Cladded Vessels Heat Treatment

You must be having a QAP for such a big job. What that QAP says?

QAP doesnt state the intermediate heat treatment requirement . but its a usual practice in fabrication industries to do a indermediate heattreatment after half forming of heavy thk dishends. hence my question .

Ill ask one more question based on this topic after i will get the answers from you.

There is no written record. In clad plate fabrication you have make compromise between corrosion properties of clad and stress releif of base plates. How ever low temperature stress relieving giving prolonged soaking at temperature 590-595°C gives quite acceptable results.

I had some practicle experience in this regard. One of big vessels made of low alloy steel, was repaired and proper stress relief temperature could not be achieved even with full current of heating elements. Maximum achieved temperature was 585 to 590°C. With prolonged soaking at that temperature, stress reief achived was quite satisfactory.

At this temperature, clad plate material do not require any treatment.

Actually the outcome of all this is in front of me .

We hav two identical jobs of what we were discussing both having top dish-non claded and bott dish -cladded one.

now we hav formed the top dish ned of those job with no issue's.

now second come this cladded dish . both the dish end gets cracked after it started got pressing after heat treatment . and that crack started to originate from the welds and goes well into the dishends .its almost like we hav to patch that particular area of dishend now.( around 1300 mm length of crack occured )

What is the hardness in the HAZ and parent metal. What is the condition of plate before start of forming process (means as rolled, normalised or annealed).

In fact for such jobs QAP are neccesarily required and are made by good manufacturer so that all such conditions are recoreded.