The distribution of hydrogen in the welding zone of HQ130 high strength steel is calculated by using finite element method (FEM). The finite element program of hydrogen in the welding zone is worked out. In the program, the effects of welding heat input (

The quality of an iron melt which refers to the soundness of melting and subsequent treatments of the melt can be identified and recognized with its thermal analysis cooling curve. To compare two cooling curves, both the separating distance of the two curves and the shape similarity of the curves should be considered. A comprehensive parameter Ω can be used to identify the difference of the two cooling curves. When Ω is at minimum, the two curves must be the closest couple among all cooling curves. It is found that the difference of every feature related to melt iron quality converges to zero when the value of Ω approaches zero. Two databases of grey and nodular cast irons have been set up, in which the thermal analysis cooling curves, composition, microstructure and mechanical properties are included. For the prediction of nodularity of ductile irons, an accuracy of 5% is realized if the value of Ω of the two matching cooling curves is less than 2 °C. This method is self-adaptive to the production condition and has been adopted in several foundries.