High strength steel plate for sour gas apparatuses and high strength steel pipe or tube using the same

Abstract

Without any restriction on the maximum hardness of the surface layer, provided is a high strength steel plate for sour gas apparatuses having, excellent SSCC resistance in an environment equivalent to ISO-15156 Region 2 where pH is 3.5 or more and the H2S partial pressure is 0.003 bar to 1 bar. The high strength steel plate for sour gas apparatuses having a chemical composition containing, in mass %, specified amounts of C, Si, Mn, P, S, N, Al, and Ca, Ni of 0.10% to 4.00%, and at least one selected from the group consisting of Cr, Mo, W, and Nb in a specified amount, with the balance being Fe and inevitable impurities, in which a ratio HVmin/HVmax of the minimum value HVmin to the maximum value HVmax of Vickers hardness HV0.1 at 0.25 mm below a surface of the steel plate is 0.77 or more.

1 . A high strength steel plate for sour gas apparatuses comprising a chemical composition containing, in mass %,
 C: 0.02% or more and 0.20% or less,   Si: 0.01% or more and 0.70% or less,   Mn: 0.10% or more and 2.50% or less,   P: 0.030% or less,   S: 0.0050% or less,   N: 0.0010% or more and 0.0100% or less,   Al: 0.010% or more and 0.200% or less,   Ca: 0.0005% or more and 0.0050% or less,   Ni: 0.10% or more and 4.00% or less, and   
       at least one selected from the group consisting of
 Cr: 0.03% or more and 1.00% or less, 
 Mo: 0.03% or more and 0.50% or less, 
 W: 0.03% or more and 0.50% or less, and 
 Nb: 0.005% or more and 0.100% or less, 
 
       with the balance being Fe and inevitable impurities, wherein
 a ratio HV min /HV max  of the minimum value HV min  to the maximum value HV max  of Vickers hardness HV0.1 at 0.25 mm below a surface of the steel plate is 0.77 or more. 
 
     
     
         2 . The high strength steel plate for sour gas apparatuses according to  claim 1 , wherein the chemical composition further contains, in mass %, Cu: 0.01% or more and 1.00% or less. 
     
     
         3 . The high strength steel plate for sour gas apparatuses according to  claim 1 , wherein the chemical composition further contains, in mass %, at least one selected from the group consisting of
 V: 0.005% or more and 0.1% or less,   Ti: 0.005% or more and 0.1% or less,   Zr: 0.0005% or more and 0.02% or less,   Mg: 0.0005% or more and 0.02% or less, and   REM: 0.0005% or more and 0.02% or less.   
     
     
         4 . A high strength steel pipe or tube using the high strength steel plate for sour gas apparatuses according to  claim 1 . 
     
     
         5 . A high strength steel pipe or tube using the high strength steel plate for sour gas apparatuses according to  claim 2 . 
     
     
         6 . The high strength steel plate for sour gas apparatuses according to  claim 2 , wherein the chemical composition further contains, in mass %, at least one selected from the group consisting of
 V: 0.005% or more and 0.1% or less,   Ti: 0.005% or more and 0.1% or less,   Zr: 0.0005% or more and 0.02% or less,   Mg: 0.0005% or more and 0.02% or less, and   REM: 0.0005% or more and 0.02% or less.   
     
     
         7 . A high strength steel pipe or tube using the high strength steel plate for sour gas apparatuses according to  claim 3 . 
     
     
         8 . A high strength steel pipe or tube using the high strength steel plate for sour gas apparatuses according to  claim 6 .