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Lets assume that the ice anvil is as resistant to physical blows much like a normal anvil and its never melting(will not explode as well). It will always maintain its negative temperature enough to turn human hands into ice with continuous use.

How would an Ice anvil(That never melts or break or explode when exposed to super high temperatures) change forging process as is?

How would it affect the metalworking?

How would it affect forging process?

Is there even a benefit using an ice anvil?

Materially speaking how would anything forged using an ice anvil compare to the normally forged ones?

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    $\begingroup$ Ice Anvils are awesome if you want terrible-quality weapons! It's like a "desenhancement" forge! $\endgroup$ – T. Sar May 12 at 16:05
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    $\begingroup$ Won't work. Ice is brittle, and will fracture from the first few hammer blows. Might as well be using a glass anvil. Or indeed, one of any sort of rock. $\endgroup$ – jamesqf May 12 at 17:23
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    $\begingroup$ @AlexP ice isnt actually really slippery, the water that comes from it melting is what causes it to be slippery, so with OPs situation that wouldnt be a worry. I might be wrong tho. $\endgroup$ – Topcode May 12 at 18:46
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    $\begingroup$ @Rob Watts: That's just the problem. Those things CAN'T be hand-waved away. You could certainly make an anvil out of some material that stayed cold, and which had the necessary toughness &c not to fragment under repeated hammer blows, but ice is not that material. Indeed, you could make a cold anvil by e.g. boring a few holes in an ordinary anvil and running liquid nitrogen through them. $\endgroup$ – jamesqf May 12 at 22:37
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    $\begingroup$ @Rob Watts: Not if you want to retain any logical consistency. There's a difference between magic and wishful thinking, you know :-) $\endgroup$ – jamesqf May 13 at 16:33
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At 0°C, your 'ice' anvil is about 1000°C below hot metal rather than 980°C below it, which is probably not significant. However real ice is 35 times less thermally conductive than iron, so if your magic ice is the same then it won't conduct the heat out of the metal being worked, and that might mean the metal stays hot longer. Compare how long it takes your hands to get cold holding an ice cube vs an iron railing - both will freeze your hand eventually but the iron 'sucks' the heat out much faster. I don't think it would end up requiring more heats than a iron anvil.

Real ice is much less stiff than iron, with a compressive strength of 6 vs over 100, so you'd need extra magic to make it a good anvil. But then you already seem to have assumed it won't just break.

Is there even a benefit using an ice anvil?

Assuming the magic allows it, you could put moulds on it and pour on water to create ice form dies for complex shapes or jigs for bending.

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    $\begingroup$ Clever; temperature only tells you what direction heat will flow, it does not tell you the rate. And we care about the rate. $\endgroup$ – Yakk May 13 at 14:06
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    $\begingroup$ My interpretation of thermal conductivity was that for materials with a low conductivity, you're effectively just heating up the boundary layer where the objects are in direct contact, but with high conductivity, the entire cold object needs to be warmed. But does that really matter when the entire anvil, including the boundary layer, is always held at a fixed temperature? You don't actually need to conduct heat anywhere, as you'd have the same effect using an always-cold sheet of paper instead of an anvil. The only temperature gradient is between the iron and anvil, but not within the anvil. $\endgroup$ – Nuclear Hoagie May 13 at 14:29
  • $\begingroup$ With normal ice, any melting creates liquid water that can touch more surface area, so for rough surfaces that wouldn't make good contact with flat iron, you can get extra cooling. Also, it takes energy to melt ice, so heat doesn't need to be conducted away from the surface, it can just melt water to keep the surface at 0 C (or lower if salt is involved). So real ice is quite good at cooling things down to the freezing point. But that won't happen with magic ice that can't melt at all, so +1, good point. $\endgroup$ – Peter Cordes May 13 at 15:27
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    $\begingroup$ @NuclearHoagie yes - effectively it's the same as electricity, V=IR, if you have no temperature gradient in the magic ice and heat flowing through it then the thermal conductivity is infinite, if you have real world conductivity and heat flowing through it then you have a temperature gradient. In the infinite case, you have a poor anvil that quenches your steel. If it's the same as real ice then there will be a temperature gradient, but the magic means the ice doesn't melt. Only one of these is a viable magic anvil, so I'd assume you would magic it that way. $\endgroup$ – Pete Kirkham May 13 at 23:17
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    $\begingroup$ I disagree with this answer. The magic ice anvil will probably drain much more heat from the metal being worked than an ordinary anvil. Heat transfer is proportional to the temperature difference, a normal anvil might draw more heat than the ice anvil at first, but eventually the normal anvil gets hot, and remain hot for as long as it is being used. But the ice anvil is magic, always cold, so it will always drain maximum heat for the heat conductivity of ice, making it a much worse anvil. $\endgroup$ – lvella May 14 at 19:02
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When you forge something on the anvil you want it to stay hot as long as you need for working it, so that it keeps its plasticity.

Cooling or quenching is done only after the forging is finished. Anything that speeds that unwanted cooling up negatively affects the work being performed.

Just to name a few potential issues, it can embrittle the piece or it can induce unwanted residual tensions.

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    $\begingroup$ this should be a relatively minor concern however, I have used normal anvil at below freezing and it is more difficult but not that much more difficult. plus the smith can use the always cold anvil to make a perpetual motion machine to run their bellows or even a rotary hammer. $\endgroup$ – John May 12 at 16:13
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    $\begingroup$ @John Without a supply of always-hot, wouldn't that just suck all the energy out of the universe over time? $\endgroup$ – wizzwizz4 May 12 at 19:47
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    $\begingroup$ @wizzwizz4 It's all relative, once you get close to the heat death of the universe you just have an always cold but not absolute 0 anvil floating around heating things up! $\endgroup$ – IrkenInvader May 12 at 21:27
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    $\begingroup$ @wizzwizz4 eventually but not for billions of billions of years. And its going to do that regardless, ight as well get some work out of it. $\endgroup$ – John May 13 at 4:47
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    $\begingroup$ @John Even better, set up an ice cream stand or a cold storage facility or an air conditioned theater (plays, not movies) and only do smithing during the winter. (Warm weather ice was financially lucrative well through Victorian times so it's going to be gold in any kind of standard medieval-style fantasy universe.) $\endgroup$ – user3067860 May 13 at 12:56
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Frame challenge

You have redefined ice and changed its properties so much that is no longer ice. If you're going to do all that, why not just redefine the melting point of ice as well and say that it is not made of hydrogen and oxygen?

A. If you want the appearance of ice, then instead have a high-melting-point transparent ceramic or mineral.

B. If you want the temperature of ice (which isn't fixed anyway - it can be anything from 0°C right down to near absolute zero), just use an iron forge and pack its base in ice of the appropriate temperature.

Conclusion

If you just want an anvil that is to be used at 0°C, put an iron one out on a freezing winter's day and let the blacksmith work outside. Compared to the temperature of the iron that is being forged, an anvil at 0°C will be no different to an ordinary anvil that is at, say 15°C.

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    $\begingroup$ Or why not just magically chill an iron anvil? $\endgroup$ – Captain Man May 14 at 17:19
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An experienced blacksmith will make it work

Blacksmithing requires thinking on your feet. It's as much an art as a science. Sometimes you have a tool that just doesn't want to behave right or your forge isn't quite the right temp or you find an imperfection in your metal, etc etc. Your question is about the final product. An experienced smith will be used to adjusting to problems that are more serious than a cold anvil.

I'm new to blacksmithing so I have to go back and reheat my metal more often than an experienced blacksmith. If you have a super cold anvil, your smiths might have to do the same since their metal could cool faster than usual. That doesn't make a big difference in the final product, but if you want to come up with some difference for your story, check out this discussion or this one about the effects of repeated reheating.

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Iron fuses at 1538ºC, and it becomes malleable at 900 C.

Assuming you mean that your ice forge is at around 0 C (and not 0 K), if the iron is retired from the furnace at 1000 C, the difference between your "ice anvil" and a regular anvil at room temperature will be a mere 3% of the difference with the metal.

Not really significative.

Even if your ice anvil is at 0 k, then the difference would be a mere 27%. Perhaps it would lead to a considerably shorter time between reheating the metal, but nothing more.

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    $\begingroup$ Iron (and steel) pieces do not like differential cooling. They do not like it at all. Having half of the piece in contact with air and cooling very slowly, and the other half in contact with ice at -100 centigrade and cooling much faster will definitely induce unwanted internal stress in the piece, and very different properties for the two halves. (Note that at 0 centigrade ice is a very soft material; it becomes harder and harder at lower and lower temperatures.) $\endgroup$ – AlexP May 12 at 12:53
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    $\begingroup$ @AlexP At which part does the OP specify that the ice anvil is at -100 C? And if the ice anvil is magic, it can be hard at -1 C (because, you know, it is magic). And the ice has the advantage that it is a worse thermal conductor than the (still cold relatively to the iron) iron anvil. $\endgroup$ – SJuan76 May 12 at 12:57
  • $\begingroup$ Well, of course, if it is magical then all reasoning about its material properties is futile. $\endgroup$ – AlexP May 12 at 12:58
  • $\begingroup$ @SJuan76 the second sentence "It will always maintain its negative temperature enough to turn human hands into ice with continuous use" makes it clear that the anvil temperature a) is really cold; and b) conducts that temperature to objects in contact with it. $\endgroup$ – KerrAvon2055 May 12 at 13:21
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    $\begingroup$ @AlexP: Even on a normal iron anvil at air temperature, the hot iron will cool much quicker when in contact with the anvil than in ambient air, because of the thermal conductivity of the anvil. (Think on a -5º calm winter’s day, exposed skin in air is fine, but touching a metal railing is painful.) If anything, the ice anvil will give less differential cooling than an iron anvil — the slightly lower temperature will be more than cancelled out by the much lower conductivity. So there won’t be more differential cooling than traditional smithing techniques account for. $\endgroup$ – Peter LeFanu Lumsdaine May 13 at 9:11
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Frame Challenge

If your magic can make the ice anvil suitable for use as an anvil, you're better off using your magic to smith your weapons. The material control to manipulate ice in that manner far exceeds creating a perfect blade. Even if you have to make your weapons out of this never melting ice material (aka only frost magic), you're manipulating far less metal.

If the answer is just "this ice anvil is awesome cus magic", that works and you can impart any properties you want on the items smithed on it in that case, but I don't think I could buy it as a reader

Sorry to be a debbie-downer, but I don't see a believable way to make it practical

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    $\begingroup$ Perhaps it takes a long time to enchant the magic ice anvil but you need to mass produce weapons. $\endgroup$ – Captain Man May 14 at 17:20
  • $\begingroup$ @CaptainMan good call! I really hate posting answers like this, but I do it when I can't come up with a good solution hoping someone else will poke holes in my argument. Might be worth an answer $\endgroup$ – TCooper May 14 at 17:25
  • $\begingroup$ It's not poking holes in an argument, questions are super open ended here. If magic is quick and easy to do in the world then this works fine. It could also be that magic is rare and this anvil is some sort of leftover artifact and all they have access to. The OP doesn't explain any more details than the ice anvil existing and how it works and asks if it would be useful. I think making assumptions about the extra details are fine. There's nothing "wrong" with this answer. :) $\endgroup$ – Captain Man May 14 at 18:15

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