Multi-directional die forging is a special process that uses a combination forging die with multiple parting surfaces on a multi-directional die forging hydraulic press to obtain a multi-directional hole forging with complex shapes without burrs and forging slope (or very small) under the action of a single stroke of the press.
In addition to the vertical working cylinder of an ordinary die forging hydraulic press, the multi-directional die forging hydraulic press is also equipped with 2 or 4 horizontal working cylinders, and a perforated working cylinder is installed in the center of the crossbeam or movable crossbeam. In this way, the multi-directional die forging hydraulic press has a total of 4 or 6 independent slides, which can act individually or in combination. Therefore, the blank can be pressurized in mutually perpendicular directions, that is, multi-directional die forging in the form of vertical parting, horizontal parting, vertical and horizontal combined parting, etc. can be realized on the press.
Die structure of multi-directional die forging The die structure of multi-directional die forging has the following forms.
1.1 Horizontal parting mold structure The parting surface of the horizontal parting mold is parallel to the horizontal plane. The forgings in the mold are mainly formed by the two-way extrusion of the horizontal working plunger. The two concave dies are fixed on the upper and lower die seats with wedge-shaped pressure plate screws, and the two horizontal punches are respectively installed on the clamping seats of the two horizontal plungers of the hydraulic press. The centering is ensured by the punch guide part and the closed guide pins and guide sleeves of the upper and lower dies.
1.2 Vertical parting mold structure The parting surface of the vertical parting mold is perpendicular to the horizontal plane. The forgings are mainly formed by the vertical plunger of the hydraulic press. One end of the two horizontal push rods is installed on the plunger clamping seat of the horizontal working cylinder, and the other end is connected to the concave die with a pin, pushing the two halves of the concave die to move on the bottom plate to open and close the die, and relying on the positioning block in the center of the bottom plate to position the punch and the center of the concave model cavity. The two halves of the concave die should have guide pins to prevent misalignment.
1.3 Joint parting mold structure The mold has a vertical parting surface and a horizontal parting surface, which is a joint parting mold. It consists of two left and right lower concave molds to form a vertical parting mold, and the upper concave mold forms a horizontal parting mold, forming a vertical and horizontal joint parting mold structure. A guide hole for the punch to extrude is opened in the center of the upper concave mold.
1.4 Special structure mold In addition, according to the shape of the forging and equipment conditions, special structure molds can also be designed. Special structure molds refer to molds that cannot meet the needs of forging forming using horizontal parting, vertical parting and joint parting structures, or are designed to make up for the lack of equipment functions.
Among the above four multi-directional mold structures, the horizontal parting structure is the most widely used one. When there are deep holes at both ends of the forging, the horizontal parting structure is often used.
When there is a deep hole at one end of the forging, horizontal parting can be used, or vertical parting can be used. If the forging is large in size and requires a larger clamping force, horizontal parting is appropriate. This is because the vertical working cylinder pressure of the multi-directional die forging hydraulic press is generally greater than the horizontal working cylinder pressure, which can obtain a larger clamping force. When the forging requires 3 or 4 concave dies to open and close on a plane, vertical parting is generally used, and a special fork-shaped structure can also be used.
It is precisely because the die of multi-directional die forging has multiple parting surfaces that multi-directional die forging can forge forgings with complex shapes that cannot or are difficult to produce by other types of forging methods.
2.3.1 Basic forms of guidance The first form of die guidance is that when the forging is deformed, the excess metal will produce transverse burrs along the diameter direction. This burr is difficult to clean and should be avoided as much as possible. Another form of die guidance is that when there is excess metal, it will flow to the outer circumference of the diameter, producing longitudinal burrs, which are easier to clean, so it is often used. 2.3.2 Clearance between the punch and the die There should be a certain clearance between the punch and the die. The main factors affecting the clearance are: the concentricity of the horizontal working cylinder, the accuracy of the die height and the workbench height, the deformation of the movable crossbeam and the elastic deformation of the die, the displacement of the punch installation, etc. Comprehensive considerations should be taken into account during design.
2.4 Design of the die for deep hole forgings For deep hole forgings, a certain ejection force is required when the punch is pulled out of the deep hole. At this time, it should be considered that the forging may be deformed when the punch is pulled out. Therefore, there should be enough shear surface between the forging and the cavity during design, so that the forging will not be broken or deformed when the punch is pulled out.
2.5 Punch design 2 Key points of multi-directional die forging die design The shape of the punch should be determined according to the inner hole shape of the forging. The punch working multi-directional die forging die design should meet the requirements of the part shape to ensure that the forgings are of qualified quality. Therefore, when designing the die, attention should be paid to the following issues 2.1 Cavity position (1) When arranging the cavity position, it should be noted that the center of the die opening force is often not equal to the center of the mold cavity geometry. Pay attention to making the center of the die opening force of the cavity close to the center of the mold closing force to avoid local die opening and burrs (2) The layout of the cavity should be conducive to the forming of the forging, especially for asymmetric, complex-shaped bosses or branch-shaped multi-directional forgings.
2.2 The positioning and centering of the die guide device are particularly important for ensuring the dimensional accuracy of multi-directional die forgings. In order to make the movement of the die have good guidance and ensure that the centers are aligned with each other after combination, on the one hand, the design of the die matching surface should be able to play a positioning role, and at the same time, a guide part must be set on the die to prevent the die from being misaligned. Generally, a cylindrical guide pin is used, and the guide pin is pressed into one die by hot pressing. A guide hole is machined on the other die (or a guide sleeve is pressed into the guide hole). The gap between them is 0.5mm. Generally, two guide pins are required for the die. When the die is composed of three dies, the guide pin can be cylindrical, and it is matched with a guide groove.
2.3 Die guide The design of the die guide should have a sufficiently long guide hole to ensure that the horizontal punch has a certain concentricity during the die forging process. The size parameters of the punch working part can be calculated and selected according to the following formulas (see): inner diameter of the forging; - linear shrinkage coefficient; A-tolerance on the inner diameter of the forging.
- Die handle
- Upper fixed plate
- Upper punch
- Right positioning plate
- Left positioning block
- Lower punch
- Spring
- Lower fixed plate
- Lower die base
3.1 Determination of key dimensions between processes Since this part has to be formed through multiple processes, in order to facilitate the subsequent process to insert the forming core into the already formed workpiece, and in order to make the core more easily pulled out of the workpiece after forming, the opening width after forming in the previous process must be larger than the opening width of the semi-finished product in the next process, that is: b, >> Run 3, see
3.2 Heat treatment for details. It has been mentioned before that the part has a large degree of bending deformation and the appearance is prone to cracking. For this reason, the cut round steel billet must be locally annealed at the bending forming part before forming to eliminate the internal stress during cold drawing and improve the plastic deformation ability, thereby avoiding cracking. However, do not use overall high temperature annealing, because overall high temperature annealing is likely to produce oxide scale, which affects the surface appearance after electroplating. The actual production is adapted to local conditions. A coke furnace is used to introduce air at the air inlet with a small blower to increase the oxygen supply and improve the firepower. Then a mesh iron plate with several C25mm~(:B0mm holes is placed at the furnace mouth. The part of the blank to be formed is placed at the mesh and baked for a few minutes. This saves the investment in high-frequency electric furnaces and electric energy, makes the production equipment simple, the preparation cycle is short, the effect is fast, the conversion is fast, and the product cost is reduced.
4 Conclusion Through the above process methods and molds, after mass production verification, the forming effect is very satisfactory. The appearance of the chrome-plated product is very beautiful, which fully meets the requirements of export products, creates foreign exchange income for the enterprise, and improves economic benefits.
(Continued from Page 29) 2.6 Push rod design In the vertical parting structure, if the horizontal push rod that pushes the die is not rigid enough, the push rod is easy to deform, which is not conducive to die closing and may produce burrs. To achieve a good die pressing effect and prevent burrs from being produced on the forging, the horizontal push rod that pushes the die must be designed to have sufficient rigidity.
2.7 Die material The multi-directional die forging hydraulic press has a slow working speed, the die and hot forging have a long contact time, the temperature is high, and the surface is repeatedly subjected to the alternating effects of cold and heat. Fatigue cracks are easy to occur, and the deformation is mainly caused by extrusion. The wear of the die is serious. Therefore, the punch and die materials are required to have high hardness and heat resistance, good red hardness, cold and hot fatigue resistance and thermal conductivity.