Please review my water quench plan
Please review my water quench plan
(OP)
What is the practicality of heating the following clevis to 1500 F (815 C) and dropping it into a water bucket?
Dimension: 3"x3"x8" (75x75x200 cm)
Weight: 16 pounds (7.5 kg)
Material: 4340
Please don't ask why not oil quench. My buddy is all set to try water quench first unless there are compelling reasons not to. Thanks.
Dimension: 3"x3"x8" (75x75x200 cm)
Weight: 16 pounds (7.5 kg)
Material: 4340
Please don't ask why not oil quench. My buddy is all set to try water quench first unless there are compelling reasons not to. Thanks.





RE: Please review my water quench plan
RE: Please review my water quench plan
You may crack your part upon quenching into water. You have too many sharp corners. A sixteen pound part into a bucket sounds real iffy. Without agitation it will not quench uniformly, soft spots and more chance to crack. Most compelling reason not to try this is it will probably fail miserably. If you insist, I would be interested in what happens.
RE: Please review my water quench plan
[1] Unnecessary in 4340. It defeats the purpose. 4340 is a deep (below the surface, that is) hardening steel, therefore only a slow quench (a good thing) is necessary for transforming the austenite to martensite. It all has to do with the way those expensive alloys in 4340 affect the thermodynamics of the transformation.
[2] Machine two pieces because the first one might crack. Quenching thick sections like this causes steep thermal gradients, internal stresses, and possible quench cracks from tensile forces, esp on the surface. Water is a faster quenchant than oil, so the cracking tendency is worsened.
[3] Also, investigate if an air-quench (i.e. Normalizing), rather than water quench & temper, would give you the desired mechanical properties.
Sorry, got carried away. To respond to your question, if you really must do this, put a big radius at the bottom of the slot and chamfer the exterior corners in order to attain a constant thickness throughout the cross section. Use a big bucket of very hot water, drop the part in – vertically constrained. NDI it afterward for cracks that you hope are not there. Letting it air-cool for a few minutes (check a CTT diagram for 4340), before the quench, probably wouldn't hurt. If the center core gets to < 800F in < 10 minutes, or so, the part should be thru hardened. (Check a metals book, e.g., Reed-Hill – Physical Metallurgical Principles, 3rd Ed.)
Also fyi, spec AMS-H-6875 recommends Austenitizing at 1500-1550F, Oil Quench, then temper 850-1200F depending on toughness/strength requirements.
Good luck. Try it.
RE: Please review my water quench plan
RE: Please review my water quench plan
Going with a water quench on the part shown made from 4340 will crack it. I've seen 4340 crack quenching in oil due to sharp fillets. I'd just machine it from heat treated material.
rp
RE: Please review my water quench plan
The part has already been made. I hope your replies convinced my buddy not to attempt water quench and take the longer route of oil quench (due to complicated fund transfer).
Someone mentioned air quench. We will look into it.
I don't know what my buddy is targeting for hardness/strength. I would say about 50 should be good enough. It will be used as fatigue test adapter. And we only have a limited number of test samples. That's why air quench may actually work.
If my buddy has further questions, he will post here. By the way, he is a mechanical engineer and I am a used-to-be metallurgist, sidetracked to non-metals, knowing little of both fields, thus my login name knowlittle.
Thanks again.
RE: Please review my water quench plan
What is the end use for this clevis?
Have you tapped the threads yet.
If it's for lifting you may fall under some specific rules and regulations depending on you jurisdiction.
RE: Please review my water quench plan
THREADS: All machining has been done including the threads.
WEAR: Yes, the holes in the clevis are for pin connection to a test sample. For extended use of the clevis beyond our immediate test need, we will consider bushing approach.
Thank you.
RE: Please review my water quench plan
You can try some stop-off methods (stop-off paints, copper plating, etc...) or stainless wrap, but your best bet in an atmosphere controlled intergral (oil) quench furnace.
As far as hardness is concerned, I wouldn't want to use 4340 in a fatigue application above about 45 HRC, and that is with excellent transformation during heat treatment. With questionable transformation, I think I'd try and hold it to below 38 HRC (I'd assume you'd get excellent transformation in an atmosphere controlled intergral quench furnace).
rp
RE: Please review my water quench plan
Thanks for the advice to protect the pin mating area. Heat treatment will be done inhouse. I will bring it up to their attention.
Thanks for 38 HRC. I was way off.
I am not familiar with the term "integral quench furnace."
RE: Please review my water quench plan
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RE: Please review my water quench plan
Clevises and pins should be fabricated from steels of sufficient strength (greater than 40 HRC) to elastically resist indentation of the clevises or pins.
Regards,
Cory
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Please review my water quench plan
Click on Spring Bushing at the bottom of the page for technical data.
http://www.connexusa.com/
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RE: Please review my water quench plan
RE: Please review my water quench plan
I believe your volume to weight ratio is way too small for any part this size. I would have a least three + gallons/per pound. Any less water and a part this size would blow all the water out of the container. I would also use agitated water or a moving basket to prevent steam blanketing, especially a blind hole.
That said I concur with all that this part should be oiled quenched at the same ratio or a least a slow polymer quench.
Aside from the yoke this part has a high potential for die cracking at the blind hole. The possibility is far less with agitated oil.
RE: Please review my water quench plan
RE: Please review my water quench plan
I read a few articles on glycol+water quenching. My buddy has 1" diameter x 4" long (25 mm dia. x 100 mm) pin that weighs about 2 lbs (1 kg). Is this a good candidate for glycol+water quenching? Is glycol+water as good as oil? He has 2 pins. He asked me to post this question here. Thanks.
RE: Please review my water quench plan
It isn't a question of water being as "good" as oil, it is a question of compatibility. Water and its solutions are capable of extracting heat very quickly from steels. The problem is that the quenching rate may be too high for higher carbon steels and they may crack. One of the reasons all of the alloying elements (Ni, Cr, Mo) are put into 4340 is to make it hardenable in oil quenchants.
The simple shape of the pin makes it less likely to crack than your clevis, but it still may crack. Also, dimensional change (diameter, straightness, etc.) may occur. It is best to use oil for alloy steels.
Regards,
Cory
Please see FAQ731-376: Eng-Tips.com Forum Policies for tips on how to make the best use of Eng-Tips Fora.
RE: Please review my water quench plan
PA Glycol quenchants can be made to provide cooling rates either faster or slower than most oils (generally a bit faster, though), depending on concentration.
Using Ethylene Glycol (anti-freeze) as a quenchant is not recommended.
rp
RE: Please review my water quench plan
RE: Please review my water quench plan