Low alloy oil-well steel pipe

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

in mass %,

C: more than 0.35 to 0.65%;

Si: 0.05 to 0.50%;

Mn: 0.10 to 1.00%;

Cr: 0.40 to 1.50%;

Mo: 0.50 to 2.00%;

V: 0.05 to 0.25%;

Nb: 0.01 to 0.04%;

sol.Al: 0.005 to 0.10%;

N: 0.007% or less;

Ti: 0 to 0.012%;

Ca: 0 to 0.005%; and

a balance being Fe and impurities,

the impurities including:

P: 0.020% or less;

S: 0.002% or less;

O: 0.006% or less;

Ni: 0.10% or less;

Cu: 0.03% or less; and

B: 0.0005% or less,

wherein

in a microstructure, a number of cementite particles each of which has an equivalent circle diameter of 200 nm or more is 200 particles/100 μm 2 or more

and

a yield strength is 827 MPa or more.

2. The low alloy oil-well steel pipe according to claim 1 , wherein the Ti content is

0.003 to 0.012%.

3. The low alloy oil-well steel pipe according to claim 2 , wherein the Ca content is

0.0005 to 0.005%.

4. The low alloy oil-well steel pipe according to claim 1 , wherein the Ca content is

0.0005 to 0.005%.