Looking to bring small scale annealing in house

[MotoX]

Our product uses mostly 1026 steel tubing. Finished part specs requires that the material be annealed. The tubing suppliers state it comes in the "annealed" state but I can tell you there is a major difference in the end result of parts that have been annealed after the fact.

Our current "heat treater" is closing the doors. I say heat treater in quotation marks, because they just throw our parts in the furnace along with theirs. I have an opportunity to buy their smallest non atmosphere electric furnace for a song.

In any case, I'm looking to anneal approx 200-400 lbs a week of various sizes of this tubing. All the same spec, all the same treatment. Largest part is 11" diameter 1/2 wall by 5" long, largest part by weight is 8-1/2 diameter 1-1/4 wall tubing by 6.5" long, Smallest part is probably 2.5" od 1/4" wall by 3. We have 60 or so part numbers.

My main question is, Is this feasible to bring in house?

There are not any heat treaters in this area. I would have to pay for freight as well.

So far this year i have spend around 8k for HT services, but i feel like they never really charged what a normal HT'r would. I expect to spend around 16-25k a year outsourcing it.

Secondary question, What other problems will i run into doing this myself?

The only HT experience i have is torch heating a small piece of W1 drill rod and quenching it. I also just ordered these two books, as recommended in another thread.

Amazon.com

Heat Treatment: Master Control Manual: Bryson, William E.: 9781569904855: Amazon.com: Books

Heat Treatment: Master Control Manual [Bryson, William E.] on Amazon.com. *FREE* shipping on qualifying offers. Heat Treatment: Master Control Manual

www.amazon.com

Third question is, How to deal with scale from a non atmosphere furnace? The current HT'r uses giant automatic shot blasting units, not feasible for our facility.
Will the scale make a mess of out coolant if i just run them dirty?

 

[MotoX]

Here is a spec for HTing 1026 from Heat Treaters Handbook.

 

[sfriedberg]

I can't say if buying their furnace is a good choice for you, but will say you can certainly bring simple HT inhouse. I have an old Thermolyne burnout furnace with a new PID controller that I use for heat treat of ordinary (non-HSS) tool steels. It's not quite big enough to handle your 200-400 lb/week requirement, but there are lots of somewhat larger HT furnaces that are.
Scale in a plain-air furnace can be a problem. I usually use SS tool wrap but that's not a good solution for bulk large tube. I would look at anti-scaling washes that can be rinsed off after HT. Proprietary compounds are expensive. Look into making your wash from boric acid dissolved in alchohol, let dry before HT, rinse off with water or sodium bisulphate solution after HT.
Since you want to anneal primarily, rather than harden, you don't have to worry about setting up for quenching. Get a good programmable controller for the furnace, ramp up to annealing temperature, soak for appropriate time, then slowly cool to below the critical temperatures. Several hour schedule per load. Can unload when at 150F for sure, quite possibly at a higher temperature than that. Have racks so your hot parts don't roll around, requiring people to grab them.
[Added in edit] Sodium bisulphate is a pickle for non-ferrous metals, so probably not an especially good choice for 1026. You may need to experiment with various rinses. And, you should finish with either a thorough plain water rinse, or an alkaline rinse. Maybe an industrial detergent like Alconox?

 

[Rickyb]

Follow friedbergs advice and you will be good. Annealing is the easiest of the heat treating processes. Not much can go wrong. To quench and temper is a huge process leap from there.

you can minimize scale by sealing the furnace to limit the amount of air available.

 

[dgfoster]

Follow friedbergs advice and you will be good. Annealing is the easiest of the heat treating processes. Not much can go wrong. To quench and temper is a huge process leap from there.

you can minimize scale by sealing the furnace to limit the amount of air available.

To expand on this idea a bit: Since you are doing parts over and over that fit within a given size envelope, then rather than using purpose made SS foil to prevent scale, I would think about making heat treating tubes or square cylinders into which you could load a batch of parts and then seal the tubes after putting some paper "getter" in the tube. It does not take much getter---a postcard-sized piece would do for a 5 gallon bucket. The paper combines with O2 in the container and that prevents scaling completely.

You might be able to make a single large cylinder to fit into the furnace you have or several smaller ones might be easier to handle. I have successfully used the analogous paper-in-foil technique many many times to heat treat steel or iron at what would otherwise be scaling temperatures. The tubes would be made from SS and could be sealed using a "gasket" of ceramic wool between lid and container. (I use such wool in my small foundry on an ongoing basis.) If you are nervous about using ceramic wool as a gasket (there is extremely low risk in the sort of use you are considering) or if OSHA regulations prevent it, you could seal the tubes with carefully applied foil perhaps held in place with stainless hose clamps. This would be a lot easier and more economical than wrapping parts in foil and would eliminate scale.

Yes, what I am suggesting would require a bit of experimentation which may or may not appeal to you. I can assure you that this is an avenue I would explore in your situation.

 

[dgfoster]

Follow friedbergs advice and you will be good. Annealing is the easiest of the heat treating processes. Not much can go wrong. To quench and temper is a huge process leap from there.

you can minimize scale by sealing the furnace to limit the amount of air available.

Follow friedbergs advice and you will be good. Annealing is the easiest of the heat treating processes. Not much can go wrong. To quench and temper is a huge process leap from there.

you can minimize scale by sealing the furnace to limit the amount of air available.

To expand on this idea a bit: Since you are doing parts over and over that fit within a given size envelope, then rather than using purpose made SS foil to prevent scale, I would think about making heat treating tubes or square cylinders into which you could load a batch of parts and then seal the tubes after putting some paper "getter" in the tube. It does not take much getter---a postcard-sized piece would do for a 5 gallon bucket. The paper combines with O2 in the container and that prevents scaling completely.

You might be able to make a single large cylinder to fit into the furnace you have or several smaller ones might be easier to handle. I have successfully used the analogous paper-in-foil technique many many times to heat treat steel or iron at what would otherwise be scaling temperatures. The tubes would be made from SS and could be sealed using a "gasket" of ceramic wool between lid and container. (I use such wool in my small foundry on an ongoing basis.) If you are nervous about using ceramic wool as a gasket (there is extremely low risk in the sort of use you are considering) or if OSHA regulations prevent it, you could seal the tubes with carefully applied foil perhaps held in place with stainless hose clamps. This would be a lot easier and more economical than wrapping parts in foil and would eliminate scale.

Yes, what I am suggesting would require a bit of experimentation which may or may not appeal to you. I can assure you that this is an avenue I would explore in your situation. In the long run it could save a ton of time and money.

Denis

 

[MotoX]

Thanks for the time and replies.

It sounds like this IS a feasible endeavor, but the biggest issue is going to be with scale.

You all have provided a lot of avenues to deal with the scale. I will have to experiment with all and find what works best for our situation.

I'm hoping that one way or another I can prevent it, rather than deal with it after the fact. The furnace is well insulated. I fired it up yesterday to 1600 and could not feel escaping heat from hardly anywhere. The only way i could tell it was on was peeking through the little peep hole in the door. I wonder if i could rig up a inert gas bleed to try to keep a positive displacement of oxygen.

It will be a couple months before we are up and running, but i will report back with successes and failures I'm sure.



One more question;
Do electric furnaces require a huge amount of ventilation?

I imagine not every piece of material is completely clean inside and out. Surely residual oils from manufacturing and or sawing coolant will smoke?

I ask because the building I will install the furnace in, is just a basic block construction garage. 3 overhead doors and windows on 2 sides.

Will the furnace turn the building into a black crusty mess? Or is the temperature so high that it burns everything completely off?

Thanks

 

[DDoug]

Looking at this another way...
Maybe don't buy the existing process oven, get something better like induction or vacuum, or at least a controlled atmosphere furnace.

 

[MotoX]

Looking at this another way...
Maybe don't buy the existing process oven, get something better like induction or vacuum, or at least a controlled atmosphere furnace.

I got 2 quotes on different types of furnace's. Vacuum furnaces were a whole 'nother animal. Induction furnaces are limited in efficiency to a certain size of material, or so Ive been told.

A controlled atmosphere unit from Lindberg Part no 12-RO-1824-18A, was 140k without the options for controlled atmosphere.

Another quote for a new uncontrolled furnace almost identical to the one mentioned in my first post was 96k.

https://www.grievecorp.com/product-category/furnaces/heavy-duty-box-furnace/?model=HD-243624#models

If you include all the support equipment and the energy costs, the ROI is not that great. Not to mention the extra labor involved.

If i can do the same thing for a 1/10th the cost, i will. Maybe after a year or so If this works out and i get the process efficient, I will upgrade. Its hard to spend that kind of dough without actually knowing what I'm doing.

I didn't realize how expensive these units were. I still don't see how. They seem to be just a weldment with ceramic insulation and some fire bricks with some heating elements and a simple control. I'm sure there's a little more to it than that but...

 

[sfriedberg]

I wonder if i could rig up a inert gas bleed to try to keep a positive displacement of oxygen.

I have not done it but in principle a low-flow regulator feeding nitrogen or argon gas from a welding tank would work. A lot will depend on how well your furnace is sealed. If you do this, and it works for you in controlling scale, please follow up with another posting about it.

 

[janc]

One of the problems with a non oxidizing electric kiln is, the heating elements rely on a layer of oxide to remain intact, they will quickly fail without this oxide layer, there are some coatings to slow this down, and I have heard doing an oxidization firing every several firings will allow the oxide layer to reform, but neither are reliable long term solutions. The best way is to have the elements seperate from the atmosphere in the kiln, like a muffle kiln, ( the heat source is in tubes running through the kiln) but that is much more complicated, expensive and takes more energy, this is why non oxidizing ceramic kilns use gas, oil, wood etc, for heat source as it is easy maintain the atmosphere oxygen levels you want.
Venting an oxidizing electric kiln is quite easy and does not require much, all that is done is, for a 20 cu ft kiln, is drill a 1/4" hole in the top in each corner, and an equal amount of hole in the bottom in the center, a small blower is affixed to the holes in the bottom and sucks a little bit of air out the bottom and into a vent pipe to the outside of the building. This venting does two things, one removing fumes, and the small amount of cool air entering the kiln from the top corners, does a pretty good job of mixing the atmosphere and helping maintain more even tempratures from top to bottom.

Thanks for the time and replies.

It sounds like this IS a feasible endeavor, but the biggest issue is going to be with scale.

You all have provided a lot of avenues to deal with the scale. I will have to experiment with all and find what works best for our situation.

I'm hoping that one way or another I can prevent it, rather than deal with it after the fact. The furnace is well insulated. I fired it up yesterday to 1600 and could not feel escaping heat from hardly anywhere. The only way i could tell it was on was peeking through the little peep hole in the door. I wonder if i could rig up a inert gas bleed to try to keep a positive displacement of oxygen.

It will be a couple months before we are up and running, but i will report back with successes and failures I'm sure.



One more question;
Do electric furnaces require a huge amount of ventilation?

I imagine not every piece of material is completely clean inside and out. Surely residual oils from manufacturing and or sawing coolant will smoke?

I ask because the building I will install the furnace in, is just a basic block construction garage. 3 overhead doors and windows on 2 sides.

Will the furnace turn the building into a black crusty mess? Or is the temperature so high that it burns everything completely off?

Thanks