In traditional powertrain companies, water-based cutting fluids are commonly mixed with tap water. Since the formulas of these fluids are often imported from abroad, the products tend to be fairly uniform. Although chemical manufacturers try to account for variations in water quality globally and develop or select products that suit specific applications, the inherent characteristics of base cutting fluids can limit their adaptability. Additionally, operating conditions and requirements vary across different sites and production phases. Meeting all these demands is a complex technical challenge. Improving the service life of cutting fluids, minimizing their impact on machining processes and overall production, and reducing environmental pollution from wastewater discharge are key concerns in our discussion about deionized water.
**What is Deionized Water?**
Deionized water refers to water that has had its ionic impurities removed. According to ISO/TC 147, deionization involves either completely or partially removing ionic substances, typically through the use of ion exchange resins. The current process usually combines reverse osmosis (RO) with ion exchange systems. While this method effectively removes anions and cations, it may not eliminate all organic contaminants, which can affect the performance of the resin over time. Moreover, stored deionized water can promote bacterial growth if not properly managed.
**How is Deionized Water Produced?**
The production of deionized water typically involves a combination of reverse osmosis and ion exchange technologies. A standard process includes: raw water → quartz sand filter → activated carbon filter → resin exchange → precision filter → high-pressure pump → reverse osmosis unit → pure water tank → pure water pump → final point of use. Each stage plays a role in purifying the water before it reaches the desired level of purity.
The quartz sand filter helps remove iron, aluminum, and silica particles, while the activated carbon filter eliminates organic compounds like chlorine and volatile phenols. Resin exchange reduces water hardness by removing calcium and magnesium ions, protecting the RO membrane. The precision filter ensures any remaining fine particles are removed.
Reverse osmosis is the core of the process, where pressure is applied to force water through a semi-permeable membrane, leaving behind impurities. This technique is widely used due to its efficiency and simplicity.
**Applications of Deionized Water**
In engine and transmission factories, deionized water has proven valuable in improving the performance of water-based cutting fluids. Based on experience with German manufacturer Dürr, the conductivity of deionized water should ideally be ≤50 μS/cm. When planning deionized water systems, several factors must be considered: raw water quality, deionized water specifications, system capacity, and the location of concentrated water discharge.
For example, in an engine factory using water-based cutting fluids, problems such as fluid instability, stratification, and increased additive consumption were observed. After switching to deionized water, the service life of the cutting fluid was significantly extended, reducing maintenance costs and improving machine tool performance.
In transmission plants, deionized water is crucial for cleaning parts before heat treatment. Using tap water can lead to scale buildup in washing machines, damaging heating elements. Deionized water helps prevent this, ensuring cleaner surfaces and better heat treatment results.
While deionized water has limited direct impact on rust prevention due to multiple influencing factors, it still offers advantages in regions with high chloride levels, such as southern China during the rainy season. Its low conductivity and reduced ion content make it more suitable for preventing corrosion in sensitive environments.
**Conclusion**
Deionized water plays a critical role in optimizing cutting fluid performance and reducing environmental impact in powertrain manufacturing. Companies like Shanghai Volkswagen and FAW-Volkswagen have integrated deionized water systems into their filtration setups to ensure consistent fluid quality and operational efficiency. However, proper monitoring and data analysis are essential to avoid misuse and maximize benefits. As technology advances, the application of deionized water is expected to expand further in major machining facilities.
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