Abstract
Surface characteristics of invar alloy for shadow mask in color picture tube were investigated by changing annealing conditions after cold rolling-such as soaking temperature and atmospheric gas composition. Results obtained are as follows:
1) Invar tends to show grain boundary oxidation by small amount of H2O in the annealing atmosphere.
2) Grain boundary oxidation is due to Si, Mn, and Cr which are commonly contained in invar and more active than main components (Fe and Ni).
3) However, behavior of each impurity depends upon annealing conditions. In case of less oxidizing annealing atmosphere, grain boundary oxide is mainly composed of mangano-silicate. On the other hand, mangano-chromic precipitatesat grain boundaries are observed in more oxidizing conditions.
4) Higher silicon content leads to severer grain boundary oxide precipitation.
