1. What are the most commonly used tool materials in China? 2. What is cemented carbide? 3. What characteristics should the tool material have?

The most traditional high-speed steel W 18Cr4V contains 18% tungsten. Later, typical W6Mo5Cr4V2(M2) and W9Mo3Cr4V also contained 6% and 9% tungsten. The tungsten content of cemented carbide is also very high. Tungsten cobalt (commonly used for processing cast iron and aluminum alloy, such as YG series in China) or tungsten cobalt titanium (commonly used for processing steel parts with long chips, such as YT series in China) is basically above 80%. For example, the tungsten carbide content of YG6 is as high as 90%. 7 G Y EA

China has the largest tungsten reserves in the world, accounting for 85% of the global supply. Tungsten is mainly used in cemented carbide, special steel including high-speed steel and other products, and is widely used in national defense industry, aerospace and information industry, and is called "the tooth of industry". Tungsten has excellent temperature resistance, so tungsten alloys are widely used in weapon industry, such as guns and cannons. The projectiles used as armor-piercing bullets in the military are all high-density alloy steel and tungsten carbide, which are much harder than tank armor. The chemical properties of tungsten are very stable, and it will not be oxidized at high temperature above 1000℃, and its hardness will not decrease obviously. This is very beneficial to the high temperature metal jet of armor-piercing projectile. The mechanical properties of tungsten alloy are almost the same as those of depleted uranium, but it is not radioactive and is beneficial to environmental protection. Tungsten has extremely high hardness and is mainly used in the alloy of steel and metal. After adding tungsten, the hardness of steel will be greatly improved. High-speed steel, a tool material in the field of metalworking, is an alloy containing tungsten. If there is no tungsten in a country, it will greatly lack the ability of metal processing under the current technical conditions, which will directly lead to the paralysis of the machinery industry, so it is called strategic metals. In addition, tungsten must also be used as a filament in the field of lighting. _L {#~ B

Next should be molybdenum. J \，wi/

High-speed steel is divided into tungsten series and tungsten-molybdenum series. Due to the shortage of tungsten resources and the good manufacturability of tungsten-molybdenum high-speed steel, tungsten-molybdenum high-speed steel has become the mainstream faction of high-speed steel. In high-speed steel, the contribution of one part of molybdenum to tool performance is approximately equivalent to two parts of tungsten. So we can see that the "tungsten equivalent" of W6Mo5Cr4V2(M2) is 16%, and that of W9Mo3Cr4V is 15%. China's molybdenum reserves rank second in the world, accounting for 24% of the global supply. Molybdenum can be used to refine various alloy steels, stainless steels, heat-resistant steels and super alloys, and is widely used in military industry, also known as "war metal". Ultraviolet & vg0j

In addition, titanium, cobalt, chromium, niobium and tantalum are also rare metals commonly used in cutting tools. -}) cofj}b

Titanium is the main component of another cemented carbide titanium-based cemented carbide (often called "cermet" in China). Titanium-based cemented carbide is a cemented carbide with TiC or Ti(C, N) as the main component (accounting for more than 60% ~ 80%) and Ni-Mo or Ni-Co-Mo as the bonding phase. The performance of titanium-based cemented carbide is between ceramic and WC-based cemented carbide, and it can cut at a higher cutting speed than ordinary tungsten-based cemented carbide, and the surface quality of the machined workpiece is good. Therefore, it is especially suitable for finishing and semi-finishing of steel and castings. In foreign countries, the proportion of TiC-based and Ti(C, N)-based cemented carbide has reached more than 30% of the total demand for indexable inserts. In recent years, with the development of coated titanium-based cemented carbide (single coating or multi-component composite coating), ultrafine and nanocrystalline and gradient structure titanium-based cemented carbide, the comprehensive properties of materials have been greatly improved and the application scope has been expanded. n ^ 5 * = P； y9h

Titanium is also one of the most important components of tool coating. TiC, TiN, Ti(CN), TiAlN, etc. It is our most common coating variety. # }hzU q

It is understood that China's titanium resources account for about 38% of the world's titanium resources, and the total reserves of TiO2 are more than 9 billion tons, ranking first in the world. Most of them are in Panzhihua area. Titanium has the highest specific strength (the ratio of tensile strength to density) among all industrial metal materials: the density of titanium is 4.54 g /mm, estimated to be 33.6-67.2 kg /mm (the highest tensile strength of pure titanium can reach 180kg/mm), the extrusion strength is 40%-55%, the overall strength is twice that of aluminum, and the specific strength is. It can maintain such high strength in a wide temperature range from -253℃ to 500℃. Titanium is mainly used in precision parts of aerospace military industry. j*l3 F d~

The role of cobalt in high-speed steel cutting tools I mentioned in the article "scribbling high-speed steel": the effect of cobalt on improving the properties of high-speed steel is also obvious, which can make carbides dissolve more in the matrix during quenching and heating, and improve the wear resistance by using high matrix hardness. This kind of high speed steel has good hardness, thermal hardness, wear resistance and grindability. 6 g street no.8

The main function of cobalt in cemented carbide is binder, which can provide certain toughness for cemented carbide tools. The tool with less cobalt content has higher hardness, but its toughness is often not enough. Therefore, people often adopt the method of increasing cobalt content to appropriately reduce hardness and improve toughness. Because once the tool breaks, no matter how high the wear resistance is, it can't be reflected. Cobalt strengthening is a new scheme discovered later. It can maintain the high hardness of cemented carbide core to provide sufficient supporting force, and at the same time, the surface has high cobalt content and can withstand high chip impact. It is said that this technology was developed by Dr. Liu Yixiong, a China scientist who worked in Kenner Metal in his early years (at that time, the brand was KC850), and now sandvik Claman and Yamagata have also provided such products. d0Qz_qzc

However, China is short of cobalt resources, and the estimated reserves of metallic cobalt have been proved to be hundreds of thousands of tons. Distributed in 24 provinces (regions) of China. Cobalt resources abroad are rich, with a reserve of about 5.2 million tons, but most of them are produced in weathered laterite nickel ore, magmatic copper-nickel sulfide ore and sedimentary sandstone copper ore, and more than 95% are concentrated in a few countries such as Democratic Republic of Congo, Australia, Cuba, Zambia, New Caledonia and Russia. o p l}gpmB

The content of chromium in all high-speed steels is almost 4%, so that the symbol of chromium content can be omitted when the International Organization for Standardization formulates the international standard of high-speed steel grades. For example, the code name of W18Cr4V2 is HS18-0-/KLOC-0 (the former 0 indicates that the Mo content is 0, and the latter 0 indicates that the Co content is 0), the code name of W6Mo5Cr4V2 is HS6-5-2-0, and the code name of W2Mo9Cr4VCo8 (American brand M42). HB PZgk| [

Some chromium-containing tool coatings have been developed. G6 coating in Balcer is an AlCrN coating. According to Balcer, the wear resistance, thermal hardness and oxidation resistance of this coating have been greatly improved. vF #； X]a

However, chromium resources in China are quite scarce. aQ & gtiNa0dh

Niobium and tantalum often appear in the composition table of cemented carbide in the form of niobium carbide and tantalum carbide, and the hardness of tantalum carbide is the highest among all cemented carbides. Niobium, tantalum, tungsten and molybdenum are rare metals with high melting point, and their properties and uses are similar. The main characteristic of niobium and tantalum is heat resistance. Their melting points are as high as 2400 degrees Celsius and nearly 3000 degrees Celsius respectively. Don't say that ordinary fires can't burn them, and even the blazing flames in the steelmaking furnace can't help them. Therefore, they also occupy a place in the composition of cutting tools.