4340 Oil Quench

[johnnyy21]

Looking for some information on oil quenching 4340. I need to find an appropriate oil to quench a 2" thick piece of slab to a rockwell 50.

Is it possible to use a brine to achieve this without cracking? What is the highest HBC an air quench will reach?

 

[redpicker]

4340 is quite quench crack sensitive. A brine is the not the way to go unless you really know what you are doing and have very tight control on the process.

Look for vendors that sell heat treathing supplies, they should have products to help you. Google "quench oils".

Air quenching 4340 in a 2" section would result in 35-45 HRC, depending. Of course, you will want to temper after quenching, so the final hardness will be somewhat less.

rp

 

[arunmrao]

Polymer quench can get you in that hardness region without cracking . But you need to monitor the quenchant closely for consistent results.

 

[johnnyy21]

How much oil/polymer would I need to avoid flashing? (20lb piece of 4340) This will be my first attemt at an oit quench so I'd like to be prepared but yet not go overboard on the volume.

What polymer would work for this application?