The effect of compressive stress on the stability of reversed austenite in gNi steel was investigated by uni- axial and hydrostatic compression. It was found that the uniaxial compressive pressure promoted the Υ-α t...The effect of compressive stress on the stability of reversed austenite in gNi steel was investigated by uni- axial and hydrostatic compression. It was found that the uniaxial compressive pressure promoted the Υ-α transformation, while the hydrostatic pressure suppressed the -Υ-α transformation. The pressure dependent transformation behavior can be explained according to thermodynamic analysis.展开更多
Oxidation rates and scale/steel interface configuration of 9Ni steels were investigated at 1000--1 250 ℃ in air. The results revealed that Cu addition caused high temperature oxidation resistance to deteriorate. High...Oxidation rates and scale/steel interface configuration of 9Ni steels were investigated at 1000--1 250 ℃ in air. The results revealed that Cu addition caused high temperature oxidation resistance to deteriorate. High tempera ture oxidation rates increased and scale/steel interface configuration became complicated due to Cu addition. Scale/ steel interface appeared to be network above certain temperature. Temperature required to form network scale/steel interface dropped more than 100 ℃ for 1.5% Cu-containing steel. （Fe,Ni,Cu）x Oy in inner oxidation layer dissocia ted to Fe-Ni-Cu phase and released active oxygen which can react with base steel easily. So the inner oxidation layer became the second source of oxidizing agent besides atmosphere. Internal stress at austenite grain boundary caused local oxide to fragment. So the scale/steel interface appeared to be network. Liquid Si-rich phase formed at sufficient ly high temperature. Penetration of the liquid Si-rich phase along austenite grain enhanced austenite grain oxidizing.展开更多
The microstructure, composition and shape of precipitated phase under as-cast and finished product state of 5Cr21Mn9Ni4N steel with different rare earth （RE） amount were studied. Mechanical properties of 5Cr21Mn9Ni4...The microstructure, composition and shape of precipitated phase under as-cast and finished product state of 5Cr21Mn9Ni4N steel with different rare earth （RE） amount were studied. Mechanical properties of 5Cr21Mn9Ni4N steels withont RE addition and with RE added by 0. 2% in mass percent were tested respectively. The results indicate that the solid solution amount of RE is about 10^-6 -10^-5 order of magnitude in 5Cr21Mn9Ni4N steel. Dendrite of as-cast condition is refined obviously and dimension of interstitial phase is shortened when RE is added by 0.10%-0.20%. But the microstructure will be coarser if surplus RE is added. Precipitated phase under finished product state distributes evenly in nearly same size with RE added by 0. 2% which leads to a largely improved high temperature mechanical property.展开更多
The oxidation resistance of 5Cr21Mn9Ni4N steel micro-alloying by RE at 700 - 900 ℃ was investigated. The results indicate that oxidation exponent n and oxidation activation energy are increased, and oxidation velocit...The oxidation resistance of 5Cr21Mn9Ni4N steel micro-alloying by RE at 700 - 900 ℃ was investigated. The results indicate that oxidation exponent n and oxidation activation energy are increased, and oxidation velocity constant kp is decreased when 0.2% RE is added in 5Cr21Mn9Ni4N steel. The addition of RE elements does not alter phase constitution of oxidation scale, however it improves the configuration of oxidation scale, and increases thermal stability and adhesivity of oxidation scale, which results in the raise of oxidation resistance of 5Cr21Mn9Ni4N steel at high temperature. The oxidation scale constitutes of refractory steel transfer from manganic oxide mostly to ferric oxide mostly with the increase of temperature, which leads to descend of compactness and desquamation resistance of oxidation scale. The mass increase of ferric oxide in the oxidation scale and the looseness of oxidation scale are the main reason to descend the oxidation resistance of refractory steel.展开更多
基金supported by the National Natural Science Foundation of China under Grant No.50871110
文摘The effect of compressive stress on the stability of reversed austenite in gNi steel was investigated by uni- axial and hydrostatic compression. It was found that the uniaxial compressive pressure promoted the Υ-α transformation, while the hydrostatic pressure suppressed the -Υ-α transformation. The pressure dependent transformation behavior can be explained according to thermodynamic analysis.
基金Item Sponsored by National High Technology Research and Development Program of China(2007AA03A228)
文摘Oxidation rates and scale/steel interface configuration of 9Ni steels were investigated at 1000--1 250 ℃ in air. The results revealed that Cu addition caused high temperature oxidation resistance to deteriorate. High tempera ture oxidation rates increased and scale/steel interface configuration became complicated due to Cu addition. Scale/ steel interface appeared to be network above certain temperature. Temperature required to form network scale/steel interface dropped more than 100 ℃ for 1.5% Cu-containing steel. （Fe,Ni,Cu）x Oy in inner oxidation layer dissocia ted to Fe-Ni-Cu phase and released active oxygen which can react with base steel easily. So the inner oxidation layer became the second source of oxidizing agent besides atmosphere. Internal stress at austenite grain boundary caused local oxide to fragment. So the scale/steel interface appeared to be network. Liquid Si-rich phase formed at sufficient ly high temperature. Penetration of the liquid Si-rich phase along austenite grain enhanced austenite grain oxidizing.
文摘The microstructure, composition and shape of precipitated phase under as-cast and finished product state of 5Cr21Mn9Ni4N steel with different rare earth （RE） amount were studied. Mechanical properties of 5Cr21Mn9Ni4N steels withont RE addition and with RE added by 0. 2% in mass percent were tested respectively. The results indicate that the solid solution amount of RE is about 10^-6 -10^-5 order of magnitude in 5Cr21Mn9Ni4N steel. Dendrite of as-cast condition is refined obviously and dimension of interstitial phase is shortened when RE is added by 0.10%-0.20%. But the microstructure will be coarser if surplus RE is added. Precipitated phase under finished product state distributes evenly in nearly same size with RE added by 0. 2% which leads to a largely improved high temperature mechanical property.
文摘The oxidation resistance of 5Cr21Mn9Ni4N steel micro-alloying by RE at 700 - 900 ℃ was investigated. The results indicate that oxidation exponent n and oxidation activation energy are increased, and oxidation velocity constant kp is decreased when 0.2% RE is added in 5Cr21Mn9Ni4N steel. The addition of RE elements does not alter phase constitution of oxidation scale, however it improves the configuration of oxidation scale, and increases thermal stability and adhesivity of oxidation scale, which results in the raise of oxidation resistance of 5Cr21Mn9Ni4N steel at high temperature. The oxidation scale constitutes of refractory steel transfer from manganic oxide mostly to ferric oxide mostly with the increase of temperature, which leads to descend of compactness and desquamation resistance of oxidation scale. The mass increase of ferric oxide in the oxidation scale and the looseness of oxidation scale are the main reason to descend the oxidation resistance of refractory steel.
