Authors’ Reply to Discussion of “Effects of Cr Reduction on High-Temperature Strength of High-Ni Austenitic Cast Steels Used for High-Performance Turbochargers”
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Previously, the current authors had fabricated austenitic cast steels by adjusting the Cr content in a commercial HK40 steel [composition; 0.4C-1.0Mn-1.2Si-25Cr-20Ni (wt pct)],[ 1] and improved the high-temperature properties by optimizing the carbide formation and by strengthening the austenite matrix.[ 2] The steel in which 6 wt pct of Ni was replaced by 6.9 wt pct of Mn is referred to as ‘N14,’[ 3] and the steel in which 1 wt pct of Mo was added to the N14 steel is referred to as ‘N14Mo1.’[ 2] To investigate the Cr effect, 4 wt pct of Cr was reduced from the N14Mo1 steel, referred to as ‘N14Mo1Cr-4.’ Nominal compositions of the HK40, N14, N14Mo1, and N14Mo1Cr-4 steel are summarized in Table I. The N14Mo1Cr-4 steel shows an improvement in high-temperature (1173 K (900 °C)) yield and tensile strengths of 6 MPa and 8 MPa, respectively, over the N14Mo1 steel. This implies that the Cr reduction beneficially affects the strength because it raises the austenite matrix hardness and reduces the...
This work was supported by the World Class 300 Project R&D Program and by Brain Korea 21 PLUS Project for Center for Creative Industrial Materials.
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