Efficient and reliable abrasion resistant steel sheet withstands harsh wear and tear whilst maintaining lasting quality – even in the most demandin
Valast 450® gives customers greater design flexibility.
If you have experience of specifying abrasion resistant (AR) steel, you will likely know by now that it comes in two forms – strip or plate. And, while you may already have a broad understanding of the differences, there can be much more to it than meets the eye.
Strip vs. plate: back to basics
The first thing to know is that steel strip has several names, sometimes being referred to as sheet (because the strip is cut into sheets) or coil (as the strip is rolled into coils) but for the sake of clarity, we will call it strip throughout this article.
Our Valast 450 is a strip product, making use of our state-of-the-art hot strip mill in IJmuiden, The Netherlands, while our main competitors typically offer a plate product.
Valast 450 strip: how it’s made
The hot strip mill that Valast 450 strip is produced on is more than 800m long. A steel slab is heated to 1250°C, is descaled and then enters the first of five roughing and edging stands. These roll the steel slab into a transfer bar that is around 70 m long and 40 mm thick.
It is descaled again, then passes through a seven stand finishing mill, which rolls the strip out further until it reaches a thickness of between 2 -12mm depending on the customer’s requirement, and a length of between 200 to 1200m (depending on the thickness of the strip). Once it passes through the finishing mill, it is cooled from about 900°C to less than 250°C and rolled into a finished coil. This can then be decoiled and cut to the desired length as needed.
How to make plate steel
Steel plate is produced on a reverse plate mill, which is typically only around 60m in length. The steel slab enters a single reverse rolling mill, and passes back and forth through the mill until it reaches the desired thickness. From this point, the plate is repeatedly heated and then cooled using water (quenched) and air (tempered). This results in plates of steel of fixed dimensions.
Strip vs. plate: how they stack up
The differing production methods for AR strip and plate mean that the resulting products can have quite different qualities. This is how they stack up in all the important areas:
The additional reheating needed for the quench and temper process in plate production can create considerable build-up of oxidation called the scale jacket. When this scale jacket is removed in shot blasting, it can create dents and scratches to the surface, which need repairs and will mean the end product doesn’t last as long.
In contrast, the single reheating used in strip production, combined with efficient descaling and direct quenching after hot rolling, creates a lighter scale jacket, which is more easily removed. This results in a better surface quality, which requires less treatment and is longer-lasting.
Product consistency and thickness tolerance
In plate production, each piece is rolled individually and, when the material enters the rolling gap, there is an element of stabilisation that must take place. This can result in slightly different thicknesses at the edges of the plate compared to the centre. Therefore, the thickness tolerance, flatness and product consistency can vary across the plate, with each plate also likely to be slightly different.
Because a single Valast 450 coil can be up to 1200m long, it isn’t impacted in the same way. There is still a variance at the first and last few metres of the strip – although using a total of 12 mill stands reduced this dramatically – but these sections can be removed when the steel is decoiled, leaving more than 95% of perfectly consistent AR steel.
Remember that a single Valast 450 coil is made from the same slab, which guarantees consistent chemistry along the full length of the strip. This means that every sheet in has been manufactured with identical production parameters, resulting in maximum consistency and, making processing easier and more efficient for the customer.
The maximum length of a steel plate tends to be 12m, so to maximise efficiency, steel plate producers provide the product in a standard set of sizes. This often means that customers need to over-order and waste a relatively high percentage of plate steel in order to manufacture their product.
Once again, because of the length of a steel strip, there are practically no limitations to the length that can be ordered. Coils of Valast 450 are cut to length according to the customer’s bespoke requirements. This helps to reduce waste and allows customers to optimise space. (See our article on minimum yield loss here).
Thickness and width
Typically, steel plate can be offered in greater thicknesses as it doesn’t need to be coiled in the same way that strip does. However, Valast 450 is still available in gauges of up to 12mm, which makes it suitable for many applications.
Strip steel also tends to be offered in narrower widths than plate, however, Valast 450 is available up to 2.0m wide, to give customers greater design flexibility.
To find out more about how Valast 450 can help make your products more beautiful for longer, as well as your manufacturing processes more efficient and sustainable, click here.