We used several type of scraps for melting grey cast iron.
(1) when we were used kind of scrap that was with trace alloy elements, so, our product were high hardness. Please notice that we use 50-50 steel scrap - return in the charge in furnace 12 tons.
(2) But when we used of bulk scrap with galvanic covered, we have products with hardness that we want and it's good.
So, I want to know what's the cause?
Is there any effective on solidification in the first mentioned scrap?
These elements have been increase in the products when we use of the first mentioned scrap:
Ti was increased from 0.01 % to about 0.03 %
Sn was increased from 0.01% to 0.05 %
Ni was increased from 0.02 % to 0.04%
What do you think about increasing hardness in our products?
And what is the maximum allowable these elements (Ti, Sn, Ni) in grey cast iron (GL 200)?
links
http://www.afsinc.org/files/MC/stories/issuearchive/webonly_0605.pdf
http://www.steel.org/making-steel/how-its-made/processes/how-a-blast-furnace-works.aspx
http://www.madehow.com/Volume-2/Iron.html
http://www.iipnetwork.org/India_Foundry_Best_Practice_Guide.pdf2
https://www.britannica.com/technology/iron-processing
Ti tends to form carbides when interacting with the C content of your melt. Obviously, this compounds are hard but brittle and have a high impact on the hardness of your product. For a more accurate investigation, you need to measure the Toughness of your product. This is as far as i can tell.
Ti & Ni is increasing hardness because they form different carbide and nitrides. But you can reduce its influence by add some modifying agent. For example, we use FeSi65 Ba12 fraction 0,8-3,2 mm. We add 90 g of it in 100 kg pouring ladle. This lets to enhance of graphitization and reduces hardness of casting. Also, you can use just FeSi65 or FeSi45. This works too but gives less effect.
Please note that boron increases the hardness of cast iron significantly with little amount (e.g. >0.008%) and mostly overlooked by foundries.
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