To date, many heat treatment processes are being done to various metals and alloys for them to acquire property alterations and improvements. Once a material undergoes a heat treatment process, its physical and structural properties are expected to improve, allowing it to be processed further.
One heat treatment process that is common among metals and alloys is annealing. It is a process wherein the physical and sometimes chemical properties of a material undergo vital changes. Most of the time, this process allows the material to obtain increased ductility and reduced hardness, ensuring that it can be workable for other processes and procedures.
For copper, the process of bright annealing is typically conducted due to the benefits it can bring.
A Quick Overview of Bright Annealing
But before knowing the benefits of bright annealing, one must know how it works first. Bright annealing is normally carried out by annealing the material in a controlled-atmosphere furnace. The furnace being utilised by the process may possess certain sizes, temperatures, and cooling rates, ensuring that it can easily carry out the bright annealing process without any problems.
The bright annealing of copper and its alloys intends to protect them from oxidation. Hence, the furnace atmosphere system should possess less partial pressure than that necessary to generate the oxide. Oxygen reduction can likewise be achieved by exposing the atmosphere to an active gas like hydrogen. Additionally, utilising a non-flammable atmosphere as well as diluting any flammable component below its flammable limit must be done to avoid oxidation-related issues. Ultimately, oxidation problems and issues can be prevented through maximising zoning technology.
Aside from preventing oxidation, the furnace atmosphere system should be able to remove unwanted processing lubricants. This specific function can be done through physical flushing or exposing the lubricant through an atmosphere component.
Bright Annealing Copper and Its Alloys
One thing about copper is that it is difficult to oxidise. Hence, it is common for copper materials to be annealed with exogas or steam. However, the use of exogas in the annealing process will only generate carbon dioxide and soot. Annealing with steam, alternatively, can be costly. One non-toxic alternative to these two elements is the use of high-purity nitrogen and a small addition of hydrogen.
For tough pitch copper, it is therefore recommended to be annealed in atmospheres that contain hydrogen of around 2%, preventing any instances of embrittlement. Annealing the copper with lower-purity nitrogen is also possible and can generate great results. The only problem with the use of hydrogen is that it can take some time. Without any intervention, the gas mixture may interact with the annealing process and just ruin the workpiece. To make things more efficient, it would be better for the gas mixture to pass over a catalyst before introducing it into the furnace.
Copper-based alloys that contain aluminium, beryllium, and zinc can also be annealed in a protective atmosphere system that consists of an exothermically generated gas. They can, however, utilise nitrogen/hydrogen mixtures to prevent toxicity and soot.
To know more about bright annealing, feel free to call us at Alpha Detroit Heat Treatment.
To date, a wide array of alloys can be utilised to create reliable parts and components. One of the alloys that are being maximised by many industries is cast iron.
Cast iron is an alloy of iron that is comprised of more than 2% carbon as well as varying amounts of manganese, silicon, sulphur, and phosphorus. The presence of these elements allows this specific alloy to possess great fluidity, low melting point, exemplary pouring characteristics, excellent machinability, and resistance to wear and deformation.
Most cast iron parts and components are used by the automotive, construction, and electronics industries. The formation of these products is possible through different heat treatment techniques. To know more about them, here is some information on various heat treatment techniques of cast irons.
Stress Relieving
Stress relieving is a heat treatment technique that subjects the cast iron to a constant temperature below its critical temperature before exposing it to controlled cooling. As the temperature gets higher, the mechanical properties of the cast iron typically change. Once the desired mechanical properties are achieved, the cast iron is then cooled. For most castings, a furnace cooling to 260°C can be done. Cooling to 95°C, alternatively, is a must for those that possess intricate shapes. This specific technique is applied to cast iron to effectively minimise residual stresses and dimensional changes.
Annealing
Another heat treatment technique that can be applied to cast iron is annealing. It is a heat treatment technique that changes the microstructure of the cast iron, therefore changing its electrical or mechanical characteristics. When applied to cast iron alloy, annealing can easily reduce its hardness, increase its ductility, and eliminate internal stresses on its structure. Annealing is typically done by heating the cast iron for a specific amount of time before letting it cool slowly to room temperature. Various types of cast iron can go through different heating and cooling cycles to achieve distinct purposes.
Quenching and Tempering
Both quenching and tempering are typically applied on cast irons to improve their ductility and relieve internal stresses. But to yield great results, various parameters should be selected and controlled. Selecting and controlling the parameters such as the temperature can then prevent the cast irons from distorting, warping, burning, or quench cracking. Before performing these techniques, the heating of the cast irons must be done gradually to avoid inducing thermal stresses. The parts that were soaked must then be quenched. Tempering is subsequently done at a temperature range of 120 to 595°C.
When processing specific types of cast iron, different heat treatment techniques can be done. For example, high-alloy white iron castings can be processed through stress relief heat treatment and tempering. Grey cast irons and ductile cast irons, alternatively, can benefit from stress relief heat treatment and annealing at varying temperatures.
To know more about heat treatment techniques of cast irons, you can contact us at Alpha Detroit Heat Treatment. We provide a wide range of services for all your heat treatment needs.
Source:
Herring, D. H. (2020, March 19). Heat Treatment of Cast Irons. 2018–12-12 | Industrial Heating. https://www.industrialheating.com/articles/94644-heat-treatment-of-cast-irons