For different types of cutting, the removal characteristics of metals are different, and the more difficult cutting requires higher cutting fluid. The degree of difficulty of the cutting process, in order from difficult to easy, is as follows: internal broaching - external broaching - tapping - threading - gear hobbing - deep hole drilling - boring - thread cutting with forming tools - high speed and low feed Thread cutting - milling - drilling - planing - turning (single edge tool) - sawing and grinding. The above order of arrangement is not absolute, because changes in the geometry of the tool and the material of the workpiece can also change the ease of machining. A brief description of how to select cutting fluid for some commonly used processing methods. 1. Turning and Boring Rough turning: During rough turning, the machining allowance is large, so the cutting depth and feed rate are large, the cutting resistance is large, a large amount of cutting heat is generated, and the tool wear is also serious. The water-based cutting fluid with cleaning, lubricating and anti-rust functions can take away the cutting heat in time, reduce the cutting temperature, and thus improve the durability of the tool. Generally, extreme pressure emulsion is better. In addition to good cooling performance, extreme pressure emulsions also have good extreme pressure lubricity, which can significantly extend tool life and improve cutting efficiency. When using water-based cutting fluids, pay attention to the maintenance of the machine tool guide surface, and the workbench before leaving work. Dry the cutting fluid on and apply lubricating oil. Fine turning: When fine turning, the cutting allowance is small, the cutting depth is only 0.05 ~ 0.8mm, the feed rate is small, and the accuracy and roughness of the workpiece are required to be guaranteed. Due to the small cutting force and low temperature during finishing, it is advisable to use high concentration (above 10%) emulsion and cutting fluid containing oily additives. Boring: The boring mechanism is the same as that of turning, but it is inner hole processing, the cutting speed is not fast, but the heat dissipation conditions are poor. Emulsion can be used as the cutting fluid, and the flow and pressure of the cutting fluid should be appropriately increased.
2. Milling Milling is intermittent cutting, and the cutting depth of each tooth changes all the time, which is prone to vibration and a certain impact force, so the milling conditions are worse than the turning conditions. When using high-speed tools for high-speed flat milling or high-speed end milling, cutting fluids with good cooling and certain lubricating properties, such as extreme pressure emulsions, are required. When milling at low speed, it is required to use cutting oil with good lubricity, such as precision cutting oil and inactive extreme pressure oil. For stainless steel and heat-resistant alloy steel, cutting oil containing sulfur and chlorine extreme pressure additives can be used.
3. Thread Processing When cutting the thread, the tool is in wedge-shaped contact with the cutting material, and the cutting edge is surrounded by the cutting material on three sides. It is difficult to remove the chips due to the large cutting torque, and the heat cannot be taken away by the chip liquid in time. In particular, the cutting conditions are more severe when threading and tapping, and sometimes chipping and broken taps may occur. The cutting fluid is required to have a low friction coefficient and high extreme pressure at the same time, so as to reduce the friction resistance of the tool and prolong the service life of the tool. , Generally, a composite cutting fluid containing both oily agent and extreme pressure agent should be used. In addition, the penetration performance of the cutting fluid is very important when tapping the thread. Whether the cutting fluid can penetrate into the cutting edge in time has a great influence on the durability of the tap. The permeability of the cutting fluid is related to the viscosity, and the oil with low viscosity has better permeability. If necessary, a small amount of diesel oil or kerosene can be added to improve the seepage effect. In some cases, such as blind hole tapping, it is difficult for the cutting fluid to enter the hole. In this case, the cutting fluid with high viscosity and strong adhesion is better.
4. Reaming Reaming is the precision machining of holes, which requires high precision. Reaming is low-speed and small-feed cutting, mainly because the tool and the hole wall are extruded and cut. The extrusion effect will destroy the machining accuracy and surface roughness, increase the cutting torque, and also generate built-up edge, which increases the tool wear and reaming basically belongs to the boundary lubrication state. Emulsion or extreme pressure cutting oil, you can get good results. For deep hole reaming, deep hole drilling cutting oil with good lubricating performance can meet the process requirements.
5. Broaching A broach is a machining tool with many teeth arranged in parallel according to the cutting edge and the teeth along the axis direction. The characteristic of broaching is that it can process workpieces with complex shapes with high precision. Because the broach is an expensive tool, the durability of the tool has a greater impact on the production cost. In addition, broaching is a finishing process, which has strict requirements on the surface roughness of the workpiece. When broaching, the cutting resistance is large, the chip removal is not easy, the cooling conditions are poor, and the surface of the workpiece is easily scratched, so the lubricity and drainage performance of the cutting fluid are required. There are special broaching oils containing sulfur extreme pressure additives in China.
6. Drilling Drilling with ordinary twist drills belongs to rough machining. It is difficult to remove chips during drilling, and the cutting heat is not easily exported, which often causes annealing of the cutting edge, which affects the service life and processing efficiency of the drill bit. The selection of cutting fluid with good performance can prolong the life of the drill several times or even more, and the productivity can also be significantly improved. Generally use extreme pressure emulsion or extreme pressure synthetic cutting fluid. The extreme pressure synthetic cutting fluid has low surface tension and good permeability, which can cool the drill bit in time, which is very effective in prolonging the life of the tool and improving the processing efficiency. For difficult-to-cut materials such as rust-producing steel and heat-resistant alloys, extreme pressure cutting oils with low viscosity can be used.
7. Deep Hole Drilling Deep hole drilling (gun drilling) is a deep hole processing technology developed in recent years. Traditional deep hole machining (also the ratio of depth to hole diameter is greater than 5) requires multiple processes such as drilling, boring, rough reaming, and grinding to process holes with higher precision and lower surface roughness. The new process uses special-structured tools and a high-pressure cooling and lubrication system, which can simplify the above-mentioned multiple processes into one continuous pass to complete deep hole machining with high precision and low surface roughness. This process has high efficiency and significant economic benefits. Deep hole drilling cutting fluid with excellent performance is one of the keys to deep hole drilling processing technology. Deep hole drilling cutting fluid must have the following properties. Good cooling effect, eliminates the heat generated by deformation and friction, and inhibits the formation of chips. Good high temperature lubricity, reduce friction and wear of cutting edge and support, and ensure that the tool maintains a good lubricating state at high temperature in the cutting area. Good permeability and chip removal, so that the cutting fluid can penetrate into the cutting edge in time and ensure that the chips can be discharged smoothly. Therefore, the deep hole drilling cutting fluid requires high extreme pressure and low viscosity.
8. Gear Processing For high-speed gear cutting, using oil-based cutting fluid will produce large oil fume and pollute the environment. Moreover, due to insufficient cooling, the surface of the workpiece will often be burned, which will affect the machining quality and aggravate tool wear. Water-based cutting fluids with strong extreme pressure, such as water-based synthetic cutting fluids containing extreme pressure additives of sulfur and phosphorus or high-concentration extreme pressure emulsions, can overcome oil pollution during high-speed cutting, and the machining quality and tool wear are better than oil. Good base cutting fluid. However, for the original gear hobbing and gear shaping machine tools, measures must be taken to prevent water from entering the rotating parts, so as to prevent the machine tool from malfunctioning. Shaving processing requires high surface quality. In order to prevent sticking to the knife, cutting oil containing active extreme pressure additives can be used, and because shaving processing generates fine chips, in order to make the chips easy to wash away, it is best to use low-viscosity cutting oil , if the chip separation is not smooth, it will deteriorate the quality of the machined surface.
9. Grinding Grinding can achieve high dimensional accuracy and low surface roughness. When grinding, the grinding speed is high and the calorific value is high, and the grinding temperature can be as high as 800-1000, or even higher, which is easy to cause burns on the surface of the workpiece, surface cracks and deformation of the workpiece due to thermal stress, wear and passivation of the grinding wheel, and abrasive particles fall off. , and the grinding debris and grinding wheel powder are easy to splash and fall on the surface of the part to affect the machining accuracy and surface roughness. When machining toughness and plastic materials, the abrasive debris is embedded in the gap on the working surface of the grinding wheel or the abrasive debris is fused with the processed metal. On the surface of the grinding wheel, the grinding wheel will lose its grinding ability. Therefore, in order to reduce the grinding temperature, wash off the grinding debris and the end of the grinding wheel, and improve the grinding ratio and the surface quality of the workpiece, it is necessary to adopt good cooling performance and cleaning performance, and have certain Cutting fluid with lubricating properties and anti-rust properties. High-speed grinding: Grinding when the linear speed of the grinding wheel exceeds 50m/s is usually called high-speed grinding. When the linear speed of the grinding wheel increases, the grinding temperature increases significantly. From the test, the grinding temperature (working average temperature) when the grinding wheel linear speed is 60m/s is about 50%~70% higher than that of 30m/s; when the grinding wheel linear speed is 80m/s, the grinding temperature is higher than that of 60m/s 15% to 20% higher. After the linear speed of the grinding wheel is increased, the number of abrasive grains participating in grinding per unit time increases, the friction effect increases, and the energy consumption also increases, which increases the surface temperature of the workpiece and increases the possibility of burns and cracks on the surface. Therefore, in high-speed grinding, ordinary cutting fluids cannot be used, but high-speed grinding fluids with good penetration and cooling properties must be used to meet high-speed grinding with a linear speed of 60m/s. process requirements. Power grinding: This is an advanced high-efficiency grinding process. For example, during high-speed power grinding, the grinding wheel with a linear speed of 60m/s has a radial power input at a feed rate of about 3.5 to 6 mm per minute. The removal rate can be as high as 20~40mm33/mm·s. At this time, the friction between the abrasive particles of the grinding wheel and the workpiece is very severe. Even under the conditions of high pressure and large flow rate, the measured surface temperature of the workpiece in the friction zone reaches 700~1000. If the cooling conditions are not good Well, the grinding process is impossible. In the power-in type strong grinding, the synthetic strong grinding fluid with excellent performance is compared with the emulsion, the total grinding volume is increased by 35%, the grinding ratio is increased by 30% to 50%, and the normal grinding time is prolonged by about 40%. The power loss is reduced by about 40%, so the performance of the coolant has a great influence on the grinding effect during strong grinding. Diamond grinding wheel grinding: This is suitable for the grinding of materials with high hardness such as cemented carbide, ceramics, glass, etc. It can be used for rough grinding and fine grinding. The ground surface generally does not produce cracks and gaps, and a lower surface can be obtained. roughness. In order to prevent excessive heat generation during grinding and cause premature wear of the grinding wheel and obtain a lower surface roughness, continuous and sufficient cooling is required. In this kind of grinding, due to the high hardness of the workpiece, the grinding fluid should mainly have cooling and cleaning properties, keep the sharp edge of the grinding wheel, and the friction coefficient of the grinding fluid should not be too low, otherwise it will cause low grinding efficiency, surface burns and other adverse effects. The chemical synthesis fluid mainly composed of inorganic salts is used as the grinding fluid. A small amount of polyethanol can be added as a lubricant during fine grinding, which can improve the surface processing quality of the workpiece. For parts with high machining accuracy, low-viscosity oil-based cutting fluid with good lubricity can be used. Thread, gear and lead screw grinding: This type of grinding pays special attention to the quality and dimensional accuracy of the machined surface after grinding. Generally, grinding oil containing extreme pressure additives should be used. This kind of oil-based grinding fluid is due to its lubricating properties. Good, it can reduce the grinding heat, and the extreme pressure additive can react with the workpiece material to generate iron sulfide film and iron chloride film with low shear strength, which can reduce the wear of abrasive particles and the tip of the cutting edge, and make the grinding smooth. conduct. In order to obtain better cooling and cleaning properties, the cutting fluid should ensure fire safety, and it is advisable to use a grinding oil with low viscosity and high flash point.
10. Honing The workpiece processed by honing has high precision and low surface roughness. The particle size of iron powder and whetstone powder produced during the processing is very small, and it is easy to be suspended in the grinding fluid, causing blockage of the whetstone hole, affecting the processing efficiency and destroying the processing quality of the workpiece surface. The cooling lubricating fluid is required to have good penetration, cleaning and settling properties. Water-based coolants have poor settling properties for fine powders and are generally not suitable for use. Oil-based grinding fluid with high viscosity is also unfavorable for powder settling, so generally, mineral oil with low viscosity (2~3mm2/s (40)) is used to add a certain amount of inactive sulfurized fatty oil as honing oil.
