Dissertation > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Metallic materials > Steel > Special performance of steels > Stainless steel, acid-resistant steel

High nitrogen nickel austenitic stainless steel microstructure and performance analysis

Author LiuJiBing
Tutor JiChangTao
School Changchun University of
Course Materials Processing Engineering
Keywords High nitrogen nickel austenitic stainless steel Microstructure Mechanical Properties Corrosion resistance
CLC TG142.71
Type Master's thesis
Year 2010
Downloads 130
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High nitrogen nickel austenitic stainless steel with respect to traditional Cr-Ni austenitic stainless steel with a section of nickel bring huge economic benefits, but also has a high strength, high toughness and excellent corrosion resistance, become materials science the focus. However, due to the extremely low solubility of nitrogen in liquid steel under normal atmospheric pressure, the equilibrium concentration of only 0.04 (wt%), all with nitrogen instead of the austenitic nickel-stabilized steel requires a minimum content of nitrogen was 0.4 (wt.%) this is usually high pressure metallurgy manufacturing high nitrogen nickel austenitic stainless steel. The actual production of the high-voltage metallurgical processes and technology is extremely complex, and dangerous, high production costs, there is no large-scale industrial manufacturers worldwide. Technical methods in recent years around the atmospheric smelting high nitrogen nickel austenitic stainless countries around the world rushed to carry out a pilot study and achieved a breakthrough, become an important way to the development of austenitic stainless steel. In this paper, the Cr-Fe alloy, nitrogen alloying in advance method smelting under atmospheric pressure to create a high-nitrogen-nickel austenitic stainless steel, and the test heat treatment process of the steel and its microstructure and the mechanical stretching conditions The performance of the system and in-depth research, analysis and discussion of the study the microstructure of the steel characteristics and nitrogen in steel. The specific contents: 1. According to nitrogen in place of the nickel to stabilize the steel austenitic microstructure principle the composition of the steel is designed, the design of the steel composition 0Cr18Mn18N. Calculation requires minimum nitrogen content of 0.37 (wt%); through the advance of nitrogen alloying nickel austenitic stainless steel process a large number of test studies of atmospheric smelting high nitrogen innovative manufacture of high nitrogen nickel austenitic stainless steel, an atmospheric pressure of this method is the key technology world are at the stage of research and confidentiality; 3. corrosion resistance of the steel for the test and 1Cr18Ni9Ti austenitic stainless steel contrast pilot study results show that the higher corrosion resistance of steel in the electrochemical corrosion conditions; 4. tested steel Wrought air cooling and heating after slow cooling microstructure and tensile mechanical performance test research and analysis, the results show that the steel under the above thermal processing conditions of nitrogen in the form of a nitride precipitates nitride morphology the lamellar similar pearlite, its decomposition reaction γ → γ 'Cr (M ) 2N, due to precipitation of nitrides lead to the deterioration of the properties of steel, especially plastic significantly decreased, the fracture mechanism of the brittle cleavage off; 5. adversely affect the performance of steel in order to prevent precipitation of nitrides, the solution treatment method to obtain a single stable austenite. While repeatedly large deformation unwrought TMT thermo-mechanical treatment of the cast steel, and then subjected to solution treatment, the test steel steel to obtain the cellular sub-structures having a nano-scale, with the structure of the test steel yield strength R0.2 740Mpa, tensile strength Rm 1370Mpa, the elongation E 30%, and to investigate the mechanism of the formation of this structure. Analysts believe is mainly caused by the steel micro-inhomogeneity of nitrogen and nitrogen strong ordering tendency. Thesis research work in the smelting process and the Toughening theoretical aspects of innovative, high-nitrogen nickel austenitic stainless steel research and development to provide a reliable experimental data, and explore in theory, actual production has important reference value.

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