Hello, you can refer to the following information:
Cutting fluid lubrication knowledge
Lubrication of metal cutting technology (Lubrication of metal processing technology 2)
p>
(2) Problems and countermeasures in the use of cutting fluid.
1. The problem of deterioration and odor of cutting wave
The main reason for the deterioration and odor of cutting fluid is that the cutting fluid contains a large number of bacteria, and the bacteria in the cutting fluid mainly include aerobic bacteria. and anaerobic bacteria. Aerobic bacteria live in mineral environments, such as water, cutting fluid concentrates and oil leakage from machine tools. Under aerobic conditions, they split into two every 20 to 30 minutes. Anaerobic bacteria live in an environment without oxygen, split into two every hour, metabolize and release SO2, which smells like rotten eggs and the cutting fluid turns black. When the number of bacteria in the cutting fluid is greater than 106, the cutting fluid will become smelly.
(1) Bacteria mainly enter the cutting fluid through the following channels:
1) Bacteria invade during the preparation process, such as bacteria in the water used to prepare the cutting fluid.
2) Bacteria in the air enter the cutting fluid.
3) The transfer of workpieces between processes causes infection of cutting fluid.
4) The operator’s bad habits, such as littering.
5) The cleanliness of machine tools and workshops is poor.
(2) Methods to control bacterial growth
1) Use high-quality, stable cutting fluid.
2) Using pure water to prepare a concentrated solution is not only easy to prepare, but also improves the lubricity of the cutting fluid, reduces the amount taken away by chips, and prevents bacterial erosion.
3) When using, the ratio of concentrated liquid in the cutting fluid must be controlled not to be too low, otherwise bacteria will easily grow.
4) Since the oil used in machine tools contains bacteria, it is necessary to minimize the mixing of oil leaked from machine tools into the cutting fluid.
5) When the pH value of the cutting fluid is between 8.3 and 9.2, bacteria cannot survive, so new cutting fluid should be added in time to increase the pH value.
6) Keep the cutting fluid clean and do not let the cutting fluid come into contact with dirt such as oil, food, tobacco, etc.
7) Use fungicides frequently.
8) Keep the workshop and machine tools clean.
9) If the equipment does not have a filter device, the floating oil should be skimmed off regularly and dirt should be removed.
2. Cutting fluid corrosion problem
(1) Causes of corrosion
1) The proportion of concentrated liquid in the cutting fluid is low.
2) The pH value of the cutting fluid is too high or too low. For example, when PH>9.2, it will corrode aluminum. Therefore, the appropriate pH value should be selected according to the metal material.
3) Contact between dissimilar metal materials.
4) Use paper or wood to place the workpiece.
5) Stacking of parts.
6) The number of bacteria in the cutting fluid exceeds the standard.
7) The humidity of the working environment is too high.
(2) Methods to prevent and control corrosion
1) Prepare cutting fluid with pure water, and the proportion of cutting fluid should be used according to the recommended value in the instruction manual of the cutting fluid used.
2) Use anti-rust fluid when necessary.
3) Control the number of bacteria and avoid the occurrence of bacteria.
4) Check the humidity and pay attention to controlling the humidity of the working environment within the appropriate range.
5) Avoid contamination of the cutting fluid.
6) Avoid contact with dissimilar materials, such as aluminum and steel, cast iron (containing magnesium) and copper, etc.
3. The problem of foam generation
When using cutting fluid, sometimes a large amount of foam will be generated on the surface of the cutting fluid.
(1) The main reasons for foaming
1) The cutting fluid level is too low.
2) The flow rate of the cutting fluid is too fast, and the bubbles do not have time to overflow. They accumulate more and more, resulting in a large amount of foam.
3) There are too many right angles in the water tank design, or the angle of the cutting fluid nozzle is too straight.
(2) Methods to avoid foam
1) In the centralized cooling system, the pipelines are connected in series in stages, and the pressure of the pipelines close to the cooling box should be lower.
2) Ensure that the cutting fluid level is not too low, check the fluid level in time, and add cutting fluid in time.
3) Control the cutting fluid flow rate not to be too fast.
4) When designing the sink, attention should be paid to not having too many right angles.
5) When using cutting fluid, attention should be paid to the angle of the cutting fluid nozzle not to be too straight.
4. Problems with skin allergies of operators
(1) The main reasons for skin allergies of operators
1) The pH value is too high.
2) The composition of cutting fluid.
3) Insoluble metals and oils used in machine tools.
4) The concentration ratio is too high.
5) Protective suspension layer on the cutting fluid surface, such as odor sealing layer and anti-foam layer. Fungicides and unclean cutting fluids.
(2) During work, in order to avoid skin allergies, the operator should pay attention to the following points
1) The operator should apply protective oil, wear work clothes, and gloves. Avoid direct contact between skin and cutting fluid.
2) The proportion of concentrated liquid in the cutting fluid must be used according to the recommended value of the cutting fluid.
3) Use fungicides according to the dosage in the instructions.
In addition, fluorine rubber and grease rubber are less deformed by the influence of cutting fluids, so they can be given priority when used as machine tool seals. In order to prevent deformation, the fat content of rubber used for machine tool seals should generally be greater than 35%. In addition, in order to effectively prevent the cutting fluid from causing the machine tool paint to peel off, you can choose epoxy resin paint or polycavity ester paint.
In short, when using cutting fluid in normal production, if the above issues can be paid attention to, unnecessary economic losses can be avoided and production efficiency can be effectively improved.
1 Development Trend of Cutting Fluid Technology
As we all know, cutting fluid has the functions of lubrication, cooling, cleaning and rust prevention, etc., and is important for improving the quality and efficiency of cutting processing and reducing tool wear. There is a significant effect. In the past ten years or so, my country's cutting fluid technology has developed rapidly. New varieties of cutting fluids have continued to appear, and their properties have been continuously improved and perfected, especially the water-based synthetic cutting fluids produced in the late 1970s and the cutting fluids developed in recent years. The promotion and application of semi-synthetic cutting fluid (microemulsion cutting fluid) in production has opened up a new path for the development of mechanical processing in the direction of energy saving, reducing environmental pollution, and reducing industrial production costs. To sum up, cutting fluid technology mainly has the following characteristics:
1) Minimum lubrication technology
Dry cutting is a process that does not use any cutting fluid. It can fundamentally eliminate the traditional Wet machining has the disadvantage of easily polluting the environment, which is a profound revolution in cutting technology. Because dry cutting meets today's requirements for developing green manufacturing technology, it is a very promising new cutting technology. However, dry cutting has the characteristics of high temperature and large cutting force, and a series of problems that do not exist in wet machining arise. At present, dry cutting technology is still very immature and its application scope is also very limited. However, traditional wet cutting has many shortcomings. Therefore, some people have proposed quasi-dry cutting technology. Quasi-dry cutting is a cutting method between wet cutting and pure dry cutting, also known as minimum lubrication technology. Quasi-dry cutting uses spray cooling, which uses very little cutting fluid to achieve better cooling and lubrication effects.
2) Liquid nitrogen cooling technology
The use of liquid nitrogen for low-temperature (ultra-low temperature) cutting is to use liquid nitrogen to keep the workpiece, tool or cutting area in a low-temperature cooling state for cutting. method. Nitrogen is the most abundant component in the atmosphere. As a by-product of the oxygen production industry, liquid nitrogen has a wide range of sources. Using liquid nitrogen as a cutting fluid, it directly volatilizes into gas and returns to the atmosphere after application without any pollutants. From an environmental perspective, it is a promising cutting alternative.
Liquid nitrogen cooling has two application methods: direct and indirect.
a. Direct application. That is, liquid nitrogen is sprayed directly into the cutting area as cutting fluid. Generally speaking, diamond tools cannot be used to process ferrous metals due to severe tool wear. An American scholar used a liquid nitrogen cooling system to turn stainless steel with diamond tools. Because the low temperature inhibited the diffusion and graphitization of carbon atoms, it greatly reduced tool wear and achieved excellent processing quality. Its surface roughness reached Ra25μm. During grinding processing, the high temperature in the grinding area often causes thermal damage to the workpiece surface, such as burns and micro-cracks. In order to effectively solve these problems, S.Paul of the Indian Institute of Technology used liquid nitrogen ultra-low temperature cooling to grind five commonly used steel materials. The results It shows that the correct and reasonable use of liquid nitrogen cooling can effectively control the temperature of the grinding zone and keep the grinding temperature below the phase change temperature of the material without grinding burns; and when the plasticity of the material increases and the feed rate increases, , this effect is more significant. Extensive research has also been carried out abroad on liquid nitrogen cooling cutting processing of non-metallic materials and composite materials. For example, FRP (Fiberglass Reinfced Plastics) is a composite material with a high strength/weight ratio and fatigue resistance. It is very difficult to process with traditional cutting methods, thus limiting the use of this material. New Zealand scholars carried out ultra-low-temperature cooling processing on it, using liquid nitrogen continuous cooling (0.4-0.5L/min), which greatly improved the cutting processability of this material. Not only did they obtain satisfactory processing surface quality, but also improved the machining ability to a great extent. Extended tool life. It also shows good cutting performance when cutting materials such as thermosetting plastics, synthetic resins, graphite, rubber and fiberglass at low temperatures.
b. Indirect utilization. Mainly the tool cooling method, that is, the tool is continuously cooled during processing, so that the cutting heat is quickly taken away from the tool, especially the tool tip, and the tool tip always works at a low temperature. Scholars from the University of Lincoln in the United States conducted experimental research using a PCBN tool equipped with a new cooling system. This kind of tool stores liquid nitrogen in a square box on the upper part of the turning tool, which is input from the inlet and flows out from the outlet. Tests have shown that when liquid nitrogen cooling is used, the life of the turning tool is extended by to times, the wear is reduced by 1/4, and lower surface roughness can be obtained.
There is also a special indirect utilization method for jet cooling. Some Japanese scholars have developed a jet cooling system. The cooling gas used in this system is cooled by liquid nitrogen in a heat exchanger, and its temperature is lower than -50°C. The cooling gas is directly injected at the grinding point. Experiments have found that the residual compressive stress of the workpiece material after grinding is greater than when grinding with grinding fluid, and the distribution area of ??the residual compressive stress also becomes wider. The residual compressive stress can improve the fatigue life of parts, which is very important for some parts, such as aircraft parts. Using CBN grinding wheels treated with solid lubricants, or adding a very small amount (101-direction super-refined vegetable oil) during processing, can play a better lubrication effect during processing.
It can be seen that in terms of environmental protection As regulations become more stringent and cutting fluid usage and disposal costs increase, liquid nitrogen may become a substitute for cutting fluid within a certain range.
3) Centralized cooling lubrication system
The centralized cooling and lubrication system combines the independent cooling and lubrication devices of multiple mechanical processing equipment into one cooling and lubrication system. The main advantages of this system are: (1) Extending the service life of the cutting fluid; (2) Easy to realize automatic control of the cutting fluid performance indicators to ensure the quality of the cutting fluid; (3) The amount of waste liquid is small and it is easy to centralized treatment. It is conducive to protecting the ecological environment, (4) convenient for maintenance, maintenance and management; (5) convenient for chip transportation and centralized processing, etc.
4) Realize the automation of cutting fluid quality management
The key to ensuring that cutting fluid can meet various quality requirements stably in the long term and give full play to economic benefits lies in strict and scientific daily management. With the continuous improvement of mechanical processing automation and the emergence of unmanned chemical factories (workshops), it is imperative to realize automatic detection and automatic control of cutting fluids in the cooling and lubrication system.
This detection and control system can automatically detect and control the working temperature, usage concentration, pH value, microbial count and odor of the cutting fluid, and can predict the failure of the cutting fluid.
5) High-performance, long-life, low-pollution cutting fluid and its waste liquid treatment technology
With the development of the overall technology of the machinery industry, machine tools have faster cutting speeds and higher cutting loads. The cutting temperature is higher, and new processes are constantly emerging to adapt to the processing of new materials. This requires new high-performance cutting fluids to meet the processing requirements; at the same time, according to the requirements of labor hygiene and environmental protection, the cutting fluid should try to contain no Substances harmful to human health and the ecological environment. In recent years, my country has imported more and more advanced equipment such as CNC machine tools and machining centers. If the cutting fluids used are imported from abroad, transportation is inconvenient and the cost is high. Therefore, it is urgent to develop high-performance cutting fluids to replace imported products. In my country, water-based cutting fluids are used more and more widely, and the transition from emulsions to synthetic cutting fluids and microemulsions with good performance and long life has begun. In developed countries, microemulsions have been widely used, and efforts are being made to develop environmentally friendly cutting fluids.
Develop long-life cutting fluids and study methods to extend the service life of cutting fluids, thereby reducing cutting fluid waste emissions; research more effective and economical waste fluid treatment methods to reduce harmful pollutants in the environment The accumulation of cutting fluids is an important part of cutting fluid research at home and abroad.
2 Cutting fluid additives
The performance of cutting fluids, the difficulty of waste fluid disposal, the harm to operators and the degree of pollution to the environment all depend on the types of these additives and performance. As a future cutting fluid additive, it must have excellent performance and be harmless to the human body and the environment. A large amount of application practice shows that the following categories of additives should be strictly restricted in use: nitrite and similar compounds, phosphate compounds, chlorine compounds, formaldehyde and similar compounds. An effective way to improve the quality of cutting fluid is to research and develop new efficient and non-toxic additives. This has attracted the attention of scholars at home and abroad, and a lot of work has been done to develop some new additives:
1) Boric acid ester additives
Borate vinegar is a Multifunctional environmentally friendly additive. ① The oil film of boric acid vinegar has high strength, low friction coefficient, and excellent anti-friction and anti-wear properties; ② It has good anti-rust properties; ③ It has antibacterial and bactericidal functions, and has no toxic effects.
2) Molybdate corrosion inhibitor
Molybdate is a positive corrosion inhibitor. When added to the cutting fluid, it can form a Fe-MoO4-Fe2O3 passivation film on the metal surface. , can obtain good corrosion inhibition effect. It is generally believed that molybdate is non-toxic and does not pollute the environment as a rust inhibitor, but it is expensive, which affects its widespread use. In order to promote its application, people have studied the synergistic effect of molybdate and other organic and inorganic corrosion inhibitors.
3) New antiseptic fungicide
The cutting fluid itself has conditions for microorganisms and fungi to breed and multiply, and is prone to spoilage. The function of antiseptic fungicides is to inhibit the growth of bacteria and mold and kill existing bacteria in the liquid, thereby extending the service life of the cutting fluid. In recent years, due to the promulgation and implementation of environmental protection regulations, many countries have restricted the use of toxic antiseptic fungicides and researched and developed new antiseptic fungicides. According to a Japanese patent, copper salts made from fusidic acid such as oleic acid and stearic acid have the ability to resist corruption for more than one year. According to American data, copper citrate also has a good antibacterial effect, and the added amount is 300PPM. Mobil Chemical Company of the United States has developed an emulsified oil called MobilmentAquaRho, which adds a compound containing phosphorus, nitrogen and boron. The service life of the emulsion is more than 4 months.
3 Conclusion
In recent years, domestic and foreign scholars have focused their research on cutting fluid-free cutting processes. However, for most materials and processing types, wet cutting has been completely replaced. Cutting and wet grinding are far away, if not possible. We cannot avoid the reality of using cutting fluid for a long time to come.
To solve the problem of cleanliness in the mechanical manufacturing process, a two-pronged approach should be taken, that is, while studying cutting fluid-free technology, we should also pay attention to the transformation and innovation of the cutting fluid itself, so that the advantages of dry machining and wet machining can complement each other. Therefore, we have proposed the research policy of “starting from the environmental harmlessness of the cutting fluid itself and developing new technologies for cutting-fluid-free machining.” The focus of research work should be on the following aspects:
Developing green cutting fluids that are completely harmless to people and the environment;
Optimizing the fluid supply method and fluid supply parameters to reduce cutting costs Fluid consumption;
Study scientific cutting fluid usage and management technology to extend its service life and reduce waste fluid emissions;
Study the recycling and harmless treatment of cutting fluid waste cones Technology;
Research on comprehensive evaluation methods of cutting fluids that consider environmental impact, and provide technical support for enterprises to correctly select cutting fluids;
Study on various cutting fluid-free machining methods, especially Dry cutting process. Research the optimal process parameters of cutting tools, workpieces and machine tools, and expand the application scope of dry cutting processes;
Research and develop new efficient and non-toxic additives.
Metal cutting fluid plays a very important role in the metal cutting and grinding process. Practice has proved that the use of appropriate metal cutting fluid can reduce the cutting temperature by 60~150℃, reduce the surface roughness to level 1~2, reduce the cutting resistance by 15~30%, and exponentially increase the service life of the cutting tool and grinding wheel. It can also wash away iron chips and dust from the cutting area, thereby improving production efficiency and product quality. Therefore, it is widely used in mechanical processing.
The cutting fluid should have the following functions:
The cooling effect during the cutting process of the workpiece can promptly and quickly reduce the temperature of the cutting zone, that is, reduce the temperature usually caused by friction. The temperature rise and cooling also affect cutting efficiency, cutting quality and tool life.
Lubrication can reduce friction between the cutting tool and the workpiece. The lubricant can infiltrate between the tool, the workpiece and its chips, reduce friction and adhesion, reduce cutting resistance, ensure cutting quality, and extend tool life.
The washing action causes the chips or abrasive particles to be flushed away from the processing area of ??the tool and workpiece to prevent them from sticking to each other and adhering to the workpiece, tool and machine tool to prevent obstruction
Prevention The rust effect should have certain anti-rust properties to prevent workpieces and machine tools from rusting. If the anti-rust performance is improved, it can also partially replace the anti-rust between processes.
The above-mentioned four properties of cooling, lubrication, washing, and rust prevention are not completely isolated. They have unified aspects and opposing aspects. For example, cutting oil has good lubrication and anti-rust properties, but poor cooling and cleaning properties; aqueous solution has good cooling and cleaning properties, but poor lubrication and anti-rust properties. Therefore, the pros and cons must be fully weighed when selecting cutting fluid.
The performance of cutting fluid must meet the following requirements:
Large heat capacity, good thermal conductivity, and good cooling effect.
Has high oiliness or adsorption on metal surfaces. It can make the formed adsorption film have high strength, firmly adsorb on the metal surface, and play a good lubrication effect.
It has good rust resistance, does not corrode metal, and will not damage the accuracy and surface roughness of machine tools and workpieces due to corrosion.
It has low surface tension, is easy to spread evenly, is beneficial to cooling and washing, and has good lubricity.
Easy to use, low price, easy to configure and preferably suitable for a variety of metal materials and various processing methods (such as turning, grinding, planing, etc.), with a certain degree of transparency, when increasing the cutting speed No smoke.
Harmless to the human body, non-toxic and odorless. Will not harm skin and nasal mucosa, and does not irritate eyes.
Good stability and long service life. During long-term use and storage, it will not stratify, precipitate, or become moldy or deteriorate.
The amount of cutting waste liquid is large. Consider waste liquid treatment to avoid environmental pollution.