There are many different types of processes that metal can go through to change the properties and make it easier to work with, stronger, or to further enhance the qualities of the alloy. Once such process is metal annealing, and it has been used as a metal working process since the beginning of metal use.
Early History
Metal annealing, which uses a heating process to soften metal and make it easier to work with, has been in use since the earliest recorded time. In history the most common metals, including copper, would be worked by pounding with crudely formed hammers, a rudimentary cold working process.
The problem with this option, and with cold working these metals, is that it is impossible to create a thin edge without it becoming brittle. This makes it impossible to form a sharp edge or a point, which was needed for tools and weapons.
To alleviate this issue, the early blacksmiths used heat treating of the metal, followed either by rapid cooling to harden or by slow cooling to create a softer metal that could be further worked. The process of metal annealing, which initially occurred through slow, natural cooling, created the softer metals which could then be formed to create the edges and shapes required.
Today’s Options
The basics of metal annealing are still the same as they were back in the early days of human civilizations and metal use. However, today different processes are available to more quickly and evenly heat the metal to above the natural recrystallization temperature for a specific amount of time, and then allowing it to cool to create the desired properties and appearance.
This is done through the use of high-efficiency continuous furnaces providing very controlled temperatures with no variations. This allows the correct recrystallization and grain growth through the process to allow a refined grain structure in the final product.
Another important difference in today’s commercial metal annealing process is the use of controlled atmospheres. These can include pure hydrogen and pure nitrogen atmospheres. By using these pure atmospheres the surface scaling, or the resulting oxidation that occurs through the process in a natural atmosphere, can be completely eliminated.
The result of the metal annealing processes of today is a very stable microstructure in the alloy itself combined with a scale-free surface. The metal going through the annealing process will have relatively low hardness, with good yield strength, flexibility, and durability.
