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发表于 2008-11-30 13:49
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另外一种....
In this article I will discuss the construction and operation of a steel refining furnace similar to those used in the traditional process. This steel was used to form the famous Japanese sword. The tatara is constructed in three layers: foundation, furnace body, and chimney. Operation of the furnace requires pre-heating, refining, and burndown stages. Construction of the tatara is shown in figures 1.
MATERIAL NEEDED
88 High temperature fire bricks
32 Half bricks
High temperature mortar
10 Concrete blocks
Steel plate 50 cm X 70 cm (minimum)
Steel air pipes 2.5 - 4 cm inside diameter minimum 1m long 2 thermocouples type Pt/Pt-13%Rh
Steel chimney 25 cm inside diameter 75 cm high 100 Kg pine charcoal
20 Kg iron sand with less than 9% titanium (Ti) 10 leters grass
Large vacuum cleaner with exhaust connection Oxygen (O2) sensor (optional)
Variable voltage transformer or other means of adjusting air supply
FURNACE CONSTRUCTION
Foundation of the tatara is constructed to provide thermal insulation as well as a moisture barrier. Size of the foundation in this example is 2 bricks wide, 3 bricks deep and 5 brick layers high. The base of the tatara foundation is a steel plate moisture barrier. Over this a layer of concrete blocks is placed for insulation. Four layers of fire brick are laid with high temperature (refractory) mortar to complete the foundation. The body of the furnace is 2 bricks wide, 3 bricks deep, and 12??? layers high. The front portion of the furnace is made so that it can be taken down quickly after the firing without destroying the entire furnace. This requires the use of half bricks for the sides. Four??? layers of brick are put down with mortar. An air supply pipe is inserted horizontally from the front of the furnace about 1/3 of the way into the furnace. Size of the pipe should be between 2.5 cm (1 inch) and 4 cm (1.75 inch) to provide enough air. Position of the pipe is adjusted to assure that the flames of the furnace are centered when the furnace is in use. A high temperature clay or furnace cement is used to coat the air supply pipe and prevent melting. Thermocouple wire - type Pt/Pt-13%Rh - is placed in the furnace at the top of the air pipe for monitoring of the furnace performance as will be described later. An Oxygen sensor can be placed in the furnace at this time Four??? layers of brick are added to the furnace and a second air supply pipe is placed 1/3 of the way into the furnace - this time from the back. This pipe is also coated with the high temperature clay. A second Pt/Pt-13%Rh is attached to the top of the pipe. The 4??? final layers of brick are laid in place to finish the furnace. At least on day must be allowed for the mortar in the furnace to harden. A steel chimney 75?? cm high and 25 cm diameter will be placed atop the furnace during operation. A (shop) vacuum cleaner exhaust is used to supply air to the furnace. The volume of air is adjusted using a variable transformer. A voltmeter is used to make initial adjustments to the airflow rate until furnace temperature can be monitored. Voltages for the vacuum cleaner are given as a percentage (%) of the maximum. That is a value of 30 % is equilivent to 30 volts for a 100 volt vacuum and 66 volts for a 220 volt unit.
FURNACE OPERATION
The initial firing of the furnace is used to complete the drying, pre-heat the furnace, and produce a layer of ash at the bottom. The furnace is filled up to a level just above the lower air supply and lit. Air is supplied using the lower air pipe with the vacuum cleaner run at about 30%. The fuel is allowed to burn completely to an ash. Pine charcoal is used to fuel the furnace because of its density, burning time, and temperature. The charcoal is cut into 5 cm (2 inch) chunks for the firing. Smaller pieces can be used under the lower air supply pipe. Use of charcoal pieces less than 5 cm as fuel above the air supply will prevent furnace exhaust flames from going up the chimney. Pieces larger than 5 cm will not have enough burning surface area to produce the high temperatures needed. Iron sand for the furnace should be contain less than 9% titanium (Ti) by weight. Higher concentrations than this will require higher furnace temperatures to melt the slag produced by the process and additional silicon sand (Si) must be added to reduce slag melt temperature. Ocean beach iron sand should be washed prior to use to remove chlorine (Cl) which will contaminate the steel. The refining operation is started by filling the furnace up to a level just above the first air supply and lighting it. Turn on the air supply voltage to 30%. When the fire becomes stable add charcoal a little at a time until it reaches the top of the furnace. Place the chimney on top of the furnace and seal around the outside with high temperature mortar. Increase the air supply to maximum voltage and continue adding charcoal slowly up to the top of the chimney. Check it make sure that flames can be seen at the top of the chimney. Verify that the temperature at the lower air pipe is now above 1000 C. One kilogram (2 pounds) of iron sand is now spread over the top of the charcoal and the furnace is allowed to burn down about 10 cm (4 inches). This should take about 10 minutes. Refill the chimney with charcoal and add another 1 kg of iron sand. Repeat this procedure until 5 kg of iron sand is used. This initial charge of iron sand will produce mostly slag to be removed later. Move the air supply from the lower pipe to the upper pipe after the 5 kg of iron sand is added. Remove the lower air supply pipe from the furnace and plug the hole (temporarily) with clay. Changing to the upper air supply pipe will reduce the oxygen (O2) low in the furnace and de-oxidize (reduce) the iron sand to iron and steel. Continue adding 1 kg of iron sand and charcoal until about 15 kg of iron sand is consumed. Remove the clay plug from the lower air supply hole and remove the slag. Do not turn off the air. An iron bar is used to scrape out the slag. Once this is completed re-plug the hole and continue the operation until at least 20 kg of iron sand is used up. Allow at least 15 minutes for the last of the iron sand to be reduced. Again remove the slang and plug the hole. Continue to run the air supply until the charcoal is burned down to the bottom of the chimney. An iron bar can be used to check the level. Remove the chimney from the furnace and cover the burning charcoal with grass. The grass is intended to prevent the steel from oxidizing. Reduce the air supply to 50%??? and allow the charcoal to burn down an additional 10 cm. Remove two layers of the brick front of the furnace. When the charcoal has burned below the air supply turn the air off and remove the hose. Wait 20 minutes to allow the furnace to cool a little. A (cracking??) sound coming from the furnace is a signal that the steel making has succeeded. Remove the remaining bricks at the front of the furnace after about 20 minutes. A red hot block of steel should be seen in the center of the furnace. The steel is removed with an iron bar and scoop.
[ 本帖最后由 草摩神威 于 2008-11-30 14:26 编辑 ] |
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发表于 2008-11-30 08:50
