A preforming method for a high-strength steel variable-diameter tubular part is provided, which belongs to the technical field of metal forming process. The preforming method for a high-strength steel variable-diameter tubular part includes: selecting a tubular blank; and preparing a tubular blank forming mold, where the tubular blank forming mold includes a preforming mold and a final forming mold; sealing and pressurizing the tubular blank; heating the tubular blank by using electrodes; preforming the tubular part at a constant temperature; maintaining a temperature T1 and moving the preformed tubular part to the final forming mold;finally forming the tubular part. Through two steps of operation of preforming and final forming, and maintaining a temperature during moving the tubular blank between the two steps, so that the conversion of intrametallic structure between the two steps is improved, and the performance of the tubular part is improved.

A method for shaping a blank comprising a metal includes a step of loading die blank onto a first die, a step of bringing the first die and a second die together, 3 step of forming a seal around the blank, and a step of injecting a pressurized molten salt into a space in die blank to supply a hydraulic pressure to the blank.

A method for shaping a blank comprising a metal includes a step of loading die blank onto a first die, a step of bringing the first die and a second die together, 3 step of forming a seal around the blank, and a step of injecting a pressurized molten salt into a space in die blank to supply a hydraulic pressure to the blank.

A forming device which expands a metal pipe material to form a metal pipe having a pipe portion and a flange portion includes a hardness lowering portion which lowers a hardness of the flange portion to be lower than a hardness of the pipe portion.

A forming device which expands a metal pipe material to form a metal pipe having a pipe portion and a flange portion includes a hardness lowering portion which lowers a hardness of the flange portion to be lower than a hardness of the pipe portion.

A method and device for manufacturing a large-sized thin-walled tubular part by gas-liquid internal high pressure forming (IHPF). A gas and a liquid are filled at a certain volume ratio into a thin-walled blank. The pressure of the gas-liquid mixed fluid is mainly determined by the gas pressure. During the deformation of the thin-walled blank, due to a large compression ratio of the gas, the gas-liquid pressure will not basically change with the change of the volume of a blank cavity. A support pressure on the cavity of the thin-walled blank is stable in the entire forming process. In addition, even if there is a slight leakage of the liquid or gas during the forming process, the medium pressure inside the blank will not fluctuate largely. In this way, embodiments lower the requirements for the sealing effect during the tubular part forming process.

Provided is a forming device that forms a heated metal material with a forming die, in which the forming die includes an angular portion formed by a first forming surface and a second forming surface that intersect each other in a cross-sectional view, the second forming surface is movable relative to the first forming surface, and during the forming, the second forming surface moves in a pressing direction in which the metal material is pressed in a stage before the angular portion and the metal material come into contact with each other.

Provided is a forming device that forms a heated metal material with a forming die, in which the forming die includes an angular portion formed by a first forming surface and a second forming surface that intersect each other in a cross-sectional view, the second forming surface is movable relative to the first forming surface, and during the forming, the second forming surface moves in a pressing direction in which the metal material is pressed in a stage before the angular portion and the metal material come into contact with each other.

Provided is a flanged member that has a tubular shape and includes a flange portion, the flanged member including: a cross-section changing portion of which a cross-sectional shape changes along an axial direction of the flanged member, in which in any two cross-sections in the cross-section changing portion, a perimeter of one cross-section is 1.25 times or less a perimeter of the other cross-section.

Provided is a flanged member that has a tubular shape and includes a flange portion, the flanged member including: a cross-section changing portion of which a cross-sectional shape changes along an axial direction of the flanged member, in which in any two cross-sections in the cross-section changing portion, a perimeter of one cross-section is 1.25 times or less a perimeter of the other cross-section.