These micrographs are teken from ASTM A229 spring steel as polished surface which failed suddenly while in operation kindly tell whether the micrographs show inclusions or not..intial one are taken at crossection and final ones in transverse
Dear Mohammed,
I don't think "inclusions" would be the proper term to use for these bodies that are created and arise during, and as a result of, improper production methods in a batch of hardened steel. It appears to be cementite.
You may be interested in the issues addressed in this paper, here:
http://www.tms.org/Students/Winners/Davidson/Davidson.html
moreover, the comments on the production of cementite in batches of "hardened" steel containing too much (or poorly mixed) carbon, and insufficient temperatures, here:
http://www.learneasy.info/MDME/MEMmods/MEM30007A/steel/steel.html
Regards,
Bob
Bob,
I concur. My first thought, considering the hardening process of steel, was that the impurities were carbon. Carbon hardens steel, but it also makes it brittle. It is always a balance between hardness and tensile strength, depending on the desired product. In the case of Damascus steel, the brittleness imbibed by the carbon is offset by the fibrous layers of steel folded upon themselves.
Hi Mohhamed,
In my opinion the objects look like graphite on cross-sections and like inclusions on transverese section: what is strange that fraction of these objects differs distinctly comparing the sections. Its nature can be easly recocgized by EDS in SEM. Try to rub out as polished surface rinsed with ethanol by sof tissue and observe the fraction of objects. Regards from Warsaw, Poland
elongated inclusion in transverse section seems to be typical manganese sulfides, MnS
Dear Mohhamed
The steel embrittled rapidly, please show their microstructure after etching at the same region. There were also Inclusions presented in the steel, it is very clear in transverse section.
The material has strength 1771 mpa and 46 % reduction area , any comments now
Dear Mohammed,
If it is spring steel, there should be low S content and therefore there shouldnt be much MnS inclusions as well. But in transverse section they are looking like MnS inclusions. The optic microscope pictures are not clear some of them also can be sample preparation defects. It s interesting the fraction of defects are quite different between two sections. and this points out that there are defects caused by sample preparation.
How much is the actual Carbon %?
seems to be MnS inclusion
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