Newbie question on heat

[TexanRebel]

I used a charcoal forge to heat up some rebar to what I think was an orange heat, placed it on the anvil and only got in about 5 hammer blows before it cooled to where I couldn't work it. :confused: Is this normal?

[TechnicusJoe]

I used a charcoal forge to heat up some rebar to what I think was an orange heat, placed it on the anvil and only got in about 5 hammer blows before it cooled to where I couldn't work it. :confused: Is this normal?

i dont know if that is normal but i think it isnt.
normal you can give more than 5 blow on some orange heat.
but if it was close to red it could

i dont know if what say is true, just my thought about it

[unkle spike]

How warm was your Anvil at this time

A cold anvil will suck the heat out of a piece pretty quick, also if you have a breeze in your shop moving air will do it quick too.

Depending on the metal you can hammer to red, re-heat and go again.

Also Small pieces lose heat fast, say 1/4" square or round.

[Rich Hale]

Leave the piece in the fire long enough that it gets really hot and may even show some little sparkles that indicate a start of m eltin. If your forge does not get that hot that may be your problem.

[ThomasPowers]

I notice that I get 2-4 times as many blows on a piece as my students do. With experience you move it faster and hit it faster.

Never taking a piece out of the fire until you have your hammer *in* your hand! When a person starts I warn them of this several times and then I let them fumble around and tell them "nope it's cold now; back in the forge" They seem to learn better that way.

[unkle spike]

And depending on the day Rebar could contain dental scrap, fillings are hard to hammer even when hot enough.

[jimmy seale]

could be alot of things. as stated above, but how far are you taking the heated piece? 1/2 way across a bigger shop will lose heat, jusy my thoughts,j

[Ross_FL]

I had the same problem, I was trying to forge a piece of 1" wide bar of steel that was 1/8" thick and only a foot long.

It would get cold really fast, I was able to hammer it 5-8 times before it needed to go back in.

To keep forging this piece into a dagger I hit the anvil with a heat gun for a few minutes and turned the reg up all the way to 10 psi and got the piece very very hot.

I've only used the forge a few times so far but I will always use the heat gun from now on.

Also, the problem went away when I forged a 1" diameter round, it stayed hot for quite a while.

[Rob Browne]

All summed up above:

• Small diameter stock will cool very quickly.
• Cold anvil, I don't tend to heat my anvil because I find it heats up quite quickly by itself from the hot metal but it does not get as cold here as it does in amy other areas.
• Stock not hot enough, if using mild steel or reobar heat it till its yellow then work it. Put it back in the forge when it gets below orange, it will reheat quicker and be easier to work.
• Organise your gear so its not far from forge to anvil, less time to cool.
• Practice will speed up your hammer strokes.
  

Its a matter of practice, practice, practice to get it right. One day you will realise you don't have the problem any more and not quite remember when it went away because it just happened and you had other things to worry about at the time.

Try using heavier stock for a while till you get used to working the metal. Edited April 8, 2009 by rmcpb

[matt87]

Even a relatively small increase in stock size will greatly increase the cross-sectional area of the piece, and so the amount of heat energy stored at a certain temperature. For instance a piece 1/4 inch square has a cross-sectional area of .0625 square inches, whereas a piece of 3/8 inch square is 0.14 square inches and 1/2 inch square is 0.25 square inches.

[Sweany]

Dental Scrap?

[unkle spike]

Yes modern non spec metals contain anything that ends up in the scrap bin. Engine blocks, refrigerators, and I always like to throw in "kitchen sinks and dentures" when I demonstrate. Not really too far from the truth, just go to the neighborhood recycling center and see what is in their incoming steel pile. When you say A36 or Rebar, it is really bottom of the barrel metal. I find hard spots in metal bars frequently. Last year I bought some 1/4" square for demo's to do nail hooks. I couldn't get any even twist to save my life, and I have made close to a hundred of these things. It would either bunch up on one end, or in the middle. With a nice even heat, and proper set up, a twist should be relatively even from end to end. When I grabbed a piece of 1/4" square I had for a while it twisted right up perfect, the only explanation I have is the metal.

[TexanRebel]

All summed up above:

• Small diameter stock will cool very quickly.
• Cold anvil, I don't tend to heat my anvil because I find it heats up quite quickly by itself from the hot metal but it does not get as cold here as it does in amy other areas.
• Stock not hot enough, if using mild steel or reobar heat it till its yellow then work it. Put it back in the forge when it gets below orange, it will reheat quicker and be easier to work.
• Organise your gear so its not far from forge to anvil, less time to cool.
• Practice will speed up your hammer strokes.
  

Its a matter of practice, practice, practice to get it right. One day you will realise you don't have the problem any more and not quite remember when it went away because it just happened and you had other things to worry about at the time.

Try using heavier stock for a while till you get used to working the metal.

Ok, thanks! I had most of these problems (exept the distance from anvil-forge, and not having the hammer in hand) and it was pretty windy that day.

[Walking Dog]

One more aspect of heating stock to add to the list . . . If the piece is fairly thick, more than 3/4-inch, and you heat it quickly, it is quite possible to have it very hot on the outside, but cold on the inside. When working heavy pieces, I often find that my initial heat doesn't last as long as the ones following, after the inside has come up to forging temperature. It's better to bring thick pieces up to temperature slowly.

[Rob Browne]

Good point and is another reason why I use a hand cranker, I find I can control the heat of the fire better. Heat large diameter metal SLOWLY so it heat right through and not just on the surface. If I am heating metal over 3/4" thick I often heat it, take it out, heat it, take it out, etc to ensure it is hot right through at the end and not just on the surface.

Happy hitting :)

[Dodge]

When its cold; 40's or below I pre-heat my anvil. This is not only to prevent heat loss, but its just not a good idea to beat on a cold anvil (30s and below?...). I have a large (3" x 1" x 24") bar for no other reason than it was free that I put in the gasser while its heating up. When the bar is good and hot (not yellow but a good red) I lay it on the anvil. When I'm ready to forge, the heat has transfered enough so the surface isn't ice cold. As you forge, the anvil continues to heat up anyway but those first few runs on a cold anvil will suck heat right out of steel.

[arftist]

Yes modern non spec metals contain anything that ends up in the scrap bin. Engine blocks, refrigerators, and I always like to throw in "kitchen sinks and dentures" when I demonstrate. Not really too far from the truth, just go to the neighborhood recycling center and see what is in their incoming steel pile. When you say A36 or Rebar, it is really bottom of the barrel metal. I find hard spots in metal bars frequently. Last year I bought some 1/4" square for demo's to do nail hooks. I couldn't get any even twist to save my life, and I have made close to a hundred of these things. It would either bunch up on one end, or in the middle. With a nice even heat, and proper set up, a twist should be relatively even from end to end. When I grabbed a piece of 1/4" square I had for a while it twisted right up perfect, the only explanation I have is the metal.

Yep. Making some wall mounts the other day by parting off 1/4" thick slices of 3" dia. 304SS. After three or four good ones, came to a bad section of bar that ran over an inch. Machined past it finaly and it was good again.