8620 is another suitable case hardening steel.
All crankpins and gears are made from EN36 .....for a very good reason they harden very well but stay ductile under the hardening. No gear cutter will use anything else.
There is 'better' material than EN36 available with higher surface hardness, higher fatigue strength and higher core strength, Ferrium C64 is one. This boutique triple vacuum remelt steel is not so easy to obtain. For the relatively lightly loaded solid or near solid pins in a 2 stroke crank the core strength of the steel is not critical compared with say, a gear, whose teeth have to resist bending loads. What matters is the hardness, cleanliness and fine grain size of the carburised layer. In other words the quality of the steel is the most important factor. From that point of view high quality 8620 will be a better choice than a cheap EN36B/9310.
Australia's pemium race gearbox builder has long been Holinger Engineering. I had a conversation with Peter Holinger about the world renowned H6S V8 Supercar gearbox that he designed and started making in the 90's. He said that a lot of it's reputation for unbreakable reliability up to it's design limit, was because Corus, formerly British Steel, supplied them with special high purity EN36 and EN39 which was then heat treated to very rigorous specifications.
