alloy 800ht

[berrojalbiz]

hi,

we have to weld some pipes in this material, with pwht , in my opinion with 875ºc 3 hours is good what do you think?

thaks

 

[metengr]

There is no post weld heat treatment required for this material.

 

[berrojalbiz]

in the new revision of asme VIII is not necessary??

 

[metengr]

No. The only requirement for solution treatment is after post bending not welding.

 

[berrojalbiz]

and stress relief?

 

[metengr]

berrojalbiz;
I am going to correct myself here, per ASME Section VIII, Div 1, UNF-56, 1 (e)

for Incoloy 800,800H, 800HT, these alloys will be subject to PWHT if they are in service above 1000 deg F.

PWHT min 885 deg C for 1.5 hours for thickness up to 1".

If you meet the conditions above, it must be 885 deg C minimum.

Alos, for welding bellows (thin section material), the PWHT does NOT apply.

 

[berrojalbiz]

operation service is above 1000ºF is the outlet of a hydrogen reformer , the design in the planes said that only need pwht in trunions 875ºC for 3 hours why?? i don´t understand it it could be because of stress concentrations in those points??

thanks a lot

 

[metengr]

berrojalbiz;
If you review the technical data sheet on Alloy 800H/HT by Special Metals, post fabrication strain is either from cold work or from welding (residual stresses). Stress relief is accomplished by the thermal treatment as mentioned above.

http://www.specialmetals.com/products/incoloyalloy800h&ht.php

Review page 10.

 

[moltenmetal]

If this piping is indeed in a steam reformer, the piping will be operating well above 1000 F- in fact, perhaps even above your proposed 885 C PWHT temperature...Does that perhaps help you understand?

 

[berrojalbiz]

yes because if in service is above this temperature we will do the treatment in service .......???

 

[ijzer]

Alloy 800Ht is succeptable to relaxation cracking when subjected to secondary stresses at temperatures 1000-1400°F.
For that reason ASME VIII requires PWHT if operating above 1000°F

 

[moltenmetal]

The process is bend/weld, heat treat, then inspect for cracking that might have occurred after your piping went through its first operational thermal cycle. Much better to find cracks now rather than during commissioning!