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Oroshigane, Refining Bloom Iron

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This post is a record of my attempt at getting some rework done ..either to another form and/or to another carbon content. Emiliano's post on refining steel in a hearth furnace inspired me to start the process . Thank you Emiliano. 

 Maybe my expectations of the oroshigane process are too big..as I have some materials that will be difficult to work with...I may have to adjust the furnace rather than just the bottom. I have to do some reading about the role of Phosphorous in steel of varying carbon concentrations. Mark Green showed a white etch on low carbon steel ( iron ) ...in my mind I am following phosphorous in as cast ingots as an indicator ( of where the carbon is ) and it appears darker than the adjacent material ( I think ).


  Below is a picture of some of the material I have to work with , there are lots of other larger shapes I will attempt later. From top to bottom : flattened bloomery iron , bloom pieces (some getting as large as 4 inches), Failed crucible ingots, and small bloomery fragments including slag fragments.

I am trying to create a list of all the variables one might encounter in the process...it can get interesting.







Edited by Jan Ysselstein
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Looking at the first trial of Oroshigane ( see picture below ), the carbon content is higher than first thought somewhere between 1% carbon and 2 % carbon.


Todays run yielded 4 lbs of very high carbon steel  at a yield of 80% as 5 lbs of flattened bloom iron were processed. No attempt was made to sort the input of the process by carbon content. Fragments were wire brushed, cut to no larger than 2.5 inches in any direction and no thicker than 5/16 inches.,See picture below.


The bloom was attached to the furnace wall which was damaged during extracting. I will be running another 10 to 20 lbs. of bloom pieces as long as the process is still working ( some of the material to be encountered is as thick as 5/8 of an inch) . I will have to work out something to avoid breaking the furnace each run.


The possibility of using this material directly in a crucible is very likely.



Flattened bloom iron , starting material for Oroshigane.  5 lbs.

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Todays yield of 4 lbs ..very high carbon steel 1.5% carbon to 2% carbon. This bloom was quenched in water.

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The first oroshigane bloom about a week old 2.5 lbs. Very high carbon steel 1% carbon to 2% carbon. 

1 (5).jpg.

Edited by Jan Ysselstein
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  The intent is not to reprocess many pounds of already consolidated bloom iron ..I am more interested in cleaning up bloom bits and what is found in the furnace after a smelt. A few more flattened bloom runs and I will go to bits. 


  The above two runs were done in a 6" diameter crucible furnace using discarded charcoal...I was shooting myself in the foot. A new furnace is in the making having an 8" diameter inside..about 12 inches high. The shell  is made of a castable  hand me down refractory at least 20 years old ( open ). This creates a very weak material which has to be brought up to a very high temperature to gain strength. I have not done that yet. 


The shape of the second (4 lbs.)  ingot showed me I had moved it from its desired location in a preformed tray,  to the air inlet side of the furnace ( I must have used a poker and lifted the tray and all to try to get more air flow through the furnace.


  Sometime in the next four days I will try another run(s) using a slightly larger furnace ..again .5 lbs additions after each charcoal addition into an either as formed in place tray or a preformed tray.


Here are some pictures

8 inch paper tube into a 10" SS sleeve 

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The sleeve is cut to allow for expansion , a filler piece of heat treating foil was used to cover the gap.

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Normally all is held together by large diameter hose clamps...but I had a slightly larger sleeve around. The orange tube is just to form the inlet.

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The refractory is drying and the paper is burning away.



Preformed trays..I have very little experience with these, just fire clay and a little sand in the bottom works just as well. Fine charcoal works also.

1 (7).jpg

Edited by Jan Ysselstein
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IMG_0174.JPGIMG_0160.JPGHeated the furnace to a good yellow heat to firm up the chalky nature of the old castable refractory shell. I tossed in a few low carbon pieces of bloom iron and created melt #3 an 800 gram ingot with a lobe of low carbon steel attached to one side. That lobe was removed and the remaining weight of high carbon steel is about 500 grams.


Today I processed Oroshigane bloom #4 staying mostly within the guidelines suggested by Emiliano. Just short of 2000 grams ( low carbon bloom ) was put into the furnace and about 1650 grams of high carbon steel was produced. Not included in this weight are the many bits of steel lost during wire brushing.

To summarize what we have so far.

Run #1  has a low carbon center and is placed in the low carbon iron bucket.

Run#2  is a very good high carbon little bloom at about 4 lbs.

Run #3 is a 1 lb. bloom of very high carbon steel.

Run #4 Weighs about 1650 grams and is a very nice bloom of high carbon content.

We now have 3800 grams of high carbon steel made from magnetite bloom iron.



I will stop at this point as I have enough in formation (with a hands on feel) to convert some iron in the future.

When the need to convert cast iron to steel comes up... or when I have the bloom bits cleaned up...I will come back to this thread.





Edited by Jan Ysselstein
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