Because of its toxicity, lead is being increasingly banned where brass comes into contact with drinking water. The EU drinking water guidelines have already restricted the lead content in drinking water to 10 micrograms per liter (µg/l) in 2013 and once again reduced by half in 2018. As a result, the usual lead-containing copper alloys (e.g. CuZn36Pb2As) or machining brass (CuZn39Pb3) used for production of plumbing components that conduct drinking water are no more on the positive list of the Federal Environmental Agency.
Lead lubricates and prevents wear
Lead significantly facilitates chipping, because it ensures good chip breaking and is slightly lubricating. For tool manufacturers therefore, the bad machinability of the lead-free brass poses a challenge. The problem here is: Many cheap, lead-free or low-leaded substitutes already available in the market increase tool-wear by material lubrication, generate long ribbon or thread chips during production and frequently render a secure process impossible.
Standard unfit for lead-free materials
At our location in the Upper Palatinate Pleystein, we have long been testing lead-free materials for production of armatures and fitting parts, among other things – with the sobering result: Standard tools made of the conventional brass chipping are unfit for their processing and do not enable effective production.
We will further optimize the chipping of lead-free copper materials together with customers and partners
Leistritz has the solution
The Tools Academy launched by us in 2017 was with the idea to jointly conduct research with partners to find a solution for lead-free brass machining. In the process, we developed a successful concept for complete workpiece machining as well as with solution approaches for materials and coatings. Machine operators, persons in charge of production and designer engineers took part in the event. Here, better results were achieved in workpiece chipping, wherein the tool geometries were optimized and a special BALINIT®-HARD-CARBON coating was used.
Modified cutting edge geometries and special coating
In fresh attempts, we have machined lead-free brass of the material CW 511 L (CuZn38As) in six spindles and modified cutting edge geometries with different rake and clearance angles as well as used an optimal coating for the flatform inserts for external and internal machining. Thus, workpieces with good surface quality could be made. The chip formation improved, even if there was further need for optimization with reference to the chip breaking.
Less wear and better chip flow
Also, for about 500 workpieces, the tools displayed no visually identifiable wear – a result of using BALINIT® HARD CARBON. The particularly hard and wear-resistant ta-C coating can be applied – unlike diamond coatings – on every conventional hard metal. It also provides ideal properties for the chipping of non-ferrous metals: best slippage and protection against adhesion in case of high thermal stability as well as high level of hardness with corresponding abrasive protection. This brings about better chip flow, more productivity and process safety. With a layer thickness of just 1 micrometer (μm), geometry and cutting edges of the tool are also not affected.
We have gained valuable knowledge, which has incidentally also been confirmed by the scientific community. With that, we can further optimize the chipping of lead-free copper materials together with customers and partners – on the basis of a comprehensive tool concept, which completely covers the machining and production of the products of our client