OUTGASSING RATE OF SOME AUSTENITIC STAINLESS-STEELS

Outgassing rates were measured and compared for 304L, 316L, and 316LN stainless steels in fully degassed condition produced by repeated pumpdown and baking. In addition, thermal desorption characteristics and surface compostion were measured. In particular, the effect of grade, vacuum remelting, and prebaking is discussed. The grade itself does not appear to affect the outgassing rate significantly, while vacuum remelting reduces hydrogen in the steel, thus giving lower outgassing rate than commercially available steel. However the effect of prebaking at 450-degrees-C appears more pronounced on reduction of diffusive outgassing of hydrogen than that of vacuum remelting. Application of prebaking to the vacuum remelted steel produces the extremely low outgassing surface, as low as 1.3 x 10(-10) Pa m3 s-1 m-2 by baking at 150-degrees-C for 14 h.