JP4009716B2 - Manufacturing method of stainless steel product by nitrogen absorption treatment and stainless steel product obtained thereby - Google Patents

Manufacturing method of stainless steel product by nitrogen absorption treatment and stainless steel product obtained thereby Download PDF

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JP4009716B2
JP4009716B2 JP2002231557A JP2002231557A JP4009716B2 JP 4009716 B2 JP4009716 B2 JP 4009716B2 JP 2002231557 A JP2002231557 A JP 2002231557A JP 2002231557 A JP2002231557 A JP 2002231557A JP 4009716 B2 JP4009716 B2 JP 4009716B2
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stainless steel
product
absorption treatment
nitrogen absorption
steel product
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JP2004068115A (en
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大介 黒田
隆夫 塙
典夫 丸山
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National Institute for Materials Science
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National Institute for Materials Science
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Priority to PCT/JP2003/010164 priority patent/WO2004015160A1/en
Priority to US10/523,678 priority patent/US20060037669A1/en
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • 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
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • 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
    • C21D1/74—Methods of treatment in inert gas, controlled atmosphere, vacuum or pulverulent material
    • C21D1/76—Adjusting the composition of the atmosphere
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—Heat treatment of ferrous alloys containing Cr
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0257—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment with diffusion of elements, e.g. decarburising, nitriding
    • C—CHEMISTRY; METALLURGY
    • C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
    • C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
    • C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
    • C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
    • C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
    • C23C8/24—Nitriding
    • C23C8/26—Nitriding of ferrous surfaces
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/001—Austenite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Solid-Phase Diffusion Into Metallic Material Surfaces (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Description

【０００１】
【発明の属する技術分野】
この出願の発明は、窒素吸収処理によるステンレス鋼製製品の製造方法とこれにより得られるステンレス鋼製製品に関するものである。さらに詳しくは、この出願の発明は、難加工材とされるオーステナイト型ステンレス鋼の加工コストを十分低く抑えることができ、強度、耐食性のいずれにおいても十分に満足することのできる特性を有するステンレス鋼製製品を製造可能とする、窒素吸収処理によるステンレス鋼製製品の製造方法とこれにより得られるステンレス鋼製製品に関するものである。
【０００２】
【従来の技術とその課題】
オーステナイト型ステンレス鋼は難加工材であり、それゆえ、所望の形状への加工が難しく、加工コストの高騰を招いている。オーステナイト型ステンレス鋼は耐食性、強度にともに優れるものであるだけに所望の形状品、複雑な形状を有する製品をも安価に提供することが望まれる。
【０００３】
粉末冶金法では、焼結成形時に窒素を吸収させるという試みがなされているが、粉末冶金法により成形された製品を製造するためには大規模な装置が必要であり、製造可能な製品の大きさや形状に制約がある。また、粉末冶金法により得られた製品にはポアと呼ばれる無数の空孔があり、これが製品の機械的特性に反映し、力学的信頼性に問題がある。
【０００４】
一方、溶製により製造されるバルク材については窒素吸収処理は行われていない。その理由は、一般に金属材料を高温度の窒素雰囲気中に長時間保持すると、ミクロ組織が粗大化し、機械的特性が大幅に低下することが常識となっていたからである。つまり、バルク材の力学的信頼性の低下が強く危惧されていたのである。
【０００５】
この出願の発明は、このような事情に鑑みてなされたものであり、難加工材とされるオーステナイト型ステンレス鋼の加工コストを十分低く抑えることができ、強度、耐食性のいずれにおいても十分に満足するのできる特性を有するステンレス鋼製製品を製造可能とする、窒素吸収処理によるステンレス鋼製製品の製造方法とこれにより得られるステンレス鋼製製品を提供することを解決すべき課題としている。
【０００６】
【課題を解決するための手段】
この出願の発明は、以上の課題を解決するものとして、フェライト型ステンレス鋼製であり、溶製され、所望の形状に加工されたバルク状の製品を、窒素ガスを含む不活性ガスと800℃以上で接触させ、製品全体をオーステナイト化させることを特徴とする窒素吸収処理によるステンレス鋼製製品の製造方法（請求項１）を提供する。
【０００７】
またこの出願の発明は、フェライト型ステンレス鋼製であり、溶製され、所望の形状に加工されたバルク状の製品に、窒素ガスを含む不活性ガスにより窒素が添加され、製品全体がオーステナイト化されたことを特徴とするステンレス鋼製製品（請求項２）を提供する。
【０００９】
以下、実施例を示しつつ、この出願の発明の窒素吸収処理によるステンレス鋼製製品の製造方法とこれにより得られるステンレス鋼製製品についてさらに詳しく説明する。
【００１０】
【発明の実施の形態】
この出願の発明の窒素吸収処理によるステンレス鋼製製品の製造方法では、前述のとおり、フェライト型ステンレス鋼製であり、溶製され、所望の形状に加工されたバルク状の製品を、窒素ガスを含む不活性ガスと800℃以上で接触させ、製品全体をオーステナイト化させる。所望の形状に加工されたバルク状の製品を窒素ガスを含む不活性ガスと800℃以上で接触させるという上記手法は、いわゆる固相吸収法に分類される窒素吸収処理に属し、窒素ガスを含む不活性ガス雰囲気中で製品を800℃以上に加熱することにより製品の全体に窒素が添加される。この出願の発明の窒素吸収処理によるステンレス鋼製製品の製造方法では、窒素を添加する対象が、フェライト型ステンレス鋼製の溶製された製品であるため、オーステナイト型ステンレス鋼に比べ加工が容易であり、所望の形状を有する製品が得られる。また、粉末冶金法における装置規模及び成形の制約、ならびに溶製についても指摘される力学的信頼性が解消される。
【００１１】
このようにして得られるこの出願の発明のステンレス鋼製製品は、製品全体がオーステナイト化された製品となる。このため、この出願の発明のステンレス鋼製製品は、優れた耐食性及び強度を併せ持ち、また、複雑な形状を有するステンレス鋼製製品であっても、その加工コストは低く抑えられ、安価な製品であるという利点を有する。フェライト型ステンレス鋼のバルク状製品への窒素の添加量は、おおむね0.5質量％以上であれば上記の効果は十分得られる。
【００１２】
【実施例】
真空アーク溶解炉を用いて、図１に示したような3.5kgのフェライト型ステンレス鋼（Fe-24質量%Cr-2質量%Mo）の鋳塊を溶製した。この鋳塊を４つに分割、切断し、25mm×25mm×110mmのブロックとした後、1100℃で熱間鍛造及び室温で冷間鍛造を行い、図２、図３にそれぞれ示したような直径９mm×90mmの丸棒材、厚さ1.5mm×１５mm×１５mmの板材を作製した。図２に示した丸棒材からは、さらに機械加工により図４に示した断面形状を有する丸棒引張試験片を作製した。これら２種類の試験片に対し、材料窒素化装置を用いて以下に示すような窒素吸収処理を行った。
【００１３】
すなわち、試験片をSUS304製のメッシュ状ボードに載せ、アセトンで脱脂洗浄後、材料窒素化装置の窒素化部内に挿入、配置し、２Paまでロータリーポンプにより真空引きした。次いで窒素化部に２リットル/minの流量で窒素ガスを含む不活性ガスを導入し、室温から５℃/minの速度で1200℃まで窒素化部を昇温させて試験片と窒素ガスを1200℃で２４時間接触させた。
【００１４】
以上の窒素吸収処理後、試験片を1200℃から氷水中に焼入れした。表面のスケールを研磨により除去した後、Ｘ線回折装置を用いてミクロ組織の同定を行った。このＸ線回折においてはＣｕＫα管球を用い、２θ/θ＝４０°〜９０°まで１°/minずつ変化させた。図５（ａ）は得られたＸ線回折パターンである。比較のために、図５（ｂ）に窒素吸収処理を行わなかった試験片同等品のＸ線回折パターンを示した。図５（ａ）（ｂ）の対比から明らかなように、窒素吸収処理後の試験片は、完全にオーステナイト型ステンレス鋼となっていることが確認される。窒素の添加量はほぼ0.9質量％であった。
【００１５】
次に、容量100kNのインストロン型引張試験機を用いてクロスヘッド速度0.5mm/minで試験片の引張試験を行った。窒素吸収処理後の試験片、窒素吸収処理を行わなかった試験片同等品及び既存合金の強度及び延性のバランスを図６に示した。図６から確認されるように、窒素吸収処理を行うと、既存合金及び窒素吸収処理を行わなかった試験片同等品に比べ、強度及び延性のバランスが優れる。この傾向は、試験片を窒素吸収処理していない冷間圧延材の場合にも同様に認められた。窒素吸収処理の有効性が再確認される。
【００１６】
さらに、試験片について耐食性の評価をも行った。
【００１７】
３７℃に調整し、窒素ガスを用いて脱気した0.9%NaCl溶液、PBS(-)溶液、Hanks溶液、Eagle's MEM溶液中に試験片、316Lステンレス鋼及び窒素吸収処理を行わなかった試験片同等品を浸漬した。図７（ａ）〜（ｄ）は、それぞれ、耐食性の評価のために行った分極試験の結果である分極曲線ある。図７（ａ）〜（ｄ）から確認されるように、いずれの試験溶液に対しても窒素吸収処理した試験片は、316Lステンレス鋼及び窒素吸収処理を行わなかった試験片同等品に比較して優れた耐食性を示し、また、図８（ａ）に示したように、孔食の発生は認められなかった。316Lステンレス鋼には、図８（ｂ）に示したように、孔食が発生した。
【００１８】
この出願の発明の窒素吸収処理によるステンレス鋼製製品の製造方法とこれにより得られるステンレス鋼製製品は、オーステナイト型ステンレス鋼が有する難加工性という欠点を解消し、たとえ複雑な形状を有する製品も低コストで実現可能であり、十分な強度及び耐食性を有する。
【００１９】
もちろん、この出願の発明は、以上の実施形態及び実施例により限定されるものではない。ステンレス鋼の組成、製品の形状及び大きさ、窒素吸収処理条件などの細部については様々な態様が可能であることはいうまでもない。
【００２０】
【発明の効果】
以上詳しく説明した通り、この出願の発明によって、難加工材とされるオーステナイト型ステンレス鋼から形成され、所望の形状を有し、加工コストを十分低く抑えることができ、強度、耐食性のいずれにおいても十分に満足するのできる特性を有するステンレス鋼製製品とその製造方法が提供される。
【図面の簡単な説明】
【図１】実施例において、真空アーク溶解炉を用いて溶製した3.5kgのフェライト型ステンレス鋼（Fe-24質量%Cr-2質量%Mo）の鋳塊を示した図面に代わる写真である。
【図２】図１に示した鋳塊から熱間及び冷間鍛造により作製された丸棒材を示した図面に代わる写真である。
【図３】図１に示した鋳塊から熱間及び冷間鍛造により作製された板材を示した図面に代わる写真である。
【図４】図２に示した丸棒材から作製された丸棒引張試験片を示した断面図である。
【図５】（ａ）（ｂ）は、それぞれ、窒素吸収処理後の試験片の、窒素吸収処理を行わなかった試験片同等品の、Ｘ線回折パターンである。
【図６】試験片、既存合金及び窒素吸収処理を行わなかった試験片同等品の強度−延性のバランスを示した相関図である。
【図７】（ａ）（ｂ）（ｃ）（ｄ）は、それぞれ、0.9%NaCl溶液、PBS(-)溶液、Hanks溶液、Eagle's MEM溶液中に試験片、316Lステンレス鋼及び窒素吸収処理を行わなかった試験片同等品を浸漬し、その耐食性を評価した分極試験の結果を示した分極曲線である。
【図８】（ａ）（ｂ）は、それぞれ、Eagle's MEM溶液中で分極試験した後の試験片の表面、316Lステンレス鋼の表面を観察した光学顕微鏡写真である。[0001]
BACKGROUND OF THE INVENTION
The invention of this application relates to a method for producing a stainless steel product by nitrogen absorption treatment and a stainless steel product obtained thereby. More specifically, the invention of this application is capable of suppressing the processing cost of austenitic stainless steel, which is difficult to process, to a sufficiently low level, and has a characteristic that can sufficiently satisfy both strength and corrosion resistance. The present invention relates to a method for producing a stainless steel product by nitrogen absorption treatment, and a stainless steel product obtained thereby.
[0002]
[Prior art and its problems]
Austenitic stainless steel is a difficult-to-process material, and therefore it is difficult to process it into a desired shape, resulting in a high processing cost. Since austenitic stainless steel is excellent in both corrosion resistance and strength, it is desired to provide a product having a desired shape or a complicated shape at a low cost.
[0003]
In the powder metallurgy method, an attempt has been made to absorb nitrogen during sintering molding. However, in order to produce a product molded by the powder metallurgy method, a large-scale apparatus is necessary, and the size of the product that can be produced is large. There are restrictions on the sheath shape. In addition, products obtained by powder metallurgy have numerous pores called pores, which are reflected in the mechanical properties of the products and have a problem in mechanical reliability.
[0004]
On the other hand, the nitrogen absorption process is not performed about the bulk material manufactured by melting. The reason is that it has become common knowledge that when a metal material is generally kept in a high-temperature nitrogen atmosphere for a long time, the microstructure becomes coarse and the mechanical properties are significantly reduced. In other words, the decline in the mechanical reliability of the bulk material was strongly feared.
[0005]
The invention of this application has been made in view of such circumstances, can reduce the processing cost of austenitic stainless steel, which is a difficult-to-process material, and is sufficiently satisfactory in both strength and corrosion resistance. It is an object to be solved to provide a method for producing a stainless steel product by nitrogen absorption treatment, and to provide a stainless steel product obtained thereby, which makes it possible to produce a stainless steel product having characteristics that can be achieved.
[0006]
[Means for Solving the Problems]
In order to solve the above problems, the invention of this application is made of ferritic stainless steel, melted, and processed into a desired shape into a bulk product, an inert gas containing nitrogen gas and 800 ° C. contacting at least, to provide a method of manufacturing stainless steel products by the nitrogen absorption process, wherein the benzalkonium is austenitizing the entire product (claim 1).
[0007]
In addition, the invention of this application is made of ferritic stainless steel, and nitrogen is added to the bulk product which has been melted and processed into a desired shape by an inert gas containing nitrogen gas, and the entire product is made austenitic. A stainless steel product (claim 2) is provided.
[0009]
Hereinafter, the manufacturing method of the stainless steel product by the nitrogen absorption treatment of the invention of this application and the stainless steel product obtained thereby will be described in more detail with reference to examples.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
In the method for producing a stainless steel product by nitrogen absorption treatment of the invention of this application, as described above, a bulk product made of ferritic stainless steel and melted and processed into a desired shape is treated with nitrogen gas. contacting in an inert gas and 800 ° C. or higher, including, Ru is austenitizing the entire product. The above-mentioned method of bringing a bulk product processed into a desired shape into contact with an inert gas containing nitrogen gas at 800 ° C. or higher belongs to a nitrogen absorption treatment classified as a so-called solid-phase absorption method, and contains nitrogen gas. nitrogen is added to the entire product by heating the product above 800 ° C. in an inert gas atmosphere. In the method of manufacturing a stainless steel product by nitrogen absorption treatment of the invention of this application, since the object to which nitrogen is added is a melted product made of ferritic stainless steel, it is easier to process than austenitic stainless steel. Yes, a product having the desired shape is obtained. Moreover, the mechanical reliability pointed out also about the scale of apparatus and the restrictions of a shaping | molding in powder metallurgy, and melting is eliminated.
[0011]
Thus stainless steel products of the invention of this application obtained is a product that the entire product is austenitized. For this reason, the stainless steel product of the invention of this application has both excellent corrosion resistance and strength, and even if it is a stainless steel product having a complicated shape, its processing cost is kept low, and it is an inexpensive product. Has the advantage of being. If the amount of nitrogen added to the ferritic stainless steel bulk product is approximately 0.5% by mass or more, the above effect can be obtained sufficiently.
[0012]
【Example】
Using a vacuum arc melting furnace, an ingot of 3.5 kg ferritic stainless steel (Fe-24 mass% Cr-2 mass% Mo) as shown in FIG. 1 was melted. This ingot is divided into four parts, cut into blocks of 25mm x 25mm x 110mm, then hot forged at 1100 ° C and cold forged at room temperature, and the diameters as shown in Fig. 2 and Fig. 3, respectively. A 9 mm × 90 mm round bar and a 1.5 mm × 15 mm × 15 mm thick plate were produced. From the round bar shown in FIG. 2, a round bar tensile test piece having the cross-sectional shape shown in FIG. These two types of test pieces were subjected to nitrogen absorption treatment as shown below using a material nitrogenation apparatus.
[0013]
That is, the test piece was placed on a mesh board made of SUS304, degreased and washed with acetone, inserted and placed in the nitrogenation part of the material nitrogenizer, and vacuumed to 2 Pa with a rotary pump. Next, an inert gas containing nitrogen gas is introduced into the nitrogenation part at a flow rate of 2 liters / min, and the temperature of the nitrogenation part is increased from room temperature to 1200 ° C at a rate of 5 ° C / min to bring the test piece and nitrogen gas into 1200 Contact was made at 24 ° C. for 24 hours.
[0014]
After the above nitrogen absorption treatment, the test piece was quenched from 1200 ° C. into ice water. After removing the surface scale by polishing, the microstructure was identified using an X-ray diffractometer. In this X-ray diffraction, a CuKα tube was used, and the angle was changed by 1 ° / min from 2θ / θ = 40 ° to 90 °. FIG. 5A is an X-ray diffraction pattern obtained. For comparison, FIG. 5B shows an X-ray diffraction pattern of a test piece equivalent product that was not subjected to nitrogen absorption treatment. As is clear from the comparison between FIGS. 5A and 5B, it is confirmed that the test piece after the nitrogen absorption treatment is completely austenitic stainless steel. The amount of nitrogen added was approximately 0.9% by mass.
[0015]
Next, the test piece was subjected to a tensile test at a crosshead speed of 0.5 mm / min using an Instron type tensile tester having a capacity of 100 kN. FIG. 6 shows the balance between the strength and ductility of the test piece after nitrogen absorption treatment, the test piece equivalent not subjected to nitrogen absorption treatment, and the existing alloy. As can be seen from FIG. 6, when the nitrogen absorption treatment is performed, the balance between strength and ductility is excellent as compared with the existing alloy and a test piece equivalent product that has not been subjected to the nitrogen absorption treatment. This tendency was also recognized in the case of a cold rolled material in which the test piece was not subjected to nitrogen absorption treatment. The effectiveness of nitrogen absorption treatment is reconfirmed.
[0016]
Furthermore, the corrosion resistance of the test piece was also evaluated.
[0017]
Specimen adjusted to 37 ° C, degassed with nitrogen gas, PBS (-) solution, Hanks solution, Eagle's MEM solution, test piece, 316L stainless steel, and test piece equivalent not subjected to nitrogen absorption treatment The product was immersed. FIGS. 7A to 7D are polarization curves that are results of polarization tests performed for evaluating corrosion resistance. As can be seen from FIGS. 7 (a) to (d), the test pieces that had been subjected to nitrogen absorption treatment for any of the test solutions were compared to 316L stainless steel and test piece equivalents that had not been subjected to nitrogen absorption treatment. Excellent corrosion resistance, and no pitting corrosion was observed as shown in FIG. As shown in FIG. 8B, pitting corrosion occurred in 316L stainless steel.
[0018]
The method for producing a stainless steel product by nitrogen absorption treatment of the invention of this application and the stainless steel product obtained thereby eliminate the disadvantage of the difficult workability of austenitic stainless steel, even if the product has a complicated shape It can be realized at a low cost and has sufficient strength and corrosion resistance.
[0019]
Of course, the invention of this application is not limited by the above embodiments and examples. It goes without saying that various aspects are possible for details such as the composition of stainless steel, the shape and size of the product, and the conditions for nitrogen absorption treatment.
[0020]
【The invention's effect】
As described above in detail, according to the invention of this application, it is formed from an austenitic stainless steel that is a difficult-to-process material, has a desired shape, can sufficiently reduce processing costs, and has both strength and corrosion resistance. A stainless steel product having fully satisfactory properties and a method of manufacturing the same are provided.
[Brief description of the drawings]
FIG. 1 is a photograph replacing a drawing showing an ingot of 3.5 kg ferritic stainless steel (Fe-24 mass% Cr-2 mass% Mo) melted by using a vacuum arc melting furnace in an example. .
2 is a photograph replacing a drawing showing a round bar material produced by hot and cold forging from the ingot shown in FIG. 1; FIG.
3 is a photograph replacing a drawing showing a plate material produced by hot and cold forging from the ingot shown in FIG. 1; FIG.
4 is a cross-sectional view showing a round bar tensile test piece made from the round bar shown in FIG. 2. FIG.
FIGS. 5A and 5B are X-ray diffraction patterns of a test piece after nitrogen absorption treatment and a test piece equivalent product not subjected to nitrogen absorption treatment, respectively.
FIG. 6 is a correlation diagram showing a balance between strength and ductility of a test piece, an existing alloy, and a test piece equivalent product not subjected to nitrogen absorption treatment.
[Fig. 7] (a), (b), (c), and (d) show a test piece, 316L stainless steel, and nitrogen absorption treatment in 0.9% NaCl solution, PBS (-) solution, Hanks solution, and Eagle's MEM solution, respectively. It is the polarization curve which showed the result of the polarization test which immersed the test piece equivalent goods which were not performed and evaluated the corrosion resistance.
FIGS. 8A and 8B are optical micrographs obtained by observing the surface of a test piece and the surface of 316L stainless steel after a polarization test in Eagle's MEM solution, respectively.

Claims (2)

フェライト型ステンレス鋼製であり、溶製され、所望の形状に加工されたバルク状の製品を、窒素ガスを含む不活性ガスと800℃以上で接触させ、製品全体をオーステナイト化させることを特徴とする窒素吸収処理によるステンレス鋼製製品の製造方法。Is made of ferritic stainless steel, is melted, shaped products bulk which is processed into a desired shape, the nitrogen gas is contacted with an inert gas and 800 ° C. or higher containing, and Turkey is austenitizing the entire product A method for producing a stainless steel product by a nitrogen absorption treatment. フェライト型ステンレス鋼製であり、溶製され、所望の形状に加工されたバルク状の製品に、窒素ガスを含む不活性ガスにより窒素が添加され、製品全体がオーステナイト化されたことを特徴とするステンレス鋼製製品。  It is made of ferritic stainless steel, and it is characterized in that nitrogen is added to the bulk product that has been melted and processed into a desired shape by an inert gas containing nitrogen gas, and the entire product is austenitized. Stainless steel product.
JP2002231557A 2002-08-08 2002-08-08 Manufacturing method of stainless steel product by nitrogen absorption treatment and stainless steel product obtained thereby Expired - Lifetime JP4009716B2 (en)

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