aluminium welding advice request

[Stan]

I am trying to weld aluminium for the first time.

I clamped two small scrap parts of aluminium in a vice after a light sanding to remove oxidation. I used pieces of ceramic tile as jaw protectors and to try and keep in some heat. I then heated an inch long part of the joint with a Dremel 2020 blowtorch using the tip of the blue flame. I did this for some time but the brazing rod did not get hot enough. Then I tried just concentrating the heat on one spot but again no joy.

Is it that the Dremel just doesn't put out enough heat? If so, can you recommend a better cheap blowtorch?

Is it that because I work outside the heat just gets lost too quickly?

Any other suggestions?

Thanks in advance.

 

[Spectric]

The thing to remember about aluminium is that the Aluminium melts at around 650°C but Aluminium Oxide melts at a far higher temperature and is why you find that one minute you have aluminium and the next a big hole where the weight of molten aluminium has fallen through the oxide skin. With a process such as TIG it deals with this oxide, with processes using gas you need the right flux. You also need not only the right temperature but sufficient heat to get the work upto temperature which may be your problem, aluminium is a good conductor of heat.

 

[guineafowl21]

Are you welding or brazing?

I think a propane/butane torch will not be hot enough for welding, and a bit inadequate for brazing. The hottest part of the flame is the tip of the inner cone, if you want to keep trying. Do some research on soft and hard soldering, as well.

MAPP gas torches might be better, but for serious work a TIG welder is by far the best.

 

[Sideways]

Everything the two guys above have said.

And unfortunately, for TIG welding you need a welder with AC capability.
These are more expensive than a DC only TIG set intended for use on steel.

Starter for 10, why don't you make sure that your torch is hot enough to just melt some thin aluminium, and that you're using low temp aluminuim brazing rod that melts more easily than the base metal.

 

[chaoticbob]

I am trying to weld aluminium for the first time.

I clamped two small scrap parts of aluminium in a vice after a light sanding to remove oxidation. I used pieces of ceramic tile as jaw protectors and to try and keep in some heat. I then heated an inch long part of the joint with a Dremel 2020 blowtorch using the tip of the blue flame. I did this for some time but the brazing rod did not get hot enough. Then I tried just concentrating the heat on one spot but again no joy.

Is it that the Dremel just doesn't put out enough heat? If so, can you recommend a better cheap blowtorch?

Is it that because I work outside the heat just gets lost too quickly?

Any other suggestions?

Thanks in advance.

A couple of things. First, what you are trying to do isn't welding but soldering. The distinction is that welding melts the base metal, soldering deposits a filler metal which adheres the the solid base metal. That's just words though.
As sideways says to actually weld aluminium you really need specialised kit - and a lot of skill.

Second, you don't say what sort of 'brazing rod' you used. I've bought aluminium soldering sticks off ebay and they simply don't work. I have had success with with SIF 555 (eg here ) though, not cheap but they do work. They melt at 350C, so comfortably below aluminium melting temperature. I use a propane torch - no need for MAPP, but maybe the Dremel (2200? - if so 290W) isn't beefy enough, it depends on the mass of metal you need to heat up. I think my smallest torch is around 1000W.
Regards, Bob.

 

[redhunter350]

Stan, Bob is correct you are soldering and I’m not familiar with the torch you are using but it sounds as though it is not powerful enough.
I have used aluminium solder successfully, it was one of the many kits sold in ME fraternity see Chronos Durafix Easyweld Aluminium Welding , Brazing & Soldering Kit - 1 Stick Kit & Brush - Chronos Engineering Supplies
My torch is a Bullfinch using Propane, you need to have a scratch stick made of stainless steel and a SS wire brush, emery etc will not do ! Wire brush the joint, heat the work until the solder will melt when touching the work then scratch the oxide film with the SS rod to allow the solder to penetrate, also use the wire brush just prior to applying the solder.
Good luck John

 

[imageel]

I'd agree with all the above wrt requiring more heat and add - since I do have an AC TIG welder and occasionally weld aluminium, that cleanliness is an absolute must!
After cleaning up the pieces to be joined to remove the surface oxidation - best is a stainless steel wire brush - if you use a plain steel one you'll contaminate the joints, then wipe down with either acetone or a cellulose thinner soaked rag, and also wipe clean the filler rod, or in your case brazing rod.

 

[Stan]

Thank you all for the above - some good food for thought. This is my first attempt at any kind of joining metal parts together. Woodwork/metalwork have become my retirement hobby. The more I learn the more I realise how much I just don't ( yet ) know.

 

[okeydokey]

Slightly off topic but years ago - about 1975 I had finished some extra qualifications at night school/tech college and I needed something to fill a couple of nights a week over a winter period. Signed up for a welding course which was entirely gas welding. All sorts of folk turned up from farmers wanting to weld hard points to something or other to others wanting to get the basics of a new skill. The trainer must have been well past retirement and used to weld aluminium on 2nd world war engines and wing components. On hearing that one of the older students announced he had a vintage water pump (unable to replace) off some almost extinct old car with a crack running its entire length. So the next couple of lessons featured the trainer with skill and artistry putting the pump with some thin components back together without creating any hint of aluminium puddle on the floor. Really good to watch.
At the end of the course I was quite proficient in easy gas welding.

 

[pgrbff]

A couple of things. First, what you are trying to do isn't welding but soldering. The distinction is that welding melts the base metal, soldering deposits a filler metal which adheres the the solid base metal. That's just words though.
As sideways says to actually weld aluminium you really need specialised kit - and a lot of skill.

Second, you don't say what sort of 'brazing rod' you used. I've bought aluminium soldering sticks off ebay and they simply don't work. I have had success with with SIF 555 (eg here ) though, not cheap but they do work. They melt at 350C, so comfortably below aluminium melting temperature. I use a propane torch - no need for MAPP, but maybe the Dremel (2200? - if so 290W) isn't beefy enough, it depends on the mass of metal you need to heat up. I think my smallest torch is around 1000W.
Regards, Bob.

Will the SIF 555 be a lot better than the many Aluminium soldering kits you find online? I bought Durafix but had little success.

 

[chaoticbob]

Will the SIF 555 be a lot better than the many Aluminium soldering kits you find online? I bought Durafix but had little success.

Can't give a definitive answer I'm afraid. The only direct points of reference I have are cheap eBay offerings and SIF 555. After complete failure with the former (didn't melt) I went for the SIF because it's a reputable brand for brazing alloys. It wasn't exactly easy going even then - I 'tinned' the parts by heating up and scrubbing with a stainless brush to get the solder to flow before making the joins. It did eventually work though.

I had a quick look at Durafix:

Durafix Easyweld is a unique 3 in 1 application. Brazing, Soldering or Welding Aluminium is now as easy as 1-2-3. There is no need for expensive equipment. No need for years of welding experience. It's convenient and can be used by both novice and professional alike.
Durafix Easyweld is the most widely used rod on the market for welding zinc based metals - white - die cast - pot metals. Welds made with the rod are clean and free from slag, and produces a sound joint which is stronger than the parent metal.
Welding aluminium without the use of flux, produces a joint sound and free from porosity. Durafix Easyweld will work on galvanised steel, also used as a Rub-on solder. Use a slightly carbonized flame (excess of acetylene), with small tip for most work.
Durafix Easyweld carries the following classifications:

• ASTM no. B240
• US Army - Engineering Corp - Spec no. MIL-R-4208

It seems to be intended primarily as a filler for welding zinc alloys rather than for soldering aluminium, which is mentioned only as an aside.
ASTM B240 refers to zinc alloys for pressure casting. MIL-R-4208 is a 1950 US Army spec for zinc alloy welding (as opposed to soldering) rods. So I'm a bit suspicious!

Good luck, Bob.

 

[hawkeyefxr]

I used to weld aluminium as part of my work but only with Tig.
My friend at the time was good at gas welding Aluminium but he had a secret, he would wipe a matchstick along the hot ally, this left a black mark one the alloy. When the black mark went away it was at the right temp for welding.
I tried it and there is very little temp change before the workpiece collapsed.
I stuck to Tig found that easy, downside for me was i would get really bad sunburn on any exposed skin, and i mean BAD.

 

[johnnyb]

Once worked on a rolls Royce resto (silver wraith) had a chap do the bodywork which was ally. he made the huge wings on site gas welding with strips cut off the sheet! the weld was simply perfect and slightly below the surface!

 

[Spectric]

I stuck to Tig found that easy, downside for me was i would get really bad sunburn on any exposed skin, and i mean BAD.

That is why you should wear the right PPE, the bonus is that with TIG you can wear light weight gloves and do not need heavy leather aprons etc.

 

[hawkeyefxr]

Some of my Tig Welding was on 8"*1 1/2 thick aluminium and that reflected a lot of heat. I had to pre-heat the metal with a O/A with a mixer head that was about 2in dia.
I was covered but any little bit of skin that was exposed would burn. This was in 1975.

 

[cerro]

The cheapest TIG AC/DC about 180amps I can find is around £398. that will do the job.

 

[Fergie 307]

Slightly off topic but years ago - about 1975 I had finished some extra qualifications at night school/tech college and I needed something to fill a couple of nights a week over a winter period. Signed up for a welding course which was entirely gas welding. All sorts of folk turned up from farmers wanting to weld hard points to something or other to others wanting to get the basics of a new skill. The trainer must have been well past retirement and used to weld aluminium on 2nd world war engines and wing components. On hearing that one of the older students announced he had a vintage water pump (unable to replace) off some almost extinct old car with a crack running its entire length. So the next couple of lessons featured the trainer with skill and artistry putting the pump with some thin components back together without creating any hint of aluminium puddle on the floor. Really good to watch.
At the end of the course I was quite proficient in easy gas welding.

Party trick of one chap I knew was to cut a coke can in half and weld it back together. Made it look so easy.

 

[Spectric]

The cheapest TIG AC/DC about 180amps I can find is around £398. that will do the job.

Having the ability to change the pulse width ratio can help, also called the "balance" , also pulse welding ability can be very useful. Just some features to look out for.