The wall thickness of at least a portion, which is plastically deformed, of a
protruding portion used for calking is reduced to less than that of the other portions.
Due to the foregoing, the bending rigidity of the protruding portion is decreased.
Therefore, it is possible to bend (plastically deform) the protruding portion by
a relatively low-intensity force. Accordingly, it is possible to easily execute
the calking work (calking process) without the need to extend the length of the
protruding portion (length from a forward end of the protruding portion to a bent
portion). As a result, even if the pressure-withstanding property of an inter-cooler
is enhanced by increasing the wall thickness of core plates, it is possible to
prevent the calking workability from deteriorating and without increasing the size
of the inter-cooler.
