Lead has almost completely disappeared from many areas of daily life.
Lead has almost entirely disappeared from many aspects of everyday life. The demand for lead-free applications continues to grow, driven by efforts to eliminate lead completely from the materials cycle. In recent years, legal requirements have become increasingly stringent. However, machining brass alloys containing lead presents new challenges for manufacturers and end users alike: significantly reducing or eliminating lead compromises the machinability of these alloys. This issue has been known for some time now, and I’ve long been committed to contributing to the search for solutions in machining what we now commonly refer to as “lead-free” or “eco brass”.
My own research has taken me around the world, studying and analysing papers and technical reports in search of useful data and insight. As is often the case with the most complex problems, there is no magic wand-no one-size-fits-all solution that can be applied instantly. A multi-faceted approach is needed to improve the machinability of lead-free materials. If you’re interested, I’ll take you with me on this journey through international sources and studies, to dive deeper into the challenges of lead-free brass machining.
Let’s begin with a study conducted in Germany.
This research project was part of an AIF initiative, carried out in collaboration with the German Copper Institute (DKI), the WZL Machine Tool Laboratory at RWTH Aachen University, and several industrial partners including tool manufacturers Schwartz and others, Willy Kreutz GmbH & Co. KG, and Aurubis Stolberg GmbH & Co. KG. The goal was clear: to improve the machinability of low-lead and lead-free brass alloys.
Experts used highly delicate tools in sliding-headstock automatic lathes. In multiple test cycles, they varied:
- Cutting speed
- Feed rate
- Cooling strategy (conventional cooling with emulsion and oil, minimum quantity lubrication with oil, and dry machining)
They then evaluated:
- Chip shape,
- Tool wear,
- Surface finish,
- Burr formation.
The test material was BlueBrass (CuZn42 with< <0.10% Pb) from Aurubis Stolberg. The lead-free brass was compared with a leaded brass alloy, known as free-machining brass (MS 58 / CuZn39Pb3), and with another lead-free brass (CuZn37).
“From the very first trials, it was immediately clear that we would not achieve any real progress using standard tools for machining lead-free copper alloys. The formation of long, tangled chips that disrupted automated processes and greatly reduced process reliability, along with extreme tool wear caused by excessive burring of the material, were major issues. Cutting-edge failures and even complete tool breakdowns were common. While chip breaking could be improved by adjusting cutting parameters, the small size of the components severely limited our options.”
Tool Optimisation: The most effective approach to tackling these challenges was optimising the geometry of the tools, with the goal of producing short chips, increasing tool life, and maintaining high efficiency.
Test Results: The optimised tools proved capable of machining over 120,000 components made of BlueBrass, maintaining good surface quality and producing short chips. Even once heavily worn, the tools remained suitable for roughing operations.
Improvements with DLC Coating: The use of special coatings such as DLC (Diamond-Like Carbon) further improved performance, reducing material build-up and extending tool life.
Conclusions: The results of the project indicate that a successful transition from leaded to lead-free brass machining is possible, provided that the correct strategies for tool and process optimisation are implemented.
Is it the definitive solution? Probably not.
It’s just one stage in a longer journey-one made up of many stops and countless variables.
Only by assembling all the pieces of the puzzle will we find a truly comprehensive solution.
As a machine builder focused on the production of brass spheres, I face the problem from my own perspective-by offering solutions that concern the machine itself, such as better ergonomics and improved lubrication.
Each case, however, has its own specific requirements and must be evaluated individually.
FONT: https://www.zerspanungstechnik.de/blog/2014/04/08/bleifreies-messing-effizient-zerspanen/