4130 Steel at HRC 30-35 1

[Customize]

I am trying to find yield strength and ultimate strength for 4130 steel at Rockwell C 30 to 35. I have an old design that I need to replicate for a much lower strength quickly, and need to verify if the advantage of the heat treatment for hardening is really required for my new application.

 

[OGMetEngr]

ASTM A370 has an approximation of the ultimate tensile strength for a particular hardness. Attempts have been made to correlate hardness with yield strength over the years, with this paper being the latest I've found. "Correlation of Yield Strength and Tensile Strength
with Hardness for Steels" by E.J. Pavlina and C.J. Van Tyne.

In the paper above, their tensile to hardness correlation matches that of A370 pretty well. The yield to hardness also correlates just as well. It should be stated though that these are only rough correlations, and the actual yield or tensile value can only be known by tensile testing.

 

[Customize]

All I have found tying 4130 to HRC is the ultimate strength change, and not the yield strength shift.

 

[metengr]

From my "old" version of ASM Databook, which I had readily available, 4130 steel quenched and tempered, hardness of 315 BHN, the minimum tensile strength is 150 Ksi and the yield strength is 132 Ksi with 17% elongation and 52% ROA.

 

[metengr]

The reduction of area should be 57%, and not 52%. My bad....

 

[redpicker]

In my experience, the Hardness to UTS correlation is pretty good for low-alloy steels.

The Yield Strength can be estimated if you know the Yield to Tensile Ratio. For Quenched and Tempered steels, this can range from around 75% to 95%, depending on composition and heat treatment. For 4130 in the Q&T condition, in thin enough section size that you can safely assume >85% martensite formation on quenching, at 30-35 HRC I'd expect a Y/T Ratio to be around 90%. For thicker sections and/or lower amounts of martensite fromed on quenching, it could be in the 75%-80% range, maybe even less.

All that said, for 30-35 HRC, I'd expect UTS to be 140-160 KSI. With a "good" quench and temper, you could expect the YS to be 125-145 KSI. With less than "good", the yield strength could be in the 100-110 KSI range

rp