The die forging is a forging method, which uses the free forging method and then forms in the die. It is a forging method between free forging and dies forging. It is widely used in small and medium-sized enterprises with less forging equipment.
There are many kinds of die used in die forging, which are commonly used in production: Die drop, buckle die, set die, cushion die, closing die, etc.
The closed die is mainly used for forging of rotary forging. For example, the gears with a boss at both ends are sometimes used for forging non rotating forging. Closed die forging belongs to non-flash forging.
For the complex shape of die forgings, it is necessary to add two half dies (i.e. add a parting surface) to the cylinder die to make a combined cylinder die, and the blank is formed in the die bore composed of two half dies.
The closing film is usually composed of upper and lower die parts. In order to make the upper and lower die fit and avoid the wrong displacement of forgings, guide post and guide pin are often used for positioning. Die closing is often used to produce non-rotating forgings with complex shapes, such as connecting rod, fork forgings, etc.
Compared with free forging, die forging has the following advantages:
(1) because the blank is formed in the die bore, the forging size is relatively accurate, the surface is relatively smooth, the distribution of streamline structure is relatively reasonable, so the quality is high;
(2) the forging with complex shape can be forged by die forging, because the shape of forging is controlled by dying bore, the blank forming is faster and the productivity is 1-5 times higher than that of free forging;
(3) there are few surplus blocks, so the machining allowance is small, which can not only save metal materials used in forging but also reduce machining time.
Disadvantages and limitations:
(1) a forging hammer with large tonnage is required;
(2) only small forgings can be produced;
(3) the service life of the mould is low;
(4) in general, the tire mould should be moved by manpower, so the labour intensity is high;
(5) die forging is used to produce medium and small batches of forgings.