JP5033584B2 - Martensitic stainless steel with excellent corrosion resistance - Google Patents
Martensitic stainless steel with excellent corrosion resistance Download PDFInfo
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- 238000005260 corrosion Methods 0.000 title claims description 53
- 229910001105 martensitic stainless steel Inorganic materials 0.000 title claims description 21
- 238000010791 quenching Methods 0.000 claims description 59
- 230000000171 quenching effect Effects 0.000 claims description 59
- 238000001816 cooling Methods 0.000 claims description 32
- 229910000831 Steel Inorganic materials 0.000 claims description 31
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- 229910052757 nitrogen Inorganic materials 0.000 claims description 28
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- 239000000203 mixture Substances 0.000 claims description 4
- 229910052802 copper Inorganic materials 0.000 claims description 3
- 239000012535 impurity Substances 0.000 claims description 3
- 229910052748 manganese Inorganic materials 0.000 claims description 3
- 229910052758 niobium Inorganic materials 0.000 claims description 3
- 229910052719 titanium Inorganic materials 0.000 claims description 3
- 229910052698 phosphorus Inorganic materials 0.000 claims description 2
- 229910052717 sulfur Inorganic materials 0.000 claims description 2
- 229910052720 vanadium Inorganic materials 0.000 claims description 2
- 239000011651 chromium Substances 0.000 description 36
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 28
- 238000010438 heat treatment Methods 0.000 description 22
- 229910001566 austenite Inorganic materials 0.000 description 21
- 229910052804 chromium Inorganic materials 0.000 description 17
- 230000000694 effects Effects 0.000 description 13
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- 230000007423 decrease Effects 0.000 description 9
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- 206010070834 Sensitisation Diseases 0.000 description 8
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- 230000008313 sensitization Effects 0.000 description 8
- 238000000034 method Methods 0.000 description 7
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- 239000010410 layer Substances 0.000 description 6
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- 239000010935 stainless steel Substances 0.000 description 6
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- 229910000859 α-Fe Inorganic materials 0.000 description 6
- 239000010949 copper Substances 0.000 description 5
- 238000005098 hot rolling Methods 0.000 description 5
- 229910000734 martensite Inorganic materials 0.000 description 5
- 150000001247 metal acetylides Chemical class 0.000 description 5
- 238000005498 polishing Methods 0.000 description 5
- 229910045601 alloy Inorganic materials 0.000 description 4
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- 238000002844 melting Methods 0.000 description 4
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- VEXZGXHMUGYJMC-UHFFFAOYSA-M Chloride anion Chemical compound [Cl-] VEXZGXHMUGYJMC-UHFFFAOYSA-M 0.000 description 3
- 239000012298 atmosphere Substances 0.000 description 3
- 238000005266 casting Methods 0.000 description 3
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- 229910000604 Ferrochrome Inorganic materials 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- BQJTUDIVKSVBDU-UHFFFAOYSA-L copper;sulfuric acid;sulfate Chemical compound [Cu+2].OS(O)(=O)=O.[O-]S([O-])(=O)=O BQJTUDIVKSVBDU-UHFFFAOYSA-L 0.000 description 2
- 238000005261 decarburization Methods 0.000 description 2
- 230000006866 deterioration Effects 0.000 description 2
- 229910052739 hydrogen Inorganic materials 0.000 description 2
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 2
- 150000004767 nitrides Chemical class 0.000 description 2
- 239000012299 nitrogen atmosphere Substances 0.000 description 2
- 150000003839 salts Chemical class 0.000 description 2
- 229920006395 saturated elastomer Polymers 0.000 description 2
- 238000005204 segregation Methods 0.000 description 2
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 2
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910000760 Hardened steel Inorganic materials 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 238000007545 Vickers hardness test Methods 0.000 description 1
- 238000005299 abrasion Methods 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
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- 238000009835 boiling Methods 0.000 description 1
- 210000000988 bone and bone Anatomy 0.000 description 1
- GVEHJMMRQRRJPM-UHFFFAOYSA-N chromium(2+);methanidylidynechromium Chemical compound [Cr+2].[Cr]#[C-].[Cr]#[C-] GVEHJMMRQRRJPM-UHFFFAOYSA-N 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
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- 150000002500 ions Chemical class 0.000 description 1
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- 229910052751 metal Inorganic materials 0.000 description 1
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- 238000003801 milling Methods 0.000 description 1
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- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—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
- C22C38/001—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
- C22C38/02—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
- C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C38/00—Ferrous alloys, e.g. steel alloys
- C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
- C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
- C22C38/42—Ferrous alloys, e.g. steel alloys containing chromium with nickel with copper
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Heat Treatment Of Steel (AREA)
- Heat Treatment Of Sheet Steel (AREA)
Description
本発明は焼き入れ後の耐食性に優れたマルテンサイト系ステンレス鋼に関する。より詳しく言えば、本発明は洋食器ナイフや織機、工具、二輪ディスクブレーキ等の製造に用いられ、空冷焼き入れを行なっても優れた耐食性を有するマルテンサイト系ステンレス鋼に関する。 The present invention relates to a martensitic stainless steel having excellent corrosion resistance after quenching. More specifically, the present invention relates to a martensitic stainless steel that is used in the manufacture of tableware knives, looms, tools, two-wheel disc brakes, etc., and has excellent corrosion resistance even when air-cooled and quenched.
洋食器ナイフ(テーブルナイフ)やはさみ、織機、ノギス等の工具には、SUS420J1、SUS420J2鋼が一般に用いられ、更に高い硬度が必要となる洋式包丁や果物ナイフ等においてはSUS440A鋼が用いられている。この様な用途においては、防錆のためのメッキや塗装、防錆油の使用が困難である事と、磨耗に強い高い硬度が必要とされるからである。これらマルテンサイト系ステンレス鋼の規格はC量によって規定されており、SUS410はC:0.15%以下でCr:11.5〜13.5%、SUS420J1はC:0.16〜0.25%でCr:12〜14%、SUS420J2はC:0.26〜0.40%でCr:12〜14%、SUS440AはC:0.60〜0.75%でCr:16〜18%と区分されている。C量が高いほど高い焼き入れ硬度が得られる反面、製造性や焼き入れ後の靭性が低下するため、洋食器ナイフなどには、SUS420J1グレードが一般に用いられている。 SUS420J1 and SUS420J2 steel are generally used for tools such as tableware knives (table knives), scissors, looms, and vernier calipers, and SUS440A steel is used for Western knives and fruit knives that require higher hardness. . This is because in such applications, it is difficult to use rust-preventive plating, coating, and rust-preventing oil, and high hardness that is resistant to wear is required. The standards of these martensitic stainless steels are defined by the amount of C, SUS410 is C: 0.15% or less, Cr: 11.5 to 13.5%, SUS420J1 is C: 0.16 to 0.25% Cr: 12-14%, SUS420J2 is C: 0.26-0.40%, Cr: 12-14%, SUS440A is C: 0.60-0.75% and Cr: 16-18% ing. SUS420J1 grade is generally used for Western tableware knives and the like because higher quenching hardness is obtained as the amount of C is higher, while manufacturability and toughness after quenching decrease.
マルテンサイト系ステンレス鋼で製造される洋式包丁の製造工程に関しては、いくつかの文献で紹介されているが、鋼板から型抜きし、加熱、焼き入れ後、各種研摩工程を経て刃物に仕上げられる。焼入れは、油焼入れが代表例として紹介されている。但し、マルテンサイト系のステンレス鋼は焼き入れ性が良好であり、空冷程度の冷却速度でも焼き入れが可能である。即ち、刃物として十分な硬度は空冷でも得られることが知られている。そのため、洋食器ナイフの製造工程では省工程化のため、空冷焼入れが一般的に行なわれている。 Regarding the manufacturing process of a Western-style kitchen knife made of martensitic stainless steel, it has been introduced in several literatures, but after cutting from a steel plate, heating and quenching, it is finished into a knife through various polishing processes. As for quenching, oil quenching is introduced as a representative example. However, martensitic stainless steel has good hardenability and can be hardened even at a cooling rate of about air cooling. That is, it is known that sufficient hardness as a blade can be obtained even by air cooling. For this reason, air-cooled quenching is generally performed in the manufacturing process of western tableware knives in order to save processes.
また、これらステンレス鋼の耐食性については、一般に成分で整理され、Cr、Mo、Nの添加により向上する事が知られている。各元素の効果について多くの検討がなされており、マルテンサイト系ステンレス鋼において、Cr+3.3Mo+30Nで整理でき、この値が大きいほど耐食性が向上するという報告もある。また、ステンレス鋼は焼き入れ後研摩して使用されるため、Alなどを下げる事で、大型の介在物を避け研摩性を向上させることも必要とされる。 In addition, the corrosion resistance of these stainless steels is generally organized by component and is known to be improved by the addition of Cr, Mo, and N. Many studies have been made on the effect of each element. In martensitic stainless steel, there is a report that it can be arranged by Cr + 3.3Mo + 30N, and that the larger this value, the better the corrosion resistance. In addition, since stainless steel is used after being quenched, it is also necessary to improve polishing properties by avoiding large inclusions by lowering Al or the like.
これらの知見を特許文献で説明する。まず、特許文献1では、Cr:12〜16%、Mo:1.3〜3.5%、N:0.06%〜0.13%を含有する耐銹性に優れた高強度マルテンサイト系ステンレス鋼線材について記載されている。
These findings are explained in the patent literature. First, in
耐銹性を向上させるCr、Moは、高価な元素であると共に、オーステナイト温度域を狭くする事で焼き入れ性を低下させる問題を抱えている。焼き入れ熱処理時にオーステナイト単相化できない場合、オーステナイトとフェライトの二相域から焼入れする事になるが、オーステナイトがマルテンサイト変態開始する温度は約300℃程度と低く、空冷焼入れのような遅い冷却速度ではCの拡散速度が速いフェライトから炭化物が析出し、その結果生じたCr欠乏層により耐食性が著しく低下する。もちろん、オーステナイト相においても冷却速度が遅いと炭化物が析出し、耐食性を低下させるが、拡散速度がフェライト中よりも小さいため、冷却速度の影響が比較的小さくなる。この様な、炭化物の析出による耐食性低下は空冷焼き入れ時に顕在化する問題である。 Cr and Mo, which improve the weather resistance, are expensive elements and have a problem of reducing the hardenability by narrowing the austenite temperature range. If austenite cannot be converted to a single phase during quenching heat treatment, quenching starts from the two-phase region of austenite and ferrite, but the temperature at which austenite begins martensitic transformation is as low as about 300 ° C, which is a slow cooling rate like air-cooled quenching. In this case, carbide precipitates from ferrite having a high C diffusion rate, and the resulting Cr-deficient layer significantly reduces the corrosion resistance. Of course, even in the austenite phase, if the cooling rate is slow, carbides are precipitated and the corrosion resistance is lowered. However, since the diffusion rate is smaller than in the ferrite, the influence of the cooling rate is relatively small. Such a decrease in corrosion resistance due to the precipitation of carbide is a problem that becomes apparent during air-cooling quenching.
一方、窒素はオーステナイト域を広げると共に、安価な元素であるが、溶解鋳造時に固溶限を超えた窒素が気泡を造り、健全な鋼塊が得られないことが問題となる。窒素の固溶限は成分や雰囲気の気圧によって変わる。成分としてはCr、C量の影響が大きく、SUS420J1,SUS420J2等のマルテンサイト系ステンレス鋼を大気圧下で鋳造した場合、窒素の溶解量は約0.1%程度と一般に報告されている。特許文献2においても、ピンホール欠陥のないマルテンサイト系ステンレス鋼として、N:0.06〜0.10%にすることが記載されている。 On the other hand, nitrogen expands the austenite region and is an inexpensive element, but nitrogen exceeding the solid solubility limit at the time of melting and casting creates bubbles, and a problem is that a healthy steel ingot cannot be obtained. The solid solubility limit of nitrogen varies depending on the components and atmospheric pressure. The effects of Cr and C as components are large, and when martensitic stainless steels such as SUS420J1 and SUS420J2 are cast under atmospheric pressure, the amount of dissolved nitrogen is generally reported to be about 0.1%. Patent Document 2 also describes that N: 0.06 to 0.10% as martensitic stainless steel having no pinhole defect.
より高い耐銹性を得る試みとして、大気圧を超える高圧力下で鋳造する技術も開発されている。例えば、特許文献3では、加圧可能な溶解炉で溶解鋳造したN:0.40%から0.80%、Cr:13.0%以上20.0%、Mo:0.2%〜4.0%を含有するマルテンサイト系ステンレス鋼について記載されている。 As an attempt to obtain higher weather resistance, a technique for casting under high pressure exceeding atmospheric pressure has also been developed. For example, in Patent Document 3, N: 0.40% to 0.80%, Cr: 13.0% or more and 20.0%, Mo: 0.2% -4. It describes a martensitic stainless steel containing 0%.
このように、耐銹性と製造性を両立させたマルテンサイト系ステンレス鋼は種々提案されている。 As described above, various martensitic stainless steels having both weather resistance and manufacturability have been proposed.
しかしながら、本発明者らの検討で、先に言及した特許文献1では、Cr、Moの添加による耐食性向上に主眼が置かれているため、合金コストが高くなると共に、凝固偏析によってCr、Moが濃化した部位が、安定なδフェライト相となって、焼き入れ熱処理時のオーステナイト単相化に長時間を要するなどの問題がある事がわかった。
However, in the study of the present inventors, the above-mentioned
また、特許文献2に記載された方法、すなわちピンホール欠陥を出さずに耐食性向上の為に窒素を0.06%〜0.10%添加する事は、特許文献1でも同様に行なわれていた事であるが、窒素添加に伴う耐食性向上の反面、固溶窒素の増加に伴って、炭化物の析出が過度に抑制され耐磨耗性を損ねる事が明らかになった。
In addition, the method described in Patent Document 2, that is, adding 0.06% to 0.10% of nitrogen for improving corrosion resistance without causing pinhole defects was also performed in
更に、特許文献3に記載された方法では、鋳造雰囲気を加圧するために専用の設備が必要となるほか、大量生産に不向きである事が問題であった。 Furthermore, in the method described in Patent Document 3, a dedicated facility is required to pressurize the casting atmosphere, and it is not suitable for mass production.
本発明はこうした現状を鑑みて、空冷焼き入れ時の耐食性が良好で、また、耐摩耗性にも優れたマルテンサイト系ステンレス鋼板を安価に提供することを目的とした。 In view of the present situation, the present invention has an object to provide a martensitic stainless steel sheet having good corrosion resistance during air-cooling and quenching and excellent wear resistance at low cost.
本発明者らは上記目的を達成するため、マルテンサイト系ステンレス鋼の耐食性に及ぼす成分や冷却速度の影響について調査すると共に、焼き入れ後の析出物の状況や耐摩耗性に対する影響について検討し、良好な耐食性を得るためは、焼き入れ時の加熱温度域におけるオーステナイトの安定度を高めると共に、空冷焼き入れ時の炭窒化物析出量を調整することが重要である事、そのためには、特にC、N、Cr、Niの成分バランスを最適化し、未固溶炭化物を分散制御することが非常に重要であるとの知見を得たものである。 In order to achieve the above object, the present inventors investigated the influence of the components and the cooling rate on the corrosion resistance of martensitic stainless steel, and examined the influence on the situation and wear resistance of the precipitates after quenching, In order to obtain good corrosion resistance, it is important to increase the stability of austenite in the heating temperature range during quenching and to adjust the amount of carbonitride deposited during air-cooling quenching. It has been found that it is very important to optimize the component balance of N, Cr and Ni and to control dispersion of insoluble carbides.
その要旨とするところは以下の通りである。
(1)質量%で、C:0.13〜0.18%、Si:0.30〜0.60%、Mn:0.10〜0.60%、P:0.035%以下、S:0.015%以下、Cr:11.0〜15.0%、Ni:0.10〜0.60%、Cu:0.50%以下、V:0.10%以下、Al:0.05%以下、N:0.03%以上0.06%未満、残部Fe及び不可避的不純物からなる鋼組成を有し、C+N:0.19〜0.23%、C/N:2.3〜4.3、γmax=420C+470N+30Ni+7Mn+9Cu−11.5Cr−11.5Si−12Mo−23V−47Nb−49Ti−52Al+189が120以上とすることを特徴とする、空冷焼入れ時の耐食性に優れたマルテンサイト系ステンレス鋼。
(2)さらに、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)記載の空冷焼入れ時の耐食性に優れたマルテンサイト系ステンレス鋼。
The gist is as follows.
(1) By mass%, C: 0.13-0.18%, Si: 0.30-0.60%, Mn: 0.10-0.60%, P: 0.035% or less, S: 0.015% or less, Cr: 11.0 to 15.0%, Ni: 0.10 to 0.60%, Cu: 0.50% or less, V: 0.10% or less, Al: 0.05% Hereafter, it has a steel composition consisting of N: 0.03% or more and less than 0.06%, the balance Fe and inevitable impurities, C + N: 0.19 to 0.23%, C / N: 2.3 to 4. 3, γmax = 420C + 470N + 30Ni + 7Mn + 9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-49Ti-52Al + 189 martensitic stainless steel excellent in corrosion resistance during air-cooling and quenching, characterized by being 120 or more.
(2) Furthermore, by mass%, Mo: 0.01 to 1.0%, Ti: 0.005 to 0.050%, Nb: 0.005 to 0.050%, or one or more of them The martensitic stainless steel having excellent corrosion resistance during air-cooling and quenching as described in (1).
マルテンサイト系ステンレス鋼の各成分バランスを最適化することで、空冷焼き入れ時の鋭敏化に起因する耐食性低下を防止し、耐摩耗性や製造性を兼ね備えた、洋食器ナイフ等の用途に最適なステンレス鋼を安価に提供する事が可能になった。 By optimizing the balance of each component of martensitic stainless steel, it prevents corrosion deterioration due to sensitization during air cooling and quenching, and is ideal for applications such as western tableware knives that combine wear resistance and manufacturability New stainless steel can be provided at low cost.
以下に本発明を詳細に説明する。 The present invention is described in detail below.
一般に、ステンレス鋼の耐食性はその成分で整理され、Cr+3.3Mo+16Nといった指標で整理され、この数値が高いほど高い耐食性を有する。このときの耐食性とは、中性の塩化物水溶液環境をさすものであり、評価方法として、例えばJIS G0577に規定されるステンレス鋼の孔食電位測定方法や、JISZ2371に規定される塩水噴霧試験方法などが上げられる。しかしながら、化学・食品プラントや温水器などの貯水槽、海浜環境で使われる用途以外、すなわち日常的な屋内環境において、高濃度の塩化物水溶液に曝される可能性は極めて少なく、洋食器ナイフとしてSUS420J1鋼が用いられている様に、13%程度のCr量で十分な耐食性が得られる。 In general, the corrosion resistance of stainless steel is arranged by its components and arranged by an index such as Cr + 3.3Mo + 16N, and the higher this value, the higher the corrosion resistance. The corrosion resistance at this time refers to a neutral chloride aqueous solution environment. As an evaluation method, for example, a method for measuring the pitting potential of stainless steel defined in JIS G0577 or a salt spray test method defined in JISZ2371. Etc. are raised. However, it is extremely unlikely to be exposed to high-concentration chloride aqueous solutions in water tanks such as chemical / food plants and water heaters, in beach environments, that is, in everyday indoor environments. As SUS420J1 steel is used, sufficient corrosion resistance is obtained with a Cr amount of about 13%.
ところが、一般的な、マルテンサイト系ステンレス鋼であるSUS420J1やSUS420J2鋼を、空冷焼き入れすると粒界へCr炭化物が析出し、粒界近傍にクロム欠乏層が生じるため(鋭敏化)、成分値ほどの耐食性が得られない。それでもまだ、日常的な屋内乾燥環境下において腐食する事は無いが、食器洗い機で洗う際など、高温の塩素イオン環境に曝されるとさびが発生する場合がある。即ち、一般的なマルテンサイト系ステンレス鋼の用途では、Crに相当する耐食性を、鋭敏化を防止して確実に維持する事が重要である。 However, when SUS420J1 or SUS420J2 steel, which is a general martensitic stainless steel, is air-cooled and quenched, Cr carbide precipitates at the grain boundary and a chromium-deficient layer is formed in the vicinity of the grain boundary (sensitization). The corrosion resistance is not obtained. Still, it does not corrode in a daily indoor dry environment, but rust may occur when exposed to a high-temperature chlorine ion environment such as when washing in a dishwasher. That is, in general martensitic stainless steel applications, it is important to reliably maintain the corrosion resistance corresponding to Cr by preventing sensitization.
鋭敏化の防止には、いくつかのポイントがある。第一には炭素量を下げる事であるが、焼き入れ硬さを低下させるため、適正範囲が存在する。第二には、焼き入れ熱処理時にオーステナイト単相化することであるが、注意すべきはオーステナイト安定化元素であるC、Nなどが、鋼材製造時や焼き入れ熱処理時において鋼材表面部で減少し、表層部のみにフェライトが生じる場合がある。炭素の減少は脱炭、窒素の減少は脱窒と呼ばれるが、高温下で雰囲気の酸素や水素と鋼中の炭素、窒素が鋼材表面で反応し、鋼中から雰囲気中へ炭素、窒素が移動する現象である。熱間圧延や焼き入れ前の加熱時における脱炭、脱窒は避けがたいため、ある程度過剰に添加する事が必要とされる。 There are several points in preventing sensitization. The first is to reduce the carbon content, but there is an appropriate range to reduce the quenching hardness. The second is to austenite single phase during quenching heat treatment, but it should be noted that austenite stabilizing elements such as C and N are reduced at the steel surface during steel manufacturing and quenching heat treatment. In some cases, ferrite is generated only in the surface layer portion. The reduction of carbon is called decarburization, and the reduction of nitrogen is called denitrification, but oxygen and hydrogen in the atmosphere react with carbon and nitrogen in the steel at high temperatures, and the carbon and nitrogen move from the steel to the atmosphere. It is a phenomenon. Since decarburization and denitrification at the time of hot rolling and heating before quenching are unavoidable, it is necessary to add excessively to some extent.
マルテンサイト系ステンレス鋼の鋭敏化防止に有効な三つ目の方法として、窒素と炭素のバランス調整がある。炭素量一定のもとにおいても、窒素量が増えるとCr炭化物の析出が抑制され、鋭敏化が抑制される。平衡論的には、炭素量が同じで窒素を増せば、Cr炭化物に加えてCr窒化物が析出し、鋭敏化を助長すると思われるが、空冷焼き入れ程度の冷却速度では、Cr炭化物、Cr窒化物共に析出が遅れ、鋭敏化が抑制される。但し、炭素と窒素の量には最適範囲が存在し、最適範囲を外れると、鋭敏化や硬度・耐摩耗性の低下など品質問題が生じる。 As a third effective method for preventing martensitic stainless steel from being sensitized, there is a balance adjustment between nitrogen and carbon. Even when the amount of carbon is constant, when the amount of nitrogen increases, precipitation of Cr carbide is suppressed, and sensitization is suppressed. Equilibriumly, if the amount of carbon is the same and nitrogen is increased, Cr nitride is precipitated in addition to Cr carbide, which may promote sensitization. However, at a cooling rate comparable to air cooling, Cr carbide, Cr The precipitation of both nitrides is delayed and sensitization is suppressed. However, there is an optimum range for the amount of carbon and nitrogen. If the amount is outside the optimum range, quality problems such as sensitization and deterioration of hardness and wear resistance occur.
以上の知見に基づき本発明は、当該用途におけるマルテンサイト系ステンレス鋼としての最適成分バランスを見出したものである。各成分の限定理由を以下に説明する。なお、以下の説明中、各元素の含有量を示す「%」は特に断りが無い限り「質量%」を示す。 Based on the above knowledge, this invention discovered the optimal component balance as a martensitic stainless steel in the said use. The reason for limitation of each component is demonstrated below. In the following description, “%” indicating the content of each element indicates “mass%” unless otherwise specified.
C:0.13〜0.18%
Cは焼き入れ硬さを支配する元素であり、洋食器ナイフに必要な硬さを得るために0.13%以上必要である。一方、過度に添加すると焼き入れ硬さが必要以上に上がり、研摩時の負荷が増えるほか、靭性も低下させる。また、空冷焼き入れ時にCr炭化物が析出し耐食性を損なう問題も生じるため0.18%以下とした。好ましくは0.17%以下とする。
C: 0.13-0.18%
C is an element that controls the quenching hardness, and is required to be 0.13% or more in order to obtain the hardness necessary for a western tableware knife. On the other hand, excessive addition increases the quenching hardness more than necessary, increases the load during polishing, and decreases toughness. In addition, Cr carbide precipitates during air-cooling and quenching, resulting in a problem that the corrosion resistance is impaired. Preferably it is 0.17% or less.
Si:0.30〜0.60%
Siは溶解精錬時における脱酸のために必要であるほか、焼き入れ熱処理時の酸化スケール生成を抑制するのにも有効であるため、0.30%以上とした。但し、Siはオーステナイト単相温度域を狭くし、焼き入れ安定性を損ねるために、0.60%以下とした。
Si: 0.30 to 0.60%
Si is necessary for deoxidation at the time of melting and refining, and is also effective in suppressing the formation of oxide scale during the quenching heat treatment, so it was set to 0.30% or more. However, Si is made 0.60% or less in order to narrow the austenite single phase temperature range and impair quenching stability.
Mn:0.60%以下
Mnは、オーステナイト安定化元素であり、他元素とバランスし、焼入れ熱処理時の表層部におけるオーステナイト単相化のために最低限0.10%以上を添加することとした。一方、焼き入れ熱処理時の酸化スケール生成を促進し、その後の研摩負荷を増加させるために0.60%を上限とした。
Mn: 0.60% or less Mn is an austenite stabilizing element, is balanced with other elements, and at least 0.10% or more is added to make austenite single phase in the surface layer part during quenching heat treatment. . On the other hand, 0.60% was made the upper limit in order to promote the generation of oxide scale during quenching heat treatment and increase the subsequent polishing load.
P:0.035%以下
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。熱延焼鈍板や焼き入れ後の靭性に対して有害な元素であるため、0.035%以下とした。
P: 0.035% or less P is an element contained as an impurity in a raw material alloy such as hot metal or ferrochrome. Since it is an element harmful to hot-rolled annealed plate and toughness after quenching, it was set to 0.035% or less.
S:0.015%以下
Sはオーステナイト相に対する固溶量が小さく、粒界に偏析して熱間加工性の低下を促進する元素であり、0.015%を超えるとその影響は顕著になるため0.015%以下とした。
S: 0.015% or less S is an element that has a small amount of solid solution in the austenite phase and segregates at the grain boundary to promote a decrease in hot workability. If the content exceeds 0.015%, the effect becomes significant. Therefore, it was made 0.015% or less.
Cr:11.0〜15.0%
Crは洋食器ナイフとしての耐食性を保持するために、少なくとも11.0%必要である。一方、オーステナイト安定温度域を狭める効果もあるため、15.0%を上限とした。これらの特性をより効果的にするためには、Crの範囲を好ましくは12〜15%、より好ましくは13〜14%とするのがよい。
Cr: 11.0-15.0%
Cr needs to be at least 11.0% in order to maintain the corrosion resistance as a western tableware knife. On the other hand, since it also has an effect of narrowing the austenite stable temperature range, the upper limit was made 15.0%. In order to make these characteristics more effective, the Cr range is preferably 12 to 15%, more preferably 13 to 14%.
Ni:0.10〜0.60%
Niは、Mnと同様にオーステナイト安定化元素である。焼き入れ熱処理時にC、N、Mn等は表層部から減少し表層部にフェライトを生成する場合があるが、Niは減少する事が無く、オーステナイト相の安定化効果に大変有効である。他元素とバランスし、焼き入れ熱処理時の表層部におけるオーステナイト単相化のために最低限0.10%以上の添加する事とした。一方で、Niは他の合金元素に比べて高価であり、コスト上昇を招くために0.60%以下とした。
Ni: 0.10 to 0.60%
Ni is an austenite stabilizing element like Mn. During quenching heat treatment, C, N, Mn, etc. may decrease from the surface layer portion to generate ferrite in the surface layer portion, but Ni does not decrease and is very effective for the effect of stabilizing the austenite phase. In order to balance with other elements and to make austenite single phase in the surface layer part at the time of quenching heat treatment, it was decided to add at least 0.10% or more. On the other hand, Ni is more expensive than other alloy elements, and is set to 0.60% or less in order to increase the cost.
Cu:0.50%以下
Cuは溶製時のスクラップからの混入等、不可避的に含有される場合が多いが、過度の含有は熱間加工性や耐食性を低下させるので、0.50%以下とした。
Cu: 0.50% or less Cu is often inevitably contained, such as mixing from scrap during melting, but excessive content reduces hot workability and corrosion resistance, so 0.50% or less It was.
V:0.10%以下
Vは合金原料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が、オーステナイト単相温度域を狭める作用が強いため、0.10%以下とした。
V: 0.10% or less V is often inevitably mixed from ferrochromium or the like, which is an alloy raw material, but is 0.10% or less because of its strong effect of narrowing the austenite single-phase temperature range.
Al:0.05%以下
Alは脱酸のために有効な元素であるが、スラグの塩基度を上げ、鋼中に可溶性介在物CaSを析出させ、耐食性を低下させる。また、アルミナ系の非金属介在物による研摩性の低下も引き起こすため、0.05%を上限とした。
Al: 0.05% or less Al is an element effective for deoxidation, but raises the basicity of slag, precipitates soluble inclusions CaS in steel, and lowers corrosion resistance. In addition, the lowering of abrasiveness due to alumina-based non-metallic inclusions is caused, so 0.05% was made the upper limit.
N:0.03%以上0.06%未満
NはCと同様に焼き入れ硬さを上げる効果を有する。また、Cと異なる効果として耐食性を次の二つの点で向上させる。一つ目は不動態皮膜を強化させる働きであり、もう一つはCr炭化物の析出抑制(Cr欠乏層の抑制)である。これらの効果を得るためにNは0.03%以上とする。但し、過剰な添加はCr炭化物の析出量を極端に低下させ、耐摩耗性を損ねるほか、製造性を損なうため、0.06%未満とした。
N: 0.03% or more and less than 0.06% N, like C, has the effect of increasing the quenching hardness. Further, as an effect different from C, the corrosion resistance is improved in the following two points. The first is to strengthen the passive film, and the other is to suppress the precipitation of Cr carbide (suppression of the Cr-deficient layer). In order to obtain these effects, N is set to 0.03% or more. However, excessive addition drastically reduces the amount of Cr carbide precipitated, impairs wear resistance, and impairs manufacturability, so it was made less than 0.06%.
以上説明したマルテンサイト系ステンレス鋼において、さらに耐食性を向上させるには、鋼中へのMo、TiあるいはNbの添加が有効に働く。 In the martensitic stainless steel described above, addition of Mo, Ti or Nb to the steel works effectively to further improve the corrosion resistance.
耐食性を向上させるには、Moを少なくとも0.01質量%以上添加する必要があるが、1.0%を超えて添加すると、耐食性の向上効果が飽和し加工性などを劣化させる原因となることから、1.0%をその上限とする。 In order to improve the corrosion resistance, it is necessary to add at least 0.01% by mass of Mo. However, if it exceeds 1.0%, the effect of improving the corrosion resistance is saturated and the workability is deteriorated. Therefore, 1.0% is the upper limit.
Tiは耐食性に有害な水溶性硫化物の析出抑制に有効な元素で、0.005%以上の含有量が必要であるが、0.050%を超えて添加すると炭化物の析出により焼き入れ硬さを低下させる原因になる。したがって、耐食性の面からTi含有量の下限は0.005%、焼き入れ性の面から上限を0.050%とした。 Ti is an element effective for suppressing precipitation of water-soluble sulfides that are harmful to corrosion resistance. A content of 0.005% or more is necessary, but if added over 0.050%, quenching hardness is caused by precipitation of carbides. It will cause the decrease. Therefore, the lower limit of the Ti content is 0.005% from the viewpoint of corrosion resistance, and the upper limit is 0.050% from the viewpoint of hardenability.
NbもTiと同様に炭窒化物形成元素である。耐食性に有害な水溶性硫化物の析出抑制のため、0.005%以上の含有量が必要であるが、0.050%を超えて添加すると炭化物の析出により焼き入れ硬さを低下させる原因になる。したがって、耐食性の面からNb含有量の下限は0.005%、焼き入れ性の面から上限を0.050%とした。 Nb is a carbonitride-forming element like Ti. A content of 0.005% or more is necessary to suppress precipitation of water-soluble sulfides that are harmful to corrosion resistance. However, if added over 0.050%, it causes quenching hardness to decrease due to precipitation of carbides. Become. Therefore, the lower limit of Nb content is 0.005% from the viewpoint of corrosion resistance, and the upper limit is 0.050% from the viewpoint of hardenability.
成分における望ましい範囲は式で規定した成分条件を満たす事で得られる。以下に規定理由を説明する。 A desirable range of components can be obtained by satisfying the component conditions defined by the formula. The reason for the regulation will be explained below.
C+N:0.19〜0.23%
洋食器ナイフに必要な焼入れ硬さを得ると共に、焼き入れ熱処理時の表層部の脱炭層、脱窒層に起因する焼き入れ不良を防止するためにはC+Nの合計量で0.19%以上が必要である。但し、C+N量が過剰になると焼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)の靭性を損ねるために、0.23%を上限とした。
C + N: 0.19 to 0.23%
In order to obtain the quenching hardness required for Western tableware knives and to prevent quenching defects due to the decarburized layer and denitrified layer of the surface layer during quenching heat treatment, the total amount of C + N is 0.19% or more is necessary. However, when the amount of C + N is excessive, the quenching hardness is excessively increased, and the upper limit is set to 0.23% in order to impair the toughness of intermediate materials (slabs and the like) in products and manufacturing processes.
C/N:2.3〜4.3
焼き入れ硬さに関して、CとNはほぼ等価に作用するが、耐食性や耐摩耗性に関しては、効果が異なってくるため、CとNの比を制御する事が必要となる。C/N下限は耐食性向上の観点から2.3を下限とした。また、耐摩耗性向上と脱炭層防止による耐食性保持のために上限を4.3とした。
C / N: 2.3 to 4.3
Regarding quenching hardness, C and N act almost equivalently, but the effect differs with respect to corrosion resistance and wear resistance, so it is necessary to control the ratio of C and N. The lower limit of C / N is 2.3 from the viewpoint of improving corrosion resistance. The upper limit was set to 4.3 in order to maintain the corrosion resistance by improving the wear resistance and preventing the decarburized layer.
γmax=420C+470N+30Ni+7Mn+9Cu−11.5Cr−11.5Si−12Mo−23V−47Nb−49Ti−52Al+189が120以上
焼き入れ前の熱処理時にオーステナイト単相化することは当該鋼において不可欠な条件であり、オーステナイト単相化温度域を十分に確保する事が必要である。主要元素について、上記式で示されるγmaxが120以上であれば、オーステナイト単相化温度域を十分に確保することができる。そこでγmaxを120以上とした。ここでγmax式における元素記号は、各元素の含有量(質量%)を表す。
γmax = 420C + 470N + 30Ni + 7Mn + 9Cu-11.5Cr-11.5Si-12Mo-23V-47Nb-49Ti-52Al + 189 is 120 or more It is an indispensable condition in the steel that it becomes austenite single phase at the time of heat treatment before quenching. It is necessary to ensure a sufficient temperature range. If γmax represented by the above formula is 120 or more for the main element, a sufficient austenite single-phase temperature range can be secured. Therefore, γmax is set to 120 or more. Here, the element symbol in the γmax formula represents the content (% by mass) of each element.
C+N、C/Nの最適範囲とC,N個々に規定された範囲に対しての関係を図1に、Cr、Niとγmaxの関係を図2に示した。なお、図2のγmaxの計算に際して、Cr、Ni以外の成分については、0.15C−0.05N−0.35Si−0.1Mn−0.05V(いずれも質量%)としている。これら、本発明の構成要件である全ての条件を満たした場合にのみ、空冷焼き入れ時の耐食性や耐摩耗性、焼き入れ硬さ全てを満たす事が可能となった。 FIG. 1 shows the relationship between the optimal range of C + N and C / N and the range defined for each of C and N, and FIG. 2 shows the relationship between Cr, Ni and γmax. In the calculation of γmax in FIG. 2, the components other than Cr and Ni are set to 0.15C-0.05N-0.35Si-0.1Mn-0.05V (both mass%). Only when all the conditions that are the constituent requirements of the present invention are satisfied, it becomes possible to satisfy all of the corrosion resistance, wear resistance, and quenching hardness during air-cooling quenching.
当該鋼の製造においては、熱間圧延時の加熱温度を1140〜1240℃とし、巻き取り温度を700〜840℃とし、熱延板焼鈍をバッチ式焼鈍炉にて700〜900℃で4時間以上行なうことが望ましい。 In the production of the steel, the heating temperature at the time of hot rolling is set to 1140 to 1240 ° C, the coiling temperature is set to 700 to 840 ° C, and hot-rolled sheet annealing is performed at 700 to 900 ° C in a batch type annealing furnace for 4 hours or more. It is desirable to do so.
即ち、熱延加熱温度が1240℃より高くなると、γ単相からγ+δのニ相域となる。δ相には、Cr、Si等が濃化し、C、N、Ni等が負偏析し、焼き入れ時のγ単相化を阻害し、焼き入れ性を損ねる。逆に1140℃未満になると、凝固偏析を解消するための拡散時間として均熱時間が2時間以上必要となり、熱延の生産性を大きく損ねるために好ましくない。 That is, when the hot rolling heating temperature is higher than 1240 ° C., the two-phase region from γ single phase to γ + δ is obtained. In the δ phase, Cr, Si and the like are concentrated, and C, N, Ni and the like are segregated negatively, hindering the γ single phase at the time of quenching and impairing the hardenability. On the other hand, when the temperature is lower than 1140 ° C., the soaking time is required for 2 hours or more as the diffusion time for eliminating the solidification segregation, which is not preferable because the productivity of hot rolling is greatly impaired.
また熱延後、鋼帯の巻き取りに際しては、巻き取り温度を700〜840℃にすることが望ましい。700℃以上にすることで、コイルの冷却に際して、耐摩耗性向上に有効な炭化物の粗大化が進む。また、840℃を超えると、表面に厚い酸化スケールが形成され、脱炭相の形成による耐食性低下や焼き入れ後の研摩性不良などの問題を生じるために望ましくない。 In addition, when the steel strip is wound after hot rolling, it is desirable that the winding temperature is 700 to 840 ° C. By setting the temperature to 700 ° C. or higher, the coarsening of the carbide effective for improving the wear resistance proceeds when the coil is cooled. On the other hand, when the temperature exceeds 840 ° C., a thick oxide scale is formed on the surface, which causes undesirable problems such as a decrease in corrosion resistance due to the formation of a decarburized phase and poor polishing properties after quenching.
次に、熱延板の焼鈍条件であるが、焼き入れ前の加工性を良くするため、軟質化させることが必要である。そのためには、連続焼鈍炉では十分な軟質化のための焼鈍時間が確保できないため、バッチ式焼鈍炉にて700〜900℃の温度域に4時間以上保持する熱処理が望ましい。700℃未満や900℃超では軟質化が不十分になる。また4時間未満では、コイル内の温度不均一に起因するコイル内材質変動が生じる。 Next, although it is the annealing conditions of a hot-rolled sheet, in order to improve the workability before quenching, it is necessary to make it soft. For this purpose, since a continuous annealing furnace cannot secure an annealing time for sufficient softening, a heat treatment is preferably performed in a batch annealing furnace in a temperature range of 700 to 900 ° C. for 4 hours or more. Softening becomes insufficient when the temperature is lower than 700 ° C or higher than 900 ° C. If the time is less than 4 hours, material variation in the coil due to temperature non-uniformity in the coil occurs.
焼き入れ熱処理に際しては、950〜1100℃の温度域で、5〜30分保定し、空冷焼入れする事が望ましい。このときの冷却速度は板厚6mmの場合、400℃までの平均冷却速度で1〜5℃/秒が好ましい。 In the quenching heat treatment, it is desirable to hold for 5 to 30 minutes in a temperature range of 950 to 1100 ° C. and perform air cooling and quenching. The cooling rate at this time is preferably 1 to 5 ° C./second at an average cooling rate up to 400 ° C. when the thickness is 6 mm.
表1に示す化学組成値(質量%)を有する鋼を、真空溶解炉にて溶解後、大気圧の不活性ガス窒素雰囲気下で鋳造し、100mm厚みの鋼塊とした。その後、1220℃に加熱後、板厚6mmまで熱間圧延し、700℃で巻き取った。引き続き850℃で4時間の熱処理後、炉冷して焼き戻しした。引き続き、窒素雰囲気の熱処理炉中で1050℃、10分間保持後、取り出して自然冷却させ、空冷焼き入れとした。得られた焼き入れ鋼板を供試材として、下記の方法で焼き入れ硬さと、耐食性、耐摩耗性を評価した。 Steel having a chemical composition value (% by mass) shown in Table 1 was melted in a vacuum melting furnace, and then cast in an inert gas nitrogen atmosphere at atmospheric pressure to obtain a steel ingot having a thickness of 100 mm. Then, after heating to 1220 ° C., it was hot-rolled to a plate thickness of 6 mm and wound up at 700 ° C. Subsequently, after heat treatment at 850 ° C. for 4 hours, the furnace was cooled and tempered. Subsequently, after being held at 1050 ° C. for 10 minutes in a heat treatment furnace in a nitrogen atmosphere, it was taken out and allowed to cool naturally, and was air-cooled and quenched. Using the obtained hardened steel sheet as a test material, the quenching hardness, corrosion resistance, and wear resistance were evaluated by the following methods.
硬さ
板厚断面において、JISZ2244に規定されるビッカース硬さ試験に基づいて、荷重50Nで測定した。
Hardness In the plate thickness section, it was measured at a load of 50 N based on the Vickers hardness test specified in JISZ2244.
耐食性
焼き入れ後の試料表面をフライス盤で研削して平坦化した後、サンドペーパーを用いて600番研摩仕上げとした。JISZ2371に規定される塩水噴霧試験を4時間行ない、発銹点数を評点付けした。
Corrosion resistance After quenching, the sample surface was ground by a milling machine and flattened, and then sanded paper was used for No. 600 polishing finish. The salt spray test prescribed in JISZ2371 was conducted for 4 hours, and the number of glazing points was scored.
また、鋼種番号2、21については、熱延焼鈍板を誘導加熱装置で1050℃、10分間加熱した後、一定の冷却速度(1〜100℃/秒)で300℃以下まで冷却し、均熱部より試験片を切り出し、全面を鏡面研摩した後、硫酸−硫酸銅腐食試験を行なって腐食減量を測定した。その際の沸騰液組成は、0.5mass%H2SO4+6mass%CuSO4で銅の小片を入れる事でCuイオンを飽和状態とした。試料は浸漬させ20hr保持した。 For steel types 2 and 21, the hot-rolled annealed plate was heated at 1050 ° C. for 10 minutes with an induction heating device, then cooled to 300 ° C. or less at a constant cooling rate (1 to 100 ° C./second), and soaking A test piece was cut out from the part and the entire surface was mirror-polished, and then a sulfuric acid-copper sulfate corrosion test was performed to measure the corrosion weight loss. The boiling liquid composition at that time was 0.5 mass% H 2 SO 4 +6 mass% CuSO 4 , and Cu ions were saturated by putting small pieces of copper. The sample was immersed and held for 20 hours.
耐摩耗性
供試材をテーブルナイフの刃先形状に加工し、牛骨、磁器に対する耐摩耗試験を実施し、基準鋼に対する比較評価を行った。
Abrasion resistance The specimens were processed into the shape of a table knife edge, subjected to wear resistance tests on cow bones and porcelain, and compared with reference steel.
表2に示す結果から分かるように、本発明鋼は、空冷焼入れした際の焼き入れ硬さが洋食器ナイフとして望まれる硬さ範囲:Hv460〜580を満たすと共に、SST試験における錆の発生が極めて少なく、かつ耐摩耗性に優れ、長期間にわたって高い切れ味を有している。 As can be seen from the results shown in Table 2, the steel of the present invention satisfies the hardness range desired for Western dishes knives: Hv 460 to 580 when subjected to air cooling and quenching, and the occurrence of rust in the SST test is extremely high. Less wear resistance and excellent sharpness over a long period of time.
これに対して、本発明範囲を外れる成分では、焼き入れ硬さ、焼き入れ後の耐食性が不良であるか、その他の特性(熱延焼鈍板靭性、熱間加工性、原料コスト、研摩性)がSUS420J1鋼として代表的な成分である鋼種番号20に対して10%以上劣るものであり、製造性、品質、コストの面で不合格のものであった。 On the other hand, components outside the scope of the present invention have poor quenching hardness, poor corrosion resistance after quenching, or other properties (hot rolled annealed sheet toughness, hot workability, raw material cost, abrasiveness) However, it is inferior by 10% or more with respect to steel type No. 20, which is a typical component of SUS420J1 steel, and is unacceptable in terms of manufacturability, quality, and cost.
図3には、本発明鋼の代表として鋼種番号2、比較鋼の代表として鋼種番号20を用いて、焼き入れ冷却速度が耐食性に及ぼす影響を詳細に調べた結果を示した。比較鋼は冷却速度が遅くなると腐食減量が急増しているが、本発明鋼では冷却速度依存性が小さくなっている事が分かる。洋食器ナイフのような厚い鋼板の場合、クロム炭化物が析出する温度域における冷却速度は約0.5℃/sになるが、当該冷却速度における発明鋼と比較鋼の腐食減量差は明確である。 FIG. 3 shows the results of detailed examination of the effect of quenching and cooling rate on the corrosion resistance using steel type number 2 as a representative of the steel of the present invention and steel type number 20 as a representative of the comparative steel. It can be seen that when the cooling rate of the comparative steel is slow, the corrosion weight loss increases rapidly, but the steel according to the present invention is less dependent on the cooling rate. In the case of a thick steel plate such as a western tableware knife, the cooling rate in the temperature range where chromium carbide precipitates is about 0.5 ° C / s, but the difference in corrosion weight loss between the inventive steel and the comparative steel at the cooling rate is clear. .
尚、洋食器ナイフのような厚い鋼板の場合、例えば板厚6mmの場合、空冷における冷却速度は約3℃/s程度である。 In the case of a thick steel plate such as a western tableware knife, for example, when the plate thickness is 6 mm, the cooling rate in air cooling is about 3 ° C./s.
本発明によれば、空冷焼入れ後の耐食性や耐摩耗性に優れたマルテンサイト系ステンレス鋼を、安価にかつ生産性良く製造することが可能になる。したがって本発明は、洋食器ナイフやステンレス包丁、工具、二輪ディスクブレーキ用のステンレス鋼製造コスト、品質を大幅に改善することに寄与するものである。 ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to manufacture the martensitic stainless steel excellent in corrosion resistance and wear resistance after air-cooling and quenching at low cost and with high productivity. Therefore, the present invention contributes to greatly improving the production cost and quality of stainless steel for Western tableware knives, stainless steel knives, tools, and two-wheel disc brakes.
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JP6124930B2 (en) * | 2014-05-02 | 2017-05-10 | 日新製鋼株式会社 | Martensitic stainless steel sheet and metal gasket |
CN104195454A (en) * | 2014-08-18 | 2014-12-10 | 常熟市新洲机械制造厂 | Fine processing machine tool for foods |
CN105909700B (en) * | 2015-02-23 | 2019-03-26 | 株式会社岛野 | Anti-corrosion bicycle disk brake rotor |
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