熱處理外文翻譯--不同熱處理電站鍋爐碳鋼省煤器管飛灰顆粒侵蝕速率的實(shí)驗(yàn)研究（英文）

1、 International Journal of Minerals, Metallurgy and Materials Volume 16, Number 5, October 2009, Page 534 MaterialsCorresponding author: S. Suresh, E-mail: ssuresh@nitt.edu Also avail

2、able online at www.sciencedirect.com © 2009 University of Science and Technology Beijing. All rights reserved. Experimental studies on the erosion rate of different heat treated carbon steel economiser tubes of po

3、wer boilers by fly ash particles T.A. Daniel Sagayaraj1), S. Suresh2), and M. Chandrasekar3) Department of Mechanical Engineering, National Institute of TechnologyTiruchirappalli-620 015, Tamil Nadu, India (Received 2008

4、-10-23) Abstract: The experimental investigations on the effect of the fly ash particle size, velocity, impingement angle, and feed rate were done with an emphasis on the effect of erosion on annealed SA 210 GrA1 (A) and

5、 normalized SA 210 GrA1 (N) carbon steel econo-mizer-tube materials. Erosion rates were evaluated with different impingement angles ranging from 15° to 90°, at four different ve-locities of 32.5, 35, 37.5, and

6、40 m/s, and at four different feed rates of fly ash particles of 2, 4, 6 and 8 g/min. The erodent used was fly ash particles, sizes ranging from 50-250 μm of irregular shapes. Erosion rate is found to be the maximum at t

7、he impingement an-gle of 30°. Erosion rates of the carbon steel tube in different heat treatment conditions, annealed and normalized, at a constant veloc-ity of 32.5 m/s with different angles were studied. In all ca

8、ses of feed rates, impingement angles, particle sizes, and velocities of fly ash particles, it has been found that the erosion rate of the annealed tube is less than that of the normalized tube. Empirical correla-tions f

9、or erosion rate relating the velocity, size, feed rate, and impingement angle of the particles and elongation property of the target materials were arrived. Morphologies of the eroded surface were examined by scanning el

10、ectron microscope (SEM). Key words: erosion rate; economiser tubes; annealing; normalizing 1. Introduction In large coal fired power stations, pulverized coal is burnt in the burners of boilers. To improve the overall

11、thermal efficiency of the boiler plant, heat exchangers are used to extract residual heat energy from the flue gas and to transfer it to the feed water flowing through the tubes by the process of conduction and convec

12、tion. In coal fired power stations, about 20% of the ash produced in the boilers is deposited on the boiler walls and the superheater tubes. The rest of the ash is en- trained in the stream of flue gas leaving the boi

13、ler. The ash particles collide with the surface of the economiser coil tubes and the material is eroded from the surfaces. In the advanced stage of erosion, the tubes become perforated. The tube elements fail once t

14、hey cannot maintain their structural integrity. Such erosion shortens the service life of the tubes. Once this happens, the power plant has to be shut down and has to incur losses. Erosion is a mechanical damage resul

15、ting in re- moval of the material from the surface by impact of particles. Earlier the mechanism behind this was be-lieved due to the micro cutting mechanism [2]. Later it was proved that for ductile materials, the ero

16、sion mechanism involves the sequential plastic deforma- tion process of platelet formation and crater formation due to forging and extrusion [3]. Through many studies and experiments done on the erosion of boiler tub

17、es, it is estimated that 25%-30% of boiler tube failure occurs due to the ash erosion. Levy et al. [3] demonstrated that for the ductile mate- rial erosion rate is lower for the materials having higher ductility. Saty

18、anathan [1] showed that fly ash erosion is the major concern for almost one third of total tube failures. The major factors influencing the erosion process are the amount of ash particles, its velocity, and the desig

19、n conditions. Finnie et al. [2] developed an analytical model to find the erosion rate based on the assumption that the erosion mechanism was due to micro cutting. Later it was demonstrated by Levy et al. [3] that mi

20、cro cutting was not the pri- mary mechanism by which ductile structural metal eroded. They conducted experiments and concluded that for the ductile material impacting particles cause severe localized plastic strain, w

21、hich exceeds the 536 International Journal of Minerals, Metallurgy and Materials, Vol.16, No.5, Oct 2009 microscope and the images are shown in Figs. 2-3. SEM images of the eroded area show excessive piling up of defo

22、rmed material that was extruded up from the craters produced by particle erosion and confirmed that the erosion mechanism was not simply by the mi- cro cutting mechanism alone. Comparatively the number of platelets fo

23、rmed in the annealed specimen is more than that formed in the normalized specimen. 4. Experimental procedure The test sample was weighed initially and then it was fitted at the Jet erosion test rig with a desired an- g

24、le. The fly ash was taken in the chamber provided. The velocity and the concentration of fly ash particles were adjusted by controlling the air flow passing through the venturi. A jet of air with the fly ash parti- cl

25、es passed through a nozzle and hit the surface of the sample with an angle chosen to place the sample. Af- ter doing the experiment for the scheduled time the sample was removed, it was cleaned and weighed to get the

26、weight loss taken place. The amount of the ash used was also measured. The erosion rate was com-puted as the ratio of weight loss in the sample to that of the ash used. Effects of impingement of fly ash par- ticles wit

27、h other angles can be studied by varying the angle of placing the sample. Fig. 1. Experimental set up. 5. Results and discussion 5.1. Effect of velocity, impingement angle, feed rate, and particle size of fly ash part

28、icles on tube erosion Fig. 4 shows the erosion rate of low carbon steel tubes at different impingement velocities ranging from 32.5 m/s to 40 m/s with the impingement angle of 30°. The data for graphs are obtaine

29、d after the steady state of the erosion rate is reached. Erosion rate for SA 210 GrA1 (N) is higher than that for SA 210 GrA1 (A) at a given velocity attributing to ductility and elongation of the materials. In ductil

30、e materials, when fly ash particles impinge at a velocity, at the impact point the particle loses a fraction of its kinetic energy to the target material for deformation of the surface and shear strains are induced i

31、n the target material. When the shear strain exceeds the elastic limit of the target material, fly ash particles penetrate the surface of the target material and form platelets, which are removed in the subsequent im