On Sat, 31 Dec 2005 01:39:52 +0000 (UTC), Christopher Tidy
wrote:
Hi folks,
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:
http://www.mythic-beasts.com/~cdt22/crossbow_ring.jpg
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.
The lower voltage tap can deliver higher current, as you note. But it
is then less of a "constant current" machine, and it has less
open-circuit voltage. Once an arc is struck with a given size and
type of electrode, the arc determines the voltage for a given
current. 6013 and 7014 are "drag rods" and are easy to strike.
6011 is *not* a drag rod and is less easy to strike, so higher
open-circuit voltage helps. Higher OCV at given current may also
help with 6013 because of the better constant-current characteristic
your welder will exhibit in that setting.
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?
Yes. It isn't as "pretty" a rod as 6013 and 7014.
I found restarts somewhat
harder than I did using 6013.
Yes.
Next I made a 2" long test piece and attempted to break it.
Here's a picture of the piece:
http://www.mythic-beasts.com/~cdt22/fillet_test14.jpg
Not bad at all!
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.
Whatever. Point is, the failure happen in the metal, not at the weld.
I was pretty happy because the weld proved stronger than
the parent metal. 6011 does appear to give a much stronger weld than
6013, even if it looks uglier.
6013 and 7014 can also make strong welds in 1/8", though they run
differently. It's a matter of watching and controlling the puddle.
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. At
80 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.
That could very well be. I bet you'd like a 40 to 225 amp buzzbox
with continuous current control. There is no voltage setting on
those; they're always 80 volts or so OCV. I had some 6011 when I had
such a buzzbox, but I very rarely used it except on really crusty
rusty metal. I could weld everthing I wanted to weld, up to 1/4" and
even 3/8", with 6013. I often ran 7014 on 1/8" and thinner. The
trick is to push the puddle into the joint since those rods have such
fluid puddles. 6011 blasts it in, which is why it doesn't make such
pretty welds.
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?
The "right" current is determined mostly by rod diameter. You
should have no problem doing 1/4" with 1/8" 6011 running at whatever
current it runs well at for you. 120 amps is certainly in the ball
park. In fact, it's about in the middle of the ballpark for 1/8"
sticks.
Weld on, m'man!