A 6013 rod should be machineable straight off the arc, hot or cold. Having said that I hate ESAB 6013 rods and won't use them, simply because whatever the blurb says for position welds with this rod I can't help but get slag inclusions in the weldment. I've been using Oerlikon 6013 rods for years and never had this problem but (other than incompetence on my part) I don't know why the difference is so pronounced. Fincord M is a lovely docile rod, try it and marvel.
The "rutile" descriptor refers to the composition of the flux, which – as we all know – never ends up in the weld metal (ho ho!). If you google rutile you will see an explanation of what it is, and how it does what it does. Rutile is simply a mineral, with a complex composition which happens to make a nice flux coating for MMA. The presence of some manganese (for example) in the rutile doesn't affect the metallurgy of the weld metal, as the flux isn't incorporated into the weld pool. The composition of the weld pool is governed by the parent metal and the composition of the added weld metal from the rod core.
I doubt that the scaffold tube is anything other than mild steel, certainly it shouldn't have enough carbon (or anything else for that matter) in it to upset its machineability after welding. For this reason the idea of annealing post weld is irrelevant. If the weld is hardened by cycling through the weld zone there is something wrong with the metallurgy of the base metal. It's vastly more likely that the hard spots are slag inclusions. A good guide to this with 6013 or similar is that the slag should fall off the weld as it cools of its own accord, if you have to do more than scrape it to get it to let go then the slag is contaminating the weld.
Please steer well clear of welding galvanised stuff, even grinding the coating off isn't guaranteed. I've had Zinc fever (no it'll be OK!!!). Never again. Oh, and zinc contamination will cause slag inclusions, it doesn't burn off completely, some of it gets trapped in the weld pool.
Damp rods (for damp read "not absolutely bone dry" can also cause slag trapping, but rutile is pretty tolerant of moderate damp and the act of passing a current through the rod to use the first inch or so will heat the rest of the rod up so much that any residual moisture is vapourised. Still, it's good practice to put the rods in the oven for an hour at 150 C or so immediately prior to use. It's also good practice not to let them get damp in the first place.
After that, you need to think about welding AC or DC, and polarity can also make a difference., But for my money all of these tweaks are missing the point, this is ESAB syndrome. They may be very good in expert hands, but I'm not that person and I like the results of following the gospel according to Oerlikon.
And, as ever and for the avoidance of doubt, I have no connection with Oerlikon, I'm just a satisfied user.
One last thought, if the rods were at all oily you're on a hiding to nowhere.
Good luck, HTH
Simon
Edited for yellow face eviction
Edited By Simon Williams 3 on 01/12/2018 22:47:35
Edited By Simon Williams 3 on 01/12/2018 22:49:38