Thursday, April 05, 2007

Pattern Welding Samples

Right now I am undertaking a couple of commissions for pattern welded blades. I'm taking the opportunity to gather footage of the process for another DVD that details the process of layered steels.

A direct scan - about half life size.

Each of these bars started as roughly the same materials. Primarily mix of mild steel and a low nickel alloy called L6, along with a layer of high carbon steel. The L6 simulates the use of meteor material in my historic blades. (L6 is .5 % nickel and a middle level .5% carbon - meterorites are closer to 5 % Ni, but with no carbon). The inital stacks were at 13 layers, these have been welded and folded to four to give a 52 layer bar.

Part of that bar is drawn and cut in two. A piece of high carbon steel is stacked between these and the whole welded to form the cutting edge (at 105 layers) This process was done for both of the billets you see. When forged to a blade and polished, this hard carbon steel is exposed to form a durable cutting edge.

Next the remainder of each billet was pulled to a long octagon and twisted. On the first (top) bar, there was enough to make three twisted bars. On the second (lower) just enough for two rods. These were then squared and welded to the prepared cutting edges. This gives a total count of 261 for the top bar and 209 for the bottom one.

The difference in colour you see is because the pieces were lightly etched in two different acids. The top one has been etched in nitric, which changes the relative heights of the layers, but not the colour all that much. The bottom on has been etched in ferric chloride, which mainly changes the surface colours. Note that the finished blades will be etched in BOTH - nitric to give a durable surface profile (what I call 'topographic') and the nitric after to give the dramatic colours.

Now - if you look at the lower edge of the top (3 twist) bar you will see a slice about mid way - This is marked by a triangle below the image. Now this is a welding flaw - basically a crack in the edge. Its a good 3/16 deep - too much to cut out. What I would normally do is cut the bar at this point and then make two smaller knives (should get two good 4" blades out of that stack.)

Since I required enough material for a 5 - 6 inch finished blade, I made the second bar you see below. It is a good solid weld right across, it is however not as tightly twisted a pattern.

There is always some extra distortion of the pattern - stretching it longer, that occurs during the blade forging. Ideally you want as tight a pitch to the diagonal lines as possible in the starting bar (like the top sample).

No comments:


February 15 - May 15, 2012 : Supported by a Crafts Projects - Creation and Development Grant

COPYRIGHT NOTICE - All posted text and images @ Darrell Markewitz.
No duplication, in whole or in part, is permitted without the author's expressed written permission.
For a detailed copyright statement : go HERE