The main quality control indicators of cutting oil include viscosity, flash point, pour point, fat content, sulfur content, chlorine content, copper strip corrosion, water, mechanical impurities, four ball test, etc. Water based cutting fluid shall be diluted with water when it is used, and its test items can also be divided into direct measurement and water measurement. The items directly measured include storage stability, sulfur and chlorine content, nonvolatile components, etc. The items to be measured after adding water include surface tension, pH value, foaming property, rust resistance, corrosivity, adaptability to paint, allowable amount of salt, antibacterial property, etc. The significance of most of these projects is relatively clear.
Quality inspection items of cutting oil
Fat content Fat is an oily additive in cutting oil and an important index to classify cutting oil. Fat in cutting oil can play a role in reducing friction coefficient and tool wear (especially effective in preventing tool flank wear). The cutting oil with more fat is especially suitable for nonferrous metal processing and the occasions where the cutting amount is small but the product precision and finish requirements are high (such as fine turning thread). Generally, saponification value can be used to roughly determine its fat content. If the fat content in the cutting oil is too high or its quality is not properly controlled, it is easy to form viscous substances on the machine, resulting in inflexible movement of the machine parts. In serious cases, it will become a paint film, which is called "wearing yellow robes". Chlorine content Chlorine in cutting oil mainly comes from extreme pressure agent containing chlorine. The effective extreme pressure effect can only be shown when the chlorine content is high (more than 1%). If the chlorine content is less than 1%, it can be considered that it is not intended to improve lubricity. Generally, the chlorine content of extreme pressure cutting oil containing chlorine is above 4%, and the maximum chlorine content can reach 30-40%. However, in consideration of occupational health and environmental protection, some countries have stipulated that the chlorine content in cutting oil should not exceed 15%. Chlorine is very effective in the processing of stainless steel and in the pull forming process. Its disadvantage is that it is not stable enough, and it will decompose and produce HCL in case of water or high temperature, causing corrosion and rust. Sulfur content The sulfur in cutting oil comes from two aspects. One is the added sulfur containing extreme pressure agent, and the other is from other sulfur compounds without extreme pressure effect, such as the original natural sulfide, rust inhibitor, antioxidant, etc. in the Base Oil. Effective sulfur only needs very low content (0.1%) to produce obvious extreme pressure effect. Sulfur containing extreme pressure agents are particularly effective in inhibiting scaling tumors, but unfortunately there is no simple method to measure sulfur with extreme pressure and sulfur without extreme pressure. Therefore, it is difficult to judge its extreme pressure property only based on its sulfur content (especially when the sulfur content is not high). However, most cutting fluid manufacturers now indicate the sulfur content of extreme pressure agent in their product specifications. Copper corrosion Different corrosion degree of copper sheet The method of determination is copper strip method. The magnitude of corrosion activity is expressed by the number of stages. Levels 1 to 2 are low activity or non activity, and levels 3 to 4 are high activity. The higher the grade, the stronger the corrosion activity. Steel is very sensitive to sulfur. This method can be used to determine whether there is sulfur containing extreme pressure agent and the activity of extreme pressure agent in cutting oil (note: this method cannot determine the amount of sulfur containing agent). This item is also an important indicator for classifying cutting oils. Four ball experiment The maximum non seizure load can be measured. This method can be used to roughly judge the extreme pressure property of cutting oil, especially when the combined sulfur, chlorine content and copper strip corrosion are used for comprehensive analysis, so as to have a more comprehensive understanding of its lubricating property. However, it should be emphasized that the extreme pressure property given by the four ball test is only the evaluation result under standard conditions, and there is no strict correspondence between this result and the cutting performance. Quality inspection items of water-based cutting fluid Stability in storage Although the concentrate of water-based cutting fluid is a uniform liquid in appearance, it is actually mostly a colloidal system and contains quite a lot of water. After long-term storage and temperature fluctuation, precipitation, stratification and other phenomena are easy to occur if the formula is improper and often cannot be recovered. Therefore, this is a very important test item. Nonvolatile component The water based cutting fluid concentrate contains water, and this item is used to determine its effective component content. Salt allowance This test is used to know whether the cutting fluid is allowed to use tap water with high chlorine content to prepare working fluid. Surface tension In most cases, the liquid with small surface tension is easy to spread on the solid surface, so many people regard the surface tension as a measure of the cutting fluid permeability. But strictly speaking, there is no direct correspondence between them. Permeability is a rather vague concept, which seems to be more closely related to wettability and fluidity (viscosity). The surface tension can be used as a criterion to determine whether the cutting fluid contains surfactant. Because a small amount of surfactant can greatly reduce the surface tension of water. In addition, the smaller the surface tension is, the better. Too small the surface tension sometimes brings other negative effects. Antibacterial test The water-based liquid, especially the lotion, is prone to bacteria and corruption, so its antibacterial ability is an important performance index. However, in the past, it has not attracted attention in China, nor has it been used as the quality index of water-based liquid. Now there are some simple determination methods abroad. Conditional units shall apply them as far as possible.
