Why is the carbon content in steel so important?

Steels, which are alloys of iron and carbon, are one of the most commonly used industrial materials. The amount of carbon that is added to the steel dramatically affects the materials microstructure and mechanical properties. In this video we cover the iron-carbon equilibrium phase diagram and explore how changing the composition of low alloy steels impacts the microstructure by analysing the phases that form.
00:00 Introduction
00:23 Why is this important?
01:54 Equilibrium phase diagrams
03:23 Different ferrous alloys
06:26 Different phases of iron - Ferrite and austenite
07:46 Iron-carbon alloys - Ferrite and cementite
08:55 Iron-carbon phase diagrams
10:58 The eutectoid composition - Pearlite
11:57 Hypo/hyper-eutectoid composition
14:42 Summary
This is a follow up video to a previous one on "How to use phase diagrams and the lever rule to understand metal alloys".
• How to use phase diagr...
Interested in learning more?
📚I highly recommend the textbook "Material Science and Engineering" by Callister and Rethwisch which you can get here amzn.to/3Ut5Efr (Amazon)
#Steel #PhaseDiagrams #Pearlite
Twitter: / icbillywu
Personal website: www.imperial.ac.uk/people/bil...
About us: www.imperial.ac.uk/design-eng...

[@JohnGreen-tw9sv]

Wow. Can't believe how clearly this video explains this topic! such fluency and teaching skill. Thanks so much, definitely made today's work easier!

[@BillyWu]

Glad it was helpful!

[@stephenokocha8364]

You are the best. I've always been confused about the different terminologies used in the microstructure of steels. Journals didn't help that much as they focus on higher concerns. This is coupled with my poor background in metallography. Now this gives me the best foundation to do more research on high carbon steel. Thank you Dr. Billy Wu, you are an outstanding teacher.

[@BillyWu]

Thanks. Glad to hear it was helpful!

[@jacksonminnear5928]

This is literally the most clear explanation of the differences between pearlite when different carbon %wt is used. Even my apprenticeship papers didn't explain this concept enough for me to understand. Thanks for putting in the effort to produce this video! Now I understand the importance of the Eutectoid point!

[@BillyWu]

Glad you found it useful

[@tjvanderloop1686]

The best "Metallurgy" lecture on the Internet. Thanks for the great job! Keep up the quality UA-cam experience as you are an outstanding instructor.
T J (Tom) Vanderloop, CMfgE; 😀Author, Educator & Consultant

[@BillyWu]

Thanks for the positive comments :)

[@NetZeroTech]

Very well explained for beginners! Great to start with Why and focus on the most important. Graphics are great, too! Well done. My PhD was in TRIP-assisted thin sheet steel, when UA-cam wasn't widely spread, yet. Exciting to see this medium support people in having access to knowledge and learning. Thank you!

[@BillyWu]

Thanks a lot!

[@61sivasoumitripudipeddi64]

Extraordinary! Thank you. Please keep making more videos of this kind. Thank you again.

[@BillyWu]

Thanks. Glad it was helpful

[@pdt.himanshutiwari3679]

you deserve more likes my friend. thanks for this INFORMATION.

[@BillyWu]

I appreciate that!

[@JZ1917]

You explained this better than I have seen anywhere, including university. Wow. Thank you

[@BillyWu]

Thanks! Appreciate it

[@VIDEOVISTAVIEW2020]

wow! this is very simple but impressive explanations of a complex subject about the consequential effect of carbon when added to iron.

[@BillyWu]

Thanks. Appreciate the comment and glad to hear it was useful

[@RomanoPRODUCTION]

You have summarized very nicely my undergrad course I have learnt 25 years ago.

[@BillyWu]

Thanks for the comments. Appreciate it

[@_neophyte]

good job to whoever named "cast iron"

[@BillyWu]

🙂

[@MatheusBalenMe]

Awesome video. Great work!

[@BillyWu]

Thanks a lot!

[@tksnail6837]

excellent explanation of why hypo and hyper eutectoid steels have either ferrite or cementite forming as 'networks'! was having a lot of trouble with that

[@BillyWu]

Glad to hear it helped

[@thejaebeing]

Thank you for explaining so clearly... You won my subscription.

[@BillyWu]

Thanks!

[@CapsCtrl]

Great video, straight to the point and explains all the relevant information, thanks! 🛡✨️

[@BillyWu]

Thanks. Glad to hear it was useful

[@ramamanikanta2223]

Very nice explanation

[@dhruvupadhaya5853]

Very well explained. Thanks.

[@BillyWu]

Glad it was helpful!

[@adityabaghel1270]

This was AMAZING!!!

[@BillyWu]

Thanks. Glad to hear it was useful

[@bjrn-oskarrnning2740]

Very useful, thank you!

[@BillyWu]

Glad it was helpful!

[@sinafadakhah9180]

Great explanation. thank you.

[@BillyWu]

Glad it was helpful!

[@miyakashi05]

TYTY I FINALLY UNDERSTAND THIS - MY TEACHER NEVER TAUGHT IT BUT YOU SUMMARISED THE PHASE DIAGRAM SO WELL THANKYOUUU

[@BillyWu]

Glad to hear it was useful!

[@foodtips8515]

Loved the explanation

[@BillyWu]

Glad you liked it

[@mohammadarifullah1108]

Great explanation.

[@BillyWu]

Glad it was helpful!

[@user-mx5we1li2l]

Incredible lecture!

[@BillyWu]

Glad it was helpful!

[@shashiyadav837]

Never in my life I have properly understood about FE-C diagram, Your Materials Playlist help me to develop the imagination and Thought Process and clear some of my basics
Thank You very much
May God bless you

[@BillyWu]

Glad to hear it helped

[@VasantKhisty]

beautifully explained

[@BillyWu]

Thanks!

[@Chuxgold]

Good video. Very compleat and well explained.

[@BillyWu]

Glad you liked it

[@av5186]

Brilliant lecture, thank you very much!

[@BillyWu]

Thanks. Glad to hear it was useful

[@sid0850]

Perfectly explained 💯❤️

[@BillyWu]

Glad to hear it was helpful

[@mohammedaghazy6161]

so awesome.
Thanks.

[@BillyWu]

Glad you liked it!

[@batobalani4787]

very nice very clear!

[@BillyWu]

Thanks!

[@sunmichoi6888]

Thank you so so much! your videos are awesome!

[@BillyWu]

Thanks. Glad to hear they're helpful

[@sleepygrumpy]

Great video!

[@BillyWu]

Thanks

[@maowtis]

Thank u! This video will help a lot in my studying for my incoming quiz

[@BillyWu]

Glad to hear it was helpful

[@abdullahhesham404]

please make more videos explaining metallurgy, you are great!

[@BillyWu]

Thanks Abdullah. Appreciate the comment and hope to add a few more videos in the near future

[@antiquarian1773]

Really good video!!!!

[@BillyWu]

Thanks!

[@dizietz]

Really great video. Amazing work! It would be even better with some references to specific steel alloys etc.

[@BillyWu]

Thanks and great suggestion. I've got a few more videos in the pipeline and suggestions always helpful

[@dizietz]

​@@BillyWu I think making this kind of metallurgy adjacent knowledge as applicable and practical is great. There are a lot of people not in the field who can benefit from the distribution of this knowledge via UA-cam etc. Not everyone has access to simpler tools like a Rockwell test, much less OES or LIBS etc techniques. Knowing the physics behind these things and applying them to common alloys etc is useful. I do wonder if there is data on alloy production volume worldwide that can supplement theoretical foundations to outline most common materials. Additional thought: ie, in the video of the type like on heat treating etc, adding some more b-roll of industrial applications of some of these techniques makes for more accessible content. Thank you again!

[@lonewolfgaming5245]

Very well made.

[@BillyWu]

Thanks

[@user-yu5no1ns2m]

This helped a lot. Thank you very much!!

[@BillyWu]

Glad it helped!

[@user-yu5no1ns2m]

@@BillyWu I managed to pass the test aswell. Thanks again!!

[@BillyWu]

@@user-yu5no1ns2m Great! Congratulations

[@Rose-nn9wb]

Thank you so much

[@fansana8641]

Thanks God, i dont speak english but still understand your video. Thanks so much. Best job

[@BillyWu]

Thanks

[@vrn42]

Very effective brief!!

[@BillyWu]

Thanks

[@happying]

Prof, may you please give more lessons on Materials related topics 😢, your explanations are so much easier to understand and clear. This really helps me to learn more and better 😊

[@BillyWu]

Thanks and glad to hear it was useful. I have other content in the pipeline, but am a bit slow producing this at the moment. Watch this space :)

[@nananone2118]

Very useful thank you 😊

[@BillyWu]

Glad you found it useful

[@moralesfabricio]

beautifully explained. Thanks a lot Dr. Wu, It will help me a lot for my tomorrow's exam

[@BillyWu]

Glad to hear it was useful

[@mohammad6002]

Thank you so much!

[@BillyWu]

Glad you found it useful

[@andresaraya3853]

Thanks!!!

[@lachlantate2379]

Fantastic

[@BillyWu]

Thanks

[@user-pu9qe1nn2r]

Plz make videos on slippage of carbon atoms in stress strain curve from Civil Engineering perspective🙏

[@ahmetcankirmizi]

this video was very helpful, thank you for uploading it.
also, if i may ask, would you have any info as to how we can learn this stuff without overcomplicating it for ourselves like you have done?

[@BillyWu]

Thanks. There's some excellent online learning material in places like Coursea. Alternatively, one our new area is to use of chatbots like chatGPT which are quite dynamic in their responses, allowing you to probe areas which weren't clear around core concepts. The approach is still quite new and users should be careful about accuracy of information but for generally well known concepts with lots of material supporting this, it can be a useful learning assistant though I'm still reflecting on the best way to use tools like this.

[@Onkar14]

Very informative video..Pls also make 1 video on Cast Iron.

[@BillyWu]

Thanks for the suggestion. Will add it to the list :)

[@AJ-sb8qk]

Do you have a video explaining Martensite?

[@fiona.e1026]

Waw that's awesome

[@plankmax8748]

thank you so much

[@BillyWu]

You're welcome!

[@germona]

Very well done Sir. I found this video by searching for grain structures. For me it is importend to know the relationship between alloys and grains structures versus magnetism. I would like to magnetise a steel alloy to the highest possible magnetic field, and i do not understand which element or phase, or grain structure is responsible for that. Some 100 years ago they used a lot of Tungsten(W) to increase magnetic properties of steel. I don't know if that is the only way. Thanks.

[@Techyhelpandiostips]

finally understand thanks

[@BillyWu]

Glad to hear this video helped

[@anushaislam6049]

this really helped...

[@BillyWu]

Glad to hear it was helpful

[@krystalvang9659]

amazing

[@BillyWu]

Thanks

[@Trohawkk]

Good thanks

[@BillyWu]

Thanks

[@UCLu80m2ixrOHYgI6ioFZFhA]

Hello can you make vid about direct reduced iron?(hydrogen reduced iron making process) ? I am very curious about its future and potential

[@dolinadanazara3282]

watching this video like reading a whole of book.. good job..

[@BillyWu]

Thanks. Glad you found it useful

[@The.Wonderful.Inspiration.Of.]

Hello :) Thanks a lot !
However I have two questions,
- At the eutectoid point when the steel is cooled, does austenite remain, I don't understand (at 11:39 the photo on the left shows austenite but the one on the right doesn't).
- I was wondering if pearlite appeared at any carbon content or if it was only near the eutectoid point?

[@BillyWu]

Great question. The key with phase diagrams is that they represent the thermodynamic state of a system (i.e. if you had infinite time for the atoms to vibrate around and find their ideal spots, what would the structure look like). From a thermodynamic perspective, once the steel is cooled below the eutectoid temperature all the austenite gets transformed into pearlite like the inset image on the phase diagram. The left image there was meant to show what a structure might look like as the pearlite is growing from the austenite, so it more of a non-equilibrium structure. When cooling more rapidly sometimes you get other phases like martensite. Also, pearlite can appear at different carbon contents, not just the eutectoid composition. If you have less or more carbon, you get pearlite but held together by either soft ferrite or hard cementite, respectively for a hypo- and hyper-eutectoid composition.

[@The.Wonderful.Inspiration.Of.]

Very clear and informative thank you very much !

[@pambudibaguswidodo9768]

Hi. Thanks for the detail explanation.
Can I request a video about stainless steel?

[@BillyWu]

Thanks. Good idea. I'll add it to the list and hopefully get round to something on the topic soon

[@Nick-qs7lw]

@ Billy Wu
I’m currently doing my CSWIP 3.1 and all the literature i’ve read states the austentic region starts at around 723 deg ?

[@BillyWu]

Hi Nick. The reference text book I normally like to recommend is Materials Science and Engineering: An Introduction by William Callister. The adapted iron-carbon phase diagram in this video was based on this which shows a Eutectoid temperature of 727 °C which is broadly aligned with your value.

[@momokara1188]

When I saw the Minecraft Iron and Coal, I knew it was going to be a great video!😁😂😅

[@BillyWu]

Thanks :)

[@snramit]

Nice vedio make vedio on ADI material

[@user-tr6yr6dc5v]

at 1:07 there is a tram which i take to work every single day in Budapest, Hungary lol. Jó öreg kettes villamos

[@BillyWu]

Ah great to know! Budapest is an amazing city

[@lukecipo]

THANK YOU THANK YOU THANK YOU

[@BillyWu]

Glad to hear it helped

[@dargue2021]

thank youuuu

[@BillyWu]

Glad it was helpful

[@yingerxu7109]

Can you help me understand the time-temperature-transformation diagram and the terms related to it? Please please please

[@BillyWu]

Sure. Here's another video where I discuss different ways of strengthening metals, including heat treatment and TTT diagrams ua-cam.com/video/7lM-Y4XndsE/v-deo.html

[@yigitcanbaysal824]

Professor I have question.If you were asked why Fe-C phase diagram is so important ,what would you say?Could you give me a short explanation.

[@BillyWu]

Good question. The iron-carbon phase diagram is important mostly because steel is one of the most commonly used engineering materials and as such we need a good understanding of how composition affects properties towards making the right material selection/design.

[@yigitcanbaysal824]

@@BillyWuOh thank you professor.Plus ,I have one more uestion if it's possible Maximum solubility of carbon in FCC iron is 2%
but steel is produced below 1.4% carbon and cast iron is produced between 3-4.5% carbon. Why?

[@marekkaspar811]

Medium carbon steel is used only for woodworking cutting tools, railway tracks is not always high carbon steel but medium carbon steel. You mentioned cast iron pans and machinery so gray cast iron is not extremely hard but rather soft because graphite in soft ferite matrix and machinability is good. White cast irons is extremely hard but not used far kitchen pans...

[@zdvxgf]

Bruh here I am paying high tuition for college while just learning every material on youtube!!

[@BillyWu]

Glad to hear you're finding material like this useful. Online videos are a great teaching assistant. In-person teaching at college/university, though, I still think has a lot of value with peer-learning, problem-based learning and feedback which is still something with online learning that we haven't fully cracked yet

[@taxfree4603]

This is a tough subject, how long did it take you to understand it completely

[@abhishekpariyar884]

Why does Iron have BCC phase at high temperatures, then it transforms to FCC ehrn it is cooled, and then again to BCC as it is cooled further?

[@met0578]

When the temperature reaches to 910 degrees Celsius another phase change occurs from FCC non magnetic (Gamma iron) to bcc non magnetic ( beta iron ). Finally at 767 degrees Celsius ferrite(alpha iron) becomes magnetic without change in lattice structure.

[@met0578]

Reply please

[@Bennethp]

The minecraft blocks were a nice addition xD

[@BillyWu]

haha thanks

[@qtrnndya]

Thank you very much. I would wish you are my lecturer in real life 💕

[@BillyWu]

Glad to hear it was helpful

[@garethtopliss350]

lovely info but you forget that an alloy means that it consists of 2 or more metals as a base before carbon is added

[@narendrakumarpatel4392]

Hi sir
Proetectiod ferrite
How it looks like in 3D
Please make it visualise

[@shab2499]

3:22 when i saw Minecraft iron icon i knew its going to be serious video😂

[@BillyWu]

:)

[@satishgowda9480]

What is Martensite micro structure

[@BillyWu]

Due to the rapid cooling of the steel, martensite generally has a very fine grain structure, with needle-like grains. The Wikipedia page has some nice additional information and an image of this. en.wikipedia.org/wiki/Martensite

[@tedarcher9120]

What makes spring steel what it is?

[@BillyWu]

Good questions. There are various types of spring steel as shown in the Wiki link (en.wikipedia.org/wiki/Spring_steel) most are low-alloy manganese, medium-carbon steel or high-carbon steels, with this composition giving high yield strength which leads to its use in a range of products.

[@tedarcher9120]

@@BillyWu i mean, why does spring steel have almost no plastic deformation compared to mild steel?

[@uduehdjztyfjrdjciv2160]

Its important because purifing iron from carbon is very expensive

[@alessandrocastelnuovo4436]

Wow

[@BillyWu]

Thanks

[@unethicalhacker2852]

U saved me❤️🥹

[@BillyWu]

Glad it was useful

[@user-cy9gu2zv2k]

我操，讲的挺好

[@keilanpouge4436]

Clears throat

[@dad_uchiha1707]

I saw the graph and got instantly confused

[@gageducote9363]

Help

[@user-hp5xh6fu7p]

Prof : can I get your email please.. I have project in annealing

[@tahy59]

This is absolutely amazing video,straight to the point,i appreciate for your effort and ime Prof Wu! God bless you!

[@BillyWu]

Glad it was helpful!