HIGH HARDNESS WEAR-RESISTANT STEEL WITH EXCELLENT TOUGHNESS AND CUTTING CRACK RESISTANCE AND METHOD FOR MANUFACTURING SAME
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.