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Hi! Question related to Gears and their chemical composition

  1. Apr 26, 2015 #1
    Hi ! This is Mustafa. I recently did my bachelor's and started working with Honda Motors.

    So my manager asked me to do a little research regarding the Gear type (SCM415H) used. I have to check how varying the chemical composition of each element will result in the properties of the gear itself. Here is the list of elements and the standard compositions:

    C (0.12-0.18%)
    Si (0.15-0.35%)
    Mn (0.55-0.90%)
    P (0.03 max)
    S (0.03 max)
    Cr (0.85-1.25%)
    Mo (0.15-0.30%)

    I am not great with chemistry (since I am a design&simulation engineer) and cant find alot of help on the internet. I need to know the specifics, how reducing and increasing the levels of each element will change the properties of the gear.

  2. jcsd
  3. Apr 26, 2015 #2


    Staff: Mentor

    Welcome to PF!

    What you are interested in is not really Chemistry but Materials science.

    Here's a reference to some of its concepts and toward the end are some plots of for how some steels respond based on carbon content...


    For gears, shearing is an important concept. I once assisted a machinist who maintained the college clock. Every winter it would freeze up and so to prevent major repairs he used a brass gear at a key spot that would shear and relieve the stress to the rest of the mechanism. He chose brass over steel because the brass sheared at a lower amount of force applied by the clock motor.
  4. Apr 26, 2015 #3

    Thankyou Jedi

    I did go through the file and it mostly covers the properties. It however does not let me know how varying their compositions will effect the material (in this case a gear)

    I did find some info but was hoping for a little specif answer.


    Manganese: Used for increasing the hardness and strength of a gear. However it decreases ductility and weldability and effects the hardenability of steel.

    I am looking for something like this about the elements mentioned above that are added in the manufacturing of a transmission gear.
  5. Apr 26, 2015 #4


    Staff: Mentor

  6. Apr 26, 2015 #5
    Thanks. I've managed to find I what I was looking for. Where can I find the microstructure details on the Jis steel scm415h?
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