A niobium alloy is one in which the most common element is niobium. A niobium alloy is one in which the most common element is niobium. The most common commercial niobium alloys are ferroniobium and nickel-niobium, produced by thermite reduction of appropriate mixtures of the oxides; these are not usable as engineering materials, but are used as convenient sources of niobium for specialist steels and nickel-based superalloys. Going via an iron-niobium or nickel-niobium alloy avoids problems associated with the high melting point of niobium. Niobium-tin and Niobium-titanium are essential alloys for the industrial use of superconductors, since they remain superconducting in high magnetic fields (30T for Nb3Sn, 15T for NbTi); there are 1200 tons of NbTi in the magnets of the Large Hadron Collider, whilst Nb3Sn is used in the windings of almost all hospital MRI machines. Niobium-titanium alloy, of the same composition as the superconducting one, is used for rivets in the aerospace industry; it is easier to form than CP titanium, and stronger at elevated (> 300°C) temperatures. Niobium-1% zirconium is used in rocketry and in the nuclear industry. It is regarded as a low-strength alloy. C-103, which is 89% Nb, 10% Hf and 1% Ti, was used for the rocket nozzle of the Apollo service module; it is regarded as a medium-strength alloy.