Why 98% of knife makers pick the wrong steel according to a metallurgist

this video is sponsored by the following people please click the links in the description below i really don't see any serious advantage in having a carbon steel knife unless [Music] i'm graham clark i'm a metallogist by profession and i run clark knives in rural wheelchair where we run knife making courses and we also run a heat treatment service for knife makers and we make damascus steel billets which we sell out to other knife makers that is a question which i'm never going to give an answer which satisfies everybody who's watching this video all i can tell you is what i consider to be the pros and cons of carbon steel and stainless steel and you can make your own mind up as to what you want to use now you hear lots of stories oh yeah carbon steel you can get it much sharper stainless steel doesn't corrode and rust all these things are partially true but if you understand the difference between them then you'll understand why people say these things now carbon steel is an alloy of iron and carbon the iron forms up with a carbon and makes iron carbides these are little tiny microscopic particles that exist within the structure of the steel iron carbides are very much harder than pure iron and when you've heat treated it properly so you generated the hard particles you make a cutting edge which will last quite well i mean i remember my mother's knives were all black had a black patina on them they were carbon steel knives and my dad used to sharpen them with a butcher steel and he would keep them sharp and this is the argument you get with carbon steel that carbon steel is much easier to sharpen the stainless steel now stainless steel is basically the same thing iron and carbon same amount of carbon in roughly but there is at least 12 to 13 percent chrome and sometimes as much as 17 to 20 chrome in there now it's the chromium that makes them rust resistant they're not totally stainless you've got to get a different kind of stainless that cannot be hardened like the stuff you make your pots and pans with that's called austenitic stainless it's not heat treatable but that stuff is very very difficult to corrode now your stainless steel knife is pretty good i mean i've made stainless steel knives i've got some that i made 15 years ago they're not showing any signs of corrosion they get used every day in our kitchen so the difference is the stainless steel knife has now got this extra bit of chromium in them if you get above that i think the theoretical figures about 11.8 chrome but you know we know it's got to be 12 13 minimum really to become stainless and that chromium forms chrome oxide on the surface of your knife blade if it's a completely clean surface with nothing on it at all no oxides on it chrome will react with oxygen at room temperature to make chrome oxide instantaneously it's only a layer that's microns possibly submicron thick i don't really know but it's very very thin but it's completely impervious to further oxygen so more oxygen can't get down to react with the iron underneath and make it go rusty and that's what stops it going rusty the other advantage that i see that you get from stainless steel is that the the carbon in the formulation of the stainless steel now remember it's still 0.8 carbon you've got your 13 14 15 chrome in there that chromium and the carbon they react to form chromium carbides and again these are microscopic particles which end up on your cutting edge and they're nice and hard and they stop it going blunt now chrome carbides are several orders of magnitude harder than iron carbide so if you've got an equally sharp knife with either a carbon steel a 0.8 carbon steel or a 0.8 carbon chrome steel your chrome steel edge is going to last much longer there were trials done in the 1980s in the states there's a there's a book i had i can't quite remember the name of it i think it's called producing a razor edge or something or the razor edge book of sharpening something like that and they did trials in an abattoir where they got knives some had red handles some had blue handles and all the butchers said no the ones with one particular color lasted four six sometimes eight times longer than the others before they had to resharpen them with their steel during the course of an eight hour shift and that was the stainless steels that were staying sharper however a lot of knife makers will say to you yeah but you can't get a stainless steel knife as sharp as a carbon steel knife you can it's just not so easy why because you've got chrome carbides in there chrome carbides are very difficult or very hard so they make your sharpening process a little bit more tedious and a little it takes a bit longer like just about anything in metallurgy and i'm sure you're going to hear this in further episodes of this video everything in metallurgy is a compromise carbon steel will hold an edge four or six times longer than a similar formulation in a carbon steel because it has the chrome carbide probably going to take you four or six times longer to sharpen it i know my ones at home i spend quite a lot of time in my butcher's steel maintaining the edge on my stainless steel knife i don't have any carbon steel knives at home i'm too lazy to keep them clean but i'm sure if i did i would be sharpening them much easier so that's really the story behind carbon and chrome steel to me i don't really see especially if you're using it for a kitchen knife a culinary knife i really don't see any serious advantage in having a carbon steel knife unless of course you want to make fancy pretty patterns like damascus and there you know your carbon steels are there as one of your you need the carbon steel stainless steel damascus is very much more difficult to make it can be made i haven't quite cracked it yet but i know what i need to do to do so it's easier to make it with carbon steel and if you pick the right kind of carbon steel for instance if i'm making damascus for a kitchen knife i don't use 1080 or 1094 or 1095 for my core i will always use one why because one's got tungsten in it and chromium in it and vanadium in it and tungsten chrome and vanadium carbide are the hardest of the ones that you get so if you use an one tool steel yes you will get it sharp and it will maintain an edge very similar to a carbon steel knife then again it's just as difficult to sharpen as a sorry as a stainless steel knife but then it makes the the o1 knife as difficult to sharpen as your stainless steel knife so like as i said before everything's a compromise if you want a better performance then you've got to start working into the tall steels like your ones i wouldn't go any further than that i've seen people i mean i've had a sword in here to heat treat which was made out of high speed steel i just cannot see any logic in making a sword out of high speed steel simply because if you if you're going to use it it's going to break and if you're not going to use it because it's it's hard you can't get the you can't get the springiness into the high speed steel that you really need it's very expensive so it's a waste of money if it's just going to sit up on the on the metal piece for you to look at and look pretty then just make it out of a piece of ordinary steel it doesn't need to be made out of fancy stuff so high speed steels and some of the top end tool steels i don't really see the point in using certainly you know if you want to go up from carbon steel to something a bit better but still stay with carbon steel and particularly when you're making carbon steel damascus it's very nice to use o1 is a great choice if you're going over to stainless steel again you've got your entry level materials aebl is a simple iron chromium carbon steel works like a dream some of the more modern steels have got nitrogen in them i think it's 14c 28n is one of the more modern steels where they've re-melted the steel inside a furnace that's under very high pressure with a nitrogen atmosphere and nitrogen gets absorbed into the surface they lower the carbon content and it still produces a knife which is just as hard it's supposed to be a bit more ductile it's supposed to be a bit tougher when you've made it to be quite honest if you've got an abl knife and you abuse it that much you're going to you break it and you need to go to 14c you shouldn't really be using the knife in the first place because an a an abl knife is still pretty tough but they are supposed to be a little bit better i think nylocks might be another one i can't quite remember which ones are which and then the only ones that are really better to go up a stage further from there is when you go to your powder metallurgy steels now powder matte steels really are in a class of their own and they're different because of the way they make the steel all the other materials you know you heat you melt your steel in a big furnish you pour it into a big ingot and let it go into an ingot mold and let it solidify now it takes quite a long time it can take hours for that steel to solidify and during that time you get what is called segregation the steel starts to solidify at one temperature the whole temperature range from when it starts to solidify to when it finishes can be anything up to 100 degrees centigrade as it cools down and during that stage you've got a combination of solids and liquids within that mold and the first bits that solidify i've got a different composition to the last i'm not going to try and explain to you how that that actually happens but it does and there's not much you can do about it to stop it except cool it a bit quicker that reduces it but then again that creates other problems so what they came up with and i think this first started probably 20 30 years ago it's not something that's brand new but it's been developed all the time and made better and better is you take that liquid steel and you spray the liquid into a room that's full of high purity nitrogen so you've got these tiny little droplets of steel which freeze almost instantaneously in the air fall down and you come in you shovel up all this powder and then you compress the powder very very high temperatures and pressures but below the melting point of the steel so it all sticks together called hydrostatic pressing or hot isostatic pressing and then you take that billet and you put it through a rolling mill again you might still have some protective atmosphere around it but it will compress everything back together and make steel out of it now the advantage of doing that is it cuts out the segregation so for instance if you're making a good quality stainless tool steel you might want to put vanadium in there because vanadium carbides are very hard i think once you get above about four or five percent vanadium the segregation becomes a problem but with powder matte steels i've seen it up as 10 12 13 14 vanadium in there so you've got an incredible large amount of these vanadium carbides which are one some of the hardest you can get therefore the material is is very much better and is very much different and you've got a very fine grain size which is also very nice so you haven't got this segregation in there again here comes the old compromise it's an absolute pigtal world if you've ever made a knife out of powder metallurgy seal you'll know what you know what i mean you know when i'm making knives i get a rough idea of how many knives i'm going to grind out of one particular grinding belt if i use powder mat seals it's how many grinding belts am i going to use per knife and it doesn't matter whether it's been heat treated or not it's an absolute pig to work with but the knife's made out at the end of the absolutely brilliant you get mirror finishes on them without any horrible patterns and that you get on some other high alloy stainless steels yeah they're just good so that's really a three i would say you've got three classes of steel really your carbon steels you've got your basic stainless steels and then you've got their powder mixed steels those top of the tree what type of steel do you prefer to work with is it 1080 carbon steel or do you like the nilex stainless please tell me more about it in the comment section below check out this other knife making video here or click this one on the top if you feel like binge watching another series

Channel: UK Bladeshow

Views: 360,730

Keywords: best steel knife making, carbon steel 1084, knife making tips

Id: swkZgWWJ8yA

Length: 11min 7sec (667 seconds)

Published: Tue Mar 22 2022