Paras Enterprises

Brazing Guidelines Continue

1: Cut Pipe Square
 
Cut to the exact length required using a tube cutter or hacksaw. If a hacksaw is used, a sawing fixture should also be used to ensure square cuts. Remove all inside and outside burrs with a reamer, file or other sharp edge scraping tool. If tube is out of round, it should be brought to true dimension and roundness with a sizing tool.

2: Clean Tube And Inside Surface Of Fitting
 
The joint surface areas should be clean and free from oil, grease, or oxide contamination. Surfaces may be properly cleaned for brazing by brushing with a stainless steel wire brush, or by a stiff rubbing with emery cloth.

If oil or grease is present, clean with a commercial solvent. Remember to remove small foreign particles, such as emery dust, by wiping with a clean dry cloth. The joint surfaces MUST be clean.
 
2: Select Brazing Alloy
 
When brazing Copper to Copper, low cost PE 15% may be used. These alloys contain phosphorus and are self-fluxing on copper. When brazing iron, steel or other ferrous metals, select a cadmium-free brazing alloy.

Do not use phosphorus bearing alloys as the joint may be brittle. To estimate the amount of brazing alloys needed, see Filler Metal Chart.

Proper Fluxing is important because the flux absorbs oxides formed during heating and promotes the flow of filler metal.  To prevent excess flux residue inside refrigeration lines , apply a thin layer of flux to only the male tubing and, if possible, revolve the fitting once or twice on the tube to ensure uniform coverage.
 
4: Assemble Tube and Fitting
 
Insert the fluxed tube end into the fitting. Maintain support to ensure the proper alignment until the brazing alloy solidifies. Maintain for a few seconds (or more) depending on the size of the joint area. The assembly is now ready to braze, using brazing alloy in rod, wire or coil form manually fed into the joint.

Adjust Torch Flames

For most brazing jobs using oxygen-acetylene gases, a ''neutral'' flame should be used. The neutral flame has a well-defined inner cone. Avoid an oxidizing flame.

Neutral Flame - Inner cone bluish white, no acetylene feather, tip Bluish to Orange.

Oxidizing Flame - Sharp inner cone bluish white, inner cone two-tenths shorter than cone of neutral flame, tip nearly colorless.

Carburizing (Excess Acetylene) Flame - Inner cone bluish white, acetylene feather bluish white with feathery edge, tip light orange.
 
5: Heating The Joint Area
 
Always keep the torch in short motion then.

Start heating the tube, first applying the flame at a point just adjacent to the fitting. Work the flame alternately around the tube and fitting until both reach brazing temperature before applying the brazing filler metal.

When a flux is used, it will be a good temperature guide. Continue heating the tube until the flux passes the ''bubbling'' temperature range and becomes quiet, completely fluid and transparent and has the appearance of clear water.

Direct the flame from the tube to the flange-base of the fitting and heat until the flux that may remain in the fitting is also completely fluid.

Sweep the flame back and forth along the axis of assembled joint...tube and fitting...to get and then maintain uniform heat in both parts.
 
Apply The Brazing Alloy
 
Feed the alloy into the joint between the tube and the fitting. Only after the base metals have been heated to brazing temperature should the filler metal be added. At that time the flame may be directed momentarily to the tip of the filler metal to begin the melting process.

Product Characteristics & Applications