[python] Re: Python Birdcage travelling

  • From: "gregoryandronaco ." <gregory.andronaco@xxxxxxxxx>
  • To: python@xxxxxxxxxxxxx
  • Date: Wed, 8 Oct 2014 03:55:22 -0600

Depends on the "black" steel.  a 4130 type CrMo steel is much better to
back purge.  Also proper filler material is important with a 4130CrMo.
Common practice is an ER80S-D2 filler wire.  ER70S-2 is a more common
acceptable alternative yet gives a slightly weaker weld joint.  Yet with
proper joint design, like a cluster or gusset, the cross sectional area and
linear weld length compensate.  Best practice is a full penetration weld to
eliminate stress risers on the inside of the tubing.  When full
penetrating, an inert purge gas is recommended to minimize oxidation.  Also
best practice is a slight pre-heat to drive water out of the system
minimizing hydrogen embrittlement.  With GTAW (tig welding), a post heat
treatment to stress relieve the weld area and heat affected zone is also
recommended.  This can be accomplished with an oxyacetylene torch, gently
heating to dull cherry red and cooling off slowly.  More professional parts
are heat treated in an oven.  When oxyacetylene welding 4130 CrMo tubing,
this post heat treatment is not necessary as the system gets so hot it
generally stress relieves and normalizes itself.  Many light aircraft
structures are still welded with this process.

On Wed, Oct 8, 2014 at 1:17 AM, Steffen R <big.skangster@xxxxxxxxx> wrote:

> Hey Marek,
>
> 'Formierung' is normally only used for stainless steels or titanium.
> Aluminium and black steel can be welded without.
>
> Cheers,
> Steffen
>
> 2014-10-07 22:30 GMT+02:00 Serge Prinz <prinz_serge@xxxxxxx>:
>
>> Hallo Marek,
>>
>> No, i didn't.
>>
>> Greetings from EastBelgium
>>
>> Serge
>>
>> Le 07/10/14 19:40, bnmm@xxxxxxx a écrit :
>>
>>> Serge,
>>>
>>>
>>> I see that your beautiful bike is tig welded--did you back purge the
>>> weld, too? ie did you protect both sides of the tubing with argon? (the
>>> German term is formieren)
>>>
>>>
>>> Cheers,
>>> Marek
>>>
>>>
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