Non-Spheridized steel

[goflyers]

What is spheridized and non-spheridized steel? We have bar stock that is 1043 steel per MS-514 which calls out for a killed fine grain steel and it was mentioned that we also want to specify the material to be "non-spheridized". What is it?
Thank you,
goflyers

 

[AlanD]

Well Spheroidized structure in steel is one where the carbides such as cementite are heat treated in such a way that the carbides are in a spheroidal or globular form.

An example would be an isothermal heat treatment of a steel containing pearlite, where the cementite appears in a lameller (plate) structure initially. Given an extended isothermal treatment the cementite would coalescence into a spheroidal form. This may also be achieved directly from the austenite phase by extremely slow cooling or isothermal treatement.

Another example would be tempered martensite, by the perciptiated carbides continuing to coalescence during the tempering.

Basically a non spheroidized structure is one where the carbides are not spheroidized by any heat treatment.

 

[ColinF]

As AlanD has mentioned, spherodisising refers to when the patches of cementite in pearlite coalasce to form "globules". This process takes place below the lower crtitical temperature, and so no phase change takes place. The balling of the cementite is purely the result of surface tension effects.

Spherodising can be thought as a type of process annealing, and can assist in the cold working of steels. However, with the improved ductility that allows easy cold work comes a loss in strength.

Hope this is some help.