microstructure identification

[fusitexa]

hi,

i need your help.i really don't know what specific grade of the material is, but it is said probably to be SPCC, low carbon steel.but i didn't seen the similar micro structure before in low carbon steel. i send to do chemical analysis, but the test is not finished yet. attached is the OM photo, pls. help me to determine what the micro structure is and what kind of heat treatment can make this happen. thanks in advance.

 

[mrfailure]

Have you looked at this structure unetched? You may simply be looking at inclusions in a ferrite structure.

Aaron Tanzer

http://www.lehightesting.com

 

[metengr]

Wait until the chemical analysis is completed and don't try to run before you walk!

 

[metman]

Like metengr says, "wait for the chem analalysis." but if it is low carbaon steel,it appears to be a spherodized structure which comes from heating between the lower and upper critical temperatures. If this is actually spherodized, it is essentailly annealed (soft) but more machinable than dead soft annealed.

Design for RELIABILITY, manufacturability, and maintainability

 

[TVP]

I like walking/running with scissors...looks like a spheroidized microstructure, as metman stated. The carbides are present as discrete spheroidal particles rather than as lamellar pearlite. Definitely low carbon, less than 0.15% by mass.

 

[stanweld]

What is the product form? Also looks like process annealed, low carbon, cold rolled sheet.

 

[fusitexa]

thanks guys for your reply.

Stanfield,
yes, it is CR steel strip. and its thickness is 3mm and stamped to form.

 

[fusitexa]

after stamping, it will be heat treated (980 centigrade for a few minutes, then cooled in furnace). and attached is the OM photo after heat treatment.
pls. review.

 

[metman]

OK now it looks like more fully annealed microstructure. At higher magnification, the the cementite grains will likely reveal lamellar Pearlite. And yes defintely low carbon < .20%

Design for RELIABILITY, manufacturability, and maintainability

 

[Guest102023]

If it is carbon steel then it is low carbon and fully spheroidized.

 

[stanweld]

I assume that the first photo is the as received cold rolled sheet, the second photo is after annealing the part at 980 C. In that case, the first is a process annealed structure - temperature near to the lower critical temp. The second is of a fully annealed low carbon steel similar to AISI/SAE 1010.

The fine grain structure is evident of aluminum killed steel used for deep drawing. You should check chemistry for Al as well.