Abrasion resistant steel having excellent hardness and impact toughness and manufacturing method therefor

Abstract

One embodiment of the present disclosure provides an abrasion resistant steel having excellent hardness and impact toughness, and a manufacturing method therefor, the steel comprising, by wt %, 0.33-0.42% of C, 0.1-0.7% of Si, 0.6-1.6% of Mn, 0.05% or less of P, 0.02% or less of S, 0.07% or less of Al, 0.55-5.0% of Ni, 0.01-1.5% of Cu, 0.01-0.8% of Cr, 0.01-0.8% of Mo, 50 ppm or less of B, and 0.02% or less of Co, further comprising one or more selected from the group consisting of 0.02% or less of Ti, 0.05% or less of Nb, 0.05% or less of V and 2-100 ppm of Ca, and comprising the balance of Fe and other inevitable impurities, wherein C and Ni satisfy the following relation 1, and the microstructure comprises 95 area % or more of martensite and 5% or less of bainite (including 0%). [Relation 1] [C]×[Ni]≥0.231

1 . An abrasion resistant steel having excellent hardness and impact toughness, comprising:
 by weight %, 0.33-0.42% of carbon (C), 0.1-0.7% of silicon (Si), 0.6-1.6% of manganese (Mn), 0.05% or less of phosphorus (P) (excluding 0), 0.02% or less of sulfur (S) (excluding 0), 0.07% or less of aluminum (Al) (excluding 0), 0.55-5.0% of nickel (Ni), 0.01-1.5% of copper (Cu), 0.01-0.8% of chromium (Cr), 0.01-0.8% of molybdenum (Mo), 50 ppm or less of boron (B) (excluding 0), and 0.02% or less of cobalt (Co) (excluding 0) and further comprising one or more selected from a group consisting of 0.02% or less of titanium (Ti) (excluding 0), 0.05% or less of niobium (Nb) (excluding 0), 0.05% or less of vanadium (V) (excluding 0) and 2-100 ppm of calcium (Ca), with a balance of Fe and other inevitable impurities,   wherein C and Ni satisfy relational expression 1 as below, and   wherein a microstructure includes 95 area % or more of martensite and 5% or less of bainite (including 0%),
   [C]×[Ni]≥0.231.  [Relational Expression 1]
 
   
     
     
         2 . The abrasion resistant steel of  claim 1 , wherein the abrasion resistant steel further includes one or more selected from a group consisting of 0.05% or less of arsenic (As) (excluding 0), 0.050 or less of tin (Sn) (excluding 0), and 0.05% or less of tungsten (W) (excluding 0). 
     
     
         3 . The abrasion resistant steel of  claim 1 , wherein the abrasion resistant steel secures hardness of 550-650 HB, and has 21 J or more at a low temperature of −40° C.,
 where HB is surface hardness of the steel measured by the Brinell hardness tester. 
 
     
     
         4 . The abrasion resistant steel of  claim 1 , wherein the abrasion resistant steel has hardness (HB) and impact absorption energy (J) satisfying relational expression 2 as below,
   HB÷J≤31.0,  [Relational Expression 2]
   where HB is surface hardness of the steel measured by the Brinell hardness tester, and J is an impact absorption energy value at −40° C.   
     
     
         5 . The abrasion resistant steel of  claim 1 , wherein the abrasion resistant steel has a thickness of 60 mm or less. 
     
     
         6 . A method of manufacturing an abrasion resistant steel having excellent hardness and impact toughness, the method comprising:
 heating a steel slab including, by weight %, 0.33-0.42% of carbon (C), 0.1-0.7% of silicon (Si), 0.6-1.6% of manganese (Mn), 0.05% or less of phosphorus (P) (excluding 0), 0.02% or less of sulfur (S) (excluding 0), 0.07% or less of aluminum (Al) (excluding 0), 0.55-5.0% of nickel (Ni), 0.01-1.5% of copper (Cu), 0.01-0.8% of chromium (Cr), 0.01-0.8% of molybdenum (Mo), 50 ppm or less of boron (B) (excluding 0), and 0.02% or less of cobalt (Co) (excluding 0) and further comprising one or more selected from a group consisting of 0.02% or less of titanium (Ti) (excluding 0), 0.05% or less of niobium (Nb) (excluding 0), 0.05% or less of vanadium (V) (excluding 0) and 2-100 ppm of calcium (Ca), with a balance of Fe and other inevitable impurities, where C and Ni satisfy relational expression 1 as below, in a temperature range of 1050-1250° C.;   obtaining a rough-rolled bar by rough-rolling the reheated steel slab in a temperature range of 950-1050° C.;   obtaining a hot-rolled steel sheet by finishing-hot-rolling the rough-rolled bar in a temperature range of 850-950° C.;   air-cooling the hot-rolled steel sheet to room temperature and reheating the steel sheet for a residence time of 1.3t+10 min−1.3t+60 min (t: sheet thickness) in a temperature range of 860-950° C.; and   water-cooling the reheated hot-rolled steel sheet to 150° C. or less.
   [C]×[Ni]≥0.231  [Relational Expression 1]
 
   
     
     
         7 . The method of  claim 6 , wherein the steel slab further includes one or more selected from a group consisting of 0.05% or less of arsenic (As) (excluding 0), 0.05% or less of tin (Sn) (excluding 0), and 0.05% or less of tungsten (W) (excluding 0). 
     
     
         8 . The method of  claim 6 , wherein a cooling rate is 10° C./s or more in the water-cooling.