@@clarkeknives4159 Hi Graham, I thought about the core issue for 15 minutes you were talking about these expanding metals and the core cracking issue. It was a good problem, I drew it in my mind and visualised the various possibilitys there could be when forces are added and see how the anatomical constructions move at the time. Perhaps I have some idea based on what you told, propably you have thought it already, but I just speak my mind out. I'm interested wonder if I see this like yiu do and hope you will allow me to think about this here, but I'm just curiouse guy and my mind focuses only on the problem at hand because its a fun topic and it happens to interests me also. So, the point, I can visualise in my mind the following and I will try to describe it in a simple brief way. I base this on a few things that have been in use already and time has proven these methoda to actually work also, Firstly Traditional Katana forging has at least roughly 800 years based on the anatomy that is there is a harder outer core in the blade than the inner layer of the blade that is softer and more flexible. The flexibility helps to absorb energy of the sword of the impacts, strikes. Lets think about forging a Katana simplified because its easier to visualise it and then move that theory in the welding and forge hammering modern knife steels. There is now a outer core that is hard and inner core that is soft. When the outer core, while quenching it, firstly forms a hard outer layer, roughly speaking and visualising the anatomical struckture is like this - > (|), If you can visualise the following in youre mind like I do it helps other wise drawing on paper helps, , so the outer core is starting of harden and when it then first cools down, its hard in that moment it makes the outer perimeter like - > 0, seamless, because the inner core is softer material it will expand inside, but slowler on the inside, but since the outer layer is harder and strong, denser metal I believe is the technical term, it will hold its form, even thou the less dense softer metal inside expands and the inner material will try to expand but if the metal ratios are correct the softer metals expanding force can not break the outer layers seal. So what will happen then? The outer layers metal will resist and the inner softer metals expanding force will be pushed back forcing the softer metal to become denser.. Its basicly physics. If there is a force there is a equal counter force and in this case outer layers counter force, the "seal" must win this battle, if not there will be a crack. If the outer layers are softer they will press the inner harder material while expanding and that would result in the cracking in the harder material in the middle of the softer outer layers if the compressing force of the outer softer seal is too much for the inner layer to withstand. The outer layer will become hard first while quenching but the heath energy moves in a wave. The outer layer then would expand on the inside because the outer layer forms a hard base it presses on breaking the harder metal core by compression. The force moves inside from all directions. Now back to present If there are more layer while youre making damascus blades, like they usually have, basicly its the same theory that would still apply, the ratios just have to logical and optimal. The theory will remaim the same. If you think about this theory in youre mind, draw it in youre mind or visualise it on paper by drawing with a pencil, maybe you find my thought path and logic behing it, perhaps this idea has some use to you in youre line of work with blades in youre shop. Sincerely "Joey" Just a plain, normal guy and a Inventor. Greetings from Finland
Forge welding steel to titanium is tricky. At forging temperatures you can start getting iron-titanium intermetallics (more or less compounds) that are very brittle. With careful time and temperature control you may be able to avoid them but the most common method is to use a nickel interlayer. Steel and titanium will both happily forge weld with nickel without much problem and you can avoid those intermetallics. Pro tip: if you want to forge weld different metals and you’re not sure if they’ll stick, stick some nickel between them. It it can alloy with pretty much anything.
@@checoleman8877 I don’t think I know what makes timascus. Is it commercially pure Ti and Ti-64? I’ve seen successfully steel/titanium friction welding done before with an Inconel “buttering” between them so it should be possible to make your San Mai. I’ve no idea what kind of interlayer thickness you’d need though.
@@UKBladeshow sure am! Glad I found these videos honestly. Idk how i ended up watching one, but they're so well made that they're kind of addictive. The editing, and camerawork is seriously on point.
I had a few episodes of cracking similar to yours but mine was round bar tool steel and it split from the edge into the center like pacman. The culprit was that the heat treated core grows and the outside can't contain it so it splits. That was caused by us quenching it and leaving it. So there is a time factor here. The proper procedure should be to TEMPER it IMMEDIATELY after the quench and not allow time for the core to expand and split it. Once tempered it is ductile enough not to crack. If I recall it has to do with Pearlite being a different volume than Martinsite or something.
Now that is what I fully appreciate!!! Informative, educational approach backed with decades of experience mixed with own thoughts! Call me me whatever you like but the likes of Alex Iron DO NOT speak to me at all as they are showmen somewhat created or rather brought up by corporate influences.
@@clarkeknives4159 please do continue the great work you are doing and sharing the vast knowledge. It is a pleasure watching your videos and learning at the same time.
@@clarkeknives4159 I’d be happy to see you do more like this. I’m slowly working my way towards lecturing on metallurgy. You’ve got a talent for cutting the subject down to what a non-metallurgist blade maker needs to know while still keeping things accurate. The ability to explain without people’s eye’s glazing over is something I’m trying to learn.
There’s a blacksmith’s welding party trick that takes some prep. Cut a couple of 2” (51mm) squares of 1/4” (6mm) mild steel. Machine one surface on each as flat as you can. Then bring those surfaces to a mirror polish. Clean and degrease them. Put them polished faces together on an anvil, cold, and hit them hard with a sledge. They will weld together at the center at room temperature. Without any serious microscopic topography or oxides to interfere with cohesion the crystals will join under pressure. Not practical, but you can win a bet. My master smith always said that it’s about two clean surfaces and pressure. Heat is a convenience to save time.
Thanks for sharing this! Interesting to hear how two substrates can be joined together, usually chemically, mechanically or thermally. Thanks again Hiltonian!
It’s a good trick. How many people accused you of using magnets? Cold welding is a particular concern in space applications. Pretty much anything metal in sliding contact with other metal needs coating (usually Molybdenum sulphide).
Centerline cracking is basically just that... ive found that when doing 304/316 jacketed sanmai, you should chose a slower hardening steel like 52100 or O1 and immediately after quenching, ONLY quench in oil right down to the martensitic transformation temp (about 400°F is where i stop), and finish with a martemper in a press. If you allow the steel to slowly pass thru martensitic transformation, youll not only avoid cracking, but have a much more stable grain structure.
Around 6:45 what Your Explaining, Reminds Me of “ Tempering Glass “. The Glass comes Out of the Furnace, and Immediately has Regulated Pressurized Air on Both sides for a Distance, Then continues to cooldown on Roller Conveyer. From what I could understand the center is still Hotter causing a Pressure against the Air Pressed sides of Glass. When Tempered Glass is Brakes You can see the Center is Different.
In a traditional weld, you'll get "heat zones" right beside where your weld is. That again means you'll end up with a structure that is weaker at both sides of the weld. If you forge metals together you fuse them. They will as Graham explained form a crystal structure together. There are several different structures depending on the metal e.g. stainless steel has an austenitic structure.
👏👏👏 That centre line crack is probably why Japanese sword smiths ‘wrapped’ the core in a U shaped jacket when they forge welded the blank together. ???🤷♂️
Imagine that the outside cools and shrinks FIRST then the next layer does and so on. You'd have a situation where the outside "skin" is smaller than the inside so it will split as it tries to shrink around the bigger core.
Thanks for the video. Can you hear the point at which the core forms a centerline crack? If so, does the crack form at the beginning of the quench sequence or later in the quench sequence? What quenching temperatures do you find result in that cracking the most? Does this happen when the core steel is completely clad on both sides and edges or does this only happen when the core steel is clad only on the sides but not on the edges? Do the cracks run completely through the core steel, only along the edges, or only in the inside with the cracks not reaching to the edges? I haven't really looked at structure-property relationship issues since going to college in the eighties. Almost all of my real world experience was in the chemical and refining industries where much of the steel we used was plain carbon steel at low strength treatments. We didn't want any martensite because we didn't want piping and equipment cracking when the equipment came down to lower temperatures. We paid a great deal of attention to the ductile-to-brittle transition temperature, and I'm sure that any of the steels used in knife-making would not work for our needs. However, my health has failed and disabled me out of my career. As a result, I see TH-cam videos about metallurgical issues and want to comment or at least ask questions. If the steel consists of a core with cladding only on the sides but not on the edges, I can imagine a fairly easy explanation for edge cracking. If you quench so that the edges quickly become a brittle martensite, residual stresses of the inner part wanting to be a greater volume while the outer part wants to be much smaller could cause tensile stresses along the outer edges. That could lead to brittle cracking of those edges. Otherwise, I still don't see why a clad part would be more susceptible to cracking than any other part would be. I particularly don't see how a non-hardenable cladding would make the core more susceptible to cracking when a hardenable cladding wouldn't make cracking more likely.
well for center core breaks that does make perfect sense ... it's the same reason why Japanese Katana's bend when quenched ... the harder steel edge cools faster and grows a bit as it solidifies harder bending the softer steel back creating the iconic curve to the blade ... with it in the middle it has no place to relieve itself so it shatters from compressions stress . and centerline cracking is actually the designers error they didnt allow for the different expansion and contraction rates of the metals used ... the softer outside metal will act as a spring pushing constantly on the core ... as the core cools it expands by making crystals eventually it overcomes the stress the core can handle and cracks because the exterior is too bulky for the interior to push out of the way ... now if the cladding was thinner near the harder core it would have less pressure on the core and allow the core to expand the softer cladding into the gaps avoiding cracking ...
Induction heating is a viable method for forging. There’s a good series of videos on the channel going through all the various options. I’d recommend it. Friction welding will produce a much stronger weld than MiG or TiG. It’s doesn’t cause melting so you avoid getting a weaker cast structure when you’re finished/ it can often create a stronger weld than the base material since it breaks up the grain structure so much. The weld might need heat treatment after, though, depending on the steel and cooling rate. You’ll not get much benefit forging from an initial cold rolled state. The strength you get from cold rolling is from work hardening and leaving stresses in the steel. Heating the steel up to forging temperature will relieve all those stresses and you won’t get them back when you cool it down again. You need to rely on martensite hardening to up the strength again after forging.
cool, some very interesting and useful information there, and far more useful than much of the bullsh*t out there, I have seen several videos done by supposed experts that me as a fairly new smith know is complete cack that just confuses people, keep this sort of thing coming please as it is a big help to many of us out here
Good morning Andy and thanks again for another lovely feedback! 🥰 The internet is full of information but it is important we share knowledge from people that have first-hand experience in this field. We are very fortunate to have the likes of Mr. Clarke sharing basic technical knowledge for the newer guys like us. Thanks for watching Andy!
Just ordered some steels to make kitchen knives (keep my fingers working) I don't know yet wether I will heat treat myself or send them to Graham, I guess it depends on when I look at them thinking "do I really want anyone else see this" 🤣
Regarding the cracking-I can add this info. Higher carbon steels can frequently have Mf temperatures that are BELOW ambient temperature (Mf=the temp at which austenite to martensite transformation is complete). So, if the Mf temp is lower than the temp in your workshop, after quenching the steel will have some austenite present. However, that austenite WILL eventually transform to martensite. When austenite transforms to martensite well outside of the austenitic range, it causes a massive amount of internal stress and leads to cracking. I’ve heard some argue that cryo treatment can somehow prevent that cracking-sounds counterintuitive to me. All this to say, the only way you could avoid this is by altering the chemical structure?? Obviously, slow heating will help (especially below A1); normalizing will help; the basic crap that you don’t need me to list. My mind always wonders, when you forge weld different steels, that intersection of the different steels must somehow alter the A1, A3, Ms, Mf, etc.
Hi Graham. I have a hypothesis for what is happening with the edge, and it's to with *"bladewise", rather than sideways differential expansion.* Consider a hypothetical core material that expands 100% in the sideways direction (towards the two cladding materials, but ZERO in the other two directions ("bladewise"and lengthwise). And assume that the cladding doesn't expand at all, in any direction. When you cool this knife down in the quench, the core will increase from, say, 1mm to 2mm, but there will be ZERO forces experienced by ANY of the materials, since there is no differential expansion on any of the joins. Now consider that the expansion in bladewise direction is 100%, and the others are zero: In this case, the 5cm wide blade tries to expand to 10cm, while the cladding tries to maintain its original 5cm dimension. Now there will be an EXTREME tension at the weld boundaries, pulling each side of the core down, and creating two opposing, outward moment arms that trie to split open the core. 👈 There's what I believe is the origin of the force causing the split. Of course, in real world, there is a LOT more going on, and much of it will make the situation worse. 1) The very edges of the core will have cooled the fastest and be extremely brittle. 2) The cladding will have cooled faster than the core, THERMALLY shrinking faster then the core, which is also trying to expand, increasing the differential expansion. 3) The "soft" steel on the outside will have become hard due to no longer being at forging temperature, markedly increasing its stiffness, and thus the force it can apply before yielding. FYI. I'm not a smith of any kind, however I do have degrees in physics and engineering (though "only" electrical).
If I'm correct, I'd expect to see the following: 1) The effect is most severe where the expansion differential is the greatest. 2) It most commonly occurs where the core is thicker, increasing the moment arms. 3) It occurs on the back, but not the edge of the knife, since the moment arms are mitigated by the exposed core edge, and there is simply more material to resist cracking from the pull. 4) It occurs more commonly at faster quench rates, due to the effect of thermal expansion, exacerbating the differential expansion rates. 5) It rarely occurs on a false edge (say, on a Bowie knife), for the same reason as it not occurring on the blade side. 6) Blade material and dimension configurations most susceptible to splitting, should be more likely to warp (though this can be mitigated by being careful with the thickness of the two cladding layers).
Really rough and potentially wrong metaphor but reading this makes me think of a hotdog "exploding" when it's boiled or microwaved for too long. The core material is expanding but the skin is much more inflexible. Now, I know the hotdog contents much more literally "explode" outwards when the skin finally does break, but every time I see it happen it creates this fairly even trench in the meat, and where my metaphor comes from is this trench is caused by the less flexible skin pulling the expanding meat fairly evenly across the length of the hotdog. If it was more literally just the meat exploding out I'd expect to see more uneven surfacing in the split. anyway, ADHD connections and all that, but your explanation helped put it into much better mentally visual context since I haven't seen the metal splitting phenomena myself (yet)
@@Solais1019 that's a reasonable visualisation, I reckon, but due to the relative thickness of the "skin" to the "meat", the result is expected to be neater.
Can't you just thermal cycle & physically forge a fusion weld to refine the structure? I've used fusion welds on high carbon steel then forged it with so far great results. Usually to attach a lower carbon handle to a higher carbon blade without the concern of whether a forge weld actually took well or not
huh I always thought forge welding worked because the surface was hot enough to melt and thus stuck to each other as it cooled down. You see sparks flying off the steel when its hot enough, so I thought that was the steel almost on the verge of melting.
I solid state welded two 1/2 1095 bars together. No cleaning off the steel, nothing. It was full of scale, rust and dirt. Used liberal borax. It stuck beautifully. Even the cross section looked like one peice of steel. Me reasoning was: did the ancients clean up their steel (no grinders) a lot of them probobly had rusty steel and still welded with it
They certainly did have grinders Water wheel powered grinding wheels were a major use in supplying armies, and prior to that they were smart enough to know that sand, pumice, and other rocks could be used as an abrasive. They would even mix a little rock dust with water and apply with a cloth as a kind of sandpaper or polishing cloth
I could listen to Graham all day. His no bull attitude is refreshing in this day and age.
Cheers man! And yeah, me and Graham can chat all day and every minute is fun! 🤩
@@UKBladeshow The cream filled donuts you bring always seem to lubricate my vocal chords 🤣🤣🤣🤣🤣🤣
Knife maker ASMR
@@clarkeknives4159
Hi Graham,
I thought about the core issue for 15 minutes you were talking about these expanding metals and the core cracking issue. It was a good problem, I drew it in my mind and visualised the various possibilitys there could be when forces are added and see how the anatomical constructions move at the time.
Perhaps I have some idea based on what you told, propably you have thought it already, but I just speak my mind out.
I'm interested wonder if I see this like yiu do and hope you will allow me to think about this here, but I'm just curiouse guy and my mind focuses only on the problem at hand because its a fun topic and it happens to interests me also.
So, the point, I can visualise in my mind the following and I will try to describe it in a simple brief way.
I base this on a few things that have been in use already and time has proven these methoda to actually work also,
Firstly
Traditional Katana forging has at least roughly 800 years based on the anatomy that is there is a harder outer core in the blade than the inner layer of the blade that is softer and more flexible. The flexibility helps to absorb energy of the sword of the impacts, strikes.
Lets think about forging a Katana simplified because its easier to visualise it and then move that theory in the welding and forge hammering modern knife steels.
There is now a outer core that is hard and inner core that is soft.
When the outer core, while quenching it, firstly forms a hard outer layer, roughly speaking and visualising the anatomical struckture is like this - > (|), If you can visualise the following in youre mind like I do it helps other wise drawing on paper helps, , so the outer core is starting of harden and when it then first cools down, its hard in that moment it makes the outer perimeter like - > 0, seamless, because the inner core is softer material it will expand inside, but slowler on the inside, but since the outer layer is harder and strong, denser metal I believe is the technical term, it will hold its form, even thou the less dense softer metal inside expands and the inner material will try to expand but if the metal ratios are correct the softer metals expanding force can not break the outer layers seal. So what will happen then? The outer layers metal will resist and the inner softer metals expanding force will be pushed back forcing the softer metal to become denser.. Its basicly physics. If there is a force there is a equal counter force and in this case outer layers counter force, the "seal" must win this battle, if not there will be a crack. If the outer layers are softer they will press the inner harder material while expanding and that would result in the cracking in the harder material in the middle of the softer outer layers if the compressing force of the outer softer seal is too much for the inner layer to withstand. The outer layer will become hard first while quenching but the heath energy moves in a wave. The outer layer then would expand on the inside because the outer layer forms a hard base it presses on breaking the harder metal core by compression. The force moves inside from all directions.
Now back to present
If there are more layer while youre making damascus blades, like they usually have, basicly its the same theory that would still apply, the ratios just have to logical and optimal. The theory will remaim the same.
If you think about this theory in youre mind, draw it in youre mind or visualise it on paper by drawing with a pencil, maybe you find my thought path and logic behing it, perhaps this idea has some use to you in youre line of work with blades in youre shop.
Sincerely
"Joey"
Just a plain, normal guy and a Inventor.
Greetings from Finland
I once had an auto mechanic like this guy. Best mechanic I ever had. Knew his stuff. Also knew what he wasn’t sure of. No BS.
Haha cheers Noah!
hell yeah, another great video with the master himself 😍
And there will be more on this series don’t you worry! 🥳🥳🥳 thanks foe the comment!
@@UKBladeshow can't wait for it😍
Forge welding steel to titanium is tricky. At forging temperatures you can start getting iron-titanium intermetallics (more or less compounds) that are very brittle. With careful time and temperature control you may be able to avoid them but the most common method is to use a nickel interlayer. Steel and titanium will both happily forge weld with nickel without much problem and you can avoid those intermetallics.
Pro tip: if you want to forge weld different metals and you’re not sure if they’ll stick, stick some nickel between them. It it can alloy with pretty much anything.
If you really want to forge titanium and steel together without using nickel then you’re looking at a process like explosive welding.
Very good addition as always Tom. We appreciate it thanks!
@@GemAppleTom This is something I have been thinking about a lot. I have been wanting to create a San Mai from Timascus and a core of damascus.
@@checoleman8877 I don’t think I know what makes timascus. Is it commercially pure Ti and Ti-64?
I’ve seen successfully steel/titanium friction welding done before with an Inconel “buttering” between them so it should be possible to make your San Mai. I’ve no idea what kind of interlayer thickness you’d need though.
Nickel will pretty much assist anything.
Thats how ive done cupronickel jacketed HC core.
Always enjoy learning from Graham :)
Hello mate! He’s always a pleasure to work with so really enjoyed putting this together too! See you on the next vid!
Great video!
I'm just getting into trying to forge weld, so this is perfect timing for me
Nice to see you again mate! Excellent! Glad to hear you enjoyed the forge welding topic! Hope you’re excited for part 2 of the series!
@@UKBladeshow sure am!
Glad I found these videos honestly. Idk how i ended up watching one, but they're so well made that they're kind of addictive. The editing, and camerawork is seriously on point.
I had a few episodes of cracking similar to yours but mine was round bar tool steel and it split from the edge into the center like pacman. The culprit was that the heat treated core grows and the outside can't contain it so it splits. That was caused by us quenching it and leaving it. So there is a time factor here. The proper procedure should be to TEMPER it IMMEDIATELY after the quench and not allow time for the core to expand and split it. Once tempered it is ductile enough not to crack. If I recall it has to do with Pearlite being a different volume than Martinsite or something.
I apprenticed for a German Blacksmith that used to use Borax Glass as a flux to give a clean surface when forge welding.
Now that is what I fully appreciate!!!
Informative, educational approach backed with decades of experience mixed with own thoughts!
Call me me whatever you like but the likes of Alex Iron DO NOT speak to me at all as they are showmen somewhat created or rather brought up by corporate influences.
Thanks for the comment Peter! 🥳
Thanks Peter, it's comments like yours that make me want to make more videos with UK Bladeshow 😊😊😊😊😊😊
@@clarkeknives4159 please do continue the great work you are doing and sharing the vast knowledge. It is a pleasure watching your videos and learning at the same time.
@@clarkeknives4159 I’d be happy to see you do more like this. I’m slowly working my way towards lecturing on metallurgy. You’ve got a talent for cutting the subject down to what a non-metallurgist blade maker needs to know while still keeping things accurate. The ability to explain without people’s eye’s glazing over is something I’m trying to learn.
Thanks very useful. I wish I was in the same country and could come for a course.
Thanks for watching!
- Vinz
There’s a blacksmith’s welding party trick that takes some prep. Cut a couple of 2” (51mm) squares of 1/4” (6mm) mild steel. Machine one surface on each as flat as you can. Then bring those surfaces to a mirror polish. Clean and degrease them. Put them polished faces together on an anvil, cold, and hit them hard with a sledge. They will weld together at the center at room temperature. Without any serious microscopic topography or oxides to interfere with cohesion the crystals will join under pressure.
Not practical, but you can win a bet.
My master smith always said that it’s about two clean surfaces and pressure. Heat is a convenience to save time.
Thanks for sharing this! Interesting to hear how two substrates can be joined together, usually chemically, mechanically or thermally.
Thanks again Hiltonian!
It’s a good trick. How many people accused you of using magnets?
Cold welding is a particular concern in space applications. Pretty much anything metal in sliding contact with other metal needs coating (usually Molybdenum sulphide).
If you get them flat enough they'll stick together like gauge blocks, no hammering needed.
This was very good. Thank you kindly.
You are very welcome! Thanks for watching!
Great information, nicely presented. Thanks for sharing.
First video watched = subscribed.
Thanks for the lovely feedback! I hope you’ll enjoy the other vids we have!
- Vinz
Love this guys infinite forge knowledge ❤
Thanks Joe!
- Vinz
Centerline cracking is basically just that... ive found that when doing 304/316 jacketed sanmai, you should chose a slower hardening steel like 52100 or O1 and immediately after quenching, ONLY quench in oil right down to the martensitic transformation temp (about 400°F is where i stop), and finish with a martemper in a press. If you allow the steel to slowly pass thru martensitic transformation, youll not only avoid cracking, but have a much more stable grain structure.
Wait til you see Inconel600 jacketed sanmai. 😁
THAT, is a REAL challenge.
Around 6:45 what Your Explaining, Reminds Me of “ Tempering Glass “. The Glass comes Out of the Furnace, and Immediately has Regulated Pressurized Air on Both sides for a Distance, Then continues to cooldown on Roller Conveyer. From what I could understand the center is still Hotter causing a Pressure against the Air Pressed sides of Glass. When Tempered Glass is Brakes You can see the Center is Different.
An absolute gem, if knowledge had weight his would be that of a mountain
Thanks for the feedback R MJ!
In a traditional weld, you'll get "heat zones" right beside where your weld is. That again means you'll end up with a structure that is weaker at both sides of the weld. If you forge metals together you fuse them. They will as Graham explained form a crystal structure together. There are several different structures depending on the metal e.g. stainless steel has an austenitic structure.
👏👏👏 That centre line crack is probably why Japanese sword smiths ‘wrapped’ the core in a U shaped jacket when they forge welded the blank together. ???🤷♂️
So it sounds like having the cladding run all the way to the edge instead of profiling before heat treatment should reduce the odds of center cracking
I tought steel shrinks when hardened. I was told it gets smaller and more dense.
Imagine that the outside cools and shrinks FIRST then the next layer does and so on. You'd have a situation where the outside "skin" is smaller than the inside so it will split as it tries to shrink around the bigger core.
It's more complicated than that. It contracts across phase boundaries when heating and expands across them when cooling as well.
Thanks for sharing Graham!! I guess brass and copper forge welding doesn't work in the same way no?
Thanks for the video.
Can you hear the point at which the core forms a centerline crack? If so, does the crack form at the beginning of the quench sequence or later in the quench sequence? What quenching temperatures do you find result in that cracking the most? Does this happen when the core steel is completely clad on both sides and edges or does this only happen when the core steel is clad only on the sides but not on the edges? Do the cracks run completely through the core steel, only along the edges, or only in the inside with the cracks not reaching to the edges?
I haven't really looked at structure-property relationship issues since going to college in the eighties. Almost all of my real world experience was in the chemical and refining industries where much of the steel we used was plain carbon steel at low strength treatments. We didn't want any martensite because we didn't want piping and equipment cracking when the equipment came down to lower temperatures. We paid a great deal of attention to the ductile-to-brittle transition temperature, and I'm sure that any of the steels used in knife-making would not work for our needs. However, my health has failed and disabled me out of my career. As a result, I see TH-cam videos about metallurgical issues and want to comment or at least ask questions.
If the steel consists of a core with cladding only on the sides but not on the edges, I can imagine a fairly easy explanation for edge cracking. If you quench so that the edges quickly become a brittle martensite, residual stresses of the inner part wanting to be a greater volume while the outer part wants to be much smaller could cause tensile stresses along the outer edges. That could lead to brittle cracking of those edges.
Otherwise, I still don't see why a clad part would be more susceptible to cracking than any other part would be. I particularly don't see how a non-hardenable cladding would make the core more susceptible to cracking when a hardenable cladding wouldn't make cracking more likely.
well for center core breaks that does make perfect sense ... it's the same reason why Japanese Katana's bend when quenched ... the harder steel edge cools faster and grows a bit as it solidifies harder bending the softer steel back creating the iconic curve to the blade ... with it in the middle it has no place to relieve itself so it shatters from compressions stress
.
and centerline cracking is actually the designers error they didnt allow for the different expansion and contraction rates of the metals used ... the softer outside metal will act as a spring pushing constantly on the core ... as the core cools it expands by making crystals eventually it overcomes the stress the core can handle and cracks because the exterior is too bulky for the interior to push out of the way ... now if the cladding was thinner near the harder core it would have less pressure on the core and allow the core to expand the softer cladding into the gaps avoiding cracking ...
Do you use induct heating to forge?
How strong are friction welds in comparison to TIG or MIG welds?
Does it mater if the steel is cold rolled or not?
Induction heating is a viable method for forging. There’s a good series of videos on the channel going through all the various options. I’d recommend it.
Friction welding will produce a much stronger weld than MiG or TiG. It’s doesn’t cause melting so you avoid getting a weaker cast structure when you’re finished/ it can often create a stronger weld than the base material since it breaks up the grain structure so much. The weld might need heat treatment after, though, depending on the steel and cooling rate.
You’ll not get much benefit forging from an initial cold rolled state. The strength you get from cold rolling is from work hardening and leaving stresses in the steel. Heating the steel up to forging temperature will relieve all those stresses and you won’t get them back when you cool it down again. You need to rely on martensite hardening to up the strength again after forging.
cool, some very interesting and useful information there, and far more useful than much of the bullsh*t out there, I have seen several videos done by supposed experts that me as a fairly new smith know is complete cack that just confuses people, keep this sort of thing coming please as it is a big help to many of us out here
Good morning Andy and thanks again for another lovely feedback! 🥰 The internet is full of information but it is important we share knowledge from people that have first-hand experience in this field. We are very fortunate to have the likes of Mr. Clarke sharing basic technical knowledge for the newer guys like us. Thanks for watching Andy!
Just ordered some steels to make kitchen knives (keep my fingers working) I don't know yet wether I will heat treat myself or send them to Graham, I guess it depends on when I look at them thinking "do I really want anyone else see this" 🤣
😂😂😂
Why do some knife makers sharpen the blade with the sharp side facing up and the sanding belt moving down? Seems very dangerous to me.
Question, how long does it take for the crystals to stop growing, in short how long do you keep pressing
Regarding the cracking-I can add this info. Higher carbon steels can frequently have Mf temperatures that are BELOW ambient temperature (Mf=the temp at which austenite to martensite transformation is complete). So, if the Mf temp is lower than the temp in your workshop, after quenching the steel will have some austenite present. However, that austenite WILL eventually transform to martensite. When austenite transforms to martensite well outside of the austenitic range, it causes a massive amount of internal stress and leads to cracking. I’ve heard some argue that cryo treatment can somehow prevent that cracking-sounds counterintuitive to me.
All this to say, the only way you could avoid this is by altering the chemical structure?? Obviously, slow heating will help (especially below A1); normalizing will help; the basic crap that you don’t need me to list.
My mind always wonders, when you forge weld different steels, that intersection of the different steels must somehow alter the A1, A3, Ms, Mf, etc.
Thanks for sharing!
What of mokume gane and cumai ?what are de chance of à bad réaction in the quench
Hi Graham. I have a hypothesis for what is happening with the edge, and it's to with *"bladewise", rather than sideways differential expansion.*
Consider a hypothetical core material that expands 100% in the sideways direction (towards the two cladding materials, but ZERO in the other two directions ("bladewise"and lengthwise). And assume that the cladding doesn't expand at all, in any direction. When you cool this knife down in the quench, the core will increase from, say, 1mm to 2mm, but there will be ZERO forces experienced by ANY of the materials, since there is no differential expansion on any of the joins.
Now consider that the expansion in bladewise direction is 100%, and the others are zero: In this case, the 5cm wide blade tries to expand to 10cm, while the cladding tries to maintain its original 5cm dimension. Now there will be an EXTREME tension at the weld boundaries, pulling each side of the core down, and creating two opposing, outward moment arms that trie to split open the core. 👈 There's what I believe is the origin of the force causing the split.
Of course, in real world, there is a LOT more going on, and much of it will make the situation worse.
1) The very edges of the core will have cooled the fastest and be extremely brittle.
2) The cladding will have cooled faster than the core, THERMALLY shrinking faster then the core, which is also trying to expand, increasing the differential expansion.
3) The "soft" steel on the outside will have become hard due to no longer being at forging temperature, markedly increasing its stiffness, and thus the force it can apply before yielding.
FYI. I'm not a smith of any kind, however I do have degrees in physics and engineering (though "only" electrical).
If I'm correct, I'd expect to see the following:
1) The effect is most severe where the expansion differential is the greatest.
2) It most commonly occurs where the core is thicker, increasing the moment arms.
3) It occurs on the back, but not the edge of the knife, since the moment arms are mitigated by the exposed core edge, and there is simply more material to resist cracking from the pull.
4) It occurs more commonly at faster quench rates, due to the effect of thermal expansion, exacerbating the differential expansion rates.
5) It rarely occurs on a false edge (say, on a Bowie knife), for the same reason as it not occurring on the blade side.
6) Blade material and dimension configurations most susceptible to splitting, should be more likely to warp (though this can be mitigated by being careful with the thickness of the two cladding layers).
Really rough and potentially wrong metaphor but reading this makes me think of a hotdog "exploding" when it's boiled or microwaved for too long. The core material is expanding but the skin is much more inflexible.
Now, I know the hotdog contents much more literally "explode" outwards when the skin finally does break, but every time I see it happen it creates this fairly even trench in the meat, and where my metaphor comes from is this trench is caused by the less flexible skin pulling the expanding meat fairly evenly across the length of the hotdog. If it was more literally just the meat exploding out I'd expect to see more uneven surfacing in the split.
anyway, ADHD connections and all that, but your explanation helped put it into much better mentally visual context since I haven't seen the metal splitting phenomena myself (yet)
@@Solais1019 that's a reasonable visualisation, I reckon, but due to the relative thickness of the "skin" to the "meat", the result is expected to be neater.
Crystals of steel and titanium that grow across the joint, to make… mixed steel and titanium crystals?
Sounds similar to corrosion jacking
Can't you just thermal cycle & physically forge a fusion weld to refine the structure? I've used fusion welds on high carbon steel then forged it with so far great results. Usually to attach a lower carbon handle to a higher carbon blade without the concern of whether a forge weld actually took well or not
In short… Yes.
The generally poorer properties you get from a weld is due to the cast structure. You can heat treat and forge to change the structure.
huh I always thought forge welding worked because the surface was hot enough to melt and thus stuck to each other as it cooled down. You see sparks flying off the steel when its hot enough, so I thought that was the steel almost on the verge of melting.
Your theory makes sense too don’t worry! But thanks for watching and hopefully this video made sense and was helpful!
Mild steel needs to be heated to the point where it's sparkling or nearly sparkling. Carbon steels don't need as much heat to create the welded bond.
2:21 soild
I solid state welded two 1/2 1095 bars together. No cleaning off the steel, nothing. It was full of scale, rust and dirt. Used liberal borax. It stuck beautifully. Even the cross section looked like one peice of steel. Me reasoning was: did the ancients clean up their steel (no grinders) a lot of them probobly had rusty steel and still welded with it
They certainly did have grinders
Water wheel powered grinding wheels were a major use in supplying armies, and prior to that they were smart enough to know that sand, pumice, and other rocks could be used as an abrasive. They would even mix a little rock dust with water and apply with a cloth as a kind of sandpaper or polishing cloth
What on earth is a soiled phase weld join??
It means the metal never get to the melting point during the joining.
It’s solid phase welding mate. “Soiled” phase weld might mean something else hahaha
@@UKBladeshow damn you autocorrect:)
Clading hard qith soft, weird