At present, in the cutting process, commonly used tool materials are high-speed steel, hard alloy, ceramic and super-hard tool materials, among which super-hard material tools include synthetic diamond (PCD) and cubic boron nitride (CBN).
1, high speed steel
High-speed steel (HSS) is a high-alloy tool steel with alloying elements such as tungsten, molybdenum, chromium, and vanadium. The hardness after heat treatment is small, 62-67HRC, and it is impossible to cut hardened steel and chilled cast iron with high hardness. In terms of heat resistance, it can only withstand cutting temperatures of up to 550-600 Â°C, so high-speed cutting is not possible. However, high-speed steel has good performance in strength, toughness, thermosetting, and processability, such as its bending strength is 5-6 times that of 2-3 ceramic materials of cemented carbide.
2, hard alloy
Cemented carbide is made by Powder Metallurgy
method with high hardness HRA89-93, can withstand high temperature of 850-1000 Â°C, cutting speed can reach 100-300m/min, wear resistance is several times or even dozens of times of high speed steel The bending strength, impact toughness and processability of the tool are not as good as high speed steel. More than 90% of turning tools and more than 55% of milling cutters in developed countries are made of hard alloy materials, and the proportion of use is still increasing. Carbide is also used to make complex tools such as drills, milling cutters, gear cutters, and reamer. Cemented carbide is replacing other tool materials for more occasions with its excellent properties and is now one of the main tool materials. At present, the world's cemented carbide tools have dominated the tool, accounting for 70%.
Ceramics were cutting tool materials that made breakthroughs in the 1980s. Ceramic materials have higher hardness, red hardness and wear resistance than cemented carbide. When machining steel, the durability of ceramic tools is 10-20 times that of cemented carbide tools. Its red hardness is 2-6 times higher than that of hard alloys, and its chemical stability and oxidation resistance are superior to those of hard alloys. However, the biggest weakness of ceramics is low bending strength and poor impact toughness, so it is mainly used for finishing of steel, cast iron, non-ferrous metals and other materials.
4, synthetic diamond
Polycrystalline diamond (PCD), which is a mixture of diamond micropowder and metal bond, sintered at high temperature and high pressure; it has high hardness and thermal conductivity, low coefficient of thermal expansion, high modulus of elasticity and lower The coefficient of friction, the blade is very sharp. Due to the affinity of carbon to iron, especially at high temperatures, diamond can chemically react with iron. Therefore, diamond tools are not suitable for cutting iron and its alloy workpieces. It is an ideal tool material for high-speed cutting aluminum alloys. Cutting speed Can reach 2500-5000m/min.
5, cubic boron nitride
Cubic boron nitride (CBN) is a superhard material synthesized in the late 1950s using diamond-like methods. Due to the poor sintering performance of CBN, the polycrystalline cubic boron nitride PCBN.CBN made in the 1970s is a dense phase of boron nitride, with high hardness (after diamond) and heat resistance (1300 Â° C, 1500 Â° C). The cutting speed is 4-6 times that of cemented carbide tools, with excellent chemical stability (far better than diamond) and thermal conductivity, and low friction coefficient. PCBN has a low affinity for Fe elements, so it is an ideal tool material for high-speed cutting of ferrous metals.
Extrusion is a metal forming process , in which billet is passed through a die , to get required cross section of component .
Non cutting process
Production of Fixed cross section
Types of extrusion process
Direct extrusion process
Indirect extrusion process
Impact extrusion process
Hydrostatic extrusion process
Tube extrusion process
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