Uddeholms Aktiebolag

Lars A Norstrom

A steel with good weldability and hardenability, a yield point of at least 600 MPa, a rupture limit of at least 900 MPa at room temperature and an impact toughness of at least 40 Joule at -20.degree. C., has the following chemical composition as % by weight: C: 0.03-0.07 Si: 0.10-1 Mn: 1.2-2.5 Cr: 1.8-3 Ni: 1.5-3 Mo: max 0.5 Nb, V, Ti total 0-0.10 with the remainder mainly only iron and impurities in normal amounts. The best impact toughness in achieved when the ratio Mn/Cr is about 2/3 or 0.6. The total content of Mn+Cr is, in accordance with a preferred embodiment, between 3 and 5, suitably between 3.5 and 4.5%. The steel is particularly suitable for anchor chains for e.g. off-shore oil drilling platforms. A recommended heat treatment after welding includes normalizing at 800.degree.-1000.degree. C., cooling to room temperature and duplex annealing.

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Hagfors, Sweden

Lars A Norstrom