Posco

Chang-Hoon Lee

Kyoo-Young Lee

Gyo-Sung Kim

Jea-Chun Jeon

Han-Chul Shin

Kee-Cheol Park

Jong-Sub Lee

Jae-Chun Jeon

Ki-Soo Kim

A carbon steel sheet having high formability due to a microscopic and uniform carbide distribution and having a good characteristic of final heat treatment, and a manufacturing method thereof. The carbon steel sheet having excellent formability includes, in wt %, C at 0.2-0.5%, Mn at 0.1-1.2%, Si at less than or equal to 0.4%, Cr at less than or equal to 0.5%, Al at 0.01-0.1%, S at less than or equal to 0.012%, Ti at less than or equal to 0.5&#xd7;48/14&#xd7;[N]% to 0.03% when the condition of B and N is not satisfied, B at 0.0005-0.0080%, N at less than or equal to 0.006%, Fe, and extra inevitable elements; an average size of carbide is less than or equal to 1 &#x3bc;m; and an average grain size of ferrite is less than or equal to 5 &#x3bc;m.

Manufacturing method of carbon steel sheet superior in formability

A method for manufacturing a fine spheroidized steel sheet having an excellent heat treatment characteristic, the method including: i) manufacturing a high carbon slab that is formed of 0.3 to 1.0 wt % C, 0.1 to 1.2 wt % Mn, 0 to 0.4 wt % Si, 0.01 to 0.1 wt % Al, 0 to 0.01 wt % S, and balance Fe and an inevitably added impurity as residuals; ii) reheating the slab to a temperature of Ar3 transformation point or more; iii) roughing rolling the slab, and manufacturing a thin plate by performing finish rolling in an austenite region; iv) cooling the thin plate at a cooling speed of 50 to 300&#xb0; C./sec; v) finishing the cooling of the thin plate at a temperature region of 400 to 650&#xb0; C. and maintaining the temperature; vi) winding the thin plate at a temperature region of 450 to 700&#xb0; C.; vii) performing cold rolling at a reduction ratio of 30% or more; and viii) spheroidizing annealing the cold rolled thin plate.

Fine spheroidized steel sheet with excellent heat treatment characteristic and method for manufacturing the same

A carbon steel sheet having high formability due to a microscopic and uniform carbide distribution and having a good characteristic of final heat treatment, and a manufacturing method thereof. The carbon steel sheet having excellent formability, includes, in wt %, C at 0.2-0.5%, Mn at 0.1-1.2%, Si at less than or equal to 0.4%, Cr at less than or equal to 0.5%, Al at 0.01-0.1%, S at less than or equal to 0.012%, Ti at less than or equal to 0.5&#xd7;48/14&#xd7;[N]% when the condition of B(atomic %)/N(atomic %)&#x3e;1 is satisfied or by 0.5&#xd7;48/14&#xd7;[N]% to 0.03% when the condition of B and N is not satisfied, B at 0.0005-0.0080%, N at less than or equal to 0.006%, Fe, and extra inevitable elements; an average size of carbide is less than or equal to 1 &#x3bc;m; and an average grain size of ferrite is less than or equal to 5 &#x3bc;m.

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Kyungsan, South Korea

Chang-Hoon Lee