and minimal distortion. Furthermore, it has been demonstrated that the servi ce life under cyclic loads may be increased by approximately one order of magnitude [54]. Intensive quenching requires appropriate quenching facilities and quenching media. Quenching media include pressurized water streams, water containing various additives, and liquid nitrogen. Figure 9.52 shows a que nching chamber for the intensive cooling of an automobile semiaxis using pressurized water flow . The water supply to the chamber and the charging and discharging of the axles are controlled by two sensors. The first sensor (5 in Figure 9.52) analyzes the process of film boiling and nucleate boiling, and the second, 6, describes the transformation of austenite into martensite by the change of the ferromagnetic state of the material. One method of intensive quenching has been used that achieve s maximum compressive stresses at the surface when sensor 6 indicates a specific magnetic phase transformation. In this case, sensor 5 is used to minimize the duration of film boiling by regulating the water flow velocity. A second method has also been used, with sensor 5 indicating the beginning and completion of nucleate boiling, while sensor 6 controls the water pressure and determines the end of intensive quenching, so that no more than 30% martensite is formed. Intensive que nching methods offer many possibilities for the successful cooling of parts with optimized strength properties and improved service life. However, a precondition for the use of this technology is the development of appropriate que nching equipment that enables precise control of the quenching performance. Ref. [4c] provides an overview of intensive quenching probes design. 9.8 PROPERTY PREDICTION METHODS There are increasing demands on the heat treater to achieve as-quenched properties while simultaneously reducing heat treatment costs. To achieve these goals it is becoming increas- ingly important that experimentally or mathematically based methods to predetermine the as- quenched strength and hardness propert ies be applied with sufficient accuracy. Currently, a computer-based selection of steels and optimization of quenching conditions according to the desired service properties are generally possible. Hardenability is one of the most important properties to be predicted because it determines as-quenched microstructure formation. The ability to predict hardenability curves from chemical composition has already been described in Chapt er 5, Secti on 5.4. How ever, these harden ability curves pro vide only lim ited informa- tion about the distribution of mechanical properties in the quenched part. It is necessary to correlate steel chemical composition, cooling rates during quenching, metallurgical trans- formation behavior, and the final physical properties. These correlations are often complex. } 1 2 3 5 6 7 8 4 FIGURE 9.52 Quenching chamber for intensive quenching of semiaxes in a pressurized water flow: 1, semiaxis; 2, quenching chamber; 3, water flow; 4, mechanical drive for the semiaxis; 5, sensor for analyzing the process of film boiling and nucleate boiling; 6, sensor for analyzing the portion of formed structures; 7, 8, amplifiers. Quenching and Quenching Technology 589 ß 2006 by Taylor & Francis Group, LLC. and minimal distortion. Furthermore, it has been demonstrated that the servi ce life under cyclic loads may be increased by approximately one order of magnitude [54]. Intensive quenching requires appropriate quenching facilities and quenching media. Quenching media include pressurized water streams, water containing various additives, and liquid nitrogen. Figure 9.52 shows a que nching chamber for the intensive cooling of an automobile semiaxis using pressurized water flow . The water supply to the chamber and the charging and discharging of the axles are controlled by two sensors. The first sensor (5 in Figure 9.52) analyzes the process of film boiling and nucleate boiling, and the second, 6, describes the transformation of austenite into martensite by the change of the ferromagnetic state of the material. One method of intensive quenching has been used that achieve s maximum compressive stresses at the surface when sensor 6 indicates a specific magnetic phase transformation. In this case, sensor 5 is used to minimize the duration of film boiling by regulating the water flow velocity. A second method has also been used, with sensor 5 indicating the beginning and completion of nucleate boiling, while sensor 6 controls the water pressure and determines the end of intensive quenching, so that no more than 30% martensite is formed. Intensive que nching methods offer many possibilities for the successful cooling of parts with optimized strength properties and improved service life. However, a precondition for the use of this technology is the development of appropriate que nching equipment that enables precise control of the quenching performance. Ref. [4c] provides an overview of intensive quenching probes design. 9.8 PROPERTY PREDICTION METHODS There are increasing demands on the heat treater to achieve as-quenched properties while simultaneously reducing heat treatment costs. To achieve these goals it is becoming increas- ingly important that experimentally or mathematically based methods to predetermine the as- quenched strength and hardness propert ies be applied with sufficient accuracy. Currently, a computer-based selection of steels and optimization of quenching conditions according to the desired service properties are generally possible. Hardenability is one of the most important properties to be predicted because it determines as-quenched microstructure formation. The ability to predict hardenability curves from chemical composition has already been described in Chapt er 5, Secti on 5.4. How ever, these harden ability curves pro vide only lim ited informa- tion about the distribution of mechanical properties in the quenched part. It is necessary to correlate steel chemical composition, cooling rates during quenching, metallurgical trans- formation behavior, and the final physical properties. These correlations are often complex. } 1 2 3 5 6 7 8 4 FIGURE 9.52 Quenching chamber for intensive quenching of semiaxes in a pressurized water flow: 1, semiaxis; 2, quenching chamber; 3, water flow; 4, mechanical drive for the semiaxis; 5, sensor for analyzing the process of film boiling and nucleate boiling; 6, sensor for analyzing the portion of formed structures; 7, 8, amplifiers. Quenching and Quenching Technology 589 ß 2006 by Taylor & Francis Group, LLC. 10 Distortion of Heat-Treated Components Michiharu Narazaki and George E. Totten CONTENTS 10.1 Introduction 614 10.2 Basic Distortion Mechanisms 609 10.2.1 Relief of Residual Stresses 609 10.2.2 Material Movement Due to Temperature Gradients during Heating and Cooling 610 10.2.3 Volume Changes during Phase Transformat ions 610 10.3 Residual Stresses 612 10.3.1 Residual Stress in Components 612 10.3.2 Residual Stresses Prior to Heat Treatment 612 10.3.3 Heat Treatment after Work-Hardening Process 612 10.4 Distortion during Manufacturing 613 10.4.1 Manufacturing and Design Factors Prior to Heat Treatment That Affect Distortion 613 10.4.1.1 Material Properties 614 10.4.1.2 Homogeneity of Material 614 10.4.1.3 Distribution of Residual Stress System 614 10.4.1.4 Part Geometry 614 10.4.2 Distortion during Component Heating 615 10.4.2.1 Shape Change Due to Relief of Residual Stress 615 10.4.2.2 Shape Change Due to Thermal Stresses 615 10.4.2.3 Volume Change Due to Phase Change on Heating 615 10.4.3 Distortion during High-Temperature Processing 616 10.4.3.1 Volume Expansion during Case Diffusion 616 10.4.3.2 Distortion Caused by Metal Creep 616 10.4.4 Distortion during Quenching Process 617 10.4.4.1 Effect of Cooling Characteristics on Residual Stress and Distortion from Quenching 617 10.4.4.2 Effect of Surface Condition of Components 624 10.4.4.3 Minimizing Quench Distort ion 625 10.4.4.4 Quench Uniformity 629 10.4.4.5 Quenching Methods 630 10.5 Distortion during Post Quench Processing 631 10.5.1 Straightening 631 10.5.2 Tempering 631 10.5.3 Stabilization with Tempering and Subzero Treatment 632 10.5.4 Metal Removal after Heat Treatment 633 ß 2006 by Taylor & Francis Group, LLC. 60 20 600 400 200 0 0 (a) (b) 10 Still water Spray (open) lateral Spray (submerged) lateral Spray (open) lateral Spray (submerged) lateral 0.3m/s upward 0.7m/s upward 0.3m/s upward 0.7m/s upward 20 30 Distance from lower end, mm 40 50 60 010 Still water 20 30 Distance from lower end, mm 40 50 60 Residual stress, MP a −200 −400 −600 −800 −1000 600 400 200 0 Residual stress, MP a −200 −400 −600 −800 −1000 A B s z s q 101064 FIGURE 10.11 Effect of agitation methods on residual stress after water quenching of JIS S45C steel rod (20-mm diameter by 60 mm long). Quenchant was 308C city water. Agitation methods were still, 0.3 m/s upward flow, 0.7 m/s upward flow, and lateral submerge in immersion quenching, and lateral open spray quenching in air. (a) Axial stress on surface, (b) tangential stress on surface. (From M. Narazaki, G.E. Totten, and G.M. Webster, in Handbook of Residual Stress and Deformation of Steel, G.E. Totten, M.A.H. Howes, and T. Inoue, Eds., ASM International, Materials Park, OH, 2002, pp. 248–295.) ß 2006 by Taylor & Francis Group, LLC. . while simultaneously reducing heat treatment costs. To achieve these goals it is becoming increas- ingly important that experimentally or mathematically based methods to predetermine the as- quenched strength and. while simultaneously reducing heat treatment costs. To achieve these goals it is becoming increas- ingly important that experimentally or mathematically based methods to predetermine the as- quenched strength and. appropriate quenching facilities and quenching media. Quenching media include pressurized water streams, water containing various additives, and liquid nitrogen. Figure 9.52 shows a que nching chamber