La hardness of metals it is one of the most important characteristics to be taken into consideration in anticipation of a possible processing. It can be useful, but above all interesting, to find out which are the hardest metals to work, that is, the strongest and most resistant. True, in theory when we think of any metal we imagine it to be hard. Still, the inherent characteristics - not only hardness, therefore, but also ductility, malleability and lucidity, as well as thermal conductivity and electrical conductivity - they change by type. Unlike what is usually imagined, steel is not the strongest metal - even if it would be more accurate to say metal alloy. By the way: the strength of a metal it has to do with its resistance to impact, its resistance to enervation, its compressive strength and its tensile strength.
The hardest metals in the world
The ranking of hardest metals in the world sees tungsten in the first place, which is used among other things for the production of missiles and bullets and is characterized by a melting point of 3422 degrees. In second place is steel, which we all know well, and which is used for the construction of buildings, infrastructures, highways and railways. The third step of the podium is occupied by the chrome, which is present in stainless steel, while the top five is completed by titanium and iron, present respectively in the aerospace spacecraft and in the pillars. Again, the sixth strongest metal on the planet is vanadium, a binder for steel, and the seventh is Lutetium, which is used for catalysts for oil production. Finally, in the ranking of the top ten there are zirconium, osmium and tantalum, present respectively in nuclear power plants, in platinum and in various alloys.
The machinability of metals
The processes to which metals can be subjected are numerous. L'laser engraving, for example, it is mainly aimed at guaranteeing the traceability of products, but it can also have many other purposes, both functional and purely aesthetic. The metallurgical state of the piece is, in any case, one of the most important factors - together with the hardness - that determine the machinability. There grain thickness, in particular, usually corresponds to good workability, except for ductile and soft materials: in this case the workability is better when the grain is fine.
The hardness
La laser marking of metals and other processes also depend on hardness. It must be said, however, that in reference to the correlation between hardness and workability of metals there are exceptions that should be taken into account. For example, it has been found that the machinability of austenitic manganese steels that do not exceed 200 Brinell hardness is very low, while normal steels are much more workable than they have a higher hardness. There is a reason, however: machinability has to do above all with the hardness at the cutting temperature, with the hardness of the individual granules and with the hardness of the chip, which can be up to 3 times higher than the cold hardness of the original metal due to the pressure exerted.
Machinability and intrinsic properties of metals
To define the more or less high difficulty of metal processing there are also other mechanical properties, such as creep resistance and resistance to tradition; however, it should be borne in mind that the values of these parameters are modified by the temperature, and that the conditions that occur during cutting or engraving are different from those encountered during static tests. Better workability, on the other hand, is guaranteed by previous processes, both hot and cold: for example the drawing. However, this is not a general rule, but an aspect that is found above all in steels with a low percentage of carbon. Finally, it should be noted that the degree of finish that is achieved is directly related to the ductility of the metal to be worked, and therefore to its ability to let the chip flow. avoiding the formation of the pre-chip, the effect of which would be to clearly compromise the finish.
