With the development of industrialization, the metalworking industry has also developed rapidly, and various new materials and new process innovations have emerged, but to ensure and improve the processing quality and efficiency of products, it has become an important link in choosing the right metal cutting fluid and minimizing the pollution to the environment. But the choice of metal cutting fluid for different machining tools is also a difficult choice.
First, the types of cutting fluid commonly used in CNC machine tools
In order to adapt to different processing occasions and process requirements, metal cutting fluid types are also diverse, which are mainly divided into two categories according to the chemical composition and state, namely water-based cutting fluid and oil-based cutting fluid.
1、Water-based cutting fluids are cutting fluids that need to be diluted with water in advance when they are used. Antirust emulsions, antirust lubricant emulsions, extreme pressure emulsions and microemulsions all belong to this broad category. The role of water-based cutting fluid is usually based on cooling and cleaning, the effect of lubrication is not obvious.
2, oil-based cutting fluid refers to the use of cutting fluids that do not require water for dilution. Pure mineral oil, fatty oil, oil additives, mineral oil, non-active extreme pressure cutting oil and active extreme pressure cutting oil all belong to this type. Contrary to water-based cutting fluids, oil-based cutting fluids have a more obvious lubricating effect, while the cooling and cleaning ability is poor.
Second, the choice of cutting fluid for different processing tools
Different processing tools, due to their different tool performance, suitable for processing the material characteristics also differ, therefore suitable for the use of different types of cutting fluid
1, for high-speed steel material tools, in the medium and low-speed cutting, heat generation is not large, suitable for the use of oil-based cutting fluid or emulsion. In high speed cutting, due to the high heat generation, the use of water-based cutting fluid can play a good cooling effect. At this time, if you use oil-based cutting fluid, it will produce a lot of oil mist, which will pollute the environment and easily cause burns on the workpiece, affecting the machining quality and the service life of the tool. In addition, it is better to use extreme pressure aqueous solution or extreme pressure emulsion during rough machining, while extreme pressure emulsion or extreme pressure cutting oil is more suitable during finishing machining.
High-speed steels use medium-speed cutting operations at a rate of about 70 m/m. High-speed steels are iron alloys containing elements such as tungsten and chromium to increase their hardness and wear resistance; even so, their hardness and wear resistance qualities are reduced to unacceptable levels by temperatures above 600°C. However, water-soluble cutting oils can be used. However, water-soluble cutting oil can be used to keep its operating temperature below 600℃.
2, for carbide tools, because of the sudden heat is more sensitive, as far as possible to make the tool evenly heated and evenly cooled, otherwise it is easy to cause chipping. Therefore, usually use oil-based cutting fluid with mild thermal conductivity and add the right amount of anti-wear additives. When cutting at high speed, the tool should be sprayed with a high flow of cutting fluid to avoid uneven heating. And this method can also effectively reduce the temperature and reduce the appearance of oil mist.
3, cast alloy (chrome cobalt tungsten) These alloys are non-iron elements, based on cobalt. When its temperature is higher than 600℃, it is harder and better wear resistance than HSS. This can be used for high-speed cutting, but also for non-cuttable alloys and cutting operations that generate high temperatures. Cast alloys are very sensitive to large changes in temperature, such as sudden interruptions in cutting operations. They are more suitable for continuous cutting operation, can use water-soluble cutting oil.
4, ceramic tools and diamond tools are often used in dry cutting process because they have more outstanding high temperature wear resistance than cemented carbide. Sometimes, in order to avoid high temperature, will also use the higher thermal conductivity of the water-based cutting fluid continuous and full pouring of the cutting area.
5, carbides are widely used in the metalworking industry and they are often called sintered carbides or superabrasives. They are made of tungsten, titanium, niobium, tantalum carbide powder added to the cobalt mold with high temperature heating sintering. Different types of sintered carbides can be produced by changing the ratio and type of metal carbide. Sintered carbides are used because they retain their hardness and wear resistance at temperatures as high as 1000°C. They are often used as inlays or can be used as a base. They are often used as inserted or replaceable cutting tips, each with different shapes and angles, which can be reassembled and stored as needed. Another easy way to make them is to cover the cutting head with a layer of carbide, which is made by vapor depositing titanium carbide onto a conventional carbide tool. Bits made in this way have high resistance to wear and the tool itself is less likely to chip. Carbide tools are often used in conjunction with water-soluble cutting oils, but they must be chosen carefully. Certain additives are will corrode the metal covered with cobalt.
6, ceramic / diamond ceramic cutting tools are mainly composed of aluminum oxide, can retain their hardness and wear resistance at high temperatures. However, as mentioned above, the harder the material, the more fragile, which makes ceramic tools are not suitable for discontinuous cutting or vibration load and temperature changes. Machining can use non-water-soluble cutting oil (oil-based cutting oil) or no cutting oil at all, to avoid the use of water-soluble cutting oil.
7、The hardest cutting tool is diamond, but it is also fragile. Diamond can engage in high content of aluminum processing operations, this alloy contains hard silicon particles, will quickly wear carbide tools. It is also suitable for grinding non-ferrous materials, such as stone and cement. Diamond can be oxidized at high temperatures, so it is not suitable for difficult alloys. Because it is particularly hard, it is often used in grinding applications. Oil-based cutting oils or water-soluble cutting oils or synthetic cutting fluids can be used.
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