White copper, brass, red copper (also known as "purple copper"), and bronze (bluish gray or grayish yellow) are distinguished by color.

Among them, white copper and brass are easily distinguishable; Red copper is slightly difficult to distinguish between pure copper (impurities<1%) and bronze (other alloy components around 5%). When unoxidized, the color of red copper is brighter than that of bronze, and bronze has a slight bluish or yellowish tint that is darker; After oxidation, red copper turns black, while bronze appears blue-green (harmful oxidation caused by excessive water) or chocolate colored.

Classification and welding characteristics of copper and copper alloys

(1) Pure copper: Pure copper is often referred to as purple copper. It has good conductivity, thermal conductivity, and corrosion resistance. Pure copper is represented by the letters+T}} (copper), such as Tl, T2, T3, etc. Pure copper with extremely low oxygen content, not exceeding 0.1%, is called oxygen free copper, represented by TU (copper free), such as TU1, TU2, etc.

(2) Brass: Copper alloys with zinc as the main alloying element are called brass. Brass with+H; (Yellow) represents elements such as H80, H70, H68, etc.

(3) Bronze: Previously, the alloy of copper and tin was called bronze, but now copper alloys other than brass are called bronze. Commonly used are tin bronze, aluminum bronze, and sensitive bronze. Bronze used "; Q，' (Green) indicates.

The welding characteristics of copper and copper alloys are:

(1) Difficult to fuse and prone to deformation

(2) Easy to generate thermal cracks

(3) Easy to produce pores

Copper and copper alloy welding mainly adopts methods such as gas welding, inert gas shielded welding, submerged arc welding, brazing, etc.

Copper and copper alloys have good thermal conductivity, so they should generally be preheated before welding and subjected to high-energy welding. Tungsten electrode hydrogen arc welding adopts DC positive connection. During gas welding, neutral flame or weak carbonization flame is used for purple copper, while weak oxidation flame is used for brass to prevent zinc evaporation.