Manufacture method of seamless steel tube for (ultra-)supercritical boiler

Abstract

The invention relates to a manufacture method of a seamless steel tube for an (ultra-)supercritical boiler. The manufacture method is characterized by comprising the process: primarily smelting with an electric arc boiler, refining with a ladle heating boiler, treating high-sulfur reduction residue with a tundish and finally refining in a vacuum oxygen-blowing ladle furnace; casting separated copper at a temperature of 1520-1530 DEG C under the protection of Ar gas to form a steel ingot; and rolling the steel ingot with a tube blank, carrying out shell rolling, softening the semi-finished tube at a high temperature and solutionizing the finished product into a product, wherein the semi-finished tube is softened at the high temperature by making the semi-finished tube through shell rolling, degreasing the semi-finished tube, keeping the temperature furnace at 1200-1260 DEG C in a high-temperature box-shaped boiler for 30-90 min and rapidly cooling with water. The steel tube made by adopting the method provided by the invention has uniform grain size, favorable technologic indexes of mechanical performance, grain corrosion, flaring, flattening, ultrasonic / vortex flaw detection, and the like and is particularly suitable for reheaters and superheaters of the (ultra-)supercritical boiler for thermal power production.

Description

technical field [0001] The invention belongs to a manufacturing method of an iron-based alloy steel product, and relates to a manufacturing method of a seamless steel pipe for a super (super) critical boiler. The present invention is particularly suitable for the manufacture of 10Cr18Ni9NbCu3NB seamless steel pipes, and the 10Cr18Ni9NbCu3NB seamless steel pipes manufactured by the present invention are mainly used for the production of reheaters and superheaters of super (super) critical boilers for thermal power generation. Background technique [0002] 10Cr18Ni9NbCu3NB is the grade of GB / T5310 (that is, SUPER304H in Japan). It is a kind of more general 18-8 developed by Sumitomo Metal and Mitsubishi Heavy Industries in the mid-1980s to meet the needs of super (super) critical boiler units. A new type of stainless steel with higher high-temperature durability; it is based on ASME SA-213TP304H, by reducing the upper limit of Mn content, adding about 3% Cu, about 0.45% Nb and...

AI Technical Summary

Problems solved by technology

Using the prior art process, there are the following disadvantages: (1) Inconsistent intergranular corrosion of steel pipes: in the composition of the smelted finished product of 10Cr18Ni9NbCu3NB steel, because carbon and niobium all control the center line, the ratio of niobium to carbon is only 4-5, and prevent this steel The intergranular corrosion niobium carbon ratio is required to be greater than 8, which leads to the incompatibility of the intergranular corrosion of the steel, which cannot meet the requirements for use; (2) Mixed crystals in steel pipes: because the 10Cr18Ni9NbCu3NB semi-finished pipe adopts a low-temperature softening process (for example: 1050-1100 ℃ heat preservation 40- After 90 minutes, rapid water cooling), the primary coarse carbonitrides in the steel (diameter is about 0.50 μm, which is formed by the separation and crystallization of the steel ingot during the solidification process) are not fully dissolved, resulting in the precipitation of fine carbonitrides during the solid solution of the finished product (about 0.10μm in diameter) and the larger particle carbonitrides that are not completely dissolved during softening are unevenly distributed in the steel, and the large particle carbonitrides cannot play the role of refining grains in the steel, so that the local position The grain size of the steel pipe is coarse, which leads to the mixed grain of the steel pipe

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