With 6011, it will run with AC. Was weird trying keyholing a V-prep butt-weld using an oil-cooled AC welding transformer - the arc crackles at mains frequency, but the keyhole and weld are just fine. Seem to recall you use about 10% more amps when AC welding, compared to DC amps setting. Would need DC for 6010's (found could keep 6010 alight on AC with open arc, but not "drag" / pushing into the root - goes out immediately on contact --- and may be different between different welding sets as in will never burn 6010, even open (drawn) arc..?).
xx13 is rutile stick with potassium in the binder - makes for a very smooth burning rod on both counts with AC or DC - but gives low mechanical properties, as weld metal has big inclusions and the only way to live with them is to make the weld metal soft - ie. not strong. (there is an xx12 - Lincoln offers one - is rutile with sodium in the binder - reputedly fiercer more penetrative version of xx13, but never tried it). xx14 is reported to be rutile stick with iron powder, so gives more metal deposit.
The xx (60, 70, etc) is the strength in thousandths of kilo-pounds-force-per-square-inch of strength. So 6010 is a sodium-in-binder cellulosic giving 60000ksi.
Reading the AWS classifications won't give you a clear picture of the types of rods. SMA/ stick welding rods are either
- Rutiles, based on Titania, TiO, which are smooth-running but give lower mechanical properties (strength and impact). Rely on moisture in the flux to give shielding, so don't bake them dry.
- Basics, based on limestone, CaCO3, giving high mechanical properties and the breakdown of CaCO3 into CaO (flux) and CO2 (gas) - the gas gives shielding so the rod doesn't rely on water vapour turning to steam for shielding so can be baked dry
- Cellulosics, based in the plant material cellulose, which gives sky-high hydrogen levels in the arc, making the arc forceful, stiff and penetrative - and leaving very little slag when the cellulose burns-off, so the weld freezes fast and there is little slag to get into the weld root and cause problems in roots and corners - hence these are often used as root-runners. Too dry and the cellulose doesn't survive into the arc, so don't dry these.
Then you can have sodium or potassium in the binder. Sodium certainly in cellulosics gives a rod which is harsher but won't run on AC. Sodium is associated with harsh burn across all rods. Potassium gives a smoother arc (?) and can be run with AC, certainly with cellulosics.
Furthermore, you can add iron powder to the flux, so you deposit more metal per pass...
Then you can choose how thick a flux you have. A thick flux will make for the ability to melt through some oxides, primers and so on - just by being hot under the flux layer. But you don't want lots of flux/slag around if you are root-running...
So there is the reality of how you really formulate your welding rods.
For example:
"Straight" Rutile potassium rods exist, but give a very unpenetrating though smooth arc. One brand here in Britain is called "Satinex". You use it for capping passes. Very smooth finish, as the name would have you imagine. Never use it for the first run fillet corner. You will get a big lack-of-fusion corner defect. What you actually use for most welding with a "rutile" is a rutile-cellulose, with about 3% cellulose. Gives it a bit of bite. The packet will be marked "rutile-cellulose", but the AWS classification will be unhelpful - it will say 6013, just as will a straight rutile capping rod.
So get to know your welding supplier... There's rods for purposes.
Would have thought that for "mild steel" (low strength unhardened and unhardenable) that any 60xx would be just fine. Forget about high and low hydrogen - it is irrelevant for unhardenable steel at the thicknesses amateurs meet. Choose cellulosic if you want penetration. Choose rutile for smooth easy-to-run welds. Experts correct me on that if called for...
Richard Smith