Copper brazing is used when increased joint strength is required or when systems operate at 350 degrees or higher temperatures.
Typical applications include the following:
- Protection against fire
- Refrigeration and air conditioning
- Distribution of fuel gas
- Supplies of water
The copper that contains oxygen or oxygen-free copper can be brazed to generate a joint with satisfactory characteristics. The total strength of an annealed copper brazed joint will be developed with a lap joint.
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The flame should have a mild carburizing effect. With the appropriate fluxes, any silver brazing alloys can be utilized. A brazed joint can be formed without flux when using copper-phosphorous or copper-phosphorous-silver alloys, although the addition of flux results in a more attractive joint.
Brazing Copper Tube Instructions in Video
Soldering Copper vs. Brazing
The majority of soldering is done between 350 and 600 degrees. Copper brazing is performed at temperatures ranging from 1100 to 1500 degrees, such as braze joints.
Joints Brazed in Copper
Copper brazed joints are utilized when extreme joint strength is required or when the joints’ system runs at temperatures more than 350 degrees.
Brazing operations employ butt, lap, and scarf joints regardless of whether the joint parts are flat, round, tubular, or have an irregular cross-section.
Except in high diameter pipe joints, clearances for filler metal penetration should not exceed 0.002 to 0.003 in (0.051 to 0.076 mm).
Large-diameter pipe fittings may have clearances ranging from 0.008 to 0.100 in (0.203 to 2.540 mm).
The joint can be formed using filler metal inserts or the filler metal can be fed in from the outside once the joint has reached the required temperature.
The scarf joint is used to join bandsaws and in other situations where the lap’s double thickness is not desirable.
Brazing Copper Tube Instructions
All of these processes should be completed on the same day. Complete instructions are available in the video at the top of this page.
- Make a note of the tube’s proper length.
- Cut the tube with a hacksaw, tube cutter, or other means of your choice.
- Ream the cut tube ends to remove any metal spurs. A reaming blade (found on tube cutters), a half-round file, or a deburring tool are all tools that can ream the tube.
- Clean the soldering locations to eliminate any oxides and grease. Utilize a sand cloth or abrasive pad for this task. .004 inches should be left between the tube and fitting.
- Insert the tube snugly into the fitting, but leaving enough room for the capillary action of the solder. Approximately.0004 inches. If possible, rotate the tube. Sustain a firm grip on the tube.
- Preheat both the tube and the fitting cup by holding the flame perpendicular to the tube. Avoid overheating, as this may cause the flux to burn. Utilize an oxyfuel torch with a neutral flame whenever possible. Maintain constant motion with the flame and avoid lingering on any portion of the tube. When removing and dissolving any oxide with a flux, wear gloves; do not apply with bare hands. Avoid wounds, the mouth, and the eyes. Brazing flux may be used but is not required when brazing copper tube to wrought copper fittings using a BCuP brazing alloy.
When employing a flux, heat it consistently until it becomes transparent (as directed by the manufacturer).
It’s worth noting that it’s more difficult to maintain the appropriate temperature uniformity in tubes with a wider circumference. It is necessary to pre-heat the entire fitting. A second torch can also assist in maintaining the required heat.
- Push the filler metal into the joint until it begins to melt. Apply to the place where the tube enters the fitting’s socket. When the filler metal has melted, direct the heat source to the cup’s base. Apply solder slightly off-center at the bottom of the joint is horizontal. Solder directly into the joint, keeping the torch at the fitting’s base and just ahead of the solder application point. (as demonstrated in the video above) Maintain a safe distance between the flame and the filler metal.
The joint’s temperature should be high enough to melt the filler metal. The flame should be somewhat ahead of the application of the filler metal. Apply the same method to vertical joints. Once you see a complete fillet, turn off the heat.
- Allow the joint to cool naturally without using water. After cooling, use a wet rag to remove any flux.
Take note that specific brazing applications, such as medical gas and ACR, need the use of inert gas during the copper brazing process.
It prevents the production of oxide on the internal tube surface.