Molybdenum News Center

To analyze the effect of molybdenum electrodes can be fused in the kiln after long-term changes in the internal organizational structure of the work, as well as structural changes in the electrode corrosion resistance. With a microscope, scanning electron microscopy and electron probe after use of molybdenum electrodes conduct metallurgical studies. 

 

Before using the electrode is rolling state, has a fibrous structure. Main electrode melting furnace factory drawing full plate electrode using chemical and biological materials, the original thickness of 10mm, at 1450 ℃ to work 375 days, the electrode surface etched 1mm. An electrode section is divided into three layers, both sides of the oxygen-impermeable layer, an oxygen content higher than the previous use of about 100 times, the surface is uneven due to uneven etching. Oxygen diffusion layer for scanning electron microscopy revealed a large spherical oxide precipitation. 

 

The flat bottom of the tank brick kiln plant's heating plate-molybdenum electrodes, electrodes for about three years, reducing the thickness of only 2mm. And raw material due to contact with the electrode surface does not penetrate the ozone layer, more uniform corrosion. 

 

Can be learned from the metallurgical studies, molybdenum electrodes after long-term work, both in raw meal, or in the clinker are no intergranular corrosion, only the surface of contact corrosion, which in the course of the electrode does not occur peeling. 

 

Molybdenum electrodes occurs after long-term high-temperature recrystallization, the original fibrous structure becomes coarse equiaxed, this structure is very brittle at room temperature, and can not withstand shock loads. Therefore, when removing the electrodes, the electrodes in order to prevent breakage, to avoid hammering. 

 

Mo powder metallurgy factory rolled plate, using smelting and rolling molybdenum alloy plate (Mo-0.5Ti-0.02C) on the furnaces, the recrystallization temperature of these two materials are not high, the former is about 1050 ℃, after by about 1250 ℃, the (1300 ℃ ~ 1400 ℃) long-term solution in the high-temperature glass fiber tissue sheet material rolled into a fully recrystallized grain structure, the corresponding section of the molybdenum alloy was observed with the naked eye, was found section of the central portion of a metallic luster is strong, and the surface portion in contact with the liquid glass (about 2mm) metallic luster difference, the former grain great latter is slightly smaller. Sampling and analysis along the Mo plate thickness, Mo found after long-term use has increased significantly in the oxygen content, oxygen content before using molybdenum alloy plate was 0.004wt%, a significant increase after use, such as Mo plate surface oxygenated has reached 0.38wt%, an increase of about 100 fold, Mo at the center of the plate is increased about 10 times. Mo plate weakly oxidizing the molten glass after long-term use, or the outer surface is less expensive molybdenum MoO2 surrounded molybdenum oxide at a high temperature oxygen atoms inside the metal leaving the long-term thermal diffusion has an oxygen content increased to varying degrees. In the outermost molybdenum alloy sheet can be seen on a photomicrograph dense oxide particles dispersed within the grains and grain boundaries. 

 

Mo plate after use, there are still many intergranular cracks, thus making these recrystallized microstructure plate brittle, so when Mo plate removal and the second iteration must be careful to avoid the use of brittle fracture, the sheet resistance after long-term use significantly lower tensile strength, such as Mo-0.5Ti alloy plate to work a year after its room temperature tensile strength values ​​of 95kg/mm2 down to 22 ~ 30kg/mm2 molten glass at 1400 ℃. Mo and Mo alloys after long-term use of high temperature molten glass into a fully recrystallized grain structure after one year Mo plate increases the oxygen content of more than about 50 times, up to 0.38%, significantly lower strength, but does not impact of continued use. 

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