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topic 51470

Hardening EN8 & EN9 parts

A discussion started in 2009 & continuing through 2017

March 2, 2009

Q. With en9 material can I get hardness of 44-48 hrc on all over the part. If yes, then can you suggest the h/t cycle. Because we are manufacturing one product which has an elliptical broach in middle in which we can't get hardness 44-48 hrc and also we found that our broach dimensions has also get variation after final heat treatment. So can you help for getting hardness 44-48 hrc?

Vishal Sachde
- Bhavnagar, India

March 6, 2009

A. En9 is a plain unalloyed medium-carbon steel. It therefore requires very severe cooling in the heat treatment cycle in order to get the sort of hardness that you want, and the thickness of the section in turn greatly affects the cooling rate that can be achieved.

Information that you must supply to get further with your query:
1. What section thickness is your component?
2. To what depth below the surface do you want 44-48 HRc?
3. Related to Q2, do you want through-hardening?
4. Do you have a soak-and-water-quench facility?
5. Do you have a flame-hardening facility?

Depending on answers to the above, there might be a heat treatment cycle that will give you what you want on En9, or it might be that you will need to change grade to one that has appropriate alloy content to allow hardening by less severe quenching.

Bill Reynolds
Bill Reynolds
consultant metallurgist
Ballarat, Victoria, Australia
We sadly relate the news that Bill passed away on Jan. 29, 2010.

March 9, 2009

A. Good afternoon:

With limited information provided, it's going to be hard to tell whether 44-48 HRC is possible. Part dimensions, thickness, quenchant, quench agitation, variation of chemistry from heat to heat...these are some of the variables that should be considered.

And since this is a 0.50-0.60 carbon material, if the quench rate is too severe, warpage or quench cracking are possibilities. This might explain the variation in the broach dimension. If these are thin parts, you might be able to austemper or marquench them to reduce warpage.

If you buy steel with a guaranteed hardenability band, you could better predict the heat treat response.

If the part is too thick to achieve adequate as quenched hardness, a change in material may be needed.

Sorry there's no quick answer. Good luck.

Steve Bizub
- St Louis, Missouri

March 12, 2009

A. Obviously it is possible to get hardness 44-49 hrc in en 9, but please specify section thickness?
Please specify whether dwg. requires thru hardening and / or surface hardening?
We are doing similar components; also specify whether dwg. specifies core hardness too?
I would advise more quenching to avoid problem of distortion
Just for sharing, had manufactured EN king pins which were toughened to 25 Rc at core then surface was induction hardened in polymer quenching to give 55 hrc hardness at surface to depth of .5 mm thus achieving strength as well as wear improved surface life.

Vikas Kaushal
- Chandigarh, India

October 6, 2011

Q. In EN9, C45 material Flats and Bars, we could not get the Hardness of our requirement of above 50 HRC as quenched condition in oil quenching.

Heat Treatment Manager - COIMBATORE, Tamilnadu, India

March 10, 2012

Q. Our Components fall within following dimensions-
LENGTH- 50 mm to 150 mm
WIDTH- 07 mm to 20 mm
THICKNESS- 0.8 mm to 1.5 mm


Can anyone please suggest an appropriate Heat Treatment process to achieve an through 40-48 HRC?

Vikas Mura
- CHENNAI, Tamil Nadu, INDIA

January 2, 2013

A. Yes, apart from my experience 0.75 ~ 1.50 mm thickness EN 9 material can get easily 40 ~ 48 HRC by doing the components at mesh belt hardening furnace which will have not much % of Carbon enrichment and decarb due to continuous hardening. As quench condition the hardness will be 55 ~ 60 HRC then have to temper it 320 ~ 340 °C for one hour. Normally this will not have major distortion issue. Otherwise the same Mesh belt furnace with Austempering (quench at 350 °C) will give 42 ~ 48 HRC and there is no need of further tempering.

- KARUR, TN, India

January 4, 2013 -- this entry appended to this thread by editor in lieu of spawning a duplicative thread

Q. What is the Maximum Hardenability of EN9 material in Oil quench. Chemical composition are C - 0.55, Si - 0.15, Mn- 0.75, P-0.003, S- 0.005.


May 7, 2014

Q. Hi sir
I want the details of the EN8 steel hardness and it is used to take a wear test on the austempered ductile iron, and I have hardness of the material of 33 HRC.

gopi nath
student - madurai,tamil nadu,india

July 3, 2014

Q. I am a Commercial heat treater
We received one tube mill roll for heat treatment
The size is 520 mm Dia. X 320 mm
What maximum hardness can I get by Oil Quenching?

Bharat V Shah
metal treatment services - Ahmedabad, Gujarat, INDIA

thumbs up sign Hi, Devarajan, Gopi and Bharat. Sorry, I have no knowledge of heat treatment and can't answer you. All I can do as the site curator is coach you that I've learned from 20 years of postings here that once a question has been answered, any questions which resemble starting over are usually ignored; whereas if you can cast your question in terms of the previous answers, they'll usually elicit enthusiastic response. Is there a way that you can study what has been said and phrase your questions in terms of the excellent help that has already been offered? Thanks!


Ted Mooney, amadeya42.com Teds signature
Ted Mooney, P.E.
Pine Beach, New Jersey

April 10, 2016

Q. Hi sir,

I want to know the heat treatment procedure of EN-9 Material to get 36- 47 HRC through hardening. actually we are doing hardening with the temp of 820/840 °Cs but we are getting as quench hardness very low (18-20 RC). Kindly give the solution for this.

Madhavi Reddy
- Pune, India

April 17, 2017

Q. Material EN9, Hardness required 300 to 350 BHN, size Dia 680 mm thickness 200 mm with bore of 135 mm. Weight is approximately 300 kgs. Please suggest the feasibility of achieving the required hardness and the process parameters.

Vijayendra T R
- Bangalore, India

How to achieve hardness up to 45-50 HRC on C45?

May 8, 2017

Q. With C45 material can I get hardness 44-50 hrc by case hardening?
Length is 91 mm. Pin diameter is 25 mm. And two steps are at both end with diameter 12g6. And surface treatment is hard chrome plating. Required case depth is 0.8-1.2 mm.

Rajkumar w
buyer - pune, Maharashtra, India

May 2017

Hi Rajkumar. Thanks for the good detail on your component. We posted your question and we hope you will receive an answer!

Readers: four people offered generous & insightful responses early on, but although the thread receives continuing questions, and tens of thousands of viewers since Deveraj's answer in 2013, no more answers have been offered in 4 years now! As explained, our experience has been that when people offer their help, they hope that posters will engage them in dialog, appreciating the opportunity to learn; but if the posters instead just try to steer them toward a flash card quiz with slightly changed materials, hardness, and dimensions, they decline to play :-(

Please try your best to follow up with requests for further clarification about the insights already provided, and to offer some specific experience and knowledge of your own, rather than just inserting your own slightly altered parameters into essentially the same question, because this appears to be a kiss of death guaranteeing that your question will be ignored. Thanks!


pic of Ted Mooney
Ted Mooney, P.E. RET
Pine Beach, New Jersey
Striving to live "Aloha"

May 17, 2017

A. Hello Rajkumar!

You need to case harden C45 up to 44-50 HRC, I should say you can achieve that hardness without difficulties.

That hardness is the case hardness or the core hardness? If it is the case hardness, is there any specification for core hardness?

If you already solved this, please let us know! Regards,

Daniel Montanes
TEL - N FERRARIS - Canuelas, Buenos Aires, Argentina

June 17, 2017

Q. Hello,

I would like to know about the volume hardening of En9 to achieve the core hardness of 330-355 BHN. The forged shaft diameter is 45 mm and length is 400 mm with one end disc diameter of 250 mm and length 30 mm. If so, please suggest the H/t cycle.

Lakshmi Machine Works Limited - Coimbatore, Tamilnadu, India

October 27, 2017

Q. We have EN8 material of cylindrical(solid), length= 300 mm, diameter= 60 mm. Our hardening company person promises to harden it at 55C, but there is too much variation in the diameter after hardening. Is it because of continuous hardening more than its capacity? What is the optimum hardness we can expect?

- Noida, India

November 8, 2017

A. Hi Saurabh!

EN8, in my experience, is not a good material for hardening. In 60 mm thick you need, at least, some boron and chromium in your composition to improve hardening depth.

Hardenability is below 50 HRC for more than 6 mm from the surface, maybe you can get this number higher with brine quenching, but not 30 mm (distance from surface to the center).

Best of luck!

Daniel Montanes
TEL - N FERRARIS - Canuelas, Buenos Aires, Argentina

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