CN107626868A - Manufacturing process is constructed in the classification of hourglass shape metal - Google Patents

Abstract

The invention discloses a step-by-step construction method for hourglass-shaped metals, which is characterized in that firstly, a conventional construction method is used to carry out one-stage construction to obtain a blank, and the blank is further forged into a circular frustum or a square frustum, which is used as a basic element of the next-stage construction; After that, N-level construction is carried out, and the two blank primitives are stacked together to form an hourglass shape as a whole; the two blank primitives stacked in an hourglass shape are packaged into an hourglass-shaped preform; The interface between the primitives is welded to make the hourglass-shaped preform into a blank; the blank is further forged into a circular or square platform, which is used as a rough primitive for N+1-level construction; repeat the above steps to achieve multi-level construction and prepare more Large rough. Due to the small middle size of the hourglass shape and the large upper and lower ends, the small middle section deforms preferentially during the deformation process, so a large deformation at the middle interface can be achieved under relatively small pressure.

Description

Forming method of hourglass-shaped metal graded construction

technical field

The invention relates to a metal material manufacturing method, in particular to a processing method for realizing metal or metal-based material forming through an hourglass-shaped hierarchical construction method. This method is not only suitable for homogeneous manufacturing of homogeneous materials, but also suitable for composite manufacturing of heterogeneous materials.

Background technique

Metal materials are the most indispensable materials in the development of human history. Based on their unique characteristics of cheapness, strength, toughness, and durability, metals have always occupied a dominant position in the contemporary material industry. After thousands of years of accumulation, human beings have mastered a set of quite mature metal material production technologies. For example, traditional steel production has gone through smelting, casting, pressure processing and heat treatment processes, and the product quality is stable and the price is low. Metal matrix composites that have emerged in recent years combine the advantages of metal materials and non-metal materials, and have the characteristics of small specific gravity and high specific strength, which further broadens the application range of metal materials.

Some key areas have high requirements for the bonding strength of the composite interface. The traditional explosive composite method is difficult to meet the requirements due to the pressure composite at room temperature and the presence of microscopic defects on the interface. It is necessary to develop a more reliable and safer new metal composite method. .

The metal building forming method is an additive manufacturing method that uses multiple smaller metal blanks as building blocks to make large metal blanks. The method prepares multiple primitives, stacks multiple primitives into a predetermined shape, packages the multiple primitives stacked into a predetermined shape into a preform, and welds the interfaces between multiple primitives by forging welding. The purpose of using smaller cast billets, forged billets or rolled billets to manufacture large forgings is achieved by making preforms into blanks. However, during the fabrication of building blocks, there is a high possibility of scrapping due to accidental factors such as interface contamination or failure of welds that break the vacuum at the interface between primitives. For super-large forgings over 100t, the failure of a single interface leads to huge losses in the scrapping of the entire forging, and effective methods are urgently needed to avoid risks. And because the total weight of the billet is too large, it is urgent to reduce the pressure required for forging by effective means.

Contents of the invention

The object of the present invention is to provide a kind of hourglass-shaped hierarchical construction forming method for preparing large-scale metal materials or composite metal materials. Get the blank. Among them, forging welding refers to the process of realizing metallurgical connection through the atomic diffusion between different elements to fully weld the interface during the high temperature forging process. After the conventional construction process is completed, the blank is forged into a circular or square frustum to obtain a blank element. After the surface processing and cleaning of the blank primitives, the two blank primitives are packaged together to form an hourglass-shaped preform, and the inside of the interface is kept in a high vacuum state, and then a forging welding process characterized by upsetting and large deformation is applied, so that Two blank primitives are joined together to form a blank. The blank can be forged again into a round or square base, and the process of forging and welding two round or square bases into a larger blank can be repeated many times. Each construction is called a first level. After multi-level construction, the manufacture of super-large forgings can be realized.

An hourglass-shaped metal graded construction forming method according to the present invention is characterized in that it includes:

First-level construction and N-level construction, where N≥2,

Described primary construction comprises the steps:

Prepare multiple primitives;

Stack multiple primitives into a cylinder or cuboid;

Pack multiple primitives stacked into cylinders or cuboids into preforms;

By forging and welding, the interface between multiple blank primitives is welded to make the preform into a blank, and the blank is further forged into a circular frustum or a square frustum, which is used as the blank primitive for the next stage of construction. The circular frustum or square frustum is The cross-sectional area of one end of the large plane of the blank is larger than the cross-sectional area of one end of the small plane;

The N-level architecture includes:

Stack two conical or square frustum-shaped blank primitives formed by N-1 level construction, so that one end of the facet with a smaller cross-sectional area contacts each other to form an hourglass shape as a whole; stacking into an hourglass The two blank primitives of the shape are packaged into an hourglass-shaped preform;

Welding the interface between the two blank primitives by forging to form the hourglass shaped preform into a blank;

The blank obtained by forging and welding is further forged into a circular or square platform, which is used as the blank basic element of the N+1 level construction;

Repeat the steps of N-level construction to prepare larger blanks, repeat the construction process until the weight of the blank reaches the target weight, and then forge the blank to the final forging size.

Technical scheme of the present invention is:

A method for forming an hourglass-shaped metal hierarchical structure, comprising the steps of:

Firstly, the blank element is prepared by the conventional construction method: multiple small-sized metal billets (which can be cast billets, forged billets or rolled billets) are stacked and then vacuum-packaged, and then a forging welding process characterized by upsetting and large deformation is applied to them , so that multiple pieces of small-sized metal blanks are combined to form a blank. The blank is further forged into a circular frustum or a square frustum to obtain the blank primitive. The cross-sectional area of one end of the large plane of the frustum-shaped or square-shaped blank is greater than the cross-sectional area of one end of the small plane;

Then the rough base unit is constructed, sealed and welded into a preform: the facet ends of two round or square base units with a smaller cross-sectional area are contacted with each other, and stacked into a large-sized rectangular parallelepiped or cylindrical hourglass shape. The metal plate encapsulates the constructed blank as a whole into a box, and vacuumizes the inside of the box; or uses vacuum welding to encapsulate the interface between the two primitives; the packaged blank is called an hourglass-shaped preform;

Then the hourglass-shaped preform is forged and welded into a blank: the packaged hourglass-shaped preform is heated to a specified temperature and released from the furnace, forged on a hydraulic press, and the measures of upsetting and large deformation are implemented to fully weld the interface and realize metallurgical connection. the blank;

After the blank is further forged, the blank is made into a blank basic unit and the construction process is repeated: the blank that is integrated after forging and welding is further forged into a circular or square platform. Use the circular frustum or square frustum-shaped blank as the blank basic unit, repeat the above construction process of making the blank basic unit into a blank, and each repetition of the construction process is called one level, until the weight of the blank reaches the target weight.

Final forming into devices: the blank is further formed by forging, rolling and other pressure processing methods, and precisely formed into the final specification size by machining.

The concrete steps of this method are as follows:

The first step is to use conventional construction methods to manufacture round or square base blanks;

The second step is to process and clean the surface of the blank primitive;

The third step is to stack two blank primitives into an hourglass shape;

The fourth step is to package the stacked blank elements so that each contact interface is in a vacuum state;

The fifth step is to heat the packaged hourglass-shaped preform before forging;

The sixth step is to perform upsetting and large deformation on the hourglass-shaped preform to obtain the blank;

The seventh step is to forge the blank into a circular or square platform to obtain the basic element of the blank, and repeat the process from the second step to the sixth step until the weight of the blank reaches the target weight;

The eighth step is to shape the blank to the final size.

In the first step of the hourglass-shaped metal hierarchical construction forming method, the conventional construction process is used to cut and prepare the metal billet into multiple primitives, surface processing and cleaning, stacking into a cylinder or a cuboid, packaging into a preform, forging After welding, it is made into a blank. This process is called the first level of construction. The blank is further forged into a circular frustum or a square frustum to obtain the blank primitive. The cross-sectional area of one end of the large plane of the frustum-shaped or square-shaped blank is larger than the cross-sectional area of one end of the small plane. The inclination angle of the side of the round or square platform relative to the axis is 0°～30°, and the side inclination angle can be kept consistent all the time, or it can be changed continuously. Small, and finally reduced to 0°, so that the facets of the two blank primitives are relatively stacked and the contact interface is smoothly transitioned. The ratio of the height of each blank primitive to the maximum width/length/diameter does not exceed 1.5:1, which is convenient for upsetting deformation.

In the second step of the hourglass-shaped metal graded construction forming method, the surface of the blank element is polished with an angle grinder and a steel brush to remove scale, and a milling machine is used to process the surface if necessary. Then use organic solvents such as acetone and alcohol to clean the surface to ensure a high degree of cleanliness and expose fresh metal.

In the third step of the hourglass-shaped metal hierarchical construction forming method, the facet ends of two circular or square-shaped blanks with a smaller cross-sectional area are contacted with each other, and stacked into a large-scale rectangular parallelepiped or cylindrical hourglass shape, so that The edges are aligned, and the ratio of the total height to the maximum width/length/diameter after stacking does not exceed 3:1.

In the fourth step of the hourglass-shaped metal hierarchical construction method, cheap metal plates are used to package the stacked blank elements into a box, and the box body is reserved for vacuuming the interface, and then the interface is sealed after vacuuming the box ; or put the stacked blank elements into a vacuum chamber as a whole, and then seal the interface between the two elements by vacuum welding, and the welding depth of the packaging interface is 10-50mm. After the encapsulation is completed, an hourglass-shaped preform is obtained.

In the fifth step of the hourglass-shaped metal hierarchical construction forming method, the welded preform is sent to a heating furnace for heating at a heating temperature of 0.8 to 0.9 Tm, where Tm is the melting point of the material in °C. A preferred temperature is 0.85Tm.

In the sixth step of the hourglass-shaped metal hierarchical construction forming method, the heated hourglass-shaped preform is placed horizontally on the operating platform of the forging press, and the blank is upset along the height direction (that is, perpendicular to the interface direction) with an upsetting plate ;Depress 10-50% of the total height of the blank. This process is called forging welding. After forging and welding, the blank is obtained. This process is called the second-level construction. During the forging process, if the interface between the two blank primitives is not fully welded, the two blank primitives are separated and forged back to the size of the blank primitives in the first step to re-build the second stage .

In the seventh step of the hourglass-shaped metal hierarchical construction forming method, the blank obtained in the sixth step is further forged into a circular frustum or a square frustum to obtain a blank basic element. Surface processing, cleaning, stacking, packaging, and forging welding are carried out on two blank primitives of the same size again, that is, the process from the second step to the sixth step is repeated. This process is called the third-level construction. This process can be repeated many times, each repetition of the construction is called a level. The weight of the blank after each construction is twice the weight of the blank primitive before the construction, and multi-stage construction is carried out until the weight of the blank reaches the target weight.

In the eighth step of the hourglass-shaped metal hierarchical construction forming method, the multi-stage construction blank is further formed by forging, rolling and other pressure processing methods, and is accurately formed into the final specification size by machining.

The present invention breaks through the traditional thinking that the base material of a metal device can only be larger than it, and uses a small metal billet with better quality and lower cost to construct and form it, which has the following advantages and beneficial effects:

1. Realize the homogeneous manufacturing of large-scale metal devices. Multiple metal billets with smaller volumes are used as building blocks. Due to the fast solidification speed, the composition uniformity is far better than that of traditional integrally cast large metal billets. Large-scale metal devices constructed on this basis do not exist. Significant macrosegregation.

2. Realize the densification of large-scale metal devices. Using multiple metal billets with smaller volumes as the building blocks, due to the fast solidification speed, almost simultaneous solidification can be achieved, so there are fewer shrinkage cavities and porosity concentrated inside the billet. After deformation, heat preservation and multi-directional forging at the welding interface, the compactness is higher than that of forgings made of traditional integral billets.

3. Realize the purified manufacturing of large-scale metal devices. Multiple metal billets with smaller volumes are used as the building blocks. Due to the low preparation cost and difficulty, various flexible refining methods can be used to realize the purification of the primitives. The large-scale metal devices constructed on this basis are pure Higher than forgings made of traditional solid billets.

4. Realize low-cost manufacturing of large-scale metal devices. Since large-scale production methods such as continuous casting can be used to prepare smaller metal billets, its manufacturing cost is much lower than the die casting method that must be used to prepare larger metal billets, so the manufacturing cost can be greatly reduced. In addition, using continuous casting slabs as building blocks, there is no riser and nozzle loss of traditional steel ingots, and the material utilization rate can be increased by more than 15%.

5. Realize the clean and stable manufacturing of large-scale metal devices. The preparation of metal billets by traditional die casting methods requires manual preparation of molds, runners, and insulation materials. At the same time, there is a large environmental pollution in the riser heating agent and covering agent after pouring. By adopting the hourglass-shaped metal grading construction method, the process can be fully automated, which not only improves the working environment, but also reduces the influence of human factors, and the product quality will be more stable.

6. Realize high-reliability graded manufacturing of super-large components. The traditional construction method is to directly construct multiple metal blanks. During the manufacturing process of the construction blanks, there is a high possibility of scrapping due to accidental factors such as interface pollution or weld failure causing the interface to break the vacuum. For example, for super-large forgings over 100t, traditional construction methods are used to construct continuous casting slabs, and the number of continuous casting slabs stacked exceeds 10 layers. The failure of a single interface between any two layers will lead to the scrapping of the forging as a whole, resulting in huge losses. . Through the step-by-step forming method, it is possible to gradually reduce the size from the small to the large. Only in the first-stage construction process, there are multiple interfaces in the blank, and in the subsequent multi-stage construction process, there is only one interface at a time, which can effectively reduce the vacuum caused by the interface breaking the overall forging. risk of obsolescence.

7. Realize the small pressure manufacturing of super large components. The traditional construction method is to directly construct a plurality of metal blanks. After construction, the preform is in the shape of a cylinder or a cuboid, and the deformation requires a large press pressure. The hourglass-shaped metal graded construction method is adopted. Since the hourglass-shaped middle size is small and the upper and lower ends are large, the middle section of the small size is preferentially deformed during the deformation process, so the large deformation at the middle interface can be realized under a small pressure, thereby realizing metal The metallurgical bonding of the interface between the basic elements reduces the pressure required for the construction of super-large components.

Description of drawings

Fig. 1a to Fig. 1h are process flow charts of the present invention, wherein, Fig. 1a shows the preform obtained by conventional construction process; Fig. 1b forges and welds the preform into a blank, and further forges it into a circular frustum or square frustum to obtain the blank element; Figure 1c shows that the surface of the blank element is flattened to expose fresh metal, and then cleaned; Figure 1d shows that the interface between the blank elements is sealed and welded in a vacuum environment to obtain an hourglass-shaped preform; Figure 1e shows Put the hourglass-shaped preform into a high-temperature furnace for heating; Figure 1f shows that an upsetting plate is used on the forging press to upset along the height direction of the hourglass-shaped preform; Figure 1g shows that the upsetting deformation is in place, and the defects are fully welded to obtain a blank; Figure 1h shows the blank being further forged and machined into the final part shape and dimensions.

Fig. 2 is the schematic diagram of the construction process of Example 1 of the present invention, the first-level construction adopts the conventional construction process to prepare the square platform-shaped blank primitive used in the second-level construction, and the second-level construction adopts the method of the present invention to obtain the first-level construction Two pieces of square truss-shaped rough base elements are made into square truss-shaped rough base elements used as the third-level construction, and the third-level construction adopts the method of the present invention to prepare the two pieces of square-shaped blank base elements obtained by the second-level construction into a larger blank.

Fig. 3 is a schematic diagram of the construction process of Example 2 of the present invention, the first-level construction adopts the conventional construction process to prepare the frustum-shaped blank primitive used in the second-level construction, and the second-level construction adopts the method of the present invention to obtain the first-level construction Two truncated conical blanks are made into a truncated conical blank used as a third-level construction, and the third-level construction adopts the method of the present invention to prepare the two truncated conical blanks obtained by the second-level construction into a larger blank.

detailed description

Fig. 1a to Fig. 1h are process flow charts of the present invention, wherein, Fig. 1a shows the preform obtained by conventional construction process; Fig. 1b forges and welds the preform into a blank, and further forges it into a circular frustum or square frustum to obtain the blank element; Figure 1c shows that the surface of the blank element is flattened to expose fresh metal, and then cleaned; Figure 1d shows that the interface between the blank elements is sealed and welded in a vacuum environment to obtain an hourglass-shaped preform; Figure 1e shows Put the hourglass-shaped preform into a high-temperature furnace for heating; Figure 1f shows that an upsetting plate is used on the forging press to upset along the height direction of the hourglass-shaped preform; Figure 1g shows that the upsetting deformation is in place, and the defects are fully welded to obtain a blank; Figure 1h shows the blank being further forged and machined into the final part shape and dimensions.

Fig. 2 is the schematic diagram of the construction process of Example 1 of the present invention, the first-level construction adopts the conventional construction process to prepare the square platform-shaped blank primitive used in the second-level construction, and the second-level construction adopts the method of the present invention to obtain the first-level construction Two pieces of square truss-shaped rough base elements are made into square truss-shaped rough base elements used as the third-level construction, and the third-level construction adopts the method of the present invention to prepare the two pieces of square-shaped blank base elements obtained by the second-level construction into a larger blank.

Example 1

The target product of this embodiment is a 316 stainless steel ring. Firstly, the continuous casting method is adopted, and the continuous casting slab with a width of 1000mm and a thickness of 300mm is poured, and its steel type is 316H. Then cut out the continuous casting slab element with a length of 1000mm, process and clean it, seal and weld it into a preform in a vacuum chamber. After the preform is forged and welded and further forged, a 10t-level blank element is obtained. After surface processing, cleaning, stacking, encapsulation, forging and welding, and further forging, 4 pieces of 10t-level rough base units were used to obtain 2 pieces of 20t-level rough base units. After surface processing, cleaning, stacking, packaging, and forging welding of two 20t-level blank elements, a 40t-level blank was obtained. Finally the blank is forged into a ring. Specific steps are as follows:

In the first step, blank primitives are fabricated using conventional construction methods. Cut out 16 continuous casting slabs with specifications of 1000×1000×300mm. After processing and cleaning, each 4 pieces of continuous casting slabs are stacked and welded into 1000×1000×1200mm preforms in a vacuum chamber. After the preform is forged and welded, a 10t-level blank is obtained. The blank is forged into a square platform with a large plane of 1240×1240mm, a small plane of 870×870mm, a height of 1050mm, and a constant side inclination angle. This blank is a 10t-level blank primitive. A total of 4 pieces of 10t-level rough primitives were obtained.

The second step is to process and clean the surface to be welded. A gantry milling machine is used to process the surface of the 10t-level blank element, and then cleaned with acetone to ensure a high degree of cleanliness of the surface and expose fresh metal.

The third step is to stack the 10t-level rough primitives. Stack two 10t-level blank primitives, and after stacking, it becomes an hourglass shape with a top and bottom surface of 1240×1240mm, the smallest part in the middle of 870×g70mm, a height of 2100mm, and a weight of about 20t.

The fourth step is to carry out vacuum electron beam welding on the 10t-level blank primitive. Vacuum electron beam welding is carried out around the stacked 10t-level blank element with a welding depth of 50mm. After welding, a 20t-level preform is obtained.

The fifth step is to heat the 20t preform before forging. The welded preform is sent into a heating furnace for heating, and the heating temperature is 1200°C.

The sixth step is to upsetting the 20t level preform. Place the heated 20t level preform on the operating platform of the forging press so that the height direction of the 20t level preform is along the vertical direction. The upsetting plate is used to upset the preform along the height direction, and press down 50% of the total height of the preform. After the deformation is completed, a 20t level blank is obtained. The blank is forged to a square platform shape with a large plane of 1550×1550mm, a small plane of 1085×1085mm, and a height of 1320mm to become a 20t-level blank basic unit. A total of 2 pieces of 20t-level rough primitives were obtained.

The seventh step is to manufacture 40t-level blanks. Surface processing, cleaning, stacking, and packaging of two 20t-level blank elements were performed to obtain a 40t-level preform. After the preform is forged and welded to become a 40t level blank, the process from the second step to the sixth step is repeated.

The eighth step is to forge the 40t-level blank to the final forging size. The forging is ring-shaped, with an inner diameter of 1030mm, an outer diameter of 2630mm, and a height of 1000mm.

Fig. 3 is a schematic diagram of the construction process of Example 2 of the present invention, the first-level construction adopts the conventional construction process to prepare the frustum-shaped blank primitive used in the second-level construction, and the second-level construction adopts the method of the present invention to obtain the first-level construction Two truncated conical blanks are made into a truncated conical blank used as a third-level construction, and the third-level construction adopts the method of the present invention to prepare the two truncated conical blanks obtained by the second-level construction into a larger blank.

Example 2

The target product of this embodiment is the rotor forging. Firstly, the continuous casting method is used to cast a continuous casting slab with a width of 1600mm and a thickness of 300mm, and its steel type is 16Mn. Then cut out the continuous casting slab element with a length of 1600mm, process and clean it, seal and weld it into a preform in a vacuum chamber. After the preform is forged and welded and further forged, a 40t-level blank element is obtained. After surface processing, cleaning, stacking, encapsulation, forging and welding and further forging, 4 pieces of 40t-level rough base units were used to obtain 2 pieces of 80t-level rough base units. After surface processing, cleaning, stacking, packaging, and forging welding, two 80t-level blank elements were used to obtain one 160t-level blank. Finally the blank is forged into a rotor. Specific steps are as follows:

In the first step, blank primitives are fabricated using conventional construction methods. Cut out 28 pieces of continuous casting slabs with specifications of 1600×1600×300mm. After the continuous casting slabs are processed and cleaned, they are stacked and welded into 1600×1600×2100mm preforms in a vacuum chamber by stacking every 7 pieces. After the preform is forged and welded, a 40t-level blank is obtained. The blank is forged into a frustum of conical shape with a large plane of φ2250mm, a small plane of φ1650mm, and a height of 1750mm. The side of the blank close to the small plane has a circular arc transition with a radius of 1000mm. The blank is a 40t-level blank primitive. A total of 4 pieces of 40t-level blank primitives were obtained. The second step is to process and clean the surface to be welded. A gantry milling machine is used to process the surface of the 40t-level blank element, and then cleaned with acetone to ensure a high degree of cleanliness of the surface and expose fresh metal.

The third step is to stack the 40t-level blank primitives. Two pieces of 40t-level blank primitives are stacked, and after stacking, the top and bottom surfaces are φ2250mm, the thinnest part in the middle is φ1650mm, and the hourglass shape is 3500mm in height. It is 80t.

The fourth part is to carry out vacuum electron beam welding on the 40t-level blank element. Vacuum electron beam welding is carried out around the stacked 40t-level blank element with a welding depth of 50mm, and an 80t-level preform is obtained after welding.

The fifth step is to heat the 80t preform before forging. The welded preform is sent into a heating furnace for heating, and the heating temperature is 1200°C.

The sixth step is to upsetting the 80t preform. Place the heated 80t level preform on the operating platform of the forging press so that the height direction of the 80t level preform is along the vertical direction. The upsetting plate is used to upset the preform along the height direction, and press down 50% of the total height of the preform. After the deformation is completed, an 80t grade blank is obtained. The blank is forged to a truncated conical shape with a large plane of φ2900mm, a small plane of φ2250mm, and a height of 2000mm. The side near the small plane is a circular arc transition with a radius of 1500mm to obtain an 80t-level blank primitive. A total of 2 pieces of 80t-level rough primitives were obtained.

The seventh step is to manufacture 160t-level blanks. After surface processing, cleaning, stacking and packaging of two 80t-level blank primitives, a 160t-level preform was obtained. After the preform is forged and welded to become a 160t level blank, the process from the second step to the sixth step is repeated.

The eighth step is to forge the 160t-level blank to the final forging size. The forging is a rotor forging with a total length of 9000mm, a maximum diameter of 3000mm, and a minimum diameter of 700mm.

Claims (11)

1. A step-by-step forming method for hourglass-shaped metal, characterized in that it comprises: First-level construction and N-level construction, where N≥2, Described primary construction comprises the steps: Prepare multiple primitives; Stack multiple primitives into a cylinder or cuboid; Pack multiple primitives stacked into cylinders or cuboids into preforms; By forging and welding, the interface between multiple blank primitives is welded to make the preform into a blank, and the blank is further forged into a circular frustum or a square frustum, which is used as the blank primitive for the next stage of construction. The circular frustum or square frustum is The cross-sectional area of one end of the large plane of the blank is larger than the cross-sectional area of one end of the small plane; The N-level architecture includes: Stacking two frustum-shaped or frustum-shaped blanks formed by N-1 level construction together, so that one end of the facet with a smaller cross-sectional area contacts each other to form an hourglass shape as a whole; Pack the two blank primitives stacked in an hourglass shape into an hourglass-shaped preform; Welding the interface between the two blank primitives by forging to form the hourglass shaped preform into a blank; The blank obtained by forging and welding is further forged into a circular or square platform, which is used as the blank basic element of the N+1 level construction; Repeat the steps of N-level construction to prepare larger blanks, repeat the construction process until the weight of the blank reaches the target weight, and then forge the blank to the final forging size. 2. The hourglass-shaped metal step-by-step construction forming method according to claim 1, characterized in that the inclination angle of the side of the circular frustum or square frustum relative to the axis is 0°-30°. 3. The hourglass-shaped metal step-by-step construction forming method according to claim 2, characterized in that the angle of inclination of the side of the circular frustum or square frustum is always consistent. 4. The step-by-step forming method of hourglass-shaped metal according to claim 2, characterized in that the inclination angle of the side of the circular or square frustum gradually decreases from one end of the large plane to one end of the small plane, and finally decreases to 0°. 5. The hourglass-shaped metal hierarchical construction forming method according to claim 1, characterized in that the ratio of the height to the maximum width/length/diameter of the hourglass shape formed by stacking two blank primitives does not exceed 3:1. 6 . The hourglass-shaped metal hierarchical construction forming method according to claim 1 , wherein the hourglass shape is a rectangular parallelepiped or a cylindrical hourglass shape. 7 . 7. The hourglass-shaped metal hierarchical construction forming method according to claim 1, characterized in that, the step of making the hourglass-shaped preform into a blank by forging and welding the interface between the two blank elements includes heating the preform Billet, the heating temperature range is between 0.8-0.9Tm, Tm is the melting point of the material, the unit is °C, preferably, the heating temperature is 0.85Tm, and then the heated hourglass-shaped preform is placed on the operating platform of the forging press for forging , deforming the hourglass-shaped preform. 8 . The step-by-step forming method for hourglass-shaped metal according to claim 7 , wherein the amount of deformation is 10%-50% of the total length of the hourglass-shaped preform in the deformation direction. 9. The hourglass-shaped metal hierarchical construction forming method according to claim 8, characterized in that the deformation direction is the height direction of the hourglass-shaped preform, that is, the direction perpendicular to the interface between two blank elements. 10. The step-by-step forming method of hourglass-shaped metal according to claim 9, during the process of forging and pressing the preform to deform the preform, the deformation is stopped when the cross-sectional area of the preform is substantially equal from both ends to the middle. 11. The metal hierarchical building forming method according to claim 1, characterized in that, when performing the N-level building step, if the interface between the two blank primitives is welded by forging welding to weld the preform In the process of making the blank, the interface between the two blank primitives cannot be completely welded, and the two blank primitives can be separated and forged back to the circular or square shape of the blank primitive at the end of the N-1 level construction Dimensions for another N-level build.