Tool life, reduce processing costs. In the mechanical industry, metal cutting fluid (hereinafter referred to as cutting fluid) is widely used in various cutting processes, such as turning, milling, drilling, grinding, tooth cutting, thread cutting and so on. Reasonable use of cutting fluid can effectively reduce cutting force, cutting temperature and thermal deformation of machining system, prolong tool life and improve machining surface quality. In addition, the use of high-performance cutting fluid is also an important measure to improve the machinability of some difficult-to-machine materials.
What is the function of A> cutting fluid?
The main functions of metal cutting fluid in mechanical removal processing are cooling, lubrication, cleaning and rust prevention. Due to the convection and vaporization of liquid, the surface temperature of tools and workpieces can be reduced, thus preventing the surface of workpieces from being burned and deformed. In addition, the cutting fluid should have foam resistance and mold deterioration resistance to meet the requirements of no environmental pollution, no harm to human body and economic use. Therefore, it is often necessary to add some special additives to the cutting fluid, such as oiliness agent (which can adsorb on the surface of the workpiece to form an oil film), extreme pressure agent (which can form a firm chemical film at high temperature and high pressure to play the role of reducing friction and preventing sticking), rust inhibitor (which can prevent metal from rusting), defoamer (which can prevent foaming when spraying the cutting fluid), antioxidant (which can prevent the cutting oil from oxidizing at high temperature and high pressure), surfactant and so on. Additives are the core elements of metal cutting fluid technology, and excellent additive formula has become a necessary condition for cutting fluid manufacturers to improve their own brand market competitiveness.
B& gt； Types of cutting fluids
According to the form, there are two kinds: liquid cutting fluid and solid lubricant. There are two kinds of liquid cutting fluids commonly used in production: oil-based cutting fluids based on lubrication and water-based cutting fluids based on cooling.
oil based cutting fluid
Oil-based cutting fluid is also called cutting oil, and its basic component is base oil (mineral oil or synthetic oil). When in use, the stock solution is used directly without dilution. According to different processing methods, tool materials, workpiece materials and processing requirements, various additives, such as oiliness agents and extreme pressure agents (such as chlorine, sulfur, phosphorus, etc. ), corrosion inhibitor and antioxidant can be added to base oil to prepare oil-based cutting fluids with different properties. According to the difference of base oil and additives, oil-based cutting fluid can be roughly divided into pure mineral oil (such as L-AN5 ~ L-AN32 brand total loss system oil, that is, mechanical oil, kerosene and light diesel oil, etc. ), pure synthetic oil (its base oil consists of synthetic fat, polyalphaolefin, polyether, polyethylene glycol, etc. ), active extreme pressure cutting oil (such as vulcanized oil) and inactive extreme pressure cutting oil (such as chlorine). ). Cutting oil based on mineral oil has the advantages of excellent lubricity and antirust performance, so it is used most; However, mineral oil is easy to produce smoke and burn at high speed, and its biodegradability is poor, which pollutes water and soil and is harmful to the health of operators. Therefore, the development trend of cutting oil mainly based on mineral oil: first, mineral oil is gradually replaced by biodegradable polyolefin synthetic substances without aromatic hydrocarbons; Second, it is gradually replaced by water-based cutting fluid to save energy. 2.2 Water-based cutting fluid Water-based cutting fluid is the most widely used cutting fluid at present, and its products account for about 70% of the total cutting fluid market share. Water-based cutting fluid needs to be diluted with water before use. According to the dilution state, it can be divided into emulsified cutting fluid, micro-emulsified cutting fluid and synthetic cutting fluid. ?
(1) emulsified cutting fluid
Emulsified liquid is an emulsified oil (called stock solution) prepared in advance with mineral oil and emulsifier (such as sodium petroleum sulfonate and sulfonated castor oil) and diluted with water. ) and additives. Because oil is insoluble in water, emulsifier must be added to mix the two. Emulsifier is a kind of surfactant, and its molecules are composed of polar groups and nonpolar groups. The former is hydrophilic and soluble in water; The latter is lipophilic and soluble in oil. When oil is stirred into fine particles in water, emulsifier molecules can be directionally arranged and adsorbed on the oil-water interface to connect oil with water, so that the separated fine particles no longer float in water due to coagulation and become floating liquid. The content of emulsified oil in emulsion is low, that is, the concentration is low (for example, the concentration is 3% ~ 5%), the cooling and cleaning effect is good, and it is suitable for rough machining and grinding; High concentration (such as 10% ~ 20%) has good lubricity and is suitable for finishing (such as broaching and reaming). In order to further improve the lubrication performance of the emulsion, a certain amount of extreme pressure additives, such as chlorine, sulfur and phosphorus, can be added to make the extreme pressure emulsion. ?
(2) Synthetic cutting fluid?
The stock solution of synthetic cutting fluid generally does not contain oil, so its lubricity is poor, but it can save energy and is beneficial to environmental protection. It is miscible with water, and the prepared cutting fluid is mostly transparent, with good visibility and long service life, especially suitable for efficient equipment such as CNC machine tools and machining centers. For example, the environment-friendly fully synthetic metal working fluid developed by Jaeger Petrochemical Company in China and the fully synthetic grinding fluids SCF600 and SCF900 introduced by Korniche Company in Britain belong to this category, which are suitable for the general processing and grinding of ferrous metals and nonferrous metals.
(3) Microemulsion cutting fluid
The oil content in the original microemulsion (that is, the content of oily additives) is small, but the content of surfactants and rust inhibitors is large. After being prepared with water, it is translucent and micro-emulsified, and its appearance and performance are between emulsion and synthetic cutting fluid. It has the advantages of emulsion and synthetic cutting fluid, and makes up for their shortcomings. It is a water-based cutting fluid that has developed rapidly and been widely used in recent ten years. At present, water-based cutting fluid products introduced by some famous foreign companies, such as SCFUniversal green metal cutting fluid developed by British Bill Company, and QUAKERCOOL370KLG synthetic ester patented cutting fluid introduced by German Quick Chemical (China) Company, all belong to this category. The synthetic ester in QUAKERCOOL370KLG is a compound generated by the reaction of fatty acids and alcohols, which has excellent lubricity, can form microemulsion after being mixed with water, and is not easy to degrade in the metalworking environment, thus ensuring that the interface between the tool and the chip and the contact area between the tool and the workpiece can maintain good liquid lubrication, boundary lubrication and extreme pressure (EP) lubrication, and is especially suitable for machining aluminum alloy, titanium alloy, chromium, nickel, iron alloy and other difficult-to-machine materials.
solid lubricant
Molybdenum disulfide (MoS2) is widely used in solid lubricants, and it is a good environment-friendly lubricant. The lubricating film formed by molybdenum disulfide has low friction coefficient (0.05 ~ 0.09), high melting point (1 185℃) and high pressure resistance (3. 1GPa). When cutting, molybdenum disulfide can be coated on the surface of the tool or workpiece, or it can be added to cutting oil. Under high temperature and high pressure conditions, it can still maintain good lubricity and wear resistance. In addition, the use of molybdenum disulfide lubricant can also prevent adhesion, inhibit the generation of chip accumulation tumor, prolong the tool life and reduce the surface roughness. MoS2 lubricant has been successfully used for reaming, deep hole, tapping and hole drawing. For example, using cemented carbide drill bit with (Ti, Al)N+MoS2 soft coating [that is, coating (Ti, Al)N hard coating on the drill bit first, and then coating MoS2 soft coating on it] to dry drill the deep hole of gray cast iron engine block, the tool life is as high as 65,438+600±44min, while the service life of the drill bit coated with TiN or TiCN is 65,438 respectively.
Selection of C> cutting fluid?
The effect of cutting fluid depends not only on the performance of cutting fluid itself, but also on processing requirements, workpiece materials, tool materials and processing methods, which should be comprehensively considered, reasonably selected and used correctly.
(1) When rough machining is selected according to machining requirements, the cutting amount is large and a lot of cutting heat is generated. In order to reduce the cutting temperature, water-based cutting fluid with good cooling performance should be selected at this time. When finishing, the workpiece is required to obtain the best surface quality and smaller surface roughness, so cutting oil should be used.
(2) It should be handled in different ways. In contemporary machining, there are various cutting methods. For example, turning, milling and drilling usually require efficient processing, so water-based cutting fluid should be selected; However, when broaching and cutting teeth, it is necessary to use expensive and complicated tools for processing. In order to ensure the machining quality and long service life of tools, it is best to choose oil-based cutting fluid. As the processing classification becomes more and more detailed. Cutting fluid also has a non-standardized development trend. Different cutting methods have different brands of cutting fluids. For example, for high-speed grinding, German OEL Holding Company developed a special high-performance grinding oil. Because its composition structure is pure alkane, it has excellent shear resistance and aging stability, which is very suitable for high-speed grinding, thus changing the previous processing method of replacing grinding oil with general cutting fluid.
(3) According to the different materials of workpieces and cutters, the high temperature resistance, machinability and hardness of cutters and workpieces made of different materials are also different. At this time, different cutting fluids should be selected respectively. For example, when machining gears with low hardness, cutting fluid with high viscosity should be used to prevent the surface of gears from being scratched; When cutting stainless steel, extreme pressure cutting oil or extreme pressure emulsion should be selected. For another example, when cubic boron nitride (CBN) superhard cutter is used to cut hardened steel and other high-hardness materials, although CBN can withstand the cutting temperature of 1250 ~ 1350℃, at the high temperature of 1000℃, CBN will react with water vapor and oxygen in the air to generate ammonia and boric acid. This chemical reaction is called hydrolysis. Therefore, when using CBN tool for wet cutting, water-based cutting fluid or extreme pressure cutting oil with extreme pressure additive must be used to weaken hydrolysis.
(4) Some efficient and expensive equipment should be selected according to the characteristics of the machine tool itself. From the point of view of maintenance, we should choose oil-based cutting fluid with stable physical and chemical properties to prevent corrosion and rust of metal parts and obstacles of moving parts. However, for some open machine tools, it is generally not appropriate to use oil-based cutting fluid to avoid a large amount of volatilization and loss of cutting oil.
(5) According to the specific processing conditions, the cutting fluid with the highest cost performance should be selected.
In addition, the selected cutting fluid also requires no negative impact on the health and environmental protection of operators. At present, due to the enhancement of global environmental awareness and the increasingly strict requirements of environmental protection legislation, the market demands more and more environmental protection performance of cutting fluid. Therefore, some biodegradable oil-based cutting fluids are favored by people. For example, HocutTR2000 series products of Hofuton Company are such an environment-friendly cutting fluid controlled by two phases (oil phase and water phase) extracted from biodegradable vegetable oil. The method of replacing toxic antirust additives in water-based cutting fluid with tungstate and molybdate has also been popularized in production.