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Author Topic: metallurgy  (Read 11486 times)

sunshaker

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Re: metallurgy
« Reply #45 on: January 19, 2010, 05:48:29 pm »

There is probably a limit imposed a by lack of knowledge as well (mostly chemistry, alternate refining techniques, and how to extract the rare metals from ore).

One of the things I will be doing once the new version comes out is making a custom workshop called a blast furnace, then I will reorganize the metal making processes (the smelter keeps the small scale easy way, the blast furnace gets the we make 10 bars minimum at a time and do it the fast way, I might even make casting reactions for objects (casting tends to make the lowest quality objects anyways)), likely the blast furnace will be dwarves only. If I feel motivated I might make a Refinery that lets you do other methods of refining (mercury amalgam, gold cyanide leaching, acid extraction and the like).
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Arrkhal

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Re: metallurgy
« Reply #46 on: January 19, 2010, 06:30:15 pm »

Quote
There is probably a limit imposed a by lack of knowledge as well (mostly chemistry, alternate refining techniques, and how to extract the rare metals from ore).

True, though trial and error played some part as well.  Hm.  Given that the dwarves do already know of nickel silver and what it is (I believe the Chinese thought that it was a certain "type" of copper, rather than a copper alloy), actually it's pretty likely they'd stumble across iron-nickel alloys at some point.  Nickel silver tarnishes much less readily than copper, brass, or bronze, so it'd be quite logical to add nickel to steel in an effort to make it stainless.

And your blast furnace idea sounds kind of similar to a mod I tried a couple months ago.  Basically, it had no-melt, and melt+flux methods for producing both iron and steel.  Bloomery and blast furnace for iron, blistering and crucible for steel.  No-melts were slower and less efficient, but melts required flux.  Ended up pretty unworkable due to the intermediate stages necessary to simulate time taken.

Hopefully the new workshop system will allow a more streamlined approach to that.
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Grimlocke

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Re: metallurgy
« Reply #47 on: January 19, 2010, 09:51:13 pm »

I figured patterened steel would be worth mentioning.

It could be included in the game as a lower tech steel, one that would not be good for making armour, but better than iron for weaponsmaking. Possibly humans and goblins could be made to have them once the game allows such modding, as I think both of those not having steel is kind of weird.

Actualy if you consider dwarven steel to be one that has an irregular carbon content, then you could even consider patterened steel to be better for weaponmaking.
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Eagle0600

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Re: metallurgy
« Reply #48 on: January 20, 2010, 01:01:38 am »

Another thing to consider with any metal forging is that there are various methods of forging that get very different results. For instance, and traditional European blacksmith would hammer an object into shape and then either leave it to cool or douse it. Both of these would have the same effect: The metal crystals would contract away from each other, leaving the metal weaker than the Asian method. The Asian method was to hammer it constantly as it cooled, so that the crystals would not draw away from each other. This would make the metal very much stronger, and therefore their weapons could be thinner and sharper, and their armour less prone to bend/break.
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Arrkhal

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Re: metallurgy
« Reply #49 on: January 20, 2010, 09:55:52 am »

Quote
Another thing to consider with any metal forging is that there are various methods of forging that get very different results. For instance, and traditional European blacksmith would hammer an object into shape and then either leave it to cool or douse it. Both of these would have the same effect: The metal crystals would contract away from each other, leaving the metal weaker than the Asian method. The Asian method was to hammer it constantly as it cooled, so that the crystals would not draw away from each other. This would make the metal very much stronger, and therefore their weapons could be thinner and sharper, and their armour less prone to bend/break.

Source?  That sounds rather off, like someone didn't understand the significance of work-hardening.  I guess cooling could make iron pull away from slag strands (which are the only "crystals" you'll find in wrought iron) a little, but the difference in strength would be negligible.  Asian irons tended to have less slag and more carbon to begin with, which would have far more of an effect.

Both cultures would also cold-work the material once it was cool, to harden key areas.

With bronze, it was once again the material.  Asians consistently favored very high tin bronzes compared to Europeans.  Higher tin basically resulted in a bronze with a higher failure point, but a more catastrophic failure.

If it was talking about steel, that has to be wrong.  Pounding on steel while air-cooling it is just about the dumbest thing a smith can possibly do with steel.  That sounds like the sort of thing Europeans thought Indian smiths did, around the 16th-ish century, due to Arabic misinformation.  Those guys loved telling Europeans the craziest crap about how damascus steel was made.
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slink

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Re: metallurgy
« Reply #50 on: January 20, 2010, 10:34:57 am »

The word "crystals" is probably a reference to the crystalline structure of the iron itself, not to some foreign material.  I don't know what effect working has on iron and steel (which is basically also iron in the case of carbon steels), but the goal of the whole process of tempering and quenching is to leave the material in some particular crystalline state.  Apparently the goal is to heat the metal to a high enough temperature that it is all in the same crystalline form.  The speed and temperature of the subsequent cooling affects the degree and uniformity of other crystalline forms of iron in the end material.  In general, slow cooling produces a less brittle metal that does not hold an edge as well because it is also not as hard.  Cooling the metal quickly produces a material that is more brittle but which will hold an edge better.  Obviously for something like a sword, you want both qualities.  Therefore the edges of a sword are cooled more quickly then the main body of the sword, in the hopes that the result will be a sword that takes a keen edge but does not break if you smack it against something hard.
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Arrkhal

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Re: metallurgy
« Reply #51 on: January 20, 2010, 11:04:02 am »

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The word "crystals" is probably a reference to the crystalline structure of the iron itself, not to some foreign material.

The thing is, wrought iron shouldn't have any kind of crystalline structure other than the slag, unless it's high enough in carbon to count as a near-steel.  And in that case, you'd want to harden it like a steel, not like an iron.

For all metals, including steel without a heat treatment, pounding on it while cold work-hardens the metal.  It will generally become harder and "stronger," but also more brittle.  Most metals become rather "crumbly" if work-hardened to too great a degree, like if you bend a metal monowire back and forth repeatedly, the break won't be clean.  That's also why many older bronze swords have edges that look crumbled.  Corrosion played some part, but that's mainly repeated work-hardening and impact.

Also, pretty much every metal except steel (including iron) is annealed by heating and quenching.  I.e., if you heat copper up until it glows, then dunk it in water, it will be at its softest state.  Then you hammer on it to make it harder.

Quenching and tempering of steel, on the other hand, is basically both more and less complicated than what you think.

The crystalline structure reaches the strongest possible point at a particular temperature (which varies by alloy; for the simple steels, you heat until the steel is no longer magnetic), but a slow cooling will cause the crystals to go back to the soft state (annealing).  So a fast quench is used to keep the steel in the harder state.  Yes, you could use a slower quench (like motor oil or air cooling) to get an intermediate stage, but that results in a steel rather different from a fully hardened and tempered one.  The only steels that usually get a slow quench are the high-alloy ones, which will shatter like glass if they're water-quenched (and the appropriate cooling speed for the high-alloy ones will still result in very hard, brittle metal).

After that the metal is tempered by baking it at a moderate temperature (a modern kitchen stove can actually be used to temper some steels) for a long time, up to 12 hours in some cases.  And in modern processes, the steel may be cryo-tempered after that.

Easiest way to think of it is there are 3 different types of steel crystals; "hard," "springy," and "soft."  Obviously, for most weapons, armor, tools, etc., you want a balance between "hard" and "springy," with no soft at all.  The main role of "soft" steel is shock absorption without vibrating, like in axe heads.

Heating and then cooling very slowly (European smiths would bury blades in thick layers of wood ash, so that it would be a couple weeks or more before you could touch the steel without burning yourself) makes the steel 100% "soft."  Heating then cooling as quickly as possible (for that particular steel) makes it 100% "hard" (if done properly; a bad quench can leave some "soft" behind).  Taking a 100% "hard" object and then tempering it turns some of the "hard" into "springy;" how much depends on the temperature and time (and once again, a bad temper can turn some "hard" into "soft" instead).  Finally, in a modern smithery, a cryro-temper will turn any remaining "soft" into "springy," so a cryo temper basically will only correct flaws in the steel, it won't improve it if it was done right the first time.  Ancient smiths had to just do it right to begin with, otherwise a sword or armor would bend rather than flex back.

However, with the vast majority of metals (certainly every metal other than steel that people had prior to 1800), you can't get "springy," at all.  All you can do is try to balance "soft" with "hard," thus the dominance of steel.

And preferential hardening of the edges pretty much didn't happen at all, with a simple quench.  A self-hardened European steel sword will have an edge and spine within a couple percent of each other, hardness-wise (unlike the earlier bronze and iron swords, where the edges were work-hardened and the spine was left alone).  Differential hardening was done different ways, like the vikings put high-carbon steel at the edge, lower-carbon in the middle (given the same heat treatment and temper, the high-carbon will be harder).  The Japanese would put a thick layer of clay over the back of the sword, so that heat would escape through the clay slower during the quench.  On the Indian subcontinent, they would pour water from a pitcher over the edge of a sword rather than dunking the whole thing.

And actually, the Japanese and Indian approaches are a bit sub-optimum, since as you can guess, that means there's "soft" steel in the back of the blade, rather than "springy."  And actually, yes, permanent bending is a huge problem with Japanese katanas, despite the ridiculous hype.  Poor technique with a katana, and you can easily bend one permanently on a bad cut.  Nepali khukuris also actually do not flex and return true, their bend tolerance is very low compared to European style sword heat treatments (of course, bending a 1/2" thick khukuri is pretty hard); but in the case of the khukuri, that's probably because the "soft" steel at the spine keeps the blade from vibrating.

The best way to differentially harden something for maximum resistance to bending would be to temper it differenly, but that's basically impossible, even with modern manufacturing techniques.  You'd need a water bath and a line of blowtorches, or something.

Edits: clarifying the role of "soft" steel in blademaking.
« Last Edit: January 21, 2010, 12:39:29 pm by Arrkhal »
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sunshaker

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Re: metallurgy
« Reply #52 on: January 20, 2010, 11:40:53 am »

Arrkhal thanks for your posts, I would have said something similar but at the time I saw that first post it was well past the time I should have been in bed... It is good to see someone else that has knowledge about metal working posting about metal mods.
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slink

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Re: metallurgy
« Reply #53 on: January 20, 2010, 01:20:43 pm »

Quote
The word "crystals" is probably a reference to the crystalline structure of the iron itself, not to some foreign material.

The thing is, wrought iron shouldn't have any kind of crystalline structure other than the slag, unless it's high enough in carbon to count as a near-steel.  And in that case, you'd want to harden it like a steel, not like an iron.

100% pure iron has a crystal structure.  Laymen don't think of metals that way, but chemists do.

From Cotton and Wilkinson, Advanced Inorganic Chemistry 3rd Edition, pg 858, re elemental iron (T is in degrees C):

Quote
At temperatures up to 906 the metal has a body-centered lattice.  From 906 to 1401, it is cubic close-packed, but at the latter temperature it again becomes body-centered.

Presumably this is the crystalline transformation to which metallurgists are referring when they talk about the phase diagram for steel, which is just slightly impure iron and not the result of some magical transformation of one metal into another.

Here is a pictorial description of the crystalline structure of iron.

http://www.webelements.com/iron/crystal_structure.html
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Arrkhal

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Re: metallurgy
« Reply #55 on: January 20, 2010, 01:53:31 pm »

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100% pure iron has a crystal structure.  Laymen don't think of metals that way, but chemists do.

Presumably this is the crystalline transformation to which metallurgists are referring when they talk about the phase diagram for steel, which is just slightly impure iron and not the result of some magical transformation of one metal into another.

I'm completely failing to see a point here.  I can only guess misunderstanding of semantics.  What I mean by "crystalline structure" is interactions between discrete micro- and nano-crystals embedded within the metal.

There's a big difference between iron itself being one big crystal (in an ideal state), and banging on it while hot "making the crystals, plural, closer together."  Work-hardening only dislocates crystalline bonds, thus making further dislocation require more effort.  It neither compresses the crystal lattice, nor does it spontaneously form a different type of lattice.  The fact that work-hardening metal turns it amorphous is kind of the reason why amorphous alloys never fatigue.

Water, it's just oxygen with a ~12.5% hydrogen impurity, right?  You can totally compare the physical and mechanical properties of oxygen and water, because hydrogen makes up such a small amount of the weight, right?

Steel production may not be "magical," but 0.60% carbon changes things a lot.

And if we're going to infodump, this is what I'd look at instead.

http://en.wikipedia.org/wiki/Cementite
http://en.wikipedia.org/wiki/Martensite
http://en.wikipedia.org/wiki/Austenite
http://en.wikipedia.org/wiki/Ferrite_(iron)
http://en.wikipedia.org/wiki/Pearlite
http://en.wikipedia.org/wiki/Bainite
« Last Edit: January 20, 2010, 02:02:36 pm by Arrkhal »
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slink

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Re: metallurgy
« Reply #56 on: January 20, 2010, 03:20:33 pm »

Quote
100% pure iron has a crystal structure.  Laymen don't think of metals that way, but chemists do.

Presumably this is the crystalline transformation to which metallurgists are referring when they talk about the phase diagram for steel, which is just slightly impure iron and not the result of some magical transformation of one metal into another.

I'm completely failing to see a point here.  I can only guess misunderstanding of semantics.  What I mean by "crystalline structure" is interactions between discrete micro- and nano-crystals embedded within the metal.

There's a big difference between iron itself being one big crystal (in an ideal state), and banging on it while hot "making the crystals, plural, closer together."  Work-hardening only dislocates crystalline bonds, thus making further dislocation require more effort.  It neither compresses the crystal lattice, nor does it spontaneously form a different type of lattice.  The fact that work-hardening metal turns it amorphous is kind of the reason why amorphous alloys never fatigue.

Water, it's just oxygen with a ~12.5% hydrogen impurity, right?  You can totally compare the physical and mechanical properties of oxygen and water, because hydrogen makes up such a small amount of the weight, right?

No, water is not oxygen with a hydrogen impurity.  Water is a chemical compound.

Steel is not a chemical compound.

Here is a layman's explanation of amorphous versus crystalline, as regards metals.  Amorphous metals are not common, and in fact steel is not amorphous, nor is iron or copper.

http://www.mrsec.wisc.edu/Edetc/background/amorphous/amorphous.html
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Arrkhal

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Re: metallurgy
« Reply #57 on: January 20, 2010, 04:09:28 pm »

You're really making too fine a distinction for most people to follow.

No, steel isn't its own chemical compound, but it's only "slightly impure iron" in the exact same sense that hydrochloric acid is "slightly impure water."

Yes, chemically, hydrochloric acid is just slightly impure water.  That doesn't change the fact that the chemical interactions change pretty significantly due to that slight impurity.  The impurity in steel is also iron carbides and secondary crystals formed around them, not just elemental carbon.

It also doesn't change the fact that "making the crystals closer together" is a pretty fallacious statement, from both a chemical and a physical point of view.

You said you don't know what effect working has on iron (and presumably also copper, brass, silver, etc., which were also all historically work-hardened).  And I did tell you what it is.

Working a crystalline metal destroys the crystal structure, making it partially amorphous; amorphous forms of metals are generally harder and brittler.  100% amorphous copper or iron would just be an ultrafine powder (probably no more than a handful of atoms per grain), so functional work-hardening will make the metal only partially amorphous, to strike some balance between malleability, hardness, and cohesion.  When the amount of amorphous metal in the mix gets too high, the metal "fatigues" and becomes brittle and crumbly, because there's an insufficient crystal matrix to hold the noncrystalline parts together.

The fancy thing about the amorphous alloys is they're already amorphous from the start, without losing cohesion.  There is no crystal structure to deform, so they do not work-harden, and do not fatigue.

And what makes steel different from iron in that respect is that iron carbides are substantially stronger and harder than amorphous iron.  Cold-working steel to any degree weakens it, while iron gets stronger up to a point.
« Last Edit: January 20, 2010, 05:07:59 pm by Arrkhal »
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slink

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Re: metallurgy
« Reply #58 on: January 20, 2010, 05:30:02 pm »

You're really making too fine a distinction for most people to follow.

No, steel isn't its own chemical compound, but it's only "slightly impure iron" in the exact same sense that hydrochloric acid is "slightly impure water."

Yes, chemically, hydrochloric acid is just slightly impure water.  That doesn't change the fact that the chemical interactions change pretty significantly due to that slight impurity.

It also doesn't change the fact that "making the crystals closer together" is a pretty fallacious statement, from both a chemical and a physical point of view.

You said you don't know what effect working has on iron (and presumably also copper, brass, silver, etc., which were also all historically work-hardened).  And I did tell you what it is.

Working a crystalline metal destroys the crystal structure, making it partially amorphous; amorphous forms of metals are generally harder and brittler.  100% amorphous copper or iron would just be an ultrafine powder, so functional work-hardening will make the metal only partially amorphous, to strike some balance between malleability and hardness.  When the amount of amorphous metal in the mix gets too high, the metal "fatigues" and becomes brittle and crumbly, because there's an insufficient crystal matrix to hold the noncrystalline parts together.

The fancy thing about the amorphous alloys is they're already amorphous from the start.  There is no crystal structure to deform, so they do not work-harden, and do not fatigue.

And what makes steel different from iron in that respect is that iron carbides are substantially stronger and harder than amorphous iron.  Cold-working steel to any degree weakens it, while iron gets stronger up to a point.

Hydrochloric acid, another chemical compound, is not impure water.  An aqueous solution of HCl, however, has properties more or less resembling the two materials in the mixture according to the proportions in which they are present.  Aqueous hydrocholoric acid is not some magical substance with new properties unknown to either water or HCl.  At least not unless you mix them in your kitchen while drinking Guiness just before calling the news media.   :D

Steel is not iron carbide.  Steel is iron with carbon impurities present within the iron crystal structure.  This does change the properties, however it does not make the iron into some other metal with properties contrary to all other metals worked by mankind.

If steel loses a valued property by a treatment which causes iron to gain that valued property "up to a point", might that not mean that the material called steel has already been given the optimal amount of that treatment as a matter of course in making the material?  This as opposed to steel being a magically reversed metal quite different from iron?

The entire field of metallurgy is riddled with contradictory and confusing terminology, partly due to attempts to keep trade secrets and partly because the people who originally discovered the processes did so before chemistry had become more than a quest to convert lead into gold. 

I have no doubt that professional metallurgists have a decent understanding of what happens with each metal and why it happens, while professional metalworkers know how to make things happen without understanding why it works.  I don't expect to find any of this information clearly stated on the Wiki, which consists of entries made by anyone who happens by.  Some of what I have read there is complete nonsense.
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Arrkhal

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Re: metallurgy
« Reply #59 on: January 20, 2010, 07:19:17 pm »

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If steel loses a valued property by a treatment which causes iron to gain that valued property "up to a point", might that not mean that the material called steel has already been given the optimal amount of that treatment as a matter of course in making the material?

Frankly, no, that's not how it works.  You're trying to understand structural chemistry from, apparently, a mixture of an aqueous inorganic chemistry background, and complete ignorance of the gross physical properties of metal as well.  No offense, but you're failing miserably.

You're just going to ignore or intentionally misinterpret any scientific data I may throw at you, so you're on your own to find your own citations, or to remain argumentatively ignorant if you'd rather do that.

I have to wonder just what kind of strength difference this person thinks there is between wrought iron (or the misnamed "low-carbon steel" which isn't really a steel at all) and high-carbon steel.

Is it really that unprecedented in solution chemistry that 0.6% by weight of an impurity will fundamentally change the properties of a solution?
« Last Edit: January 20, 2010, 07:32:03 pm by Arrkhal »
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