IRON FROM LAKE ORE

Front Page | Exhibitions | Möhkö Ironworks 1849-1908 | Iron from lake ore | 

Möhkö Ironworks area | Möhkö for children |  Links

 

     IRON FROM LAKE ORE

IRON SMELTING SHOWS   | PIG HUT  | LAKE ORE   | CALCINATION   
REDUCTION   | REFINEMENT   | FORGING

---

 

IRON SMELTING SHOWS

A hundred years old way of manufacturing iron has been revived at Möhkö ironworks. Iron was made in a pig hut in a rustic manner. The first pig hut irons were smelted in the summer of 2002. There are several iron smelting shows at ironworks in the summertime.

PIG HUT

The building of Möhkö’s pig hut has been done according to the instructions by Carl Rinman from 1794. Pig hut is an iron manufacturing method, which was industrially used until the late 1800. 

Ingot iron was made in the pig hut. Iron produced as solid does not dissolve in itself neither carbon or embrittling impurities. Carbon needed for the reduction of iron is produced by burning pine logs in the pig hut. 

LAKE ORE

In Finland, the rustic manner of producing iron was based on the use of lake and bog ores. The lakes in Eastern Finland were very rich in ore. The ore was 2-5 metres deep in the lake, from where it was lifted by nets in summer and from the top of the ice in winter. 

Lake ore is produced when iron hydroxide in the ground water drains through the gravel course and coagulates around a granulate of stone or the like. Lake ore is called pea ore, money ore or rusk ore according to its appearance. Its iron content is 20-50%.

At its best,15 000 tons of lake ore were lifted at Möhkö ironworks in the late 1800. They were used to produce iron in the blast furnace. Koitere lake was one the richest in ore. For rustic iron lake ore was lifted in small amounts as needed.

CALCINATION

Lake ore has a lot of humidity and impurities. They were removed by burning the lake ore over a fire before putting it into the pig hut. This operation was called calcination.

Calcination fire was built by layering lake ore on top of pine logs. When ready, the composition was set on fire. 

REDUCTION

Iron is reduced from lake ore by putting lake ore on top of the burning ember of the pig hut  and blowing air by bellows to the stove on the bottom of the pig hut. As oxygen in the air reacts with the burning coals, coal gas is produced and it reduces the lake ore. One regulates the amount of air blowed by observing the slag coming from the pig hut and lake ore is added on the ember as needed. 

The reduction of iron from lake ore takes place in the hottest zone of the stove. Brood in ore together with iron oxide forms slag, which is smelted and heaped on the stove. The produced sponge iron particles form a bar of the sponge iron lump inside the smelted slag. During reduction, so much slag is produced that it has to be run off through a hole made in the lateral wall of the stove.

When the coals in the pig hut have decreased to the level of the stove, blowing is stopped and sponge iron is removed through the orifice of the pig hut or by breaking the lateral wall of the stove.

REFINEMENT

Pieces of sponge iron contain a lot of slag. They must purified by forging before they are forged into products. The produced sponge iron is chopped and seal forged. If one wishes to make cold steel or tools from the iron produced in the pig hut the products must be coaled and quenched.   

FORGING

Iron is forged into different products in the smithy.  Blacksmith Urpo Parviainen specialises in knives, which have also been made of Möhkö’s lake ore iron. There are forging shows in the smithy of Möhkö ironworks.    

Möhkön ruukki, Möhköntie 209, 82980 Möhkö
tel. +358(0)13 844 111 or + 358(0)50 342 8825
email: mohkoruukki(at)ilomantsi.fi
www.mohkonruukki.fi