High pressure sodium lamp is a kind of high brightness street lamp. What kind of material is its tube material?
The wick wick is the electric arc tube and getter ring fixed on the stem with metal stent, two electrodes of the arc tube are respectively connected with the guide wire in the two columns. The core is composed of a guide wire, the exhaust pipe and the horn by high temperature flame fused into one. The expansion coefficient of the metal guide wire and the sealing part of the glass shall be matched with the expansion coefficient of the two sealing materials, so that the glass at the sealing point can generate stress and burst or the bulb will be chronically leaking.
The arc tube is the key component of high pressure sodium lamp. When the arc tube works, the sodium vapor with high temperature and high pressure is very corrosive, and the general sodium silicate and quartz glass can not do so. But the translucent polycrystal alumina and the ceramic tube are ideal for the arc tube. It not only has good resistance to high temperature and corrosion of antibiotic sodium vapor, but also has good visible light crossing capability. In addition, the performance of single crystal alumina ceramic tubes is superior to polycrystalline al ceramic tubes in high temperature resistance, antibiotic, sodium vapor corrosion and light transmittance. Because of their high price, they are seldom used nowadays. The arc tube electrode, polycrystalline alumina ceramic, the children cap, solder ring assembly together into sealing furnace sealing with sodium amalgam; at the same time filled with a small amount of xenon lamp, in order to improve the starting characteristics. The electrode is made of a high-purity tungsten filament, spirally wound, inserted into the core in the spiral hole, impregnated with the electronic powder, and then welded at one end of the electrode core and the closed end of the niobium tube. Polycrystalline alumina ceramic tube (CAP) is made of polycrystalline alumina ceramic powder by mixing powder, fountain, fog drying, isostatic pressing, plain burning, high temperature sintering and cutting process. The light and electrical parameters of the high pressure sodium lamp are closely related to the inner diameter of the arc tube and the length of the arc (the distance between the two electrodes).
Glass shell of glass shell is made of high temperature hard glass. The bell mouth of the bulb and the wick is melted and sealed by a high temperature flame, then vacuum or filled with inert gas, and then put on a lamp cap, and the whole bulb is basically formed. As the arc tube works at high temperatures, its bare metal is easily oxidized and brittle, and the arc tube must be placed in a vacuum or inert gas envelope. In this way, the heat loss of the arc tube can be reduced, the cold end temperature can be increased, and the luminous efficiency can be improved.
The function of the lamp holder is to facilitate the connection of the bulb with the lamp holder and the circuit. The bulb of long life requires that the lamp head be connected with the bulb firmly, so that there is no looseness or falling off. Therefore, the general use of threaded mechanical fastening technology, to prevent the welding mud naturally aging and fall off. Generally, the brass band is used to make the lamp holder. It can keep the contact resistance with the lamp holder and reduce the oxide layer of the metal surface. If the bulb is used in a special environment, chromium coating or nickel coating can be applied on the surface of the brass lamp holder. Its specifications are: E27, E40 two.
The glass shell by vacuum, the vacuum degree is only 6.6X10 -2 Pa, can make the oxidation of metal parts, lighting effect and stable work; so the amount of getter placed in a glass bulb, bulb can be increased to 1.4X10 the degree of vacuum in a high vacuum state -4 Pa. At present, high pressure sodium lamp generally uses barium getter, it is the barium titanium alloy in the metal ring, and then fixed on the getter evapotranspiration does not affect the position of the output light. After the lamp is evacuated, the metal ring is heated by high-frequency induction, so that the inner ring of the barium titanium alloy is heated to evapotranspiration, and the residual harmful gas is absorbed during the evaporation process, and a black mirror surface is formed at the neck of the glass bulb. It must be pointed out that the getter placement is very important, the black mirror does not hinder the light output is appropriate; in the use of the process found in the black mirror of all or part of a gray white, indicating the bulb has leak, can not continue to use, must be changed to a new bulb.
