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Selection of grinding fluid in cemented carbide tool manufacturing

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Update time : 2020-11-06 09:36:10
Since entering the 21st century, the global manufacturing industry has become more competitive, and metal processing is facing a huge challenge. In order to adapt to the high precision, high speed, automation, multi-function and high productivity of machining, cutting tools are required to have higher strength and toughness, and have the characteristics of long life, high reliability, high temperature resistance, wear resistance, oxidation resistance and impact resistance. This puts forward new requirements for the design and manufacture of cutting tools and the development and application of metalworking fluid products.           
1. Carbide tools and their characteristics           
Due to the high hardness, high brittleness and small thermal conductivity of the carbide tool material, it is very difficult to grind the cutting edge of the tool, especially the whole carbide tool with large grinding allowance. Among them: ① the tool material has high hardness and requires a large grinding pressure; ② the tool material has low thermal conductivity and is not allowed to generate excessive grinding heat; ③ the tool material has high brittleness, which increases the possibility of cracks.           
Therefore, the grinding of cemented carbide tools requires not only good self sharpening of grinding wheel, but also reasonable grinding technology and good cooling performance.           
When grinding carbide tools, if the grinding temperature is higher than 600 ℃, the surface of the tools will be oxidized and discolored, which will cause different degrees of grinding burns. In serious cases, the carbide tools will be cracked. These cracks are usually small, and the grinding surface near the cracks often has different tungsten oxide colors such as blue, purple, brown or yellow.           
2. Selection of grinding fluid in the manufacturing of cemented carbide tools           
For tool manufacturers, in the process of tool manufacturing, in addition to equipment, grinding wheel and other factors, there is also a problem that can not be ignored, that is, reasonable selection of grinding fluid and grinding oil.           
(1) selection of grinding fluid. The hardness of cemented carbide is high and its brittleness is high. The grinding temperature can reach about 1000 ℃, but only 15% of the heat generated is taken away with the grinding chips and 8% with the workpiece. The grinding fluid used for cemented carbide tool manufacturing should have the following characteristics:
a. better lubricity and extreme pressure performance; b. excellent cooling performance, which can timely remove abrasive debris and abrasive grains worn out by grinding; c. better anti foaming property, so as to ensure that the grinding fluid does not generate foam in large flow rate and high speed grinding state, and effectively ensures cooling and cleaning properties. d. effectively prevent the precipitation of cobalt.           
(2) selection of grinding oil. In contrast to grinding fluid, the primary purpose of using grinding oil is not to cool the cutting area, but to reduce heat generation by providing high lubricity. Generally, the requirements for grinding oil used in carbide tool manufacturing are as follows:
① base oil with higher flash point and lower evaporation quality, such as hydrocracking base oil or synthetic base oil, can be used to greatly reduce oil loss and improve the cleanliness of working environment under the same viscosity. ② the grinding oil has proper viscosity to ensure excellent flushing performance and settling performance. ③ the grinding oil adopts a reasonable formula system, such as avoiding the use of extreme pressure additives containing sulfur and chlorine to prevent the grinding oil from corroding the non-ferrous metal parts of the machine tool. The grinding site of cemented carbide tool with grinding oil is shown in Figure. The grinding site of carbide bit when grinding oil is used is shown in Fig.