Application of potassium aluminum fluoroaluminate brazing flux
Application of potassium aluminum fluoroaluminate brazing flux
Potassium fluoroaluminate is a colorless powder crystal with a solubility of 1.4299/1000gHZO at room temperature (25℃). Its general formula is nKF·AIF3, and n is generally 1 to 3. It is commonly known as potassium cryolite in industry. It can be used in metallurgy, ceramics and welding sectors. It is mainly used as brazing flux for aluminum and aluminum alloy, flux for glass ceramic industry and active filler for friction agent. Especially with the development of brazing technology, potassium fluoroaluminate equivalent to the eutectic composition of AIF3 and KF (weight% ratio: 45.2% KF, 54.5% AIF.) was found, with a composition formula of 1.195 KF·AIF. The eutectic temperature is 560℃.
Scanning electron microscopy and potentiodynamic polarization experiments were used to study the microstructure of the fin after heating by potassium fluoroaluminate welding flux and its corrosion behavior in 0.6 mol/L NaCl (pH6) solution. The results show that potassium fluoroaluminate welding flux The anode activity of the fin material after heating is improved, but the cathode activity is reduced.
Among the aluminum brazing fluxes, it has many advantages over chloride fluxes. It does not absorb moisture and is called "non-corrosive" fluxes. Therefore, it has received extensive attention. In the processing of automobile radiators, a controlled gas welding method is usually used, using nitrogen and a non-hygroscopic organic solvent. This solvent is usually a mixture of potassium fluoroaluminate. The melting point is 540~560°C, which is low The eutectic temperature of aluminum and silicon is 577℃. In the process of controlled gas welding, the potassium fluoroaluminate solvent is completely melted, which can dissolve the oxides generated on the aluminum surface, thereby improving the entire welding.