Strengthened ferrite series heat-resistant steel with nano precipitated phase and manufacturing method thereof

Abstract

The invention provides a ferritic heat-resistant steel with nano-precipitation phase strengthening and its manufacturing method, which is characterized in that its chemical composition is: chromium: 8.5-10.0%, molybdenum: 0.3-0.5%, tungsten: 1.5-2.0% %, cobalt: 3.0-4.5%, nickel: 0-1.0%, nitrogen: 0.01-0.03%, vanadium: 0.18-0.25%, niobium: 0.05-0.08%, titanium: 0.003-0.01%, carbon: 0.002-0.03% , the balance is iron and unavoidable impurities, and there are high-density and uniformly distributed MX-type nano-precipitated phases distributed in the steel matrix, the size of which is between 5 and 50nm, and the number of particles per square micron is greater than 300. The manufacturing method adopts the following steps: after melting, pouring, forging or rolling the raw material composition of the constituting elements in sequence, first keeping the temperature at 1050-1150° C. for 0.5-1.5 hours for normalizing treatment, and then tempering treatment. The MX-type nano precipitates of the heat-resistant steel are evenly distributed on the steel matrix with a high density, and the microstructure stability and creep resistance at a high temperature of 650°C are good.

Description

technical field [0001] The invention relates to a ferritic heat-resistant steel with nano-precipitation phase strengthening for thermal power generating units and a manufacturing method thereof, belonging to the technical field of metallurgy. Background technique [0002] Climate warming has become a hot spot of global concern, reducing CO 2 The emission of greenhouse gases has attracted the attention of various countries. Coal-fired power generation companies are CO 2 Major source of gas release. In order to improve the efficiency of thermal power generation units and reduce CO 2 The key to gas emission is to improve the steam parameters of the generating set. At present, the parameters of thermal power units in various countries in the world have developed from subcritical parameters to supercritical, and even ultra-supercritical (ultra-supercritical, USC) parameters. The key technology for the development of USC units is to develop materials with high thermal strengt...

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Problems solved by technology

However, due to its composition and processing technology, the MX type precipitates are mainly distributed on the grain boundary and the interface within the grain, and the strengthening effect is not significant

The literature [R.L Klueh, et al. Development of new nano-particle-strengthened martensitic steels. Scripta Materialia, 53 (2005) 275-280] adopts the method of thermomechanical treatment (thermomechanical treatment), the matrix in the martensitic lath A large number of distributed MX-type nano-precipitated phases were obtained, but the material appeared anisotropic due to the existence of deformed structures

The inventor's previous work [Feng-shi Yin, et al. Microstructure and creep rupture characteristics of an ultra-low carbon ferritic / martensitic heat-resistant steel. Scripta Materialia 57 (2007) 469-472] Although by adjusting the The composition and thermal processing process also obtained high-density MX-type nano-precipitates in the martensite lath, but due to the instability of the obtained MX-type nano-precipitates, the fracture strength at 650 ° C and long-term creep conditions is not no improvement

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