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Tig Welding volume 2

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Old 02-08-2008, 02:45 AM   #1
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Here is some more info on tig welding. This is a little bit more in-depth on techniques and positions.

One of the main things about welding is being comfortable while you are welding. Unfortunately this is not always possible. When I am welding in a circle I use a welding turntable, this is a variable speed unit that has a grounding lug on the back of it. It makes it much easier and keeps your hands free. Don't be afraid to use a vise to hold something in a certain position. Deep throat vise grips work well too. It is always best to have your work firmly attached to the table. Sometimes during welding the piece may "jump" due to the current and the grounding. It is both annoying and makes it very hard to weld. Some pieces are heavy enough to weld without this, but if there is only a small contact area to the table then you should clamp it down or ground directly to it.

Following are some ways of keeping your piece immobile:

1) use clamps
2) tack it directly to the table (if it is metal, and it should be!)
3) magnets (warning: using a magnet too close to the weld ca cause arc blow out)

Arc blow out is the arc getting deflected from the area due to a magnetic field on the material. sometimes the metal s magnetized prior to welding. If there is any questions about the material being magnetic or not, demagnitize it.

Always check your welders settings before you start to weld. This is especially important when others use the machine.

Whenever possible, use a test piece of metal to make sure your settings are correct. This is the time to dial in your settings to the thickness and material you are using. I like to keep my setting about 10 - 15 amps above what is needed to get full penetration, this way if you need to stop and start again you have enough current to melt the previous weld. Steel does not need nearly enough heat to melt as aluminum and bronze materials.

Here is a good example of a complete weld setup start to finish:

On Tuesday I had to cut a magnetic level gage apart to make it shorter. It is made from 1-1/4" 316SS tubing, wall thickness is under 1/8". This was my first time doing this procedure on this type of gage so I was a bit nervous. The main eason was because it needs to be very accurate. The tubing needs to be perfectly straight or the float will not be able to move ll the way up through the tubing. The connections need to a specified distance apart within about 1/8" and also need to be on the exact same plane or they will not go into the connections on the tank. Here is a picyre of the gage before I had at it:

In order to keep things aligned during welding I made an insert out of aluminum. This would also serve as a heat sink to keep from melting through and also to keep the weld from penetrating too deep. The ID of the tubing is 1.08" so the slug needed to be very close to this. I used some 1.5" solid aluminum barstock and machined if on our lathe.

Here is a video during machining, thank god for auto feed!:

Here is the piece finished:

I bored and tapped the piece so that it would accept a 1/4-20 rod so I could pull it out after i was done. After machining this piece was completely degreased and washed to make sure there were no contaminants on it.

After cutting the unit apart we machined the ends square on the lathe and also machined a chamfer into each piece. This is important to ensure proper penetration as this gage will be rated for up to 400 PSIG. Proper chamfer angle is about 30.

Prior to beginning welding I made 2 marks on the table 48" apart. after putting the 2 pieces together with the slug I made sure it was square and lined up the fittings on the marks. I then tacked the pieces together to make sure there was no movement in case the unit was bumped or fell. I also degreased and washed the pieces near the welding area inside and out.

I would need to use filler on this weld so to prep the rods it is a good idea to cut them in half, this makes it easier to handle them. During welding I always keep the second piece close and also hand it off the end of the table so it is easy to grab without taking a glove off. Because this is a thin material I decided to use 1/16" electrode and filler rod. I used the cut off piece of tubing as a test piece to dial in the heat. I set the heat about 20 amps higher than needed because I would need to make up the heat lost to the aluminum slug.

Here is a picture of he unit on the table and a full length rod and a rod cut in half, note the mark on the table:

Here is a picture of the unit on the table after being tacked. Note the chamfer on the tube:

On to the welding:

I moved the piece to a vise near the welding area. You can ground directly to the vise, but in this case I grounded to the unit itself, either way would be fine. Rather than attempt to weld all the way around the tube I had to reposition it a few times.

I started the arc at low amperage and heated the area around the chamfer. This is to get the metal ready for welding and also to get some heat into the aluminum. After a few seconds I slowly increased the heat until the 2 pieces fused. I then began moving the puddle adding filler as needed. I actually added more filler than I had to to ensure that there was enough material in the chamfer while moving the puddle. At the end of each weld I wire brushed the area. When I restarted the arc I started about 1/8" on the previous weld and allowed it to become fluid. I then would start to move the puddle and add fitter. I did this 3 times before I was done.

Here is a close up of the weld and the chamfer, the unit is in the vise at this time:

Note the piece has already been wire brushed after the weld was stopped and cooled to make sure there are no contaminants on the surface. It is important to use the same brush for the same materials to avoid cross contamination.

After welding the weld was ground smooth and the tubing was buffed. The unit came out exactly straight and on center.

Here are some pics of the finished product:

Checking to make sure its straight:

Close up of the welded area:

can you tell where it was welded? No the clamp is NOT over the weld.

Unit completely assembled with 2 explosion proof switches for high and low level detection:

As you can see there are a lot of small details that go into welding properly. I didn't need to backfill this unit with shielding gas because of the slug bing in the unit. If this was a freeweld the unit would need to be purged and backfilled with the shielding gas. This is to keep the back end of the weld from getting contaminated by the gases created during welding.




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Last edited by lincolnmetal; 02-08-2008 at 02:49 AM..
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Old 03-02-2008, 06:53 PM   #2
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4 inches of fun, 15 inches of billet, 33 inches of pure run over your crappy minitruck joy. custom seats, column shifter, some other cool stuff
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aluminum, backer, blow out, filler, gas, gtaw, melt, puddle, tig, weld, welding

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