PWHT-HEAT INPUT

[JATE]

hello
When i have a WPS than indicate than welding should be PWHT , the control of the HEAT INPUT IN THE WELDING is unnecessary, that is true?

Thanks for your help

Juan

 

[metengr]

No, it is false. For a WPS, the maximum interpass temperature controls heat input regardless of PWHT.

 

[CWEng]

Heat input control (energy per inch of weld) is a supplementary essential variable, so is only required when impact testing is mandated. See QW-409.1. There is also a relationship to PWHT. If the PWHT is above the upper critical temperature, or a solution anneal for austenitic or duplex material, then it does relieve the requirement to limit heat input to that qualified.

 

[DekDee]

metengr,
What does interpass temperature have to do with heat input ?
Heat input is the relationship between amps, volts and travel speed.
Regards,
Shane

 

[metengr]

Maximum interpass temperate indirectly controls the amount of heat input introduced into the weld during welding and is an essential parameter because it is listed on the WPS. Measurement of heat input or rate using travel speed, volts and current is a supplementary essential variable.
Two different concepts. Neither of which relates to the need for PWHT.

 

[pradipgoswami]

Hi Juan,
The "control of heat input criteria" depends on what grade of steel being welded and what's the notch toughness requirement is asked for. Conventional PWHT such as Stress Relieving below Lower Critical Temperature relieves residual stresses, does not cause significant refinement of grain structures(Weld & HAZ). Hence some judicious control of heat input irrespective of PWHT is always desired.

Pradip Goswami,P.Eng.IWE
Welding & Metallurgical Specialist
Ontario,Canada.
ca.linkedin.com/pub/pradip-goswami/5/985/299

 

[weldstan]

Regardless of whether or not PWHT is required, heat input controls are required when impact testing is required. Heat input controls are not required if impact testing is not required.

 

[JATE]

thanks
Thank you all for your time, metengr ,CWEng,DekDee, weldstan and pradipgoswami.

Juan