If there is no vacuum outside the pressure should be no problem, but also should be more attention to the substrate, because the matrix once the interference will interfere with the lining.
Vacuum is a kind of external pressure. If it is a vacuum state, it should be noted that the stainless steel flange lining in the matrix of the degree of integration to be reliable, because it is possible to vacuum to the lining to Pa down. So in addition to the edge of the ring welding, but also may be done to ensure that plug welding.