What are the three ISO grades of cemented carbides?
Cemented carbides, also known as hard metals, are composite materials made of tungsten carbide particles and a metallic binder such as cobalt, nickel, or iron. These materials are widely used in cutting, drilling, and wear-resistant applications due to their high hardness, toughness, and chemical stability.
To classify cemented carbides according to their properties and applications, the International Organization for Standardization (ISO) has established a system of grades based on the amount of tungsten carbide and binder, as well as the grain size and overall toughness of the material. The three main ISO grades of cemented carbides are ISO K, ISO P, and ISO M.
ISO K grades
ISO K grades are characterized by having a high percentage of tungsten carbide (WC) and a low percentage of binder metal (Co, Ni, or Fe). These grades are often called "ultra-hard" or "hard plus" carbides because they offer exceptional hardness, wear resistance, and thermal stability. ISO K grades are mainly used in cutting tools for machining cast iron, hardened steels, and other difficult-to-machine materials.
There are several sub-grades within the ISO K range, with different WC-binder ratios and grain sizes. For example, ISO K05 to K10 grades have a WC content of 85-94% and a Co content of 6-15%, and are suitable for turning hardened steels and milling titanium alloys. ISO K40 to K44 grades have a WC content of 94-96% and a Co content of 4-6%, and are ideal for drilling and grooving in stainless steel and high-temperature alloys.
ISO P grades
ISO P grades are characterized by having a medium to high percentage of tungsten carbide and a medium percentage of binder metal. These grades offer a balanced combination of toughness, strength, and wear resistance, making them suitable for a wide range of cutting and drilling applications.
The most common ISO P grades are P10 to P25, with a WC content of 80-90% and a Co content of 10-20%. These grades are used in milling, turning, and drilling operations for general-purpose steels, cast iron, and non-ferrous metals. Other ISO P grades, such as P30 to P35 and P40 to P45, have higher WC contents (up to 94%) and are suitable for high-speed machining of stainless steels and heat-resistant alloys.
ISO M grades
ISO M grades are characterized by having a higher percentage of binder metal and a lower percentage of tungsten carbide than ISO K and P grades. These grades offer good shock resistance and toughness, making them suitable for applications where the material is subjected to impact or vibration.
The most common ISO M grades are M10 to M25, with a WC content of 70-80% and a Co content of 20-30%. These grades are used in mining, construction, and machining operations where wear and impact resistance are crucial. Other ISO M grades, such as M30 to M35 and M40 to M45, have lower WC contents and are ideal for high-speed drilling and milling of aluminum and non-metallic materials.
Conclusion
In summary, the three ISO grades of cemented carbides – K, P, and M – offer a wide range of properties and applications, from ultra-hard cutting tools to shock-resistant wear parts. Choosing the right grade for a specific application requires a careful consideration of factors such as the workpiece material, machining conditions, and desired performance. By understanding the differences between these grades, engineers and manufacturers can optimize their processes and achieve better results.
