Cemented carbide is known as the "industrial tooth" and has a wide range of applications, including engineering, machinery, automobiles, ships, optoelectronics, military industry and other fields. Tungsten consumption in the cemented carbide industry accounts for more than half of the total tungsten consumption. We will introduce it from its definition, characteristics, classification, uses, as well as hardness testing and testing characteristics and applications.
First,let’s take a look at the definition of cemented carbide.
Cemented carbide is an alloy material made from hard compounds of refractory metals and bonding metals through a powder metallurgy process. The main material is tungsten carbide powder, and the binder includes cobalt, nickel, molybdenum and other metals.
Secondly, let’s take a look at the characteristics of cemented carbide. Carbide has high hardness, wear resistance, strength and toughness. Its hardness is very high, reaching 86~93HRA, which is equivalent to 69~81HRC. When other conditions remain unchanged, if the tungsten carbide content is higher and the grains are finer, the hardness of the alloy will be greater. At the same time, its wear resistance is very good. The service life of tools made of carbide materials is very high, 5 to 80 times longer than that of high-speed steel cutting; the life of grinding tools made of carbide materials is also very long, 20 to 150 times longer than that of steel grinding tools. . Carbide has excellent heat resistance. The hardness remains basically unchanged at 500°C, and the hardness is still very high even at 1000°C. Its toughness is excellent. The toughness of cemented carbide is determined by the bonding metal. The higher the bonding phase content, the greater its flexural strength. It has strong corrosion resistance. Under normal circumstances, cemented carbide does not react with hydrochloric acid or sulfuric acid and has strong corrosion resistance. This is also the reason why it can withstand corrosion and is not affected by many harsh environments. Also, cemented carbide is very brittle. This is one of its shortcomings. Because of its high brittleness, it is difficult to process. It is difficult to make tools with complex shapes and cannot be used for cutting.
Next,We will further understand the cemented carbide from the classification. Carbide can be divided into the following three categories. Let’s take a look at the detailed introduction.
1. Tungsten-cobalt alloy
Made of sintered WC and cobalt powder. The most widely used grades include YG3, YG6, YG8, etc. The number after YG indicates the cobalt content, such as YG6, which indicates a tungsten-cobalt cemented carbide with w (Co) of 6% and w (WC) of 94%. The higher the cobalt content, the better the toughness, but the hardness and wear resistance are slightly reduced. YG carbide cutting tools are suitable for processing brittle materials (such as cast iron).
2. Tungsten titanium cobalt alloy
Made of sintered WC, TiC and cobalt powder. The most widely used grades are YT5, YT15, YT30, etc., where "YT" represents tungsten titanium cobalt carbide, and the following number represents the TiC content. For example, YT15 means w (TiC) is 15%, and the others are tungsten-titanium-cobalt cemented carbide with WC and cobalt. YT alloy has high hardness, good wear resistance and thermal hardness. YT carbide cutting tools are suitable for processing plastic materials (such as steel, etc.).
3. Tungsten, cobalt and tantalum alloys
It is sintered from three powders of TaC (tantalum carbide), TiC and WC and cobalt binder. Commonly used grades include YW1 and YW2. The number in the grade represents the sequence number. The larger the number, the higher the cobalt content in the cemented carbide.
Next, about the hardness testing and testing characteristics of cemented carbide
The hardness testing of cemented carbide mainly uses a Rockwell hardness tester to test the HRA hardness value. PHR series portable Rockwell hardness tester is very suitable for testing the hardness of cemented carbide. The instrument weighs only 0.7kg, has the same accuracy as the desktop Rockwell hardness tester, and is very convenient to use and carry.
Cemented carbide is a kind of metal. The hardness test can reflect the differences in mechanical properties of cemented carbide materials under different chemical compositions, organizational structures and heat treatment process conditions. Therefore, hardness tests are widely used to inspect the performance of cemented carbide and supervise heat treatment. The correctness of the process and the research of new materials. The characteristics of the cemented carbide hardness test are that it is a non-destructive test and the test method is relatively simple. The hardness testing of cemented carbide has strong adaptability to the shape and size of the test piece and high testing efficiency. In addition, there is a certain correspondence between the hardness of cemented carbide materials and other physical properties.
Finally, regarding the application of cemented carbide with different hardness
Carbide has high hardness and wear resistance and is often used to manufacture metal cutting tools, measuring tools, molds, etc. Usually when the hardness of the material is high, the wear resistance is also high; when the flexural strength is high, the impact toughness is also high. But the harder the material, the lower its flexural strength and impact toughness. High-speed steel is still the most widely used tool material due to its high bending strength, impact toughness, and good machinability, followed by cemented carbide.
One type of cemented carbide is made with one or several carbides (such as TiC, WC, etc.) as the hardening phase and alloy steel (such as high-speed steel, molybdenum-chromium steel, etc.) powder as the binder. It is called steel structure. Carbide. Its hardness is between steel and cemented carbide, but its toughness is greatly improved and it can be machined and heat treated. The typical hardness of this kind of steel structure cemented carbide is: after quenching and tempering, the hardness is 69~73HRC, high speed steel 65%
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