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Austenitic cast iron microsturcture

Austenitic cast iron microsturcture

Austenitic cast iron microsturcture

(OP)
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.

RE: Austenitic cast iron microsturcture

(OP)
Sorry, how to upload my photos?

RE: Austenitic cast iron microsturcture

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?

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

RE: Austenitic cast iron microsturcture

(OP)
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

RE: Austenitic cast iron microsturcture

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?

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

RE: Austenitic cast iron microsturcture

(OP)
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?

RE: Austenitic cast iron microsturcture

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

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

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