The Researches Into The Grain Refinement And Corrosion Resisting Property Of The Ferritic Stainless Steel

The paper introduces the way that different content of high-carbonitride-forming element titanium and appropriate silicon, manganese and aluminum are added into Armco iron and ferritic stainless steel to affix interstitial atom like C and N and produce titanium ferritic stainless steel through the strong congenial among the titanium and C and N atoms. The paper also includes the design of chemical composition in trial steel and design of refining, forging and general rolling technology. With the metallographic microscope, TEM and test method of mechanical properties and electrochemistry, the structure, grain boundary and precipitation particles of trial steel features are observed and analyzed. Besides, the effect of titanium on trial steel strengthening-toughening as well as the corrosion resisting property of trial steel are studied and the paper also roundly discusses micro-alloying steel of stainless steels. According to the analysis of mechanical properties and microanalysis for trial steel, it is thought that the material will become deformed when its temperature is lower than austenite recrystallization and higher than Ar3 phase transformation temperature, which could have a phase transformation in higher termperature and get critical nucleus radius of smaller radii. In order to get uitrafine grain ferrite, the iron and steels must have a great distortion. The high carbonitride can refine the ferrite grain through the way that the carbonitride is heated to stop austenite grain grow, the prevention of austenite recrystallization during hot rolling and irresolvable titanium carbonitride is used to promote transition from γ→α. Test result indicates that titanium can refine 0Cr13 ferrite stainless grain, increase its strength and improve its ductility to provide better processing properties. Addition amount of titanium has an optimum scope, more or less can not get the ideal result, except when content of titanium is 6～9 times more than carbon. The analysis indicates that hauling force of the second phrase particle to ferrite grain boundary mainly depends on its size and volume percentage. The smaller Ti (C,N) particle will occupy more volume percentage, and it also can more effectively to refine ferrite grain and increase steel and iron combination properties. After we analyse the second phrase of aging precipitation with the thermodynamics and kinetics, we can get a conclusion that the smaller the Ti (C,N)is, the easier the Ti (C,N) becomes coarsening, so it is difficult to finest second phrase particle. With the analysis of electrochemistry test result, it indicates that capability of the intergranular attack resistance of general 0Cr13 ferrite stainless is poor. With addition of titanium, carbon in steel and high-carbonitride-forming element titanium can produce steady titanium carbides and restrain the simultaneity precipitation of intergranular (Fe,Cr)7C3. And it also can eliminate C and N interstitial atoms in steel, restrain the creation of pearlite, clean ferrite grain boundary, increase ferrite evenness and obviously increase corrosion resisting property.