In need of better understanding on 300M 2

[havok91]

Hey guys,
I have a few questions regarding 300M due to some opinions from others on axle and shaft design. 300M is called that due its high tensile strengh potential (300 ksi), right? Or, is named such based on its composition like other steels ( I don't believe so, but someone told me.....)?
Does this material have to be heat treated up to its normal range (270-300 ksi) to be an effective steel? How is its fatigue resistance? What about case hardening or carburizing, how do they affect its torsional properties?

Would a maraging steel be better in high stressed axle design?

I'm a recent mechanical graduate and I'm looking for answers from the experienced.

Thanks,

Mike

 

[CoryPad]

Yes, the name is derived from the potential to reach 300 ksi ultimate tensile strength. It is a modified SAE 4340.

No, you could change the heat treatment to have lower strength and it would be an "effective steel". However, if you aren't going to use the high strength, then you may as well use 4140 or 4340 and save some cost.

300M has outstanding fatigue resistance. Along with high static strength, the high fatigue resistance is the reason to use this alloy.

You would not carburize this alloy - it is for high through hardness. If you wanted a similar alloy for carburizing, you would use SAE 4320. You could produce a case on 300M by induction hardening, but that would be more for contact wear resistance (think bearings and gears) rather than torsional strength of a shaft.

Maraging steels would compete directly with 300M. Maraging steels harden by precipitation hardening rather than martensitic transformation, so they have essentially no shape distortion during manufacturing compared with 300M. They have much higher fracture toughness, and are weldable. All of this comes with a big disadvantage - the cost is much higher due to the high nickel, molybdenum and cobalt concentrations.

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[TVP]

There is some useful information on 300M from Latrobe steel. Use the following links for more info:

http://www.latrobesteel.com/assets/documents/Sheets/High_Strength/300M.pdf

http://www.latrobesteel.com/assets/documents/Sheets/High_Strength/300M-HS.pdf

 

[havok91]

Hey thanks you guys. I have been digesting all the info.

Mike

 

[EdStainless]

While these alloys all have great strength and fatigue resistance, you need to remember that they are very notch sensitive. This is a characteristic of all very high strength materials, not just these alloys.

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Plymouth Tube

 

[UconnMaterials]

havok91,

What kind of torsional loads do are you carrying? You have to design against torsional failure and fatigue, but selecting the highest yield strength steel will not do you any service because as EdStainless said you have to be careful of the notch sensitivity of the material. Either way, I think your material should have some sort of surface hardening treatment with enough bulk ductility to withstand stress concentrations.

 

[havok91]

This is more of a conceptual question for me as I'm not looking for a 300M axle. It just seems that there are a lot of companies claiming that they have a 300M axle and it is unbreakable and guys on other forums I frequent are getting duped into that notion.

Thank you for your input guys