How to Harden Mild Steel? (Impossible!)
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- Опубліковано 14 січ 2018
- So they say it's impossible to harden mild steel. Well, here's how to do it... (hint: start with "mild" steel that isn't really "mild" steel.)
Tip: When grinding metal ALWAYS use a good filter/respirator to protect your lungs from particles. Here's a link to the model I ordered from Amazon:
amzn.to/2DBfpAk
(Disclaimer: I have an affiliate account, so if you make a purchase using this link I will receive a small commission.)
A couple of weeks ago I made a cleaver/wood chopper using a scrap of structural or "mild" steel.
For that project I used a 4.5 inch angle grinder as my only power tool and I showed how to put a decent age on a knife made of mild steel. An edge that WILL chop and cut wood without going dull... at least for a while.
But I noticed large bursts coming from the sparks while grinding that scrap of steel. That's usually an indication of higher carbon content so for this video I'm testing to see if that steel can actually be hardened and tempered.
NOTE: I haven't been posting as often as I'd like because of upgrades and technical issues, but regular schedule of 3 to 4 uploads per week should resume very soon.
In the meantime, check out my blog at: www.fargofx.com
It's pretty weak right now, but I'm planning to do a lot more with it in the new year.
If you enjoy DIY blacksmithing, bladesmithing, metal work, and random "how to" projects please consider subscribing and watching a few of my other videos. Cheers!
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Working in sandals, no gaurds on your grinders, work bench that looks like it could walk out the door. I'm impressed!!!
But yeah, make sure you wear your mask!
if you look at my videos you can see me work with slippers
but at the end of the winter they were busted and had to throw em away ;o;
It was up to the Swanson code
“Stable platform”
Come with me and you’ll see a world of OSHA violations
If you want to forge strong, flexible, no nonsense knives, forge them from leaf springs you get from the junkyard. Leaf springs are 5160, a superb forging steel, which is also easy to heat treat and temper, and has commonly known heat treating recipes.
Be sure to forge the spring to shape with a hammer, that way any stress micro cracking are forge-welded.
good advice
Although you are correct about 5160 being a great, forgiving, and easy for beginners with basic tools to work with not every leaf spring on the planet is 5160 steel, I recommend getting a set of hrc files and harden a test piece to see what it reaches, beginners without these files can do a simple spark test if the sparks are bright and have a firework effect its a good sign thst you've got a higher carbon steel on your hands, happy forging!!
FYI never have the sparks shooting away from you. It sounds counter productive, but if that zip disk grabs, that grinder is coming directly at you. Have fun, but play safe.
Learning about quadrants is borderline a necessity for using an angle grinder, like full stop
He don't even know how to use the grinder🤣🤣
Out of ALL the videos I've watched on this subject, telling you to heat the steel to this or that degree this was by FAR the most comprehensible. Thanks 👍
Structural steel has sometimes more carbon in it. Rebar is any scrap they could find, so also may vary in carbon content.
there is no such thing as "structural steel".... when I ordered raw material at the structural production fitting/welding shop, I couldn't just call them up and say I need 3'x3' structural steel angle iron....... I say I need 3"x3" angle, if I don't specify, they will send mild steel... Mild steel is what most structural applications use (unless corrosion is an issue and zinc coating won't work)
That’s very interesting..you should try and grind out a quick bevel, sharpen it, and test a thinner edge. Funny thing is, I think most cheap “stainless steel kitchen knives” are made from the cheapest stainless they can get their hands on. The steel you have there will probably hold an edge better than most kitchen knives under $30.
If you used a wood or coke forge you are adding carbon (if steel is in cherry red or more the atoms of carbon can pass true the Fe). By the other hand seams like 1045 or close to that when you cut the piece, if is the case you can tampering this steel.
If you work with mild steel you can add more carbon using 80% of charcoal and 20% of borax, you heat the piece to orange and let cool in this mix, more times you do more steel you get (each time is like 0.5mm deep of high carbon steel). I hope helps you. Best regards from Argentina and sorry for my rusty English haha
it's the cheapest steel because it needs low chromium concentration to be able to harden through martensite transformation.
it's not really intentional. the best stainless steels for hardening have low additions of other carbide forming elements (Mo, Ti and W), to decrease grain boundary corrosion. But they are still incredible cheap when compared to regular austenitic stainless steel.
forging with sandals? you are a brave man
Some thoughts after watching the video:
1, Structure steel also come with different grades, can be low or medium carbon.
2, Salt water has much higher cooling rate if you want higher as-quenched hardness. Temper as usual.
3, Easy way to do break test, is to grind a small notch (stress riser) on the test piece, put it notch nown on the anvil with something under one end, and hit the back side with a hammer.
Hope it helps.
I'm not so much worried about the particles as I am the guardless angle grinder.
Guards are an obstruction. For a small wheel like that and at those low speeds, there isn't much danger. A catastrophic failure might break the skin. You have to hit 10k with heavier wheels to do damage. Stones are more dangerous. Much more so and you should do a ring test. I was a chipper and grinder at an iron Foundry for 8 years. I never once had an abrasive wheel, flanged cup stone or disc failure.
@@joesikkspac7904 if that disk tears apart it's going straight into your eyeball. google images "angle grinder accident".
@@chrishayes5755 that's why you wear a full face mask
@@joesikkspac7904 exactly. And disk don't break just because. If they break its because the person did something wrong
@@chrishayes5755 read the maximum RPM on the grinder and the wheel and if the wheel doesnt exceed that then have a ball
Back in the day, I used to use an oxy/acetylene torch with a carburizing flame to put a thin wear-resistant coating onto the business-end of some gardening tools.
From what I have seen, rebar is basically the shepherd's pie of steels -- it's made of left-overs, and you never know how it will behave outside of its intended use.
The carburising process that you describe is still a legitimate means of local hardening of low carbon steels.
Hello, I must thank you!!!
I used an old drill bit to turn it to a mini lathe knife. On second try, I managed to harden it.
It works great.
Many thanks!
Mild steel can be case hardened by burying it in carbon in a fireproof box and placed in a furnace/oven at 850 deg C.
Steel dowels are hardened this way.
About breathing protection: keep the mask on your face after you finished grinding indoors. The fumes and dust particles stay airborne longer than you'ld expect.
Very interesting video. When making little rebar knifes, I've always hardened and quenched them just for practice. Never really put them through much use. One test I think would be really cool for you to try with the mild steel knife, is called the "brass rod test." There are videos out on the interned about it, but basically, you push and slide the edge of your knife across a brass rod and if it bends and stays bent, its too soft, If the edge chips, its too hard. But if it flexes with the curve of the brass rod, then springs back into place, you are in good shape. Of course there are alot of factors that effect the outcome of the test, such as thickness of the edge, and the angle it is sharpened at, but you know you did something right if your knife passes the test.
Nice video and great work. Thanks
3:27 The good old days when you could just go out and buy a face mask and TP...
As a "Tradesman" of Multiple Trades? I learned of an actual QC test named the "JEEP TEST!" believe it "or Not?" an inspector charged with inspecting my exothermic welds used a 2lb hammer and let the hammer fall an arm's length swing almost under almost it's own weight, if my weld survived with little to no signs of impact or damages, I passed. "Supposedly?" this test was named after the Hammers issued in WWII jeeps tool kits and a Seabee's test development for testing welds in the field.
Testing it after the quench with a file might have told you something...
Missed the previous rebar vid - but relieved to see from the insert I am not the only one forging with flip flops! 😂
Just found your channel. I love your videos! Thanks for the great presentation 😎
Tas Hortobagyi thank you!
Very cool show 😊 watching dit before school 👍
Greetings from germany!
Very enjoyable video 🤌
Lovely job. Thanks.
Just expected the tempered piece to act somewhere between the other two pieces, but it didn't!!
Nice work!
Thanks. You expressed some good info.
British Standard EN 1 is for low carbon steel. EN 8 is a basic medium carbon alloy steel with few alloying additives. EN 19 is a medium high alloy steel used for machine shafts etc. EN 24 is a high carbon alloy steel for hard heavy duty parts.
At 4:30 he's talking about the recrystallization temperature. When a metal reaches this temperature the crystalline structures within the metal begins to grow and merge with each other causing the metal to be softer and less brittle.
It would be interesting to see how the different pieces would drill.
Interesting teste. Thanks.
Grinder is upside down to me; if it bites the metal, it's gonna bite you next
thanks for the video
Structural steels will harden. They are generally either A36, A572, A500, or A992 ASTM grades. They aren't usually intended to be hardened, so it requires some different techniques and temperatures. Quench in as fast a quench as you can find. Icy salt water comes to mind. There are no elements in these steels to allow them to harden with slower quench baths like oil. Heat these steels to a higher temperature than normal. 1600 F is a good starting point and may require more. Lower carbon content raises the temperature needed to harden these steels when quenching. The magnet trick only tells you the temperature is above ~1425 F. Some high carbon steels like 1080, 1075, 1084, will harden below 1400 F, but you need very good temperature and time control to do it consistently.
Good information
Ive seen steel similar to this before. Early(ish) military tank. I believe from an English model. Wanted a knife made from old tank armer that had been deployed in WWII. it was a very peculiar "mild" steel. It had all the properties of a fabrication steel. Yet, hardened better than I could have ever hoped from a hunk of steel that was never meant to hold a fine edge. Its almost like they ran out of plates and threw in whatever they could find including the kitchen sink.
lol! talks about safety equipment, forges in flipflops, nice!
a blow drier and a toaster oven... brilliant sir i love this
I do Commercial Demolition and come across old steel all the time and always take home. Anything you recommend is the strongest to look for?
Have you tested anymore scraps since making this video? How did the edge hold up when u hardened that butcher knife u made from mild steel?
Dear Sir can you tell what type of liqued you use for hardning please tell me
EXCELENT VIDEO! THANKS
I picked up a really nice bit of scrap metal recently and my brother reckons it's make a great knife. Now I just need to figure out if it's carbon or not
Is it possible to make leaf spring from Mild steel Flat bar carbon contains approx. 0.17% by Heat treatment? please reply.
Good vid, although I want to encourage you to forging in slippers. It is very clever and safe, you can be sure that hot sparks and scales won't ever burn your feet.
How do you sharpen a knife after tempering? I'm a novice at this and would really like to know
Did I miss the temperature units (Fahrenheit or Celsius) here? Please, explain.
What is the anvil you are using? I am looking for a small anvil that won't break the bank. Any advice?
Excellent video. Thanks for taking the time to film and edit it and of course for positing it for our benefit. Keep up the good work! -Migs
An Aussie guy done it years ago. If you punch/quench through the TT curve fast enough you can harden steel with less than 0.04 carbon. The product/formula he developed was quenchall.
can you explain what is quenchall
The most common type of steel for structural members (looks like a C channel there) is ASTM A36. Probably what you've got there. It's similar to 1018.
I suggest viewers look up in back copies of "Home Shop Machinist" for a couple articles I read there about this specific concept: that mild steel is unpardonable. My recollection of the writer"s conclusions is that mild steel is indeed hardenable to a limited degree varying with the carbon and manganese content, the cross section (thickness for practicale purposes,) and rapidity of the quench.
My reading of the sparks in this video suggests to me the mystery metal may be a low alloy structural steel, not A36 structural steel at all. It might very well be suited for heavy duty chopping tools like brush hooks, froes, wedges, pick axes, cleavers etc where a strong tough edge is preferred over a hard edge where chipping might be a concern.
It might be nice to learn the actual Rockwell C hardness of the test samples but that may not be necessary for back yard smithing. I suggest tests with a center punch struck with care for blow consistancy, and comparing impressions for depth etc as a means of comparative surface hardness.
I also suggest you hacksaw, file, hand polish to a smooth matte finish with clean wet of dry sand paper all three of you samples to obtain a flat cross section unaffected by heat (as from grinding.) Etch the samples with phosphoric acid (NOT muriatic or sulfuric) until dark with etching smut. My preferred etchant is metal surface prep solution. Take 10 to 30 minutes depending on merchant strength and temperature. Scrub the etched surface with clear water and a fingernail brush to expose clean but darkened metal. Examine under strong mangification like a 10X jeweler's loupe. Note differences in etched appearance between annealed and hardened sample. The annealed sample will be of uniform appearance. The hardened sample will shade from the center to the surface. This will tell you the "case" thickness attainable with the material represented but that particular sample.
Home metallurgy can be made to be quite sophisticated using simple low tech processes.
man you seem like a connoisseur in this subject. im from tunisia and i make butterfly knives ( i just started and only sold a couple) a customer complained that the edge broke and im looking for a solution to harden it even buy 10 percent im using mild steel (please dont ask why as i can go on a rant for hours on how not industrial my country is and i dont have a forge to blacksmith my own blades ..) long story short can you help me with suggesting whats the best solution for a slightly longer edge witout breaking? (he sent me a picture its actually bent/crushed in the blade)
I restored an old hand plane. It needs a new iron. Could I take a piece of mild steel and get it red hot and dunk it in cold water.
Can i do this to my non hardened steel baton tubes to make them hardened?
thanks for infomation
Hi all, i am a complete newbie at this and my question may be stupid but would cold roll steel be better than hot roll steel as far as hardening quality goes?
Would you get better toughness in your sample that you reheated to straw color by using another heat source -- so you can immediately see the surface color change?
Also, what is your feeling on trying to add more carbon to the steel by heating a more-or-less finished piece in the presence of come carbon? Doesn't some carbon get into the steel?
I think the use of the charcoal in the forge actually introduces some carbon into the steel so maybe that is why he had a harder result than expected
you dont necessarily need a lot of carbon for martensizing if the steel is martensitic. then it'll get hard. not sure about the edge retention
Leaf springs, lots of steel bedframes. Ive used old brick layers chisels and saw bldes too.
So what do u do to harden steel heat it and then cool it very quickly? yeah
Dude. You have GOT to use the right side of the disc when cutting/grinding. That's how you grenade the disc. Start using the opposite side. Yes, it throw a the sparks in your direction, but if you have the right PPE on it's not a big deal. Definitely not as big a deal as blowing up a disc anyway. I learned the hard way, you don't have to lol.
bingo oatmeal you've got no clue what you're talking about. It's not really which side of the disc you use, it depends on direction of travel. And REALLY even that doesn't matter, they'll blow up either way. Go witj American or German made and you should be fine. And that's why you always wear a face shield when cutting.
I'd love an explanation of how a composite cutoff wheel can explode from rotating one way but not the other.
@@wanderingcalamity360 you're talking to the op right?
@@ryankabcenel9700
Yeah.
@@wanderingcalamity360 Long story short, same reason chainsaws throw chips at you instead of away. Easier to control when it's pulling away, and when it grabs it pulls up and away instead of down and back, which is was safer
black smiting in sandals at 2:00 .... one minute later. recommends particulate mask.... you know... cuz ppe is only for your face
CNoreen. Yeah, I noticed that! Steel toed shoes/boots as a must. A lot of youtubers neglect their feet. Even in a woodshop the possibility of a dropped tool or plank is very real, not to mention the wood shavings and sawdust being an irritant, same must be true of a metalwork shop. Real smiths always dress for protection, as witnessed by the state of their clothes!
I was thinking along the same line but with the mis use of the grinder A: no gard and B:cutting the wrong direction, cut with the wheel not against it so if it grabs it pulls it away from you not push’s it into you
I have a friend who dropped her kitchen knife on her bare boot and sustained a severe injury. It cut major important things in her foot and she was laid up for weeks.
Those are safety sandals. I agree with theshauny, however, regarding the grinder with no guard. Using a grinder with no guard (like in the video) is one of the leading causes of injury in industrial settings.
stick ppe right up your rear end. ppe is for Snowflake's who don't know how to do their jobs correctly
Wicked vid for a newbie bro..
My bet is that was A32 structural steel if that was a piece of channel. Most big plants have their machinists and welders work with that. Oh and try using thinner pieces of steel for bend break tests to check the grain. Just my two cents.
For a spark test you want to use a belt grinder or bench grinder. Angle grinder discs do something funky with the sparks.
a bench grinder and angle grinder physically function identically, how would an angle grinder be any different from a hard-wheeled bench grinder? this is internet gear-addict theory and not real life.
@@tragikk03 diffrent makeups for the stones vs the discs
Adding hardening powder works dont know what is in there but it does give mild steel a bit more strength do too many cycles and its snaps off with bending it to far.
spark testing isnt really accurate when using an angle grinder . the wheel throws its own sparks with any ferrous metal
Lol! I agree that it's not accurate but....
In order to throw sparks, it would have to be worn away substantially and produce a high enough temperature to nearly melt the material being ground. The silicon carbide and silicon oxide of the grinding wheels won't be raised to a high enough temperature to do that.
@@baddoggie101 i posted that two years ago how far down the comments page was this ?
Hello we harden mild steel with water or oil
Would auto leaf springs be a good source of high carbon steel?
sure
Structural angle iron like that is actually usually a bit higher carbon than mild steel. (1035-40, very Approximately) You want structural steel to be fairly rigid, and not deform. It’s definitely not a real high carbon steel, but you can make a decent knife from it. However with knives, there’s a huge difference between decent and good.
Great video, very interesting results. Two questions for you. 1: what angle grinder would you recommend for a beginning knife maker. And 2: is the 55lb harbor freight anvil you're using a good starting place for knife making or is it too soft?
I have been using a 55lb harbor freight for 3 years. Railroad track cut offs are better. The anvil is soft and will deform and dent easily. I stopped using it for knives a month in and only use it for making hooks and various odd projects
I've gone through over 5 angle grinders in the last few years. Buy one with a good warranty and if you can find one that has over 900 watts of power then treat it good. Also, you want a angle grinder that has a on/off switch as close to the spinning head as possible for comfort. As with anvils it also doesn't actually matter. I forge weld sanmai billets and damascus by hand into high grade kitchen knives on a really shitty soviet anvil and it really doesn't make a difference. I've used logs as anvils to make high end knives too so don't worry too much about what the right tools are to use since you only really need the one between your ears.
Just look up clickspring, he's got a video about how the Greeks and Romans case hardened their iron.
So quenching in water hardens steel? I'm brazing sheet steel. I'd like a strong joint
Consider also the composition of the grinding material when you’re comparing sparks
I have case hardened mild steel with a cutting torch adjusted with less oxygen then normal so that it has a black smoke flame. Then a cherry red and quench. It only does a 1/2 to 1 1/2 thousands of hardening. But that is good enough for some things.
What will I use to make it the hardest?
Grade 8 bolts (the yellow chrome finished ones) can be used to make a nice hard knife. They're relatively inexpensive (my local hardware store sells them for $4.39/pound). A 1" x 5" bolt can be stretched into a decent knife. Yes, there is better steel out there, but those bolts are cheap and easy to obtain. Be sure to grind off the threads before you start.
That's not a chrome finish, it's zinc... DO NOT BREATH IN THE FUMES! They're fairly dangerous!
Also, why cut off the head? It'll stretch just fine, I made a miniature knife out of a 5/16x1 inch bolt, the handle was the threads, the blade was the head, the blade was a little longer and a little beefier than the handle which was just kind of flattened enough to make the threads look like they were part of a knife handle rather than threads from a bolt.
case hardening is possible to mild steel if no then why?
I engaged my safety squints even watching this
Judging from the spark pattern thrown from your grinder in the intro of your video the steel plate you obtained from the the welder is a carbon steel not mild steel.
I have a friend that builds industrial equipment. He commonly uses carbon steel but also 304 and 304L stainless. He has other stainless but it’s not always marked. I get scraps and have started making knifes. I can get steel up to an “1 thick. The practice is free except for my time and a little electric. I haven’t been able to make a knife yet that I would want to spend the money on for knife steel. Maybe after I do it for a while I’ll buy a piece.
I was expecting something here, but due to the fact I see blacksmithing in flipflops, I am not taking any statements or recommendations seriously. Simple as that!
Good thing none of us were taking *YOU* seriously, anyway.
So if he told you the metal was hot coming out of the fire, you wouldn't take him seriously because he's wearing flip-flops. Admittedly, not the wise thing to, but you only continue in your ignorance and pettiness if you let something like that close your mind to any knowledge that might be gained.
@@HiTechDiver people watch these videos and they usually take examples and/or recommendations how to make things in videos like this. People directly or indirectly can take some practices of this into their workshops, intentionally or not "wearing flipflops" drop something on they foot and loose fingers for example. Not everyone will do that or whatsoever, but my main point is that if you are of some sort of content creator like this, please advise SAFETY in videos. Do whatever you like and how you like when your alone or so, but do not promote bad safety habbits in workshop. It's not the ignorance I close my mind to, I am not taking serious this type of attitude. No need to jump in and defend anyone here, that was just my opinion, like it or not, I have some point in it.
As an Ironworker, i work with all different carbon steels on the daily. The color of the sparks is really how you can get a ballpark rating. From bright yellow to dark red is low carb to high carbon. Heat kills magnets so dont check when its hot
Roast to red heat in an oven while surrounded with carbon. Pack within a steel tube. Six hours will give you a 1/32" skin of carbon steel. The inside will be tough, the outside will be hard. There are proprietary surface-hardening mixtures, but plain carbon, graphite or charcoal, will work.
If you pack apiece of 2mm wall tube with charcoal powder you get inside carburized, then you weld the two carburized sides together and get steel with "soft" outside and hard inside great for small carving knives and the "soft" steel is less prone to rust as bonus (large part of blade)
By the way, by weld i mean forgeweld, normalize after weld then treat as O1
That's a perfectly good idea. You need a hard edge, and pure iron hardly rusts at all.
It has been used for knives here in sweden since vikings roamed, modern laminated Mora knives re more or less a more controled way of doing it.
Yep that's how it's done you can turn a nail into W1 on the outside and a good tough core in the center.
So you can use water if u don’t have any oil to quench the knives in?
it depends on the steel, some steels can be quenched in water , somes in both , others just air
water cools faster so it can cause more tension with high carbon or very alloy steels so it can break it
ua-cam.com/video/mzSCxtHccFA/v-deo.html this guy have pretty good videos about it
the dust mask looked perfectly fine. Of course the outside is going to be dirty, the inside was clean. A respirator will do nothing more than a dust mask except for filtering out fumes/chemicals
Even that depends on the mask, some of the better ones will filter out a lot of fumes as well.
there is colour charts for temperature
OK, I'm not a blacksmith, nor am I a welder or have any qualifications a a metal worker, but my humble "common" knowledge of smithing tells me that when you hammered the three pieces of steel, no matter what they where, they now have qualities which promote hardening. So you upgraded the quality of the metal by merely hammering it into shape.
When hammering at the vice, hammer into the rear jaw, going the other way puts impact on the screw threads and might break it
what about using your cut off wheel backwards
what if you use carbonated water ?
Haha. My dad use to pull me away from saws like that. 😂 pulling clothes are quite effective. Now a few times if it was at a range he would use a chunk of wood and throw it at me. Lol.
So can mild steel be hardened?
How about some protective footwear. I was worried about your feet all video. So much knowledge required for making blades. Thanks Dan
I like how your son was entranced by the fire and you pulled him away by his shirt. That made me laugh.
You can see from the flower-pattern sparks that the chopper knife steel was not mild-steel but high-carbon.
thanks for the video,, but you did not say how to harden steel,, or can you harden this kind of steel so can you do a video an use cold an hot rolled steel the piece you used not should what it was,,ok now i want to make some dies for my bead roller ,,.can i use rolled steel these will not be used everyday, so tell me what you think
if i try them,they will work, might work,, don't want to give your thought ,or wasting my time ,i will need 70set or more,,remember ,, why try,, got to cut140 cuts or more,, bore,, lathe & milling,,i know buy an make a set of 2
i kno this ,,i may do ,,but i'm asking you what you think,,,thanks great video site,, bye from NORTH CAROLINA
(6:15) - "...usually somewhere between 350 and 400 degrees..."
Fahrenheit I guess? Could you confirm?
yes farenheit , between 200-300 ºc
but the best is check the heat treatment chart from the manufacturer of the steel
That's A36 low carbon mild steel, I can see it from here!
to case harden Mild steel you need to add carbon try enclosing your part in a source of carbon (powdered carbonised leather and salt ) then wrapping it in a clay wrap to make it air tight then heat it bright red /orange for 25 mins then break open the package and then quench in oil then you need to temper the part to a golden colour with a blowtorch careful not to let it go blue or all your hard work will be ruined
Thanks
Mild steel does not mean soft steel. Structural steel AKA mild steel is 1020 ( 19-22 points is the tolerance most steel mills rate it at.) and can reach a hardness of about 50 + Rockwell C when quenched in water. Its not a good choice for knives but can become harder than most assume.
The term Mild steel was introduced about 1800s and actually meant semi - steel. Re bar, nails and rivets are very soft and are about 1008 which is less than half the carbon content of structural steel. You were more than likely working with mild steel,
welding shops don't usually work with tool steels.
I like how 95% of knifemakers don't pay attention to what engineers have to say about the basics of steel theory. They waste so much time testing ghetto heat treatments when they could just check the graphs. They generally think that bringing any random steel to non magnetic means the steel is fully austenized. Or that normalizing more than once is necessary on a knife profile.