Flux Basicity Index
The weld flux basicity index shows the ratio of basic to acidic oxides in a flux. A high basicity means more oxygen binding and less hydrogen, which reduces porosity and improves strength.
Physicochemical mechanism of action
The basicity index of welding powder measures the ratio between basic (e.g., silica) and acidic (e.g., potassium hydroxide) oxides in the powder. A high basicity index means more oxygen is bound and less hydrogen is released.
Metallurgical relevance & risks in welding
Too high a basicity index can lead to excessive oxygen binding, resulting in porosity and low weld strength. Conversely, too low a basicity index can release too much hydrogen, leading to hot cracking and distortion.
Workshop practice & instructions
For hard steels (e.g., martensitic) with high strength requirements, choose a powder with a basicity index of 1.5 to 2.0. For soft steels (e.g., austenitic) with low strength and high formability requirements, use a powder with a basicity index of 0.8 to 1.2. Always pay attention to the correct powder amount and the proper welding process.