# Looking for stress relieving advice



## Shotgun (Mar 19, 2021)

The project for this week is to build a sine bar.  I know I could buy one for not too much money, but this is an exercise in how closely can I hit the mark I'm aiming at.

So far, I have the 1" bar squared up and the holes laid out.  I'm using a piston wrist pin, cut in half, for the pivot.  The plan is to drill holes for the pivots just above the bottom edge of the bar, drill several lightening holes along the length, and then cut off the bottom of the bar with the bandsaw in order to expose the pivots.  With all that done, I'll clamp it to my mill table and run a grinding wheel across the top.

My expectation is that a week later it'll be as twisted as a wet noodle.  I'd like to head that off by heat treating it, but all I have is a toaster oven that gets up to about 400F.  Am I kidding myself that 400F will do anything to stress relieve it after I've done the rough cutting?


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## cathead (Mar 19, 2021)

My thinking is that it depends on what material you made the bar with.  The one I made was just mild steel
so figured it didn't need heat treating.  Out of curiosity, what kind of steel did you use to make it?


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## Weldingrod1 (Mar 19, 2021)

Clean it, toaster oven it to burn off the last oil, then sneak it in the kitchen and run the oven all the way up OR do the self clean cycle. Or BBQ grill it... 
It's not going to help much, but with cold rolled, you want all the help you can get!

Check out the spread on this cut! It finished at about an inch opened on a 26" long part! I baked it at nearly 600F and the slots didnt do anything noticeable. 
	

	
	
		
		

		
			








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## Shootymacshootface (Mar 19, 2021)

I would never want one of those. That would mean that I would have to figure out trig!


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## Shotgun (Mar 19, 2021)

cathead said:


> My thinking is that it depends on what material you made the bar with.  The one I made was just mild steel
> so figured it didn't need heat treating.  Out of curiosity, what kind of steel did you use to make it?


I think it is hot-rolled A36.  But, that is just a guess.


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## MrWhoopee (Mar 19, 2021)

The self-cleaning oven cycle is probably the best way to go at something like 800° F, although the pieces are small enough that you can probably get there with a propane torch and some patience.


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## Technical Ted (Mar 19, 2021)

When I make weldments out of mild steel I throw them in my wood stove and let them cook for all day, then cool slowly still inside the stove over night. They will get dull to medium cherry red when fully up to heat. They will have a slight scale on them in the morning which cleans right off and no hard spots from welding/torch cutting operations. I'm sure there are better ways, but that's all I've got and it seems to work very well for me. From the research I've done, it gets them to around the correct temperature for stress relieving.

Ted


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## Shotgun (Mar 19, 2021)

I think I'll try the wood fire.  I guess it might also add a small amount of carbon.  I'd stick it in the oven, but. . .Lord. . .I'd never hear the end of that one.


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## Technical Ted (Mar 19, 2021)

Not sure if it will be adding carbon or actually losing some.... You'll most likely want to finish pieces after the heat treat if size and finish are important to you. Being a sine bar, size certainly would be a concern.

Ted


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## MrWhoopee (Mar 19, 2021)

Technical Ted said:


> When I make weldments out of mild steel I throw them in my wood stove and let them cook for all day, then cool slowly still inside the stove over night. They will get dull to medium cherry red when fully up to heat. They will have a slight scale on them in the morning which cleans right off and no hard spots from welding/torch cutting operations. I'm sure there are better ways, but that's all I've got and it seems to work very well for me. From the research I've done, it gets them to around the correct temperature for stress relieving.
> 
> Ted


Being a woodburner myself, I really like this. It should give you a full anneal without risking the wife getting out of sorts. Of course it won't fly in the summer.


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## Technical Ted (Mar 19, 2021)

MrWhoopee said:


> Being a woodburner myself, I really like this. It should give you a full anneal without risking the wife getting out of sorts. Of course it won't fly in the summer.



Use a camp fire!

Ted


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## MrWhoopee (Mar 19, 2021)

Technical Ted said:


> Use a camp fire!
> 
> Ted


We go directly from woodburning season to wildfire season, very narrow window. Maybe I need an old woodburner outside.


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## graham-xrf (Mar 19, 2021)

I put a couple of old blunt files into the woodburner hoping to anneal them somewhat, so to use the metal for another purpose. I think it sort of worked because I can now file on the metal with another file.
BUT..
.. it begs the question as to whether "stress relieving" need be the same thing as "annealing"?

 I get it that if you heat the metal fully to annealing temperature, then cool slowly, then you will definitely have relieved stresses, but can being cooked at a temperature well short of annealing also relieve stresses?

I ask because we know that you can temper fully quenched near glass-hard steel back to less hard, yet not brittle, using temperatures much lower than getting it to red heat. The internals of the metal structure clearly _can_ be altered by much lower temperatures, possibly like those easily achieved in a domestic oven.

If you do use a woodburner, make sure there is a nice layer of wood ash under the part, and before the overnight cool-down, cover it with hot wood coals and ash. The ash is such a good insulator, I have raked apparently cold ashes aside in the morning, and found coals in them still glowing red!


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## Shotgun (Mar 19, 2021)

MrWhoopee said:


> We go directly from woodburning season to wildfire season, very narrow window. Maybe I need an old woodburner outside.


My plan was to use the chiminea.


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## MrWhoopee (Mar 19, 2021)

graham-xrf said:


> I put a couple of old blunt files into the woodburner hoping to anneal them somewhat, so to use the metal for another purpose. I think it sort of worked because I can now file on the metal with another file.
> BUT..
> .. it begs the question as to whether "stress relieving" need be the same thing as "annealing"?
> 
> ...


They are not the same.

Annealing is heating and holding above the critical temperature (between 1330 and 1670° F, depending on the alloy), then slowly cooling, resulting in the softest condition of the steel.




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						Annealing / Normalising - Heat Treatment - Bodycote plc
					

Annealing is a heat treatment process which alters the microstructure of a material to change its mechanical or electrical properties. Typically, in steels, annealing is used to reduce hardness, increase ductility and help eliminate internal stresses.




					www.bodycote.com
				




Stress-relieving is heating to a temperature below the critical temperature (between 1000 and 1200°F) which allows internal stresses to relax without reducing the hardness of the steel.




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						Stress relieving on metal products - Heat treatment - Bodycote Plc
					

Minimising residual stresses in the component structure thereby reduces the risk of dimensional changes during further manufacturing or final use of the component.




					www.bodycote.com


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## Weldingrod1 (Mar 20, 2021)

Full stress relief will reduce the yield stress for anything that was hardened or cold worked. Once you have hardened and tempered running up to or near the tempering temperature will generally not do anything.

However, precipitation hardened materials like many Aluminum alloys and 17-4PH also have a time at temperature dependence below the dissolving temperature.

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## Shotgun (Mar 20, 2021)

Well, this is just a sine bar.  I don't expect it to carry any loads.  I just want it to stay the same dimensions that I cut it at.

Just cause it was easy, and I was in the shop anyway, I threw it in the toaster oven today.  It turned a bright, irridescent blue.  Quite pretty actually.  I don't know if that give any clue as to what the composition of the material is, though.


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## Shotgun (Apr 5, 2021)

Don't know if this link will come through, but it is the only graph I could find that would plot temperature against the amount of stress relief that could be achieved.  It looks like leaving it in the oven longer will help, but the toaster over is only going to do the barest amount of stress relieving.



			https://image.slidesharecdn.com/weldinglectures14-16-150902090349-lva1-app6891/95/welding-lectures-14-16-7-638.jpg?cb=1441184748
		


Just more justification for me to get this furnace build finished up.


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## Weldingrod1 (Apr 6, 2021)

Interesting data! Any idea where it came from?

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## Shotgun (Apr 6, 2021)

Weldingrod1 said:


> Interesting data! Any idea where it came from?
> 
> Sent from my SM-G892A using Tapatalk


Slide show for a class on welding is as close as I could tell.


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