Generally speaking, the vast majority of oil-based metalworking fluids are pre-formulated. Customers use them directly after purchase, so there are no on-site mixing issues. A few concentrated oil-based products require dilution and blending with a base oil before use. In this case, the main considerations are the viscosity, flash point, and pour point of the base oil. There is no issue regarding the order of addition.
Water-based metalworking fluids, on the other hand, generally need to be diluted with tap water or other compliant water sources to prepare a working fluid with a specific concentrate concentration. When doing this, the water quality of the dilution water and the dilution process have a significant impact on the quality of the prepared working fluid.
Water Quality
When mixing metalworking fluids, it is best to use soft water with low calcium and magnesium ion content. Diluted fluids prepared with hard water will become turbid in appearance, and their lubrication and rust prevention performance will decline. Furthermore, using hard water to prepare the working fluid will also accelerate the reproduction of microorganisms. Additionally, impurities in natural water should be filtered out. Turbid water sources cannot be used to prepare metalworking fluids.
The ideal water quality for metalworking fluids should meet the following requirements:
| No. | Item | Ideal Range | Description |
|---|---|---|---|
| 1 | pH Value | Close to neutral | Normal tap water requires no special treatment. |
| 2 | Total Bacteria Count | No specific industry regulation yet | The less, the better. |
| 3 | Total Hardness (as CaCO3) | 80~125 ppm | Too high or too low is detrimental. |
| 4 | Chloride Ions | < 50 ppm | The less, the better. |
| 5 | Sulfate | < 100 ppm | The less, the better. |
| 6 | Phosphate | < 1 ug/g | The less, the better. |
| 7 | Impurity Content | No mechanical impurities or suspended solids | Normal tap water requires no special treatment. |
A Real-World Lesson:
Once, a customer tried to save costs by using well water near the seaside to prepare their metalworking working fluid. As a result, the working fluid had extremely poor stability and experienced severe phase separation. Serious corrosion occurred on both the machine tools and the workpieces, ultimately ending in total failure. No matter how high-quality a metalworking fluid is, it requires good supporting materials to meet its application requirements!
Mixing Method
For products with good water dispersibility, customers in many situations pour water directly into the drum containing the concentrate, and it can still be stirred evenly. However, for some products with poor water dispersibility, such as soluble oils, it is highly recommended to pour the concentrate into the water and stir continuously, just to be safe.
The Golden Rule: “Add Water First, Then Add the Concentrate” (Oil in Water)
An incorrect mixing method may generate gel-like substances in the diluted fluid. These substances are very difficult to dissolve, leading to problems such as increased viscosity of the working fluid and insufficient dispersion.
Another crucial point is to use room-temperature water for mixing. Do not use hot water with an excessively high temperature. High-temperature hot water might wash dishes cleaner, but it is completely unsuitable for mixing metalworking fluids.
Currently, there are many automatic proportional mixers available on the market. They are highly efficient tools that save a lot of time and effort, and their use is highly recommended for B2B manufacturing facilities.
