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  • Steel is the most important material to human society.


  • It has been the skeleton of human industry for centuries, and the advent of the methods


  • to mass produce it from iron ore was the impetus to transform human society from a mostly agricultural


  • lifestyle to urban industrialisation.


  • It forms the backbone of our skyscrapers, it paves the way for our railways, it shapes

    它被製成引擎,為文明供給電力 甚至用來製造這些東西的工具,也正是以鋼鐵製成

  • the engines that powers our society, and the very tools that forge these objects are made


  • from steel.


  • We have spoken before about how the refining processes of iron determines whether the resulting


  • material will be steel or iron and how the exact percentage of carbon present in the


  • material has dramatic results on the final material properties, and how the production


  • methods through time has taken steel from an expensive material reserved for swords,


  • armour and toolmaking, to one that has permeated into nearly every technology we use in our

    讓它從一個相對較弱的材料搖身一變, 甚至足以開啟整個工業革命

  • lives.


  • But I failed to tell why that simple addition of carbon has such a huge effect on the iron,

    我們對於鋼鐵加工的知識 大部分來自鐵匠們一代一代的傳承

  • turning it from a relatively weak material to one capable of launching an industrial


  • revolution, which is what we are going to learn about today.

    因此,為了更了解「鐵」這個神奇的材料 以及鐵匠如何小心翼翼地改變鐵的特性

  • Much of our knowledge in crafting steel was passed down over the centuries from blacksmith

    我拜訪了Alec Steele的工作室 從頭開始製作一把屬於我的刀

  • to blacksmith, creating tools for their communities, so to learn more about this amazing material


  • and how blacksmiths carefully tailor it's material properties, I visited Alec Steele's


  • workshop to create my own knife from scratch.

    好讓我能用我瘦小的手臂 在接下來的一小時裡,努力揮著3磅重的鐵鎚

  • We started our forging process with round stock 1055 steel with 0.55% carbon content,


  • placed it in the forge and gradually shaped it with a power hammer to a rectangular bar


  • that could be more precisely shaped into the shape of our blade using a 3 pound hammer

    結束這個步驟後的刀胚 會再透過研磨完成最終的刀型

  • that my wee arms struggled to swing after an hour.


  • Once we had roughed out the shape we began to grind and refine our blade.


  • Eventually producing our blade blank that would later be grinded to it's final shape,

    為了強調這個步驟有多麼的重要 我們分別測試了4個樣本

  • but before that could happen we needed to perform some metallurgy wizardry through the

    它們來自相同的材料 分別代表了熱處理製程中的不同階段

  • heat treatment process.


  • To drive home how important this step is, we tested 4 samples of the same material at


  • different stages of the heat treatment process.

    而這個是正常化(normalised)的樣本 它的降服應力(yield stress)小而較軟

  • This was our sample before the heat treatment process, which you will quickly see was the

    它吸收了幾次的錘擊的外力產生塑性變形(plastic deformation)

  • weakest of the bunch.


  • This is the normalised sample, which was ductile with a low yield stress.


  • It took several hammer blows, which it absorbed through plastic deformation, not ideal characteristics


  • for a sword or knife.


  • Next we tested our quench hardened sample, which is stupid and dangerous and should not

    最後我們測試回火(tempered )後的樣本 它吸收了每一下的錘擊,只產生了些微的塑性變形

  • be tried at home.

    只有在我們切割了一個缺口 產生應力集中點(stress concentration point)時才斷裂

  • This fractured explosively and tore a hole through Alec's reflector.

    這樣的材料相當強韌 能吸收外力而不會產生永久的形變

  • Finally we tested the tempered material, which absorbed every hammer blow with minimal plastic


  • deformation and only broke when we cut a notch into the material to create a stress concentration


  • point.

    如果這些名詞讓你感到困惑的話,我做了一部影片叫做Material Properties 101

  • This material is tough, capable of absorbing energy without deforming permanently, and


  • hard allowing it to resist damage to the cutting edge.


  • It is the ideal material for a blade.


  • If any of these terms confused you, I created a video called Material Properties 101 that

    我們可以透過特定的加熱與冷卻流程 小心地控制材料內部的金屬晶體結構組成

  • you can check out to get a better understanding of material property terminology.

    首先讓我們來看看在鐵中添加碳如何影響其結晶組織(crystalline structure)

  • So how can the same steel alloy change so radically by simply applying heat?

    未含碳的純鐵會形成稱作體心立方晶體(body centred cubic )的晶體結構

  • Well this is the magic of the iron carbon alloy.


  • We can careful control how the internal metallic crystal structure forms with heating and cooling


  • cycles.

    稱為滑移面(slip plane)

  • First let's see how adding carbon to iron affects it's crystalline structure.


  • With no carbon present pure iron will form a crystal structure called body centred cubic


  • with an iron atom at each of the eight corners and another in the centre.


  • Each crystal structure has a direction it most easily wants to deform, called a slip

    當金屬冷卻時 這些結晶從各個成核點(nucleation points)開始增長

  • plane.


  • For body centred cubic the slip plane occurs along this planes.


  • Metals with Body centred cubic crystals like iron and tungsten tend to be harder and less


  • malleable than metals with face centred cubic crystals like aluminium, lead and gold.

    晶粒會想朝某個特定方向滑移 並把力傳給此方向上的下一個晶粒

  • When a metal is cooling, these crystals grow from individual nucleation points and form

    然而這個晶粒的滑移面角度並不相同 因此必須施加更大的外力

  • grains where each grain has the same orientation of slip plane but neighbouring grains may


  • not have the same slip plane.

    這就好像試著要推動鐵軌上的火車 推的卻是側邊

  • Let's think about this 2 dimensionally, when a force is applied, the grain wants to


  • slip in a particular direction, and passes the force onto the next grain in that direction


  • too, but this grains slip plane is at a different angle, so that force needs to be greater in


  • order to cause deformation.


  • It's like trying to push a train down a railway track, by pushing on its side.


  • It's not going to go anywhere easily.

    要探討這點,我們先來看看碳鋼的相圖(phase diagram)

  • So smaller and more numerous grains results in a stronger material.


  • Pure iron tends to always has the same crystal structure as it cools and it's crystal structure


  • doesn't change meaningfully with heat treatment.


  • This is where alloying with carbon comes in.


  • To explore this let's look at our phase diagram for carbon steel.


  • On this diagram we have our carbon content percentage on the x-axis and the temperature

    當我們移動到相圖的右手邊 形成肥粒鐵的結晶越來越少

  • of the metal on the y-axis.


  • This tells us the crystalline structure of the metal at various temperatures and carbon

    現在如果我們從溫度軸往上移動 我們會看到這些代表轉變溫度(transition temperature )的線條

  • contents.


  • On the left hand side we have pure iron, which as we explained earlier forms only one crystal


  • structure, called ferrite.

    再繼續往上 這邊我們看到的線條代表金屬轉變為液態

  • As we move across the diagram to the right hand side, less and less of the crystal structure


  • forms ferrite, and more forms an iron carbide alloy, commonly called cementire.


  • Now if we move up in temperature we start to see these lines that represent transitional


  • temperatures, where the crystal structures of the steel begin to transform into a new

    它仍然擁有足夠的間隙 讓較鐵原子小的碳原子,能舒服的容身其中

  • crystal structure called Austenite.


  • Moving further up again we see lines representing the transition of the material to a liquid


  • state.


  • Austenites primary difference to ferrite is that it forms that face centred cubic crystal


  • structure that we saw early, while ferrite is body centred cubic.

    正常化的主要功用是釋放在鍛造過程中產生的內應力(internal stresses)與應變(strains)

  • And while this packing pattern is denser than body centred cubic, it does open up spaces


  • in the crystal structure that interstitial carbon atoms, which are smaller than iron,

    它就像鋼材的「重啟」按鈕 讓鋼材產生整齊、平均的晶粒大小與分佈

  • can snuggly fit.


  • Allowing austenite to have a higher solubility to carbon over ferrite.

    這裡我們將刀胚放在鋼管中, 避免刀胚直接接觸火源

  • Using all of this information, let's take our 1055 steel with 0.55% carbon content and


  • see how it transforms from the start of our heat treatment cycle to the end.


  • The first step is called normalisation.


  • Normalisation is primarily functions to relieve internal stresses and strains that formed


  • during the forging process and return the material to its original crystal structure


  • before forging began.

    如果我們拿含碳量0.8%的碳鋼 等等,我們需要大一點的圖

  • It's effectively a reset button for the steel and creates nice even grain size and

    如果我們拿含碳量0.8%的碳鋼, 讓它冷卻並通過轉變溫度

  • distribution, increasing its strength.


  • Here we placed the knife blank inside a steel tube to prevent the metal from receiving heat


  • directly from the flame, but instead a more even radiative heat from the tube.


  • Once it reaches this transition temperature we let it soak to give the crystal structure


  • time to settle.


  • The next step in normalising is to allow the steel to slowly air cool.


  • What happens now depends on the carbon content.


  • If we take a 0.8% carbon steel, no hang on we're gonna need a bigger graph for this,

    直到剩餘的沃斯田鐵有足夠0.8%的碳 並由此開始形成波來鐵

  • If we take a 0.8% carbon steel and cool it to it's through transitional temperature


  • the austenite and the interstitial carbon will slowly transform to a mixture of ferrite


  • and cementite, which takes this laminar structure called pearlite.


  • Pearlite only forms at a 0.8% carbon solution

    這是純鐵,其為100%的肥粒鐵,顏色較淡,甚至可以看到晶界(grain boundaries)

  • Now if we take a 0.55% 0.2% steel, like the one we used.

    這是含碳量0.5%的碳鋼,與我們所使用的很像 在此僅有非常少量的肥粒鐵形成

  • And slowly cool it, to its first transitional temperature here.


  • Where ferrite first begins to form, ferrite is pure iron so as it forms the carbon percentage


  • begins to rise, this will continue to happen until the remaining austenite has a carbon


  • percentage of 0.8% and it will then form pearlite from this point on.


  • This forms a crystal structure dominated by ferrite, showing here as a lighter colour,


  • surrounded by the darker pearlite.

    它對鋼鐵的剛性影響不大 然而波來鐵的含量增加

  • Comparing these microstructures to another 2 we can see the effect carbon has on the

    對材料的降服點(yield point)有戲劇性的影響 令其能吸收更多能量而不產生永久的形變

  • microstructure.


  • Here we have pure iron, with 100% ferrite, showing as this light colour, you can even

    假如我們將鋼材重新加熱到形成沃斯田鐵 但這次,不是讓它徐冷而是浸入油中快速冷卻

  • see the grain boundaries.


  • This is a 0.5% carbon steel similar to ours, where a very small amount of ferrite formed


  • before we reaching the point of pearlite formation, and this is 0.8% carbon steel where the entire

    無法自晶格(crystal lattice)中擴散出去形成雪明碳鐵, 而困在其中

  • structure is pearlite, with our previous example showing pearlite under 500 times magnification


  • where you can readily see that laminar structure.


  • How Pearlite strengthens steel is not well understood.


  • It has little effect on the steels stiffness, but increasing the pearlite content has dramatic


  • effects on the materials yield point, making it much more capable of absorbing energy without


  • permanently deforming.


  • But we can increase the materials stiffness and hardness with our next step.


  • If we heat the metal back up to form austenite once again, but this time instead of letting


  • it cool slowly, we rapidly cool it in oil, while casually burning your arm hair off and


  • barely flinching, the carbon atoms that spread out throughout the hot austenite structure

    如果你有看過Smarter Every Days的頻道裡 魯珀特之淚(Saint Rupert’s Drop)的影片

  • cannot diffuse out of the crystal lattice to form cementite, and instead gets stuck


  • in solution, creating a new crystal structure called martensite.

    這個材料特性叫做硬度, 我們希望我們的刀鋒夠硬,在切割時不會受損

  • This crystal structure has a huge amount of internal stretching.


  • In part because the carbon trapped within the crystal structure causes the crystal lattice


  • to deform, but also because during the rapid cooling the surface cooled much faster than


  • the internal material.

    這時最後一個步驟就派上用場了 稱為回火(tempering)

  • This causes internal tension in the material.


  • These internal strains make it harder for additional deformation to occur, but this

    我們僅用了烤箱,設定200度C 其中的碳再度聚合形成雪明碳鐵

  • does not make the material stronger.


  • It simply means it will not stretch and bend before breaking, and when it finally does


  • fracture all of this internal tension is suddenly released in an explosive expansion.


  • If you have watched Smarter Every Days video on the Saint Rupert's Drop, you will have


  • seen this principle demonstrated in incredible slow motion.


  • This material property is called hardness, and we want our cutting edge to be hard to


  • resist damage when cutting, but we do not want our entire blade to be hard as it will

    而又足夠強韌而不會永久的變形 同時又擁有足夠的硬度確保刀鋒無損

  • not be able to absorb a lot of energy.


  • It needs to be able to dissipate some of that energy through heat and deformation.


  • This is where the final step of the process comes in, called tempering.

    與Alec學習這些技術非常有趣 我也極力推薦你一定要到他的頻道看看

  • Tempering raises the temperature enough to allow the carbon trapped in solution to escape,

    他對工作的態度非常了不起 啟發我今年開始學習一些新的技術

  • we just used an oven set at 200 degree, the carbon then coalesces to form cementite once


  • again, but instead of forming pearlite like before.

    我在skillshare上找到的這個課程 對所有想學習這個技術的人來說,是個很棒的起跑點

  • It gathers in globules surrounded by ferrite.


  • Tempering also relieves some of that internal tension caused by the rapid cooling.This reduces


  • the hardness, but increases toughness.

    現今的社會 你幾乎可以透過網路自學所有技術 而Skillshare正是這樣一個非常棒的地方

  • This produces a material that has the perfect balance of characteristics between the normalised


  • material and the hardened material.


  • It is ductile enough to absorb hammer blows without shattering, but strong enough to not

    高級會員每個月10美元起 就可無限制的訪問所有課程

  • permanently deform, and with enough hardness to ensure it doesn't gather damage on the


  • cutting edge.


  • This process gave our steel the perfect material properties and a lot of that is thanks to


  • the quality of the steel we started off with.


  • Learning these skills with Alec was a lot of fun and I highly recommend you check his


  • channel out.


  • His incredible attitude to work really inspired me to start learning some new hands on skills


  • this year and I am hoping to start that off by learning how to programme and create robotics


  • with an arduino.


  • This course I found on skillshare is the perfect jumping off point for anyone looking to learn

    一如往常的,謝謝觀賞 也感謝我所有的Patreon支持者

  • the same skills.

    如果你想要從我這了解更多的話, 我的twitter, facebook和instagram網址如下

  • Skillshare is home to thousands of other classes in graphic design, animation, web development,

  • music, photography, video game design and more.

  • These days you can teach yourself pretty much any skill online and Skillshare is a fantastic

  • place to do it.

  • With professional and understandable classes, that follow a clear learning curve, you can

  • dive in and start learning how to do the work you love.

  • . A Premium Membership begins around $10 a month

  • for unlimited access to all courses, but you can get your first 3 months for just 99 cent

  • if you sign up with this link.This offer was supposed to be only valid until the end of

  • Jan, but I talked to Skillshare and was able to get this extended for ye until Feb 15.

  • In those 3 months you could easily learn the skills you need to start a new hobby or business.

  • So ask yourself right now.

  • What skill have you been putting off learning.

  • What project have you been dreaming of completing, but you aren't sure if you have the skills

  • to do it.

  • Why not start right now and sign up to Skillshare using the link below.

  • You have nothing to lose and a valuable life skill to gain.

  • As usual thanks for watching and thank you to all my Patreon supporters.

  • If you would like to see more from me, the links to my twitter, facebook and instagram

  • pages are below.

Steel is the most important material to human society.



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熱處理(Heat Treatment -The Science of Forging (feat. Alec Steele))

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    joey joey 發佈於 2021 年 06 月 09 日