The types of cutting fluids have diverse characteristics, and their properties are quite different. The scientific selection of cutting fluids depends on the processing properties, process and workpiece. The selection principle of cutting fluid mainly includes the following aspects.
Selection standard of conventional cutting fluid The meaning of cutting fluid is lubrication function and cooling function. On the basis of incorporating special additives, it also has certain cleaning and antirust functions, thus comprehensively protecting machine tools, tools and workpieces. The types of cutting fluid mainly include oil-based cutting fluid, water-based cutting fluid and emulsion. Through the time study, it is found that oil-based cutting fluid has strong lubrication specificity, but it is not easy to cool. Compared with oil-based cutting fluid, water-based cutting fluid has weaker lubricity, but better cooling performance. Conventional slow cutting needs to have certain lubricity. Generally, oil-based cutting fluid is selected when the cutting speed is ≤ 30 m/min. However, the cutting fluid containing extreme pressure additives has certain effect when the cutting speed does not reach 60m/min during the cutting of relevant materials. Under the condition of high-speed cutting, because it will emit a certain amount of heat, the thermal conductivity of oil-based cutting fluid is poor, and then the temperature within the cutting range will be increased. In this way, the cutting fluid will generate smoke, and even burn. At the same time, the workpiece temperature will be too high to cause deformation and other problems, which will weaken the accuracy, so the water-based cutting fluid is more applicable. The emulsion combines the lubricating and antirust properties of oil and water, and has excellent cooling properties, so it has a remarkable effect on metal cutting at high speed and low pressure. Compared with oil-based cutting fluid, the emulsion has excellent heat dissipation and is easy to clean. It is economical and safer to dilute with water. In fact, in addition to very special processing materials, the emulsion can be well used for processing light and medium load cutting, and the emulsion can also be used for most grinding processing. However, the internal quality problem of the emulsion is easy to produce bacteria and mold, which will cause chemical reaction of the effective components in the emulsion, thus leading to deterioration. Based on this, a certain amount of organic fungicides will be added to the emulsion during use. The types of cutting fluids have diverse characteristics, and their properties are quite different. The scientific selection of cutting fluids depends on the processing properties, process and workpiece. The general selection principles of cutting fluid mainly include the following aspects. Rough machining has high machining allowance and cutting amount, so certain cutting heat will be generated during cutting, which will lead to tool wear. For this problem, the temperature within the cutting range should be controlled as much as possible, so the emulsion and synthetic cutting fluid based on cooling should be selected. In order to control the friction between the workpiece and the tool and deepen the machining accuracy and surface quality of the workpiece, the extreme pressure cutting oil and high-density extreme pressure emulsion with excellent lubrication performance should be selected. Semi-closed machining, such as drilling, reaming and deep-hole machining, has some problems of chip removal and heat dissipation, which will not only cause tool wear and annealing. Therefore, the EP emulsion and EP cutting oil with low viscosity should be selected, and the pressure and flow of the cutting fluid should be deepened at the same time, so that not only the corresponding cooling and lubrication can be carried out, but also some chips can be washed. Common problems in cutting fluid selection NaNO2 is a common additive in cutting fluid, and the cutting fluid added with NaNO2 has certain antirust property. NaNO2 has been widely used as antirust additive in the past, but NaNO2 has a strong carcinogenic effect on human body and will have a certain impact on the health of users. At present, the World Chemical Organization prohibits the use of NaNO2 in chemicals. Therefore, in order to ensure the antirust ability of cutting fluid products, relevant enterprises are developing new additives to replace NaNO2. Through research, it is found that the additives that can replace NaNO2 include organic substances and inorganic substances, the former mainly includes C3-H7-N-O, C18H34O2 and RNH2; Inorganic additives include Na2B4O5 (OH) 4 • 8H2O, MMoO, etc. In the process of research and development, relevant enterprises have developed non-toxic and harmless cutting fluid by replacing NaNO2 with the above two types of anti-rust additives. Some enterprises use vegetable oil to meet the requirements of environmental protection standards and new material processing, including palm oil, rapeseed oil and soybean oil. The above base oils can be effectively biodegradable. Compared with mineral oils, their tribological quality is excellent. However, the research and application of vegetable oils have certain limitations. In the process of application, they will be affected by thermal oxidation, hydrolysis stability and high cost. Water-soluble cutting fluid of synthetic grease developed through biological stabilization technology is a relatively mature and stable lubricating and cooling medium at this stage, and is the major trend of metalworking cutting fluid products in the future. This kind of synthetic grease not only has excellent heat resistance and oxidation resistance, but also has strong water resistance and biodegradability. Selection standard of aluminum cutting fluid Cast aluminum will be widely used in the processing of automobile parts and communication parts. During processing, these enterprises will generally encounter moldy changes caused by moldy parts after casting aluminum processing, which will lead to problems such as scrapping of parts and uncontrollable costs. For the above problems of customers, the article puts forward a targeted selection standard for aluminum casting cutting fluid based on the analysis of the factors leading to mildew. 1. External factors causing moldy aluminum castings The external factors causing moldy aluminum castings mainly include the following four aspects: first, the external environment in which the products are stored mainly includes temperature and humidity; Secondly, the outer layer of the product has hyper-soluble substances, which will absorb the moisture in the air, and then lead to the corrosion reaction of the primary battery, which provides the basis for the growth of mold; Because of the corrosion reaction of the primary battery, the outer layer of cast aluminum precipitates alkaline compounds, and mold grows on the basis of deliquescence reaction and temperature and humidity reaching a certain coefficient; The surface layer of cast aluminum parts contains oil, vegetable fiber and other substances, which will provide convenient conditions for mold growth. If the humidity and temperature reach a certain coefficient, mold will grow rapidly. 2. Selection standard It is not allowed to use refining modification slag remover containing NaCl, select refining modification agent with NaF composition, or N2 gas refining. Do not use release agents containing plant additives; Replace the cutting fluid of biosynthetic grease as much as possible, such as CCF-21 series and CCF-10 products. Do not store the product outdoors for a long time to avoid dust accumulation on the outer layer of the product. The product packaging cartons stacked on the pallet shall be sealed and wrapped with waterproof bread on six sides; After the waterproof product is soaked with water, it should be placed in the ventilated area and sprayed with anti-mildew agent. 3. Standard case of casting aluminum cutting fluid selection The mildew problem occurred in a company after machining cast aluminum workpiece with cutting fluid, which has not been effectively solved. Based on the research of the company's process, it is found that the company processes parts made of AlS12 and As9Cu3Fe on the processing center. Therefore, it is recommended to select CCF-10G bio-stabilized micro-emulsion cutting fluid. After using for a period of time, the company reported the same problem. After communicating with the engineers of the company's process department, it was found that the customer had increased the processing of ASi10Mg cast aluminum workpiece. Therefore, it is recommended to use CCF-21 bio-stable emulsified cutting fluid, thus fundamentally solving the mildew problem of all cast aluminum processing materials of the company from the product essence. Through the above cases, it is not difficult to find that the selection of cutting fluid for differential material processing has very different processing results, that is, the so-called same processing material has different process standards for the selection of cutting fluid due to the difference of metal composition in the material. This needs to follow the comprehensive analysis principle of "equipment - process - material".
