How can I prevent copper filler metal from spreading away from the brazed joints in my steel parts?
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||Tom Philips |
Sr. Principal Applications Engineer
In furnace brazing, this tendency for the melted copper filler to flash and spread is generally caused by one of four factors:
- Your brazing zone temperature is set too high. Copper melts at 1984ºF. For carbon steel brazing, the brazing zone should be set at 2050 ± 10ºF.
- The reducing power of your atmosphere is too high, caused by too low a dew point or too high a concentration of hydrogen in the brazing zone. For carbon steels in a muffle type furnace, dew points should range from -10º F to +10ºF, with 5% hydrogen.
- The joint gap is too wide, producing lower capillary forces for the melted copper to flow into the joint; this causes the copper to flow away from the joint.
- The part is in the "hot zone" of your furnace for too long.
You can help prevent this tendency by avoiding these scenarios.
For a free copy of our technology guide, "Introduction to Furnace Brazing," please call us at 800-654-4567.