Abstract
A considerable number of crack tip opening displacement tests in the heat affected zone (HAZ) of multipass welds, performed in accordance with standards BS 5762 and EEMUA, are rejected since the crack is not inside the coarse grain region at 0.5 mm from the fusion border, as well as the quantity of the crack length in percentage, that the crack goes through the intercritical region instead of in the grain coarse region as it would correspond. This circumstance make advisable to carry out a metallographic study of the intercritical zone in the HAZ as well as the corresponding tests, in order analyze the intercritical region brittleness reasons. The study is performed on a HSLA 75 mm thick panel 450 EMZ type II, welded under a SAW process with heat input and welded parameters controlled, without any post weld heat treatment
Highlights
A considerable number of crack tip opening displacement tests in the heat affected zone (HAZ) of multipass welds, performed in accordance with standards BS 5762 and EEMUA, are rejected since the crack is not inside the coarse grain region at 0.5 mm from the fusion border, as well as the quantity of the crack length in percentage, that the crack goes through the intercritical region instead of in the grain coarse region as it would correspond
This circumstance make advisable to carry out a metallographic study of the intercritical zone in the HAZ as well as the corresponding tests, in order analyze the intercritical region brittleness reasons
The study is performed on a HSLA 75 mm thick panel 450 EMZ type II, welded under a SAW process with heat input and welded parameters controlled, without any post weld heat treatment
Summary
Los aceros microaleados de alto límite elástico y bajo contenido en carbono son aceros de diseño utilizados en ambientes corrosivos a bajas temperaturas[1], con alta tenacidad, bajo estas condiciones. Los aceros 450 EMZ tipo II, que se encuentran dentro de los aceros microaleados de alto límite elástico, se sueldan bajo un proceso de soldadura por arco sumergido (SAS), con una energía calorífica aportada de 2,4 KJ/mm y han demostrando tener una adecuada tenacidad. Los porcentajes de tamaño de grano atravesado por la grieta en la región intercrítica-subcrítica, es decir, para tamaños de granos entre 11 y 6 mm, correspondientes a valores de 10 ASTM E112 y 11,5 ASTM E112, respectivamente, dieron para cada una de las cinco probetas obtenidas del panel soldado, las siguientes cantidades: 87,3%, 31,2%, 39%, 39,3 %, 49,2%, porcentajes altos para estos tamaños de grano bastante finos, lo que demuestra un fenómeno de fragilidad de la región intercrítica, que se estudiará a continuación
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