C+n austenitic stainless steel having high strength and excellent corrosion resistance, and fabrication method thereof

Abstract

A C+N austenitic stainless steel with high mechanical strength and excellent corrosion resistance and a fabrication method thereof are provided. The C+N austenitic stainless steel consists of: 8 to 12 wt. % manganese; 15 to 20 wt. % chromium; 2 wt. % or less nickel; 4 wt. % or less tungsten; 2 wt. % or less molybdenum; 0.6 to 1.0 wt. % of total C+N content; a balance of iron; and unavoidable impurities. The austenitic stainless steel fabricated provides mechanical properties of a tensile strength of 850 MPa or higher and an uniform elongation of 45% or higher, obtained through controlling the contents of the interstitial elements and those of the substitutional elements. The alloy also provides corrosion resistance and a biocompatibility due to the minimized content of nickel which causes allergic reaction to the human body. Therefore, the C+N austenitic stainless steel is applicable in the fabrication of a variety of functional components and structural fields.

1 . The C+N austenitic stainless steel with high mechanical strength and excellent corrosion resistance comprising:
 8 to 12 wt. % manganese (Mn);   15 to 20 wt. % chromium (Cr);   2 wt. % or less nickel (Ni);   0.6 to 1.0 wt. % of total C+N content;   4 wt. % or less tungsten (W);   2 wt. % or less molybdenum (Mo);   a balance of iron (Fe); and   unavoidable impurities.   
     
     
         2 . The C+N austenitic stainless steel of  claim 1 , wherein the wt. % of tungsten (W) is 1 to 4 wt. %, and the wt. % of molybdenum (Mo) is 0 wt. %. 
     
     
         3 . The C+N austenitic stainless steel of  claim 1 , wherein the wt. % of tungsten (W) is 0 wt. %. 
     
     
         4 . The C+N austenitic stainless steel of  claim 1 , wherein the wt. % of tungsten (W) is 1 to 4 wt. %. 
     
     
         5 . The C+N austenitic stainless steel of  claim 1 , wherein the ratio of manganese (Mn) to chromium (Cr) (Mn/Cr) ranges from 0.5 to 1.0. 
     
     
         6 . The C+N austenitic stainless steel of  claim 1 , wherein the total content of manganese (Mn) and chromium (Cr) ([Mn+Cr]) is 30 wt. % or less. 
     
     
         7 . The C+N austenitic stainless steel of  claim 1 , wherein the nitrogen (N) content is 0.3 wt. % or more. 
     
     
         8 . The C+N austenitic stainless steel of  claim 1 , wherein the total content of tungsten (W) and molybdenum (Mo) (0.5W+Mo) is 3 wt. % or less. 
     
     
         9 . The C+N austenitic stainless steel of  claim 1 , further comprising mechanical properties including a tensile strength of 850 MPa or higher, and an uniform elongation of 45% or more. 
     
     
         10 . A fabrication method of the C+N austenitic stainless steel with high mechanical strength and excellent corrosion resistance, the fabrication method comprising:
 master alloy charging in which a master alloy is charged into a vacuum melting furnace;   vacuum maintaining in which the vacuum melting furnace with the master alloy charged therein is maintained under vacuum;   master alloy melting in which the vacuum melting furnace is heated and the master alloy is melted;   nitrogen (N) content adjusting in which nitrogen gas is injected into the vacuum melting furnace;   melted alloy agitating in which the melted master alloy is agitated;   ingot forming in which an ingot is formed by pouring the agitated melted alloy from the vacuum melting furnace;   hot-rolling the formed ingot; and   performing water quenching of the hot-rolled stainless steel to prevent precipitation of carbide which degrades the mechanical property and corrosion resistance.   
     
     
         11 . The fabrication method of  claim 10 , wherein in the vacuum maintaining step, the vacuum level inside the vacuum melting furnace is kept at 10 −3  torr or lower. 
     
     
         12 . The fabrication method of  claim 10 , wherein the nitrogen (N) content adjusting comprises:
 nitrogen gas injecting in which nitrogen gas is injected to the interior of the vacuum melting furnace; and   pressure adjusting in which the partial pressure of nitrogen gas of the interior of the vacuum melting furnace is adjusted to 1 atm.