Why is it important to ensure copper and copper alloys are deoxidised before annealing?
Stefan says: Annealing generally takes place under a nitrogen + hydrogen (N2 + H2) furnace atmospheres. If the copper or copper alloys are not sufficiently deoxidised, at temperatures above 400 C, the hydrogen dissolves readily into the copper and diffuses rapidly and reacts with the copper oxide (Cu2O) particles to produce (H2O), which is insoluble in copper. Instead, at furnance temperatures, the H2O molecules lead to the formation of steam — or vapour pockets — which results in a porous structure which can drastically reduce the strength of the part. Q: How can I avoid these problems when working with copper or copper alloys? Stefan says: To avoid problems with copper materials that were not sufficiently deoxidised, the proportion of hydrogen in the nitrogen + hydrogen furnace atmosphere should be reduced to about 2% H2. Sticking of coils of copper wire requires a different solution. The sticking is caused by the presence of a layer of copper oxide. Under reducing atmospheres copp
