Fushun Special Equipment Supervision Test Institute

Fushun, China

Fushun Special Equipment Supervision Test Institute

Fushun, China
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Hu C.-S.,Liaoning University | Qin H.,Liaoning University | Ma X.-L.,Liaoning University | Zhu J.,Fushun Special Equipment Supervision Test Institute
Shiyou Huagong Gaodeng Xuexiao Xuebao/Journal of Petrochemical Universities | Year: 2012

Through SEM observation, EDS analyses, the effect of dual thermal cycle on microstructure of 2.25Cr1Mo steel was analyzed. The results show that dual thermal cycle results in the formation of bainite. However, grain boundary of coarse prior austenite resulted from first thermal cycle does not become finer and still appears to maintain the original forms of it even though subjected second thermal cycle. EDS analyses indicate that micro zone composition are uniformly distributed which means that austernitizing homogenization is completed more sufficiently after subjected second thermal cycle. Micro zone Cr content of granular structure increases compared with matrix. It is assumed that carbides mainly composed of Fe, Cr element are formed among granular structure.


Hu C.-S.,Liaoning University | Qin H.,Liaoning University | Ma X.-L.,Liaoning University | Zhu J.,Fushun Special Equipment Supervision Test Institute
Dongbei Daxue Xuebao/Journal of Northeastern University | Year: 2012

By use of LSCM, the specimen of 2.25Cr1Mo0.25V steel was treated with a designed thermal cycle curve of 1000°Cpeak temperature and 500s holding time. The phase transformation of the specimen subjected to the thermal cycle of heating and continuous cooling was observed in situ and in real time. Meanwhile, the microstructure after cooling was analyzed through SEM. The results indicate that phase transformation upon cooling occurs at the temperature range of bainite formation. The initial phase bainite begins to separate out along the austenitic boundary at 510°C and finishes at 455°C. Although the actual specimen temperature reaches 1085°C and the holding time lasts 2.5 s in the thermal cycle, with holding time as long as 60 s and temperature higher than 1 000°C, fine bainite can be obtained with a designed thermal cycle for the reason that undissolved carbides prevent grains from growing when temperature rises.


Hu C.-S.,Liaoning University | Qin H.,Liaoning University | Zhu J.,Fushun Special Equipment Supervision Test Institute | Zhao Z.-X.,Fushun Special Equipment Supervision Test Institute
Dongbei Daxue Xuebao/Journal of Northeastern University | Year: 2012

Through chemical composition analysis, metallographic observation and fracture morphology analysis, the causes of valve stem nut fracture in shut-off valves were explored. The main alloy elements of valve stem nut are up to the chemical composition standards of aluminum brass and the microstructures are composed of α+precipitated phases. An analysis of fracture morphology shows that sliding deformation perpendicular to trans-crystalline fracture path near the inner wall can be observed. Fracture near the inner wall of valve stem nut is flat and smooth, whose surface is covered with oily substance, confirming that there are initial cracks on valve stem nut. The existence of initial cracks brings about larger stress concentration, likely to cause cracks and crack propagation. When screw nuts are subjected to a larger load when valves are in operation or seal, fracture occurs due to a sudden increase of stress on the changed diameter sections of valve stem nut.


Wang H.-Z.,Liaoning University | Hu C.-S.,Liaoning University | Pan X.-L.,Fushun Special Equipment Supervision Test Institute | Liang P.,Liaoning University | And 2 more authors.
Shiyou Huagong Gaodeng Xuexiao Xuebao/Journal of Petrochemical Universities | Year: 2011

To study the corrosion of Ni-Cu-P electroless coating in different concentrations HF solution, surface morphology of Ni-Cu-P coating was analyzed by metalloscope graphic. The corrosion resistance of Ni-Cu-P coating was tested by soaking method and electrochemical impedance spectroscopy testing in different concentrations HF solution. The results show that Ni-Cu-P coating is uniform, dense and has good corrosion resistance in HF solution. With the increase of HF concentration, the corrosion rate of the coating appears to increases then decreases in different concentrations of HF solution.

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