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I Forge Iron

Working in the shop in the winter.


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Steel gets more brittle when it's cold.  We are talking about the anvil not the hot metal.Most anvil failures I am personally aware of have happened with a cold anvil.  Also a warm anvil does not cool the workpiece as fast, as I recall cooling rate is something like the 3rd power of the temperature differential.  35 years of experience in the forge has taught me that a warm anvil helps forging in cold weather.

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Yes steel becomes more brittle when cold and I would be careful about chisels but my anvil has a fair safety margin and I do not forge at very low temperatures.

I am unable to submit my whole repy

You probably refer to heat transfer by radiation which is the fourth power of temperature in degrees Kelvin but it is not the fourth power of the differential but the differential of the fourth power. Assuming heat transfer from 1000°C to +20° and -10° respectively, the difference is a tenth of a percent.

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Since I was unable to get my post through I start a new thread.

Yes Thomas, steel becomes more brittle when cold and I would be careful about chisels but my anvil has a fair safety margin and I do not forge at very low temperatures.

You probably refer to heat transfer by radiation which is the fourth power of temperature in degrees Kelvin but it is not the fourth power of the differential but the differential of the fourth power. Assuming heat transfer from 1000°C to +20° and -10° respectively, the difference is a tenth of a percent. Assuming heat transfer to 20°C the difference between 1000° and 900° respectively is 28 percent. (besides: radiation heat transfer is not only to the anvil but to the whole room) I rashly assumed that transfer between stock and anvil would be by conduction where transfer is directly proportional to the differential. The percentage changes for conduction would be 3 percent versus 10 percent.

I have not thought about it but I am sure you are right that steel cools down mostly by radiation (unless we dip it in the slack tub). However, since the radiation is mainly influenced by the steel temperature, there is not much we can do about it. A shiny aluminium anvil might reduce the radiation but I doubt that it would be hard enough. Aluminium has a very low emission ratio and I know from personal experience that molten pure aluminium radiates surprisingly little heat.

Your experience of  blacksmithing is enormous compared to mine and I do not doubt what you say but heat transfer calculation and design has been a part of my education and my 50 years of professional engineering. I very much doubt that heat transfer between stock and anvil is what makes the difference you describe.         

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There is a conduction issue, which is related to time in contact with the metal. An anvil gains a lot of heat during a day of working large billets, the much smaller hammer gains suprisingly little.

You can keep heat longer in small pieces if you lift it slightly off the anvil between hits.

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Gote, you may be absolutly right, but a word of caution. You may be dead wrong too. Their was a tread concerning steel being heated by the kinetico energy of striking it with a hammer. 

A couple of guys had some great math form the engineering text about how it was insignificant. moony simply posted a vidio, heated a cold 1/4" bar to red heat by hammering in about 10 seconds. Others have sence posted youtub vidioes lighting theit forges and smokes with the same trick. 

A large cold mass of steel will suck the heat out of a peice of stock, and hiting it with a hammer just insures a near oerfact contact surface for conduction. Radiation indead is a way to tranfer heat, but convection and conduction are beter at it. 

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If I recall correctly conduction is the fastest way to transfer heat between materials. Smooshing HOT steel against cold steel is not only going to conduct heat efficiently it will be more efficient than just laying them together for an equal time. The force of the blow will form the hot steel into much closer contact it will "extrude?" into every nook and cranny of the anvil's face. It will also be under pressure.

This is why the technique Brian Brazeal showed us about rotating stock 1/4 turn after every blow is so effective. When struck the stock is flattened against the face increasing the contact area while thinning it for less heat reserve depth. Rotating the stock exposes the contact surface as a compound curve with a very small fraction in contact with the anvil face but a much greater depth of heat reserve depth. It stays hotter longer as an expression of simple physics.

Energy fills a vacuum meaning the higher energy state WILL seek and transfer to the lowest energy state possible. Water flows downhill till stopped. This means the colder the anvil and hotter the stock, the faster energy MUST transfer. Simple physics and I'm poor enough at math I can't write a formula but a handle on what's happening is enough for me to work with it.

From personal experience a hot anvil lets me work stock longer no matter what time of year but winter temps mean extraordinarily FAST cooling of stock. I've watched 1/2" sq. cool below working temp in 2-3 fast blows. 1/4 turn really improves working times but still. . .

I have an old skid shoe off one of the snow blowers, the 20tons a minute kind of road clearing blowers. The shoe is larger than either of my anvil's faces and is a good inch think. I lay it on my barrel stove when I start the take the chill off the shop fire and when I come back from a cup f coffee it's hot enough to take the chill off the anvil I'll be using. Even wrapped in insulation 2 magnetic engine heaters aren't enough to warm it appreciably even in mild cold weather.

My next little project is to make a nice shiny stake tool from thick plate stock as the preheat plate. This'll allow me to preheat the anvil and still do some forging on the plate. It'll also help correct the dings and nicks in the Trenton for finish forging and not to be underestimated increase the working height by 2" for finish work.

Speaking of aluminum anvils brings to mind the aluminum farrier's anvils available now. Aluminum may not radiate heat but it sure conducts it faster than steel and also has a lower specific heat. I even use a piece of plate aluminum to speed up air quenching steel, it may not radiate heat well but it sure conducts heat to air well. The thing has been known to quench thin air hardening steel too quickly.

Black surely facilitates heat transfer by radiation so how about chrome plating our anvils for cold climate use? Not the face of course and maybe only the bottom half of the horn. Hmmmm? It's sure look better than wrapping my anvil in a wool blanket. (which actually helps a lot)

Ah, a nice pre Sunday brunch windy ramble. I feel much better now. B)

Frosty The Lucky.

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My shop is the yard, so working in winter means extra warm clothes and a few of those warmer packets thrown into my boots to help keep the ground chill off of my feet. I'm currently working on setting up a small shed for light work that can be done indoors. Which reminds me... I need to get a door. A small heater would be nice too. Electric isn't an option but I might be able to get hold of a second hand Kero-Sun that should do the trick.

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I usually start a wood fire in the forge and let it burn for a while to take the chill off the shop. Dress warm and wear gloves until things warm up.  If it gets below 30 Celsius, it gets a little cold to take the gloves off.  I always make sure my boots have good, thick tread. That makes a world of difference when working on snow. Never forget your long underwear.     

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Going a up a size or two and adding a wool insole and a couple pair od socks helps with ground chill. As dose a vest and a benie

I've been trying to get used to wearng hats. A bandanna I can almost stand but hats bother me for some reason. The one hat I did like was a furry one with ear flaps I bought a few years ago at a gas station. My girlfriend was pretty surprised when I jumped back in the car looking like a Teddy Bear! Unfortunately, I think the dog got hold of that one. It hasn't been seen in some time.

Edited by jumbojak
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When you are dressed you loos a lot of heat from the noggin, and when your bidy starts to get cold it restricts cerculation to your extremities.

So, first rule, if your feet are cold put on dry socks and a hat. Grew up in the dessert, hats are a must.

 

Now my profile looks like the chesire cat with a hat, lol

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A lot of great tips here, loving this forum. Started smithing earlier this summer out of a bbq grill that i filled with a mixture of plaster/sand, a brakedrum and some piping. Been a lot of trial and error through the summer since I am alone in this, got no one around me with experience in smithing. Now I've built my "real" forge, still using the brakedrum as a fire pot, and I've also constructed a side-draft chimney that works pretty well! 
All I can add to this thread is wear thick socks, heavy shoes and a hat, and maybe but down some plywood where you usually stand (if you've got stone-flooring like I do).

Maybe I should consider heating my anvil before use, -20C is fairly common in the winter where I live. 

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OK I was wrong. The is fine because it means that I have learnt something new. Now remains the question: why was I wrong. This means a new thread since this is the forum of missed posts.

 

If you're referring to aluminum being a poor radiator you're right.

What we are talking about is it's conductance, it's a GOOD conductor, thermal or electric I use aluminum half sheet pans for thawing and cooling pies, etc. when no cooking on them. However, I can take one right out of a 375f oven and you can't feel heat at a little distance unless you feel air warmed by it.

Aluminum is a poor radiator but a great conductor. Two different things.

Frosty The Lucky.

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