Heat Treatment on Drawing (8620)

or do I have to specify that as well?

Hi,
It's not my field of expertise, but experience says specify absolutely everything because if you don't someone will find a way of buying the wrong thing or doing the wrong process to save money (or to be 'helpful')

Ideally you should refer to recognised standards, but if all else fails you could write, 'heat to cherry red and quench in oil', (or whatever the process you require is) on the drawing.

Actually you could always add your comment...
This part can and will fail if it is not heat treated correctly
to the drawing
Del

Turn the question around. When you receive the part(s) back from the vendor, how will you know if the correct heat treat was done? In other words, you need to spec what you can measure.

Jim,

You are already half way there.

You need to look up the steel spec sheet for your material (8620).
This will have detailed heat treating instructions for this exact material.

Attach this to your job sheet and specifiy that the materials and the Heat Treatment are as per the Job Card, design and Spec Sheet.

As an amateur Blacksmith I tend to collect them.

I think I have a copy of the spec sheet at home, if I do I will send it to you as a direct CR4 mail rather than a post. The other option is to contact your material supplier and ask them for it.

Regards,
Sapper

Jim,

This Link should get you to a Data Sheet for you Material.

http://metals.lincdigital.com.au/files/Product%20datasheets/Atlas8620H.pdf

You can then download and attach as required or just cut & paste the relevant bits.

Regards,
Sapper.

Thanks SAPPER!

here is 8620 fact sheet as promised.

Since we can;'t attach pdf's i'm sending it as aphoto

Thenumbers along the left side are for case properties; thoseon the right are core. Look carefully at the units headers and you should be OK.

milo

In our industry we do the following

a) The heat tretment in the drawing is mentioned in the note as "case carburize to 1.5 mm deep to 60-62 HRC"

b) In certain cases we provide the total heat treatment cycle

"Case carburize to std ...."

This can be your own std or even international standards are available. But the case depth must be specified.

c) The raw material and supply coditions are always spelt out in the drawing

"Raw material 40CrNiMo65 in HT condition" etc

Ed,

Blacksmiths (Modern anyway) will not argue with you.
Thats why Case Hardening was created.

The reason I keep Spec Sheets for material is so when I need to know if a material will do what I want\need it to do, I know if it will or wont and if it will, what do I have to do.

A good blacksmith will send the finished part for heat treating by a specialist in heat treating if the treatment is specific as in this case.

In the course I did on blacksmithing at Tech, we spent six (6) months on heat treating as it is so important to know where to draw the line as to DIY or outsource.

But before you can make that call you need the spec sheet to make an informed decision.

So I start from there.

Regards,
Sapper

For what I know, the carbon content affects the heat treatability of metal ie. you have metal with small carbon content you will get a limit of hardness with heat treating. This hardness however is called core hardness. In your case, surface hardness is what you need, then carburizing or carbo nitriding will do. You need to specify the heat treating process - carburize, case depth, case hardness, and no decarburization between case and core allowed.

All these required specifications are measurable.

Guys,

Thanks for all the comments so far. I know a little about heat treating (Enigineering school and a very little from industry experience, so this help has been tremendous. I have a couple metals handbooks and the machinery handbook and of course the WWW. All of this does not add up to much when your making a number of different items, all needing treatment and each item having critical requirements.

The roller I am working on is a new design for an old high performance rocker arm roller from and overhead cam engine. Since I asked for help on the forum, someone has sent me a copy of an old print, and the original material was specified as SAE 51100 (which seems to something the SAE has "deadlisted" The print only called out the material, the hardness R "C" 60-64. Not the heat treat or tempering specifications.

I thought 8620 would be a good substitute due to it's ability to take (Case Hardening) carburization and the Metals Handbook indicates a R "C" of somewhere around 62 is possible.

At this point I am not sure if it's the best material. The part will be ground after heat treat and the section through the part is constant at about .21" x .45"

It would seem like the 8620H is a good choice is it is "certified" hardenable. Also it seems like I need to understand what condition the bar stock is delivered in.

The treatment times and temperature for 8620 seem to be pretty well known along with the formulas for time at certain temps due to thickness, it's just that when I look up information, differentiating between Carburizing, Hardening, Tempering and Annealing is not always done in the literature, so it can be a pretty confusing thing to self learn.

I was thinking I should specify a Case Depth of .03-.04 before grinding to have something thick enough to be able to use a Rockwell "C" test.

Any additional feedback would be greatly appreciated, the responses so far have been really great.

Thank you

You might look into 52100 as a replacement material.

52100 is the steel used for ball and roller bearings. It is a pretty high quality material with special melting requirements in the steel mill for bearing use. You may have trouble finding bar stock in small quantities; or you may get lucky.

You don't case harden 52100. It already has 1% carbon in it's composition. I'm sure the bearing manufacturers have highly developed heat treating processes involving heating, quenching and tempering. In all my years of working with ball bearings I've never heard a whisper on the subject other than vague hardness specs in the bearing catalogs.

Roller rockers and lifters are common technology in the world of automobile racing and there are small manufacturers in the USA who make that stuff. Should be lots of info on the internet; but you may have to dig to find mention of the material used for rollers. If I drew a blank on that I'd take a look at one of the standard tool steels. They are usually readily available in bar stock though a bit pricey for most production applications.

Comments anyone closer to this corner of automotive technology?

Ed Weldon

Ed you are correct about 52100, including difficulty to find in small quantities.

We produced it in Bearing Quality for automotive applications described. It will need to be spheroidized annealed, and spheroidal struture, lack of decarb, and carbide network are all issues specific to this grade as opposed to 8620.

I hesitated to suggest this 1% carbon alloy steel as a substitute for the original .20 Carbon Alloy grade, thinking that there was already a design intent for the .20 carbon grade- Ie- avoidance of through hardening and better differentiation of core/case structures/properties.

I will be providing data sheets in AM.

milo