Guide to the construction and operation of a local type of fining hearth in Dabieshan, 1958

[The text is taken from a brochure which was published in connection with the campaign for iron production under the Great Leap Forward. It refers to the diagram here.]

Construction

Fining hearth in Dabieshan, 1958. Top and front views and a section through A. Dimensions are given in millimeters. (Tufa liantie, Zhengzhou 1958, p. 19, redrawn from a poor photocopy).

The fining hearth is made of a mixture of loess and quartz sand.  . . . Because of the violence of the fining operation the furnace opening is made of three pieces of iron.  . . . The supplementary equipment required is:

• one windbox
  
• two anvils
  
• four flat-headed hammers
  
• two pairs of long-handled tongs
  
• 3–5 iron bars, diameter 30–40 mm, length 1500–1600 mm, for fining
  
• two long-handled ladles, for removing slag
  

Operation

Operation is fairly simple: it may be divided into the following steps.

Charging. The dried hearth is charged with 7 kg of wood and 7 kg of charcoal. This is ignited, and the blast is started. Immediately 70 kg of broken-up pig iron (each piece 20–30 mm) is charged, and the furnace opening is closed. The iron is covered with a layer of powdered charcoal, and fining begins.

Fining. After about 20 minutes white flames begin to appear; this indicates that it is time to begin fining. The furnace opening is opened, and the operators begin violently stirring the iron. After about 20 minutes of fining they begin removing the iron from the furnace and hammering it.

Discharging. The fined iron is removed from the furnace with tongs and hammered to squeeze out slag and compact the iron. The complete discharging of the iron takes about 20 minutes. Generally 30–40 wrought-iron bars are produced. Finally the hearth is cleared of slag with a ladle and the cycle can begin again. Each cycle requires about 60 minutes.