Walking the Cup TIG Pipe

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This page is all about walking the cup on 3" pipe.

The pipe is 3" carbon steel schedule 40 and the flange is stainless steel.

I like to freehand the root pass using a TIG finger because I use a forward and back technique a lot. 

But after the root pass, cup walking is often the best and quickest way to weld pipe.

I know I say this a lot but walking the cup is like rolling a 55 gallon drum across a shop floor.

If you have ever done that, then you know exactly what I am talking about.

If not, then hopefully the video explains it for you.

Walking the cup on the hot pass

Once you get the root welded in its time for the hot pass.

Even though we call it a "hot pass" it is not always welded hotter than the root but sometimes a few more amps is called for.

I welded the root at 95 amps and the hot pass, fill pass, and cap at 105 amps.

In most situations, the main goal of the hot pass is to not screw up the root pass.

That means not melting thru so you want to move pretty quickly across the middle of the hot pass and keep your travel speed pretty fast.

And for stainless steel welds, keep purge going for the hot pass...and maybe even the next pass just in case.

Fill Pass

I switched to a #8 cup and used about 20 cfh of argon for the first fill pass after the hot pass.

On a schedule 40 3" pipe, sometimes you can cap right after the hot pass and sometimes you need a fill pass.

Either way is fine unless there is some procedure specifying how many passes to make.

I like to be pretty much flush before welding the cap so that I dont have to forced feed the puddle.

I used a 1/8" filler rod for the hot pass, fill pass, and the cap.

I think a 5/32" filler rod would have been better for the cap though....but I only had 1/8".

Cap

I let things cool down for 5 minutes or so before the cap.

Still at 105 amps with a #8 cup, I walked the cup on the cap.

I tried to really watch the toes or edges of the weld to make sure I didnt leave any low areas and I was thinking a 5/32" filler rod would really be nice for this.

For Stainless steel pipe welds, the discoloration heat tint wire brushes off easily at a certain temperature range.

just a minute or so after welding, seems to be the best time to wire brush the cover pass...not immediately after welding and not after its completely cooled off either...but after a minute or so.