Knowledge of cutting fluid use and cooling in the

2022-09-23
  • Detail

Summer is gone, and the use of cutting fluid and cooling knowledge

* is close to the autumn equinox, and most southern regions really bid farewell to the hot and hot weather at this time. However, in the eyes of machining people, what they need to face all year round is the same "hot" cutting fluid. How to use cutting fluid reasonably and control temperature are necessary skills. Let's take a look at how to choose cutting fluid among the top 10 machining types and the six methods to cool the cutting fluid at high temperature

Part. How to correctly select cutting fluid for the top 10 machining types

for different machining types, the cutting characteristics of metals are different, and the more difficult machining requires higher cutting fluid. The degree of difficulty in the cutting process is arranged in the order from difficult to easy: internal broaching - External broaching - tapping - thread machining - gear hobbing - deep hole drilling - boring - cutting threads with forming tools - adding long glass fibers can actually reduce the total cost of composite materials. Cutting threads with high speed and low feed - Milling - Drilling - planing - turning (single edge tool) - sawing and grinding

I. turning and boring

extreme pressure/high concentration emulsion

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. It is mainly necessary to choose water-based cutting fluid with cooling effect and certain cleaning, lubrication and rust prevention effects, so as to take away the cutting heat in time, reduce the cutting temperature, and improve the tool durability, Generally, extreme pressure emulsion is better. In addition to good cooling performance, EP emulsion also has good EP lubricity, which can significantly prolong the service life of the tool and improve the cutting efficiency. When using water-based cutting fluid, pay attention to the maintenance of the machine tool guide rail surface. Before going off work, wipe the cutting fluid on the workbench dry and apply lubricating oil

finish turning: during finish turning, the cutting allowance is small, the cutting depth is only 0.05 ~ 0.8mm, and the feed rate is small. It is required to ensure the accuracy and roughness of the workpiece. Due to the small cutting force and low temperature during finish turning, it is appropriate to use emulsion with high concentration (more than 10%) and cutting fluid with oily additives

boring: the boring mechanism is the same as turning, but it is inner hole processing, and the cutting speed is not fast, but the heat dissipation condition is poor. Emulsion can be used as cutting fluid, and the flow and pressure of cutting fluid should be appropriately increased when using

II. Milling

extreme pressure emulsion and inactive extreme pressure oil

milling is intermittent cutting, and the cutting depth of each cutter tooth changes from time to time, which is easy to produce vibration and certain impact force, so the milling condition is worse than the turning condition. 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 emulsion, are required

in low-speed milling, 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 with sulfur-containing and chlorine extreme pressure additives can be used

III. thread machining

composite cutting fluid of oily agent + extreme pressure agent

when cutting threads, the tool is in wedge contact with the cutting material, and the three sides of the blade are surrounded by the cutting material. The cutting torque is large, and it is difficult to remove chips. The heat cannot be taken away by the cutting fluid in time, so the tool is easy to be worn, and the chip fragments are jammed and prone to vibration

especially when turning and tapping threads, the cutting conditions are more stringent, and sometimes there will be broken edges and taps. The cutting fluid is required to have 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, the composite cutting fluid containing both oily agent and extreme pressure agent should be selected

in addition, the permeability of cutting fluid during tapping is very important. Whether the cutting fluid can penetrate into the blade in time has a great impact on the durability of the tap. The permeability of cutting fluid is related to viscosity. Oil with low viscosity has better permeability. If necessary, a small amount of diesel or kerosene can be added to improve the permeability. In some cases, such as blind hole tapping, it is difficult for cutting fluid to enter the hole. At this time, the effect of using cutting fluid with high viscosity and strong adhesion is better

IV. reaming

high concentration extreme pressure emulsion

reaming is the precision machining of holes, which requires high precision. Reaming belongs to low-speed and small feed cutting. It is mainly the extrusion cutting between the tool and the hole wall. Chip fragments are easy to stay in the tool slot or adhere to the edge of the tool, which affects the extrusion effect of the blade belt, destroys the machining accuracy and surface roughness, increases the cutting torque, and also produces chip buildup, Increasing tool wear and reaming basically belongs to the boundary lubrication state. Generally, high concentration EP emulsion or EP cutting oil with good lubrication performance and certain goodness can be used to obtain good results

for deep hole reaming, deep hole drill cutting oil with good lubrication performance can be used. 6. The system has relatively perfect protective measures to meet the process requirements

v. broaching

the lubricity of cutting fluid is better

broach is a processing tool with many cutter teeth juxtaposed according to the blade and tooth rise along the axis direction. The characteristic of broaching is that it can process workpieces with complex shapes with high precision. Because broach is a valuable tool, the tool durability has a great impact on the production cost

in addition, broaching is precision machining, which requires strict surface roughness of the workpiece. During broaching, the cutting resistance is large, it is not easy to remove chips, the cooling condition is poor, and the workpiece surface is easy to be scratched, so the lubrication of the cutting fluid is required to be good. There is a special broaching oil containing sulfur extreme pressure additives in China

VI. drilling

EP synthetic cutting fluid

drilling with a general fried dough twist drill belongs to rough machining. It is difficult to remove chips during drilling, and the cutting heat is not easy to export, which often leads to the annealing of the blade, affecting the service life and processing efficiency of the drill. Selecting cutting fluid with good performance can prolong the service life of the drill several times or even more, and the productivity can also be significantly improved

EP emulsion or EP synthetic cutting fluid is generally selected. EP synthetic cutting fluid has low surface tension and good permeability. It can cool the drill bit in time, which is very effective in prolonging tool life and improving machining efficiency. For stainless steel, heat-resistant alloy and other difficult cutting materials, extreme pressure cutting oil with low viscosity can be selected

VII. Deep hole drill

needs good cooling and high temperature lubricity

deep hole drill (gun drill) is a deep hole processing technology developed in recent years. Traditional deep hole machining (the ratio of cutting depth to hole diameter is greater than 5) requires multiple processes such as drilling, boring, rough reaming, grinding and so on to process holes with high precision and low surface roughness. The new process adopts a tool with special structure and a high-pressure cooling and lubrication system, which can simplify the above-mentioned multiple processes into a continuous tool path to complete a considerable depth of high-precision and low surface roughness hole machining. This process has high efficiency and remarkable economic benefits

deep hole drilling cutting fluid with excellent performance is one of the keys of deep hole drilling processing technology. Deep hole drilling cutting fluid must have the following properties:

good cooling effect, eliminate the heat generated by deformation and friction, and inhibit the formation of chip nodules

good high-temperature lubricity, reduce the friction and wear of the blade and support, and ensure that the tool maintains a good lubrication state under the high temperature of the cutting area

good permeability and chip removal make the cutting fluid penetrate into the blade in time and ensure the smooth discharge of chips. Therefore, the cutting fluid of deep hole drill is required to have high extreme pressure and low viscosity

VIII. Gear machining

oil based cutting fluid should not be used

for high-speed gear cutting, using oil-based cutting fluid will produce large oil smoke and pollute the environment. Moreover, due to insufficient cooling, it will often cause workpiece surface burns, affect the processing quality, and increase the wear of cutting tools. At this time, * it is better to choose water-based cutting fluid with strong extreme pressure, such as sulfur The water-based synthetic cutting fluid or high concentration EP emulsion with phosphorus EP additive can overcome the oil pollution during high-speed cutting, and the machining quality and tool wear are better than oil-based cutting fluid. However, for the original gear hobbing and gear shaping machine tools, measures must be taken to prevent water from entering the rotating part, so as to avoid machine tool failure

shaving requires high surface quality. In order to prevent tool sticking, cutting oil containing active extreme pressure additives can be used. In addition, because shaving produces fine chips, in order to make the chips easy to wash away, * low viscosity cutting oil should be used. If the chips are not separated smoothly, the machined surface quality will deteriorate

IX. grinding

requires good cooling and cleaning performance

grinding can obtain high dimensional accuracy and low surface roughness. During grinding, the grinding speed is high, the heat is large, and the grinding temperature can be as high as 800 ~ 1000, or even higher, which is easy to cause workpiece surface burns, surface cracks and workpiece deformation due to the effect of thermal stress, grinding wheel wear passivation, abrasive particles fall off, and grinding debris and grinding wheel powder are easy to splash, falling on the surface of parts and affecting the machining accuracy and surface roughness, processing toughness and plastic materials, Grinding chips are embedded in the gap on the working surface of the grinding wheel or fused with the processing metal on the surface of the grinding wheel, which will make the grinding wheel lose the grinding ability. Therefore, in order to reduce the grinding temperature, wash off the grinding chips and grinding wheel dust, and improve the grinding ratio and workpiece surface quality, cutting fluid with good cooling performance and cleaning performance, as well as certain lubrication performance and rust prevention performance must be used

high speed grinding: generally, grinding with a linear speed of more than 50m/s is called high speed grinding. When the linear speed of the grinding wheel increases, the grinding temperature increases significantly. According to the test, the grinding temperature (average working temperature) when the linear speed of the grinding wheel is 60m/s is about 50% - 70% higher than that of 30m/s; When the linear speed of the grinding wheel is 80m/s, the grinding temperature is 15% - 20% higher than that of 60m/s. After the linear speed of the grinding wheel is increased, the number of abrasive particles participating in grinding per unit time increases, the friction effect intensifies, and the energy consumption also increases, which increases the surface temperature of the workpiece and increases the possibility of surface burns and cracks. This needs to be solved with coolant with high-efficiency cooling performance. Therefore, in high-speed grinding, ordinary cutting fluid cannot be used, but high-speed grinding fluid with good permeability and cooling performance should be used, In order to meet the requirements of high-speed grinding process with a linear speed of 60m/s

power grinding: This is an advanced and efficient grinding process. For example, when power input high-speed power grinding, the grinding wheel with a linear speed of 60m/s has radial power input at a feed speed of about 3.5 ~ 6mm per minute, and the power removal rate can be as high as 20 ~ 40mm33/mm · S. at this time, the friction between the grinding wheel abrasive particles and the workpiece is very intense. Even under high pressure and large flow, the measured surface temperature of the workpiece in the friction area ranges from 700 to 1000. If the cooling conditions are not good, Grinding is impossible. In strong grinding, using synthetic strong grinding fluid with excellent performance, compared with emulsion, the total grinding amount is increased by 35%, the grinding ratio is increased by 30% - 50%, the normal grinding time is prolonged by about 40%, and the power loss is reduced by about 40%. Therefore, in strong grinding, the performance of coolant has a great impact on the grinding effect

diamond wheel grinding: it is suitable for grinding materials with high hardness such as cemented carbide, ceramics and glass. It can be rough and fine ground. Generally, there are no cracks and notches on the ground surface, and a lower surface roughness can be obtained. In order to prevent excessive heat and premature wear of the grinding wheel during grinding and obtain low surface roughness, continuous and sufficient cooling is required. Due to the high hardness of the workpiece, the grinding fluid should mainly have the cooling and cleaning performance to keep the grinding wheel sharp and smooth

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