Welded tube joint (mild steel)

This is a joint which would be found on a typical bicycle. I used a 7/8" hole saw mounted in my milling machine to notch the end of a tube. It fits up against another tube of the same diameter. I TIG welded at about 80 amps with a standard #7 gas cup, 15 cfh argon, 1/16" tungsten and rod.

The tube was originally chromed, but I ground the chrome off prior to welding.

After welding, I ground one side of the weld flat. Is this structurally sound? I don't know.

Improved stainless welds with large gas lens

My new TIG parts just arrived today, and I had to do a quick test. In short, the large gas lens makes a huge difference. Take a look at this beast: #12 cup with "large gas lens" and 1/16 tungsten


I am using the same exact 1/16" thick SS304 sheet metal that I have been practicing with all along:

Compare that weld bead to the pair of beads in my previous post. All settings are exactly the same except for the gas lens. Well, I guess I was using .040" tungsten in the previous post, but that should have helped if anything.


Here's a few more. I've heard that "salmon color" is the best thing a stainless welder can hope for. I changed the flow rate from 10 to 20 CFH going from top to bottom -- not much difference. The bottom bead had a longer post-flow, so the tail of the bead has less purple/blue.

The backsides of these welds are pretty messed up. I'll report about the Solar flux later.

First attemps at TIG welding stainless steel

I've spent most of my TIG welding practice time on aluminum, but have recently started to experiment with stainless steel (all 304 for now). It's difficult! Most welders say that aluminum is the most difficult because it liquefies quickly and has oxide layer problems, but in my opinion, stainless is more difficult because of the shield gas requirements.
Here's my setup:
.040" tungsten -- my local welding shop convinced me to try this instead of 1/16" tungsten. They somehow thought I could weld with less heat while using .040". I didn't understand it when they explained it so me, and I still don't -- especially since it makes no difference that I can tell.

no. 8 cup with gas lens

less than 1/4" stickout




Here's a 1/16" thick 304 sheet. The upper bead was done with 10CFH argon, the lower bead was 20 CFH. The picture shows the front and back of a simple bead with 1/16" filler. I was using as absolutely little heat as possible, sometimes solidifying the weld pool as I moved, making for an irregular bead. These beads both have major problems. They are pretty gray except on the left side where I finshed the weld and the post-flow cooled off the bead. The rest of the weld cooled outside of the gas shield, turning it gray, which is bad because the structure of the stainless steel has been altered. This will likely lead to corrosion or stress cracks.

I prepped the left side of the top surface to see if it would be any different than the un-prepped right side. The metal has a smooth almost plastic-like feel, so I was unsure if this was normal. It didn't seem to make any difference.

The backside shows major problems too. The upper bead looks better because there was more sheet metal all around the weld to soak up excess heat. The lower bead is "sugared" because it got very hot in an oxygen atmosphere. The weld is close to the edge of the sheet metal, so the heat built up more quickly.

To attempt to fix the topside problems, I've ordered a "large gas lens" setup with some huge gas cups from an online welding store. I tried to order these parts at my local welding shop, but they didn't have them, and were somewhat hesitant to even order them for me. I have no idea if the large gas lens will work, but the parts are relatively cheap.

To attempt to fix the backside problems, I've ordered some Solar Flux B, which was originally made for gas welding stainless steel. The alternative to flux is to build an argon purge for the backside of welds. This purge could be a box, a nozzle, or some other device to make sure the backside is flooded with argon. The problem is that every weld situation (tubes, sheet metal, angle, etc, etc) requires a custom purge setup, and argon isn't exactly cheap either. I'll definitely be posting more information about the flux in the coming weeks.


Here's a weld made on thicker (about 1/8") stainless. The grade of stainless is unknown. Don't mind the soot. I was just too lazy to regrind my tungsten after I hit it with the filler rod. Notice the bead is NOT gray. The thick metal is able to pull heat out quickly enough to prevent problems. Unfortunately, most of my stainless welding will be on tanks and tubes that will never be 1/8" thick. I need to find a solution that will work down to .049" at least.

Aluminum welding progress

I ordered a bunch of aluminum parts from eBay and McMaster. I've spent a few afternoons just cutting the metal into random parts and TIG welding it back together


I've made a few coupons to test the five basic weld types:

* Butt
* T-joint
* Open corner
* Lap joint
* Edge

The above picture only shows a T-joint and open corner, since those are my best types.



This pipe doesn't do anything useful, unfortunately. I just made random cuts on my miter saw, rotated the two pieces 180*, then welded them.


I'm still working on getting nice, consistent beads, but they have good penetration, and I'm getting a lot more confident with aluminum.

Aluminum welding progress: T-joint

I ordered a bunch of aluminum bars and cut them into 6" pieces to practice basic welding joints. It's going pretty well. Here's a list of quick tips that I have learned:

1/16" electrods seem good enough to handle almost any task at 150A or less. I'm not yet sure why anyone would use anything bigger or smaller for less than 150A.

The filler rod must be forcibly pushed into the puddle, then quickly retracted. It cannot be brought near the arc slowly, as it will melt before it gets to the puddle! I have found that I move the torch in the direction of the weld to get the base metal molten, then move it backwards slightly while I add filler, then move forwards again. I use this one-step-back, two-steps-forward approach for the entire weld.

The AC balance control can be pretty heavily shifted to DC EN. I usually keep mine at %70 to %80.

It helps to have the part propped up off the table. For the first T-joint that I welded, I had the plat laying flat on my metal table. This makes the angle of the torch more difficult, but worse, it sucks a lot of heat out of the aluminum that is touching the table. This is really a pain, because it makes the weld asymmetric in terms of heat required, and finding the magic torch angle to melt both sides evenly becomes more difficult.

Harbor Freight welding auto-darkening hood

Harbor Freight sells an auto-darkening welding hood (Item# 46092) for about $50 -- depending on the current sale. It is cheaply made (of course), but not ridiculously so, and has proved to be worthwhile to me. However, I had a very unusual problem that I could not find documented anywhere else on the 'net. Hopefully my blog post will help others in my situation.

For the first month I owned my TIG welder, I only welded aluminum. That is the main reason I bought the machine, and I was practicing quite a bit. Eventually I got curious about stainless steel, and switched the machine over to DC and tried some welds. I'll write more about welding stainless in another post, but the first thing that I noticed was that my welding hood flickered badly during the welds. Strangely, at low power arcs (10-20 amps), it was dark all of the time, but when I cranked it up to 150A, the lens would be become clear, and only ocassionally flicker into the dark mode. At the time, I didn't make the connection between using DC mode on the machine and the hood flickering. It had been a week since I last used the machine, and there seemed to be no reason why DC would cause the hood to fail. I also noticed that aiming the hood at a normal fluorescent light would cause it to darken. I thought the thing must be broken.

I took the hood apart and looked at its circuit board: 3 opamp ICs, 2 logic gate ICs, an oscillator, and two ICs that had their numbers scratched off. The board itself is multi-layered with an apparent ground plane on the bottom, so determining the wiring between chips is damn near impossible. I was expecting to find a soldering problem, dead battery, dead solar cell, etc, but all testable components were good. After connecting my oscilloscope and learning a little about how auto-darkening hoods work, I decided to return the thing. I figured one of those unmarked ICs might have fried. Harbor Freight gave me a new hood and tried to sell me a 2-year warranty. When I politely declined, the saleperson smirked and said "I'll sell you another one in 6 months." Gotta love Harbor Freight.

I really expected the new hood to work properly, but alas it flickered in exactly the same manner as the first hood. By this time, I had noticed that the hood worked flawlesly for AC welding, was darkened by fluorescent lights, and even was darkened by me waving my fingers in front of the sensor. It was NOT darkened by pointing it at the sun, or a DC welding arc. So, my conclusion was that the hood only responds to high-frequency changes in light -- not high-intensity changes. Apparently, the DC arc on my inverter welder is so stable, it does not have enough ripple to cause the hood to trigger. The solution: I set the machine to "pulse" at 200 Hz, with the background current %90 of the peak current. The current pulsing is so slight, that it doesn't really affect the weld, but it is enough to reliably trigger the hood.

Everlast 200A TIG welder: welding aluminum

Here's the parameters for AC TIG welding aluminum (about 1/8" thick 6061):

Torch setup:
1/16" ceriated tungsten electrode
#6 gas cup
3/16" of electrode stickout
electrode is ground into a sharp point

Gas:
pure argon at about 7 lpm or 15 cfh (The Chinese regulator reads out in lpm, not cfh !)

Welder:
No pulse
75% electrode negative balance
5 s post-gas
Zero arc force
Max amperage of about 100A

Rod:
4043 1/16" or 3/32"

In order to strike the arc, I usually have to push the pedal pretty far down, sometimes all the way. Having a really clean, sharply-ground electrode, and a really clean metal surface will make striking an arc a lot easier.


Here's some points that I learned from my first few hours playing with the machine:

Arc force: This control is only useful for stick welding, not TIG. I searched the internet for a long time trying to figure out what this control actually does. Here's the best explanation:
http://www.millerwelds.com/education/articles/article108.html This "arc force" control is also called "dig" and describes how forcibly the stick welding arc can push material away. A high arc force setting will boost the arc current when the machine senses the arc voltage is dropping too low (meaning a short-circuit is about to happen). This boosted current blasts away base metal and rod, preventing the stick from welding itself to the base metal. Anyway, I had no idea about this control for the first few sessions that I used the TIG welder, and left it all the way up (50A). I noticed that it made striking the arc much easier. On thick materials, this was not a problem, but on thin stuff, I would blow through the material upon striking the arc. The arc force control is supposed to be enabled only for stick welding, but that is not the case on this machine (super200P). During TIG welding, I assume the voltage is low enough to cause the arc force control to set a "minimum" amperage of 50A, which is why it was a big problem for thin material. For TIG welding, be sure the arc force control is turned all the way down!

AC balance: This machine has a strangely configured balance control. The range is %20 to %80 electrode positive. It's unusual to indicate the electrode positive percentage, and anything over %50 positive is considered not useful at all. I am sure there are crazy situations that require it, but the electrode melts so easily, and the base metal has such a huge etched area at those levels, I can't see it ever being that useful for common operations. So, never set the balance past %50 even though the machine's range makes it seem like it might be a useful thing to do. In fact, having a minimum of %20 electrode positive is still quite a lot. It would be nice if the machine went down to %5 or %10.

Gas flow: The Chinese flow meter is calibrated in liters per minute, not cubic feet per hour. Watch those units! lpm is approximately half of cfh.

Electrodes: No one uses pure tungsten anymore. The information on the web is old, and repeated by people who have never used modern electrodes or modern welders. You can weld all common metals with a ceriated electrode ground to a fine tip. The tip will round-over a little bit during AC welding, but there is no point in "balling" the tip of the electrode. All it does, is make the arc difficult to control.

Pulse feature: I have tried it a few times, but I haven't noticed any big difference in welding ease or speed. I'll try it later, and write more about it.

Finger-tip control: After using the welder for a while with the pedal, I switched to the plasma cutter, and hooked up the finger-tip control switch. It didn't plasma cut. The machine would not strike an arc at all. After futzing for a long time, I hooked up the pedal control (even for plasma cutter), and it started to cut like a dream. I tried the same for the stick welder setting, and it too, required the pedal to be connected in order to weld. It seems the finger-tip control circuit in the welder either died, or never worked properly. Hmmm. I'll bet this has to do with the "background" "max" and "arc force" settings.