This study aims at showing the influence of transformation-induced plasticity (TRIP) on the residual stresses and magnetic permeability of AISI 304 stainless steels and the resulting effect on its fatigue performance. Samples were pre-strained to different levels of plastic deformation, and characterised through metallography, hardness, tensile testing, X-ray diffraction (XRD) and with the MWM®-array electromagnetic method. Fatigue tests were then conducted on these samples to obtain the S-N curves for each condition, and the resulting fracture surfaces were analysed using scanning electron microscopy (SEM). Residual stress distributions in martensite and austenite were significantly affected by the transformation, although in different ways, and this is thought to be the reason for the improvement in fatigue performance in samples with higher pre-deformation values. Magnetic permeability measurements corroborated XRD results and proved to be a useful tool for non-destructively determining martensite transformation distributions in manufactured components. transformationinduced induced TRIP (TRIP 30 prestrained pre strained deformation metallography hardness testing Xray X ray (XRD MWM®array MWMarray MWM® array MWM method SN S N condition SEM. SEM . (SEM) ways predeformation values nondestructively non destructively components 3 (SEM

Continuous cooling bainitic steels has been widely used in industrial processes owing to its excellent mechanical properties and toughness. Although the surface properties of them are acceptable for many purposes, for their use in mechanical components like gears, it is necessary to improve their surface properties. Plasma nitriding treatments was carried out of a DIN 18MnCrSiMo6-4 steel at 500 °C, with three different nitrogen gas composition: 76, 24 and 5 vol.% nitrogen in hydrogen, for 3, 6 and 9 hours. The surfaces were characterized concerning the microstructure, microhardness, fracture toughness, nitrogen concentration and carbon composition, phase composition and residual stress states. Based on the results presented, layer growth constants (k) for different nitrogen gas composition was determined. The carbon profiles of samples indicate that there was decarburization during the plasma nitriding. The nitrided samples with thicker compound layers presented a fracture behavior dominated by the formation of Palmqvist cracks. X-ray phase analysis indicated the formation of biphasic compound layer on the surface of all nitrided samples with 76 and 24 vol.% nitrogen, while the nitrided samples with 5 vol.% nitrogen indicated the formation of monophasic compound layer. The diffusion zone presented compressive residual stresses with highest values near the surface.

This paper aims at analyzing the effects of the roller pre-straightening of wire-rods on residual stress distributions in SAE 1045 steel bars. The combined drawing process is used in industrial production of bars in order to obtain a good surface quality and improved mechanical properties complying with specifications of the final products. In this process, prior to the drawing step, a roller straightening of the steel wire-rod is essential, because it provides the minimum straightness necessary for drawing. Metallographic analysis and hardness test were done for selected samples after different processing steps. Also, residual stress analysis of pre-straightened wire-rods by X-ray diffraction and neutron diffraction were carried out. The hardness tests show higher values near the surface and lower in the center of the wire-rod. Besides, the residual stresses results show a big inhomogeneity from one peripheral position to another and also in the evaluated cross section.

In this work, a drawing processed was simulated to calculate forces and the resulting residual stresses in the material. The calculated residual stresses were compared with experimentally measured residual stresses by the Neutron Diffraction Method. The modeled process was the Wire Drawing. The necessary parameters to model the process were taken from an industrial currently used process. Rods of an AISI 1045 steel with nominal diameters of 21.46 mm were reduced to 20.25 mm by drawing with an drawing angle of 15°. Compression tests were used to determinate flow curves of the real material an used in the simulation models. The possibility to estimate drawing forces by numerical simulation was evaluated by comparing simulated results with values from empirical equations given by the literature. The results have shown a sufficient accuracy for the calculation of forces, but the comparison of residual stresses has shown differences to the experimentally determined ones that can be minimized by the consideration of high strain rates in the compression tests, anisotropy of the material and kinematic hardening.

Nesse trabalho foi simulada a etapa de trefilação na produção de barras redondas do aço AISI 1045 através do processo de trefilação combinada. Foram determinados diversos parâmetros para a simulação com base em processos industriais de trefilação combinada. Foi realizado o teste do anel, e sua simulação, a fim de obter-se o valor de atrito para utilização na simulação numérica e cálculos analíticos. Dos resultados da simulação numérica, através da comparação desta com equações empíricas e analíticas, foi avaliada a capacidade da simulação de prever a força de trefilação. Além disso, foi realizado um esforço no sentido de determinar as tensões residuais após a trefilação. Os valores simulados de tensões residuais foram comparados com valores experimentais obtidos através de análise de tensões residuais por difração de Nêutrons realizada em amostras trefiladas da industria. Com base neste trabalho, foi discutida a possibilidade de usar-se a simulação para prever quantitativamente as tensões residuais após o processo de trefilação. As análises poderão ser utilizadas para o desenvolvimento de futuros melhoramentos no processo de trefilação.

In this work, the wire-drawing production step for the production of AISI 1045 steel bars was numerically simulated. Different parameters necessary for the simulation were estimated based on current combined industrial drawing processes. Ring compression tests were carried out and simulated aiming at the determination of the friction value to be used in the simulation. From the numerical simulation results, the capacity of the simulation for estimating the drawing forces by comparison with analytical and empirical equations was evaluated. Besides this, an effort was made to simulate the residual stresses after drawing. The simulated residual stress profiles were then compared to experimental residual stresses profiles, which were obtained in a Neutron Diffraction experimental analysis carried out on industrial samples. Based on this work, the possibility of using simulation to quantitatively calculate residual stresses after the cold drawing was discussed. The carried out analysis will be used to implement improvements in the drawing process.