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

Abstract

The present invention is one kind of nanometer precipitate phase reinforced ferritic heat resisting steel and its making process. The steel has the chemical components including Cr 8.5-10.0 %, Mo 0.3-0.5 %, W 1.5-2.0 %, Co 3.0-4.5 %, Ni 0-1.0 %, N 0.01-0.03 %, V 0.18-0.25 %, Nb 0.05-0.08 %, Ti 0.003-0.01 %, C 0.002- 0.03 %, and Fe and inevitable impurity for the rest. Inside the steel, there are homogeneously distributed MX type nanometer precipitate phases in the size of 5-50 nm and density over 300 / square micron. Its making process includes the following steps: smelting, casting, forging or rolling, normalizing treatment at 1050-1150 deg.c for 0.5-1.5 hr and final tempering. The nanometer precipitate phase reinforced ferritic heat resisting steel has high structure stability and high creep resistance at temperature of 650 deg.c.

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...

AI Technical Summary

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), and 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

Images