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Dornstetten, Germany

Gretzki T.,Leibniz University of Hanover | Rodman D.,Leibniz University of Hanover | Wolf L.,Leibniz University of Hanover | Dalinger A.,Leibniz University of Hanover | And 3 more authors.
HTM - Haerterei-Technische Mitteilungen | Year: 2011

The objective of the current investigation is a cost analysis of spray cooling based on the assessment of a machine-hour schedule.Here, a gear toothed component is used as an example which is induction hardened by means of the simultaneous dual frequency method and compared with conventional polymer quenching. By using hardness measurements and light-microscope examinations, it is demonstrated that comparable results are obtained for the induction hardening by employing spray cooling and those by polymer quenching. By investigating the influence of the spray's parameters on the hardness results, it was possible to draw inferences regarding the ratios of water to air pressures which lead to the desired hardness profiles. Estimating the costs of employing the two quenching methods have shown that the spray cooling is the more cost-effective of the two methods. Source


Rodman D.,Leibniz University of Hanover | Nurnberger F.,Leibniz University of Hanover | Dalinger A.,Leibniz University of Hanover | Schaper M.,Leibniz University of Hanover | And 3 more authors.
Steel Research International | Year: 2014

Induction hardening is a surface hardening process in which severe temperature gradients occur due to limiting the heating to the sub-surface layer. High residual stresses result from these gradients, which can negatively influence the fatigue strength and induce cracking. To reduce the residual stresses, induction hardening is followed by a tempering, which is usually carried out for several hours in a furnace. Substituting furnace tempering by tempering from the residual heat motivated the current investigations. During induction hardening of helical gearwheels made of 42CrMo4 heat-treating steel using a controlled quenching by means of spray cooling, an additional tempering from the residual heat was performed. The result of the heat treatment was analyzed with the aid of hardness, residual stress, and distortion measurements. The obtained hardening results demonstrate the equivalence of the two tempering processes considered here. During induction hardening of helical gearwheels made of 42CrMo4 heat-treating steel using spray cooling, a self-tempering was performed. The result of the heat treatment was analyzed with the aid of hardness, residual stress, and distortion measurements. The obtained hardening results demonstrate the equivalence of self-tempering and conventional furnace tempering. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source


Rodman D.,Leibniz University of Hanover | Krause C.,Eldec Schwenk Induction GmbH | Nurnberger F.,Leibniz University of Hanover | Bach F.-W.,Leibniz University of Hanover | And 2 more authors.
International Journal of Materials Research | Year: 2012

The objective of the current investigation consists of testing the interchangeability of polymer solutions used during induction hardening with water-air spraying regarding compressive residual stresses. Gearwheels made of 42CrMo4 steel were induction hardened and subsequently quenched using water-air spray cooling. The effect of different cooling parameters on the surface's residual stresses in the gearwheel's tooth flanks was analysed by means of X-ray diffraction. The microstructure was characterised by means of hardness measurements and light-microscopy. Residual stresses could be specified after using water-air spray cooling and are comparable to those using polymer quenching. Quench parameters leading to maximum compressive residual stresses in tooth flanks were determined. © 2012 Carl Hanser Verlag GmbH & Co. KG. Source


Stiele H.,EFD Induction GmbH | Krause C.,Eldec Schwenk Induction GmbH
Elektrowaerme International | Year: 2013

Using surface hardening processes (flame-, induction, laser-, electron beam hardening) normally a fraction of the work piece volume is austenized. This happens usually with high heating rates compared to a heating by furnace. This is the reason why the term short time austenitization is closely connected to the methods of surface hardening. In the following article the metallurgical processes and the characteristics during fast heating and short soaking times are described. Source


Krotz H.,Institute of Machine Tools and Manufacturing | Krotz H.,Eldec Schwenk Induction GmbH | Roth R.,Institute of Machine Tools and Manufacturing | Wegener K.,Institute of Machine Tools and Manufacturing
International Journal of Advanced Manufacturing Technology | Year: 2013

In this work, single discharges of electrochemical arc machining are examined. The heat-affected zone is analyzed, and a model is set up to simulate the heat transfer into the workpiece. As an input parameter of the simulation, the temperature of the electrochemical arc machining process was determined to be 3,500 K by means of emission spectroscopy. The simulation shows that the diameter of the heat-affected zone is less dependent on discharge duration and heat transfer due to heat flux than on the arc spot diameter. As a result of the investigation, it became clear that varying diameters of the heat-affected zone have to evolve from different diameters of the plasma channel's arc spot. Understanding the heat distribution into the workpiece in electrochemical arc machining with micro-machining parameters allows the further development of a micro-drilling process for electrically conductive materials based on electrochemical arc machining. © 2013 Springer-Verlag London. Source

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