Técnicas metalográficas para caracterização microestrutural em juntas soldadas do aço Cr-Mo

Abstract

Metallography is the record of the constitution and structure of metals in order to relate them to the mechanical properties and manufacturing processes. This structure reveals the aggregates and phases of a metal alloy depending on their chemical composition or transformation processes applied to it. Low alloy steels are steels with the intentional addition of small contents of other alloying elements, in order to obtain differentiated properties. They are widely used due to the low cost and versatility of their properties. The objective of this work is to discuss and discuss the experimental knowledge and procedures required for the observation and analysis of steels using optical microscopy and scanning electron microscopy techniques, allowing the identification of existing microconstituents. The process consisted in the evaluation of A-387 (1,25Cr- 0,5Mo) steel submitted to MIG / MAG welding with variation of current parameter (136A, 180A and 200A). The norms NBR 13284, NBR 15454 and NBR 14842 based all the experimental procedures. The results of the microscopies presented a great amount of martensite in the Thermally Affected Zone, the Vickers hardness test verified a high hardness in this region.