|Collaborative Study on Steel Phase Transformations Results in New ASTM Standard
A collaborative study on quantitative measurement of steel phase transformation (QMST) done by the American Iron and Steel Institute (AISI), in cooperation with over a dozen companies, has resulted in a recently-approved new ASTM standard, A 1033, Practice for Quantitative Measurement and Reporting of Hypoeutectoid Carbon and Low-Alloys Steel Phase Transformations. The collaborative study, sponsored by the U.S. Department of Energy under AISIs Technology Roadmap Project, also resulted in the production of extensive and detailed steel phase transformation data for medium-carbon grade SAE 1050 and alloy steel SAE 8620.
This type of information has become important because it is necessary for process simulation models that are used to predict residual stress, distortion and microstructure evolution that occurs during manufacturing practices such as steelmaking, forging, and heat treating. Prior to the study, this type of data had been collected using non-standardized techniques, resulting in a wide variety of data that was not always useful for process optimization in manufacturing operations.
In the practice, dilatometer equipment is used to detect and measure the changes in dimension that occur as functions of both time and temperature during defined thermal cycles. The resulting data are converted to discrete values of strain for specific values of time and temperature during the thermal cycle that can be used to determine the beginning and completion of one or more phase transformations.
The practice can be used to provide data for computer models used in the control of steel manufacturing, forging, casting, heat-treating, and welding processes. In addition, the practice can be used to provide data for the prediction of microstructures and properties to assist in steel alloy selection for end-use applications, as well as to provide data needed for the construction of transformation diagrams that depict the microstructures developed during the thermal processing of steels as functions of time and temperature.
Organizations involved in the QMST study with AISI included steel producers, automakers, heavy equipment manufacturers, suppliers, academia, and laboratories. The new standard is under the jurisdiction of ASTM Subcommittee A01.13 on Mechanical Chemical Testing and Processing Methods of Steel Products and Processes, which is part of ASTM Committee A01 on Steel, Stainless Steel and Related Alloys.
According to Manish Mehta, director, collaborative programs and executive director, Technologies Research Corporation, a subsidiary of the National Center for Manufacturing Sciences that organized and managed the 21-member QMST consortium, the new standard offers several benefits to the steel industry. A 1033 enables a cross-industry set of users and suppliers in the steel supply chain to obtain and archive more accurate and consistent, continuously sampled data inputs for process modeling and optimization, says Mehta. He also notes that specific benefits to the automobile and heavy vehicle industry include improved steel product quality and yields, lower cost, and fewer greenhouse gas emissions.
Mehta says the QMST consortium steering committee is encouraging feedback on A 1033 from any interested parties, especially since the new standard represents the first attempt to standardize collection, reporting and sample preparation methods using digital, continuously sampled experimental transformation data. Mehta expects to gather significant feedback during a follow-up project being formed to use A 1033 to populate a larger database of common steel alloys and product forms, but says that any input from users outside the project would be welcome.
For further technical information, contact Manish Mehta, National Center for Manufacturing Sciences, Ann Arbor, Mich. (phone: 734/995-4938) or David Anderson, director, bar and rod market development, AISI, Southfield, Mich. (phone: 248/945-4764). Committee A01 meets Nov. 8-11 during the November Committee Week in Washington, D.C. For membership or meeting details, contact George Luciw, ASTM International (phone: 610/832-9710). //
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