How to bring heat treating in house.

Guest · Jun 25, 2018

I am losing out on a lot of work lately because I do not heat treat. When I was in Cali I had a dozen heat treaters within a 50 mile radius, there are none in a 100 mile radius in the Confederacy and maybe none in the state. I have never used any outside processing that I could not will call from or they delivered to me by company truck and I am not going to start now. I would say the largest part I normally make would be 1/2" diameter 8" long in batches of 100. Materials needing heat treating would mostly be 400 series stainless, 4140, and tool steels.

I am just wondering what the best size oven to buy would be, looking for as small as could serve my needs. Also I do not have natural gas here, so a gas oven would need a holding tank installed and the gas trucked in. Wondering if an electric oven does just as good as a gas one, just more expensive. I do live in an area where electricity is reasonable $.12 per KWH and no demand charges. Also wondering how long it takes to heat treat the above items on average for calculating cost. Also are there any downsides to doing small batch heat treating yourself? Thanks in advance. Also for those people who post "Google is your friend" I mostly trust the PM crowd for good info and I have satellite internet which can drop out 6 times in an hour and be down for hours at a time on a frequent basis, internet searches can suck, along with the capped data.

DMF_TomB · Jun 25, 2018

Dualkit said:
I am losing out on a lot of work lately because I do not heat treat. When I was in Cali I had a dozen heat treaters within a 50 mile radius, there are none in a 100 mile radius in the Confederacy and maybe none in the state. I have never used any outside processing that I could not will call from or they delivered to me by company truck and I am not going to start now. I would say the largest part I normally make would be 1/2" diameter 8" long in batches of 100. Materials needing heat treating would mostly be 400 series stainless, 4140, and tool steels.

I am just wondering what the best size oven to buy would be, looking for as small as could serve my needs. Also I do not have natural gas here, so a gas oven would need a holding tank installed and the gas trucked in. Wondering if an electric oven does just as good as a gas one, just more expensive. I do live in an area where electricity is reasonable $.12 per KWH and no demand charges. Also wondering how long it takes to heat treat the above items on average for calculating cost. Also are there any downsides to doing small batch heat treating yourself? Thanks in advance. Also for those people who post "Google is your friend" I mostly trust the PM crowd for good info and I have satellite internet which can drop out 6 times in an hour and be down for hours at a time on a frequent basis, internet searches can suck, along with the capped data.

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better off hiring someone with vast technical expertise and experience. some countries hire professors and or consultants. some companies that sell heat treating equipment might offer assistance, training, expertise, etc

Guest · Jun 25, 2018

DMF_TomB said:
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better off hiring someone with vast technical expertise and experience. some countries hire professors and or consultants. some companies that sell heat treating equipment might offer assistance, training, expertise, etc

What kind of response is that? Honestly, plenty of times I have hired so called "experts" and fired them due to incompetence and done the job myself much better than the incompetent "expert" did. Once again why are you responding in a shop owner thread and management thread, last I checked you were nether.

DMF_TomB · Jun 25, 2018

Dualkit said:
What kind of response is that? Honestly, plenty of times I have hired so called "experts" and fired them due to incompetence and done the job myself much better than the incompetent "expert" did. Once again why are you responding in a shop owner thread and management thread, last I checked you were nether.

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i have been a consultant before and worked with expert consultants from other companies. i have often worked for companies that bought turn key machines
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you buy machine / equipment factory people setup test prove it works and train people in factory how to use their machines
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its good advice which you are free to ignore

M.B. Naegle · Jun 25, 2018

We did this 12 or 15 years ago. We now have 2 ovens, both electric.

It's a whole new world in that you have to learn a process for each kind of material. But it's not that hard. We do alot of A2 and D2 and have worked it out. Tool steel manufactures give out the specifics for treating their materials. Case hardening requires some special materials, but air hardening is easy. You just need an oven and a roll of heat treating foil to encase the parts in.

We re-purposed a manual foot operated folding machine used for making wallets to fold/close the edges of foil bags to enclose the parts. We learned that if you throw in a little square of cardboard in the bag, it burns off any oxygen in the bag so the part doesn't oxidize and scale. Most heat treating involves bringing a part up to a temperature, holding it there, then cooling it down in a controlled fashion, all in the oven. Afterwards a quick polish with a wire wheel and you have a decent looking part.

You'll need a hardness tester if you don't already have one. That's your "QC" for the process.

m98custom1212 · Jun 25, 2018

Were I worked previously we did some small batch oven ( <50) heat treating 4140, O2 and A2. It was 220/240v oven dont remember the max temperate or cost. It was around 20X20X12 inside we could for you if put some racks inside. Yes it can be done in-house.. It was me I would only do a narrow range of materials.

DMF_TomB · Jun 25, 2018

M.B. Naegle said:
We did this 12 or 15 years ago. We now have 2 ovens, both electric.

It's a whole new world in that you have to learn a process for each kind of material. But it's not that hard. We do alot of A2 and D2 and have worked it out. Tool steel manufactures give out the specifics for treating their materials. Case hardening requires some special materials, but air hardening is easy. You just need an oven and a roll of heat treating foil to encase the parts in.

We re-purposed a manual foot operated folding machine used for making wallets to fold/close the edges of foil bags to enclose the parts. We learned that if you throw in a little square of cardboard in the bag, it burns off any oxygen in the bag so the part doesn't oxidize and scale. Most heat treating involves bringing a part up to a temperature, holding it there, then cooling it down in a controlled fashion, all in the oven. Afterwards a quick polish with a wire wheel and you have a decent looking part.

You'll need a hardness tester if you don't already have one. That's your "QC" for the process.

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you can buy a book on it but obviously experts with decades of experience might make better decisions than trying to learn your self. i run machines with 2000 pages of operator manuals and 1000 pages of maintenance manuals. i for one would rather have a expert train me or work with expert than just read and try to understand 3000 pages all by myself
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ASM Handbook: volume 4: Heat Treating (Asm Handbook) (Asm Handbook): Asm: 9783798: Amazon.com: Books

billzweig · Jun 25, 2018

I all my heat treatment, quite a lot of it actually, in my own shop. I work with small parts seldom larger than 4-5" long/wide. All kinds of tool steel (mostly air harden, but occasionally oil as well) , stainless and beryllium-copper (and other forms of heat treatment as annealing etc) I have three muffle furnaces: two up 1100C and one up to 1600C as well as one small vacuum tight oven I use with inert or hydrogen atmosphere. All electric and quite small, about one cubic foot. I got all used and added new temperature controllers with thermocuples and SSRs. I have as well two low temperature ovens (up to about 350C). For one off small parts I often use induction heater.
Heat treatment is rather straightforward if one keeps to the prescribed procedures. Electric ovens with controllers certainly make this simpler.

M.B. Naegle · Jun 25, 2018

IMO it all depends on how in depth you are getting into it. Doing heat treating in house is no different than buying a lathe and turning parts in house. Depending on what you are doing it can be dirt simple, or a big headache, but the end goal is control over your product and cutting costs. If you can't do those two things, it's probably better to leave it to someone else.

Guest · Jun 25, 2018

M.B. Naegle said:
We did this 12 or 15 years ago. We now have 2 ovens, both electric.

It's a whole new world in that you have to learn a process for each kind of material. But it's not that hard. We do alot of A2 and D2 and have worked it out. Tool steel manufactures give out the specifics for treating their materials. Case hardening requires some special materials, but air hardening is easy. You just need an oven and a roll of heat treating foil to encase the parts in.

We re-purposed a manual foot operated folding machine used for making wallets to fold/close the edges of foil bags to enclose the parts. We learned that if you throw in a little square of cardboard in the bag, it burns off any oxygen in the bag so the part doesn't oxidize and scale. Most heat treating involves bringing a part up to a temperature, holding it there, then cooling it down in a controlled fashion, all in the oven. Afterwards a quick polish with a wire wheel and you have a decent looking part.

You'll need a hardness tester if you don't already have one. That's your "QC" for the process.

Thank you very much for your response, is the foil wrap to keep the scale or discoloration down? Most of the general parts I mentioned above I have had heat treated before and they always came back discolored and that was easily removed. I did have some warpage issues on long skinny 416 parts that varied that appeared to be cased by how they were loaded in the oven.

Guest · Jun 25, 2018

M.B. Naegle said:
IMO it all depends on how in depth you are getting into it. Doing heat treating in house is no different than buying a lathe and turning parts in house. Depending on what you are doing it can be dirt simple, or a big headache, but the end goal is control over your product and cutting costs. If you can't do those two things, it's probably better to leave it to someone else.

I have done a lot of things decent with little training or self taught, jack of all trades master of none. I have hired many a job out when I was too busy and after firing the expert (machine repair tech, electrician, carpenter) I took over the job and did better than they did. I consider myself B grade at a lot of things, but have hired educated and licensed people that did work sub standard to mine, maybe I should increase my opinion of myself.

I am just applying common sense here, on a guess a heat treat oven the size of a large microwave will work. The parts I want to heat treat are simple, like drill bushings, spacers and shafts with open tolerances. I just need to make the materials harder on the RC scale.

Guest · Jun 25, 2018

DMF_TomB said:
.
.
you can buy a book on it but obviously experts with decades of experience might make better decisions than trying to learn your self. i run machines with 2000 pages of operator manuals and 1000 pages of maintenance manuals. i for one would rather have a expert train me or work with expert than just read and try to understand 3000 pages all by myself
.
ASM Handbook: volume 4: Heat Treating (Asm Handbook) (Asm Handbook): Asm: 978�8717�3798: Amazon.com: Books

Go away please, you have nothing to contribute here.

M.B. Naegle · Jun 25, 2018

Dualkit said:
Thank you very much for your response, is the foil wrap to keep the scale or discoloration down? Most of the general parts I mentioned above I have had heat treated before and they always came back discolored and that was easily removed. I did have some warpage issues on long skinny 416 parts that varied that appeared to be cased by how they were loaded in the oven.

Yes the foil creates an individual chamber for each part or batch. Our second oven we bought has an air tight chamber and the connections to fill the chamber with gas. We bought it so we could purge the air and fill it with Carbon Dioxide for case hardening parts but we have yet to actually use the feature. If I understand right, you could also purge it with air hardened parts to eliminate the oxygen in the air.

Parts moving or warping is akin to having parts deflect in your vice. It's all about the set-up. We've had long skinny plates that we bolted together in one big stack and the connected mass kept them stable. Others you have to plan for post heat-treating ops to get the parts to spec. You'd cut critical features oversize and grind them to spec. after treating.

Zahnrad Kopf · Jun 25, 2018

This is not black magic. It's not even rocket science. We heat treat almost every day. Get yourself one of the old Orange colored Crucible books and the ASM Heat Treater's Guide if you want to be very prepared. It's knowledge easily learned like most others. Yes, some materials have idiosyncrasies. Yes, orientation of soak and quench both have a large effect. Yes, it can be dangerous. Yes, it can be troublesome. Yes, it can easily be learned and done.

Conrad Hoffman · Jun 25, 2018

I have a small kiln and a bench torch and do my own tools. It would be really nice to have an oven with a controlled atmosphere, as wrap isn't always good enough for precision parts.

Rob F. · Jun 25, 2018

A small electric oven like a Blue M should do you fine. If you are lucky they can be had cheaply. I got mine at the scrapyard for $80 and it works great. It is a M30A that heats to 1850F 4x4x12 chamber, I think it draws 14 amps 240V. I use it for doing HT on smithing tools. If looking at electic ones pay attention to max temps, some do not get hot enough.
If you go with a gas one a bbq or rv sized cylinder should be fine for several runs. In regards to time 1 hr per inch of thickness comes to mind, so your 1/2" rounds aprox 1/2 hr or a bit less. (preheated oven or add warm up time)
This is like mine but it may be a bit small for your needs:
BLUE M LAB-HEAT MUFFLE FURNACE MODEL M3A-1C | eBay

guest · Jun 25, 2018

Company I used to work, we brought heat treat in house. Spent well over $1 M doing it. Atmosphere furnaces, endo generator, draw furnaces, all the associated racking and baskets, etc

Heat treating your own stuff and heat treating for customers are not the same thing.

Will you need to provide certs? You will need data recording on everything- furnace and quench temps, atmosphere, tempering temps, times, etc.

And of course, any failures the customer is going to blame your heat treat...

adh2000 · Jun 25, 2018

I have to side a bit with DMFTom here. I've done heat treating myself with success. Yes you can do it and if you don't have a shop near you then what choice have you got. But here I have Thermtech just down the street. They run three shifts so if you've got something common like 8620 or 4140 and you get it in by 5:00PM it's ready to pick up at 7:00AM the next morning. Can't beat that. More important they have lots of different furnaces and ovens with lots of different controlled atmospheres and lots of different quenches. So they can pick and choose what's best for the part size, cross section, and material. Parts come out nice and shiny due to controlled atmosphere, uniform, no twisting warping or cracking. Also they are excellent with technical knowledge and advice on what material to use how to harden it, how to quench and drawback all that good stuff. No way would I go back to trying to do any heat treating in house. I guess I'm suggesting you keep looking.

ignator · Jun 25, 2018

You don't need a PHD to do heat treat. I was a green horn 25 years ago. I needed a 3/4 inch shaft to fix my skid steer loader. It had to be hardened to Rc=55. My first material I learned to use was O2 tool steel.
The materials you indicated in your original post are easy, and the size small that you don't need to worry about temperature and stress excursions from thin to thick cross sections.
I purchased a glass maker kiln from Paragon, as their heat treat or knife maker kilns were 2x the price with the only difference the front door swinging down vs hinged to the side. Same inside dimensions.
The max temperature was the same, and the electronic controller the same. You do need a Rockwell hardness tester to verify hardness after tempering. I assume you understand it to be a 2 step process, first to make it as hard as the base material will become, and then a tempering process to reduce the brittleness.

TNFE14 Kiln is a kiln used for China Painting,Enameling,Glass. Paragon Kilns.

For reference I purchased a Chinese Rockwell hardness tester, and it continues to be accurate against the test coupons.

One of the useful things the oven can do is anneal tool steel so it is soft, you can do normal machining operations, then heat treat it back for cutting. With air hardening tool steels the controller will perform a slow cooling rate to anneal (overnight).

Modelman · Jun 25, 2018

Dualkit said:
Thank you very much for your response, is the foil wrap to keep the scale or discoloration down? Most of the general parts I mentioned above I have had heat treated before and they always came back discolored and that was easily removed. I did have some warpage issues on long skinny 416 parts that varied that appeared to be cased by how they were loaded in the oven.

No one fully addressed this question. The scale is a symptom, but the real problem is heating carbon steel in air will burn the carbon out of the surface (called "de carb") and leave a soft mild steel skin on the part, the exact opposite of case hardening. Not good. I don't have enough experiance with heat treatment of stainless to comment. Perhaps someone else can.

Dennis

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