Pooled iron is the solidified Hot Metal due to some problem in downstream steel making. As its melting profile is differnt from scrap with higher carbon than scrap. Please suggest what are the advantages or disadvantages in replacing scrap from pooled iron?
Pooled iron contains higher composition of Si, C as compared to normal steel scrap. Therefore, addition of pooled iron ingots as a replacement of scrap maked the blow highly unstable in terms of de-siliconization and de-caburization respectively thereby frequent occurance of soft and hard blow. Furthermore, slag evolution process and foam height is also gets disturbed. These important factors of the blow get hampered, making the pooled iron unsuitable as a substitute for steel scrap.
Pooled Iron will have more or less same carbon content as in hot metal. More addition of carbon carrying material will lead to exothermic reactions which will increase the bath temperature on releasing heat. The heat will be used to melt the granshot or pooled iron. Latent heat of pooled iron will require some heat to be molten. Hence low carbon scrap would be favorable in my opinion. Please correct me if I am wrong.
The size of the pooled iron and time of addition would also play a role here in dissolution because that would affect the kinetics of dissolution.
Apart from size and time of addition, as the difference in concentration of elements present in pooled iron and the liquid iron bath is always more along with the CO gas evolution at the contact boundary between the pooled ingot and liquid iron increases the kinetics of dissolution. However, the heat transfer between them may be slow.
Size is quite important, as sometimes after blow ends pooled iron not melted completely. May be due to low heat transfer coefficient because of CO boundary layer explained by Sir. In case of pooled iron melting occurs layerwise.
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