brazing

[Haze]

never done brazing before, does it require oxygen mix with my gas or not? I hae two types of rod to play with - 880 c white coated rods, and 915 c blue coated nickel silver rods, im just doing this for practise so as when I do actually need to do a job I dont have to fart around practising first..

if anyone feels like writing a rough guide or pointing me in the direction of a helpful website it would be much appreciated

 

[shenion]

I have the blue rods here, have used them for years.

They will work with a MAPP gas torch, although you would want a bit more heat.

Works real well with my acetylene/Oxy torch using propane instead of acetylene.

Brazing is real easy as long as the metal is clean.

 

[Haze]

flame pattern seems a bit vague, would i get better results with a tighter nozzle, cus right now im not even melting the rod.

 

[Cappy]

Hi Haze,

Do you mean Brazing or Bronze welding as I think you'll find that the processes are slightly different.

As far as I can recall from the college days, Brazing is carried out using a flux and brass spelter (brass rod basically) and can be done with a really big propane torch. Involves, cleaning the two surfaces, applying the flux (usually borax to with stand the high temperature), bring to red heat and then applying the spelter which flows into the joint.

Bronze welding is carried out using, more or less, the same technique as gas welding but using a silicon bronze filler rod instead of the more usual steel wire, and suitable proprietary high temperature flux - e.g. Sifbronze

However things do change

 

[Moseph]

If you have an Arc welder then carbon arc is tricky, but very satisfying when you become skilled at it. Oxy-acetylene is still the best gas combination as the high intensity of the heat keeps the haz much smaller than with other gas mixtures.

If you get the base metal (assuming its steel) upto cherry red and start pushing the rod into the join, you can't go far wrong. You shouldn't really be heating the rod directly as it won't be flowing into the joint properly and will tend to look ok on the outside, but with no penetration.

Rust etc, should all be removed, but I've never found the need to make it perfectly clean as the flux cleans as you go.

When I completed my gas qualifications, the pipe brazed joint I made broke through the base metal rather than the joint. Done well, it is quite amazing how strong it can be.

 

[shenion]

flame pattern seems a bit vague, would i get better results with a tighter nozzle, cus right now im not even melting the rod.

Is this propane?

If so, you probably need a better torch. Mine will do MAPP or LP. It is not like most LP torches. The barrel is about 8" long with 3 air inlets at the base. This gives a long time for the air/gas to mix. With this torch and propane, I can barely melt the rod. With MAPP gas it is a bit easier.

Don't know how readily available MAPP has is over there. You might try it. Some torches are designed for both gases.

 

[Moseph]

Oxy-propane works fine for brazing. It still achieves a flame temperature of around 2800c, it just has a very large amount of its heat energy in the secondary cone (hence very large heating area) and also has a much higher oxygen consumption rate (around 3x as much) when compared to Acetylene.

 

[shenion]

I set up may Acetylene/O2 torch for propane (use gas grill tank).

It works great for brazing. Like Moseph said, it does heat a large area, but works well.

I was also surprised ho well it cuts. Takes abit to heat up, but then works.

 

[Haze]

I'm using a rothenberger Superfire 2 Brazing torch with the standard nozzle on MAPP gas, I can get the metal up to cherry red and the rod wont melt, even if i direct the torch at the rod it glows red but doesnt melt :S

 

[Moseph]

The difference between the temperature of propane in air and propane with oxygen is about 1000c!

 

[shenion]

I'm using a rothenberger Superfire 2 Brazing torch with the standard nozzle on MAPP gas, I can get the metal up to cherry red and the rod wont melt, even if i direct the torch at the rod it glows red but doesnt melt :S

My MAPP gas torch will barely work and only on small stuff. Anything thick will suck too much heat out to work.

Sounds like you will need a better torch, the steel needs to be bright red.

 

[Haze]

sigh,

maybe a portapack then? or is it worth getting something bigger for versatility.

 

[shenion]

Not real familiar with the Portapack. Looks like it comes with only a few tips.

What I did was get a Victor torch clone off Ebay. Cost me $50US. Then I can easily get different tips if needed (and replace parts easily.)

I adapted the regulator for a LP gas tank from a gas grill. Works great and is cheap to run as I only need to fill the O2 tank at the welding supply. LP can be filled or exchanged anywhere.

I found some propane cutting tips on ebay fro $0.99. Torch came with 3 welding/brazing tips that work fine on LP.

 

[Moseph]

Cheapest way is to get a big bottle of Oxygen from BOC/Airproducts/whoever and Propane from Calor. A 19Kg bottle of Propane is just over £20.

 

[Alex]

I think I read the Aerial Atom is made using Brazing, so it must be fairly strong.

 

[shenion]

I think I read the Aerial Atom is made using Brazing, so it must be fairly strong.

Check out the MIG brazing in the advanced section on this site.

The test shows the metal breaking instead of the braze.

 

[Alex]

An update..

They are bronze welded....Whats this?

 

[DIY Welding]

The melting point of the filler rod is the important thing, as brazing is a caperillery joint then the temp of the flame is important, I sell the Oxy Turbo brazing kit this uses disposable bottles one is Oxy the other is a fuel gas the temp of the flame is 3050c which is much higher than Oxy/Propane, the melting point of your filler rod should be about 600c

 

[Moseph]

The melting point of the filler rod is the important thing, as brazing is a caperillery joint then the temp of the flame is important, I sell the Oxy Turbo brazing kit this uses disposable bottles one is Oxy the other is a fuel gas the temp of the flame is 3050c which is much higher than Oxy/Propane, the melting point of your filler rod should be about 600c

What's the fuel gas? MAPP is about 2900-2950c, Propane about 2800c and Acetylene about 3100c. The heat distribution within the flame, calorific value of the fuel gas, flame speed + many others are almost as important as the absolute temperature of the flame in order to both weld and braze well with gas, not to mention how much oxygen is used to achieve the temperature.

 

[Haze]

my rods are melting point as mentioned in the OP, so why arent they melting im sure the flame of the mapp gas is higher than both ??