Austenitic stainless steel having excellent orange peel resistance and manufacturing method therefor

Abstract

An austenitic stainless steel having excellent orange peel resistance and a method for producing the same are disclosed. In the austenitic stainless steel having excellent orange peel resistance, according to an embodiment of the present disclosure, a ratio Gs/Gi of an average crystal grain size Gs of surface crystal grains included in a first area corresponding to a depth of 10% or less of a total thickness of the austenitic stainless steel from the surface of the austenitic stainless steel with respect to an average crystal grain size Gi of internal crystal grains included in a second area corresponding to a depth that is deeper than 10% of the total thickness of the austenitic stainless steel from the surface of the austenitic stainless steel may be 0.5 or smaller. Therefore, it is possible to prevent deterioration of surface roughness due to orange peel of the steel surface even after post-processing of the austenitic stainless steel while increasing the sizes of crystal grains in order to reduce strength of the austenitic stainless steel, and also to reduce cost by replacing copper pipes

1 . Austenitic stainless steel having excellent orange peel resistance, wherein a ratio Gs/Gi of an average crystal grain size Gs of surface crystal grains included in a first area corresponding to a depth of 10% or less of a total thickness of the austenitic stainless steel from the surface of the austenitic stainless steel with respect to an average crystal grain size Gi of internal crystal grains included in a second area corresponding to a depth that is deeper than 10% of the total thickness of the austenitic stainless steel from the surface of the austenitic stainless steel is 0.5 or smaller. 
     
     
         2 . The austenitic stainless steel of  claim 1 , comprising silicon (Si) of 0.1 to 0.65 weight %, manganese (Mn) of 1.0 to 3.0 weight %, nickel (Ni) of 6.5 to 10.0 weight %, chrome (Cr) of 16.5 to 18.5 weight %, copper (Cu) of 6.0 weight % or less (except for zero), carbon (C) and nitrogen (N) of 0.13 weight % or less (except for zero), iron (Fe), and other inevitable impurities. 
     
     
         3 . The austenitic stainless steel of  claim 1 , wherein the average crystal grain size Gs of the surface crystal grains is 100 μm or less. 
     
     
         4 . The austenitic stainless steel of  claim 1 , manufactured by strip casting. 
     
     
         5 . The austenitic stainless steel of  claim 4 , wherein when the austenitic stainless steel is casted by strip casting, a delta ferritic phase content remaining upon solidification is 5 weight % or more 
     
     
         6 . The austenitic stainless steel of  claim 5 , wherein a delta ferrite phase content of a cold-rolled structure of the austenitic stainless steel is 0.5 weight % or more. 
     
     
         7 . A method of manufacturing austenitic stainless steel having excellent orange peel resistance by strip casting of passing stainless steel between a pair of rotating rolls to freeze the stain steel into a solid, the method comprising,
 casting austenitic stainless steel, and controlling elements of the austenitic stainless steel according to Equation (1) such that a content Delta of delta ferritic phase remaining upon solidification is 5 wt % or more to manufacture a hot-rolled steel sheet:
   Delta=((Cr+Mo+1.5Mn+0.5Nb+2Ti+18)/(Ni+0.3Cu+30*(C+N)+0.5Mn+36)+0.262)×161−161,  Equation (1)
 
   wherein element symbols of Equation (1) represent weight percentages (weight %) of the corresponding elements   
     
     
         8 . The method of  claim 7 , wherein the austenitic stainless steel comprises silicon (Si) of 0.1 to 0.65 weight %, manganese (Mn) of 1.0 to 3.0 weight %, nickel (Ni) of 6.5 to 10.0 weight %, chrome (Cr) of 16.5 to 18.5 weight %, copper (Cu) of 6.0 weight % or less (except for zero), carbon (C) and nitrogen (N) of 0.13 weight % or less (except for zero), iron (Fe), and other inevitable impurities. 
     
     
         9 . The method of  claim 7 , further comprising performing heat-treatment on the hot-rolled steel sheet, and then performing cold rolling on the hot-rolled steel sheet at a total reduction ratio of 50% or higher, thereby manufacturing a cold-rolled steel sheet,
 wherein a delta ferritic phase content of a cold-rolled structure of the cold-rolled steel sheet is 0.5 weight % or more.