how can weldding glass to iron ?
Gerdb, Sorry, wrong answer. If you are talking about glass to metal hermetic seals such as those used in pressure containing vessels that have to have connectors on them, the metal used in the connector pins is actually a controlled expansion alloy of iron, with all kinds of other elements that make it's thermal expansion co-efficient match the glass (borosilicate glass). the pins are not actually glued or welded, they are merely inserted into the mold and the glass is cast around them which cools around the pins and lock them in place. The pins are usually circumfrentially ribbed to give some axial strength. the pins are also electroplated with nickel, copper, and gold for conductivity before being molded in place.