抛丸清理机对板材轧辊进行抛丸处理外文文献翻译中英文翻译外文翻译.docx

1、抛丸清理机对板材轧辊进行抛丸处理外文文献翻译中英文翻译外文翻译外文翻译原文SHOT BLASTING MACHINES FOR THE BLASTING OF SHEET MILL ROLLSV. I. Meleshko, A. P. Kachailov, V. G. Boikov,V. L. Mazur, T. P, Kobka and I. I. KrivolapovAt the present time much attention is being devoted to increasing the quality of rolled products, partieularly sh

2、eet. To a significant degree this depends upon the preparation of the roll surface. Many plants are engaged in improving the quality of working the roll surface in preparing them for rolling.This article was written by personnel from Zaporozhstal Plant, Magnetogorsk Metallurgical Combine, the Instit

3、ute for Ferrous Metallurgy, Dnepropetrovsk, and Magnetogorsk Mining and Metallurgical Institute on this very real problem.The surface microrelief, or roughness, of cold rolled constructional sheet has an influence on the mechanical and production properties of metal, and also on the finish quality o

4、f parts made from this sheet. The final surface microrelief of thin sheet steel is formed in a skin pass on work roils which have been given a rough finish with metal shot.Normally the rough surface finish on the work rolls of skin pass stands is produced in pneumatic and rotor shot blasting machine

5、s. Experience in their use has shownthat the pneumatic machines used in the countrys steel plants do not fill the need for high quality blasting of roll surfaces.In 1969 the Institute for Ferrous Metallurgy, Dnepropetrovsk, did work on the SM-2 shot blasting machine in No. 1 Cold Roiling Mill of Zap

6、rozhstal Plant, which revealed a number of shortcomings in its construction.To provide sheet with the surface roughness required by the specifications of Volga Automobile Plant (R a =0.8-1.6 g),the basic requirements for the design of shot blasting machines were determined, The machine must provide:

7、1. a constant shot size during operation, in other words, effective removal of shot of the specified size fromworn shot;2. the possibility of controlling air pressure in the collector of the shot blast machine during stable operations;3. the handling of work rolls of different diameters (400-500 mm)

8、 without special equipment on the machine;4. simplicity in control and convenience in maintenance.Fig.1The SM-2 machine (Fig. 1) consists of a stationary closed chamber ! with a trolley on wheels aad movab!enozzles 2 which under the action of compressed air discharge shot on to the roll surface, a w

9、orm conveyor 8, an elevator with a separator 4, the shot blast equipment 5, and an exhaust system 6. The equipment is mounted on a special foundation 1905 mm below the floor level The length of the machine withthe trolley out is 15fl00 ram, the height 4070 ram, and the width 4600 mr The dimensions o

10、f the rolls handled are 400-500 mm in diameter and 2000-4000 mm in length. The total weight of the equipment is 15 tons.As research has shown, the dynamics of the wear of a working mixture of abrasive and the original condition of the shot changes during operation. During blasting, the shot takes on

11、 a wider size range and is worn down, forming many fine particles. The conditions under which the parts are blasted depend upon the size of the shot used. The contamination of the specified size by fine particles disrupts the process, producing a poor quality surface on the rolls and consequently on

12、 the sheet. To eliminate these problems it is necessary to either regularly measure the composition of the shot and make appropriate changes in the blasting sequence, which is difficult to do in practice, or to screen the shot during operation of the machine to provide the specified particle size.St

13、ability in the blasting process is also determined by the quantity of shot delivered to the nozzles. It was experimentally established that supplying 0.3-0.4 kg/sec of shot to the two nozzles in operating with an air pressure of 2.5-4.0 atm provided stable operation. Equipping the machine with scree

14、ning devices is an effective method for maintaining a constant shot size mix. This is confirmed both by data in the literature and by experience in the operation of SM-1 and TsKb_P-1 shot blast machines at Zaporozhstal Plant.The shot is delivered to the surface of the roll by the shot blast equipmen

15、t, the chamber of which is divided by two diaphragms with charging vents into three compartments and is equipped with an electropneumatic control device. The working mixture from the upper compartment of the chamber drops to the lower and then to the collector. During operation of the machine,the ve

16、nts are closed (turned on). The shot is poured in either after turning off the valves by the electropneumatic control device, or after shutting down the machine by the operator. When it is turned off, the vent descends, and between it and the diaphragm a circular gap 5 mm wide is formed. The vent is

17、 a cone with a slope of about 30% The shot drops slowly through this gap but not completely, and therefore it increases to t0 ram. The loading vents are alternately turned on by the control device. The first time the SM-2 machine was repaired, it was discovered that the control device frequently did

18、 not operate because of corrosion of the parts. With normal charging of abrasive (375 kg according to the nameplate), blasting must be stopped after each alternate pass of the nozzles, since after another pass the shot in the lower compartment is insufficient, and during blasting, With nonoperation

19、of the control device, it does not drop from the upper compartment to the lower. Delivery of the nextportion of shot must be done only after the operator disconnects the shot blast equipment from the air system. In this case both charging vents are opened, and the abrasive is fed to the lower compar

20、tment. Continuous operation of the machine for three or four passes of the nozzles with nonoperation of the control device and the delivery of shot described above became possible after increasing the standard charge to 650 kg. However, the basic solution of this problem is stable operation of the c

21、ontrol device.The used shot is collected by the collecting bunker of the working chamber and drops into the receiving chute of the worm conveyor. The plates parallel to the worm conveyor are at a greater angle, and those perpendicular are at less of an angle, which tends to collect shot on them. The

22、refore, after blasting one roll it is necessary to shut the machine down to push the accumulated shot on to the screw conveyor. To eliminate this shortcoming, it is possible to lengthen the screw conveyor, which is half the length of the working chamber. In addition, the smaller plate is removed com

23、pletely,and the parallel plates are elongated to correspond with the length of the worm conveyor.The compressed air supplied to the collector of the shot blast equipment is dried by an oil moisture separator. However, this method of drying is inadequate. Water vapor condenses in the main line and in

24、 the shot blast equipment, and as a result shot sticks together in the lower compartment and forms a solid mass. The solid mass clogs the vertical channels along which the abrasive is transported to the collector and disrupts the optimum ratio of shot to air in the blast. This has a detrimental effe

25、ct on the blasting process and the quality of the roll surface. The presence of moisture in the air causes corrosion of the equipment and causes operation of the pneumatic equipment of the machine to be poorer. Therefore, in designing shot blast equipment,it is necessary to specify equipment for dry

26、ing the air. Foreign firms, for example, use special drying equipment utilizing water absorbing substances such as silica gel and activated alumina for drying compressed air.The mechanism for moving the nozzle has a number of shortcomings. Application of the jet of abrasive material on to the roll i

27、s through a nozzle mounted in an elbow shaped gun (Fig. 2). A shortcoming of the gun is the throttling of the mixture of compressed air and shot where the vertical and horizontal channels join. The junction is a right angle, which causes quick wearing away of the elbow. The cross sections of the cha

28、nnels and nozzle was increased. However, with an increase in the nozzle diameter from 10 to 12 mm (the allowable maximum) the consumptionof air increased from 13 to 19 mS/h, which changed the ratio of shot to air in the blast. However, thisratio must be kept constant. Since during blasting it is dif

29、ficult to make corrections, it was necessary o improve the design and increase the wear resistance of the parts.Fig.2For this purpose a new design of blast guns, in which the diameter of the channels was increased (Fig. 2 b) and the shape of the transition from the channel to the channel and nozzle

30、was changed, was proposed and tested, The new nozzle design is much more effective. After five months of operation,noticeable signs of wear in the elbowand nozzle have not been found, while the old design elbows wore out in a month.The blast guns are moved along the roll by a conveyor belt. Under th

31、e action of the weight of the troJ.ley and oscillations caused by its movement along the guides on which shot falling from the surface of the rolls accumulates, the belt gets out of alignment. As a result, the impact of the stream of shot on the surface is not at a right angle, but glancing, which p

32、roduces a poorer surface quality. Placing a strip under the gun eliminated this problem, and the roll surface quality became satisfactory.In the first period of operation the compressed air tn the SM-2 machine was obtained from the shop main i,ine, which has a pressure of 6 atm. According to reading

33、s on a manometer placed before the collector of the shot btaat unit, the air pressure in it did not exceed 4.0 aim. With this pressure, even with the use of the finest shot (DChK-0.8), the roughness of the rolls is at the upper limit (R a = 2.7 #).Therefore, it was necessary to reduce the working pressure of the air. An air val