Anealing sheet metal

[Dennis Glazener]

I ran across this info on anealing sheet metal with a torch and thought it might be of interest to some of you:

Basic Annealing With A Torch

Many of the more practical applications for annealing are found in the work shop where a kiln is not available, but a torch is. Be sure that theres is nothing in contact with, or around the sheet metal you’re annealing before beginning.  Use a large torch tip with a softer flame and try to heat the area you wish to anneal as quickly and evenly as possible. The metal should just begin to glow red under dim lighting.  If you have a bright  environment  then you can draw concentric lines with a  permanent  marker around the area you are annealing.  The lines will turn white or  disappear  entirely once the  temperature  of the steel is correct.  Try to maintain the part at this temperature for a minute or so.  Then quench the area with water.  If may be necessary to clean with acid in order to restore the metal’s color.

It comes from this site: http://sheetmetal.me/annealing/

Dennis

[heinz]

Dennis, I would be a little concerned with the water quench.  Generally the sheet metal will be thin enough and the carbon content low enough that you will get the annealining effect on any work hardening following these instruction exactly; but I was taught to let it cool to where a water drop would not "dance" on the surface before quenching even mild steel.  Anything with a significant carbon content you want to cool much slower.  For brass, a fast quench is fine, even the best way.
Thanks fopr posting, I like the marker circle suggestion.

[Pete G.]

I have see shipfitters use the same technique to straighten decks made from 1/2" plate. It is astounding what these guys can do. Sometimes a misalignment as much as 6" can be flattened when heat and quenching is applied in the proper places.

[Dennis Glazener]

Dennis, I would be a little concerned with the water quench.  Generally the sheet metal will be thin enough and the carbon content low enough that you will get the annealining effect on any work hardening following these instruction exactly; but I was taught to let it cool to where a water drop would not "dance" on the surface before quenching even mild steel.  Anything with a significant carbon content you want to cool much slower.  For brass, a fast quench is fine, even the best way.
Thanks fopr posting, I like the marker circle suggestion.

Heinz,
I was a little taken back about the water quenching and the first time I annealed I waited until all the red/orange had disappeared, it seemed to work well (making hinges for a steel patchbox). The next few times I did not quench and it seemed to work as well if not better.
Thanks for the tip,
Dennis

[LRB]

  It is not necessary to quench brass in annealing. Only if you don't want to wait for it to cool. The end result is the same.

[Dennis Glazener]

It is not necessary to quench brass in annealing. Only if you don't want to wait for it to cool. The end result is the same.

I have no problem with brass its the steel sheet metal that is the problem. Even after anealing its tough stuff to do tight bends but at least it doesn't crack after annealing it.
Dennis

[heinz]

Dennis, I find even dull red will help in bending sheet steel.  If you get it hot enough to anneal just go right into bending, provided you are not going up against the wood :-)  Or using your bare hands.

[R.W.D.]

I was taught that you can't harden mild sheet steel. Stuff like HRP&O, HR, or CR steel dosen't have enough carbon content to harden. It will work harden or the thicker stuff will crack when bent but I've not had any problems with the thin stuff like 16ga. I prefer to heat the metal and then bend while it is hot. As far as annealing steel I was taught to heat it cherry red and then bury it in a bucket of lime to cool.

Ross

[Acer Saccharum]

Certain steels are really good for forming, and others crack on first bend. I don't know the right alloy for forming.

Old car fenders are probably the right steel, stamped lawnmower decks, etc.


McMaster has sheet 4130 in .04" thick on up.

Easy-to-Weld Aircraft-Grade 4130 Alloy Steel
This steel is very similar to 4140, but has a lower carbon content, giving it better weldability and formability while retaining good fatigue, abrasion, and impact resistance.

[Old Ford2]

Where can I get information charts on the properties of different grades of steel?
Thank you!
Fred

[James Wilson Everett]

Guys,

My opinion:

We will have less trouble if we stress relieve thin iron/steel while bending or working it as opposed to annealing.  The difference is this.  .  .  .

When we stress relieve steel we heat it to a red hot temperature and allow it to cool slowly.  This will allow more bending/working of the material without the danger of cracking.  Air cooling is satisfactory if we are not using what is known as air hardening steel.  Some Land Pattern musket lock frizzens marked "GRICE" are air hardening.  

When we anneal steel we heat it to a much hotter temperature, orange or yellow hot, and allow it to cool slowly.  This is above the transition temperature and allows significant changes to the metal microstructure.  That is the steel structure can actually change.  At times this can lead to trouble, like the material not acting as you expect after the anneal.  This is most especially true when forging springs, try to do the forging and bending red hot.  If you heat some spring steel a lot hotter, it may alter the steel microstructure and cause a later failure.  The only time I heat spring steel to the transition temperature is for the final hardening step.

So, my 2 cents is to stress relieve (red hot) and not anneal (yellow hot) whenever possible.  We may find less problems.

Jim

[T*O*F]

Old car fenders are probably the right steel,

Depends on what you consider old.  1960's and earlier are good.  You remember all the rust-out problems with cars of the 70's and subsequent lawsuits, which forced the auto manufacturers to offer rust-out warranties.  That steel was largely the result of steel mill decline problems and it contained a mish-mash of recycled products.  Move forward a few years as unibodies became the norm and they switched to a high tensile steel for auto bodies.  Any you may find that some later cars don't even have steel fenders.

[bgf]

Dennis,
The cold rolled sheet sold at Lowes, Tractor Supply, etc., as "weldable steel" is pretty safe -- both in 16 and 22g.  It will work as long as you can expect without hardening too much and will file/polish beautifully and easily.  Not terribly expensive given the small quantities in a rifle -- one sheet of 16g. will do more than 1 to several rifles depending on how much you use it for.

PB hinges, however, are a pain.  You only get one or maybe 2 chances to roll that bit over for the knuckles.  Heating might help, but the best thing seems to be just to go slow and hit your mark as close as possible the first time and then file and hammer discretely to cover up any small boo-boos.  There is one alternative in a pinch (as in when you get tired of cutting out finials or lids : you can use 22g steel sheet to make an applied hinge like the one on the rifle Larry Luck shows in another thread (which I filed mentally the first time I saw it!).  I think it adds a decorative element to an unengraved iron box, and it may allow you to up the knuckle count.  On the one I did, I could not get more than five knuckles successfully in 16g material, even when thinning it out with file and hammer before rolling, but I managed to get 7 with the applied hinge after a couple of attempts.  I intend to get 9 knuckles on the next one, hopefully in the same material as the PB, but I won't hesitate to improvise if it doesn't pan out!

[Dennis Glazener]

Dennis,
The cold rolled sheet sold at Lowes, Tractor Supply, etc., as "weldable steel" is pretty safe -- both in 16 and 22g.  It will work as long as you can expect without hardening too much and will file/polish beautifully and easily.  Not terribly expensive given the small quantities in a rifle -- one sheet of 16g. will do more than 1 to several rifles depending on how much you use it for.

PB hinges, however, are a pain.  You only get one or maybe 2 chances to roll that bit over for the knuckles.  Heating might help, but the best thing seems to be just to go slow and hit your mark as close as possible the first time and then file and hammer discretely to cover up any small boo-boos.  There is one alternative in a pinch (as in when you get tired of cutting out finials or lids Smiley): you can use 22g steel sheet to make an applied hinge like the one on the rifle Larry Luck shows in another thread (which I filed mentally the first time I saw it!).  I think it adds a decorative element to an unengraved iron box, and it may allow you to up the knuckle count.  On the one I did, I could not get more than five knuckles successfully in 16g material, even when thinning it out with file and hammer before rolling, but I managed to get 7 with the applied hinge after a couple of attempts.  I intend to get 9 knuckles on the next one, hopefully in the same material as the PB, but I won't hesitate to improvise if it doesn't pan out!

BGF,
Thanks for the info, I appreciate it. I looked at the sheet metal at tractor supply and almost bought some of it but I have lots of automotive sheet metal left over from body work on my 57 Chev so I am using that. Its not the original metal but from new sheetmetal panels so I am not sure how good it is. I was able to finish up the bends/folds with 1/16 music wire through them and they look fairly good and hopefully will finish up fine. I did manage to silver solder (hard solder) one of the pins in place! Dummy me didn't think to remove them. I feel sure I can heat them up and remove the pin.

9 knuckles! not me I have enough trouble with three!
Dennis