Quality improvement of copper rod production for magnet wire application

摘要

The finished product quality of enameled wire is determined to a large degree by the surface quality of bare wire. The formation of any surface defect on the wire would seriously affect the surface integrity of the wire and enamel film during the enameling process. In the case of magnet wire, a microcrack or any defect on the copper wire surface could act as a stress concentrator against the thin enamel coating and this is thought to be the major cause of magnet wire damage or failure during the application or during in-service. Recent investigations have indicated several sources that may cause the formation of surface defect in copper wire. One group originates from the casting/rolling process and includes: impurity level, oxygen content, inclusions, etc. Equally important, surface problems can occur by the drawing factor and other mechanical damage or by the formation of surface oxides during handling and transportation. Some chemical impurities usually damage the material by producing cracks in the grain boundaries during the casting and rolling operations. These cracks readily oxidize and become submerged under the copper surface during subsequent hot rolling. It is also possible for these cracks to pick up the copper oxide layers which can build up on the processing rolls, causing a sub-surface oxide discontinuity.