R-Pro › Field cases › Components
Brazed Joint Cold Cracking — Residual Flux Corrosion
Likely causes
Flux not removed after brazing
Check: Check for white/yellow powder around joint (borax residue); scan all joints with leak detector
What to do: Disassemble leaking joint → remove old filler → re-braze at 700~850°C with nitrogen purge (0.03MPa) → wipe flux immediately → nitrogen pressure test 600kPa for 30 min
Insufficient brazing temperature (below 700°C)
Check: Gray powder or uneven filler color (no silver sheen) at joint → incomplete fusion; remove and inspect fracture surface
What to do: BCuP-5 rods: self-fluxing — always use with nitrogen purge. BAg-7 rods: apply flux, preheat sufficiently → hold heat until filler flows into joint on its own
No nitrogen purge → internal oxidation
Check: Cut joint and check for black oxide scale on inner surface; copper color = no oxidation
What to do: Before brazing, flow nitrogen at 0.02~0.05MPa through pipe — maintain throughout torch work; cut nitrogen after full cooling
Silver sheen on filler after brazing = good; gray powder = oxidized, rework needed. Without nitrogen, inside chars black.
All 565 cases work offline in R-Pro, with error codes for 62 brands and P-T data for 108 refrigerants.
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