Gray cast iron processing tool material
2018-08-27
First, gray cast iron processing tool material
Although the application of nodular cast iron and vermicular cast iron is increasing, the application of grey cast iron is still strong. In the automotive industry, it will also continue to retain a large number of gray cast iron processing . However, the processing conditions today are different from those in the past. Due to the use of CBN tools, the cutting speed has increased by approximately 335 m/min compared to 10 years ago. The higher temperatures produced by high speed cutting may dissolve the coated carbide of the cutting insert in much the same way as the chemical reaction between the cubic boron nitride cutting tool and ferrite. Cast iron workpieces are hard and brittle. When turning cast iron workpieces, CNC blades need to withstand higher cutting heat and cutting forces. At present, the numerically controlled blades for turning cast iron workpieces are mostly carbide coated blades, and the coating thickness is generally 8 micrometers. 20-micron, coated CNC blades exposed the coating after fracture due to casting defects, revealing the alloy body, resulting in a low durability of coated carbide CNC blades turning cast iron workpieces.
Second, ductile iron and vermicular cast iron machining tools
Although polycrystalline cubic boron nitride tools have proven to be a superior cutting tool material, virtually unlimited tool life can be achieved when cutting grey cast iron. Unfortunately, when machining cubic ductile cast iron and vermicular cast iron with cubic boron nitride tools, they are affected by chemical dissolution. In these processes, the tool material interacts with the higher iron content in cast iron, which can cause rapid tool wear. This problem has driven the need to develop a tool grade that resists chemical action. CBN was developed based on the above ductile iron machining mechanism. It is commonly used in pearlite ductile iron high-speed cutting, such as QT500, QT600, QT700, QT800, QT900 and other high-strength ductile iron in the rough finishing.
In order to process these new types of cast iron materials, it is required that the tools not only improve the wear resistance but also have very good toughness, and these two properties are difficult to achieve at the same time. In response to this challenge, many tool manufacturers are working hard to develop tools that provide the best combination of these two properties.
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