Introduce the type of forging

When the temperature exceeds 300-400°C (blue brittle zone of steel) and reaches 700-800°C, the deformation resistance will decrease sharply and the deformation energy will be greatly improved. According to the forging performed in different temperature regions, according to the different forging quality and forging process requirements, it can be divided into three forming temperature regions: cold forging, warm forging and hot forging. Originally, there is no strict limit to the division of this temperature zone. Generally speaking, forging in a temperature zone with recrystallization is called hot forging, and forging without heating at room temperature is called cold forging.

During low-temperature forging, the size of the forging changes very little. Forging below 700°C, there is little oxide scale formation, and there is no decarburization on the surface. Therefore, as long as the deformation energy is within the forming energy range, cold forging is easy to obtain good dimensional accuracy and surface finish. As long as the temperature and lubrication cooling are well controlled, the warm forging below 700°C can also obtain good accuracy. During hot forging, large forgings with complex shapes can be forged due to the small deformation energy and deformation resistance. To obtain forgings with high dimensional accuracy, hot forging can be used in the temperature range of 900-1000°C. In addition, pay attention to improving the working environment of hot forging. The life of the forging die (hot forging 2-5 thousand, warm forging 10,000 to 20,000, cold forging 20,000 to 50,000) is shorter than forging in other temperature ranges, but it has a large degree of freedom and low cost .

The blank undergoes deformation and work hardening during cold forging, which makes the forging die bear high load. Therefore, it is necessary to use a high-strength forging die and a hard lubricating film treatment method to prevent wear and adhesion. In addition, in order to prevent cracks in the blank, intermediate annealing is carried out when necessary to ensure the required deformability. In order to maintain a good lubrication state, the blank can be phosphated. In the continuous processing of bars and wire rods, the section can not be lubricated at present, and the possibility of using phosphating lubrication methods is being studied.

According to the moving mode of the blank, forging can be divided into free forging, upsetting, extrusion, die forging, closed die forging, and closed upsetting. Because there is no flash in closed die forging and closed upsetting, the material utilization rate is high. It is possible to complete the finishing of complex forgings with one process or several processes. Because there is no flash, the force-bearing area of u200bu200bthe forging is reduced, and the required load is also reduced. However, it should be noted that the blanks cannot be completely restricted. For this reason, the volume of the blanks should be strictly controlled, the relative position of the forging dies and the measurement of the forgings should be controlled, and efforts should be made to reduce the wear of the forging dies.

According to the movement mode of the forging die, forging can be divided into swing rolling, swing swivel forging, roll forging, cross wedge rolling, ring rolling and cross rolling. Pendulum rolling, pendulum rotary forging and ring rolling can also be processed by precision forging. In order to improve the utilization rate of materials, roll forging and cross rolling can be used as the pre-process processing of slender materials. Rotary forging, like free forging, is also partially formed. Its advantage is that it can be formed even when the forging force is small compared with the size of the forging. In this forging method, including free forging, the material expands from the vicinity of the die surface to the free surface during processing. Therefore, it is difficult to ensure accuracy. Therefore, the movement direction of the forging die and the swaging process can be controlled by a computer. The forging force of this product can obtain products with complex shapes and high precision. For example, forgings such as steam turbine blades with a wide variety of large sizes are produced.

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

Limiting forging force form: hydraulic press that directly drives the slider by hydraulic pressure.

Quasi-stroke limitation method: hydraulic press with hydraulic drive crank and connecting rod mechanism.

Stroke limitation method: mechanical press with crank, connecting rod and wedge mechanism driving slider.

Energy limitation method: Use screw and friction press with screw mechanism.

In order to obtain high accuracy, attention should be paid to prevent overload 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 be paid to adjusting the gap between the slider guide rails, ensuring rigidity, adjusting the bottom dead center, and using auxiliary transmission devices.

In addition, according to the slider motion mode, there are vertical and horizontal slider motion (used for forging of slender parts, lubrication cooling and high-speed production of parts). The compensation device can increase the motion in other directions. The above methods are different, the required forging force, process, material utilization rate, output, dimensional tolerance and lubrication cooling method are different. These factors are also factors that affect the level of automation.