Selection of cutting fluid

Selection of cutting fluid
1. The role of cutting fluid
The main function of cutting fluid is cooling and lubrication, and after adding special additives, it can also play a role in cleaning and rust prevention to protect machine tools, tools, workpieces, etc. from being corroded by surrounding media.
2. Types of cutting fluids
(1) Aqueous solution The main components of aqueous solution are water and preservatives, antifungal agents, etc. In order to improve the cleaning ability, you can add a cleaning agent. For lubricity, oil-based additives can also be added.
(2) Emulsion Emulsion is a milky white liquid formed by mixing water and emulsified oil. Emulsified oil is a kind of ointment, which is prepared by mineral oil and surfactant emulsifier (sodium petroleum sulfonate, sulfonated sesame oil, etc.), the molecule of the surfactant emulsifier has a polar end affinity with water, and the non-polar end is affinity with oil, so that the water and oil are evenly mixed. (3) Synthetic cutting fluid Synthetic cutting fluid is a high-performance cutting fluid that is widely used at home and abroad, which is composed of water, various permeable agents and chemical additives. It has good cooling, lubrication, cleaning and anti-rust properties, good thermal stability and long service life.
(4) Cutting oilCutting oil mainly plays a lubricating role, and the commonly used mineral oils and vegetable oils such as No. 10 mechanical oil, No. 20 mechanical oil, light diesel oil, kerosene, soybean oil, vegetable oil, castor oil, etc.
(5) Extreme pressure cutting fluid Extreme pressure cutting fluid is prepared by adding gas, sulfur, phosphorus and other extreme pressure additives to mineral oil. It does not destroy the lubricating film at high temperatures and has a good lubricating effect, so it is widely used.
(6) Solid lubricants Solid lubricants are mainly molybdenum disulfide (Mos,). The lubricating film formed by molybdenum disulfide has a very low friction factor and a high melting point (1185°C). Therefore, it is not easy to change its lubricating properties at high temperatures, has high compressive properties and firm adhesion ability, and also has high chemical stability and temperature stability.
3. Selection of cutting fluid
(1) According to the processing nature of the selection of rough machining, because the machining allowance and cutting amount are larger, therefore, in the cutting process to produce a large amount of cutting heat, easy to make the tool wear quickly, then the temperature of the cutting area should be reduced, so the emulsion or synthetic cutting fluid based on cooling should be selected.
During finishing, in order to reduce the friction between chips, workpieces and tools, and ensure the machining accuracy and surface quality of the workpiece, extreme pressure cutting oil or high-concentration extreme pressure emulsion with good lubrication performance should be selected.
In semi-closed machining (such as drilling, reaming or deep hole machining), the chip evacuation and heat dissipation conditions are very poor, which not only makes the tool wear seriously and easy to anneal, but also the chips are easy to pull the machined surface. For this purpose, it is necessary to choose an extreme pressure cutting fluid or an extreme pressure cutting oil with low viscosity, and increase the flow and pressure of the cutting fluid.
(2) Selection according to the workpiece material
1) For general steel parts, emulsion is selected for rough machining; Vulcanized emulsion is used for finishing.
2) In order to avoid fine chips blocking the cooling system or sticking to the machine tool and being difficult to remove, cutting fluid is generally not used for brittle metals such as cast iron and cast aluminum. 7%~10% emulsion or kerosene can also be used. 3) When processing non-ferrous metals or copper alloys, it is not advisable to use sulfur-containing cutting fluids to avoid corrosion of the workpiece. 4) When processing magnesium alloy, do not use cutting fluid to avoid combustion and fire. If necessary, it can be cooled with compressed air. 5) When processing difficult-to-process materials such as stainless steel and heat-resistant steel, 10%~15% extreme pressure cutting oil or extreme pressure emulsion should be selected.
(3) Selection according to the tool material
1) High-speed steel tools, rough machining, use emulsion: finishing, use extreme pressure cutting oil or high concentration of extreme pressure emulsion.
2) For cemented carbide tools, in order to avoid the blade chipping due to sudden cooling and heating, cutting fluid is generally not used. If cutting fluid is used, it must be poured continuously and sufficiently.
4. The use of cutting fluid for CNC machine tools, the use of cutting fluid is generally used by pouring method. For deep hole machining, machining of difficult-to-machine materials, and high-speed or high-power cutting, the high-pressure cooling method should be used. The working pressure of cutting fluid is 1-10MPa, and the flow rate is 50~150Lmin. Spray cooling is also a good way to use cutting fluid, which is atomized by a spraying device under high pressure and sprayed into the cutting zone at high speed.