Brazing flux suitable for brazing aluminium and steel

The invention relates to a brazing flux suitable for brazing aluminium and steel, and belongs to the field of non-metallic brazing materials. The brazing flux comprises the following components in percent by mass: 0.001-0.01 percent of rubidium fluoride, 11.0-45.0 percent of cesium fluoride, 0.01-2.0 percent of aluminium hydroxide, 0.01-5.0 percent of potassium fluoride, 0.01-0.04 percent of zinc fluoride, and the balance of aluminum fluoride. The brazing flux can meet the requirements of aluminium-steel brazing, aluminium-copper brazing and aluminium-aluminium brazing synchronously and is high in activity.