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[TowerTalk] Welding Chrome Moly

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Subject: [TowerTalk] Welding Chrome Moly
From: (Bill Coleman AA4LR)
Date: Fri, 11 Jul 97 10:42:51 -0400
On 7/2/97 8:36 PM, Joe Shuey NE3H at wrote:

>Ken - while welding Chrome Moly is no trick - just use mild steel rod -
>be very careful about doing it, and perhaps consult a professional
>engineer.  I would not use an electric welder to 'run a bead down each
>side' - I would gas weld it, as the temperature transients are much mre
>severe with electric welding. Or .. conversely .. reheat and draw the
>metal after the welding.

This topic is much debated in aviation homebuilding circles: if you MIG 
or TIG weld, do you need to stress relieve the joints after welding? The 
high temperature transients leave minute stresses in the welds which 
could lead to cracking later on.

These stresses can be relieved by heating the joint up to a cherry red 
color (using a gas welding rig) and letting it cool slowly.

The perceived need for this stress relief is the major reason why 
homebuilders opting to weld their own aircraft use oxy-acetalyne welding. 
(Otherwise, you'd need BOTH a MIG or TIG welder and an oxy-acetalyne rig 
to do the stress relief)

The real irony is that most aircraft factories that produced steel-tube 
aircraft (Piper, et al) used TIG welding with NO stress relief step. They 
don't seem to have a tremendous problem with stress cracking if a good, 
professional welding job is done.

Bill Coleman, AA4LR, PP-ASEL        Mail:
Quote: "Not in a thousand years will man ever fly!"
            -- Wilbur Wright, 1901

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