Banca de DEFESA: EDUARDO RODRIGUES DA SILVA

Uma banca de DEFESA de MESTRADO foi cadastrada pelo programa.
DISCENTE : EDUARDO RODRIGUES DA SILVA
DATA : 26/08/2017
HORA: 14:00
LOCAL: Sala de aulas do PPGCEM
TÍTULO:

EFFECT OF HEAT INPUT IN THE MICROSTRUCTURE OF WELD BEADS DEPOSITED WITH E81T1-Ni1C TUBULAR WIRE IN 3 VARIANTS OF API X-65 STEELS

PALAVRAS-CHAVES:

API X65 steels, FCAW, microstructure, hardness, heat affected zone, fusion zone.

PÁGINAS: 90
GRANDE ÁREA: Engenharias
ÁREA: Engenharia de Materiais e Metalúrgica
RESUMO:

The objective of the present work is the microstructural characterization of weld beads deposited with E81T1-Ni1C tubular wire in 3 variants of X65 API steels. These are alternative materials used in the assembly of pipelines for the transportation of oil and gas, where the qualification of the welding procedures is a prerequisite for guaranteeing the mechanical properties of the component in service. In this context, the detailed characterization of the microconstituents that compose the three sub-regions of the weld is an essential tool, since it contributes with important elements to the understanding of the correlation between process variables and the final properties of the fabricated assembly.

For this research weld beads were deposited under controlled conditions by the FCAW process, which allowed thermal inputs of 7.3; 11.3 and 22.1 KJ / cm corresponding to cooling times (Δt 8/5) estimated at 3.5; 6.5 and 20s. The microstructural characterization was made by optical microscopy and scanning electron microscopy with Field Emission Gun, where the high quality of the contrast in the images allows the identification and more detailed classification of the microconstituents present. The results for the welding deposits with medium thermal input and Δt 8/5 = 6.5 s, showed that the fused zone (ZF) of the three alloys is predominantly formed by the microconstituint acicular ferrite (AF), with average hardness of the order of 240 HV0,3, aspects that according to the literature are requirements of excellent toughness. When welded with low thermal input, the ZF had AF and average hardness of 260 HV0.3 and Δt 8/5 = 3.5 s. The high thermal input provided a hardness lower than 200 HV0.3 and AF formation in the ZF, and greater Δt 8/5 of approximately 20s. The area affected by the coarse grain heat (ZAC-GG) showed for the 3 steels microstructure basically formed by second phase ferrite (FS) and small fraction of primary ferrite. According to the microhardness profile along the sub-regions of the weld, the maximum peaks located in the ZAC-GG are lower than 340 HV for the bead made with medium heat input, which is indicative of absence of martensite and good toughness for this critical region of the heat affected zone. A hardness profile made in ZAC-GG, with values higher than 350 HV0,3, indicates the risk of formation of martensite in the three alloys of API X65 welded steel with low thermal input.

MEMBROS DA BANCA:
Presidente - 2156996 - AUGUSTO JOSE DE ALMEIDA BUSCHINELLI
Externo à Instituição - CELINA LEAL MENDES DA SILVA - IFRN
Interno - 1652765 - MAURÍCIO MHIRDAUI PERES
Externo ao Programa - 1938946 - NICOLAU APOENA CASTRO