Optim 550 W weather resistant structural steels

Tolerances

Tolerances on dimensions and shapes

The thickness, width and length of cut lengths: EN 10051.

The flatness of cut lengths: 3 mm/m maximum.

Cut lengths (i.e. sheets) are delivered with Ruukki’s Dead Flat guarantee, which ensures that residual stresses are low and the flatness is excellent.

Download dimensional and shape tolerances for hot-rolled steels

Surface quality

Cut lengths are delivered in as rolled condition.

Cut lengths can be delivered in a pickled condition, by a separate agreement, on a limited dimensional range.

Properties

Thanks to its advanced properties, the steel promotes environmentally sound construction and sustainable development.

Excellent weather resistance

The anti-corrosion properties of Optim 550 W are much better than those of the ordinary structural steels which are commonly used in many outdoor applications. The enhanced weather resistance is based on the oxide layer, i.e. patina. The elegantly brown patinated surface is architecturally distinguished.

Thanks to the excellent resistance to atmospheric corrosion, there is no need for the additional coatings, such as painting, of steel structures. Therefore, a significant cost advantage can be achieved in applications, where a dark brown patina is desired on the steel surface. However, the steel surface can be colour coated, using the same methods as when painting ordinary steel grades. As a result of the special alloying of the steel, the lifespan of the colour coating is double that of an ordinary steel grade.

Mechanical properties

Optim 550 W is not directly compliant with any standards for structural steels. However, Optim 550 W meets the EN 10149-2 requirements concerning strength and exceeds the standard requirements set for elongation and impact strength.

The yield and tensile strengths are tested longitudinal to the rolling direction, and guaranteed in both the longitudinal and transverse directions. The elongation is tested longitudinal to the rolling direction. The impact strength is tested by the Charpy V test in accordance with EN ISO 148-1:2010. The requirement value, 40 J, refers to tests carried out with 10 x 10 longitudinal standard test pieces. When testing thicknesses under 10 mm, the width of the test pieces corresponds to the strip thickness and the required values decrease in direct relation to the surface area of the test piece. The impact strength is guaranteed both in the longitudinal and transverse directions. No impact tests are carried out for thicknesses less than 6 mm.

Materials testing

Materials testing and sampling are carried out in compliance with EN 10149-1. 

Chemical composition

Content % (ladle analysis)

Processing instructions

Bending properties

For thicknesses between 3 - 8 mm, the minimum inside bending radius for a 90º bend is 0.5 x t, t=thickness.
There are no limitations on bending direction. The springback is about 5 - 8º.

Welding

The weldability is excellent and all conventional welding methods can be used. Preheating is not required.

Carbon equivalent value (CEV)

CEV = C + Mn/6 + (Cr + Mo + V)/5 + (Ni + Cu)/15