US20250230530A1 - Steel component and method of producing same - Google Patents

Steel component and method of producing same

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Publication number
US20250230530A1
US20250230530A1 US18/727,884 US202318727884A US2025230530A1 US 20250230530 A1 US20250230530 A1 US 20250230530A1 US 202318727884 A US202318727884 A US 202318727884A US 2025230530 A1 US2025230530 A1 US 2025230530A1
Authority
US
United States
Prior art keywords
less
steel
cooling rate
average
crystal grain
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
US18/727,884
Other languages
English (en)
Inventor
Masafumi TADA
Kazuaki Fukuoka
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.)
JFE Steel Corp
Original Assignee
JFE Steel Corp
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 JFE Steel Corp filed Critical JFE Steel Corp
Assigned to JFE STEEL CORPORATION reassignment JFE STEEL CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: FUKUOKA, KAZUAKI, TADA, MASAFUMI
Publication of US20250230530A1 publication Critical patent/US20250230530A1/en
Pending legal-status Critical Current

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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
    • C22C38/38—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
    • C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
    • C21D1/02—Hardening articles or materials formed by forging or rolling, with no further heating beyond that required for the formation
    • 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 of ferrous metals or ferrous alloys by deformation combined with, or followed by, heat treatment
    • C21D8/005—
    • 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
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • 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
    • C22C38/06—Ferrous alloys, e.g. steel alloys containing aluminium
    • 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
    • C22C38/24—Ferrous alloys, e.g. steel alloys containing chromium 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
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C22C38/28—Ferrous alloys, e.g. steel alloys containing chromium with titanium or zirconium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J1/00—Preparing metal stock or similar ancillary operations prior, during or post forging, e.g. heating or cooling
    • B21J1/06—Heating or cooling methods or arrangements specially adapted for performing forging or pressing operations
    • 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
    • C21D2211/002—Bainite
    • 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
    • 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
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • 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
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing 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
    • C22C38/60—Ferrous alloys, e.g. steel alloys containing lead, selenium, tellurium, or antimony, or more than 0.04% by weight of sulfur

Definitions

  • the present disclosure relates to steel components, for example, steel components used in the undercarriages of automobiles and trucks, more specifically knuckles and front axles, and methods of producing same.
  • Non-heat-treated components are those for which heat treatment to build up component strength is omitted, that is, thermal refinement processing of steel is omitted.
  • the omission of heat treatment is made possible, for example, by technology that allows component strength to be built up during cooling of the component after the hot forging process in the component production process.
  • Non-heat-treated components are broadly classified into two categories based on their metallic microstructure. That is, the main metallic microstructure consists of two phases, ferrite and pearlite, or the main metallic microstructure consists of bainite.
  • the former non-heat-treated steel mainly consisting of ferrite and pearlite, strengthening by precipitation entirely due to vanadium is used.
  • vanadium carbides precipitate finely during the cooling process after hot forging of the component, strengthening the microstructure by precipitation, and therefore component strength equivalent to when thermal refining treatment is performed in the state after hot forging is obtainable.
  • the strengthening mechanism for non-heat-treated components with bainitic microstructure is transformation strengthening.
  • the second is to control a crystal grain shape.
  • the aspect ratio (minor axis length/major axis length) of crystal grains needs to be 0.5 or more, and an average ratio of crystal grain boundary length to crystal grain circumference needs to be 60 or less.
  • F ⁇ 1 C + Si / 24 + Mn / 6 + Ni / 40 + Cr / 5 + Mo / 4 + V / 14 ( 1 )
  • the ratio of yield stress to tensile strength can be 0.60 or more without tempering because a bainitic microstructure satisfying desired conditions is obtainable in an area fraction of 85% or more during cooling after hot forging.
  • C is a beneficial element that forms a solute or carbide in steel, and improves steel strength.
  • Bainitic microstructure is a microstructure of precipitated fine cementite, and therefore when a certain amount of C is not present in steel, there is not enough cementite to obtain sufficient strengthening by precipitation, resulting in low yield stress and unsatisfactory yield ratio. C addition of 0.21% or more is therefore required. However, when added in excess, the amount of cementite, a dislocation source, becomes too high, and this too means that a satisfactory yield stress is not maintained. Accordingly, an upper limit to the amount added is 0.24%.
  • P phosphorus
  • P is a beneficial element that is a solute in steel and increases steel yield stress. To obtain this effect, addition of 0.014% or more is required. However, P segregates at crystal grain boundaries of austenite after hot forging and has an aspect of deteriorating toughness at room temperature. To avoid this, P content is 0.025% or less. Content is preferably 0.014% to 0.022%.
  • Cr chromium
  • Cr chromium
  • chromium is an important element that is a solute in steel and has a variety of beneficial effects, such as increasing steel strength and increasing steel quench hardenability. To obtain these effects, addition of 0.55% or more is required. However, when Cr is added in excess, the amount of retained austenite becomes too high and high yield stress is not maintained. Accordingly, an upper limit to the amount added is 0.65%.
  • V vanadium
  • V vanadium
  • a beneficial element that is a solute in steel, and causes solid solution strengthening of steel as well as increasing steel quench hardenability. To obtain such effects, addition of 0.15% or more is required. However, V also acts to deteriorate steel toughness by combining with C to form precipitates. To avoid this, an amount of V added is 0.20% or less. Content is preferably 0.16% to 0.19%.
  • the aspect ratio of a crystal grain is obtained as follows. First, the center of gravity of a crystal grain obtained by observation is determined. Two arbitrary straight lines are drawn on the crystal grain orthogonal to each other intersecting at the center of gravity. When the center of gravity is not located in the crystal grain, as in a C-shape crystal grain, a point on the crystal grain boundary closest to the obtained center of gravity is used as the center of gravity. In any line of two straight lines drawn in this way, a distance between the two points on the line that intersect the circumference of the crystal grain is an “intersection distance”.
  • the bainite area fraction was determined by a point-counting method from optical micrographs of observation planes that were appropriately etched with a nital solution.
  • the point-counting method is an area fraction measurement method that determines the percentage of points of the microstructure for which the area fraction is to be determined out of the total number of points appropriately located on an optical micrograph.
  • the points are typically arranged at intersections of lines disposed equally and orthogonally on the micrograph, that is, a grid of points.
  • line thickness There is no rule for line thickness, but grid points are typically configured with lines that are 0.5 pt to 0.75 pt thick on a slide in Microsoft's PowerPoint application, for example.
  • Steel No. 1 to Steel No. 34 are examples that satisfy the chemical composition of the present disclosure.
  • Steel Nos. 1 to 34 were steel material that was cooled after hot forging within the cooling rate range according to the present disclosure, and the resulting Steel component Nos. 1 to 34 had the microstructure and excellent mechanical properties specified in the present disclosure.
  • Steel component Nos. A13, A14, A15, and A16 were partially 30 mm in diameter.
  • Steel component Nos. A13 and A14 are examples where cooling rate differences from 800° C. to 550° C. exceeded 25%, and therefore sub-surface hardness differences in the components exceeded 10%.
  • steel component Nos. A15 and A16 are examples where the cooling rate differences were less than 25%, and therefore sub-surface hardness differences in the components were suppressed to 10% or less.

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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)
US18/727,884 2022-01-28 2023-01-26 Steel component and method of producing same Pending US20250230530A1 (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
JP2022012396 2022-01-28
JP2022-012396 2022-01-28
PCT/JP2023/002508 WO2023145838A1 (ja) 2022-01-28 2023-01-26 鋼部品およびその製造方法

Publications (1)

Publication Number Publication Date
US20250230530A1 true US20250230530A1 (en) 2025-07-17

Family

ID=87471532

Family Applications (1)

Application Number Title Priority Date Filing Date
US18/727,884 Pending US20250230530A1 (en) 2022-01-28 2023-01-26 Steel component and method of producing same

Country Status (6)

Country Link
US (1) US20250230530A1 (https=)
EP (1) EP4464810A4 (https=)
JP (1) JP7380957B1 (https=)
KR (1) KR20240118819A (https=)
CN (1) CN118591647A (https=)
WO (1) WO2023145838A1 (https=)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20230193440A1 (en) * 2020-03-31 2023-06-22 Jfe Steel Corporation Free-cutting steel and method for manufacturing same
US12404573B2 (en) 2019-12-23 2025-09-02 Jfe Steel Corporation Free-cutting steel and manufacturing method thereof

Families Citing this family (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US12562415B1 (en) 2024-10-29 2026-02-24 Sumitomo Riko Company Limited Thermal insulation sheet between battery cells for electric automobile

Family Cites Families (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH04285118A (ja) 1991-03-13 1992-10-09 Nippon Steel Corp 高強度高靭性熱間鍛造非調質鋼の製造方法
JP3339587B2 (ja) 1991-12-04 2002-10-28 愛知製鋼株式会社 熱間鍛造用焼入省略鋼の製造方法
JPH05279788A (ja) * 1992-03-31 1993-10-26 Sumitomo Metal Ind Ltd 強度および靱性に優れた熱間鍛造用非調質鋼
JPH05287373A (ja) 1992-04-14 1993-11-02 Nippon Steel Corp 高強度高靱性熱間加工非調質鋼の製造方法
JPH09111412A (ja) * 1995-10-19 1997-04-28 Sumitomo Metal Ind Ltd 高強度・高降伏比・低延性非調質鋼
JPH10298703A (ja) 1997-04-21 1998-11-10 Mitsubishi Seiko Muroran Tokushuko Kk 降伏比、耐久比に優れたベイナイト型高強度高靭性熱間鍛造用非調質鋼
JP2001200332A (ja) 2000-01-21 2001-07-24 Sanyo Special Steel Co Ltd 高靱性非調質鋼
KR20040037738A (ko) * 2002-10-30 2004-05-07 현대자동차주식회사 고강도 고인성 로워 암 커넥터 제조방법
KR20140056767A (ko) * 2012-10-31 2014-05-12 현대제철 주식회사 액슬빔 및 그 제조 방법
US20140283954A1 (en) * 2013-03-22 2014-09-25 Caterpiller Inc. Bainitic microalloy steel with enhanced nitriding characteristics
ES2733805T3 (es) * 2015-11-16 2019-12-03 Deutsche Edelstahlwerke Specialty Steel Gmbh & Co Kg Acero fino estructural con estructura bainitica, pieza forjada fabricada a partir del mismo y procedimiento para fabricar una pieza forjada
JP6617852B2 (ja) * 2017-02-24 2019-12-11 日本製鉄株式会社 熱間鍛造用棒鋼

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US12404573B2 (en) 2019-12-23 2025-09-02 Jfe Steel Corporation Free-cutting steel and manufacturing method thereof
US20230193440A1 (en) * 2020-03-31 2023-06-22 Jfe Steel Corporation Free-cutting steel and method for manufacturing same
US12522906B2 (en) * 2020-03-31 2026-01-13 Jfe Steel Corporation Free-cutting steel and method for manufacturing same

Also Published As

Publication number Publication date
EP4464810A4 (en) 2025-11-19
KR20240118819A (ko) 2024-08-05
CN118591647A (zh) 2024-09-03
EP4464810A1 (en) 2024-11-20
JPWO2023145838A1 (https=) 2023-08-03
WO2023145838A1 (ja) 2023-08-03
JP7380957B1 (ja) 2023-11-15

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