Low alloy oil-well steel pipe

1. A low alloy oil-well steel pipe characterized by comprising a chemical composition consisting of:

in mass %,

C: 0.25 to 0.35%;

Si: 0.05 to 0.50%;

Mn: 0.10 to 1.50%;

Cr: 0.40 to 1.50%;

Mo: 0.40 to 2.00%;

V: 0.05 to 0.25%;

Nb: 0.010 to 0.040%;

Ti: 0.002 to 0.050%;

sol.Al: 0.005 to 0.10%;

N: 0.007% or less;

B: 0.0001 to 0.0035%;

Ca: 0 to 0.005%; and

a balance being Fe and impurities,

the impurities including:

P: 0.020% or less;

S: 0.010% or less;

O: 0.006% or less;

Ni: 0.10% or less; and

Cu: 0.10% or less,

wherein

in a microstructure of the low alloy oil-well steel pipe, a number of cementite particles, each of which having an equivalent circle diameter of 200 nm or more, is 100 to 250 particles/100 μm 2 , and

a yield strength is 793 MPa or more.

2. The low alloy oil-well steel pipe according to claim 1 , wherein Ca ranges from 0.0005 to 0.005%.