• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2003.10a
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• pp.97-99
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• 2003

In order to confirm the possibility of application of laser welding process to 2.25Cr-1Mo steel, the characteristic of residual stress distribution in welds by SMAW and $CO_{2}$ Laser welding process have been investigated and compared using the numerical analysis. As the Result of the numerical analysis, the possibility of application of laser welding process has been found out in respect to the welding residual stress distribution and mechanical properties in welds.

• Proceedings of the KWS Conference
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• 2003.05a
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• pp.251-253
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• 2003

• Proceedings of the KWS Conference
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• 2003.05a
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• pp.247-250
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• 2003

• Journal of Welding and Joining
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• v.26 no.3
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• pp.37-44
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• 2008

Charpy V-Notch test is commonly used to evaluate fracture toughness. However, since the region to be evaluated is limited to bulk material due to the specimen size required, individual evaluation of micro-structures on weldment is very difficult. In this study, ASP(Advanced Small Punch) test was carried out to evaluate material degradation and fracture toughness on the B.M, W.M and each micro-structures of HAZ for X20CrMoV121 and 2.25Cr1Mo steels with artificial aging time. In addition, to evaluate fracture toughness and material degradation of B.M and W.M of X20CrMoV121 steels with aging times, CVN (Charpy V-notch) test was performed. And then the correlation between ASP and CVN test on X20CrMoV121 steels was obtained. Furthermore, through this correlation, material degradation property of each micro-region of the HAZ in weldment, which was impossible to be evaluated by the CVN test, can be estimated and determined.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.9 s.180
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• pp.2381-2386
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• 2000

Surface replication is playing an important role in the assessment of creep damage and remaining life of high temperature components. As the replication procedures, however, have not been standardized in domestic industry, its standardization is proposed in this study. For this purpose, the 2.25Cr-IMo steel was heat treated(5 min at 1,300 0C and oil quenched) to produce a simulated HAZ microstructure, and crept in air at 575 0C and under 120 MPa to produce artificial cavities. Then, the effect of surface preparation procedures on the quality of replicas was investigated using this sample. As a result, it was demonstrated that the presence of cavities may be observed readily or missed depending on the surface preparation procedures followed. Therefore it is essential to repeat three polishing/etching cycles at least in order to reveal cavitation damage accurately, even though it may be tedious or time-consuming.

• Journal of Ocean Engineering and Technology
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• v.19 no.1 s.62
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• pp.49-56
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• 2005

In spite of the merits of laser welding being able to obtain the high welding quality such as smaller width of melting and heat affected zone, smaller welding deformation and fine grains of weldment compared to arc welding, laser welding is mainly used in joining of thin steel parts of electronics industry. Laser welding is getting widely used in joining thick plate and special kinds of steel due to its high power. While the arc welding is still applied for 2.25Cr-1Mo steel which is the essential material of atomic power generation equipment, the laser welding is not yet applied despite its high quality. So it has a trial to a special case demanding high welding quality such as atomic power plant. Accordingly, in this research, the mechanical properties of weldments by arc and laser welding were investigated using FEM to confirm the applicability of laser welding to 2.25Cr-1Mo steel. The Charphy test was carried out to understand the effect on the fracture toughness of weldments. The results of examination and test of the mechanical properties showed the validity of this research.

• Journal of the Korean Society of Safety
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• v.12 no.2
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• pp.45-56
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• 1997

Fracture behavior of ex-serviced 1Cr-0.5Mo steel was measured at room($24^{\circ}C$) and elevated($538^{\circ}C$) temperature and compared with that measured with virgin 1Cr-0.5Mo steel. Compact C(T) specimens were machined from the base and welded test materials. In case of the C(T) specimens of the weld, fatigue precrack was introduced along the fusion line so that following crack growth should occurs along the region of heat affected zone. It was observed that the J-R curve of the serviced material was significantly lower than that of the virgin material at room temperature. Brittle fracture was observed in the serviced material. On the other hand, at elevated temperature no noticeable difference was found between the J-R curves of the virgin and the serviced material. The measured J-R curves were also compared with those of the 1.25Cr-0.5Mo steel obtained from the other literatures. Optical microscopy and SEM examination of the serviced material reveal the carbide in/along the grain boundary which shows material degradation due to long-term usage. An example of application of the measured J-R curves is shown.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.5
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• pp.1372-1381
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• 1996

As recieved boiler tuve steel was aged artificially at $650^{\circ}C$ and$690^{\circ}C$ for various time duration to simulate the material deterioration which could be occurred during the operation of fossiol power plants. And the tensile tests, the microhardness tests and the characterization of carbides formed in the aging process were performed to asses the relationship between the mechanical properties and the effect of thermal aging. Furthernore, the amout of Mo-rich carbide were investigated by ondestructive method by noticing the fact that formation of Mo-rich carbide were investigated by ondestructive melthod by noticing the fact that formation of Mo-rich carbides($Mo_6C$) which stabilizes lastly affects the mechanical properties. It was known that the microhardness results of service exposed materials were similar to the ones which are aged at $650^{\circ}C$. The room temperature measurement showed small variation in the yield points and ultimate strength in materials aged at $650^{\circ}C$. Those properties at $540^{\circ}C$ showed the abrupt decrease compared with as received material even if short aging time. And it was found that $650^{\circ}C$ $690^{\circ}C$ aging cause different effects on mechanical properties, although the temperature time parameters(LMP;Larson-Miller parameter) are same. And it was concluded that the aigng at $650^{\circ}C$ is more appropriate to simulate the service exposed condition. Finally, the relationship between high temperature tensile properties and Ip values were established, which offers a potential way of reliability tests onthe power plant components.

• Journal of the Korean Society for Nondestructive Testing
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• v.19 no.6
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• pp.411-419
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• 1999

It has been well recognized that a long term service at elevated temperature of $350^{\circ}C{\sim}550^{\circ}C$ induces embrittlement damage due to carbide precipitation and/or P, Sb and Sn segregation at grain boundaries and thereby deteriorates the grain boundary strength of heat resisting components in the energy-related plants. Therefore, it is very important to assess quantitatively the extent of embrittlement damage of heat resisting components to secure the reliable and efficient service condition and to prevent brittle failure in service. However, because fracture tests are limited in size and number of specimen obtained from the structural components, nondestructive test method is required. In this study, the optimum electrochemical parameters are investigated and discussed to evaluate nondestructive embrittlement damage for aged 2.25Cr-1Mo steels by means of electrochemical polarization test method (ECPTM) in proper corrosive environment. In addition, the electrochemical test results are compared with embrittlement degree evaluated by semi-nondestructive SP test.

• Journal of the Korean Society for Nondestructive Testing
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• v.25 no.5
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• pp.377-383
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• 2005

Because explosive fluid is used at high temperature or under high pressure in petrochemistry and refined oil equipment, the interest about safety of equipments is intensive. Specially, the safety of high pressure reactor vessel is required among them. The material selected in this study is 2.25Cr-1Mo steel that is widely used for high pressure reactor vessel material of petrochemical plant. Eight kinds of artificially aged specimens were prepared by differing from aging periods under three different temperatures. The material was iso-thermally heat treated at higher temperatures than $391^{\circ}C$ that is the operating temperature of high pressure reactor vessel. Vickers hardness properties and electrical resistivity properties about artificially aged material as well as un-aged material were measured, and master curves were made out from the correlation with larson-Miller parameter. And electrical resistivity properties as well as Victors hardness properties measured at high pressure reactor vessel of the field were compared with master curves made out in a laboratory. Degradation evaluation possibility in the field of high pressure reactor vessel by using electrical resistivity method was examined. Electrical resistivity property measured in the field is similar with that of artificially aged material in similar aging level.