SAF 2707 UNS S32707 HD Hyper-duplex Stainless Steel Seamless Pipe for Heat Exchangers

Description

SAF 270UNS S32707 HD Hyper-duplex Stainless Steel Seamless Pipe for Heat Exchangers

With a nominal PRE (%Cr + 3.3%Mo+16%N) of 49, the new grade 2707 HD has significantly improved corrosion resistance in chloride solutions compared with currently super duplex stainless steels (e.g. F53, UNS S32750) and the 6Mo austenitic stainless steels (e.g. 254SMO, UNS S31254). This makes SAF 2707 HD particularly interesting for use in applications involving hot seawater. Compared with the current super-duplex grades, SAF 2707 HD also extends safe operating conditions in a number of other chloride containing acidic environments, e.g. in critical heat exchangers in oil refineries. Some references for SAF 2707 HD in industrial heat exchanger applications are highlighted. 

Since their introduction more than 15 years ago, super-duplex stainless steels, such as UNS S32750, S32760 and S32520, have found widespread use in industries such as oil and gas, petrochemical and chemical processing. Their popularity is attributed to an attractive combination of high corrosion resistance, excellent mechanical properties and also a relatively low cost compared to other higher performance materials, such as super austenitic stainless steels and Ni-based alloys.

Despite a very broad range of applications for superduplex stainless steels, there are areas where the corrosion resistance of these grades is insufficient for a long service life, and where more expensive materials, with even higher corrosion resistance, are needed.

As an example, the corrosion resistance for different duplex stainless steels in seawater applications has been much discussed during the last decade, and even though the existing super-duplex stainless steels do not corrode in seawater at lower temperatures, they have some limits in higher temperature service. There was a clear desire, therefore, for new grades with a higher corrosion resistance than was available from existing super-duplex stainless steels.

To that end, SAF 2707 HD was developed. In addition to a high chloride corrosion resistance, it also offers increased mechanical properties over e.g. SAF 2507 (UNS S32750). The improved corrosion resistance extends the use of duplex stainless steels in aggressive chloride environments, such as in hot tropical seawater.

With the high costs often associated with maintenance, and the desire to prolong the periods between planned inspections, increased reliability is a key factor in lowering overall life cycle costs. The selected materials of construction need to withstand the often variable service conditions experienced, and to perform also in cases of shorter periods of non-stable operating conditions. With this background, a further development of the super-duplex stainless steels has been a natural step in order to meet the current and future industry demands for economical, high performance materials.

Advantages

 • SAF 2707 HD has excellent resistance to pitting and crevice corrosion in chloride containing environments, as well as to chloride induced stress corrosion cracking. SAF 2707 HD also shows very good results against general corrosion in organic acids.

• The mechanical properties of SAF 2707 HD are high. The high yield strength may give design and cost advantages compared to other high performance materials.

• The weldability of SAF 2707 HD is good.

• The excellent corrosion performance of SAF 2707 HD has been verified in a number of process plant heat exchanger installations.