The steel 25CrMoTi (/%: 0.23 〜0.29C

0. 15 〜0. 35Si

0. 50 ~0.70Mn

0.015 ~QO35Ti

≤0. 015P

≤0. 003S

0. 50 -0. 70Cr

0. 25 〜0. 35Mo

0. 010 -0. 025Alt) for petroleum casing tube (φ139. 7 mm x 7. 72 mm) has been developed by 100 t DC arc furnace- LF-VD-5 strand 260 mm x 340 mm bloom casting-rolling process. With adding 50% hot metal in arc furnace steelmaking to control the deleterious elements content in steel (As + Sn + Pb + Sb + Bi ≤0. 035%)

refining with high basicity slag- (CaO)/ (SiO2) = 4 to control [S] ≤0. 002%

after VD process feeding Ti wire and carrying out calcium treatment to control Ca/S = 1.5 ~2. 0

whole process shield casting and using M-EMS and F-EMS

the rating of tube bloom central porosity is 1.0

the rating of general porosity and the rating of central segregation are 0. 5

and the rating of each kind of inclusions is W0. 5. After stress corrosion test in saturated H2S solution for 720 h the tube surface hasn't crack that meets the requirement for service of C90-1 grade petroleum casing tube.