Red copper bar, also known as red copper or pure copper, is named for its purplish-red color. Its various properties are similar to those of copper. Red copper is industrial pure copper with a melting point of 1083°C, no allotropic transformation, and a relative density of 8.9. Its mass per unit volume is about 15% heavier than that of ordinary steel. Due to its rose-red color and the purple appearance after an oxide film forms on the surface, it is commonly referred to as red copper. It is copper containing a certain amount of oxygen, hence also known as oxygen-containing copper. Red copper bars are named for their purplish-red hue. They are not necessarily pure copper; sometimes, a small amount of deoxidizing elements or other elements are added to improve material quality and performance, thus they are also classified as copper alloys. In China, processed red copper bars can be divided into four categories based on composition: ordinary red copper (T1, T2, T3, T4), oxygen-free copper (TU1, TU2, high-purity, and vacuum oxygen-free copper), deoxidized copper (TUP, TUMn), and special copper with small amounts of alloying elements (arsenic copper, tellurium copper, silver copper). The electrical and thermal conductivity of red copper bars is second only to silver, making them widely used in the production of conductive and thermal conductive equipment. Red copper bars exhibit good corrosion resistance in atmospheres, seawater, certain non-oxidizing acids (hydrochloric acid, dilute sulfuric acid), alkalis, salt solutions, and various organic acids (acetic acid, citric acid), making them suitable for the chemical industry. Additionally, red copper bars have good weldability and can be processed through cold and hot plastic deformation into various semi-finished and finished products. In the 1970s, the production of red copper bars exceeded the total production of all other types of copper alloys.