FROM DUST TO EDGE
My version of East meets West
By Jesus Hernandez
 

Hosted by BLADESIGN
 

“From Dust to Edge” is the documentation of a long journey in the efforts of making a blade out of homemade steel. My interest in blades started with the legendary Japanese katana and as a result of wanting to learn more about how they were made I ended up becoming a bladesmith. I combined the traditional Japanese techniques and the current knowledge of the Western smith in this pictorial representation. The project will be divided in several sections. It is primarily a visual description through photographs.

1.- The TATARA project: This will be the first section and will describe the making and running of a tatara-like smelter.
2.- Forging TAMAHAGANE: The second part will deal with the processing of the KERA or BLOOM, including compacting and forming into a bar of steel.
3.- OROSHIGANE: Manipulating the carbon content of the steel to create different quality bars of steel.
4.- Forge-welding and folding of the different steel bars to create a billet and forging it into a SUNOBE, then into a blade.
5.- Heat treat: Clay-coating, hardening and tempering of the blade.
6.- Polishing, fittings and presentation: Description of one of the many hybrid methods of polishing, making of a habaki and shirasaya and final assembly.

PART ONE: TATARA PROJECT

This will describe the building and running of a tatara-like smelter. Operating the tatara alone proved to be exhausting and very gratifying in the end when steel was recovered from the bottom of the smelter.

Charcoal is the fuel, the heat source and the source of carbon for the smelter. Charcoal has to be chopped to a specific size for the operation to run smoothly. I chopped mine during the days before the run in little chunks about a cubic inch or less. The bore of the furnace is 11 inches so that seems to be the right size for the charcoal: 8-10% of the inner diameter of the furnace.

The ore is from a ceramic supply place. The name of this particular compound is Spanish Red which I thought was quite appropriate for me having been born in Spain. It is a light dust that stains everything almost permanently red and contains 80% hematite. Half way into the run I realized that the field where I was working had turned red from quite a bit of the ore dust being blown out of the furnace.

The furnace design is based on the shell of a water heater. It has been cut in three sections for easier assembly and disassembly. Here is a diagram.

The parts were cast with refractory made mostly of sand and cement with an inner lining of high temperature furnace cement. It held up pretty well to the heat but crumbled at the time of taking it apart.

The tuyeres were made of simple black iron pipe fittings. They stayed cool by the constant air flow through them and since they don’t protrude in the inner chamber they don’t become melted away.

Here is an additional picture of the bottom part of the assembly after pouring the refractory and letting it dry. It is shaped like a funnel as in the Japanese tatara

Here is the setup with the smelter put together and starting the pre-heat. It is 7:30 AM and I am using a gas burner for the first hour.

At this point I have covered the smelter in refractory blanket to increase the thermal efficiency. That actually worked really well. The temperature measured at the bottom of the top third of the smelter reads 1000 degrees F.

I used a home made manometer to gauge the air flow pressure. I was hoping that it will identify leaks (pressure drop) and show if the tuyeres were blocked (pressure increase). It was helpful to detect leaks but not to detect obstruction of the tuyeres. When you have 4 tuyeres if one stays open the pressure reading does not seem to change. On the other hand it was very helpful in setting the air flow level from the shop vac. I used a variable voltage knob from a broken halogen lamp to regulate the power to the shop vac. The manometer was indirectly reading the amount of air flow very accurately. The air flow was kept at about 15%.

Here it is running on charcoal now and with the first charge in. It is 9:00 AM now. The temperature reads 1800 degrees F and it remained there or above for most part of the run. I did not dare to read the temperature in the bottom third of the smelter (around the tuyeres). It would have melted the probe. My charges started at 1/2 kilogram of ore and half the way through the run I went up to 1.25 kilograms. I was using about 2 kilograms of charcoal per charge.

The manometer is indicating the change in pressure during the run.

At 10:30 AM I heard bubbling at the tuyeres. From that point on I had to work hard on taping the arches and keeping the tuyeres open and trying to keep up with the schedule of charges. I lost several pounds in sweat during the day. A big design mistake was obvious at this point: the tuyeres were set too low and the build up of the bloom and the slag chocked the reaction too soon. The first time I tapped the arches I only had a little bit of slag coming out but I don't think I was too aggressive clearing up a path for the slag to come out. When I did poke a good hole in the arches I had quite a bit of slag coming out pretty much on its own until it cool down and clogged the arch.

Even at this point 2 hours into the run there are lots of sparks coming out of the tap arches every time I open them. I took that as a good sign that carbon was being taken up by the iron and kept going for one more hour when I couldn't keep up with all the different tasks and I was exhausted.

So I let it burn down after the last charge at 12:00 PM and started to take it apart. The top third of the smelter lift off easily but the refractory crumble to pieces on the rims. It held very well in the inner chamber. So much from trying to have a system that was reusable! The parts will need to be repaired each time.

The middle third has now been removed as well as the tuyeres. I went to have lunch and came back after one hour to see what I had at the bottom.

After cleaning up the charcoal a little bloom is peaking inside. It looked like Mount Fuji covered in snow.

After cleaning up all the debris and removing the bloom it turned out that the walls held up pretty well.

Here is the bloom. A total of 5 pounds of steel were consolidated and lots of smaller chunks were recuperated with tongs or with a magnet

The spark test looked pretty good.

After polishing the surface and etching a bit you can see all these beautiful dendrites. This is an indication that the core of the bloom had reached liquidus.

Summary of the process:
Preheat took one hour with the gas burner and reached a temperature of 1000 degrees F which was enough to ignite the charcoal immediately. After that I used 25# of charcoal and reached 1800 degrees F in half an hour.
The total time spend putting charges in was 3 hours. I used 80# of charcoal and 30# of ore over 17 charges.
The bloom weighted 5# for the consolidated section and about 10# more of smaller chunks.
Total recovery was about 15# of steel.

TO PART TWO