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topic 51470

Hardening EN8 & EN9 parts

A discussion started in 2009 but continuing through 2020

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 [dec.]
   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.

DEVARAJ [last name deleted for privacy by Editor]
- 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

Ed. note: Hi Gopi. Welcome! This is a place of camaraderie and we have postings from several people named "gopi nath". Please give us a more complete name so we know which one you are or whether you are another person of the same name. Thanks.

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, Bharat.
Sorry, I've no knowledge of heat treatment but 20 years of running this forum ... and questions which ignore people's previous efforts and simply start over are almost always ignored, whereas if you can figure out how to cast your question in terms of the answers already offered, they usually elicit enthusiasm. Thanks!


Ted Mooney, Teds signature
Ted Mooney, P.E. - Pine Beach, New Jersey
Striving to live Aloha

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

sidebar2 May 2017

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

Readers: four people offered generous & insightful responses early on; and although the thread receives continuing questions, and enjoys thousands of viewers, no more answers have been offered in years now!

Our experience shows that when readers offer their help, they hope the posters will engage them in dialog, appreciating the opportunity to learn; please try your best to follow up with requests for clarification about insights already provided, and offering some specific experience & knowledge of your own. When posters try to steer the responders into a "flash card quiz" of slightly changed materials, hardness, and dimensions, they invariably simply stop playing :-(



pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Aloha -- an idea worth spreading

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

March 24, 2018

Q. Hello there, we make pins from 3 mm to 16 mm dia. and 8 mm to 150 mm length, only in EN8D material. We do hardening process with docking and cooling in salted water. Still we get variation in hardening. We want 48-52 hardness. But very few times do we achieve the target. So can anyone help me with the exact formula to get proper hardness?
Minimum size:- 3 dia x 8 length to 60 mm
Maximum size:- 16 dia x 40 length to 100 mm

Ketankumar Patel
Vijay Engineering works, Ahmedabad. - Ahmedabad, Gujarat, India

May 11, 2018

Q. Hi.

I want to know how to achieve hardening in material EN8D.

We did arc quenching and oil quenching. But it didn't help us.

If anyone knows, kindly help.


Prashant Parsana
- Rajkot. India

July 19, 2018

Q. Hi sir,
We are facing same problem re. hardness in EN8 round bar . The surface of the material is reaching 34-35 HRC but at the core of the material is getting 25-26 only. Please suggest how to rectify the problem.

Dinesh Venugopalsamy
Quality incharge - Coimbatore, Tamilnadu, India

Insufficient hardness achieved in heat treating C45 Material

July 24, 2018

Q. My situation:We have taken C45 grade 4.00 mm thick 70 mm wide material for hardening. Carbon % 0.425 and Mn% 0.66. In last lot used with same heat material hardness achieved 46 to 48 HRC, this month lot achieving hardness 37 to 38 HRC only. What are the probable reasons for non achievement of hardness?

Ashish kekre
Buyer - Dombivli, Thane, Maharashtra, INDIA

November 4, 2018
Laser Hardening

A. We can achieve a surface hardness of 52-54 HRC in C45 material by laser hardening. We are sure about it.


August 2, 2019

Q. Hi sir, I'm Ghadge Dnyaneshwar.
We are using EN8 For washer, but point-to-point variation in 1 piece (32-44 hrc) at checking 180 direction on job. What is the problem?

Dnyaneshwar Ghadge
  ^- Privately contact this inquirer -^

January 17, 2020



Blacksmith's EN9 hammers aren't hardening right

March 12, 2020

Q. Hello I'm looking for some advice. I'm a blacksmith who is starting to make his own hammers I've opted for EN9. I've forged the heads & quenched them and had mixed results. I started with an oil quench and the end result of this seemed soft, leaving dings in the face when hitting high carbon chisels and such.

So I went for a water quench: the first one was successful, and I ended up with a lovely hard face that didn't dent. The three I made after this all suffered with cracking in the cheeks of the hammer. So I tried water quench with alternating between the face and the pen leaving the cheeks to cool slower, and this left me with what I felt was still too soft.

So my question is: what kind of hardness should I expect to achieve on a EN9 hammer, and are there any hints tips or advice on the heat treating process for hammer-making. Thank you in advance.

David Baynes
Fire Monkey Forge - SPALDING

March 15, 2020

Q. Hi
We are manufacturers of steel shoe shanks using EN9 material.

We always had problems in hardening process and quenching and rusting issues after few weeks.

Kindly give us expert advice to solve our problems.


Sardhar Latheef
General Manager - Vellore, Tamil Nadu, India

March 2020
(courtesy of

A. Hi Sardhar. I am not knowledgable in heat treatment and can't help you on that, but short of the readers referring you to a technical library, I'm sure it will have to start with the specifics of your process sequence, not just "had problems in hardening process and quenching and rusting" :-)

Please tell us what you are currently doing for heat treating & quenching. You apply no corrosion preventative of any sort? Are you not allowed to? Thanks!


pic of Ted Mooney
Ted Mooney, P.E. RET - Pine Beach, New Jersey
Aloha -- an idea worth spreading

August 19, 2020

A. Just to answer a couple of questions about EN9 material. This is what we heat treaters call ****. It has very very variable hardnesses from basic hardening and tempering. You would benefit from case hardening the material; however, I don't thing this would be great for hammers.

You need to be looking at high carbon steels (0.6% and above) and harden and temper them to a hard and strong condition.

Hope this helps

James Bailey
- United Kingdom

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