Process reliable brazing of copper – stainless steel joints using Penetration Depth Induction and cored wire rings

A well known situation: The first joint when using plate heat exchangers is to braze a copper fitting into the stainless steel socket. While brazing copper on copper with an oxy-acetylene or oxy-propane flame is easily learned, this is much more tricky, as soon as there is stainless steel on one side of the joint.

A real bad heat transfer coefficient and a sensitive surface are what makes brazing a challenge. Penetration Depth Induction using a ring or hook-shaped inductor enable to reach brazing temperature fast and with nearly no overtemperature at the surface. By the way, purely time-controlled, no need for actual temperature regulation. As brazing material, wired metal rings with high silver contents are used. This way, the amount of flux on the joint is as little as possible - and especially the actual total amount of silver used is as small as possible. That the actual brazing time is the same or less compared to the flame, and that brazing quality is reliably high, are the appreciated side effects.

This way of brazing is easy to learn. Described in a heating process specification (HPS), then qualified. The brazer will undergo a brazer qualification. All shown application photographs and videos were made in VauQuadrat’s own chiller manufacturing, where the compressor driven R-455A circuit is being manufactured.

The presentation specifically also addresses those with prior (often negative) “induction brazing” experience. Ease of use, and process reliability were difficult to reach with conventional induction.