Broke it

[Gijotoole]

First time making a knife using my gasser (waaaaay too much air) and a coil spring. I quenched in warm water and took it inside to clean it up. The blade was a bit warped and I thought "if I try to straighten it, I'm going to sna that thing. I wonder what it looks like inside..."

Crack. More like a crinkle-ping. It's amazing to see what happens to steel internally when it cools quickly-exact same effect as rocks; phanaritic or aphanitic formation of the crystals. I'm impressed with how a little science goes a long way. I've already started on my new paring knife. This time I'm hardening, grinding, tempering, finishing.

You knife makers are something else. Don't know how you all do it consistently, hat's off to y'all.

[jmccustomknives]

Crystals or grain in a knife usually means you got it too hot.  This happens from not following good forge theory.  There's a lot of info in the knife making section.  On your next try, start hot and finish at red.  The final heat isn''t to move the metal so much as it refines the grain.  Then comes the normalization and annealing.  After that the heat treat. 

Steel will tell on you, it holds on to the story of your forge.  Modern automotive springs are usually 5160, or some version there of. 

Good luck.

[Rich Hale]

May want to rethink water quench also.....

[Stormcrow]

Large grain is not a good thing in a blade.  Fine grain is much tougher.  At the end of your shaping, normalize three times and it will relieve stress and refine the grain to make a tougher blade.  And a water quench is most likely too severe for the coil spring, possibly causing micro-cracks that won't show up for a while.  Then when it breaks the rest of the way, you see that part of the break is rusty where it's been broken for a while.  Try using canola oil at 130 degrees instead.

 

A little science goes a long way, but there's so much science involved that it can be overwhelming.  I keep it as simple as possible cuz I know I'll never understand it all.  :)  Well-executed simple heat treatment on simple steel can provide some pretty amazing performance.

[Gijotoole]

Fellas,

I'm not disappointd in the outcome at all. I think it's impressive how steel acts. This project was a throw-away attempt anyway. I just wanted to see how thin I could get the metal before I started to run into issues. I don't even have a belt sander or a grinder aside form my dremel or a hand file. I'm moving soon so those will be acquired on the gaining location. Steve: I have absolutely no experience in this sort of thing but I'm starting to read up about it via IFI threads. Rich: I used motor oil to quench my chisels and punches, I just wanted to see if the water quench would break it while submerged. JMC and Storm: I'll read up on said theory behind blades and the treatments involved.

 

I'm interested in the "whole knife thing" but right now I am mainly working on making tools to be used with the forge and I'm more interested in the tools and simple stuff than perfecting how to make a stellar blade. I'll still try to make them, but they won't be pretty.

 

I appreciate the advice. I'll peruse the other forum threads, I was just excited to break the blade and see the guts of the steel. I'll work on a fine grain through quench techniques and thermal cycling/normalizing (if I can use those terms interchangeably). This stuff is neat!

[Eddie Mullins]

Why do you want to harden before you grind, particularly if your going to use a hand file?

[ThomasPowers]

As noted:  large crystals/grain is bad, fine crystals are good and no crystals = a "metal glass" a very odd state of things and one you will probably NEVER see or be able to accomplish.  I know of a research metallurgist who has done odd stuff with metal glasses and his son who held a patent on using it to make pattern welding for cutlery.

[Gijotoole]

I was under the impression that hardening could make the metal warp, so I thought harden and then grind to final shape. I guess that's a no. Like I said, I'll do more reading on it. I'll check back often.

[Eddie Mullins]

If you harden it, properly, your file will just skate over it. Belt grinders are a differnt story, but for hand work, I would anneal , shape then complete HT.

[Gijotoole]

Good point, missed that fact. Hammer, normalize (x?), shape, harden, finish. Before I have had a chance to read I am assuming normalizing will help the steel "settle" or relax which should help me with the final product. I want a nice, fine grain, that won't rupture and has a smoother bond internally. The red, cool, red, cool cycle will relieve the stress and help the fine grain structure.

[Frosty]

It's good to see you up and forging and I understand the temptation to try something advanced early on, it's even gooder to see you didn't really expect success. Try not to get too involved in the how tos re. heat treat you read in what is essentially an informal discussion, namely this one. As Steve pointed out in his soooo delicate and round about way, the subject has been covered in depth and detail in the heat treatment section.

 

While I'm not a bladesmith guy I do know enough about the subject, especially heat treatment to at least grasp what's being said. Without at least a good handle on the processes it's really hard to filter the facts from the myths from the kids who got all their learnin from playing Worlds of Warcraft. Some seemingly simple things can really screw you up. For instance, calling normalizing or annealing "thermal cycling" is like calling architecture, stacking and connecting stuff. It's just too general a process to mean much of anything specific. Isn't baking a wedding cake just thermal cycling? Stop by sometime and I'll be thrilled to thermal cycle some grub for you.

 

Yeah, that's an extreme example but it's apt.

 

whatever you do, do NOT stop playing with fire and hammers but do start reading the sections specific to your goals. I heartily suggest printing the parts that cover your next experiment the best. It's really good to be able to review the next step before it drops in the pot after you do it.

 

Frosty The Lucky.

[ThomasPowers]

Well there is another way of refining grain size and that is by forging or work hardening and renucleation of crystals during subsequent heating.  So Thermal Cycling vs Mechanical Methods.  With modern alloys  Thermal Cycling is often a much better method!  ("edge packing" was a mechanical method that was useful with early steels---though the explainations of what was happening was usually totally barking mad.)

[jmccustomknives]

When you follow good forge theory on carbon steels there's the point were the steel is nonmagnetic.  This temp is your reference point.  When you start out keep your forging above that temp, but well below the burning point.  When you are almost done reduce your working temp with the final heats being below the nonmagnetic.  The steel really doesn't want to move, don't force it.  Use this part to smooth up hammer marks.

I said all that to show you a test.  take a piece of mild steel round stock (9mm) and arc weld it onto the 5160.  When it cools try to bend it.  The weld will break like glass and have a very rough grain.  Do the same thing again, but this time heat the weld back up to just below nonmagnetic and work it over with a light hammer.  When it cools try to break it.  If you did it right the weld wont fail, your round stock should just bend.  What you did was refine the grain.  That changed the weld and made it strong.

[Gijotoole]

Well there is another way of refining grain size and that is by forging or work hardening and renucleation of crystals during subsequent heating.  So Thermal Cycling vs Mechanical Methods.  With modern alloys  Thermal Cycling is often a much better method!  ("edge packing" was a mechanical method that was useful with early steels---though the explainations of what was happening was usually totally barking mad.)

Mr Powers, I have no idea what you said up there. I'm going through the Knife Making 101 thread with Mr Sells and Mr Hale. Even some of that is a little aloof but I understand most of it. I have a 4-day weekend coming up for St Patty's Day so I'll try to refine my little paring knife and, if nothing else, make another neat looking mistake. I don't have a welder but I should have one after I move in a few more months after all of my stuff shows up. Again, I appreciate the help, gents. Have a great day.

[Rich Hale]

G,  my guess is that alot of these folks on here that either say they make knives,,or actually do....Started in a similiar manner that you have. I know I did anyway.  I am impressed that you not only made something,,but youi tossed the results in here for us all to have a shot at. I am also impressed that you have been given so much information is such a short time to possibly help you along youir new path. Keep forging and learning...and enjoy the site.

[Gijotoole]

Okay, yesterday I pounded two separate coil spring pieces into equal-sized billets. I then heated to orange three times and set aside on a vermiculite board. Today I heated, one at a time, to non-magnetic and then quenched one in motor oil and the other in cold water. I waited until they were cool to the touch and then ran them through their paces: the file bit into both of them, but just barely; the water-quenched bar snapped easily with VERY fine grains inside, almost that of it's coil spring parent (yay, me, I think), the oil quenched bar deforms plasticaly and just won't break. I'm assuming that this test wants the steel to be annealed/normalized (one of those terms) at least once, and then quenched in water at it's lower, non-mag temp. I was really impressed with the grain size this time-no cubes visible, it looks like dark gray plaster.

I'm guessing the springs are 4063, per a document I found on knifeforums, so I don't expect it to skate a file when hardened.

What say you, experts?

[Gijotoole]

Here's a shot of my old knife grain

And here is today's

[Gijotoole]

New issue: I am still using coil spring as my steel source. I forged to a flat-ish billet, normalized (3x), ground to initial shape, hardened (in motor oil), tempered, and then found this in the morning. I tempered at 350* for 1 hour and left the oven open overnight to cool off. I had blades quenched in water and oil do this. One thing I noticed in common with all of the blanks was the crack happening only where ground.

 

 

My hypothesis: the grinding prior to the hardening/tempering added another cycle of stress that was not relieved.

 

My two Courses of Action (COAs): 1) hammer to shape and use a cut-off dremel wheel for the refinements, or 2) normalize after I grind and before the hardening/tempering. Also, I noticed that quenching in motor oil does not yield a blank as hard as I would like it to be as the file is still biting pretty well. The water quench does yield some small, smooth grains, but I'm not sure if that is is adding stress due to the fast quench. Again, from reading the "classes" I'm guessing that the lower carbon content (~.63) is the culprit, not allowing it to be as hard as, say, 1095 or 1080, and therefore more susceptible to the file.

 

Next time I'm going to temper after I belt grind. I'm really worried about grinding out my temper.

 

Any ideas?
 

[LastRonin]

I'm not a knife maker (yet), but out of curiosity... was the oil heated? If so, to what temperature?

[rhitee93]

Those grind marks are pretty course, and each one of them creates a stress riser that can be the starting point of a crack.  A finer grit prior to heat treating might help.

 

It certainly sounds like this mystery spring material is more trouble than it's worth...

[Steve Sells]

I mix 30 wt oil with Automatic Transmission fliud, for a little faster quench speed, and I always tell my students normalize then harden then temper.

 

I also finish grinding and such after the heat treat, and by using bare hands, it is easy to monitor the temperature of the blade, and dunk in cool water as needed to prevent it getting too hot to hold, will also be prevention of it getting hot enough to effect the temper

[Gijotoole]

A friend of mine here mentioned that I should have just hammered to shape, cleaned up with a dremel, and then finished the heat treat prior to my final finish. I still have a few ground blanks left that I'm going to normalize again after I hammer some more. I'll try it his way and still quench in motor oil, warmed up prior (as the "class" states). The oil is motorcycle oil, nothing special. Thanks guys, I'll file the rough grind off before I run it through the hardening this round to get rid of those stress points.

You're all wonderful folks. Thanks for the help. The knife making/HT classes were a big help, too.

[brimic]

Hey! I broke my first one too! Forged from an okd file, WATER quenched, and mine made that same squeak-ping sound right before it broke as well. I went ahead and tempered and sharpened the handle end and use it as my 'garage' knife. It cuts cardboard and holds an edge like a champ.


 

[Gijotoole]

I mix 30 wt oil with Automatic Transmission fliud, for a little faster quench speed, and I always tell my students normalize then harden then temper.

I also finish grinding and such after the heat treat, and by using bare hands, it is easy to monitor the temperature of the blade, and dunk in cool water as needed to prevent it getting too hot to hold, will also be prevention of it getting hot enough to effect the temper

What ratio ATF/oil? I sent my remaining blanks through another three rounds of normalizing today and realized I forgot to hammer out to shape. I'll go back and redo them, again, tomorrow or monday and see where I stand. The movers come to pick up my stuff tuesday so I'll be out of the loop for a couple months at least. It's been great working with you guys and I hope I can still finish these things up before I actually move. If not, I'll be back in a couple months.

[Steve Sells]

AFT is a faster quench than oil so mix accordinly to what you wish, if its not fast enough at 50/50  try adding a little diesel., which I do not use, but my teacher did.