High Strength Hot Rolled Steel Sheet Containing High Mn Content with Excellent Workability and Method for Manufacturing the Same

Abstract

A hot rolled steel sheet used for a bumper reinforceing material or for an impact absorption material in a door of automobiles, and a method for manufacturing the same are disclosed. The steel sheet comprises, by weight%, C: 0.2%˜1%, Mn: 8˜15%, S: 0.05% or less, P: 0.03% or less, and the balance of Fe and other unavoidable impurities. A product of tensile strength and total elongation (TS×ToLEl) of the steel sheet is 24,000 MPa % or more. The method provides a high strength hot rolled steel sheet, which has a high strength-elongation balance value, ensuring excellent workability.

1 . A high strength hot rolled steel sheet containing a high Mn content with excellent workability, comprising, by weight %:
 C: 0.2%˜1%, Mn: 8˜15%, S: 0.05% or less, P: 0.03% or less, and the balance of Fe and other unavoidable impurities,   wherein a product of tensile strength and total elongation (TS×Tot.El) of the steel sheet is 24,000 MPa % or more.   
     
     
         2 . The steel sheet according to  claim 1 , further comprising: at least one selected from the group consisting of Al: 0.3˜3%, Ni: 2˜7% and Cu: 2˜5%. 
     
     
         3 . The steel sheet according to  claim 1 , wherein the hot rolled steel sheet has a single phase austenite structure. 
     
     
         4 . A method for manufacturing a high strength hot rolled steel sheet containing a high Mn content with excellent workability, comprising:
 reheating a steel slab at a temperature of 1,180˜1,220° C., the steel slab comprising, by weight %: C: 0.2%˜1%, MN: 8˜15%, S: 0.05% or less, P: 0.03% or less, and the balance of Fe and other unavoidable impurities;   finish hot rolling the reheated steel slab at a temperature of 800° C. or more; and   cooling the hot rolled steel sheet at a temperature of 600° C. or more, followed by coiling the cooled steel sheet,   wherein a product of tensile strength and total elongation (TS×Tot.El) of the steel sheet is 24,000 MPa % or more.   
     
     
         5 . The method according to  claim 4 , wherein the steel slab comprises at least one selected from the group consisting of Al: 0.3˜3%, Ni: 2˜7% and Cu: 2˜5%. 
     
     
         6 . The method according to  claim 4 , wherein the hot rolled steel sheet has a single phase austenite structure. 
     
     
         7 . The steel sheet according to  claim 2 , wherein the hot rolled steel sheet has a single phase austenite structure. 
     
     
         8 . The method according to  claim 5 , wherein the hot rolled steel sheet has a single phase austenite structure.