Dear Qamar

I suppose that increasing in the reduction rate before normalization may result in a some reduction in the grain size after normalization.

Normalization is done from the temperature of the austenite (i.e, c.a 30-50 C above the A3 temp, so, 830-850C for 0.4%C steel ). The grain size reduction can also be obtained by precise selection of the normalization time and the temperature (i.e., A3+30C better than A3+50 C, so you can reduce the temperature a little - if the element size and the process control precision allow it ). Heating time is about 1-1.5 min per 1mm of the element thickness crosssection.

I can recoment rather quick cooling in the temperature of the transformation range of the austenite (i.e. up to approx. 700 C) if it is technically possible.

With the New Year wishes

Yours

M. Wrobel

Dear Qamar,

It is not clear whether you have determined the grain size after close die forging. If the grain size after close die forging is ASTM 4 after described normalizing process you should achieve required grain size if temperature controlling is OK. In opposite case you should check grain size after closed die forging. If grain size so high you should reduced forging temperature and/or soaking time on forging temperature to reduce grain size after close die forging to achieve ASTM 6-8 after normalizing. For normalizing use heating time 1 min per 1 mm of the element thickness cross section + soaking time 1 min per 1 mm of the element thickness cross section.

B. Omer