Low-alloy steel for oil well pipe and method of manufacturing low-alloy steel oil well pipe

A method of manufacturing a low-alloy steel oil well pipe, comprising:

• preparing a raw material having a chemical composition consisting of, by mass percent, C:
• more than 0.45 and up to 0.65%;
• Si:
• 0.05 to 0.50%;
• Mn:
• 0.10 to 1.00%;
• P:
• up to 0.020%;
• S:
• up to 0.0020%;
• Cu:
• up to 0.1%;
• Cr:
• 0.40 to 1.50%;
• Ni:
• up to 0.1%;
• Mo:
• 0.50 to 2.50%;
• Ti:
• up to 0.01%;
• V:
• 0.05 to 0.25%;
• Nb:
• 0.005 to 0.20%;
• Al:
• 0.010 to 0.100%;
• B:
• up to 0.0005%;
• Ca:
• 0 to 0.003%;
• O:
• up to 0.01%;
• N:
• up to 0.007%;
• and the balance:
• Fe and impurities;
• casting the raw material to produce a cast material;
• hot working the cast material to produce a hollow shell;
• quenching the hollow shell;
• and
• tempering the quenched hollow shell,
• wherein, in the casting, a cooling rate for a temperature range of 1500 to 1000° C. at a position of ¼ of a wall thickness of the cast material is 10° C./min or higher.