DEPHOSPHORIZATION AND DESULFURIZATION OF MOLTEN DUCTILE IRON AND ITS EFFECT ON DUCTILITY

1 DEPHOSPHORIZATION AND DESULFURIZATION OF MOLTEN DUCTILE IRON AND ITS EFFECT ON DUCTILITY By Rub Nawaz Ansari (Deputy Manager, Bolan Castings Ltd. Pakistan) PROBLEM: The importance of phosphorus in the chemistry of the Ductile is vital. It is kept at a level of 0.045 % maximum. The only way to keep it at this level is to use the raw material which should be low in the phosphorus. The consistency in the raw material of the foundry is not much appreciable in Pakistan. The chemistry fluctuates from supplier to supplier and source to source. Therefore it becomes sometimes very hard to keep the phosphorus below the desired level. The surprises result in sub standard production of the ductile iron which has not the up to the mark mechanical properties and premature failure is observed at the end. If there is some fluctuation in sulfur level that has been treated with the soda ash. The sulfur issue is obvious as higher values of sulfur in the melt simply do effect the Mg treatment and consequently nodules are not produced. In other words if the sulfur level is high it do not let the ductile iron to be produced and the problem is highlighted at the earlier stages and addressed accordingly. But it is not in the case of phosphorus. Phosphorus let the ductile iron to be produced but with some low ductility. After mechanical testing or even in service of the part foundry man comes to know that the mechanical properties were not up to the mark. Ductile Iron foundries do not have any method to reduce the phosphorus level in the melt if is introduced through the raw material. In this research it is tried to keep the phosphorus level at minimum level through dephosphorization of the liquid metal. The principles used in dephosphorization in Pig Iron and

DEPHOSPHORIZATION AND DESULFURIZATION OF MOLTEN DUCTILE IRON AND ITS EFFECT ON DUCTILITY

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ductile iron

phosphorus

dephosphorization

slag