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Molybdenum Glass Melting Electrode Organizational Structure Change

Using microscope, scanning electron microscopy and electron probe to study molybdenum glass melting electrode’s metallographic structure, we can understand molybdenum electrode organizational change after long-term melting furnace operation, as well as the influence of structural changes on electrode corrosion.

Before operation, electrode is rolling state and has fibrous structure. Plate electrode used in marble furnace contacts with the raw material and the original thickness is 10mm. Operated at 1450 ℃ for 375 days and the electrode surface was etched 1mm. Electrode fracture surface is divided into three sections. Both sides are the oxygen diffusion layer and the oxygen content is higher than before about 100 times. Besides, due to uneven corrosion, the surface is uneven. Using scanning electron microscopy to observer oxygen diffusion layer found there were large spherical oxide precipitations. The plate electrode used in flat glass furnace for about three years and the thickness only reduced 2mm. Due to un-contact with raw material, the electrode surface is not oxygen diffusion layer and has more uniform corrosion. From metallurgical studies, molybdenum electrode after long-term work, both in raw meal or clinker are no intergranular corrosion, only surface corrosion, so during operation the electrode does not peel off.

Molybdenum electrodes after long-term high-temperature operation will have recrystallization occurred. The original fibrous structure will turn into coarse equiaxed structure. At room temperature this structure is very fragile and can not withstand the impact load. Therefore, to remove the electrodes should avoid hammering to prevent breakage.

After operation, Mo plate has many intergranular cracks and the recrystallized structure is brittle, so during disassembly and second reuse should careful to avoid brittle fracture. After long-term use, the tensile strength of Mo plate is significantly lower, such as Mo-0.5Ti alloy plate at 1400 ℃ molten glass worked for one year the room-temperature tensile strength values ​​decreased from 95kg / mm² to 22-30kg / mm_². Mo and Mo alloy long-term used in high temperature molten glass turns into fully recrystallized grain structure. After one year, Mo plate oxygen content increased about 50 times, the highest is up to 0.38% and the strength has significantly reduce, but not affect the continued use.

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