Continuous-cast P91-steel round pipe billet and production process thereof

Abstract

The invention provides a continuous-cast P91-steel round pipe billet and a production process thereof. The production process includes 1) injecting molten steel into a tundish (3) and controlling degree of superheat of molten steel; 2) adding mold flux (13) to the surface of molten steel of a crystallizer (4) and solidifying the molten steel into a billet casing (20) with a liquid core (19); 3) stirring the front of the solidified molten steel by the aid of a one-way rotary magnetic field, applying a thrust force to the liquid core of the cast billet by a traveling wave magnetic field, and stirring the tail end (17) of the solidified molten steel by a two-way alternative rotary magnetic field; 4), drawing the billet casing to an arc guide segment (18) to form an initial round billet and cooling the initial round billet by a secondary cooling region which is divided into three sections; 5) straightening the cooled cast billet by eight rollers; and 6) cutting the cast billet into fixed-length billet sections by torch flame and annealing the same to obtain continuous-cast round pipe billets. The round pipe billets produced by the production process solves the problems that diameters of round pipe billets in the prior art are too small and surface cracks, middle cracks and straightened cracks of the round pipe billets in large diameter are hard to meet industry requirements.

Description

technical field [0001] The invention relates to the technical field of metallurgy, in particular to a production process for a continuous casting round tube blank and a P91 steel round tube blank produced by the process. Background technique [0002] T91 / P91 is a martensitic heat-resistant steel, which was successfully researched by the United States in the 1970s. In 1984, ASME and ASTM included T91 / P91 in the SA 213 / SA 335 and A 213 / A 335 standards respectively. Since then, P91 steel pipes have been widely used in large-capacity thermal power generation units to replace the original thick-walled P22 steel pipes. For supercritical and ultra-supercritical thermal power units developed in recent years, P91 steel pipes have been used as a preferred hot section of the main steam pipeline and its Corresponding high-temperature header steel, the use of P91 steel pipe plays an important role in improving boiler parameters and thermal efficiency. my country's high-pressure boiler t...

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