Tubes for the toughest applications
Andreas is keen to tell Stainless Steel World readers about Sanicro® 35, Sandvik’s innovative new alloy, which combines the best features of a superaustenitic stainless steel and a nickel alloy. The grade has excellent corrosion resistance for service in seawater applications and other highly corrosive environments.
“When selecting material for severe applications, normally a choice is made to either select duplex or higher nickel alloys such as alloy 625,” explains Andreas. “But what if you could combine all the desirable properties of these grades into a single material? To achieve this, our R&D team set out with a clear objective; to produce a new grade that bridges the gap between high nickel alloys and duplex, which could be manufactured in any Sandvik mill in the world. The successful result saw Sanicro® 35 launched in August 2020 in heat exchanger and hydraulic and instrumentation (H&I) sizes. We have high expectations that this will be at the same level of innovation as SAF 2507™ was for Sandvik once upon a time.”
The composition of Sanicro® 35 makes it a cost-effective alternative to more expensive alloys, explains Andreas. “In severe applications for heat exchangers where alloy 625 is often specified, for example REAC air coolers, this grade can do the same job at a lower lifetime cost. With just half as much nickel, the material provides excellent resistant to pitting and crevice corrosion as well as stress corrosion cracking, while also being more economical.”
Ongoing heat exchanger trials in different regions are proving the value of the new grade.
H&I tube and fittings trials
Sanicro® 35 is ideal for H&I programs that typically require tubes ranging from 6 to 12 mm (1/4 to ½ inch). “At the same time, we have potential partners trialling the grade to produce small bore fittings which can be used with the tubing to provide a complete package,” explains Andreas. “Ongoing galvanic trials will demonstrate that this tubing can be successfully used with other types of fitting, for example 6Mo, so you don’t have to switch the whole system.” Andreas explains that the vast majority of H&I tubing is specified in 316L, with the remainder being spread over nickel alloys such as alloy 625, 400, duplex, super duplex, 904L, etc. Sanicro® 35 can effectively replace all these grades, eliminating the need for a distributor or supplier to keep multiple products in stock.
“So not only is it more cost effective, it will also streamline the supply chain While it will take some time for this to be implemented, we are working closely with end-users to gain their acceptance of the grade and start integrating it into their standards.”