What is steel forging?

What is forging?

Upset forging: A method of forming and processing plastic parts, including workpieces, tools, or blanks, by applying external force to metal blanks (excluding plates) to cause plastic deformation, change size, shape, and improve performance.
Types and characteristics of steel forging

When the temperature exceeds 300-400 ℃ (blue brittle zone of steel) and reaches 700-800 ℃, 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 was no strict limit on the division of this temperature region. Generally speaking, forging in a temperature region with recrystallization is called hot forging, and forging without heating at room temperature is called cold forging.

When low temperature forging, the dimensional change of the forging is small. Forging below 700 ℃, the formation of oxide scale is small, and the surface is not decarburized. Therefore, as long as the deformation energy is within the range of forming energy, cold forging can easily obtain good dimensional accuracy and surface finish. As long as the temperature and lubrication and cooling are controlled, warm forging below 700 ℃ can also obtain good accuracy. During hot forging, large forgings with complex shapes can be forged because the deformation energy and resistance are small. 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. Forging die life (2 to 5,000 for hot forging, 10,000 for warm forging, 2 to 50,000 for cold forging) is shorter than forging in other temperature ranges, but it has a large degree of freedom and low cost .

When the blank is deformed and work hardened during cold forging, the forging die is subjected to high loads. 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 cracking of the blank, intermediate annealing is performed when necessary to ensure the required deformation ability. In order to maintain a good lubricating state, the blank can be phosphated. When continuous processing is performed with rods and wire rods, the section cannot be lubricated at present, and the possibility of using a phosphating method is being studied.

Forging can be divided into free forging, upsetting, extrusion, die forging, closed die forging, and closed upsetting according to the movement of the billet. Closed die forging and closed upset forging do not have flash, so the utilization rate of the material is high. It is possible to finish the complex forgings in one operation or several operations. Because there is no flash, the load bearing area of ​​the forging is reduced, and the required load is also reduced. However, it should be noted that the billet cannot be completely restricted. For this reason, it is necessary to strictly control the volume of the billet, control the relative position of the forging die and measure the forging, and strive to reduce the wear of the forging die.

According to the movement mode of the forging die, forging can be divided into swing rolling, swing swing forging, roll forging, cross wedge rolling, ring rolling and diagonal rolling. Swing, swivel and ring forging can also be precision forged. In order to improve the utilization rate of materials, roll forging and cross rolling can be used as the previous process of slender materials. Rotary forging, which is the same as free forging, is also locally formed. Its advantage is that compared with the size of the forging, the forging force can also be formed in a small case. 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 computer can control the movement direction of the forging die and the spin forging process. The forging force is used to obtain products with complex shapes and high accuracy. For example, the production of various types and large-sized steam turbine blades and other forgings.

的 The mold movement and degree of freedom of the forging equipment are inconsistent. According to the characteristics of the bottom dead center deformation limitation, the forging equipment can be divided into the following four forms:
• Limited forging force form: Hydraulic press that directly drives the slider.
• Quasi-stroke limitation mode: Hydraulic press with hydraulically driven crank and linkage mechanism.
• Stroke limitation: mechanical press with crank, connecting rod and wedge mechanism driving the slider.
• Energy-limiting method: Screw and friction presses using screw mechanism.
In order to obtain high accuracy, care should be taken to prevent overload at the bottom dead point, and to 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 gap, ensuring stiffness, adjusting the bottom dead point, and using auxiliary transmissions.

At the same time, the required forging force, process, material utilization, yield, dimensional tolerance, and lubrication and cooling methods are different. These factors are also factors that affect the level of automation.

What are the characteristics of upset forgings compared to castings
Rhenium metal can improve its microstructure and mechanical properties after forging. Due to the deformation and recrystallization of the metal after hot working deformation of the forged method, the original coarse dendrites and columnar grains become equiaxed recrystallized structures with finer grains and uniform sizes, which causes the original segregation, The compaction and welding of looseness, pores, and slag inclusions make the structure more compact, which improves the plastic and mechanical properties of the metal.

In general, the mechanical properties of castings are lower than those of forgings of the same material. In addition, the forging process can ensure the continuity of the metal fiber structure,

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