Weathering grade steel, sometimes known as Cor-Ten® is not new, having been extensively used for over half a century.  However, increasing drivers for sustainability, economy, safety and aesthetics, combined with improved availability in a variety of structural forms, are making it the sought-after material of the 2020’s. It’s no accident that we are seeing increased interest in our Celsius^® Weathering Grade hollow sections.

Weathering grade steel forms a dense patina when exposed to successive wet-dry cycles. This rusty patina effectively forms a barrier, preventing further corrosion of the underlying steel. Structures made from weathering grade steel need no further corrosion protection, such as galvanising or painting and can have extended lifetimes over 50 or even 100 years with virtually no maintenance.

The lack of any requirement for further corrosion protection has obvious cost benefits as well as minimising environmental impact, while the extended lifetime of weathering grade structures improves their lifecycle impact. The lack of maintenance requirement can also be a significant factor in their popularity, keeping maintenance workers away from dangerous situations.

Weathering grade steel has been used for many landmark structures over the years, such as the famous Angel of the North sculpture by Antony Gormley. But we are seeing increasing use of this now in smaller structures and in particular in bridges and gantries. This is, at least in part, due to increased availability.

For a long time, weathering grade steel was most widely available in plate form. Large structures such as road bridges often use fabricated-plate girders and so weathering grade steel was easily adopted for such structures. However, for smaller structures such as footbridges, the usual construction method would more likely be a truss-type structure, often using structural hollow sections. While it is usually feasible to fabricate box-sections from plate, it is costly and has historically prevented use of weathering grade steel in structures like this.

In 2019, we expanded our range of Celsius^® true hot finished hollow sections to be available in a weathering grade steel. This unique combination of weathering grade steel with all the benefits of fully normalized hollow sections opens up a whole new world of economic design possibilities.

Since we launched Celsius^® Weathering Grade, we have seen huge interest in this unique product. Over the last two years, and through discussion with many engineers and fabricators, we have seen our product used in many different types of structures.

In some cases, our Celsius^® Weathering Grade hollow sections are used in large structures such as the award-winning Camp Adventure tower in Denmark which really showcases the product, while at the same time blending naturally into the woodland. At the other end of the spectrum, we have seen a lot of interest in mid-span structures such as footbridges.

There are over 300 unique cross-sectional sizes available in the Celsius^® Weathering Grade range. While each of these could have its place, we have found that there is a core of sizes which are particularly useful in smaller structures. At the same time, these smaller structures generally require smaller amounts of each size and so we have recently introduced our Enhanced Availability offering on a select range of sizes.

Our Enhanced Availability offering is available across a range of square and rectangular section sizes in the Celsius^® Weathering Grade range. The sizes in this range have been specially selected to not only be popular, but to give a good range of structural capability for small-to-mid size structures such as footbridges.

The 18 Enhanced Availability sizes of Celsius^® Weathering Grade cover the range from 60x60x6.3mm to 300x300x16mm for squares and 80x40x6.3mm to 400x200x16mm for rectangular hollow sections. Depending on the size and our production route, they are available with minimum order quantities between 1.0 tonnes and 5 tonnes. In some cases, this is equivalent to as little as four 12m lengths.

The full range of over 300 sizes of Celsius^® Weathering Grade is still available from rollings, with minimum quantities between 15t and 30t, depending on the production route, but we are sure that the Enhanced Availability range will prove particularly popular and will satisfy many requirements. Utilising these sizes at an early stage in engineering design will help to ensure availability in the right quantities when it comes to fabrication.

With this range of true hot finished, weathering grade hollow sections now available in small quantities, designing small-to-mid-sized structures using this material just got a whole lot easier!

Full details of Celsius^® Weathering Grade, including the Enhanced Availability sizes, are available in our new, updated datasheet which can be downloaded here.

To learn more about sustainable structural steel design you may be interested in booking the new Sustainable Structural Hollow Sections CPD

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