1). Analysis of the cause of damage to high-strength castings on the upper part of the aluminum melting furnace.
1. Influence of thermal stress: When the aluminum melting furnace is in operation, the temperature inside the furnace can reach 700~900°C. During the frequent heating and cooling process, different parts of the upper part of the furnace will expand and contract to different degrees, which will generate thermal stress. When the thermal stress exceeds the load-bearing limit of the forming material, cracks and delamination will occur. For example, when the oven is opened and heated, the surface will expand rapidly due to heat, but the inside will heat more slowly and the expansion will decrease. The difference in expansion between the inside and the outside is likely to cause cracks.
2. Chemical attack: During the melting process, aluminum liquid will produce volatile substances such as alkali metal oxides, which will chemically react with the soluble substances on the upper part of the furnace. When some components of the forming material react with alkali metal oxides, substances with low melting points will be generated, which will cause the performance of the forming material to deteriorate at high temperatures and accelerate the damage.
3. Mechanical impact: When adding materials to the aluminum melting furnace, the impact of the material may directly affect the molten material on the top of the melting furnace. In particular, when the raw material is supplied by pneumatic conveying, the raw material is discharged at a high speed and a certain impact force is generated on the top of the furnace. After long-term use, the surface of the molding material will gradually wear out and peel off.
4. Manufacturing quality problems: If the mixing is not even during the production of the molding material, the distribution of the internal components of the molding material will be uneven, resulting in unstable performance. In addition, the loose vibration will cause the pores of the molding material to increase, which will reduce the strength and corrosion resistance, and will be more likely to be damaged during use.
2). Improvement measures for high-strength castings on the top of the aluminum melting furnace
5. Optimize the thermal system. Develop an appropriate heating and cooling curve to reduce the heating and cooling speed. For example, the heating speed is controlled at 50~80℃ per hour, and the cooling speed is controlled at 30~50℃ per hour to reduce the occurrence of thermal stress. At the same time, keep the oven temperature stable and ensure that the temperature change is not large.
6. Choose anti-corrosion molds: Choose molds rich in aluminum, corundum or other elements. This kind of moldable material has good resistance to chemical corrosion. High-alumina casting products have high alumina content, which can effectively prevent the erosion of volatile substances in molten aluminum and extend the service life of the upper casting products in the furnace.
7. Improve the feeding method. Change the air transport to bottom or side feeding to prevent the material from directly impacting the top of the furnace. At the same time, place buffer devices such as buffer baffles in the feeding port to wet the material before it reaches the top of the furnace, thereby reducing the impact force on the moldable material at the top of the furnace.
8. Strictly control the construction quality. Provide professional training to construction personnel before starting work to ensure that they learn the correct construction method. During the coating process, the mixing should be strictly carried out according to the ratio, and the mixing time should not be shorter than the specified time to ensure uniform mixing. Use appropriate vibration devices to ensure compaction. Observe whether there are bubbles on the surface of the moldable material to determine whether the vibration is sufficient.
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