Grinding of high-vanadium high-speed steel
High-speed steel is a type of quenched steel with special purposes. Due to its vanadium content ranging from 1% to 5%, especially when it exceeds 3%, it is called high-vanadium high-speed steel. Vanadium forms a large amount of vanadium carbide in steel. Due to the hardness of vanadium carbide being as high as 2800HV, which is much higher than that of hard alloys and ceramics, grinding is extremely difficult. In the past, many grades of high-performance high-speed steel had a high vanadium content. Although their performance in use and tool durability were several times higher than those of ordinary high-speed steel, their poor grinding performance (when grinding with corundum abrasive wheels) directly affected their promotion and application. Nowadays, it is very easy to use grinding wheels with cubic boron nitride (CBN) as the abrasive to grind high-speed steel containing vanadium.
When grinding high-speed steel with corundum grinding wheels, especially high-vanadium high-speed steel which is extremely difficult to grind, the grinding force is large, the grinding temperature is high, it is prone to burning, the abrasive grains of the grinding wheel wear out quickly, are prone to clogging and grain shedding, and the grinding is extremely difficult. With CBN grinding wheel grinding W18Cr4V, W2Mo9Cr4VCo8W6Mo5Cr4V5SiNbA1, W6Mo5Cr4V2A1, W10M04Cr4V3AI 5 kinds of high speed steel bar, accumulative total to 17 mm grinding wheel is still sharp. For instance, when grinding W6Mo5Cr4V5SiNbAI high-speed steel with a copper-plated CBN grain grinding wheel, 150 cutting teeth can be ground, while a white corundum grinding wheel cannot grind a single tooth. Single crystal corundum and microcrystal corundum grinding wheels can only grind 7 to 8 cutting teeth. The grinding of high-speed steel with CBN grinding wheels has the following characteristics.
(1) The grinding wheel has high durability
The wear of CBN grinding wheels when grinding the above-mentioned high-speed steel is 1/64 of that of single crystal corundum grinding wheels, 1/104 of that of green silicon carbide grinding wheels, and 1/99 of that of white corundum grinding wheels.
(2) It has a very high grinding ratio
The grinding ratio of W12Cr4V5Co high-vanadium high-speed steel ground with CBN grinding wheels is 140, while that of corundum grinding wheels is only 10. The grinding ratio of W2Mo9Cr4VCo8 super-hard high-speed steel with CBN grinding wheels is 660, while that of corundum grinding wheels is only 10. The grinding ratio of W6Mo5Cr4V2 tungsten-molybdenum high-speed steel ground with CBN grinding wheels is 980, while the grinding ratio of corundum grinding wheels is also 10.
(3) It can prevent burns
When grinding high-speed steel with corundum grinding wheels, the abrasive grains of the grinding wheel wear out very quickly. If not dressed in time, the surface of the workpiece will be burned, directly affecting the surface quality of the workpiece. Grinding is carried out with CBN grinding wheels until the working layer of the grinding wheel is completely worn out without the need for dressing. Generally, there will be no burning phenomenon on the grinding surface of the workpiece.
(4) Low grinding power. CBN grinding wheels have a very high grinding capacity, and their unit grinding power is 2/3 to 5/6 lower than that of corundum grinding wheels.
