Properties of industrial grade zirconium and zirconium alloys

Zirconium and zirconium alloy are widely used in the nuclear industry and chemical industry because of their low thermal neutron cross section absorption rate, low density and thermal expansion coefficient, and good mechanical properties and corrosion resistance in the harsh environment of high temperature and pressure. According to the content of hafnium in zirconium, zirconium and zirconium alloy are divided into nuclear grade zirconium and industrial grade zirconium products, which give content less than 100 ug/g for nuclear grade zirconium, and the total content of zirconium and hafnium between 95.2%~99.5% for industrial grade zirconium. At present, the main companies producing industrial alloy abroad are Huachang, Canada Cameco and Sweden Sandvik. Industrial zirconium and zirconium alloy under extreme conditions, such as hydrofluoric acid, concentrated sulfuric acid, anhydrous halide environment is not easy to form oxide film, cobalt surface will appear corrosion phenomenon; There are also pitting and stress corrosion phenomena in industrial zirconium under oxidation condition. Some data show that fluorine solution and sulfuric acid solution are sensitive to crevice corrosion and can easily cause local failure of zirconium products.

With the continuous deepening of the production and theoretical research of industrial zirconium and zirconium alloys, the company has realized the production, scientific research and physical and chemical properties testing of industrial zirconium and zirconium alloys. The products produced have been widely used in chemical, medical and seawater corrosion (fasteners) industries.

Principle of metal zirconium alloying

The purpose of zirconium alloying is to inhibit the harmful effects of other impurity elements and improve the corrosion resistance. There is no definite theory about metal zirconium alloying at present. A relatively mature viewpoint is the Wagner-Hauffe hypothesis, which holds that anions in oxide film will diffuse along the vacancy, pass through the oxide film to the metal surface, and electrons will move outward from the metal surface to make the oxide film grow in the metal and oxide film. The corrosion rate is controlled by the equilibrium rate of the oxide film or the replacement rate of the vacancy in the oxide film. Therefore, any foreign interstitial cations will reduce the number of anion vacancies and reduce the diffusion of oxygen ions, but replacement cations below the tetrovalent junction and anions above the divalent oxygen will increase the number of anion vacancies and accelerate the corrosion.

Zirconium is located in the IVB group of the periodic table. According to the Hauff valence law, if the elements of the same group or VB, VIB and VII are added as alloying elements, when they enter the oxide film, the electron concentration in the oxide film will be increased and the anionic vacancy in the film will be reduced, so as to inhibit

The diffusion of oxygen ions reduces the corrosion rate. The beneficial effect of containing small amount of iron, chromium and nickel in the wrong ion may be related to this. The ammonia element in zirconium metal has a serious harmful effect, the reason may be that N3- can replace the oxygen ion in the oxide lattice, produce additional vacancy, thus accelerating the wrong corrosion, but if the content of tin is increased, because of N3- and oxygen ion vacancy try to stay near Sn3+, the three junction After combination, the mobility is poor, so that the vacancy mobility is reduced, so tin can reduce the harmful effect of nitrogen, reduce the corrosion rate of the junction.

According to the above rules, alloying with zirconium is the most beneficial to improve the corrosion resistance of cobalt theoretically. In the periodic table, Ti, Hf(IVB group) and Si, Pb, Ge, Sn, C(IVA group) have bad corrosion resistance. Hf tends to deteriorate the anti-corrosion effect of the wrong; Pb melting point is very low; Si and Ge cells are diamond cubic structure, and the atomic radius is too big to dissolve in the close-packed cubic structure

As a result, Sn is the only element in group IVA that can be used as an alloying element for zirconium metal. In the periodic table, the corrosion resistance of N and V in V, Nb, Ta(group VB) and N, P, As, Sb, Bi (group VA) is harmful. As, Sb, Bi low melting point; Ta is expensive and weakens the mechanical properties of the product, so only Nb can be used as an alloying element of zirconium metal. In addition, Cr and Mo in group VIB and Fe and Ni in group VIIIB can be used as alloying elements of zirconium

When Cr, Fe and Ni are added to zirconium at the same time, the corrosion resistance of zirconium alloy can be improved, but too much Ni will induce the tendency of hydrogen absorption.

At present, relatively mature junction and cobalt alloy are respectively:

Zr-4(principal component Zr-Sn-Fe-Cr system)

E110(Zr-Nb series) and Zirlo(Zr-Sn-Nb series), which belong to nuclear grade zirconium, have been successfully used as structural materials and cladding materials in nuclear reactors.

According to the difference of oxygen content in the alloy, industrial zirconium alloy is divided into R60700, R60702, R60703, R60704, R60705 and R60706 series alloys abroad. R60700 is low oxygen pure zirconium, R60702 and R60703 are pure zirconium, R60704 are zirconium tin alloy, R60705 and R60706 are zirconium niobium alloy.

Main zirconium metal products:

Zirconium metal, zirconium target, ZR702 zirconium, zirconium plate, zirconium sheet, zirconium tape, zirconium foil, 702 zirconium plate, zirconium plate target, polished zirconium plate, cold rolled zirconium plate, zirconium rod, 702 zirconium rod, zirconium ingot, zirconium circle, zirconium round target, zirconium wire, zirconium tube, zirconium capillary, zirconium ring, zirconium tube target, zirconium cup, zirconium cyanochia, zirconium forgings, industrial zirconium, zirconium screws, zirconium nuts, zirconium standard parts, zirconium processing workpiece, zirconium steel, zirconium Zirconium flanges and zirconium alloys.