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Effects of Copper on the Hardenability of a Medium-Carbon Steel
ERIK J. PAVLINA, SEOK-JAE LEE,EERO T. VIRTANEN, LEE M. ROTHLEUTNER, and CHESTER J. VAN TYNE
Scrap-based steelmaking is gradually increasing the levels of residual copper present in modern steels. End-quench hardenability tests were conducted on medium-carbon steels containing up to 0.4 wt pct copper to evaluate if current methods are still accurate for predicting the ideal critical diameter as residual copper levels rise. The results indicate that coppers contribution to hardenability, especially at lower concentrations, may be greater than conventional calculation methods indicate.
DOI: 10.1007/s11661-011-0906-6 The Minerals, Metals & Materials Society and ASM
International 2011
Current scrap-based electric arc furnace (EAF) steelmaking methods are leading to increased residual copper levels in most commercial steels.[1] This increase is coming under greater scrutiny because excessive amounts of copper can negatively impact the hot workability of steels.[27] The eects of copper on the diusional transformation of austenite to ferrite are also undergoing more detailed examination.[8] Despite these investigations, there has been a less substantial focus on the eect of copper on the martensitic transformation of austenite.
Hardenability can be simply dened as the ability to suppress the diusion-controlled transformation of austenite to ferrite or other products at high temperatures in favor of the transformation to martensite at lower temperatures. The hardenability of a given steel is highly dependent on carbon and other alloying elements dissolved in austenite prior to transformation.[9] The
ideal critical diameter (DI) is a parameter that has been used to quantify the hardenability of a given steel. The ideal critical diameter is dened as the diameter for a given steel composition, which, when quenched from
austenite in a medium of innite quench severity, would transform to 50 pct martensite at the center. The ideal critical diameter can be experimentally determined through any one of several methods, such as quenching bars of varying diameter, quenching conical geometries, or end-quench hardenability tests. It can also be determined based on some criterion of hardness and martensite volume fraction.[10] The ideal critical diameter can also be calculated from the chemical composition of the steel using empirically determined multiplying factors for each alloying element.[1113]
Multiplying factors are provided by the American Society for Testing Materials (ASTM) International in their...