A method of stress relief of a weld joint of a metal substrate for building forming

Abstract

The application provides a kind of built-up metal base weld stress relief method for forming, and belongs to the technical field of machining.The method processes wedge-shaped boss of specific height and length on the construction surface of built-up metal base by machining;pressure deformation is carried out on the built-up metal base by cold deformation process, so that the boss area disappears under the condition that the base itself does not occur plastic deformation;the built-up base after pressure forming can be stacked and welded with other bases treated in the same way.The pre-deformation of the built-up base before welding can solve the cracking problem caused by welding stress and avoid the gas leakage problem caused by cracks, which provides protection for subsequent construction forming.

Description

Technical Field

[0001] This invention relates to a method for stress relief of weld seams in metal substrates used for construction and forming, belonging to the technical field of machining. Background Technology

[0002] Metal construction combines the advantages of traditional high-temperature large-scale casting with similar 3D printing technology. By selecting additive manufacturing units of appropriate size for solid-state connection, it not only effectively solves the problems of solidification shrinkage and segregation in large ingots, but also shortens the performance gap between laboratory materials and engineered components.

[0003] The process flow of metal construction forming technology is as follows: (1) Select high-quality initial blanks and perform surface cleaning treatment; (2) Stack the original blanks and perform vacuum sealing welding to prevent oxidation pollution; (3) High temperature and pressure forging; (4) Multi-directional forging to achieve complete healing and seamless connection.

[0004] In process flow (2), due to the large size of the substrate and the high welding speed, large residual stress in the weld is easily generated, leading to weld cracking. Weld cracking prevents the substrate interface area from being sealed, making it difficult to prevent oxidation contamination and requiring re-welding, resulting in a significant increase in cost. At the same time, since welding is carried out in a vacuum, it is difficult to use stress relief methods that require additional equipment, such as ultrasonic vibration. Therefore, existing construction forming technology urgently needs a new method for simultaneous stress relief of the weld. Summary of the Invention

[0005] The purpose of this invention is to provide a method for stress relief of weld seams in metal substrates for construction, in order to solve the problems existing in the prior art, and to solve the problem of synchronous stress relief of the substrate during the welding process without introducing additional ultrasonic devices.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] A method for stress relief of weld seams in metal substrates used for construction and forming. This method utilizes the pre-deformation of the substrate before welding to solve the cracking problem caused by welding stress, avoid gas leakage caused by cracks, and provide a guarantee for subsequent construction and forming. The method includes the following steps:

[0008] First, for the construction surface of the metal substrate used in construction, a wedge-shaped boss of appropriate size is machined, where size refers to a specific height and length.

[0009] Secondly, a cold-pressing deformation process is used to deform the metal substrate for construction, eliminating the wedge-shaped protrusion area while ensuring that the substrate itself does not undergo significant plastic deformation. In other words, the wedge-shaped protrusion is deformed to make it disappear.

[0010] Finally, the pressure formed construction base material is stacked with other base materials treated in the same way and subsequent welding is performed.

[0011] Further, the construction base material includes but is not limited to stainless steel, alloy steel, aluminum alloy, copper alloy, titanium alloy and other suitable metal materials for construction forming. These materials are usually deformable alloys used to prepare various forgings, rolled pieces or extruded pieces.

[0012] Further, the construction base material is a flat cuboid, and the large size plane defined by the length and width is the construction surface. A plurality of cuboids are stacked in a form of contacting the construction surfaces to obtain a shape suitable for subsequent deformation processing in terms of length, width and height.

[0013] Further, the mechanical processing is performed on the construction surface, and the upper surface, lower surface or both surfaces of the construction surface are processed. Depending on the stacking position during the construction process, only one surface of the uppermost layer and the lowermost layer after stacking needs to be processed, but both surfaces of the intermediate layer must be processed.

[0014] Further, the wedge-shaped boss is located at the edge of the construction surface and must be in a ring structure and cannot be interrupted.

[0015] Further, the height H of the wedge-shaped boss is 0.5-10mm, and the percentage value of the boss height H to the base material height should not exceed the cold deformation limit deformation amount of the metal.

[0016] Further, the length L of the wedge-shaped boss is L≥H, and L≥h. L≥H can ensure that there is no excessive stress concentration during cold pressure deformation, and L≥h ensures that the cold deformation area can cover the entire weld depth. The weld depth is different depending on the welding process.

[0017] Further, the cold pressure deformation usually uses various forging presses, rolling mills and extrusion machines, etc. The cold pressure deformation only deforms the plasticity of the wedge-shaped boss, and pressure is applied to the upper and lower surfaces of the construction base material to uniformly deform the wedge-shaped boss as a whole. After deformation, the height H of the wedge-shaped boss is 0 to ensure the level of the upper and lower surfaces of the construction base material.

[0018] Further, the overall deformation of the construction base material should not be greater than 5%. Although the metal base material used for construction forming usually has high plasticity and can meet the needs of small size cold pressure deformation, it should not be subjected to large cold deformation, which may cause cracks and other damage to the construction base material, and may also affect the internal quality of the base material due to large plastic deformation, affecting the subsequent process.

[0019] The beneficial effects of the present application are as follows:

[0020] This invention utilizes the introduction of wedge-shaped bosses to generate a residual compressive stress field by cold deformation of the building substrate. The cold deformation effectively maintains this compressive stress field, which can effectively offset the welding tensile stress during subsequent welding processes, significantly reducing the possibility of weld cracking and providing a guarantee for subsequent building formation. Attached Figure Description

[0021] Figure 1 A schematic diagram of a construction substrate for machining an annular wedge-shaped boss on one side.

[0022] Figure 2 A plan view of a substrate for fabricating an annular wedge-shaped boss on one side; where L = 6 mm and H = 4 mm.

[0023] Figure 3 This is a schematic diagram of a substrate constructed using a three-layer stack.

[0024] Figure 4 shows a comparison of the microstructure of different parts of the aluminum alloy structural substrate after cold pressing deformation. Figure 4a This is a non-deformable region. Figure 4b This is the deformation region.

[0025] Figure 5 This study compares the residual stress at different depths of the weld after welding of cold-pressed aluminum alloys. Detailed Implementation

[0026] The present invention will be further described below with reference to specific implementation examples.

[0027] This embodiment uses 2219 aluminum alloy for forging. Two 2219 alloy substrates with dimensions of 200mm × 160mm × 30mm were selected. Wedge-shaped bosses were machined on a 200mm × 200mm plane of each substrate. The dimensions of the bosses were height H = 4mm and length L = 6mm. A schematic diagram of the substrate morphology with a single-sided annular wedge-shaped boss is shown below. Figure 1 As shown, the dimensions of the wedge-shaped boss are as follows: Figure 2 As shown.

[0028] A 300t four-column hydraulic press was used for cold pressing deformation to eliminate the wedge-shaped bosses, achieving H=0mm. Due to the precision of process control, the overall height of the 2219 aluminum alloy was reduced by 0.6mm, with a deformation amount of 2%. Figure 4 shows a comparison of the microstructure of different parts of the aluminum alloy substrate after cold pressing deformation. Figure 4a This is a non-deformable region. Figure 4b The deformation zone shows no significant difference in the microstructure between the two zones, and the deformation of the wedge-shaped boss will not affect the subsequent construction process.

[0029] Deformed 2219 aluminum alloy base Figure 3The stacking principle is shown, two deformation surfaces are stacked in contact with each other, and subsequent welding is carried out, in order to ensure that the aluminum alloy has a deep weld penetration, laser / arc hybrid welding process is used for welding. Figure 5 After welding, the residual stress of the weld at different depths is compared with the welding, the measurement position is selected as the weld fusion zone part which is most affected by the weld residual stress, the residual compressive stress generated by the wedge boss is the maximum residual stress value of the welding, which decreases from 120MPa to 64MPa, and the overall downward trend is shown on different thicknesses, which shows good ability to eliminate weld residual stress.

[0030] The above-described embodiments are only to describe the preferred modes of the present application, and not to limit the scope of the present application, and various modifications and improvements to the technical solutions of the present application made by those skilled in the art without departing from the design spirit of the present application shall fall within the protection scope determined by the claims of the present application.

Claims

1. A method for stress relief of a weld in a metal substrate for construction forming, characterized by, The method comprises the following steps: First, a wedge-shaped boss with a specific height H and length L is machined on the construction surface of the metal base material; Second, the metal base material is subjected to pressure deformation by cold pressure deformation process, and the wedge-shaped boss area disappears under the condition that the base material itself does not undergo large plastic deformation; Finally, the construction base material after pressure forming is stacked with other base materials subjected to the same treatment and then welded.

2. A method of stress relieving a weld in a metal substrate for building forming according to claim 1, wherein The construction base material is made of alloy steel, aluminum alloy, copper alloy, and titanium alloy.

3. A method of stress relieving a weld in a metal substrate for building forming according to claim 1, wherein The construction base material is a flat cuboid, and the large-size plane defined by length and width is the construction surface. Multiple cuboids are stacked in contact with the construction surface to obtain a shape suitable for subsequent deformation processing in terms of length, width, and height.

4. A method of stress relieving a weld in a metal substrate for building forming according to claim 1, wherein The mechanical processing is performed on the construction surface, and the upper surface, lower surface, or both surfaces are machined. The uppermost and lowermost layers are machined on one side, and the intermediate layers are machined on both sides.

5. A method of stress relieving a weld in a metal substrate for building forming according to claim 1, wherein The wedge-shaped boss is a ring structure at the edge of the construction surface and cannot be interrupted.

6. A method of stress relieving a weld in a metal substrate for building forming according to claim 1, wherein The height H of the wedge-shaped boss is 0.5-10mm, and the percentage of height H to the height of the base material should not exceed the cold deformation limit of the metal base material.

7. A method of stress relieving a weld in a metal substrate for building forming according to claim 1, wherein The length of the wedge-shaped boss is L, L≥the height of the wedge-shaped boss, and not less than the weld depth h.

8. A method of stress relieving a weld in a metal substrate for building forming according to claim 1, wherein The cold pressure deformation only deforms the wedge-shaped boss, and the wedge-shaped boss deforms uniformly as a whole; after deformation, the height H of the wedge-shaped boss is 0, ensuring the levelness of the upper and lower surfaces of the construction base material.

9. A method of stress relieving a weld in a metal substrate for building forming according to claim 1, wherein The overall deformation of the construction base material should not be greater than 5%.

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