Steel plate for submerged arc welding

Abstract

A steel plate for submerged arc welding having good low temperature toughness at a fusion line vicinity part and a boundary with the base material in HAZ as well as at the base material and the weld metal is provided. The steel plate for submerged arc welding according to the invention contains, by mass, 0.03% to 0.09% C, 1.5% to 2.5% Mn, 0.005% to 0.025% Nb, 0.005% to 0.02% Ti, 0.01% to 0.06% Al, at most 0.0005% B, 0.001% to 0.008% N, at most 0.015% P, at most 0.015% S, and at most 0.006% O, and the balance consists of Fe and impurities. Therefore, the steel plate according to the present invention has good low temperature toughness not only at the fusion line vicinity part and the boundary with a base material in the HAZ but also in the base material and weld metal.

1 . A steel plate for submerged arc welding comprising, by mass, 0.03% to 0.09% C, 1.5% to 2.5% Mn, 0.005% to 0.025% Nb, 0.005% to 0.02% Ti, 0.01% to 0.06% Al, at most 0.0005% B, 0.001% to 0.008% N, at most 0.015% P, at most 0.015% S, and at most 0.006% O, the balance consisting of Fe and impurities. 
   
   
       2 . The steel plate for submerged arc welding according to  claim 1 , further comprising at least one of at most 0.6% Cu, at most 1.5% Ni, at most 0.04% V, at most 0.08% Mo, and at most 0.5% Cr, the following Expressions (1) and (2) being satisfied,
   (Mo/15+V/3+Nb/2)≦0.015  (1)     (Mn/20+Cu/20+Ni/60)≧0.09  (2)   
     where the symbols represent the contents of the elements (% by mass). 
   
   
       3 . The steel plate for submerged arc welding according to  claim 1 , further comprising at most 0.3% Si. 
   
   
       4 . The steel plate for submerged arc welding according to  claim 1 , further comprising at least one of at most 0.005% Ca, at most 0.005% Zr, at most 0.005% Mg, and at most 0.005% Ce. 
   
   
       5 . The steel plate for submerged arc welding according to  claim 2 , further comprising at most 0.3% Si. 
   
   
       6 . The steel plate for submerged arc welding according to  claim 2 , further comprising at least one of at most 0.005% Ca, at most 0.005% Zr, at most 0.005% Mg, and at most 0.005% Ce. 
   
   
       7 . The steel plate for submerged arc welding according to  claim 3 , further comprising at least one of at most 0.005% Ca, at most 0.005% Zr, at most 0.005% Mg, and at most 0.005% Ce. 
   
   
       8 . The steel plate for submerged arc welding according to  claim 5 , further comprising at least one of at most 0.005% Ca, at most 0.005% Zr, at most 0.005% Mg, and at most 0.005% Ce.