Air from our environment has various elements that can easily react with metals and cause undesirable results. Under room temperature, the moisture, oxygen, carbon dioxide, and hydrogen that are present in the atmosphere can each cause small but varying reactions with metals. Most of the time, however, these reactions can accelerate drastically if the metals are exposed to heat or a hot environment.
One instance where metals would be subjected under heat would be their fabrication process. The colour of a polished metal that is held over a heat source can ultimately turn to blue or black as it reacts to the elements present in the atmosphere. Without any intervening processes, some types of metals would truly have worse reactions and severe property changes than the mentioned example.
Basic Principles of Vacuum Heat Treatment
Fortunately, more and more metal fabrication companies have been applying the processes of vacuum heat treatment for their works. Vacuum heat treatment is comprised of a series of processes that can prevent metals from interacting directly with reactive elements. Some of the undesirable results that vacuum heat treatment can avoid include discolouration, scale, and contamination.
To effectively remove the reactive elements, the metal product is placed in a tightly sealed heat-treating chamber. The vacuum pumping system on this chamber is guaranteed to remove most of the air that would affect the overall quality and integrity of the metal material. At the same time, in this very same chamber, the metal is heated to a suitable temperature for it to possess the desired properties. Inert gases are then used for the cooling process of the processed metal material.
Advantages of Vacuum Heat Treatment
The advantages brought by vacuum heat treatment are abundant. One great advantage of this process is that it ensures the absence of oxidation, decarbonisation, and other presence of carbon inside the metal material. The absence of these processes and elements will then allow the workpiece to be formed without unnecessary scaling or discolouration. Additionally, the very same workpiece would emerge ready for further processing and forming, all without the need to clean it again.
As for the properties of the metal material, vacuum heat treatment can significantly improve its plasticity, toughness, and fatigue strength. Improvements over the thermal efficiency of metal materials are likewise expected right after all necessary vacuum heat treatment processes are done.
Common Vacuum Heat Treating Services
Some of the most common services that are conducted for vacuum heat treatment are the following:
- Quenching: This specific process enables the steel to be austenitized and cooled at an appropriate cooling temperature. The metal workpiece under this process can be effectively prevented from obtaining unnecessary phase transformations.
- Tempering: A metal material that has been quenched is heated below the critical point for a specific time and then cooled. All the desired microstructure and properties can be obtained by this specific vacuum heat treatment process.
- Annealing: The annealing process can heat a hypoeutectoid steel workpiece to a certain temperature so that its physical and chemical properties can be altered. After some time, the same material is then cooled so that it can possess more ductility, making it more workable to other processes.
Other vacuum heat treating services that can be used for metal materials are normalising, solution heat treatment, and aging treatment.