February 2023 Volume 5

EQUIPMENT & TECHNOLOGY

higher than water. Therefore, the carrier remains, and provides parting (physical separation between surfaces) and hydrodynamic lubrication between the die and the workpiece. This low coefficient of friction hydrodynamic lubrication, along with the boundary lubrication of the graphite allow very large, long metal flow pieces to be formed at high temperatures. A similar action occurs in synthetic forging lubricants to that of graphite in water boundary lubricants, however the action between the workpiece and die is slightly different during forging. Similar to graphite in water lubricants, once the fluid is applied to a hot die it ‘wets out’ or dries onto that die forming a dry film of salt and the water carrier is driven off. However, unlike a lubricant that strictly operates on the boundary, synthetics exhibit a sort of ‘middle ground’ between hydrodynamic and boundary lubrication regimes known as ‘electrohydrodynamic’ or ‘mixed’ lubrication. This means that the solid film formed by the salt solution is liquified at high temperatures and gives partial hydrodynamic lubrication, which is shown in the middle of the Stribeck curve at coefficients of friction between boundary and hydrodynamic lubrication. This type of lubricant is used often for simpler forging operations which involve rolling or flattening rather than intricate metal flow in deep impressions forming near net shapes. Each of these lubricants acts differently tribologically in the die, and each has a specific purpose for different applications.

These tribological principles which govern how forging lubricants operate are important for forging professionals to understand. If these functionalities are well understood, principles of proper lubricant application become a priority and the correct choices of lubricant based on the process can be made. This will lead to an improved forging process, reduced scrap rate, and better forging die life. The experts at AML would love to help you choose the right lubricant for your forging process. We keep things running smoothly!

Frank Sobnosky Jr. Chemical Engineer AML Industries, Inc Office: 330-399-5000 Email: fsobnosky@amlube.com www.amlube.com

References: https://www.sciencedirect.com/topics/materials-science/lubricant-film thickness https://www.merriam-webster.com/dictionary/tribology

YOUR TRUSTED STEEL PARTNER

We make steel. But at our core, we’re committed to continuously investing in the people and technologies to better serve our customers.

CONNECT WITH US AT FORGE FAIR!

23-CHS-0017-FIA-HalfPage-PrintAd-Final.indd 1

1/25/23 3:45 PM

FIA MAGAZINE | FEBRUARY 2023 7