METHOD FOR PRODUCING HOT ROLLED STEEL SHEET HAVING HIGH FORMABILITY

摘要

PURPOSE: A method for manufacturing a high-formable hot rolled steel sheet is provided to increase the elongation and the plastic strain ratio (r) value of the steel sheet. CONSTITUTION: A method for manufacturing a high-formable hot rolled steel sheet includes: a step of firstly cooling a hot rolled slab at a first velocity; a step of firstly maintaining the slab in a first temperature range, and secondly cooling the slab at a second velocity; a step of secondly maintaining the slab in a second temperature range, and heating the slab at a third velocity; and a step of thirdly maintaining the slab in a third temperature range, and winding the slab. The step of firstly maintaining the slab is implemented at a temperature range of 650 to 700°C for 5 to 10 seconds. The step of secondly maintaining the slab is implemented at a temperature range of 300 to 400°C for 5 to 10 seconds. The step of thirdly maintaining the slab is implemented at a temperature range of 830 to 870°C for 10 to 20 seconds. [Reference numerals] (AA) Temperature; (BB) Hot rolling; (CC) First cooling; (DD) First maintenance; (EE) Second cooling; (FF) Second maintenance; (GG) Reheating; (HH) Third maintenance; (II) Winding; (JJ) Cooling; (KK) Time