Hardness (Jonimy?) Curves for 50CrMo4 or 4150 Alloy Steel

[JCJackson]

Can anybody point me to a referance/website (where I don't have to take out a mortgage to get a hay stack with the pertinent needle)that publishes Hardness Curves for 50CrMo4 Chrome-Moly alloy. SAE/AISI 4150 IS an equiv' alloy and so would suffice for my purposes.

 

[unclesyd]

I have the curve for AISI 4150.
The curve is essential a straight line form 1/16" to 2" from the quenched end. The value at 1/16" is Rc 60.5 while Rc 41 @ 2"

Do you need the curve and just specific values of equivalent diameters for oil or water quench?

 

[JCJackson]

Thanks unclesyd, I'm investigating a machine failure where the probable cause is inadequate flame hardening of a plate cam. The surface hardness at 60.5HRc is slightly over spec' (56-60HRc) but the hardness profile passes through the lower limit at only 0.5mm (0.02") deep. The case depth spec' on the drawing is 1-2mm, but is not qualified as effective or total depth. Do you have a definitive explanation of "effective"? The only quantative definition I have is from AGMA, "5 HRc points below surface hardness or 50HRc, whichever is the lower".

I also consider the core to be "soft" at <200Hv, I would prefer this to be 300Hv or better to help support the case. There is no spec' on the drawing for the core, so I presume the material was supplied annealed as indicated by the hardness.

The avilability of the curve would help to elucidate the conclusion in my report.

 

[rob768]

isn't effective hardness sometimes specified as the depth where hardness is 550 Vickers or above?

 

[JCJackson]

Hi rob768, I believe the effective hardness should relate to the surface hardness. Some medium carbon steels would struggle to get much above 550Hv at the surface, never mind into the case.

 

[unclesyd]

One test for "effective case depth" is SAE J423 which calls for 50Rc/510HV as the depth measurement criteria. This is defined by the use of a microhardness tester.

Effective essentially defines where case contributes to the wear properties of the base metal. This is sticking point with me as any significant improvement I've seen in wear properties began at a hardness of 58Rc and above.

My data shows a surface hardness of 62Rc on a 1" oil quenched round. As stated in my previous post the 1/16" hardness in the 60.5Rc. The annealed hardness is 210HV

I concur with you observations and conclusions about your failure as you seem to have an old fashion case of "Case Crushing". You might want to heat treat the cam prior to the flame hardening proceure.