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Rolling mill


Rolling mill
Rolling - one of the most important inventions made by man during his centuries of love with metals. It has been long been observed that products having the same cross section along its entire length (e.g., rails, angles, beams, plates, rods) is much easier to obtain by passing them between two rollers than by the conventional forging. You could even say that this method is not only the most convenient, but in general the best. Without it there could be no question of the construction of the cheap railways, railway bridges, railways, ships and much more, and much more. After all, it is thanks to the opportunity to give rolled iron and steel billets complete uniformity. It is easy to imagine how much effort would be required from a blacksmith, for example, otkovka each rail or railroad car wheels. Meanwhile, using rolled to obtain such products difficult, moreover, in large quantity and high quality. Therefore, at the end of the XVIII century rolling it has become one of the main links in the production cycle of metallurgical plants, gradually displacing the forging. And she was born in the Middle Ages in the manufacture of thin sheets of soft metal (such as lead), which could be rolled by hand, without pre-heating. The oldest image of the simple rolling machine can be seen in an engraving in 1615.

Rolling hot became known only at the beginning of the XVIII century, and the first in this way preparing a more or less thin iron sheets, but since 1769 started in a similar way to roll the wire. The first rolling mill for iron ingots was offered the English inventor of the court, where he worked on his method of puddling. Court first realized that the production of some products more rational to entrust the hammer only scrap obtained slag and to give final shape by rolling. In 1783 he received a patent for his invention of the method of rolled iron shaped using special rollers. From puddling furnaces bloom came under the hammer here and got it prokovyvalas original form, and then passed through the rollers. This method was then widespread. But only in the XIX century, rental equipment was delivered to the proper level, it was largely due to the intensive construction of railroads. Then it was invented mills for the production of rails and wagon wheels, and then for many other operations.

The rolling mill - a machine for metal forming between rotating rolls. The device of the rolling mill in the XIX century it was simple. Counter-rotating rolls captured incandescent metal strip and contracting more or less force, carried it between their surfaces. During the passage of the workpiece occurred two closely linked processes. Firstly, the metal product subjected to strong compression at high temperature, and, secondly, the blank acquired a desired shape. Thus, for example, getting properties of iron which was not from nature. The individual metal grains which were located in the rolling up his weight in a mess in the process of a strong compression stretched and form long fibers. Soft and brittle iron became thereafter a resilient and durable.

The rolls were placed between the platens powerful. rollers placed in the trunnion bearings. Typically, the lower bearing m has been fixed. The upper bearing is able to move up and down using bolts h. e Screw, by which installed liner, taking care of all the pressure on him. Between him and the liner is usually inserted a safety cap i, burst as soon as the pressure on the shaft has reached a dangerous limit. This cap is a cheap, easy to replace that acted as a preservative against breakage of other more important parts of the mechanism (breakage could easily occur if the rolls are too thick workpiece captured and maintained pressure). When rolling the upper roll pins lying on the yoke d, e, and fitted with a liner suspended on two bolts. For communication between two of the trails are served four thick bolts pass through the hole n the cross and lays the recess b. Engaging roll served with the engine clutch. The lower roller is driven directly by the steam engine, and its axis coincides with the main axis of its shaft. The upper roll motion was passed by a gear.

Form products depended on the shape of the rolls. The rollers with a smooth surface used to manufacture a flat iron, such as sheets. For rolling curly varieties of supplying relevant target recesses - calibrated. Passing between them received the required blank form that is transformed into a strip of a rounded, square, oblong, rectangular or other cross-section. The desired profile of the product was given not at once, but gradually. Billets successively passed through a series of rolls, of which only the last one was in the form of finished high-quality iron. The black color shows a profile which gradually acquired the crude metal as rolling in different rolls.

By the end of the century rolling technique is so perfected that in this way began to receive not only solid, but hollow articles. In 1885 Mennesmany brothers invented a way of rolling of seamless steel pipes. Before that the pipe had to produce a sheet of iron - they bent and welded. It was long and expensive. The mill Mennesmanov circular disc is passed between two obliquely to each other rolls set by acting on it in two ways. Firstly, due to the frictional forces between the rollers and the workpiece is started to rotate the latter. Secondly, due to the form of rolls of their average surface point rotates faster than the extreme. Therefore, due to the oblique arrangement of rolls like preform screwed into the space between them. If the pig was hard, she would not be able to pass. But as much of its pre-heated to white-hot metal billet began to twist and stretch, and held in the axial zone of its loosening - arose cavity which gradually spread over the entire length of the workpiece. After passing through the rollers, the workpiece is placed on a special rod (mandrel), so that the inner cavity was attached to the right a circular cross section. The result came out a thick-walled tube.

To reduce the wall thickness of the tube is passed through the so-called second piligrimny mill. He had two rolls of variable profile. When rolling the tube distance between the rollers first and then gradually decreased done more than the pipe diameter. rolling cycle consisted of two periods - the working and idle. During the working period of the pipe into which the spiral mandrel was introduced, exciting rolls and crimped to the diameter of the finished pipe. At the same time its walls were made thinner, and she stretched (as it rolls shot annular layer of metal and rolled it to the desired thickness). Then began the idle period when the gauge diameter greater than the diameter of the pipe. At this time, the preform coming out of contact with the rollers and the processing portion of the end. Harvesting moved forward and rotated around its axis by 90 degrees (for a more uniform finish). The cycle thus repeated in subsequent sections of the pipe.

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