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What is the forming process for ellipsoidal heads?
The head is an important component of chemical, nuclear power and other equipment. In order to ensure long-term and efficient operation of the equipment under high temperature and high pressure, the performance requirements are also getting higher and higher. The head obtained through integral forging has higher strength and high temperature. 3. It has a large resistance under high pressure hydrogen and has a wide application prospect.
The integrity of nuclear power heads will directly affect the safety and life of nuclear reactors. The head is subjected to high temperature and pressure during the working process, and special service conditions also impose strict requirements on the materials used in the nuclear reactor pressure vessel:
Appropriate strength and high toughness at room temperature and working temperature and the lowest brittle transition temperature possible. Good solderability and hot and cold workability. Has greater tissue stability at operating temperatures. Sufficient hardenability and uniformity of thick section texture.
Common heads are ellipsoidal heads and ball heads. Through numerical simulation, the head forming aids were optimized to ensure uniform wall thickness of the ball head after punching.
Steel ingot cutting ingot bottom, riser pressing jaw → upsetting compaction → drawing long blanking → upsetting compaction → upsetting finished product → forging slab heat treatment after forging → slab rough machining → slab inspection → slab bending Forming.
During the forming process of the ball head, the forming upper die is connected with the movable cross beam of the hydraulic press, the forming lower die is placed on four corner posts, and the punching stroke H = 1300mm. After the punching is completed, the movable cross beam of the hydraulic press is lifted, and the finished head is lifted by a crane.
During the slab forming process, the forming slab is defined as a deformed body, and the forming die is defined as a rigid body. The friction between the forming slab and the mold is a very complicated physical phenomenon, which is related to various factors of the contact surface, such as the relative hardness between the contact surfaces, surface roughness, temperature, normal stress and relative sliding speed, etc. Advantages also change during deformation.
The direct friction coefficient between the deformed body and the upper mold is defined as μ = 0.4, and the friction coefficient between the deformed body and the lower mold is defined as μ = 0.3. The punching temperature was set to 1000 ° C.
After the punching is finished, the comparison between the ball head forging and the fine drawing. The numerical simulation of the head forgings obtained according to this scheme can meet the finishing requirements. The remaining margin at the bottom of the ball head is about 10mm on one side, the inner end of the open end of the ball head and the outer side is about 25mm. It can be seen that the forging of the ball head meets the size requirements for finishing.
The equivalent stress after the punching is completed, the deformation of the open end of the ball head is relatively large, which is equivalent to the closing process, which causes the concentration of stress, which is about 40MPa. The deformation of the bottom of the ball head is the smallest and the forming stress is also the smallest. The iso effect becomes 0.02 to 0.2 mm / mm. The forming force is shown in Fig. 8. The maximum forming force is about 2600t.