From scrap to innovative steel for the Einstein Telescope

Roughly ten thousand tonnes of stainless steel will soon be required for the Einstein Telescope’s 120-kilometre-long tube. Aperam, based in Genk, is one of the candidates to supply this specialised steel. A technical challenge, even for a specialist company with over sixty years’ experience.

It doesn’t seem that complicated: producing stainless steel plates for tubes one metre in diameter and one and a half millimetres thick. Not even if they have to be ten kilometres long. For a specialist like Aperam, it’s not rocket science, is it? Patrick Toussaint smiles. The engineer and Einstein Telescope project manager at Aperam knows better.

“Because the steel has to meet very high standards and the tubes must never fail,” says general manager Jimmy De Wilde. “After years of research and testing, I dare say we’ve found the right composition.”

But that was no simple task. “Firstly,” he explains, “we’re talking about tubes that are evacuated to a vacuum. This creates a risk of implosion; the tubes could collapse in on themselves or shrink over time. But ideally there should be no movement whatsoever, and certainly no vibration. That places high demands on the thickness of the steel. Secondly, the surface of the steel inside the tubes must be completely smooth. Any bump, burr or whatever will eventually interfere with the measurements. The outer walls must be resistant to moisture, mould and insects. There must be no damage, no corrosion, let alone a hole. And then there are the welded joints, traditionally the weak points in piping systems. They mustn’t fail either.”

Investing in innovation

So, plenty of hurdles and challenges. “Over five years ago, we were asked by the University of Antwerp to contribute ideas for the Einstein Telescope. Naturally, we said yes,” explains Jimmy De Wilde.

Aperam Genk is a company that continuously invests in innovation, in new products and steel grades. To the outside world, stainless steel may seem like a simple type of steel, but we produce it in countless grades and thicknesses. It is intended for industries that use it to make parts for dishwashers and washing machines, for example, as well as components for cars, silos, pipes or construction projects. Supplying the material for the vacuum tubes of the Einstein Telescope would, certainly, be a tremendous honour. We have therefore been working on this for years in our labs and with various test batches. We would very much like to be the company that supplies the tubes for the Einstein Telescope.”

Stainless steel as a niche

The steel company on the outskirts of Genk was founded in 1961 as one of the firms set up to cushion the blow of the mine closures. From the outset, the focus was on specialist stainless steel, which was also the reason why multinational Aperam decided to acquire the company, which now employs 1,300 people.

“In the steel world, stainless steel is a niche,” explains Jimmy De Wilde. “Around forty million tonnes of steel are produced in Europe every year; ten per cent of that is stainless steel, and we handle over one million tonnes. So, certainly in this region, we are a major player with a strong focus on innovation. We have to be, because our customers are setting ever-higher standards and there is fierce global competition. Participating in the Einstein project is attractive to us from a PR perspective, but it also attracts specialists and engineers who help us create even better and newer products. It’s a boost for our innovations. For instance, we’re meeting the growing demand for special stainless steel for quantum computers. These computers are also housed in freezing-cold vacuum chambers, just like the mirrors of the Einstein Telescope. So we are developing steel that can be used for multiple applications. We are well advanced. Once the decision on the location is made and the tender process begins, we will be ready. We can supply that steel, that’s for sure.”

Unrolling the spiral

It is not just the composition and properties that are crucial, adds Patrick Toussaint. “Our plan is to produce steel tubes in the shape of a spiral, 500 metres long, from the coils. These will be transported to the construction site and unrolled and installed underground using a special machine being developed by one of our partners, Werkhuizen Hengelhoef in Genk. The benefits are enormous. A single roll fits on one lorry, and only twenty welds are required per pipe. Using the traditional method, you would need a weld every ten metres. That’s a hundred per pipe and twelve hundred for the entire project. Our joint approach saves costs and time and is more sustainable.”

To this end, Aperam is part of the Beampipes4ET consortium, which, in addition to the aforementioned Werkhuizen Hengelhoef and SBE in Eijsden (Netherlands), also includes RWTH Aachen University and the universities of Antwerp and Hasselt. One of the objectives is to develop vacuum technology for the underground piping system of the Einstein Telescope.

Reuse of scrap

Speaking of sustainability: Aperam Genk produces its stainless steel using electric arc furnaces. Powered by 55,000 solar panels and a wind turbine. “Enough to power a significant part of our processes,” says a proud Jimmy De Wilde, “and thanks to which we emit almost no CO₂ anymore, partly because we start mainly with scrap. So it is possible to make industry more sustainable, but that requires investments you can only make with a strong parent company like Aperam. A good decision, I think, when you look at developments in the energy market.”

It is not only Aperam’s business processes that are sustainable, but also the raw materials used. Whereas not so long ago the stainless steel coils from the United States arrived by boat via the Albert Canal, now only scrap is used.

“Used steel and iron from all over Europe,” explains Patrick Toussaint, who was previously involved in the construction of CERN’s particle accelerator at a former employer. “We melt it down here into high-quality stainless steel and roll and cut it into new semi-finished products for hundreds of customers across Europe. And perhaps soon for the construction of the Einstein Telescope.”

Dozens of companies

Jimmy De Wilde nods. “And then just about every Limburg resident could say they once had a component of the telescope in their home. As a fridge, car, freezer or whatever. Because we also process scrap from this region. How wonderful would it be to use it to search for the origins of the universe, of our existence? Certainly, it would be fantastic if the telescope were also built in this region. But if, against all odds, that doesn’t happen, then all the efforts won’t have been in vain. The network surrounding the project is growing bigger and bigger. We are developing knowledge and skills, with dozens of companies taking part. The telescope is already worth its weight in gold.”

Aperam Genk
Aperam Genk is part of an international steel producer with branches in sixteen countries, an annual turnover in 2025 of nearly 6.5 billion euros and customers in 40 countries.