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I Forge Iron

Where do you stand on wet forging?


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minaraimono,

Back during the Civil War they used hydrogen filled observation baloons, Abraham Lincoln was the first to recieve an electric message from one! Anyway, the(one of at least) technique that they used to produce the required hydrogen was to heat up some strips of iron in a chamber and pass steam over them. The iron stips at an elevated temperature absorbed the oxygen from the steam and left hydrogen to go to the container. These were very large wagons with a giant box on them, this technique was not very rapid, but it did work.

Having said that, I don't think that what is heard or seen with the wet forging technique is an explosion of the hydrogen after it is seperated from the oxygen. It is much more likely that what is happening is that the water is being held in the surface inperfections in the anvil. When the yellow hot steel is stuck with a hammer it deforms at a micro scale for a micro second to fill in completely the microscopic hills on the anvil. Doing so it would of course vaporize all of the water or a great part of it and , beacuse it would in effect make a very high force seal for the produced steam, produce a pressure much greater then required to force the hammer and steel off of the anvil, most likely during the hammer impact, thusly causing a very rapid and aggresive expulsion of steam and a violent rebound of the steel on the anvil.

One other item of interest is a technique which was used in the 1950's where they would place the blanks to be forged into a rotating furnace drum which had a pool of molten glass at the required forging temperature.

The glass not only rapidly and evenly heated the steel, but it also gave the steel a very thin protective coating to exclude the contact of air and thus virtually destroy the chances of surface oxidation.

Not exactly a simple do it your self technique, but interesting none the less.

Caleb Ramsby

Edited by Ramsberg
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Pass steam over red hot coke and will seperate into hydrogen and oxygen. It may reach that temp on the anvil but it would take a spark to ignite it. More likely a droplet of water is turned into steam suddenly and escapes violently from a confined space. Steam is about 135 X the volume of the water it was.

Good Luck!

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It seems like it hasn't been mentioned, but my understanding of the reason wet forging removes scale is because the scale on the surface of the steel will be cooled by the water much faster than the rest of the material causing the scale to contract and pop off. I know a lot of us do the opposite by running a torch over cool ironwork to expand the scale and pop it off. If you don't forge the scale into the steel before you pop it off you get a very smooth surface.

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  • 2 months later...

Have you ever coated the surface you want to keep clean with flux? This seems like an obvious answer but Borax is awesome for this. The best way is to use it like you're forge welding--heat to orange, remove from fire, brush off scale using a steel brush, coat liberally with borax, then return to fire and heat to yellow or desired working heat. The borax will bubble and liquidize the oxides, and when you remove the iron the remaining scale can be brushed off easily. Just remember that since the scale is liquidized, it no longer flakes, but splashes at you when you strike it, yum.

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The 'pops' are not the result of the hydrogen and oxygen separating, they are 'steam' explosions. When you have moisture on the anvil and lay the hot steel on it you are causing the water to 'flash' to steam. Normally water boils to produce steam but with the temperature of the steel far above the normal boiling point of water (212 deg F) the water goes directly to steam with no boiling first. The steam to water ratio is about 1600 times! That is a significant change in volume and it is contained in a very small area. The 'pop' is the pressure of the expanding steam escaping.

This is a 'SIGNIFICANT' factor around molten metals of any type. I have seen and heard significant steam explosions when molten slag from steel making or iron making has been dumped and there was a VERY small amount of water trapped under it. Also have seen the roof blown off the pig cast foundry at Algoma when I worked there. Only a luck would have it no one was killed. That was from water that was in 'ONE' of the 'Pigs' as the molds are called. Surprising how much power it generates!

Terry

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The 1,600:1 steam from water ratio is for 212f water to 212f steam the ratio goes up with temp. At 300f it's 2,000:1.

I don't have a chart to tell me what it is at 1,000f but it's significant. I'm not going to search one out either. :P

Frosty

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Frosty, that's true. But steam has to be at about 65 psi to reach 300 degrees F. I don't think there's much superheating going on in wet forging. The moment the pressure rises enough to push the work up off the anvil, the pressure dissipates and the steam drops to 212 F.

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Or come in contact with something that will superheat it before it can get out of the way. We had to learn the volumetric changes associated with the temperatures of the asphalt it might come in contact with when loading trucks.

My very first solo asphalt tanker inspection involved a steam explosion, fortunately more like a punctured paint can than a bomb. The guy on the loading stand was probably 30 secs from closing and locking the lid and a seriously bad situation when we heard the frying bacon sound and everybody ran for the roofed safety zone.

Se stood under the safety roof and watched about 7,500gls of 350f asphalt spray out of the manhole of a 10,000 gl tanker. Just a little condensation at the high end where I couldn't see it when I inspected it.

The accident investigator estimated 3-3.5 gl of condensation.

Still, you're right, as soon as the steam escapes containment or contact with super heated material the temp drops rapidly.

Frosty

Edited by Frosty
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