What are the types of forging and what are their characteristics?

According to the forging temperature, it can be divided into hot forging, warm forging and cold forging. The starting recrystallization temperature of steel is about 727°C, but 800°C is generally used as the dividing line. Above 800°C is hot forging; between 300 and 800°C is called warm forging or semi-hot forging, and forging is performed at room temperature. is called cold forging. Forgings used in most industries are hot forgings. Warm forging and cold forging are mainly used for forging parts such as automobiles and general machinery. Warm forging and cold forging can effectively save materials.

According to the forming mechanism, forging can be divided into free forging, die forging, ring rolling, and special forging.

1. Free forging. It refers to the processing method of forgings that use simple general-purpose tools or directly apply external force to the blank between the upper and lower anvils of the forging equipment to deform the blank to obtain the required geometric shape and internal quality. Forgings produced by free forging are called free forgings. Free forging mainly produces small batches of forgings. Forging equipment such as forging hammers and hydraulic presses are used to shape the blanks to obtain qualified forgings. The basic processes of free forging include upsetting, drawing, punching, cutting, bending, twisting, staggered shifting and forging. Free forging adopts hot forging method.

2. Die forging. Die forging is divided into open die forging and closed die forging. The metal blank is compressed and deformed in a forging die chamber with a certain shape to obtain forgings. Die forging is generally used to produce parts of small weight and large batches. Die forging can be divided into hot die forging, warm forging and cold forging. Warm forging and cold forging are the future development directions of die forging, and also represent the level of forging technology.

According to materials, die forging can also be divided into ferrous metal die forging, non-ferrous metal die forging and powder product forming. As the name suggests, the materials are ferrous metals such as carbon steel, non-ferrous metals such as copper and aluminum, and powder metallurgy materials.

Extrusion should be classified as die forging and can be divided into heavy metal extrusion and light metal extrusion.

Closed die forging and closed upsetting are two advanced processes of die forging. Since there is no flash, the material utilization rate is high. It is possible to complete the finishing of complex forgings in one or several processes. Since there is no flash, the stress-bearing area of the forging is reduced and the required load is also reduced. However, care should be taken not to completely restrict the blank. To this end, it is necessary to strictly control the volume of the blank, control the relative position of the forging die and measure the forgings, and strive to reduce the wear of the forging die.

3. Roll the ring. Ring rolling refers to the production of ring-shaped parts of different diameters through special equipment ring rolling machines. It is also used to produce wheel-shaped parts such as automobile hubs and train wheels.

4. Special forging. Special forging includes roll forging, cross wedge rolling, radial forging, liquid die forging and other forging methods. These methods are more suitable for producing parts with certain special shapes. For example, roll forging can be used as an effective pre-forming process to significantly reduce subsequent forming pressure; cross wedge rolling

It can produce steel balls, transmission shafts and other parts; radial forging can produce large gun barrels, stepped shafts and other forgings.

forging die

According to the movement mode of the forging die, forging can be divided into oscillating rolling, oscillating forging, roll forging, cross wedge rolling, ring rolling and cross rolling. Oscillating rolling, oscillating forging and rolling rings can also be processed by precision forging. In order to improve material utilization, roll forging and cross rolling can be used as front-end processing of slender materials. Rotary forging, like open forging, is also locally formed. Its advantage is that it can be formed with a small forging force compared to the size of the forging. In this forging method including free forging, the material expands from near the die surface to the free surface during processing. Therefore, it is difficult to ensure accuracy. Therefore, by using a computer to control the movement direction of the forging die and the rotary forging process, a lower The forging power is used to obtain products with complex shapes and high precision, such as forgings such as steam turbine blades with many varieties and large sizes.

The die movement and degree of freedom of forging equipment are inconsistent. According to the deformation limitation characteristics of the bottom dead center, forging equipment can be divided into the following four forms:

1. Form of limiting forging force: hydraulic press with hydraulic pressure directly driving the slider.

2. Quasi-stroke limitation method: Hydraulic press with hydraulically driven crank and connecting rod mechanism.

3. Stroke limitation method: a mechanical press in which the crank, connecting rod and wedge mechanism drive the slider.

4. Energy limitation method: spiral and friction press using spiral mechanism.

In order to obtain high accuracy, care should be taken to prevent overloading at the bottom dead center and control the speed and mold position. Because these will have an impact on forging tolerances, shape accuracy and forging die life. In addition, in order to maintain accuracy, attention should also be paid to adjusting the slider guide rail clearance, ensuring stiffness, adjusting the bottom dead center, and using auxiliary transmission devices.

slider

There are also vertical and horizontal movements of the slider (for forging of slender parts, lubrication and cooling, and forging of parts for high-speed production). The compensation device can be used to increase movement in other directions. The above methods are different, and the required forging force, process, material utilization, output, dimensional tolerance and lubrication and cooling methods are different. These factors also affect the level of automation.