August 2021 Volume 3

EQUIPMENT & TECHNOLOGY

It All Comes Down to the Right Choice of Lubricant By Marius Schmid and Dr. Marcel Eberle

Why AreThere Lubricants in Forging? Every employee in the forging value chain has a different answer to this question, and yet they all have one thing in common: all the answers are correct. The advantages for using a lubricant in forging range from reduced wear of the press, to the surface finish of the forged product, to cost savings due to a longer die life. In detail, the advantages become clearer. Due to reduced friction, the press force can be set lower, which reduces the load on the machine and its components. With an improved sliding effect of the material in the die, wear and small cracks are delayed. This not only extends the service life, but also improves the surface quality of the components over the life cycle of a die. Finally, yet importantly, it is also possible to shape difficult-to-flow alloys, e.g. chrome, nickel or titanium, in a forging process so that all corners and shapes of the finished component are completely filled. So, one thing can be said with great certainty: Die forging cannot be done without a lubricant/release agent. What Properties Does a Lubricant Need for Forging? The criteria that a die lubricant needs to match are numerous. The most important are a good sliding effect, excellent separating properties and a temperature resistance that corresponds to the process. Besides the fact that a smooth production process must be established, the well-being of the employees and the environment should also be considered. What Types of Lubricants AreThere in Forging? In order to better divide the selection of a suitable lubricant, lubricants are roughly categorized into three groups: Coatings; Graphite Products; and Synthetic Products. 1. Coatings Coatings are protective films that seal the surface of the alloys. The closed protective layer reduces hot gas diffusion, which improves the surface quality of the manufactured component. In addition, the heat is better retained in the component and cooling during transport between the furnace and the press is prevented. Glass Coating range is most commonly used in aerospace applications. The glass protects the titanium or nickel alloys from the reactive oxygen and a clean and, above all, defect-free surface is achieved after forging. The glass coatings are applied to the workpieces by brushing, spraying or even by an electrostatic application process. The user can adjust the thickness of the applied glass coating to the respective process by diluting the product with water to the appropriate consistency on site.

Turbine blades forged with Coating Product

2. Graphite Products Black products get their color from the graphite they contain. This naturally black solid has excellent properties that make it valuable for lubricants. In addition to a good lubricating effect, these also include outstanding separation performance. With graphite- containing lubricants, the carrier fluid can be varied; there are both water- and oil-based products.

Crankshaft forged with Black Graphite product.

2.1. Water Graphite The water used is cooling the parts which it comes in contact with and prevents the die from overheating. These products can be mixed with water on site, allowing the user to mix his own suitable concentration depending on the complexity of the part, quality of the die, and application method.

FIA MAGAZINE | AUGUST 2021 13