Seamless steel tubes and pipes for use in oil well

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 %).

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 %).

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 %).