Strength of Carbuized part. 3

[NickE]

In a very general way how would a case of 59HRc on 4130 steel effect the strength, impact strength, ductile to brittle transition, and fatigue life?

I haven't sectioned and mounted to determine core hardness yet, the case depth was given by the processor at 0.25-0.50mm and the part is 6mmx13mmx50mm.

Will I have residual compressive streses in the case?

Would impact at low temperatures cause the case to crack and "spall"?

The part is subject to repeated impacts and forces at the tip of ~90kg, the max Von-Mises stress (From FEA) is around 650MPa.

Temperature of operation is roughly from -25C-120C.

Thanks- the carburization was a mistake, how bad of sorts are we in now is why I'm asking.

nick

 

[NickE]

Swall- First time the part has existed.

Carburize- Any tensile stresses in the surface, or near, would be very bad for the operation of this part.

metengr- thanks.

I think that tempering down will likely be the only solution as opposed to anything else. The customer will be well informed from my end.

8600 isnt available in coil is it?

nick


Nick
I love materials science!

 

[CoryPad]

What is the thickness tolerance for the part. If you decided to go all the way back to the beginning as suggested by [blue]unclesyd[/blue], you might be concerned about losing thickness due to oxidation, decarburization, etc.

Regards,

Cory

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

 

[NickE]

cory- thickness isnt going to be toomuch of an issue.

 

[unclesyd]

CoryPad,
If there is no atmosphere in the furnace you can always wrap the part in brown paper, bury in spent pitch coke or CI shavings, and proceed with no concern for carb or decarb. Or you could drop in a mothball every once and a while

NickE,
I've been trying to see if my old Bethlehem Data Book is still around to see if you could compromise between the 4130 core and the 41xx in the case by judicious quenching and tempering based on the value of xx. My small book only goes to 4152. I still looking and thinking about the problem and ways and means to remediate your problem.

meteng,
We use hundreds of pressure containing parts made from 31xx and 41xx in our process and have worked with many a vendor and our shop in the reclaiming or modification of components by re-heat treating without detrimental effects. My only worry is my lack of knowledge on the effect on the low temperature impact properties on the material in his application. A redeeming thought is that his material is fairly forgiving based on the treatment received in daily use in the cold country.
I like the reminder of mutual understanding in any process of altering the original conception of the part and processes, it doesn't happen enough.