The aim of this investigation was to study and evaluate the fracture toughness (KICV) of an AISI M3:2 high speed steel that was prepared by powder metallurgical processing, which consisted of uniaxial cold compaction of irregularly shaped water atomized powders, without and with 0.3% of carbon in the form of graphite, followed by vacuum sintering to obtain compacts with densities close to its theoretical value. The sintered steels were then hardened by austenitizing, quenching and triple tempering. Chevron fracture toughness test samples were prepared from the compacts and the tests conducted to determine KICV. The microstructures of the specimens were examined by scanning electron microscopy (SEM), and the composition of the phases determined by x-ray diffraction analysis (XRD). The sizes of the primary carbides and of the austenite grains were determined using Quantikov digital analysis software. No significant difference in fracture toughness (KICV) between the two high speed steels AISI M3:2, austenitized at the different temperatures, was observed. KICV (KICV M32 M M3 2 M3: processing powders 03 0 3 0.3 graphite value austenitizing tempering SEM, SEM , (SEM) xray x ray XRD. XRD . (XRD) software M32, 2, temperatures observed 0. (SEM (XRD

Resumo Diante de um cenário econômico onde a concorrência é cada vez mais acirrada, a busca por processos, técnicas e equipamentos de soldagem que proporcionem ganhos na produtividade é uma exigência para garantir a competitividade das empresas no mercado. Com o desenvolvimento e a adoção de novas tecnologias é possível inovar os processos convencionais, otimizando o desempenho e aumentando a produtividade dos mesmos, sem detrimento dos requisitos de qualidade exigidos. O processo de soldagem arco submerso permite a obtenção de juntas soldadas de excelente qualidade e produtividade e, com a utilização de múltiplos arames, é possível aumentar ainda mais a taxa de deposição. Entretanto, o emprego de múltiplos arames implica na necessidade de maiores correntes e, mesmo com o aumento da velocidade de soldagem, o aporte de calor sofre um acréscimo considerável, o que pode afetar a tenacidade da junta. Assim, em estruturas soldadas onde há requisitos de impacto torna-se necessário avaliar os efeitos dos altos aportes de calor. Neste trabalho foi comparada a tenacidade de duas juntas soldadas em aço carbono ASTM A36 pelo processo arco submerso, sendo a primeira soldada com arco simples e a outra com arco duplo (Tandem-Arc). Após a soldagem, as peças de testes foram submetidas ao tratamento térmico de alívio de tensões (TTAT) e submetidas aos ensaios de tração, dobramento, impacto Charpy, perfil de dureza Vickers, exame macrográfico e caracterização microestrutural realizada por meio de microscopia óptica. Os resultados obtidos em todos os ensaios foram considerados satisfatórios e aprovados, mostrando assim que é possível o emprego do processo Tandem-Arc na soldagem de aços carbono quando há requisitos de impacto.

Abstract Faced with an economic scenario where competition is increasingly intense, the search for processes, techniques and welding equipment that provide gains in productivity is a requirement to ensure the competitiveness of companies in the market. With the development and adoption of new technologies it is possible to innovate the conventional processes, optimizing the performance and increasing their productivity, without detriment to the required quality requirements. The process of submerged arc welding allows the obtainment of welded joints of excellent quality and productivity and, with the use of multiple wires, it is possible to increase the deposition rate even further. However, the use of multiple wires implies the need for higher currents and, even with increasing welding speed, the heat input increases considerably, which can affect the tenacity of the joint. Thus, in welded structures where there are impact requirements it becomes necessary to evaluate the effects of high heat inputs. In this work the strength of two welded joints in ASTM A36 carbon steel was compared by the submerged arc process, the first being welded with single arc and the other with double arc (Tandem-Arc). After welding, the test pieces were submitted to tensile stress treatment (TTAT) and subjected to tensile tests, folding, Charpy impact, Vickers hardness profile, macrographic examination and microstructural characterization performed using optical microscopy. The results obtained in all tests were considered satisfactory and approved, thus showing that it is possible to use the Tandem-Arc process in the welding of carbon steels when there are impact requirements.

Powder Metallurgy has been reported as a suitable alternate processing route for the manufacture of tool steels. The advantage of this technique is in being able to obtain a refined and more uniform microstructure that improves properties such high wear resistance and toughness. A molybdenum containing AISI M3:2 tool steel, (trade name Sinter 23), manufactured from spherical gas-atomized powders by hot isostatic pressing followed by hot working was tested in three-point bending tests after various heat treatments. Transverse rupture strength (TRS) samples were cut and heat treated at four distinct austenitizing temperatures. Each austenitizing temperature was combined with three tempering temperatures, giving a total of twelve different hardening conditions. Hardness tests were carried out to establish correlations among the effectiveness of heat treatment, the hardness values and the TRS results. At least five parallel samples were tested in each heat treatment condition.