Avaliação da influência da variação de temperatura sobre a ductilidade em cordões de solda através de ensaios de impacto

Abstract

One of the most widely used manufacturing processes in the industry today is welding. Through it, metal products and structures are manufactured that, depending on their application, may face very different conditions (variations in temperature, pressure, humidity, etc.) and may result in changes in their physical, chemical and mechanical characteristics. Thus, in this work the effects of low temperatures on weld beads were evaluated through impact tests. The profiles used to create the specimens to be tested were fabricated from the union of sheets of the base metal (ASTM A36 steel) in the planar position, by means of the automatic MAG process, using gaseous protection based on argon (75%) + CO2 (25%) and gas flow rate of 16 l/min. The solid wires used were AWS ER70S-6 and AWS ER110S-G, both with 1,2 mm diameter and individually employed. For each specimen tests were performed at room temperature (26 °C) and at -25 °C. At room temperature, both samples showed ductile behavior, with significant plastic deformations in the weld beads. In the tests with the cooled specimens, however, there was a change to a fragile behavior, where there was the appearance of cracks in the heat affected zones (ZAC) and less severe plastic deformations. However, the cooled specimens showed higher energy absorption, especially those welded with the ER70S-6 wire (lower mechanical strength), compared to those tested at room temperature, which may mean a more desirable behavior of soft steels (steels with up to 0.02% carbon) at lower temperatures.