Seamless steel tubes and pipes for use in oil well

Abstract

Disclosed are seamless steel tubes for oil well use, comprising C: 0.14-0.35%, Si: 0.05-1.0%, Mn: 0.05-2.0%, Cr: 0.05-1.5%, Mo: 0.05-2.0%, Ti: 0-0.05%, V: 0-0.1%, and Al: not less than 0.010%, wherein the concentration product by Al and N content, corrected by Ti and V, is within the range of 0.00001 to 0.00050, and the residuals are Fe and impurities including P: 0.025% or less, and S: 0.010% or less. Ti, V, Nb, or B is preferably contained to enhance the quench hardenability as well as the resistance to sulfide stress corrosion cracking, and further Ca, Mg and/or REM is preferably contained to improve the shape of non-metallic inclusions, enhancing the resistance to sulfide stress corrosion cracking. Thus, said tubes by the invention can be produced by efficient means realizing energy savings, and widely used as ones having excellent stability in mechanical strength.

1 . Seamless steel tubes for use in oil well, comprising, by mass %, C: 0.14-0.35%, Si: 0.05-1.0%, Mn: 0.05-2.0%, Cr: 0.05-1.5%, Mo: 0.05-2.0%, Ti: 0-0.05%, V: 0-0.1%, and Al: not less than 0.010%, wherein each content of Al, N, Ti and V satisfies the relationship expressed by the equation (i) below, and wherein the residuals are Fe and impurities including P: not more than 0.025% and S: not more than 0.010%,  
       0.00001≦Al×{N−14×(Ti/144+V/153)}≦0.00050  (i),  where each symbol of elements in equation (i) denotes the content (mass %).    
   
   
       2 . Seamless steel tubes for use in oil well, comprising, by mass %, C: 0.14-0.35%, Si: 0.05-1.0%, Mn: 0.05-2.0%, Cr: 0.05-1.5%, Mo: 0.05-2.0%, Ti: 0-0.05%, V: 0-0.1%, and Al: not less than 0.010%, further comprising one or two of Nb: 0.005-0.040% and B: 0.0003-0.005%, wherein each content of Al, N, Ti and V satisfies the relationship expressed by the equation (i) below, and wherein the residuals are Fe and impurities including P: not more than 0.025% and S: not more than 0.010%,  
       0.00001≦Al×{N−14×(Ti/144+V/153)}≦0.00050  (i),  where each symbol of elements in equation (i) denotes the content (mass %).    
   
   
       3 . Seamless steel tubes for use in oil well, comprising, by mass %, C: 0.14-0.35%, Si: 0.05-1.0%, Mn: 0.05-2.0%, Cr: 0.05-1.5%, Mo: 0.05-2.0%, Ti: 0-0.05%, V: 0-0.1%, and Al: not less than 0.010%, further comprising one or more of Ca: 0.0003-0.005%, Mg: 0.0003-0.005% and REM: 0.0003-0.005%, wherein each content of Al, N, Ti and V satisfies the relationship expressed by the equation (i) below, and wherein the residuals are Fe and impurities including P: not more than 0.025% and S: not more than 0.010%,  
       0.00001≦Al×{N−14×(Ti/144+V/153)}≦0.00050  (i),  where each symbol of elements in equation (@) denotes the content (mass %).    
   
   
       4 . Seamless steel tubes for use in oil well, comprising, by mass %, C: 0.14-0.35%, Si: 0.05-1.0%, Mn: 0.05-2.0%, Cr: 0.05-1.5%, Mo: 0.05-2.0%, Ti: 0-0.05%, V: 0-0.1%, and Al: not less than 0.010%, further comprising one or two of Nb: 0.005-0.040% and B: 0.0003-0.005%, and also one or more of Ca: 0.0003-0.005%, Mg: 0.0003-0.005% and REM: 0.0003-0.005%, wherein each content of Al, N, Ti and V satisfies the relationship expressed by the equation (i) below, and wherein the residuals are Fe and impurities including P: not more than 0.025% and S: not more than 0.010%, 
 0.00001≦Al×{N−14×(Ti/144+V/153)}≦0.00050  (i),        where each symbol of elements in equation (i) denotes the content (mass %).