Lubricating-cooling liquid (coolant): classification, application
The metalworking process is inherently associated withstrong friction that occurs between the workpiece and the tool. This is especially true for turning and milling operations, when the cutter is very hot, with cold extrusion, high-speed multi-position landing. Intensive friction contributes to premature wear of the tool, plastic deformation of the workpiece, changes in the properties of the metal due to overheating. To reduce the frictional force and reduce the temperature, a special lubricating-cooling liquid (coolant) is needed.
Classification parameters of cutting fluids
General classification of lubricating-cooling liquids is carried out according to several basic parameters:
- By origin of components. Oil coolants are produced, based on petroleum oils, animal or vegetable fats.
- By the way of layout. Emulsol - a finished product with a long shelf life or technical coolant, prepared immediately before use from the concentrate in accordance with GOST.
- By industry applications. Various types of coolant are produced for different operating conditions. Synthetic lubricating-cooling liquid for operations of plastic deformation, coolant for turning or milling machines.
- According to physical and mechanical properties - viscosity, acid number, flash point. The latter characteristic stipulates the use of oil coolants for hot stamping.
Classification of coolant by composition
By composition, the following types of coolant are distinguished:
- Oils - compounds from components that are notmixed with water. The base of oil coolants are paraffin, mineral or oil oils (60-95%). To enhance the effectiveness against wear, friction, corrosion, the composition includes various additives and inhibitors. Oily coolants have excellent lubricating properties. Used for soft metals under simple operating conditions.
- Mineral - the base is made from oilby catalytic hydrogenation. To increase the efficiency, the composition includes additives from fats, chlorine, sulfur, phosphorus compounds. These compounds are used for such types of metalworking as: cutting steel, aluminum, brass, thread-cutting, milling works on alloyed steels.
- Water-miscible - an aqueous solution on a mineralbasis. These compounds have excellent cooling properties and low toxicity, but low lubricity characteristics. Scope of application - easy and medium mode of copper and bronze turning, milling and drilling of all kinds of non-ferrous metals, grinding and stamping of steel.
- Synthetic and semi-synthetic - a mixture of water,surfactants, water-soluble polymers, antifoam and antibacterial additives, corrosion inhibitors. Anti-wear additives are also introduced to the synthetic compositions to increase the lubricating properties.
- Emulsions are compositions with an increased concentration of dispersed particles. Reduces the wear and tear of tools and equipment in almost all metalworking operations.
Structure and mechanism of coolant action
Ubiquitous use of coolant in processesmetalworking is due to the effective separation of friction surfaces of the workpiece and tool and to reduce their temperature. The most effective cutting fluid can include the following components:
- The basis of synthetic oils or animal fats.
- Additives that increase antifriction and extreme pressure.
- Components that prevent the stratification of the formulation during storage.
- Additives that prevent corrosion and fracture.
- Components that reduce foaming and improve the wettability of surfaces in metalworking.
Application of coolant
Lubricating-cooling liquids are used forlubrication and cooling of the working area for metalworking. The properties of the coolant make it possible to reduce friction in the treatment zone, thereby reducing tool wear, increasing product quality, improving the intensity of the process and, as a result, the overall productivity of labor.
Due to its lubricating properties, coolant is goodreduce the frictional force between the surface of the workpiece and the edge of the cutting tool, internal friction in the sheared layer of metal. Some technical lubricants have chemical properties that help to reduce not only the frictional force, but also the cutting force. Most coolants are surface-active substances with high adsorption properties. They are able to form a stable film on the surface of the metal, which significantly reduces friction. Some special surface-active additives have a "wedge" effect on the metal. The elongated molecules of such additives fall into the microcracks on the surface of the metal, like a wedge, thereby weakening the bond between the particles of the material. Thus, the coolant helps the working tool cut the layer from the base metal.
The most common coolant compositions for machine tools
For metal working on lathes and milling machines, the following types of liquids are produced:
- Emulsols based on mineral and petroleum oils.
- Emulsifiers with synthetic fatty acids.
- Turning and milling works providinghigh-speed processing of stainless and alloyed steels, are produced in accordance with GOST 38.01445-88. For these purposes, synthetic compounds are provided, based on tall oil, high-alcohol alcohols, triethanolamine.
- Sulfofrezols are mixtures of highly purified oil and sulfur-containing compounds. Do not contain water, alkalis, acids. Such coolants for machine tools effectively reduce friction, do not cause corrosion.
Application of coolant for metal forming with pressure
This method of metalworking is accompanied byconsiderable specific forces and relative slippage between the workpiece and the tool. The coolant used in such processes must have a significantly higher viscosity. Characteristic features of compositions for metal working with pressure are:
- Sufficient viscosity.
- Resistance against fracture and delamination under high temperature conditions.
- Wet graphite formulations with inclusion of thin-scaled graphite on the basis of an oil suspension are used.
Features of the application of cutting fluids
For more effective use of coolant, several simple rules should be considered.
- The minimum flow rate, regardless of whether the aqueous solution is or the emulsion - 10-15 l / min.
- It is very important that the supply of coolant is carried out to the place of formation of the maximum amount of heat. When turning - this is the area where the chips are separated from the workpiece.
- The supply of coolant must be carried out immediately. When the coolant is supplied after a while, the hot cutter will cool down sharply, resulting in the formation of cracks in it.
- Lubricating-cooling liquid is not used whenturning of brittle metals (bronze, cast iron, etc.). When turning these materials, small chips are formed, which, mixing with the coolant, can clog the working units of the machine (carriage, caliper, guide frame), which leads to premature wear and breakage of these assemblies.
Production and storage of lubricating and cooling liquids
In addition to ready-made long storage formulations,concentrates and components are produced for the preparation of liquids adapted to the conditions of a particular enterprise. Coolant, coolant, the price of which depends mainly on the composition that corresponds to a certain type of work, in the modern market is sold for 70-160 rubles / liter for ready-made compositions of domestic producers and 105-290 rubles / liter of foreign production. The average cost of the concentrate is 240 r / liter. Before applying the liquid, the following procedures are performed:
- Stirring of components is carried out at temperatures established on structure and mark (60-110 0С).
- Analysis of the composition for compliance with GOST.
- The prepared compositions are stored in specialized containers, allowing periodic heating and mixing.
- In the preparation of coolant, it is possible to introduce additives, which is carried out on the vibration control of fine emulsification.
- Filling of continuous feeders.
- During use, the formulations are contaminated. The systems for cleaning the coolant from residual metal are envisaged. Waste products that can not be effectively cleaned must be disposed of. </ ul </ p>