A Low Cost Ferritic Stainless Steel Microalloyed by Higher Nb for Automotive Exhaust System

Abstract

Automotive engine exhaust gas after combustion of fuel, and the gas will be liquefied in the rear of automotive exhaust system. A lot of corrosive anions existing in the condensate make corrosion of the exhaust system materials. Therefore, once pitting perforation, automotive exhaust system will fail directly. In 1980s, automotive exhaust manifold was made of Si-Mo ductile iron, mufflers and the tail pipe were made of carbon steel or aluminized steel. But with higher emission standards carried out, the improvement of engine performance and the higher exhaust temperature as well as the needs of the automotive light-weighting, we need the higher corrosion resistance of the material for automotive exhaust systems to meet the requirements.

With the improvement of oil refining technology, the quality of domestic oil will be better. The S% has reduced greatly and has reached the level of developed countries. With the environmental protection requirements more stringent, domestic fuel quality will be improved in the next period. There will be less SO_X, NO_X and other harmful gases in the exhaust gas so that the corrosive anions will be reduced greatly. Based on the fact, Efficient, low-cost and low-Cr 409 stainless steel will have a broader marke to take place of 429 steel stainless or 439 stainless steel . The study has found that new 409Nb-Ti stainless steel perform better in high temperature resistance, anti-condensate corrosion property, intergranular corrosion resistance and pitting potential than the traditional 409Ti.In particular,409Ti-0.3%Nb has the best high-temperature property. Therefore, the research will pay more attention to 409Ti-0.3%Nb.