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unnormal microstructure

unnormal microstructure

unnormal microstructure

(OP)
hi,

could anyone tell me how the unnormal microstructure form in the attached file?
what i know about the material is: its grade is SAE1018, and the raw material is round bar.
does that make the properties worse, any idea is appreciated.

RE: unnormal microstructure

I've seen that referred to as acicular ferrite and pearlite. For 1018, it is formed at somewhat more rapid cooling rates that produce the more common ferrite and pearlite structure.

As to whether or not it makes properties worse, it really depends on what properties you are interested in and what you consider worse.

rp

RE: unnormal microstructure

Was this the only anomoly or were there many more similar structures. I would suspect some minor segregation as the culprit if only one.

RE: unnormal microstructure

(OP)
rp, thanks for your reply.
stan, no, there are many similar structures.

RE: unnormal microstructure

There is nothing abnormal with this microstructure, as mentioned previously it is produced by more rapid cooling rates. It is typical to see some variability in grain size with variable cooling rates because of section thickness and geometry affects.

RE: unnormal microstructure

Agree with metengr, anomolous structure is cooling rate dependent. Is the anomolous structure concentrated toward the surface?

RE: unnormal microstructure

(OP)
stan, they are uniformly distributed in it.

RE: unnormal microstructure

The appearance is acicular ferrite within the big size pearlite. The fast cool rating and over heating or long soaking time during normalization are the main reasons. If it uniformly and widely appears in the matrix, it damages the impact property severely.

RE: unnormal microstructure

I'd say it's pearlite and bainitic ferrite.

RE: unnormal microstructure

Looks like Widmanstatten Structure

Design for RELIABILITY, manufacturability, and maintainability

RE: unnormal microstructure

I agree about the Widmanstatten appearance; too much of this and machining can be troublesome.

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