as the one of professional clean tungsten filament manufacturers,BaoJi Yuan Da Metal Materials Co., Ltd share the general making process of clean tungsten filament with you what is roasting from ammonium para tungstate into tungsten trioxide in the air around 500 degrees C, or slightly reducing to blue tungsten oxide in hydrogen around 450.

      Tungsten filament which is used for making incandescent lamp filament needs to add a small amount of potassium oxide, silica and alumina into tungsten trioxide or blue tungsten oxide. The total amount of the three is not more than 1%.This is the tungsten doped process invented by Baz in 1922.

     The doped tungsten oxide is reduced to tungsten powder by using hydrogen.The reduction process is generally divided into two steps: the first step is reduction to two tungsten oxide (brown tungsten oxide) at about 630 degrees,  the second step is reduced to metal tungsten powder at about 820 degrees.The purpose of the two step reduction is making the doped potassium fully to play the role and control the particle size of the powder. The doped tungsten powder is then pressed into elongated strips in a special mold. The square strip is electrified in hydrogen and is sintered by the method of self resistance heating (the temperature is about 3000 degrees C). The density of the tungsten strip can reach more than 85% of the theoretical value after sintering.The tungsten bars can be machined to a 3mm tungsten rod by means of rotary forging, and then further processed into various tungsten wires with different thickness.

     For example, 15W 220V incandescent tungsten filament's diameter is about 15 m,The diameter of tungsten wire for 10000W bromine tungsten lamp is about 1.25mm.Fine tungsten wire such as 220V and 10W incandescent tungsten filament diameter is about 12 m method is to make use of electrolytic corrosion to make.

        When the diameter of tungsten wire reaches micron level, it is difficult to measure its diameter accurately by conventional calipers. Therefore, the thickness of the wire is usually represented by the weight of the tungsten wire which is cut below 0.2mm in diameter at the 200mm length. For example, the diameter of the tungsten filament of the above 15W incandescent lamp can be expressed by 0.679mg/200mm.

       Baoji Refractory Metal Developer Co.,Ltd is one of the leading China tungsten wire manufacturers and suppliers, and as a professional company we have productive factory, welcome to wholesale tungsten wire products from us.

contact information:rmd1994@yeah.net