This content is not included in your SAE MOBILUS subscription, or you are not logged in.
Austempering Process for Carburized Low Alloy Steels
ISSN: 0148-7191, e-ISSN: 2688-3627
Published April 08, 2013 by SAE International in United States
Annotation ability available
There is a continual need to apply heat treatment processes in innovative ways to optimize material performance. One such application studied in this research is carburizing followed by austempering of low carbon alloy steels, AISI 8620, AISI 8822 and AISI 4320, to produce components with high strength and toughness. This heat treatment process was applied in two steps; first, carburization of the surface of the parts, second, the samples were quenched from austenitic temperature at a rate fast enough to avoid the formation of ferrite or pearlite and then held at a temperature just above the martensite starting temperature to partially or fully form bainite. Any austenite which was not transformed during austempering, upon further cooling formed martensite or was present as retained austenite. The final result was a high-carbon surface layer of bainite or martensite which is expected to have good wear and fatigue resistance and a low carbon bainite and/or martensite core to provide toughness.
The effect of the austempering temperature and time was studied for the three types of steel. A combination of three austempering temperatures, 260, 288 and 304°C and three times 1, 2 and 4 hours provided seven different heat treatments that were applied to the three types of alloy steel selected for the tests. Charpy tests were done on all the heat-treated steels to determine the differences in toughness due to the material and heat treatment conditions. The surface hardness and the geometric distortion were measured as well. The results obtained for the carburize/austemper process were compared to results obtained for the more traditional carburize/quench/temper process. One of the important conclusions was that the distortion produced by the carburize/austemper process was significantly less than the distortion produced by the carburize/quench/temper process. The results can be used to help select the best heat treatment conditions and materials for applications that include transmission shafts, output shafts, pump shafts, differential pinions, splines and parking pawls.
CitationLumbreras, R., Sun, X., Barber, G., and Zou, Q., "Austempering Process for Carburized Low Alloy Steels," SAE Technical Paper 2013-01-0949, 2013, https://doi.org/10.4271/2013-01-0949.
- Zhang Shun X. Torque Transferring Low Carbon Steel Shafts with Refined Grain Size United States Patent number: US 7,481,896 B2 Jan 27 2009
- Callister William D. Jr. Wiley Materials Science and Engineering an Introduction seventh 2007
- Rajan T. V. , Sharma C. P. , Sharma Ashok Heat treatment: Principles and Techniques Prentice Hall India Pvt., Limited 2003
- Putatunda Susil K. Development of a high strength high toughness bainitic steel United States Patent Application Publication number: US 2011/0114233 A1 May 19 2011
- Hayrynen , K. , Brandenberg , K. , and Keough , J. Carbo- Austempering™ - A New Wrinkle? SAE Technical Paper 2002-01-1478 2002 10.4271/2002-01-1478
- ASTM A370 Standard Test Methods and Definitions for Mechanical Testing of Steel Products 06 November 2006
- Sheikh Muhammad Ashraf Effects of heat treatment and allowing elements on characteristics of austempered ductile iron PhD Thesis University of Engineering and Technology Lahore, Pakistan 2008