Metalurgické a technologické charakteristiky hliníkových slitin třídy 2xxx a 6xxx

Abstract

The aim of this work was to develop a machinability test for aluminium alloys. It means finding the best machining conditions in turning operation, to distinguish between good and bad machinability, and defining rating criteria to evaluate machinability by a numerical value. The challenge of aluminium alloys machining is explicated and described in the theoretical part on the base of recent publications treated this subject. The theoretical part of the work deals with metallurgical and technological properties of aluminium alloys. The text summarizes machining conditions and tools. The practical part includes experimental work on universal centre lathe in workshop at Alcan CRV (Centre de Recherche de Voreppe). So, the machinability tests were made on the centre lathe with single-point cutting tool in the form of cutting insert. In order to find the best machinability results, different cutting conditions which could be easily changed were used, like as cutting speed, feed rate, depth of cut, cutting tool and dry or wet cutting mode with or without cutting fluid. The evaluation of machinability was focused only on shapes of the removed chips. Results of experimental work constitute bases for the specification of two new machining tests used at Alcan Děčín Extrusions, s.r.o. (Czech Republic) and Alcan CRV (France). Děčín Extrusions, s.r.o. uses a machinability test to follow production quality of aluminium alloy bars with diameter larger than 24 mm. New test conditions, closer to the real turning conditions at Alcan’s customers, were defined in this work for bars with typical diameter 30 mm. The reference aluminium alloys machined in this part of the work were 6082, 6012, 6912, 6026, 6064A, 6262A, 6023, 2030 and 2028. Their machinability is related with the presence of intermetallic particles. The chip breaking quality was evaluated by chip shapes illustrated by photographs, and a rating criteria table was defined. Further, effect of intermetallic phases on the alloy machinability was studied in relation of microhardness measurements and phase microanalysis of selected aluminium alloys performed at VSB – Technical university Ostrava. Second test realised on small bars with typical 7 mm in diameter was developed for Alcan CRV. The new test is needed for determination of machinability of new alloys under development. The reference aluminium alloys machined in this part of the work were 6082, 6262, 6064A, 6023, 2030 (based on LME particles) and 9003 (“Bosh Al alloy” based on hard particles – below of this work).