Low Pressure Die Casting (LPDC) is a process that is being widely used in the automobile component industry. Stalk tube is a critical component of the casting machine. Various types of Stalk Tubes are being used in the Low Pressure Die Casting process by automotive component manufacturers. Due to cost advantages and strength over the ceramic tubes, Cast Iron Stalk tubes are being preferred by many casters. However, the following are the major issues faced with these tubes:
- These tubes get corroded very fast due to oxidation as molten aluminium is quite aggressive
- The ferrous particles mix with the molten aluminium and impact the quality of the casting
- It is very difficult to remove the deposited aluminium metal from the stalk tube
Boron Nitride Coatings have been tried and have been found to be quite effective on Cast Iron Stalk Tubes. The tube can be coated with EPC/GPC grade coating of Momentive(formerly GE Advanced Materials) Boron Nitride. The tube has to be coated from both inside as well outside with a thin layer of Boron Nitride. Spray coating method can be used as otherwise it is difficult to cover the inside surface of the tube. After the coating, it should be dried thoroughly either at room temperature or by blowing hot air at 80 deg C. The second coat is to be done once the first coat is completely dry. Wipe the tube with a soft cloth so that excess boron nitride is removed. Use the tube.
Boron Nitride coatings can withstand temperature of 850 deg C in oxidising environment and up to 1850 deg C in reducing environment. So the layer of these coatings protect the tube from aggressive molten aluminium, not allow traces of ferrous metal to mix with aluminium melt as well as deposited aluminium metal can be removed easily as these coatings also act as release agent.
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| Boron Nitride Coatings GPC/EPC now come as Momentive |
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