FCTM Esope

S3.3 - COMPREHENSIVE CHARACTERIZATION ON 9CR-1MO-V ALLOY STEEL FOR PETROCHEMICAL PRESSURE EQUIPMENT

6 oct. 2021 | 14:00 - 14:30

Long Métrage

Description

9Cr-1Mo-V alloy steel has been developed around the 70’ to be adopted mainly for power plant pressure equipment. Since then P91 and its variants such as P92 are operating safely in the TPI approved creep range. In the 90’ a further development has been carried out, aimed to the possibility to use such material also for refinery process plant, in this case an increase of the design temperature would be considered for pressure equipment in this sector. However, such event didn’t occur leading to consider not useful to use this material in lieu of the 2¼Cr-1Mo-¼V alloy, actually largely adopted. Furthermore, more recent interest has been noted toward the petrochemical sector with chemical products obtained by high temperature cracking process (range 550 to 600°C). In this case the use of 9Cr-1Mo-V could be a preferred solution due to its high allowable stresses over the standard 2¼Cr-1Mo, being the V modified version limited by the ASME code to 482°C max In this paper it will be presented a very comprehensive data reporting the behaviour of both base metal and weld metal mechanical properties. Among other tests, potential embrittlement behaviour of both base and weld material has been also investigated. Since sometimes the inherent corrosion (oxidation) resistance of 9Cr-1Mo-V alloy is not considered fully adequate, the necessity of a stainless steel corrosion resistance weld overlay, has been also verified. Stainless steel type 308 ESW process single layer weld overlay has been selected to verify its behaviour while subjected to the severe PWHT condition and high service temperature foreseen for this alloy steel. The inherent tests results will be shown.

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