X8Ni9 hot-rolled strip for cryogenic applications

Salzgitter Flachstahl has been delivering high Ni-alloyed materials such as X8Ni9 as slabs to Ilsenburger Grobblech GmbH for heavy plate production for several years. In order to expand the possible application areas, X8Ni9 hot-rolled strip was produced in a size of 5.0 x 1,410 mm. The rolling trial ran smoothly and now hot-rolled strips in thicknesses from 3.0 mm are possible after consultation and depending on the width and maximum coil weight.

Salzgitter Mannesmann Line Pipe GmbH in Hamm, Germany processed the hot-rolled strip into HFI-welded pipes measuring 219.1 x 5.0 mm. A subsequent heat treatment allowed specific adjustment of the required product characteristics.

X8Ni9 features a high level of toughness – also at the lowest temperatures. Thanks to these properties, the material is suitable for such uses as tank construction and the transport of LNG (Liquefied Natural Gas). When natural gas is liquefied, the volume drops to 1/600, but this requires cooling to at least -163° C (-261° F). Materials that are employed in this application area must exhibit the required mechanical characteristics, as well as good toughness even at these extremely low temperatures.

The suitability of X8Ni9 steel for HFI-welded line pipes in the temperature range down as far as -196° C (-321° F) (liquid nitrogen) was tested in the framework of a steel casing pipe test line at FW-FERNWÄRME-TECHNIK GmbH in Celle, Germany [1]. The pipes delivered for this test showed toughness exceeding 80 J at -196° C, compared to the minimum 40 J that was required. The yield strength for the heat-treated pipe stood at roughly 600 MPa, which substantially exceeded the required minimum of 490 MPa.

The trial results were consistently positive.  FW-FERNWÄRME-TECHNIK GmbH installed the X8Ni9 pipes delivered by MLP into a three-in-one pipe system, the "FW-KAMMER PIPE".  This was used to build a test line to transport LNG. During the trials the pipe with liquid nitrogen was cooled to an operating temperature of -196° C.

Salzgitter Mannesmann Line Pipe GmbH processed the hot-rolled strip made of X8Ni9 from Salzgitter Flachstahl into HFI-welded pipes and then applied a heat treatment. FW-FERNWÄRME-TECHNIK GmbH in Celle, Germany verified the suitability for the transport of Liquefied Natural Gas (LNG).

In addition to the growing sector for the transport and storage of LNG, however, other applications in the field of refrigeration technology and the chemical industry are conceivable.

With X8Ni9 hot-rolled strip, Salzgitter Flachstahl has succeeded in adding another superior material to its product portfolio.

 
[1] FW-FERNWÄRME-TECHNIK GmbH, Celle, Germany, EFRE Project 80136748, "Product maturity development of a three-in-one pipe system for underground transport of LNG and crude oil/environmentally hazardous products"