Effect of phosphorus on the properties of copper
In the field of metal materials, the influence of phosphorus on the properties of copper is multi - faceted. First of all, in terms of thermal and electrical conductivity, phosphorus can be regarded as a "negative role". After phosphorus atoms enter the lattice structure of copper, they will destroy the regularity of the arrangement of copper atoms and interfere with the directional movement of free electrons. The probability of free electrons colliding with phosphorus atoms during the movement increases, and the energy loss increases, resulting in a decrease in the electron mobility, which in turn significantly reduces the thermal and electrical conductivity of copper.
However, phosphorus is not entirely useless. It shows positive effects on the mechanical and welding properties of copper. In terms of mechanical properties, phosphorus can form some fine strengthening phases with copper, and these strengthening phases can impede the movement of dislocations. The hindered movement of dislocations makes it more difficult for copper to deform when subjected to external forces, thereby improving the strength and hardness of copper. In terms of welding properties, phosphorus can reduce the surface tension of copper, making it easier for copper to fuse with welding materials during the welding process, reducing the formation of pores and cracks, and improving the quality of welded joints.
For materials like high-conductivity copper, which have extremely high requirements for electrical conductivity, the phosphorus content must be strictly controlled. Generally speaking, its phosphorus content should not exceed 0.001%. This is because even a very small amount of phosphorus may have a significant negative impact on the electrical conductivity of high-conductivity copper. Only by controlling the phosphorus content at an extremely low level can high-conductivity copper be ensured to have excellent electrical conductivity and meet its application requirements in fields such as electronics and power.
Effect of hydrogen on oxygen-containing copper
Oxygen-containing copper faces a special problem - "hydrogen disease" during specific processing, such as annealing in a hydrogen atmosphere. When oxygen-containing copper is in a hydrogen atmosphere, hydrogen atoms are highly active and will undergo a chemical reaction with Cu₂O in copper. Specifically, hydrogen atoms take the oxygen atoms from Cu₂O to form water vapor.
Since the annealing process is usually carried out in a closed or semi-closed environment, the generated water vapor cannot be discharged in time and will accumulate inside the copper. As the reaction progresses, the amount of water vapor continuously increases and the pressure gradually rises. When the internal pressure exceeds the bearing limit of the copper, the copper will rupture. This phenomenon is vividly called "hydrogen disease". "Hydrogen disease" will seriously affect the quality and performance of oxygen-containing copper, reduce its service life, and even lead to product rejection. Therefore, when processing oxygen-containing copper, the hydrogen atmosphere environment must be strictly controlled to avoid the occurrence of "hydrogen disease".
Effect of oxygen on the properties of high-purity copper
Although the content of oxygen in high-purity copper is trace, it plays a non-negligible role. First of all, trace oxygen can oxidize the trace impurities in high-purity copper. In the production process of high-purity copper, even after strict purification processes, there are still some trace impurity elements. These impurity elements may have an adverse impact on the performance of copper. The presence of oxygen can react with these impurities to oxidize them into oxides.
This oxidation process helps to improve the electrical conductivity of copper. On the one hand, the form of the oxidized impurities in copper has changed, reducing the obstruction of the impurities to the movement of free electrons. On the other hand, the oxidation process may make the lattice structure of copper more regular, which is beneficial to the directional movement of free electrons.
In addition, deliberately retaining a certain amount of oxygen can also improve the grain boundary properties of copper. In copper, some impurity elements such as Bi, Sb, As, etc. will segregate at the grain boundaries, leading to an increase in grain boundary brittleness. Oxygen can react with these impurity elements to form spherical particles with high melting points. These spherical particles will be distributed within the grains rather than aggregating at the grain boundaries. In this way, the grain boundary brittleness is eliminated, and the toughness and comprehensive properties of copper are improved. By reasonably controlling the oxygen content, high-purity copper can achieve a good balance in terms of electrical conductivity and mechanical properties.