Effect of carbon content on intergranular corrosion resistance of 430 ferritic stainless steel
430 ferritic stainless steel has the advantages of small coefficient of linear expansion, high thermal conductivity, high chloride resistance, good corrosion resistance and good cold working properties. It is widely used in construction, decoration, food machinery, household electrical appliances and other industries. 430 ferritic stainless steel generally does not contain nickel or nickel, its prices are affected by fluctuations in the international nickel prices less, so the amount of use continues to increase. The traditional ferritic stainless steel is more sensitive to intergranular corrosion because of its high carbon content, which limits its wider application to some extent.
Researchers at the Shanghai Univer through the carbon content change in 430 ferritic stainless steel, and the use of double loop potentiokinetic reactivation (DL-EPR) sensitivity of corrosion of materials with different carbon content of intergranular, for the rational design of 430 ferritic stainless steel components to provide a theoretical basis for.
The test material is 430 ferritic stainless steel hot rolled steel plate produced by an enterprise. The final rolling temperature is 850 DEG C, annealed at 820 DEG C after hot rolling, and 1H is cold. From the chemical composition of 430 ferritic stainless steel, it can be seen that according to the carbon content, the numbers are C1, C2 and C3 respectively. The test materials into 10mm * 10mm * 2mm (2mm is the original thickness) samples of samples processed at 950 DEG C, 30, 10 respectively. 60 and 120min were sensitized, samples after heat treatment, encapsulated in epoxy resin, the working area of 1cm2, polished by carbon silicon water sandpaper, then rinse with alcohol, drying for standby.
Using CHI600C electrochemical workstation, the intergranular corrosion sensitivity of test steel was evaluated by DL-EPR method. DL-EPR method is to study the sensitization behavior of steel by the passivation and reactivation characteristics of stainless steel and the content of the main alloy elements in the passive film and the characteristics of the film. Scanning electron microscopy (SEM) was used to observe the surface morphology of the samples after DL-EPR test and sensitized treatment, and the composition was analyzed by energy spectrometer. Test results show that:
1) the rate of re activation could not evaluate the intergranular corrosion sensitivity of 430 ferritic stainless steel. It was also necessary to make a comprehensive evaluation of the surface morphology of DL-EPR after sem.
2) the sensitivity of intergranular corrosion of 430 ferritic stainless steel increases sharply with the increase of sensitization time at 950 C, but the sensitivity of intergranular corrosion increases slowly when the sensitization time is over 60min.
3) higher carbon content leads to an increase in intergranular corrosion of 430 ferritic stainless steel, but the trend is less pronounced when the mass fraction of carbon exceeds 0.0454%.
