Hull Ferrite Number Calculation
The ferrite factor according to Hull is a mathematical formula for calculating the delta ferrite content in austenitic chromium-nickel welding rods. It helps in quality control and prevention of hot cracking.
Physico-Chemical Mechanism of Action
The Hull ferrite factor calculates the amount of ferrite in an austenitic chromium-nickel weld metal. This factor takes into account alloying properties and thermal deformation during welding.
Metallurgical Relevance & Risks in Welding
Too high a ferrite content can lead to hot cracking, as ferrite is a brittle phase. The ferrite factor helps to estimate this proportion in advance and adjust welding parameters to avoid cracking.
Workshop Practice & Action Guidelines
To use the Hull ferrite factor, note alloying properties such as chromium and nickel content as well as thermal deformation. Based on these data, you can predict the expected ferrite development and optimize welding parameters such as temperature and time.