Abrasion-resistant steel excellent in formability and production method thereof

Abstract

An abrasion resistant steel excellent in bending formability and suitable for members, e.g., power shovels, which come into contact with earth and sand, and a production method thereof are provided. Specifically, the steel contains, on a percent by mass basis, 0.05% to 0.35% of C, 0.05% to 1.0% of Si, 0.1% to 2.0% of Mn, 0.1% to 1.2% of Ti, 0.1% or less of Al, at least one element of 0.1% to 1.0% of Cu, 0.1% to 2.0% of Ni, 0.1% to 1.0% of Cr, 0.05% to 1.0% of Mo, 0.05% to 1.0% of W, and 0.0003% to 0.0030% of B, if necessary at least one element of 0.005% to 1.0% of Nb and 0.005% to 1.0% of V, and the remainder including Fe and incidental impurities, where DI* represented by the following formula is less than 60: DI*=33.85×(0.1×C*) 0.5 ×(0.7×Si+1)×(3.33×Mn+1)×(0.35×Cu+1)×(0.36×Ni+1)×(2.16×Cr+1)×(3×Mo*+1)×(1.5×W*+1)  (1) where C*=C−1/4×(Ti−48/14N), Mo*=Mo×(1−0.5×(Ti−48/14N)), and W*=W×(1−0.5×(Ti−48/14N)).

1 . An abrasion resistant steel comprising, on a percent by mass basis, 0.05% to 0.35% of C, 0.05% to 1.0% of Si, 0.1% to 2.0% of Mn, 0.1% to 1.2% of Ti, 0.1% or less of Al, at least one element of 0.1% to 1.0% of Cu, 0.1% to 2.0% of Ni, 0.1% to 1.0% of Cr, 0.05% to 1.0% of Mo, 0.05% to 1.0% of W, and 0.0003% to 0.0030% of B, and the remainder including Fe and incidental impurities, where DI* represented by Formula (I) is less than 60:
   DI*= 33 . 85 ×(0.1×C*) 0.5 ×(0.7×Si+1)×(3.33×Mn+1)×(0.35×Cu+1)×(0.36×Ni+1)×(2.16×Cr+1)×(3×Mo*+1)×(1.5×W*+1)  (1)   
     where C*=C−1/4×(Ti−48/14N), Mo*=Mo×(1−0.5×(Ti−48/14N)), W*=W×(1−0.5×(Ti−48/14N)), and C, Si, Mn, Cu, Ni, Cr, Mo, W, Ti, and N represent contents (percent by mass). 
   
   
       2 . The abrasion resistant steel according to  claim 1 , further comprising at least one element of 0.005% to 1.0% of Nb and 0.005% to 1.0% of V on a percent by mass basis. 
   
   
       3 . The abrasion resistant steel according to  claim 1 , wherein a microstructure of base metal comprises a ferrite and pearlite phase as a base phase, and a hard phase is dispersed in the base phase. 
   
   
       4 . The abrasion resistant steel according to  claim 3 , wherein the dispersion density of the hard phase is 400 particles/mm 2  or more. 
   
   
       5 . A method for producing an abrasion resistant steel comprising:
 hot rolling a steel slab having the composition according to  claim 1 ; and   conducting cooling to 400° C. or lower at a cooling rate of 2° C./s or less after hot rolling.   
   
   
       6 . The method according to  claim 5 , wherein the hot rolling reduction rate at 920° C. or lower is specified to be 30% or more and the rolling finishing temperature is specified to be 900° C. or lower. 
   
   
       7 . The abrasion resistant steel according to  claim 2 , wherein a microstructure of base metal comprises a ferrite and pearlite phase as a base phase, and a hard phase is dispersed in the base phase. 
   
   
       8 . The abrasion resistant steel according to  claim 7 , wherein a microstructure of base metal comprises a ferrite and pearlite phase as a base phase, and a hard phase is dispersed in the base phase. 
   
   
       9 . A method for producing an abrasion resistant steel comprising:
 hot rolling a steel slab having the composition according to  claim 2 ; and   conducting cooling to 400° C. or lower at a cooling rate of 2° C./s or less after hot rolling.   
   
   
       10 . The method according to  claim 5 , wherein the hot rolling reduction rate at 920° C. or lower is specified to be 30% or more and the rolling finishing temperature is specified to be 900° C. or lower.