MANGANESE STEEL.
The glassy hardness, brittleness, and friability of ferro-manganese and of spiegel-eisen are well known; these are products of the blast-furnace, and the manganese ranges all the way from say 10% up to 80%.
Steel containing from 1% to 3% of manganese is about as brittle and almost as unworkable as spiegel-eisen, and a fair deduction would be that manganese above very small limits will not form any useful alloy with iron. Many a general law of nature has been based upon much more meagre data and has been announced with a great flourish of trumpets; such discoveries are usually heard of no more after the first blare has died away.
R. A. Hadfield, of Sheffield, England, is an inquirer who wants to know, and who is willing to travel the whole road in order to find out. Hadfield discovered that an alloy of iron and manganese containing from 7% to 20% of manganese was a compound possessing many remarkable properties. This alloy is now known as manganese steel.
Manganese steel is both hard and tough to a degree not found in any other metal or alloy.
It is so hard and strong that it cannot be machined with the best of tools made of the finest steel. Castings made of it may be battered into all sorts of shapes as completely as if they were made of the mildest dead-soft steel; still they are too hard to be machined.
The ordinary hardening process toughens this steel instead of hardening it to brittleness.
This steel is non-magnetic, and this property alone would give it exceedingly great value if the steel could only be worked into the required shapes.
Up to this time all attempts to anneal this steel have failed, and this persistent hardness is the best proof that manganese is the real hardener in self-hardened steel. So far carbon and manganese have not been separated in this steel or in any other. Persistent attempts have been made to produce manganese steel low in carbon, but all have been failures, because any operation that burned out the carbon took the manganese with it. The hope was that a non-magnetic alloy might be produced that would be soft enough to work. This may yet be accomplished, and if it should be another great step in the arts will have been taken.
Hard, tough, strong, non-magnetic—what great things may not come out of this when it has been worked out finally?
Since this was written carbonless manganese has been produced which is claimed to contain 98% + of manganese and no carbon, but at present it is sold at $1 per pound. If it can be produced more cheaply, it may lead to a workable non-magnetic alloy of iron and manganese which may prove to be of great value to electricians and to watchmakers.
The uses of manganese steel are large and growing, and it must be regarded as having an established and a prominent place.
It has been stated that in self-hardened steel and in manganese steel manganese is the hardener; it should be borne in mind that carbon is always present, that it is the one great hardener, but its hardening property in the absence of manganese depends directly upon rapidity of cooling. By rapid cooling steel containing carbon is made harder than glass, and by slow cooling it may be made softer and more ductile than ordinary wrought iron.
Self-hardened steel may be annealed so that it can be machined, but it is by no means as soft and ductile as well-annealed carbon steel. Manganese steel has not been annealed at all; it cannot be annealed by any of the well-known annealing processes; some new way of doing it must be discovered. Therefore it is proper to say that the peculiar hardening properties of these two steels are due to manganese.