1998-02-23

Requirements for P/M Stainless Steel Materials in Order to Meet Future Exhaust System Performance Criteria 980311

Due to more stringent regulatory restrictions, the requirements for exhaust system components have become more demanding. The flanges, in particular, must provide tight sealing capability, and they must maintain this sealing capability for countless numbers of thermal cycles. The tough creep and oxidation criteria, coupled with the increased corrosion resistance required to meet the long term durability and weld integrity is moving exhaust system components toward Stainless Steel materials. The competitive cost benefits offered by the Powder Metal forming technology for fabricating Stainless steel exhaust system flanges has driven extensive study and testing of a variety of P/M exhaust flange applications.
Preliminary tests have shown that porosity, by far, is the number one detriment to the survival of P/M stainless steel flanges in the tough test cycles of combined thermal stresses/quenching, hot corrosion, and oxidation, and has a strong influence on the ability to weld these materials to wrought tube as well.
The closely monitored cascading of Design Requirements, from the OEM system certification requirements, to the Tier 1 System Supplier manufacturing requirements, to the final Material Property and geometry requirements for the flange fabricator is critical to the success of P/M stainless steel exhaust flanges in these environments.

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