Time-temperature diagram

VanderVoort, G. Atlas of Time-Temperature Diagrams for Nonferrous AUoys, ASM International, Materials Park, OH, 1991. 

Vender Voort G F (ed) Atlas of time-temperature diagrams for irons and steels . ASM, 1991. 

The susceptibility to intergranular corrosion of a chemically resistant steel depends on the carbon content, the duration of the sensitizing temperature, and the temperature of prior solution annealing, it is represented in a time-temperature diagram. Curves of this type are shown in Fignre 20.26 for an austenitic steel with approximately 18% chromium, 8% nickel, and various carbon contents. The curve encompasses the respective area of susceptibility. 

The reader is urged to reread the first 11 pages of this chapter concerning the inevitable discontinuous operation of continuous furnaces, the costly consequences thereof, and the necessary design corrections. Chapter 8 includes original and corrected time-temperature diagrams from an actual case. 

The temperature resulting from this type of on-off control will be fluctuating around the setpoint. The frequency and amplitude of the temperature fluctuations will be determined by the thermal lag of the particular machine. A problem of on-off control is the possible effect of process disturbances and electrical noise Interference, which can cause the output to cycle rapidly as the temperature crosses the setpoint. This condition can be detrimental to most final control elements such as contactors. To prevent this, an on-off differential or hysteresis is added to the controller function. This function requires that the temperature exceed the setpoint by a certain amount (half the differential) before the output will turn on again. Hysteresis will prevent the output from chattering if the peak-to-peak noise is less than the hysteresis. The amount of hysteresis determines the minimum temperature variation possible. However, process characteristics will add to this differential. Figure 4.23 shows a time-temperature diagram for an on-off controller with hysteresis. 

G. Vander Voort Atlas of Time Temperature Diagrams, Vol. 1, 2 (ASM, Materials Park 1991)... 

The susceptibility to intergranular corrosion depends on the carbon content of the alloy and the duration and temperature of sensitizing. A typical time-temperature diagram for austenitic steel containing 18% Cr, 8% Ni and different carbon contents is shown in Fig. 1-7 (Rocha, 1962). The lines encompass the beginning of the susceptibility for intergranular attack. 

Figure 5.236 Time-temperature diagram of the embrittiement of soft rubber mixtures with a Shore hardness of 50 [795]...

Carr et al. 32] have produced a time-temperature diagram (Fig. 2) for the embrittlement of the steel SAE 3140. The diagram indicates that heat-treating to temperatures between. 500 and 550°C for times between 1 and 100 h produces... 

A, austenite B, bainite F, proeutectoid ferrite M, martensite P, pearlite. (Adapted from Atlas of Time-Temperature Diagrams for Irons and Steels, G. F. Vander Voort, Editor, 1991. Reprinted by permission of ASM International, Materials Park, OH.)... 

Fig. 1.11. Time-temperature diagram of the mechanical properties of PVC (after Retting [22]). 8...

A molten metal alloy would normally be expected to crystallize into one or several phases. To form an amorphous, ie, glassy metal alloy from the Hquid state means that the crystallization step must be avoided during solidification. This can be understood by considering a time—temperature—transformation (TTT) diagram (Eig. 2). Nucleating phases require an iacubation time to assemble atoms through a statistical process iato the correct crystal stmcture... 

Fig. 2. Time—temperature—transformation (TTT) diagram where A represents the cooling curve necessary to bypass crystallization. The C-shaped curve separates the amorphous soHd region from the crystalline soHd region. Terms are defined ia text.

Alternative representations of stream temperature and energy have been proposed. Perhaps the best known is the heat-content diagram, which represents each stream as an area on a graph (3) where the vertical scale is temperature, and the horizontal is heat capacity times flow rate. Sometimes this latter quantity is called capacity rate. The stream area, ie, capacity rate times temperature change, represents the enthalpy change of the stream. 

Figure 6.4 The time-temperature-transformation diagram of the iron-carbon system, beginning at the composition of austenite...

Fig. 8.5. The diffusive f.c.c. —> b.c.c. transformation in iron the time-temperature-transformation (TTT) diagram, or "C-curve". The 1% and 99% curves represent, for oil practical purposes, the stort and end of the transformation. Semi-schematic only.

Sketch the time-temperature-transformation (TTT) diagram for a plain carbon steel... 

Fig. 3.21 Temperature-time-sensitisation diagrams for three austenitic Cr-Ni steels solution treated at 1 0S0°C. The curves enclose the treatments causing susceptibility to intercrystalline corrosion in a boiling CUSO4 -F H2SO4 test reagent...

Time-temperature-transformation (T-T-T) diagrams are used to present the structure of steels after isothermal transformation at different temperatures for varying times. The T-T-T diagram for a commercial eutectoid steel is shown in Fig. 20.48a. Also shown on the curves are the points at which the microstructures illustrated in Figs. 20.46 and 20.47 are observed, and the thermal treatments producing these structures. When a steel partially transformed to, say, pearlite, is quenched from point a in Fig. 20.48a to below nif, the untransformed austenite transforms to martensite. 

Aronhime, M. T., Gillham, J. K. Time-Temperature Transformation (TTT) Cure Diagram of Thermosetting Polymeric Systems. Vol. 78, pp. 81 — 112. 

Figure 11 Example of time-temperature transformation (TTT) diagram. (Increasing time in vertical direction). Reprinted from Roller and Gillham [4], published by the Federation of Societies for Coatings Technology, with permission of publisher.

The most important data during main drying is the temperature at the moving sublimation front which cannot be measured by Ths or RTDs. In 1958, Neumann and Oetjen 11.651 showed that the barometric temperature measurement (BTM) measures exactly this data. In Fig. 1.77 this is schematically shown if the drying chamber is separated from the condenser by a valve for a short time the pressure in the chamber rises to the saturation vapor pressure (ps) corresponding to the temperature of the sublimation front. ps can be converted into the ice temperature by the water vapor- temperature diagram (e. g. 0.3 mbar = -30 °C). Data for accurate conversion are given in Table 1.11 the temperatures between -100 and -1 °C. 

Time-temperature-transformation (TTT) diagram, 70 422-423 diagram(s), 72 567, 23 278 Timet, titanium contract with Boeing, 24 846... 

Characteristics and implementation of the treatments depend on the expected results and on the properties of the material considered a variety of processes are employed. In ferrous alloys, in steels, a eutectoid transformation plays a prominent role, and aspects described by time-temperature-transformation diagrams and martensite formation are of relevant interest. See a short presentation of these points in 5.10.4.5. Titanium alloys are an example of the formation of structures in which two phases may be present in comparable quantities. A few remarks about a and (3 Ti alloys and the relevant heat treatments have been made in 5.6.4.1.1. More generally, for the various metals, the existence of different crystal forms, their transformation temperatures, and the extension of solid-solution ranges with other metals are preliminary points in the definition of convenient heat treatments and of their effects. In the evaluation and planning of the treatments, due consideration must be given to the heating and/or cooling rate and to the diffusion processes (in pure metals and in alloys). 

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