Processing of non-ferrous metals
Features of processing of non-ferrous metals. Material properties, processing problems and ways to solve them.
Non-ferrous alloys are used everywhere:
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transport: cars, trucks, buses and trains, where the use of aluminum reduces weight. Cylinder blocks, pistons and radiators are made of it.
- mechanical engineering: manufacturing of various structures, including specially designed profiles. aluminum alloys are used in electromechanical devices, construction and as a packaging material.
The reason for this is an attractive combination of low density, high strength, good conductivity and ease of disposal.
Non-ferrous alloys, with their lightness, have a good margin of safety. According to the criterion of specific strength (the ratio of the strength parameter to the mass of the metal), they surpass even some grades of steels. In simple terms, a kilogram of non-ferrous alloy can be used to make a part of greater strength than a kilogram of steel.
Also, non-ferrous metal alloys are practically not subject to corrosion. An impermeable oxide film is quickly formed on the surface of the parts, which is chemically inert and protects the metal from atmospheric exposure.
Non–ferrous metals are a soft and plastic material that lends itself well machining (milling, drilling, turning, etc.). In this case, the cutting modes can be much higher than when processing structural steels. This is due to lower loads when removing chips, as well as a high coefficient of thermal conductivity of non-ferrous metals, thanks to which heat from the cutting zone is well removed together with the chips, without overheating the tool.
Sometimes, when processing non-ferrous metal alloys, negative effects also occur.
The first is the high viscosity of some alloys. In this case, there is a tendency to form long chips that wind up on the tool and clog the grooves, which leads to breakage of the milling cutter or drill. Therefore, large chip grooves are made on the tool for processing non-ferrous alloys. Although this limits the number of teeth on the cutter to two or three.
The second negative effect is build–up. This is a phenomenon in which a point surfacing of the processed material occurs on the cutting edge of the tool in the cutting zone. The consequence of this is the blunting of the cutting edge and an increase in the load on the tool, as well as the difficult chip gathering due to the deterioration of the roughness of the front surface of the tool. Tool manufacturers are struggling with this phenomenon by increasing the smoothness of the front surface (for example, by additional polishing or applying an ultra-smooth coating), and by setting certain values of the front and rear corners.
When surfacing the material, the groove is clogged, which leads to an imbalance of the tool. When the cutting edge is blunted, the tool overheats, which can lead to jamming and, as a result, to the breakdown of an expensive tool. The degree and depth of the surfacing of the material is influenced by the cutting modes, the geometry of the cutting tool, the degree of its bluntness, i.e. all factors that determine the course of plastic deformation in the cutting zone.
An increase in the cutting speed affects a decrease in the depth and degree of surfacing, and the feed and depth of cutting leads to an increase in them.
To eliminate negative effects when processing aluminum alloys, it is recommended to use special series of carbide tools.
To summarize, here are the recommendations for processing non-ferrous metals and alloys:
- when processing, use a tool with sharp cutting edges and positive geometry.
- the correct choice of cutting speed and feed is very important to reduce the formation of build-up and improve chip crushing.
- for processing aluminum alloys with a silicon content of more than 6% that have abrasive properties, choose a coated tool.
- usage СОЖ important when processing aluminum alloys
Information used : recommendations of carbide tool manufacturers Kennametal, Dormer Pramet, Sandvik.