Method for manufacturing a steel sheet
AssigneeNKK Corporation
InventorsTadashi Inoue, Yoichi Motoyashiki, Hiroshi Nakata, Takayuki Odake, Toru Inazumi
Life of this patent
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Abstract
The method for manufacturing steel sheet comprises the steps of: rough-rolling to form a sheet bar; finish-rolling the sheet bar to form a steel strip; applying primary cooling and secondary cooling to the finish-rolled steel strip; and coiling the secondary-cooled steel strip. The primary cooling is conducted at cooling speeds of 120° C./sec or more down to the temperatures of from 500 to 800° C. The secondary cooling is conducted at cooling speeds of less than 60° C./sec.
Claims30
A method for manufacturing steel sheet comprising the steps of:
- rough-rolling a continuously cast slab consisting essentially of 0.8% or less C, by weight to form a sheet bar;
- finish-rolling the sheet bar at finishing temperatures of (Ar3 transformation point −20° C.) or more to form a steel strip;
- rapid cooling the steel strip after completed the finish-rolling at cooling speeds of higher than 120° C./sec down to temperatures of from 500 to 800° C.;
- and
- coiling the steel strip after completed the rapid cooling at coiling temperatures of from 400 to 750° C.
A method for manufacturing steel sheet comprising the steps of:
- rough-rolling a continuously cast slab consisting essentially of more than 0.8% and 1% or less C, by weight to form a sheet bar;
- finish-rolling thus obtained sheet bar at finishing temperatures of (Acm transformation point −20° C.) or more to form a steel strip;
- rapid cooling the steel strip after completed the finish-rolling at cooling speeds of higher than 120° C./sec down to temperatures of from 500 to 800° C.;
- and
- coiling the steel strip after completed the rapid cooling at coiling temperatures of from 400 to 750° C.
A method for manufacturing steel sheet comprising the steps of:
- forming a slab consisting essentially of 0.05 to 0.14% C, 0.5% or less Si, 0.5 to 2.5% Mn, 0.05% or less P, 0.01% or less S, 0.005% or less O, and less than 0.0005% Ca, by weight, by continuous casting conducting treatment to reduce segregation;
- hot-rolling the slab at finishing temperatures of finish-rolling of Ar3 transformation point or more to form a hot-rolled steel sheet;
- starting primary cooling within 2 seconds after completed the hot-rolling at cooling speeds of from 100 to 2,000° C./sec to cool the hot-rolled steel sheet to a temperature range of from 600 to 750° C.;
- applying secondary cooling, after cooling to the temperature range, at cooling speeds of less than 50° C./sec;
- and
- coiling the secondary-cooled hot-rolled steel sheet at temperatures of from 450 to 650° C.
A method for manufacturing steel sheet comprising the steps of:
- hot-rolling a steel consisting essentially of 0.03 to 0.12% C, 1% or less Si, 0.5 to 2% Mn, 0.02% or less P, 0.01% or less S, further at least one element selected from the group consisting of 0.005 to 0.1% Nb, 0.005 to 0.1% V, and 0.005 to 0.1% Ti, by weight, at temperatures of 1,070° C. or below to accumulated reductions in thickness of 30% or more;
- and
- cooling the hot-rolled steel sheet within 6 seconds after completed the rolling at average cooling speeds of not less than 80° C./sec to temperatures of from above 500° C. to not more than 700° C.
A method for manufacturing steel sheet comprising the steps of:
- hot-rolling a steel consisting essentially of 0.03 to 0.12% C, 1% or less Si, 0.5 to 2% Mn, 0.02% or less P, 0.01% or less S, and 0.05 to 0.5% Mo, by weight, at temperatures of 1,070° C. or below to accumulated reductions in thickness of 30% or more;
- and cooling the hot-rolled steel sheet within 6 seconds after completed the rolling at average cooling speeds of not less than 80° C./sec to temperatures of from above 500° C. to not more than 700° C.
Dependencies are inferred from the claim text.