Michael Kemp

OK then - my grain is somewhere between your two examples. As mentioned at the top of this thread, after the forge welding I assumed I had huge grain size - and for the first set of 3 normalizations started pretty high: 1650f then 1600f then 1575f. Then an anneal at 1475f and into in pre-heated vermiculite. Then ground to final shape. Then 3 more normalizations all at 1575f +- 7f for 5 minute soak - air cooled in still air to where I could hold the blade in bare hand. This is the grain size I got. Any helpful hints are appreciated!!!

Heya all - entertaining reading. While I *am* using a forge rather than a Paragon or Evenheat - the blade was normalized set vertically on it's spine on a bridge across the forge above the burner. I use a pyrometer mounted near the center top of the forge. The kiln shelving bridge and blade support were at forge temp. Visually speaking left and right side of the forge were the same color. I soaked the blade for 5 minutes on each normalization once the blade visually reached the forge interior color. That said the blade is friggin' thin (0.062" spine at the point that the warp reappeared - see above). And the initial warp appeared in the 2nd set of normalizations - after grinding to shape... and got a little more pronounced during the quench. So I wouldn't say that the quench caused the warp. As noted above I had the warp straightened out during tempering - but it reappeared while finish sanding. I just *had* to see the pattern - so I did a quick etch & bluing to see the Damascus pattern. And I wanted to take the opportunity to see how the grain looked - so I broke it at the start of the warp. What the heck - here's a snap of (1) the blade profile (2) closeup of the pattern (3) closeup of the broken edge - to the naked eye the grain looks a little rough but not "bad" to me. Here's a closeup of the pattern: And here's the broken end - approx. 0.062" at the spine - you can see the etched/blued layers on the sides of the break. To the naked eye there is a texture to the surface of the break but I can't resolve individual grains. If this closeup photo can be trusted I'm guessing the grain size is around 0.002" to 0.003" - which is larger than I'd like. What is your definition of "fine grain"? (in microns or thousandths, please)

Update: I've tossed the chef knife in the "oops" drawer. I was down sick for a few days - so this was about a week ago. I had it straightened - but while cleaning up the bevels I let part of the blade get hot. Not hot enough to color - just hot enough to warn me ?200f? - and the warp returned to that section of the blade. I'm making up a couple of new Damascus billets - but will only be making small knives until I can get some hands-on mentoring. David Lisch is 4 hours away so I'm watching for him to post his next Damascus class - I believe he's in the process of moving. John Emmerling is busy for a month or two and then I might be able to work with him (3 or 4 hours away). The Bells (Dragonfly Forge) work with cable - which is a different beast. Murray Carter is out of my price range these days. I'm particularly curious how folks who do layered Damascus with integral bolsters do their heat treat. Somehow I doubt if they harden a slab the full bolster thickness and then grind all the way down to blade thickness?!? - so I doubt if they plate quench. Damn shame too about the chef knife - I loved the glimpse I got of the Damascus pattern.

Thanks Niels - I've always taken it out of tempering and used a 3 point jig in a vice... I *have* to remember to try your way next time... and despite all efforts, I'm confident there will be a "next time." ;-]

I've been having a side conversation with John Emmerling about this - and he also grinds after heat treat. And when he hardens he quenches in oil for 8 seconds, then clamps between aluminum plates. So the warping issue isn't just me... I just can't treat Damascus like it was 5160.

Good points Joshua - and if Ed Caffrey warns about 1095 Damascus warping - well then.

Matthew - you may be right about thin blades - they've sure given me fits. As for extra thermal cycling impacting hardenability, I believe it also improves toughness - so kind of a trade-off. I've been getting around 57 Rc on my Damascus kitchen knives which I consider appropriate. Hrisoulas noted in one of his books that Damascus tests low in Rc - and heck - my Wusthof knives test the same. But yah, the only real "cure" may be to harden a profiled but un-beveled blank before grinding and sacrifice more Damascus to the grinding gods. I'll try flipping sides more during grinding (and an improved forge) first... but I may just be delaying the inevitable.

Peter - good queries. I *believe* that the forge temp is even - but that may be the culprit. I'll be building a new forge with better temp control at austenitizing temps - so in a month or two we'll see if that's the culprit. For cooling in "still air" I have a rectangular chamber of firebricks with one end open - the floor is those soft refractory bricks - and I have a couple of fragments of kiln shelving that barely contact the blade to keep it vertical. Hmm. As for thinking of "anything that might have made" heat gradients - I'm at wits end (not that I'm all that long in the wit to start with) hence posting this thread. This isn't the 1st blade I've had issues with - I just paid more attention this time to try to spot where the problem occurred. It's curious to me that the 1st round of normalizings and an anneal did not bring out a warp - but the 2nd round of normalizings and quenching did. As close as I could see the forge and "air cool" were consistent between 1st round and 2nd round. And the warp started to appear in the 2nd round of normalizings, even before the quench. Maybe I should just get the next forge built and see how it goes. As I say - at wits end - grasping at straws. The blade is *almost* straightened out - just a slight wow left in the edge about 1/3 up from the heel. It's soaking in the oven again for the next straightening round. I have to say I'm impressed with how springy the edge is. I'll be curious to see what the Rockwell is.

James - the blade sat vertically in the forge - and I'm of the opinion that the heat in the forge was even... but that could be an issue. It did not warp in the initial set of 3 normalizations and an anneal. Of course it was slightly thicker steel at that point. At any rate it was straight when I started grinding (and when I finished grinding). Maybe it had something to do with my grinding techniques - but I thought I worked on front and back about equally. Hmmm.

I'm supposed to know these things, but obviously I don't have it down yet. My current 8" chef knife started warping in my final set of normalizations?!? Any insights welcome (even those I've heard or read a dozen times). Blade history: Billet of 1095/15N20 I forged - several hundred layers (theoretically 700+ but I know I burned off some and ground off some layers between cutting & stacking for each round). Forged pretty much to shape & thickness - bevel & distal taper. Mainly using drawing dies on a press - some flat dies on power hammer and some hammer & anvil work. 3 normalizations starting pretty high (since the billet had been forge welded it seemed reasonable to start high) 1650f then 1600f then 1575f. Then an anneal in pre-heated vermiculite - from 1475f. Then ground to final shape. Straight & true. 3 more normalizations all at 1575f +- 7f for 5 minute soak - air cooled in still air to where I could hold the blade in bare hand. At each normalization I noted a slightly increased warp toward the back of the blade (to the right looking down the blade). Heat to 1475f - soak 5 min - quench in Parks 50. And the general warp that developed during normalizations was slightly enhanced - plus a couple of small wobbles at the thin blade edge. Temper 3 times for 90 min at 375f. Straightening a little between each temper. Got most of the warp out. Will head to the shop this afternoon to get the last bit out of the blade edge (heating to 375f). It's probably silly to ask for advice when nobody was watching me to see where I might have *caused* the warpage - but here I go: Any advice?

Bits & parts - the guy at the propane shop sold me on a fail-over switch for 2 propane tanks - hook up both, open both, set the gizmo to one tank and the flag goes green and it runs off that tank until empty then fails over to tank 2 and the flag goes red. You set the valve over to tank 2 and replace tank one. Repeat as needed. I'm hoping it works as slick as advertised in practice. I've got one hose & bell in the truck to remind me to pick up proper connector fittings.

Kenon - looking forward to seeing what you come up with. At this point I think I'll build a couple of ribbon burners set up for forge welding temp... then play with reducing the pressure until I get nervous - if it *doesn't* get down to austenitizing temps then I'll build a couple more burners with fewer holes that I can swap in as needed. I certainly don't want to make a pipe bomb. I hope you folks are patient with me - it always takes me a LOOOOOOONG time to get a project done. I haven't even got the steel for the forge shell yet. Or the Inswool & Insboard... just Kast-O-Lite, some black pipe, some fittings and buckles, & most of the propane fittings. The needle valve on my current forge works well to control the propane on its own (after the regulator) so I'm hoping my new needle valves will be up to the job and not require an extra valve - like Joshua's ball valve.

Joshua - thanks! So even with the ball valve and gate valve choked down for heat treat the flame never creeps back inside the ribbon burner? Excellent! Thanks for the info. And no - I don't expect to take the forge down to tempering temps - I've got an old kitchen stove oven for that (with a deep tray of sand that I put the blade in to even out the temp swings).

Joshua/Wayne - Thanks guys - I've visited John's shop and watched the burner in action - impressive! Welding heat is obviously no problem - HOWEVER - I'm concerned about running a burner with that many holes down at heat treat temps. I'll be choking the air with a gate valve and the propane with a needle valve. Like I do on my current blown burner. When I choke it waaaaay down on my black-iron-pipe blown burner the flame will flutter back up the tube - which is annoying but not dangerous. On a ribbon burner I'd think that would turn the gas/air mix area of the pipe into sort of a pipe bomb if the flames crawled inside the ribbon burner. Which makes me think I should build 2 sets of burner that I can swap in and out - one for welding - the other for heat treat (with 1/3 the number of holes). Does anyone have experience running a ribbon burner (one that performs admirably at welding heat) down at heat treat temps (1420-1575 F)?

I'll be building a ribbon burner powered forge next. It'll be 24" deep so I can heat treat brush blades (I don't have a place to put an Evenheat or Paragon if I bought one). It must perform at forge welding temps and at heat treat temps. Preferably built so it can be disassembled and reassembled at a hammer-in. Better protection of the insulating wool than my current forge. Dual 20# propane tanks to humor my bad back and allow tank swaps during forging. I've been happy with the bottom of my current forge: an inch or two of kitty litter on an inch of Insboard. I want the burners below the work area like my current forge and I like having kiln shelving to rest my work on - but I'm thinking of replaceable kiln shelving ribs for better heat flow and flux drip (on the rare occasions when I use flux). Yadda yadda ... I'd planned on getting some better schematics drawn today but got delayed in getting the 5160 Club newsletter out - so all I have to share at the moment is some preliminary sketches. I'll add more details later. Some things I'm set on - but in general I'm open to suggestions.