The Φ130-170 mm bar of steel SAE4137M for petroleum drill pipe connecting sleeve (/% : 0.35-0.38C

0.15-0.35Si

0.85-l.00Mn

≤ 0.015P

≤ 0.008S

0.90-1.20Cr

0.28-0.33Mo，≤ 0.005Ca

≤ 0.0090N) has been pilot-produced by hot metal pretreatment-150 t top and bottom combined blown converter-LF-RH-350 mm x 470 mm casting with M-EMS-continuous rolling process at Bengang. With adding compound deoxidizer during converter tapping

diffusion deoxidizing with argon stirring in LF refining

soft argon blowing and strict-controlling feeding calcium wire amount in RH refining

and controlling liquid overheating extent within 20-30 ℃

in steel products the oxygen content is (13-15 ) x 10

-6

hydrogen content (0.4~0.5) x 10

-6

nitrogen content (35-44)

x 10

-6

residual calcium content ( 12-18) x 10

-6

and Al/N is ensured ≥ 2

that all meet the requirement for petroleum steels