I was chatting with a chap the other day, and he said “pity you cannot weld star pickets anymore” wanting to raise an existing fence 600mm to try and keep kangaroos out (exclusion fencing).
You can buy a section of star picket with a socket to put on top of an existing picket, but they are quite expensive.
So, the problem arises because a lot of star pickets sold in Australia in the last 20 years or so are made in China from “rail steel”, a higher carbon steel (~0.6%) that allows thinner section, less weight, lower transport cost etc.
If you arc weld these with ordinary general purpose electrodes (E6013 in Australia), they are likely to crack and fail under load.
I have used two options:
- stick weld with E7018 2.5mm electrodes; or
- MIG weld with AWS A5.20 E71T-GS 0.9mm flux cored wire.
To extend an existing picket in situ, you can lap the extension and do two vertical welds, or but the sections (see jig below) and do horizontal three welds.
Above is a jig using a short piece of water pipe and two locking chain clamps. Of course you would straddle the join to clamp the pieces and remove the jig after two welds are completed.
Above is the result. This was performed downhand on stands, a single pass at 60A, butted ends, no bevels. Horizontal welds on in-situ pickets might use a little less current. About half a stick of 2.5mm 7018 per picket.
Now… E7018 is a low hydrogen electrode and MUST be dry to minimise hydrogen cracking… so Google for precautions. I dry mine in an electrode oven for a few hours to ensure good weld performance. One of the advantages of the E71T-GS wire is that the flux is inside the wire, and atmospheric moisture is not a problem.
All that aside, E7018 is a nice rod to run, the flux is quick freezing and it produces a nice bead. You probably won’t get it at Bunnings or the local rural store, especially in small quantities, but it is readily available on eBay.