Water-Based Metal Cutting Fluids: Performance and Selection
Metal cutting is an important operation in many manufacturing processes. Appropriate lubrication is essential to obtain good performance and quality of the components, as well as to reduce cost and prolong the tool life. The use of cutting fluids is the most common method of lubrication and cooling of cutting tools and workpieces.
Conventional neat oils have been used as cutting fluids for many years, showing excellent lubrication and cooling performance. However, neat oils have several disadvantages, such as high cost, delivery problems, environmental issues, and their toxicity. Water-based metal cutting fluids (WCMs) have become increasingly popular in recent decades due to their cost-effectiveness and environmental compatibility. Although WCMs can provide satisfactory performance in many applications, the fluid selection must be conducted carefully.
This paper presents a review of the performance of WCMs as cutting fluids. It describes the different formulations of WCMs and their various characteristics, and reviews the main performance parameters of WCMs, including lubrication, cooling, anti-corrosion and anti-foaming. Additionally, approaches for the selection of suitable WCMs for specific applications are discussed and evaluated.
Water-based metal cutting fluids (WCMs) are aqueous lubricants that are designed to provide sufficient lubricity, cooling and anti-corrosion properties during metal-cutting operations. The base of WCMs is usually composed of water, surfactants and corrosion inhibitors. The addition of other components, such as emulsifiers, microemulsions and special functional surfaces, can further improve the efficacy of WCMs.
WCMs can be further classified according to the type of base fluid used, such as neat oil emulsions, soluble oils, semi-synthetic fluids and fully synthetic fluids. Neat oil emulsions are the most commonly used, and are the major type of WCMs available in the market. They are obtained from the emulsification of neat cutting oils in water and contain residual neat oils in the form of micro-emulsions. These fluids provide a good balance between lubricity, cooling and cost. Soluble oils are also composed of water and oil, but do not contain neat oils. Semi-synthetic and fully synthetic fluids are prepared from synthetic base components, such as esters, and usually contain additives to enhance their performance.
The performance of WCMs is mostly dependent on their formulation. Many factors, including the base fluid, surfactant types, concentrations of additives, and the presence of neat oils, influence their performance. The main performance parameters that should be considered while selecting suitable WCMs are lubricity, cooling, corrosion protection, and foam reduction.
Lubricity is one of the most important performance parameters of WCMs. It is usually measured as the coefficient of friction (COF) between a cutting tool and the workpiece. It is desirable for WCMs to exhibit low COF values, as this allows for easy cutting and reduced tool wear. Cooling is also an important parameter for WCMs. As during the cutting process, high temperatures can be generated, which can reduce tool life. Thus, it is desirable for WCMs to provide effective cooling and reduce the temperature of the cutting zone. Additionally, WCMs should also provide protection against corrosion of the tool and workpiece surface, as well as effective foam reduction.
In order to choose the most appropriate WCMs for a specific application, several criteria should be taken into account, including the type of material to be machined, the cutting parameters and the need for cleanliness. Additionally, factors such as cost, health, safety and environmental issues should also be evaluated. It is also important to consider the compatibility of the WCMs with the materials and components used in the machining process, such as pumps and hoses, as these materials may be affected by the presence of the fluids.
In conclusion, water-based cutting fluids (WCMs) are a cost-effective and environmentally friendly alternative to neat cutting oils. Despite their cost-effectiveness, it is important to select the most appropriate fluids for a specific application in order to maximize performance and extend the life of the tool. The selection process should consider the different performance parameters of WCMs and the nature of the material to be machined. Additionally, cost and environmental issues should also be taken into account to ensure the most effective and cost-efficient WCMs are selected.
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