Lower tensile strength and elongation level in heat resistant CC steel
Lower tensile strength and elongation level in heat resistant CC steel
(OP)
Hi guys,
I have one question for you...
We have heat resistant austenitic stainless steel made by centrifugal casting. It is chromium-manganese steel (20:10 %) with tensile strength about 700 MPa and elongation about 15%, but the tensile strength and elongation level is sometimes suddenly decreased. The chemical composition did not show us any correlation. Process parameters as well.
What is your opinion: What can decrease both, the tensile strength and elongation together in this case?
Thank you!
I have one question for you...
We have heat resistant austenitic stainless steel made by centrifugal casting. It is chromium-manganese steel (20:10 %) with tensile strength about 700 MPa and elongation about 15%, but the tensile strength and elongation level is sometimes suddenly decreased. The chemical composition did not show us any correlation. Process parameters as well.
What is your opinion: What can decrease both, the tensile strength and elongation together in this case?
Thank you!





RE: Lower tensile strength and elongation level in heat resistant CC steel
I donot expect a large elongation with 10% Mn. Do you have a high N content?
RE: Lower tensile strength and elongation level in heat resistant CC steel
RE: Lower tensile strength and elongation level in heat resistant CC steel
a) Sample selection and preparation
b) presence of unsoundness in the sample
c) Any carbides at grain boundaries. ( This is common in Hadfield steel)
d)Is the Nitrogen content varying ?
e) Are these castings heat treated ?
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( read somewhere on the internet)
RE: Lower tensile strength and elongation level in heat resistant CC steel
The first two that I would check are nitrogen content and grain size.
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RE: Lower tensile strength and elongation level in heat resistant CC steel
thank you...
to MagBen: Yes, we have nitrogen content about 0,15 % (standard requires 0,1 - 0,3 %)
to metengr: it was typical randomly testing, no in-service failure
I have to write this steel has 0,1 - 0,15 % of sulphur after solidification and the morfology of manganese sulphides is very crazy, MnS size is sometimes too big and looks "slaggy":
Link
Link
Castings are not heat treated. I think some submicroscopic precipitates may play a role in this case, but I can't check it in our conditions.
RE: Lower tensile strength and elongation level in heat resistant CC steel
Microstructure of specimen with good properties: Link
Microstructure of specimen with lower properties: Link
How to determine the grain size for this kind of microstructure? According to ASTNM E 112-10 subclause 17.3-5 it is a problem. And as well is a problem to distinguish the grain boundaries for this type of steel castings.
RE: Lower tensile strength and elongation level in heat resistant CC steel
Castings have variability with regard to mechanical properties. Are the castings with lower properties below the minimum requirement for acceptance or simply lower in value and by how much in comparison to a "good" casting.
RE: Lower tensile strength and elongation level in heat resistant CC steel
tensile strength required min. 690, our typical 720, sometimes, like now 677 MPa
elongation required min. 15, our typical 16, sometimes, like now 12 %
RE: Lower tensile strength and elongation level in heat resistant CC steel
Possible solutions: 1. increase cooling rate during solidification. 2. decrease casting temperature if possible.
RE: Lower tensile strength and elongation level in heat resistant CC steel
Those are poor microstructures.
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