Effect of heat treatment

Recently published laboratory creep studies22 have shown that the rupture strength and rupture ductility of 2.25Cr-lMo steel are diminished when tested in hydrogen as compared to their values in air. These tests were a continuation of previously-reported tests23, 25 that showed somewhat conflicting results in shorter term tests. 

Annealed samples (0 percent strain) had an incubation period followed by a decrease in specific gravity. Steels with 5 percent strain had shorter incubation periods, and specific gravity decreased at a more rapid rate. Steels with 39 percent strain showed no incubation period at any test temperature, indicating that fissuring and cracking started immediately upon exposure to hydrogen. 

These tests are considered significant in explaining the cracks sometimes found in highly stressed areas of an otherwise apparently resistant material. In addition, Cherrington and Ciuffreda27 have emphasized the need for removing notches (stress concentrators) in hydrogen service equipment. 

Both industry experience and research work indicate that postweld heat treatment (PWHT) of chromium-molybdenum steels in hydrogen service improves resistance to high temperature hydrogen attack. The PWHT stabilizes alloy carbides. This reduces the amount of carbon available to combine with hydrogen, thus improving high temperature hydrogen attack resistance. 

The user must balance the advantages of high PWHT temperatures with other factors, such as the effect upon strength and notch toughness. Note higher PWHT temperatures can affect the ability to meet ASME Code Class 2 strength requirements. 

Under this category, three different variables are considered heating rate, as well as time and temperature of heat treatment. These parameters affect the activation process independently of the activating agent (KOH or NaOH) and the precnrsor used. 

The effect of soaking time can be seen in Table 1.4, corresponding to the activation process of an anthracite using KOH (experimental conditions KOH/ anthracite, 2/1 (weight) activation temperature, 700°C flow rate, 800 mL/min  

FIGURE 1.12 (a) Nj adsorption isotherms corresponding to samples prepared from 

Porosity characterization for chemically activated carbons prepared from anthracite with NaOH activation by impregnation and physical mixing (5°C/min, 500 mL/min, 700°C, 1 h) 

FIGURE 1.13 Comparison of the micropore volumes calculated from N2 adsorption at 77 K for different ACs prepared by NaOH, using either impregnation or physical mixing method and different NaOH/anthracite ratios (redrawn from Lillo-Rodenas, M.A., Lozano-Castelld, D., Cazorla-Amords, D., and Linares-Solano, A. Carbon 39(5) 751-759, 2001. With permission). 

---

Table 1. Effect of Heat Treatment on Tensile Properties of Al—4.5% Cu ...

Shin, S,. Jang, J., Yoon, S. H. and Mochida, I., A study on the effect of heat treatment on functional groups of pitch-based activated carbon fiber using FTIR, Carbon, 1997,35(12), 1739 1743. 

Effect of heat treatment on heat-treatable aluminum alloys. 89... 

Streicher, M. A., Effect of Heat Treatment, Composition and Microstructure on Corrosion of 18Cr-8Ni-Ti Stainless Steel in Acids , Corrosion, 20, 57t (1964)... 

Steiner, A., Effect of Phosphorous Level on General and Intercrystalline Corrosion in 18/8 Type Steel , Pr. Inst. Hutn., 24, 255 (1972) C.A., 80, 6185n Anisimova, M. S. and Chikurova, A. A., Effects of Heat-treatment Conditions and Structure of Khl8N9TL Cast Steel on its Susceptibility to Intercrystalline Corrosion , Optimiz Met. Protsessov, 6, 163 (1972)... 

Funamoto, Y. et al.. Effects of heat treatment on chlorophyll degrading enzymes in stored broccoli (Brassica oleracea L.), Postharvest Biol.TechnoL, 24, 163, 2002. 

Effect of heat treatment on PG inhibitor activity Suitable aliquots of D. maculata stem inhibitor were kept in a boiling water bath for various periods of time, cooled quickly and assayed for residual PG inhibitory activities. 

Effect of heat treatment on PG inhibitor of D. maculata stem. 

Zhang L, Lee K, Zhang JJ. 2007. The effect of heat treatment on nanoparticle size and ORR activity for carbon-supported Pd-Co alloy electrocatalysts. Electrochim Acta 52 3088-3094. 

A4. R. Chiba, K. Ohnishi, K. Ishii, and K. Maeda, Effect of Heat Treatment on the Resistance of C-0.5Mo Steel Base Metal and Its Welds to Hydrogen Attack, 1985 Proceeding, Refining Department, Volume 64, American Petroleum Institute, Washington, D.C., pp. 57-74. 

Cho, S.B., Nakanishi, K., Kokubo, T., Soga, N., Ohtsuki, C., Nakamura, T., Kitsugi, T. and Yamamuro, T. (1995) Dependence of apatite formation on silica gel on its structure effect of heat treatment Journal of the American Ceramic Society, 78, 1769—1774. 

Chen, Q., Miyata, N., Kokubo, T. and Nakamura, T. (2001) Effect of heat treatment on bioactivity and mechanical properties of PDMS-modified Ca0-Si02-Ti02 hybrids via sol-gel process. Journal of Materials... 

No single volume could contain the complete description of the composition, properties, and structures of ferrous alloys. Further, the effect of heat treatment and other methods of changing the properties of alloys constitutes an entire science unto itself. Accordingly, the description given of ferrous metallurgy will be only an overview of this enormously important area. 

Wang CY. 2000. Effect of heat treatment on postharvest quality of kale, collard and Brussels sprouts. Acta Hort 518 71-78. 

Table I. Effect of Heat Treatment Temperature (HTT) on Chemisorption of Oxygen... 

Jimenez-Gonzalez, A. Suarez-Parra, R. 1996. Effect of heat treatment on the properties of ZnO thin films prepared by successive ion layer adsorption and reaction (SILAR)./. Cryst. Growth 167 649-655. 

Fate of plant viruses after a soil solarization treatment was almost completely ignored by researchers, as only one study documented a stabilizing effect of heat treatment on tobacco mosaic virus degradation in a sandy loam soil (Triolo and Materazzi 1992). 

W.G. Haines and H.R. Bube, Effects of heat treatment on the optical and electrical properties of indium-tin oxide films, J. Appl. Phys., 49 304—307, 1978. 

One final test was conducted on a heat treated sample to elucidate the effect of heat treatment and sensitization on the fracture behavior of this steel. A CF sample was heated for 24 hours at 650°C to see if the fracture mode would continue to change with an even larger amount of carbide precipitation. Note in Figure 15-a this heavily sensitized steel has a fracture appearance that is completely dominated by small microvoids associated with carbides. The bimodal distribution of microvoids like those in Figure 7 has been eliminated. In fact, the fracture appearance is remarkably similar to that of the tritium-exposed-and-aged steels albeit at a different magnification (Figure 15-b). It appears that carbides in the microstructure affect the fracture mode in a similar manner as the decay helium bubbles but on a different scale. 

In a study of the effect of heat treatment upon the durability of spruce and larch heated at 200 °C in a vacuum, both spruce and larch exhibited good resistance to decay by G. trabeum, but treated spruce exhibited a decay mass loss of 9 % compared to 1 % with larch against C. puteana in an 8-week mini soil block test (Rep etal, 2004). 

Hirai, N., Sobue, N. and Asano, I. (1972). Studies on piezoelectric effect of wood. IV. Effects of heat treatment on cellulose crystaUites and piezoelectric effect of wood. Mokuzai Gakkaishi, 18(11), 535-542. 

Lin, R.T. (1969). Effect of heat treatment on some properties of Douglas-fir. Wood Science, 2(2), 112-119. 

Viitanen, H., Jamsa, S., Paajanen, L., Nurmi, A. and Viitaniemi, P. (1994). The effect of heat treatment on the properties of spruce. A preliminary report. International Research Group on Wood Preservation, Doc. No. IRGAVP 94-40032. 

Yun, K.-E., Kim, G.-H. and Kim, J.-J. (1999). Effect of heat treatment on the dimensional stability and bending properties of radiata pine sapwood. Journal of Korean Wood Science and Technology, 27(4), 30-37. 

Lurrie, S., Fallik, E., and Klein, J. D., 1996, The effect of heat treatment on apple epiculticular wax and calcium uptake. Postharvest Biology and Technology 8 271-277. 

---