Ductile Iron casting with high Si 3

[Hercules28]

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

 

[arunmrao]

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?

 

[Hercules28]

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

 

[arunmrao]

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.

 

[Hercules28]

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