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Ductile Iron casting with high Si
3

Ductile Iron casting with high Si

Ductile Iron casting with high Si

(OP)
Hello,

I am looking into increasing the Si content of my ductile iron castings. Bring it closer to 3%. However it is known that raising the Si you lower the ductile to brittle transition Temp.

Do you know of any method/ additive that would keep the transition T up and still allow adding more SI?

Thanks,

Herc

RE: Ductile Iron casting with high Si

3
By increasing silicon beyond normal threshold value 2.5% (safe 2.2%),we are making iron more brittle,by raising the DBT . This is a serious issue,as I have witnessed brittle failures in cold countries. Why do you need to increase silicon ?

You can consider Ni addition  or alternately try austempering. What is the section thickness of the casting?  

RE: Ductile Iron casting with high Si

(OP)
I want to increase Si in order to adress carbide formation issues.
Casting thickness varies from 1/2" to 2"
Heat treatment is out of the question.

Why did you propose Ni?

Thanks for your reply, Herc

RE: Ductile Iron casting with high Si

If you are having carbide related issues,you need to address,your post inoculation issue and presence of tramp elements in your metal. Increasing silicon may not be a solution. Nickel is a very friendly element and aids graphitization without promoting carbides.

RE: Ductile Iron casting with high Si

(OP)
Is the DTB temperature dropping because the CE (Carbon equivalent) is increasing? Is there a correlation between these two?

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