JP2014051739A - Method of manufacturing two-phase stainless steel using post heat treatment - Google Patents

Method of manufacturing two-phase stainless steel using post heat treatment Download PDF

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JP2014051739A
JP2014051739A JP2013183278A JP2013183278A JP2014051739A JP 2014051739 A JP2014051739 A JP 2014051739A JP 2013183278 A JP2013183278 A JP 2013183278A JP 2013183278 A JP2013183278 A JP 2013183278A JP 2014051739 A JP2014051739 A JP 2014051739A
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stainless steel
steel
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JP5708739B2 (en
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Tae Ho Lee
テホ イ
Heon-Young Ha
ヒョンヨン ハ
Joonoh Moon
ジュノ ムン
Chul Hwang Byoung
ビョンチョル ファン
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Korea Institute of Machinery and Materials KIMM
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    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D6/00—Heat treatment of ferrous alloys
    • C21D6/002—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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/18—Hardening; Quenching with or without subsequent tempering
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/34—Methods of heating
    • 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
    • C21D6/005—Heat treatment of ferrous alloys containing Mn
    • 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/38—Ferrous alloys, e.g. steel alloys containing chromium with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • 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)
  • Heat Treatment Of Steel (AREA)
  • Treatment Of Steel In Its Molten State (AREA)

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing two-phase stainless steel excellent in mechanical physical properties by reducing contents of alloy components such as nickel and forming ferrite and austenite with using a post heat treatment at the same time.SOLUTION: A method of manufacturing a two-phase stainless steel includes melting a mother alloy containing, by wt.%, C:0.05% or less, N:0.3 to 0.5%, Cr:17.5 to 18.5%, Mn:9.5 to 10.5%, Si:0.01 to 0.1% and the balance iron with inevitable impurities in vacuum with a vacuum melting furnace to control a nitrogen content and manufacture a semifinished steel, and rolling the semifinished steel, heating the rolled steel with a velocity of 300 to 450°C/sec., appling it to annealing treatment at 1200 to 1350°C, and cooling with a velocity of 30 to 75°C/sec. to form a two-phase structure containing austenite of 40 to 75 vol.% and ferrite of 25 to 60 vol.%.

Description

本発明は、ステンレス鋼の製造方法に関するものであり、より詳しくは、後熱処理を利用した２相ステンレス鋼の製造方法に関する。   The present invention relates to a method for producing stainless steel, and more particularly to a method for producing duplex stainless steel using post-heat treatment.

ステンレス鋼は、微細組織によってオーステナイトステンレス鋼、フェライトステンレス鋼、２相ステンレス鋼に大きく分類される。   Stainless steel is roughly classified into austenitic stainless steel, ferritic stainless steel, and duplex stainless steel depending on the microstructure.

これらのうち２相ステンレス鋼は、フェライトとオーステナイトをそれぞれ約５０％ 前後含むことにより、応力腐食割れに対する抵抗性および機械的強度を同時に確保したステンレス鋼である。このような２相ステンレス鋼は、既存の炭素鋼やオーステナイト系ステンレス鋼に比べて優れた耐食性、機械的特性を有することにより、構造材適用時の維持費用削減等の長所を有しているため、多くの分野で活用されている。   Among these, the duplex stainless steel is a stainless steel that simultaneously secures resistance to stress corrosion cracking and mechanical strength by including about 50% of ferrite and austenite. Such a duplex stainless steel has advantages such as a reduction in maintenance costs when structural materials are applied because it has superior corrosion resistance and mechanical properties compared to existing carbon steel and austenitic stainless steel. It is used in many fields.

２相ステンレス鋼は通常、ニッケル（Ｎｉ）、クロム（Ｃｒ）、モリブデン（Ｍｏ）等の耐食性向上元素を多量に含む。特に、２相ステンレス鋼の場合は、オーステナイト系ステンレス鋼に比べて低いニッケルを含有しているが、炭素鋼に比べて多量のニッケルを含有することにより、製造原価の上昇および環境汚染の問題を起こし得る。   The duplex stainless steel usually contains a large amount of corrosion resistance improving elements such as nickel (Ni), chromium (Cr), and molybdenum (Mo). In particular, duplex stainless steel contains nickel that is lower than austenitic stainless steel, but it contains a large amount of nickel compared to carbon steel, which raises manufacturing costs and environmental pollution. It can be awakened.

本発明と関連する背景技術としては、特許文献１に開示されている金属間相の形成が抑制された耐食性、耐脆化性、鋳造性および熱間加工性に優れたスーパーデュープレックスステンレス鋼がある。   As background art related to the present invention, there is a super duplex stainless steel excellent in corrosion resistance, embrittlement resistance, castability and hot workability, which is disclosed in Patent Document 1, in which the formation of intermetallic phases is suppressed. .

韓国公開特許公報第１０−２００３−００７７２３９号（２００３．１０．０１．公開）Korean Published Patent Publication No. 10-2003-0077239 (2003. 10.01. Published)

本発明の目的は、ニッケル等の高価な合金成分含量を低くし、同時に後熱処理を利用してフェライトとオーステナイトを形成することにより、機械的物性に優れた２相ステンレス鋼の製造方法を提供することである。   An object of the present invention is to provide a method for producing a duplex stainless steel having excellent mechanical properties by lowering the content of expensive alloy components such as nickel and simultaneously forming ferrite and austenite using post heat treatment. That is.

前記目的を達成するための本発明の実施例にかかる２相ステンレス鋼の製造方法は、ステンレス系合金組成を有する半製品鋼を製造すること；前記半製品鋼を圧延すること；及び前記の圧延された鋼を熱処理してオーステナイト及びフェライト分率を調節すること；を含むことを特徴とする。   In order to achieve the above object, a method for producing a duplex stainless steel according to an embodiment of the present invention comprises: producing a semi-finished steel having a stainless-based alloy composition; rolling the semi-finished steel; Heat treating the formed steel to adjust the austenite and ferrite fraction.

このとき前記半製品鋼は、重量％で、炭素（Ｃ）：０．０５％以下、窒素（Ｎ）：０．３％ないし０．５％、クロム（Ｃｒ）：１７．５％ないし１８．５％、マンガン（Ｍｎ）：９．５％ないし１０．５％、シリコン（Ｓｉ）：０．０１％ないし０．１％、及び残りは鉄（Ｆｅ）と不可避な不純物からなり得る。この場合、前記熱処理は、昇温段階、アニーリング段階及び冷却段階を含み、前記アニーリング段階は１２００℃ないし１３５０℃で行われることが好ましい。   At this time, the semi-finished steel is, by weight, carbon (C): 0.05% or less, nitrogen (N): 0.3% to 0.5%, chromium (Cr): 17.5% to 18. 5%, manganese (Mn): 9.5% to 10.5%, silicon (Si): 0.01% to 0.1%, and the remainder may be composed of iron (Fe) and inevitable impurities. In this case, the heat treatment includes a temperature raising step, an annealing step, and a cooling step, and the annealing step is preferably performed at 1200 ° C. to 1350 ° C.

前記目的を達成するための本発明の他の実施例にかかる２相ステンレス鋼の製造方法は、重量％で、炭素（Ｃ）：０．０５％以下、窒素（Ｎ）：０．３％ないし０．５％、クロム（Ｃｒ）：１７．５％ないし１８．５％、マンガン（Ｍｎ）：９．５％ないし１０．５％、シリコン（Ｓｉ）：０．０１％ないし０．１％及び残りは鉄（Ｆｅ）と不可避な不純物からなる半製品鋼を製造すること；前記半製品鋼を圧延すること；及び前記の圧延された鋼を熱処理してオーステナイト４０ｖｏｌ％ないし７５ｖｏｌ％及びフェライト２５ｖｏｌ％ないし６０ｖｏｌ％を含む２相組織を形成すること；を含むことを特徴とする。   In order to achieve the above object, a method for producing a duplex stainless steel according to another embodiment of the present invention includes carbon (C): 0.05% or less, nitrogen (N): 0.3% to 0.3% by weight. 0.5%, chromium (Cr): 17.5% to 18.5%, manganese (Mn): 9.5% to 10.5%, silicon (Si): 0.01% to 0.1% and The remainder is to produce a semi-finished steel consisting of iron (Fe) and inevitable impurities; rolling the semi-finished steel; and heat treating the rolled steel to austenite 40 vol% to 75 vol% and ferrite 25 vol% Or forming a two-phase structure containing 60 vol%.

このとき前記熱処理は、昇温段階、アニーリング段階及び冷却段階を含み、前記アニーリング段階は１２００℃ないし１３５０℃で行われることが好ましい。   At this time, the heat treatment includes a temperature raising step, an annealing step, and a cooling step, and the annealing step is preferably performed at 1200 ° C. to 1350 ° C.

本発明にかかる２相ステンレス鋼の製造方法は、高価な元素であるニッケル（Ｎｉ）の添加を排除し、クロム（Ｃｒ）の含量を大きく下げ、これにより発生し得るオーステナイト安定化問題および強度低下問題を、マンガン（Ｍｎ）及び窒素（Ｎ）の含有及び後熱処理を通じて解決することができる。   The method for producing a duplex stainless steel according to the present invention eliminates the addition of nickel (Ni), which is an expensive element, greatly reduces the content of chromium (Cr), and this can cause austenite stabilization problems and reduced strength. The problem can be solved through the inclusion of manganese (Mn) and nitrogen (N) and post heat treatment.

また、本発明にかかる２相ステンレス鋼の製造方法によると、アニーリング温度によってフェライトとオーステナイト分率を自由に変えることができ、これにより多様な物性を有する２相ステンレス鋼を製造することができる。よって、本発明にかかる方法で製造された２相ステンレス鋼は、化学プラント、船舶等の多様な分野に適用できる。   In addition, according to the method for producing a duplex stainless steel according to the present invention, the ferrite and austenite fractions can be freely changed depending on the annealing temperature, and thereby a duplex stainless steel having various physical properties can be produced. Therefore, the duplex stainless steel produced by the method according to the present invention can be applied to various fields such as chemical plants and ships.

本発明の実施例にかかる２相ステンレス鋼の製造方法を概略的に表す順序図である。It is a flowchart showing roughly the manufacturing method of the duplex stainless steel concerning the example of the present invention. 本発明に適用される合金組成において温度によるオーステナイト及びフェライト分率変化を表したグラフである。It is a graph showing the austenite and ferrite fraction change by temperature in the alloy composition applied to this invention. 比較例に該当する鋼試片１の微細組織写真である。It is a microstructure picture of the steel specimen 1 applicable to a comparative example. 比較例に該当する鋼試片２の微細組織写真である。It is a microstructure photograph of the steel specimen 2 applicable to a comparative example. 実施例に該当する鋼試片３の微細組織写真である。It is a microstructure photograph of the steel specimen 3 applicable to an Example. 実施例に該当する鋼試片４の微細組織写真である。It is a microstructure photograph of the steel specimen 4 applicable to an Example. 実施例に該当する鋼試片５の微細組織写真である。It is a microstructure photograph of the steel specimen 5 applicable to an Example.

以下、添付の図面を参照して、本発明にかかる後熱処理を利用した２相ステンレス鋼の製造方法について詳しく説明する。
図１は、本発明の実施例にかかる２相ステンレス鋼の製造方法を概略的に表す順序図である。 Hereinafter, a method for producing a duplex stainless steel using post-heat treatment according to the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a flow chart schematically illustrating a method for producing a duplex stainless steel according to an embodiment of the present invention.

図１を参照すると、本発明にかかる２相ステンレス鋼の製造方法は、半製品鋼の製造段階（Ｓ１１０）、圧延段階（Ｓ１２０）及び後熱処理段階（Ｓ１３０）を含む。
半製品鋼の製造段階（Ｓ１１０）では、ステンレス系合金組成を有する半製品鋼を製造する。 Referring to FIG. 1, the method for producing a duplex stainless steel according to the present invention includes a semi-finished steel production step (S110), a rolling step (S120), and a post heat treatment step (S130).
In the semi-finished steel production stage (S110), semi-finished steel having a stainless alloy composition is produced.

より好ましくは、本発明に適用されるステンレス系合金組成は、重量％で、炭素（Ｃ）：０．０５％以下、窒素（Ｎ）：０．３％ないし０．５％、クロム（Ｃｒ）：１７．５％ないし１８．５％、マンガン（Ｍｎ）：９．５％ないし１０．５％、シリコン（Ｓｉ）：０．０１％ないし０．１％及び残りは鉄（Ｆｅ）と不可避な不純物からなり得る。   More preferably, the composition of the stainless steel alloy applied to the present invention is, by weight, carbon (C): 0.05% or less, nitrogen (N): 0.3% to 0.5%, chromium (Cr). : 17.5% to 18.5%, Manganese (Mn): 9.5% to 10.5%, Silicon (Si): 0.01% to 0.1%, and the rest is inevitable with iron (Fe) It can consist of impurities.

前記ステンレス系合金組成の場合、ニッケル（Ｎｉ）及びモリブデン（Ｍｏ）の添加が排除されて価格競争力が高く、クロム（Ｃｒ）の含量が１７．５重量％ないし１８．５重量％であり従来より相対的に低いという特徴がある。また、前記合金組成の場合、低いクロム含量等に起因してオーステナイト安定性が低下することを防ぐために、マンガン（Ｍｎ）：９．５重量％ないし１０．５重量％及び窒素（Ｎ）：０．３重量％ないし０．５重量％が含まれるという特徴がある。   In the case of the stainless steel alloy composition, the addition of nickel (Ni) and molybdenum (Mo) is eliminated and the price competitiveness is high, and the chromium (Cr) content is 17.5 wt% to 18.5 wt%. It is characterized by being relatively lower. Further, in the case of the alloy composition, manganese (Mn): 9.5 wt% to 10.5 wt% and nitrogen (N): 0 to prevent the austenite stability from being lowered due to a low chromium content or the like. .3 wt% to 0.5 wt% is included.

より具体的には、本発明では、炭素（Ｃ）、窒素（Ｎ）、クロム（Ｃｒ）、マンガン（Ｍｎ）及びシリコン（Ｓｉ）を含む。前記成分以外に残りは鉄（Ｆｅ）と不可避な不純物である。   More specifically, the present invention includes carbon (C), nitrogen (N), chromium (Cr), manganese (Mn), and silicon (Si). In addition to the above components, the remainder is iron (Fe) and inevitable impurities.

ここで、不可避な不純物とは、意図的に含まれるものではない製鋼過程等で不可避に含まれる成分であって、ニッケル（Ｎｉ）：０．０１重量％以下、リン（Ｐ）：０．０４重量％以下、硫黄（Ｓ）：０．０１％以下、アルミニウム(Ａｌ）：０．０５重量％以下等になり得る。不純物として含まれ得る元素のうち、ニッケルは環境問題を引き起こし、リンと硫黄は機械的物性の低下を引き起こし、アルミニウムは窒素添加効果を低下させるため、製鋼時に除去されることが好ましく、不純物として残留しても前記範囲に制限されることが好ましい。   Here, the inevitable impurities are components inevitably included in the steel making process and the like that are not intentionally included. Nickel (Ni): 0.01 wt% or less, phosphorus (P): 0.04 It may be less than or equal to wt%, sulfur (S): 0.01% or less, aluminum (Al): 0.05 wt% or less. Of the elements that can be included as impurities, nickel causes environmental problems, phosphorus and sulfur cause mechanical properties to deteriorate, and aluminum reduces the effect of nitrogen addition. Therefore, it is preferably removed during steelmaking, and remains as an impurity. Even so, it is preferable to be limited to the above range.

以下、本発明にかかる２相ステンレス鋼が製造方法に適用される合金組成について説明する。   Hereinafter, the alloy composition in which the duplex stainless steel according to the present invention is applied to the production method will be described.

炭素（Ｃ）
炭素（Ｃ）は、ステンレス鋼の機械的物性、高温強度の向上を助ける。前記炭素は、鋼全体重量の０．０５重量％以下で含まれることが好ましい。炭素の含量が０．０５重量％を超える場合、結晶粒界に炭化クロム（Ｃｒ２３Ｃ６）析出によって腐食抵抗性を低下させる要因になる。 Carbon (C)
Carbon (C) helps improve the mechanical properties and high temperature strength of stainless steel. The carbon is preferably contained at 0.05% by weight or less of the total weight of the steel. When the carbon content exceeds 0.05% by weight, corrosion resistance is reduced by precipitation of chromium carbide (Cr 23 C 6 ) at the grain boundaries.

窒素（Ｎ）
窒素（Ｎ）は、オーステナイト安定化元素であって、ニッケルを代替できる元素で、孔食抵抗性を大きく増加させ得る。前記窒素は、鋼全体重量の０．３重量％ないし０．５重量％で含まれることが好ましい。窒素の含量が０．３重量％未満だとその添加効果が十分でない。逆に、窒素の含量が０．５重量％を超えると、常圧下での製鋼時に窒素含量調節に困難がある。 Nitrogen (N)
Nitrogen (N) is an austenite stabilizing element that can replace nickel, and can greatly increase pitting resistance. The nitrogen is preferably included at 0.3 wt% to 0.5 wt% of the total weight of the steel. If the nitrogen content is less than 0.3% by weight, the effect of addition is not sufficient. Conversely, if the nitrogen content exceeds 0.5% by weight, it is difficult to control the nitrogen content during steelmaking under normal pressure.

クロム（Ｃｒ）
クロム（Ｃｒ）は、鋼表面にクロム酸化層を生成して耐食性の向上を助ける。
前記クロムは、鋼全体重量の１７．５重量％ないし１８．５重量％で含まれることが好ましい。クロムの含量が１７．５重量％未満だとその添加効果が十分でない。逆に、クロムの含量が１８．５重量％を超えると、フェライト安定性が増加することにより２相組織制御時に困難がある。 Chrome (Cr)
Chromium (Cr) helps to improve corrosion resistance by forming a chromium oxide layer on the steel surface.
The chromium is preferably included at 17.5 wt% to 18.5 wt% of the total weight of the steel. If the chromium content is less than 17.5% by weight, the effect of addition is not sufficient. Conversely, if the chromium content exceeds 18.5% by weight, there is a difficulty in controlling the two-phase structure due to increased ferrite stability.

マンガン（Ｍｎ）
マンガン（Ｍｎ）は、オーステナイトを安定化させ、窒素固溶度を増加させるのに有効な元素である。前記マンガンは、鋼全体重量の９．５重量％ないし１０．５重量％で含まれることが好ましい。マンガンの含量が９．５重量％未満の場合、本発明においてニッケルが添加されないことを考慮すると、オーステナイト安定性の確保が困難になり得る。逆に、マンガンの含量が１０．５重量％を超えると、オーステナイト安定性が増加することにより、２相組織制御時に困難があり、腐食抵抗性が減少する。 Manganese (Mn)
Manganese (Mn) is an effective element for stabilizing austenite and increasing nitrogen solid solubility. The manganese is preferably contained in an amount of 9.5 to 10.5% by weight based on the total weight of the steel. When the manganese content is less than 9.5% by weight, it is difficult to ensure austenite stability, considering that nickel is not added in the present invention. On the other hand, if the manganese content exceeds 10.5% by weight, the austenite stability is increased, thereby causing difficulty in controlling the two-phase structure and reducing the corrosion resistance.

シリコン（Ｓｉ）
シリコン（Ｓｉ）は、フェライト形成元素であり、また脱酸剤として作用する。前記シリコンは、鋼全体重量の０．０１重量％ないし０．１重量％で含まれることが好ましい。シリコンの含量が０．０１重量％未満だとその添加効果が十分でない。逆に、シリコンが０．１重量％を超えて過剰添加されると、鋼の靭性を低下させるという問題点がある。 Silicon (Si)
Silicon (Si) is a ferrite forming element and acts as a deoxidizer. The silicon is preferably contained in an amount of 0.01% to 0.1% by weight of the total steel weight. If the silicon content is less than 0.01% by weight, the effect of addition is not sufficient. On the other hand, when silicon is excessively added exceeding 0.1% by weight, there is a problem that the toughness of the steel is lowered.

前記合金成分からなる半製品鋼は、スラブ、インゴット、ビレット等の形態になり得る。   The semi-finished steel made of the alloy component can be in the form of a slab, ingot, billet or the like.

このような半製品鋼は、多様な方式で製造でき、一つの例として真空溶解方式を提示できる。   Such semi-finished steel can be manufactured by various methods, and a vacuum melting method can be presented as an example.

真空溶解は、母合金装入段階、真空維持段階、母合金溶融段階、窒素含量調節段階、溶融合金攪拌段階、半製品鋼形成段階を含む一連の過程で行うことができる。   The vacuum melting can be performed in a series of processes including a master alloy charging stage, a vacuum maintaining stage, a master alloy melting stage, a nitrogen content adjusting stage, a molten alloy stirring stage, and a semi-finished steel forming stage.

母合金装入段階では、電解鉄、Ｆｅ−５０重量％Ｍｎ、Ｆｅ−６０重量％Ｃｒ、Ｆｅ−５８．８重量％Ｃｒ−６．６重量％Ｎ等のような、母合金を製造しようとする２相ステンレス鋼の合金組成比に応じて秤量した後、真空溶解炉に装入する。   In the mother alloy charging stage, an attempt is made to produce a mother alloy such as electrolytic iron, Fe-50 wt% Mn, Fe-60 wt% Cr, Fe-58.8 wt% Cr-6.6 wt% N, etc. After weighing according to the alloy composition ratio of the duplex stainless steel to be performed, it is charged into a vacuum melting furnace.

次に、真空維持段階では、真空溶解のために、真空溶解炉内部を約１０−３ｔｏｒｒ以下の真空に維持する。 Next, in the vacuum maintenance step, the inside of the vacuum melting furnace is maintained at a vacuum of about 10 −3 torr or less for vacuum melting.

次に、母合金溶融段階では、電気抵抗加熱、誘導加熱等を通じて真空溶解炉を約１６００℃以上に加熱して、母合金を溶融させ溶融合金を形成する。   Next, in the master alloy melting stage, the vacuum melting furnace is heated to about 1600 ° C. or higher through electric resistance heating, induction heating, etc., and the master alloy is melted to form a molten alloy.

次に、窒素含量調節段階では、窒素ガス注入を通じて溶融合金の窒素含量を０．１重量％ないし０．３重量％に調節する。このとき、目標とする窒素含量を得るために真空溶解炉内部を加圧することができるが、必ずしもこれを行わなければならないのではない。   Next, in the nitrogen content adjusting step, the nitrogen content of the molten alloy is adjusted to 0.1 wt% to 0.3 wt% through nitrogen gas injection. At this time, in order to obtain a target nitrogen content, the inside of the vacuum melting furnace can be pressurized, but this does not necessarily have to be performed.

次に、溶融合金攪拌段階では、溶融合金を攪拌して合金元素の片石を除去したり合金元素片石の発生が抑制されるようにする。   Next, in the molten alloy agitation step, the molten alloy is agitated to remove the alloy element schist and to suppress the generation of the alloy element schist.

次に、半製品鋼形成段階では、真空溶解炉内部から溶融合金を出湯して、インゴット、スラブ、ビレット等の形態の半製品鋼を形成する。   Next, in the semi-finished steel forming stage, the molten alloy is discharged from the inside of the vacuum melting furnace to form semi-finished steel in the form of an ingot, slab, billet or the like.

次に、圧延段階（Ｓ１２０）では半製品鋼を圧延する。
圧延は、前記半製品鋼をオーステナイト単相域で再加熱して均質化する段階と、前記の再加熱された半製品鋼を約９００℃ないし１０００℃で熱間圧延する段階を含み得る。熱間圧延以降は、室温までクエンチング（ｑｕｅｎｃｈｉｎｇ）する過程を行うことができる。 Next, in the rolling stage (S120), the semi-finished steel is rolled.
Rolling may include reheating and heating the semi-finished steel in an austenitic single phase region and hot rolling the reheated semi-finished steel at about 900 ° C to 1000 ° C. After hot rolling, a process of quenching to room temperature can be performed.

次に、後熱処理段階（Ｓ１３０）では圧延された鋼を熱処理してオーステナイト及びフェライト分率を調節する。
このとき、熱処理は昇温段階、アニーリング段階及び冷却段階を含み得る。 Next, in the post heat treatment step (S130), the rolled steel is heat treated to adjust the austenite and ferrite fractions.
At this time, the heat treatment may include a heating step, an annealing step, and a cooling step.

本発明では、アニーリング段階を１２００℃ないし１３５０℃で約１時間以内に行う。
このようなアニーリング条件下で、オーステナイト４０ｖｏｌ％ないし７５ｖｏｌ％及びフェライト２５ｖｏｌ％ないし６０ｖｏｌ％を含む２相組織を形成できる。これは図２を参照するとより明確に理解できる。 In the present invention, the annealing step is performed at 1200 ° C. to 1350 ° C. within about 1 hour.
Under such annealing conditions, a two-phase structure including austenite 40 vol% to 75 vol% and ferrite 25 vol% to 60 vol% can be formed. This can be more clearly understood with reference to FIG.

図２は、本発明に適用される合金組成において、温度によるオーステナイト及びフェライト分率変化を示したグラフであり、Ｔｈｅｒｍｏ−Ｃａｌｃプログラム（Ｔｈｅｒｍｏ−Ｃａｌｃ Ｓｏｆｔｗａｒｅ Ｉｎｃ．）を利用した。   FIG. 2 is a graph showing changes in the austenite and ferrite fraction with temperature in the alloy composition applied to the present invention, and a Thermo-Calc program (Thermo-Calc Software Inc.) was used.

図２を参照すると、後熱処理時にアニーリング温度が１２００℃以上、そして１３５０℃以下でフェライト分率が２５ｖｏｌ％ないし６０ｖｏｌ％になり得る。アニーリング温度が１２００℃未満だったり１３５０℃を超えると、フェライト分率が低くなり過ぎたり高くなり過ぎて２相ステンレス鋼の特性を発揮し難くなる。   Referring to FIG. 2, the ferrite fraction may be 25 vol% to 60 vol% when the annealing temperature is 1200 ° C. or higher and 1350 ° C. or lower during the post heat treatment. If the annealing temperature is less than 1200 ° C. or exceeds 1350 ° C., the ferrite fraction becomes too low or too high, making it difficult to exhibit the characteristics of the duplex stainless steel.

一方、後熱処理時にアニーリング温度までの昇温は３００℃／ｓｅｃないし４５０℃／ｓｅｃの速度で約１００℃ないし４００℃まで行うことがより好ましい。昇温速度が３００℃／ｓｅｃ未満だと、結晶粒粗大化により製造される鋼の強度が低下し得る。逆に、昇温速度が４５０℃／ｓｅｃを超えると、過度な加熱によって鋼の製造コストが大きく増加し得、昇温速度の制御が難しくなり得る。   On the other hand, it is more preferable to raise the temperature to the annealing temperature during post-heat treatment from about 100 ° C. to 400 ° C. at a rate of 300 ° C./sec to 450 ° C./sec. If the rate of temperature rise is less than 300 ° C./sec, the strength of the steel produced by the coarsening of crystal grains can be reduced. On the other hand, when the rate of temperature rise exceeds 450 ° C./sec, the manufacturing cost of steel can be greatly increased due to excessive heating, and the control of the rate of temperature rise can be difficult.

また、後熱処理時のアニーリング以降の冷却は、３０℃／ｓｅｃないし７５℃／ｓｅｃの速度で行うことがより好ましい。冷却速度が３０℃／ｓｅｃ未満 の場合は、目的とする層変態が発生し得る。逆に、冷却速度が７５℃／ｓｅｃを超えると、冷却速度の制御に困難がある。   Further, it is more preferable that the cooling after the annealing in the post heat treatment is performed at a rate of 30 ° C./sec to 75 ° C./sec. When the cooling rate is less than 30 ° C./sec, the desired layer transformation can occur. Conversely, when the cooling rate exceeds 75 ° C./sec, it is difficult to control the cooling rate.

実施例
以下、本発明の好ましい実施例を通じて本発明の構成及び作用をより詳しく説明する。但し、これは本発明の好ましい例示として提示するものであり、如何なる意味でもこれによって本発明が制限されると解釈してはならない。ここに記載していない内容は、本技術分野の熟練者であれば技術的に類推できるもののため、その説明は省略する。 EXAMPLES Hereinafter, the configuration and operation of the present invention will be described in more detail through preferred examples of the present invention. However, this is presented as a preferred illustration of the present invention and should not be construed as limiting the invention in any way. Since the contents not described here can be technically analogized by those skilled in the art, the description thereof will be omitted.

１．鋼試片の製造
表１に記載した組成及び残りの鉄からなる鋼試片１ないし５を製造した。
1. Production of Steel Specimens Steel specimens 1 to 5 having the composition shown in Table 1 and the remaining iron were produced.

鋼試片１及び２は、該当合金組成からなるインゴットを１０００℃で１時間再加熱し、９００℃まで熱間圧延した後、室温までクエンチングして製造した。   Steel specimens 1 and 2 were manufactured by reheating an ingot made of the corresponding alloy composition at 1000 ° C. for 1 hour, hot rolling to 900 ° C., and then quenching to room temperature.

鋼試片３ないし５は、該当合金組成からなるインゴットを１０００℃で１時間再加熱し、９００℃まで熱間圧延し、室温までクエンチングする過程までは鋼試片１及び２と同一だが、クエンチング後、表２に記載した条件で後熱処理を行って製造した。
Steel specimens 3 to 5 are the same as steel specimens 1 and 2 until the ingot composed of the corresponding alloy composition is reheated at 1000 ° C. for 1 hour, hot rolled to 900 ° C., and quenched to room temperature. After quenching, post-heat treatment was performed under the conditions described in Table 2.

２．物性評価
鋼試片１ないし５に対して、ＡＳＴＭ試験片による引張試験を行い、その結果を表３に示した。
2. Evaluation of Physical Properties Steel specimens 1 to 5 were subjected to a tensile test using an ASTM specimen, and the results are shown in Table 3.

表３を参照すると、本発明で提示した後熱処理を含む方法で製造された鋼試片３ないし５は、ニッケル、モリブデン等の元素が添加されていないにもかかわらず、後熱処理が行われなかった鋼試片１ないし２に比べて強度特性が相対的に優れていることが分かる。   Referring to Table 3, the steel specimens 3 to 5 manufactured by the method including post-heat treatment presented in the present invention are not subjected to post-heat treatment even though elements such as nickel and molybdenum are not added. It can be seen that the strength characteristics are relatively superior to those of the steel specimens 1 and 2.

３．微細組織評価
図３及び図４は、比較例に該当する鋼試片１（図３）、及び鋼試片２（図４）の微細組織写真である。図５ないし図７は、実施例に該当する鋼試片３（図５）、鋼試片４（図６）及び鋼試片５（図７）の微細組織写真である。 3. Microstructure Evaluation FIGS. 3 and 4 are photographs of the microstructure of steel specimen 1 (FIG. 3) and steel specimen 2 (FIG. 4) corresponding to the comparative example. 5 to 7 are microstructural photographs of the steel specimen 3 (FIG. 5), the steel specimen 4 (FIG. 6), and the steel specimen 5 (FIG. 7) corresponding to the embodiment.

図３ないし図７を参照すると、鋼試片１ないし５全てがフェライトとオーステナイト２相組織を有することが分かる。つまり、鋼試片１及び２の場合のように、クロム、ニッケル及びモリブデンが多量含有されると２相組織が形成できるが、本発明で提示した後熱処理を行うと、このようなニッケル及びモリブデンを排除し、クロムの含量を低くした状態でも２相組織の形成が可能になる。   3 to 7, it can be seen that all the steel specimens 1 to 5 have a two-phase structure of ferrite and austenite. That is, as in the case of steel specimens 1 and 2, when a large amount of chromium, nickel, and molybdenum is contained, a two-phase structure can be formed. However, when heat treatment is performed after the present invention is presented, such nickel and molybdenum And a two-phase structure can be formed even when the chromium content is low.

一方、図３ないし図５を参照すると、鋼試片１ないし２（図３ないし４）は、典型的な２相ステンレス組織を表すのに対し、鋼試片３ないし５（図５ないし７）は、オーステナイト粒界にフェライトが形成されている２相ステンレス組織を表すことが分かる。   On the other hand, referring to FIGS. 3 to 5, steel specimens 1 to 2 (FIGS. 3 to 4) represent a typical duplex stainless steel structure, whereas steel specimens 3 to 5 (FIGS. 5 to 7). Represents a two-phase stainless steel structure in which ferrite is formed at the austenite grain boundaries.

本発明は、実施例を参考にして説明したが、これは例示的なものに過ぎなく、当該技術が属する分野で通常の知識を有する者であれば、これにより多様な変形および均等な他実施例が可能だという点を理解できると考える。よって、本発明の真正な技術的保護範囲は、特許請求の範囲によって定めなければならない。   The present invention has been described with reference to the embodiments. However, the embodiments are merely illustrative, and various modifications and equivalent other implementations may be performed by those having ordinary knowledge in the art. I think you can understand that an example is possible. Therefore, the true technical protection scope of the present invention must be defined by the claims.

Ｓ１１０：半製品鋼製造段階
Ｓ１２０：圧延段階
Ｓ１３０：後熱処理段階 S110: Semi-finished steel manufacturing stage S120: Rolling stage S130: Post heat treatment stage

Claims (12)

ステンレス系合金組成を有する半製品鋼を製造すること；
前記半製品鋼を圧延すること；及び
前記の圧延された鋼を熱処理してオーステナイト及びフェライト分率を調節すること；を含むことを特徴とする２相ステンレス鋼の製造方法。 Producing semi-finished steel with stainless steel alloy composition;
Rolling the semi-finished steel; and heat-treating the rolled steel to adjust the austenite and ferrite fractions. 前記半製品鋼は、
重量％で、炭素（Ｃ）：０．０５％以下、窒素（Ｎ）：０．３％ないし０．５％、クロム（Ｃｒ）：１７．５％ないし１８．５％、マンガン（Ｍｎ）：９．５％ないし１０．５％、シリコン（Ｓｉ）：０．０１％ないし０．１％、及び残りは鉄（Ｆｅ）と不可避な不純物からなることを特徴とする請求項１に記載の２相ステンレス鋼の製造方法。 The semi-finished steel is
By weight, carbon (C): 0.05% or less, nitrogen (N): 0.3% to 0.5%, chromium (Cr): 17.5% to 18.5%, manganese (Mn): 2. The method according to claim 1, comprising 9.5% to 10.5%, silicon (Si): 0.01% to 0.1%, and the remainder consisting of iron (Fe) and inevitable impurities. A method for producing phase stainless steel. 前記熱処理は、昇温段階、アニーリング段階及び冷却段階を含み、
前記アニーリング段階は１２００℃ないし１３５０℃で行われることを特徴とする請求項２に記載の２相ステンレス鋼の製造方法。 The heat treatment includes a heating step, an annealing step, and a cooling step,
The method of claim 2, wherein the annealing step is performed at 1200 to 1350 ° C. 前記昇温段階は、
３００℃／ｓｅｃないし４５０℃／ｓｅｃの速度で行われることを特徴とする請求項３に記載の２相ステンレス鋼の製造方法。 The heating step includes
The method for producing a duplex stainless steel according to claim 3, wherein the method is performed at a rate of 300 ° C / sec to 450 ° C / sec. 前記冷却段階は、
３０℃／ｓｅｃないし７５℃／ｓｅｃの速度で行われることを特徴とする請求項３に記載の２相ステンレス鋼の製造方法。 The cooling step includes
The method for producing a duplex stainless steel according to claim 3, wherein the method is performed at a rate of 30 ° C / sec to 75 ° C / sec. 重量％で、炭素（Ｃ）：０．０５％以下、窒素（Ｎ）：０．３％ないし０．５％、クロム（Ｃｒ）：１７．５％ないし１８．５％、マンガン（Ｍｎ）：９．５％ないし１０．５％、シリコン（Ｓｉ）：０．０１％ないし０．１％及び残りは鉄（Ｆｅ）と不可避な不純物からなる半製品鋼を製造すること；
前記半製品鋼を圧延すること；及び
前記の圧延された鋼を熱処理してオーステナイト４０ｖｏｌ％ないし７５ｖｏｌ％及びフェライト２５ｖｏｌ％ないし６０ｖｏｌ％を含む２相組織を形成すること；を含むこと を特徴とする２相ステンレス鋼の製造方法。 By weight, carbon (C): 0.05% or less, nitrogen (N): 0.3% to 0.5%, chromium (Cr): 17.5% to 18.5%, manganese (Mn): Producing semi-finished steel consisting of 9.5% to 10.5%, silicon (Si): 0.01% to 0.1% and the balance iron (Fe) and inevitable impurities;
Rolling the semi-finished steel; and heat-treating the rolled steel to form a two-phase structure including austenite 40 vol% to 75 vol% and ferrite 25 vol% to 60 vol%. A method for producing duplex stainless steel. 前記熱処理は、昇温段階、アニーリング段階及び冷却段階を含み、
前記アニーリング段階は１２００℃ないし１３５０℃で行われることを特徴とする請求項６に記載の２相ステンレス鋼の製造方法。 The heat treatment includes a heating step, an annealing step, and a cooling step,
The method of claim 6, wherein the annealing step is performed at 1200 to 1350 ° C. 前記昇温段階は、
３００℃／ｓｅｃないし４５０℃／ｓｅｃの速度で行われることを特徴とする請求項７に記載の２相ステンレス鋼の製造方法。 The heating step includes
The method for producing a duplex stainless steel according to claim 7, wherein the method is performed at a rate of 300 ° C / sec to 450 ° C / sec. 前記冷却段階は、
３０℃／ｓｅｃないし７５℃／ｓｅｃの速度で行われることを特徴とする請求項７に記載の２相ステンレス鋼の製造方法。 The cooling step includes
The method for producing a duplex stainless steel according to claim 7, wherein the method is performed at a rate of 30 ° C / sec to 75 ° C / sec. 前記半製品鋼は、
真空溶解方式で製造されることを特徴とする請求項１ないし９のいずれかに記載の２相ステンレス鋼の製造方法。 The semi-finished steel is
The method for producing a duplex stainless steel according to any one of claims 1 to 9, wherein the duplex stainless steel is produced by a vacuum melting method. 前記真空溶解は、
母合金を真空溶解炉に装入することと、
前記真空溶解炉内部を真空に維持することと、
前記母合金を溶融して溶融合金を形成することと、
前記溶融合金の窒素含量を調節することと、
前記溶融合金を攪拌することと、
前記溶融合金から半製品鋼を形成することを含むことを特徴とする請求項１０に記載の２相ステンレス鋼の製造方法。 The vacuum melting is
Charging the mother alloy into a vacuum melting furnace;
Maintaining a vacuum inside the vacuum melting furnace;
Melting the mother alloy to form a molten alloy;
Adjusting the nitrogen content of the molten alloy;
Stirring the molten alloy;
The method for producing a duplex stainless steel according to claim 10, comprising forming semi-finished steel from the molten alloy. 前記圧延は、
前記半製品鋼を再加熱することと、
前記の再加熱された半製品鋼を熱間圧延することを含むことを特徴とする請求項１ないし９のいずれかに記載の２相ステンレス鋼の製造方法。 The rolling is
Reheating said semi-finished steel;
The method for producing a duplex stainless steel according to any one of claims 1 to 9, comprising hot rolling the reheated semi-finished steel.
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