A kind of grain boundary precipitation strengthened austenitic heat-resistant steel and its preparation method

Abstract

The invention discloses crystal boundary precipitation hardening austenite heat-resistant steel and a preparation method thereof, and belongs to the technical field of high-temperature metal material manufacture. Under the high-temperature service conditions, the heat-resistant steel precipitates hardening phases of Laves and Fe2Nb replacing common carbide precipitated phases. Through solid solution treatment and aging treatment, the Laves and Fe2Nb phases are precipitated on the crystal boundary. The austenite heat-resistant steel comprises Cr, Ni, Nb, B and Fe. The preparation method comprises the following steps of putting the above raw materials into a magnesium oxide crucible, putting the magnesium oxide crucible with the raw materials into a vacuum furnace, carrying out vacuum-pumping, heating furnace burden so that the furnace burden in the magnesium oxide crucible is melt, refining the furnace burden to remove oxygen, nitrogen and hydrogen in the furnace burden, carrying out cooling, adding a final deoxidizer into the furnace burden, taking the furnace burden out of the vacuum furnace at a temperature higher than a melting point, pouring the melt furnace burden into a steel ingot mold, carrying out solid solution and aging treatment and then carrying out quenching. The crystal boundary precipitation hardening austenite heat-resistant steel has excellent high-temperature lasting strength, contains less component elements and simple components and can be easily used in industrial production.

Description

technical field [0001] The invention belongs to the technical field of manufacturing high-temperature metal materials, and in particular relates to an austenitic heat-resistant steel with good high-temperature durable strength and a manufacturing method thereof. Background technique [0002] Thermal power generation is still the main body of my country's electricity production. Improving steam parameters (temperature, pressure) of thermal power generating units is an effective way to improve thermoelectric efficiency. The development of efficient and clean supercritical and ultra-supercritical units has a very obvious impact on improving the efficiency of thermal power generation, while the materials for the superheater and reheater high temperature section of the unit boiler are the main restrictive factors for the development of supercritical units in my country. [0003] Generator set boiler superheater and reheater materials need to have excellent high temperature creep...

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Problems solved by technology

[0004] In the austenitic heat-resistant steels disclosed in patents CN1340109, US7731895B2, and US6939415B2, the main alloying elements are chromium (Cr), nickel (Ni), niobium (Nb) and carbon (C), and the strengthening principle is without exception By adding the alloying element carbon (C) to the steel, relying on the chromium-containing carbide M precipitated during high-temperature long-term service 23 C 6 And NbC, MX phase precipitation strengthening, the second phase precipitation can effectively pin dislocation movement at high temperature, so as to achieve the creep strength of heat-resistant steel in the temperature range of 600-650 °C, but the main precipitation phase M 23 C 6 During the long-term service of heat-resistant steel, it is easy to coarsen and grow, the stability is not good, and the resistance to high temperature creep is unfavorable. At the same time, the addition of carbon (C) elements will also reduce the welding performance of the material, which is not conducive to the production and application of the material.

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