Special heat treatment processes are the tool of choice here, with extreme temperatures altering the internal structure of a metal component until it shades through red and white hot intensity. As the part cools, brittleness is gone and the now toughened metal is stronger than ever. The Secret is in the Processing Mix Heating and cooling techniques gift unrefined metals with extraordinary properties. These new and improved capabilities are controlled by carefully managed furnaces and cooling facilities, by superheated induction furnaces and giant pools of cooling oil. Carbon steel, for example, changes as the heat cooks the carbon, forcing the iron atoms to shift, and the result is a permanent strengthening of the bonds that lock the crystalline structure in place. Heat treatment, even in this simplified description, can be seen as an essential engineering system for hardening metal components.
The key to changing the state of a metal has been the subject of research for over a thousand years, and, while lead can’t be transmuted into gold, furnaces can manage the next best result, the alteration of metallurgical properties. Of course, if this practice was reserved for hardening, then the word would likely feature in the label, but that’s not the case. The discipline is all about heat treatment, a process that isn’t limited by hardening. Above and beyond mechanical rigidity, the technique also highlights ductility and workability, two essential parts of the metalworking craft. Indeed, it’s fairer to say that structural alterations on the atomic scale emphasize some traits while minimizing or entirely eliminating others. Here’s a summarized list of some of the techniques that cause these metallurgical changes.
- Tempering – A heating and cooling process that alters hardness and ductility
- Quench Hardening – The heated metal is “quenched in water, though oil is the preferred medium today. Modifies hardness
- Annealing – The rapid heating and timed cooling of metallurgical stock
- Normalization – The temperature change is sustained until a microcrystalline change occurs
Heating and cooling cycles are typically partnered with one or more of the above methods, which means a tempering cycle accompanies a quench phase, and so on until the metal reaches equilibrium. A new molecular form now cools, one that displays the desired surface finish and hardness quotient.