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Participant

Join Date: Mar 2010
Posts: 1

welding

03/27/2010 9:33 AM

is it necessary to pre and post heat pipes before welding?

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Anonymous Poster
#1

Re: welding

03/27/2010 9:51 AM

depending on material and thickness. But is is rare under normal circumstances. Except some rare occasions, no preheating has ever been necessiated in my career. And post heating - unlss you call burning the pipes in furnace to remove the residues before solvent clean/pickling as post heat, never.

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Guru

Join Date: Jul 2006
Location: "Dancing over the abyss."
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#2

Re: welding

03/27/2010 10:31 AM

Presuming you are talking about steel pipes.

http://pmpaspeakingofprecision.com/2009/12/29/carbon-equivalent-and-weldability/

milo

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Guru
Hobbies - DIY Welding - New Member

Join Date: Apr 2008
Location: Bristol, Tennessee
Posts: 1176
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#3

Re: welding

03/28/2010 2:45 PM

It depends upon the alloy of the pipe, and the temperature of the site. They had to preheat the Alaska pipeline to get the metal to a safe welding temp. If a weld cools too quickly, it could crack. A post heat would allow the stresses to relax in a more uniform nature. Soft metals don't care too much, hard, or brittle metals, like cast iron, require a lot of experienced technique.

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mike k
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