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AssigneeNippon Steel Corporation
InventorsKatsuhiro Sasai, Wataru Ohashi, Tooru Matsumiya, Yoshiaki Kimura, Junji Nakashima
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The present invention provides a low carbon steel sheet and a low carbon steel slab on which formation of surface defects can be surely prevented by preventing aggregation of inclusions in the molten steel and finely dispersing inclusions in the steel sheet or slab, and a process for producing the steel sheet and slab. The present invention provides a process comprising the steps of decarburizing a molten steel so as to produce a carbon concentration of up to 0.01% by mass, pre-deoxidizing the molten steel by adding Al thereto so as to produce a dissolved oxygen concentration from 0.01 to 0.04% by mass, adding thereto Ti and at least La and/or Ce, and casting the molten steel, and a steel sheet and a steel slab obtained by the process.
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A low carbon steel sheet characterized in that not less than 60% by mass of oxide inclusions present therein contain at least La and/or Ce.
A low carbon steel sheet characterized in that not less than 60% by mass of oxide inclusions present therein are spherical or spindle-like oxide inclusions containing at least La and/or Ce.
A low carbon steel sheet characterized in that not less than 60% by mass of oxide inclusions present therein are oxide ones containing not less than 20% by mass of at least La and/or Ce in the form of La2O3 and/or Ce2O3.
A low carbon steel sheet characterized in that not less than 60% by mass of oxide inclusions present therein are spherical or spindle-like oxide inclusions containing not less than 20% by mass of at least La and/or Ce in the form of La2O3 and/or Ce2O3.
A low carbon steel sheet characterized in that fine oxide inclusions having a diameter from 0.5 to 30 μm are dispersed therein with the number being from not less than 1,000 to less than 100,000 pieces/cm2, and that not less than 60% by mass of the oxide inclusions contain at least La and/or Ce.
A low carbon steel sheet characterized in that fine oxide inclusions having a diameter from 0.5 to 30 μm are dispersed therein with the number being from not less than 1,000 to less than 100,000 pieces/cm2, and that not less than 60% by mass of the oxide inclusions are spherical or spindle-like oxide inclusions containing at least La and/or Ce.
A low carbon steel sheet characterized in that
A low carbon steel sheet characterized in that fine oxide inclusions having a diameter from 0.5 to 30 μm are dispersed therein with the number being from not less than 1,000 to less than 100,000 pieces/cm2, and that not less than 60% by mass of the oxide inclusions are spherical or spindle-like oxide inclusions containing not less than 20% by mass of La and/or Ce in the form of La2O3 and/or Ce2O3.
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A low carbon steel slab characterized in that not less than 60% by mass of oxide inclusions present in the surface layer of the slab from the surface to the depth of 20 mm contain at least La and/or Ce.
A low carbon steel slab characterized in that not less than 60% by mass of oxide inclusions present in the surface layer of the slab from the surface to the depth of 20 mm are spherical or spindle-like oxide inclusions containing at least La and/or Ce.
A low carbon steel slab characterized in that not less than 60% by mass of oxide inclusions present in the surface layer of the slab from the surface to the depth of 20 mm are oxide inclusions containing not less than 20% by mass of at least La and/or Ce in the form of La2O3 and/or Ce2O3.
A low carbon steel slab characterized in that not less than 60% by mass of oxide inclusions present in the surface layer of the slab from the surface to the depth of 20 mm are spherical or spindle-like oxide inclusions containing not less than 20% by mass of at least La and/or Ce in the form of La2O3 and/or Ce2O3.
A low carbon steel slab characterized in that fine oxide inclusions having a diameter from 0.5 to 30 μm are dispersed in the surface layer of the slab from the surface to the depth of 20 mm with the number being from not less than 1,000 to less than 100,000 pieces/cm2, and that not less than 60% by mass of the oxide inclusions contain at least La and/or Ce.
A low carbon steel slab characterized in that fine oxide inclusions having a diameter from 0.5 to 30 μm are dispersed in the surface layer of the slab from the surface to the depth of 20 mm with the number being from not less than 1,000 to less than 100,000 pieces/cm2, and that not less than 60% by mass of the oxide inclusions are spherical or spindle-like oxide inclusions containing at least La and/or Ce.
A low carbon steel slab characterized in that fine oxide inclusions having a diameter from 0.5 to 30 μm are dispersed in the surface layer of the slab from the surface to the depth of 20 mm with the number being from not less than 1,000 to less than 100,000 pieces/cm2, and that not less than 60% by mass of the oxide inclusions are oxide inclusions containing not less than 20% by mass of at least La and/or Ce in the form of La2O3 and/or Ce2O3.
A low carbon steel slab characterized in that fine oxide inclusions having a diameter from 0.5 to 30 μm are dispersed in the surface layer of the slab from the surface to the depth of 20 mm with the number being from not less than 1,000 to less than 100,000 pieces/cm2, and that not less than 60% by mass of the oxide inclusions are spherical or spindle-like oxide inclusions containing not less than 20% by mass of at least La and/or Ce in the form of La2O3 and/or Ce2O3.
A process for producing a low carbon steel slab comprising the steps of:
A process for producing a low carbon steel slab comprising the steps of:
A process for producing a low carbon steel slab comprising the steps of:
A process for producing a low carbon steel slab comprising the steps of:
A process for producing a low carbon steel slab comprising the steps of:
A process for producing a low carbon steel slab comprising the steps of:
A process for producing a low carbon steel slab comprising the steps of:
A process for producing a low carbon steel slab comprising the steps of:
30 The process for producing a low carbon steel slab according to any one of claims 19 to 26 wherein, during casting the molten steel, the molten steel is continuously cast.
Dependencies are inferred from the claim text.