Based on the framework of "metallo-thermo-mechanics" proposed by the authors, a CAE system, "HEARTS" (HEAt tReaTment Simulation system), has been developed to simulate metallic structure, temperature, and stress]strain in the heat treatment processes associated with phase transformation, such as quenching and tempering by means of the finite element method. In the first part of the paper, the governing theory is introduced; fundamental equations of metallurgical change due to phase transformation, heat conduction, and stress analysis are presented; and the effect of coupling among these three fields is discussed. The development strategy, methodology, structure, and directions for use of the HEARTS system are stated in the following sections. Simulated results on temperature, structural change, and stress/strain, as well as carbon content during the heat treatment process, are illustrated for engineering components in two-and three-dimensional shape and a Japanese sword by use of the system combined with a pre-/post-processor. The validity of the system is evaluated by comparison with the experimental data.

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Heat treatment simulation has progressed to the stage where several commercial software are available. Validations of simulation functions using experimental results contributed to this realization. Organizing information on the validations may be effective for maintaining the functions and educating users about the nature of the phenomena. For this reason, the author here briefly reviews mainly his validation cases. Since experiments using specimens having relatively simple shapes can reveal the essence of complex phenomena, the results have been used in the validations. When the basic functions such as heat transfer, phase transformation, latent heat, and hardness prediction were comprehensively validated in the early stages of software development, the author used experimental results of the inverse hardening in quenched steel cylinders. After that, his validations of the software at the stage where adding stress and strain analysis functions, used effectively measurement data of length and diameter changes, and residual stress distributions in normally quenched steel cylinders. While, it was also worth to validate curving in long specimens cooled unevenly, which included a case of specimens with a similar cross-section to the Japanese sword. In addition, the author validated distortions and residual stresses in carburized and quenched, induction hardened, and also nitrided specimens.