Blade streightening failure and a new leason

[lyuv]

Broke a blade while attempting to streighten a slight bend (from quenching), using the 3 points method, and under heat. It should have worked. But I kept bending and bending more, but it would not take. Until it broke. Only when I looked at the cross section, the mistery was solved: It was crescent shaped, which means the blade was dished rather than flat. So it had stractural strength and resisted bending. But why dished? I have ground it flat.

Mental playback...

Before quenching, I heated to normalize, and a bend appeared. So I placed the red hot blade on the anvil. Belly up, and tapped it with the hammer. THERE - I hammered on the center, and that dished it. Probably causing the bend in the quench, and preventing me from un-bending.

 

[Jim L.]

Have ever tried using a maul or billie club instead of a hammer? The wood, being softer than metal won't ding the blade nearly as bad.

If it bends during normalizing there may still be stress in the steel. My experience has been to normalize again if I have to give the steel another whack.

I've seen the 3 pin method done on just hardened blades and it makes me grit my teeth. The maul comes in handy where you have a few seconds for a sraightening whack without stressing the steel too much.

That is a shame anout the break. It looks.to jabe had a nice profile.

The profile could be reground as an interesting skinner in an effort to save it.

 

[Sly]

Well to help with your problems, what is the steel, was it annealed prior to normalizing, how are you normalizing, what Austenite time are you holding/ temp and is it water/oil?

also if you work it at all you have to reundo any stresses.

[Frosty]

Did you put something between the blade and the teeth on the clamp's heel jaw? If not the concentration of force teeth use to grip stock also make, stress risers, initiation points, for failure. Just like scoring glass when cutting. 

Frosty The Lucky.

[Sly]

also blacksmiths dont make mistakes, make the first part into a cleaver.

 

[swedefiddle]

Happy New Year,

You had hardened it (?) and not Tempered it, before trying to straighten the Blade?
Welcome to the lives of Bladesmith's.

Treat it as a lesson. A Positive Lesson, not a negative lesson.

Neil

[ThomasPowers]

Some alloys have a very brief window where you can straighten before full hardness develops; me I'm chicken!

[BartW]

Well; all (knife) steels have this window after quench, in some it's just so short you can't use it. 

check the picture in this blogpost, which is marked ttt diagram for 1050 steel :  steel TTT diagram .

Read the time below on the X-axis. given that we're talking about knives; let's assume 10 to 15 seconds to cooldown in the quenchant. You're basically drawing a straight line from top left to the x-axis where it says 10. Your straight line barely doesn't touch the pearlite/ bainite formation nose. Now untill you reach the horizontal line; your steel is still "malleable"; as if it was copper or pure iron. You can straighten a knife for example in this window with a wooden mallet on a flat piece of wood for example. This is also why if you aircool 1050 steel; it'll remain soft

Any standard steels have room under that "nose", and if you remove the knife from your quench tank at say 450 °C; you have a couple of seconds to straighten knives; which will oddly enough keep this form and snap like glass 10 seconds later (once under the martensite formation line).

I have a piece of L6 which I use to demonstrate this; heat to non-magnetic; soak a bit; quench in oil; a second after it loses red colour; take it out (it will burst into flames again when use organic oil); blow those out; bend it 30 degrees in a vise; back in the quenchant. a minute later; and cool; try to straighten the 30 degree bend, and it will shatter. I only show this to advanced bladesmiths; as there really is no time to do or think about anything else (or I'm too slow; also possible  ).

So; the "myth" that you can quench a steel; and straighten it very fast after; then back in the quench tank is scientifically correct . In fact I think you see Ilyia do this several times in the men at armes reforged series.

However ... I've *never* been able to straighten a knife perfectly. The only perfectly straight knives I've had came out the quench straight or were ground perfectly straight.

[Sly]

ennnngh thats correct and so incorrect at the same time. 

So to attempt and correct as well as compliment your statement; Martensite is not in a stable state after quenching, it has its own unstable phase state, which is not listed on most diagrams like other unstable points, so give or take it requires a cooling period to stabilize. There are two schools of thought on quenching depending on the method. the first is to allow the steel to cool all the way down allowing for (some) the martensite to dissolve back into iron matrixes and carbides, straitening/grinding and then tempering afterwards. The more common secondary method is to quench the steel but keep it above 275 with room to spare for transport into the tempering method maintaining a continuous phase transfer where the martensite is potentially brought back up for an extended period of time to the desire phase state, potentially developing bainite because it has gone UNDER the magic S curve if so desired.

The first method requires a specific higher austenizing temperature which usually thoroughly hardens the steel but retains austenite which independently resolves back into iron and carbide depending on the steel.

phase states are a form of dissolution and formation, it takes time for the structures to reconfigure, the higher the temp the steel is exposed to the faster this happens.
so to say you can VERY rapidly normalize steel up to forging temp 3 times and have sufficient austenite to quench, or you can maintain an exact temperature just above where you want to quench but it will take a VERY long time to get there. Same stretch of road the speed you use just determines how fast you get there basically.

same principle with tempering, if you do several very quick high heat tempers it can achieve the same possible results as a very long soak time at exact tempering temp. it is in a sense a matter of how the heat and matter slowly or quickly shifts.

another important factor is not just the phase state or the real important factor is the grain size, when the steel is austenized it forms nice neat structures in the grain boundries. when you quench they shrink down and compress giving you your hardness, the tempering allows for those grains to grow, the time and heat again determines how large they become allowing for the steel to become ductile again. The smaller your grains the harder the material is but also the more brittle (not factoring in carbides which have their own hardness independent of grain size) the larger they are the tougher they are. Train tracks deliberately are austenized for days until the austenite expands so much the grains burst and reform into extra large grain spheres and their sized is maximized, basically hot rolling but the mechanic to this is that the internal structures are destroyed and reformed into the most ideal and evenly spaced out as they can get because in a state of dissolution the matter wants to be as far away from itself as it can get.

you can also use this principle to weld steel because the grains will eat the welded material and reform it, in a sense repairing the steel, bloomeries are welding in this fashion, either very hot for hours or mild for days, achieving the same effect, but you wont find weld lines on bloom steel where the steel has bonded and mills hot roll steel for days in the same matter to ensure the steel is what it should be. However those spheroid austenite grains will turn into spheriod martensite and then disolve back into iron and cementite (not martensite), if you quench them because they are inconsistent with the rest of the material. you only see this effect after hours but if you were to continously forge your steel and keep it always at austenite and then quench it, it can happen. This is why we cool our steel all the way down, restart the phase diagram, normalize and then specifically quench and temper. The Spherite has its own unstable and stable points NOT found on the phase Diagram. (so basically if you dunk a part youv been continously working on it may have stable austenite and small amounts of spheriod austenite that isnt yet stable, bad idea.) You always want a sufficiently stable point at the start and relative stable point at the end. 

So looping back around it is possible to have a blade you can quench to martensite but have large enough grains for your blade to be ductile enough to cold forge strait without tempering where the steel decides it really likes its formation, or you can have something so brittle it will shatter if you touch it. it depends on your grain size.

Where and when you can hit it depends on your phase states stability as well as its size.

This is sort of a sweeping statement but http://www.hybridburners.com/documents/verhoeven.pdf this pretty much outlines the exact details.

Hope that helps -Sly

[BartW]

Well; I'm not a metalurgist, I was just telling was I was told... I honestly don't know the background; but you did provide a really nice paper which i'm defenitely going to read.

Thanks Sly.

 

 

[Sly]

unstable phase states are something us smiths know exist and play around from experience and theres alot of times a smith will just put the steel down and leave it alone for a time period but never really explain why, same thing with heating the steel and working it, in videos the smith doesnt exactly say: im going to austenize it to do this to do that. In fact most smiths dont know the specifics but they have a passive comprehension of whats going on from experience.

Just remember grain size matters equally to the phase state.

If youre working on steel you are an applied metallurgist, the more you know or the more experience you have the better your results  I just spend my free time doing my homework

[lyuv]

OK. I think the point I was trying to make, was quickly lost to an extremely educated discussion on heat treating. But the point was not the heat treat itself, but the new way I found to fail - If a blade has a dish/crater banged into it (even very slighy), it's WAY harder to straighten.

Jim - Yes. Wood mallet would be better. That's one lesson. I did normalize again after the first warp, but as the blade is only 2mm, it bent again in the quench.

Frosty - For the pressure points I used the coins in the picture with the clamp. Far from ideal, but I did use that exact set up on more chalenging patient without fail. But I do intend to make a proper device.

Sly - Thanks, but I have enough Mistake-Cleavers...

Anyway, took the opurtunity for another leason, and broke the blade some more, to see check on the grains.

it's O1 steel. Heated only for the heat treatment. At one time, It seemed the center got a LITTLE hotter than that non-magnetized temp. and only for few seconds,

Well, the picture tells that this "little" diversion had a BIG impact.

I find this very educational.

BTW,  this is what it should have looked like (the second attempt)

[Sly]

Ima go with uneven heating. are you using charcoal or propane, I have tips for both.

Assuming the enlarged grains were in the center and thats where you first broke the blade where it would be the toughest with the grains that large you should have had unstable transformation.

if you want to have more fun with this sand down the broken edges and etch them.

[ThomasPowers]

Note when heat treating in a solid fuel forge it can help to bury a pipe in the fuel with one end sealed, (I also like to add powdered chunk charcoal as an O2 scavanger) and heat the blade in the pipe to get a more even heat.  Some folks will push and pull and rotate the pipe till it all comes up to an even temp.

[Sly]

well its also O1 using a 1050 diagram... O1 is also nothing like 1050 in the diagram. you have .85-.1 carbon, roughly .5 Tungsten, .3 Vanadium, much higher manganese and some nickle. it's a really deep hardening steel.

your normalizing temp needs to be above 1600.
 

[ThomasPowers]

good catch!

[Gibson]

lyuv, that second attempt came out lovely.

Out of curiosity, how thick was the cross section on that first attempt?

[JHCC]

I just want to know how you got those pieces back together so cleanly for the second attempt!

 

[ThomasPowers]

Elvish smithing; like forging Anduril from the shards of Narsil. 

[JHCC]

Quenya gonna engrave the runes?

[ThomasPowers]

Ghost Busters

[rockstar.esq]

2 hours ago, JHCC said:

I just want to know how you got those pieces back together so cleanly for the second attempt!

 

I must admit, that made me chuckle!

[Sly]

LOL!

in all seriousness though xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx i'll leave this link to xxxxxxxxxxxxxx. (hes an ABS mastersmith) Hes also got some info on other steels.

On a different note fun fact: it was fairly common to have a scarf weld on swords in the center of the blade because the smith did not have enough material or the sword broke and then forged back into shape, possibly the material was deliberately change. lots of wootz blades have them.

(so he could potentially fix that thing that way never done it but experiment for next spring? maybe? lol)

this is the last time I want to have to remove this link

[Sly]

Apperently a Mod doesnt like me adding a webpage with heat treatment info on O1 from an abs master smith. Dunno how that is advertising content. also sorry mod I didnt see the email.

If you read the ToS that you agreed to follow when you joined, you would know not to send people off site for info, post the pertinent inforfmation here instead of directing traffic to a commercial site,   It was removed twice already .

[lyuv]

10 hours ago, JHCC said:

I just want to know how you got those pieces back together so cleanly for the second attempt!

 

It's a proccess I perfected through many repetitions. It's lengthy, painfull and requires you to sacrifie piece of your soul. However, due to it's vile nature, I can't provide detailed description. I"l only say that it involves the usual pleges (blood, first born ect.), bitter disappointment, old and new swear words (tears optional), calling for dark forces, some more tears and finaly - draging yourself to the shop to buy new steel (and lose some more self respect).

Gibson - Thanks. It's about 2-2.2mm in the middle section.

Sly - I Use coal forge, which makes it hard to judge exact temp and maintain uniform temp. Thomas - The pipe is a great idea. Will try that next time.