Suitable Material for Taper Shank (DIN 69871 or 69893) with Mill (indexable inserts)

[Matbol]

Dear Forum Team
I made a research about toolholders, specially taper shank's, and the material used for this are Case Hardening Materials, like 8620, 4320, or others, not case hardened, like H13.
My question is: what material is better for a combined taper shank, like DIN 69871 or 69893, with a helical/flute mill with indexable inserts? I know that for taper shank's is better the use of case harening steel's but on the other hand, I need the front end with a hardness of 40 HRC, hardness that the core wont achieve.
Please, can someone help me?

Matbol

 

[TVP]

16MnCr5/5120 and 8620 will typically have core hardness of 30-35 HRC when case hardened to 56-60 HRC. 4320 can have core hardness of 40-44 HRC together with case hardness of 56-60 HRC when oil quenched (oil temperature ~ 90-120 C) and subsequently tempered at 150-200 C.

 

[Matbol]

Dear TVP
Perfect your explanation, but, if I need diferent treatments on the taper shank 56 - 60 HRC, and on the front, were the indexable insert's are, something like 38 - 40 HRC, does the induction hardening reach this hardness on steel 4320?