Traditionally oroshigane is the name of two different processes that take place at the Japanese smithy in the preparation of the steel for welding and it also has extended its meaning to the steel made in this way. Since not all the steel that comes from the tatara has the ideal carbon content (TAMAHAGANE) the Japanese smith will either by reduction or oxidation alter the carbon content of those pieces of steel that have either too little or too much carbon and adjust it to the desired level to make either shingane (core steel) or kawagane (jacket steel).

I now have the results of the chemical analysis of the steel:

I have no idea where all the extra stuff came from. I was expecting high Si and Al from the erosion of the walls of the smelter but all the other impurities must have come from that unknown 20% in the composition of my ore.

I have modified the traditional process and adjusted it to better suit my needs. At this point I have made several bars of steel that I have ranked according to estimated carbon content or whether they came from the larger bloom (kera) or from other chunks of steel from the smelter. The bars will be stacked up together alternating according to carbon content to hopefully create some contrast in the final billet.

By weight I have about 7# of steel after I processed all the chunks.

I am going to divide the bars in half and make two separate billets. The first billet will used primarily to make two tantos that I will use to experiment with the heat treating process. Here is a picture of the bars bound with wire. I did not tack-weld with the MIG so as to no introduce any "foreign" steel. The wires will be removed as soon as I get the distal end of the bars to weld. They are there just to hold the bars in place temporarily and get the welds started.

In to the forge it goes.

Getting hotter.

Flipped on the side to even out the heat.

By this picture I had already made the first welding pass and removed the wire and did a second pass to consolidate the bar and draw it out a bit.

I asked my wife the help take some pictures while I flatten the bar and draw it out further so you can see the process.

First I used the press to speed up the drawing out. Then I hammer it straight.

And it is back in the forge to get hot enough to split it in the middle

So that I can put the first fold into it.

Like so.

I decided to add flux at this point to ensure that the welds go well.

Back in the forge to get hot for welding.

At this point it has reached the right temperature and I am taking the bar out of the forge and to the press for welding. Sparks are flying off the steel. Maybe that was a little too hot but better safe than sorry.

After that you do it again and again, as many times as you want. For me it was 5 folds. I noticed that by the second fold the steel was behaving like regular factory steel and needed higher psi to weld and definitively flux to complete the welds.

The last step was to draw out the bar.

The bar is now split in two halves to make the two tantos.

I polished and etched one section of the bar to see the grain. The face of the bar will have itame grain (random pattern). My first impression is that the pattern is very subtle. Very little contrast. The color of the steel is different from refinery steel. It looks grey-blueish. Similar to what I have seen in blades from Japan made during the koto period.

The side of the bar will have a straight laminate pattern (masame). Again very subtle and difficult to photograph.

FINAL SCORES:

I started with 7# of steel bars. I separated 3 and 1/2 pounds for this first billet and ended up with a bar of steel weighing 2.2#. So that means I lost about 40% of the steel in the folding-welding process. The final dimensions of the bar are 1 inch wide by 1/2 inch thick by 17 inches long.

Next step would be forging of a sunobe and the rough forging of a tanto. Click here.