QW-193 - Base metal representing cladding material

[Genetix]

Dear everyone,

Qw-193 specify - "The cladding may be represented by the base material of essentially equivalent chemical composition to the cladding composition.essentially equivalent chemical composition"

The question is how to confirm if cladding material chemical composition is essentially equivalent to base material.

Thank you.

 

[SJmetallurgist]

As such, ASME Sec IX is concerned with 'essential' elements in regards with weldability of the material. However, in terms of weld overlay there are evident concerns of dilution of weldment, which is a prominent factor of -
1. the welding process being used
2. the chemistry of base metal.

Main purpose of performing weld overlay is to get a certain thickness of undiluted chemistry from the top of the overlay. Any 'significant' change in base metal chemistry will certainly affect the dilution in barrier layer and subsequent pass.

This is not to be confused with P nos. assigned by this section. For an example, if your production base metal os SS304, then use of SS-316 for qualification of weld overlay procedure will affect the dilution of barrier layer more than the use of SS321 for qualification purposes, eventhough SS304, SS316 & SS321 belong to the same P no.
For this reason code has left this to the conscious Engineering judgement of the perfmormer and reviewer to select a material best suited for application. Let me know if I can be of further help.

Cheers!
Shashank Jain

 

[metengr]

The concept is that Section IX allows for wrought material of similar composition to the clad material used for a tube to tubesheet groove or seal weld to qualify a WPS. So, I have a piece of Inconel 625 plate and the tubesheet is clad with 625 weld metal, I can qualify a WPS for tube to tubesheet welding using the wrought 625 because it is equivalent to 625 weld metal versus having a clad tube sheet with 625 weld metal on carbon steel.