ResumoNeste trabalho, uma chapa de aço de alta resistência (AHSS -Advanced High Strength Steel) tipo TRIP (Transformation Induced Plasticity) empregado atualmente no setor automotivo foi soldado usando o processo de soldagem a arco com arame solido sob proteção gasosa (GMAW) e soldagem com LASER de CO 2 (LBW). As propriedades mecânicas das amostras soldadas quanto a tração e microdureza foram determinadas e os resultados foram relacionados com as microestruturas apresentadas. Verificou-se que a solda com LBW chegou a valores realtivamente altos de dureza na zona fundida (ZF), indicando que a microestrutura resultante foi predominantemente de martensita. Na zona termicamente afetadas (ZTA), encontrou-se uma mistura de fases de bainita e ferrita. Misturas de fases semelhantes foram encontrados na ZTA e na ZF das amostras feitas com o processo GMAW. A microestrutura apresentada não sofreu degradação mecânica quando as amostras foram testadas à tração com todas as fraturas ocorrendo no metal de base (MB). Em contraste, a maioria das amostras de tração soldadas usando LBW falharam por clivagem frágil na região adjacente a ZTA. Aparentemente, nesta região ocorreu uma têmpera devido à dissipação de calor no processo LBW promovendo o crescimento de carbonetos e uma microestrutura relativamente grosseira. Nenhum fragilização foi encontrada que pudesse ser associada com o desenvolvimento da martensita.Palavras-chave: aços AHSS, aço TRIP, Soldagem com LASER CO 2 , GMAW.
Abstract: In this work an Advanced High Strength Steel (AHSS) sheet of the Transformation Induced Plasticity (TRIP) type currently employed in the automotive sector was welded using a Gas Metal Arc Welding (GMAW) and a CO 2 Laser Beam Welding (LBW) processes. The mechanical properties of welded tensile specimens including microhardness were determined and the results were related to the exhibited microstructures. It was found that LBW lead to relatively high hardness in the fusion zone (FZ) indicating
The wear phenomenon may occur for a variety of work conditions in the material. It causes losses in terms of time and costs in the components which are used for heavy machinery due to its re-pair or even replacement. It is important to select suitable materials that exhibit high-quality weldability and resistance to abrasive wear such as the high strength low alloy (HSLA) steel grade 950A. Therefore, it is necessary to study the wear behavior of this kind of steel after components are joined by multi-pass gas metal arc welding (GMAW) process, specifically on the heat affected zone (HAZ). The aim of this research was to evaluate wear resistance by pin on disc test and hardness on heat affected zone of HSLA steel plates with thickness of 14 mm joined by using GMAW process varying different parameters as wire feed speed and voltage. The influence of microstructural features such as carbide precipitation on wear behavior and hardness was investigated using optical microscopy (OM) and scanning electron microscopy (SEM). The results show that microstructure is modified by the heat input of the welding process, affecting the material properties and causing more susceptibility to wear on the welded area.
In this paper the effect of hybrid laser arc welding on longitudinal joints for pipes of 1.27cm thick is investigated. For the investigation, an API X70 steel was welded with the HLAW process and then subjected to tensile, bending and micro hardness tests under standards for pipe manufacturing. Images of the weld seams were taken to observe the structure and size of the weld zones. Analysis was made by light microscopy to determine the phases present in the weld zones and to observe if there is a variation of grain size in the weld zones that adversely affects the mechanical properties of the API X70 steel. Results show that the mechanical properties of the joints meet the requirements for their use in pipe manufacturing; one reason is the low thickness of the weld zone that barely affects the original properties of API X70 steel. Also the presence of bainite in the microstructure of weld zones provides resistance to the joints.
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