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[MW:1295] RE: 1294] max. Heat Input on WPS?

By Materials & Welding
  -----Original Message-----
From: materials-welding@googlegroups.com [mailto:materials-welding@googlegroups.com]On Behalf Of PREM SHANKARDUTT NAUTIYAL
Sent: Tuesday, November 11, 2008 3:25 PM
To: materials-welding@googlegroups.com
Subject: [MW:1294] max. Heat Input on WPS?
Dear friends
How do we specify heat input requirements for a particular process / material as per ASME Sec IX. 
it depends on supporting PQR, any increase over PQR value requires new qualification, essential when impact testing is required for base material,
there is exception when PWHT temp is above upper transformation temp.
 
 Now i have seen many clients specifying max. heat input as 2KJ/mm for Carbon steel welding. Some clients like BHAVINI / NPCIL specify max. heat input as 1200 J/mm for stainless TIG welding. 
when you require to follow the predefined HI as in the above case, it can be done by faster speeds (normally I select the welders who can weld faster and bigger dia pipes for qualification) 
DO we have to put this heat input requirement on the WPS as per ASME Sec.IX if the construction code calls for impact testing ?? If there is impact testing involved then heat input becomes an supplementary essential variable, then how do we specify the max.heat input on the preliminary WPS before conducting the PQR ?? 
Normally in PWPS specify only when we have restriction by contract specification, or you can put assumed value based on ur past experience (we know the theoretical values of A,V,S). otherwise it will be as per the supporting PQR.
yes we need to specify on the WPS based on the supporting PQR (QW409.1) 
Are there any guidelines / thumbrule / literature available ? 
thumb rule is select the welder who can weld faster and in case of pipes select larger dia pipe, so that welder can manipulate with higher travel speeds. 
How to calculate the optimum heat input requirement for various materials like Carbon steel , LAS, Stainless steel ( i am not talking about basic formula HI=V*I*60/Travel speed)
Even I have never thought of this, probably you can refer all ur company existing PQR's and calculate/summarize/tabulate the HI for deferent materials.
you may get some idea what is optimum for deferent materials (of course it depends on thickness too, that's why a restriction in QW403.6)  
Please share ur valuable advice / experience .
it also depends on preheat temperature (u may preheat to get less HI and fine grain structure), higher the HI coarser the micro grain structure. 
Regards

Prem Nautiyal
Godrej, Mumbai
PREM S NAUTIYAL
CELL : 9820313278


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