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Influence of Heat Treatment and Precipitation on the Former Austenite Grain Size in Cold Forged, Case-Hardened Steel Components∗

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Published/Copyright: August 10, 2020
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HTM Journal of Heat Treatment and Materials
From the journal HTM Journal of Heat Treatment and Materials Volume 75 Issue 4

Abstract

In case-hardened steel components, fine-grain stability is one of the most important properties of the microstructure, since a single coarse grain in a fine-grain matrix is often sufficient to cause premature failure of the component under appropriate loading. In order to better understand the influence of heat treatments on cold formed components, the case hardened microstructure of 16 different heat treatment combinations was investigated on the case hardening steel 20MnCr5 (1.7168). The process chain influences grain growth inhibiting precipitations, which in turn influence the fine grain stability. For this reason, aluminium nitrides in size ranges from approx. 15 to 250 nm were analysed in two samples using high-resolution scanning electron microscopy in both fine and coarse-grained areas. The respective areas examined had an average area of 1,250−2,000 μm2. The statistical analysis showed that within the samples no significant difference in morphology and density between aluminium nitrides in fine and coarse-grained areas could be found. On the other hand, more clusters appear in larger grains. Furthermore, a significant influence of the heat treatments on the aluminium nitrides could be detected.

Kurzfassung

In einsatzgehärteten Stahlbauteilen ist die Feinkornstabilität eine der wichtigsten Eigenschaften des Gefüges, da oftmals ein einzelnes grobes Korn in einer feinkörnigen Matrix genügt, um bei entsprechender Belastung zum vorzeitigen Versagen des Bauteils zu führen. Um den Einfluss von Wärmebehandlungen an kaltumgeformten Bauteilen besser zu verstehen, wurde das einsatzgehärtete Gefüge von 16 verschiedenen Wärmebehandlungskombinationen am Einsatzstahl 20MnCr5 (1.7168) untersucht. Die Prozesskette beeinflusst kornwachstumshemmende Ausscheidungen, die ihrerseits die Feinkornstabilität beeinflussen. Deshalb wurden in zwei Proben Aluminiumnitride in Größenbereichen von ca. 15 bis 250 nm mittels hochauflösender Rasterelektronenmikroskopie in fein- sowie grobkörnigen Bereichen analysiert. Die jeweiligen untersuchten Bereiche hatten eine Fläche von im Durchschnitt 1.250–2.000 μm2. In der statistischen Auswertung ergab sich, dass innerhalb der Proben kein signifikanter Unterschied in der Morphologie und Dichte zwischen Aluminiumnitriden in Fein- und Grobkornbereichen gefunden werden kann. Dafür scheinen mehr Cluster in größeren Körnern aufzutreten. Zudem konnte ein signifikanter Einfluss der Wärmebehandlungen auf die Aluminiumnitride erkannt werden.

Keywords: Case hardening steel; case hardening; fine grain stability; cold forging; heat treatment; aluminium nitrides
Schlüsselwörter: Einsatzstahl; Einsatzhärten; Feinkornstabilität; Kaltmassivumformung; Wärmebehandlung; Aluminiumnitride
2 (corresponding author/Kontakt)
∗

Lecture held at the HeatTreatingCongress, HK; October 22–24, 2019 in Cologne, Germany

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Published Online: 2020-08-10
Published in Print: 2020-08-13

© 2020, Carl Hanser Verlag, München

Articles in the same Issue

  1. Praxis-Informationen/From and for Practice
  2. AWT Info
  3. HTM-Praxis
  4. Kurzfassungen/Abstracts
  5. Kurzfassungen
  6. Inhalt/Contents
  7. Inhalt
  8. Editorial
  9. Editorial
  10. Scientific Contributions/Fachbeiträge
  11. Prediction of Hardness after Industrialized Bainitization of 100Cr6 based on Process Parameters by Application of Machine Learning Methods∗
  12. Influence of Heat Treatment and Precipitation on the Former Austenite Grain Size in Cold Forged, Case-Hardened Steel Components∗
  13. Experience in the Eddy Current Testing of Rolling Element Bearing Components
  14. Investigation of the Application of a C-ring Geometry to validate the Stress Relief Heat Treatment Simulation of Additive Manufactured Austenitic Stainless Steel Parts via Displacement∗
https://doi.org/10.3139/105.110416
Keywords for this article
Case hardening steel; case hardening; fine grain stability; cold forging; heat treatment; aluminium nitrides

Articles in the same Issue

  1. Praxis-Informationen/From and for Practice
  2. AWT Info
  3. HTM-Praxis
  4. Kurzfassungen/Abstracts
  5. Kurzfassungen
  6. Inhalt/Contents
  7. Inhalt
  8. Editorial
  9. Editorial
  10. Scientific Contributions/Fachbeiträge
  11. Prediction of Hardness after Industrialized Bainitization of 100Cr6 based on Process Parameters by Application of Machine Learning Methods∗
  12. Influence of Heat Treatment and Precipitation on the Former Austenite Grain Size in Cold Forged, Case-Hardened Steel Components∗
  13. Experience in the Eddy Current Testing of Rolling Element Bearing Components
  14. Investigation of the Application of a C-ring Geometry to validate the Stress Relief Heat Treatment Simulation of Additive Manufactured Austenitic Stainless Steel Parts via Displacement∗
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