High manganese high strength steel sheets with excellent crashworthiness and method for manufacturing of it

Abstract

There are provided a high-workability high strength steel sheet with excellent workability due to the high elongation and excellent crashworthiness due to the high yield strength, and a method for manufacturing of it. The high manganese steel sheet includes, by weight: carbon (C): 0.2 to 1.5%, manganese (Mn): 10 to 25%, aluminum (Al): 0.01 to 3.0%, phosphorus (P) 0.03% or less, sulfur (S): 0.03% or less, nitrogen (N): 0.040% or less, at least one selected from the group consisting of silicon (Si): 0.02 to 2.5%, titanium (Ti): 0.01 to 0.10% and niobium (Nb): 0.01 to 0.10%, and the balance of Fe and other inevitable impurities. The high manganese steel sheet may be a hot-rolled steel sheet, a cold-rolled steel sheet, or a plated steel sheet, and is suitable for elaborate internal sheets as well as structural members of a car body since it has press workability due to the high elongation and high strain hardening index. Also, the high manganese steel sheet may be used for parts such as a front side member of an automobile since, among its characteristics, the steel sheet has an excellent impact absorbing ability.

1 . A high manganese high strength steel sheet with excellent crashworthiness, comprising, by weight: carbon (C): 0.2 to 1.5%, manganese (Mn): 10 to 25%, aluminum (Al): 0.01 to 3.0%, phosphorus (P) 0.03% or less, sulfur (S): 0.03% or less, nitrogen (N): 0.040% or less, at least one selected from the group consisting of silicon (Si): 0.02 to 2.5%, titanium (Ti): 0.01 to 0.10% and niobium (Nb): 0.01 to 0.10%, and the balance of Fe and other inevitable impurities. 
   
   
       2 . The high manganese high strength steel sheet of  claim 1 , having an austenite single-phase structure. 
   
   
       3 . The high manganese high strength steel sheet of  claim 1 , having a yield strength of 600 MPa or more and a tensile strength of 900 MPa or more. 
   
   
       4 . A method for manufacturing a high manganese high strength steel sheet with excellent crashworthiness, comprising: cold-rolling the steel sheet of  claim 1  at a reduction ratio of 10 to 80%. 
   
   
       5 . The method of  claim 4 , wherein the rolling is selected from the group consisting of temper rolling, dual rolling and hot final rolling. 
   
   
       6 . The method of  claim 4 , wherein the steel sheet is selected from the group consisting of a hot-rolled steel sheet, a cold-rolled steel sheet and a plated steel sheet. 
   
   
       7 . The method of  claim 4 , wherein the steel sheet is selected from the group consisting of a hot-rolled steel sheet, a cold-rolled steel sheet and a plated steel sheet prepared according to at least one operation selected from the group consisting of the following operations (a), (b) and (c);
 (a) homogenizing a steel slab at 1050 to 1300° C., followed by hot-rolling the steel slab at a finish rolling temperature of 850 to 1000° C. and winding the hot-rolled steel slab at a temperature range of 700° C. or below,   (b) cold-rolling the hot-rolled steel sheet at a reduction ratio of 30 to 80% and annealing the resultant steel sheet at 600° C. or above to prepare a cold-rolled steel sheet, and   (c) plating the hot-rolled steel sheet or the cold-rolled steel sheet using a process selected from the group consisting of hot plating, electroplating and deposition to prepare a plated steel sheet.