Caracterização do cordão na soldagem FCAW com um arame tubular "metal cored" Bead characterization on FCAW welding of a metal cored tubular wire

Este trabalho objetivou o estudo do efeito de algumas condições operacionais nas características do cordão produzido por um arame tubular "metal cored" (ASME SFA-5.18: E70C-3M) de fabricação nacional com 1,2 mm de diâmetro, destinado à soldagem de aços carbono comuns estruturais de baixo e médio teor de carbono. Realizaram-se testes de soldagem, na posição plana, sobre chapas grossas (espessura de 12 mm) de aço de baixo carbono utilizando-se uma fonte operando no modo "tensão constante" e com monitoração dos sinais de corrente e tensão do arco e velocidade de alimentação (fusão) do arame. Variaram-se a composição do gás de proteção (75%Ar-25%CO2 e 100%CO2), a polaridade do eletrodo (positiva e negativa) e a velocidade de alimentação do arame (7 e 9 m/min). Os demais parâmetros de soldagem foram mantidos fixos, incluindo-se os comprimentos energizado do eletrodo (16 mm) e do arco (3,5 mm). Avaliaram-se os efeitos das condições operacionais nas principais características do cordão incluindo a sua geometria (penetração, reforço, largura, área fundida, área depositada e diluição), presença de descontinuidades, microestrutura e dureza. Levantaram-se, para o arame "metal cored", as condições operacionais de maior produtividade (maior taxa de deposição) associadas a um cordão com características adequadas à soldagem de chapas grossas de aços estruturais.<br>This work evaluates the relationship between operational conditions and the characteristics of weld beads deposited with a 1.2 mm produced in Brazil metal cored tubular wire (ASME SFA-5.18: E70C-3M). Welding trials were performed in downhand position on 12mm thick low-carbon steel plates using a constant voltage power supply. Welding current and voltage, and wire feed rate were monitored in all trials. While the shielding gas composition (75%Ar-25%CO2 and 100%CO2), wire polarity, and wire feed rate (7 and 9 m/min) were changed, other process variables, including electrode and arc lengths (16 mm and 3.5 mm, respectively) were kept constant throughout the experimental program. Weld bead geometry parameters (penetration depth, reinforcement, width, fused and deposited areas, and weld dilution), presence of weld discontinuities, microstructure, and fusion zone hardness were measured and correlated to the operational conditions. Operational conditions that yielded both high productivity levels (high deposition rates) and weld bead characteristics favored for the welding of thick plates of structural steels were determined

Global impact of COVID-19 on stroke care

Background: The COVID-19 pandemic led to profound changes in the organization of health care systems worldwide. Aims: We sought to measure the global impact of the COVID-19 pandemic on the volumes for mechanical thrombectomy, stroke, and intracranial hemorrhage hospitalizations over a three-month period at the height of the pandemic (1 March–31 May 2020) compared with two control three-month periods (immediately preceding and one year prior). Methods: Retrospective, observational, international study, across 6 continents, 40 countries, and 187 comprehensive stroke centers. The diagnoses were identified by their ICD-10 codes and/or classifications in stroke databases at participating centers. Results: The hospitalization volumes for any stroke, intracranial hemorrhage, and mechanical thrombectomy were 26,699, 4002, and 5191 in the three months immediately before versus 21,576, 3540, and 4533 during the first three pandemic months, representing declines of 19.2% (95%CI, −19.7 to −18.7), 11.5% (95%CI, −12.6 to −10.6), and 12.7% (95%CI, −13.6 to −11.8), respectively. The decreases were noted across centers with high, mid, and low COVID-19 hospitalization burden, and also across high, mid, and low volume stroke/mechanical thrombectomy centers. High-volume COVID-19 centers (−20.5%) had greater declines in mechanical thrombectomy volumes than mid- (−10.1%) and low-volume (−8.7%) centers (p &lt; 0.0001). There was a 1.5% stroke rate across 54,366 COVID-19 hospitalizations. SARS-CoV-2 infection was noted in 3.9% (784/20,250) of all stroke admissions. Conclusion: The COVID-19 pandemic was associated with a global decline in the volume of overall stroke hospitalizations, mechanical thrombectomy procedures, and intracranial hemorrhage admission volumes. Despite geographic variations, these volume reductions were observed regardless of COVID-19 hospitalization burden and pre-pandemic stroke/mechanical thrombectomy volumes. © 2021 World Stroke Organization