The composition of the pump castings is selected. Under normal circumstances, the pump castings with small wall thickness are not easy to form ferrite, which is easy to produce white mouth. Increasing the silicon to carbon ratio can effectively prevent the formation of a port at the thin wall, which is beneficial to improve the uniformity, strength and hardness of the casting structure and reduce the residual stress. However, when the carbon equivalent is high, the chance of occurrence of ferrite in the cast iron structure is significantly increased, which is extremely disadvantageous for improving the overall performance of the casting. Among them, the control of carbon content is the core, when the carbon equivalent is high, the manganese content can be appropriately increased, and the requirement of UHT200 can be stabilized in this range.
The charge requirements of the water pump castings will effectively use the locally produced coke and liters during the operation, and can directly add 5% to 15% of the scrap during the production. The thickness of scrap steel is ≥3mm, and the blockiness is greater than 1/5 of the diameter of the furnace. It is required to be rust-removed. The rest of the furnace block is not more than 1/3 of the diameter of the furnace. In order to reduce the burning loss of silicon, iron alloy with lower silicon content is selected as much as possible. In order to ensure the melting temperature, coke with a higher fixed carbon should be used, and the blockiness should be between 90 and 130 mm.
The melting operation of the water pump castings, the important indicator of the high-quality molten iron that can be obtained during the operation is the boiling temperature of the molten iron. In the operation, especially for the high silicon-carbon ratio cast iron, the melting temperature is high, which is beneficial to reduce the silicon. Burning, but will increase the tendency to increase carbon. Therefore, it should be considered that during the smelting, the bottom height is appropriately increased, the air volume is increased to increase the melting rate, and the tendency of the iron to increase carbon is controlled. While obtaining high temperature molten iron, the carbon content is controlled within an ideal range.
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