Ferritic Stainless Steel and Pipes for Automotive Exhaust system to Meet Weight Reduction and Stricter Emission Requirements

摘要

High formability heat-resistance ferritic stainless steel and pipes for automotive exhaust system parts were developed to reduce auto weight and meet stricter emission requirements by making full use of the advanced production facilities recently constructed at Chiba Works. The average γ-value of the newly developed stainless steel was improved by more than 1.3 times in comparison with the conventional steel while retaining the same level of heat resistance. This increase in the γ-value resulted in a remarkable improvement in various forming properties which are important for automotive exhaust system parts, including (1)limit drawing ratio, (2)stretch flanging ratio, (3)limit expansion ratio of pipe, and (4) thickness reduction ratio of pipe after fending. In particular, the formability of the newly developed stainless steel pipes was nearly equal to that of conventional stainless steel pipes after stress relief annealing.