阅读说明：本技术 一种大截面差空心结构件轴压胀锻工艺方法 (Large-section-difference hollow structural member axial compression expansion forging process method ) 是由 初冠南 苑世剑 孙磊 于 2019-10-17 设计创作，主要内容包括：一种中空零件成形方法,特别涉及一种大截面差空心结构件轴压胀锻工艺方法。本发明解决了目前大截面差零件内高压成形存在的壁厚减薄的问题。方法如下：先制造大截面差预成形坯,然后在内部充填流体介质,相当于将管材变为实心棒材,再沿轴向压缩大径区,在内部介质支撑下,随着压缩进行各部位逐渐贴模；最后再进一步压缩大径区使其长度缩短壁厚增厚到目标值,成形结束。本发明是提高该类零件壁厚均匀性的方法,同时还能起到提高形状精度的作用。(a method for forming a hollow part, in particular to a method for carrying out axial compression and expansion forging on a hollow structural member with a large section difference. The invention solves the problem of wall thickness reduction in the existing high-pressure forming of parts with large section difference. The method comprises the following steps: firstly, manufacturing a large-section-difference preform, then filling fluid medium in the preform, namely changing a pipe into a solid bar, axially compressing a large-diameter area, and gradually attaching the mould to each part along with compression under the support of the internal medium; finally, the large-diameter area is further compressed to shorten the length of the large-diameter area and thicken the wall to a target value, and the forming is finished. The invention is a method for improving the uniformity of the wall thickness of the parts, and can also play a role in improving the shape precision.)

1. A large-section-difference hollow structural member axial compression expansion forging process method is characterized by comprising the following steps: the method comprises the following steps:

step one, forming a large-section-difference preformed part (1) through diameter-changing processes such as hydraulic forming or spinning; for the convenience of expression, dividing the preformed part 1 into three characteristic areas, namely a large-diameter area a, a transition area b and a small-diameter area c; in the diameter-changing process, the wall thickness of the large-diameter area is certainly smaller than that of the transition area and the small-diameter area, and the preforming quality requirement of the preformed part (1) is that the shape of the small-diameter area is the same as that of the small-diameter area of the final formed part (7); the shape of the transition area is close to that of the final forming part (7), and specifically, the shape error is not more than 30%; the length of the large-diameter area is greater than that of the large-diameter area of the final forming part (7), and is 1% -50% greater than that of the large-diameter area of the final forming part 7; the perimeter of the section profile of the large-diameter area is not more than that of the section profile of the final forming part (7), and is specifically 0-20% smaller than that of the large-diameter area of the final forming part (7);

Step two, a final forming die comprises an end punch head (2), an end punch head (3), an upper die (4) and a lower die (5), the preformed part (1) is placed into the lower die (5), the dies are closed, then the preformed part (1) is filled with fluid medium and sealed, namely the preformed part is converted into a solid structure,

step three, the end punch head (2) and the end punch head (3) push the large-diameter area along the axial direction, the tube blank material moves to the area without die attachment under the support of the internal fluid medium, the die cavity is filled, the deformation mode is similar to closed die forging,

step four, when the sticking degree reaches more than 90 percent, controlling the supporting pressure p of the internal fluid medium through a pressure regulating valve (6), wherein the internal pressure p needs to ensure that the pipe blank which is already attached to the mold in the step five is always attached to the mold cavity,

Step five, the end part punch head (2) and the end part punch head (3) continuously move oppositely along the axial direction to compress the large-diameter area, so that the axial length of the large-diameter area is shortened, the wall thickness of the large-diameter area is thickened, when the wall thickness of the large-diameter area is thickened to a target value, the compression is stopped,

and sixthly, removing the internal fluid medium, opening the mould and taking out the part 7.

2. the axial compression and expansion forging process method for the large-section-difference hollow structural part according to claim 1, characterized by comprising the following steps of: the fluid medium is a liquid or a gas.

3. The axial compression and expansion forging process method for the large-section-difference hollow structural part according to claim 1, characterized by comprising the following steps of: the internal pressure p is 1-1000 MPa.

Technical Field

the invention relates to a forming method in the technical field of industrial manufacturing, in particular to a process method for axial compression and expansion forging of a large-section-difference hollow structural part.

Background

The large-section-difference reducer pipe is a key shape of an automobile exhaust system and is characterized by large section reducing rate which generally exceeds 1.5. The large-variable-diameter-rate part is manufactured by adopting a welding and assembling method at the earliest time, and has the defects of multiple working procedures, easy corrosion of a welding line, large welding thermal deformation and the like. With the improvement of the quality requirements of automobiles on the parts, the welding and assembling process cannot meet the high-quality manufacturing requirements. Hydroforming has been used in recent years to manufacture such parts. The introduction of welding seams is avoided in the hydraulic forming process, but the problem of wall thickness reduction exists, the wall thickness reduction rate of a large-diameter area exceeds 20%, and the use performance of parts is seriously reduced. Patent CN106311857A proposes a forming method capable of reducing wall thickness reduction, but the method is to compress the cross section, that is, the circumference of the cross section of the formed part is reduced, so that the method cannot be used for manufacturing parts with enlarged cross sections. More importantly, the wall thickness of the part cannot be uniform along the axial direction without improving the wall thickness. Aiming at the problem, the invention provides a method for improving the wall thickness uniformity of the parts, and simultaneously has the function of improving the shape precision.

Disclosure of Invention

in order to solve the problems, the invention provides a process method for axial compression and expansion forging of a large-section-difference hollow structural part.

the technical scheme adopted by the invention is as follows:

step one, forming a large-section-difference preformed part 1, and performing diameter-changing processes such as hydraulic forming or spinning; for the convenience of expression, dividing the preformed part 1 into three characteristic areas, namely a large-diameter area a, a transition area b and a small-diameter area c; in the diameter-changing process, the wall thickness of the large-diameter area is certainly smaller than that of the transition area and the small-diameter area, and the preforming quality requirement of the preformed part 1 is that the shape of the small-diameter area is the same as that of the small-diameter area of the final-formed part 7; the shape of the transition area is close to that of the final forming part 7, and specifically, the shape error is not more than 30%; the length of the large-diameter area is greater than that of the large-diameter area of the final forming part 7, and is more specifically 1% -50% greater than that of the large-diameter area of the final forming part 7; the perimeter of the section profile of the large-diameter area is not more than that of the section profile of the final forming part 7, and is specifically 0-20% smaller than that of the large-diameter area of the final forming part 7;

Step two, a final forming die comprises an end punch 2, an end punch 3, an upper die 4 and a lower die 5, the preformed part 1 is placed into the lower die 5, the dies are closed, then the preformed part 1 is filled with fluid medium and sealed, which is equivalent to converting the preformed part into a solid structure,

Step three, the end part punch 2 and the end part punch 3 push the large-diameter area along the axial direction, the tube blank material moves to the area without being attached with the die under the support of the internal fluid medium, the die cavity is filled, the deformation mode is similar to closed die forging,

step four, when the sticking degree reaches more than 90 percent, the supporting pressure p of the internal fluid medium is controlled by the pressure regulating valve 6, the internal pressure p needs to ensure that the pipe blank which is already attached to the mould in the step five is always attached to the mould cavity,

Step five, the end part punch 2 and the end part punch 3 continuously move oppositely along the axial direction to compress the large-diameter area, so that the axial length of the large-diameter area is shortened, the wall thickness of the large-diameter area is thickened, when the wall thickness of the large-diameter area is thickened to a target value, the compression is stopped,

And sixthly, removing the internal fluid medium, opening the mould and taking out the part 7.

The above embodiments are not intended to limit the present invention, and the present invention is not limited to the above examples, and those skilled in the art may make variations, modifications, additions or substitutions within the technical scope of the present invention.

Compared with the prior art, the invention has the beneficial effects that:

1. Compared with a manufacturing method of welding and assembling, the method has the advantages that no welding seam exists, the corrosion resistance of parts is good, the appearance is attractive, and the shape precision is high;

2. the large-diameter area of the formed part has no wall thickness reduction, and the structural performance is excellent;

3. the sticking dies are pressed to make the parts expand and stick the dies like air blowing balls instead of increasing the internal pressure, the required pressure is small, and particularly sharp contour lines can be formed;

4. The material is always in compression deformation in the forming process, and is not easy to break under the action of three-dimensional compressive stress, so that the technology can be used for forming low-plasticity materials;

the invention has reasonable design, reliable work, obvious effect and stronger popularization value.

drawings

FIG. 1 is a schematic view of a starting part and a final forming die.

FIG. 2 is a schematic view of the mold closing for placing the preform part into the final mold.

FIG. 3 is a schematic view of a 90% axial thrust of a large diameter section against a mold.

FIG. 4 is a schematic view of the pressure regulating tube blank attached to a mold cavity.

FIG. 5 is a schematic view of the compression of the large diameter region by moving the end punches toward each other.

figure 6 shows a schematic view of a molded part 7.

1-preformed part 2-end punch 3-end punch 4-upper die 5-lower die 6-pressure regulating valve 7-final formed part

Detailed Description

The present invention is described in further detail below with reference to the accompanying drawings and the detailed description, as shown in fig. 1-6.

the first method is as follows: step one, forming a large-section-difference preformed part 1, and performing diameter-changing processes such as hydraulic forming or spinning; for the convenience of expression, dividing the preformed part 1 into three characteristic areas, namely a large-diameter area a, a transition area b and a small-diameter area c; the wall thickness of the large-diameter area is surely smaller than that of the transition area and the small-diameter area in the diameter-changing process. The preforming quality requirement of the preformed part 1 is that the shape of the small diameter area is the same as that of the final formed part 7; the shape of the transition area is close to that of the final forming part 7, and specifically, the shape error is not more than 30%; the length of the large-diameter area is greater than that of the large-diameter area of the final forming part 7, and is more specifically 1% -50% greater than that of the large-diameter area of the final forming part 7; the perimeter of the section profile of the large-diameter area is not more than that of the section profile of the final forming part 7, and is specifically 0-20% smaller than that of the large-diameter area of the final forming part 7;

step two, a final forming die comprises an end punch 2, an end punch 3, an upper die 4 and a lower die 5, the preformed part 1 is placed into the lower die 5, the dies are closed, then the preformed part 1 is filled with fluid medium and sealed, which is equivalent to converting the preformed part into a solid structure,

Step three, the end part punch 2 and the end part punch 3 push the large-diameter area along the axial direction, the tube blank material moves to the area without being attached with the die under the support of the internal fluid medium, the die cavity is filled, the deformation mode is similar to closed die forging,

Step four, when the sticking degree reaches more than 90 percent, the supporting pressure p of the internal fluid medium is controlled by the pressure regulating valve 6, the internal pressure p needs to ensure that the pipe blank which is already attached to the mould in the step five is always attached to the mould cavity,

Step five, the end part punch 2 and the end part punch 3 continuously move oppositely along the axial direction to compress the large-diameter area, so that the axial length of the large-diameter area is shortened, the wall thickness of the large-diameter area is thickened, when the wall thickness of the large-diameter area is thickened to a target value, the compression is stopped,

And sixthly, removing the internal fluid medium, opening the mould and taking out the part 7.

The second method comprises the following steps: the support pressure p in this embodiment is 1 to 1000 MPa. The rest is the same as the first embodiment.