.Name the fuels used in hand forging
. qualities of a good forge fire
. the correct method of placing stock in fire
For heating metals to be forged, different types of fuels are used. Fuels are combustible materials capable of generating heat energy.
Forge furnaces are fired with petroleum gas, producer gas, oil, coal and charcoal.
For hand forging, the hearths are heated with soild fuels like coal or charcoal with low sulphur content.
For heating tools steels charcoal is preferred as the fire burns more evenly when charcoal is used.
Heating and metal stock
For efficient heating, the way in which the fire is maintained is important.
Thr fire which is maintained on the top surface will be thin and not suitable for heating the metal to carry out forging.
The fire should come from deep in the hearth.
The forge fire should be maintained clean i.e, free from ash, clinkers and dust.
Clinkers is formed as the coke burns. This settles down at the bottom of the hearth and solidifies. Accumulation of clinker will obstruct the tuyere nozzle.
Placing the stock
If the stock is kept on the top of the fire, it will be heated underneath and the top surface will not get heated sufficiently as it is exposed to the atmosphere, and hence gets cooled.
If the work is placed too low in the fire and very near to the tuyere, the cold air may cool one side of the work. This will also lead to oxidation of the steel surface.
The correct position of the stock in the forge fire will be as follows.
The stock is placed away from the tuyere ensuring that the cold air does not fall directly on the stock.
The top surface of the work shoul have a thick layer of fuel.
The work should be covered on all sides with the fuel coal charcol etc.
Forging temparatures
While forging the metal should be heated to temparature when it becomes plastic. The forging temparature for steel depends on its carbon content and the alloying elements.
Heating temparature of steel
The heating temparature for steel are
-low carbon steel 1300°c
-high carbon steel 1100°c
-low alloy steel 1100°c
(Only steel with carbon content up to 1.7% is forgeable )
If the forging is carried out at very low temaprature, the work may develop cracks or will be work hardened. If heated excessively, it will lead to scaling on the outer layers.
A work to be forged may require several heating to complete the forging. But it is always better however to complete the work with the minimum number of heatings.
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