The invention relates to a
rare earth containing, high-strength and high-
toughness seamless steel
pipe for the L555Q pipeline and a production method thereof. The seamless steel
pipe is composed of 90 wt% of
blast furnace molten iron and 10 wt% of high-quality waste steel in percentage by weight. The
pipe blank comprises the following chemical components in percentage by weight: 0.06 to 0.13 wt% of C, 0.15 to 0.35 wt% of Si, 1.10 to 1.40 wt% of Mn, not more than 0.020 wt% of P, not more than 0.010 wt% of S, 0.10 to 0.30 wt% of Cr, 0.03 to 0.09 wt% of V, 0.01 to 0.03 wt% of Ti, 0.01 to 0.04 wt% of Al, 0.0005 to 0.0100 wt% of
rare earth (RE), not more than 0.10 wt% of Cu, and the balance being substrate Fe and undetectable trace
impurity elements. The mechanical properties of the seamless steel pipe are as follows: the yield strength is 600 to 680 MPa, the
residual stress is smaller than or equal to 30 MPa, the
impact value is more than or equal to 160 J / cm<2>, and the grain size is more than or equal to 8.5 grade. The technology process can be simplified as the following steps: molten iron pre-treating,
smelting in a top-bottom combined blowing converter, refining in a LE furnace, VD vacuum
processing, round
continuous casting,
cutting, heating the pipe blank, perforating,
continuous rolling,
sizing (stretch reducing), cooling, sawing,
heat treating, straightening, flaw detecting, and chamfering. The product has the advantages of low
impurity element content, high roughness matching degree, uniform and fine tissue, and good
welding performance.