Welding Tips and Tricks

I performed an experiment with stainless pipe (sch 80):

Problem: Stainless pipe can get too hot which leads too poor weld quality
I attempted to provide a heat sink by wrapping braided copper wire around the pipe , on each side of weld. I wrapped the copper wire around the pipe twice, with the copper positioned 1 1/2" from each side of the weld. The copper wire was from a 2/0 welding lead (insulation stripped off).

What made me think of this? Well, when welding stainless plate, copper bar stock can be clamped next to the weld in order to provide a heat sink--Jody does this in one of his videos and I was taught to do this in welding school. So I reasoned that this would also work with stainless pipe. But it didn't, the weld zone was actually 115F hotter with the copper vs without copper.
Methods:
I used an infrared heat thermometer to record the starting and ending temperatures. Each start temp was the same (90F). The pipe was in a turntable which rotated the pipe (horizontally) at about 1 revolution/min. I used a stop watch and heated the pipe with a TIG torch at 100 amps for 4 min. I did not add filler wire, just heated the pipe. Each test was identical except for the copper wraps (one with copper and one without copper).

Results:
With copper wraps: the start temp was 90F--end temp was 355F
Without copper wraps: the start temp was 90F--end temp was 240F

Can anyone explain these results? I expected the opposite results.

The copper wire, with lots of surface area above the pipe, was capturing a ton of radiant heat from the arc, and transmitting some of it into the pipe.

A method I have available at work (though I've not used it), is a spray cooling-gel made specifically for this purpose. It's designed to protect valves, sensors, and other items near the weld zone that are impratical to disassemble. The idea is to mask the immediate weld zone, then spray a medium coat for a couple inches either side of the weld, remove the mask, and weld. It can also be sprayed post-weld for rapid cooling.

Here's an example, with explanations of it's use as both a heat-shield for stuff near your weld, and a heat-sink for what your welding:

http://www.dytecservices.com/page944785.htm

Kimball-Midwest (and likely others) offer it in an aeorsol can, but this is what I found in a quick search:

https://kimballmidwest.com/Catalog/Cata ... 3.242.2275

Steve S

good info,
thanks

you can also get heat sink putty, sheet guys use it for bodywork from time to time, but I don't know offhand where they get it from.

Why cant you get a 1 or 2 inch wide piece of copper thats long enough to wrap around the pipe a few times.
If you wrap it tight enough it should function as a single piece?

I don't know a lot about welding, so I wouldn't bank on my idea, but might not hurt to test it.

Wlhb.

Since I am assuming you are talking about austenitic stainless steel (example: 304, 316, etc.), you might consider locating tubing onto your pipes and circulate a liquid or gas coolant. And/or, after the hot pass is in, you could also pass a coolant (liquid or gas) through the bore of the piping too.

Alexa