CN-122007241-A - Precision forming process of multicellular variable-section metal pipe fitting and metal pipe fitting

CN122007241ACN 122007241 ACN122007241 ACN 122007241ACN-122007241-A

Abstract

The application relates to the technical field of metal plastic processing and advanced manufacturing, in particular to a precision forming process of a multicellular variable-section metal pipe fitting and the metal pipe fitting. The precise forming process comprises the steps of heating a multicellular blank to a preset thermoplastic forming temperature interval, placing the heated multicellular blank into a lower die cavity with the final shape of a target member, filling gas with a first set pressure into each independent cavity in the multicellular blank through the multi-channel inflation valve system in a first stage, controlling an upper die to descend under the support of internal gas pressure, controlling the internal pressure of each cavity to reach a second set pressure in real time in the descending process of a second stage, and entering a die locking and pressure maintaining stage after the die is completely closed. The application forms the metal tubular structural member with the multi-cell structure and the sectional shape and the size of the metal tubular structural member continuously changing along the axial direction, thereby meeting the design and manufacturing requirements of an integrated, high-performance and lightweight vehicle body structure.

Inventors

MENG XIANMING
ZHANG SAI
SONG TONG
REN PENGFEI
WU XIAOZHONG
LI TAO
CAO XINGFENG
ZHENG XINFU

Assignees

中国汽车技术研究中心有限公司

Dates

Publication Date: 20260512
Application Date: 20260319

Claims (8)

1. The precise forming process suitable for the multicellular variable-section metal pipe fitting is characterized by comprising the following steps of: selecting a proper multicellular blank according to the material requirement of a target member, and heating the multicellular blank to a preset thermoplastic forming temperature range; placing the heated multicellular blank into a lower die cavity with the final shape of a target member, reserving a space matched with the initial section of the blank by an upper die, and establishing an independent and sealed fluid pressure channel between each channel of the multi-channel inflation valve system and each independent cavity in the multicellular blank; in the first stage, gas with a first set pressure is filled into each independent cavity in the multicellular body blank through the multichannel inflation valve system, and under the support of the internal gas pressure, an upper die is controlled to descend, and the multicellular body blank is forged and pressed in the first stage to complete 60% bending deformation and initial compression of the section; in the second stage, the upper die is controlled to continue to move downwards to finally die-close, and in the descending process of the second stage, the internal pressure of each cavity is controlled to a second set pressure in real time; After the mold is completely closed, entering a mold locking and pressure maintaining stage; and after the pressure maintaining is finished, sequentially releasing the internal pressure of each cavity, opening the die, and taking out the formed target member.
2. The precision forming process for a multicellular body variable cross-section metal tube fitting of claim 1 wherein the material of the multicellular body blank is an aluminum alloy and the thermoplastic forming temperature range is 400 ℃ to 500 ℃.
3. The precision forming process for a multiple cell variable cross-section metal tube as defined in claim 2, wherein the first set pressure for each individual chamber is determined according to the following equation: ; Wherein P i1 is the first set pressure of the ith chamber in the first stage, sigma s (T) is the yield strength of the multicellular blank at the current temperature T, A 0i 、A fi is the initial cross-sectional area and the target cross-sectional area of the ith chamber, T is the pipe wall thickness of the outer pipe, R bend is the bending radius of the pipe, and K 1 、K 2 is the empirical coefficient, respectively.
4. The precision forming process for a multi-cell variable cross-section metal tube according to claim 3, wherein the first set pressure of the first cell in the multi-cell blank is 1.8 MPa, the first set pressure of the second cell is 2.2 MPa, and the first set pressure of the third cell is 2.0 MPa; in the first stage, the upper die descends at a speed of 5 mm/s.
5. The precision forming process for a multiple cell variable cross-section metal tube as defined in claim 4, wherein the second set pressure for each individual chamber is determined according to the following equation: ; ; Wherein S actual (T) is the die attaching distance between the pipe fitting with the wall thickness of T and the die, S target is the maximum die attaching distance, and sigma b (T) is the tensile strength (MPa) at the temperature of T; is the minimum fillet radius of the cross section of the ith chamber of the pipe fitting, and alpha i ,β i is the correction coefficient of the ith chamber respectively; A second set pressure change ratio of the i-th chamber; is the second set pressure of the ith chamber in the tube with wall thickness t in the second stage.
6. The precision forming process for a multicellular variable cross-section metal tube as recited in claim 5 wherein, The second set pressure of the first cell body in the multicellular body blank is stabilized at 8.0 MPa, the second set pressure of the second cell body is stabilized at 7.5 MPa, and the second set pressure of the third cell body is stabilized at 7.8 MPa; in the second stage, the upper die continues to move downwards at the speed of 15 mm/s to finally die.
7. The precision forming process for a multicellular body-variable cross-section metal tube as recited in claim 6 wherein the dwell time is 10s.
8. The multi-cell variable cross-section metal pipe fitting is characterized in that the metal pipe fitting is manufactured by adopting the precise forming process of the multi-cell variable cross-section metal pipe fitting provided by any one of claims 1-7.

Description

Precision forming process of multicellular variable-section metal pipe fitting and metal pipe fitting Technical Field The application relates to the technical field of metal plastic processing and advanced manufacturing, in particular to a precision forming process of a multicellular variable-section metal pipe fitting and the metal pipe fitting. Background As automobile body structures move toward lighter weight, high safety and integrated designs, the form of the structural members becomes increasingly complex. For the tubular beam of the vehicle body structure, the main current vehicle body application in the industry is steel and aluminum tubular beam, wherein the steel tubular beam is usually in a hollow structure due to high material strength and large mass, but for the aluminum structural part, the aluminum tubular beam for the vehicle body is a multi-cell extrusion profile due to lower material strength and density than steel. The current aluminum multi-cavity tubular beam of the vehicle body mainly adopts a process route of extrusion and secondary bending. And extruding and forming, namely passing the heated aluminum bar through a die hole with a fixed cross section shape to obtain the linear multicellular profile with the uniform cross section. This method cannot directly obtain a member having a cross-sectional shape or a dimension varying in the longitudinal direction. The secondary bending/forming is to put the extruded section with uniform section into a bent pipe or a forming die for plastic bending so as to adapt to the assembly space. The process has two inherent defects that firstly, the variable cross section design cannot be realized, the cross section of the final product is consistent with the extrusion initial cross section, the cross section shape and the wall thickness cannot be optimally matched according to the actual stress states (optimal force transmission paths) of the structure in different sections, and the further improvement of the structural performance is limited. Secondly, the forming quality is poor, the yield is low, in the bending or integral bending process, the complex rib plate (cell wall) material in the multi-cavity is extremely uncoordinated in flow, and defects such as local folds, collapse, cracking or section distortion are extremely easy to generate, so that the forming precision of complex components with long size, multi-cavity and small bending radius is poor, and the service performance can be influenced when serious. Therefore, a new process for realizing continuous variable cross-section precision forming of multi-cavity metal pipe fittings along an axis is needed to be developed in the industry so as to solve the problem of material flow control and meet the design and manufacturing requirements of an integrated, high-performance and lightweight vehicle body structure. Disclosure of Invention The application aims to provide a precision forming process of a multicellular variable-section metal pipe fitting and the metal pipe fitting, so as to form a metal tubular structural member with a multicellular structure and continuously variable cross-section shape and dimension along the axial direction, and meet the design and manufacturing requirements of an integrated, high-performance and lightweight vehicle body structure. In order to achieve the above purpose, the present application adopts the following technical scheme: in a first aspect, the present application provides a precision forming process for a multicellular variable cross-section metal tube, comprising: selecting a proper multicellular blank according to the material requirement of a target member, and heating the multicellular blank to a preset thermoplastic forming temperature range; placing the heated multicellular blank into a lower die cavity with the final shape of a target member, reserving a space matched with the initial section of the blank by an upper die, and establishing an independent and sealed fluid pressure channel between each channel of the multi-channel inflation valve system and each independent cavity in the multicellular blank; in the first stage, gas with a first set pressure is filled into each independent cavity in the multicellular body blank through the multichannel inflation valve system, and under the support of the internal gas pressure, an upper die is controlled to descend, and the multicellular body blank is forged and pressed in the first stage to complete 60% bending deformation and initial compression of the section; in the second stage, the upper die is controlled to continue to move downwards to finally die-close, and in the descending process of the second stage, the internal pressure of each cavity is controlled to a second set pressure in real time; After the mold is completely closed, entering a mold locking and pressure maintaining stage; and after the pressure maintaining is finished, sequentially releasing the internal pressure of each cavity, o