Quasi-isothermal forging method of nickel-based superalloy
Application number/patent number:? 2003 10 103692
Forging a forging blank (56) of an malleable nickel-based superalloy in a forging press (40) with forging dies (52, 54), wherein the forging dies (52, 54) are made of nickel-based superalloys used for dies. Heating a forging blank (56) to a forging blank starting temperature of about1850 f to about1950 f, heating forging dies (52, 54) to a forging die starting temperature of about1500 f,
Hungary's comments on traditional and quasi-isothermal and quasi-isobaric synchronous thermal analysis methods also mentioned that "quasi-isothermal" is a temperature range.
The concept of "quasi-isothermal" is also used in "temperature modulated differential scanning calorimetry (TMDSC)";
In recent years, a new method called "temperature modulated differential scanning calorimetry (TMDSC)" claims that the temperature-related process can be separated from the time-related process. The basic idea is to change the traditional linear uniform heating method into time uniform heating method, and at the same time superimpose an instantaneous sinusoidal modulated thermal signal. The combination of the two results is equivalent to superimposing random temperature pulses (sawtooth waves) with different periods on the quasi-isothermal or dynamic heating (cooling) program. In this way, two experiments were carried out on the sample system (sample and reference) at the same time: one is equivalent to DSC under traditional heating mode, and the other is under faster sinusoidal modulation heating. The experimental results show that (1) slow heating rate improves the spectral peak resolution; The rapid instantaneous heating rate improves the sensitivity.
TMDSC is well reflected in the research and application of polymer samples:
Cebe's review focuses on the new in-depth understanding of polymer melting and glass transition, which is obtained through the progress of temperature modulation DSC and ultra-microcalorimetry. This technology can be used to study its thermal performance under quasi-isothermal conditions (zero heating rate) and rapid heating conditions (heating rate of several thousand degrees per second). Wunderlich speculated that the crystallization ability of macromolecules is closely related to whether they are in the large-size conformation of extended chain or folded chain. Because the same macromolecule may have these two conformations, it can be proved that there are two independent processes of irreversible melting and reversible melting, which are related to the large conformation of extended chain and folded chain respectively. Quasi-isothermal temperature modulation DSC is considered as a powerful tool to detect this phenomenon. In particular, Qiu et al.' s DSC study on temperature modulation of polyoxyethylene shows that its ideal chain extension and molar mass are 1 100? In fact, the melting of mono-folded or bi-folded crystals of oligomers above Da is completely irreversible, while the folded chain crystals with large molar mass show some local reversible melting. Minakov et al. discussed the reason for the multi-peak melting of DSC curve observed for polyethylene terephthalate. In this study, they used a microcalorimeter, which can heat up quickly. It is inferred from the results that when the heating rate is 2700Ks- 1, the melting-recrystallization-remelting process which is usually observed does not occur, but only the melting process occurs. ?
Temperature modulated DSC (TMDSC) is usually used to study the thermal effects of overlap, which can be applied not only to universities or research institutes, but also to industrial research. The TMDSC method can separate the temperature-related process from the time-related process.
The basic idea of temperature modulation DSC (TMDSC) is to superimpose random temperature pulses with different periods on isothermal or dynamic temperature programs. At present, the common method in TMDSC technology is to superimpose sine temperature modulation on isothermal or heating program. In contrast, Topem &；; Reg is a new and advanced multi-frequency temperature modulation technology, which uses many different frequencies (multi-frequency). TMDSC has three basic parameters: basic (average) heating rate, sinusoidal modulation period and modulation temperature range. For example, the sample is polyester (PET), and its TMDSC spectrum uses the following test conditions: the basic heating rate is 2 ℃/ min, the modulation period is100s, and the modulation amplitude is 1℃. ..
The advantages of temperature modulation DSC technology (TMDSC) are:
1. One-time test: simultaneously test two functions of sample properties changing with time or temperature in a wide frequency range.
2. Measuring specific heat capacity cp from impulse response: Measuring quasi-steady specific heat capacity very accurately.
3. Synchronous high sensitivity and high resolution: low-energy transition test and/or overlapping temperature-related effect test can be carried out.
4. Separation of reversible process and irreversible process: Heat capacity can be measured very accurately, even in the case of overlapping effect.
5. Simplified curve analysis: frequency-related effects (such as glass transition) and non-frequency-related effects (such as water loss) can be easily separated.
6. Expand PEM technology-eliminate instrument influence and expand test frequency range.
With the help of frequency information, you can easily distinguish frequency-related effects from frequency-independent effects. This greatly simplifies the analysis of spectral curves of samples with overlapping thermal effects. At the same time, the temperature modulation DSC (TMDSC) technology can measure the quasi-steady specific heat independent of frequency. ?
In the attached drawings, the uppermost figure is a schematic diagram of the heating mode of TMDSC.