Developing new technique to weld copper

Apr 25, 2018, 04:41 PM

Some like it hot…like copper, which requires roughly twice as much heat input than steel to get it to fuse correctly. Being a high-heat conductive alloy, copper is notorious for being a challenge to weld using both traditional methods and 3D metal laser printing. However, products made from copper and its alloys are in high demand. So, Honeywell engineers at the Kansas City National Security Campus set out to solve the challenge of fluctuating temperatures.

Additive Manufacturing (AM) is a continuous welding process, where the powder is melted and welded to the previously deposited layers. The part’s creation is made by repetitively welding material together layer by layer; therefore, issues seen during traditional welding are eliminated in AM.

However, the majority of the AM laser energy reflects off the material surface and is not absorbed due to the high-optical reflectivity of copper. Copper’s high-thermal conductivity causes large thermal losses within the build area, resulting in under melting and solidification defects.

Engineers Chris Barr and Wes Everhart developed a new patent-pending, beam control algorithm, which is able to account for these large thermal losses in powder bed AM systems. The advanced beam control software takes into consideration the material properties and geometry to maintain a constant processing temperature. It also has the ability to predict and control cooling rate to avoid solidification micro-cracking. Its predictive ability informs the parameter selection of the design of experiments and is able to focus in on fewer combinations, with fewer samples needing analyzation.

Thanks to the development of this software, what would typically take over six months is reduced to three weeks for adapting new materials to AM, such as Oxygen-Free High Conductivity (OFHC) copper and high-strength aluminums.

We are now making progress towards the ability to apply these methodologies to the production of complex components of solid copper and employing AM for new applications. With optimized control parameters, the build processes are exhibiting high efficiency and fast build rates. This is accomplished by using pure OFHC copper without any alloys, additives or infiltrants needed.

AM is not a replacement for traditional welding, but an alternative manufacturing method to other processes such as forging or casting. The main benefits of AM are the ability to manufacture shapes that are more complex, minimal increase in costs and the opportunity to reduce the amount of material waste.

Watch the latest KCNSC Tech Talk video series to learn more about this team.