Restoration of elevated temperature tensile strength in 2.25Cr-1Mo steel

Wada, Tsunemi; Blšs, V. A.

doi:10.1007/bf02644287

Cited by 20 publications

(10 citation statements)

References 7 publications

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“…2 for comparison. The fact that the 0.28% of Mo was dissolved in the matrix reported by Wada and Biss 4) confirmed the similarity to present results. Figure 3 shows the results of X-ray diffraction analysis of electrolytically extracted carbides.…”

Section: Microstructure and Mechanical Propertysupporting

confidence: 92%

“…Comparing the results of diffraction pattern analysis of several carbides with their composition, it was found that carbides had distinct composition depending on the type of carbide such as Cr rich M 23 C 6 , Mo rich M 6 C, Mo 2 C (M 2 C), Fe 3 C (M 3 C). [3][4][5] Gope et al 6) and Watanabe and Shoji 7) reported an increase in M 6 C carbide, which had been previously reported by Baker and Nutting 8) to be a stable carbide, in thermally degraded 2.25Cr-1Mo steel. The increase of Mo rich M 6 C in Cr-Mo type of low alloy steel is reported to cause irreversible carbide-induced embrittlement.…”

Section: Introductionmentioning

confidence: 95%

“…As aging time increased the amount of Mo dissolved in the matrix decreased to about 0.3% (46% of the total amount of Mo), the remaining 0.67% is thought to be combined to the carbides. The result of Wada and Biss, 4) who reported depletion of Mo in 2.25Cr-1Mo steel used on site for about 100000 hours at 500 to 570 C, was also plotted in Fig. 2 for comparison.…”

Section: Microstructure and Mechanical Propertymentioning

confidence: 99%

“…In order to simulate the typical microstructure of the rotor steel in service at 540 C for about 20 years, an accelerated isothermal heat treatment 3) was performed at 630 C for up to 4800 hours. 4) a specimen in a solution of 90% methanol and 10% hydrochloric acid was subjected to a voltage of 3 volts. After selectively dissolving the matrix, the remaining residue (carbide) was separated for X-ray diffraction analysis.…”

Section: Materials and Heat Treatmentmentioning

confidence: 99%

“…[1][2][3][4][5][6][7] In order to evaluate the microstructural degradation of CrMo type steel arising from long time exposure to high temperature, composition [3][4][5] or morphology 6) analysis of carbides has been performed to identify the different kind of carbides. Comparing the results of diffraction pattern analysis of several carbides with their composition, it was found that carbides had distinct composition depending on the type of carbide such as Cr rich M 23 C 6 , Mo rich M 6 C, Mo 2 C (M 2 C), Fe 3 C (M 3 C).…”

Section: Introductionmentioning

confidence: 99%

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Nondestructive Evaluation of Thermally Degraded 2.25Cr-1Mo Steel by Electrical Resistivity Measurement

Byeon

Kwun

2003

Mater. Trans.

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An attempt was made to evaluate nondestructively the degradation of thermally aged 2.25Cr-1Mo steel by electrical resistivity measurement. Artificial aging was performed to simulate the microstructural changes in 2.25Cr-1Mo steel arising from long time exposure at 540 C. Microstructural parameter (amount of dissolved Mo in the matrix), mechanical property (ductile-brittle transition temperature) and electrical resistivity were measured to investigate the relationship among these parameters. Both the amount of dissolved Mo and the electrical resistivity decreased rapidly in the initial 1000 hours of aging and then changed little thereafter. On the other hand, the ductile-brittle transition temperature (DBTT) increased rapidly in the initial stage of aging and then saturated afterward. Electrical resistivity was found to have linear correlation with the amount of dissolved Mo and DBTT, respectively. Electrical resistivity was suggested as a potential nondestructive evaluation parameter for assessing DBTT of the thermally degraded 2.25Cr-1Mo steel.

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Section: Microstructure and Mechanical Propertysupporting

confidence: 92%

Section: Introductionmentioning

confidence: 95%

Section: Microstructure and Mechanical Propertymentioning

confidence: 99%

Section: Materials and Heat Treatmentmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Nondestructive Evaluation of Thermally Degraded 2.25Cr-1Mo Steel by Electrical Resistivity Measurement

Byeon

Kwun

2003

Mater. Trans.

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Carbide transformations in Cr−Mo steels in the process of long-term aging and operation

1997

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Chromium-molybdenum steels are widely used in machine-building as a material for pipes for different purposes. They operate at elevated temperatures for long durations and undergo structural changes that can worsen their mechanical properties. For this reason, it is interesting to study their structural changes as a function of the temperature and time of aging or operation in order to determine the regular features of the redistribution of the alloying elements in the process of phase transformations. The given work is devoted to carbide transformations in steels with different contents of chromium and molybdenum in the process of aging after heat treatment and in the process of long-term operation in industrial installations.The nature of carbide reactions as a function of the content of the alloying elements, the regimes of heat treatment, and long-term operation of Cr-Mo-V steels have been considered in [1,2].The present work is devoted to the results of a study of Cr-Mo steels (Table 1 ).These steels are commonly used after a heat treatment that consists of quenching or nonJaalizing followed by tempering in a temperature range of 700 -750~ or after annealing.We studied the carbide transformations in steels after aging at 450 -600~ Before the aging the specimens were subjected to a preliminary heat treatment using various regimes. Specimens 20 x 20 • 80 mm in size after a hold at 960-1000~ were cooled in water, in air, and in the furnace. The use of different cooling media made it possible to imitate the possible range of cooling rates of industrial parts. The study after a long-term operation was conducted for specimens cut from parts that have operated for various times.The carbide transformations were studied by the method of phase analysis. The carbides were isolated from the matrix by an electrochemical method in an electrolyte based on methanol. The obtained TABLE 2 powders were studied by the method of x-ray diffraction analysis in cobalt K,~-radiation. The amount and the composition of the carbides I5 were determined by a chemical analysis of the 100 precipitates. 1000 Steel 12MKh. In this steel the formed carbides can be of three types, namely, cementite M3C based on iron, carbide of M2C type based on molybdenum, and a composite cubic carbide of M23C 6 type. The proportion of the carbides in the steel varies with the aging conditions and the rate of preliminary cooling from the y-region, which can be seen clearly from the data of Table 2.The type of molybdenum carbides segregating in the aging process depends on the cooling rate in the preliminary heat treatment. After a rapid cooling the main result of the

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Effect of long-term service exposure on microstructure and mechanical properties of a crmov steam turbine rotor steel

1991

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Restoration of elevated temperature tensile strength in 2.25Cr-1Mo steel

Cited by 20 publications

References 7 publications

Nondestructive Evaluation of Thermally Degraded 2.25Cr-1Mo Steel by Electrical Resistivity Measurement

Nondestructive Evaluation of Thermally Degraded 2.25Cr-1Mo Steel by Electrical Resistivity Measurement

Carbide transformations in Cr−Mo steels in the process of long-term aging and operation

Effect of long-term service exposure on microstructure and mechanical properties of a crmov steam turbine rotor steel

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