To carry out a machining process, it is necessary to know the physical characteristics of the material to be machined, important when selecting the tools, cutting angles, speeds, among other parameters. Here are some important aspects to machine aluminum.
Physical Characteristics of Aluminum
The aluminum It is one of the most used metals due to its special physical characteristics:
– Excellent Thermal conductivity, which can reach up to 230 W/m K., this characteristic allows it to perform very well in heat dissipation tasks, used for the manufacture of auto parts such as radiators for cars in the automotive industry, also in component heat sinks in the mechanical, electrical and especially electronic industries.
– Highly corrosion resistant in humid environments, except in the presence of hydrochloric acid or alkalis. When it is outdoors, a layer of aluminum oxide is formed, which prevents its corrosion process. This property allows aluminum an excellent performance in the mechanical and architectural industry.
– It is a good electrical conductor, its electric conductivity is approximately 35 m/Ω mm2, which makes it an excellent candidate for applications of generation, transport and use of electrical energy.
– It is also a low-density metal (2,700 kg/m3), it has low mechanical resistance but it is easily improved by means of alloy processes, allowing it to reach up to 690 MPa. Its weight is close to a third of the weight of steel, these characteristics make it especially useful in the aerospace and automotive industry, since its lightness contributes to energy savings in transportation.
– hardness of aluminum ranges from HB=15 for very pure soft aluminum to approximately HB=110 for alloyed (AlZnMgCu) and thermally hardened 7075 aluminum.
– The ductility or Aluminum’s elastic limit is approximately 0.2%, it is highly deformable, a very useful property in the production of electrical conductors, mechanical systems to absorb impact energy, among others.
– The excellent malleability of aluminum makes it useful in the production of thin sheets used as aluminum foil, cans for the food industry.
– His melting point it is rather low, around 660ºC, therefore it requires little energy to manufacture parts through injection processes and metal extrusion.
Because it is very abundant in nature and its easy recovery in the recycling process, it is an inexpensive metal.
Thanks to its characteristics the aluminum It has become a highly used metal in the industry to produce parts through the use of different production and manufacturing processes such as injection, extrusion and machining.
For machine aluminum Relatively little energy is required, since to achieve the cut of the material thanks to its mechanical characteristics, it uses a third of the energy compared to the energy used in the steel machining. The aluminum machining can be achieved with high speeds and removal rates without generating excessive stresses between the material and the cutting tool. high speed of machining means higher productivity and better surface finishes.
Cutting tools for machining aluminum
For machine aluminum it is required that the tool has certain special characteristics, it is desirable that the cutting tools used for this type of material allow the efficient evacuation of the material to avoid clogging that can ruin the piece and the cutting tool, likewise, the rake angles must be greater than those Used for machine steels.
Thanks to the high thermal conductivity of aluminium, the cooling process of the cutting tool does not require a large flow of coolant, only enough to evacuate loose material.
In the market there is a variety of cutting tools with different properties and costs. For the processes of aluminum machining, as with steel, it is desirable that the tools are very efficient and durable over time. Thanks to technological advances it is possible to find tools with hard coatings such as DLC (diamond like carbon), which provide hardness and tribological properties to the tool, to complex coating processes such as PVD (vapor phase deposition) treatments, with which titanium nitride coatings capable of protecting the tool with superficial layers with titanium. Some materials for cutting tools for aluminum they are:
- high speed steels, are special high-performance steels with high hardness up to 500 ºC and high resistance to wear thanks to alloying elements such as tungsten, molybdenum, vanadium and chromium, capable of forming carbides. Cobalt is added to increase hardness. The high speed steel tools are suitable for machining of aluminum alloys with low silicon content. Supports the use of large rake angles for better cutting conditions.
- Heavy metal, is a mixture of tungsten carbide and cobalt (CW+Co). This coating provides a longer life tool. They are used in aluminum machining with a high silicon content and for mechanized at high cutting speeds.
- Diamond, polycrystalline diamond (PCD) is obtained by sintering fine powders of granulated diamond crystals at high temperatures and pressures into the desired shape. The diamond tools They are characterized by their high durability, even if they are used in the machining of alloys with a high silicon content. They are normally used for finishing work on aluminum alloys that generate long chips, or for automatic machines working with aluminum that generate short chips.
In conclusion, it can be said that thanks to the physical and mechanical properties of aluminium, it is one of the metals most used by humanity in numerous fields of industry, therefore it is one of the metals that are most mechanized in production processes. The processes of aluminum machining they require much less energy than that used in the machining of steel, it is carried out at high cutting and feed speeds, providing quality surface finishes.