Alternative Heat Treatments for Complex-Alloyed High-Cr Cast Iron Before Machining

Alternative Heat Treatments for Complex-Alloyed High-Cr Cast Iron Before Machining Four heat treatment schedules were applied to 14.6 wt pct Cr-2.2 wt pct Mn-1 wt pct Ni cast iron to improve its machinability: (a) one-step continuous annealing [holding at 1123 K (950 °C), 2 hours, cooling at 20 to 150 K/h], (b) three-step isothermal annealing [1123 K (950 °C), 2 hours + 923 K (650 °C), 6 hours + 998 K (725 °C), 15 hours], (c) two-step isothermal annealing [923 K (650 °C), 6 hours + 998 K (725 °C), up to 25 hours], (d) quenching [1123 K (950 °C), 2 hours] and tempering [998 K (725 °C), up to 15 hours]. Heat treatments (a) and (b), which include high-temperature holding at 1123 K (950 °C), result in secondary carbide precipitation, and lead to a “martensite/austenite” or “martensite/austenite/pearlite” matrix and a bulk hardness of 56 to 62 HRC with poor machinability. Heat treatments (c) and (d) provide a matrix of “ferrite + granular carbides” with a bulk hardness lower than 40 HRC. Quenching and tempering result in the elimination of retained austenite to 11.6 vol pct. The kinetics of spheroidization and coagulation of eutectoid carbides and carbides as precipitated from martensite are presented and discussed. Drill testing showed that after quenching and tempering, cast iron has a superior machinability compared with other heat treatments. http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Metallurgical and Materials Transactions A Springer Journals

Alternative Heat Treatments for Complex-Alloyed High-Cr Cast Iron Before Machining

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Publisher
Springer US
Copyright
Copyright © 2018 by The Minerals, Metals & Materials Society and ASM International
Subject
Materials Science; Metallic Materials; Characterization and Evaluation of Materials; Structural Materials; Surfaces and Interfaces, Thin Films; Nanotechnology
ISSN
1073-5623
eISSN
1543-1940
D.O.I.
10.1007/s11661-018-4722-0
Publisher site
See Article on Publisher Site

Abstract

Four heat treatment schedules were applied to 14.6 wt pct Cr-2.2 wt pct Mn-1 wt pct Ni cast iron to improve its machinability: (a) one-step continuous annealing [holding at 1123 K (950 °C), 2 hours, cooling at 20 to 150 K/h], (b) three-step isothermal annealing [1123 K (950 °C), 2 hours + 923 K (650 °C), 6 hours + 998 K (725 °C), 15 hours], (c) two-step isothermal annealing [923 K (650 °C), 6 hours + 998 K (725 °C), up to 25 hours], (d) quenching [1123 K (950 °C), 2 hours] and tempering [998 K (725 °C), up to 15 hours]. Heat treatments (a) and (b), which include high-temperature holding at 1123 K (950 °C), result in secondary carbide precipitation, and lead to a “martensite/austenite” or “martensite/austenite/pearlite” matrix and a bulk hardness of 56 to 62 HRC with poor machinability. Heat treatments (c) and (d) provide a matrix of “ferrite + granular carbides” with a bulk hardness lower than 40 HRC. Quenching and tempering result in the elimination of retained austenite to 11.6 vol pct. The kinetics of spheroidization and coagulation of eutectoid carbides and carbides as precipitated from martensite are presented and discussed. Drill testing showed that after quenching and tempering, cast iron has a superior machinability compared with other heat treatments.

Journal

Metallurgical and Materials Transactions ASpringer Journals

Published: Jun 5, 2018

References

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