Controle da umidade em eletrodos e sua influência nas trincas a frio no metal de solda.

Abstract

In this work, the variation of the moisture content in the coatings of the basic electrodes under hydrogen, environmental AWS E 7018 and controlled conditions of temperature and relative humidity. The results demonstrate the great sensitivity of the moisture absorption rate with changes in temperature and / or relative humidity. They also show that levels above the limits permitted by the standards are achieved within a few hours of exposure to normal environmental conditions. In order to evaluate the influence of the moisture thus obtained, in the appearance of cold cracks in the weld bead caused by hydrogen, TEKKEN tests, with symmetrical Y bevel, were made with sheets of steel ASTM-A 516- gr 65. With the content of After dissection, the samples were assayed with the two types of electrodes where the heat input was varied from 1.55 KJ / mm to 2.60 KJ / mm. There was no cracking when AWS E 7018 electrodes were used. When AWS E 11018 type was used, cracks occurred when critical conditions of absorbed moisture and heat input were used; and a minimum energy level of 2.0 KJ / mm was required to avoid cracking even with those resected electrodes.