Based on standard API 5L the designed chemical composition of pipe line steel tube X52QS is (/% ): 0.11~0. 14C

0.20~0.35Si

0.95~1.20Mn

≤0.010P

≤0.0015S

0.10~0.20Ni

0.10~0.20Cu

0.008~0.020Ti

and 0.0015~0.0040Ca. The batch production of pipe line steel tube X52QS is carried out by process of 100t EAF-LF + VD refinig-Φ210mm round bloom casting-ACCU ROLL mill rolling-heat treatment quenching at 880°C -tempering at 655 ℃.The main process measures are EAF end controlling liquid temperature 1620~1640℃

0.05%~0.08%C

≤0.008%P

refining slag ingredient (/%): 58CaO

7SiO

2

22Al

2

O

3

8MgO and 3% fluoride

and feeding Ca-Si wire after VD process. The

examination results show that the main structure of pipe line steel tube X52QS is ferrite + tempered bainite

the rating of grain size ≥8.5

the total rating of various inclusions ≤2

the mechanical properties and antihydrogen sulfide corrosion performance meet the requirement of standard API 5L

and the steel tube has excellent weld and low temperature impact toughness and its ductile-brittle transition temperature is -95℃.