5B

5B

FORGING PROCESSES COMPACTION EQUIPMENT

1. Two preform production methods were developed for powder forging. They eliminate completely the need for compaction equipment. In the loose-pack process, the first method, a mixture of powder and organic binder is poured into an inexpensive pressed paper-pulp mould, vibrated to increase the density, and then baked. In the baking step the powder mass gains enough strength for further handling.

2. There are two versions of this process. In the first, baking is carried out at relatively low temperature so that the mould can be raised, whereas in the second version the mould burns away in the baking step, which is com­parable to the preheating step for forging. This method appears very attractive from an economic viewpoint.

3. A second recently introduced powder forging pro­cess, so called Osprey process (the second method), simi­larly does not require compaction equipment. A spray of hot particles from an atomizing unit is directed into shaped moulds. On impact the particles flatten and weld together to form a hot high-density preform which can be

forged directly. The rate of deposition can be substantial and steel forgings can be produced from the molten state within seconds. Osprey preforms reach densities of up to 99% theoretical density, which should guarantee practi­cally inclusion- and pore-free forgings.

4. Accurate weight control seems difficult, however, and therefore it will also be impossible to produce flash-less high-precision forgings. Furthermore, it appears doubt­ful whether the process can be fully automated and still be well controlled under large-scale production conditions.

Therefore, in the two processes just discussed, one is really considering a range of products where dimension­al control is much less critical than it is in precision pow­der forging. It is highly probable that for the high-quality powder forgings which are made to final dimensions only traditional powder compaction methods will have to be used.