Rare earth containing, high-strength and high-toughness seamless steel pipe for L555Q pipeline and production method thereof

Abstract

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.

Description

Technical field: [0001] The invention belongs to the field of ferrous metal smelting and metal pressure processing, and relates to a rare earth-containing high-strength and high-toughness L555Q seamless steel pipe and a production method thereof. Background technique: [0002] Pipeline transportation is widely used because of its cost-effective, uninterrupted and pollution-free characteristics. In order to realize the long-distance transportation of pipelines, high-pressure transportation is used. In order to reduce the cost of laying pipelines and the use of steel materials, high-grade steel is used. Thin-walled pipes adopt low carbon equivalent design components in order to ensure the welding performance of line pipes. Low carbon equivalent and high strength are contradictory. L555Q is an ultra-high steel grade for pipeline branch lines. L555Q steel grade pipeline pipes have been developed at home and abroad, and both can adopt the heat treatment process of quenching + hig...

AI Technical Summary

Problems solved by technology

L555Q is an ultra-high steel grade for pipeline branch lines. L555Q steel grade pipeline pipes have been developed successively at home and abroad. They can all adopt the heat treatment process of quenching + high temperature tempering. After retrieval, the Chinese invention patent "a hot-rolled steel plate without MoNbX80 pipeline steel Manufacturing method" (patent application number: CN 1011857945), this invention belongs to the field of pipeline steel, and the manufacturing method of seamless pipe has not been reported

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