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Optimization of Compsition and Heat Trestment Technics for Fe-Cr-Mo-V Series Heat Strength and Corrosion Resistance Steel

Author: HouYang
Tutor: LaiZhongHong
School: Harbin Institute of Technology
Course: Materials Science
Keywords: Hot strong corrosion resistant steel Composition design Heat treatment Red hardness Corrosion resistance
CLC: TG161
Type: Master's thesis
Year: 2008
Downloads: 41
Quote: 0
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Abstract


Some hot strong steel structure prior to use long-term preservation process are subject to certain corrosion, the existing heat resistant steel research focus on its mechanical properties and its resistance to corrosive less, Therefore, the development of high red hard and a room temperature corrosion resistance of the new thermal strength corrosion resistant steel has a very important significance. In this paper based on the kinds of ingredients commonly used heat resistant steel, EET, the use of orthogonal experimental method to optimize the design of the new thermal strength corrosion resistant steel components; melting to prepare a series of samples of the alloy system, test the effects of alloy composition on the hardness of the new steel grades, red hardness and corrosion resistance; through multiple linear regression method to establish new hot strong corrosion steel quenching hardness, tempering hardness, red hardness and polarization voltage and alloy composition relationship equation, and the regression equation and regression coefficients significant test; optimized Based on these findings a new type of hot strong corrosion resistant steel composition, melting the preparation of steel samples using optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) analysis of testing methods to characterize the microstructure of the new steel grades investigated heat treatment process for new kinds of steel hardness, red hardness, corrosion resistance and mechanical properties, and to determine the optimum heat treatment. The results show that, in the orthogonal design composed of sub-components content with high hardness, red hardness and corrosion resistance. F test method to determine the equation of the regression is significant, and can be used for actual prediction; T test method determines the performance of the regression coefficient significant shows the elements of C are the main factors affecting the hardness after quenching, and Cr elements and C elements for tempering hardness and red hardness, the main factors affecting the polarization voltage is Cr, V, Mo. In the 980 ° C to 1200 ° C temperature range quenching temperature on the microstructure and properties of new steel grades. Results showed that the different temperatures inside the material after quenching are martensite, accompanied by precipitation of carbides; with the quenching temperature, the grain size gradually increases, the temperature higher than 1140 ° C, the abnormal grain major phenomenon. Hardness, red hardness and corrosion resistance with the quenching temperature increases. The tempering process in the course of the study, As tempering time extension a decrease in hardness, secondary hardening when tempered at 560 ℃ 2h. With the tempering temperature, hardness as a whole was a gradual downward trend, the tensile strength of the material is reduced and the increase in toughness carbide precipitation gradually increased and the occurrence of segregation. Tempered at 1120 ° C quenched 560 ° C (2h) sample the following mechanical properties: tensile strength of 1607MPa, 30.56% of the impact energy of 8.2J section shrinkage, elongation of 4.4%; corrosion tests showed that the new steel grades for NaCl corrosion environment but can not be used in dilute sulfuric acid corrosive environments.

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CLC: > Industrial Technology > Metallurgy and Metal Craft > Metallurgy and Heat Treatment > Heat treatment > Heat treatment of steel
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