Wrought iron is made from pig iron. The pig iron is remelted in a
so-called puddling furnace by charging about half a ton at one time
into the furnace. While in a molten state it is stirred up with large
iron hooks by the puddler. It is kept boiling so as to expose every
part of the iron bath to the action of the flame in order to burn out
the carbon. The other impurities will separate from the iron and run
out of the furnace as slag.
The temperature in the puddling furnace is high enough to melt pig iron
but not high enough to keep wrought iron in a liquid state. So, as soon
as the small particles of iron become purified the partially congealed
portion forms a spongy mass, in which small globules of iron ore are
in a semi-plastic state. These are gathered up by the puddler and his
helper and are formed into a ball on the bottom of the furnace by means
of long rabble bars used for this purpose. The ball is about 150 to 200
pounds in weight. These lumps of iron are taken to a large hammer or
squeezer.
There they are shaped into long blooms to fit the rolls. They are taken
right from the squeezer to the rolling mill and rolled out into bars
4 ins. or 5 ins. wide and 3/4 in. thick. These bars are called muck
bars owing to their spongy-like appearance and the large quantity of
cinders which they contain. The muck bars are now cut into lengths of
3 ft. and 4 ft. and are piled on top of each other in blocks of 200
lbs. The blocks are put into a heating furnace and heated to a welding
heat. While at this heat they are put through the rolls, thus welding
the whole mass together, at the same time reducing the pile to sizes
required by the market. When cold these are cut into lengths for use.
This is the iron used in most blacksmiths' shops.