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Special steel Corrodur 4418 Mod for high-performing Well Completion equipment

15th May 2018

In oil and gas exploration and extraction, the materials handling and production systems are constantly subject to corrosion due to contact with acid gases (carbon dioxide and hydrogen sulfides), chlorides at high temperatures.

Completion tool for oil and gas extraction, source: Deutsche Edelstahlwerke / © iStockphoto-mikeuk

In introducing special steel Corrodur 4418 Mod (also known as Super 13 Cr), Deutsche Edelstahlwerke offers a material solution that surpasses the performance of conventional martensitic 13%-Chromium steels. The unique features of the new special steel are its high strength, outstanding toughness as well as good resistance to pitting corrosion and stress corrosion cracking. This makes this special steel ideal to increase the lifecycle of completion tools. Deutsche Edelstahlwerke became one of the first steel producers to achieve qualification by Statoil ASA for the special steel Corrodur 4418 Mod.

In oil and gas exploration the well fluids often contain acidi gases (CO2 and H2S) and chlorides. The hydrogen sulfides reaction with steel components used can in the worst case suffer sulphide stress corrosion cracking. The chlorides present in well fluids are also corrosive, causing pitting corrosion. To limit or prevent the failure of the well equipment, Oil & Gas companies approve only selected materials for use in this demanding environment. In introducing Corrodur 4418 Mod, Deutsche Edelstahlwerke offers a high-grade steel superior in durability to the conventionally used 13%-Chromium steel grades such as 1.4006 (AISI 410) and 1.4021 (AISI 420).

Material modification for specific applications

Corrodur 4418 was modified based on the material properties data suitable for mild sour gas (less than 0.01 bar ppH2S) conditions as defined by leading Oil & Gas companies like Statoil ASA. Employing controlled heat treatment, the steel company belonging to the SCHMOLZ + BICKENBACH Group systematically improved the steel properties. With a tensile strength of at least 862 MPa, a yield strength of at least 758 MPa and ductility (toughness) of at least 68 J at –10 °C, Corrodur 4418 Mod is clearly superior to conventional 13%-Chromium steels. Another feature is the material's excellent resistance to pitting corrosion and stress corrosion cracking. Its high strength gives users more flexibility in the design of components or to improve performance while keeping the same dimensions. Corrodur 4418 Mod is the first stainless steel in this performance class to be recently qualified to NORSOK M650 by Statoil ASA.

Corrodur 4418 Mod is available in the diameters 50 to 216 mm, rolled and peeled. Additional qualification projects with lower hardness and thus higher resistance to stress corrosion cracking are underway. This grade is also described in international standard NACE MR 0175. The range of dimensions covers sizes up to 280 mm in forged and peeled condition.

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