Just looking for some input on techniques for building damascus on a hydraulic press as i recently switched from a trip hammer to a hydraulic press and now I seem to get inclusions in some of the billets that I never had trouble before. Do i need to change the way that I forge or has anyone had the same problem when they have changed over? The worst part is that the outside of the billets look great but when you get down to the final grinds I seem to be getting a few small inclusions thus making the knife useless. I am using the same forging temperatures and the same procedures when making the billets.Thanks in advance.
It could be a couple of things.... 1. The type of dies (flat/drawing, etc.) that you use on the press. The type/configuration of the dies may require you to "re-learn" how to forge weld on the press to avoid the inclusions.
2. There is a distinct difference between how a hammer and a press "works" the steel. A hammer works hot steel from the outside in...meaning that the exterior of the billet is worked inward to the middle/core. Where as a press is just the opposite...it works the steel from the inside...out. This is because as soon as the press dies contact the steel, it cools the exterior surface(s), and the steel "works" more on the interior, and less of the exterior. Depending on the type of dies this can be a benefit or a determent.
I am using the same forging temperatures and the same procedures when making the billets.
This particular line caught my eye....my instincts tell me that this is where you problem lies. Generally speaking because of the way press dies "suck" the heat out of a billet, I find it necessary to use a bit higher temp, and allow the billet just a bit of soak time. You didn't say exactly if the inclusions were near the middle/center/core of the billets, or more towards the surface......but I'm assuming they are towards the middle/center/core....that would indicate to me that you might want to try a bit of soak time when using the press.....possibly the middle/center/core of the billet wasn't hot enough.
As an example, I don't even put a billet in the forge, until the temp is 2350F.....and depending on the size/mass of the billet, will not pull it out until the temp hits 2360-2375F.....that's just my way of knowing that the proper heat has made it's way completely through the entire billet. If that procedure causes excessive grain growth for you, then just ensure you thermal cycle 3X prior to annealing.
Hope that makes sense!<img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//smile.gi f' class='bbc_emoticon' alt=':)' />
Ed Caffrey, ABS MS
"The Montana Bladesmith"
www.CaffreyKnives.net
Thanks Ed. I am religning my forge and then I will run it a little hotter and try that.
Kelly
Kelly,
When I used a trip hammer, the dies were relatively flat but had slight taper from the middle of the die to the edge of the die in all four directions. I sometime weld under a screw press which functionally contacts the billet in the same manner as a hydraulic press. I ground a very slight taper into my dies (upper and lower). My thought on this was the movement of flux out of the billet with pressure as the dies came together from the center to the edges of the billet. I do not have data on this but it seemed to help.
Also, I weld then draw and stack. Before each weld the pieces are ground to clean away all scale. Even here I try to have the slightest convex curvature on the pieces so that the flux can move out of the billet when compressed. If you have "small occlusions" in the final forging and not larger section of a poor weld between layers, then you may be getting trapped flux. I found this to be more of an issue with the press since the dies were often very flat and larger in surface area.
Just my experience and what seemed to help.
Dan
Two words......kerosene "flux" At least for the intial welding pass. <img src=' http://www.americanbladesmith.com/ipboard/public/style_emoticons//wink.gi f' class='bbc_emoticon' alt=';)' />
Kelly,
I do all of my welding on a press and use this technique which has worked well:
Bring the billet to forging (bright red)temp and give it a small quick squeeze in the press. This will insure that all surfaces are together tightly and will drive out any flux from between them.
Then return the billet to the forge until it has soaked at temp long enough that you are confident of having a good welding temperature throughout and give it another quick small squeeze and then back in the forge for another soak. The second time that I weld the billet I will compress it fully in the press. By doing a second welding cycle each time I have eliminated most problems.
Hope this makes sense. If you have questions feel free to PM me.
Gary
