Period 6 element between barium and hafnium, and radium and rutherfordium, respectively. This convention is entirely a matter of aesthetics and formatting practicality; a rarely used wide-formatted periodic table inserts the lanthanide and actinide series in their proper places, as parts of the table's sixth and seventh rows (periods). Lanthanum is a chemical element with the symbol La and atomic number 57. It is the first element in the lanthanide series. It is a soft, ductile, silvery-white metal that tarnishes rapidly when exposed to air and is soft enough to be cut with a knife. It is the eponym of the lanthanide series,
Non-metallic inclusions During deformation, which occurs from flatting, forging, and stamping, non-metallic inclusions can cause cracks and fatigue failure in steel. When investigating the influence of non-metallic inclusions on the quality of steel, of great importance are the properties of these inclusions: size, shape, chemical and physical characteristics. All these properties depend on the chemical composition of steel, method of smelting and for certain steel grade. These properties can change within wide limits even within the same mode of production. Different methods for analysis of non-metallic inclusions have been developed and are now in use. These make it possible to determine content,