Lead-free casting brasses. Investigations of the corrosion resistance and shaping of microstructure and properties

Abstract

The ecological factor is very important in shaping properties of alloys. It leads to a limitation or elimination, from the surroundings, of harmful elements from the heavy metals group. The so-called eco-brasses group comprises common lead-free brasses containing 10 to 40% of zinc and arsenic brasses of a high dezincification resistance. Among standardized alloys, CW511L alloy (acc. to EN standard) or MS-60 alloy (acc. to DIN) can be mentioned. Investigations were performed on two different kinds of metal charges: ingots cast by gravity and the ones obtained in the semi-continuous casting technology with using crystallizers. The casting quality was analysed on the basis of the microstructure images and mechanical properties. The investigations also concerned increasing the corrosion resistance of lead-free alloys. This resistance was determined by the dezincification tendency of alloys after the introduction of alloying additions, i.e. aluminium, arsenic and tin. The investigations focused on the fact that not only alloying additions but also the production methods of charge materials are essential for the quality of produced castings. The introduced additions of aluminium and tin in amounts: 0÷1.2 wt% decreased the dezincification tendency, while arsenic, already in the amount of 0.033 wt%, significantly stopped corrosion, limiting the dezincification process of lead-free CuZn37 brass. At higher arsenic contents, corrosion occurs only within the thin surface layer of the casting (20 µ).