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公开(公告)号：EP3495528A1
公开(公告)日：2019-06-12
申请号：EP17837115.9
申请日：2017-08-04
发明人： SANO, Kohichi , UNO, Makoto , NISHIYAMA, Ryoichi , YAMAGUCHI, Yuji , SUGIURA, Natsuko , NAKATA, Masahiro
摘要： A steel sheet has a specific chemical composition and has a structure represented by, by area ratio, ferrite: 30 to 95%, and bainite: 5 to 70%. When a region that is surrounded by a grain boundary having a misorientation of 15° or more and has a circle-equivalent diameter of 0.3 µ m or more is defined as a crystal grain, the proportion of crystal grains each having an intragranular misorientation of 5 to 14° to all crystal grains is 20 to 100% by area ratio. An average aspect ratio of ellipses equivalent to the crystal grains is 5 or less. An average distribution density of the total of Ti-based carbides and Nb-based carbides each having a grain size of 20 nm or more on ferrite grain boundaries is 10 carbides/ µ m or less.
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公开(公告)号：EP3495527A1
公开(公告)日：2019-06-12
申请号：EP17837114.2
申请日：2017-08-04
发明人： SANO, Kohichi , UNO, Makoto , NISHIYAMA, Ryoichi , YAMAGUCHI, Yuji , SUGIURA, Natsuko , NAKATA, Masahiro
摘要： A steel sheet has a specific chemical composition and has a structure represented by, by area ratio, ferrite: 5 to 60%, and bainite: 40 to 95%. When a region that is surrounded by a grain boundary having a misorientation of 15° or more and has a circle-equivalent diameter of 0.3 µ m or more is defined as a crystal grain, the proportion of crystal grains each having an intragranular misorientation of 5 to 14° to all crystal grains is 20 to 100% by area ratio. A precipitate density of Ti(C,N) and Nb(C,N) each having a circle-equivalent diameter of 10 nm or less is 10 10 precipitates/mm 3 or more. A ratio (Hvs/Hvc) of a hardness at 20 µ m in depth from a surface (Hvs) to a hardness of the center of a sheet thickness (Hvc) is 0.85 or more.
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公开(公告)号：EP3495530A1
公开(公告)日：2019-06-12
申请号：EP17837117.5
申请日：2017-08-04
发明人： SANO, Kohichi , UNO, Makoto , NISHIYAMA, Ryoichi , YAMAGUCHI, Yuji , SUGIURA, Natsuko , NAKATA, Masahiro
摘要： A steel sheet has a specific chemical composition and has a structure represented by, by area ratio, ferrite: 0 to 30%, and bainite: 70 to 100%. When a region that is surrounded by a grain boundary having a misorientation of 15° or more and has a circle-equivalent diameter of 0.3 µ m or more is defined as a crystal grain, the proportion of crystal grains each having an intragranular misorientation of 5 to 14° to all crystal grains is 20 to 100% by area ratio. A grain boundary number density of solid-solution C or a grain boundary number density of the total of solid-solution C and solid-solution B is 1 piece/nm 2 or more and 4.5 pieces/nm 2 or less. An average grain size of cementite precipitated at grain boundaries is 2 µ m or less.
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公开(公告)号：EP3495529A1
公开(公告)日：2019-06-12
申请号：EP17837116.7
申请日：2017-08-04
发明人： SANO, Kohichi , UNO, Makoto , NISHIYAMA, Ryoichi , YAMAGUCHI, Yuji , SUGIURA, Natsuko , NAKATA, Masahiro
摘要： A steel sheet has a specific chemical composition and has a structure represented by, by area ratio, ferrite: 5 to 95%, and bainite: 5 to 95%. When a region that is surrounded by a grain boundary having a misorientation of 15° or more and has a circle-equivalent diameter of 0.3 µ m or more is defined as a crystal grain, the proportion of crystal grains each having an intragranular misorientation of 5 to 14° to all crystal grains is 20 to 100% by area ratio. Hard crystal grains A in which precipitates or clusters with a maximum diameter of 8 nm or less are dispersed in the crystal grains with a number density of 1 × 10 16 to 1 × 10 19 pieces/cm 3 and soft crystal grains B in which precipitates or clusters with a maximum diameter of 8 nm or less are dispersed in the crystal grains with a number density of 1 × 10 15 pieces/cm 3 or less are contained, and the volume% of the hard crystal grains A/(the volume% of the hard crystal grains A + the volume% of the soft crystal grains B) is 0.1 to 0.9.
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