1、 1 外文翻译原文 SHOT BLASTING MACHINES FOR THE BLASTING OF SHEET MILL ROLLS V. I. Meleshko, A. P. Kachailov, V. G. Boikov, V. L. Mazur, T. P, Kobka and I. I. Krivolapov At the present time much attention is being devoted to increasing the quality of rolled products, partieularly sheet. To a significant de
2、gree 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 Institute for Ferrous Metallur
3、gy, 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 of parts made from this
4、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 machines. Experience in their
5、 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 Zaprozhstal Plant, which
6、 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: 1. a constant shot
7、size during operation, in other words, effective removal of shot of the specified size from 2 worn 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) without speci
8、al equipment on the machine； 4. simplicity in control and convenience in maintenance. Fig.1 The 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 worm conveyo
9、r 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 of the rolls
10、 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 a wider s
11、ize 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 the sheet
12、. To eliminate these problems it is necessary to either 3 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. Stability
13、 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 screening de
14、vices 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 equipment, the
15、 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 vents ar
16、e 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 a con
17、e 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 not o
18、perate 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 of the
19、 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 compartment.
20、 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 control device. The used shot is collected by the collecting bunker of the working chamber and drops into
