EP4265799A1 - Austenitic stainless steel with improved corrosion resistance and machinability and method for manufacturing same - Google Patents

Austenitic stainless steel with improved corrosion resistance and machinability and method for manufacturing same Download PDF

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Publication number
EP4265799A1
EP4265799A1 EP21911342.0A EP21911342A EP4265799A1 EP 4265799 A1 EP4265799 A1 EP 4265799A1 EP 21911342 A EP21911342 A EP 21911342A EP 4265799 A1 EP4265799 A1 EP 4265799A1
Authority
EP
European Patent Office
Prior art keywords
less
excluding
stainless steel
corrosion resistance
austenitic stainless
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP21911342.0A
Other languages
German (de)
English (en)
French (fr)
Inventor
Hyung-Gu KANG
Mi-Nam Park
Youngjun Kim
Youngjin Kwon
Gyujin JO
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Posco Holdings Inc
Original Assignee
Posco Co Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Posco Co Ltd filed Critical Posco Co Ltd
Publication of EP4265799A1 publication Critical patent/EP4265799A1/en
Pending legal-status Critical Current

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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
    • C21D6/004—Heat treatment of ferrous alloys containing Cr and Ni
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/58—Ferrous alloys, e.g. steel alloys containing chromium with nickel with more than 1.5% by weight of manganese
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C21D8/0263—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment following hot rolling
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/46—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for sheet metals
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • 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
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/44—Ferrous alloys, e.g. steel alloys containing chromium with nickel with molybdenum or tungsten
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/40—Ferrous alloys, e.g. steel alloys containing chromium with nickel
    • C22C38/54—Ferrous alloys, e.g. steel alloys containing chromium with nickel with boron
    • 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
    • C21D2211/004—Dispersions; Precipitations

Definitions

  • the disclosure relates to an austenitic stainless steel with improved corrosion resistance and machinability and a manufacturing method the same, and more specifically, to an austenitic stainless steel with improved corrosion resistance and machinability for use in corrosive environments such as salt water and in an environment requiring machinability, and a manufacturing method the same.
  • Austenitic stainless steels used in mechanical parts such as frames, chambers, molds, and the like, are manufactured into final shapes by cutting processes such as milling. Machinability of stainless steels is required to reduce cutting load, increase cutting speed and improve tool life.
  • MnS compounds A type of steel to which Mn and S are added and uses MnS compounds which are a non-metallic inclusion is widely known as stainless steels with excellent machinability.
  • MnS compounds readily elute in corrosive environments such as salt water or act as a starting point for pitting, which deteriorates the corrosion resistance of stainless steels. Therefore, stainless steels utilizing MnS compounds are limited in applications where corrosion resistance is required due to exposure to corrosive environments. Thus, stainless steels that are both machinable and corrosion resistant are required to be developed.
  • An aspect of the disclosure provides an austenitic stainless steel with improved corrosion resistance and machinability and a manufacturing method the same.
  • an austenitic stainless steel with improved corrosion resistance and machinability comprises, in percent by weight (wt%), 0.05% or less of C (excluding 0), 2% or less of Si (excluding 0), 2% or less of Mn (excluding 0), 0.01% or less of S, 16 to 22% of Cr, 9 to 15% of Ni, 3% or less of Mo (excluding 0), 0.15 to 0.25% of N, 0.004 to 0.06% of B, and the remainder being Fe and inevitable impurities. 10 or more BN precipitates are distributed per 100 ⁇ 100 ⁇ m 2 .
  • 10 or less MnS precipitates may be distributed per 100x100 ⁇ m 2 .
  • the austenitic stainless steel with improved corrosion resistance and machinability may further comprise, in percent by weight (wt%), 1 % or less of Cu (excluding 0).
  • a pitting potential may be 300 mV or more.
  • a manufacturing method of an austenitic stainless steel with improved corrosion resistance and machinability may comprise: heating a stainless steel comprising, in percent by weight (wt%), 0.05% or less of C (excluding 0), 2% or less of Si (excluding 0), 2% or less of Mn (excluding 0), 0.01% or less of S, 16 to 22% of Cr, 9 to 15% of Ni, 3% or less of Mo (excluding 0), 0.15 to 0.25% of N, 0.004 to 0.06% of B, and the remainder being Fe and inevitable impurities at 1150 to 1250 °C for 1 hour and 30 minutes or more; hot rolling the heated stainless steel; and maintaining the hot-rolled steel at 1100 to 1250 °C for 30 seconds or more.
  • the present disclosure provides an austenitic stainless steel with improved corrosion resistance and machinability and a manufacturing method the same.
  • An austenitic stainless steel with improved corrosion resistance and machinability comprises, in percent by weight (wt%), 0.05% or less of C (excluding 0), 2% or less of Si (excluding 0), 2% or less of Mn (excluding 0), 0.01% or less of S, 16 to 22% of Cr, 9 to 15% of Ni, 3% or less of Mo (excluding 0), 0.15 to 0.25% of N, 0.004 to 0.06% of B, and the remainder being Fe and inevitable impurities, and 10 or more BN precipitates are distributed per 100 ⁇ 100 ⁇ m 2 .
  • MnS deteriorating corrosion resistance is excluded to prevent the formation of MnS precipitates.
  • BN compounds are introduced to replace MnS to improve machinability.
  • the austenitic stainless steel with improved corrosion resistance and machinability comprises, in percent by weight (wt%), 0.05% or less of C (excluding 0), 2% or less of Si (excluding 0), 2% or less of Mn (excluding 0), 0.01% or less of S, 16 to 22% of Cr, 9 to 15% of Ni, 3% or less of Mo (excluding 0), 0.15 to 0.25% of N, 0.004 to 0.06% of B, and the remainder being Fe and inevitable impurities.
  • the austenitic stainless steel with improved corrosion resistance and machinability may further comprise, in percent by weight (wt%), 1% or less of Cu (excluding 0).
  • the content of carbon (C) is 0.05% or less (excluding 0).
  • Carbon (C) is an austenite forming element and acts as an inevitable impurity.
  • the content of C exceeds 0.05%, the corrosion resistance of the welded part may be impaired, and thus the content of C is controlled to 0.05%.
  • the content of silicon (Si) is 2% or less (excluding 0).
  • Si is added as a deoxidizer and is an element for improving corrosion resistance.
  • toughness may be deteriorated, and thus the Si content is controlled to 2% or less in the present disclosure.
  • the content of manganese (Mn) is 2% or less (excluding 0).
  • Mn is an austenite phase-stabilizing element.
  • corrosion resistance may be deteriorated, and thus the Mn content is controlled to 2% or less in the present disclosure.
  • the content of sulfur (S) is 0.01% or less.
  • the S content is controlled to 0.01% or less in order to prevent the formation of MnS to be excluded in the present disclosure.
  • the content of chromium (Cr) is from 16 to 22%.
  • Cr is an element for improving corrosion resistance of an austenitic stainless steel.
  • the Cr content exceeding 22% may increase the raw material cost and decrease toughness. Therefore, the Cr content is controlled from 16 to 22% or less in the present disclosure.
  • the content of nickel (Ni) is from 9 to 15%.
  • Ni is an austenite phase-stabilizing element.
  • the Ni content is less than 9%, the above-described effect may not be obtained.
  • the Ni content exceeding 15% causes an increase in raw material cost. Therefore, the Ni content is controlled from 9 to 15% or less in the present disclosure.
  • the content of molybdenum (Mo) is 3% or less (excluding 0).
  • Mo is an element for improving corrosion resistance.
  • the Mo content exceeding 3% causes an increase in raw material cost, and thus the Mo content is controlled to 3% in the present disclosure.
  • the content of boron (B) is from 0.004 to 0.06%.
  • B is added to secure BN.
  • the content of B is less than 0.004%, sufficient BN targeted by the present disclosure may not be formed, and when the content of B exceeds 0.06%, fracture occurs during hot rolling. Therefore, the content of B is controlled to 0.004 to 0.06% in the present disclosure.
  • the content of nitrogen (N) is 0.15 to 0.25%.
  • N is added to secure BN.
  • the content of N is less than 0.15%, sufficient BN may not be formed, and when the content of N exceeds 0.25%, toughness is deteriorated. Therefore, the content of N is controlled to 0.15 to 0.25% in the present disclosure.
  • the content of copper (Cu) is 1% or less (excluding 0).
  • Cu is an element for improving corrosion resistance, and is added as required in the present disclosure. However, when the content of Cu exceeds 1%, hot workability may deteriorate, and thus the Cu content is controlled to 1% in the present disclosure.
  • the remaining component of the alloy composition of the present disclosure is iron (Fe).
  • the austenitic stainless steel with improved corrosion resistance and machinability of the present disclosure may include other impurities that may be included in a typical industrial production process of steel. Since these impurities are known to those skilled in the art to which the present disclosure belongs, the type and content thereof are not specifically limited in the present disclosure.
  • MnS precipitates whose length of a major axis of 1 ⁇ m or more per 100x100 ⁇ m 2 are distributed.
  • the MnS precipitate may comprise 50 at.% or more of the sum of Mn and S.
  • a pitting potential of the austenitic stainless steel of the present disclosure may be 300 mV or more.
  • BN precipitates per 100 ⁇ 100pm 2 are distributed.
  • the BN precipitates may comprise 50 at.% or more of the sum of B and N.
  • MnS is replaced with BN, thereby securing machinability while suppressing deterioration of corrosion resistance.
  • the austenitic stainless steel with improved corrosion resistance and machinability according to an embodiment of the present disclosure may be manufactured in various methods, and the manufacturing method is not particularly limited. As an embodiment, however, the austenitic stainless steel with improved corrosion resistance and machinability according to an embodiment of the present disclosure may be manufactured as described below.
  • the manufacturing method of austenitic stainless steel with improved corrosion resistance and machinability comprises, heating a stainless steel comprising, in percent by weight (wt%), 0.05% or less of C (excluding 0), 2% or less of Si (excluding 0), 2% or less of Mn (excluding 0), 0.01% or less of S, 16 to 22% of Cr, 9 to 15% of Ni, 3% or less of Mo (excluding 0), 0.15 to 0.25% of N, 0.004 to 0.06% of B, and the remainder being Fe and inevitable impurities, at 1150 to 1250 °C for 1 hour and 30 minutes or more; hot rolling the heated stainless steel; and maintaining the hot-rolled steel at 1100 to 1250 °C for 30 seconds or more.
  • the heating is a process for forming as many BNs as possible, and may be performed at 1150 to 1250 C for 1 hour and 30 minutes or more.
  • the hot rolling may be performed up to a thickness of 8 mm, without being limited thereto, since the thickness may vary depending on the use.
  • the maintaining process after hot rolling is for forming BN again, and may be performed at 1100 to 1250 °C for 30 seconds or more.
  • An alloy satisfying the alloy composition of Table 1 was melt-cast, and the austenitic stainless steel cast was heated at 1200 °C for 1 hour and 30 minutes. Thereafter, the heated steel cast was hot-rolled to become a thickness of 8 mm. Subsequently, the hot-rolled steel was maintained at a temperature of 1150 °C for 30 seconds or more to form BN precipitates, thereby obtaining a hot-rolled steel specimen.
  • FIG. 1A and FIG. 1B are photographs showing the appearances of Example 7 and Comparative Example 2 after hot rolling. Referring to FIG. 1A , it may be confirmed that the appearance of the steel plate in Example 7 according to the present disclosure has no fracture. On the contrary, referring to FIG. 1B , it may be confirmed that Comparative Example 2 has a satisfactory B content, but the N content did not reach the lower limit proposed in the present disclosure, and thus fracture occurred during hot rolling.
  • BN precipitates and MnS precipitates were mirror-polished on an arbitrary cut surface of the steel plate, and then the number of MnS precipitates of 1 ⁇ m or more per 100x100 ⁇ m 2 and the number of BN precipitates per 100x100 ⁇ m 2 were observed using a Scanning Electron Microscope (SEM) to which an Energy Dispersive Spectrometer (EDS) is attached, and the numbers are shown.
  • SEM Scanning Electron Microscope
  • EDS Energy Dispersive Spectrometer
  • Corrosion resistance was evaluated by pitting potential.
  • the pitting potential is measured by immersing a hot-rolled steel specimen in an aqueous solution containing 3.5 wt% NaCl, connecting the electrodes, applying voltage, and measuring a voltage at the point where the current reaches 0.1mA when the voltage was gradually raised from the natural potential.
  • FIGS. 2A and 2B are photographs of cross sections of stainless steels of Example 7 and Comparative Example 1 observed by SEM, respectively. Referring to FIG. 2A , it may be confirmed in Example 7 that a large amount of BN to be implemented in the present disclosure was formed. Referring to FIG. 2B , however, it may be confirmed in Comparative Example 1that BN was not formed because conditions for forming BN were not formed. Some black areas appear to be oxide rather than BN.
  • Comparative Example 1 shows satisfactory corrosion resistance with a pitting potential of 550 mV because MnS was not formed.
  • BN was not formed because B was not added, and the cutting load was inferior to that of Examples.
  • Comparative Example 6 shows satisfactory corrosion resistance with a pitting potential of 1000 mV because MnS was not formed. However, the cutting load was inferior because the content of B did not reach the lower limit proposed in the present disclosure.
  • an austenitic stainless steel with improved corrosion resistance and machinability and a manufacturing method the same.

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  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Heat Treatment Of Steel (AREA)
EP21911342.0A 2020-12-21 2021-12-10 Austenitic stainless steel with improved corrosion resistance and machinability and method for manufacturing same Pending EP4265799A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
KR1020200179748A KR102570524B1 (ko) 2020-12-21 2020-12-21 내식성과 절삭성이 향상된 오스테나이트계 스테인리스강 및 그 제조방법
PCT/KR2021/018701 WO2022139275A1 (ko) 2020-12-21 2021-12-10 내식성과 절삭성이 향상된 오스테나이트계 스테인리스강 및 그 제조방법

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EP4265799A1 true EP4265799A1 (en) 2023-10-25

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EP21911342.0A Pending EP4265799A1 (en) 2020-12-21 2021-12-10 Austenitic stainless steel with improved corrosion resistance and machinability and method for manufacturing same

Country Status (5)

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EP (1) EP4265799A1 (ko)
JP (1) JP2024500905A (ko)
KR (1) KR102570524B1 (ko)
CN (1) CN116848283A (ko)
WO (1) WO2022139275A1 (ko)

Family Cites Families (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH02209454A (ja) * 1989-02-08 1990-08-20 Nkk Corp 快削ステンレス鋼
JPH07113144A (ja) * 1993-10-18 1995-05-02 Nisshin Steel Co Ltd 表面性状に優れた非磁性ステンレス鋼及びその製造方法
JPH07197205A (ja) * 1993-12-29 1995-08-01 Nkk Corp オーステナイト系ステンレス鋼薄板及びその製造方法
KR102015510B1 (ko) * 2017-12-06 2019-08-28 주식회사 포스코 내식성이 우수한 비자성 오스테나이트계 스테인리스강 및 그 제조방법
JP7077033B2 (ja) 2018-02-02 2022-05-30 日鉄ステンレス株式会社 接合体の製造方法

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KR102570524B1 (ko) 2023-08-24
KR20220089276A (ko) 2022-06-28
JP2024500905A (ja) 2024-01-10
WO2022139275A1 (ko) 2022-06-30
CN116848283A (zh) 2023-10-03

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