Brazing Steel with a Propane Torch

Written By: Liam Bryant

Reviewed By: Russell Egan

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Brazing steel with a propane torch involves cleaning joint surfaces, applying flux, heating the joint with the torch until red-hot, and feeding a brazing filler rod into the joint. The filler melts and flows into the joint, forming a strong bond when cooled. Propane torches work best for small-scale projects.

Brazing is one of the most effective ways to join metals such as steel. It has many advantages over welding. For example, it is more friendly to beginners than welding, which can get complex. 

Brazing is also popular because you don’t need that much equipment. Some say you can even braze with a propane torch, not a full machine. However, is using a propane torch even possible for brazing? If so, how do you do it?

Here is your guide to everything you need to know about brazing steel with a propane torch.

Can You Braze Steel with a Propane Torch?

First, it’s important to establish whether you can braze steel with a propane torch. Yes, you can braze steel with a propane torch. Regular blowtorches that you can get in any home utility kit work well for brazing.

Most people know that you need a special machine for welding and a regular propane torch is not good enough for this task. However, for brazing, the situation is different. The difference has to do with how brazing works

Brazing combines two pieces by melting a filler alloy that acts as a very strong glue. On the other hand, when you weld, you melt the metal pieces themselves. The brazing alloy has a much lower melting point than steel, so you need to heat the pieces to a lower temperature than you would when welding. 

To get to the right temperature for brazing, which is usually 800–2,000 degrees Fahrenheit depending on the alloy, you can use equipment that is not as powerful as a welding machine, including propane torches. The accessibility and lower brazing demands are part of why it is such a popular welding alternative.

How to Braze with a Propane Torch

Now that you know you can combine two metals using your trusty propane torch, here is how you can go about the process.

Prepare the Metal

The first step in any process involving joining two metals is preparing the steel. Brazing with a propane torch is no different.

Preparing the steel (and your workspace) is important because any dirt or impurities could affect the strength of your braze. Plus, brazing requires a carefully prepared joint to set properly. If there are any rough edges, you will have trouble connecting your pieces.

Here are the steps you need to take to prepare your metal before brazing.

  1. Clean dirt and debris off of the steel. Use soap and water, making sure to wipe everything down afterward. 
  2. Rub the steel with acetone. Sometimes, it is hard to detect traces of grease with your eyes, and going over the metal with acetone makes sure that all of the grease particles are gone.
  3. Go over the edges of the metals you are brazing with sandpaper. Sandpaper removes layers of oxidation on the metals which can prevent brazing from working. Sandpaper also helps remove any particles that are stuck on the metal.
  4. Chamfer the edges. Chamfering is cutting away bits of the edge so the metal ends on a gentle slope. Sometimes, it helps the brazed metals fit together better.

Whether using a propane torch or a welding machine for brazing, you still need to prepare your metals for the process. All of these preparation steps are necessary to make sure your job is well done in the end. 

How to Braze

Once you prepare your metal for brazing, it’s time to get into brazing itself. Brazing with a propane torch is very easy, but it still has a bit of a learning curve if you’ve never done it before. Here is a guide that can help you navigate this process.

  1. Prepare your workspace. After dedicating a lot of time to preparing your metal, you must also prepare your workspace. Make sure your table or workstation is fireproof and cleared of debris—you don’t want to set anything on fire accidentally. Then, hold the metals in place using clamps, a vise, or binding wire.
  2. Add flux to the joint. You can use chemical flux or an argon gas shielding flux. Flux prevents oxidation and other impurities that might affect the quality of the joint. Before using any flux, make sure you use the right one for the base materials you are working with.
  3. Prepare the propane torch. Make sure your torch is stocked with its fuel and oxygen mixture. Preheat the torch until it reaches the appropriate temperature for the braze. You want it to be at the temperature that will melt the brazing alloy you use. Usually, once you see that the tip of the flame is blue, that’s a sign that your torch is hot enough.
  4. Preheat the metals. Brazing works best when the metals are at a similar heat to the brazing alloy. The residual heat from the metals also helps melt the alloy.
  5. Apply the brazing alloy. Whether you are using a brazing wire or an alloy in another form, apply it to the joint. 
  6. Melt part of the brazing alloy. Hold your blowtorch over the beginning of the seam until the brazing alloy melts, forming a small weld pool. Make sure you hold your blowtorch as close to the weld as possible to concentrate the heat on the seam. Moving the blowtorch in small circles also helps create the welding pool.
  7. Move the torch along the seam. Once the brazing alloy melts, move the torch along the seam to melt it along the joint. Make sure you are moving at a consistent speed and holding the propane torch at the same angle throughout. 
  8. Let the braze rest. Before you can use your new project, you have to let the braze joint cure, or rest. Let the metals cool to room temperature before touching or moving your project. Brazing joints need to cure, or harden in place, before you can use them. A good rule of thumb is to leave your project overnight before doing anything else.

Once you have the technique down and perfect your steady hand, then brazing is easy, even if you are a newcomer to metalworking.

Brazing Steel with a Propane Torch

Equipment Needed

Before getting started on brazing with a propane torch you need to have the following equipment:

  • A propane blowtorch. 
  • Filler metal. You need the filler metal or brazing alloy to melt in between your two pieces.
  • Fuel and oxygen. The blowtorch needs to have enough fuel to keep going.
  • Cleaning equipment. You need sandpaper, acetone, soap, water, brushes, and cloths to make sure the metal is clean enough for brazing.
  • Protective equipment. Even though brazing is easier than welding, it is still risky. Protect yourself with a helmet, gloves, apron, and respirator.
  • Carbon monoxide detector. Propane torches burn a lot of carbon monoxide, so make sure your work area is well-ventilated and you have a detector that can alert you to danger.

Final Thoughts

If you don’t have a welding machine, you can braze steel using a propane torch. Follow these tips for success.