Brazing with the Acetylene ‘B’ tank

Getting going with the oxygen/acetylene torch can be both exciting and overwhelming.  It is kinda like learning to drive and learning how to operate a manual transmission.  You have to focus on the rules of the road and do a great job driving while at the same time learning about the clutch.  It also reminds me of learning to ride a bike.  You have to learn to balance and pedal at the same time.  If we break these down into individual lessons we can focus on the getting the required skills to move up.  In this case I find students overwhelmed with 2 tanks, managing pressures, using a large torch and making great welds at the same time.  I brought in this little ‘B’ tank to help with most of that.  The ‘B’ tank only uses an acetylene tank and grabs air from the room rather than an oxygen tank.  The advantage is easy starting.  The disadvantage is a huge reduction in heat.    The ‘B’ tank will only be useful for brazing, but it’s main purpose is to teach the skills necessary to be successful with the oxygen/acetylene torch.

Brazing: Combining 2 metals together with addition of a dissimilar metal.  Generally, in our class, brazing attaches 2 pieces of steel together with bronze.  Brazing can also attach stainless to regular steel as well.  Brazing is generally done with bronze.  A braze can be identified by the gold color attaching metals together. By this definition, lead soldering would fall into a braze, as you are attaching 2 copper wires together with lead/tin.  I believe that soldering and brazing are separated by how much heat is needed to make it happen.  Soldering can be done at fairly low temperatures.

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Some things you will need to get going:

Regulator: this attaches to the tank and allows for a certain amount of gas to flow out.

Torch and hose: this creates the flame

Striker: This flint/steel tool creates a spark to ignite the fuel coming out of the torch

Material to braze: steel, stainless, carbide

Filler material: we have 3/32 bronze rod.

Flux: All brazes, welds, and solders need flux.  I will go into this in more detail in class, but for this, just know what kind of flux you need.  I have a can of powdered flux.  lightly heat up the bronze rod and stick it in the top of the can.  The flux will stick to the rod.

Fire brick: find something that will not burn as the flame goes past your part.  I use fire bricks for small parts and the welding tables for larger parts

Here is the tank:

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To open the tank, turn the square key on top to the left.  When you are done, turn it to the right

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Turn the knob on the torch on slightly till you hear gas coming through.

 

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To light the torch lie the torch sideways over a striker and ignite the striker.

The reason to do this sideways is to allow the flame to get lit and not blow back into the striker cup.

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Here is our uncleaned part ready for brazing.  If I would’ve cleaned the part, my final braze would’ve looked good.

 

 

 

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Heat the desired braze joint up till it is red hot.  I seem to find most students not heating this up enough.  Here is an advantage to this torch.  I have yet to see this torch get hot enough for welding temperatures, so I have yet to see someone over heat with this torch yet.

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Once it is red hot you can add the bronze filler rod.  If you added flux and got it red hot, the bronze should seem like it disappears into the joint.  This next picture shows it with the bronze and it is still hot.

 

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This is what it looks like cooled off.  Again, the uncleaned metal parts helped to create the red around the edges and impart the black specks into the braze.  For these parts, I would’ve recommended sandblasting the parts prior to brazing.

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