Allen Bolt Material

Allen (or Hex Soc Head) bolts/screws are generally of property class 12.9. You can search the material for the above in google.
CR4 had a previous thread too

or see here click on

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However please ensure that the material is suitable for the application (environment, temperature etc)

Same property class bolts for a gearbox will be different from that used in Steam Turbine to that used in Gas Turbines to that used in say a Ship.