促進させ、その後の研磨負荷を増大させるため、0.60%以下とする。また、過剰に添加するとMnSが多く生成し耐食性も低下させる。 Mn: 0.10 to 0.60%
Mn is an austenite-stabilizing element and is necessary for ensuring hardness and the amount of martensite during quenching. Therefore, it is contained in an amount of 0.10% or more. However, in order to promote the formation of oxide scale during quenching and increase the subsequent polishing load, the content is set to 0.60% or less. Further, if it is added excessively, a large amount of MnS is generated and the corrosion resistance is also lowered.
Pは原料である溶銑やフェロクロム等の合金中に不純物として含まれる元素である。熱延焼鈍後や焼き入れ後の鋼板の靱性に対して有害な元素であるため、その含有量は0.035%以下とする。過剰に添加すると熱間加工性や耐食性を低下させる。 P: 0.035% or less P is an element contained as an impurity in alloys such as hot metal and ferrochrome, which are raw materials. Since it is an element harmful to the toughness of the steel sheet after hot rolling annealing and quenching, its content shall be 0.035% or less. Excessive addition reduces hot workability and corrosion resistance.
Sはオーステナイト相に対する固溶度が小さく、粒界に偏析して熱間加工性の低下を促進する。また、過剰に含有するとMnSが多く生成し耐食性も低下させる。そのため、Sの含有量が0.015%以下とする。 S: 0.015% or less S has a small solid solubility in the austenite phase and segregates at the grain boundaries to promote a decrease in hot workability. Further, if it is contained in an excessive amount, a large amount of MnS is generated and the corrosion resistance is also lowered. Therefore, the S content is set to 0.015% or less.
Crは洋食器ナイフとして耐食性を保持するために、少なくとも11.0%以上必要である。一方、オーステナイト安定温度を狭める効果もあるため、15.0%以下とする。好ましくは、12.0以上である。また上限は14.0%以下が好ましい。範囲としては12.0~14.0%とするのが良い。 Cr: 11.0 to 15.0%
Cr is required at least 11.0% or more in order to maintain corrosion resistance as a Western tableware knife. On the other hand, since it also has the effect of narrowing the stable temperature of austenite, it should be 15.0% or less. Preferably, it is 12.0 or more. The upper limit is preferably 14.0% or less. The range is preferably 12.0 to 14.0%.
Niは、Mnと同様にオーステナイト安定元素であり、焼き入れ時の硬さとマルテンサイト量確保のために必要である。また、耐食性を向上させる効果もある。そのため、0.05%以上含有させる。しかし、過剰の添加はγ相の安定度を増加させマルテンサイト量が減少することもあり、また、Niは他の元素と比較して高価であるため、その上限は0.60%とする。 Ni: 0.05-0.60%
Like Mn, Ni is an austenite-stable element and is necessary for securing hardness and the amount of martensite during quenching. It also has the effect of improving corrosion resistance. Therefore, it is contained in an amount of 0.05% or more. However, excessive addition may increase the stability of the γ phase and decrease the amount of martensite, and Ni is more expensive than other elements, so the upper limit is set to 0.60%.
Cuは、Mn、Niと同様にオーステナイト安定元素であり、また、耐食性を向上させる元素である。製鋼時のスクラップからの混入が避けられない元素でもあるが、耐食性向上のために、0.006%以上含有させる。0.02%以上含有させるのが好ましい。0.05%以上の含有がより好ましい。一方、過度の含有は熱間加工性等を低下させるので、0.50%以下とする。Niよりは安価であるが比較的高価であるため、その添加はできるだけ低くしたい元素である。 Cu: 0.006 to 0.50%
Cu is an austenite-stable element like Mn and Ni, and is an element that improves corrosion resistance. Although it is an element that cannot be avoided from scrap during steelmaking, it is contained in an amount of 0.006% or more in order to improve corrosion resistance. It is preferably contained in an amount of 0.02% or more. More preferably, the content is 0.05% or more. On the other hand, excessive content reduces hot workability and the like, so the content should be 0.50% or less. Although it is cheaper than Ni, it is relatively expensive, so its addition is an element that we want to keep as low as possible.
Vは合金元素であるフェロクロム等から不可避的に混入する場合が多い元素である。その削減は困難であり、製鋼工程に負荷を掛けすぎるので、0.010%以上を含有させる。しかし、過度の含有はオーステナイト形成温度域を狭めるので、0.10%以下とした。また、過剰に添加するとVNを形成し、Nを固定化するため、硬さ低下や耐食性低下を引き起こすため好ましくない。 V: 0.010 to 0.10%
V is an element that is often inevitably mixed with ferrochrome or the like, which is an alloy element. Since it is difficult to reduce the load and the steelmaking process is overloaded, 0.010% or more is contained. However, since excessive content narrows the austenite formation temperature range, it was set to 0.10% or less. Further, if it is added in an excessive amount, VN is formed and N is immobilized, which causes a decrease in hardness and a decrease in corrosion resistance, which is not preferable.
Alは脱酸のために有効な元素であるが、過度の含有は熱延時に可溶性介在物であるCaSを生成させ、耐食性を低下させるので、その含有は0.05%以下とする。Al含有量が0.001%以上であると好ましい。Alは含有しなくても良い。 Al: 0.05% or less Al is an effective element for deoxidation, but its content is 0.05 because excessive content produces CaS, which is a soluble inclusion, during hot rolling and reduces corrosion resistance. % Or less. The Al content is preferably 0.001% or more. Al may not be contained.
NはCとともに焼き入れ硬さを決める元素であるとともに、耐食性を向上させる本発明では重要な元素である。そのため、本発明では0.040%以上含有させる。0.045%以上が好ましい。しかし、Nを過剰に含有させると、スラブ中に気泡欠陥ができやすく逆に耐食性を低下させるとともにVOD等による二次精錬では製造コストを増加させる元素である。特に連続鋳造では気泡欠陥を避けて安定に製造することが難しいため、Nは低めが良く、その含有量は0.060%未満とする。好ましくは、0.057%以下である。 N: 0.040% or more and less than 0.060% N is an element that determines quenching hardness together with C and is an important element in the present invention that improves corrosion resistance. Therefore, in the present invention, it is contained in an amount of 0.040% or more. 0.045% or more is preferable. However, if N is excessively contained, bubble defects are likely to occur in the slab, and conversely, the corrosion resistance is lowered, and the manufacturing cost is increased in the secondary refining by VOD or the like. In particular, in continuous casting, it is difficult to avoid air bubble defects and stably produce the product. Therefore, N should be low, and the content thereof should be less than 0.060%. Preferably, it is 0.057% or less.
鋼中のマルテンサイト相の硬さを決める元素はCとNであり、その合計が硬さに寄与する。本発明者の検討によれば、硬さに対するNの寄与はCの半分であり、洋食器ナイフとして必要な硬さを得るにはC+1/2Nが0.130%以上であることが必要である。好ましくは0.150%以上である。一方、C+1/2Nが過剰になると、焼き入れ硬さが上がりすぎて、製品や製造工程における中間材(鋳片等)の靱性を損ねるために、0.190%以下とする。好ましくは0.180%以下であり、0.175%以下としても良い。 C + 1 / 2N: 0.130 to 0.190%
The elements that determine the hardness of the martensite phase in steel are C and N, the sum of which contributes to the hardness. According to the study of the present inventor, the contribution of N to hardness is half that of C, and it is necessary that C + 1 / 2N is 0.130% or more in order to obtain the hardness required for a Western tableware knife. .. It is preferably 0.150% or more. On the other hand, if C + 1 / 2N is excessive, the quenching hardness is excessively increased, and the toughness of the intermediate material (slab or the like) in the product or manufacturing process is impaired. It is preferably 0.180% or less, and may be 0.175% or less.
加えて、本発明では、鋼組成が、上記に説明してきた元素に加えて、前記Feの一部に替えて、耐銹性、耐食性を向上させるために、Mo、Nb、TiおよびSn、Biの元素を添加できる。 The steel composition of the present invention contains the above components, and the balance consists of Fe and impurities.
In addition, in the present invention, in order to improve the rust resistance and corrosion resistance in place of a part of the Fe in addition to the elements described above, the steel composition is Mo, Nb, Ti and Sn, Bi. Elements can be added.
Moは耐食性を向上させる元素であり、0.01%以上の添加でその効果を発現する。しかし、Moは高価な元素でもあり、過度に添加しても効果が明確でなく、1.0%を上限とする。 Mo: 0.01-1.0%
Mo is an element that improves corrosion resistance, and its effect is exhibited by adding 0.01% or more. However, Mo is also an expensive element, and even if it is added excessively, the effect is not clear, and the upper limit is 1.0%.
Tiは、炭窒化物を形成することでステンレス鋼におけるクロム炭窒化物の析出による鋭敏化や耐食性の低下を抑制する元素である。その効果は0.005%で発現する。しかし、過度に添加すると、マルテンサイト相を不安定にし、硬さが低下するため、0.050%を上限とする。 Ti: 0.005 to 0.050%
Ti is an element that suppresses sensitization and deterioration of corrosion resistance due to precipitation of chromium carbonitride in stainless steel by forming carbonitride. The effect is expressed at 0.005%. However, excessive addition destabilizes the martensite phase and reduces the hardness, so the upper limit is 0.050%.
Nbは、炭窒化物を形成することでステンレス鋼におけるクロム炭窒化物の析出による鋭敏化や耐食性の低下を抑制する元素である。その効果は0.005%で発現する。しかし、過度に添加すると、マルテンサイト相を不安定にし、硬さが低下するため、0.050%を上限とする。 Nb: 0.005 to 0.050%
Nb is an element that suppresses sensitization and deterioration of corrosion resistance due to precipitation of chromium carbonitride in stainless steel by forming carbonitride. The effect is expressed at 0.005%. However, excessive addition destabilizes the martensite phase and reduces the hardness, so the upper limit is 0.050%.
Snは焼入れ後の耐食性向上に有効な元素であり、0.01%以上が好ましく、必要に応じて0.05%以上添加することが好ましい。但し、過度な添加は熱延時の耳割れを促進するため0.10%以下にすることが好ましい。 Sn: 0.01 to 0.10%
Sn is an element effective for improving corrosion resistance after quenching, preferably 0.01% or more, and preferably 0.05% or more if necessary. However, excessive addition is preferably 0.10% or less because it promotes ear cracking during hot spreading.
Biは、耐食性を向上させる元素である。その機構については明確になっていないが、発銹起点となり易いMnSをBi添加により微細化する効果あるため、発銹起点となる確率を低下させると考えている。0.01%以上の添加で効果を発揮する。0.20%超添加しても効果は飽和するだけなので、上限を0.20%とする。 Bi: 0.01% to 0.20%
Bi is an element that improves corrosion resistance. Although the mechanism has not been clarified, it is considered that the addition of Bi has the effect of miniaturizing MnS, which tends to be the starting point of rusting, and thus reduces the probability of becoming the starting point of rusting. It is effective when added at 0.01% or more. Even if more than 0.20% is added, the effect is only saturated, so the upper limit is set to 0.20%.
本発明者らは鋼板の板厚中央部に存在するδフェライト(δFe)が鋼板の端面耐食性に大きく影響することを見出した。鋼板を冷却速度の遅い空冷程度で焼き入れた場合、δFeと母相(γ相)との粒界が冷却中のCr炭化物の析出サイトとなり、析出したCr炭化物近傍の鋭敏化を引き起こし、端面耐食性を低下させると考えている。また、Nが端面耐食性を向上させる理由として、Cr炭化物の析出を抑制する効果もあると推定している。
したがって、本発明ではN含有とともに、鋼中の板厚中央部に存在するδFeの抑制が有効である。 <δ ferrite phase ratio of steel plate and steel member>
The present inventors have found that δ ferrite (δFe) existing in the central portion of the thickness of the steel sheet has a great influence on the end face corrosion resistance of the steel sheet. When the steel sheet is hardened at an air cooling rate with a slow cooling rate, the grain boundary between δFe and the matrix phase (γ phase) becomes a precipitation site for Cr carbides during cooling, causing sensitization in the vicinity of the precipitated Cr carbides and end face corrosion resistance. I think it will reduce. It is also presumed that the reason why N improves the end face corrosion resistance is that it also has an effect of suppressing the precipitation of Cr carbides.
Therefore, in the present invention, it is effective to suppress δFe existing in the central portion of the plate thickness in the steel together with N content.
本発明の鋼板の製造方法は、常法が使用される。溶解・鋳造により、成分が調整されたスラブを得、それを熱間圧延したのち、箱焼鈍を行い、ショット、酸洗して製品とする。
ただし、δFe量を0.1%未満に制御するために、スラブの予備加熱を行う。これによりδFeの生成量をこれまでより低減でき、良好な端面耐食性をえることができる。この時の加熱条件は、1100~1150℃で、均熱時間50時間超100時間以下とすることが良い。加熱温度が1150℃超であると、二相(γ+δ)が安定となり、δFe量が急増し好ましくない。また、急増したδFeはこの後工程でも多量に残存するため硬さも低下させる要因となる。一方、1100℃未満であると、長時間加熱してもδFeが減少せず、好ましくない。δFe量は1150℃超の場合よりも少ないため、後工程次第で硬さを維持できる場合もある。また、50時間以下ではδFeが多くなりすぎて好ましくなく、100時間超では高コストなり好ましくない。
この予備加熱は熱間圧延前のスラブ加熱として行い、そのまま熱間圧延しても良い。 <Manufacturing method of steel sheet>
As the method for producing the steel sheet of the present invention, a conventional method is used. A slab with adjusted components is obtained by melting and casting, which is hot-rolled, then box-annealed, shot, and pickled to obtain a product.
However, in order to control the amount of δFe to less than 0.1%, the slab is preheated. As a result, the amount of δFe produced can be reduced more than before, and good end face corrosion resistance can be obtained. The heating conditions at this time are preferably 1100 to 1150 ° C. and the soaking time is more than 50 hours and 100 hours or less. When the heating temperature exceeds 1150 ° C., the two phases (γ + δ) become stable and the amount of δFe rapidly increases, which is not preferable. In addition, the rapidly increased δFe remains in a large amount even in the subsequent process, which causes a decrease in hardness. On the other hand, if it is less than 1100 ° C., δFe does not decrease even if it is heated for a long time, which is not preferable. Since the amount of δFe is smaller than that in the case of exceeding 1150 ° C., the hardness may be maintained depending on the post-process. Further, if it is 50 hours or less, the amount of δFe becomes too large, which is not preferable, and if it exceeds 100 hours, the cost becomes high, which is not preferable.
This preheating may be performed as slab heating before hot rolling, and hot rolling may be performed as it is.
本発明では、得られた鋼板を打ち抜き、焼き入れ、焼き戻しを行い、研磨して鋼部材を作成する。打ち抜き後焼き入れ前に、鍛造を行い、形を整えることを行うこともある。なお、焼き入れ、焼き戻しの条件として以下が好ましい。焼き入れ温度は1000~1150℃が好ましい。焼き入れ温度が1000℃未満であると、高温時にオーステナイト相が少なく、焼き入れ後の硬さが低くなるため好ましくない。一方、焼き入れ温度が1150℃超であると、δ相や安定オーステナイト相が増加し、この場合も硬さが低下するため好ましくない。また、焼き入れ時の保持時間は、1分~1時間が好ましい。保持時間が1分未満であると、高温時にオーステナイト相が少なく、焼き入れ後の硬さが低くなるため好ましくない。一方、保持時間が1時間超であると、安定オーステナイト相が増加し、この場合も硬さが低下するため好ましくない。焼き入れ時の冷却速度は、焼き入れ温度から600℃までの平均冷却速度で、1℃/sec以上が好ましい。これ未満であると、硬さが低下するため好ましくない。焼き入れを空冷とすることにより、前記好ましい冷却速度を実現することができる。焼き戻し温度は、100℃~250℃が好ましい。焼き戻し温度が100℃未満では焼き戻しの効果が乏しく、焼き戻し温度が250℃を超えると、硬さ低下が大きくなりすぎるため、好ましくない。 <Manufacturing method of steel parts>
In the present invention, the obtained steel sheet is punched, hardened, tempered, and polished to produce a steel member. After punching and before quenching, forging may be performed to shape the shape. The following are preferable conditions for quenching and tempering. The quenching temperature is preferably 1000 to 1150 ° C. If the quenching temperature is less than 1000 ° C., the austenite phase is small at the high temperature, and the hardness after quenching becomes low, which is not preferable. On the other hand, if the quenching temperature exceeds 1150 ° C., the δ phase and the stable austenite phase increase, and in this case as well, the hardness decreases, which is not preferable. The holding time during quenching is preferably 1 minute to 1 hour. If the holding time is less than 1 minute, the austenite phase is small at high temperature and the hardness after quenching is low, which is not preferable. On the other hand, if the holding time is more than 1 hour, the stable austenite phase increases, and in this case as well, the hardness decreases, which is not preferable. The cooling rate at the time of quenching is an average cooling rate from the quenching temperature to 600 ° C., preferably 1 ° C./sec or more. If it is less than this, the hardness is lowered, which is not preferable. By air-cooling the quenching, the preferable cooling rate can be realized. The tempering temperature is preferably 100 ° C to 250 ° C. If the tempering temperature is less than 100 ° C., the tempering effect is poor, and if the tempering temperature exceeds 250 ° C., the hardness decrease becomes too large, which is not preferable.
上述のとおり、本発明の鋼板は、熱間圧延したのち、箱焼鈍を行い、ショット、酸洗して製品とする。さらに、得られた鋼板について、鋼板を打ち抜き、焼き入れ、焼き戻しを行い、研磨して、本発明の鋼部材を作成する。即ち、本発明の鋼板は、焼き入れ前であって、鋼板の鋼組織はフェライト等を主体とした結晶組織を有している。一方、鋼板について加工を行った後に焼き入れ、焼き戻しを行った本発明の鋼部材は、その鋼組織がマルテンサイトを主体とした組織となる。このような性質を有する鋼については、焼き入れ熱処理前の鋼板(鋼組織はフェライトを主体とする)であっても、一般に「マルテンサイト系ステンレス鋼板」と呼ばれている。そのような事情から、本発明について、鋼板に関しても「マルテンサイト系ステンレス鋼板」と記載することとした。 <Steel structure of steel plate and steel member>
As described above, the steel sheet of the present invention is hot-rolled, box-annealed, shot, and pickled to obtain a product. Further, the obtained steel sheet is punched, hardened, tempered, and polished to prepare the steel member of the present invention. That is, the steel sheet of the present invention is before quenching, and the steel structure of the steel sheet has a crystal structure mainly composed of ferrite or the like. On the other hand, the steel member of the present invention, which has been hardened and tempered after processing the steel sheet, has a structure in which the steel structure is mainly martensite. Steels having such properties are generally called "martensitic stainless steel sheets" even if they are steel sheets before quenching heat treatment (the steel structure is mainly ferrite). Under such circumstances, the present invention is also described as "martensite-based stainless steel sheet" with respect to the steel sheet.
得られた鋼板を評価するため、鋼板から評価用の試料を切り出し、当該試料について、焼き入れ・焼き戻し処理として1050℃に加熱して30分保持した後、空冷し、150℃、30分の焼き戻しを行って鋼部材とした。その後、δFe量測定、硬さ測定、端面耐食性の各評価を行った。得られた結果を表3に示す。 <Example 1>
In order to evaluate the obtained steel sheet, a sample for evaluation is cut out from the steel sheet, and the sample is heated to 1050 ° C. for 30 minutes as a quenching / tempering process, held for 30 minutes, and then air-cooled at 150 ° C. for 30 minutes. It was tempered to make a steel member. After that, each evaluation of δFe amount measurement, hardness measurement, and end face corrosion resistance was performed. The results obtained are shown in Table 3.
得られた鋼板から切り出した部材を用いて、表4に示す条件で焼き入れ焼き戻しを行い、鋼部材とした。焼き入れは1050~1150℃で加熱し、その後焼き入れ温度から600℃までの冷却速度を表4に記載した冷却速度に制御して冷却した。さらに、150~250℃で1~2hの焼き戻し処理を実施して、鋼部材とした。また、A2’鋼、A2”鋼も同様に処理した。 <Example 2>
Using the member cut out from the obtained steel sheet, quenching and tempering were performed under the conditions shown in Table 4 to obtain a steel member. Quenching was performed by heating at 1050 to 1150 ° C., and then cooling was performed by controlling the cooling rate from the quenching temperature to 600 ° C. to the cooling rate shown in Table 4. Further, a tempering treatment for 1 to 2 hours was carried out at 150 to 250 ° C. to obtain a steel member. Further, A2'steel and A2'steel were also treated in the same manner.
Claims (4)
- 質量%で、
C:0.100~0.170%、
Si:0.25~0.60%、
Mn:0.10~0.60%、
P:0.035%以下、
S:0.015%以下、
Cr:11.0~15.0%、
Ni:0.05~0.60%、
Cu:0.006~0.50%、
V:0.010~0.10%、
Al:0.05%以下
N:0.040%以上0.060%未満
C+1/2N:0.130~0.190%
であり、残部がFeおよび不純物からなる鋼組成を有し、
下記式(1)で示されるγpが120以上であるマルテンサイト系ステンレス鋼板において、
前記マルテンサイト系ステンレス鋼板を1050℃で30分保持後空冷焼き入れし、150℃、30分の焼き戻しを行ったとき、板厚中央部に存在するδフェライト(δFe)の板厚断面における面積率が0.1%未満となることを特徴とするマルテンサイト系ステンレス鋼板。
γp=420C+470N+30Ni+7Mn+9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-52Al+189 ・・・ 式(1)
式(1)中の元素記号は、当該元素の含有量(質量%)を意味する。 By mass%
C: 0.100 to 0.170%,
Si: 0.25 to 0.60%,
Mn: 0.10 to 0.60%,
P: 0.035% or less,
S: 0.015% or less,
Cr: 11.0 to 15.0%,
Ni: 0.05-0.60%,
Cu: 0.006 to 0.50%,
V: 0.010 to 0.10%,
Al: 0.05% or less N: 0.040% or more and less than 0.060% C + 1 / 2N: 0.130 to 0.190%
Has a steel composition with the balance consisting of Fe and impurities.
In a martensitic stainless steel sheet having a γp of 120 or more represented by the following formula (1),
When the martensitic stainless steel sheet is held at 1050 ° C. for 30 minutes, then air-cooled and quenched, and tempered at 150 ° C. for 30 minutes, the area of δ ferrite (δFe) present in the center of the plate thickness in the plate thickness cross section. A martensitic stainless steel sheet having a rate of less than 0.1%.
γp = 420C + 470N + 30Ni + 7Mn + 9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-52Al + 189 ... Equation (1)
The element symbol in the formula (1) means the content (mass%) of the element. - 前記鋼組成が、さらに前記Feの一部に替えて、質量%で、
Mo:0.01~1.0%、
Ti:0.005~0.050%、
Nb:0.005~0.050%
の1種または2種以上を含有することを特徴とする請求項1に記載のマルテンサイト系ステンレス鋼板。 The steel composition is further replaced with a part of the Fe in mass%.
Mo: 0.01-1.0%,
Ti: 0.005 to 0.050%,
Nb: 0.005 to 0.050%
The martensitic stainless steel sheet according to claim 1, wherein the martensitic stainless steel sheet contains one or more of the above. - 前記鋼組成が、さらに前記Feの一部に替えて、質量%で、
Sn:0.01~0.10%、
Bi:0.01~0.20%
の1種または2種を含有することを特徴とする請求項1または請求項2に記載のマルテンサイト系ステンレス鋼板。 The steel composition is further replaced with a part of the Fe in mass%.
Sn: 0.01 to 0.10%,
Bi: 0.01 to 0.20%
The martensitic stainless steel sheet according to claim 1 or 2, wherein the martensitic stainless steel sheet contains one or two of the above. - 請求項1~請求項3の何れか1項に記載の鋼組成を有するマルテンサイト系ステンレス鋼部材において、
前記式(1)で示されるγpが120以上であり、
さらに、板厚中央部に存在するδフェライト(δFe)の板厚断面における面積率が0.1%未満であることを特徴とするマルテンサイト系ステンレス鋼部材。 In the martensitic stainless steel member having the steel composition according to any one of claims 1 to 3.
The γp represented by the above formula (1) is 120 or more, and
Further, a martensitic stainless steel member characterized in that the area ratio of δ ferrite (δFe) existing in the central portion of the plate thickness in the plate thickness cross section is less than 0.1%.
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- 2021-01-20 TW TW110102197A patent/TWI747722B/en active
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JP2005163176A (en) * | 2003-12-03 | 2005-06-23 | Posco | Martensitic stainless steel having no pinhole defect and its production method |
JP2008163452A (en) * | 2006-12-08 | 2008-07-17 | Nippon Steel & Sumikin Stainless Steel Corp | Martensitic stainless steel excellent in corrosion resistance |
JP2010215995A (en) * | 2009-03-19 | 2010-09-30 | Nippon Steel & Sumikin Stainless Steel Corp | Martensitic stainless steel having excellent corrosion resistance |
JP2017171990A (en) * | 2016-03-23 | 2017-09-28 | 日新製鋼株式会社 | Martensitic stainless steel sheet and metal gasket manufacturing method |
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TW202134450A (en) | 2021-09-16 |
KR20220115621A (en) | 2022-08-17 |
TWI747722B (en) | 2021-11-21 |
EP4095279A1 (en) | 2022-11-30 |
JP2023046414A (en) | 2023-04-05 |
CN115003838B (en) | 2023-06-02 |
CN115003838A (en) | 2022-09-02 |
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