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Question:

Why does casting coke require phosphorus?

Do not understand why some of the indicators of coke is the cause of the full analysis of phosphorus or foundry use of this time?It is best to use the foundry requirements? Thank you

Answer:

As everyone knows, sulfur and phosphorus is harmful substances in the metal, because the sulfur is out in coke processing, so this index is not required, but the phosphorus in this process has not been effectively removed, so this is the requirement of foundry process or smelting plant. Phosphorus can reduce the strength of the metal, will lead to the metal "cold crisp", so to control the phosphorus content of coke, to prevent phosphorus into the metal.
Foundry coke is used in cupola melting iron will fuel. Because the blast furnace cupola and metallurgical industry is different, only melting effect, without reduction reaction, the furnace is not so dephosphorization, the phosphorus in coke, some will come back to this in the metallurgical molten iron, called "Rephosphorized", this is decided by the principle of thermodynamics and kinetics. To make the original low phosphorus iron phosphorus increased harmful phosphorus. Therefore, the general foundry to buy Coke require low phosphorus coke. Some foundry with part of lime and dolomite in dephosphorization of iron in cupola, in the process, can relax the requirements for coke. However, this is suitable for large-scale, continuous production of iron.
Phosphorus increased the brittleness of cast iron, the use of metal damage. Therefore, the requirements of the foundry phosphorus is the lower the better. Because of the large cupola furnace in the furnace is acidic, can not effectively dephosphorization, so the foundry coke in the phosphorus requirements as low as possible, and require the supplier to provide a quality guarantee form.
Phosphorus is a kind of harmful element in metal, which reduces the mechanical properties of castings. Under normal circumstances, GB castings of phosphorus content requirements of less than 0.06%, the lower the special requirements

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