A while back I posted a thread about fillet welding. Having followed people's suggestions about technique (Roy, Grant, Randy, Don and a few others) I found I was getting neat but weak welds. Gunner suggested using 6011 electrodes instead of 6013. After much searching I tracked down an 11 lb box of 1/8" 6011. No one seems to stock it in this area, which was no doubt how I ended up with 6013. The place I got my welder from only keeps 6013. The place where I found some just had one box in stock, which I bought.
Soon afterwards I was helping a friend build a large crossbow. He wanted a ring welding to a piece of flat bar to create an anchor point. Tried with 6013. Useless: one big slag inclusion with a little metal deposited down each side. I guess there is a lot of opportunity for a slag inclusion here as there's a deep crevice where the round section rests against the flat bar. So I got out the 6011. Got the job done nicely, but striking the arc seemed hard. Here's a picture of the ring:
Last night I had chance to experiment properly with the 6011. It was a bitterly cold night here in England! I put the heater on, but had to keep the shed door open to let the fumes escape. I noticed it said "AC min. 70 V" on the box. I was running on 50 V before, so I switched over to 80 V. No problem striking the arc now. I welded some fillets on 1/8" mild steel, starting at 120 A. On the 50 V setting 115 A was a little low, and 145 A too high. Now here's something I don't understand. If I switch from 50 V to 80 V, but keep the same current setting, does the arc dissipate 8/5 as much power? Or does the voltage across the arc drop to a similar value in both cases (perhaps 25 V) as soon as the arc is struck? I believe my welding set uses a tapped inductor to control current. But I'm not familiar with the electrical characteristics of the welding arc, so I haven't yet figured out how it works. If anyone knows of a site which explains how welding current controllers work, or is willing to explain, I'd be most interested to know.120 A seemed a bit hot. It caused small undercuts and large areas of the metal were red hot after welding. Also, the tip of the electrode was glowing red when I lifted the mask. I remember someone (perhaps Roy) saying that this is a clear sign that you're using too much current, so I turned it down. 110 A still seemed a bit hot, but 100 A perfect. 90 A was too low. I used maybe 10 or 12 rods practising at 100 A. I had no problems with slag inclusions, and could lay a reasonably neat bead. But I couldn't get as neat a bead as I could with 6013. I've read that this is a characteristic of the rod. Is this true? I found restarts somewhat harder than I did using 6013. The arc seemer brighter and the rate of deposition faster, so I found it hard to see the solidified weld pool. They weren't too messy, though. Here's a picture of one of my fillets:
I also tried the drag rod technique with 6011. It didn't work at all. The bead was rough, the rod stuck, and the weld metal ended up on one side. I also noticed this weird jet of flame emerging between the rod and the deposited metal. I assume 6011 just isn't meant for the drag rod technique. Next I made a 2" long test piece and attempted to break it. Here's a picture of the piece:
I bent it back and forth using a mole wrench (vise grips) and counted the number of complete cycles of bending required to break it. It took four complete cycles and the parent metal broke rather than the weld. This is fewer cycles that it took with some of my earlier test pieces, but I think the amplitude of bending was greater, so fatigue probably set in earlier. I was pretty happy because the weld proved stronger than the parent metal. 6011 does appear to give a much stronger weld than6013, even if it looks uglier. Here's a picture of the broken test piece:
I've wondered recently if I need another welder. At 50 V (AC) my welder offers the following current settings: 65, 90, 115, 145, 165, 180 A. At80 V (AC) it offers 30, 40, 50, 60, 70, 80, 90, 100, 110, 120 A. I've been finding that the current control on the 50 V range is a bit coarse. I didn't used to find this, but maybe I'm noticing it because I'm getting better at welding. Soon I'm going to be using 1/4" mild steel (both plate and sections) for a project. If I weld using 6011 at 80 V, do you think 120 A is enough? I'm guessing that it is if I grind a chamfer on the edges, but I'm not sure. Any thoughts?
Thanks for all the advice!