Tempering Curve of BS 970: 665M17 (EN34) 1

[SoftLev]

Hi,


I can't find a tempering curve of BS 970: 665M17 (EN34).

I want to check the typical properties of this material, carburised hardened and tempered to HRC 60 to 62 to see what the core is like after the treatment.. with particular reference to the yield and the ultimate strenghts, elongation and fracture toughness of the core (Charpy Impact Energy could do if Kc not available).

Can anyone point me in the right direction?

Thanks

 

[TVP]

The properties will vary depending on the heat treatment parameters used, because there is more than one way to achieve 60-62 HRC. If the parts are direct quenched from a carburizing temperature of 925 C and tempered at 150 C then the core properties will be approximately as follows:

yield = 800 MPa
tensile = 1000 MPa
elongation ~ 17%
hardness ~ 33 HRC (311 HB)


If the parts were carburized at 925 C, slow cooled, reheated to 815 C, quenched & tempered at 150 C then the core properties will be approximately as follows:

yield = 575 MPa
tensile = 800 MPa
elongation ~ 19%
hardness ~ 29 HRC (277 HB)
Izod impact ~ 58 J for t < 13 mm (up to ~ 100 J for larger sizes)


The latter process improves the impact properties, so using direct quenching you can expect Izod values at least 20% lower. The source of this data is the ASM Heat Treater's Guide for alloy SAE 4620/4620H.