Research Of Fishscale Performance Evaluation Technology And Hydrogen Storage Properties On Enamel Steel

Enamel steel is widely used in the enamel industry as a matrix material,enamel products made by enamel steel with high temperature, easy to clean, artistic, high strength characteristics, therefore it is widely used in household appliances, chemicals industry,building, etc.. But fishscale defects often occur, resulting in product failure. And fishscale defects may occur immediately after enameled or 24 hours or even a month later, so the fishscale happens is hard to predict, the correct evaluation of the fishscale performance of enameled steel becomes the focus of research at home and abroad.The results show that fishscale performance is closely related to hydrogen storage capacity of enamel steel, the trap theory is also accepted by many scholars, that it to say the hydrogen atomic into molecule in steel, and then large part of the molecular hydrogen is stored in the dislocations, holes, grain boundary segregation, inclusion, etc., so these hydrogen storage places are also known as hydrogen trap. According to the size of the binding energy between hydrogen and trap, hydrogen trap is divided to reversible and irreversible trap. The number of irreversible traps can improve steel hydrogen storage capacity.and effectively improve the resistance of fishscale performance, reduce the incidence of fishscale explosion.At present, there are being three kinds of fishscale evaluation standards at home and abroad, international standard of ISO 17081, european standard of EN 10209 and Chinese national standard GB/T29515.The fishscale evaluation index of international standard is Deff, which called valid hydrogen diffusion coefficient, and the critical value is defined as 2.0 X 10-6cm2/s, the fishscale evaluation index of european standard is TH, the critical value is defined as 6.7,while china national standard has the same evaluation index as european standard, but no specific critical value.The issue through many fishscale experiments of enameled steel sheet, statistics the date of fishscale experiments and compared with enmeal experimental results, the similarities and differences are studied among the three evaluation methods, what is more, the effect of annealing micro structure and the types and quantities of precipitates to hydrogen storage performance is also studied, Obtain the following results.1)International standard and Chinese national standard are not suitable to evaluate the fishscale performance of steel sheet which thickness is greater than 1.5mm, particularly the international standard, their misjudgment occurs mainly in sheet thickness greater than 1.5 mm or more. European standard evaluation of the accuracy rate of 100%, the accuracy of international standard based on hydrogen diffusion coefficientis 70%, while the chinese national standard miscalculation appears no regularity, its accuracy rate is 30%.2) The effects of fishscale performance relative hydrogen storage capacity and precipitation of vanadium and titanium micro ultra-low carbon steel are studied by international standards and simulate continuous annealing process, the results showed that 5, 6 and 7minutes annealed at 750?, the effective diffusion coefficient corresponding respectively 2.23×10-6,2.12×10-6 and 1.74×10-6cm2/s, with increasing annealing time, the effective diffusion coefficient decreases, corresponding to the enhancement of fishscale performance of enamel steel. After annealing, ultra-low carbon vanadium and titanium micro-alloy steel will precipitate a lot of particles such as Ti4C2S2, Ti(C.N), VC, carbonitride and carbon sulfide, and the number of particles per unit volume of steel increaseswith annealing time, however, the average particle size decreases.3)The effects of fishscale performance relative hydrogen storage capacity and precipitation of niobium and titanium micro ultra-low carbon steel are studied by european standard and simulate continuous cold rolling and annealing process, the results showed that the ability of resistance of fishscale and the capacity of hydrogen storage are better and better as the rate of cold reduction increase, when the cold reduction rate is 80%, the steel fishscale properties and hydrogen storage capacity are the strongest.Under the state of 80% cold reduction, after annealed by750,800,850?, TH values were 9.93,9.93 and 10.96, Obviously, TH maximum value at 800? annealing, resistance of fishiscale is the best. The precipitates of steel are mainly Ti4C2S2 and TiC, large size Ti4C2S2 particles and a large number of fine size of TiC particles can improve fishscale resistance and hydrogen storage capacity.