The composition and processing of aluminum cutting
Aluminum alloys generally respond well to machining. In contrast, pure aluminum, aluminum alloys have a complex metallurgical structure. It gives them an advantage in the machining compared to unalloyed aluminum.
various components, which are part of aluminum alloys, have an important impact on the performance, which provide their attitude towards machining. Non-abrasive components alloys have a positive effect, and insoluble abrasive components have an adverse effect on tool life and surface quality. Components, which are insoluble, but soft and non-abrasive can be useful for machining, as they promote chip breaking. Such components are specially added, for example, in aluminum alloys for automatic machining on high speed machines mehanoobrabatyvajushchih.
In general, softer aluminum alloys and, less, some high-strength aluminum alloys tend to form metal buildup on the cutting edge of the tool. It consists of sticking aluminum particles, are melted and welded to the tool cutting edge.
Features of aluminum-silicon alloys
Adhesion of the cutting edge can be reduced to a minimum by the use of effective ohlazhdayuschesmazochnyh fluids and by the use of high-quality tools. alloys, which contain more 10 % silicon - a casting alloys, They are the most difficult for machining, as the solid free silicon particles cause rapid wear of the cutting tool. In alloys, which contain more 5 % silicon, you can not get a shiny finished surface, which happens in other high-strength aluminum alloys. In these alloys, chips departs from parts mainly due to separation, and not cut. Typically, the processing of such alloys special measures apply, to prevent aluminum from sticking to the cutting edge.
Classification of aluminum alloys
Алюминиевые сплавы подразделяются на:
- casting alloys and
- wrought alloys.
Среди литейных и деформируемых сплавов различают:
- термически упрочняемые сплавы;
- thermally alloys neuprochnyaemye.
Thermally neuprochnyaemye deforiruemye alloys are usually regarded as
- деформационно упрочняемые сплавы (или нагартовываемые сплавы).
Casting alloys, which comprise as major alloying elements copper, magnesium or zinc does not cause any problems when machining. Generally, these alloys are used for cutting tools with a small rake angle with minimum problems with the formation of burrs on the workpiece or metal buildup on the cutting edge.
Aluminum alloys with silicon as the main alloying element require a cutting tool with increased cutting angle. These alloys are better to handle at low speeds and with small feed.
Most wrought aluminum alloys respond well to machining. Some of them are well-suited for multi-operational processing.
Strain hardening alloys
Strain hardening alloys, including commercially pure aluminum, contain no alloying elements, which would make them heat-reinforcing. However, these alloys are able to improve their mechanical properties, if they are subjected to cold plastic deformation. When machining these alloys form long chips. Therefore, the tool should be designed, which provides retraction of the chip from the workpiece, not to damage the surface. This is usually achieved enlarged rear and side corners. Feature of this chip is, she receives a significant strain hardening and therefore has a high hardness.
These alloys respond well to machining, but require well-honed tool, because they are fairly viscous. Machinability increases with increasing degree autofrettage. Therefore, to maximize the work-hardened alloys easier to obtain a good surface quality, than for alloys in the "softer" conditions, for example, after annealing.
Thermally hardenable alloys
Most of the alloys of this group contain a sufficiently large amount of alloying elements, such as copper, silicon, magnesium and zinc. These alloys can be machined with good surface quality as a coolant, and without it. At the same time, the use of coolants is recommended in most cases. Chips in most has the form of long twisted curls, except special alloys for automatic machining, which contain special additives for chip breaking.
Thermally reinforcing alloys are more amenable to machining in a thermally hardened state, than "softer" conditions, such as the annealed condition.
Grouping alloys machining
Для удобства выбора подходящего режущего инструмента все алюминиевые сплавы подразделяют на пять групп: A, B, C, D and E in the ascending order of the chip length and in reverse order on the quality of the treated surface by cutting. Examples of aluminum alloys for each group, and the typical form of chips for them is shown in Figure.
Figure - Typical view chips for different groups of aluminum alloy, differing in cutting.
All the chips were obtained when cutting with the rake angle and 20º
depth of cut 2,5 мм (остальные параметры – см. таблицу ниже) .
- Machining of Aluminum and Aluminium Alloys, ASM Handbook, Volume 16: Machining, 1989.