I have a doubt regarding PWHT requirement of SS316 Clad Vessel.Does PWHT of cladded vessel will result in lowering corrosion resistance of SS316 alloy because of it's sensitisation?
The PWHT temperature of carbon steel is indeed in the worst range for sensitization of stainless steel. However, it takes time to sensitize the SS, which depends on the carbon content. Figure 4 of the following document gives a set of curves for 304, which is simliar to 316. 10 hours to sensitization with 0.030%C and 100 hours with 0.019%C.
There should be a WPS that gives the welding prematures and a PQR that shows the weld gives the expected results. If you have these you have no argument, if not, then there should be no welding!
Post weld heat treatment used in case of low alloy and carbon steel material. PWHT does not applied in case of using high alloy steel like material ST. ST. 316 cause the elongation value which used in calculations using part UHA is higher than 20 % not like the value which used in carbon steel from UCS. 5 %.
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PWHT of SS 316 Clad Vessel 
Re: PWHT of SS 316 Clad Vessel
