Fluorescent Penetrant
Fluorescent penetrant is a chemical agent used in molten metal to bind oxygen and prevent porosity. It flows easily through the molten metal and fluoresces under UV light, making its position and effect in the weld pool visually traceable.
Physico-chemical mechanism of action
Fluorescent penetrant contains organic compounds that are active in the liquid metal phase. It reacts with oxygen molecules and forms stable complex compounds that do not lead to porosity. The organic molecules contain fluorescent groups that emit under UV light and visually mark the penetrant's position in the weld pool.
Metallurgical relevance & welding risks
Using fluorescent penetrant reduces porosity in the weld, leading to a finer and stronger joint. It also reduces the risk of hot cracks and increases the toughness of the metal. However, too much penetrant can cause loss of fusion or a heavy weld if not dosed correctly.
Workshop practice & instructions
Use fluorescent penetrant at a concentration of 0.5 to 1% in the liquid weld pool. Make sure UV light is used correctly to check the position of the agent. Cool the metal slowly to ensure even distribution of the penetrant. Inspect the weld for porosity and cracks after cooling.