In this paper we describe some practical experiences concerning the fabrication of duplex and superduplex vesselheads.

Hot forming of duplex stainless steel. A new production procedure for hot forming of duplex stainless steel vesselheads where heating and cooling rates are the key factors. The major item of the paper will be based on investigations into a new production procedure for DSS vesselheads. We have investigated the key factors for hot pressing for top-quality DSS vesselheads. It is a method of hot forming followed by immediate water cooling which ensures high-quality products and deletes the necessity for a separate final heat treatment.

Repair on repair. Determination of the influence of multiple repair welding on mechanical properties and corrosion resistance. We have encountered this problem in the rules which forbids to perform a repair on repair welding procedure.

Heat treatment after cold forming. Different design codes instruct fabricators to order DSS vesselheads in different ways. Some codes instruct you to perform a final heat treatment, some codes do not have this requirement. We have done some research on the corrosion resistance of cold formed vesselheads in the different areas. Results will be shown to give the fabricators some idea about the possible risks.

Who is afraid of sigma phase? It is not commonly known that during heating up the product will be in sigma phase zone for a certain time. We will show some results of heat treatments which caused sigma phase. The minimum temperatures and soaking time to resolve this sigma phase again are discussed. We will highlight the risks of temperature measurement and the need of calibrating the furnace and thermocouples.