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Audio systems in automobiles are under intense development to improve volume and clarity of sound. With the advent of high performance rare earth magnets, the magnetic properties of the mating components becomes a significant factor in loudspeaker performance. This paper describes the initial testing of various P/M irons for use in the design of shellpots.

For structural components that require improved fatigue and wear resistance, shallow case carbonitriding has traditionally been specified by the automotive industry. A typical specification might call for .003 to .010 inch case depth consisting of clear martensite and a surface file hardness of Rc 58 file hardness. A problem with this treatment has been excessive distortion in precision components such as fine blanked stampings, screw machine parts, and powder metal parts. In many cases, these parts have to be finish ground or sized in some manner to return the parts to print tolerances. Another problem has been a severe loss of fatigue strength because of over-casing. This embrittles parts with thin cross sectional thicknesses. Lindberg Corporation has developed the Lindure process to provide an alternative to carbonitriding. Lindure is a gaseous nitrocarburizing treatment which takes place at temperatures below the lower critical (AC1) where the austenite transformation begins.