How to choose cutting fluid

When cutting, the force generated by the high-speed operation of the equipment is mainly used for cutting. In this way, high heat will be generated in the processing process, causing harm to the cutting tools and blanks. Therefore, the help of cutting fluid is needed when cutting. Cutting fluid plays a great role in reducing friction and cutting temperature in the cutting process.

1、 Function of cutting fluid
1. Cooling effect: through the heat conduction, convection and vaporization of the cutting fluid, it can effectively improve the heat dissipation conditions and reduce the temperature of the cutting area, so as to improve the service life of the tool and reduce the thermal deformation of the workpiece.
2. Lubrication: after the cutting fluid penetrates into the contact surface between the chip, the tool and the workpiece, it adheres to the metal surface to form a lubricating film, which can reduce the friction coefficient between the chip and the front of the tool and the back of the workpiece and the tool, reduce the bonding phenomenon, inhibit the chip buildup, reduce the surface roughness, and improve the tool life.
3. Washing and chip removal: the cutting fluid can wash away the fine chips generated in the cutting process, so as to achieve the purpose of mechanical cleaning and prevent the machining surface or machine tool damage. In deep hole machining, cutting fluid can also play the role of chip removal.
4. Antirust effect: after adding antirust additives to the cutting fluid, a protective film can be formed on the metal surface, so that the machine tool, workpiece and cutting tool will not be corroded by the surrounding medium and play the role of antirust.

 Types and selection methods of cutting fluid
1. Types of cutting fluids: commonly used cutting fluids include aqueous solution and cutting oil.
(1) Aqueous solution: aqueous solution is a cutting fluid with water as the main component. Although the cooling and washing effect of natural water is good, it is easy to rust machine tools and workpieces. At present, emulsion is the most commonly used in aqueous solution. Emulsion is a mixture of oil and water, because oil cannot be dissolved in water. In order to mix the two, emulsifiers (fatty acids, sodium soap, potassium soap) must be added. When in use, as long as the prepared emulsified oil is added with water, emulsions with different contents can be obtained. Emulsion with low content has strong cooling and washing effect, which is suitable for rough machining and grinding; The emulsion with high content has strong lubricating effect and is suitable for finishing.
(2) Cutting oil: the cooling and washing effect of this kind of cutting fluid is worse than that of aqueous solution, but its lubrication and rust prevention effect are better. Pure mineral oil has poor lubrication, but it is rich in resources. Among them, mineral oils with low viscosity, such as l-an15 and l-an32 oils, light diesel oil, kerosene, etc., are widely used. Vegetable oil and animal oil contain polar molecules, which can form a stronger lubricating film. The lubricating effect is better than that of pure mineral oil, but it is not suitable for general use because of its high price.

2. Selection of cutting fluid: there are many kinds of cutting fluid, which should be selected reasonably according to the cutting conditions and the requirements of cutting fluid. The general principles for selecting cutting fluid mainly include the following aspects:
(1) Select cutting fluid according to the material properties of the workpiece: when cutting brittle materials such as cast iron and bronze, in order to avoid the fine crumbs adhering to the machine tool and difficult to remove, generally do not use cutting fluid. However, when finishing cast iron, kerosene with good lubricity and low viscosity can be selected as cutting fluid in order to reduce the surface roughness value. When cutting general steel materials and workpieces with large plasticity, emulsion or vulcanized oil is usually used.
(2) Choose cutting fluid according to the processing properties: during rough machining, the surface is rough and generates more heat. Generally, choose emulsion with strong cooling effect; During finish machining, in order to refine the surface roughness, cutting oil mainly used for cooling can be used.
(3) Select cutting fluid according to the tool material: when planing with high-speed steel tools, generally cutting fluid can be used; When planing with cemented carbide tools, generally do not use cutting fluid to avoid cracks caused by sudden cooling and heating of the blade.