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Post by tsmspace on Oct 26, 2019 17:41:54 GMT
I don't ACTUALLY know anything about blacksmithing. my knowledge can be understood as "pub knowledge", or "grapevine knowledge".
With steel blades, the steel is heated, which reforms the "grain" of the alloy, then the blade is quenched. (this grain is crystalline molecular, not like the layers of folded steel, which would each have their own crystalline structures).
with bronze swords, this is also what happens (annealing) , but bronze is not quenched. (right??) ,, the edge of the blade is hammered to make the bronze more dense, which is called work-hardening.
if you anneal steel for long enough, it should "puff back up" , or anyway when it reforms its crystalline structures, it should expand to this crystalline density. Or does it?? Are modern knives made from cold-rolled steel, and then not quenched, and swords are made from the less dense unrolled steel, ,,,, hammering would be similar to rolling if the edge were "cold hammered", but is this done?? Would this work??
so basically, are steel swords through history also work hardened by cold-hammering??
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Post by AndiTheBarvarian on Oct 26, 2019 18:42:58 GMT
Afaik work hardening works with iron or steel that isn't quenched. But bronze swords were cast and hammered later while wrought iron/steel swords were always hammered into shape and not cast. With modern cast steel you have all positive effects of work hardening in the rolling process already, that's why blades can be milled afterwards. Heat treated steel is better than work hardened materials. www.cashenblades.com/images/articles/lowdown.html
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christain
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It's the steel on the inside that counts.
Posts: 2,835
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Post by christain on Oct 26, 2019 18:59:51 GMT
YES---steel and iron WILL get a bit harder with enough hammering, but not as hard as forging and tempering. I've made several 'iron-age' blades using nothing but hardware store bar stock, and nothing but hammer and anvil. They will take a sharp, usable edge but it won't last nearly as long as a tempered steel blade.
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Post by MOK on Oct 27, 2019 13:48:34 GMT
This is also why repeatedly bending almost any metal object one way and then the other with enough force makes it change color, grow brittle and finally snap. It gets work hardened and loses elasticity until it becomes too brittle to bear the stress.
PS. Also why, if you bend a piece of wire, you can never quite bend it back 100% straight again: the bent bit gets work hardened and becomes more rigid than the surrounding parts.
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Post by unistat76 on Oct 31, 2019 4:21:09 GMT
A small correction, if I may. As I understand it, metals do not get "more dense" or have their density effected in any way by heat treating or work hardening.
If you are using as a metaphor, well, I'm not a terminology Nazi, as long as we all understand that the metal is not literally changing density.
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Post by tsmspace on Oct 31, 2019 7:00:03 GMT
A small correction, if I may. As I understand it, metals do not get "more dense" or have their density effected in any way by heat treating or work hardening. If you are using as a metaphor, well, I'm not a terminology Nazi, as long as we all understand that the metal is not literally changing density. well. I have read that before, but I certainly am running with actually they do get more dense. for example with cold-rolling, they absolutely do. So by hammering, you should be able to produce a similar effect to cold-rolling, as well as produce some of the effects of techniques like pulling (like pulling strings through a draw) at the same time, resulting in a denser, non-homogeneous metallurgy. Heating the metal will eventually result in annealing but if you don't heat it too far then it won't be able to properly anneal and it will maintain some of these qualities through quenching, resulting in a truly non-homogeneous metal, with varying density and crystalline organization producing similar effects to the layers found in "damascus" or japanese layered products. I would love to hear more , but I will also surely have more to say, because cold-rolling metal absolutely changes its density.
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Post by AndiTheBarvarian on Oct 31, 2019 7:22:58 GMT
From what I've read work hardening doesn't make the metal more dense, it has other effects on the structure. Hammering a bloom to a solid piece of steel makes it more dense, but after that you can't compress it any more.
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Post by Timo Nieminen on Oct 31, 2019 7:33:32 GMT
because cold-rolling metal absolutely changes its density. By how much are you claiming it changes? According to MatWeb, the densities for cold-rolled and annealed 1020 are: - cold-rolled: 7.87 g/cc - annealed: 7.87 g/cc
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Post by MOK on Oct 31, 2019 11:04:24 GMT
Yeah, it's not the density that changes, just the structure. Otherwise hardening a piece of metal would also make it shrink, which it doesn't.
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Post by Sir Thorfinn on Oct 31, 2019 12:34:34 GMT
I may be wrong, but I understood hammering helps chance the internal crystalline structure of the metal. Or is that quenching/tempering?
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Post by AndiTheBarvarian on Oct 31, 2019 13:45:01 GMT
Afaik that is quenching/tempering. Cold hardening makes the rows of crystals more chaotic so that they slide less against each other, a bit like a stack of paper sheets with or without kinks.
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LeMal
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Post by LeMal on Oct 31, 2019 15:23:30 GMT
It's not a dumb question on his part though. (Speaking here as a very long term science educator. ;) ) It's easy to confuse principles of hardness with density, density with being "packed," and hardening ability DOES relate to different alloys, which DO have different densities, the info I have on iron alloys going from 7.15 to 7.87.
The irony, tsmpspace? (Pun intended.) The highest of these densities is ... pure iron.
Plus remember that pure lead is pretty soft, and more dense.
But to reiterate, it's an honest and understandable cognitive error, speaking as someone who understands how common these are when it comes to scientific principles. (Now folks, don't let me go off on, technically, how heavier objects indeed do fall faster than lighter ones, contrary to how it's taught, and we shouldn't be mocking that cognitive error but redirecting it to asking how MUCH faster. :) )
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Post by AndiTheBarvarian on Oct 31, 2019 15:51:01 GMT
Tbh until my second post here 8 hours ago I also thought cold hardening makes the metal more dense. Thanks god I looked it up before I posted. Real questions can't be dumb, only the answers!
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Post by MOK on Oct 31, 2019 18:01:16 GMT
Oh, dumb questions do exist! They're quite different from just being unaware of some particular thing, though. There's no shame in not knowing, only in not wanting to know.
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Post by Timo Nieminen on Oct 31, 2019 21:31:13 GMT
Both work-hardening and quenching/tempering change the crystal structure. Work-hardening increase the number of dislocations/defects in the crystal lattice (which doesn't significantly change the density), and quenching and tempering change the crystal phases (i.e., the types of crystals). Since the different types of crystals have different crystal structures, they have different densities.
The density changes during heat treatment depend on the carbon content, but the main thing is the difference between the densities of pearlite (the soft stuff) and martensite (the hard stuff).
For 0.76% carbon: Pearlite: 20HRC, density of 7.84g/cc Martensite: 65HRC, density of 7.81g/cc
But usually one doesn't get pure martensite, and there will be perhaps 5-10% retained austenite: Austenite: density of 7.96g/cc and the density won't decrease so much (and hardness will be lower).
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Post by AndiTheBarvarian on Oct 31, 2019 21:43:34 GMT
This metallurgical dirty talk makes the katana really wobbling while quenching!
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Post by Timo Nieminen on Oct 31, 2019 21:47:43 GMT
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Post by dc on Nov 1, 2019 2:14:54 GMT
A small correction, if I may. As I understand it, metals do not get "more dense" or have their density effected in any way by heat treating or work hardening. If you are using as a metaphor, well, I'm not a terminology Nazi, as long as we all understand that the metal is not literally changing density. well. I have read that before, but I certainly am running with actually they do get more dense. for example with cold-rolling, they absolutely do. So by hammering, you should be able to produce a similar effect to cold-rolling, as well as produce some of the effects of techniques like pulling (like pulling strings through a draw) at the same time, resulting in a denser, non-homogeneous metallurgy. Heating the metal will eventually result in annealing but if you don't heat it too far then it won't be able to properly anneal and it will maintain some of these qualities through quenching, resulting in a truly non-homogeneous metal, with varying density and crystalline organization producing similar effects to the layers found in "damascus" or japanese layered products. I would love to hear more , but I will also surely have more to say, because cold-rolling metal absolutely changes its density. Cold rolling will only change the density if the metal being rolled has voids in it (which would be filled in the rolling process).
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Post by dc on Nov 1, 2019 2:28:26 GMT
Yeah, it's not the density that changes, just the structure. Otherwise hardening a piece of metal would also make it shrink, which it doesn't. Not only does it not shrink, it expands! When steel is quenched it changes from dense to austentite to various less dense crystaline structures, the hardest of which (martensite) is less dense than the softer ones - this is why a Katana curves the way it does when differentialy quenched: the hardened edge expands more the unhardened spine.
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Post by natasharobsonss on Nov 11, 2019 5:31:14 GMT
Good Discussion about the bronze Sword.
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