Welding heating temperature higher than 450 ℃ is called brazing

 Welding heating temperature higher than 450 ℃ is called brazing, brazing joints have high strength, and some can work at high temperatures. There are many types of brazing filler metals, with aluminum, silver, copper, manganese and nickel based filler metals being the most widely used. Aluminum-based brazing filler metal is often used for brazing aluminum products. Silver-based and copper-based solders are often used for brazing copper and iron parts. Manganese-based and nickel-based solders are mostly used to weld parts such as stainless steel, heat-resistant steel, and high-temperature alloys that work at high temperatures. For welding refractory metals such as beryllium, titanium and zirconium, as well as materials such as graphite and ceramics, brazing materials such as palladium-based, zirconium-based and titanium-based are commonly used. The characteristics of the base material and the requirements for joint performance should be considered when selecting the brazing filler metal. Brazing flux is usually composed of alkali metal and heavy metal chlorides and fluorides, or borax, boric acid, fluoroborate, etc., and can be made into powder, paste and liquid. In some solders, lithium, boron and phosphorus are also added to enhance their ability to remove oxide films and wetting. After welding, the flux residue should be cleaned with warm water, citric acid or oxalic acid.