Historical progress and future prospects of the ho

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The historical progress and future prospects of tool materials

1 the important role and development process of tool materials

the development of tool materials is closely related to the development of human social life and production. For ancient humans, the understanding and application of "knife" and "fire" are two of the greatest inventions and an important symbol for mankind to enter the stage of history. The improvement of tool materials promotes the development of human social culture and material civilization. For example, in human history, there have been Paleolithic age, Neolithic age, bronze age and iron age. Corresponding to the stone age is the primitive society of mankind; Corresponding to the bronze age is the slave society of mankind; Corresponding to the iron age is the feudal society of mankind and its subsequent era

in traditional machining, tool material, tool structure and tool geometry are the three requirements that determine the cutting performance of tools, in which tool material plays a key role. After the emergence of computer integrated advanced manufacturing system, the problem of "tool system" should also be considered in the use of tools. In recent years, the emergence and application of various difficult to machine materials, the development and application of advanced manufacturing systems, high-speed cutting and ultra-high speed cutting, precision machining and ultra precision machining, "green manufacturing" and "clean manufacturing", all put forward higher and newer requirements for cutting tools, especially for cutting tool materials

ancient humans can still find natural materials to make tools in nature, such as jade, stone, natural diamond and even meteorite iron. In the slavery society, tools were made of bronze; At the turn of the spring and Autumn period and the Warring States period, especially in the Qin Dynasty, when people entered the feudal society, steel and iron tools began to appear, and carbon tool steel began to be used. At that time, carbon tool steel was very close to modern T10, T12 and other steel grades. Compared with stone and copper, carbon tool steel has higher hardness, and the cutting edge can be ground very sharp, so the cutting efficiency and processing quality are relatively high. However, carbon tool steel can only bear the cutting temperature of ℃, and the cutting speed of m/min can only be used to cut general steel, which can not meet the requirements of higher cutting efficiency. In 1865, rohert Mushet of Britain invented alloy tool steel, with grades of CrWMn, 9CrSi, etc., which can withstand the cutting temperature of 350 ℃, and the cutting speed can be increased to m/min when processing general steel. In order to meet the requirements of further improving processing efficiency, American mechanical engineer Taylor and metallurgical engineer ite invented high-speed steel in 1898. At that time, the composition was c0.67%, w18.91%, cr5.47%, v0.29%, mn0.11%, and Fe was the surplus. It can withstand the cutting temperature of ℃, and the cutting speed of m/min can be used to cut general steel, so that its processing efficiency is more than 4 times and 2.5 times higher than that of carbon tool steel Qia metal tool steel respectively. From the end of the 19th century to the beginning of the 20th century, it has made a leap in the cutting level of the United States, Britain and other major capitalist countries, thus obtaining huge economic benefits, and the machinery manufacturing industry also relies on rapid development

with the improvement of human production and production level, high-speed steel cutting tools can no longer meet the requirements of high-efficiency machining, high-quality machining and cutting of difficult to machine materials. From the 1920s to the 1930s, tungsten cobalt and tungsten titanium cobalt cemented carbides were invented. Their normal temperature hardness reached HRA, they can withstand high temperatures above ℃, and their cutting speed can be more than times that of high-speed steel tools. Therefore, they are rapidly promoted and applied. During the Second World War, due to the needs of military production, the United States, Britain, the Soviet Union and Germany began to use cemented carbide cutting tools in part; After World War II, it was gradually expanded. In the early 1950s, China imported a small amount of cemented carbide from the Soviet Union to replace high-speed steel tools in production. Later, with the assistance of the Soviet Union, China built Zhuzhou Cemented Carbide plant; Through self-reliance, Zigong Cemented Carbide plant was built with domestic technology and strength. After 40 years of efforts, the output of cemented carbide tool materials in China has ranked in the forefront of all countries in the world and has become a large country producing cemented carbide. In the second half of the 20th century, the variety of workpiece materials has been increasing, their mechanical properties have been improving, and the batch size and machining accuracy of workpieces have also been increasing and improving. Therefore, the use performance of tools has been constantly updated and higher requirements. In order to meet the new requirements, cemented carbide tool materials have their own updated development, and many new varieties have appeared, and their performance has been greatly improved compared with the past. Compared with high-speed steel tools, cemented carbide tools are brittle, lack of toughness and poor machinability, so they were only used for general turning tools at the beginning, and later developed to face milling tools and other tools; But so far, it can not be used for all kinds of cutting tools. High speed steel cutting tools have also developed, and many new varieties have appeared. However, in the past half century, more than half of high-speed steel tools have been replaced by cemented carbide tools; With its good toughness and roughening ability, high-speed steel tool materials still cling to less than half of the cutting tools. Nowadays, cemented carbide and high-speed steel are the two most important cutting tool materials. Their sum should account for more than 95% of all cutting tools

cemented carbide tools still cannot meet the requirements of modern high hardness workpiece materials and ultra precision machining, so newer tool materials appear one after another. Alumina and alumina based composite ceramics appeared in the mid-20th century, and later silicon nitride and silicon nitride based composite ceramics appeared. In the middle and late 20th century, two kinds of superhard tool materials, artificial cubic boron nitride and artificial diamond, were manufactured. Their hardness was significantly higher than that of cemented carbide and ceramics. Due to the lack of toughness and machinability, as well as price and other reasons, the application of ceramics, boron nitride and diamond tool materials was still more limited

to sum up, the development of cutting tool (tool) materials has played an extremely important role in the development of human society. In the 20th century, the development of cutting tool (tool) materials is much faster than that in the past decades. The variety, type, quantity and performance of C cutting tool materials have been greatly developed and improved. "Let a hundred flowers bloom and bring forth the new"; In the 20th century, especially in the late 20th century, the cutting tool materials have developed and improved greatly, which is dazzling and dizzying, thus promoting the rapid progress of human material civilization

2 chemical composition of tool materials

in ancient times, most of the tool materials used by humans were natural substances, such as stone, natural diamond, etc. The vast majority of cutting tool materials used in modern and contemporary times are man-made, so as to ensure a large supply and make the texture uniform and reliable

looking at all kinds of cutting tool materials in modern times, except that the raw material of diamond is graphite (carbon element), other varieties are inseparable from carbides, nitrides, oxides and borides. As shown in the table, these compounds have high hardness, high melting point, high modulus of elasticity and other properties, which are the properties required by tool materials. Table properties of various compounds

properties density

10 kg/m melting point

℃ hardness

HV modulus of elasticity

GPA carbide tic4 ZrC6.. HfC12.. VC5.. TaC14.. NbC7.WC15.. Mo2C8.B4C2.. SiC3.. Disassemble cr3c26 Cr7C36.-Cr23C66..- Fe3C -- nitride tin5 ZrN7.-HfN13.- VN6.-TaN14. NbN8.. Nb2n8.-bn (cubic) 3 Decompose si3n 191900 decomposition aln3 Therefore, decompose crn6- Cr2N6.-Mo2N8.- Wn-800 -- oxide tio24 ZrO26.~HfO29.- VO53.--Ta2O58.- Nb2O54.-WO26.-- Al2O33.Cr2O45.- Boride tib24 ZrB26.HfB210.- VB25.. TaB212.NbB26. W2B211.CrB25. FeB7.Fe2B27.

it can be seen from the table that most of the compounds in the table are carbon, nitrogen, oxygen or boron and metal elements; However, there are exceptions, such as SiC, B4C and Si3N. Silicon (SI) and boron (b) are not metals, but after combination, they also have high hardness and can be used as tool materials. The combination of nitrogen (n) and boron (b) can form superhard tool material CBN

carbides are used most in the composition of tool materials. People have studied carbides thoroughly and obtained more test data. Various metal carbides are divided into types 1, 2, 3, 6, 7, 23, etc., namely MC (such as WC, tic, ZrC, etc.), M2C (such as Mo2C, m3c (such as Fe3C, Cr3C2, etc.), M6C (such as Fe3 (W, Mo) 3c6, etc.), m3c (such as Cr7C3, etc.), m23c (such as Cr23C6). The formation of all types of carbides follows certain rules and can also form composite carbides, but the physical and mechanical properties are not enough, so it is difficult to find accurate data

for carbon tool steel, its main component is Fe3C, that is, cementite alloy tool steel has composite carbides, such as the new standard cementite (F, Cr) 3C of cupping tester of alloy Jinan testing machine factory. There are more complex carbides in high-speed steel. For example, in tungsten high-speed steel, M6C (fe3w3c, fe4w2c) is the main component. In tungsten high-speed steel, M6C is also the main component, in the form of Fe3 (W, Mo) 3C and FE4 (W, Mo) 2C

the hard phase in cemented carbide is mainly MC (WC, TIC), but it is often added with TA, Nb and other elements to form composite carbides, and Co, Ni and other elements must be used as bonding materials. Al2O3 and Si3N4 are commonly used as matrix materials in ceramics, but carbides, other oxides, other nitrides or borides are often added to form composite ceramics. Non metallic nitride Si3N4 plays an important role in ceramics and forms an important branch of ceramic tool materials. Cubic boron nitride is also a non-metallic nitride

the compounds in the table are only part of carbides, nitrides, oxides and borides; Only a few of them have been applied and known by people. Therefore, when people develop new tool materials, there is still room for choice and great potential in the chemical composition. Of course, not all the compounds listed in the table can be applied, because in addition to considering their comprehensive performance, we should also consider the factors such as resources, price, process, etc.

3. The matching of tool materials and workpiece materials

the mechanical, physical and chemical properties of tool and workpiece materials must be reasonably matched, The cutting process can be carried out normally and the normal tool life can be obtained. Otherwise, the tool may be rapidly worn and its life is very short. For example, workpiece materials with high hardness must be processed with harder cutters; The hardness of high-speed steel tools is not enough to be used to cut hardened steel and chilled cast iron, while cemented carbide and ceramic tools are competent. CBN tools are better to process hard and brittle materials, which requires not only high hardness, but also high modulus of elasticity, otherwise the edge is difficult to support. When machining hardened steel and other hard and brittle materials with cemented carbide tools, class k or m brands with high elastic modulus and high WC content must be used. The above is the matching of mechanical properties. Not only the mechanical properties of tool materials at room temperature, but also their high temperature properties should be considered. When machining workpieces with poor thermal conductivity, tools with good thermal conductivity should be used, so the inventory space is increased to export the cutting heat and reduce the cutting temperature. This is an example of physical performance matching

if the chemical elements in the materials of both workpiece and cutting tool are easy to combine, interact with each other or diffuse, try to avoid them. For example, titanium containing metal materials - titanium alloys, superalloys, austenitic stainless steels, etc., cannot be cut with titanium containing tools. In other words, p-type cemented carbides, tic based and Ti (C, n) based cemented carbides, and coated cemented carbides (most coating materials contain Qin) ordered to refund the overcharge of 1.36 billion yuan cannot be used; Should adopt

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