Allow me to introduce myself, my name is Fritz (figure 1). Actually, my surname should be 'Krupp', however, this combination is world-renowned as, 'Friedrich Krupp', the founder of the steel-works bearing the same name. 'Fritz' is a 1-ton forging hammer, which started operating in 1861 and which is raised using steam power, it has a stroke of approx. 0,3 meters, and is dropped, onto the material to be forged, with a force of about 50 tons. Fritz was used until 1911, when the period of hammer-forging for large components was over.
There are also various other construction types, e.g., those operated through compressed air. We however, would like to turn our attention to the forging-presses, the first of which, (figure 2) was developed by the Scot, John Haswell, in 1860 and was introduced, with enourmous success in 1862 at the Paris World Exhibition. In the meantime, the machines are substantially larger and , above all, have become much more efficient. Pressing is done in the free-form procedure with pressures of about 100 tons and in the forging-die with even much higher pressures.
Try to imagine the crankshaft of a big ships diesel engine, weighing in at about 90 tons, with its up to 14 cylinders and a perfomance of nearly 100.000 kW. Such parts also have to be forged (pressed) to achieve a high degree of rigidity with a relatively low weight. Large parts are often freely compressed and stretched, until they are within centimeters of the end-product. Even with a great deal of experience, such a process is not completed in just a few days. In between times, the component must be left in peace, then brought back to forging temperature, over and over again.
If the preparation and casting of such a cylinder block takes three months, how long does it take until the engine is finished?, apart from that, it still has to be test-mounted. The crankshaft is of course, also cast. In this case, the percentages of the alloying constituents are important. Nothing may disturb the structural composition. Ultrasonics are used to help with the checking and examination. Specific heating heals the scars caused by forging. After that, the quick cooling down process, e.g., in an oil-bath and the reheating, whereby, this time the temperature is lowered more slowly.
The majority of all forged components are carried out in the die method. Through the heating of a slightly malleable mass, the upper- and lower form are also heated. This is called extrusion moulding and also hollow components can be produced. In drop-forging the material can either, not yield at all, or only in a pre-selected direction. This is why, in this case, the pressures are so much higher. The advantage is, the components are so precise that they can be mounted in the gearbox without going through a finishing process, even though they do have a certain surface roughness. 03/10