Improve Molybdenum Electrode CharacteristicsⅠ

Molybdenum is widely used in high-grade molten optical glass, glass fiber, rock wool and other fire-resistant electrode material for many years. And this is due to it’s good characteristics such as high melting point of (2630℃), good electrical and thermal conductivity, low thermal expansion coefficient, high temperature strength and resistance glass corrosion and other advantages. But molybdenum at high temperatures oxidizing atmosphere are easily oxidized, and also due to the vitreous humour will cause intergranular corrosion of molybdenum electrodes and lead to electrode surface grain peeling and loss. Therefore, improving molybdenum electrode product quality and performance become a problem which manufacturers are common concern. Besides impurity content and grain size of electrode will directly affect the performance of the electrode. Add a small amount of rare earth alloy elements can improve the grain size and the use performance of electrodes.

1.Electrode Production Processes Control
Paramolybdate after heating and roasting become molybdenum trioxide, molybdenum trioxide reduced to molybdenum powder by pass through hydrogen and heating, molybdenum powder put into the oil resistant rubber container then sealed in Ф820 mm × 1 600 mm isostatic press at 200~300MPa pressure forming molybdenum powder with a certain density and intensity. The molybdenum powder sinter to obtain compact molybdenum sintered billet in intermediate frequency induction furnace with hydrogen protect. And then molybdenum sintered billet doing hot and warm forging under hydrogen protection to obtain electrode blank. Finally, after machined electrode blank to get finished electrodes.

molybdenum electrodesmolybdenum electrodes

2. Electrode Raw Materials Control
Impurities control can guarantee high quality molybdenum powder and molybdenum powder is the necessary step for produce high quality electrodes. Because the impurities of molybdenum powder will directly affect the electrode which cause cracks or hidden cracks on it and C, N, and others can also cause glass bubble, affecting the quality of the glass. On the other hand, Ti, Ni, Cu, Cd and other metal elements make glass coloring. In order to obtain high purity molybdenum powder should follow the following measures:
(1) select high purity ammonium molybdate as raw materials
Ammonium molybdate impurities content show in Table 1.
(2) appropriate powder producing technology
Select appropriate producing technology for can remove low melting point impurities and reduce the nitrogen content significantly. Molybdenum chemical composition is shown in as below Table 2.
(3) molybdenum powder particle and particle composition control
Control the production process of molybdenum powder to control molybdenum powder particle size and particle size distribution. After many production experience and data analysis showed that the middle particles and close to normal distribution molybdenum powder suitable for produce high quality electrode of molybdenum.

Table1

Elements Al Bi Ca Co Cr Cu Fe K Mg Mn Na Ni Pb Sb Si Sn
Impurities Content 5 1 5 5 2 3 5 50 5 3 3 3 3 2 3 1

Table2

Elements Al Bi Ca Co Cr Cu Fe K Mg Mn
Impurities Content 6 1. 5 6 5 2. 5 3 6 60 5. 5 5. 3
Elements Na Ni Pb Sb Si Sn C N O
Impurities Content 2 3. 2 3 2 3.5 1 20 30 30

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