Structural strength of ladder pattern ?

L

lcf

Joined
Nov 28, 2006
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What are some of the thoughts of other makers on the strength of the ladder pattern? I have been using modeling clay in different colors to predict the results of the patterns and designs and have come to wonder. Clay does not "weld up" like steel does but it does show what the layers are doing and when. Also there are several different "camps" on how thick to cut,how many layers to have, and how thick to forge to before the quench. I have come to the point of only doing the ladder pattern in the San Mai technique, after doing some testing on the ladder pattern.
Also would like to add that Im proud to be in with a group that shares ideas so freely when the rest of the world keeps secrets.
 
Not that I believe it makes a whole lot of difference in structural integrity (IMHO, if your welds are solid, it's one piece of metal. It will be as strong as a similarly sized piece of monosteel if done right), but do you plan to produce the ladder via stock removal or via forging? If I HAD to pick which would be stronger, I'd say that forging the ladder in would be the "stronger" of the two, but not for any specific reason.

I'm interested to see what Joe Caswell, Delbert Ealy, etc have to say on this subject though.

-d
 
deker, thanks for your reply. I have done both, forge&cut in the pattern. To be more specific, my observation is the way the steel compresses and strech's and i agree that it does become one piece.
But to get a good pattern, after the final grind, the cut needs to be somewhat deep. In closing up the cuts, the middle section that is uncut, can become thin. In comparison to a random that would be stronger all the way through?
 
Impact testing I have done on various flat patterns shows no significant effects of the ladder patterning, but I could do much more testing to find if there is no effect at all. The only noticeable effect on impact strength comes when the welds run traverse instead of longitudinal, for example I have found a slightly lower impact strength in twist patterns. But mind you that this is all done with serious impact to the breaking point in order to measure a few foot pounds of difference, the chances of ever noticing the effects in a blade being used as a knife are slim to none.
 
lcf said:
deker, thanks for your reply. I have done both, forge&cut in the pattern. To be more specific, my observation is the way the steel compresses and strech's and i agree that it does become one piece.
But to get a good pattern, after the final grind, the cut needs to be somewhat deep. In closing up the cuts, the middle section that is uncut, can become thin. In comparison to a random that would be stronger all the way through?
Click to expand...

If you're concerned about the cross section of the center becoming too thin, I'd suggest starting with thicker stock. The rule of thumb that I've been told is tha you should cut/fuller your ladders to 1/3 the thickness of the stock. Consequently, make the stock 3 times as thick as the final piece should be. Eg. for 1/8" final thickness, start at 3/8" and cut/forge your ladder 1/8" deep.

-d
 
Kevin, in your testing and work on heat treating do you see any advantage or disadvantage in the number of layers. IE. the higher number of layers increases the time, increases the carbon loss??
deker, thanks for confirming the 1/3 thickness, that is where im at at this point.
 
The variables are out of sight when dealing with these materials so it is very hard to say anything definitively but depending upon the steel mix the higher the layer count the more homogeneous the behavior. Carbon loss and benefits of more foldig also bring into the play the mass of the billet and number of starting layers. Starting with fewer yet very thick layers allows for more compression and homogenizing with less loss of overall carbon.
 
I have not done any serious testing with traditional ladder pattern, I favored twist patterns for a long time because there is less material loss. My intuition is that there would be no serious issues with ladder pattern at all. My experience is that structural issues only become an issue with "last welds" This refers to composite patterns like turkish and some "mosiac" patterns that involve several bars being welded together with minimal compression or deformation after the weld. In random or ladder pattern this weld is in the center of the billet (at least it is the way I do it) and is compress alot and therefore has the time to be welded soundly with no problems. I am not talking about any flawed welds here. It takes a combination of temperature and pressure to insure the strongest weld grain boundries. I am also specifically address the comparison of one pattern to another using the exact same mix of materials. This is also why you must choose your steel mixes very carefully, the traditional idea of hard and soft layers of steel in a damascus is one to be avoided. The strongest damascus blade is on in which, when broken shows no pattern at all only the crystaline structure of the steel. 1095 and l-6 is a good example of this, 1095 is a very fast quench steel and l-6 is a slow quench, in fact its air-hardening in thin sections. If you quench a damascus made of thes two steels for hardening the 1095 you will microfracture the l-6 and have a blade that will be weakened. If you quench for the l-6 then you will wind up with soft layers of 1095 that won't cut.
In this modern world with lots of steel tools around there is little reason that a knife has to do more than cut, and the difference in well-made damascus patterns of compatable steels may not be easily measurable. That being said there are still a very few instances where this is not the case, like a combat knife actually use in the field, or other field exercises where a particular knife is your only available tool, then I personally would choose a random, ladder or twist pattern over more complex patterns for my own peace of mind
Thanks,
Del
 
Del, thanks for the good input on the entire thread. In the combination of 1095 and l6 I agree (sadly due to first hand experience) that 1095 and l6 are far apart in the HT. The two different steels will sometimes delaminate on the grind area/ where thick meets thin. I am currently useing o1 l6 and have had exellent results, in cutting, edgeholding, and looks!
Thanks to Kevin Cashen for shareing his combo!!!
But I do have alot of 1095 left. Any suguestions for a good match to this? Or should 1095 be used all on its own due to the HT that it requires?
 
1095 works well with 15n20 after I got into it seriously that was my favorite mix, I still think its a good mix, but I am using O-1 & L-6 now too.
Thanks,
Del
 
lcf said:
delbert ealy, what did you use to etch your 1095/15n20 mix. and how were the colors compared to o1-l6? how many:grumpy:
times in the acid? For some reason 1095 doesn't work well with ferric for me?
thanks, lcf.http://www.bladeforums.com/forums/images/smilies/grumpy.gif
:grumpy:
Click to expand...

Just out of curiosity, what's not working well with the 1095? You're not likely to get a very dark color with 1095 due to the relatively low Mn content (0.30-0.50%). Mn (and heat treatment) determine much of the darkness of the etch. This explains why folks like the 1084 from Aldo (0.90% Mn) and O-1 (1.00%-1.40% Mn) for damascus.

As for mechanics of the etching process, here's what I do:

- Finish the steel to 600 grit or so
- Buff to a nice shine
- Clean with acetone (don't touch areas to be etched after this!)
- Hang in 3:1 Water:FeCl mix for 10 minutes
- Remove from etch
- Neutralize with Windex
- Rinse with water while rubbing with 000 steel wool to remove surface oxidation
- Repeat from step 3 until the depth of etch you want is achieved (I tend to etch 5-6 times)

If you want to keep the nice dark etch on the simple carbon steel (1084/1095/etc) flush the piece with acetone immediately after removal from the last etching. After that dries, neutralize with Windex and rinse with clear water. Then, take some 2000 grit wet/dry paper and wrap it around a hard backer (I use wood w/ leather glued to it) and LIGHTLY sand the highs back to a nice shine.

-d
 
Icf,
Thanks,
The reason you don't get the best colors with the 1095 is that it does not contain very much manganese, the element that seems to have a marked effect on the darkness of the steel. With 1095/15n20 you get a dark grey/light grey and with O-1/L-6 you get a nice black/silver. How many times in the acid bath depends mostly on the depth of the etch, which I usually judge by what I'm making. 10 min. for most of my knives, but a knife that will se hard or serious use I might go 20 min. Axes may get etched for 30-45 min and the same with hammers.
 
Deker thanks for the list of steps that you use. I'm at the same, until the acetone step, for the cleaning and the final rinse,> Deker wrote:
If you want to keep the nice dark etch on the simple carbon steel (1084/1095/etc) flush the piece with acetone immediately after removal from the last etching. After that dries, neutralize with Windex and rinse with clear water. Then, take some 2000 grit wet/dry paper and wrap it around a hard backer (I use wood w/ leather glued to it) and LIGHTLY sand the highs back to a nice shine. I'll try this soon thanks. lcf.
 
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