56 



SCIENCE. 



[N. S. Vol. XVII. No. 419. 



economically, by steam or compressed air; 

 but in forging operations where heavy pres- 

 sures are required hydraulic power is infi- 

 nitely better than either. 



The compressibility of air is an objection 

 in many lines of work, and it is now well 

 recognized that the effect of a hammer 

 blow is oftentimes merely local. As Mr. 

 H. F. J. Porter has so ably shown else- 

 where,* the pressure applied in forging a 

 body of iron or steel should be sufficient 

 in amount and of such a character as to 

 penetrate to the center and cause flowing 

 throughoiit the mass; as this flowing of 

 the metal requires a certain amount of time 

 the pressure should be maintained for a 

 corresponding period. 



Hydraulic pressure, instead of a ham- 

 mer, should, therefore, be used to work it 

 into shape. Under its action the forging 

 is slowly acted upon and the pressure is 

 distributed evenly throughout the mass, 

 whereas under the high velocity of impact 

 of the hammer the metal does not have time 

 to flow, and thus internal strains are set 

 up in the mass, which may cause serious 

 results, especially with certain steels which 

 have not the property of welding. 



Besides the fundamental defects incident 

 to the method, it is very troublesome to 

 use a hammer in certain lines of work, on 

 account of mechanical difficulties of manip- 

 ulation. 



The quality of the steel is very much im- 

 proved by the processes of hydraulic for- 

 ging, and we find a marked tendency to 

 substitute this method in a wide variety of 

 work in which presses are employed vary- 

 ing in capacity from 20 tons to 14,000 tons. 



We are all familiar with the fact that the 

 magnificent 125-ton hammer made by the 

 Bethlehem Steel Co. lies idle, while the 

 work for which it was intended is done by 

 a 14,000-ton hydraulic press operated by 



* Trans. A. S. M. E., Vol. XVIT. 



an engine of 15,000 horse-power; it may 

 not be so generally known, however, that 

 all forgings except small pieces are done on 

 hydraulic presses, and that the largest 

 hammer in actual operation is one of 6 tons 

 capacity in the blacksmith shop. 



The pressure used in these works is 7,000 

 pounds per square inch, but the present 

 tendency indicates the use of a so-called 

 low-pressui-e transmission service under a 

 pressure of 400 or 500 pounds, with an in- 

 tensifier at the press which raises the pres- 

 sure to 2,500, 5,000, 7,000 pounds, or what- 

 ever may be required. 



In this case the lifting and lowering of 

 the ram of the press is effected by low- 

 pressure water, so that the cylinder always 

 remains filled, and the high pressure is only 

 brought to bear the moment the dies come 

 in contact with the pieces to be forged. 

 The intensifier is built in multiple, which 

 permits of a variable force to suit the work 

 to be done; its action and control are ex- 

 tremely simple, and results are produced 

 which show a marked increase in speed and 

 a decided economy in operation. Some of 

 the recent German hydraulic forging ma- 

 chines equipped with intensifier operate at 

 a speed of forty to seventy strokes per 

 minute, on finishing, and twenty to thirty 

 strokes per minute for the heaviest work. 



The success which has attended the use 

 of hydraulic power in forging is causing it 

 to be applied to other and similar work to 

 an increasing extent. In boiler works, 

 railroad and locomotive shops, bridge works 

 and ship-yards it is used along with com- 

 pressed air, but where heavy pressures are 

 desired hydraulic power is greatly to be 

 preferred; hence we find it operating ma- 

 chines for punching and shearing heavy 

 plates and sectional beams, riveting ma- 

 chines, stationary and portable, flanging 

 and bending machines, tube upsetting ma- 



