High-Hardness Martensitic Stainless Steel with Excellent Antibacterial Property and Preparation Method Therefor

Abstract

A high-hardness martensitic stainless steel with excellent antibacterial property and a preparation method therefor are disclosed. The high-hardness martensitic stainless steel with excellent antibacterial property comprises: 0.45-0.65 wt % of C; 0.02-0.06 wt % of N; 0.1-0.6 wt % of Si; 0.3-1.0 wt % of Mn; 0.1-0.4 wt % of Ni; 13-14.5 wt % of Cr; 0.4-0.6 wt % of Mo; 0.8-1.2 wt % of W; 1.5-2.0 wt % of Cu; and the balance of Fe and inevitable impurities. According to the present disclosure, there is an advantage enabling the preparation of the martensitic stainless steel for knives, the martensitic stainless steel having high hardness, high corrosion resistance and excellent antibacterial property, by uniformly distributing fine chromium carbide and e-Cu precipitates in the microstructure of a batch annealed material of a high-carbon martensitic stainless steel containing Cu. In addition, there is an advantage of causing no rust formation on a material after an antibacterial evaluation.

1 . A high-hardness martensitic stainless steel with excellent antibacterial properties comprising: 0.45 to 0.65 wt % of carbon (C); 0.02 to 0.06 wt % of nitrogen (N); 0.1 to 0.6 wt % of silicon (Si); 0.3 to 1.0 wt % of manganese (Mn); 0.1 to 0.4 wt % of nickel (Ni); 13 to 14.5 wt % of chromium (Cr); 0.4 to 0.6 wt % of molybdenum (Mo); 0.8 to 1.2 wt % of tungsten (W); 1.5 to 2.0 wt % of copper (Cu); and the balance of iron (Fe) and inevitable impurities. 
     
     
         2 . The high-hardness martensitic stainless steel with excellent antibacterial properties according to  claim 1 , wherein the martensitic stainless steel has an elongation of 18% or more. 
     
     
         3 . The high-hardness martensitic stainless steel with excellent antibacterial properties according to  claim 2 , wherein a chromium carbide is distributed in a martensitic stainless steel structure in an amount of 90 pieces/100 μm 2  or more. 
     
     
         4 . The high-hardness martensitic stainless steel with excellent antibacterial properties according to  claim 3 , wherein the martensitic stainless steel satisfies Pitting Resistance Equivalent Number (PREN) described below, does not have surface deterioration during evaluation of antibacterial activities using an inoculum containing NaCl, and exhibits a bacterial reduction rate of 99% or more:
 Pitting Resistance Equivalent Number (PREN) Cr+3.0(Mo+½W)+16N≧17.   
     
     
         5 . The high-hardness martensitic stainless steel with excellent antibacterial properties according to  claim 2 , wherein a batch annealing process to prepare the martensitic stainless steel comprises: a first soaking process to uniformly distribute Cu precipitates in a structure of the martensitic stainless steel; a second soaking process to uniformly distribute the chromium carbide in the structure of the martensitic stainless steel; and a third soaking process to spheroidize fine particles of the chromium carbide. 
     
     
         6 . The high-hardness martensitic stainless steel with excellent antibacterial properties according to  claim 5 , wherein the first soaking process is performed at 500 to 600° C., the second soaking process is performed at 800 to 900° C., and the third soaking process is performed at 600 to 750° C. 
     
     
         7 . The high-hardness martensitic stainless steel with excellent antibacterial properties according to  claim 6 , wherein the first soaking process continues for 5 to 15 hours, the second soaking process continues for 15 to 25 hours, and the third soaking process continues for 5 to 15 hours. 
     
     
         8 . The high-hardness martensitic stainless steel with excellent antibacterial properties according to  claim 7 , wherein the batch annealing process further comprises: a heating process of elevating a temperature at a rate of 40 to 200° C./h until the second soaking process after the first soaking process; a cooling process of lowering the temperature at a rate of 10° C./h or higher until the third soaking process after the second soaking process; and an air-cooling process performed after the third soaking process. 
     
     
         9 . A method of producing a high-hardness martensitic stainless steel with excellent antibacterial properties, the method comprising:
 producing a hot-rolled steel sheet by hot rolling a cast strip;   softening the hot-rolled steel sheet by a batch annealing process; and   producing a cold-rolled steel sheet by cold rolling the annealed steel sheet treated by the softening process,   wherein the batch annealing process comprises: a first soaking process to uniformly distribute Cu precipitates in a structure of the martensitic stainless steel; a second soaking process to uniformly distribute a chromium carbide in the structure of the martensitic stainless steel; and a third soaking process to spheroidize fine particles of the chromium carbide.   
     
     
         10 . The method for producing a high-hardness martensitic stainless steel with excellent antibacterial properties according to  claim 9 , wherein the first soaking process is performed for 5 to 15 hours at a temperature of 500 to 600° C.; the second soaking process is performed for 15 to 25 hours at a temperature of 800 to 900° C.; and the third soaking process is performed for 5 to 15 hours at a temperature of 600 to 750° C. 
     
     
         11 . The method for producing a high-hardness martensitic stainless steel with excellent antibacterial properties according to  claim 10 , wherein the batch annealing process further comprises: a heating process of elevating a temperature at a rate of 40 to 200° C./h until the second soaking process after the first soaking process; a cooling process of lowering the temperature at a rate of 10° C./h or higher until the third soaking process after the second soaking process; and an air-cooling process performed after the third soaking process. 
     
     
         12 . The method for producing a high-hardness martensitic stainless steel with excellent antibacterial properties according to  claim 11 , further comprising performing a hardening heat treatment on the cold rolled steel sheet,
 wherein the hardening heat treatment comprises austenitizing the cold-rolled steel sheet at 1000 to 1150° C. for 10 seconds to 5 minutes to re-solidify the uniformly distributed chromium carbide, quenching the austenitized cold-rolled steel sheet to room temperature, subzero treating the quenched resultant at a temperature of −70° C. for 10 seconds to 5 minutes to transform remaining austenite to martensite, and tempering the resultant at 400 to 600° C. for 30 minutes to 2 hours.   
     
     
         13 . The high-hardness martensitic stainless steel with excellent antibacterial properties according to  claim 3 , wherein a batch annealing process to prepare the martensitic stainless steel comprises: a first soaking process to uniformly distribute Cu precipitates in a structure of the martensitic stainless steel; a second soaking process to uniformly distribute the chromium carbide in the structure of the martensitic stainless steel; and a third soaking process to spheroidize fine particles of the chromium carbide. 
     
     
         14 . The high-hardness martensitic stainless steel with excellent antibacterial properties according to  claim 4 , wherein a batch annealing process to prepare the martensitic stainless steel comprises: a first soaking process to uniformly distribute Cu precipitates in a structure of the martensitic stainless steel; a second soaking process to uniformly distribute the chromium carbide in the structure of the martensitic stainless steel; and a third soaking process to spheroidize fine particles of the chromium carbide.