Metal strips thixorolling with high solidification interval

• Grant number: 06/03284-6
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: September 01, 2006
• End date: December 31, 2007
• Field of knowledge: Engineering - Mechanical Engineering
• Principal Investigator: Antonio de Pádua Lima Filho
• Grantee: Leandro Akita Ono
• Host Institution: Faculdade de Engenharia (FEIS). Universidade Estadual Paulista (UNESP). Campus de Ilha Solteira. Ilha Solteira , SP, Brazil

Abstract

The focus of this research work is the study of metallic mush/slurry flow during thixorolling of 70%Pb-30%Sn alloy strips with thickness varying from 0.5mm to 1.0mm. The experimental procedure uses a two roll high mill built at the Department of Mechanical Engineering/UNESP- Ilha Solteira Campus. The speed of the mill is controlled to achieve an optimum drag on the mush/slurry as it is pulled at the lower roller and formed at the upper roller. The mill is fed with alloy that has been poured onto a cooling slope. This enables a continuous cooling of the liquid alloy to promote the formation of metallic mush with the necessary rheocasted structure for successful thixoforming. It was verified from preliminary assays, that 70%Pb-30%Sn alloy cast at 350°C, unlike 50%Pb-50%Sn, does not form a continuous strip. This is due to a higher solidification interval for the former (75°C) in comparison with the latter (31°C). Alloys with higher solidification intervals result in coarse dendrites which make it difficult to obtain a plastic mush.In this work, the 70%Pb-30%Sn will first be inoculated with sulfur before pouring, to verify the inoculant’s effect on the plasticity of the metallic mush. This should make it possible to obtain a continuous strip from this alloy. The thixorolled metallic strip will be characterized by surface quality and micro-constituent utilizing optical microscopy and possibly scanning electronic microscopy (AMR/CTA).