Large-caliber thick-wall marine seamless steel tube and TMCP (thermomechanical rolling process) production method thereof

Abstract

The invention provides a large-caliber thick-wall marine seamless steel tube and a TMCP (thermomechanical rolling process) production method thereof. The seamless steel tube comprises the following components in percentage by mass: 0.05-0.09% of C, 0.17-0.37% of Si, 1.4-1.85% of Mn, at most 0.015% of P, at most 0.008% of S, 0.06-0.08% of V, 0.03-0.05% of Nb, 0.02-0.04% of Ti, at most 0.10% of Ni, at most 0.15% of Cu, 0.20-0.40% of Mo, 0.10-0.30% of Cr, at most 0.0005% of B, 0.015-0.045% of Al (Al / N is greater than or equal to 2), at most 0.25 of CEpcm, and the balance of Fe and trace impurity elements. The production technique comprises the following steps: smelting, and continuously casting into a circular tube blank; heating the blank, perforating, rolling and carrying out rotary sizing; carrying out controlled cooling; and naturally cooling to room temperature for later use. Compared with the seamless steel tubes produced by the traditional production modes at home and abroad, the seamless steel tube provided by the invention has the advantages of higher rolling ratio, more stable mechanical properties and favorable low-temperature impact resistance; and by adopting the TMCP, the production method has the advantages of simple technique and high production efficiency, and can produce the medium-thickness-wall seamless steel tube while the mechanical properties of the high-strength thick-wall seamless steel tubes produced by the traditional technique are always unacceptable.

Description

technical field [0001] The invention relates to a large-diameter thick-wall seamless steel pipe for marine use and a production method thereof, in particular to a production method for a large-diameter medium-thick-wall steel pipe for marine use produced by a TMCP production method. Background technique [0002] With the development of offshore and deep-sea oilfields, the demand for large-scale and thick-walled pipelines is gradually increasing. In order to transport farther and deeper oil and gas to the coast, the corresponding pipeline requires longer length, higher strength and thicker wall. Therefore, the pipeline requires not only good welding performance, high strength and higher low temperature toughness, but also high Excellent anti-collapse performance and anti-corrosion performance. To achieve high anti-collapse performance requirements, on the one hand, it is improved by increasing the steel grade, and the other way is to increase the wall thickness. For pipelin...

AI Technical Summary

Problems solved by technology

[0003] The production of traditional large-diameter marine seamless steel pipes generally adopts the production of perforation + continuous rolling + sizing, perforation + grinding (machining), perforation + thermal expansion. These production methods have certain disadvantages, such as: The size of the rolling mill is relatively small, and the largest continuous rolling mill in China is the Φ460 unit of a certain factory; the process of piercing + grinding or thermal expansion produces too little rolling deformation, the process performance of the steel pipe is poor, and the thermal expansion There are many defects in pipes, so these production methods have restricted the development of marine pipelines

Moreover, there are few large-diameter and medium-thick-walled marine pipelines in China. Generally, the wall thickness is about 20mm. It is difficult to meet the mechanical properties of steel pipes exceeding 20mm.

Images