Hydraulic oil for CNC machine tools: selection and requirement of hydraulic oil for press brake bending machine

Views: 476     Author: DURMAPRESS     Publish Time: 2021-09-10      Origin: DURMAPRESS


Hydraulic oil for CNC machine tools: selection and requirement of hydraulic oil for press brake bending machine

What kind of hydraulic oil is best for press brake bending machine?

In order to make the hydraulic system of the hydraulic press can better transfer power and movement, the hydraulic oil used should have the following properties:

1. It is necessary to have suitable viscosity and good viscosity temperature characteristics (that is, within the range of using temperature, the smaller the viscosity changes with temperature, the better);

2, good lubrication, in the specified range there is enough oil film strength, so as to avoid friction;

3, the composition is more pure, less impurities, good foam resistance, if the hydraulic oil contains some mechanical impurities, it is easy to block the oil path, if it contains volatile substances will make the oil bubble, affect the stability of the movement;

4, the flow point and freezing point is relatively low, flash point and flash point is relatively high, when used in some high temperature occasions, in order to fire safety, high flash point requirements; When working in a low temperature environment, the freezing point is required to be low. The flash point of the hydraulic oil used in the hydraulic system of the general hydraulic press is about 130~150 degrees, and the freezing point is about -15~-10 degrees.

5, it is best to have good thermal stability, hydrolysis stability and oxidation stability, shear stability and compatibility;

6, with good anti-emulsification and rust resistance, corrosion resistance, so as not to erode the parts and sealing elements;

7, low expansion coefficient, high specific heat capacity and heat transfer coefficient;

8, with good safety, harmless to human body, low cost.


Hydraulic press requirements for hydraulic oil:

(1) Appropriate viscosity and good viscosity-temperature characteristics

Too much viscosity will lead to an increase in viscous resistance loss. Temperature rise; The suction of the pump can become poor, difficult to start, and even produce cavitation; Control sensitivity decreased. Too low viscosity will increase leakage and reduce volume efficiency; Control accuracy decreased; Liquid lubrication film becomes thin, and even can not form liquid lubrication, so that the wear is intensified.

Hydraulic oil can improve viscosity index and viscosity-temperature characteristics by adding viscosity index additives. Such as poly isobutene, poly methacrylate and so on.

(2) Good wear resistance (lubricity)

Antiwear is a property that is independent of viscosity, but reduces wear by adding additives to oil to form an oil film on the dual surface of the friction pair. High viscosity does not necessarily have good lubrication performance, such as silicone oil, but if the viscosity is low, the liquid film is too thin to cover the surface roughness, and the wear resistance is not good, such as water.


Through the oiliness additive is added in the hydraulic oil (oleic acid, sulfide and whale oil sulfide olefin cotton seed oil, etc.) and extreme pressure antiwear additive (phosphorus, sulfur, zinc and other substances, such as dialkyl disulfide generation of zinc phosphate, molybdenum disulfide, etc., can be used high temperature and overloading), make the hydraulic oil in metal surface form of physical or chemical adsorption film, the film also called boundary film, The boundary film forms the boundary lubrication between the friction pairs and prevents the direct contact between the matrix, which is beneficial to reduce friction and wear.

(3) Good oxidation stability and thermal stability

Oxidation stability refers to the ability of oil to resist oxidation. Oil is affected by heat, oxygen in the air, water and metal substances will oxidize and generate organic acids and polymers. The color of hydraulic oil deepens, the acid value increases, the viscosity changes and the formation of precipitated material (tar). Therefore, the corrosion of hydraulic oil increases, the holes of hydraulic components are blocked and the wear is intensified.

Thermal stability refers to the ability of oil to resist chemical reactions and decomposition at high temperatures. The oil accelerates the cracking and polymerization at high temperatures, and the metal surface acts as a catalyst. So the hydraulic oil must withstand a certain high temperature, and avoid working at extremely high temperature.

Generally, antioxidant is added to improve the oxidation stability and thermal stability of hydraulic oil.

(4) Good demulsification and hydrolysis stability of the hydraulic press


The ability of oil to resist mixing with water to form an emulsion is called demulsification. The ability of oil to resist decomposition by chemical reaction with water is called hydrolytic stability.

Water is a pollutant in the hydraulic system. It is brought into the system by moist air from the tank's breathing hole or by retracting the piston rod of the cylinder. Hydraulic oil has water absorption, which depends on the performance of the base oil, additives and temperature. After intense agitation, the water in the oil is easy to precipitate and form an emulsion with the oil. At this time, the water exists in the continuous phase of the oil as tiny droplets of water.

Water can cause corrosion, accelerate oil deterioration (putrefaction), destroy oil film, and reduce the lubricity of hydraulic fluids. Adding demulsifier (petroleum sulfonate, a surfactant) can improve the demulsification of hydraulic oil.

How to use hydraulic oil in hydraulic press reasonably

The hydraulic oil in the hydraulic press is believed to be used, but if we want to use it reasonably, then I think we should introduce the reasonable use of hydraulic oil in the hydraulic press.

1. The system should also be cleaned before oil change. The hydraulic system must be thoroughly cleaned before using the hydraulic oil for the first time. When replacing the same hydraulic oil, the new hydraulic oil should also be washed 1-2 times.

2. Hydraulic oil can not be mixed at will. If a certain grade of hydraulic oil has been selected, it must be used separately. Without the consent of the hydraulic equipment manufacturer and without scientific basis, it is not allowed to mix with hydraulic oil of different viscosity brand or hydraulic oil of the same viscosity brand but not the same manufacturer, let alone with other types of oil.

3. Pay attention to the good sealing of the hydraulic system. The hydraulic system using hydraulic oil must be strictly sealed to prevent leakage and the mixing of various external pollutants.

4. Replace the hydraulic oil in time according to the oil change index. The hydraulic oil in the hydraulic press should be sampled regularly and tested. Once the physical and chemical indexes in the oil reach the oil change index, the oil should be changed.

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