Analysis of the C260 brass after mechanical forming and annealing

Abstract

Copper alloys such as brass are highly used in the most varied branches of industry due to their characteristics such as corrosion resistance and formability. Among the processes used to manufacture parts made with such alloys, processes such as deep stamping or inlaying and stretching stand out. Such mechanical conformation processes require the use of thermal treatments such as annealing, in order to obtain specific properties in the resulting material. Therefore, this work aimed to evaluate the mechanical behavior of C260 brass when subjected to mechanical shaping (blanking and stretching) and annealing heat treatment. For this, a script clipping of an ammunition component was used, taking samples step by step including the raw material and dividing them into different regions, when in the shape of a cup, to understand the processes. Metallographic tests were carried out where, along with the microstructural evaluation, it was possible to determine grain size in addition to the Vickers microhardness. The grain size data were treated statistically, thus making it possible to judge the significance of each microstructure alteration. Thus, it was possible to observe that the mechanical forming steps actually hardened the material with an increase in hardness, unlike the annealing. However, a difference in behavior was noted in two different regions of the cups, where the wall region showed significant microstructural variations as well as its hardness, unlike the bottom region. The percentage of cold work parameters was identified as responsible for this difference both for recrystallizations to occur, as well as for the resulting microstructure and consequent hardness. The evaluation of the data referring to the raw material confirmed the fulfillment of its technical requirements.