Metalworking Fluids (MWF) or machining coolants are essential in machining and grinding processes. These fluids are utilized where a grade of metal is used, referred to as the tool, to remove metal from another source, referred to as the part. Fluid is required to prevent the tool and part from welding to each other and this fluid is called a MWF or sometimes also referred to as a cutting fluid. They are divided into two groups. Namely,

• Neat Oil, either mineral oil-based or synthetic
• Water-based lubricants

In this blog, we focus on water-based MWFs. These are complex chemical formulations that fulfil many roles in the metal removal process. Essentially, they are oil in water complexes that are held in a single phase by a group of chemicals called emulsifiers. The emulsifiers are the structure that keeps the MWF homogeneous (a single and stable phase).  MWFs need to endure extremely strong forces and temperatures in the process of metal removal all the while remaining stable over a long period. The primary functions are:

• cooling of the tool and part
• lubrication during metal removal
• providing corrosion protection to the tool, part, and the machine

The process of metal removal generally takes place within a CNC machine due to the precision required in machining and grinding, the high speed required for successful metal removal and the exact feed rate of the tool in the process.

Water-based MWFs are diluted with water to a concentration of 5% to 20% depending on the severity of the operation and the material being machined. Thus, in any given solution the major component is water. The quality of the water has a direct effect on the performance of the MWF.

One of the measurements of water quality is water hardness. The hardness of the water is determined by measuring the amount of calcium and magnesium present in the water. Calcium and Magnesium cause instability in a MWF product. These two elements attack the emulsifier package and negatively affect the emulsifiers’ ability to keep the MWF stable.

The choice of MWF is determined by the severity of the operation (type of removal process) and the type of material being removed. The different types of metals that are machined include ferrous (contains iron) metals and non-ferrous (aluminium, yellow metals, titanium) metals.

Ferrous metals are more common and the main requirements for machining ferrous metals include:

• corrosion protection; with the exception of stainless steel
• lubrication
• cooling

Non-ferrous metals do not require corrosion protection but are susceptible to staining and thus require MWFs with additional additives (chemicals to prevent or enhance products) to prevent staining.

Water-based MWFs can be divided into three groups based on the amount of mineral oil in the concentrate:

• synthetic – no mineral oil
• Semi-synthetic – 1% to 39% mineral oil
• Emulsion – 40% and more mineral oil in the concentrate

The most common type of water-based MWF is called semi-synthetics. Semi-synthetics are oil in water formulations that contain a moderate amount of mineral oil (less than 40%) synthetic lubricants, water, emulsifiers, and additives in the concentrated form. Semi-synthetics are designed to machine different materials within varying degrees of operational difficulty and include the following additional components:

• pH buffers
• corrosion prevention agents
• biocides
• extreme pressure additives
• lubricity enhancers
• fungicides
• antifoaming agents
• passivation agents

All of the above are held together in either the oil or water phase by the emulsifier package.

The world of MWF is vast and as technology improves so do MWFs. This blog is simply an introduction, and we invite you to contact Chemical Solutions and Innovations (CSI) for any MWF related questions that you may have.