Heat Treatment of Sintered Steels – what is different?*

Danninger, Herbert; Dlapka, M.

doi:10.3139/105.110353

Cited by 13 publications

(5 citation statements)

References 8 publications

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“…After cold rolling, heat treatment is carried out by case hardening. Conventional process conditions with porosity can lead to undesirable case hardening depths (CHDs) and carbide precipitation [10,11]. Therefore, the local density must be considered during heat treatment.…”

Section: Introductionmentioning

confidence: 99%

Influence of heat treatment and densification on the load capacity of sintered gears

et al. 2022

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The powder metallurgical manufacturing of gears offers a promising opportunity in terms of reducing the noise emission and increasing the power density. Sintered gears weigh less than conventional gears and potentially have a better noise-vibration-harshness behaviour, due to the remaining porosity. However, the potential of sintered gears for highly loaded applications is not fully utilised yet. Six variants of surface densified and case-hardened sintered gears from Astaloy Mo85 are tested to analyse the impact of the densification and case hardening depths on both the tooth root and flank load bearing capacities. Experimental investigations including metallography and computer tomography are carried out to characterise the microstructure. Furthermore, a simulation model is developed to quantitatively describe the residual stress and hardness profiles after the heat treatment. The load bearing capacity was improved by increasing the densification and case hardening depths, where the effect of the case hardening was identified to be predominant.

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Section: Introductionmentioning

confidence: 99%

Influence of heat treatment and densification on the load capacity of sintered gears

et al. 2022

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“…Most importantly, the Eigenfrequency changes by a couple of hundred Hz, which can make the sonotrode useless for application. A change of the grain shape and size by thermal treatment was not distinguishable in microstructural investigations, characteristic for metal-based sintered material [ 29 ]. The relatively large changes of the acoustic properties of a Z-M4 rod are shown in Figure 9 .…”

Section: Resultsmentioning

confidence: 99%

Detection of Microstructural Changes in Metastable AISI 347, HSS Z-M4 and Tool Steel Ferrotitanit WFN by Mechanical Loss Coefficient at Ultrasonic Frequencies

et al. 2022

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Ultrasonic processes such as ultrasonic welding or ultrasonic fatigue testing use power ultrasound to stimulate materials with amplitudes in the range of 1–100 µm. The ultrasonic welding process is sensitive to any changes in the system or even the environment that may result in lower joint quality. The welding tools, so called sonotrodes, have to be accurately designed to endure high mechanical and thermal loads while inducing a sufficient amount of welding energy into the joining zone by oscillation with the Eigenfrequency of the whole system. Such sonotrodes are often made of thermally treated metals where the heat treatment is accompanied by microstructural changes. During ultrasonic stimulation, the material may further change its properties and microstructure due to cyclic loading. Both are expected to be recognized and identified by loss coefficients. Therefore, the loss coefficient was determined by modal analysis of rods and fatigue specimen made of different materials to correlate microstructural changes to attenuation. The determined loss coefficients indicated microstructural changes in all materials investigated, confirming results from previous investigations that showed an increasing attenuation due to cyclic loading for AISI 347. For the sonotrode materials Z-M4 PM and Ferrotitanit WFN, the loss coefficients decreased due to thermal treatments. Technically most relevant, changes in elastic modulus due to thermal treatments were quantitatively related to frequency changes, which can significantly simplify future sonotrode development.

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“…Basically, same processes can be applied to heat-treat sintered parts as in the case of wrought steel parts. However, the effect of the porosity on the material response and the final result of the heat treatment should be considered to choose the optimal treatment strategy and process parameters (Danninger and Dlapka 2018). To study the potential in optimizing the bearing capacity by surface densification and case hardening, an ICME approach is developed, which links simulation blocks that consecutively represent the process steps of carburizing, quenching, tempering and loading of the gear.…”

Section: Sintered Gear -Surface Hardening and Load-bearing Capacitymentioning

confidence: 99%

Materials in the Drive Chain – Modeling Materials for the Internet of Production

Rajaei

Becker

Deng

et al. 2023

Interdisciplinary Excellence Accelerator Series

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In this chapter, the focus lies on a predictive description of the material response to the thermomechanical loads within different process steps by means of physical and data-driven models. The modeling approaches are demonstrated in examples of innovative production technologies for components of a drive chain: Fine blanking of parts; powder metallurgical (PM) production of gears; open-die forging and machining of drive shafts. In fine blanking, material, process, and quality data are acquired to model interactions between process and material with data-driven methods. Interpretable machine learning is utilized to non-destructively characterize the initial material state, enabling an optimization of process parameters for a given material state in the long-term. The PM process chain of the gear includes sintering, pressing, surface densification, case hardening, and finishing by grinding. Several modeling and characterization approaches are applied to quantitatively describe the microstructure evolutions in terms of porosity during sintering, density profile after cold rolling, hardness and residual stresses after heat treating and grinding and the tooth root load bearing capacity. In the example of the open-die forging, a knowledge-based approach is developed to support the decision-making process regarding the choice of the proper material and optimized pass schedules. Considering the microstructure of the forged shaft, the elastoplastic material behavior is described by a dislocation-based, multiscale modeling approach. On this basis, process simulations could be carried out to predict the process forces, chip form, residual stresses, and the tool life among other output data.

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Heat Treatment of Sintered Steels – what is different?*

Cited by 13 publications

References 8 publications

Influence of heat treatment and densification on the load capacity of sintered gears

Influence of heat treatment and densification on the load capacity of sintered gears

Detection of Microstructural Changes in Metastable AISI 347, HSS Z-M4 and Tool Steel Ferrotitanit WFN by Mechanical Loss Coefficient at Ultrasonic Frequencies

Materials in the Drive Chain – Modeling Materials for the Internet of Production

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