Influência da umidade e da microestrutura na formação de trincas induzidas pelo hidrogênio no metal de solda.

Abstract

In this work the unit content contained in the coating of the AWS electrodes E 8018 and AWS E 1018 in the condition of dried and, when exposed to the ambient conditions and controlled conditions of temperature and relative humidity, was evaluated. The results demonstrate the high sensitivity of the moisture absorption rate, with changes in temperature and / or relative humidity, where the maximum levels established by the standards are reached in a few hours of exposure to normal environmental conditions. In order to evaluate the influence of the humidity thus obtained, in the appearance of cold cracks induced by the hydrogen in the weld metal, TEKKEN tests, with symmetrical Y bevel, were performed with steel plates ASTMA 516 - gr 65.0 total moisture content ranged from 0.19 % to 3.04% and the energy from 0.74 kJ / mm to 2.27 kJ / mm. No cracking was observed with the AWS E 8018 electrode, which presented a high percentage of acicular ferrite. With AWS E 1018, cracks arose when critical conditions of total moisture and heat input were used. A minimum energy level of around 1.6 kJ / mm was required to avoid cracking, even as dry electrodes. In these samples the percentage of acicular ferrite was not so great, however a significant amount of primary ferrite formed.