Microstructure and quality of ASTM A439 type D2. 2

[AjSCCMelt]

Dear all,
I wanted to ask whether is it necessary to do magnesium treatment in ASTM A439 type D2 if we are using the scrap of the exact scrap of ASTM A439 type D2? Also what effects will it cause if it is not treated with magnesium but it will be heat treated as per the standards. Wouldn't heat treatment alone be sufficient for forming the required microstructure?
Waiting for valuable feedback and suggestions from the community.
Thanks

 

[EdStainless]

Yes, Mg treatment is required.
First it is poor practice to melt 100% scrap heats.
We used to limit to 60% and found that it required less Mg, but still needed it.
The graphite takes its form on solidification.
You can use a long-term HT to generate spheroidal graphite, but the properties will be different.

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P.E. Metallurgy, consulting work welcomed

 

[MagBen]

when Mg is melted down and alloyed with cast iron, it loses most of its nodulizing effect. The remained Mg could help, but you will need to re-do Mg treatment. Note remelting can evaporate quite a lot of Mg and the spheroidal graphite form be lost. you possibly get grey cast iron without a Mg treatment.

 

[AjSCCMelt]

Ok. Thanks for your feedbacks.@EdStainless @MagBen We are planning using magnesium ingots and breaking it into small pieces for magnesium treatment and using Ferro Silicon Barium Inoculant while pouring the metal into the mould. Will it form the microstructure required? Or is there any other better method for the same?
Kindly note that we have used standard pouring ladle of 500kgs and covered it with steel sheet to get Mg recovery while pouring the metal into the ladle from the furnace. Is this method sufficient or is it mandatory to use SG iron treatment ladle for this process?

 

[EdStainless]

Mg recovery and forming a good ductile structure are highly dependent on oxygen in melt.
The more oxygen the less recovery and the greater the chances for a marginal structure.
As I recall we used CaSiFe for deox, and then added the FeMg.
All of the treatment was in the ladle.
Our ladle was half the size of yours.
We melted in a 3000# induction furnace and poured from a 500# ladle.
Our individual parts were all under 15# each.
We were pouring into oil bonded sand with resin bonded cores.

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P.E. Metallurgy, consulting work welcomed