In order to join an aluminum pipe to an iron pipe in air, we inserted the zinc-plated iron pipe into the aluminum, and heated them to given temperatures. The optimum joining conditions were determined, and the properties of a joint and the joining process were metallurgically examined. The results obtained are summarised as follows.
An aluminum pipe could be joined successfully to an iron pipe in air by zinc-plating on the faying surface of the iron pipe. The strength and the bonded area of the joint increased with the bonding temperature and inserting rate of the pipe.
Al-Zn eutectic liquid, which formed by the reaction between Al and δ phase (FeZn8), acted mainly as filler metal in this joining system. As the joining temperature was higher, the amount of eutectic liquid formed at the interface increased, resulting in the increase of bonded area. As the inserting rate increased, the joining process finished within shorter time and the supply of Zn from δ phase continued till the last stage of the joining. Consequently, sufficient eutectic liquid for joining was formed and the joined area increased.
