Abrasion resistant steel and method for producing same

Abstract

Abrasion resistant steel having a chemical composition comprising, by mass %, C: 0.10 to 0.20%, Si: 0.01 to 1.20%, Mn: 0.01 to 2.00%, P: less than 0.017%, S: 0.010% or less, Cu: 0.01 to 0.70%, Ni: 0.01 to 1.00%, Cr: 0 to 1.50%, Mo: 0 to 0.80%, W: 0 to 0.50%, Nb: 0 to 0.050%, V: 0 to 0.20%, Ti: 0 to 0.030%, B: 0 to 0.0030%, N: 0.0001 to 0.0070%, Al: 0.001 to 0.10%, Ca: 0 to 0.0050%, Zr: 0 to 0.0050%, Mg: 0 to 0.0050%, REM: 0 to 0.0050%, and a balance of Fe and impurities, having metal structures at a position of ¼ of the thickness from the surface in a thickness direction, which have a total of the area ratios of martensite and lower bainite of 50 to 100% and a prior austenite average grain size of 5 to 23 μm, and having a Brinell hardness at a position of 1 mm from the surface in the thickness direction of 360 to 440, and a method for producing the same.

1 - 4 . (canceled) 
     
     
         5 . Abrasion resistant steel having a chemical composition comprising, by mass %,
 C: 0.10 to 0.20%,   Si: 0.01 to 1.20%,   Mn: 0.01 to 2.00%,   P: less than 0.017%,   S: 0.010% or less,   Cu: 0.01 to 0.70%,   Ni: 0.01 to 1.00%,   Cr: 0 to 1.50%,   Mo: 0 to 0.80%,   W: 0 to 0.50%,   Nb: 0 to 0.050%,   V: 0 to 0.20%,   Ti: 0 to 0.030%,   B: 0 to 0.0030%,   N: 0.0001 to 0.0070%,   Al: 0.001 to 0.10%,   Ca: 0 to 0.0050%,   Zr: 0 to 0.0050%,   Mg: 0 to 0.0050%,   REM: 0 to 0.0050%, and   a balance of Fe and impurities,   having metal structures having a total area ratios of martensite and lower bainite of 50 to 100% and a prior austenite average grain size of 5 to 20 μm at a position of ¼ of a thickness from a surface in a thickness direction, and   having a Brinell hardness of 360 to 440 at a position of 1 mm from the surface in the thickness direction.   
     
     
         6 . The abrasion resistant steel according to  claim 5 , wherein a thickness is 15 mm or more. 
     
     
         7 . A method for producing abrasion resistant steel, the method comprising:
 heating a slab having a chemical composition according to  claim 5  to 1000 to 1350° C.,   hot rolling the heated slab at 1000 to over 825° C. by a 20% or more rolling reduction, then at 825 to 730° C. by a 10% or more rolling reduction, and ending the hot rolling at a temperature of 730° C. or more,   cooling the hot rolled steel plate, and reheating the cooled steel plate to 860° C. or more, then quenching the reheated steel plate.   
     
     
         8 . The abrasion resistant steel according to  claim 5 , wherein a prior austenite average grain size is 18 μm or less. 
     
     
         9 . A method for producing abrasion resistant steel, the method comprising:
 heating a slab having a chemical composition according to  claim 6  to 1000 to 1350° C.,   hot rolling the heated slab at 1000 to over 825° C. by a 20% or more rolling reduction, then at 825 to 730° C. by a 10% or more rolling reduction, and ending the hot rolling at a temperature of 730° C. or more,   cooling the hot rolled steel plate, and reheating the cooled steel plate to 860° C. or more, then quenching the reheated steel plate.   
     
     
         10 . The abrasion resistant steel according to  claim 6 , wherein a prior austenite average grain size is 18 μm or less.