"Our job is to adapt our formulas accordingly," explains Nathalie Mottu-Bellier, an engineer at Industeel-Le Creusot. "It's all a matter of chemistry..."
From the first mockups and prototypes for the ITER vacuum vessel produced in 2004 to present orders from the industries in Korea, India, Russia and Europe for ITER, the steelworks in Le Creusot has booked some 10,000 tonnes of steel plates in a dozen different grades and ranging in thickness from 5 to 150 millimetres. "Such a large tonnage for a single project is quite exceptional," emphasizes Nathalie. "The grades of steel we're providing are clearly the top of our line of production."
Components in the ITER machine (and oftentimes parts within the components) must meet various functional, safety and technological requirements. Some are exposed to the ultra-hot plasma and high vacuum, others to the extreme cold of the cryogenic fluid; some must be completely permeable to magnetic fields, others, on the contrary, must act to influence them...
The required steel quality is achieved through the subtle dosage of various elements (such as boron, chrome, nickel, niobium, molybdenum, etc.) and through particular manufacturing processes.
Steel manufacturing often resembles the elaboration of a sophisticated perfume, where fragrances combine to realize the desired effect. In French, the steelmakers use the word "nuance" to characterize the different grades they produce.
Chemistry is a key element, but in some cases the manufacturing process can also be crucial. "The Korean company SFA Engineering Corp, who's procuring the thermal shield system, will add a thin layer of silver to the plates that we supply," explains Jean-Christophe Gagnepain, the sales manager at Industeel-Le Creusot. "The quality of this layer depends on the quality of the plate's surface, and ultimately on our production expertise."