Die forging refers to the method of using die processing to make the blank finally form the forging. This forging method is widely applicable to the mass production of small parts, such as shafts, gears and other parts in bearing, automobile, machinery and other manufacturing industries.
Die forging has various classification methods. According to the classification of mechanical equipment, die forging can be divided into tire die forging, die forging on press and die forging on hammer. Among them, the so-called tire die forging refers to the use of free forging equipment, on which the die is installed and can move freely on the equipment; Die forging on the press is to press and heat the blank at the same time, and use the press to forge it; Die forging on hammer uses forging hammer to process metal. According to the number of die cavities, it can be divided into single cavity die forging and multi cavity die forging. The so-called single cavity die forging means that the shape of the formed forging is relatively simple. Only one cavity is needed in the die and can be formed in one step; Multi cavity die forging means that the shape of the formed forging is complex and needs to be divided into multi-step die forging. If it cannot be formed at one time, the multi-step cavity will be placed in the same forging die. This forging method is multi cavity die forging. According to the type of die, die forging can be divided into open die forging and closed die forging. Among them, open die forging with flash groove and closed die forging without flash groove. Aiming at the die forging process of driven spiral bevel gear blank of automobile rear axle, the methods adopted include open die forging and closed die forging.
1、 Open die forging:
Open die forging is the earliest forging process of driven spiral bevel gear blank. With the continuous improvement of forging production technology, ring rolling process and swing rolling have been gradually developed. The forming process of open die forging is divided into: heating → pre forging → final forging → trimming and punching.
Disadvantages: large production investment, low material utilization rate, low productivity, high noise, large vibration, very bad labor environment and high production cost.
2、 Closed die forging:
Closed die forging process: blanking → heating → pier roughening → pre forging → final forging → punching and connecting skin.
It has the following advantages:
- The internal structure of formed forgings is dense and the mechanical properties are good;
- The forming size and geometry of forgings are closer to the accuracy requirements of finished forgings;
- Closed die forging is adopted, and there is no flash groove design in the die, which reduces the consumption of raw materials, consumes less materials and costs.
At the same time, closed die forging has the following disadvantages:
- The blanking volume of the blank must be accurate;
- The forging force is large, so the equipment tonnage is large and the cost investment is high;
- Poor production environment and high labor intensity.