Metalworking Fluids – What should metalworking Suppliers know about them?

Metalworking Fluids can ideally be stated as a game-changer in the industrial sector, in terms of several benefits it offers during the production of a metal product. Let’s get into detail about them!

1. Metalworking Fluids – A brief introduction
2. History of Metalworking Fluids
3. Metalworking Fluids – Types
4. How to select a Metalworking Fluid (MWF) for an industrial process?
5. Maintenance of Metalworking Fluids
6. Resources

1. Metalworking Fluids – A brief introduction

Metalworking fluids are the coolants and lubricants used in the Metalworking processes like metal-cutting, metal-forming, metal-stamping and machining. In different parts of the industry, MWFs are otherwise known as cutting oil, cutting fluid, cutting compound, coolant or fluid depending on the colloquial usage by the habitant metalworking suppliers.

Why are Metalworking Fluids used?

Several benefits line-up as the industrial benefits of Metalworking fluids and its impact on the industrial process it is used for. Below mentioned are the primary reasons for the choice made by metalworking suppliers when it comes to metalworking fluids.

Metalworking Fluids (MWFs),
• Improves the quality of a tool enhancing its work-life
• Provides smoother finish on metal workpieces
• Removes the chips from a process and prevents it from disturbing the tool/ work-metal
• Suppresses corrosion
• Lowers the friction between the work-metal and cutting machine, thereby lowering the heat.
• Reduces smokes and burns on a work-metal

Where are Metalworking fluids used?

Metalworking suppliers involve lubricants and coolants in almost all metalworking operations. MWFs are quite commonly used in,

• Processes that produce large quantities of metal parts and chips
• In machines that need long production run times
• In machine/ tool maintenance for optimal life and downtime
• For processes that require an accurate and precise finish
• To maintain the surface properties of a work metal

Do all metalworking processes require Metalworking Fluids (MWFs)?

Although almost all processes require a lubricant or a coolant for smoother operation and finish, exceptions are possible in certain processes. Subsequently, the concept of Dry Machining clarifies the theory of cutting fluid exceptions in metalworking processes. Dry machining is a process that does not require a metalworking fluid due to suffice fulfillment of working conditions, metal and machine characteristics, temperature requirement, and cutting angle. This is one case where a Metalworking fluid is not a mandatory requirement.

On the other hand, metalworking fluids can be avoided while machining aluminum alloys that require low cutting temperatures. The chips that scatter during the process is prevented from interrupting the operation by using sharp edges of cutting tools at appropriate rake angles.

2. History of Metalworking fluids

The record of animal and vegetable oil in the ancient civilizations makes the metalworking suppliers speculate over an inference of the metalworking fluid usage in the times before iron age. However, obvious evidence is unavailable till date to prove this as a fact.

During the Greek and Roman era, the skills of a metalworking craftsman were considered as the utmost possession of value. Hence the secrets of their crafts were concealed and were only disclosed to their professional heirs. This practice proves a pacifying theory of no records about MWFs in ancient history.

Just when the industry progressed towards the industrial revolution, an awake in the technology of friction mechanics made way to an epiphany of a complete sect of a significant unit of the industry, that we call today as the Metalworking fluids.

The influence of Metalworking fluids so grown to play a vital role in the cost of a metal product in today’s market. According to the recent statistics, MWFs account for about 15% to 17% of the shop production cost of the metalworking product.

3. Metalworking Fluids – Types

Metalworking fluids can be found in different forms depending on the process that requires its application. The major types of MWFs include:

• Liquids
• Pastes or gels
• Aerosols (mists)
• CO2 coolant
• Other gases or Air

• Liquids
Liquid metalworking fluids are categorized based on several factors.

Based on metalworking fluid formulation, they can be further classified into

1. Oil-based MWFs
2. Water-based MWFs

Several metalworking additives are used to alter the properties of an MWF to match the requirement of the process. Some common MWF additives include sulphurated or chlorinated compounds, antifoams, emulsifiers, corrosion inhibitors, extreme pressure additives, metalworking biocides, etc.

Based on the quantity, they may be,

1. Flooding
2. MQLs

Based on manufacturing processes, they are,

1. Cutting oil
2. Forming oil
3. Grinding oil, etc.

However, we will investigate details of the classification that is based on the nature of the liquid

a. Mineral oils
b. Semi-synthetic
c. Synthetic

a. Mineral Oils
Mineral oils are petroleum-based oils that were first used in the 19th century. They are relatively thin, light, and clear and are majorly employed in the cutting operations.

b. Semi-synthetic metalworking fluid
As the name indicates, these coolants are a mixture of oils and minerals. They are otherwise known as soluble oil and are colloquially known as SUDS in the British-English workshops. The origin of their usage dates to the 1930s.

c. Synthetic metalworking fluid
Synthetic metalworking fluids are water-based coolants

• Pastes
The paste form of MWFs is usually applied to the tool of the metalworking process. Due to its natural characteristics, pastes are usually consumed during the metalworking operation.

Aerosols are cutting fluids that are found in the form of air which contains tiny droplets of water. This form of MWFs is problematic for workers as it hinders easy breathing during the operation.

• CO2 coolant
CO2 in the gaseous form is converted into solid by expansion accompanied by a temperature drop. The solid CO2 coolant is then used in the operation by delivery through nozzles or spindles.

• Gases or Air
Ambient, compressed, decompressing air are used as coolants in metalworking operations. The force of air in the operation removes the swarfs from the work-metal.

4. How to select a metalworking fluid for an industrial process?

As important as other factors of a metalworking process, the selection of metalworking fluid is equally crucial. Below are the factors that a metalworking supplier checks for selecting the right metalworking fluid:

• Machining conditions
• Tool/machine material
• Tool/machine design
• Fluid sump size
• Material of the work-metal
• Machining temperature

A metalworking supplier must also ensure that he checks on factors exclusive for certain processes. Each MWF has its own strength and weakness that may largely impact the quality of the work-metal, on the other hand, the quality of the tool/ machine it is worked on. Therefore, a cautious selection of MWF is highly preferred for a metalworking process.

5. Maintenance of MWFs

Different maintenance practices are carried out by metalworking suppliers largely focusing on optimal removal of impurities (fluids in varied densities) from the MWFs. Below are the common methods of impurity separation:

This set up has its functionality based on the centrifugal force. The conic excavation consists of 2 vortices. The primary vortex is the outer region which consists of a narrow tube-like space right across its midline tangent. The MWF let into the primary vortex starts to curl due to the pressure exerted to cause a cyclone. This curl separates the contaminants from the fluid.

The clean fluid outflows from the primary vortex, reaches the bottom of the cone and gets reversed into the secondary vortex. During the upward motion of the fluid into the narrow secondary vortex, an even better purification is achieved. The residual contaminants left behind in the primary vortex is removed from the bottom of the hydrocyclone through discharge.

The principle of this set up is similar to that of hydrocyclone method, where an overflow caused by centrifugal force separates the clean MWF from the sludge. However, the setup difference is that, a solid bowl centrifuges with an overflow rim is used in this method. In this method, the sludge can be removed automatically or manually. In general, automatic purification comes with the limitation of an external filter requirement in order to remove the residual fluid from the sludge.

This less commonly preferred method of MWF cleaning has its highest value in the liquid-solid separators. This expensive method which is also sensitive to abrasive wear requires frequent cleaning of its separators.

In conclusion, MWFs are regarded as a crucial and influencing agent for quality production in the metalworking market. It highly impacts the physical, chemical and economic value of a product, making it mandatory for a metalworking supplier to contribute momentous effort to choose the right metalworking fluid for a process.

6. Resources:

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