CN106424287A - Stepwise precise spin-forming process method for large thin-wall dome - Google Patents

Abstract

The invention relates to a step-by-step precise spinning forming process for a large thin-walled spherical head. The first step: the tapered piece shearing and spinning process. The plate is spun into a conical piece through the shear spinning process, and the large displacement deformation of the slab is realized under the shear deformation condition from the plane to the cone surface, and the slab changes from a plane to a cone. The second step: multi-pass ordinary spinning process. Anneal the conical part formed in the first step and fix it on the spherical mandrel. The conical part rotates with the spherical mandrel, and the two rotary wheels feed and extrude the cone from the periphery to the center along the generatrix of the spherical mandrel. After a multi-pass spinning process, the conical surface gradually approaches the complex curved surface, realizing the precise forming of the spherical head with small displacement, and finally forming a high-precision large spherical head. This method can realize the integral molding of the spherical head in engineering, eliminate the short-plate effect of the weld, and improve the bearing capacity of the head; it can reduce the weight of the head and realize the lightweight manufacturing of the head; the wall thickness of the head is uniform, and high precision is achieved. take shape.

Description

Step-by-step precise spinning method for large thin-walled spherical heads

technical field

The invention relates to a step-by-step precise spinning forming process for a large thin-walled spherical head.

Background technique

A country's space exploration capability depends on the carrying capacity of its launch vehicle. The Long March 5 rocket developed by our country has a diameter of 5.25m and a near-earth carrying capacity of 25 tons. In the future, manned moon landings, Mars exploration and other aerospace projects The carrying capacity of the rocket is required to reach the 100-ton level. This heavy-duty launch vehicle requires its body diameter to reach 8-12m. As the main structural component of the launch vehicle, the fuel tank is the main load-bearing structure of the rocket. The service environment is extremely harsh. The thin-walled structure of the tank is subjected to a huge internal pressure. The maximum dynamic load it can withstand exceeds 10,000t, and the working temperature is as low as -253° C, the flight acceleration reaches 2-6g, so it puts forward extremely high requirements for its high performance, high precision and light weight.

For the spherical head of the fuel tank, due to its large diameter-to-thickness ratio and weak rigidity, traditional processing methods are prone to deformation and incongruity, resulting in the instability of the head, making it difficult for the processing accuracy to meet the requirements of the aerospace industry. It is urgent to accelerate the research on integral forming technology of thin-walled lightweight structural parts, and achieving breakthrough research results is crucial to the development of my country's aerospace industry.

1. Split-flap stretch bending and tailor welding

The split welding forming process adopts the forming idea of "breaking the whole into parts", that is, a head is divided into 6 to 8 splits, and each split is obtained by stamping or drawing one by one, and then the formed splits are tailored and welded into a single piece by assembly welding. Overall head. Figure 1 is a schematic diagram of the head formed by split welding. The fuel tank head processed by the split welding process in China has a maximum diameter of 5.25m and is used in the Long March 5 rocket.

However, this process method also has shortcomings: low strength and poor reliability of the welded structure; large residual stress, large deformation, and low precision of the formed head; large thickness is required, and lightweight manufacturing cannot be realized, which affects the rocket flight distance.

2. Ordinary spinning forming

Ordinary spinning forming is to fix the sheet metal or prefabricated blank on the mandrel, drive the mandrel and the workpiece to rotate at the same time through the rotation of the spindle, and use the rotary wheel to press the blank to make it gradually cling to the mandrel, so as to obtain the required Metal forming method for parts of revolution. Figure 2 is a schematic diagram of spinning forming.

This process has the following disadvantages: the spinning of large-diameter heads is prone to instability, and the wall thickness deviation reaches more than 30% (the middle is thicker and the edges are thinner); therefore, chemical milling or mechanical milling is required after forming, and this process will lead to head material structure Defects or high residual stress, the workpiece produces additional deformation, and the final accuracy cannot be controlled.

Contents of the invention

In view of the shortcomings of the above-mentioned forming methods, our research group has applied for and obtained a patent for a large-diameter-thickness ratio and a high-bow-height ratio head punching and spinning method through research on the forming equipment (Notice No. CN104275378A).

On the basis of the original patent, the patent of the present invention further proposes a step-by-step precise spinning forming process method,

The forming process is described in detail as follows:

The first step: the workpiece is spun into a conical piece through the shear spinning process, and the plane is formed into a conical surface under the condition of shear deformation, which realizes the large displacement deformation of the slab, and the large slab is formed into a conical piece from a circular plate .

The typical feature of shear spinning of conical parts is to satisfy the sinusoidal law, that is, the relationship between the wall thickness of the blank and the wall thickness of the workpiece during shear spinning: (t is the wall thickness of the workpiece after spinning, t ₀ is the wall thickness of the blank thick, half the cone angle). According to the principle of equal volume of plastic deformation of metal materials, the unit rectangular area abcd of the blank is equal to the area a'b'c'd' of the deformed parallelogram, and the semi-cone angle is a constant value, so the wall thickness of the tapered part is uniform.

The second step: the multi-pass ordinary spinning process is based on the shearing and spinning process of the tapered parts. The slabs used in the multi-pass ordinary spinning process are annealed conical parts. Fix the flange side and the flange part of the conical part, and spin the conical part into a spherical head part through the joint action of the rotary wheel and the spherical mandrel. From the theory of metal plastic deformation, this kind of small displacement deformation approaching the complex curved surface from the conical surface has small stress and strain during the forming process, which can reduce the cracking defects of thin-walled heads, and the small displacement deformation is stable and the material flow is orderly , can improve the forming quality of the workpiece.

The multi-pass ordinary spinning device is shown in Figure 6. The outer diameter flange of the conical piece 62 is fixed on the end surface of the spherical mandrel 61 through the annular pressure plate 63 and the bolt 72 , and the flange of the conical piece is clamped on the inner end surface of the spherical mandrel 61 by the tensioning device 65 . During the spinning process, the conical piece, the tensioning device and the spherical mandrel rotate synchronously with the main shaft of the machine tool, and the rotary wheel 64 forms a certain angle with the rotational axis of the spherical mandrel, and moves from outside to inside along the direction of the generatrix of the spherical mandrel. Give movement. The workpiece contact area produces plastic deformation under the interaction between the rotary wheel and the core mold, and finally forms a spherical head with the advancement of the rotary wheel. This method adopts internal and external restraint cooperation control to ensure the directional deformation of the workpiece.

The invention has the following advantages: 1) In engineering, it can realize the integral molding of the spherical head, eliminate the short plate effect of the welding seam, and improve the bearing capacity of the head; 2) It can reduce the weight of the head and realize the lightweight manufacturing of the head; 3) The wall thickness of the forming head is uniform, which can realize high-precision forming.

Description of drawings

Figure 1 is a schematic diagram of a head formed by split welding.

Figure 2 is a schematic diagram of ordinary spinning forming,

Fig. 3 is a schematic diagram of the first step of cone shear spinning,

Figure 4 is a schematic diagram of the wall thickness of the tapered part,

Figure 5 is a schematic diagram of multi-pass ordinary spinning forming of the head piece,

Figure 6 is a schematic diagram of a multi-pass common spinning device,

Fig. 7 is a schematic diagram of the final forming of the tapered piece shear spinning workpiece,

Figure 8 is a schematic diagram of the final forming of the spherical head spinning workpiece,

Figure 9 is the track diagram of the multi-pass ordinary spinning wheel for spherical head.

detailed description

The step-by-step precise spinning forming process of the large thin-walled spherical head of the present invention, the specific steps are as follows:

The first step: the workpiece is spun into a conical piece through the shear spinning process, and the plane is formed into a conical surface under the condition of shear deformation, which realizes the large displacement deformation of the slab, and the large slab is formed into a conical piece from a circular plate .

Shear Spinning of Conical Parts

The conical mandrel is made of 45# steel, and the working cone surface is quenched. The half-cone angle of the mandrel is 50° to ensure that its surface hardness reaches above 50HRC. In order to ensure the precision of the formed parts, the surface roughness of the working surface of the designed conical mandrel is Ra=3.2um.

As shown in Figure 7, the workpiece 71 is fixed on the conical mandrel 74 through the cooperation of the bolt 72 and the clamping disc 73, the workpiece rotates with the conical mandrel, and the two rotary wheels 64 are respectively from the center to the four sides along the conical mandrel. Feed and extrude the workpiece in the direction of the generatrix to gradually form the tapered part 62 .

The second step: multi-pass ordinary spinning process. The conical part is formed into a spherical head through the multi-pass ordinary spinning process, and the conical part gradually approaches the complex curved surface from the conical surface under the multi-pass ordinary spinning forming condition, so as to realize the precise forming of the spherical head with small displacement. The pieces are spun into spherical head pieces.

Spherical Head Spinning Forming

The inner surface of the spherical mandrel 82 is the forming working surface, so the surface is quenched to 52HRC, and the surface roughness is required to reach 3.2um. 6 evenly distributed holes of Φ9 are evenly distributed on the outer end surface, and cooperate with the blank holder ring to restrain the flange edge of the workpiece; 4 M6 threaded holes are evenly distributed on the inner end surface, and cooperate with the clamping disc to restrain the flange edge of the workpiece.

As shown in Figure 8, anneal the conical piece 62 formed in the first step, and the flange side and flange part of the conical piece are respectively fixed on the spherical mandrel with the annular pressure plate 63, the clamping plate 73 and the bolt 72. The shaped part rotates with the spherical mandrel, and the two rotary wheels 64 respectively feed and extrude the conical part from the periphery to the center along the direction of the generatrix of the spherical mandrel. After a multi-pass spinning process, a high-precision large-scale spherical head is finally created. 81.

The track diagram of the multi-pass spinning wheel is shown in Figure 9. The first two spinning passes are diameter-expanding spinning in which the conical part is not attached to the spherical mandrel, and the third spinning is that the conical part is close to the spherical mandrel. Final forming pass.

Claims (3)

1. the substep of large thin-wall sphere end socket accurate spinning forming process method is it is characterised in that include

Step one：Workpiece rotation is made by Tapered Cup by shear spinning technique, plane is configured to the conical surface under the conditions of detrusion, Achieve slab big displacement deformation, heavy slab is configured to Tapered Cup by plectane,

Step 2：Tapered Cup is configured to by sphere end socket by multi-pass conventional spinning technique, Tapered Cup is commonly revolved in multi-pass Gradually approached by the conical surface complex-curved under the conditions of pressing formation, realize sphere end socket thin tail sheep Accurate Shaping, Tapered Cup spinning balling-up Face end socket part.

2. the substep of large thin-wall sphere end socket accurate spinning forming process method is it is characterised in that the concrete mistake of described step one Cheng Wei：Workpiece is fixed on taper core, workpiece rotates with taper core, two spinning rollers respectively from center to surrounding along taper Core generatrix direction feeding extruding workpiece, gradually forms Tapered Cup.

3. the substep of large thin-wall sphere end socket accurate spinning forming process method is it is characterised in that the concrete mistake of described step 2 Cheng Wei：The Tapered Cup that step one is shaped makes annealing treatment, and Tapered Cup is fixed on spherical core, Tapered Cup is revolved with spherical core Turn, two spinning rollers feed extruding Tapered Cup from four circumferences centrally along spherical core generatrix direction, respectively through multi-pass spinning work Skill, forms large spherical surface end socket.