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Differences between closed die forging & open die forging

In modern society, forging industry is involved in various industries for construction machines,agricultural machinery, automotive, oilfield equipments, ect. Steel billets could be processed by various forging processes,among them the common used forging ways are closed die forging and open die forging. Although these two forging methods all belong to forging, it is not difficult to tell the difference between closed die forging and open die forging. The biggest difference of them is forging dies. Now let us have a deeper comparison on the differences between them.
closed die forging and open die forging
Open die forging is also named free forging,means metal billets compressed under external compressive force and deformed to desired demensions or shapes in a free way without forging dies. Closed die forging, also referred to impression die forging, is a process that heated by medium frenquency induction heating furnace to high temperature and forged between upper and lower dies to get expected shapes like the drawing.

Closed die forging and open die forging are also different in side of their processes. In general, molding dies are firstly made for closed die forging, and then forged steel bars are placed on the dies and drop forged to any shapes we need. With closed die forging ,less machining or no machining is needed, we could get net shape products. For open die forging, it involves enormous compressive force imposed by continuous strike of hammer to make the metal billets deformed.

In addtion, forging products made by open die forging and closed die forging are also not the same in their application scope. We all know that metals will be much more stronger than before after forging because of the change of its internal grain. Also, the toughness and ductility of forged parts will also get improved. Open die forging will require further rough machining due to its free forging and imprecise dimensions may be reached by second precision machining. Open die forging technique is more suitable for large parts in a number of tons, typical products made in such process is like forged long shaft, forged rollers, forged cylinders, ect. for in railway system, aeroplane application, and so on. However, closed die forging is more popular in small parts for its high precision. It is often used to make forged fittings, forged flange, forged automotive parts, ect.

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