Zirconium alloys in most of the organic acid, inorganic acid, alkali, salt solution and has the very strong corrosion resistance in molten salt, for example, wear-resisting pipe in a wider range of concentration (5% 99.7%), the temperature of 200 ℃, the corrosion rate is less than 1 mpy. But the corrosion resistance of zirconium alloy is better than titanium alloy in hydrochloric acid system. Zirconium alloys are expensive, four times as expensive as graphite and two times as expensive as titanium, but they can withstand high temperatures but not high pressures in corrosive environments. The use of zirconium alloy, pressure gauge buffer tube to extend the life of the equipment, reduce maintenance costs, reduce parking time, but also eliminate the corrosion products caused by product pollution. A great deal of experience shows that zirconium alloys show economic superiority in high temperature and high corrosion environment.
Zirconium -4 alloy is a kind of zirconium alloy. Its standard composition is: Zr-1.5%, Sn-0.2% Fe-0.1 %Cr. Nickel in zirconium -2 alloy has the function of accelerating hydrogen absorption embrittlement. In order to overcome hydrogen embrittlement tendency in zirconium -2 alloy, zirconium -4 alloy was developed. The properties of zirconium - alloys are similar to those of zirconium -2 alloys except hydrogen absorption. The hydrogen absorption rate of zirconium -2 and zirconium -4 alloys obtained from out - of - heap test is fixed. Zirconiumalloys to join other elements for zirconium based alloys. Zirconium alloy in 300 ~ 400 degrees Celsius in the high temperature and high pressure steam and water has good corrosion resistance, suitable mechanical properties, low thermal atomic absorption cross section zirconium (0.18) and has good compatibility to the nuclear fuel, therefore, can be used as a water cooled nuclear reactor core structure materials (fuel cladding, pressure pipe, bracket and pore), which is the main purpose of the zirconium alloy.
Due to the low mechanical strength of zirconium alloy materials, when adopting zirconium alloy flange, the design conditions must be checked within the flange Rating data (p-t Rating).
Loose sleeve flanges are often used to reduce costs and increase ratings. Flange ring material should not be carbon steel to prevent ferrite contamination. 316 stainless steel, duplex steel and hastelloy alloy are available, depending on the design conditions. The author thinks that, in order to reduce the cost, under certain conditions, the appropriate increase in the pressure level and the use of 316 stainless steel instead of two-phase steel or hashish alloy flange ring, basket filter is likely to be a good choice. What is worth mentioning here is, although loose sleeve flange can reduce cost, but the performance that bears internal pressure is far inferior to pair welding flange (point to and flange ring are same material), when checking rated pressure, should leave room. Caution should be taken when using in full specified conditions.
