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Introduction to the archaeometallurgy of iron
Donald B. Wagner

Crucible smelting in Yining,
Xinjiang, in 1872

Translated from J. H. Langer’s German translation of an article in Russian by Davidov, a Russian mining engineer.

The article describes the geology and the mining industry of the Khanate of Kuldza, the region around present Gulja / Yining 伊宁, Ili Kazakh Autonomous Prefecture 伊犁哈萨克自治州, Xinjiang. The excerpt translated here (Langer 1872: 397–398) describes the iron smelting technology in use there.

Translation

The ore is limonite and some hematite. ... This is transported to the ironworks in small four-wheeled wagons pulled by oxen or horses. The distance from the mine to the smelting works is ¼–3 verstas, so transport is not a major expense. [1 versta = 1.07 km.]

Figure 10. Iron smelting furnace.

Figure 11. Wooden blower.

In this region the ore is roasted in ovens or pits filled with coal and pieces of ore 2–3 cubic inches [30–50 ml] in size. The roasted ore is charged in the smelting furnace shown in Figure 10. The furnace is constructed of unburned bricks, mortared with clay. The length of the furnace is 6½ arshin [4.6 m], the breadth 3 arshin [2.1 m], and the height 2½ arshin [1.5 m]. On one of the short sides (i.e. end-walls) are placed two openings for the blast. The blast is supplied by a wooden blower like that shown in Figure 11. It consists of a wooden box with slits and flaps in which a cross-board moves horizontally. The length of the blower is 1 arshin [71 cm], the height 12 vershok [53 cm], and the breadth 10 vershok [44 cm]. Each furnace has two such blowers, and each is worked by two men.

Smelting is carried out as follows. On the bottom of the furnace a layer of brushwood and wood chips is laid, followed by a layer of coal 1½ arshin [106 cm] thick. On this fuel are placed crucibles of fireclay. Each crucible has the form of a truncated cone with diameters 4 and 3 vershok [18 and 13 cm] and holds ½ cubic foot [14 litres] of ore. The crucibles are placed in the furnace with the broader end downward. The number of these is most often 250 per furnace run.

After the crucibles have been placed in the furnace they are filled with broken-up ore. Coal is filled in the interstices between crucibles and between the furnace wall and the crucibles. The wood underlay is ignited through an opening and the blowers are set in motion. The furnace campaign generally lasts two to three days, during which eight men, divided into two teams, work the blowers.

With regard to the change of shifts there is a curious custom. Each team, when they begin their shift, lights a candle or a piece of pinewood of a certain size. They work until this burns out, whereafter the other team takes over.

In the course of the smelt the smelting master shakes the crucibles using tongs with wooden grips. The purpose of this is to prevent the ore from sticking to the side of the crucible. As soon as the ore is smelted, the crucibles are removed, and this is done in such a way that the smelted mass sinks and remains on the layer of coal. Blowing continues while this is being done, in fact until all of the coal is burned away. Then the blowers are removed, the other end-wall is broken down, and the glowing pieces of metal are thrown into a water-filled ditch for cooling.

The reason for using bottomless crucibles appears to be that small, easily worked, pieces of metal are desired, rather than the entire contents of a crucible in one compact mass, which would be difficult to break up. The larger pieces are broken up as small as possible with sledgehammers, and the whole production sorted into good and inferior pieces.

The inferior pieces consist most often of incompletely reduced ore, pieces of coke, and black iron-rich slag.

Pieces considered to be good are, depending on the extent of smelting, either wrought iron or pig iron.

Figures 12–13. Chafery.

In the further processing of the wrought iron the Kalmyks use the furnace (or rather, chafery [? Schweissherd, ‘welding hearth’]) shown in Figures 12 and 13. In this furnace the blast comes from above, and an opening for slag drainage is placed directly below. It is filled with coal to a certain height, the iron is spread on this, the coal is ignited, and blast is supplied until the pieces of iron begin to glow strongly. From time to time a piece is taken out and its malleability is tested. If it is judged inferior it is returned to the furnace. This continues until an acceptable product is obtained.

Casting of the pig iron from the smelt is done in Kuldza using a round furnace with a wooden blower. The pig iron is charged in a crucible of fireclay lined with coal. Four to five such crucibles, each with a volume of 200 cubic inches [3 litres], are placed in one furnace. The spaces between the individual crucibles and the furnace wall are filled with coal.

The blast is started and the ignited coal comes to glow brightly. After a short time the crucibles are full of molten cast iron. This is cast in moulds made of sand mixed with clay.

If larger pieces are to be cast, for which the contents of one crucible are not sufficient, the contents of several crucibles are poured into a larger crucible in the form of a kettle, made of fireclay, with an opening closed with a clay plug. The cast iron in the individual castings is most often impure, containing blowholes.

Concerning what can be learned of the technical aspects and profitability of this branch of industry, the following can be gleaned from the uncertain and unreliable data which is available.

For iron smelting the requirement per furnace is 450 pood [7,300 kg] of coal for a charge of 250 pood [4,100 kg] of ore, given that in general one pood [16.4 kg] of ore is charged in each crucible. These 250 pood of ore give, according to the smelting master, 25–75 pood [410–1,230 kg] of kritz-iron (the total amount of wrought iron and pig iron). Taking the average output of one furnace to be 50 pood, the coal requirement is 5 pood per pood of ore. The reworking of the kritz-iron produces from one pood [16.4 kg] about 30 funt [12.8 kg] of iron, consuming 1.5 pood [24.6 kg] of coal. Thus the requirements to produce one pood of iron are 14–15 pood of coal and 7–7½ pood of ore. These figures apply in general to wrought iron as well as cast iron and iron castings.

The division of labour is as follows. Two or three masters form together a company and put ten men to work extracting ore, roasting and smelting, supplying coal, making crucibles, and in fact all of the tasks involved in the production of the raw iron (kritz-iron).

The processing of the raw iron to wrought iron and cast iron is done by the masters alone, assisted by one or two workers.

One furnace runs two campaigns per month, i.e. gives 100 pood [1,640 kg], which after processing gives ca. 75 pood [1,230 kg] of wrought and cast iron.

The workers’ pay is the same as that of the coal miners, so that the support of a team of ten Kalmyk men amounts to 16 rubles. Assuming production of 75 pood, the calculation is as follows.

Labour 16 rubles
Coal 12 rubles
        (15 pood per 1 pood iron @ 1 kopek [0.01 ruble]

This gives an outlay of 28 rubles, or 38 kopeks per pood of iron [2.3 kopeks/kg].

In Kuldza iron costs 80 kopeks per pood, so that the masters receive 31½ rubles. From this must be deducted the price of the sheep to be sacrificed before each smelt and various smaller outlays.

References

Davidov, — (mining engineer). 1872. ‘O mineral’nyikh bogatstvakh Kul’dzhi i o sposobakh razrabotki ikh tuzemtsami’ (On the mineral resources of Kul’dzhi and on the indigenous methods of exploiting them). Gornyii Zhurnal (St. Petersburg), 2: 193–212 + ill.

Langer, J. H. 1872. ‘Montanindustrie an der Grenze Chinas’. Berg- und Hüttenmännischen Zeitung, 31: 394–400 + Taf. 11. ‘Aus dem Russ. Bergjournal nach Davidov von J. H. Langer, k. k. Hüttenbeamter in Przibram.’

 

Davidov’s original Figure 5, corresponding to Langer’s Figures 12–13.

Davidov’s original Figures 3–4, corresponding to Langer’s Figures 10–11.


Last edited by DBW 2 March 2023