The development of knives occupies an important position in the history of human progress. As early as the 28th to 20th centuries BC, brass cones and copper cones, drills, knives and other copper knives had appeared in China. In the late Warring States period (third century BC), copper knives were made due to the mastery of carburizing technology. Drills and saws at that time had some similarities with modern flat drills and saws.
The rapid development of knives came with the development of machines such as steam engines in the late 18th century.
In 1783, René of France first produced milling cutters. In 1923, Germany’s Schrotter invented cemented carbide. When cemented carbide is used, the efficiency is more than twice that of high-speed steel, and the surface quality and dimensional accuracy of the workpiece processed by cutting are also greatly improved.
Due to the high price of high-speed steel and cemented carbide, in 1938, German Degusa Company obtained a patent on ceramic knives. In 1972, General Electric Company of the United States produced polycrystalline synthetic diamond and polycrystalline cubic boron nitride blades. These non-metallic tool materials allow the tool to cut at higher speeds.
In 1969, the Swedish Sandvik Steel Works obtained a patent for producing titanium carbide-coated carbide inserts by chemical vapor deposition. In 1972, Bangsha and Lagolan in the United States developed a physical vapor deposition method to coat a hard layer of titanium carbide or titanium nitride on the surface of cemented carbide or high-speed steel tools. The surface coating method combines the high strength and toughness of the base material with the high hardness and wear resistance of the surface layer, so that the composite material has better cutting performance.
Due to the high temperature, high pressure, high speed, and parts working in corrosive fluid media, more and more difficult-to-machine materials are used, and the automation level of cutting processing and the requirements for processing accuracy are getting higher and higher. When selecting the angle of the tool, it is necessary to consider the influence of various factors, such as workpiece material, tool material, processing properties (rough, finishing), etc., and must be selected reasonably according to the specific situation.
Common tool materials: high-speed steel, cemented carbide (including cermet), ceramics, CBN (cubic boron nitride), PCD (polycrystalline diamond), because their hardness is harder than one, so generally speaking, the cutting speed is also One is taller than the other.
Tool material performance analysis
High speed steel:
It can be divided into ordinary high-speed steel and high-performance high-speed steel.
Ordinary high-speed steel, such as W18Cr4V, is widely used in the manufacture of various complex knives. Its cutting speed is generally not too high, and it is 40-60m/min when cutting common steel materials.
High-performance high-speed steel, such as W12Cr4V4Mo, is smelted by adding some carbon content, vanadium content, cobalt, aluminum and other elements to ordinary high-speed steel. Its durability is 1.5-3 times that of ordinary high-speed steel.
Carbide:
According to GB2075-87 (with reference to the 190 standard), it can be divided into three categories: P, M, and K. P-type cemented carbide is mainly used for processing ferrous metals with long chips, and blue is used as a mark; M-type is mainly used for processing ferrous metals. And non-ferrous metals, marked with yellow, also known as general-purpose hard alloys, K type is mainly used for processing ferrous metals, non-ferrous metals and non-metallic materials with short chips, marked with red.
The Arabic numerals behind P, M, and K indicate its performance and processing load or processing conditions. The smaller the number, the higher the hardness and the worse the toughness.
ceramics:
Ceramic materials have good wear resistance and can process high-hardness materials that are difficult or impossible to process with traditional tools. In addition, ceramic cutting tools can eliminate the power consumption of annealing processing, and therefore can also increase the hardness of the workpiece and prolong the service life of the machine equipment.
The friction between the ceramic blade and the metal is small when cutting, the cutting is not easy to stick to the blade, and it is not easy to produce built-up edge, and it can perform high-speed cutting. Therefore, under the same conditions, the surface roughness of the workpiece is relatively low. The tool durability is several times or even dozens of times higher than that of traditional tools, which reduces the number of tool changes during processing; high temperature resistance, good red hardness. It can cut continuously at 1200°C. Therefore, the cutting speed of ceramic inserts can be much higher than that of cemented carbide. It can perform high-speed cutting or realize “replacing grinding with turning and milling”. The cutting efficiency is 3-10 times higher than that of traditional cutting tools, achieving the effect of saving man-hours, electricity, and number of machine tools by 30-70% or more.
CBN:
This is the second highest hardness material currently known. The hardness of CBN composite sheet is generally HV3000~5000, which has high thermal stability and high temperature hardness, and has high oxidation resistance. Oxidation occurs, and no chemical reaction occurs with iron-based materials at 1200-1300 ° C. It has good thermal conductivity and low friction coefficient
Polycrystalline diamond PCD:
Diamond knives have the characteristics of high hardness, high compressive strength, good thermal conductivity and wear resistance, and can obtain high processing accuracy and processing efficiency in high-speed cutting. Since the structure of PCD is a fine-grained diamond sintered body with different orientations, its hardness and wear resistance are still lower than those of single crystal diamond despite the addition of a binder. The affinity between non-ferrous metals and non-metallic materials is very small, and chips are not easy to stick to the tip of the tool to form built-up edge during processing
The respective fields of application of the materials:
High-speed steel: mainly used in occasions requiring high toughness such as forming tools and complex shapes;
Cemented carbide: the widest range of applications, basically capable;
Ceramics: Mainly used in rough machining and high-speed machining of hard parts turning and cast iron parts;
CBN: Mainly used in hard parts turning and high-speed machining of cast iron parts (generally speaking, it is more efficient than ceramics in terms of wear resistance, impact toughness and fracture resistance);
PCD: Mainly used for high-efficiency cutting of non-ferrous metals and non-metallic materials.
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Post time: Jun-02-2023
