Steel grain growth after forging

[Forger50]

Hello everyone,

I need technical support regarding grain growth after forging. First, it is needed to say that the grain size is measured after a carburizing process simulation (50hours, 950ºC). Is there anything the forger can do to avoid grain growth besides selecting appropiate raw material with alleation?

Thanks in advanced.

 

[arunmrao]

50 hours holding time at 950C is your process cycle!This is way too high,please confirm once again,grade of steel,size of the component,any pretreatment before carburizing, carburizing process,process parameters,case depth desired and achieved,any post carburizing operations. This will enable you get useful replies.

Learn the rules,so you know how to break them properly.
Dalai Lama

_____________________________________

 

[Forger50]

It is not that the carburizing process is 950º C, 50h. But we must do that process and measure the grain size afterwards in order to assure no grain growth will occur in real carburizing process (which will probably be at 935º C). This "simulation" process is only done with a small sample part, which of course does not have the geometry of the real part. The grade is 18CrNiMo7-6.

We have found, in some cases, duplex grain size. Most of the grains are ASTM 5 or 6 but ASTM 1 or 2 can also be found.

I´ve read that finishing forging at too low temperatures can cause segregations and this could maybe create big grain sizes in the areas with, for example, no Al, V or Ti.

Any help will be appreciated.

Thanks in advanced.

 

[arunmrao]

Is the finish forging temperature lower than 900C. Is it followed by a normalising process,before carburizing?(Please note, I am not an expert on heat treatment,)

Learn the rules,so you know how to break them properly.
Dalai Lama

_____________________________________

 

[Forger50]

In some areas of the part the finish forging temperature will definitely be under 900ºC (not the hole part, but certain critical areas). It is indeed followed by a normalizing process but this does not help with the segregations neither with the grain growth after "simulation" (50h, 950ºC).

Thanks in advanced.