Jominy test data in practice

[miham]

Hi everybody!

Need an advise on steel heat treatment please. A drawing specifies induction hardening 56-61 HRC with 3mm case depth for a 42CrMo4 steel pin 200mm in diameter. The supplier claims that in this case only hardness 50-55 HRC is achievable. The engineer that made the drawing refers to the standard where for this steel grade the hardness values obtained from Jominy test are 56-61 HRC up to 3mm from the quenched end.

Who is right in this case? Can the specified hardness range can be achieved?

How the Jominy data should be applied in practice treating parts considerably larger than the test specimen?

Many thanks!

 

[CoryPad]

SAE J1268 Hardenability Bands for Carbon and Alloy H Steels shows that 4142H alloy (similar to 42CrMo4) with a mild water quench (similar to water + polymer generally used in induction hardening) of a 4 inch diameter bar would have a surface hardness of around 55-60 HRC. For the much thicker 200-mm diameter bar, the quench severity will need to be very high to keep the surface hardness in the same range. Are you concerned about distortion? The supplier range is reasonable for the alloy and product size.

 

[swall]

How is case hardness defined? Direct Rockwell on the part or on a cross section at some designated depth with microhardness?
How is case depth defined?

 

[miham]

Thanks for the answers. It seems that we found a supplier that can deliver specified hardness. The case hardnes is defined as effective. How is it normally measured? Is it possible to do non-destructively?

 

[CoryPad]

It is most common for induction case hardened parts to measure surface hardness by the Rockwell C method or Vickers method, while measuring effective case depth (to 550 HV or 50 HRC) by using Vickers microindendation hardness.

 

[dbooker630]

On some induction hardened parts we have used the superficial Rockwell HR15N scale for effective case depth measurement after correlation with microhardness traverses. It will reduce sample prep time.