A method for equal strength welding of cold-worked stainless steel welded structures

Abstract

The application discloses a cold work-hardened stainless steel welding structure equal-strength welding method. The main welding seam joint of the strengthened stainless steel welding structure is designed in a butt joint form, and a reinforcing backing plate is arranged below or above the main welding seam. When the backing plate is arranged below the main welding seam, the butt joint interface of the main welding seam and the overlapping interface of the main welding seam and the reinforcing backing plate are completely welded through one-time welding, and the reinforcing backing plate can not be penetrated. When the backing plate is arranged above the main welding seam, the main welding seam should be welded first, and then the backing plate is arranged above the main welding seam for reinforcing welding. The backing plate-structure main body is connected through a line welding seam or a welding point in a perpendicular manner to the main welding seam, so that when the main welding seam is subjected to an acting force, the stress is transmitted to the reinforcing plate through the overlapping joint, and part of the stress is shared by the reinforcing plate, thereby improving the stress bearing capacity of the overall structure. The reinforcing effect is provided by the overlapping welding seam of the reinforcing backing plate and the main welding seam and the horizontal overlapping welding seam of the reinforcing backing plate and the main body, and the overall structure strength after the reinforcing reaches the equal strength of the structure in the strengthened state of the base material.

Description

Technical Field

[0001] This invention relates to a method for equal-strength welding of cold-worked austenitic stainless steel structures, and more particularly to welding structures of cold-worked austenitic stainless steel or other strain-strengthened metal materials. Background Technology

[0002] With the development of the commercial aerospace sector, the demand for low-cost, safe, and reliable propellant tanks is constantly increasing. Currently, SpaceX is using stainless steel to manufacture cryogenic propellant tanks and has completed relevant flight tests. Some domestic commercial aerospace companies are also following suit, and stainless steel tanks are expected to become a new way to achieve low-cost space transportation. Stainless steel tanks are characterized by high strength, corrosion resistance, and high temperature resistance, while also possessing advantages such as recyclability and low cost, making them an ideal choice for the commercial aerospace field. Austenitic stainless steel, due to its high Ni content, has good low-temperature performance, cold forming ability, and weldability, and is widely used in cryogenic pressure vessels. To achieve the goal of lightweight austenitic stainless steel structures, strain strengthening treatment is required. After strain strengthening treatment, the yield strength of austenitic stainless steel is improved, and the wall thickness can be reduced by 30% to 50%, which is beneficial for saving materials and significantly improving economic efficiency. However, after welding the strengthened stainless steel thin plates, problems such as joint softening and deformation will occur. For fully cold-worked 304 stainless steel, the joint strength decreases by more than 30%, requiring thickening design to compensate for the strength reduction, which is particularly detrimental to the weight reduction of stainless steel structures.

[0003] To address the joint softening problem, Han Yanfa et al. proposed a welding process method to improve joint softening (202310451204.6). This method involves welding two isolation layers using CMT (Chemical Metal Mesh), followed by a filler layer between the isolation layers, and then welding layer by layer until the entire bevel is filled, forming a complete welded joint. However, this method requires butt gaps and material filling, making it unsuitable for laser welding of thin-plate stainless steel and reducing productivity. Furthermore, Peng Yun et al. proposed a method to reduce the softening degree of laser-welded joints in high-strength, high-ductility manganese steel (201810257705.X). This method employs higher laser power and welding speed, rationally adjusts process parameters, and cools the back side of the welded steel during welding. This reduces the width of the heat-affected zone and effectively reduces the degree of softening in the heat-affected zone of the welded joint. While this method reduces the impact of joint softening, its effect is limited; it cannot completely eliminate softening and increases welding costs. Therefore, new methods are needed to solve the joint softening problem. Summary of the Invention

[0004] In view of the above problems, this invention proposes a method for equal-strength welding of reinforced stainless steel welded structures to solve the problem of joint softening after welding cold-worked austenitic stainless steel. To ensure the quality of the welded structure and improve the overall structural rigidity, it is necessary to reinforce the weak load-bearing structures. A reinforcing backing plate is placed below or above the main weld of the cold-worked stainless steel welded structure, i.e., the main weld of the reinforced stainless steel welded structure; the main weld joint is designed as a butt joint.

[0005] The reinforcing pad is connected to the main structure via a line weld or weld point lap joint perpendicular to the main weld.

[0006] The lap weld between the reinforcing pad 1 and the main weld 4, and the lateral lap weld between the reinforcing pad and the main structure 2, together provide a reinforcing effect, and the overall structural strength after reinforcement reaches the same strength as the structure in the reinforced state of the base material.

[0007] Preferably, when the backing plate is located below, the butt joint interface of the main weld and the lap joint interface of the main weld and the reinforcing backing plate can be completely welded through in one welding, and the reinforcing backing plate may not be fully welded; when the backing plate is located above, the main weld should be welded first, and then the backing plate should be placed above the main weld for reinforcing welding.

[0008] Preferably, the backing plate is lapped to the main structure via a line weld perpendicular to the main weld. The lap welds of the reinforcing backing plate and the main weld, as well as the transverse lap welds of the reinforcing backing plate and the main structure, together provide a reinforcing effect, achieving the same strength as the reinforced base material. The reinforcing welds disperse the forces acting on the main plate through the lap joint, improving the overall load-bearing capacity of the structure, thereby increasing its strength and stability. Preferably, laser welding is more suitable for the repair weld, using different parameters than the main weld to ensure that the predetermined weld form and size requirements are met.

[0009] Preferably, when using this welding method, it is only necessary to form an lap joint between the reinforcing pad and the main structure, and the main structure should not be fully penetrated as much as possible. The lap joint welds between the reinforcing pad and the main structure should be evenly distributed, and the number and size should be determined according to the actual situation.

[0010] Preferably, the position of the backing plate is relative to the laser irradiation surface as a reference; the laser irradiation surface is considered upper, and the backing plate is on top, and vice versa. If the backing plate is lower, it may not be fully welded; if the backing plate is upper, it must be fully welded.

[0011] When the reinforcing plate is located below, first fully weld the butt joint interface of the main weld, then assemble the reinforcing plate, and weld the lap joint interface between the reinforcing plate and the main body. If the excess height of the main weld affects the installation of the front reinforcing plate, the excess height can be ground down before assembly.

[0012] Preferably, the direction of the reinforcing line weld is perpendicular to the direction of the main weld and is located on both sides of the main weld. It only needs to form an lap connection and should not penetrate the main structure as much as possible. The lap reinforcement welds are evenly distributed, and the number and size are determined according to the actual situation. The reinforcement welds are evenly distributed to reduce stress concentration, thereby ensuring the ability of the reinforcement welds to share the force on the main board.

[0013] Preferably, the reinforcing plate and the main plate are connected by an lap joint. The force on the main plate is distributed to the reinforcing plate through the lap joint. The type of reinforcing weld is a spot weld or a line weld, which is kept at a certain distance from the main weld. The lap area and distribution pattern are determined according to the actual situation.

[0014] Preferably, if the strength of the reinforcing pad is the same as that of the base material, then the thickness should meet the following requirements:

[0015] Preferably, the length of the reinforcing weld should meet the following requirements:

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0017] (1) It can effectively solve the problem of joint softening after welding of reinforced stainless steel, and improve the stability and reliability of the overall structure;

[0018] (2) No additional equipment is needed to achieve the reinforcement effect. The operation is simple and the cost is low. Attached Figure Description

[0019] Figure 1 It is a back-side reinforcement solution;

[0020] Figure 2 For reinforcement of the longitudinal section of the weld;

[0021] Figure 3 A schematic diagram of laser incidence on the main weld seam;

[0022] Figure 4 This is a front view diagram showing the reinforcing plate in place.

[0023] Figure 5 This is a cross-sectional diagram;

[0024] Figure 6 This is a schematic diagram of a reinforcing weld in the form of a weld point;

[0025] Figure 7 This is a schematic diagram of a reinforcing weld in the form of a weld. Detailed Implementation

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0027] This invention provides a method for equal-strength welding of reinforced stainless steel welded structures, addressing the joint softening problem that occurs after longitudinal seam welding in storage tanks with reinforced stainless steel as the base material. This method is used to reinforce weld areas with weak load-bearing capacity. By employing a through-lap joint structure, when the main plate is subjected to force, the lap joint transfers the stress to the reinforcing plate, which then shares part of the stress, improving the overall load-bearing capacity of the structure and thus ensuring its reliability and stability.

[0028] like Figure 1 As shown, this is the back-side reinforcement scheme. The main weld 4 joint of the reinforced stainless steel welded structure is designed as a butt joint. The reinforcing backing plate 1 is placed below the main weld 4. The butt joint interface of the main weld 4 and the lap joint interface of the main weld and the reinforcing backing plate are completely penetrated in one weld. The reinforcing backing plate 1 may not be fully penetrated. The reinforcing backing plate 1, the base material 3, and the base material 5 are welded into a whole. The backing plate and the main structure are connected by a linear reinforcing weld 2 perpendicular to the main weld. The lap joint of the reinforcing backing plate 1 and the main weld 4, and the transverse lap joint of the reinforcing backing plate and the main structure 2 together provide a reinforcement effect. The overall structural strength after reinforcement reaches the same strength as the reinforced base materials 3 and 5. Figure 2 Longitudinal cross-section of the reinforced weld. Figure 3 This is a schematic diagram of laser incidence on the main weld. Reinforcing weld 2 is a lap weld, as shown in the side view. Figure 4 As shown.

[0029] Figure 4 This assumes the reinforcing plate is on the front side. Assemble parts 3 and 5 by butt welding them together via the main weld 4 to form a single unit. Then assemble reinforcing plate 1. If the excess height of the main weld 4 on the front side affects the assembly of the reinforcing plate, it can be appropriately ground before assembly. Finally, weld the reinforcing weld 2 onto reinforcing plate 1.

[0030] The reinforcing plate and the main plate are connected by a lap joint, and the force on the main plate is distributed to the reinforcing plate through the lap joint. The type of reinforcing weld 2 is a weld point and a weld seam, which is kept at a certain distance from the main weld seam and is evenly distributed, which can reduce stress concentration and thus ensure the ability of the reinforcing weld seam to share the force on the main plate. Figure 6 The image shows a reinforcing weld in the form of a weld point. When the reinforcing weld 2 is a weld point, its size and number are related to the size of the reinforcing plate. The base material is 1mm thick stainless steel. The diameter and number of weld points are related to the allowable shear stress and the magnitude of the force applied to the lap weld point. Based on the cross-sectional area and bearing capacity of the weld point, the number of rows of weld points can be calculated.

[0031] Figure 7 The diagram shows a reinforcing weld of type 2. Factors affecting the reinforcement effect include the lap area, the length of the reinforcing weld, and the spacing. When the strength of the reinforcing plate is the same as that of the base material, the thickness of the reinforcing plate is related to the joint strength coefficient of the main weld and the thickness of the base material of the main weld, and should satisfy the following:

[0032] The total length of the reinforcing weld is related to the spacing of the reinforcing welds, the joint strength coefficient, the thickness of the main weld, and the width of the reinforcing lap weld, and should meet the following requirements:

[0033]

[0034] Furthermore, both the main weld and the reinforcing weld are laser welded. To meet the predetermined weld type and lap area requirements, the process parameters for the reinforcing weld are determined based on actual conditions and do not need to be the same as those for the main weld. The placement of the backing plate is relative to the laser irradiation surface; the laser irradiation surface of the main weld is on top, and the backing plate is on top, and vice versa. If the backing plate is on the bottom, it may not be fully penetrated; if the backing plate is on top, the main weld is performed first, followed by the reinforcing weld.

[0035] Furthermore, different lap areas and distribution patterns can be designed based on the size and stress conditions of the reinforcing plate. Different lap areas and distributions will affect stress concentration and the load-bearing capacity of the lap weld. The weld direction is perpendicular to the main weld direction and located on both sides of the main weld. It only needs to form a lap connection and cannot penetrate the main structure. The lap reinforcement welds are evenly distributed, and the number and size are determined according to the actual situation. Even distribution of reinforcement welds reduces stress concentration, thereby ensuring the ability of the reinforcement welds to share the force on the main plate.

[0036] Any simple modifications, equivalent changes, and alterations made to the above embodiments based on the technical essence of the present invention shall fall within the protection scope of the present invention.

Claims

1. A method for welding equal-strength stainless steel structures in a cold-worked state, characterized in that: Specific methods include: A reinforcing pad is placed below or above the main weld of the cold-worked stainless steel welded structure, i.e., the main weld body; the joint of the main weld is designed as a butt joint. The reinforcing pad is connected to the main structure by a line weld or weld point lap joint perpendicular to the main weld. The lap weld of the reinforcing pad (1) and the main weld (4), and the lateral lap weld (2) of the reinforcing pad and the main structure provide a reinforcing effect together, and the overall structural strength after reinforcement reaches the same strength as the structure in the reinforced state of the parent material.

2. The equal-strength welding method for cold-worked stainless steel welded structures according to claim 1, characterized in that, The reinforcing pad is positioned above or below the main structure with reference to the laser-acting surface of the main weld; if the laser-irradiated surface is above, the reinforcing pad is above, and vice versa.

3. The equal-strength welding method for cold-worked stainless steel welded structures according to claim 2, characterized in that, When the reinforcing plate is located below, the butt joint interface of the main weld and the lap joint interface between the main weld and the reinforcing plate are completely welded through in one welding operation, and the reinforcing plate may not be fully welded through; when the plate is located above, the main weld is welded first, and then the reinforcing weld is welded.

4. The equal-strength welding method for cold-worked stainless steel welded structures according to claim 3, characterized in that, The direction of the lap weld between the reinforcing pad and the main structure is perpendicular to the direction of the main weld and is located on both sides of the main weld.

5. The equal-strength welding method for cold-worked stainless steel welded structures according to claim 4, characterized in that, When using this welding method, it is only necessary to form an lap joint between the reinforcing plate and the main structure. The main structure should not be fully penetrated as much as possible. The lap joint welds between the reinforcing plate and the main structure should be evenly distributed, and the number and size should be determined according to the actual situation.

6. The equal-strength welding method for cold-worked stainless steel welded structures according to claim 5, characterized in that, If the strength of the reinforcing pad is the same as that of the base material, then the thickness should meet the following requirements:

7. The equal-strength welding method for cold-worked stainless steel welded structures according to claim 5, characterized in that, The length of the reinforcing weld should meet the following requirements:

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