Austenitic cast iron microsturcture

[HT007]

Hello metallurgical wizards!! The material is Austenitic cast iron. The chemical composition limits are C: max.3.0%; Si: 2%~3%; Mn: 6%~7%; Ni: 12%~13%. The delivery condition of the product is unknown (The customer did not give me heat treatment process). The appearance of the micro-structure is austenite + graphite + white nubby structure (Marked with Zone 1 in Fig.100 006) surrounded by granular particles (Marked with Zone 2 in Fig.100 006). The HV0.3 hardness in zone 1 is about 500; about 240 HV0.3 in zone 2; about 180 HVO.3 in the austenite (white area). I think the Zone 2 is carbide within austenite. Is the Zone 1 steadite (P-Fe) or carbide? i do not have the SEM to analyze the chemical composition of the zone. Any comments is appreciated.

 

[HT007]

Sorry, how to upload my photos?

 

[metengr]

http://www.thaithavorn.com/pdf/microstructure.pdf

 

[EdStainless]

I'll wait for pictures, but I have tried this chemistry before (though I changed it a bit).
Is it actually non-magnetic?
You may need to play with a series of anneals to try to minimize secondary phases.
you can go too hot as well as too cold.
What about mechanicals, is the strength and ductility about right?

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Plymouth Tube

 

[HT007]

Hello EdStainless! Yes it is non-magnetizable. The mechanical properties are acceptable except the Si% is 4.8%. I cannot find any essay about this kind material in china.

The below link is the microstructure picture. I am not sure whether foreign IP can login. But you can try. Many thanks!

http://tieba.baidu.com/p/2272092181

 

[EdStainless]

Looking at the structure and the high Si would have guessed that the strength is fine but the ductility is low.
That is more secondary phases than I would expect if it has been properly annealed.
Yes you should have C nodules, carbides will be almost impossible to avoid, a nice austenite matrix, and maybe a few Si/N/P intermetallics.
What is the P level?

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Plymouth Tube

 

[HT007]

Hello EdStainless! You are right. The elongation A is only 15.3% and the limitation is Min.15%. The P% is 0.05%. Do you think that the p% is too little to form so much steadite shown in the pictures? So it is carbide?

 

[EdStainless]

I am leaning toward calling them carbides.
You need to try some anneals and see if you can reduce the level of carbides.

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Plymouth Tube