It has been a requirement that manufacturers of demanding materials; eg. 22Cr and 25Cr duplex stainless steel and 6Mo type stainless steels shall be technically evaluated prior to being accepted as suppliers to Norwegian oil and gas developments. At the start the assessment was carried out without written guidelines or standards. The assessment was carried out at each project and/or persons discretion.

Some improvement was achieved with the issue of NORSOK standard M650, rev. 1, Qualification of Manufacturers of Special Alloys, in 1994. This standard based the qualification mostly on testing and did not clarify responsibilities. Some of the requirements were ambiguous and therefore subject to different interpretations. It was used by some manufacturers to achieve an undeserved quality stamp.

The trend today is that more and more manufacturers want to start manufacturing these special alloys, often having limited knowledge of the materials and with unsatisfactory production facilities.

We have also recently experienced major problems with inferior quality of supplied materials and components resulting in major rejections at high costs. Typical quality problems are low toughness properties, unsatisfactory microstructure and inferior corrosion properties. The certificates in such cases always show satisfactory properties with only limited relevance to the actual properties in the rejected materials.

This recent experience greatly influenced the revision of the NORSOK material standards, which was started in the beginning of 1997.

This paper explains the requirements to be complied with to be qualified for manufacture of special alloys, eg. Duplex steels, 6Mo type steels, superaustenites, etc., according to rev. 2 of NORSOK standard M650. In addition some of the changes pertaining to testing in the revised, rev. 2, of the NORSOK piping material standards will be highlighted.