Corrosion-Resistant Steel Excellent in Toughness of Base Metal and Weld Portion, and Method of Manufacturing the Same

Abstract

A corrosion-resistant steel excellent in toughness of a base metal and a weld portion said steel slab contains, in % by weight, C: 0.2% or less; Si: 0.01 to 2.0%; Mn: 0.1 to 4% or less; P: 0.03% or less; S: 0.01% or less; Cr: 3 to 11%; Al: 0.1 to 2%; and N: 0.02%, and has values of 1150 or above, and 600 or above respectively for Tp and Tc expressed by the equations below using concentrations of Cr, Al, C, Mn, Cu and Ni respectively given as % Cr, % Al, % C, % Mn, % Cu and % Ni. Tp=1601−(34% Cr+287% Al)+(500% C+33% Mn+60% Cu+107% Ni); and Tc=910+80% Al−(300% C+80% Mn+15% Cr+55% Ni).

1 . A corrosion-resistant steel excellent in toughness of a base metal and a weld portion, containing, in % by weight:
 C: 0.2% or less;   Si: 0.01 to 2.0%;   Mn: 0.1 to 4%;   P: 0.03% or less;   S: 0.01% or less;   Cr: 3 to 11%;   Al: 0.1 to 2%; and   N: 0.02% or less, and   
       having values of 1150 or above, and 600 or above respectively for Tp and Tc expressed by the equations below using concentrations of Cr, Al, C, Mn, Cu and Ni respectively given as % Cr, % Al, % C, % Mn, % Cu and % Ni.
     Tp= 1601−(34% Cr+287% Al)+(500% C+33% Mn+60% Cu+107% Ni); and 
     Tc= 910+80% Al−(300% C+80% Mn+15% Cr+55% Ni). 
 
     
     
         2 . The corrosion-resistant steel excellent in toughness of a base metal and a weld portion according to  claim 1 , further containing, in % by weight, any one of, or two or more elements selected from the group consisting of:
 Cu: 0.1 to 4%;   Ni: 0.1 to 4%;   Mo: 0.01 to 1%;   V: 0.01 to 0.1%;   Nb: 0.005 to 0.050%;   Ti: 0.005 to 0.03%;   Ca: 0.0005 to 0.05%;   Mg: 0.0005 to 0.05%; and   REM: 0.001 to 0.1%.   
     
     
         3 . A method of manufacturing a corrosion-resistant steel excellent in toughness of a base metal and a weld portion, comprising the steps of:
 heating a steel slab;   the steel slab containing, in % by weight:   C: 0.2% or less;   Si: 0.01 to 2.0%;   Mn: 0.1 to 4%;   P: 0.03% or less;   S: 0.01% or less;   Cr: 3 to 11%;   Al: 0.1 to 2%; and   N: 0.02% or less, and   
       having values of 1150 or above, and 600 or above respectively for Tp and Tc expressed by the equations below using concentrations of Cr, Al, C, Mn, Cu and Ni respectively given as % Cr, % Al, % C, % Mn, % Cu and % Ni,
 forming a steel plate by hot rolling of the steel slab; and 
 cooling the steel plate by air.
     Tp= 1601−(34% Cr+287% Al)+(500% C+33% Mn+60% Cu+107% Ni); and 
     Tc= 910+80% Al−(300% C+80% Mn+15% Cr+55% Ni). 
 
 
     
     
         4 . The method of manufacturing a corrosion-resistant steel excellent in toughness of a base metal and a weld portion according to  claim 3 , wherein the steel slab further contains, in % by weight, any one of, or two or more elements selected from the group consisting of:
 Cu: 0.1 to 4%;   Ni: 0.1 to 4%;   Mo: 0.01 to 1%;   V: 0.01 to 0.1%;   Nb: 0.005 to 0.050%;   Ti: 0.005 to 0.03%;   Ca: 0.0005 to 0.05%;   Mg: 0.0005 to 0.05%; and   REM: 0.001 to 0.1%.   
     
     
         5 . The method of manufacturing a corrosion-resistant steel excellent in toughness of a base metal and a weld portion according to  claim 3 , further comprising, after said step of cooling the steel plate by air, tempering the steel plate at a temperature of A c1  transformation point or below. 
     
     
         6 . The method of manufacturing a corrosion-resistant steel excellent in toughness of a base metal and a weld portion according to  claim 4 , further comprising, after said step of cooling the steel plate by air, tempering the steel plate at a temperature of A c1  transformation point or below.