The metalworking process is inextricably linked to the strong friction that occurs between the workpiece and the tool. This is especially evident during turning and milling operations, when the cutter is very hot, when cold extruded, high-speed multi-position landing. Intensive friction contributes to premature tool wear, plastic deformation of the workpiece, a change in the properties of the metal due to overheating. To reduce the friction force and lower the temperature, a special cutting fluid (coolant) is required.
Coolant classification parameters
General classification of cutting fluids is carried out according to several main parameters:
- The origin of the components. Oil coolants are produced, the basis of which are petroleum oils, animal or vegetable fats.
- By the layout method. Emulsol is a finished product with a long shelf life or technical coolant prepared immediately before use from a concentrate in accordance with GOST.
- By industry application. Various types of coolant are produced for different operating conditions. Synthetic cutting fluid for plastic deformation, coolant for turning or milling machines.
- According to physical and mechanical parameters - viscosity, acid number, flash point. The latter characteristic causes the use of oil coolants for hot stamping.
Coolant classification by composition
The composition distinguishes coolant of the following types:
- Oily - formulations of components that do not mix with water. The base of oil coolants are paraffin, mineral or petroleum oils (60-95%). To enhance effectiveness against wear, friction, and corrosion, various additives and inhibitors are included. Oil coolants have excellent lubricating properties. Used for soft metals under simple operating conditions.
- Mineral - the base is made from oil by catalytic hydrogenation. To increase efficiency, additives from fats, chlorine, sulfur, and phosphorus compounds are included in the composition. These compounds are used for such metalworking as: cutting steel, aluminum, brass, threading, milling work on alloy steels.
- Water miscible - an aqueous solution based on a mineral. These compounds have excellent cooling properties and low toxicity, but at the same time low lubricating characteristics. Scope - light and medium mode of turning copper and bronze, milling and drilling of all types 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. To increase lubricity, antiwear additives are also added to synthetic formulations.
- Emulsions are compositions with a high concentration of dispersed particles. Reduce the degree of wear of tools and equipment in almost all metalworking operations.
The structure and mechanism of action of the coolant
The widespread use of coolant in metalworking processes is due to the effective separation of the friction surfaces of the workpiece and tool and reduce their temperature. The most effective cutting fluid may include the following components:
- The basis of synthetic oils or animal fats.
- Additives that increase anti-friction and extreme pressure.
- Components that prevent stratification of the composition during storage.
- Additives that prevent corrosion and destruction.
- Components that reduce foaming and improve the wettability of surfaces during metal processing.
Coolant application
Cutting fluids are used to lubricate and cool the working area during metalworking. The properties of the coolant make it possible to reduce friction in the processing zone, thereby reducing tool wear, increasing product quality, improving the intensity of the process and, as a result, overall labor productivity.
Due to their lubricating properties, coolants well reduce the friction force between the surface of the workpiece and the edge of the cutting tool, internal friction in the sheared metal layer. Separate technical lubricants have chemical properties that contribute to the reduction of not only the friction force, but also the cutting force. Most coolants are surfactants with high adsorption properties. They are able to form a stable film on the metal surface, which significantly reduces friction. Some special surface-active additives have a proppant effect on the metal. The elongated molecules of such additives fall into microcracks on the metal surface, like a wedge, thereby weakening the bond between the particles of the material. Thus, the coolant "helps" the working tool to cut the layer from the base metal.
The most common coolant formulations for machine tools
For metalworking on turning 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 work, involving high-speed processing of stainless and alloy steels, are performed according to GOST 38.01445-88. For these purposes, synthetic compounds are provided, the basis of which are tall oils, high atomic alcohols, triethanolamine.
- Sulfofresols are mixtures of highly refined 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
This method of metal working is accompanied by significant specific efforts and relative slippage between the workpiece and the tool. The coolant used in such processes must have a significantly higher viscosity. The characteristic features of the compositions for metal working with pressure are:
- Sufficient viscosity.
- Resistance to fracture and delamination under high temperature conditions.
- Water-graphite compositions with the inclusion of thin-flake graphite based on an oil suspension are used.
Features of the use of cutting fluids
To use the coolant more efficiently, a few simple rules should be considered.
- The minimum liquid flow rate, regardless of whether it is an aqueous solution or an emulsion, is 10-15 l / min.
- It is very important that coolant is supplied to the place where the maximum amount of heat is generated. When turning, this is the area in which the chips are separated from the workpiece.
- The supply of cutting fluid should be carried out immediately. When coolant is supplied after some time, a very hot cutter will cool sharply, which will lead to the formation of cracks in it.
- Cutting fluid is not used for turning brittle metals (bronze, cast iron, etc.). When turning such materials, small chips are formed, which, when mixed with coolant, can clog the machine's working units (carriage, support, guide bed), which leads to premature wear and breakage of these units.
Production and storage of cutting fluids
In addition to ready-made long-storage formulations, concentrates and components for the preparation of liquids adapted to the conditions of a particular enterprise are produced. Coolant, coolant, the price of which mainly depends on the composition that meets a certain type of work, is sold on the modern market for 70-160 rubles / liter for finished formulations of domestic manufacturers and 105-290 rubles / liter of foreign production. The average cost of the concentrate is 240 r / liter. Before applying the fluid, the following procedures go through:
- Mixing of the components is carried out at the temperatures established by composition and brand (60-110 0).
- Analysis of the composition for compliance with GOST.
- The prepared formulations are stored in specialized containers that allow for periodic heating, mixing.
- In the preparation of coolant, the introduction of additives is possible, which is carried out on vibration systems for fine emulsification.
- Refueling continuous feed units.
- During use, the compounds are contaminated. Systems for cleaning coolant from metal residues are provided. Waste products that are not subject to efficient cleaning should be disposed of.