Improvement of Yield Strength-Transition Temperature Balance by Microstructural Refinement

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概要

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• Grain-refinement simultaneously increases yield strength and toughness while the strengthening without the grain-refinement still deteriorates the toughness. It is worth assessing how the strengthening relates to the toughness to strengthen steels most appropriately. In this study, different mechanisms for strengthening are compared with respect to the relationship between yield strength and ductile-brittle fracture transition temperature. Considered are the grain-refinement by solute copper or thermo-mechanical control process (TMCP), the precipitation-hardening by copper, and the bainite-transformation hardening with alloying elements such as boron, molybdenum, and nickel, The transition temperature rises with strengthening by the precipitation-hardening and the transformation-hardening. In this case, the relationship is approximately linear with the gradient of 0.46°C/MPa. In contrast, the transition temperature lowers in the case of the strengthening by the grain-refinement achieved by the solute copper and the TMCP. This study aims at relating the yield strength to the transition temperature on a dislocation crack model of brittle fracture. Considering the energy balance for brittle crack initiation and the temperature dependence of the friction stress for the Hall-Petch relationship gives the linear lowering of transition temperature with increasing yield strength by grain-refinement, of which gradient is estimated at approximately 0.80°C/MPa. The comparison of experimental results with this relationship indicates that the strengthening by solute copper effectively utilizes the grain-refinement.

• 社団法人 日本鉄鋼協会の論文
• 1996-03-15

著者

• TAKAHASHI Akihiko

  Yawata R & D Laboratory, Nippon Steel Corporation

• Takahashi Akihiko

  Yawata R & D Laboratory Nippon Steel Corporation

• Iino Makio

  Nippon Steel Corporation

関連論文

• Comparison between Full Scale Tests and Small Scale Tests in Evaluating the Cracking Susceptibility of Line Pipe in Sour Environment
• Influence of Softened Heat-affected Zone on Stress Oriented Hydrogen Induced Cracking of a High Strength Line Pipe Steel
• Influence of Microhardness and Inclusion on Stress Oriented Hydrogen Induced Cracking of Line Pipe Steels
• Improvement of Yield Strength-Transition Temperature Balance by Microstructural Refinement
• Microstructural Refinement by Cu Addition and Its Effect on Strengthening and Toughening of Sour Service Line Pipe Steels
• Thermo-mechanical Control Process as a Tool to Grain-refine the Low Manganese Containing Steel for Sour Service Line Pipe

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