High hardness wear-resistant steel with excellent toughness and cutting crack resistance and method for manufacturing same

Abstract

The present invention relates to a high hardness wear-resistant steel with excellent toughness and cutting crack resistance, and a method for manufacturing the same. A high hardness wear-resistant steel according to one aspect of the present invention has a composition containing, by weight ratio, 2.1 to 4.0% of manganese (Mn), 0.15 to 0.2% of carbon (C), 0.02 to 0.5% of silicon (Si), 0.2 to 0.7% of chromium (Cr), a remainder of iron (Fe) and other unavoidable impurities, has a microstructure in which prior austenite grain size is 25 μm or less and martensite is included as a main phase, and has excellent toughness and cutting crack resistance which satisfies a condition in which Ac3-Ac1 is 100° C. or lower.

1 . A high hardness wear-resistant steel:
 having a composition containing, by weight ratio, 2.1 to 4.0% of manganese (Mn), 0.15 to 0.2% of carbon (C), 0.02 to 0.5% of silicon (Si), 0.2 to 0.7% of chromium (Cr), a remainder of iron (Fe) and other unavoidable impurities;   having a microstructure in which prior austenite grain size is 25 μm or less and martensite is included as a main phase; and   having excellent toughness and cutting crack resistance which satisfies a condition in which Ac3-Ac1 is 100° C. or lower.   
     
     
         2 . The high hardness wear-resistant steel according to  claim 1 , further comprising, by weight ratio, 0.1% or less of niobium (Nb), 0.02% or less of boron (B), and 0.1% or less of titanium (Ti). 
     
     
         3 . The high hardness wear-resistant steel according to  claim 1 , wherein the structure of martensite comprises 95% or more in area fraction. 
     
     
         4 . The high hardness wear-resistant steel according to  claim 1 , wherein Brinell hardness is 420 to 480, and Charpy impact energy is 35 J or more at −40° C. 
     
     
         5 . The high hardness wear-resistant steel according to  claim 1 , wherein the martensite does not contain carbides therein. 
     
     
         6 . A method of manufacturing a high hardness wear-resistant steel having excellent toughness and cutting crack resistance, comprising:
 hot-rolling a slab having a composition containing, by weight ratio, 2.1 to 4.0% of manganese (Mn), 0.15 to 0.2% of carbon (C), 0.02 to 0.5% of silicon (Si), 0.2 to 0.7% of chromium (Cr), a remainder of iron (Fe) and other unavoidable impurities, to provide a steel plate,   quenching the steel plate to a temperature of 200° C. or lower at a cooling rate of 3° C./sec or higher,   reheating the quenched steel plate to an austenite temperature range, and   secondarily quenching the reheated steel plate to a temperature of 200° C. or lower at a cooling rate of 3° C./sec or higher.   
     
     
         7 . The method according to  claim 6 , wherein the high hardness wear-resistant steel further comprising, by weight ratio, 0.1% or less of niobium (Nb), 0.02% or less of boron (B), and 0.1% or less of titanium (Ti). 
     
     
         8 . The method according to  claim 6 , wherein an finishing temperature of the hot-rolling is an Ar3 or higher. 
     
     
         9 . The method according to  claim 6 , wherein a heating temperature in the reheating operation is in the range of an Ar3 to 960° C. 
     
     
         10 . The method according to  claim 6 , wherein an austenite grain size of the steel plate to be secondarily quenched is 25 μm or less. 
     
     
         11 . The high hardness wear-resistant steel according to  claim 2 , wherein the structure of martensite comprises 95% or more in area fraction. 
     
     
         12 . The high hardness wear-resistant steel according to  claim 2 , wherein Brinell hardness is 420 to 480, and Charpy impact energy is 35 J or more at −40° C. 
     
     
         13 . The high hardness wear-resistant steel according to  claim 2 , wherein the martensite does not contain carbides therein 
     
     
         14 . The method according to  claim 7 , wherein an finishing temperature of the hot-rolling is an Ar3 or higher. 
     
     
         15 . The method according to  claim 7 , wherein a heating temperature in the reheating operation is in the range of an Ar3 to 960° C. 
     
     
         16 . The method according to  claim 7 , wherein an austenite grain size of the steel plate to be secondarily quenched is 25 μm or less.