Cutting fluid testing items

What are the quality inspection items for cutting oil.
The main quality control indicators of cutting oil include viscosity, flash point, pour point, fat content, sulfur content, chlorine content, copper corrosion, moisture, mechanical impurities, four ball test, etc. Regarding the determination method, relevant test method standards can be referred to, and only a brief explanation is provided for some items.
fat content
Fat is an oily additive in cutting oil and an important indicator for classifying cutting oil. Fat in cutting oil can play a role in reducing friction coefficient and reducing tool wear (especially effective in preventing wear on the back cutting surface). Cutting oil with a high amount of fat is particularly suitable for non-ferrous metal processing and situations where the cutting amount is not large but the product accuracy and smoothness requirements are high (such as precision turning screws). Generally, the saponification value can be used to roughly determine its fat content. Excessive fat content in cutting oil or improper quality control can easily form viscous substances on the machine, causing inflexibility in the movement of the parts. In severe cases, it can turn into a paint film, also known as "wearing a yellow robe".
Chlorine content
Chlorine in cutting oil mainly comes from extreme pressure agents containing chlorine. Chlorine needs to be present at a high content (greater than 1%) in order to exhibit effective extreme pressure effects. If the chlorine content is less than 1%, it can be considered that it is not intended to improve lubrication. Generally, chlorine containing extreme pressure cutting oil has a chlorine content of over 4%, with a maximum of 30% to 40%. However, due to considerations of occupational health and environmental protection, some countries have established regulations on the maximum chlorine content in cutting oil, such as Japan's JIS which stipulates that the chlorine content should not exceed 15%. Chlorine is highly effective in the processing of stainless steel and in drawing and forming processes. Its disadvantage is that it is not stable enough. When it comes into contact with water or at high temperatures, it will decompose and produce HCl, causing corrosion and rusting.
Sulfur content
Sulfur in cutting oil comes from two sources. One is the added sulfur-containing extreme pressure agent, and the other is from other sulfur-containing compounds that do not have extreme pressure effects, such as natural sulfides, rust inhibitors, antioxidants, etc. in the base oil. Effective sulfur only requires a very low content (0.1%) to produce significant extreme pressure effects. Sulfur-containing extreme pressure agents are particularly effective in inhibiting chip deposits, and there is no simple method to separately measure sulfur with extreme pressure and sulfur without extreme pressure. So it is difficult to determine its extreme pressure solely based on its sulfur content (especially when the sulfur content is not high). However, most cutting fluid manufacturers indicate the sulfur content of the added extreme pressure agent in their product manuals.
copper corrosion
The method of measurement is the copper plate method. The magnitude of corrosion activity is expressed in series, with levels 1-2 indicating low activity or non activity, and levels 3-4 indicating high activity. The larger the level, the stronger the corrosion activity. Copper is very sensitive to sulfur, and this method can be used to determine whether there are sulfur-containing extreme pressure agents and the activity level of extreme pressure agents in cutting oil (note: this method cannot determine the amount of sulfur-containing agents). This project is also an important indicator for dividing cutting oil categories.