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Join Date: May 2013
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Best Heat Treatment Cycle for 34CrNiMo6 [DIN] or 4340,4337 [AISI]

05/22/2013 4:29 PM

Hi every one.I have a question about 34CrNiMo6 [in DIN standard] (or in AISI 4340 or 4337) steel. I am a student of Materials Engineering and i compete in a national students competition. I need to find out what is the best cycle of heat treatment for take 47 HRC for pins and 48 HRC for bushes. while we have maximum elongation, maximum Tensile and ultimate stress and maximum reduction area.
Can any body guide me on this issue?

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#1

Re: Best Heat Treatment Cycle for 34CrNiMo6 [DIN] or 4340,4337 [AISI]

05/22/2013 8:56 PM
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#2
In reply to #1

Re: Best Heat Treatment Cycle for 34CrNiMo6 [DIN] or 4340,4337 [AISI]

05/31/2013 3:18 AM

Thanks, But read these before.

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Participant

Join Date: Sep 2015
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#7
In reply to #1

Re: Best Heat Treatment Cycle for 34CrNiMo6 [DIN] or 4340,4337 [AISI]

11/30/2015 3:21 AM

I think this is what you will need, the complete data of 4340 steel,including the heat treatment information. Hope it helps.

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Guru

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#3

Re: Best Heat Treatment Cycle for 34CrNiMo6 [DIN] or 4340,4337 [AISI]

05/31/2013 5:30 PM

Two Several points,

1) Expecting to get a single point of hardness is not going to happen, the error in the hardness tester alone (Rockwell c ) will probably be half a point. I don't know any one that will assure a single hardness.

2) You don't say what the diameter is. mass effect is a big deal.

3) Back to that 48 vs 47 for different parts. Really? your application can tell the difference?

4) You want maximum elongation, maximum tensile, and maximum reduction in area. you can have either maximum tensile or maximum ductuility, you can't have both. TS and %elong And %red are negatively correlated, as TS increases, ductility decreases. WHAT do you really need, and why are you worried about TS, and not Yield? typically Yield is used by designers as it is the greatest amounts of stress while remaining in the same dimension and form as installed...

5) The hardness is finalized by the post quench Tempering operation. The lower the temper temperature, the higher the hardness, higher the Tensile , the lower the ductility.

I personally DO NOT like to use tempers below 800 degrees F because of blue brittleness see my post here :http://pmpaspeakingofprecision.com/2010/11/30/blue-brittleness-temper-embrittlement-400-500-degree-c-embrittlement-and-more/ ( I know I said 1100 degrees in my blog post )

6) You want 48 HRC that is ~461 BHN; at 800 degree F temper, 4340 yields a 440 BHN hardness; at a <gasp> 600 degree F temper, my data says 490 BHN or 51.6 HrC (danger Will Robinson! Blue brittle Range)< I would not go there professionally.>

7) For the fun seekers and risk takers I have data that suggests that a 400 degree F temper will give a 520 BHN hardness. Make sure you get adequate soaking time or you will have untempered martensite and brittle parts that will fail.

8) The diameter is important factor. people use the alloy steels to get through hardness. Do you need through hardness for a pin / for a bush/ I would humbly suggest that a high surface hardness on the od (where the surface is, thank you captain obvious) and a tough core would be a more robust application. but that is my experience, and I a m not the designer.

9) To get these high hardnesses, you will need 4340, not 4337 4337 will not get above 430 BHN with an 800 degree temper

10) If the pin and bush sections are greater in diameter- forget it. my data shows that with an 800 degree F temper, niether a 1" nor 3' thick section will not get above 410 BHN on OD, and a 6" thick section will not get above 395 on the OD, and not more than 360 BHN at half section.

Hope that this helps.

Regardless, if you take only one thing from this too long post, remember that tensile strength and hardness are one side of the coin, and %elong and % red of area are the other. You can call either heads or tails, but you can't call both.

Milo

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Participant

Join Date: May 2013
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#4
In reply to #3

Re: Best Heat Treatment Cycle for 34CrNiMo6 [DIN] or 4340,4337 [AISI]

05/31/2013 7:21 PM

Thanks Milo,

Thanks for your points. But just for your information, i am a materials engineer, and obviously know relationships between hardness, %el, UTS, TS, toughness and ...

I meant, I need a cycle that gives me this Hardness and have largest possible amounts of %el, toughness and ... . Because, my score is calculated according to an equation, in which, for mentioned hardness, if the amounts of %el and ... will be the largest possible amount, i will get the most score.

The diameter is 12.5mm. and i have not to use surface hardener cycles like carburizing and nitriding. and i just have permission to use bulk heat treatments.

according to my researches, for about 40 HRC, tempering temprature is about 500C and i need a temperature about 400C (~750F).

Thank you for your reminder about Blue brittle Range, because this grades are sensitive to this type of brittleness. I'm so nerves about this brittleness, and i fear that my final part have such a brittleness. I have to consider this. :)

thanks for your remarks. I look forward to your additional remarks. :)

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#5
In reply to #4

Re: Best Heat Treatment Cycle for 34CrNiMo6 [DIN] or 4340,4337 [AISI]

05/31/2013 8:29 PM

Your score? Is this homework?

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Participant

Join Date: May 2013
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#6
In reply to #5

Re: Best Heat Treatment Cycle for 34CrNiMo6 [DIN] or 4340,4337 [AISI]

06/01/2013 2:56 AM

No. It's a competition. between Materials engineer students. It's award is about 2000$! :)

And want to win.

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