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Development of an Aluminium-Reduced Niobium-Microalloyed Case Hardening Steel for Heavy Gear Manufacturing

  • G. Kripak , M. Sharma , R. Kohlmann , B. Clausen , U. Prahl , H.-W. Zoch and W. Bleck
Published/Copyright: February 6, 2019
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HTM Journal of Heat Treatment and Materials
From the journal HTM Journal of Heat Treatment and Materials Volume 74 Issue 1

Abstract

Fatigue strength is a key mechanical property for heavy transmission components, which are subjected to dynamic loading conditions. Oxidic steel cleanliness is known to greatly influence the fatigue strength of steel. The underlying research project work aimed to improve the oxidic cleanliness of the case hardening steel grade 18CrNiMo7-6 (DIN EN ISO 10084), whilst maintaining a fine austenite grain size during high temperature carburising. The hypothesis thereby is to lower the aluminium content of steel in order to reduce the probability of formation of aluminium oxide inclusions. In the absence of aluminium nitride precipitates, the prevention of undue austenite grain coarsening has been ensured in this work by alloying the steel with the appropriate amount of niobium. The optimum content of niobium was selected based on thermodynamic calculations using Thermo-Calc®. The results indicate the basic feasibility of obtaining fine grain stability on an industrial scale for application to high temperature carburising at 995°C for 14.4 hours.

Kurzfassung

Für dynamisch belastete Großgetriebe ist die Dauerfestigkeit eine zentrale Eigenschaft, welche stark durch den oxidischen Reinheitsgrad des Stahles beeinflusst wird. Das hier zugrundeliegende Forschungsvorhaben zielte auf die Verbesserung des oxidischen Reinheitsgrades im Einsatzstahl 18CrNiMo7-6 (DIN EN ISO 10084) unter Beibehaltung der Feinkornbeständigkeit bei hohen Aufkohlungstemperaturen. Der werkstoffkundliche Ansatz ist die Reduktion des Aluminiumgehaltes, um die Wahrscheinlichkeit des Auftretens unerwünschter Aluminiumoxide zu verringern. Der Erhalt der Feinkornbeständigkeit wird in diesem Konzept ohne Aluminiumnitride durch eine Anpassung des Niobgehaltes ermöglicht. Die benötigte Menge an Niob wurde durch thermodynamische Simulationen mit Thermo-Calc® berechnet. Die Ergebnisse weisen die prinzipielle Machbarkeit des Erhaltens der Feinkornbeständigkeit im industriellen Maßstab bei Einsatztemperaturen bis 995 °C für 14,4 Stunden nach.

Keywords: Fatigue strength; cleanliness; fine grain stability; simulation
Schlüsselwörter: Dauerfestigkeit; Reinheitsgrad; Feinkornbeständigkeit; Simulation
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Published Online: 2019-02-06
Published in Print: 2019-02-14

© 2019, Carl Hanser Verlag, München

Articles in the same Issue

  1. Praxis-Informationen/From and for Practice
  2. AWT Info
  3. HTM-Praxis
  4. Inhalt/Contents
  5. Inhalt
  6. Kurzfassungen/Abstracts
  7. Kurzfassungen
  8. Scientific Contributions/Fachbeiträge
  9. Can Carbides resist Nitriding?*
  10. Deep Cryogenic Treatment and Nitriding of 42CrMo4 Steel*
  11. Experimental and Simulative Studies on Residual Stress Formation for Laser-Beam Surface Hardening*
  12. Development of an Aluminium-Reduced Niobium-Microalloyed Case Hardening Steel for Heavy Gear Manufacturing
  13. Analysis of the Chemical and Tribological Properties of Phosphate Glass Layers Developing during Metalworking Processes on Manual Transmission Synchronizers*
https://doi.org/10.3139/105.110367
Keywords for this article
Fatigue strength; cleanliness; fine grain stability; simulation

Articles in the same Issue

  1. Praxis-Informationen/From and for Practice
  2. AWT Info
  3. HTM-Praxis
  4. Inhalt/Contents
  5. Inhalt
  6. Kurzfassungen/Abstracts
  7. Kurzfassungen
  8. Scientific Contributions/Fachbeiträge
  9. Can Carbides resist Nitriding?*
  10. Deep Cryogenic Treatment and Nitriding of 42CrMo4 Steel*
  11. Experimental and Simulative Studies on Residual Stress Formation for Laser-Beam Surface Hardening*
  12. Development of an Aluminium-Reduced Niobium-Microalloyed Case Hardening Steel for Heavy Gear Manufacturing
  13. Analysis of the Chemical and Tribological Properties of Phosphate Glass Layers Developing during Metalworking Processes on Manual Transmission Synchronizers*
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