A method for forming an internal high-pressure forming die for forming a stepped pipe fitting

Abstract

The invention discloses an internal high-pressure forming die for forming a pipe fitting of a step structure and a forming method thereof. The die comprises an upper die body, a lower die body, a left lining, a right lining, a left puncher pin and a right puncher pin. In the early stage of forming, an initial distance exists between the left lining and the side wall of a cavity of the pipe fitting as well as between the right lining and the side wall of the cavity of the pipe fitting, and the middle expansion portion is supplemented with materials by properly increasing the axial feeding amount through the left pincher pin and the right pincher pin. In the later stage of forming, the left pincher pin and the right pincher pin stop axial feeding, the left lining and the right lining move opposite to each other, pushing force is exerted on the middle expansion portion, and the friction force between a pipe and the die is greatly reduced since the side wall of the expansion portion is incompletely attached to the left lining and the right lining. Therefore, pressure required for forming of fillets is remarkably lowered, the wall thickness is obviously decreased, and requirements for the maximum tonnage of a die closing press, the bearing capability required for the die, the reliability of a sealing structure and pressure of a supercharger are lowered while requirements for forming the pipe fitting of the step structure are met.

Description

technical field [0001] The invention belongs to the technical field of plastic forming of pipe fittings, and in particular relates to an internal high-pressure forming die for forming stepped pipe fittings and a forming method thereof. Background technique [0002] In the past ten years, increasingly severe market competition and environmental protection policies have forced the automobile manufacturing industry to change its product types to produce light-duty vehicles to achieve low fuel consumption, low emissions and ensure safety. In order to achieve this goal as effectively as possible at low cost, it is necessary to develop or use new lightweight materials, alloys or composite materials; and to develop and improve new manufacturing technologies to convert the above lightweight materials into light weight, low cost, high strength and stable quality functional structure. Since the 1990s, internal high pressure forming of pipes has been widely used in the manufacture of ...

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Problems solved by technology

[0003] Existing internal high pressure forming dies for pipe fittings with stepped structures are integral, and the bulging diameter, wall thickness thinning and forming fillet radius of the middle cavity can only be adjusted by changing the axial feed and internal pressure loading path. Optimization, this mold structure has an obvious disadvantage. When the bulging is basically over and the rounded corners of the forming stepped structure dominate, due to the friction between the pipe and the mold, it will be difficult to change the means of axial feed and internal pressure loading path. However, with the increase of pipe wall thickness and the application of high-strength pipes, the forming pressure of the sharp corner structure will be further increased by using the traditional internal high-pressure forming die, and even the equipment cannot meet the requirements. In addition, with the increase of forming pressure increase, the friction between the pipe and the mold also increases significantly, resulting in excessive thinning or even cracking of the wall thickness during fillet filling

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