@phdthesis{oai:kyutech.repo.nii.ac.jp:00005428,
 author = {Hu,  Kejun},
 month = {2018-03-07},
 note = {1. Introduction||2. Residual Stress Simulation during Uniform Heating Quenching|| 3. Usefulness of Non-Uniform Heating and Quenching Method for Residual Stress of Bimetallic Roll|| 4. Effect of Creep behavior and Tempering Process on Residual Stress Reduction for Bimetallic Roll|| 5. Accuracy of Disk Method to Predict Roll Residual Stress by Measuring the Sliced Disk Stress|| 6. Summary, Bimetallic rolls are widely used in hot rolling mills because of excellent hardness, wear resistance and high temperature properties. During hot rolling process, thermal tensile-compressive stresses are caused by a cyclic sequence of heating – cooling over the roll surface due to hot strip contact and water cooling, resulting in thermal crack at the roll surface. Therefore, suitable compressive stresses at the roll surface are necessary for preventing the thermal crack extension. However, the tensile residual stress always appears at the roll center to balance the surface compressive residual stress. Under the combined action of tensile thermal stress and tensile residual stress at the roll center, another form of roll fracture known as thermal barrel breakage is originating near to the roll center and breaking out to the barrel surface. Therefore, keeping optimum surface compressive residual stress and minimizing the center tensile residual stress are desirable to reduce the risk of roll fracture and improve bimetallic roll using life. Since the residual stress can be controlled by the heat treatment, thus this thesis concentrated on the residual stress analysis of bimetallic roll during the heat treatment.  Chapter 1 gives the introduction of the high speed steel （HSS） bimetallic rolls used for hot strip rolling. In this chapter, the characteristics of the HSS rolls were introduced compared with the conventional single material rolls. An in addition, the development, applications and the different manufacturing methods of the HSS rolls were briefly introduced. Then the issues of the research on residual stress in the rolling rolls were reviewed. Chapter 2 analyzes the residual stress of bimetallic roll during uniform heating quenching process. A thermo-elastic-plastic finite element simulation was performed by using large amount of shell and core material properties depending on the temperature. The residual stress generation mechanism and stress distribution during the uniform heating quenching process was investigated. Then, the effects of the shell-core ratio, roll diameter, phase transformation and material heat treatment process on the residual stress are discussed. Chapter 3 analyzes the residual stress of bimetallic roll during non-uniform heating quenching process. In this chapter, the residual stress simulation was preformed including rapid heating and quenching process. The residual stresses were compared between uniform heating quenching process and non-uniform heating quenching process. The reason of the center tensile residual stress reduction in non-uniform heating quenching was investigated. Then, the usefulness of non-uniform heating quenching decreasing the roll center tensile residual stress is discussed considering the thermal stress during hot rolling process.   Chapter 4 briefly describes and explains the effect of creep analysis and tempering process on residual stress reduction of bimetallic roll during uniform heating quenching and non-uniform heating quenching processes. In this chapter, creep analysis was applied to the core material during the keeping process. Firstly, the creep equations were calculated based on the creep test using the time hardening law. Then the accuracy of creep equations is verified by the comparison of stress relaxation between FEM result and experimental result. At the last, the comparison of residual stress reduction considering tempering process after uniform heating quenching process and non-uniform heating quenching process was also discussed. Chapter 5 analyzes the accuracy of disk method to predict roll residual stress. The disk method has been widely used in predicting the roll residual stress by measuring the stress of the thin sliced disk from the roll. The relation of stress between the original roll and the sliced disk stress should be discussed. In this chapter, therefore, the accuracy of disk method was investigated on the basis of thermo-elastic-plastic FEM analysis. Firstly, the stress simulations of single material rolls were performed using thermo-elastic analysis and thermo-elastic-plastic analysis considering the different quenching time, and in addition, the effect of disk thickness on the residual stress was also discussed. Then, the stress simulations of real bimetallic rolls were performed using thermos-elastic-plastic analysis under the different quenching time. Chapter 6 gives the conclusions summary of this study., 九州工業大学博士学位論文 学位記番号：工博甲第433号 学位授与年月日：平成29年3月24日, 平成28年度},
 school = {九州工業大学},
 title = {Study on Residual Stress for Hot Strip Rolling Bimetallic Rolls during the Heat Treatment Process},
 year = {}
}