The present paper describes the microstructural evolution of AZ31 alloy along the process chain, from the melt treatment, the direct chill casting up to the extrusion process. Each step in the process chain will be considered in order to design the appropriate properties of the endproducts. The research has been done in industrial scale at ARC Leichtmetallkompetenzzentrum Ranshofen GmbH (LKR), in order to analyse the grain size dependency of AZ31 alloy on different casting conditions. The casting trials with and without grain refinement were carried out at the vertical direct chill casting machine MAGNUMCAST®. After the extrusion process metallographic analysis and mechanical tests were carried out.