Diego Tolotti de Almeida

This study aims to evaluate the microstructural changes of DIN 22MnB5 Niobium and Molybdenum modified alloy (22MnB5+NbMo) related to cutting processes after the press hardening step. Seven-millimeter press hardened thick sheets were Laser and Abrasive Water Jet (AWJ) cut to be adapted to their final application. The sheets were hot formed obtaining predominantly martensitic structures. The Laser cutting process was employed with 2,5 and 3,0 kW available power. In the AWJ cutting process, the employed cutting pressure was 60 kPsi. The microstructural changes related to the three cutting conditions post press hardening were investigated by optical microscopy analyzes (macro and micrograph). Scanning Electron Microscopy (SEM) and Electron Backscattered Diffraction (EBSD) were also employed. In this investigation, the relationship between the cutting processes and the microscopic aspects was also confirmed by microhardness tests. The results showed that the addition of Nb and Mo to the former alloy was important in the martensitic transformation and grain refinement. Water jet cutting did not show microstructural modifications related to the uncut material. On the other hand, Laser cutting showed some microstructural modifications for both employed conditions (2,5 and 3,0 Kw). These modifications are related much more to microhardness than to grains size and roughness. These differences can become even smaller when the cutting speed differences between the processes are taken in account (0,1 mm/min for Water Jet and 0,6 mm/min for Laser Cut). The presence of a double white zone suggests that the Laser cutting process is much time dependent than power dependent itself. These double white regions were observed only in the right exit region of the samples in the 2,5 KW condition.

This study evaluates the effect of through-tool high-pressure coolant (HPC) on internal boring of ST52-3 steel under production-representative industrial conditions, focusing on tool wear, cutting power, surface finish, and chip evacuation. Conventional flood cooling at 20 bar was compared with through-tool HPC at 25, 40, and 50 bar in an industrial machining line. Cutting speed and depth of cut were kept constant ( v _c = 220 m/min, a _p = 3 mm), while the feed was increased in the HPC trials (from 0.194 to 0.265 mm/rev) to assess whether HPC could sustain more severe and potentially more productive conditions. The results showed that HPC significantly delayed flank-wear progression: the VB growth rate decreased from 0.01220 mm·part⁻¹ under conventional cooling to 0.00486, 0.00405, and 0.00311 mm·part⁻¹ at 25, 40, and 50 bar, respectively, revealing diminishing returns beyond about 40 bar. Extended tests further showed that the 40 bar condition maintained consistently lower wear up to 65 machined parts. In addition, HPC at 40 and 50 bar reduced cutting power, while 40 bar provided the most consistent chip fragmentation and evacuation. Surface roughness met the component specification after run-in for all HPC conditions, and the 40 bar condition satisfied the requirement from the first checkpoint. Overall, the study shows that through-tool HPC can improve the robustness of industrial internal boring under more demanding cutting conditions, with ~ 40 bar providing the best overall balance between tool-life extension, energetic stability, surface-finish compliance, and chip control.

The influence of cold and warm tensile deformation on the microstructural stability and corrosion behavior of a ZE10A magnesium alloy sheet was investigated. Tensile tests were performed from room temperature to 300 °C to impose thermomechanical histories relevant to sheet forming. Microstructural evolution was assessed by optical microscopy and grain size analysis, while corrosion behavior was evaluated by open circuit potential (OCP), potentiodynamic polarization (PDP), and electrochemical impedance spectroscopy (EIS) in naturally aerated 3.5 wt.% NaCl solution. The mechanical response showed a strong temperature dependence, with yield stress decreasing by more than 60% from room temperature to 300 °C, consistent with enhanced dislocation mobility and recovery-controlled deformation. In contrast, microstructural changes were limited: the average grain size increased moderately from ~10.3 µm at 25 °C to ~14.2 µm at 250 °C, with no evidence of extensive grain growth or fully developed dynamic recrystallization. Electrochemical results indicated that thermodynamic corrosion tendency was only weakly affected by prior deformation. Stabilized OCP values remained within a narrow window, and PDP curves showed active corrosion without passivation, with corrosion current densities within the same order of magnitude across conditions. EIS revealed a gradual increase in interfacial resistance with deformation temperature; fitting with an Rs–(Rct‖CPE) circuit showed Rct rising from ~0.37 kΩ·cm² (25 °C) to ~1.54 kΩ·cm² (300 °C). Overall, the results demonstrate a decoupling between mechanical softening and corrosion response in ZE10A, where corrosion changes are secondary and mainly reflected by modest increases in interfacial resistance.

Manufacturing operations produce surface characteristics that, although stochastic, can significantly affect functionality, especially in forming tools, impacting contact and lubrication conditions during operation. This study investigates the influence of stochastic microtextures resulting from milling on the tribological performance of cold work tool steels with two different carbon contents (0.8 and 2 wt%). Different surface textures were observed resulting from the different C contents, with 3D roughness parameters indicating rougher surfaces for the 2.0% wt. C steel. Tribological behavior was assessed using the strip drawing test to analyze friction, wear coefficients, and wear mechanisms. Surface analysis before and after testing was executed employing SEM, EDX, and CLSM, with CLSM also used to determine 3D roughness parameters of the worn tracks. Post-test macrographic analyses and 2D roughness measurements were conducted on the pulled sheets. Tribological test data revealed lower friction and wear coefficients for the 2.0 wt% C tool steel, with susceptibility to abrasion wear, while the 0.8 wt% C tool exhibited a higher tendency towards adhesion wear. Post-test analysis suggested smoother surfaces for the 2.0 wt% C steel compared to the 0.8 wt% C steel. Macrographic analysis showed no visible wear marks on sheets tested with the 2.0 wt% C steel, contrasting with wear grooves visible on sheets pulled against the 0.8 wt% C steel. Additionally, 2D roughness measurements indicated higher roughness after pulling against the 0.8 wt% C tool compared to the 2.0 wt. C tool. Overall, the study demonstrates that manufacturing-induced textures without the need of post-manufacturing texturing influence the tribological performance of the evaluated steels, opening an avenue to be explored to improve the tribological performance of forming tools.

O processo de contínua atualização de tecnologias, processos e produtos, tem colocado a inovação no centro das discussões de diferentes instituições. Uma vez que a necessidade de se manter competitiva, e para além disso, estar na vanguarda dessas modificações, se tornou algo necessário para a sobrevivência das organizações, o processo de renovação dos portfólios de projetos, bem como o gerenciamento desses é fundamental para trilhar o caminho rumo a inovação. Diversas metodologias estão disponíveis para promover a geração de ideias e potencializar os processos já em curso. Dentre essas, o Mapa de Rotas Tecnológicas (MRT) se mostra uma importante ferramenta para a coleta de ideias, auxiliando tanto no processo de formulação estratégica, quanto na definição das ações relativas ao planejamento de novos produtos, processos e tecnologias. A utilização da metodologia do MRT permitiu a uma empresa do segmento metalmecânico delinear seu portfólio de projetos a partir do levantamento e priorização de ideias de forma colaborativa. Assim, o processo de estampagem a quente foi considerado no ano de 2019 como um processo alinhado ao direcionamento estratégico da empresa, sendo priorizado e incorporado ao portfólio de projetos. A partir da utilização de corpos de prova com o aço para estampagem a quente 22MnB5 com 8,00 mm de espessura, por meio da análise de taxa de resfriamento, microestrutura e microdureza foi possível verificar comportamento mecânico e metalúrgico satisfatórios, possibilitando a utilização do aço para estruturas de veículos rodoviários comerciais

Anais do Congresso Internacional de Engenharia Mecânica e Industrial (2764-4294) - Análise Microestrutural Do Aço 22Mnb5 + Nbmo Após Diferentes Tratamentos Térmicos

The application of press hardening steels is spreading from automobiles, where crashworthiness demands are critical, to other segments, such as the agricultural and road transport industries. However, the operational conditions to which such equipment is exposed requires the application of heavier sheet gages and adapted joining processes. In this context, fatigue is recognized as the critical failure mode. The present article describes the procedures and results of fatigue testing performed on GMAW-CSC and PAW butt-welded specimens of 1500 MPa press hardening steel. Both methods are suitable alternatives to laser welding when joining relatively heavy-gaged components. The obtained fatigue results are also related to heat-affected zone characteristics and weld bead surfaces. Additionally, some ground-flush GMAW-CSC specimens were tested. The test results indicate that both welding procedures provide suitable fatigue performance. As-welded GMAW-CSC joints on this ultra-high strength steel accomplished a fatigue performance similar to welds of conventional steel. However, a remarkable performance increase was observed after flush grinding the weld beads. The plasma welding process presented less good results due to the more extensive manufacturing and geometric variability. The results indicate that adopting a suitable arc welding process, in association with post-weld geometry improvement, provides a fatigue performance that is competitive with laser-welded press hardening steels.

Neste artigo é abordado o problema da estimativa da eficiência térmica da soldagem a arco elétrico, especialmente em relação ao processo \textit{Gas Metal Arc Welding}. Apesar de ser um parâmetro de grande relevância, a eficiência muitas vezes é determinada a partir de valores tabelados pelas normas técnicas, o que pode acabar prejudicando as análises metalúrgicas, visto que esses valores nem sempre conseguem contemplar todas as variações possíveis nos parâmetros da solda. Nesse contexto, neste artigo é proposto o desenvolvimento de um modelo matemático através de Redes Neurais Artificiais (RNAs) para ser utilizado em conjunto com um calorímetro de fluxo contínuo, a fim de se obter uma estimativa prévia para a eficiência e evitar despesas com ensaios experimentais que produziriam resultados abaixo do ideal. Os dados experimentais foram obtidos através de ensaios do processo de soldagem na empresa Bruning Tecnometal Ltda, e as simulações foram realizadas na ferramenta computacional Matlab. O modelo proposto foi validado por meio do método \textit{k-fold cross-validation} e apresentou baixo erro relativo médio.