Casting ferritic stainless steel 1

[SthlmHank]

Does anyone have any experience in casting ferritic stainless steel UNS S43940/X2CrTiNb18/1.4509?
We experince alot of shrinkage pores and possibly other defects.
There seems to be very few standardized ferritic stainless steel casting grades, compared with austenitic , martensitic and duplex.
Are ferritic stainless steel difficult to cast in general?

 

[arunmrao]

The low carbon content 0.02% max along with 18%Cr, makes it a tough alloy to cast in open air induction melting . Special precautions during melting and tapping is advised. Also proper degassing of metal will help. Keeping the metal covered during the complete campaign helps.

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"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[EdStainless]

And the alloy is Ti stabilized, but you don't want you ti burned up as a deoxidizer.
Good Ar gas cover, deox with Si, and make the Ti add right before you pour.
Limit the superheat, lower temp is better as long as you fill the molds.
You also have to keep hydrogen and nitrogen levels to a minimum of you will have not change a good mechanical properties.

I hope that you are casting thin sections or the grain size will be huge.

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Plymouth Tube

 

[arunmrao]

@ SthlmHank

Just curious, does the foundry have AOD converter ? Else,I see it a big challenge,to produce an extremely low carbon melt technically and economically.

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[EdStainless]

Technically it is no problem, 1002 steel, electrolytic Cr, pure Ti.
Economy is where it becomes a real pain.

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Plymouth Tube

 

[SthlmHank]

Thanks Arunmrao and EdStainless for the good replies!
The foundry has an AOD converter and the carbon content is very low.
Why is the low carbon content and high Cr content a problem from a metallurgical point of view (high melting temp, viscosity...)?
Thanks for the casting process input and the reflections regarding Ti.
The thickness is maximum 10 mm.
Could 475C embrittlement be an issue?

 

[arunmrao]

Good SthlmHank,that you have a converter,makes life easier. The high Cr in the metal makes it viscous and slag removal is difficult. Also the metal is prone to pick up gases from the atmosphere.In order to improve the fluidity,the foundry leans towards increasing the pouring temperature,thereby introducing newer defects.

What is the pouring temperature. What is the casting size and weight being poured? As a casting are you able to meet the test bar requirements for this grade?

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[EdStainless]

These will have to be solution annealed and force cooled. I would expect serious embrittlement issues in the castings.
Be careful that you use a low annealing temp, you don't want to re-dissolve the TiC, if you do that you will end up sensitizing the parts.

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Plymouth Tube

 

[SthlmHank]

Thanks for all the tips.
We buy the component and are nor casting ourself. Therefore I don't know much about the process.
Anyhow, I know understand much better why there is a lack of standardized cast ferritic stainless steel grades.
I also have a better unerstanding wht the part I'm analysing look crappy.