Non-magnetic high manganese steel sheet with high strength and manufacturing method thereof

Abstract

The present invention relates to a non-magnetic high manganese steel sheet with high-strength, which has superior strength and moldability, and at the same time, can obtain superior non-magnetic characteristics, and a method for manufacturing the same.

1 . A non-magnetic high manganese steel sheet with high strength, the steel sheet comprising, by weight %, C: 0.4% to 0.9%, Mn: 10% to 25%, Al: 0.01% to 8.0%, Si: 0.01% to 2.0%, Ti: 0.05% to 0.2%, Si: 0.01% to 2.0%, B: 0.0005% to 0.005%, S: 0.05% or less (excluding 0%), P: 0.8% or less (excluding 0%), N: 0.003% to 0.01%, and the balance of Fe and inevitable impurities. 
     
     
         2 . The steel sheet of  claim 1 , wherein the steel sheet has a microstructure comprising 1 volume % or less of carbides. 
     
     
         3 . The steel sheet of  claim 1 , wherein the steel sheet has a relative permeability of 1.10 or less in a magnetic field of 25 kA/m. 
     
     
         4 . The steel sheet of  claim 1 , wherein if the content Al in the steel sheet ranges from 1.3% to 8.0%, the steel sheet has a stacking fault energy of 30 mJ/cm 2  or more. 
     
     
         5 . The steel sheet of  claim 4 , wherein the steel sheet has a relative permeability of 1.05 or less in a magnetic field of 50 kA/m. 
     
     
         6 . The steel sheet of  claim 1 , wherein the steel sheet has a tensile strength of 800 MPa or greater and an elongation of 15% or greater. 
     
     
         7 . A method of manufacturing a non-magnetic high manganese steel sheet having high strength, the method comprising:
 reheating a steel slab to a temperature within a range of 1100° C. to 1250° C., the steel slab comprising, by weight %, C: 0.4% to 0.9%, Mn: 10% to 25%, Al: 0.01% to 8.0%, Si: 0.01% to 2.0%, Ti: 0.05% to 0.2%, Si: 0.01% to 2.0%, B: 0.0005% to 0.005%, S: 0.05% or less (excluding 0%), P: 0.8% or less (excluding 0%), N: 0.003% to 0.01%, and the balance of Fe and inevitable impurities;   performing a hot-rolling process by hot-rolling the reheated steel slab and finish-rolling the steel slab at a temperature within a temperature range of 800° C. to 950° C., so as to form a hot-rolled steel sheet;   coiling the hot-rolled steel sheet at a temperature within a temperature range of 400° C. to 700° C.;   cold-rolling the steel sheet with a reduction ratio of 30% to 60%; and   continuously annealing the cold-rolled steel sheet at a temperature within a temperature range of 650° C. to 900° C.