Miilux Oy to supply HY-100 steel for Turkey's MILDEN-class submarines

Miilux Oy HY-100 steel. (Janes/Prathamesh Karle)

Miilux Oy will produce and supply high-yield HY-100 steel for Turkey's MILDEN-class submarines, a company official told Janes at the 16th International Defence Industry Fair (IDEF) held from 25 to 28 July in Istanbul.

A contract to supply HY-100 steel for Turkey's national submarine project MILDEN was signed with the Turkish Navy in 2022, and a sample of the steel was delivered to the navy in May 2023, the official added. The steel will also be used in the manufacturing of frames for the pressure hull of the submarine.

Miilux Oy, a Finnish company specialised in the production of heat treatment steel, was acquired by Turkey's Ministry of National Defense-managed Oyak Group in 2019.

Steel plates (the raw material) are sourced from Oyak Group subsidiary Eregli Demir ve Çelik Fabrikaları (Erdemir). The steel then undergoes heat treatment and further processing at Miilux Oy's facility to produce the high-yield HY-100 steel, which has a thickness between 15 and 60 mm. The company has also produced a model of HY-80 steel and its research and development team are currently working to produce HY-130 steel that has a yield strength higher than the HY-100.

HY-100 steel has a minimum yield strength of 100 ksi and hence has found several applications including military use. It features high impact strength, weldability, and pressure integrity making it an ideal material for submarine's pressure hulls as they face high pressure at increasing depths.