If you are trying to silver solder a copper joint or braze it, you have to keep in mind a few important things. Only then it will be easy for you to make it in the right order. Of course, if you are skipping any of these steps, the joint will not be proper. Joining two or more metal parts into a joint is an art.
- Know the Difference
It may sound that joining of two metal pieces together is called soldering, and then what is brazing all about? So, this brazing process involves filler material as much as soldering, and the difference comes from the temperature used.
- Soldering is done at a lower temperature for filler.
- It is applicable for low-pressure joints like water systems and pipeline.
- Brazing is a process that is done for HVAC systems where maximum strength of the joint is needed.
- This is more careful and important than soldering.
- Tools You Need
Now that you know some difference between brazing and soldering, you would want to know the tools that are needed for the process. The brazing process is limited by its applications as well as the tools they use.
- For soldering, you need a solder that is called 95/5.
- This is used for potable water lines and has to be used there, but not for brazing.
- The brazing process needs a filler material, and the right one depends on your work and application.
- For example, Stay-slide 15 is filler that contains 80% copper, 15% silver and 5% phosphorous.
- The Heat You Need
Along with the filler and solder materials we talked about before, we also have to find the right heat. Usually, the brazing process requires more heat to melt and this cannot be achieved from small propane torches.
- Larger torches with pipes more than 1 inches and up are used here.
- An oxy-acetylene torch is generally preferred for this kind of job.
- This burns at around 3500 degrees Celsius which is the right heat for brazing applications.
- They come in kits with two pipes one for controlling the oxygen, and other for acetylene.
- They have regulators and 2 tanks for the gases and the torch.
- Make Sure of Flashback Arrestors
This is an important safety requirement for the torches. Most new torches come built with them mandatorily but some old ones didn’t have them.
- These flashback arrestors are put on each tank, both on oxygen and acetylene side.
- Earlier days they were also installed on the hoses themselves.
- They stop the flame from going back into the tank itself that can cause an explosion
- Also, keep safe.
- Coming to the Brazing Process
Some other additional safety tools are also recommended but let us now talk about the brazing process and what all you need to take care of. Taking care come because of the kind of application you are doing, such as those involving costly refrigeration units.
- Try using an inert gas like argon to purge your lines during the brazing process.
- Because the brazing process creates a lot of scales during oxidation, this might clog the lines.
- Brazing on refrigeration or cooling unit is a must recommended site for this use.
- Before proceeding makes sure to clean your pipe and fittings well, as well as de-burr is the inside of the pipes as well using round files.
- Choosing Tip and Setting up Tanks
Once you have done with all the cleaning thing from inside and out, you have to move to the actual brazing process itself. For that, you have to look for the right things. The first thing you will need to choose is a tip depending on the thickness of the material you are going to braze.
- Most manufacturers specify the right tip size using a chart for it.
- Brazing kits come disassembled and have to be set up properly.
- First, set up the tank valves on both the tanks without any thread or sealants.
- Purge them to see that no contaminants are going inside the torch assembly.
- Connect now the two hoses and the torch to it.
- Always remember how to open valves, check the pressure, and set the right flame.
- Which Flame Type is it?
You need to know the type of flame you are seeing so that you know which one you need and which one you do not. A wrong flame type can compromise your joint and lose its strength. It is simple to set up using the right amount of oxygen and acetylene you have mixed from the two regulators
- A neutral flame is what we need because it does not carburize or oxidize.
- It is a perfect mix of oxygen and acetylene.
- Avoid an oxidizing flame or a carburizing flame.
- The neutral flame is clean blue in color.
- Important Points on Brazing
Usually, when heating, the pipe comes first, and the fitting later. There is a small gap of air between them and so that they both join perfectly they need to heat separately.
- Heat the pipe first and make sure it reaches the brazing temperature.
- Then start heating the fitting’s hub.
- Keep noticing with your filler material if it is hot or not and begins to melt, this is the right temperature.
- Don’t overheat the pipe after red hot as we want this heat to melt the filler and not the melt it directly.
- Proper Wetting is Always Necessary
If you do not take care of the wetting this does not allow the capillary action to take place making it an improperly welded joint. This capillary action allows the liquid to enter narrow spaces, at times against gravity.
- When you are filling the joint notice if that it is not overheated and the capillary action is working.
- Once the melted filler is absorbed nicely, you can feel that the joint is filled completely.
- Apply a small cap where the pipe and fitting meet each other.
- This keeps them in place.
- Finishing it up
After the brazing is over you do have to close the valves in order, apply water and purge the hoses.
- First, close the oxygen knob slowly, then followed by acetylene.
- Close both the tanks and their valves.
- Purge your hoses neatly.
- Allow braze to cool down naturally. Do not apply water as it can cause a fracture to it.
- Get some wire brush and remove any scaling on the surface.
- Always open the acetylene valve first and light up the flame, next set the oxygen valve and slowly allow the oxygen to come and mix.
Make sure there are no voids in them after everything is over.