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Mechanical properties vs hardness for AISI 4140 material

Mechanical properties vs hardness for AISI 4140 material

Mechanical properties vs hardness for AISI 4140 material

I am trying to find a traceable source of mechanical properties vs hardness for AISI 4140 cr-moly steel that is quench and tempered to achieve Rockwell C hardness of 40.

I have this table of properties from a unreferenced paper:

I understand it was derived from the 1965 SEA Handbook and MIL-HNBK-5, both I which I do not have copies.

Does any one have a current reference that enables me to estimate mechanical props for 4140 cr-moly steel based upon hardness?

I searched my Machinery's Handbook to no avail.

Thank you.

RE: Mechanical properties vs hardness for AISI 4140 material

If I go by the AMS spec it says to quench from 1575F and for 180ksi min the temper should be about 850F.
At this strength you would want to double temper.
Somewhere I have a table for adjusting temper based on the as quenched hardness, but of course I can't find it right now.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

RE: Mechanical properties vs hardness for AISI 4140 material

Ingenuity... You need several documents with overlapping/corresponding information for a 'complete assessment'.

AMS2759/1 Heat Treatment of Carbon and Low-Alloy Steel Parts Minimum Tensile Strength Below 220 KSI (1517 MPa)
NOTE1. AMS2759/1 contains everything You need to validate HT of 4140 to the nominal tensile strength RANGE HT180-to-200-KSI with relationship to hardness.
NOTE2. AMS2761 [for raw steel materials] 'mostly' replaced/superseded MIL-H-6875 [all steel forms] and AMS-H-6875 [raw steel materials], contains somewhat similar info.
NOTE3. I am NOT considering vacuum HT for suitable parts [AMS2769]... which is somewhat more-complicated and waaaaay beyond our discussion.

MIL-HDBK-5 replaced by MMPDS-*
These documents have formal/authoritative metallic materials mechanical allowables data for 4140... and similar alloys... in the RANGE HT180-to-200-KSI. Alloys/tempers are based on 'industry standards'.
NOTE4. Be careful!!! Independent corporate standards for materials and HT processes may actually attain different mechanical allowables... and will be independently documented per authoritative corporate design manuals.

NAS531 Charts, Rockwell Hardness
This document is unique/low-key. It presents Rockwell hardness values for a wide range of metallic materials/tempers... magnesium, aluminum, copper, SStl, CRES/HRA and carbon/low-alloy steels... but NOT titanium. On sheet 11 of the latest revision is a table labeled APPROXIMATE HARDNESS – TENSILE STRENGTH RELATIONSHIP FOR CARBON AND LOW ALLOY STEELS. This table shows that RHC hardness VS tensile strength for MOST carbon & low alloy steels is remarkably consistent across the spectrum of steel alloys.

For giggles...

Aerospace Structural Metals Handbook [ASMH] Code 1203 '4140' presents a wide-range of authoritative/useful info specifically about 4140.

Regards, Wil Taylor
o Trust - But Verify!
o For those who believe, no proof is required; for those who cannot believe, no proof is possible. [variation, Stuart Chase]
o Unfortunately, in science what You 'believe' is irrelevant. ["Orion", HBA forum]
o Only fools and charlatans know everything and understand everything." -Anton Chekhov

RE: Mechanical properties vs hardness for AISI 4140 material

Thank you all for some great references.

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