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Quantitative Analysis of Microstructure in Low Carbon Steel after Thermomechanical Process in (α+γ) Region

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Published/Copyright: October 12, 2013
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Practical Metallography
From the journal Practical Metallography Volume 50 Issue 10

Abstract

This paper presents results of quantitative analysis of ferrite grains in low carbon steel C15V with microalloying addition of vanadium. Thermomechanical treatment in the intercritical (α+γ) region was performed using the dilatometer DIL805A. On the basis of dilatometric researches the critical temperatures of α ↔ γ transformation for C15V steel during heating with v5−8=0.5 K/s and cooling with v8−5=1 K/s were estimated. The steel deformation was carried out with application of two different variants: deformation in (α+γ) region after cooling from full austenitization temperature and deformation in (α+γ) region after heating from ambient temperature (ferritic-bainitic microstructure). The effects of these treatments were observed by means of a light optical microscope in bright and polarized field.

The quantitative analysis of microstructure was investigated using Image Pro Plus (IPP) program. Characteristic parameters for ferrite grains such as: field area, average diameter, shape factor were estimated. For each of these parameters, histograms and maps of average grain diameter distribution were performed using STATISTICA 9 and IPP programs. It was observed that deformation in the intercritical range (α+γ) promotes the occurrence of many ferrite nucleus in the obtained structures, especially at grain boundaries. For low carbon steel this results in formation of very fine microstructure.

Kurzfassung

Diese Arbeit präsentiert die Ergebnisse der quantitativen Analyse von Ferritkörnern in kohlenstoffarmem Stahl C15V mit dem Mikrolegierungselement Vanadium. Die thermomechanische Behandlung im interkritischen (α+γ)-Bereich wurde mit dem Dilatometer DIL805A durchgeführt. Auf Grundlage dilatometrischer Untersuchungen wurde die kritische Temperatur der α ↔ γ-Umwandlung für C15V-Stahl während dem Erwärmen mit v5–8=0,5 K/s und dem Abkühlen bei v8–5=1 K/s bestimmt. Die Stahlumformung wurde in zwei unterschiedlichen Varianten durchgeführt: Umformung im (α+γ)-Bereich nach dem Abkühlen von der Temperatur der vollständigen Austenitisierung und Umformung im (α+γ)-Bereich nach dem Anwärmen von der Raumtemperatur (ferritisch-bainitische Mikrostruktur). Die Auswirkungen dieser Behandlungen wurden mit einem Lichtmikroskop im Hellfeld und mit polarisiertem Licht betrachtet.

Die quantitative Analyse der Mikrostruktur wurde mit der Software Image Pro Plus (IPP) durchgeführt. Charakteristische Parameter für Ferritkörner wie beispielsweise Feldbereich, durchschnittlicher Durchmesser und der Formfaktor wurden abgeschätzt. Für jeden dieser Parameter wurden anhand der Software STATISTICA 9 und IPP Histogramme und Karten der durchschnittlichen Korndurchmesserverteilung erstellt. Es konnte beobachtet werden, dass die Umformung im interkritischen Bereich (α+γ) das Auftreten zahlreicher Ferritkerne in den erzielten Strukturen, insbesondere an den Korngrenzen, begünstigt. Bei kohlenstoffarmem Stahl führt dies zur Bildung einer sehr feinen Mikrostruktur.

References / Literatur

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Received: 2012-9-28
Accepted: 2013-7-12
Published Online: 2013-10-12
Published in Print: 2013-10-11

© 2013, Carl Hanser Verlag, München

Articles in the same Issue

  1. Contents/Inhalt
  2. Contents
  3. Editorial
  4. Editorial
  5. Technical Contributions/Fachbeiträge
  6. Microstructure Evolution and Mechanical Properties Investigation of Al-6 %Cu Alloy Laser and GTA Welds
  7. Preparation and Microstructural Characterisation of Metal Injection Moulded Powder Metallurgical Components (MIM) in the Green and Sintered Conditions
  8. Quantitative Analysis of Microstructure in Low Carbon Steel after Thermomechanical Process in (α+γ) Region
  9. Embrittlement of Fuel Gas Piping Made of Wrought Nickel-Based Superalloy Due to Inadequate Heat Treatment
  10. Meeting Diary/Veranstaltungskalender
  11. Meeting Diary
https://doi.org/10.3139/147.110210

Articles in the same Issue

  1. Contents/Inhalt
  2. Contents
  3. Editorial
  4. Editorial
  5. Technical Contributions/Fachbeiträge
  6. Microstructure Evolution and Mechanical Properties Investigation of Al-6 %Cu Alloy Laser and GTA Welds
  7. Preparation and Microstructural Characterisation of Metal Injection Moulded Powder Metallurgical Components (MIM) in the Green and Sintered Conditions
  8. Quantitative Analysis of Microstructure in Low Carbon Steel after Thermomechanical Process in (α+γ) Region
  9. Embrittlement of Fuel Gas Piping Made of Wrought Nickel-Based Superalloy Due to Inadequate Heat Treatment
  10. Meeting Diary/Veranstaltungskalender
  11. Meeting Diary
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