S13  Integridade Estrutural    Titulo: EFFECT OF THE INTERCRITICAL HEAT TREATMENT ON THE MECHANICAL PROPERTIES OF A TI-NB MICROALLOYED STEEL   Resumo : ABSTRACT THE EFFECT OF THE INTERCRITICAL HEAT TREATMENT ON THE MECHANICAL PROPERTIES OF THE API 5L X65 STEEL, MICROALLOYED WITH TI AND NB, WIDELY USED IN WELDED STRUCTURES, WAS INVESTIGATED. THE EMBRITTLEMENT, OBSERVED BY SEVERAL AUTHORS IN THE INTERCRITICAL REGION OF THE HEAT AFFECTED ZONE OF WELDS PERFORMED IN HSLA STEELS, IS CLOSELY RELATED TO THE VOLUME FRACTION OF M-A CONSTITUENT, FORMED IN THE COOLING. JUST UPON THE HOMOGENIZATION AND NORMALIZING HEAT TREATMENTS, THE SPECIMENS WERE SUBMITED TO DIFERENT INTERCRITICAL HEAT TREATMENTS, PERFORMED AT 780 OC FOR 30 MIN AND COOLED WITH DIFERENTS D T8/5 RATES, WITH THE PURPOSE OF VARYING THE MICROSTRUCTURE. HIGH FRACTURE TOUGHNESS WAS OBTAINED WITH THE LOWER COOLING RATE, AND, IT WAS VERIFIED THAT THE LOW M-A CONSTITUENT VOLUME FRACTION WAS NOT ENOUGH TO PROMOTE REDUCTION ON THE FRACTURE TOUGHNESS. KEY-WORDS: FRACTURE TOUGHNESS, M-A CONSTITUENT, HSLA STEEL, HEAT TREATMENT     Autores : DeAquino, Carlos Tasso Eira Ferreira, Itamar 0 Gomes, Samuel Irati Novaes Sant Anna, Pedro Carneiro     Trabalho Completo :   COBEM99 | Comissão  Organizadora | Palestras | Sessões Técnicas | Autor | Simpósios e Sessões Especiais | Revisores |  Título  dos  Trabalhos | Local