Welding of Zinc based Alloys

[jimrunciman]

I'd be grateful to hear from the experienced respondents if its possible to TIG weld Mazak which is a zinc based alloy which was popular between the late 1930's and the mid 50's.
For the general interest of all who read the posts this material was used for many applications inn the automotive industry such as carburetors and door handles to name a couple of the more common applications.
Apparently it is possible to braze or solder this material with commonly available filler rods however I'm told the incidence of a molten pool of material is more common than a nice repair.
Jim Runciman

[Grahame Collins]

Jim,
My take on it would be to not use tig.

Why ? Because the zinc in the alloy will flash at a lower temperature than the other alloy materials will melt at.The cast is performed under pressure and the zinc can't flash in that state -is my understanding.


Instead I would be looking at one of the low departure alloy filler rods that the trade names of which elude my memory at this moment.Basically they can be applied with a LPG torch as a heat source.I am nearly sure I have seen one that specifically addresses this need.

I sure one of our forum members with a better memory of the trade names will be along shortly.

Also if you tell us of your intended use it may assist in refining the technique or application etc.

Grahame

[Master Splinter]

This stuff:

Durafix Australia - Aluminium Fluxless Repair Rods (http://www.durafix.com.au/index.php)

[jimrunciman]

Thanks Grahame and others.
I have some Magna Alloy rods and have just wished to enquire if it was possible to use TIG instead of gas brazing method as I have had mixed results previously. With the brazing or soldering technique the temperature is very critical and when the section varies I have experienced major problems.
I am endeavoring to repair a pair of pre-world war 2 SU carburettors where a previous owner has slotted the mounting holes in a very bad manner and I'd like to fill them and redrill.
Greatly appreciate the response from this wonderful forum.
Cheers
Jim Runciman

[Jekyll and Hyde]

If I'm reading your posts correctly, I suspect you're asking about Tig welding it, which I wouldn't try - with a high zinc content, you're likely end up with molten metal exploding everywhere.

Tig brazing, however, should be viable, with the right choice of rod (not quite sure what Magna Alloy is, I'm guessing it is a welding rather than a brazing rod). Would obviously be good to have some others to practice on, but I suspect that is out of the question.... With Tig brazing, the idea is to start with very low current, and increase just enough to melt the rod without melting the parent metal. It might offer you more control than brazing with an oxy?

[Karl Robbers]

The first question I would pose is, "how necessary is the repair, is it for appearance sake or does the part in it's current state not work". My reason is this.
You have a presumably rare and irreplaceable item that is made of a material that presents difficulties from a welding/brazing perspective. Failure would mean total loss of the component. Perhaps let sleeping dogs lie if possible? Or consider one of the industrial metal filling epoxies. Obviously they will not be a colour match, but this may not be an issue due to the area probably being covered by a nut etc.
Having said that I would echo previous comments regarding tig welding, (I am aware of tig brazing but have personally never done it).
A previous employer of mine, while restoring a Ford Mustang, (christined the "Rustang" by us), repaired the die cast headlamp mounting castings with good old zinc sticks, the type used for galvanising welds etc. Heat source was oxy acetylene but lpg would have been far better.
The best technique for castings of varying thickness would I reckon be to heat the whole job up and then turn your flame back to a lower level and actually go about your brazing/soldering as required, this should minimise the effects of thickness variations.
Purely out of curiousity, what are these carbies off?

[Jarh73]

The first question I would pose is, "how necessary is the repair, is it for appearance sake or does the part in it's current state not work". My reason is this.
You have a presumably rare and irreplaceable item that is made of a material that presents difficulties from a welding/brazing perspective. Failure would mean total loss of the component. Perhaps let sleeping dogs lie if possible? Or consider one of the industrial metal filling epoxies. Obviously they will not be a colour match, but this may not be an issue due to the area probably being covered by a nut etc.
Having said that I would echo previous comments regarding tig welding, (I am aware of tig brazing but have personally never done it).
A previous employer of mine, while restoring a Ford Mustang, (christined the "Rustang" by us), repaired the die cast headlamp mounting castings with good old zinc sticks, the type used for galvanising welds etc. Heat source was oxy acetylene but lpg would have been far better.
The best technique for castings of varying thickness would I reckon be to heat the whole job up and then turn your flame back to a lower level and actually go about your brazing/soldering as required, this should minimise the effects of thickness variations.
Purely out of curiousity, what are these carbies off?

I reckon that is good advice. :2tsup:

I can understand how annoying the elongated holes would be but some epoxy combined with a slightly oversize washer would solve the problem.

Seems to me the risk of repair far outweighs the benefit.

Cheers

Justin

[jimrunciman]

Hi Justin and Karl
Thanks for your replies
The crabs would have come off a late 30's Jaguar or some other large capacity car. They were sold to me as having sand cast bronze bodies which would have been easy to repair.
My use was going to be an ex works Riley competition car but however even the shape is incorrect.
Now that I've had the benefit of advice from this forum I'm going to have a go using the Magna alloy rods because I'd like to be more proficient using this excellent product - the demonstrations you see at trade shows are amazing. Fortunately I have a number of unserviceable units to practice on.
Keep up the great work
Jim Runciman