Ni-containing steel plate

Abstract

An object of the present invention is to provide an Ni-containing steel plate which is low in cost and has excellent low-temperature toughness. In view of the object, the Ni-containing steel plate of the present invention has a chemical composition containing by mass % C: 0.01% to 0.15%, Si: 0.02% to 0.20%, Mn: 0.45% to 2.00%, P: 0.020% or less, 5: 0.005% or less, Al: 0.005% to 0.100% Ni: 5.0 to 8.0%, and the balance being Fe and incidental impurities, and has a microstructure containing less than 1.7% by volume fraction of retained austenite when cooled to liquid nitrogen temperature, and having an average grain size of crystal grains surrounded by high-angle grain boundaries with an orientation difference of 15° or more of 5 μm or less by equivalent circle diameter.

1 . An Ni-containing steel plate having a chemical composition containing by mass % C: 0.01% to 0.15%, Si: 0.02% to 0.20%, Mn: 0.45% to 2.00%, P: 0.020% or less, S: 0.005% or less, Al: 0.005% to 0.100%, Ni: 5.0% to 8.0%, and the balance being Fe and incidental impurities, wherein
 the steel plate has a microstructure containing less than 1.7% by volume fraction of retained austenite when cooled to liquid nitrogen temperature, and having an average grain size of crystal grains surrounded by high-angle grain boundaries with an orientation difference of 15° or more of 5 μm or less by equivalent circle diameter.   
     
     
         2 . The Ni-containing steel plate according to  claim 1 , wherein the chemical composition further contains by mass % at least one element selected from Cr: 1.00% or less and Mo: 1.000% or less. 
     
     
         3 . The Ni-containing steel plate according to  claim 1 , wherein the chemical composition further contains by mass % at least one element selected from Cu: 1.00% or less, V: 0.100% or less, Nb: 0.100% or less, Ti: 0.100% or less, and B: 0.0030% or less. 
     
     
         4 . The Ni-containing steel plate according to  claim 1 , wherein the chemical composition further contains by mass % at least one element selected from Ca: 0.0050% or less and REM: 0.0050% or less. 
     
     
         5 . The Ni-containing steel plate according to  claim 2 , wherein the chemical composition further contains by mass % at least one element selected from Cu: 1.00% or less, V: 0.100% or less, Nb: 0.100% or less, Ti: 0.100% or less, and B: 0.0030% or less. 
     
     
         6 . The Ni-containing steel plate according to  claim 2 , wherein the chemical composition further contains by mass % at least one element selected from Ca: 0.0050% or less and REM: 0.0050% or less. 
     
     
         7 . The Ni-containing steel plate according to  claim 3 , wherein the chemical composition further contains by mass % at least one element selected from Ca: 0.0050% or less and REM: 0.0050% or less. 
     
     
         8 . The Ni-containing steel plate according to  claim 5 , wherein the chemical composition further contains by mass % at least one element selected from Ca: 0.0050% or less and REM: 0.0050% or less.