Forging is a forming and processing method that uses external force to deform the blank, that is, to apply external force to the metal blank (excluding plates) to produce plastic deformation, change the size, shape and improve the performance, and is used to manufacture mechanical parts, workpieces, tools or blanks. Forging equipment refers to the mechanical equipment used for plastic forming and separation of workpieces in forging processing, and forging equipment is mainly used for metal forming, so it is also called metal forming machine tools. Forging equipment includes forging hammers, mechanical presses, hydraulic presses, screw presses and flat forging machines for forming, as well as auxiliary equipment such as forging manipulators, uncoilers, straightening machines, and shearing machines. There are also many kinds of forging, such as friction presses, forging punches, air hammers, etc., as well as heating equipment, such as medium and high frequency heating machines.
Due to the different forging processes, the corresponding forging equipment is also different, so the following is a brief introduction to the relationship between different processes and different equipment.
For the commonly used metal materials suitable for forging, when the temperature exceeds 300~400°C (the blue brittle area of steel) and reaches 700~800°C, the deformation resistance will be sharply reduced, and the deformation energy will be greatly improved. According to the forging carried out in different temperature regions, according to the different requirements of forging quality and forging process, it can be divided into three forming temperature zones: cold forging, warm forging and hot forging. Generally speaking, forging in the temperature region with recrystallization is called hot forging, and forging at room temperature without heating is called cold forging. The corresponding machines are cold forging machine, warm forging machine and hot forging machine.
When forging at low temperatures, the size of the forging changes very little. In forging below 700°C, there is less oxide scale formation and no decarburization on the surface, so as long as the deformation can be within the forming energy range, cold forging is easy to obtain good dimensional accuracy and surface finish. As long as the temperature and lubrication are well controlled, good accuracy can be obtained at temperatures below 700°C. In hot forging, large forgings with complex shapes can be forged because the deformation energy and deformation resistance are very small. To obtain forgings with high dimensional accuracy, they can be processed by hot forging in the temperature range of 900~1000°C. In addition, attention should be paid to improving the working environment of hot forging. The forging die life (2~5,000 for hot forging, 1~20,000 for warm forging, and 2~50,000 for cold forging) is shorter compared to forging in other temperature ranges, but it has a large degree of freedom and low cost.
The blank is subjected to high loads due to deformation and work hardening during cold forging, so it is necessary to use a high-strength forging die and a hard lubricating film treatment method to prevent wear and sticking. In addition, in order to prevent cracking of the blank, intermediate annealing is carried out when necessary to ensure the required deformation capacity. In order to maintain good lubrication, the blank can be phosphated. In the case of continuous processing with rods and wire rods, the section cannot be lubricated at present, and the possibility of using phosphate lubrication method is being studied.